CN111884507B - Control circuit for power converter and control method thereof - Google Patents

Control circuit for power converter and control method thereof Download PDF

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Publication number
CN111884507B
CN111884507B CN202010572933.3A CN202010572933A CN111884507B CN 111884507 B CN111884507 B CN 111884507B CN 202010572933 A CN202010572933 A CN 202010572933A CN 111884507 B CN111884507 B CN 111884507B
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signal
compensation signal
compensation
output
voltage
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CN111884507A (en
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黎坚
施周渊
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Hangzhou Ainuo Semiconductor Co ltd
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Hangzhou Ainuo Semiconductor Co ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The invention relates to the technical field of power electronics, and provides a control circuit for a power converter and a control method thereof, the power converter comprises a first power switch tube and an inductor which are connected between the input end and the output end of the power converter in series, and a second power switch tube connected between the first power switch tube and the connection node of the inductor and the ground, and the control circuit provides a switch control signal for controlling the operation of the first and/or second power switching tubes to cause the inductor to charge and discharge to produce an inductor current, thereby providing an output current, wherein the control circuit obtains a first compensation signal according to a comparison result of a sampling signal of an output voltage of the power converter and a reference voltage, the first compensation signal is filtered by a high-pass filter to obtain a high-frequency component of the first compensation signal, and the period of a switch control signal is adjusted according to the high-frequency component of the first compensation signal. Thereby improving the transient response to the load.

Description

Control circuit for power converter and control method thereof
Technical Field
The invention relates to the technical field of power electronics, in particular to a control circuit for a power converter and a control method thereof.
Background
Currently, the peak current mode control technology is widely applied to Buck converters (Buck), Boost converters (Boost), Flyback converters (Flyback), and the like, and the technology adopts a voltage control loop and a current control loop to realize control of output. In the control circuit of the fixed-frequency peak current mode in the prior art, the output voltage is sampled and then subjected to error processing with the corresponding reference voltage to obtain a feedback compensation signal, and the feedback compensation signal is compared with the value of an inductance current to obtain a comparison result which is used for generating a duty ratio signal for controlling a main power tube together with a clock signal.
Fig. 1a and 1b show a circuit configuration diagram of a buck power converter and a circuit configuration diagram of a control circuit in the power converter shown in fig. 1a, respectively, and fig. 1c shows an operation timing diagram of each signal in the control circuit shown in fig. 1 b. Referring to fig. 1a and 1b, in the power converter 10, the output voltage Vo is sampled by the resistor divider R1 and R2 to obtain a sampled voltage signal VFB, and the sampled voltage signal VFB is provided to the inverting input terminal of the transconductance amplifier 123, and the non-inverting input terminal of the transconductance amplifier 123 is connected to a fixed reference voltage Vref; the output of the transconductance amplifier 123 is subjected to filtering and amplitude modulation processing by the signal processing module 124 and then sent to the inverting input terminal of the comparator 122, the non-inverting input terminal of the comparator 122 is connected to a sampling signal VL which is obtained by the sampling module 112 and has the inductor current iL, the equivalent resistance of the sampling module 112 is Ri, and the value of the sampling signal VL can be the product of the inductor current iL and the equivalent resistance Ri; the output of the comparator 122 is connected with the reset terminal R of the RS flip-flop 121; the set terminal S of the RS flip-flop 121 is connected by a Voltage Controlled Oscillator (VCO) 100; the output of the RS flip-flop 121 sends a switching control signal PWM to a driving circuit 111, and the driving circuit 111 controls the on/off of an upper power switch Q1 and a lower power switch Q2 of the power converter 10, wherein the Voltage Controlled Oscillator (VCO)100 is used for generating a clock signal CLK with a fixed frequency.
When Buck controlled in a conventional peak current mode works, an output voltage Vo sends a sampling voltage VFB to the inverting input end of a transconductance amplifier 123 through a connecting node of a resistor divider R1 and R2, and then the sampling voltage VFB is compared with Vref of the non-inverting input end by the transconductance amplifier 123, so that a signal Vc about the difference of the sampling voltage VFB and the Vref is output by the transconductance amplifier 123; the output Vc of the transconductance amplifier 123 is generated by the first filtering of the filter capacitor C2 and the second filtering of the resistor Rc series capacitor C1 circuit, and then is subjected to the amplitude modulation processing of the amplitude modulation unit 1241 to obtain the feedback compensation signal Vc1, which is sent to the non-inverting input terminal of the comparator 122 as the equivalent setting value of the peak current. Meanwhile, in order to eliminate the sub-harmonic oscillation which may exist under the condition that the duty ratio of the main power tube is more than 50%, the current sampling signal VL is subjected to slope compensation (not shown), namely, the current sampling signal VL is added with a slope signal and then is compared with the feedback compensation signal Vc 1.
When the Buck upper tube Q1 is turned on, the inductor current iL rises, and since the inductor current iL is sampled, the sampling signal VL obtained at the inverting input terminal of the comparator 122 also rises, the comparator 122 outputs a low level, and the RS flip-flop outputs a high level to control the power driving circuit to turn on the upper tube Q1 and turn off the lower tube Q2; along with the increase of the sampling signal VL, when the sampling VL is more than or equal to Vc1, the comparator 122 inverts to output high level to reset the RS trigger connected with the comparator; the RS flip-flop outputs a low level to control the power driving circuit to turn off the upper tube Q1 and turn on the lower tube Q2, at which time the inductor current drops until the next on-period of the clock signal CLK sets the RS flip-flop, and then the Buck converter enters the next period and repeats, as shown in fig. 1c, wherein the rising edge of the switching control signal PWM is determined by the clock signal and the falling edge is determined by the comparison result of the sampling signal VL and the feedback compensation signal Vc 1.
As can be seen from the above, when the output voltage Vo is higher than the value Vref set by the transconductance amplifier 123, the output of 123 decreases, causing the comparator 122 to flip threshold voltage to decrease, i.e., the inductor current peak value to decrease, so that the energy output to the load decreases, thereby suppressing the output voltage from increasing, and vice versa. In the peak current mode, the peak value of the inductive current is set by sampling the output voltage, and the obtained energy is controlled to be output, so that the stability of the output voltage is maintained.
Since the above-mentioned prior art power converter is based on constant frequency control, but it is known that when the load dynamically changes, if the original constant frequency operation is still maintained, the system response is poor, referring to fig. 3a to 3c, when the output current changes, the output voltage can only respond when the next on-period of the power transistor Q1 arrives (as shown in fig. 3 c), which not only causes the response delay of the t1 period (as shown in fig. 3 b), but also causes the voltage drop increase within the delay time t1, as shown in fig. 3 a.
Therefore, the constant-frequency peak current control circuit cannot realize variable-frequency operation with dynamically changed load, and the system response is poor.
Disclosure of Invention
In order to solve the above technical problems, the present invention provides a control circuit for a power converter and a control method thereof, which can improve transient response to a load by generating a first compensation signal according to a comparison result between a sampling signal of an output voltage and a reference voltage and adjusting a period of a switching control signal according to a high frequency component of the first compensation signal.
In one aspect the present invention provides a control circuit for a power converter comprising a first power switching tube and an inductor connected in series between an input terminal and an output terminal of the power converter, and a second power switching tube connected between a connection node of the first power switching tube and the inductor and ground, the control circuit providing a switching control signal for controlling the operation of the first and/or second power switching tubes such that charging and discharging of the inductor produces an inductor current, thereby providing an output current,
the control circuit obtains a first compensation signal according to the output voltage of the power converter, filters the first compensation signal through a high-pass filter to obtain a high-frequency component of the first compensation signal, and adjusts the period of the switch control signal according to the high-frequency component of the first compensation signal.
Preferably, the control circuit includes:
the transconductance amplifier is used for comparing a sampling voltage signal obtained by sampling the output voltage with a reference voltage to generate the first compensation signal;
the signal processing module is connected with the output end of the transconductance amplifier and is used for processing the direct current and low-frequency components of the first compensation signal to generate a second compensation signal;
the first comparator is used for comparing a sampling current signal obtained by sampling the inductor with the second compensation signal and outputting a reset signal;
the clock generation module is connected with the output end of the transconductance amplifier and is used for processing the high-frequency component of the first compensation signal to generate a clock signal;
and the RS trigger has a reset end connected with the output end of the first comparator, a set end connected with the clock generation module and an output end providing the switch control signal.
Preferably, the clock generation module includes:
a first current source and a first capacitor connected in series to ground, a connection node of the first current source and the first capacitor providing a detection signal;
the non-inverting input end of the second comparator is connected with a preset threshold voltage, the inverting input end of the second comparator is connected with the detection signal, and the output end of the second comparator provides the clock signal;
the first switch element is connected between the inverting input end of the second comparator and the ground, the control end of the first switch element is connected with the output end of the second comparator, and the on-off state of the first switch element is controlled by the clock signal;
and the processing unit is connected between the transconductance amplifier and the second comparator, and generates a third compensation signal according to the high-frequency component of the first compensation signal, wherein the third compensation signal is used for adjusting the period of the clock signal.
Preferably, the clock generation module further comprises:
and the input end of the signal selection module is respectively connected with the threshold voltage and the third compensation signal, and the output end of the signal selection module is connected with the non-inverting input end of the second comparator and is used for selecting the smaller value of the third compensation signal and the threshold voltage as the peak reference voltage of the detection signal.
Preferably, the processing unit includes:
the non-inverting input end of the first amplifier is connected with the first compensation signal, and the inverting input end of the first amplifier is connected with the output end of the first amplifier;
the reverse input end of the second amplifier is connected with the output end of the first amplifier through a first resistor, the non-inverting input end of the second amplifier is connected with the compensation voltage, and the output end of the second amplifier is connected with the reverse input end of the second amplifier through a second resistor;
a second current source and a third resistor connected in series to ground, a connection node of the second current source and the third resistor serving as an output terminal of the processing unit to provide the third compensation signal;
a second capacitor connected between an output of the second amplifier and an output of the processing unit,
the second capacitor and the third resistor form the high-pass filter, so that a high-frequency component of the first compensation signal is obtained through a connection node of the second current source and the third resistor, and the third compensation signal is generated.
Preferably, the third compensation signal is used for adjusting a peak reference voltage of the detection signal.
Preferably, the clock generation module further comprises:
a third current source connected to the processing unit for receiving the third compensation signal, and an output terminal of the third current source is connected to an inverting input terminal of the second comparator.
Preferably, the processing unit includes:
the non-inverting input end of the first amplifier is connected with the first compensation signal, and the inverting input end of the first amplifier is connected with the output end of the first amplifier;
the non-inverting input end of the second amplifier is connected with the output end of the first amplifier, the compensation voltage is connected to the output end of the second amplifier through a first resistor and a second resistor which are sequentially connected in series, and the connecting node of the first resistor and the second resistor is connected with the inverting input end of the second amplifier;
a second current source and a third resistor connected in series to ground, a connection node of the second current source and the third resistor serving as an output terminal of the processing unit to provide the third compensation signal;
a second capacitor connected between an output of the second amplifier and an output of the processing unit,
the second capacitor and the third resistor form the high-pass filter, so that a high-frequency component of the first compensation signal is obtained through a connection node of the second current source and the third resistor, and the third compensation signal is generated.
Preferably, the third compensation signal is used to adjust the time for the detection signal to reach the threshold voltage.
Preferably, the first switching element is any one selected from a relay and a switching tube.
Preferably, the third compensation signal follows dynamic variations of a load connected to the output of the power converter.
Preferably, the power switch tubes include a first group of power switch tubes and a second group of power switch tubes, the control circuit obtains a first switch control signal and a second switch control signal of different switching periods according to a high-frequency component of the first compensation signal, and the first switch control signal and the second switch control signal are respectively used for controlling operations of the first group of power switch tubes and the second group of power switch tubes, so that the power converter provides different output currents.
In another aspect, the present invention further provides a method for controlling a control circuit of a power converter, the power converter including a first power switch tube and an inductor connected in series between an input terminal and an output terminal of the power converter, and a second power switch tube connected between a connection node of the first power switch tube and the inductor and ground, the control circuit providing a switch control signal for controlling the operation of the first and/or second power switch tubes, so that the inductor charges and discharges to generate an inductor current, thereby providing an output current,
wherein the control method comprises the following steps:
obtaining a first compensation signal according to the output voltage of the power converter;
high-pass filtering the first compensation signal to obtain a high-frequency component of the first compensation signal; and
adjusting a period of the switching control signal according to a high frequency component of the first compensation signal,
when the load dynamically changes, the period of the switch control signal changes along with the change of the first compensation signal so as to adapt to the change of the load dynamic.
Preferably, the adjusting the period of the switching control signal according to the high frequency component of the first compensation signal includes:
processing the direct current and low-frequency components of the first compensation signal to generate a second compensation signal;
comparing a sampling current signal obtained by sampling the inductor with the second compensation signal, and outputting a reset signal;
processing the high-frequency component of the first compensation signal to generate a clock signal;
and generating the switch control signal according to the reset signal and the clock signal.
Preferably, processing the high frequency component of the first compensation signal to generate a clock signal comprises:
providing a detection signal through a clock generation module;
processing the high-frequency component of the first compensation signal to generate a third compensation signal;
selecting the smaller value of the preset threshold voltage and the third compensation signal as the peak reference voltage of the detection signal, and generating a clock signal according to the comparison result of the peak reference voltage and the detection signal, or adjusting the detection signal according to the third compensation signal to generate a clock signal according to the comparison result of the preset threshold voltage and the detection signal,
and the third compensation signal is used for adjusting the period of the clock signal.
Preferably, the third compensation signal for adjusting the period of the clock signal comprises:
and when the smaller value of the preset threshold voltage and the third compensation signal is selected as the peak reference voltage of the detection signal, adjusting the peak reference voltage of the detection signal according to the third compensation signal so as to adjust the period of the clock signal.
Preferably, the third compensation signal for adjusting the period of the clock signal comprises:
and when the detection signal is adjusted according to the third compensation signal, adjusting the time for reaching the threshold voltage of the detection signal according to the third compensation signal so as to adjust the period of the clock signal.
Preferably, the third compensation signal follows the dynamic variations of the load.
Preferably, the power switch tubes include a first group of power switch tubes and a second group of power switch tubes, and the control method further includes: and respectively acquiring a first switch control signal and a second switch control signal of different switching periods according to the high-frequency component of the first compensation signal, wherein the first switch control signal and the second switch control signal are respectively used for controlling the work of the first group of power switching tubes and the second group of power switching tubes, so that the power converter provides different output currents to adapt to the change of the load.
The invention has the beneficial effects that: the invention provides a control circuit and a control method for a power converter, which can generate a first compensation signal according to a comparison result of a sampling signal of an output voltage of the power converter and a reference voltage, and adjust the period of a clock signal generated by a clock generation module through a high-frequency component of the first compensation signal. The control circuit provided by the invention can follow the dynamic change of the load, and improve the transient response to the load by adjusting the period of the switch control signal.
According to the control circuit for the power converter, the generated switching control signal is linear along with the dynamic change of the load, namely the switching frequency of the clock signal is higher when the change of the load is larger.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings.
FIG. 1a shows a circuit configuration diagram of a prior art power converter;
FIG. 1b illustrates a circuit block diagram of a control circuit in the power converter shown in FIG. 1 a;
FIG. 1c shows timing diagrams of the operation of various signals in the control circuit shown in FIG. 1 b;
fig. 2a and 2b respectively show a circuit structure diagram of the voltage-controlled oscillator in fig. 1a and an operation timing diagram of each signal;
FIGS. 3 a-3 c are schematic diagrams illustrating the output signal and the operating waveform of node A in FIG. 1a, respectively;
FIG. 4 is a circuit diagram of a control circuit for a power converter according to an embodiment of the present invention;
FIG. 5 illustrates a circuit block diagram of one embodiment of the clock generation module of FIG. 4;
FIG. 6 shows a circuit configuration diagram of a processing unit in the embodiment shown in FIG. 5;
FIGS. 7a to 7c are timing diagrams illustrating operation of respective signals in FIG. 5;
FIG. 8 illustrates a circuit block diagram of another embodiment of the clock generation module of FIG. 4;
FIG. 9 shows a circuit configuration diagram of a processing unit in the embodiment shown in FIG. 8;
FIGS. 10a to 10c are timing diagrams illustrating operation of respective signals in FIG. 8;
FIG. 11 is a diagram illustrating simulation results of a power converter output signal provided by an embodiment of the invention;
fig. 12 is a circuit block diagram of another bi-phase power converter provided by an embodiment of the present invention;
FIG. 13 illustrates an operational timing diagram of the various clock signals generated in FIG. 12;
fig. 14 is a flowchart illustrating a control method of a control circuit according to an embodiment of the present invention.
Detailed Description
To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. The invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
The present invention will be described in detail below with reference to the accompanying drawings.
Following the above description of the power converter shown in fig. 1a in the prior art, fig. 2a and 2b respectively show a circuit structure diagram of the voltage-controlled oscillator 100 in fig. 1a and an operation timing diagram of each signal, and referring to fig. 2a, the voltage-controlled oscillator 100 in the prior art includes: the voltage-controlled current source Ivco is connected in series with the capacitor Cvco to the ground, a connection node of the voltage-controlled current source Ivco and the capacitor Cvco is connected with an inverting input end of the comparator 101 to provide a detection signal Vvco, a non-inverting input end of the comparator 101 is connected with a preset threshold voltage Vth, an output end of the comparator 101 is used for providing a clock signal CLK, and the switching element SW1 is connected between the inverting input end of the comparator 101 and the ground and is controlled by the clock signal CLK to be switched on and off.
In the working starting stage, when Vvco is less than Vth, the voltage-controlled current source Ivco charges the capacitor Cvco, the detection signal Vvco received by the inverting input end of the comparator 101 rises, the clock signal output by the comparator 101 is in a low level state, and the switching element SW1 is in an open state; with the increase of the Vvco signal, when Vvco ≧ Vth, the clock signal output by the comparator 101 flips to a high state, the switching element SW1 is closed and turned on, the capacitor Cvco discharges, the detection signal Vvco is pulled down to a low level of ground, then Vvco < Vth, the clock signal flips to a low state again, the switching element SW1 is opened, the voltage-controlled current source Ivco charges the capacitor Cvco, the detection signal Vvco rises, and the above process is repeated, thereby generating the periodic clock signal CLK, as shown in FIG. 2 b.
The voltage controlled oscillator 100 generates a clock signal with a fixed frequency based on the above operation principle, so that the power converter shown in fig. 1a is based on the fixed frequency control, and cannot maintain a fast system response even when the load dynamically changes.
Based on the above, the present invention provides a control circuit for a power converter and a control method thereof, wherein a first compensation signal is generated according to a comparison result between a sampling signal of an output voltage of the power converter and a reference voltage, and a period of a switching control signal is adjusted according to a high frequency component of the first compensation signal, so as to improve transient response to a load.
Fig. 4 shows a circuit configuration diagram of a control circuit for a power converter according to an embodiment of the present invention, fig. 5 shows a circuit configuration diagram of an implementation manner of a clock generation module in fig. 4, fig. 6 shows a circuit configuration diagram of a processing unit in the embodiment shown in fig. 5, and fig. 7a to 7c respectively show operation timing diagrams of respective signals in fig. 5.
The control circuit provided by the embodiment of the invention can be applied to Buck, Boost, Flyback and other power topologies controlled by a peak current mode, and is also applicable to other variable frequency applications controlled by fixed frequency.
The control circuit applied to the buck power converter shown in fig. 1a and shown in fig. 4 is taken as an example for explanation. In fig. 4, a power converter to which the control circuit 120 of the present invention is applied is similar to the power converter shown in fig. 1a, an input terminal of the power converter 10 is connected with an input voltage Vi, and an output terminal thereof is used for providing an output voltage Vo, the power converter 10 includes: a power tube Q1 and an inductor Ls connected in series between the input end and the output end; the connection node of the power tube Q1 and the inductor Ls is A, a power tube Q2 is connected between the connection node A and the ground, and the control ends of the power tubes Q1 and Q2 are both connected to the driving circuit 111; the sampling voltage VFB includes a resistor Rco and a capacitor Co connected in series between the output terminal of the power converter 10 and ground, a resistor RL connected between the output terminal of the power converter 10 and ground, and a connection node of a resistor R1 and a resistor R2 connected in series between the output terminal of the power converter 10 and ground, and a resistor R1 and a resistor R2 connected in series to provide the sampling voltage VFB.
The control circuit 120 includes: the circuit comprises a transconductance amplifier 123, a comparator 122, an RS trigger 121 which are connected in sequence, a signal processing module 124 connected between the output end of the transconductance amplifier 123 and the non-inverting input end of the comparator 122, and a clock generation module 200.
Specifically, the non-inverting input terminal of the transconductance amplifier 123 is connected to the fixed reference voltage Vref, the inverting input terminal is connected to the sampling voltage VFB, the output terminal of the transconductance amplifier 123 outputs a first compensation signal Vc, the signal processing module 124 includes a resistor Rc and a capacitor C1 connected in series between the output terminal of the transconductance amplifier 123 and ground, a capacitor C2 connected between the output terminal of the transconductance amplifier 123 and ground, and an amplitude modulation unit 1241 connected between the output terminal of the transconductance amplifier 123 and the non-inverting input terminal of the comparator 122, the first compensation signal Vc forms a compensation signal Vc1 after filtering and amplitude modulating the dc and low frequency components of the first compensation signal by the signal processing module 124 and is connected to the inverting input terminal of the comparator 122, the non-inverting input terminal of the comparator 122 is connected to the second terminal of the inductor Ls through the sampling module 112 for sampling the inductor current iL, a sampled signal VL is obtained.
Further, the sampling module 112 may employ a prior art sampling circuit (not shown) which utilizes the voltage across the inductor Ls proportional to the rate of change of the inductor current iL to realize sampling, and the equivalent resistance of the sampling module 112 is simply referred to as Ri herein.
The output end of the comparator 122 is connected with the reset end R of the RS flip-flop 121; the set end S of the RS flip-flop 121 is connected to the clock generation module 200; the output end of the RS flip-flop 121 sends the switching control signal PWM to the driving circuit 111, and the driving circuit 111 controls the on/off of the power transistors Q1 and Q2 of the power converter respectively.
Further, the clock generating module 200 is, for example, a Voltage Controlled Oscillator (VCO) for generating the clock signal CLK. Meanwhile, in order to eliminate subharmonic oscillation which may exist under the condition that the duty ratio of the main power tube is greater than 50%, the current sampling signal VL can be subjected to slope compensation (not shown), namely, the current sampling signal VL is superposed with a slope compensation signal and then is compared with the feedback compensation signal Vc 1.
It should be noted that, except for the clock generating module 200, the circuit connection relationship and the operation principle of the control circuit are the same as those of the control circuit 120 in the prior art shown in fig. 1b, and are not described herein again.
The difference lies in that: the clock generation module 200 provided in the embodiment of the present invention is connected between the output end of the transconductance amplifier 123 and the set end S of the RS flip-flop 121, as shown in fig. 4. Specifically, referring to fig. 5, in one embodiment, the clock generation module 200 includes: the voltage-controlled current source Ivco, the capacitor Cvco, the comparator 201, the switching element SW1, the processing unit 210, and the signal selection module 220, wherein the voltage-controlled current source Ivco is connected in series with the capacitor Cvco to ground, and a connection node of the voltage-controlled current source Ivco and the capacitor Cvco is connected with an inverting input terminal of the comparator 201 to provide the detection signal Vvco; the first compensation signal Vc is subjected to signal processing on the high-frequency component thereof by the processing unit 210 to generate a threshold control signal Vth _ Vc; the signal selection module 220 receives a preset threshold voltage Vth on one hand and a valve control signal Vth _ vc on the other hand, and the output end of the signal selection module is connected with the non-inverting input end of the comparator 201, the signal selection module 220 is used for selecting the smaller value of the threshold control signal Vth _ vc and the threshold voltage Vth as the peak reference voltage of the detection signal Vvco, the output end of the comparator 201 is used for providing a clock signal CLK, and the switching element SW1 is connected between the inverting input end of the comparator 201 and the ground and is controlled by the clock signal CLK to be turned on or off.
Further, the first switch element SW1 may be, but is not limited to, any one of a relay and a power transistor, and the voltage-controlled current sources may be generated by, for example, a voltage-controlled current source generating circuit in the prior art, which is not limited herein.
During operation, the first compensation signal Vc output by the transconductance amplifier 123 performs signal processing on a high-frequency component thereof through the processing unit 210 to generate a threshold control signal Vth _ Vc, the threshold control signal Vth _ Vc and the threshold voltage Vth are used as a reference voltage of the detection signal Vvco together, and a working principle of the clock generation module 200 is similar to that of the clock signal generating the fixed frequency of the voltage-controlled oscillator 100 described above, which is not described herein again, except that the clock generation module 200 in this embodiment can dynamically adjust a peak reference voltage of the detection signal Vvco according to the high-frequency component of the generated first compensation signal Vc to adaptively adjust a switching period of the generated clock signal CLK.
The clock signal CLK is used to control the control circuit 120 to generate a switching control signal PWM for turning on the power transistors Q1 and Q2 in the power driving circuit 210, and the switching control signal PWM determines the switching frequency of the main power transistors Q1 and Q2; when the load dynamically changes, the period of the switch control signal PWM is adjusted through the high-frequency component of the first compensation signal Vc so as to adapt to the dynamic change of the load; furthermore, when the load changes dynamically, the magnitude of the control voltage of the voltage-controlled current source IVco can be adjusted to further realize variable frequency operation, and the response speed of the power converter to the dynamic change of the load end is improved.
According to the control circuit for the power converter, the generated switching control signal is linear along with the dynamic change of the load, namely the switching frequency of the clock signal is higher as the load is increased.
Referring to fig. 5, in the clock generating module 200, the processing unit 210 is configured to obtain the first compensation signal Vc after the zero offset processing, and perform level inversion on the first compensation signal Vc after the zero offset processing; the processed first compensation signal Vc is then filtered to obtain a threshold control signal Vth _ Vc, as shown in fig. 7a to 7 b.
Specifically, referring to fig. 6, the processing unit 210 includes an amplifier 2101, an amplifier 2102, a voltage-controlled current source Ioffset and a resistor R5 connected in series to ground, and a capacitor C3, wherein a non-inverting input terminal of the amplifier 2101 is connected to the first compensation signal Vc, and an inverting input terminal is connected to its own output terminal; the inverting input end of the amplifier 2102 is connected with the output end of the amplifier 2101 through a resistor R3, the non-inverting input end of the amplifier is connected with the offset voltage Voffset, and the output end of the amplifier is connected with the inverting input end of the amplifier through a resistor R4; the connection node between the voltage-controlled current source Ioffset and the resistor R5 is used as the output terminal of the processing unit 210 to provide the threshold control signal Vth _ vc, and the capacitor C3 is connected between the output terminal of the amplifier 2102 and the output terminal of the processing unit 210.
The obtained output voltage of the amplifier 2102 is:
Figure GDA0003135653750000131
meanwhile, for the threshold control signal Vth _ Vc, the magnitude of the threshold control signal Vth _ Vc should be smaller than or equal to the product of the current value of the voltage-controlled current source Ioffset and the resistor R5, that is, the divided voltage obtained by the resistor R5, and for the alternating current component of the threshold control signal Vth _ Vc, the alternating current component is the high-frequency component of the first compensation signal Vc obtained by filtering the output voltage V2 of the amplifier 2102 through the high-pass filter composed of the capacitor C3 and the resistor R5, which is used for adjusting the peak reference voltage of the detection signal Vvco to adaptively adjust the switching period of the generated clock signal CLK, so as to achieve the purpose of adjusting the switching period of the switching control signal PWM.
Referring to fig. 7a to 7c, when the load dynamically changes, the first compensation signal Vc undergoes signal processing such as level shift, level inversion and high-pass filtering adjustment to generate a threshold control signal Vth _ Vc as shown in fig. 7b, when the clock generation module 200 operates, the signal selection module 220 selects a smaller value of the threshold control signal Vth _ Vc and the threshold voltage Vth as a peak reference voltage of the detection signal Vvco that dynamically changes along with the load, compares the obtained peak reference voltage with the detection signal Vvco to generate a frequency-converted clock signal CLK, and as shown in fig. 7c, compared with a conventional control circuit in which a comparison between the detection signal and a fixed reference voltage is performed to obtain a fixed-frequency clock signal, the control circuit of the present invention can adaptively adjust the switching period of the generated clock signal CLK according to the dynamic change of the load. The clock signal CLK controls the control circuit 120 to generate the switching control signal PWM for turning on the power transistors Q1 and Q2 in the power driving circuit 210, so as to change the period of the switching control signal PWM to adapt to the dynamic changes of the load.
Fig. 8 is a circuit configuration diagram of another embodiment of the clock generation block shown in fig. 4, fig. 9 is a circuit configuration diagram of a processing unit in the embodiment shown in fig. 8, and fig. 10a to 10c are operation timing diagrams of respective signals in fig. 8, respectively.
In another preferred embodiment of the present invention, referring to fig. 8, the clock generation module 200 includes: the voltage-controlled current source Ivco, the capacitor Cvco, the comparator 201, the switching element SW1, the processing unit 210, and the voltage-controlled current source Ivc, wherein the voltage-controlled current source Ivco is connected in series with the capacitor Cvco to ground, a connection node of the two is connected with an inverting input terminal of the comparator 201 to provide the detection signal Vvco, the processing unit 210 receiving the first compensation signal Vc is connected with an inverting input terminal of the comparator 201 through the voltage-controlled current source Ivc, a non-inverting input terminal of the comparator 201 is connected with a preset threshold voltage Vth, an output terminal of the comparator 201 is used for providing the clock signal CLK, and the switching element SW1 is connected between the inverting input terminal of the comparator 201 and ground and is controlled by the clock signal CLK.
Further, the first switch element SW1 may be, but is not limited to, any one of a relay and a power transistor, and the voltage-controlled current sources may be generated by, for example, a voltage-controlled current source generating circuit in the prior art, which is not limited herein.
In operation, the first compensation signal Vc output by the transconductance amplifier 123 is processed by the processing unit 210 to generate a control voltage Vctrl, which is used as a control voltage of the voltage-controlled current source Ivc, and the voltage-controlled current source Ivc and the voltage-controlled current source Ivco are used together as a charging/discharging current source of the capacitor Cvco to provide the detection signal Vvco, which is compared with the threshold voltage Vth to generate the clock signal CLK. The working principle of the clock generation module 200 is similar to that of the voltage controlled oscillator 100 described above, and is not described herein again.
What is different, the clock generating module 200 in this embodiment can obtain the high frequency component of the first compensation signal Vc through the processing unit 210, and dynamically adjust the time from the detection signal Vvco to the peak reference voltage (threshold voltage Vth) through the control voltage Vctrl generated by signal processing, so as to adaptively adjust the switching period of the generated clock signal CLK.
The clock signal CLK is used to control the control circuit 120 to generate a switching control signal PWM for turning on the power transistors Q1 and Q2 in the power driving circuit 210, and the switching control signal PWM determines the switching frequency of the main power transistors Q1 and Q2; when the load dynamically changes, the period of the switch control signal PWM is adjusted through the high-frequency component of the first compensation signal Vc so as to adapt to the dynamic change of the load; further, when the load changes dynamically, the time for the detection signal Vvco to reach the peak reference voltage (threshold voltage Vth) can be further controlled by adjusting the magnitude of the control voltage of the voltage-controlled current source Ivco, so that the variable-frequency operation is realized, and the response speed of the power converter to the dynamic change of the load end is improved.
According to the control circuit for the power converter, the generated switching control signal is linear along with the dynamic change of the load, namely the switching frequency of the switching control signal is higher when the load changes.
Referring to fig. 8, in the clock generating module 200, the processing unit 210 is configured to obtain the first compensation signal Vc after the zero offset processing, filter the processed first compensation signal Vc, and process to obtain the high frequency component thereof to generate the control voltage Vctrl, as shown in fig. 10a to 10b, for controlling the charge and discharge compensation of the voltage-controlled current source Ivc on the capacitor Cvco.
Specifically, referring to fig. 9, the processing unit 210 includes: an amplifier 2101, an amplifier 2102, resistors R3 and R4, a capacitor C3, a voltage-controlled current source Ioffset and a resistor R5, wherein a non-inverting input terminal of the amplifier 2101 is connected to the first compensation signal Vc, a non-inverting input terminal of the amplifier 2101 is connected to an output terminal of the amplifier 2101, an output terminal of the amplifier 2101 is connected to a non-inverting input terminal of the amplifier 2102, a compensation voltage Voffset is connected to the output terminal of the amplifier 2102 through a resistor R3 and a resistor R4 which are sequentially connected in series, and a connection node of a resistor R3 and a resistor R4 is connected to the non-inverting input terminal of the amplifier 2102; the capacitor C3 is connected between the output terminal of the amplifier 2102 and the output terminal of the processing unit 210, the voltage controlled current source Ioffset series resistor R5 is connected to ground, and the connection node of the voltage controlled current source Ioffset and the resistor R5 serves as the output terminal of the processing unit 210 for providing the control voltage Vctrl.
The obtained output voltage of the amplifier 2102 is:
Figure GDA0003135653750000161
meanwhile, for the control voltage Vctrl, the magnitude of the control voltage Vctrl should be smaller than or equal to the product of the current value of the voltage-controlled current source Ioffset and the resistor R5, that is, the divided voltage obtained by the resistor R5, and for the alternating current component of the control voltage Vctrl, the high-frequency component of the first compensation signal Vc obtained by filtering the output voltage V2 of the amplifier 2102 through the high-pass filter composed of the capacitor C3 and the resistor R5 is used for adjusting the time when the detection signal Vvco reaches the peak reference voltage (threshold voltage Vth) so as to adaptively adjust the switching period of the generated clock signal CLK, so as to achieve the purpose of adjusting the switching period of the switching control signal PWM.
Referring to fig. 10a to 10c, when the load dynamically changes, the first compensation signal Vc is subjected to signal processing such as high-pass filtering and level offset adjustment to generate a control voltage Vctrl for voltage control of the voltage-controlled current source Ivc as shown in fig. 10b, when the clock generation module 200 operates, the voltage-controlled current source compensates the detection signal Vvco according to the change of the control voltage Vctrl, so that the time when the detection signal Vvco reaches the peak reference voltage (threshold voltage Vth) follows the load dynamically changes, and a variable-frequency clock signal CLK is generated, as shown in fig. 10c, compared with the conventional control circuit in which the detection signal is compared with the fixed reference voltage to obtain a fixed-frequency clock signal, the control circuit of the present invention can adaptively adjust the switching period of the generated clock signal CLK according to the dynamic change of the load. The clock signal CLK controls the control circuit 120 to generate the switching control signal PWM for turning on the power transistors Q1 and Q2 in the power driving circuit 210, so as to change the switching period of the switching control signal PWM to adapt to the dynamic changes of the load.
Fig. 11 is a diagram illustrating simulation results of an output signal of a power converter according to an embodiment of the present invention.
Referring to fig. 11, when the load (e.g., the output current Io and the output voltage Vo) dynamically changes, the power converter provided in the prior art may cause a response delay of a time period t1 due to a clock signal with a fixed frequency, and at the same time, the output voltage Vo may have a voltage drop change of Δ V within the delay time, which may cause an output voltage to be unstable, whereas the power converter applying the control circuit provided in the above embodiment of the present invention may generate a clock signal with a variable frequency, a switching period of the clock signal may change along with the dynamic change of the load, which effectively reduces the response delay to t2, and also reduces the voltage drop of the response delay, which effectively improves a response speed of the power converter to the dynamic change of the load terminal.
The invention is not only suitable for single-phase power converters, but also suitable for control of multiphase power converters.
Fig. 12 is a circuit configuration diagram of another two-phase power converter according to an embodiment of the present invention, and fig. 13 is a timing diagram illustrating operation of each clock signal generated in fig. 12.
Referring to fig. 12, in another preferred embodiment of the present invention, there is provided a bi-phase power converter 30 comprising: a first group of power switching tubes Q1 and Q2, a driving circuit 1111 connected with the first group of power switching tubes Q1 and Q2, a second group of power switching tubes Q3 and Q4, a driving circuit 1112 connected with the second group of power switching tubes Q3 and Q4, and a control circuit 300, wherein the control circuit 300 comprises a transconductance amplifier 123 connected with the output end of the power converter 30 through a voltage dividing resistor R1, a comparator 1221 connected with the transconductance amplifier 123, an amplitude modulation unit 1241 connected between the transconductance amplifier 123 and the comparator 1221, a sampling module 1121, and an RS flip-flop 1211 connected between the comparator 1221 and the driving circuit 1111; a comparator 1221 connected to the transconductance amplifier 123, an amplitude modulation unit 1242 connected between the transconductance amplifier 123 and the comparator 1221, a sampling module 1122, and an RS flip-flop 1211 connected between the comparator 1221 and the driving circuit 1112; a clock generation module 310; a capacitor C2 connected in series between the output terminal of the transconductance amplifier 123 and ground, a resistor Rc and a capacitor C1 connected in series between the output terminal of the transconductance amplifier 123 and ground, and an output filter circuit composed of a resistor RL connected in series between the output terminal of the power converter 30 and ground, a resistor Rco and a capacitor Co connected in series between the output terminal of the power converter 30 and ground.
Referring to the above embodiment, similarly, the output voltage Vo is sampled by the resistor voltage divider R1 and R2 to obtain a sampled voltage signal VFB, and the sampled voltage signal VFB is provided to the inverting input terminal of the transconductance amplifier 123, and the non-inverting input terminal of the transconductance amplifier 123 is connected to a fixed reference voltage Vref; the output Vc of the transconductance amplifier 123 is subjected to amplitude modulation processing by the amplitude modulation unit 1241 to obtain a feedback compensation signal Vc1, and the feedback compensation signal Vc1 is respectively sent to the inverting input terminal of the comparator 1221 and the inverting input terminal of the comparator 1222, the non-inverting input terminal of the comparator 1221 is connected to the sampling signal VL1 which obtains the inductor current iL1 through the sampling module 1121, and the non-inverting input terminal of the comparator 1222 is connected to the sampling signal VL2 which obtains the inductor current iL2 through the sampling module 1122; the output of the comparator 1221 is connected to the reset terminal R of the RS flip-flop 1211, the set terminal S of the RS flip-flop 1211 is connected to the control circuit 310, the output of the RS flip-flop 1211 sends the switching control signal PWM1 to the driving circuit 1111, and the driving circuit 1111 controls the on/off of the first group of power switching transistors Q1 and Q2 of the power converter 30; the output of the comparator 1222 is connected to the reset terminal R of the RS flip-flop 1212, the set terminal S of the RS flip-flop 1212 is connected to the clock generation module 310, the output of the RS flip-flop 1212 sends the switching control signal PWM2 to the driving circuit 1112, and the driving circuit 1112 controls the on/off of the second group of power switching transistors Q3 and Q4 of the power converter 30; the clock generating module 310 generates the clock signal CLK according to the high-frequency component of the first compensation signal Vc, the generated clock signal CLK can be divided into a first clock signal CLK1 and a second clock signal CLK2 with different switching periods, the relationship between the working timing waveforms of the first clock signal CLK1 and the second clock signal CLK2 and the clock signal CLK is shown in fig. 13, the periods of the first clock signal CLK1 and the second clock signal CLK2 are the same and are both 2 times of the clock signal CLK, and the same-phase superposition of the first clock signal CLK1 and the second clock signal CLK2 is the clock signal CLK.
The control circuit 300 generates a first switch control signal PWM1 and a second switch control signal PWM2 according to the first clock signal CLK1 and the second clock signal CLK2, respectively, and the first switch control signal PWM1 and the second switch control signal PWM2 are respectively used for controlling the operations of the first group of power switches Q1 and Q2 and the second group of power switches Q3 and Q4, so that the power converter provides different output currents to adapt to the load variation.
The difference from the previous embodiment is: the power switch tubes comprise a first group of power switch tubes Q1 and Q2 and a second group of power switch tubes Q3 and Q4, the control circuit 300 can generate a first clock signal CLK1 and a second clock signal CLK2 with different switching periods by comparing a sampled signal VFB obtained by sampling the output voltage Vo with a reference voltage Vref, the first clock signal CLK1 and the second clock signal CLK2 are used for respectively adjusting the switching periods of the first switching control signal PWM1 and the second switching control signal PWM2, and the transient response of the converter is improved by obtaining different response rates in the power converter through two-phase frequency conversion control.
Furthermore, when the load changes dynamically, the magnitude of the control voltage of the voltage-controlled current source IVco can be adjusted to further realize variable frequency operation, and the response speed of the power converter to the dynamic change of the load end is improved.
When the load dynamically changes, the single-output two-phase frequency conversion controlled power converter has small output voltage transient variation, short regulation time and good load transient performance, and can reduce the risk of abnormal work caused by serious instability of the converter when the load suddenly changes in the frequency conversion control.
It should be noted that the present invention is not limited to the Buck converter controlled by the two-phase frequency conversion, and may also be a power converter controlled by multiple frequency conversion based on the above control principle, and of course, the type of the power converter includes but is not limited to the Buck converter, and may also be applied to power topologies such as Boost and Flyback, etc., and the control principle is similar to that described above, and is not described herein again or limited.
In addition, the present invention mainly describes the power converter controlled in the peak current mode, but is not limited to this, and may also be applied to the power converter in the current valley detection control mode, and is not limited thereto.
Fig. 14 is a flowchart illustrating a control method for a control circuit of a power converter according to an embodiment of the present invention.
In another aspect, the present invention further provides a control method for a control circuit of a power converter, where the control method is applicable to the control circuit in the foregoing embodiment, the power converter includes a power switch tube and an inductor connected to each other, and the control circuit is configured to provide a switch control signal for controlling the operation of the power switch tube, so that the inductor in the power converter is charged and discharged to generate an inductor current, thereby providing an output current, and the control method specifically includes the following steps:
step S110: a first compensation signal is obtained according to the output voltage of the power converter.
Step S120: the period of the switching control signal is adjusted according to the high frequency component of the first compensation signal.
The control method can enable the period of the switch control signal to change along with the change of the first compensation signal when the load of the power converter changes dynamically so as to adapt to the change of the load dynamic.
In step S110, the output voltage of the switching converter is sampled to obtain a sampled voltage signal, and then the sampled voltage signal is compared with a reference voltage to generate a first compensation signal.
In step S120, the first compensation signal is processed by filtering and amplifying to generate a second compensation signal; comparing a sampling current signal obtained by sampling an inductor in the power converter with the second compensation signal, and outputting a reset signal; simultaneously, obtaining a clock signal according to the high-frequency component of the first compensation signal; and generating the switch control signal according to the reset signal and the clock signal.
Further, the obtaining the clock signal according to the high frequency component of the first compensation signal specifically includes:
providing a detection signal through a clock generation module; generating a third compensation signal by processing a high frequency component obtained by filtering the first compensation signal; the clock signal is generated according to the detection signal, a preset threshold voltage and a third compensation signal.
In the above control method, the third compensation signal is used to adjust the period of the clock signal. Specifically, in a preferred embodiment, the peak reference voltage of the detection signal is adjusted according to the third compensation signal to adjust the period of the clock signal. In conjunction with the embodiment shown in fig. 5, the control circuit can generate the first compensation signal Vc according to the comparison between the sampled voltage VFB of the output signal Vo and the fixed reference voltage Vref, and process the high-frequency component obtained by filtering the first compensation signal Vc to generate the threshold control signal Vth _ Vc, where the threshold control signal Vth _ Vc and the threshold voltage Vth are used together to dynamically adjust the peak reference voltage of the detection signal Vvco so as to adaptively adjust the switching period of the generated clock signal CLK.
In another preferred embodiment, the time for the detection signal to reach the peak reference voltage (threshold voltage) is adjusted according to the third compensation signal to adjust the period of the clock signal. In conjunction with the embodiment shown in fig. 8, the processing unit 210 processes the first compensation signal Vc output by the transconductance amplifier 123 to obtain a high-frequency component thereof, and generates a control voltage Vctrl, where the control voltage Vctrl is used as a control voltage of the voltage-controlled current source Ivc, and the voltage-controlled current source Ivc and the voltage-controlled current source Ivco are used together as a charging/discharging current source of the capacitor Ccvo to compensate the detection signal Vvco, and adjust a time when the detection signal Vvco reaches a peak reference voltage (threshold voltage Vth) so as to adaptively adjust a switching period of the generated clock signal CLK.
The third compensation signal (the threshold control signal Vth _ vc or the control voltage Vctrl) follows the dynamic change of the load.
Further, based on the power converter shown in the embodiment of fig. 12, the power converter includes the first group of power switching tubes and the second group of power switching tubes, so the control method further includes: and respectively acquiring a first switch control signal and a second switch control signal of different switching periods according to the high-frequency component of the first compensation signal, wherein the first switch control signal and the second switch control signal are respectively used for controlling the work of the first group of power switching tubes and the second group of power switching tubes, so that the power converter provides different output currents to adapt to the change of the load.
According to the control method for the power converter control circuit provided by the embodiment of the invention, the transient response of the converter can be improved by obtaining different response rates in the power converter through two-phase frequency conversion control.
It should be noted that in the description of the present invention, it is to be understood that the terms "upper", "lower", "inner", and the like, indicate orientation or positional relationship, are only for convenience of describing the present invention and simplifying the description, but do not indicate or imply that the referenced components or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the present invention.
Further, in this document, the contained terms "include", "contain" or any other variation thereof are intended to cover a non-exclusive inclusion, so that a process, a method, an article or an apparatus including a series of elements includes not only those elements but also other elements not explicitly listed or inherent to such process, method, article or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
Finally, it should be noted that: it should be understood that the above examples are only for clearly illustrating the present invention and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of the invention may be made without departing from the scope of the invention.

Claims (19)

1. A control circuit for a power converter, the power converter comprising a first power switch and an inductor connected in series between an input of the power converter and an output thereof, and a second power switch connected between a connection node of the first power switch and the inductor and ground, the control circuit providing a switch control signal for controlling the operation of the first and/or second power switch such that charging and discharging of the inductor produces an inductor current, thereby providing an output current,
wherein the control circuit obtains a first compensation signal according to the output voltage of the power converter, filters the first compensation signal through a high-pass filter to obtain a high-frequency component of the first compensation signal, and generates a third compensation signal by processing the high-frequency component of the first compensation signal through a clock generation module in the control circuit, wherein the third compensation signal is used for adjusting the switching period of the clock signal generated by the clock generation module,
the clock generation module generates a peak reference voltage of a detection signal according to a preset threshold voltage and the magnitude of the third compensation signal, and generates the clock signal according to a comparison result of the peak reference voltage and the detection signal, or adjusts the time for the detection signal to reach the threshold voltage according to the third compensation signal, so as to generate the clock signal according to a comparison result of the preset threshold voltage and the detection signal,
and the clock generation module adjusts the switching period of the clock signal according to the third compensation signal, so as to control the period of the switching control signal.
2. The control circuit of claim 1, further comprising:
the transconductance amplifier is used for comparing a sampling voltage signal obtained by sampling the output voltage with a reference voltage to generate the first compensation signal;
the signal processing module is connected with the output end of the transconductance amplifier and is used for processing the direct current and low-frequency components of the first compensation signal to generate a second compensation signal;
the first comparator is used for comparing a sampling current signal obtained by sampling the inductor with the second compensation signal and outputting a reset signal;
and the RS trigger has a reset end connected with the output end of the first comparator, a set end connected with the clock generation module and an output end providing the switch control signal.
3. The control circuit of claim 2, wherein the clock generation module comprises:
a first current source and a first capacitor connected in series to ground, a connection node of the first current source and the first capacitor providing a detection signal;
the non-inverting input end of the second comparator is connected with a preset threshold voltage, the inverting input end of the second comparator is connected with the detection signal, and the output end of the second comparator provides the clock signal;
the first switch element is connected between the inverting input end of the second comparator and the ground, the control end of the first switch element is connected with the output end of the second comparator, and the on-off state of the first switch element is controlled by the clock signal;
and the processing unit is connected between the transconductance amplifier and the second comparator, and generates a third compensation signal according to the high-frequency component of the first compensation signal, wherein the third compensation signal is used for adjusting the period of the clock signal.
4. The control circuit of claim 3, wherein the clock generation module further comprises:
and the input end of the signal selection module is respectively connected with the threshold voltage and the third compensation signal, and the output end of the signal selection module is connected with the non-inverting input end of the second comparator and is used for selecting the smaller value of the third compensation signal and the threshold voltage as the peak reference voltage of the detection signal.
5. The control circuit of claim 4, wherein the processing unit comprises:
the non-inverting input end of the first amplifier is connected with the first compensation signal, and the inverting input end of the first amplifier is connected with the output end of the first amplifier;
the reverse input end of the second amplifier is connected with the output end of the first amplifier through a first resistor, the non-inverting input end of the second amplifier is connected with the compensation voltage, and the output end of the second amplifier is connected with the reverse input end of the second amplifier through a second resistor;
a second current source and a third resistor connected in series to ground, a connection node of the second current source and the third resistor serving as an output terminal of the processing unit to provide the third compensation signal;
a second capacitor connected between an output of the second amplifier and an output of the processing unit,
the second capacitor and the third resistor form the high-pass filter, so that a high-frequency component of the first compensation signal is obtained through a connection node of the second current source and the third resistor, and the third compensation signal is generated.
6. The control circuit of claim 5, wherein the third compensation signal is used to adjust a peak reference voltage of the detection signal.
7. The control circuit of claim 3, wherein the clock generation module further comprises:
a third current source connected to the processing unit for receiving the third compensation signal, and an output terminal of the third current source is connected to an inverting input terminal of the second comparator.
8. The control circuit of claim 7, wherein the processing unit comprises:
the non-inverting input end of the first amplifier is connected with the first compensation signal, and the inverting input end of the first amplifier is connected with the output end of the first amplifier;
the non-inverting input end of the second amplifier is connected with the output end of the first amplifier, the compensation voltage is connected to the output end of the second amplifier through a first resistor and a second resistor which are sequentially connected in series, and the connecting node of the first resistor and the second resistor is connected with the inverting input end of the second amplifier;
a second current source and a third resistor connected in series to ground, a connection node of the second current source and the third resistor serving as an output terminal of the processing unit to provide the third compensation signal;
a second capacitor connected between an output of the second amplifier and an output of the processing unit,
the second capacitor and the third resistor form the high-pass filter, so that a high-frequency component of the first compensation signal is obtained through a connection node of the second current source and the third resistor, and the third compensation signal is generated.
9. The control circuit of claim 7, wherein the third compensation signal is used to adjust the time for the detection signal to reach the threshold voltage.
10. The control circuit according to claim 3, wherein the first switching element is any one selected from a relay and a switching tube.
11. A control circuit according to claim 6 or 9 wherein the third compensation signal follows dynamic variations of a load to which the power converter output is connected.
12. The control circuit of claim 1, wherein the power switch transistors include a first group of power switch transistors and a second group of power switch transistors, the control circuit obtains a first switch control signal and a second switch control signal for different switching cycles according to the high-frequency component of the first compensation signal, and the first switch control signal and the second switch control signal are respectively used for controlling operations of the first group of power switch transistors and the second group of power switch transistors, so that the power converter provides different output currents.
13. A control method for a power converter control circuit, the power converter comprising a first power switch tube and an inductor connected in series between an input terminal and an output terminal of the power converter, and a second power switch tube connected between a connection node of the first power switch tube and the inductor and ground, the control circuit providing a switch control signal for controlling the operation of the first and/or second power switch tube such that charging and discharging of the inductor generates an inductor current, thereby providing an output current,
wherein the control method comprises the following steps:
obtaining a first compensation signal according to the output voltage of the power converter;
high-pass filtering the first compensation signal to obtain a high-frequency component of the first compensation signal;
processing the high-frequency component of the first compensation signal to generate a third compensation signal, wherein the third compensation signal is used for adjusting the switching period of a clock signal generated by a clock generation module in the control circuit; and
adjusting the switching period of the clock signal according to the third compensation signal to control the period of the switching control signal,
and the adjusting the switching period of the clock signal according to the third compensation signal comprises: generating a peak reference voltage of a detection signal according to a preset threshold voltage and a magnitude of the third compensation signal, and generating the clock signal according to a comparison result of the peak reference voltage and the detection signal, or adjusting a time for the detection signal to reach the threshold voltage according to the third compensation signal to generate the clock signal according to a comparison result of the preset threshold voltage and the detection signal,
when the load dynamically changes, the period of the switch control signal changes along with the change of the first compensation signal so as to adapt to the change of the load dynamic.
14. The control method of claim 13, wherein the period of the switch control signal changing with the change in the first compensation signal comprises:
processing the direct current and low-frequency components of the first compensation signal to generate a second compensation signal;
comparing a sampling current signal obtained by sampling the inductor with the second compensation signal, and outputting a reset signal;
processing the high-frequency component of the first compensation signal to generate a clock signal;
and generating the switch control signal according to the reset signal and the clock signal.
15. The control method of claim 14, wherein the step of processing the high frequency component of the first compensation signal to generate a third compensation signal comprises:
providing a detection signal through a clock generation module;
processing the high-frequency component of the first compensation signal to generate a third compensation signal;
selecting the smaller value of the preset threshold voltage and the third compensation signal as the peak reference voltage of the detection signal, and generating the clock signal according to the comparison result of the peak reference voltage and the detection signal, or adjusting the detection signal according to the third compensation signal to generate the clock signal according to the comparison result of the preset threshold voltage and the detection signal.
16. The control method of claim 15, wherein said adjusting a switching period of the clock signal according to the third compensation signal comprises:
and when the smaller value of the preset threshold voltage and the third compensation signal is selected as the peak reference voltage of the detection signal, adjusting the peak reference voltage of the detection signal according to the third compensation signal so as to adjust the period of the clock signal.
17. The control method of claim 15, wherein said adjusting a switching period of the clock signal according to the third compensation signal comprises:
and when the detection signal is adjusted according to the third compensation signal, adjusting the time for reaching the threshold voltage of the detection signal according to the third compensation signal so as to adjust the period of the clock signal.
18. The control method of claim 15, wherein the third compensation signal follows dynamic changes of the load.
19. The control method of claim 13, wherein the power switching tubes comprise a first set of power switching tubes and a second set of power switching tubes, the control method further comprising:
respectively acquiring a first switch control signal and a second switch control signal of different switching periods according to the high-frequency component of the first compensation signal,
the first switch control signal and the second switch control signal are respectively used for controlling the operation of the first group of power switching tubes and the second group of power switching tubes, so that the power converter provides different output currents to adapt to the change of the load.
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CN112713756B (en) * 2020-12-23 2022-03-08 杰华特微电子股份有限公司 Control circuit and control method of power switch tube
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