CN111628654B - Switching power supply circuit - Google Patents
Switching power supply circuit Download PDFInfo
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- CN111628654B CN111628654B CN201910151825.6A CN201910151825A CN111628654B CN 111628654 B CN111628654 B CN 111628654B CN 201910151825 A CN201910151825 A CN 201910151825A CN 111628654 B CN111628654 B CN 111628654B
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- 238000004804 winding Methods 0.000 claims abstract description 66
- 239000003990 capacitor Substances 0.000 claims abstract description 57
- 238000005070 sampling Methods 0.000 claims description 108
- 238000000034 method Methods 0.000 claims description 11
- 230000003111 delayed effect Effects 0.000 claims description 6
- 238000004378 air conditioning Methods 0.000 claims 1
- 230000001276 controlling effect Effects 0.000 description 13
- 230000002441 reversible effect Effects 0.000 description 9
- 238000010586 diagram Methods 0.000 description 7
- 230000007423 decrease Effects 0.000 description 5
- 230000003071 parasitic effect Effects 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 238000001914 filtration Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000002596 correlated effect Effects 0.000 description 1
- 230000000875 corresponding effect Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 230000005669 field effect Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
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Classifications
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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
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
- H02M3/33576—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/14—Arrangements for reducing ripples from dc input or output
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/0048—Circuits or arrangements for reducing losses
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/0048—Circuits or arrangements for reducing losses
- H02M1/0054—Transistor switching losses
- H02M1/0058—Transistor switching losses by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
Abstract
The application relates to a switching power supply circuit comprising: the primary circuit comprises a transformer, a primary winding of the transformer is connected with the first switching tube in series, a secondary winding of the transformer is connected with the second switching tube in series, and a resonance capacitor is connected between the second switching tube and the secondary winding and connected with the secondary winding in parallel; the control circuit is connected with the control end of the first switching tube on one hand and is used for controlling the first switching tube to be turned on and off, and is connected with the control end of the second switching tube on the other hand and is used for controlling the second switching tube to be turned off when the secondary side current is reduced to zero during the conduction period of the first switching tube and controlling the second switching tube to be turned on when the resonance capacitor is charged during the turn-off period of the second switching tube. According to the switching power supply, the switching tube is used for rectification, and compared with the traditional diode rectification, the rectifying loss of the circuit can be reduced.
Description
Technical Field
The application relates to the field of switching power supplies, in particular to a switching power supply circuit.
Background
The switching power supply circuit generally comprises a power conversion circuit at an input end and a rectifying and filtering circuit at an output end, wherein the power conversion circuit comprises a transformer and a switching tube connected with the transformer, and the power conversion is performed by controlling the switching tube to be turned on and off; the rectifying and filtering circuit comprises a rectifying diode and outputs direct current by utilizing the unidirectional conduction characteristic of the diode. As shown in fig. 1, in a switching power supply circuit in the conventional technology, a switching tube Q is connected to a primary winding of a transformer, a rectifying diode D is connected to a secondary winding of the transformer, and is controlled to be turned on and off. However, since the rectifier diode has a certain on-resistance, the rectifier diode also generates a certain loss during the operation of the switching power supply circuit, which increases the overall power consumption of the switching power supply circuit and is not beneficial to improving the power density of the switching power supply circuit.
Disclosure of Invention
Based on this, it is necessary to propose a new switching power supply circuit for the problem of large rectifier diode loss in the switching power supply circuit.
A switching power supply circuit, comprising:
the main circuit comprises a transformer, a resonant capacitor, a first switch tube and a second switch tube, wherein the transformer comprises a primary winding and a secondary winding, the primary winding is connected with an input end and an output end of the first switch tube in series to form a primary branch, the primary branch is used for being connected with an input power supply, the secondary winding is connected with the input end and the output end of the second switch tube in series to form a secondary branch, and the resonant capacitor is connected between the second switch tube and the secondary winding and is connected with the secondary winding in parallel, and the secondary branch is used for being connected with a load;
the control circuit controls the on and off of the first switching tube and the second switching tube, wherein when the first switching tube is on and the current flowing from the input end of the second switching tube to the output end of the second switching tube is reduced to zero, the second switching tube is controlled to be turned off; and when the first switching tube is turned off and the resonance capacitor is charged, controlling the second switching tube to be turned on.
In the switching power supply circuit, the secondary side branch adopts the second switching tube to rectify, and the second switching tube does not have unidirectional conduction characteristic, so that the second switching tube is utilized to rectify, and the control circuit is adopted to timely control the on and off of the second switching tube. In the switching and switching-off process of the first switching tube, the current of the secondary side branch is controlled by the current of the primary side branch to fluctuate, the current flowing from the input end of the second switching tube to the output end of the second switching tube in the secondary side branch is defined as forward current, the direction opposite to the forward current is reverse current, after the first switching tube is switched on, the forward current in the secondary side branch gradually drops, and when the forward current in the secondary side branch drops to zero, the second switching tube is controlled to be switched off, which is equivalent to that in the prior art, when the secondary side branch generates reverse current, the diode is switched off; after the first switching tube is turned off, the secondary side resonance capacitor resonates with inductance in the circuit such as leakage inductance of a transformer, the resonance capacitor is charged forward after being discharged reversely in the resonance process, when the resonance capacitor is charged, the charging current is forward current, the control circuit controls the second switching tube to be conducted, and the control circuit is equivalent to the conduction of a diode when the secondary side branch circuit generates forward current in the prior art. The control circuit timely controls the on and off of the second switching tube, so that the second switching tube has rectifying characteristics and can replace the traditional rectifying diode. Meanwhile, the second switching tube has lower on resistance compared with the rectifier diode, accordingly, in the working process of the switching power supply circuit, the forward voltage drop of the second switching tube is smaller, the rectifying loss is lower, and the overall power consumption of the switching power supply circuit is reduced.
In one embodiment, the main circuit further comprises a resonant inductor, the resonant inductor being connected in series in the primary leg.
In one embodiment, in the primary side branch, an input end of the resonant inductor is used for being connected with an input power supply, an output end of the resonant inductor is connected with a first end of the primary side winding, a second end of the primary side winding is connected with an input end of the first switching tube, and an output end of the first switching tube is grounded;
in the secondary side branch, a third end of the secondary side winding is connected with an input end of the second switching tube, a fourth end of the secondary side winding and an output end of the second switching tube are used for being connected with a load, the resonance capacitor is connected with the secondary side winding in parallel, one end of the resonance capacitor is connected with an input end of the second switching tube, and the second end and the third end are homonymy ends.
In one embodiment, the main circuit further includes an input filter capacitor and an output filter capacitor, wherein the input filter capacitor is connected between the input end of the resonant inductor and ground, and the output filter capacitor is connected between the output end of the second switching tube and the fourth end of the secondary winding.
In one embodiment, the control circuit is configured to control the second switching tube to be turned on when a potential between the input terminal of the second switching tube and the output terminal of the second switching tube drops to zero during charging of the resonance capacitor.
In one embodiment, the control circuit is configured to control the first switching tube to be turned on when a potential between an input terminal and an output terminal of the first switching tube is at a valley, and to control the first switching tube to be turned off when a current flowing through the first switching tube is zero.
In one embodiment, the transformer further comprises a primary auxiliary winding, the main circuit further comprises a first sampling resistor, a second sampling resistor and a delay resistor, the first sampling resistor and the second sampling resistor are connected in series between a fifth end and a sixth end of the primary auxiliary winding, a sixth end of the primary auxiliary winding is grounded, one end, connected with the second sampling resistor, of the first sampling resistor is used as a first sampling point, one end of the delay resistor is connected with the first sampling point, the other end of the delay resistor is used as a second sampling point, and a fifth end of the primary auxiliary winding and a third end of the secondary winding are homonymous ends;
the control circuit comprises a sampling module, a calculation module and a driving module, wherein the sampling module is respectively connected with the first sampling point and the second sampling point to sample a first sampling voltage of the first sampling point and a second sampling voltage of the second sampling point, the calculation module comprises a comparator, the positive input end of the comparator is connected with the first sampling voltage, the negative input end of the comparator is connected with the second sampling voltage, and the driving module is connected with the calculation module and is used for controlling the second switching tube to be conducted when the output end of the comparator jumps from high level to low level; the calculation module is further used for calculating a first inflection point of the first sampling voltage during the on period of the first switching tube, and the driving module is used for controlling the second switching tube to be turned off at the inflection point.
In one embodiment, the computing module further includes a delay circuit and an exclusive-or gate, the output end of the comparator is connected to the first input end of the exclusive-or gate on one hand, and is connected to the input end of the delay circuit on the other hand, the output end of the delay circuit is connected to the second input end of the exclusive-or gate, and the driving module is configured to control the second switching tube to be turned on when the output end of the exclusive-or gate outputs a high level, and to keep the state of the second switching tube unchanged when the output end of the exclusive-or gate outputs a low level.
In one embodiment, the second sampling voltage is delayed by 1ns to 2ns from the first sampling voltage.
In one embodiment, the main circuit further includes a third sampling resistor, the primary winding is connected in series with the first switching tube and the third sampling resistor in sequence and then grounded, one end of the third sampling resistor connected with the first switching tube is used as a third sampling point, the control circuit is used for sampling a third sampling voltage of the third sampling point, and is used for controlling the first switching tube to be turned on when the third sampling voltage reaches an even number of zero points, and controlling the first switching tube to be turned off when the third sampling voltage reaches the even number of zero points during the turn-on period of the first switching tube.
Drawings
FIG. 1 is a circuit diagram of a conventional switching power supply;
FIG. 2 is a circuit diagram of a switching power supply according to an embodiment of the application;
FIG. 3 is a circuit diagram of a switching power supply according to another embodiment of the present application;
FIG. 4 is a waveform diagram of related current and voltage of a switching power supply circuit in a control period according to an embodiment of the present application;
FIG. 5 is a block diagram of a computing module architecture in accordance with one embodiment of the present application;
FIG. 6 is a schematic diagram showing waveform processing in a computing module according to an embodiment of the application;
FIG. 7 is a schematic diagram of a secondary side branch resonant capacitor and parasitic inductance resonant circuit according to an embodiment of the application.
Detailed Description
In order that the application may be readily understood, a more complete description of the application will be rendered by reference to the appended drawings. Preferred embodiments of the present application are shown in the drawings. This application may, however, be embodied in many 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 application belongs. The terminology used herein in the description of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.
Fig. 2 shows a switching power supply circuit according to an embodiment of the present application, which includes a main circuit and a control circuit. The primary circuit comprises a transformer Lp, a resonant capacitor Cr, a first switching tube Q1 and a second switching tube Q2, wherein the transformer Lp comprises a primary winding Np and a secondary winding Ns, the primary winding Np and the input end and the output end of the first switching tube Q1 are connected in series to form a primary branch, the primary branch is used for being connected with an input power supply, the current of the input power supply flows through the input end and the output end of the first switching tube Q1 in sequence and then flows back to the input power supply, the secondary winding Ns and the input end and the output end of the second switching tube Q2 are connected in series to form a secondary branch, in the secondary branch, the resonant capacitor Cr is connected between the second switching tube Q2 and the secondary winding Ns and is connected in parallel with the secondary winding Ns, and the secondary branch is used for being connected with an external load to provide an output voltage V for the external load O The induced current generated by the secondary winding Ns sequentially flows through the input end and the output end of the second switching tube Q2And flows into an external load after the end. The control circuit is connected with the control end of the first switching tube Q1 on the one hand, outputs a first control signal duty for controlling the on and off of the first switching tube Q1, and is connected with the control end of the second switching tube Q2 on the other hand, outputs a second control signal duty SR for controlling the on and off of the second switching tube Q2. For the control of the second switching tube Q2, specifically, during the on period of the first switching tube Q1, when the current flowing from the input end to the output end of the second switching tube Q2 decreases to zero, the second switching tube Q2 is controlled to be turned off, and during the off period of the first switching tube Q1, the resonance capacitor Cr resonates with the inductor in the circuit, the resonance capacitor Cr is reversely discharged and then positively charged, and when the resonance capacitor Cr is positively charged, the second switching tube Q2 is controlled to be turned on.
In the present application, the control circuit controls the on and off of the first switching tube Q1 through the first control signal duty, the primary current Ip fluctuates during the on and off period of the first switching tube Q1, and the secondary branch is controlled and connected with the primary branch, the secondary current I D The second switching tube Q2 for rectifying in the secondary side branch does not have the unidirectional conduction characteristic of the traditional rectifying diode and can not be automatically disconnected and connected according to the fluctuation of current, so that a control circuit is required to timely control the connection and disconnection of the second switching tube Q2 to define the secondary side current I in the secondary side branch D The direction from the input end to the output end of the second switching tube Q2 is forward, and the reverse direction, when the secondary side current I D In the reverse direction, the second switch tube Q2 is turned off, and the secondary side current I D In the forward direction, the second switching transistor Q2 is turned on. The control circuit is used for timely controlling the on and off of the second switching tube Q2 specifically comprises the following steps: after the first switching tube Q1 is turned on, the primary current Ip will rise and the secondary current I in the forward direction D Will decrease when the secondary current I D When the current drops to zero, the secondary side current I D When the current is about to be reversed, the control circuit is used for judging the secondary side current I D Whether the second switching tube falls to zero or not, if so, the second switching tube Q2 is controlled to be turned off; after the first switching tube Q1 is turned off, the resonance capacitor Cr resonates with an inductance in the circuit such as leakage inductance of the transformer Lp, and the resonance capacitor Cr is reversedAnd after discharging, the capacitor is charged forward, the current generated by forward charging is forward current, and the control circuit is used for judging whether the resonant capacitor is charged forward, and if the resonant capacitor is charged forward, the second switching tube Q2 is controlled to be conducted. In the control process, when the secondary side current I D In the reverse direction, the second switching tube Q2 is turned off, and the secondary side current I D In the forward direction, the second switching tube Q2 is conducted, which is equivalent to the state that the rectifying diode in the prior art is cut off when receiving reverse current and is conducted when receiving forward current, so that the rectifying function of the secondary side branch is realized. In the application, the second switching tube Q2 is sampled for rectification, and the second switching tube Q2 has lower conduction voltage drop and smaller rectification loss because of lower conduction resistance than the traditional diode.
In an embodiment, as shown in fig. 3, the main circuit further includes a resonant inductor Lres, and the resonant inductor Lres is connected in series in the primary leg. In the switching power supply circuit, the transformer Lp has leakage inductance, and the leakage inductance can participate in resonance, and when the leakage inductance of the current transformer Lp meets the requirement of resonance frequency, an additional resonance inductance Lres can not be set. When the resonant frequency is required to be in the megahertz level, the required resonant inductance Lres is in the microhenry level, and the leakage inductance of the transformer Lp is generally in the nanohenry level and is smaller than the required resonant inductance Lres, so that an additional resonant inductance Lres needs to be added to make the resonant parameter meet the requirement.
In a specific embodiment, as shown in fig. 3, the primary side branch of the main circuit is: the input end of the resonant inductor Lres is used as the input end of the switching power supply circuit and is used for being connected with an input power supply, the output end of the resonant inductor Lres is connected with the first end of the primary winding Np, the second end of the primary winding Np is connected with the input end of the first switching tube Q1, and the output end of the first switching tube Q1 is grounded; the secondary side branch of the main circuit is as follows: the third end of the secondary winding Ns is connected with the input end of the second switching tube Q2, the fourth end of the secondary winding Ns and the output end of the second switching tube Q2 are used as output ends of a switching power supply circuit and are used for connecting a load, one end of the resonance capacitor Cr is connected with the input end of the second switching tube Q2, the resonance capacitor Cr is connected with the secondary winding Ns in parallel, and the second end of the primary winding Np and the third end of the secondary winding Ns are the same-name ends. In this embodiment, in the primary leg,the direction of the primary current Ip flowing from the input end of the resonant inductor Lres to the output end of the resonant inductor Lres is defined as the forward direction, and the reverse direction is defined as the reverse direction. When the control circuit controls the first switching tube Q1 to be conducted, the primary current Ip is a forward current and gradually increases, and the secondary current I D Is forward current and gradually decreases, when the secondary current I D When the current is reduced to zero, the control circuit controls the second switching tube Q2 to be turned off, which is equivalent to the secondary side current I D In reverse, the diode turns off. Then the first switching tube Q1 is controlled to be turned off, during the turn-off period of the first switching tube Q1, the resonant capacitor Cr, the leakage inductance of the transformer Lp, the resonant inductance Lres and the output capacitor Coss of the first switching tube Q1 form a resonant circuit, the resonant capacitor Cr is charged forward after being discharged reversely, and forward charging current is formed in the charging process of the resonant capacitor Cr, at the moment, the control circuit conducts the second switching tube Q2, and the diode is conducted when the secondary side branch circuit induces forward current. The control circuit timely controls the on and off of the second switching tube Q2 to realize the rectification characteristic of the secondary side branch.
In one embodiment, as shown in FIG. 3, the main circuit further includes an input filter capacitor C1 and an output filter capacitor C L An input filter capacitor C1 is arranged in the primary side branch and is connected between the input end of the resonant inductor Lres and the ground, and an output filter capacitor C L Is located in the secondary leg and is connected between the output of the second switching tube Q2 and the fourth terminal of the secondary winding Ns. By setting an input filter capacitor C1 and an output filter capacitor C L The input electrical signal and the output electrical signal can be filtered to generate stable direct current. In an embodiment, as shown in fig. 3, the primary side branch further includes a rectifier bridge, the output end of the rectifier bridge is connected to the input end of the resonant inductor Lres, the input end of the rectifier bridge is used as the input end of the switching power supply circuit, the ac power can be connected, the external ac power is rectified by the rectifier bridge and then is changed into dc power, and then the dc power is subjected to pulse width modulation to obtain the required output voltage.
In one embodiment, the control circuit is used for controlling the second switching tube Q2 to be conducted, particularly for controlling the first switching tube Q2 when the potential between the input end and the output end of the second switching tube Q2 is reduced to zero during the charging process of the resonant capacitor CrThe two switching transistors Q2 are turned on. In the forward charging process of the resonance capacitor Cr, the voltage V across the resonance capacitor Cr Cr Gradually rising, the potential between the input end and the output end of the second switching tube Q2 gradually falls, and when the potential between the output end and the output end of the second switching tube Q2 falls to zero, the second switching tube Q2 is controlled to be conducted. Because the switching tube has switching loss in the switching process, in order to reduce the switching loss, a soft switching technology is generally adopted at present, the soft switching technology refers to a zero-voltage switch (Zero Voltage Switching, ZVS) or a zero-current switch (Zero Current Switching, ZCS), when the voltage is zero, the device is turned on, and when the current is zero, the device is turned off, so that the switching loss is zero, and the circuit power consumption is reduced. In this embodiment, the second switching tube Q2 in the switching power supply circuit is turned off when the current drops to zero, and turned on when the voltage drops to zero, so as to implement Zero Voltage Switching (ZVS) or Zero Current Switching (ZCS), reduce the switching loss of the second switching tube Q2, and further reduce the power consumption of the circuit. In one embodiment, when the resonant capacitor Cr is directly connected to the external load through the second switching tube Q2, the voltage of the resonant capacitor Cr rises to the output voltage V of the switching power supply circuit O The potential between the input and output of the second switching tube Q2 is then zero.
In an embodiment, the control circuit is configured to control on and off of the first switching tube Q1, specifically, to control the first switching tube Q1 to be turned on when a potential between an input end and an output end of the first switching tube Q1 is in a valley, and to control the first switching tube Q1 to be turned off when a current flowing through the first switching tube Q1 is zero. The switching of the first switching tube is designed into a soft switching mode, so that Zero Voltage Switching (ZVS) or Zero Current Switching (ZCS) is realized, the switching loss of the first switching tube Q1 is reduced, and the power consumption of the circuit is further reduced.
In the above embodiment, the control circuit controls the on and off of the second switching tube Q2 according to each current and voltage information in the main circuit, and specifically may directly acquire the required voltage and current information, or may indirectly acquire the required voltage or current information. In a specific embodiment, as shown in fig. 3, in the main circuit, the transformer Lp further includes a primary auxiliary winding Naux, the main circuit further includes a first sampling resistor R1, a second sampling resistor R2, and a delay resistor Rs, the first sampling resistor R1 and the second sampling resistor R2 are connected in series between a fifth end and a sixth end of the primary auxiliary winding Naux, the sixth end of the primary auxiliary winding Naux is grounded, one end of the first sampling resistor R1 connected to the second sampling resistor R2 is used as a first sampling point, one end of the delay resistor Rs is connected to the first sampling point, the other end of the delay resistor Rs is used as a second sampling point, and the fifth end of the primary auxiliary winding Naux and the third end of the secondary winding Ns are mutually identical ends; in the control circuit, the control circuit comprises a sampling module, a calculating module and a driving circuit module, wherein the sampling module is connected with a first sampling point to sample a first sampling voltage Vsense of the first sampling point, the sampling module is also connected with a second sampling point to sample a second sampling voltage V 'sense of the second sampling point, the calculating module comprises a comparator, a positive input end of the comparator is connected with the first sampling voltage Vsense, a negative input end of the comparator is connected with the second sampling voltage V' sense, the driving module is connected with the calculating module and is used for controlling the second switching tube Q2 to be conducted when an output end of the comparator jumps from a high level to a low level, the calculating module is also used for calculating a first inflection point of the first sampling voltage Vsense during the conduction period of the first switching tube Q1, and the driving module is used for controlling the second switching tube Q2 to be turned off at the inflection point. In this embodiment, a primary modulation mode is adopted, that is, a primary auxiliary winding Naux is adopted to obtain current and voltage information in a primary branch and a secondary branch, compared with the method of adopting an optocoupler to obtain a secondary electric signal, the primary modulation mode does not need to use the optocoupler, the cost is low, the design difficulty of a peripheral feedback loop is reduced, and the reliability is higher.
In the above embodiment, as shown in fig. 4, after the first switching tube Q1 is turned on at time t0, the secondary side current I D When the waveform of the first sampling voltage Vsense gradually decreases to zero, an inflection point appears and drops rapidly, the inflection point is the first inflection point of the first sampling voltage Vsense in the on period of the first switching tube Q1, and is defined as an off inflection point B, the calculating module is used for detecting the off inflection point B, and the driving module turns off the second switching tube Q2 at the time t1 when the off inflection point appears. In the present embodiment, after the second switching tube Q2 is turned off, the resonance electricityWhen the voltage of the resonance capacitor Cr rises to the output voltage, the first sampling voltage Vsense presents an inflection point which is defined as a conduction inflection point C, so that the calculation module is used for detecting the conduction inflection point C, and the driving module can turn on the second switching tube Q2. In this embodiment, the calculation module detects the turn-on point C through the comparator. As shown in fig. 6, the second sampling voltage V 'sense is obtained after the first sampling voltage Vsense is delayed by the delay resistor Rs, the delay range of the delay resistor Rs is 1 ns-2 ns, during the turn-off period of the second switching tube Q2, the first sampling voltage Vsense and the second sampling voltage V' sense are input into the comparator, when the comparator output voltage Vcomp jumps from high level to low level for the first time, namely, before the intersection a, the first sampling voltage Vsense is greater than the second sampling voltage V 'sense, the comparator output is high level, after the intersection a, the first sampling voltage Vsense is less than the second sampling voltage V' sense, the comparator output is low level, the intersection a is slightly delayed from the turn-on inflection point C, when the calculation module detects that the output voltage jumps from high level to low level for the first time during the turn-off period of the second switching tube, namely, the driving module Q2 is turned on corresponding to the intersection a when the intersection a occurs. It should be noted that, the second switching tube Q2 is controlled to be turned on at the moment of the intersection point a, and the intersection point a is actually delayed from the turning-on inflection point, and when the turning-on time of the second switching tube Q2 is longer than the ideal value, the current will flow back to the primary side branch, damage the first switching tube Q1, and turn on the second switching tube Q2 after reaching the turning-on inflection point C for a period of time delay, so as to protect the circuit.
In an embodiment, as shown in fig. 5, the above-mentioned calculation module further includes a delay circuit and an exclusive-or gate, the output end of the comparator is connected to the first input end of the exclusive-or gate on one hand, and is connected to the input end of the delay circuit on the other hand, the output end of the delay circuit is connected to the second input end of the exclusive-or gate, and the driving module is configured to control the second switching tube Q2 to be turned on when the output end of the exclusive-or gate outputs a high level, and keep the state of the second switching tube Q2 unchanged when the output end of the exclusive-or gate outputs a low level. In this embodiment, as shown in fig. 6, the comparator output voltage Vcomp is a rectangular pulse, at the intersection point a, the comparator output voltage Vcomp jumps from high level to low level, the comparator output voltage Vcomp is delayed by the delay circuit to generate the delay pulse vcomp_de, the delay pulse vcomp_de and the comparator output voltage Vcomp generate the voltage dutySR 'through exclusive or logic operation, when the delay pulse vcomp_de is opposite to the comparator output voltage Vcomp level, the output voltage dutySR' of the exclusive or gate is high level, and the rest outputs low level, so that at the intersection point a, the output voltage dutySR 'of the exclusive or gate is high level, the second switching tube Q2 can be controlled to be turned on when the output voltage dutySR' of the exclusive or gate is high level, and the state of the second switching tube Q2 is kept unchanged when the output of the exclusive or gate is low level.
The control circuit controls the on and off of the first switching tube Q1 according to the current and voltage information of the primary side branch, in an embodiment, the main circuit further includes a third sampling resistor Rsense, the primary side winding Np is connected with the first switching tube Q1 and the third sampling resistor Rsense in series and then grounded, one end of the third sampling resistor Rsense connected with the first switching tube Q1 is used as a third sampling point, the control circuit is used for sampling a third sampling voltage Vp of the third sampling point, when the third sampling voltage Vp reaches an even number of zero points, the first switching tube Q1 is controlled to be turned on, and during the on period of the first switching tube Q1, the first switching tube Q1 is controlled to be turned off when the third sampling voltage Vp reaches the even number of zero points. The third sampling voltage Vp is positively correlated with the primary current Ip, V P ＝R sense *I P When the third sampling voltage Vp is at an even number of zero points, namely the primary side current Ip is at the even number of zero points, the electric potential between the input end and the output end of the first switching tube Q1 is at the valley bottom, and at the moment, the first switching tube Q1 is conducted to realize zero voltage conduction; during the on period of the first switching tube Q1, when the third sampling voltage Vp is at an even number of zero points, namely when the primary side current Ip is at an even number of zero points, the first switching tube Q1 is controlled to be turned off, zero current turn-off is realized, and therefore the switching loss of the first switching tube Q1 is reduced.
In one embodiment, a first switchThe transistor Q1 and the second switch transistor Q2 are Metal-Oxide-Semiconductor Field-Effect Transistor (MOS transistor), and the first switch transistor Q1 and the second switch transistor Q2 are NMOS transistors. The working process of the switching power supply circuit in the application is described below by taking the first switching tube Q1 as a first NMOS tube and taking the second switching tube Q2 as a second NMOS tube, wherein the potential between the input end and the output end of the first switching tube Q1 is the source-drain voltage V of the first NMOS tube ds . As shown in fig. 4, during one control period, the operation is divided into four time phases:
time period t 0-t 1: at time t0, the primary current Ip passes through an even number of zero points, and the source-drain voltage V of the first NMOS tube ds At the valley bottom, the first control signal duty is at high level to control the first switch tube Q1 to be turned on, the primary current Ip is linearly increased, and the secondary current I D Linearly decrease, at time t1, the secondary side current I D The voltage drops to zero, the first sampling voltage Vsense has a turn-off inflection point B, at the moment, the second control signal dutySR jumps to a high level, and the second switching tube Q2 is controlled to be turned off, so that zero current turn-off is realized;
time period t 1-t 2: at time t1, the second switching tube Q2 is turned off, the resonance capacitor Cr, the resonance inductance Lres and the transformer Lp leak inductance resonate, the energy of the primary winding Np is transferred to the secondary winding Ns, and the resonance capacitor Cr is reversely discharged and then positively charged, so that the third sampling voltage Vp is gradually increased after rapidly decreasing to a negative value. The primary current Ip gradually rises and then resonates to a negative value, and when the primary current Ip reaches an even number of zero points, the first control signal duty jumps to a low level to control the first switching tube Q1 to be turned off. In this embodiment, the device is turned on in the first switching tube Q1, and when the primary current Ip reaches the second zero point, the first switching tube Q1 is controlled to be turned off, so as to realize zero current turn-off. Turning off the first switching tube Q1 at zero points of the second even number of primary side currents Ip, so that the primary side branches are subjected to switching action after being full of an integer number of resonance periods;
time period t 2-t 3: at time t2, the first switching tube Q1 is turned off, the resonance capacitor Cr, the resonance inductor Lres, the transformer Lp leakage inductance and the first switching tube Q1 source-drain output capacitor resonate, and the resonance capacitor Cr is charged in the forward direction and reaches the output voltage V at the time t3 O At this time, the source-drain voltage of the second switching tube Q2 is zero, the first sampling voltage Vsense presents a conduction inflection point C, the second control signal durysr jumps to become high level, and the second switching tube Q2 is controlled to be turned on, so as to realize zero-voltage conduction;
time period t 3-t 4: at time t3, the second switching tube Q2 is turned on, the primary side branch is resonant, that is, the resonant inductance Lres, the transformer Lp leakage inductance and the source-drain output capacitance of the first switching tube Q1 form a resonant loop, the primary side current Ip is resonant current, during the turn-on period of the first switching tube Q1, when the primary side current Ip is at the even number of zero points, the source-drain voltage of the first switching tube Q1 is just at the valley bottom, at this time, the first control signal duty becomes high level, the first switching tube Q1 is controlled to be turned on, and zero voltage conduction is realized. This completes one cycle of control in which the on-time and the off-time of the first switching tube Q1 are determined according to the circumstances.
It should be noted that, during the period from t3 to t4, the second switching tube Q2 is turned on, and the parasitic circuit includes the leakage inductance of the transformer Lp and the parasitic inductance of the conductive wire, and in the secondary branch, the parasitic inductance and the resonance capacitance Cr form a resonant circuit as shown in fig. 7, and the resonance capacitance Cr has a voltageI.e. the voltage of the resonance capacitor Cr at this stage fluctuates due to resonance, resulting in a fluctuation of the first sampling voltage Vsense during this period.
The foregoing examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.
Claims (9)
1. A switching power supply circuit, comprising:
the main circuit comprises a transformer, a resonant capacitor, a first switch tube and a second switch tube, wherein the transformer comprises a primary winding and a secondary winding, the primary winding is connected with an input end and an output end of the first switch tube in series to form a primary branch, the primary branch is used for being connected with an input power supply, the secondary winding is connected with the input end and the output end of the second switch tube in series to form a secondary branch, and the resonant capacitor is connected between the second switch tube and the secondary winding and is connected with the secondary winding in parallel, and the secondary branch is used for being connected with a load; a kind of electronic device with high-pressure air-conditioning system
The control circuit controls the on and off of the first switching tube and the second switching tube, wherein when the first switching tube is on and the current flowing from the input end of the second switching tube to the output end of the second switching tube is reduced to zero, the second switching tube is controlled to be turned off; and in the charging process of the first switching tube and the resonant capacitor, when the electric potential between the input end of the second switching tube and the output end of the second switching tube is reduced to zero, controlling the second switching tube to be conducted.
2. The switching power supply circuit of claim 1 wherein said main circuit further comprises a resonant inductor, said resonant inductor being in series in said primary leg.
3. The switching power supply circuit according to claim 2, wherein,
in the primary side branch, the input end of the resonant inductor is used for being connected with an input power supply, the output end of the resonant inductor is connected with the first end of the primary side winding, the second end of the primary side winding is connected with the input end of the first switching tube, and the output end of the first switching tube is grounded;
in the secondary side branch, a third end of the secondary side winding is connected with an input end of the second switching tube, a fourth end of the secondary side winding and an output end of the second switching tube are used for being connected with a load, the resonance capacitor is connected with the secondary side winding in parallel, one end of the resonance capacitor is connected with an input end of the second switching tube, and the second end and the third end are homonymy ends.
4. The switching power supply circuit according to claim 3, wherein said main circuit further comprises an input filter capacitor connected between an input terminal of said resonant inductor and ground, and an output filter capacitor connected between an output terminal of said second switching tube and a fourth terminal of said secondary winding.
5. The switching power supply circuit according to claim 1, wherein the control circuit is configured to control the first switching tube to be turned on when a potential between an input terminal and an output terminal of the first switching tube is at a valley, and to control the first switching tube to be turned off when a current flowing through the first switching tube is zero.
6. The switching power supply circuit according to claim 5, wherein,
the transformer further comprises a primary auxiliary winding, the main circuit further comprises a first sampling resistor, a second sampling resistor and a delay resistor, the first sampling resistor and the second sampling resistor are connected in series between the fifth end and the sixth end of the primary auxiliary winding, the sixth end of the primary auxiliary winding is grounded, one end, connected with the second sampling resistor, of the first sampling resistor is used as a first sampling point, one end, connected with the first sampling point, of the delay resistor is used as a second sampling point, and the fifth end of the primary auxiliary winding and the third end of the secondary winding are homonymous ends;
the control circuit comprises a sampling module, a calculation module and a driving module, wherein the sampling module is respectively connected with the first sampling point and the second sampling point to sample a first sampling voltage of the first sampling point and a second sampling voltage of the second sampling point, the calculation module comprises a comparator, the positive input end of the comparator is connected with the first sampling voltage, the negative input end of the comparator is connected with the second sampling voltage, and the driving module is connected with the calculation module and is used for controlling the second switching tube to be conducted when the output end of the comparator jumps from high level to low level; the calculation module is further used for calculating a first inflection point of the first sampling voltage during the on period of the first switching tube, and the driving module is used for controlling the second switching tube to be turned off at the inflection point.
7. The switching power supply circuit according to claim 6, wherein the computation module further comprises a delay circuit and an exclusive-or gate, the output end of the comparator is connected to the first input end of the exclusive-or gate on the one hand and the input end of the delay circuit on the other hand, the output end of the delay circuit is connected to the second input end of the exclusive-or gate, and the driving module is configured to control the second switching tube to be turned on when the output end of the exclusive-or gate outputs a high level, and to keep the state of the second switching tube unchanged when the output end of the exclusive-or gate outputs a low level.
8. The switching power supply circuit according to claim 6, wherein said second sampled voltage is delayed by 1ns to 2ns from said first sampled voltage.
9. The switching power supply circuit according to claim 5, wherein the main circuit further comprises a third sampling resistor, the primary winding is connected in series with the first switching tube and the third sampling resistor in sequence and then grounded, one end of the third sampling resistor connected with the first switching tube is used as a third sampling point, the control circuit is used for sampling a third sampling voltage of the third sampling point and controlling the first switching tube to be turned on when the third sampling voltage reaches an even number of zero points, and the control circuit is used for controlling the first switching tube to be turned off when the third sampling voltage reaches the even number of zero points during the conduction of the first switching tube.
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| CN113708640B (en) * | 2021-08-25 | 2023-01-20 | 深圳中科乐普医疗技术有限公司 | Active clamping flyback converter, control method thereof and switching power supply system |
| CN117498510B (en) * | 2024-01-03 | 2024-03-05 | 唐泽制动器(天津)有限公司 | Constant voltage charging circuit of electric vehicle battery |
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| CN102386779A (en) * | 2011-12-06 | 2012-03-21 | 上海新进半导体制造有限公司 | Switching power supply |
| CN107147298A (en) * | 2017-05-31 | 2017-09-08 | 青岛大学 | A kind of microwave oven magnetic supply unit with pull-up active clamp branch road |
| CN108539986A (en) * | 2017-12-15 | 2018-09-14 | 杰华特微电子（杭州）有限公司 | A kind of inverse-excitation type switch power-supply |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102386779A (en) * | 2011-12-06 | 2012-03-21 | 上海新进半导体制造有限公司 | Switching power supply |
| CN107147298A (en) * | 2017-05-31 | 2017-09-08 | 青岛大学 | A kind of microwave oven magnetic supply unit with pull-up active clamp branch road |
| CN108539986A (en) * | 2017-12-15 | 2018-09-14 | 杰华特微电子（杭州）有限公司 | A kind of inverse-excitation type switch power-supply |
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