CN103475217B - DC DC circuits and its over-current protection method - Google Patents
DC DC circuits and its over-current protection method Download PDFInfo
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- CN103475217B CN103475217B CN201310405115.4A CN201310405115A CN103475217B CN 103475217 B CN103475217 B CN 103475217B CN 201310405115 A CN201310405115 A CN 201310405115A CN 103475217 B CN103475217 B CN 103475217B
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Abstract
The present invention discloses a kind of DC DC circuits and its over-current protection method; wherein DC DC circuits are connected with load; including input power, input filter module, PWM control modules and switch module; the PWM control modules include PWM controller, and the PWM controller includes voltage detection unit and drive control unit.In the DC DC circuits of the present invention; input power provides input voltage; ripple voltage is produced when the alternating component of electric current flows through input filter module in switch module; ripple voltage in voltage detection unit detection input filter module; input voltage is compared with the difference of ripple voltage with default reference voltage; and the output of output current is controlled according to comparative result; so as to by detecting that ripple voltage can realize the detection to output current; with in DC DC circuit excessively streams; the output of output current is cut off, the purpose of overcurrent protection is reached.
Description
Technical field
The present invention relates to power technique fields, more particularly to a kind of DC-DC circuit and its over-current protection method.
Background technology
At present, voltage-dropping type（BUCK）The DC-to-dc of topological structure（DC-DC）Circuit is widely used in electronics industry.
The topological DC-DC circuits of common BUCK have two kinds of concrete forms：One kind is that PWM controller and metal-oxide-semiconductor become one（Or
PWM controller only integrated upper metal-oxide-semiconductor）, as shown in Figure 1；Another is the completely not integrated metal-oxide-semiconductor of PWM controller, it is necessary in PWM
Two metal-oxide-semiconductors above and below the outside use of controller, as shown in Figure 2.
For the overcurrent protection of DC-DC circuit in Fig. 1, designer is often internally integrated one in PWM controller
Current detection circuit, by flowing through drain electrode, source electrode in the upper metal-oxide-semiconductor Q11 or lower metal-oxide-semiconductors Q12 of the current detection circuit directly detection
Between electric current.When finding upper metal-oxide-semiconductor Q11 or lower metal-oxide-semiconductor Q12 excessively streams, overcurrent protection will be started.But for Fig. 2 China and foreign countries
The DC-DC circuit of metal-oxide-semiconductor is put, just upper MOS can not be directly detected by being integrated in the current detection circuit inside PWM controller
Electric current in pipe Q21 or lower metal-oxide-semiconductors Q22.
The content of the invention
The main object of the present invention is to propose a kind of DC-DC circuit and its over-current protection method, it is intended to by being integrated in PWM
Voltage detection unit detection ripple voltage inside controller, realizes the detection to output current, realizes overcurrent protection.
In order to achieve the above object, the present invention proposes a kind of DC-DC circuit, and the DC-DC circuit is connected with load, including defeated
Enter power supply, input filter module, PWM control modules and switch module, the PWM control modules include PWM controller, described
PWM controller includes voltage detection unit and drive control unit；
The input power via input filter module input respectively with the voltage detection unit, described open
Close the input connection of module；The output end of the voltage detection unit is connected with the control end of the drive control unit, institute
The input for stating drive control unit is connected with the output end of the switch module, the output end of the drive control unit and institute
The control end connection of switch module is stated, the output end of the switch module is connected with the load；
The voltage detection unit detects the ripple voltage in the input filter module, and the input power is provided
Input voltage is compared with the difference and default reference voltage of the ripple voltage, and protects letter according to comparative result output overcurrent
Number, control whether the drive control unit drives the switch module, to control whether output current exports.
Preferably, the PWM control modules also include feeder ear and sample resistance；One end of the sample resistance with it is described
Feeder ear is connected and is connected with the reference edge of the voltage detection unit, the other end ground connection of the sample resistance.
Preferably, the voltage detection unit includes constant-current source and first voltage comparator；The first voltage comparator
In-phase input end be connected via the constant-current source with the feeder ear and via the sample resistance be grounded, it is described first electricity
The inverting input of pressure comparator is connected with the input power and the input filter module respectively, and the first voltage compares
The output end of device is connected with the control end of the drive control unit.
Preferably, the drive control unit includes reference voltage source, operational amplifier, saw-toothed wave generator, the second electricity
Press comparator, triple gate, with phase device and phase inverter；
The in-phase input end of the operational amplifier is connected with the reference voltage source, the operational amplifier it is anti-phase defeated
Enter end to be connected with the output end of the switch module, the output end of the operational amplifier is same with the second voltage comparator
Phase input is connected；The inverting input of the second voltage comparator connects with the signal output part of the saw-toothed wave generator
Connect, the output end of the second voltage comparator is connected with the input of the triple gate；The control Enable Pin of the triple gate
It is connected with the output end of the first voltage comparator, the output end of triple gate input respectively with the same phase device,
The input connection of the phase inverter, the output end of the same phase device, the output end of the phase inverter with the switch module
Control end connection.
Preferably, the input filter module includes input filter capacitor；One end of the input filter capacitor with it is described
The positive pole connection of input power, and the input of inverting input respectively with first voltage comparator, the switch module connects
Connect, the other end ground connection of the input filter capacitor, the negative pole ground connection of the input power；
The switch module includes the first metal-oxide-semiconductor and the second metal-oxide-semiconductor；The grid of first metal-oxide-semiconductor and the same phase device
Output end connection, the drain electrode of first metal-oxide-semiconductor is connected with the common port of the input filter capacitor and the input power,
The source electrode of first metal-oxide-semiconductor is connected with the drain electrode of second metal-oxide-semiconductor and is connected with the load；Second metal-oxide-semiconductor
Grid is connected with the output end of the phase inverter, the source ground of second metal-oxide-semiconductor.
Preferably, the loaded work piece voltage of the DC-DC circuit output is Vout, the input electricity that the input power is provided
Press as Vin, the ripple voltage that the voltage detection unit is detected is Δ V, and the voltage detection unit is by detecting the line
Wave voltage, detects the average output current of the DC-DC circuit, and Io and Δ V relational expression are as follows：
Wherein, Cin is the capacitance of the input filter capacitor, and f is the switching frequency of the DC-DC circuit.
Preferably, the difference of the input voltage and the ripple voltage is Vm, and the reference voltage is Vp, the input
When the difference of voltage and the ripple voltage is equal to the reference voltage, the over-current protection point critical current of the DC-DC circuit
Equal to average output current：
Preferably, the DC-DC circuit also includes output filter module and output feedback module, the output filter module
It is connected between the output end of the switch module and the load, the output feedback module is connected to the output filtering mould
Between the input of the output end of block and the drive control unit；
The output filter module includes filter inductance and output filter capacitor；Opened with described one end of the filter inductance
Close module output end connection, the other end of the filter inductance be grounded via the output filter capacitor and with the load
Connection；
The output feedback module includes the first feedback resistance and the second feedback resistance；One end of first feedback resistance
It is connected with the common port of the filter inductance and the output filter capacitor, the other end of first feedback resistance drives with described
The input of dynamic control unit is connected and is grounded via second feedback resistance.
DC-DC circuit proposed by the present invention, voltage detection unit and drive control unit are internally integrated in PWM controller,
Ripple voltage in input filter module, the input voltage that input power is provided and ripple electricity are detected by voltage detection unit
The difference of pressure and default reference voltage compare, and according to comparative result output overcurrent protection signal, control drive control unit
Whether driving switch module, so as to control whether output current exports.Because ripple voltage is the exchange of electric current in switch module
Composition flows through input filter module and produced, therefore the output current of DC-DC circuit output is relevant with ripple voltage, so that
It can realize the detection to output current by detecting that ripple voltage just can detect output current, reach the purpose of overcurrent protection.
The present invention also proposes a kind of over-current protection method of DC-DC circuit, and the over-current protection method comprises the following steps：
Ripple voltage in voltage comparison unit detection input filter module；
Input voltage is compared and compared with the difference of the ripple voltage detected and default reference voltage
Relatively result；
The overcurrent protection signal generated by comparative result is sent to drive control unit, to control output current whether defeated
Go out.
Preferably, it is described to send the overcurrent protection signal generated by comparative result to drive control unit, it is defeated to control
Go out whether electric current exports specially：
When the difference of input voltage and ripple voltage is more than default reference voltage, low level overcurrent protection is generated
Signal is sent to drive control unit, to control output current normally to export；
When the difference of input voltage and ripple voltage is less than default reference voltage, the overcurrent protection of high level is generated
Signal is sent to drive control unit, to cut off the output of output current.
The over-current protection method of DC-DC circuit proposed by the present invention, detects the ripple voltage in DC-DC circuit first, its
It is secondary to be compared input voltage with default reference voltage with the difference of ripple voltage, then protected according to comparative result output overcurrent
Signal is protected, controls whether output current exports by the output overcurrent protection signal, reaches the purpose of overcurrent protection.
Brief description of the drawings
Fig. 1 is the electrical block diagram of the existing embodiment of DC-DC circuit one；
Fig. 2 is the electrical block diagram of another embodiment of existing DC-DC circuit；
Fig. 3 is the theory diagram of DC-DC circuit preferred embodiment of the present invention；
Fig. 4 is the electrical block diagram of DC-DC circuit preferred embodiment of the present invention；
Fig. 5 is the voltage waveform and the first metal-oxide-semiconductor, the second metal-oxide-semiconductor, the current wave of filter inductance branch road of A, PH point in Fig. 4
Shape；
Fig. 6 is the electrical block diagram of drive control unit in DC-DC circuit of the present invention；
Fig. 7 is the schematic flow sheet of the over-current protection method preferred embodiment of DC-DC circuit of the present invention.
The realization, functional characteristics and advantage of the object of the invention will be described further referring to the drawings in conjunction with the embodiments.
Embodiment
Technical scheme is further illustrated below in conjunction with Figure of description and specific embodiment.It should be appreciated that this
The specific embodiment of place description is not intended to limit the present invention only to explain the present invention.
The present invention proposes a kind of DC-DC circuit.
Reference picture 3, Fig. 3 is the theory diagram of DC-DC circuit preferred embodiment of the present invention.
In present pre-ferred embodiments, DC-DC circuit 10 is connected with load 20, including input power 11, input filter mould
Block 12, PWM control modules 13 and switch module 14, the PWM control modules 13 include PWM controller 131, the PWM controller 131
Including voltage detection unit 1311 and drive control unit 1312.
Input, switch module 14 of the input power 11 via input filter module 12 respectively with voltage detection unit 1311
Input connection；The output end of voltage detection unit 1311 is connected with the control end of drive control unit 1312, drive control
The input of unit 1312 is connected with the output end of switch module 14, output end and the switch module 14 of drive control unit 1312
Control end connection, the output end of switch module 14 is connected with loading 20；Voltage detection unit 1311 detects input filter module
Ripple voltage in 12, the difference and default reference of the input voltage that input power 11 is provided and the ripple voltage detected
Voltage ratio compared with, and according to comparative result output overcurrent protection signal, control drive control unit 1312 whether driving switch module
14, to control whether output current exports.
In the present embodiment, the alternating component of electric current flows through defeated in the offer of input power 11 input voltage, switch module 14
Ripple voltage is produced when entering filtration module 12, voltage detection unit 1311 and drive control list are internally integrated in PWM controller 131
Member 1312, the ripple voltage in input filter module 12 is detected by voltage detection unit 1311, by input voltage and ripple electricity
The difference of pressure is compared with reference voltage, when the difference of input voltage and ripple voltage is more than reference voltage, is exported low level
Overcurrent protection signal, control output current is normally exported；It is defeated when the difference of input voltage and ripple voltage is less than reference voltage
Go out the overcurrent protection signal of high level, cut off the output of output current.Because ripple voltage is the friendship of electric current in switch module 14
Stream composition flows through input filter module 12 and produced, therefore the output current that DC-DC circuit 10 is exported is relevant with ripple voltage
Connection, when overcurrent condition occurs in DC-DC circuit 10, the ripple voltage that voltage detection unit 1311 is detected exceedes predeterminated voltage
Value, so as to by detecting that ripple voltage just can detect output current, realize the detection to output current, reach overcurrent protection
Purpose.
In the present embodiment, DC-DC circuit 10 also includes output filter module 15 and output feedback module 16, output filtering mould
Block 15 is connected between the output end of switch module 14 and load 20, and output feedback module 16 is connected to output filter module 15
Between the input of output end and drive control unit 1312.Output filter module 15 is filtered defeated after processing to output current
Go out loaded work piece voltage to power to load 20, the loaded work piece voltage that 16 pairs of feedback module of output is exported is sampled and fed back
One feedback voltage to drive control unit 1312, drive control unit 1312 generates square-wave signal, then root according to the feedback voltage
The overcurrent protection signal exported according to voltage detection unit 1311, controls whether the square-wave signal is exported with driving switch module 14.
Fig. 4 is referred again to, Fig. 4 is the electrical block diagram of DC-DC circuit preferred embodiment of the present invention, the DC- shown in Fig. 4
DC circuits are to be directed to the improvement that existing DC-DC circuit is done in Fig. 2.
As shown in figure 4, PWM control modules 13 also include feeder ear VCC and sample resistance RS；Sample resistance RS one end with
Feeder ear VCC connections and it is connected with the reference edge of voltage detection unit 1311, sample resistance RS other end ground connection.This implementation
Example obtains reference voltage by sample resistance RS, and is input to the reference edge of voltage detection unit 1311, according to actual needs, really
The fixed sample resistance RS to be selected resistance, so that the reference edge of voltage detection unit 1311 receives a default reference electricity
Pressure.
Specifically, voltage detection unit 1311 includes constant-current source IR and first voltage comparator U1；First voltage comparator
U1 in-phase input end is connected with feeder ear VCC via constant-current source IR and is grounded via sample resistance RS, first voltage comparator
U1 inverting input is connected with input power 11 and input filter module 12 respectively, first voltage comparator U1 output end with
The control end connection of drive control unit 1312.
In voltage detection unit 1311, constant-current source IR obtains a constant current by the feeder ear VCC supply voltages inputted,
The constant current flows through sample resistance RS flow directions ground, and sampling voltage is produced on sample resistance RS, is exported due to constant-current source IR
It is constant current, therefore the sampling voltage is also constant, the sampling voltage is input to voltage detection unit as the reference voltage
1311 reference edge, so that reference voltage Vp=Iref × Rcs of first voltage comparator U1 in-phase input end is input to, its
Middle Iref is the constant current that constant-current source IR is exported, and Rcs is sample resistance RS resistance.
Fig. 6 is referred again to, Fig. 6 is the electrical block diagram of drive control unit in DC-DC circuit of the present invention.
As shown in fig. 6, drive control unit 1312 includes reference voltage source U3, operational amplifier U4, saw-toothed wave generator
U5, second voltage comparator U2, triple gate U6, with phase device U7 and phase inverter U8.
Operational amplifier U4 in-phase input end is connected with reference voltage source U3, operational amplifier U4 inverting input with
The output end connection of switch module 14, operational amplifier U4 output end connects with second voltage comparator U2 in-phase input end
Connect；Second voltage comparator U2 inverting input is connected with saw-toothed wave generator U5 signal output part, and second voltage compares
Device U2 output end is connected with triple gate U6 input；Triple gate U6 control Enable Pin is defeated with first voltage comparator U1's
Go out end connection, input, the phase inverter U8 input of triple gate U6 output end respectively with same phase device U7 are connected, with phase device U7
Control end with switch module 14 of output end, phase inverter U8 output end be connected.
In Fig. 4, input filter module 12 includes input filter capacitor C1；Input filter capacitor C1 one end and input power
11 positive pole connection, and inverting input, the input of switch module 14 respectively with first voltage comparator U1 be connected, input
Filter capacitor C1 other end ground connection, the negative pole ground connection of input power 11.
Switch module 14 includes the first metal-oxide-semiconductor M1 and the second metal-oxide-semiconductor M2, in the present embodiment, the first metal-oxide-semiconductor M1, second
Metal-oxide-semiconductor M2 is NMOS tube；First metal-oxide-semiconductor M1 grid is connected with same phase device U7 output end, the first metal-oxide-semiconductor M1 drain electrode with
The common port connection of input filter capacitor C1 and input power 11, the first metal-oxide-semiconductor M1 source electrode and the second metal-oxide-semiconductor M2 drain electrode connects
Connect and be connected with load 20；Second metal-oxide-semiconductor M2 grid is connected with phase inverter U8 output end, and the second metal-oxide-semiconductor M2 source electrode connects
Ground.
Specifically, output filter module 15 includes filter inductance L1 and output filter capacitor C2；Filter inductance L1 one end
It is connected with the output end of switch module 14, i.e., the source electrode with the first metal-oxide-semiconductor M1 is connected, and the filter inductance L1 other end is via output
Filter capacitor C2 is grounded and is connected with load 20.
Further, output feedback module 16 includes the first feedback resistance RF1 and the second feedback resistance RF2；First feedback
Resistance RF1 one end is connected with filter inductance L1 and output filter capacitor C2 common port, the first feedback resistance RF1 other end
It is connected with the input of drive control unit 1312, i.e., the inverting input with operational amplifier U4 is connected, and the first feedback electricity
The resistance RF1 other end is grounded via the second feedback resistance RF2.
Fig. 5 is referred again to, Fig. 5 is the voltage waveform and the first metal-oxide-semiconductor, the second metal-oxide-semiconductor, filter inductance branch of A, PH point in Fig. 4
The current waveform on road.
In Fig. 5, VAFor the voltage waveform of voltage input end A points in Fig. 4, VPHFor the voltage waveform of PH points in Fig. 4, IM1For
Electric current in electric current between one metal-oxide-semiconductor M1 drain electrode, source electrode, i.e. the first metal-oxide-semiconductor M1, IM2For the second metal-oxide-semiconductor M2 drain electrode, source
Electric current in electric current between pole, i.e. the second metal-oxide-semiconductor M2, ILFor the electric current in filter inductance L1, as DC-DC circuit 10 is defeated
Go out electric current, Io is average output current, andWherein I1 is minimum electricity when the first metal-oxide-semiconductor M1 is turned on
Stream, I2 is maximum current when the first metal-oxide-semiconductor M1 is turned on.The switching frequency of DC-DC circuit 10 shown in Fig. 4 is f, and the cycle is T,
Dutycycle is D, and the first metal-oxide-semiconductor M1 ON times are Ton, andWherein Vout
The loaded work piece voltage exported for DC-DC circuit 10, Vin is the input voltage that input power 11 is provided.
In Fig. 4, the electric current I in the first metal-oxide-semiconductor M1M1In alternating component electric current all will be flowed by input filter capacitor C1
Xiang Di.If input filter capacitor C1 selects ESR（Equivalent Series Resistance, equivalent series resistance）Very little
Ceramic condenser, then the electric current I in the first metal-oxide-semiconductor M1M1In alternating component electric current by input filter capacitor C1 when, it will
Ripple voltage is produced on input filter capacitor C1.When being turned on due to the first metal-oxide-semiconductor M1, the electric current I in the first metal-oxide-semiconductor M1M1Will
I2 is gradually increased to from I1, at this moment input filter capacitor C1 is that the voltage on electric discharge, input filter capacitor C1 progressively drops to
The lowest point, therefore the ripple voltage of the ripple voltage produced on input filter capacitor C1, i.e. voltage input end A points can be calculated（Electricity
The ripple voltage that pressure detection unit 1311 is detected）：
In above formula, Cin is input filter capacitor C1 capacitance, SHLKJFor the area of trapezoidal HLKJ in Fig. 5.
As can be seen here, the ripple voltage Δ V of average output current Io and voltage input end A points is relevant, voltage detecting list
Member 1311 detects the average output current of DC-DC circuit 10, Io and Δ V relational expression are as follows by detecting ripple voltage：
As long as therefore voltage detection unit 1311 detects the ripple voltage of voltage input end A points, just energy indirect detection is averaged
Output current, so as to when ripple voltage occurs abnormal, can detect that the output current excessively stream now exported, thus can realize
Stream protection.
When the voltage of input power 11 reaches minimum, the electricity of first voltage comparator U1 inverting input is input to
Pressure：
And due to the reference voltage of the in-phase input end that is input to first voltage comparator U1：
Vp=Iref×Rcs。
Therefore, when Vm is less than Vp, the overcurrent protection signal Voc of first voltage comparator U1 outputs is high level, works as Vm
During more than Vp, the overcurrent protection signal Voc of first voltage comparator U1 outputs is low level.
In Fig. 6, the feedback voltage V f that output feedback module 16 is exported is input to operational amplifier U4 inverting input, base
The reference voltage of reference voltage source U3 outputs is input to operational amplifier U4 in-phase input end, and operational amplifier U4 is by feedback voltage
After Vf amplifications, second voltage comparator U2 in-phase input end is input to, in addition, the sawtooth waveforms letter of saw-toothed wave generator U5 outputs
Number it is input to second voltage comparator U2 inverting input, second voltage comparator U2 is by the feedback voltage V f and saw after amplification
After tooth ripple signal is compared, the input of output square-wave signal to triple gate U6.
Because the first voltage comparator U1 overcurrent protection signal Voc exported are input to triple gate U6 control Enable Pin,
And triple gate U6 is that low level is effective, therefore, when the first voltage comparator U1 overcurrent protection signal Voc exported are low electricity
Usually, triple gate U6 is enabled, so that triple gate U6 output end also exports square-wave signal.When the square-wave signal is high level,
High level, driving the first metal-oxide-semiconductor M1 conductings, phase inverter U8 output low levels, the second metal-oxide-semiconductor M2 cut-offs are also exported with phase device U7；
When the square-wave signal is low level, low level, the first metal-oxide-semiconductor M1 cut-offs, the high electricity of phase inverter U8 outputs are also exported with phase device U7
It is flat, driving the second metal-oxide-semiconductor M2 conductings.It follows that when the first voltage comparator U1 overcurrent protection signal Voc exported are low electricity
Usually, the output of drive control unit 1312 square-wave signal, the first metal-oxide-semiconductor of driven M1, the second metal-oxide-semiconductor M2 conducting so that defeated
Go out electric current normally to export.
When the overcurrent protection signal Voc that first voltage comparator U1 is exported is high level, triple gate U6 is in high-impedance state,
PWM controls are stopped, and cut off the output of square-wave signal, it is impossible to drive the first metal-oxide-semiconductor M1 or the second metal-oxide-semiconductor M2 to turn on, from
Without output current output, i.e., when overcurrent condition occurs in DC-DC circuit 10, cut off the output of output current, namely cut-out
The output of loaded work piece voltage, reaches the purpose of overcurrent protection.
In summary, the over-current protection point critical current of DC-DC circuit 10 of the present invention is met：
Therefore, when the difference of input voltage and ripple voltage is equal to the reference voltage, the overcurrent protection of DC-DC circuit 10
Point electric current is equal to average output current：
I.e. the over-current protection point critical current of DC-DC circuit 10 is met：
When the difference of input voltage and ripple voltage is equal to the reference voltage, the over-current protection point electricity of DC-DC circuit 10
Flow and be：
From above formula, the Rcs and Cin different by setting can set different over-current protection point electric currents, so that real
Specific requirement in the application of border according to DC-DC circuit 10 to overcurrent protection, the sample resistance RS and input appropriate by choosing is filtered
Ripple electric capacity C1 value, to meet specific requirement of the DC-DC circuit 10 to overcurrent protection.
Relative to prior art, DC-DC circuit 10 of the invention is internally integrated voltage detection unit in PWM controller 131
1311 and drive control unit 1312, ripple voltage is detected by the first voltage comparator U1 in voltage detection unit 1311,
To realize the detection to average output current, so as to by detecting the ripple voltage in DC-DC circuit 10, to judge DC-DC
The output current that circuit 10 is exported whether excessively stream, with output current excessively stream, control drive control unit 1312 is stopped,
The output of output current is cut off, overcurrent protection is realized.
The present invention also proposes a kind of over-current protection method of DC-DC circuit.
Reference picture 7, Fig. 7 is the schematic flow sheet of the over-current protection method preferred embodiment of DC-DC circuit of the present invention.
In present pre-ferred embodiments, the over-current protection method of DC-DC circuit comprises the following steps：
Step S10：Ripple voltage in voltage comparison unit detection input filter module.
Step S20：Input voltage is compared with the difference of the ripple voltage detected and default reference voltage
Relatively obtain comparative result.
Step S30：The overcurrent protection signal generated by comparative result is sent to drive control unit, to control output electricity
Whether stream exports.
The over-current protection method of the present embodiment is over-current protection method corresponding with the DC-DC circuit of the invention described above,
In the present embodiment, input voltage is provided by the input power in DC-DC circuit, and ripple voltage is by the switching molding in DC-DC circuit
Produced when the alternating component of electric current flows through input filter module in block, DC-DC circuit is internally integrated voltage detecting in PWM controller
Unit and drive control unit, by voltage detection unit detect input filter module in ripple voltage, by input voltage with
The difference of ripple voltage is compared with default reference voltage, and according to comparative result output overcurrent protection signal, it is defeated by this
Go out whether overcurrent protection signal control output current exports, when overcurrent condition occurs in DC-DC circuit, to cut off output current
Output, reaches the purpose of overcurrent protection.
Specifically, step S30 is specially：
When the difference of input voltage and ripple voltage is more than default reference voltage, low level overcurrent protection is generated
Signal is sent to drive control unit, to control output current normally to export；When the difference of input voltage and ripple voltage is less than
During default reference voltage, the overcurrent protection signal of generation high level is sent to drive control unit, to cut off output current
Output.
Therefore, when the ripple voltage detected becomes big, the difference of input voltage and ripple voltage diminishes, in output current
During excessively stream, the difference of input voltage and ripple voltage is less than reference voltage, and the overcurrent protection signal generated is high level, cut-out
The output of output current, so as to by detecting the ripple voltage in DC-DC circuit, to judge the output of DC-DC circuit output
Electric current whether excessively stream, with output current excessively stream, cut off the output of output current, realize overcurrent protection.
The preferred embodiments of the present invention are the foregoing is only, are not intended to limit the scope of the invention, it is every to utilize
Equivalent structure or equivalent flow conversion that description of the invention and accompanying drawing content are made, or directly or indirectly it is used in other correlations
Technical field, be included within the scope of the present invention.
Claims (10)
1. a kind of DC-DC circuit, is connected with load, including input power, input filter module, PWM control modules and switching molding
Block, it is characterised in that the PWM control modules include PWM controller, the PWM controller includes voltage detection unit and drive
Dynamic control unit；
Input, the switching molding of the input power via the input filter module respectively with the voltage detection unit
The input connection of block；The output end of the voltage detection unit is connected with the control end of the drive control unit, described to drive
The input of dynamic control unit is connected with the output end of the switch module, and the output end of the drive control unit is opened with described
The control end connection of module is closed, the output end of the switch module is connected with the load；
The voltage detection unit detects the ripple voltage in the input filter module, the input that the input power is provided
Voltage is compared with the difference and default reference voltage of the ripple voltage, and according to comparative result output overcurrent protection signal,
Control whether the drive control unit drives the switch module, to control whether output current exports.
2. DC-DC circuit as claimed in claim 1, it is characterised in that the PWM control modules also include feeder ear and sampling
Resistance；The voltage detection unit includes constant-current source；One end of the sample resistance connects through the constant-current source and the feeder ear
Connect, the reference edge of one end of the sample resistance also with the voltage detection unit is connected, another termination of the sample resistance
Ground.
3. DC-DC circuit as claimed in claim 2, it is characterised in that the voltage detection unit include the constant-current source and
First voltage comparator；The in-phase input end of the first voltage comparator is connected via the constant-current source with the feeder ear,
And be grounded via the sample resistance, the inverting input of the first voltage comparator respectively with the input power and described
Input filter module is connected, and the output end of the first voltage comparator is connected with the control end of the drive control unit.
4. DC-DC circuit as claimed in claim 3, it is characterised in that the drive control unit includes reference voltage source, fortune
Calculate amplifier, saw-toothed wave generator, second voltage comparator, triple gate, with phase device and phase inverter；
The in-phase input end of the operational amplifier is connected with the reference voltage source, the inverting input of the operational amplifier
It is connected with the output end of the switch module, the output end of the operational amplifier is same mutually defeated with the second voltage comparator
Enter end connection；The inverting input of the second voltage comparator is connected with the signal output part of the saw-toothed wave generator, institute
The output end for stating second voltage comparator is connected with the input of the triple gate；The control Enable Pin of the triple gate with it is described
The output end connection of first voltage comparator, it is the output end of triple gate input respectively with the same phase device, described anti-
The input connection of phase device, the control of the output end, the output end of the phase inverter of the same phase device with the switch module
End connection.
5. DC-DC circuit as claimed in claim 4, it is characterised in that the input filter module includes input filter capacitor；
One end of the input filter capacitor is connected with the positive pole of the input power, and anti-phase defeated with first voltage comparator respectively
Enter end, the input connection of the switch module, the other end ground connection of the input filter capacitor, the negative pole of the input power
Ground connection；
The switch module includes the first metal-oxide-semiconductor and the second metal-oxide-semiconductor；The grid of first metal-oxide-semiconductor is defeated with the same phase device
Go out end connection, the drain electrode of first metal-oxide-semiconductor is connected with the positive pole and the input filter capacitor of the input power, described the
The source electrode of one metal-oxide-semiconductor is connected with the drain electrode of second metal-oxide-semiconductor and is connected with the load；The grid of second metal-oxide-semiconductor with
The output end connection of the phase inverter, the source ground of second metal-oxide-semiconductor.
6. DC-DC circuit as claimed in claim 5, it is characterised in that the loaded work piece voltage of the DC-DC circuit output is
Vout, the input voltage that the input power is provided is Vin, and the ripple voltage that the voltage detection unit is detected is Δ V, institute
Voltage detection unit is stated by detecting the ripple voltage, the average output current Io, Io and Δ of the DC-DC circuit is detected
V relational expression is as follows：
Wherein, Cin is the capacitance of the input filter capacitor, and f is the switching frequency of the DC-DC circuit.
7. DC-DC circuit as claimed in claim 6, it is characterised in that the difference of the input voltage and the ripple voltage
For Vm, the reference voltage is Vp, described when the difference of the input voltage and the ripple voltage is equal to the reference voltage
The over-current protection point critical current of DC-DC circuit is equal to average output current：
8. DC-DC circuit as claimed in any of claims 1 to 7 in one of claims, it is characterised in that the DC-DC circuit also includes
Output filter module and output feedback module, the output filter module are connected to the output end of the switch module and described negative
Between load, the output feedback module is connected to the input of the output end and the drive control unit of the output filter module
Between end；
The output filter module includes filter inductance and output filter capacitor；One end of the filter inductance and the switching molding
The output end connection of block, the other end of the filter inductance is grounded via the output filter capacitor and is connected with the load；
The output feedback module includes the first feedback resistance and the second feedback resistance；One end of first feedback resistance and institute
The common port connection of filter inductance and the output filter capacitor is stated, the other end of first feedback resistance is controlled with the driving
The input of unit processed is connected and is grounded via second feedback resistance.
9. a kind of over-current protection method of DC-DC circuit, it is characterised in that comprise the following steps：
Ripple voltage in voltage detection unit detection input filter module；
Input voltage is compared with the difference of the ripple voltage detected and default reference voltage and obtains being compared knot
Really；
The overcurrent protection signal generated by comparative result is sent to drive control unit, passes through triple gate in drive control unit
Whether level state control output current exports.
10. over-current protection method as claimed in claim 9, it is characterised in that described to protect the excessively stream generated by comparative result
Shield signal is sent to drive control unit, controls whether output current exports by triple gate level state in drive control unit
Specially：
When the difference of input voltage and ripple voltage is more than default reference voltage, low level overcurrent protection signal is generated
Send to drive control unit, to control output current normally to export；
When the difference of input voltage and ripple voltage is less than default reference voltage, the overcurrent protection signal of high level is generated
Send to drive control unit, to cut off the output of output current.
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| CN103944386B (en) * | 2014-04-30 | 2016-01-13 | 常州信息职业技术学院 | DC-DC boost converting device and boost conversion method of work thereof |
| US9948401B1 (en) * | 2016-10-04 | 2018-04-17 | Finisar Corporation | Individual DC and AC current shunting in optical receivers |
| CN106300235B (en) * | 2016-10-09 | 2018-09-28 | 中国电子科技集团公司第三十六研究所 | A kind of power-supply system |
| CN108696972B (en) * | 2017-04-10 | 2019-12-03 | 赤多尼科两合股份有限公司 | A kind of dimming device and system |
| CN107918429B (en) * | 2017-11-29 | 2019-10-29 | 郑州云海信息技术有限公司 | A kind of checking of great current feedback control circuit and control method |
| CN109327141A (en) * | 2018-11-20 | 2019-02-12 | 武汉精鸿电子技术有限公司 | A kind of wide-range voltage and High-current output method and power-supply system |
| CN109861511A (en) * | 2018-12-30 | 2019-06-07 | 惠州华科电器有限公司 | Current foldback circuit and Over Current Protection System |
| CN110299831A (en) * | 2019-07-08 | 2019-10-01 | 珠海格力电器股份有限公司 | PWM wave adaptive generation circuit and inverter circuit and air conditioner |
| CN111999545B (en) * | 2020-08-14 | 2023-03-21 | Oppo广东移动通信有限公司 | Current measurement method, power supply device and power supply chip |
| CN112730959B (en) * | 2020-12-25 | 2024-04-02 | 意美旭智芯能源科技有限公司 | Overcurrent detection circuit of buck conversion circuit controller |
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| CN1691454A (en) * | 2004-04-23 | 2005-11-02 | 汤姆森特许公司 | Protection circuit for a switched mode power supply |
| CN101931334A (en) * | 2009-06-18 | 2010-12-29 | 快捷韩国半导体有限公司 | Frequency modulation controller, switch mode power supply, and switching operation frequency modulation method |
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| JP2002252986A (en) * | 2001-02-26 | 2002-09-06 | Canon Inc | Inverter, power supply system and method for reducing leakage current in power supply system |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1691454A (en) * | 2004-04-23 | 2005-11-02 | 汤姆森特许公司 | Protection circuit for a switched mode power supply |
| CN101931334A (en) * | 2009-06-18 | 2010-12-29 | 快捷韩国半导体有限公司 | Frequency modulation controller, switch mode power supply, and switching operation frequency modulation method |
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