CN103683204A - Switching power supply over-current protection circuit - Google Patents
Switching power supply over-current protection circuit Download PDFInfo
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- CN103683204A CN103683204A CN201210364908.1A CN201210364908A CN103683204A CN 103683204 A CN103683204 A CN 103683204A CN 201210364908 A CN201210364908 A CN 201210364908A CN 103683204 A CN103683204 A CN 103683204A
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Abstract
A switching power supply over-current protection circuit includes an alternating-current rectification and filtering circuit, a transformer, a direct-current rectification and filtering circuit, a switching circuit, a control circuit and a feedback circuit; the control circuit comprises a pulse width modulation chip and a sampling resistor. When voltage outputted by the direct-current rectification and filtering circuit is higher a voltage threshold value, the feedback circuit sends a feedback signal to a frequency compensation end of the pulse width modulation chip, such that the potential of the frequency compensation end is pulled low; the pulse width modulation chip compares a current signal collected by the sampling resistor with the voltage of the frequency compensation end; and the output end of the pulse width modulation chip outputs a PWM signal to control the switching on and switching off of the switching circuit, such that the switched-on and switched-off states of the transformer can be controlled, and therefore, stabilized voltage output can be realized. Since the feedback signal is sent directly to the frequency compensation end of the pulse width modulation chip, the feedback signal does not need to pass through a high-gain error amplifier inside the pulse width modulation chip, and therefore, the transmission time of the feedback signal is shortened. The switching power supply over-current protection circuit is advantageous in sensitive response over-current protection and short response time.
Description
Technical field
The present invention relates to switching power circuit field, particularly relate to a kind of Switching Power Supply current foldback circuit.
Background technology
The application of Switching Power Supply is more and more extensive, in order to improve the reliability of Switching Power Supply, and must protective circuit reasonable in design.Overcurrent protection is one of protective circuit, for the protection to power supply and device for power switching when output overloading or the short circuit.Switching Power Supply overcurrent protection has pulse-width modulation and two kinds of modes of frequency modulation(FM) conventionally, and pulse-width modulation (PWM) mode is that pulse frequency is constant, by changing pulse duration, controls output voltage, is the most frequently used Switching Power Supply modulation system.
Fig. 2 is the inside theory diagram of a kind of pulse width modulating chip UC3842.Please refer to Fig. 2; the Switching Power Supply that adopts pulse width modulation mode to carry out power supply overcurrent protection; the pwm signal that its pulse width modulating chip produces is exported through output (pin 6); drive external switching power tube work; the signal that power tube work produces is converted to the current sample end (pin 3) that low-voltage dc signal feeds back to pulse width modulating chip, the normal work of maintenance system through sample circuit.After the normal work of system, the low-voltage dc signal of sample circuit feedback is delivered to the error amplifier 210 of pulse width modulating chip inside through the pressure feedback port (pin 2) of pulse width modulating chip, compare with inner reference voltage, the error signal producing is delivered to the pulse-width modulation circuit of pulse width modulating chip inside, complete the modulation of pulse duration, thereby reach the object of regulated output voltage.If output voltage is because the reasons such as power supply overload or output short-circuit uprise, the voltage of sample circuit feedback also uprises, and pulse-width modulation circuit can make to export the narrowed width of pulse, the ON time of switching power tube shortens, output voltage step-down, thus make output voltage stabilization, and vice versa.In addition, between pin 3 and ground, be connected to sampling resistor, when its voltage is during higher than 1V, will make comparator 220 upsets of pulse width modulating chip inside, by 230 zero setting of PWM latch, make pulse-width modulation circuit in closed condition, thereby realize the overcurrent protection of circuit.
Traditional Switching Power Supply current foldback circuit; it is the pressure feedback port receiving feedback signals by pulse width modulating chip; therefore after feedback signal need to compare by the high-gain error amplifier of pulse width modulating chip inside; output comparative voltage is also adjusted the pwm signal of pulse width modulating chip; and amplifier not output set up with input simultaneously, to feed back signal to response time of output pwm signal longer from getting can to cause pulse width modulating chip.And the sampling resistor conventionally adopting is all metal film or oxide-film resistance, this resistance is thoughts, when electric current flows through sampling resistor, and certain perceptual voltage of can inducting.The impedance meeting that this inductive component presents when high frequency is very large, so it will consume very large power.Increase along with frequency, due to pulse width modulating chip, from getting, to feed back signal to the required response time of output pwm signal longer, the electric current that flows through sampling resistor did not likely also discharge before arriving next cycle of oscillation, the electric current that sampling resistor bears is by increasing, the misoperation of pulse width modulating chip will be caused like this, even aircraft bombing can be caused.
Summary of the invention
Based on this, be necessary to provide a kind of pulse width modulating chip from getting the shorter Switching Power Supply current foldback circuit of response time that feeds back signal to output pwm signal.
A Switching Power Supply current foldback circuit, comprising: AC rectification filter circuit, for by AC rectification filtering and from the output output rectification filter voltage of described AC rectification filter circuit, transformer, comprises primary coil, secondary coil and self-feed line circle, and described primary coil is connected with the output of described AC rectification filter circuit, and described transformer is for carrying out step-down to described rectifying and wave-filtering voltage, direct-current rectification filter circuit, is connected with described secondary coil, for the rectifying and wave-filtering voltage to after step-down, carries out rectifying and wave-filtering and exports VD from the output of described direct-current rectification filter circuit, switching circuit, the input of described switching circuit is connected with described primary coil, output head grounding, described switching circuit is for carrying out switch control to described rectifying and wave-filtering voltage, control circuit, described control circuit comprises pulse width modulating chip, sampling resistor, timing resistor, timing capacitor, the first resistance, the second resistance and the 3rd resistance, described the first resistance and the second resistance are connected in series, the frequency compensation end of described pulse width modulating chip is connected with the common port of the second resistance with described the first resistance by described the 3rd resistance, the other end of described the first resistance is connected with the pressure feedback port of described pulse width modulating chip, the other end ground connection of described the second resistance, the reference voltage terminal of described pulse width modulating chip is connected with the common port of the second resistance with described the first resistance, described timing resistor and timing capacitor are connected in series, the timing end of described pulse width modulating chip is connected with the common port of described timing resistor and timing capacitor, the other end of described timing resistor is connected with the reference voltage terminal of described pulse width modulating chip, the other end ground connection of described timing capacitor, the earth terminal ground connection of described pulse width modulating chip, one end of described sampling resistor connects the current sample end of described pulse width modulating chip and the output of described switching circuit, other end ground connection, the output of described pulse width modulating chip is connected with the control end of described switching circuit, the power end of described pulse width modulating chip is connected with the output of described AC rectification filter circuit by the first divider resistance, described self-feed line circle is connected with the power end of described pulse width modulating chip, for operating voltage being provided to described pulse width modulating chip, feedback circuit, is connected with the output of described direct-current rectification filter circuit, and for gathering described VD, described feedback circuit sends feedback signal in described VD during higher than voltage threshold, and the current potential of described frequency compensation end is dragged down, the described feedback signal that the signal that described pulse width modulating chip obtains according to described current sample end sampling and described feedback circuit send is controlled the turn-on and turn-off of described switching circuit by the output output pulse width modulation signal of pulse width modulating chip.
In an embodiment, described transformer also comprises the first rectifier diode and the first filter capacitor therein, and the Same Name of Ends of described primary coil is connected with the output of described AC rectification filter circuit, and different name end is connected with the input of described switching circuit; The Same Name of Ends ground connection of described secondary coil, different name end is connected with described direct-current rectification filter circuit; The Same Name of Ends of described self-feed line circle is connected with the positive pole of described the first rectifier diode, different name end ground connection; The negative pole of described the first rectifier diode is connected with the common port of described the first divider resistance with the power end of described pulse width modulating chip; Described first filter capacitor one end is connected with the negative pole of described the first rectifier diode, and the other end is connected with the different name end of described self-feed line circle.
Therein in an embodiment, described transformer comprises for absorbing the absorption circuit of peak voltage, described absorption circuit comprises absorption resistance, Absorption Capacitance and diode, described absorption resistance is connected in parallel with Absorption Capacitance and one end is connected with the Same Name of Ends of described primary coil, the other end is connected with the negative pole of described diode, and the positive pole of described diode is connected with the different name end of described primary coil.
Therein in an embodiment, described direct-current rectification filter circuit comprises the second rectifier diode and the second filter capacitor, the positive pole of described the second rectifier diode is connected with the different name end of described secondary coil, the negative pole of described the second rectifier diode is the output of described direct-current rectification filter circuit, described second filter capacitor one end is connected with the negative pole of described the second rectifier diode, other end ground connection.
Therein in an embodiment, described switching circuit comprises N-channel MOS FET, biasing resistor and the first current-limiting resistance, the drain electrode of described N-channel MOS FET is the input of described switching circuit, the source electrode of described N-channel MOS FET is the output of described switching circuit, the grid of described N-channel MOS FET is the control end of described switching circuit and is connected with the output of described pulse width modulating chip by described the first current-limiting resistance, and described biasing resistor is connected between the grid and source electrode of described N-channel MOS FET.
Therein in an embodiment, described control circuit comprises filter network, described filter network comprises filter resistance and the 3rd filter capacitor, the current sample end of described pulse width modulating chip connects by filter resistance one end that described sampling resistor is connected with the output of described switching circuit, described the 3rd filter capacitor one end connects one end that described filter resistance is connected with the current sample end of described pulse width modulating chip, other end ground connection.
Therein in an embodiment, described feedback circuit comprises optocoupler, control switch, the second current-limiting resistance, the second divider resistance and the 3rd divider resistance, described optocoupler comprises reflector and receiver, the input of described reflector is connected with the output of described direct-current rectification filter circuit by described the second current-limiting resistance, the output of described reflector is connected with the input of described control switch, the input of described receiver is connected with the frequency compensation end of described pulse width modulating chip, output head grounding; Described the second divider resistance and the 3rd divider resistance are connected in series, the control end of described control switch is connected with the common port of the 3rd divider resistance with described the second divider resistance, the other end of described the second divider resistance is connected with the output of described direct-current rectification filter circuit, the other end ground connection of described the 3rd divider resistance; The output head grounding of described control switch; Described control switch is in the conducting during higher than described voltage threshold of described VD.
In an embodiment, the frequency compensation end of described pulse width modulating chip is directly by described receiver ground connection therein.
Therein in an embodiment, described feedback circuit comprises compensating network, described compensating network comprises building-out capacitor, the first compensating resistance and the second compensating resistance, described building-out capacitor one end is connected with the input of described control switch, the other end is connected with one end of described the first compensating resistance, the other end of described the first compensating resistance is connected with the control end of described control switch, described second compensating resistance one end connects the control end of described control switch, and the other end connects the common port of described the second divider resistance and the 3rd divider resistance.
Therein in an embodiment, described feedback circuit comprises and is arranged on the input of described receiver and the 4th filter capacitor between output.
Above-mentioned Switching Power Supply current foldback circuit, VD by feedback circuit collection from the output output of direct-current rectification filter circuit, when VD during higher than voltage threshold feedback circuit send the frequency compensation end that feeds back signal to pulse width modulating chip, the current potential of described frequency compensation end is dragged down, pulse width modulating chip is inputted respectively inner comparator by the voltage of the current signal of sampling resistor collection and frequency compensation end and is compared, and comparative result is inputted to inner PWM latch, output pwm signal is also exported by the output of pulse width modulating chip, the turn-on and turn-off of control switch circuit, thereby the on off operating mode of control transformer, reach the object of output voltage stabilizing.When passing through the Current rise of transformer; the pressure drop at sampling resistor two ends also can be along with rising, and when pressure drop is more than or equal to 1V, the driving meeting of pulse width modulating chip inside immediately reset enable switch circuit is turn-offed; stop electric current further to rise, thereby realized the overcurrent protection of circuit.Owing to feedback signal directly being sent to the frequency compensation end of pulse width modulating chip; feedback signal does not need the high-gain error amplifier through pulse width modulating chip inside; shortened the transmission time of feedback signal, had the advantages that overcurrent protection is quick on the draw, the response time is short.
Accompanying drawing explanation
Fig. 1 is the circuit theory diagrams of Switching Power Supply current foldback circuit in an embodiment;
Fig. 2 is the inside theory diagram of pulse width modulating chip UC3842.
Embodiment
A Switching Power Supply current foldback circuit, as shown in Figure 1, comprises AC rectification filter circuit 110, transformer 120, direct-current rectification filter circuit 130, switching circuit 140, control circuit 150 and feedback circuit 160.
AC rectification filter circuit 110 is for also passing through the output output rectification filter voltage of AC rectification filter circuit 110 by the AC rectification filtering of input.In the present embodiment, AC rectification filter circuit 110 comprises rectifier bridge BR1 and filter capacitor C1, the output port 1 of rectifier bridge BR1 is as the output of AC rectification filter circuit 110, output port 3 ground connection, filter capacitor C1 is arranged between output port 1 and output port 3.
Direct-current rectification filter circuit 130 is connected with secondary coil T1b, for the rectifying and wave-filtering voltage to after step-down, carries out rectifying and wave-filtering and exports VD from the output end vo of direct-current rectification filter circuit 130.
The input of switching circuit 140 is connected with primary coil T1a, and output head grounding for rectifying and wave-filtering voltage is carried out to switch control, thereby obtains stable magnitude of voltage.
The feedback signal that the pulse width modulating chip U1 signal that sampling obtains according to current sample end Ics and feedback circuit 160 send is by the turn-on and turn-off of the output GD output pulse width modulation signal control switch circuit 140 of pulse width modulating chip U1.
Above-mentioned Switching Power Supply current foldback circuit, by feedback circuit 160, gather from the VD of the output end vo output of direct-current rectification filter circuit 130, when VD during higher than voltage threshold feedback circuit 160 send feedback signals, the current potential of frequency compensation end COMP is dragged down, the signal that pulse width modulating chip U1 obtains current sample end Ics sampling and the voltage of frequency compensation end COMP are inputted respectively inner comparator and are compared, and comparative result is inputted to inner PWM latch, output pwm signal is also exported by the output GD of pulse width modulating chip U1, the turn-on and turn-off of control switch circuit 160, thereby the on off operating mode of control transformer 120, reach the object of output voltage stabilizing.When the Current rise of the primary coil T1a by transformer 120; the pressure drop at sampling resistor R8 two ends also can be along with rising; when pressure drop is more than or equal to 1V; the driving meeting of pulse width modulating chip U1 inside immediately reset enable switch circuit 140 is turn-offed; stop electric current further to rise, thereby realized the overcurrent protection of circuit.Owing to feedback signal directly being sent to the frequency compensation end COMP of pulse width modulating chip U1; feedback signal does not need the high-gain error amplifier through pulse width modulating chip U1 inside; shortened the transmission time of feedback signal, had the advantages that overcurrent protection is quick on the draw, the response time is short.This circuit is because directly the reference voltage terminal Vref of pulse width modulating chip U1 is received to pressure feedback port FB has saved compensating network; if the resistance of sampling resistor R8 is Ra; make the current maxima that flows through sampling resistor R8 be limited in 1/Ra; do not need constantly by feedback ratio, to obtain maximum current signal; shorten the reaction time of protective circuit, also reduced the power bracket of circuit simultaneously.
In an embodiment, transformer 120 also comprises the first rectifier diode D2 and the first filter capacitor C3 therein, and the Same Name of Ends of primary coil T1a is connected with the output of AC rectification filter circuit 110, and different name end is connected with the input of switching circuit 140; The Same Name of Ends ground connection of secondary coil T1b, different name end is connected with direct-current rectification filter circuit 130; The Same Name of Ends of self-feed line circle T1c is connected with the positive pole of the first rectifier diode D2, different name end ground connection; The negative pole of the first rectifier diode D2 is connected with the common port of the first divider resistance R1 with the power end Vcc of pulse width modulating chip U1; First filter capacitor C3 one end is connected with the negative pole of the first rectifier diode D2, and the other end is connected with the different name end of self-feed line circle T1c.The power end Vcc that the voltage of responding in self-feed line circle T1c is received pulse width modulating chip U1 after the rectifying and wave-filtering of the first rectifier diode D2 and the first filter capacitor C3 provides operating voltage for pulse width modulating chip U1.
Wherein, transformer 120 also comprises absorption circuit 122, for absorbing the peak voltage producing because of reasons such as transformer leakage inductances, absorption circuit 122 comprises absorption resistance R2, Absorption Capacitance C2 and diode D1, absorption resistance R2 is connected in parallel with Absorption Capacitance C2 and one end is connected with the Same Name of Ends of primary coil T1a, the other end is connected with the negative pole of diode D1, and the positive pole of diode D1 is connected with the different name end of primary coil T1a.
Therein in an embodiment, direct-current rectification filter circuit 130 comprises the second rectifier diode D3 and the second filter capacitor C8, the positive pole of the second rectifier diode D3 is connected with the different name end of secondary coil T1b, the negative pole of the second rectifier diode D3 is the output end vo of direct-current rectification filter circuit 130, second filter capacitor C8 one end is connected with the negative pole of the second rectifier diode D3, other end ground connection.
Therein in an embodiment, switching circuit 140 comprises N-channel MOS FET Q1, biasing resistor R7 and the first current-limiting resistance R10, the drain electrode of N-channel MOS FET Q1 is the input of switching circuit 140, source electrode is the output of switching circuit 140, the grid of N-channel MOS FET Q1 is the control end of switching circuit 140 and is connected with the output GD of pulse width modulating chip U1 by the first current-limiting resistance R10, and biasing resistor R7 is connected between the grid and source electrode of N-channel MOS FET Q1.The output GD output pwm signal of pulse width modulating chip U1 is controlled the turn-on and turn-off of N-channel MOS FET Q1, thus the on off operating mode of control transformer 120.
Therein in an embodiment, control circuit 150 also comprises filter network 152, filter network 152 comprises filter resistance R9 and the 3rd filter capacitor C6, the current sample end Ics of pulse width modulating chip U1 connects by filter resistance R9 one end that sampling resistor R8 is connected with the source electrode of N-channel MOS FET Q1, the 3rd filter capacitor C6 one end connects one end that filter resistance R9 is connected with current sample end Ics, other end ground connection.
Therein in an embodiment, feedback circuit 160 comprises optocoupler OC1, control switch, the second current-limiting resistance R11, the second divider resistance R14 and the 3rd divider resistance R15, in the present embodiment, control switch adopts TL431 chip U2, the reference edge of chip U2 is the control end of control switch, the negative electrode of chip U2 is the input of control switch, the output that the anode of chip U2 is control switch.Optocoupler OC1 comprises reflector and receiver, the input of reflector is connected with the output end vo of direct-current rectification filter circuit 130 by the second current-limiting resistance R11, output is connected with the negative electrode of chip U2, the input of receiver is connected with the frequency compensation end COMP of pulse width modulating chip U1, the output head grounding of receiver, in the present embodiment, the 4th filter capacitor C4 is set between receiver input and output.The second divider resistance R14 and the 3rd divider resistance R15 are connected in series, the reference edge of chip U2 is connected with the common port of the 3rd divider resistance R15 with the second divider resistance R14, the other end of the second divider resistance R14 is connected with the output end vo of direct-current rectification filter circuit 130, the other end ground connection of the 3rd divider resistance R15.The plus earth of chip U2.
The resistance of supposing the second divider resistance R14 is Rb, the resistance of the 3rd divider resistance R15 is Rc, when the VD of the output end vo output of direct-current rectification filter circuit 130 is greater than 2.5(Rb+Rc) during/Rc, chip U2 conducting, the reflector of optocoupler OC1 is luminous makes receiver conducting, the frequency compensation end COMP current potential of pulse width modulating chip U1 is dragged down, the pwm signal pulsewidth of pulse width modulating chip U1 output is narrowed down, the ON time of switching circuit 140 shortens, VD is with the work step-down of load, until VD is 2.5(Rb+Rc lower than the voltage threshold of setting)/Rc.
In the present embodiment, the frequency compensation end COMP of pulse width modulating chip U1 is directly by receiver ground connection; be between receiver and compensation end COMP, other components and parts such as contact resistance not between receiver and ground wire; after receiver conducting, make frequency compensation end COMP current potential to drag down fast, make overcurrent protection reaction sensitiveer.
Therein in an embodiment, feedback circuit 160 also comprises the compensating network 162 of chip U2, compensating network 162 comprises building-out capacitor C7, the first compensating resistance R12 and the second compensating resistance R13, building-out capacitor C7 one end is connected with the negative electrode of chip U2, the other end is connected with one end of the first compensating resistance R12, the other end of the first compensating resistance R12 is connected with the reference edge of chip U2, second compensating resistance R13 one end connects the reference edge of chip U2, and the other end connects the common port of the second divider resistance R14 and the 3rd divider resistance R15.
The above embodiment has only expressed several execution mode of the present invention, and it describes comparatively concrete and detailed, but can not therefore be interpreted as the restriction to the scope of the claims of the present invention.It should be pointed out that for the person of ordinary skill of the art, without departing from the inventive concept of the premise, can also make some distortion and improvement, these all belong to protection scope of the present invention.Therefore, the protection range of patent of the present invention should be as the criterion with claims.
Claims (10)
1. a Switching Power Supply current foldback circuit, comprising:
AC rectification filter circuit, for by the AC rectification filtering of input and from the output output rectification filter voltage of described AC rectification filter circuit;
Transformer, comprises primary coil, secondary coil and self-feed line circle, and described primary coil is connected with the output of described AC rectification filter circuit, and described transformer is for carrying out step-down to described rectifying and wave-filtering voltage;
Direct-current rectification filter circuit, is connected with described secondary coil, for the rectifying and wave-filtering voltage to after step-down, carries out rectifying and wave-filtering and exports VD from the output of described direct-current rectification filter circuit;
It is characterized in that, also comprise:
Switching circuit, the input of described switching circuit is connected with described primary coil, output head grounding, described switching circuit is for carrying out switch control to described rectifying and wave-filtering voltage;
Control circuit, described control circuit comprises pulse width modulating chip, sampling resistor, timing resistor, timing capacitor, the first resistance, the second resistance and the 3rd resistance, described the first resistance and the second resistance are connected in series, the frequency compensation end of described pulse width modulating chip is connected with the common port of the second resistance with described the first resistance by described the 3rd resistance, the other end of described the first resistance is connected with the pressure feedback port of described pulse width modulating chip, the other end ground connection of described the second resistance, the reference voltage terminal of described pulse width modulating chip is connected with the common port of the second resistance with described the first resistance, described timing resistor and timing capacitor are connected in series, the timing end of described pulse width modulating chip is connected with the common port of described timing resistor and timing capacitor, the other end of described timing resistor is connected with the reference voltage terminal of described pulse width modulating chip, the other end ground connection of described timing capacitor, the earth terminal ground connection of described pulse width modulating chip, one end of described sampling resistor connects the current sample end of described pulse width modulating chip and the output of described switching circuit, other end ground connection, the output of described pulse width modulating chip is connected with the control end of described switching circuit, the power end of described pulse width modulating chip is connected with the output of described AC rectification filter circuit by the first divider resistance, described self-feed line circle is connected with the power end of described pulse width modulating chip, for operating voltage being provided to described pulse width modulating chip,
Feedback circuit, is connected with the output of described direct-current rectification filter circuit, and for gathering described VD, described feedback circuit sends feedback signal in described VD during higher than voltage threshold, and the current potential of described frequency compensation end is dragged down;
The described feedback signal that the signal that described pulse width modulating chip obtains according to described current sample end sampling and described feedback circuit send is controlled the turn-on and turn-off of described switching circuit by the output output pulse width modulation signal of pulse width modulating chip.
2. Switching Power Supply current foldback circuit according to claim 1, it is characterized in that, described transformer also comprises the first rectifier diode and the first filter capacitor, the Same Name of Ends of described primary coil is connected with the output of described AC rectification filter circuit, and different name end is connected with the input of described switching circuit; The Same Name of Ends ground connection of described secondary coil, different name end is connected with described direct-current rectification filter circuit; The Same Name of Ends of described self-feed line circle is connected with the positive pole of described the first rectifier diode, different name end ground connection; The negative pole of described the first rectifier diode is connected with the common port of described the first divider resistance with the power end of described pulse width modulating chip; Described first filter capacitor one end is connected with the negative pole of described the first rectifier diode, and the other end is connected with the different name end of described self-feed line circle.
3. Switching Power Supply current foldback circuit according to claim 2; it is characterized in that; described transformer comprises for absorbing the absorption circuit of peak voltage; described absorption circuit comprises absorption resistance, Absorption Capacitance and diode; described absorption resistance is connected in parallel with Absorption Capacitance and one end is connected with the Same Name of Ends of described primary coil; the other end is connected with the negative pole of described diode, and the positive pole of described diode is connected with the different name end of described primary coil.
4. Switching Power Supply current foldback circuit according to claim 2; it is characterized in that; described direct-current rectification filter circuit comprises the second rectifier diode and the second filter capacitor; the positive pole of described the second rectifier diode is connected with the different name end of described secondary coil; the negative pole of described the second rectifier diode is the output of described direct-current rectification filter circuit; described second filter capacitor one end is connected with the negative pole of described the second rectifier diode, other end ground connection.
5. Switching Power Supply current foldback circuit according to claim 1; it is characterized in that; described switching circuit comprises N-channel MOS FET, biasing resistor and the first current-limiting resistance; the drain electrode of described N-channel MOS FET is the input of described switching circuit; the source electrode of described N-channel MOS FET is the output of described switching circuit; the grid of described N-channel MOS FET is the control end of described switching circuit and is connected with the output of described pulse width modulating chip by described the first current-limiting resistance, and described biasing resistor is connected between the grid and source electrode of described N-channel MOS FET.
6. Switching Power Supply current foldback circuit according to claim 1; it is characterized in that; described control circuit comprises filter network; described filter network comprises filter resistance and the 3rd filter capacitor; the current sample end of described pulse width modulating chip connects by filter resistance one end that described sampling resistor is connected with the output of described switching circuit; described the 3rd filter capacitor one end connects one end that described filter resistance is connected with the current sample end of described pulse width modulating chip, other end ground connection.
7. Switching Power Supply current foldback circuit according to claim 1, it is characterized in that, described feedback circuit comprises optocoupler, control switch, the second current-limiting resistance, the second divider resistance and the 3rd divider resistance, described optocoupler comprises reflector and receiver, the input of described reflector is connected with the output of described direct-current rectification filter circuit by described the second current-limiting resistance, the output of described reflector is connected with the input of described control switch, the input of described receiver is connected with the frequency compensation end of described pulse width modulating chip, output head grounding; Described the second divider resistance and the 3rd divider resistance are connected in series, the control end of described control switch is connected with the common port of the 3rd divider resistance with described the second divider resistance, the other end of described the second divider resistance is connected with the output of described direct-current rectification filter circuit, the other end ground connection of described the 3rd divider resistance; The output head grounding of described control switch; Described control switch is in the conducting during higher than described voltage threshold of described VD.
8. Switching Power Supply current foldback circuit according to claim 7, is characterized in that, the frequency compensation end of described pulse width modulating chip is directly by described receiver ground connection.
9. Switching Power Supply current foldback circuit according to claim 7, it is characterized in that, described feedback circuit comprises compensating network, described compensating network comprises building-out capacitor, the first compensating resistance and the second compensating resistance, described building-out capacitor one end is connected with the input of described control switch, the other end is connected with one end of described the first compensating resistance, the other end of described the first compensating resistance is connected with the control end of described control switch, described second compensating resistance one end connects the control end of described control switch, the other end connects the common port of described the second divider resistance and the 3rd divider resistance.
10. according to the Switching Power Supply current foldback circuit described in any one in claim 7-9, it is characterized in that, described feedback circuit comprises and is arranged on the input of described receiver and the 4th filter capacitor between output.
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| CN107276436A (en) * | 2017-08-08 | 2017-10-20 | 广西南宁驰信电子科技有限公司 | A kind of single-end flyback switching power supply circuit |
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| CN104104153A (en) * | 2014-06-30 | 2014-10-15 | 安徽国科电力设备有限公司 | Simple and reliable energy storage power supply circuit |
| CN104253546A (en) * | 2014-09-23 | 2014-12-31 | 惠州市可立克科技有限公司 | Switching power supply circuit |
| US9660539B2 (en) | 2015-01-30 | 2017-05-23 | 02Micro Inc. | Switching power supplies, and switch controllers for switching power supplies |
| TWI589106B (en) * | 2015-01-30 | 2017-06-21 | 凹凸科技國際股份有限公司 | Switching power supplies and switch controllers |
| CN107979150A (en) * | 2016-10-21 | 2018-05-01 | 广州市君盘实业股份有限公司 | Numerical control dynamical output charger based on SG3525 chips |
| CN107979150B (en) * | 2016-10-21 | 2024-02-06 | 广州市君盘实业股份有限公司 | Digital control dynamic output charger based on SG3525 chip |
| CN107482573A (en) * | 2017-08-08 | 2017-12-15 | 芜湖市凯鑫避雷器有限责任公司 | A kind of overload-protective intelligent regulator device of low-voltage electrical apparatus |
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| CN113169674A (en) * | 2018-12-28 | 2021-07-23 | 深圳市柔宇科技股份有限公司 | Drive control circuit of light modulation glass and light modulation glass |
| CN109936290A (en) * | 2019-04-29 | 2019-06-25 | 深圳市力生美半导体股份有限公司 | Switching power circuit |
| CN109936290B (en) * | 2019-04-29 | 2024-05-28 | 深圳市力生美半导体股份有限公司 | Switching power supply circuit |
| WO2023221526A1 (en) * | 2022-05-16 | 2023-11-23 | 华为数字能源技术有限公司 | Overcurrent protection circuit of power supply system, and device |
| CN118337192A (en) * | 2024-06-17 | 2024-07-12 | 欣捷安汽车电子有限公司 | Control circuit, method, equipment and medium based on pulse width modulation signal |
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