CN220775385U - Output overvoltage protection circuit and switching power supply - Google Patents
Output overvoltage protection circuit and switching power supply Download PDFInfo
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- CN220775385U CN220775385U CN202322283817.1U CN202322283817U CN220775385U CN 220775385 U CN220775385 U CN 220775385U CN 202322283817 U CN202322283817 U CN 202322283817U CN 220775385 U CN220775385 U CN 220775385U
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Abstract
The utility model discloses an output overvoltage protection circuit and a switching power supply, wherein the switching power supply comprises a feedback loop and an output overvoltage protection circuit, the feedback loop comprises a control chip and a feedback optocoupler, a transmitting end of the feedback optocoupler is connected with an output end of the switching power supply, a collecting electrode of a receiving end is connected with a feedback pin of the control chip, and an emitting electrode of the receiving end is connected with a grounding end of the switching power supply, wherein the output overvoltage protection circuit comprises: the overvoltage detection circuit is connected with the output end of the switching power supply and outputs a first current signal when the output voltage of the switching power supply exceeds a threshold voltage; the current amplifying circuit is connected with the output end of the overvoltage detection circuit and the transmitting end of the feedback optocoupler, amplifies the first current signal into a second current signal and enables the second current signal to flow through the transmitting end of the feedback optocoupler, and then the second current signal is transmitted to a feedback pin of the control chip through the feedback optocoupler in an isolated mode to control the control chip to stop working. The utility model can quickly respond to the overvoltage state of the output voltage of the switch power supply.
Description
Technical Field
The utility model relates to the field of switching converters, in particular to an output overvoltage protection circuit and a switching power supply.
Background
The switching converter is generally used for outputting a stable voltage, when a feedback loop of the output voltage of the switching converter fails or a load suddenly changes, the output voltage is higher than a design voltage value, so that a post-stage circuit and a switching device in the switching converter in a system to which the switching converter is applied bear higher voltage, and the problem of damage to the post-stage circuit or the switching converter can occur, so that most switching converters are designed with an output voltage overvoltage protection function.
As shown in fig. 1, which is a schematic diagram of an existing output overvoltage protection circuit, the specific working principle of the circuit of fig. 1 is as follows: when the output voltage rises, the sampling voltage divided by the resistor R1 and the resistor R2 rises synchronously, when the sampling voltage is higher than the reference voltage in the voltage comparison chip IC431, current is generated on a loop of the voltage comparison chip IC431, the resistor R3 and the transmitting end of the photoelectric coupler OC1, and is coupled to the receiving end through the photoelectric coupler OC1, the current of the feedback voltage pin FB of the control chip U0 is increased, the voltage of the FB pin is pulled down, and the output voltage is further controlled to be reduced; the resistor R3 is used for adjusting the current in the voltage comparison chip IC431; the capacitor C1, the resistor R4 and the capacitor C2 are used to compensate the feedback loop.
In the output overvoltage protection circuit of fig. 1, because the resistor R3 exists, the voltage comparison chip IC431 cannot bear a larger current, so that the resistor R3 has a larger value, which can cause the current generated in the transmitting end of the photoelectric coupler to be limited; due to the existence of the compensation capacitor C1, from the perspective of the open-loop transfer function of the product, the capacitor C1 and the resistor R3 form a pole, so that the bandwidth of the output voltage feedback loop is reduced, and the response time of the output voltage feedback loop is prolonged; meanwhile, due to the existence of the compensation resistor R4 and the compensation capacitor C2, the voltage of the feedback voltage pin FB of the control chip U0 cannot be quickly reduced. Therefore, the output overvoltage protection circuit of fig. 1 will respond slowly, when the output voltage is too high, the output voltage cannot be pulled down in time, and in the response time of the overvoltage protection circuit, the output voltage continues to rise, and at this time, the risk of damage to the post-stage circuit and the internal switching devices of the converter exists, so that effective protection cannot be formed.
Disclosure of Invention
The technical problem to be solved by the utility model is to provide an output overvoltage protection circuit and a switching power supply, which can overcome at least one defect in the prior art to at least a certain extent.
As a first aspect of the present utility model, an embodiment of an output overvoltage protection circuit is provided as follows:
the utility model provides an output overvoltage protection circuit, is applied to switching power supply, switching power supply includes feedback loop for realize the control that switching power supply output's electric parameter reaches the expected value, feedback loop includes control chip and feedback opto-coupler, the transmitting terminal of feedback opto-coupler is connected switching power supply's output, the collecting electrode of feedback opto-coupler receiving terminal is connected control chip's feedback pin, the projecting electrode of feedback opto-coupler receiving terminal is connected switching power supply's ground terminal, wherein, output overvoltage protection circuit includes:
the overvoltage detection circuit is used for being connected with the output end of the switching power supply and outputting a first current signal when the output voltage of the switching power supply exceeds a threshold voltage;
and the current amplifying circuit is used for connecting the output end of the overvoltage detection circuit and the transmitting end of the feedback optocoupler, amplifying the first current signal into a second current signal and enabling the second current signal to flow through the transmitting end of the feedback optocoupler, and then, the second current signal is transmitted to the feedback pin of the control chip in an isolated manner by the feedback optocoupler to control the control chip to stop working.
Preferably, the overvoltage detection circuit includes: the voltage comparison circuit comprises a resistor R1, a resistor R2, a resistor R3 and a voltage comparison chip IC431, wherein one end of the resistor R1 is connected with one end of the resistor R3 to serve as an input end of the overvoltage detection circuit and used for inputting output voltage of the switching power supply, the other end of the resistor R1 is connected with one end of the resistor R2 to be simultaneously connected with a sampling end of the voltage comparison chip IC431, the other end of the resistor R2 is connected with an anode end of the voltage comparison chip IC431 to serve as a grounding end of the overvoltage detection circuit and used for being connected with a grounding end of the switching power supply, and the other end of the resistor R3 is connected with a cathode end of the voltage comparison chip IC431 to serve as an output end of the overvoltage detection circuit and used for outputting the first current signal.
Preferably, the current amplifying circuit includes: and the base electrode of the triode Q1 is used as an input end of the current amplifying circuit and is used for inputting the first current signal, the base electrode of the triode Q1 is also connected with the emitting electrode of the triode Q1 and then is used for being connected with the cathode of the feedback optocoupler emitting end, and the collecting electrode of the triode Q1 is used for being connected with the grounding end of the switching power supply.
Further, the current amplifying circuit further comprises a diode D2, wherein an anode of the diode D2 is used for being connected with a cathode of the feedback optocoupler transmitting end, and a cathode of the diode D2 is connected with an emitter of the triode Q1; and/or the current amplifying circuit further comprises a diode D3, wherein the anode of the diode D3 is connected with the base electrode of the triode Q1, and the cathode of the diode D3 is connected with the emitter electrode of the triode Q1.
Further, the current amplifying circuit further comprises a capacitor C2, one end of the capacitor C2 is connected with the emitter of the triode Q1, and the other end of the capacitor C2 is connected with the collector of the triode Q1.
Further, the current amplifying circuit further comprises a resistor R4, one end of the resistor R4 is used for being connected with the cathode of the transmitting end of the feedback optocoupler, and the other end of the resistor R4 is used for being connected with the emitter of the triode Q1.
As a second aspect of the present utility model, a technical solution of an embodiment of a switching power supply is provided as follows:
the switching power supply comprises a feedback loop, wherein the feedback loop is used for realizing control of the electric parameter output by the switching power supply to reach an expected value, the feedback loop comprises a control chip and a feedback optocoupler, the transmitting end of the feedback optocoupler is connected with the output end of the switching power supply, the collector of the receiving end of the feedback optocoupler is connected with the feedback pin of the control chip, and the emitter of the receiving end of the feedback optocoupler is connected with the grounding end of the switching power supply, wherein the switching power supply further comprises any one of the output overvoltage protection circuits in the first aspect.
Further, the switching power supply further comprises a compensation circuit, wherein the compensation circuit is used for compensating a feedback loop of the switching power supply, the compensation circuit comprises a resistor R5 and a capacitor C3 which are connected in series, one end of the compensation circuit is connected with a feedback pin of the control chip, and the other end of the compensation circuit is connected with a grounding end of the switching power supply; the output overvoltage protection circuit further comprises a rapid discharging circuit, wherein the rapid discharging circuit is connected with the resistor R5 in parallel, and when the receiving end of the feedback optocoupler receives the second current signal, the charge in the capacitor C3 is rapidly released.
Preferably, one end of the resistor R5 is connected to a feedback pin of the control chip, the other end of the resistor R5 is connected to one end of the capacitor C3, and the other end of the capacitor C3 is connected to a ground end of the switching power supply; the rapid discharging circuit is a diode D1, an anode of the diode D1 is connected with one end of the resistor R5, and a cathode of the diode D1 is connected with the other end of the resistor R5.
Preferably, one end of the capacitor C3 is connected to a feedback pin of the control chip, the other end of the capacitor C3 is connected to one end of the resistor R5, and the other end of the resistor R5 is connected to a ground terminal of the switching power supply; the rapid discharging circuit is a diode D1, an anode of the diode D1 is connected with one end of the resistor R5, and a cathode of the diode D1 is connected with the other end of the resistor R5.
Compared with the prior art, the utility model has the beneficial effects that: the output overvoltage protection circuit is provided with a current amplifying circuit which can amplify a first current signal into a second current signal and enable the second current signal to flow through the transmitting end of the feedback optocoupler, so that when the output voltage of the switching power supply exceeds a threshold voltage, the current of the feedback pin of the control chip is larger, the voltage drop speed is faster, the control chip can trigger overvoltage protection rapidly, the output voltage of the switching power supply is pulled down rapidly, and the later-stage circuit and the internal switching devices of the switching converter are protected.
Drawings
FIG. 1 is a schematic diagram of a prior art output overvoltage protection circuit;
FIG. 2 is a schematic diagram of one particular embodiment of an output overvoltage protection circuit for use with the switching power supply of the present utility model;
FIG. 3 is a simulated waveform of the circuit of FIG. 1 applied to a switching power supply;
fig. 4 is a simulated waveform of the circuit of fig. 2 applied to a switching power supply.
Detailed Description
So that the manner in which the above recited objects, features and advantages of the present utility model can be understood in detail, a more particular description of the utility model, briefly summarized below, may be had by reference to embodiments, some of which are illustrated in the appended drawings. All other embodiments, which can be made by one of ordinary skill in the art based on the embodiments herein without making any inventive effort, shall fall within the scope of the present application.
It should be noted that the terms "comprising" and "having," and any variations thereof, as described in the specification and claims of this application are intended to cover a non-exclusive inclusion, such as an inclusion of a list of elements, unit circuits, or control sequences that are not necessarily limited to those elements, unit circuits, or control sequences explicitly listed, but may include elements, unit circuits, or control sequences not explicitly listed or inherent to such circuits.
In addition, embodiments and features of embodiments in this application may be combined with each other without conflict.
It will be understood that, in the description and in the claims, when an element is described as being "connected" to another element, the element may be "directly connected" to the other element or "connected" to the other element through a third element; when it is described that a step is continued to another step, the step may be continued directly to the another step or through a third step to the another step.
First embodiment
The embodiment provides an output overvoltage protection circuit, be applied to switching power supply, switching power supply includes feedback loop, be used for realizing the control that switching power supply output's electric parameter reaches the expected value, feedback loop includes control chip and feedback opto-coupler, the output of switching power supply is connected to the transmitting terminal of feedback opto-coupler, the feedback pin of control chip is connected to the collecting electrode of feedback opto-coupler receiving terminal, the earth terminal of switching power supply is connected to the projecting electrode of feedback opto-coupler receiving terminal, its characterized in that, output overvoltage protection circuit includes:
the overvoltage detection circuit is used for being connected with the output end of the switching power supply and outputting a first current signal when the output voltage of the switching power supply exceeds a threshold voltage;
the current amplifying circuit is used for connecting the output end of the overvoltage detection circuit and the transmitting end of the feedback optocoupler, amplifying the first current signal into the second current signal, enabling the second current signal to flow through the transmitting end of the feedback optocoupler, and then isolating and transmitting the second current signal to the feedback pin of the control chip by the feedback optocoupler to control the control chip to stop working.
The output overvoltage protection of the utility model has universality, wherein the topology types of the switching power supply can be forward, flyback, push-pull and the like, the electric parameters reach the expected values, the utility model is not limited to the output voltage stabilization in the background technology, the output current stabilization, the output power stabilization and the like, the specific selection of the topology is realized, and the electric parameters reach the expected values are not specified, so that the utility model can be designed by a person skilled in the art according to the needs.
The output overvoltage protection circuit of the embodiment is provided with the current amplifying circuit, and can amplify the first current signal into the second current signal and enable the second current signal to flow through the transmitting end of the feedback optocoupler, so that when the output voltage of the switching power supply exceeds the threshold voltage, the current of the feedback pin of the control chip is larger, the voltage dropping speed is higher, the control chip can trigger overvoltage protection rapidly, the output voltage of the switching power supply is pulled down rapidly, and the post-stage circuit and the internal switching device of the switching converter are protected.
Preferably, the overvoltage detection circuit includes: the resistor R1, the resistor R2, the resistor R3 and the voltage comparison chip IC431 are connected together at one end of the resistor R1 and one end of the resistor R3 to serve as an input end of an overvoltage detection circuit and used for inputting output voltage of the switching power supply, the other end of the resistor R1 and one end of the resistor R2 are simultaneously connected with a sampling end of the voltage comparison chip IC431, the other end of the resistor R2 and an anode end of the voltage comparison chip IC431 are connected together to serve as a grounding end of the overvoltage detection circuit and used for connecting a grounding end of the switching power supply, and the other end of the resistor R3 and a cathode end of the voltage comparison chip IC431 are connected together to serve as an output end of the overvoltage detection circuit and used for outputting a first current signal.
Preferably, the current amplifying circuit includes: and the base electrode of the triode Q1 is used as an input end of the current amplifying circuit and is used for inputting a first current signal, the base electrode of the triode Q1 is also connected with the emitter electrode of the triode Q1 and then is used for being connected with the cathode of the feedback optocoupler emitting end, and the collector electrode of the triode Q1 is used for being connected with the grounding end of the switching power supply.
Further, the current amplifying circuit further comprises a diode D2, wherein the anode of the diode D2 is used for being connected with the cathode of the transmitting end of the feedback optocoupler, and the cathode of the diode D2 is connected with the emitter of the triode Q1; and/or the current amplifying circuit further comprises a diode D3, wherein the anode of the diode D3 is connected with the base electrode of the triode Q1, and the cathode of the diode D3 is connected with the emitter electrode of the triode Q1; diode D2 and said diode D3 are used to prevent current reversal, disturbing the circuit operating logic.
Further, the current amplifying circuit further comprises a capacitor C2, one end of the capacitor C2 is connected with the emitter of the triode Q1, the other end of the capacitor C2 is connected with the collector of the triode Q1, and the capacitor C2 is used for filtering and stabilizing the base voltage of the triode Q1.
Further, the current amplifying circuit further comprises a resistor R4, one end of the resistor R4 is used for being connected with a cathode of the transmitting end of the feedback optocoupler, the other end of the resistor R4 is used for being connected with an emitting electrode of the triode Q1, and the resistor R4 is used for adjusting the first current signal.
Second embodiment
The embodiment provides a switching power supply, the switching power supply includes a feedback loop, and is used for realizing the control that the electric parameter that switching power supply output reaches the expected value, and the feedback loop includes control chip and feedback opto-coupler, and the output of switching power supply is connected to the transmitting terminal of feedback opto-coupler, and the feedback pin of control chip is connected to the collecting electrode of feedback opto-coupler receiving terminal, and the earth terminal of switching power supply is connected to the projecting pole of feedback opto-coupler receiving terminal, its characterized in that, switching power supply still includes any one of the above-mentioned first embodiment output overvoltage protection circuit.
The switching power supply of this embodiment, due to any one of the output overvoltage protection circuits of the first embodiment, controls the current of the chip feedback pin to be larger and the voltage to drop faster when the output voltage of the switching power supply exceeds the threshold voltage, so that the control chip can trigger the overvoltage protection fast, pull down the output voltage of the switching power supply fast, and protect the post-stage circuit and the internal switching devices of the switching converter.
Further, the switching power supply further comprises a compensation circuit, the compensation circuit is used for compensating a feedback loop of the switching power supply, the compensation circuit comprises a resistor R5 and a capacitor C3 which are connected in series, one end of the compensation circuit is connected with a feedback pin of the control chip, and the other end of the compensation circuit is connected with a grounding end of the switching power supply; the output overvoltage protection circuit further comprises a rapid discharging circuit which is connected with the resistor R5 in parallel, and charges in the capacitor C3 are rapidly released when the receiving end of the feedback optocoupler receives the second current signal, so that the speed of triggering overvoltage protection by the control chip can be further improved.
Preferably, one end of the resistor R5 is connected with a feedback pin of the control chip, the other end of the resistor R5 is connected with one end of the capacitor C3, and the other end of the capacitor C3 is connected with the grounding end of the switching power supply; the rapid discharging circuit is a diode D1, the anode of the diode D1 is connected with one end of a resistor R5, and the cathode of the diode D1 is connected with the other end of the resistor R5.
Fig. 2 is a schematic diagram of an embodiment of an output overvoltage protection circuit applied to a switching power supply of the present utility model, please refer to fig. 2, wherein: the overvoltage detection circuit 101 in the output overvoltage protection circuit includes the resistor R1, the resistor R2, the resistor R3, and the voltage comparison chip IC431 described in the first embodiment; the current amplifying circuit 102 in the output overvoltage protection circuit includes the transistor Q1, the diode D2, the diode D3, the capacitor C2, and the resistor R4 described in the first embodiment; in addition, the switching power supply further includes the compensation circuit and the rapid discharging circuit 103 described in this embodiment, one end of a resistor R5 in the compensation circuit is connected to a feedback pin of the control chip, the other end of the resistor R5 is connected to one end of a capacitor C3, and the other end of the capacitor C3 in the compensation circuit is connected to a ground terminal of the switching power supply; the rapid discharging circuit is a diode D1, the anode of the diode D1 is connected with one end of a resistor R5, and the cathode of the diode D1 is connected with the other end of the resistor R5.
As an equivalent alternative of fig. 2, the connection relationship is that one end of a capacitor C3 is connected with a feedback pin of the control chip, the other end of the capacitor C3 is connected with one end of a resistor R5, and the other end of the resistor R5 is connected with a ground end of the switching power supply; the rapid discharging circuit is a diode D1, the anode of the diode D1 is connected with one end of a resistor R5, and the cathode of the diode D1 is connected with the other end of the resistor R5.
In fig. 2, D2 and R4 are connected in series, and the positions can be interchanged.
The following is an analysis of a specific working principle of the switching power supply of the present embodiment for realizing short-circuit protection with reference to fig. 2, and is as follows:
the output voltage VO of the switching power supply is divided by the resistor R1 and the resistor R2, the divided voltage (namely, sampling voltage) is connected to the sampling end of the voltage comparison chip IC431, the sampling voltage is compared with an internal reference voltage source by the voltage comparison chip IC431, when the output voltage VO is normal, the sampling voltage is smaller than the reference voltage by setting the resistance values of the resistor R1 and the resistor R2, the voltage comparison chip IC431 does not flow current, the triode Q1 is not conducted, the circuit does not increase optocoupler current, and the normal work of a feedback loop is not influenced; when the output voltage VO exceeds the threshold voltage, the sampling voltage of the voltage comparing chip IC431 is greater than the reference source therein, the voltage comparing chip IC431 starts to flow a current (i.e., a first current signal) from the cathode to the anode, and at this time, the PNP transistor Q1 is turned on, so as to form a current (i.e., a second current signal) sequentially passing through the emitter of the photo coupler OC1, the diode D2, the resistor R4, the emitter of the switching transistor Q1, the collector of the switching transistor Q1, and the output ground GND of the switching power from the output terminal of the switching power, and the current amplifying circuit 102 may amplify the first current signal flowing through the voltage comparing chip IC431 and convert the first current signal into the second current signal flowing through the emitter of the photo coupler OC 1.
In order to realize the rapid protection function, the resistance value of the resistor R4 is generally set to be far smaller than that of the resistor R3, so that a second current signal in the transmitting end of the photoelectric coupler OC1 can be increased, the second current signal can be transmitted to the voltage feedback FB pin of the control chip by the photoelectric coupler OC1 in a certain current transmission ratio, and the voltage of the feedback pin FB of the control chip is lower as the current signal of the receiving end of the photoelectric coupler OC1 is larger, the diode D1 can rapidly release the charge of the capacitor C3 at the moment, the voltage of the feedback pin FB of the control chip is pulled down as soon as possible, and the output overvoltage protection of the switching power supply is realized as soon as possible. Diode D2 and diode D3 are used to prevent reverse current problems, resulting in logic upsets in the circuit. The capacitor C2 is used to stabilize the emitter voltage of the transistor Q1, and its effect can increase the soft start effect for the power switching converter.
The effect of the output short-circuit protection of the switching power supply can be intuitively felt through simulation waveforms, and in the simulation experiment, the setting conditions are consistent, and the response speed of the control chip feedback pin voltage pulled down when the output voltage of the switching power supply exceeds the threshold voltage is mainly compared.
As shown in fig. 3, a simulation waveform of the circuit of fig. 1 applied to a switching power supply is shown, wherein Time in abscissa is Time, and unit is mS; VO in the ordinate is the output voltage of the product, the unit is V, VFB is the feedback pin FB voltage of the control chip, the unit is V, VREF is the sampling end voltage of the IC431, and the unit is V. As can be seen from fig. 3, when the output voltage VO rises to the threshold voltage 24V, the circuit does not pull the voltage of the feedback pin of the control chip down immediately due to the slow response speed, but pulls down the voltage of the feedback pin of the control chip after 12.5 ms, and in this 12.5 ms period, the output voltage continuously rises, which results in too high output voltage, resulting in too high voltage stress of the system post-stage circuit applied by the switching power supply and the internal devices of the switching converter, and increasing the damage risk.
In fig. 4, for the simulation waveform, the code and unit meanings in the abscissa and the ordinate of the circuit of fig. 2 applied to the switching power supply, when the output voltage VO rises to the threshold voltage 24V, the feedback pin voltage of the control chip is immediately pulled down to zero volt, so as to prevent the output voltage from rising continuously, and the circuit response speed is high, so that safer and faster overvoltage protection of the output voltage can be provided, the voltage stress of the post-stage circuit of the system and the internal devices of the switching converter applied by the switching power supply is reduced, and the reliability of the system is increased.
The present utility model is not limited to the above-described embodiments, and according to the above-described matters, the present utility model may be modified, replaced or altered in various equivalent ways without departing from the basic technical spirit of the present utility model, all falling within the scope of the present utility model, according to the general technical knowledge and conventional means in the art.
Claims (10)
1. The utility model provides an output overvoltage protection circuit, is applied to switching power supply, switching power supply includes feedback loop for realize the control that switching power supply output's electric parameter reaches the expected value, feedback loop includes control chip and feedback opto-coupler, the transmitting terminal of feedback opto-coupler is connected switching power supply's output, the collecting electrode of feedback opto-coupler receiving terminal is connected control chip's feedback pin, the projecting electrode of feedback opto-coupler receiving terminal is connected switching power supply's ground terminal, its characterized in that, output overvoltage protection circuit includes:
the overvoltage detection circuit is used for being connected with the output end of the switching power supply and outputting a first current signal when the output voltage of the switching power supply exceeds a threshold voltage;
and the current amplifying circuit is used for connecting the output end of the overvoltage detection circuit and the transmitting end of the feedback optocoupler, amplifying the first current signal into a second current signal and enabling the second current signal to flow through the transmitting end of the feedback optocoupler, and then, the second current signal is transmitted to the feedback pin of the control chip in an isolated manner by the feedback optocoupler to control the control chip to stop working.
2. The output overvoltage protection circuit of claim 1, wherein the overvoltage detection circuit comprises: the voltage comparison circuit comprises a resistor R1, a resistor R2, a resistor R3 and a voltage comparison chip IC431, wherein one end of the resistor R1 is connected with one end of the resistor R3 to serve as an input end of the overvoltage detection circuit and used for inputting output voltage of the switching power supply, the other end of the resistor R1 is connected with one end of the resistor R2 to be simultaneously connected with a sampling end of the voltage comparison chip IC431, the other end of the resistor R2 is connected with an anode end of the voltage comparison chip IC431 to serve as a grounding end of the overvoltage detection circuit and used for being connected with a grounding end of the switching power supply, and the other end of the resistor R3 is connected with a cathode end of the voltage comparison chip IC431 to serve as an output end of the overvoltage detection circuit and used for outputting the first current signal.
3. The output overvoltage protection circuit of claim 1, wherein the current amplifying circuit comprises: and the base electrode of the triode Q1 is used as an input end of the current amplifying circuit and is used for inputting the first current signal, the base electrode of the triode Q1 is also connected with the emitting electrode of the triode Q1 and then is used for being connected with the cathode of the feedback optocoupler emitting end, and the collecting electrode of the triode Q1 is used for being connected with the grounding end of the switching power supply.
4. An output overvoltage protection circuit according to claim 3, wherein: the current amplifying circuit further comprises a diode D2, wherein the anode of the diode D2 is used for being connected with the cathode of the transmitting end of the feedback optocoupler, and the cathode of the diode D2 is connected with the emitter of the triode Q1; and/or the current amplifying circuit further comprises a diode D3, wherein the anode of the diode D3 is connected with the base electrode of the triode Q1, and the cathode of the diode D3 is connected with the emitter electrode of the triode Q1.
5. An output overvoltage protection circuit according to claim 3, wherein: the current amplifying circuit further comprises a capacitor C2, one end of the capacitor C2 is connected with the emitter of the triode Q1, and the other end of the capacitor C2 is connected with the collector of the triode Q1.
6. An output overvoltage protection circuit according to claim 3, wherein: the current amplifying circuit further comprises a resistor R4, one end of the resistor R4 is used for being connected with the cathode of the feedback optocoupler transmitting end, and the other end of the resistor R4 is used for being connected with the emitting electrode of the triode Q1.
7. A switching power supply, the switching power supply includes a feedback loop, and is used for realizing the control that the electric parameter that switching power supply output reaches the expected value, the feedback loop includes control chip and feedback opto-coupler, the transmitting end of feedback opto-coupler is connected the output of switching power supply, the collecting electrode of feedback opto-coupler receiving end is connected the feedback pin of control chip, the projecting electrode of feedback opto-coupler receiving end is connected the ground terminal of switching power supply, characterized in that, switching power supply still includes the output overvoltage protection circuit of any one of claims 1 to 6.
8. The switching power supply of claim 7 wherein: the switching power supply further comprises a compensation circuit, wherein the compensation circuit is used for compensating a feedback loop of the switching power supply, the compensation circuit comprises a resistor R5 and a capacitor C3 which are connected in series, one end of the compensation circuit is connected with a feedback pin of the control chip, and the other end of the compensation circuit is connected with a grounding end of the switching power supply; the output overvoltage protection circuit further comprises a rapid discharging circuit, wherein the rapid discharging circuit is connected with the resistor R5 in parallel, and when the receiving end of the feedback optocoupler receives the second current signal, the charge in the capacitor C3 is rapidly released.
9. The switching power supply of claim 8 wherein: one end of the resistor R5 is connected with a feedback pin of the control chip, the other end of the resistor R5 is connected with one end of the capacitor C3, and the other end of the capacitor C3 is connected with the grounding end of the switching power supply; the rapid discharging circuit is a diode D1, an anode of the diode D1 is connected with one end of the resistor R5, and a cathode of the diode D1 is connected with the other end of the resistor R5.
10. The switching power supply of claim 8 wherein: one end of the capacitor C3 is connected with a feedback pin of the control chip, the other end of the capacitor C3 is connected with one end of the resistor R5, and the other end of the resistor R5 is connected with the grounding end of the switching power supply; the rapid discharging circuit is a diode D1, an anode of the diode D1 is connected with one end of the resistor R5, and a cathode of the diode D1 is connected with the other end of the resistor R5.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202322283817.1U CN220775385U (en) | 2023-08-23 | 2023-08-23 | Output overvoltage protection circuit and switching power supply |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202322283817.1U CN220775385U (en) | 2023-08-23 | 2023-08-23 | Output overvoltage protection circuit and switching power supply |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN220775385U true CN220775385U (en) | 2024-04-12 |
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| CN202322283817.1U Active CN220775385U (en) | 2023-08-23 | 2023-08-23 | Output overvoltage protection circuit and switching power supply |
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