Overvoltage protection circuit for flyback switching power supply

Abstract

The utility model relates to the technical field of protection circuits, and discloses an overvoltage protection circuit for a flyback switching power supply, which comprises an overvoltage protection circuit and a FLYBACK circuit, and the overvoltage protection circuit is connected with the FLYBACK circuit. The overvoltage protection circuit is triggered when the FLYBACK circuit is in an overvoltage state and can be recovered only when the whole circuit is powered off, and overvoltage protection of the driving motor of the scroll compressor is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of protection circuits, and is used for an overvoltage protection circuit of a flyback switching power supply. Background Art

[0002] The driving motor of a common scroll compressor has an overvoltage problem. Currently, the overvoltage protection of the driving motor of the scroll compressor has the problems of complex structure, difficult layout and poor safety performance. Utility Model Content

[0003] The purpose of the present application is to provide an overvoltage protection circuit for a flyback switching power supply to solve the technical problems raised in the above background technology.

[0004] To achieve the above-mentioned purpose, the present application discloses the following technical solutions: a flyback switching power supply overvoltage protection circuit, comprising an overvoltage protection circuit and a FLYBACK circuit; the overvoltage protection circuit is connected to the FLYBACK circuit;

[0005] Preferably, the overvoltage protection circuit includes a mainboard U1, a PNP transistor Q1, an NPN transistor Q2, a Schottky diode ZV1, a diode D1, a capacitor C1, a capacitor C2, a capacitor C3, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8 and a transformer N2 winding;

[0006] Pin 1 of the capacitor C3, pin 1 of the resistor R7 and pin 1 of the resistor R8 are all connected to pin 2 of the mainboard U1, pin 3 of the mainboard U1, pin 8 of the mainboard U1 and pin 10 of the mainboard U1 are all connected to the FLYBACK circuit, pin 2 of the resistor R2, pin 2 of the capacitor C1, pin 2 of the resistor R3, pin 2 of the capacitor C2, the emitter of the NPN transistor Q2, pin 2 of the capacitor C3, pin 2 of the resistor R8, pin 4 of the mainboard U1, pin 5 of the mainboard U1 and pin 7 of the mainboard U1 are connected to ground; pin 2 of the resistor R7 is connected to pin 1 of the resistor R6; pin 2 of the resistor R6 is connected to pin 10 of the mainboard U1 and then connected to the FLYBACK circuit; pin 1 of the resistor R7, pin 2 of the resistor R8 Pin 1 of the resistor R4 and pin 1 of the capacitor C2 are all connected to pin 1 of the capacitor C3; pin 2 of the resistor R5 is connected to the emitter of the PNP transistor Q1; the base of the PNP transistor Q1 is connected to the collector of the NPN transistor Q2, and pin 1 of the resistor R4, pin 1 of the capacitor C2 and the base of the NPN transistor Q2 are all connected to the collector of the PNP transistor Q1; pin 1 of the resistor R3 and the positive electrode of the Schottky diode ZV1 are all connected to pin 2 of the resistor R4; the negative electrode of the diode D1, pin 1 of the resistor R2 and pin 1 of the capacitor C1 are all connected to the negative electrode of the Schottky diode ZV1; pin 1 of the resistor R1 is connected to the positive electrode of the diode D1; the transformer N2 winding is connected to the FLYBACK circuit.

[0007] Preferably, the FLYBACK circuit comprises a winding N1, a transformer N2 winding and a winding N5;

[0008] The winding N1 includes a MOS tube Q3; the pin 1 of the winding N1 is connected to B+, and the pin 2 of the winding N1 is connected to the drain of the MOS tube Q3; the gate of the MOS tube Q3 is connected to PWM, and the source of the MOS tube Q3 is grounded;

[0009] The winding N5 includes a Schottky diode D2, a polar electrolytic capacitor EC1, an optocoupler sensor U2, a resistor R9, a resistor R10, a resistor R11, a capacitor C4 and a thyristor U3; pin 5 of the winding N5 is connected to the positive electrode of the Schottky diode D2, and pin 5 of the winding N5 is connected to the negative electrode of the polar electrolytic capacitor EC1 and then grounded; the negative electrode of the Schottky diode D2, the positive electrode of the polar electrolytic capacitor EC1 and pin 1 of the resistor R10 are all connected to pin 1 of the resistor R9, and pin 2 of the resistor R9 is connected to pin 1 of the optocoupler sensor; pin 1 of the capacitor C4, pin 1 of the thyristor U3 and pin 1 of the resistor R11 are all connected to pin 2 of the resistor R10; pin 2 of the optocoupler sensor and pin 2 of the thyristor U3 are all connected to pin 2 of the capacitor C4; pin 3 of the thyristor U3 is connected to pin 2 of the resistor R11 and then grounded.

[0010] Beneficial effect: The overvoltage protection circuit for flyback switching power supply of the present application monitors the voltage of the FLYBACK circuit by adding the transformer N2 winding, and triggers the overvoltage protection circuit when there is obvious overvoltage. The overvoltage protection circuit has a simple structure, occupies a small space, and is convenient to be arranged on the driver board, which solves the problem of complex structure and difficult arrangement of common protection circuits; the overvoltage protection circuit will not recover by itself after being triggered, and can only recover when the entire circuit is powered off, which can prevent the circuit from restarting in an overvoltage state, prevent damage to the control chip, and improve the safety performance of common overvoltage protection circuits. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0012] Figure 1 A schematic diagram of an overvoltage protection circuit for a flyback switching power supply provided in an embodiment of the present application.

[0013] Figure 2 This is a schematic diagram of the FLYBACK circuit provided in an embodiment of the present application. DETAILED DESCRIPTION

[0014] The technical solutions in the embodiments of the present application are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0015] In this article, the term "comprising" is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of more restrictions, the elements defined by the sentence "comprising..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0016] This embodiment discloses Figure 1-2 The overvoltage protection circuit for a flyback switching power supply shown includes an overvoltage protection circuit and a FLYBACK circuit; the overvoltage protection circuit is connected to the FLYBACK circuit.

[0017] In this embodiment, a flyback switching power supply overvoltage protection circuit is characterized by comprising an overvoltage protection circuit and a FLYBACK circuit; the overvoltage protection circuit is connected to the FLYBACK circuit;

[0018] Specifically, the overvoltage protection circuit includes a mainboard U1, a PNP transistor Q1, an NPN transistor Q2, a Schottky diode ZV1, a diode D1, a capacitor C1, a capacitor C2, a capacitor C3, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8 and a transformer N2 winding;

[0019] Pin 1 of capacitor C3, pin 1 of resistor R7 and pin 1 of resistor R8 are all connected to pin 2 of mainboard U1, pin 3 of mainboard U1, pin 8 of mainboard U1 and pin 10 of mainboard U1 are all connected to FLYBACK circuit, pin 2 of resistor R2, pin 2 of capacitor C1, pin 2 of resistor R3, pin 2 of capacitor C2, emitter of NPN transistor Q2, pin 2 of capacitor C3, pin 2 of resistor R8, pin 4 of mainboard U1, pin 5 of mainboard U1 and pin 7 of mainboard U1 are connected to ground; pin 2 of resistor R7 is connected to pin 1 of resistor R6; pin 2 of resistor R6 is connected to pin 10 of mainboard U1 and then connected to FLYBACK circuit; pin 1 of resistor R7, pin 1 of resistor R8 and Pin 1 of resistor R5 is connected to pin 1 of capacitor C3; pin 2 of resistor R5 is connected to the emitter of PNP transistor Q1; the base of PNP transistor Q1 is connected to the collector of NPN transistor Q2, pin 1 of resistor R4, pin 1 of capacitor C2 and the base of NPN transistor Q2 are connected to the collector of PNP transistor Q1; pin 1 of resistor R3 and the positive electrode of Schottky diode ZV1 are connected to pin 2 of resistor R4; the negative electrode of diode D1, pin 1 of resistor R2 and pin 1 of capacitor C1 are connected to the negative electrode of Schottky diode ZV1; pin 1 of resistor R1 is connected to the positive electrode of diode D1; the winding of transformer N2 is connected to the FLYBACK circuit.

[0020] In this embodiment, the FLYBACK circuit includes a winding N1, a transformer N2 winding, and a winding N5;

[0021] Specifically, the winding N1 includes a MOS tube Q3; the pin 1 of the winding N1 is connected to B+, and the pin 2 of the winding N1 is connected to the drain of the MOS tube Q3; the gate of the MOS tube Q3 is connected to PWM, and the source of the MOS tube Q3 is grounded;

[0022] Specifically, the winding N5 includes a Schottky diode D2, a polar electrolytic capacitor EC1, an optocoupler sensor U2, a resistor R9, a resistor R10, a resistor R11, a capacitor C4 and a thyristor U3; pin 5 of the winding N5 is connected to the positive electrode of the Schottky diode D2, and the pin 5 of the winding N5 is connected to the negative electrode of the polar electrolytic capacitor EC1 and then grounded; the negative electrode of the Schottky diode D2, the positive electrode of the polar electrolytic capacitor EC1 and the pin 1 of the resistor R10 are all connected to the pin 1 of the resistor R9, and the pin 2 of the resistor R9 is connected to the pin 1 of the optocoupler sensor; the pin 1 of the capacitor C4, the pin 1 of the thyristor U3 and the pin 1 of the resistor R11 are all connected to the pin 2 of the resistor R10; the pin 2 of the optocoupler sensor and the pin 2 of the thyristor U3 are all connected to the pin 2 of the capacitor C4; the pin 3 of the thyristor U3 is connected to the pin 2 of the resistor R11 and then grounded.

[0023] In actual operation, when the MOS tube Q3 is turned on, energy is stored on the primary side of the transformer. The amount of energy is related to the on-time. The larger the duty cycle, the longer the on-time, and the more energy is stored. When the switch tube is turned off, the energy is released to the side pole. The energy stored on the primary side of the transformer will be released to the side pole. According to the principle that the flux increment must be equal when it is turned on and when it is turned off, otherwise it will cause core saturation, that is: Vin*Ton / Np=Vo*Toff / Ns. The turns ratio is fixed, but the ratio of the on-time Ton and the off-time Toff is very large, resulting in a large change in Vo. Once the feedback fails , which will increase the on-time Ton and reduce the off-time Toff. At this time, it enters the destruction state. The output voltage of the transformer N2 winding will become very large. The voltage here is passed through the resistor R1, diode D1, resistor R2 and capacitor C1 to form a rectifier filter circuit, and the voltage is stored in the capacitor C1. If this voltage continues to increase without decreasing, the voltage stored in the capacitor C1 will also continue to increase. When it reaches a certain value, it will trigger the latch circuit of the subsequent stage. It is determined by the voltage value of the Schottky diode ZV1. The voltage amplitude is Vzv1+Vbe. When the voltage across the capacitor C1 rises to Vzv1+Vb e, Schottky diode ZV1 is turned on, current flows through the base Ib of NPN transistor Q2, and current flows through Ic. NPN transistor Q2 reaches saturation, and Vce saturation voltage drop is 0.1-0.3V. Then the base of PNP transistor Q1 is pulled down to 0.1-0.3V. When Vbe is greater than negative 0.7V, collector VCE enters the saturation region, PNP transistor Q1 is turned on, and the emitter voltage is approximately equal to the collector voltage, with a saturation voltage drop of 0.1-0.3V, which is applied to the base of NPN transistor Q2, forming positive feedback and being in an interlocking state. PNP transistor Transistor Q1 and NPN transistor Q2 are both in saturation state, so that the voltage across capacitor C3 is clamped at 0.6-1.0V, so that the mainboard U1 is in under-voltage lock state. The under-voltage value of mainboard U1 is 1.43V, the output of mainboard U1 stops, and the power supply circuit no longer works. Because PNP transistor Q1 and NPN transistor Q2 form a simple self-locking circuit, this circuit is still locked after the trigger voltage is lost. Because this overvoltage situation is a serious problem, it will not cause the overvoltage circuit to be triggered under normal circumstances, and it will not recover by itself after being triggered. It needs to be powered off in the entire circuit to recover.

[0024] In summary, in the overvoltage protection circuit for the flyback switching power supply of this embodiment, the FLYBACK circuit is connected to the drive motor of the scroll compressor, and the overvoltage protection circuit is connected to the FLYBACK circuit. The FLYBACK circuit voltage is monitored based on the transformer N2 winding, and the overvoltage protection is triggered when there is an obvious overvoltage, thereby realizing overvoltage protection for the drive motor of the scroll compressor and ensuring its safety.

[0025] Finally, it should be noted that the above is only a preferred embodiment of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. An overvoltage protection circuit for a flyback switching power supply, characterized in that: It includes an overvoltage protection circuit and a FLYBACK circuit; the overvoltage protection circuit is connected to the FLYBACK circuit; The overvoltage protection circuit includes a mainboard U1, a PNP transistor Q1, an NPN transistor Q2, a Schottky diode ZV1, a diode D1, a capacitor C1, a capacitor C2, a capacitor C3, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8 and a transformer N2 winding; Pin 1 of the capacitor C3, pin 1 of the resistor R7 and pin 1 of the resistor R8 are all connected to pin 2 of the mainboard U1, pin 3 of the mainboard U1, pin 8 of the mainboard U1 and pin 10 of the mainboard U1 are all connected to the FLYBACK circuit, pin 2 of the resistor R2, pin 2 of the capacitor C1, pin 2 of the resistor R3, pin 2 of the capacitor C2, the emitter of the NPN transistor Q2, pin 2 of the capacitor C3, pin 2 of the resistor R8, pin 4 of the mainboard U1, pin 5 of the mainboard U1 and pin 7 of the mainboard U1 are connected to ground; pin 2 of the resistor R7 is connected to pin 1 of the resistor R6; pin 2 of the resistor R6 is connected to pin 10 of the mainboard U1 and then connected to the FLYBACK circuit; pin 1 of the resistor R7, pin 2 of the resistor R8 Pin 1 of the resistor R4 and pin 1 of the capacitor C2 are all connected to pin 1 of the capacitor C3; pin 2 of the resistor R5 is connected to the emitter of the PNP transistor Q1; the base of the PNP transistor Q1 is connected to the collector of the NPN transistor Q2, and pin 1 of the resistor R4, pin 1 of the capacitor C2 and the base of the NPN transistor Q2 are all connected to the collector of the PNP transistor Q1; pin 1 of the resistor R3 and the positive electrode of the Schottky diode ZV1 are all connected to pin 2 of the resistor R4; the negative electrode of the diode D1, pin 1 of the resistor R2 and pin 1 of the capacitor C1 are all connected to the negative electrode of the Schottky diode ZV1; pin 1 of the resistor R1 is connected to the positive electrode of the diode D1; the transformer N2 winding is connected to the FLYBACK circuit.

2. The overvoltage protection circuit for a flyback switching power supply according to claim 1, characterized in that: The FLYBACK circuit includes a winding N1, a transformer N2 winding and a winding N5; The winding N1 includes a MOS tube Q3; the pin 1 of the winding N1 is connected to B+, and the pin 2 of the winding N1 is connected to the drain of the MOS tube Q3; the gate of the MOS tube Q3 is connected to PWM, and the source of the MOS tube Q3 is grounded; The winding N5 includes a Schottky diode D2, a polar electrolytic capacitor EC1, an optocoupler sensor U2, a resistor R9, a resistor R10, a resistor R11, a capacitor C4 and a thyristor U3; pin 5 of the winding N5 is connected to the positive electrode of the Schottky diode D2, and pin 5 of the winding N5 is connected to the negative electrode of the polar electrolytic capacitor EC1 and then grounded; the negative electrode of the Schottky diode D2, the positive electrode of the polar electrolytic capacitor EC1 and pin 1 of the resistor R10 are all connected to pin 1 of the resistor R9, and pin 2 of the resistor R9 is connected to pin 1 of the optocoupler sensor; pin 1 of the capacitor C4, pin 1 of the thyristor U3 and pin 1 of the resistor R11 are all connected to pin 2 of the resistor R10; pin 2 of the optocoupler sensor and pin 2 of the thyristor U3 are all connected to pin 2 of the capacitor C4; pin 3 of the thyristor U3 is connected to pin 2 of the resistor R11 and then grounded.

Images