High-voltage isolation detection overvoltage protection circuit

Abstract

The utility model relates to a high-voltage isolation detection overvoltage protection circuit, which comprises a linear voltage stabilizing circuit with an input end connected with a high-voltage power supply; the transformer comprises a primary winding, an auxiliary winding, a first secondary winding and a second secondary winding, the primary winding is connected with the high-voltage power supply, and the auxiliary winding is connected with the output end of the linear voltage stabilizing circuit; one input end of the input voltage detection circuit is connected with the second secondary winding, and the other input end is connected with the input voltage provided by the high-voltage power supply; one input end of the comparison circuit is connected with the first secondary winding, and the other input end is connected with the output end of the input voltage detection circuit; the input end of the isolation overvoltage protection circuit is connected with the output end of the comparison circuit; and the second switching circuit is connected in series with the high-voltage power supply and is connected with the output end of the linear voltage stabilizing circuit and the output end of the isolation overvoltage protection circuit. According to the utility model, the power supply voltage is subjected to multiple attenuation isolation detection through the transformer, and the overvoltage protection function is realized according to the voltage detected through isolation.

Description

Technical Field

[0001] The utility model relates to the field of power supply circuits, in particular to a high-voltage isolation detection overvoltage protection circuit. Background Art

[0002] The power supply system used in electronic equipment uses high-voltage direct current for power supply, and the output power is several kilowatts. The power supply system needs to detect the system's power supply voltage at all times and can play a protective role when the power supply voltage is too large, so as to ensure that the power supply system can run smoothly. The existing technology usually uses multiple resistors in series to divide the voltage to detect the power supply voltage of the power supply system. If the design scheme of using multiple resistors in series to divide the voltage to detect the power supply voltage of the power supply system is adopted, it is impossible to achieve isolated sampling and it is difficult to achieve the overvoltage protection function. Utility Model Content

[0003] The technical problem to be solved by the utility model is to provide a high-voltage isolation detection overvoltage protection circuit, which realizes the detection and protection functions of the power supply system by isolating and detecting the power supply voltage and comparing the detection voltage with the set overvoltage protection voltage.

[0004] The utility model solves the above technical problems with the following technical solutions: A high voltage isolation detection overvoltage protection circuit, comprising:

[0005] A linear voltage stabilizing circuit, the input end of which is connected to a high voltage power supply;

[0006] A transformer, comprising a primary winding, an auxiliary winding, a first secondary winding and a second secondary winding, wherein the primary winding is connected to the high voltage power supply, and the auxiliary winding is connected to the output end of the linear voltage stabilization circuit;

[0007] A first switch circuit is connected in series with the primary winding;

[0008] An isolation feedback circuit, an input end of which is connected to the first secondary winding;

[0009] A PWM chip, whose input end is connected to the output end of the isolation feedback circuit, and whose output end is connected to the first switch circuit;

[0010] An input voltage detection circuit is provided with two input terminals, one of which is connected to the second secondary winding, and the other is connected to the input voltage provided by the high voltage power supply;

[0011] A comparison circuit having two input terminals, one of which is connected to the first secondary winding, and the other is connected to the output terminal of the input voltage detection circuit;

[0012] An isolated overvoltage protection circuit, the input end of which is connected to the output end of the comparison circuit;

[0013] The second switch circuit is connected in series with the high-voltage power supply and is connected to the output end of the linear voltage stabilization circuit and the output end of the isolation overvoltage protection circuit.

[0014] On the basis of the above technical solution, the present invention can also be improved as follows.

[0015] Further, the primary winding and the first secondary winding form a flyback working mode, the primary winding and the second secondary winding form a forward working mode, and the auxiliary winding and the first secondary winding have the same end.

[0016] Furthermore, the linear voltage stabilization circuit comprises:

[0017] A first capacitor, one end of which is the input end of the linear voltage stabilization circuit and connected to the high voltage power supply, and the other end of which is grounded;

[0018] A second capacitor, one end of which is grounded;

[0019] A third capacitor, one end of which is grounded;

[0020] a voltage stabilizing diode, with a positive electrode being grounded and a negative electrode being connected to the other end of the third capacitor;

[0021] A first resistor, one end of which is connected to the high voltage power supply;

[0022] A second resistor, one end of which is connected to the high voltage power supply, and the other end of which is connected to the cathode of the voltage stabilizing diode;

[0023] A first switch tube, a gate of which is connected to the cathode of the voltage stabilizing diode, and a drain of which is connected to the other end of the first resistor;

[0024] The first diode has an anode connected to the source of the first switch tube and a cathode connected to the other end of the second capacitor, and serves as the output end of the linear voltage stabilization circuit.

[0025] Further, the first switch circuit comprises:

[0026] A second switch tube, whose source and drain are connected in series between the primary winding and the ground, and whose gate is connected to the output end of the PWM chip;

[0027] A third resistor has one end connected to the gate of the second switch tube and the other end grounded.

[0028] Further, the isolation feedback circuit includes:

[0029] A first optocoupler, wherein the positive electrode of the light-emitting end is the input end of the isolation feedback circuit and is connected to the first secondary winding, the emitter of the light-receiving end is grounded, and the collector of the light-receiving end is the output end of the isolation feedback circuit and is connected to the input end of the PWM chip;

[0030] a fourth resistor, connected between the positive electrode of the light-emitting end and the negative electrode of the light-emitting end of the first optical coupler;

[0031] a fifth resistor, one end of which is connected to the positive electrode of the light-emitting end of the first optical coupler;

[0032] a sixth resistor, one end of which is connected to the negative electrode of the light-emitting end of the first optical coupler;

[0033] a seventh resistor, one end of which is connected to the other end of the fifth resistor, and the other end of which is connected to the isolation ground;

[0034] an eighth resistor, one end of which is connected to the other end of the sixth resistor;

[0035] a fourth capacitor, one end of which is connected to the other end of the eighth resistor, and the other end of which is connected to the other end of the fifth resistor;

[0036] A bidirectional thyristor, wherein the negative electrode is connected to the other end of the sixth resistor, the positive electrode is connected to the isolation ground, and the control electrode is connected to the other end of the fifth resistor;

[0037] a fifth capacitor, one end of which is connected to the light receiving end collector of the first optical coupler;

[0038] A ninth resistor has one end connected to the other end of the fifth capacitor and the other end grounded.

[0039] Furthermore, the input voltage detection circuit comprises:

[0040] A second diode, an anode of which is an input terminal of the input voltage detection circuit and is connected to the second secondary winding;

[0041] a tenth resistor, one end of which is connected to the cathode of the second diode;

[0042] a sixth capacitor, one end of which is connected to the other end of the tenth resistor, and the other end of which is connected to the isolation ground;

[0043] an eleventh resistor, one end of which is another input end of the input voltage detection circuit and is connected to the other end of the tenth resistor;

[0044] The twelfth resistor has one end which is the output end of the input voltage detection circuit and is connected to the other end of the eleventh resistor, and the other end which is connected to the isolation ground.

[0045] Further, the comparison circuit comprises:

[0046] A comparator, wherein the positive terminal of the power supply is connected to the first secondary winding, the negative terminal of the power supply is connected to the isolation ground, and the output terminal is the output terminal of the comparison circuit;

[0047] a thirteenth resistor, one end of which is an input end of the comparison circuit and connected to the first secondary winding, and the other end of which is connected to the negative input end of the comparator;

[0048] a fourteenth resistor, one end of which is connected to the other end of the thirteenth resistor, and the other end of which is connected to the isolation ground;

[0049] a seventh capacitor connected in parallel with the fourteenth resistor;

[0050] A fifteenth resistor, one end of which is the other input end of the comparison circuit and connected to the output end of the input voltage detection circuit, and the other end of which is connected to the positive input end of the comparator;

[0051] A sixteenth resistor, one end of which is connected to the other end of the fifteenth resistor, and the other end of which is connected to the isolation ground;

[0052] an eighth capacitor connected in parallel with the sixteenth resistor;

[0053] A seventeenth resistor is connected between the positive input terminal and the output terminal of the comparator;

[0054] An eighteenth resistor has one end connected to the output end of the comparator and the other end connected to the isolation ground.

[0055] Furthermore, the isolation overvoltage protection circuit is provided with two power supply terminals, one of which is connected to the first secondary winding, and the other is connected to the output terminal of the linear voltage regulator circuit; the isolation overvoltage protection circuit comprises:

[0056] A nineteenth resistor, one end of which is a power supply end of the isolated overvoltage protection circuit and is connected to the first secondary winding;

[0057] A second optical coupler, wherein the positive electrode of the light-emitting end is connected to the other end of the nineteenth resistor, and the emitter of the light-receiving end is grounded;

[0058] A third switch tube, the gate of which is the input end of the isolated overvoltage protection circuit and connected to the output end of the comparison circuit, the drain of which is connected to the negative electrode of the light-emitting end of the second optical coupler, and the source of which is connected to the isolation ground;

[0059] A twentieth resistor, one end of which is another power supply end of the isolated overvoltage protection circuit and connected to the output end of the linear voltage regulator circuit, and the other end of which is connected to the light receiving end collector of the second optical coupler;

[0060] A twenty-first resistor is connected between the light receiving end collector and the light receiving end emitter of the second optical coupler;

[0061] A twenty-second resistor, one end of which is connected to one end of the twenty-second resistor;

[0062] A fourth switch tube, having a drain connected to the other end of the twenty-second resistor, a gate connected to the light-receiving end collector of the second optical coupler, and a source grounded;

[0063] A twenty-third resistor is connected between the source and the drain of the fourth switch tube;

[0064] A fifth switch tube, having a gate connected to the drain of the fourth switch tube, a source grounded, and a drain as the output end of the isolation overvoltage protection circuit and connected to the second switch circuit.

[0065] Further, the second switch circuit comprises:

[0066] A twenty-fourth resistor, one end of which is connected to the output end of the linear voltage stabilization circuit, and the other end of which is connected to the output end of the isolation overvoltage protection circuit;

[0067] A twenty-fifth resistor, one end of which is connected to the other end of the twenty-fourth resistor and the other end of which is grounded;

[0068] a sixth switch tube, the gate of which is connected between the twenty-fourth resistor and the twenty-fifth resistor, and the source and the drain of which are connected in series to the high-voltage power supply;

[0069] The twenty-sixth resistor is connected between the gate and the source of the sixth switch tube.

[0070] Furthermore, the first secondary winding is provided with a first rectifying and filtering circuit, and the first rectifying and filtering circuit comprises:

[0071] a third diode, the anode of which is connected to the first secondary winding;

[0072] a ninth capacitor, one end of which is connected to the cathode of the third diode and the other end of which is grounded;

[0073] The auxiliary winding is provided with a second rectifying and filtering circuit, and the second rectifying and filtering circuit comprises:

[0074] a fourth diode, a cathode connected to the output end of the linear voltage stabilizing circuit, and a positive electrode connected to the auxiliary winding;

[0075] A tenth capacitor has one end connected to the cathode of the fourth diode and the other end grounded.

[0076] The beneficial effects of the utility model are as follows: the utility model is a high-voltage isolation detection overvoltage protection circuit, which performs isolation detection on the power supply voltage with multiple attenuation through a transformer, and realizes the detection and protection function of the power supply system by comparing the detection voltage with the set overvoltage protection voltage, and realizes the overvoltage protection function of the voltage detected according to the isolation. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] Figure 1 This is a structural block diagram of a high voltage isolation detection overvoltage protection circuit of the utility model;

[0078] Figure 2 The utility model is a schematic diagram of a high-voltage isolation detection overvoltage protection circuit. DETAILED DESCRIPTION

[0079] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0080] like Figure 1 As shown, a high voltage isolation detection overvoltage protection circuit comprises:

[0081] A linear voltage stabilizing circuit 1, wherein the input end is connected to a high voltage power supply;

[0082] A transformer, comprising a primary winding NP1, an auxiliary winding NP2, a first secondary winding NS1 and a second secondary winding NS2, wherein the primary winding NP1 is connected to the high voltage power supply, and the auxiliary winding NP2 is connected to the output end of the linear voltage regulator circuit 1;

[0083] A first switch circuit 2, connected in series with the primary winding NP1;

[0084] An isolated feedback circuit 3, an input end of which is connected to the first secondary winding NS1;

[0085] A PWM chip, whose input end is connected to the output end of the isolation feedback circuit 3, and whose output end is connected to the first switch circuit 2;

[0086] An input voltage detection circuit 4 is provided with two input terminals, one of which is connected to the second secondary winding NS2, and the other is connected to the input voltage provided by the high voltage power supply;

[0087] The comparison circuit 5 is provided with two input terminals, one of which is connected to the first secondary winding NS1, and the other is connected to the output terminal of the input voltage detection circuit 4;

[0088] An isolated overvoltage protection circuit 6, whose input end is connected to the output end of the comparison circuit 5;

[0089] The second switch circuit 7 is connected in series with the high-voltage power supply, and is connected to the output end of the linear voltage regulator circuit 1 and the output end of the isolation overvoltage protection circuit 6 .

[0090] Specifically, the primary winding NP1 and the first secondary winding NS1 form a flyback working mode, the primary winding NP1 and the second secondary winding NS2 form a forward working mode, and the auxiliary winding NP2 and the first secondary winding NS1 have the same end.

[0091] The voltage UP1 across the primary winding NP1 and the voltage US1 across the first secondary winding NS1 are in a turns ratio relationship, that is, NPS*US1=NS1*UP1.

[0092] In this specific embodiment, Figure 2 As shown, the linear voltage stabilizing circuit 1 comprises:

[0093] A first capacitor C1, one end of which is the input end of the linear voltage regulator circuit 1 and connected to the high voltage power supply, and the other end of which is grounded;

[0094] A second capacitor C2, one end of which is grounded;

[0095] A third capacitor C3, one end of which is grounded;

[0096] A voltage stabilizing diode Z, with a positive electrode being grounded and a negative electrode being connected to the other end of the third capacitor C3;

[0097] A first resistor R1, one end of which is connected to the high voltage power supply;

[0098] A second resistor R2, one end of which is connected to the high voltage power supply, and the other end of which is connected to the cathode of the voltage stabilizing diode;

[0099] A first switch tube Q1, a gate of which is connected to the cathode of the voltage stabilizing diode, and a drain of which is connected to the other end of the first resistor R1;

[0100] The first diode D1 has an anode connected to the source of the first switch tube Q1 and a cathode connected to the other end of the second capacitor C2 and serves as an output end of the linear voltage regulator circuit 1 .

[0101] The linear voltage regulator circuit 1 is used to convert the input voltage provided by the high voltage power supply into a low voltage V1, and the low voltage V1 is mainly determined by the voltage regulator tube Z and the first diode D1. Figure 2 As shown, the first switch circuit 2 includes:

[0102] A second switch tube Q2, whose source and drain are connected in series between the primary winding NP1 and the ground, and whose gate is connected to the output end of the PWM chip;

[0103] The third resistor R3 has one end connected to the gate of the second switch tube Q2 and the other end grounded.

[0104] PWM chip( Figure 1 and Figure 2 The device (not shown) provides a PWM signal to drive the second switch tube Q2 to turn off.

[0105] In this specific embodiment, Figure 2 As shown, the first secondary winding NS1 is provided with a first rectifying and filtering circuit 8, and the first rectifying and filtering circuit 8 includes:

[0106] A third diode D3, an anode of which is connected to the first secondary winding NS1;

[0107] a ninth capacitor C9, one end of which is connected to the cathode of the third diode D3, and the other end of which is grounded;

[0108] The auxiliary winding NP2 is provided with a second rectifying and filtering circuit 9, and the second rectifying and filtering circuit 9 includes:

[0109] A fourth diode D4, a cathode of which is connected to the output end of the linear voltage regulator circuit 1, and a positive electrode of which is connected to the auxiliary winding NP2;

[0110] The tenth capacitor C10 has one end connected to the cathode of the fourth diode D4 and the other end grounded.

[0111] In this specific embodiment, Figure 2 As shown, the isolated feedback circuit 3 includes:

[0112] A first optical coupler OT1, wherein the positive electrode of the light-emitting end is the input end of the isolation feedback circuit 3 and is connected to the first secondary winding NS1, the emitter of the light-receiving end is grounded, and the collector of the light-receiving end is the output end of the isolation feedback circuit 3 and is connected to the input end of the PWM chip;

[0113] A fourth resistor R4 is connected between the positive electrode of the light emitting end and the negative electrode of the light emitting end of the first optical coupler OT1;

[0114] A fifth resistor R5, one end of which is connected to the positive electrode of the light-emitting end of the first optical coupler OT1;

[0115] A sixth resistor R6, one end of which is connected to the negative electrode of the light-emitting end of the first optical coupler OT1;

[0116] a seventh resistor R7, one end of which is connected to the other end of the fifth resistor R5, and the other end of which is connected to the isolation ground;

[0117] an eighth resistor R8, one end of which is connected to the other end of the sixth resistor R6;

[0118] a fourth capacitor C4, one end of which is connected to the other end of the eighth resistor R8, and the other end of which is connected to the other end of the fifth resistor R5;

[0119] A bidirectional thyristor U1, with a negative electrode connected to the other end of the sixth resistor R6, a positive electrode connected to the isolation ground, and a control electrode connected to the other end of the fifth resistor R5;

[0120] A fifth capacitor C5, one end of which is connected to the light receiving end collector of the first optical coupler OT1;

[0121] A ninth resistor R9 has one end connected to the other end of the fifth capacitor C5 and the other end grounded.

[0122] The isolated feedback circuit 3 generates a feedback voltage according to the output of the first secondary winding NS1. The PWM chip adjusts the duty cycle of the PWM signal according to the feedback voltage connected to the COMP pin to step down the supply voltage and output a stable voltage V2. The voltage V2 is determined by the reference voltage provided by the bidirectional thyristor U1 and the fifth resistor R5 and the seventh resistor R7.

[0123] In this specific embodiment, Figure 2 As shown, the input voltage detection circuit 4 includes:

[0124] A second diode D2, an anode of which is an input terminal of the input voltage detection circuit 4 and connected to the second secondary winding NS2;

[0125] a tenth resistor R10, one end of which is connected to the cathode of the second diode D2;

[0126] A sixth capacitor C6, one end of which is connected to the other end of the tenth resistor R10, and the other end of which is connected to the isolation ground;

[0127] an eleventh resistor R11, one end of which is another input end of the input voltage detection circuit 4 and is connected to the other end of the tenth resistor R10;

[0128] The twelfth resistor R12 has one end which is the output end of the input voltage detection circuit 4 and is connected to the other end of the eleventh resistor R11 , and the other end which is connected to the isolation ground.

[0129] The second secondary winding NS2 obtains a DC voltage after rectification and filtering by the second diode D2, the tenth resistor R10 and the sixth capacitor C6. The DC voltage increases with the increase of the input voltage and the duty cycle of the PWM signal. As the input voltage increases, the product of the input voltage and the PWM duty cycle also increases, thereby causing the voltage of the second secondary winding NS2 to increase after rectification and filtering. Therefore, the voltage of the second secondary winding NS2 after rectification and filtering is positively correlated with the input voltage.

[0130] In this specific embodiment, Figure 2 As shown, the comparison circuit 5 comprises:

[0131] The comparator U2 has a positive power supply terminal connected to the first secondary winding NS1, a negative power supply terminal connected to the isolation ground, and an output terminal that is the output terminal of the comparison circuit 5;

[0132] A thirteenth resistor R13, one end of which is an input end of the comparison circuit 5 and connected to the first secondary winding NS1, and the other end of which is connected to the negative input end of the comparator;

[0133] A fourteenth resistor R14, one end of which is connected to the other end of the thirteenth resistor R13, and the other end of which is connected to the isolation ground;

[0134] a seventh capacitor C7 connected in parallel with the fourteenth resistor R14;

[0135] A fifteenth resistor R15, one end of which is the other input end of the comparison circuit 5 and connected to the output end of the input voltage detection circuit 4, and the other end of which is connected to the positive input end of the comparator;

[0136] A sixteenth resistor R16, one end of which is connected to the other end of the fifteenth resistor R15, and the other end of which is connected to the isolation ground;

[0137] an eighth capacitor C8 connected in parallel with the sixteenth resistor R16;

[0138] A seventeenth resistor R17, connected between the positive input terminal and the output terminal of the comparator;

[0139] An eighteenth resistor R18 has one end connected to the output end of the comparator and the other end connected to the isolation ground.

[0140] The voltage of the second secondary winding NS2 after rectification and filtering through the second diode D2, the tenth resistor R10 and the sixth capacitor C6 is divided by the eleventh resistor R11 and the twelfth resistor R12 to obtain a voltage V3. The voltage V3 is divided by the fifteenth resistor R15 and the sixteenth resistor R16 to provide a voltage V4 for the comparator U2. The voltage V2 of the first secondary winding NS1 after rectification and filtering through the third diode D3 and the ninth capacitor C9 is used to power the comparator U2, and is divided by the thirteenth resistor R13 and the fourteenth resistor R14 to provide a voltage V5 for the comparator U2. The comparator U2 determines whether to turn on or off the third switch tube Q3 by comparing the voltages V4 and V5.

[0141] In this specific embodiment, Figure 2 As shown, the isolated overvoltage protection circuit 6 is provided with two power supply terminals, one of which is connected to the first secondary winding NS1, and the other is connected to the output terminal of the linear voltage regulator circuit 1; the isolated overvoltage protection circuit 6 includes:

[0142] A nineteenth resistor R19, one end of which is a power supply end of the isolation overvoltage protection circuit 6 and is connected to the first secondary winding NS1;

[0143] A second optical coupler OT2, the positive electrode of the light-emitting end is connected to the other end of the nineteenth resistor R19, and the emitter of the light-receiving end is grounded;

[0144] The third switch tube Q3 has a gate connected to the input end of the isolated overvoltage protection circuit 6 and the output end of the comparison circuit 5, a drain connected to the negative electrode of the light-emitting end of the second optical coupler OT2, and a source connected to the isolation ground;

[0145] A twentieth resistor R20, one end of which is another power supply end of the isolation overvoltage protection circuit 6 and is connected to the output end of the linear voltage regulator circuit 1, and the other end of which is connected to the light receiving end collector of the second optical coupler OT2;

[0146] A twenty-first resistor R21 is connected between the light receiving end collector and the light receiving end emitter of the second optical coupler OT2;

[0147] A twenty-second resistor R22, one end of which is connected to one end of the twenty-second resistor R20;

[0148] A fourth switch tube Q4, a drain connected to the other end of the 22nd resistor R22, a gate connected to the light receiving end collector of the second optical coupler OT2, and a source grounded;

[0149] A twenty-third resistor R23 is connected between the source and the drain of the fourth switch tube Q4;

[0150] The fifth switch tube Q5 has a gate connected to the drain of the fourth switch tube Q4 , a source grounded, and a drain as the output end of the isolation overvoltage protection circuit 6 and connected to the second switch circuit 7 .

[0151] In this specific embodiment, Figure 2 As shown, the second switch circuit 7 includes:

[0152] A twenty-fourth resistor R24, one end of which is connected to the output end of the linear voltage stabilizing circuit 1, and the other end of which is connected to the output end of the isolation overvoltage protection circuit 6;

[0153] A twenty-fifth resistor R25, one end of which is connected to the other end of the twenty-fourth resistor R24, and the other end of which is grounded;

[0154] a sixth switch tube Q6, having a gate connected between the twenty-fourth resistor R24 ​​and the twenty-fifth resistor R25, and a source and a drain connected in series to the high voltage power supply;

[0155] The twenty-sixth resistor R26 is connected between the gate and the source of the sixth switch tube Q6.

[0156] The working principle of the utility model is as follows:

[0157] When the high-voltage isolation detection overvoltage protection circuit detects the input voltage normally, the voltage obtained after the input voltage passes through the linear voltage regulator circuit 1 and the auxiliary winding NP2 is divided on the twenty-fourth resistor R24 ​​and the twenty-fifth resistor R25 to turn on the sixth switch tube Q6; at the same time, the first secondary winding NS1 obtains a stable output voltage through rectification and filtering to power the comparator U2, and the second secondary winding NS2 obtains the detection voltage through rectification and filtering. Since the voltage V4 obtained by the detection voltage after voltage division is lower than the voltage V5, the comparator U2 outputs a low level, the third switch tube Q3 is turned on, and the second optical coupler OT2 does not work, thereby causing the fourth switch tube Q4 to be turned on and the fifth switch tube Q5 to be turned off, thereby ensuring that the sixth switch tube Q6 is in the on state and the high-voltage direct path is connected.

[0158] When the high-voltage isolation detection overvoltage protection circuit triggers the overvoltage protection, due to the relatively large input voltage, the voltage detected after rectification and filtering of the second secondary winding NS2 also increases, thereby causing the voltage V4 between the fifteenth resistor R15 and the sixteenth resistor R16 to increase, but the voltage U2 after rectification and filtering of the first secondary winding NS1 remains unchanged, which means that the voltage V5 between the thirteenth resistor R13 and the fourteenth resistor R14 remains unchanged. When the voltage V4 is greater than the voltage V5, the comparator U2 outputs a high level, causing the third switch tube Q3 to turn on, and current flows through the light-emitting end of the second optical coupler OT2, causing the voltage at the light-receiving end of the second optical coupler OT2 to drop, so that the fourth switch tube Q4 is turned off. When the fourth switch tube Q4 is turned off, the voltage between the twenty-second resistor R22 and the twenty-third resistor R23 is at a high level, thereby driving the fifth switch tube Q5 to turn on, thereby making the voltage between the twenty-fourth resistor R24 ​​and the twenty-fifth resistor R25 at a low level, causing the sixth switch tube Q6 to turn off, thereby disconnecting the high-voltage direct path.

[0159] The utility model discloses a high-voltage isolation detection overvoltage protection circuit, which performs isolation detection of multiple attenuation of the power supply voltage through a transformer, realizes the detection and protection functions of the power supply system by comparing the detection voltage with the set overvoltage protection voltage, and realizes the overvoltage protection function of the voltage detected according to the isolation.

[0160] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high voltage isolation detection overvoltage protection circuit, characterized in that: include: A linear voltage stabilizing circuit, the input end of which is connected to a high voltage power supply; A transformer, comprising a primary winding, an auxiliary winding, a first secondary winding and a second secondary winding, wherein the primary winding is connected to the high voltage power supply, and the auxiliary winding is connected to the output end of the linear voltage stabilization circuit; A first switch circuit is connected in series with the primary winding; An isolation feedback circuit, an input end of which is connected to the first secondary winding; A PWM chip, whose input end is connected to the output end of the isolation feedback circuit, and whose output end is connected to the first switch circuit; An input voltage detection circuit is provided with two input terminals, one of which is connected to the second secondary winding, and the other is connected to the input voltage provided by the high voltage power supply; A comparison circuit having two input terminals, one of which is connected to the first secondary winding, and the other is connected to the output terminal of the input voltage detection circuit; An isolated overvoltage protection circuit, the input end of which is connected to the output end of the comparison circuit; The second switch circuit is connected in series with the high-voltage power supply and is connected to the output end of the linear voltage stabilization circuit and the output end of the isolation overvoltage protection circuit.

2. The high voltage isolation detection overvoltage protection circuit according to claim 1, characterized in that: The primary winding and the first secondary winding form a flyback working mode, the primary winding and the second secondary winding form a forward working mode, and the auxiliary winding and the first secondary winding have the same end.

3. The high voltage isolation detection overvoltage protection circuit according to claim 1, characterized in that: The linear voltage stabilization circuit comprises: A first capacitor, one end of which is the input end of the linear voltage stabilization circuit and connected to the high voltage power supply, and the other end of which is grounded; A second capacitor, one end of which is grounded; A third capacitor, one end of which is grounded; a voltage stabilizing diode, with a positive electrode being grounded and a negative electrode being connected to the other end of the third capacitor; A first resistor, one end of which is connected to the high voltage power supply; A second resistor, one end of which is connected to the high voltage power supply, and the other end of which is connected to the cathode of the voltage stabilizing diode; A first switch tube, a gate of which is connected to the cathode of the voltage stabilizing diode, and a drain of which is connected to the other end of the first resistor; The first diode has an anode connected to the source of the first switch tube and a cathode connected to the other end of the second capacitor, and serves as the output end of the linear voltage stabilization circuit.

4. The high voltage isolation detection overvoltage protection circuit according to claim 1, characterized in that: The first switch circuit comprises: A second switch tube, whose source and drain are connected in series between the primary winding and the ground, and whose gate is connected to the output end of the PWM chip; A third resistor has one end connected to the gate of the second switch tube and the other end grounded.

5. The high voltage isolation detection overvoltage protection circuit according to claim 1, characterized in that: The isolated feedback circuit comprises: A first optocoupler, wherein the positive electrode of the light-emitting end is the input end of the isolation feedback circuit and is connected to the first secondary winding, the emitter of the light-receiving end is grounded, and the collector of the light-receiving end is the output end of the isolation feedback circuit and is connected to the input end of the PWM chip; a fourth resistor, connected between the positive electrode of the light-emitting end and the negative electrode of the light-emitting end of the first optical coupler; a fifth resistor, one end of which is connected to the positive electrode of the light-emitting end of the first optical coupler; a sixth resistor, one end of which is connected to the negative electrode of the light-emitting end of the first optical coupler; a seventh resistor, one end of which is connected to the other end of the fifth resistor, and the other end of which is connected to the isolation ground; an eighth resistor, one end of which is connected to the other end of the sixth resistor; a fourth capacitor, one end of which is connected to the other end of the eighth resistor, and the other end of which is connected to the other end of the fifth resistor; A bidirectional thyristor, wherein the negative electrode is connected to the other end of the sixth resistor, the positive electrode is connected to the isolation ground, and the control electrode is connected to the other end of the fifth resistor; a fifth capacitor, one end of which is connected to the light receiving end collector of the first optical coupler; A ninth resistor has one end connected to the other end of the fifth capacitor and the other end grounded.

6. The high voltage isolation detection overvoltage protection circuit according to claim 1, characterized in that: The input voltage detection circuit comprises: A second diode, an anode of which is an input terminal of the input voltage detection circuit and is connected to the second secondary winding; a tenth resistor, one end of which is connected to the cathode of the second diode; a sixth capacitor, one end of which is connected to the other end of the tenth resistor, and the other end of which is connected to the isolation ground; an eleventh resistor, one end of which is another input end of the input voltage detection circuit and is connected to the other end of the tenth resistor; The twelfth resistor has one end which is the output end of the input voltage detection circuit and is connected to the other end of the eleventh resistor, and the other end which is connected to the isolation ground.

7. The high voltage isolation detection overvoltage protection circuit according to claim 1, characterized in that: The comparison circuit comprises: A comparator, wherein the positive terminal of the power supply is connected to the first secondary winding, the negative terminal of the power supply is connected to the isolation ground, and the output terminal is the output terminal of the comparison circuit; a thirteenth resistor, one end of which is an input end of the comparison circuit and connected to the first secondary winding, and the other end of which is connected to the negative input end of the comparator; a fourteenth resistor, one end of which is connected to the other end of the thirteenth resistor, and the other end of which is connected to the isolation ground; a seventh capacitor connected in parallel with the fourteenth resistor; A fifteenth resistor, one end of which is the other input end of the comparison circuit and connected to the output end of the input voltage detection circuit, and the other end of which is connected to the positive input end of the comparator; A sixteenth resistor, one end of which is connected to the other end of the fifteenth resistor, and the other end of which is connected to the isolation ground; an eighth capacitor connected in parallel with the sixteenth resistor; A seventeenth resistor is connected between the positive input terminal and the output terminal of the comparator; An eighteenth resistor has one end connected to the output end of the comparator and the other end connected to the isolation ground.

8. The high voltage isolation detection overvoltage protection circuit according to claim 1, characterized in that: The isolated overvoltage protection circuit is provided with two power supply terminals, one of which is connected to the first secondary winding, and the other is connected to the output terminal of the linear voltage stabilization circuit; The isolated overvoltage protection circuit comprises: A nineteenth resistor, one end of which is a power supply end of the isolated overvoltage protection circuit and is connected to the first secondary winding; A second optical coupler, wherein the positive electrode of the light-emitting end is connected to the other end of the nineteenth resistor, and the emitter of the light-receiving end is grounded; A third switch tube, the gate of which is the input end of the isolated overvoltage protection circuit and connected to the output end of the comparison circuit, the drain of which is connected to the negative electrode of the light-emitting end of the second optical coupler, and the source of which is connected to the isolation ground; A twentieth resistor, one end of which is another power supply end of the isolated overvoltage protection circuit and connected to the output end of the linear voltage regulator circuit, and the other end of which is connected to the light receiving end collector of the second optical coupler; A twenty-first resistor is connected between the light receiving end collector and the light receiving end emitter of the second optical coupler; A twenty-second resistor, one end of which is connected to one end of the twenty-second resistor; A fourth switch tube, having a drain connected to the other end of the twenty-second resistor, a gate connected to the light-receiving end collector of the second optical coupler, and a source grounded; A twenty-third resistor is connected between the source and the drain of the fourth switch tube; A fifth switch tube, having a gate connected to the drain of the fourth switch tube, a source grounded, and a drain as the output end of the isolation overvoltage protection circuit and connected to the second switch circuit.

9. The high voltage isolation detection overvoltage protection circuit according to claim 1, characterized in that: The second switch circuit comprises: A twenty-fourth resistor, one end of which is connected to the output end of the linear voltage stabilization circuit, and the other end of which is connected to the output end of the isolation overvoltage protection circuit; A twenty-fifth resistor, one end of which is connected to the other end of the twenty-fourth resistor and the other end of which is grounded; a sixth switch tube, the gate of which is connected between the twenty-fourth resistor and the twenty-fifth resistor, and the source and the drain of which are connected in series to the high-voltage power supply; The twenty-sixth resistor is connected between the gate and the source of the sixth switch tube.

10. The high voltage isolation detection overvoltage protection circuit according to claim 1, characterized in that: The first secondary winding is provided with a first rectifying and filtering circuit, and the first rectifying and filtering circuit comprises: a third diode, the anode of which is connected to the first secondary winding; a ninth capacitor, one end of which is connected to the cathode of the third diode and the other end of which is grounded; The auxiliary winding is provided with a second rectifying and filtering circuit, and the second rectifying and filtering circuit comprises: a fourth diode, a cathode connected to the output end of the linear voltage stabilizing circuit, and a positive electrode connected to the auxiliary winding; A tenth capacitor has one end connected to the cathode of the fourth diode and the other end grounded.

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