Output discharge circuit suitable for wide-range direct-current output power supply

Abstract

The invention provides an output discharging circuit suitable for a wide-range direct-current output power supply, which is used for solving the technical problem that an output discharging circuit of an existing switching power supply is only suitable for a safe voltage power supply with the discharging voltage being lower than 30V and is not suitable for a high-voltage direct-current output power supply. According to the output discharging circuit suitable for the wide-range direct-current output power supply, a switching tube driving circuit is designed, and a plurality of voltage dividing resistors, a voltage dividing resistor R10 and a voltage stabilizing diode are arranged in the voltage dividing module; a power supply output voltage Vout is divided by a plurality of divider resistors and a divider resistor R10 to generate a driving voltage of a switching tube V1, when the driving voltage exceeds the voltage of a voltage stabilizing diode VD1, the driving voltage is clamped by the voltage stabilizing diode VD1, no matter how high the power supply output voltage Vout is, the driving voltage is always maintained at a set value, and the voltage stabilizing diode VD1 is switched on. Therefore, the voltage stress of each component in the drive circuit is ensured to be within a reasonable range, and the discharge circuit can be suitable for the discharge of a wide-range direct-current output power supply.

Description

Technical Field

[0001] The invention relates to an output discharge circuit of a DC output power supply, and in particular to an output discharge circuit suitable for a DC output power supply with a wide range. Background Art

[0002] At present, in order to meet the requirements of dynamic performance and ripple, the power module is often designed with a larger output capacitor. However, when the power module is repaired or replaced, the voltage on the output capacitor may cause electric shock to the operator. In order to solve this problem. The traditional operation is to discharge the output capacitor of the power module through an external discharge device, but this operation requires additional discharge equipment and operation steps, which is cumbersome and has the risk of omission. Therefore, it is necessary to design an autonomous discharge circuit for the power module. When the power supply is working, the discharge circuit does not work and does not affect the power supply efficiency. When the power supply is shut down, the discharge circuit starts to discharge the output capacitor, so that the output capacitor voltage drops quickly to a safe voltage.

[0003] The Chinese patent with publication number CN220368603U discloses Figure 1 The output discharge circuit of a switching power supply shown in the figure, however, since the maximum driving voltage of the electronic switch tube is ±30V, and the maximum voltage of the secondary side of the optocoupler is less than 100V, when the discharge voltage exceeds 30V, the gate of the electronic switch tube will be damaged by overvoltage, and the optocoupler will be damaged by overvoltage on the secondary side, making the discharge circuit ineffective. Therefore, the output discharge circuit of the switching power supply is only applicable to safe voltage power supplies with a discharge voltage below low voltage 30V. It is mainly used in auxiliary power supplies to solve the problem of asynchronous power-on and power-off timing of the control unit, and cannot be applied to the output discharge of high-voltage DC output power supplies. Summary of the invention

[0004] The purpose of the present invention is to provide an output discharge circuit suitable for a wide range of DC output power supplies to address the technical problem that the output discharge circuit of the existing switching power supply is only suitable for a safe voltage power supply with a discharge voltage below low voltage 30V, but cannot be used for a high voltage DC output power supply.

[0005] In order to achieve the above purpose, the technical solution provided by the present invention is as follows:

[0006] An output discharge circuit suitable for a wide range DC output power supply, which is special in that it includes an optocoupler drive circuit, an optocoupler isolation circuit, a switch tube drive circuit and a discharge circuit;

[0007] The optocoupler driving circuit is used to drive the optocoupler isolation circuit to be turned on and off according to the input signal CTR-IN; the input signal CTR-IN is a signal output by the system controller of the DC output power supply;

[0008] The optocoupler isolation circuit is an isolation optocoupler PHT1, the input cathode of the isolation optocoupler PHT1 is connected to the output end of the optocoupler drive circuit, the input anode is connected to the voltage source, and the output emitter is connected to the power supply output ground;

[0009] The switch tube driving circuit includes a voltage dividing module, a voltage dividing resistor R10, a voltage stabilizing diode VD1, a driving resistor R11 and a driving capacitor C1;

[0010] The discharge circuit includes a switch tube V1 and a plurality of discharge resistors connected in series;

[0011] The voltage divider module includes a plurality of voltage divider resistors connected in series, the other end of the first voltage divider resistor in the voltage divider module is connected to the DC-OUT end of the DC output power supply, and the other end of the last voltage divider resistor is connected to the output collector of the isolation optocoupler PHT1; one end of the voltage divider resistor R10 is connected to the other end of the last voltage divider resistor in the voltage divider module, and the other end thereof is connected to the power output ground; the positive electrode of the voltage zener diode VD1 is grounded, and the negative electrode is connected between the voltage divider resistor R10 and the voltage divider resistor R9; one end of the driving resistor R11 is connected to the negative electrode of the voltage zener diode VD1, and the other end is respectively connected to the gate of the switch tube V1 and one end of the driving capacitor C1, and the other end of the driving capacitor C1 is connected to the power output ground;

[0012] The other end of the first discharge resistor is connected to the DC-OUT terminal of the DC output power supply, the other end of the last discharge resistor is connected to the drain of the switch tube V1, and the source of the switch tube V1 is connected to the power output ground.

[0013] Further, the optical coupler driving circuit includes a comparator LM1A, a voltage dividing resistor R1, a voltage dividing resistor R4, a voltage dividing resistor R2, a voltage dividing resistor R3 and a resistor R5;

[0014] One end of the voltage-dividing resistor R1 is connected to the control ground GND, one end of the voltage-dividing resistor R4 is connected to the voltage source, and the other ends of the voltage-dividing resistor R1 and the voltage-dividing resistor R4 are both connected to the non-inverting input end of the comparator LM1A; one end of the voltage-dividing resistor R2 is connected to the input signal CTR-IN, one end of the voltage-dividing resistor R3 is connected to the control ground GND, and the other ends of the voltage-dividing resistor R2 and the voltage-dividing resistor R3 are both connected to the inverting input end of the comparator LM1A;

[0015] The output end of the comparator LM1A is connected to the negative input terminal of the isolation optical coupler PHT1.

[0016] Furthermore, the optical coupler driving circuit also includes a resistor R5;

[0017] The positive input electrode of the isolation optical coupler PHT1 is connected to a voltage source via a resistor R5.

[0018] Further, the voltage dividing module includes a voltage dividing resistor R6, a voltage dividing resistor R7, a voltage dividing resistor R8 and a voltage dividing resistor R9 which are sequentially connected in series;

[0019] The other end of the voltage-dividing resistor R6 is connected to the DC-OUT end of the DC output power supply, and the other end of the voltage-dividing resistor R9 is connected to the output collector of the isolation optical coupler PHT1.

[0020] Further, the number of the discharge resistors is four, including a discharge resistor R12, a discharge resistor R13, a discharge resistor R14 and a discharge resistor R15 connected in sequence;

[0021] The other end of the discharge resistor R12 is connected to the DC-OUT end of the DC output power supply, and the other end of the discharge resistor R15 is connected to the drain of the switch tube V1.

[0022] Furthermore, the voltage source is a +5V voltage source;

[0023] The resistance of the voltage divider resistor R1 is 10kΩ

[0024] The resistance of the voltage dividing resistor R4 is 20kΩ;

[0025] The resistance of the voltage dividing resistor R2 is 1 kΩ;

[0026] The resistance of the voltage dividing resistor R3 is 10 kΩ.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The present invention provides an output discharge circuit suitable for a wide range of DC output power supplies. The switch tube drive circuit is designed. Through the arrangement of multiple voltage-dividing resistors, the voltage-dividing resistor R10 and the voltage-stabilizing diode in the voltage-dividing module, the power supply output voltage Vout is divided by the multiple voltage-dividing resistors and the voltage-dividing resistor R10 to generate a driving voltage for the switch tube V1. When the driving voltage exceeds the voltage of the voltage-stabilizing diode VD1, it is clamped by the voltage-stabilizing diode VD1. No matter how high the power supply output voltage Vout is, the driving voltage is always maintained at the set value, thereby ensuring that the voltage stress of each component in the driving circuit is within a reasonable range, so that the discharge circuit can be suitable for the discharge of a wide range of DC output power supplies. At the same time, the present invention enables the power supply output to discharge quickly when the power is cut off, and has the advantages of low cost, simple control, high efficiency, etc.

[0029] 2. The input signal CTR-IN of the optocoupler driving circuit of the present invention is the signal output by the controller of the DC output power system, so that the output discharge circuit can meet the conventional requirements. The discharge circuit works after the power is cut off, so that the output voltage drops quickly to a safe voltage. At the same time, it can meet the requirement that when the control circuit is normal, whether the output discharge circuit works or not can be independently controlled. For example, when the DC output power is shut down but not cut off, the power output needs to be assembled and repaired, and the power output can be quickly discharged to a safe voltage by controlling the input signal CTR-IN. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A circuit topology diagram of an output discharge circuit of an existing switching power supply;

[0031] Figure 2 The circuit topology diagram of an output discharge circuit embodiment of the present invention is suitable for a wide range DC output power supply. DETAILED DESCRIPTION

[0032] In order to make the advantages and features of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] An output discharge circuit suitable for a wide range DC output power supply is used to discharge the output capacitor in the DC output power supply, such as Figure 2 As shown, it includes an optocoupler driving circuit, an optocoupler isolation circuit, a switch tube driving circuit and a discharge circuit.

[0034] The optocoupler driving circuit is used to drive the on and off of the optocoupler isolation circuit according to the input signal CTR-IN. In this embodiment, the optocoupler driving circuit includes a comparator LM1A, a voltage-dividing resistor R1, a voltage-dividing resistor R4, a voltage-dividing resistor R2 and a voltage-dividing resistor R3. One end of the voltage-dividing resistor R1 is connected to the control ground GND, one end of the voltage-dividing resistor R4 is connected to the +5V voltage source, and the other ends of the voltage-dividing resistor R1 and the voltage-dividing resistor R4 are both connected to the in-phase input end of the comparator LM1A; one end of the voltage-dividing resistor R2 is connected to the input signal CTR-IN, one end of the voltage-dividing resistor R3 is connected to the control ground GND, and the other ends of the voltage-dividing resistor R2 and the voltage-dividing resistor R3 are both connected to the inverting input end of the comparator LM1A. Among them, the input signal CTR-IN comes from the system controller of the DC output power supply. In this embodiment, the resistance value of the voltage-dividing resistor R1 is 10kΩ, the resistance value of the voltage-dividing resistor R4 is 20kΩ, the resistance value of the voltage-dividing resistor R2 is 1kΩ, and the resistance value of the voltage-dividing resistor R3 is 10kΩ.

[0035] The optocoupler isolation circuit is an isolated optocoupler PHT1, which is used to achieve isolation between power supply output and control. The output end of the comparator LM1A is connected to the negative input of the isolated optocoupler PHT1, and the positive input of the isolated optocoupler PHT1 is connected to the +5V voltage source through the resistor R5. The output collector of the isolated optocoupler PHT1 is connected to the input end of the switch tube drive circuit, and the output emitter of the isolated optocoupler PHT1 is connected to the power supply output ground.

[0036] The switch tube driving circuit includes a voltage-dividing resistor R6, a voltage-dividing resistor R7, a voltage-dividing resistor R8, a voltage-dividing resistor R9, a voltage-dividing resistor R10, a voltage-stabilizing diode VD1, a driving resistor R11 and a driving capacitor C1, and is used to generate a driving signal for the switch tube V1 according to the on-off of the isolation optocoupler PHT1. The discharge circuit includes a discharge resistor R12, a discharge resistor R13, a discharge resistor R14, a discharge resistor R15 and a switch tube V1, and is used to discharge the output of the DC output power supply through the discharge resistor by turning on the switch tube V1.

[0037] The voltage-dividing resistors R6, R7, R8 and R9 are connected in series in sequence, the other end of the voltage-dividing resistor R6 is connected to the DC-OUT end of the DC output power supply, the other end of the voltage-dividing resistor R9 is connected to the output collector of the isolation optocoupler PHT1, one end of the voltage-dividing resistor R10 is connected to the other end of the voltage-dividing resistor R9, and the other end is connected to the power output ground, which is used to divide the power output voltage Vout through the voltage-dividing resistors R6, R7, R8, R9 and R10. The positive electrode of the voltage-dividing diode VD1 is grounded, and the negative electrode is connected between the voltage-dividing resistor R10 and the voltage-dividing resistor R9, which is used to stabilize the voltage when the voltage across the voltage-dividing resistor R10 exceeds the set voltage, and control the conduction and cutoff of the switch tube V1 through the voltage across the voltage-dividing resistor R10; wherein the power output voltage Vout is the voltage at the DC output power supply DC-OUT end, that is, the discharge voltage. The driving resistor R11 and the driving capacitor C1 form an RC filter. Specifically, one end of the driving resistor R11 is connected to the cathode of the voltage-stabilizing diode VD1, and the other end is connected to the gate of the switch tube V1 in the discharge circuit and one end of the driving capacitor C1. The other end of the driving capacitor C1 is connected to the power output ground to prevent interference from causing malfunction of the switch tube V1.

[0038] The discharge resistor R12, the discharge resistor R13, the discharge resistor R14, and the discharge resistor R15 are connected in series in sequence, the other end of the discharge resistor R12 is connected to the DC-OUT end of the DC output power supply, the other end of the discharge resistor R15 is connected to the drain of the switch tube V1, and the source of the switch tube V1 is connected to the power output ground.

[0039] The parameter calculation of each device in the output discharge circuit of the present invention is described as follows:

[0040] The voltage level of the non-inverting input terminal of the comparator LM1A is: 5 / (R1+R4)R1=1.67V; the voltage level of the inverting input terminal of the comparator LM1A is: Vin / (R2+R3)R3, Vin is the voltage of the input terminal CTR-IN.

[0041] The isolation optocoupler PHT1 is selected according to the power safety regulations.

[0042] The value of the voltage regulator diode VD1 is related to the driving voltage of the switch tube V1, and the voltage regulator voltage is generally 15V.

[0043] The specific number of voltage divider resistors (voltage divider resistors R6, R7, R8, R9) in the switch tube drive circuit is related to the size of the power supply output voltage Vout and must meet safety regulations. The values ​​of voltage divider resistors R6, R7, R8, R9, and R10 are related to the current Id of the voltage zener diode VD1, the secondary current Ice of the isolation optocoupler PHT1, the final discharge voltage, and the driving threshold voltage Vth of the switch tube V1. The final discharge voltage is generally a safe voltage of 24V, and the relationship is as follows:

[0044]

[0045] The specific number of discharge resistors (discharge resistor R12, discharge resistor R13, discharge resistor R14, discharge resistor R15) in the discharge circuit is related to the size of the power supply output voltage Vout and must meet safety regulations. The resistance values ​​of discharge resistors R12, R13, R14, and R15 are related to the required discharge time t and the capacity C of the output capacitor in the DC output power supply. The specific relationship is as follows:

[0046] Vt=V0×e(-t / RC)

[0047] In the above formula, V0 is the capacitor voltage before discharge, Vt is the capacitor voltage during discharge, and R=R12+R13+R14+R15.

[0048] The circuit works as follows:

[0049] After the power supply is powered on, the power supply system controller outputs a 3.3V high-level input signal CTR-IN, which enters the inverting input terminal of the comparator LM1A after being divided by the voltage-dividing resistors R2 and R3. The level of the inverting input terminal of the comparator LM1A is 3V, which is greater than the level of the non-inverting input terminal of the comparator LM1A, 1.67V, and the output of the comparator LM1A is low. At this time, the primary side of the isolation optocoupler PHT1 is turned on, and then the secondary side is turned on, the voltage across the voltage-dividing resistor R10 is pulled to 0, the switch tube V1 is turned off, and the power supply does not discharge.

[0050] After the power supply is turned off, the power supply control voltage is 0, the control circuit does not work, the secondary side of the isolation optocoupler PHT1 is open, and the voltage across the voltage-dividing resistor R10 is determined by the voltage after the power supply output voltage Vout is divided by the voltage-dividing resistors R6 to R9 and the voltage-dividing resistor R10. When the voltage-dividing resistor R10 exceeds 15V, it is clamped to 15V by the voltage-dividing diode VD1, and the switch tube V1 is driven to conduct through the driving resistor R11 and the driving capacitor C1, so that the DC-OUT end of the DC output power supply is discharged through the discharge resistor R12 to R15. As the discharge time increases, the power supply output voltage Vout decreases, and accordingly, the voltage-dividing resistor R10 decreases. When the voltage-dividing resistor R10 is less than 15V, the voltage-dividing diode VD1 no longer works, and the voltage-dividing resistor R10 drives the switch tube V1 to conduct until the voltage-dividing resistor R10 is less than the threshold voltage Vth of the switch tube V1, and the switch tube V1 is no longer turned on, and the power supply is no longer discharged.

[0051] The above description is only used to illustrate the technical solution of the present invention rather than to limit it. For ordinary professional and technical personnel in the field, the specific technical solution recorded in the above embodiment can be modified, or some of the technical features therein can be replaced by equivalents, and these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solution protected by the present invention.

Claims

1. An output discharge circuit suitable for a wide range DC output power supply, characterized in that: It includes an optocoupler driving circuit, an optocoupler isolation circuit, a switch tube driving circuit and a discharge circuit; The optocoupler driving circuit is used to drive the optocoupler isolation circuit to be turned on and off according to the input signal CTR-IN; the input signal CTR-IN is a signal output by the system controller of the DC output power supply; The optocoupler isolation circuit is an isolation optocoupler PHT1, the input cathode of the isolation optocoupler PHT1 is connected to the output end of the optocoupler drive circuit, the input anode is connected to the voltage source, and the output emitter is connected to the power supply output ground; The switch tube driving circuit includes a voltage dividing module, a voltage dividing resistor R10, a voltage stabilizing diode VD1, a driving resistor R11 and a driving capacitor C1; The discharge circuit includes a switch tube V1 and a plurality of discharge resistors connected in series; The voltage divider module includes a plurality of voltage divider resistors connected in series, the other end of the first voltage divider resistor in the voltage divider module is connected to the DC-OUT end of the DC output power supply, and the other end of the last voltage divider resistor is connected to the output collector of the isolation optocoupler PHT1; one end of the voltage divider resistor R10 is connected to the other end of the last voltage divider resistor in the voltage divider module, and the other end thereof is connected to the power output ground; the positive electrode of the voltage zener diode VD1 is grounded, and the negative electrode is connected between the voltage divider resistor R10 and the voltage divider resistor R9; one end of the driving resistor R11 is connected to the negative electrode of the voltage zener diode VD1, and the other end is respectively connected to the gate of the switch tube V1 and one end of the driving capacitor C1, and the other end of the driving capacitor C1 is connected to the power output ground; The other end of the first discharge resistor is connected to the DC-OUT terminal of the DC output power supply, the other end of the last discharge resistor is connected to the drain of the switch tube V1, and the source of the switch tube V1 is connected to the power output ground.

2. The output discharge circuit suitable for a wide range DC output power supply according to claim 1, characterized in that: The optocoupler driving circuit includes a comparator LM1A, a voltage dividing resistor R1, a voltage dividing resistor R4, a voltage dividing resistor R2, a voltage dividing resistor R3 and a resistor R5; One end of the voltage-dividing resistor R1 is connected to the control ground GND, one end of the voltage-dividing resistor R4 is connected to the voltage source, and the other ends of the voltage-dividing resistor R1 and the voltage-dividing resistor R4 are both connected to the non-inverting input end of the comparator LM1A; one end of the voltage-dividing resistor R2 is connected to the input signal CTR-IN, one end of the voltage-dividing resistor R3 is connected to the control ground GND, and the other ends of the voltage-dividing resistor R2 and the voltage-dividing resistor R3 are both connected to the inverting input end of the comparator LM1A; The output end of the comparator LM1A is connected to the negative input terminal of the isolation optical coupler PHT1.

3. The output discharge circuit suitable for a wide range DC output power supply according to claim 2, characterized in that: The optical coupler driving circuit also includes a resistor R5; The positive input electrode of the isolation optical coupler PHT1 is connected to a voltage source via a resistor R5.

4. An output discharge circuit suitable for a wide range DC output power supply according to any one of claims 1 to 3, characterized in that: The voltage dividing module includes a voltage dividing resistor R6, a voltage dividing resistor R7, a voltage dividing resistor R8 and a voltage dividing resistor R9 connected in series in sequence; The other end of the voltage-dividing resistor R6 is connected to the DC-OUT end of the DC output power supply, and the other end of the voltage-dividing resistor R9 is connected to the output collector of the isolation optical coupler PHT1.

5. The output discharge circuit suitable for a wide range DC output power supply according to claim 4, characterized in that: There are four discharge resistors, including a discharge resistor R12, a discharge resistor R13, a discharge resistor R14 and a discharge resistor R15 connected in sequence; The other end of the discharge resistor R12 is connected to the DC-OUT end of the DC output power supply, and the other end of the discharge resistor R15 is connected to the drain of the switch tube V1.

6. The output discharge circuit suitable for a wide range DC output power supply according to claim 2, characterized in that: The voltage source is a +5V voltage source; The resistance of the voltage dividing resistor R1 is 10 kΩ; The resistance of the voltage dividing resistor R4 is 20kΩ; The resistance of the voltage dividing resistor R2 is 1 kΩ; The resistance of the voltage dividing resistor R3 is 10 kΩ.

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