Direct-current capacitor discharge control circuit of power module

Abstract

The utility model discloses a direct current capacitor discharge control circuit of a power module, which comprises a constant current discharge branch circuit which is connected in parallel at two ends of a capacitor C and is used for discharging the capacitor C, and a voltage stabilization source branch circuit which is used for providing stable voltage for the constant current discharge branch circuit and is provided with an optocoupler control branch circuit which is used for controlling the on-off of the constant current discharge branch circuit. The input end of the optocoupler control branch is connected with the output end of the power module CPU, one end of the output end of the optocoupler control branch is connected with the control end of the constant voltage source branch, the other end of the output end of the optocoupler control branch is connected with the negative electrode of the capacitor C, and the output end of the constant voltage source branch is connected with the controlled end of the constant current discharge branch. According to the utility model, the circuit is flexible and controllable, the discharge branch is switched on for discharging only when the balanced discharge needs to be started and the capacitor charge needs to be released after the equipment stops working, and the discharge branch is in an off state when the discharge is not needed, so that the circuit loss is extremely low, and the loss of the discharge circuit is greatly reduced.

Description

Technical Field

[0001] This utility model relates to the field of capacitor discharge technology, and more specifically to a DC capacitor discharge control circuit for a power module. Background Technology

[0002] With the rapid development of power electronics technology, SVG, energy storage devices and other related products have been widely used. The power module design is an important part of these products. Generally, a large-capacity capacitor is connected in parallel at the DC end of such power modules. When power is lost, a capacitor discharge circuit is designed to meet safety requirements. In the design of high-voltage cascaded SVG or energy storage PCS, there is also a requirement to control capacitor discharge in order to achieve voltage balance on the DC side of all power modules when the equipment is in standby mode.

[0003] Generally, a discharge resistor is connected directly in parallel with the DC capacitor of the power module to achieve the discharge function. In standby mode, the resistance value of the discharge resistor is changed by optocoupler control or the discharge circuit is directly controlled to achieve DC voltage balancing. When the power module is working, the connection of the discharge resistor will have a large loss and heat generation problem. Even if the discharge resistor is cut off during operation, the discharge circuit still has the problem of selecting the discharge resistor to consider the maximum discharge power. The resistor power is usually large. Utility Model Content

[0004] The technical problem to be solved by this utility model is to provide a power module DC capacitor discharge control circuit that is flexible and controllable, has low loss, and low discharge resistance power.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is as follows.

[0006] A power module DC capacitor discharge control circuit includes a constant current discharge branch connected in parallel across capacitor C for discharging capacitor C and a voltage regulator branch for providing a stable voltage to the constant current discharge branch. The voltage regulator branch is equipped with an optocoupler control branch for controlling the on / off state of the constant current discharge branch. The input terminal of the optocoupler control branch is connected to the output terminal of the power module CPU. One end of the output terminal of the optocoupler control branch is connected to the control terminal of the voltage regulator branch, and the other end of the output terminal of the optocoupler control branch is connected to the negative terminal of capacitor C. The output terminal of the voltage regulator branch is connected to the controlled terminal of the constant current discharge branch.

[0007] The technical solution is further optimized, and the constant current discharge branch includes discharge resistors R connected in series. L Transistor T and constant current control resistor R r Discharge resistor R L The constant current control resistor R is connected to the positive terminal of the capacitor. r The base of transistor T is connected to the negative terminal of capacitor C, the base of transistor T is connected to the output terminal of optocoupler control branch, and the emitter of transistor T is connected to the output terminal of voltage regulator branch.

[0008] The technical solution is further optimized by including a current-limiting resistor R connected in series in the voltage regulator branch. S The adjustable voltage regulator TL431 has its cathode K connected to the output terminal of the optocoupler control branch and the base of the transistor T in the constant current discharge branch. The reference terminal R of the adjustable voltage regulator TL431 is connected to the emitter of the transistor T in the constant current discharge circuit.

[0009] To further optimize the technical solution, the optocoupler control branch includes an optocoupler U. The input terminal K1 of the optocoupler U is connected to the output terminal of the power module CPU. One end of the output terminal of the optocoupler U is connected to the cathode K of the adjustable voltage regulator TL431 and the base of the transistor in the constant current discharge branch. The other end of the output terminal of the optocoupler U is connected to the negative terminal of the capacitor C.

[0010] Due to the adoption of the above technical solutions, the technological progress achieved by this utility model is as follows.

[0011] This utility model provides a DC capacitor discharge control circuit for a power module. The circuit is flexible and controllable. The discharge branch is connected only when equalization discharge is needed or when the capacitor charge needs to be released after the equipment stops working. When discharge is not needed, the discharge branch is in an open state. The circuit loss is minimal, which greatly reduces the loss of the discharge circuit. During discharge, it is a constant current discharge, which can effectively reduce the power selection of the discharge resistor and facilitate the calculation of discharge time. Attached Figure Description

[0012] Figure 1 This is the circuit diagram of this utility model. Detailed Implementation

[0013] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0014] A power module DC capacitor discharge control circuit, combined with Figure 1 The system includes a constant current discharge branch, a voltage regulator branch, and an optocoupler control branch. The constant current discharge circuit is connected in parallel across capacitor C to discharge capacitor C. The voltage regulator branch is also connected in parallel across capacitor C to provide a stable voltage to the constant current discharge branch. The optocoupler control circuit is located on the voltage regulator branch to control the on / off state of the constant current discharge branch, thus achieving the discharge of capacitor C. The input terminal of the optocoupler control branch is connected to the output terminal of the power module CPU. One end of the output terminal of the optocoupler control branch is connected to the control terminal of the constant voltage regulator branch, and the other end is connected to the negative terminal of capacitor C. The output terminal of the constant voltage regulator branch is connected to the controlled terminal of the constant current discharge branch.

[0015] The constant current discharge branch includes discharge resistors R connected in series. L Transistor T and constant current control resistor R r Discharge resistor RL The constant current control resistor R is connected to the positive terminal of the capacitor. r The base of transistor T is connected to the negative terminal of capacitor C, the base of transistor T is connected to the output terminal of optocoupler control branch, and the emitter of transistor T is connected to the output terminal of voltage regulator branch.

[0016] The voltage regulator branch includes a current-limiting resistor R connected in series. S The adjustable voltage regulator TL431 has its cathode K connected to the output terminal of the optocoupler control branch and the base of the transistor T in the constant current discharge branch. The reference terminal R of the adjustable voltage regulator TL431 is connected to the emitter of the transistor T in the constant current discharge circuit.

[0017] The optocoupler control branch includes optocoupler U. The input terminal K1 of optocoupler U is connected to the output terminal of the power module CPU. One end of the output terminal of optocoupler U is connected to the cathode K of the adjustable voltage regulator TL431 and the base of the transistor in the constant current discharge branch. The other end of the output terminal of optocoupler U is connected to the negative terminal of capacitor C.

[0018] When K I When the voltage is low, the output of optocoupler U is cut off, the voltage regulation of TL431 in the voltage regulator branch is normal, the cathode K provides the conduction voltage for transistor T, transistor T conducts, and I... R =I b +I L Ignore I b , then I R ≈I L resistance R r The voltage is The TL431 reference voltage R output voltage is constant at 2.5V, I R =2.5V / R r , then I R Constant, i.e., I L The constant current discharge branch enables constant current discharge of capacitor C.

[0019] When K I When the voltage is high, the output of optocoupler U is in the on state, the voltage difference between the cathode K and anode A of the regulated power supply branch TL431 is zero, TL431 stops working, the transistor T in the constant current discharge branch is in the off state, and the circuit stops discharging capacitor C.

[0020] The working process of this utility model is as follows:

[0021] When the power module is powered on, K I Invalid, low level, the circuit is in a discharging state;

[0022] When the power module powers on and starts up, the CPU outputs a control signal to control K. I When the signal is high, the circuit stops discharging capacitor C.

[0023] When direct voltage equalization is required, the CPU outputs a control signal to control K. I When the signal is low, the circuit performs constant current discharge.

[0024] When the power module loses power and stops working, the CPU loses power, K I Invalid, low level, start constant current discharge, quickly discharge the charge on capacitor C to the safety voltage.

Claims

1. A power module DC capacitor discharge control circuit, characterized by: The constant current discharging branch and the constant voltage source branch are arranged in parallel on both ends of the capacitor C, and the light coupling control branch is arranged on the constant voltage source branch to control the on-off of the constant current discharging branch.

2. The DC capacitor discharge control circuit for a power module according to claim 1, characterized by: The constant current discharging branch comprises a discharging resistor R L , a triode T and a constant current control resistor R r , the discharging resistor R L is connected with the positive pole of the capacitor, the constant current control resistor R r is connected with the negative pole of the capacitor C, the base of the triode T is connected with the output end of the photo-coupling control branch, and the emitter of the triode T is connected with the output end of the voltage stabilizing source branch.

3. The DC capacitor discharge control circuit for a power module according to claim 2, characterized by: The voltage stabilizer branch comprises a current-limiting resistor R S and an adjustable voltage regulator TL431, the cathode K of the adjustable voltage regulator TL431 is connected with the output end of the photocoupling control branch and the base of the transistor T of the constant current discharge branch, and the reference electrode R of the adjustable voltage regulator TL431 is connected with the emitter of the transistor T of the constant current discharge circuit.

4. The DC capacitor discharge control circuit for a power module according to claim 3, characterized by: The light coupling control branch comprises a light coupling U, an input end K1 of the light coupling U is connected with the output end of the power module CPU, one end of an output end of the light coupling U is connected with a cathode K of a TL431 adjustable voltage stabilizer and a base of a transistor of the constant current discharging branch, and the other end of the output end of the light coupling U is connected with a negative electrode of the capacitor C.

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