Direct current bus capacitor discharge circuit

Abstract

The utility model relates to a direct current bus capacitor discharge circuit, which comprises a rectifier bridge DB1, a voltage-regulator tube D1, a TVS tube D2, a capacitor C1, a triode Q1, an MOS tube Q2 and an IGBT tube GB1, the rectifier bridge DB1 is connected with the direct current bus capacitor in parallel, two pins of the capacitor are respectively connected with output ends V1 and V2 of the rectifier bridge DB1, an input end of the rectifier bridge DB1 is connected with the voltage-regulator tube D1, and an output end of the capacitor C1 is connected with the TVS tube D2. A stable voltage VD1 end of the voltage-regulator tube D1 is connected with a grid electrode G of the IGBT tube GB1; in order to limit peak voltage, the grid electrode G of the IGBT tube GB1 is further connected with a TVS tube D2, the TVS tube D2 is connected with the voltage-regulator tube D1 in parallel, the emitting electrode E of the IGBT tube GB1 is connected with a resistor R21, the resistor R21 is connected with a resistor R23, and the TVS tube D2 is connected with a resistor R22 in parallel. According to the utility model, a two-stage discharge mode is adopted, firstly, low-current discharge is carried out, and high-current discharge is carried out several seconds later; the problem of sparking in the connection process is avoided, and meanwhile, the discharge time is ensured to be short enough to avoid potential safety hazards caused by high voltage.

Description

Technical Field

[0001] The utility model relates to the technical field of emergency protection circuits, in particular to a DC bus capacitor discharge circuit. Background Art

[0002] In the power electronics industry, DC bus capacitors are often used in high-voltage and high-power applications, which means that DC bus capacitors are high voltage and large capacitance. When the power is turned off, if the output load is in a light load state, the DC bus capacitor cannot be discharged quickly and still has a high voltage. If the voltage on the capacitor is not discharged in time, the product maintenance worker may cause sparks and damage the device during the operation, and there is a personal safety hazard.

[0003] The current solution is to connect a resistor in parallel across the capacitor, but this has the following problems: (1) If the resistor is too small, the discharge speed will be too fast, and a resistor that is too small will cause sparks; (2) If the resistor is too large, although there will be no sparks, the discharge speed will be very slow, and there will still be high voltage; (3) If the resistor is manually held to discharge, there will be a high voltage across the capacitor, which poses a safety hazard. Summary of the invention

[0004] The purpose of the utility model is to overcome the above-mentioned shortcomings and provide a DC bus capacitor discharge circuit to ensure that there will be no sparking problem during the connection process and to ensure that the DC bus capacitor is discharged quickly during the discharge time to avoid safety hazards.

[0005] The purpose of the utility model is achieved in this way:

[0006] A DC bus capacitor discharge circuit comprises a rectifier bridge DB1, a voltage regulator tube D1, a TVS tube D2, a capacitor C1, a triode Q1, a MOS tube Q2 and an IGBT tube GB1, wherein the rectifier bridge DB1 is connected in parallel with the DC bus capacitor, two pins of the capacitor are respectively connected to output terminals V1 and V2 of the rectifier bridge DB1, an input terminal of the rectifier bridge DB1 is connected to the voltage regulator tube D1, and a stable voltage VD1 terminal of the voltage regulator tube D1 is connected to a gate G of the IGBT tube GB1;

[0007] In order to limit the peak voltage, the gate G of the IGBT tube GB1 is also connected to a TVS tube D2, the TVS tube D2 and the voltage regulator tube D1 are connected in parallel, the emitter E of the IGBT tube GB1 is connected to the resistor R21, the resistor R21 is connected to the resistor R23, and the resistors R10, R11, R12, R13, R14, R15, R16, R17, R18, R19, R25 and R26 are also connected in series between the collector C of the IGBT tube GB1 and the rectifier bridge DB1; the TVS tube D2 is connected in parallel with the resistor R22.

[0008] A DC bus capacitor discharge circuit, wherein the emitter E of the IGBT tube GB1 is also connected to the base of the transistor Q1, the transistor Q1 is connected in parallel with the resistor R22 and the TVS tube D2, the collector of the transistor Q1 is connected to the gate G of the IGBT tube GB1 and the resistor R22, and the emitter of the transistor Q1 is connected to the drain D of the MOS tube Q2.

[0009] A DC bus capacitor discharge circuit, wherein the gate G of the MOS tube Q2 is connected to the resistor R22 and one end of the capacitor C1 respectively, and the source S of the MOS tube Q2 is connected to the other end of the capacitor C1.

[0010] A DC bus capacitor discharge circuit, wherein 10 resistors are arranged between the rectifier bridge DB1 and the gate G of the IGBT tube GB1: resistors R0-R9 connected in series.

[0011] A DC bus capacitor discharge circuit, wherein the resistors R10-R15 and the LED lamp D3 are connected in parallel.

[0012] A DC bus capacitor discharge circuit, wherein one end of the LED lamp D3 is connected to the resistor R10 through the current limiting resistor R20, and the other end is connected to the resistor R15.

[0013] Compared with the prior art, the beneficial effects of the utility model are:

[0014] The utility model provides a DC bus capacitor discharge circuit, which adopts a two-stage discharge mode and performs discharge in two stages. First, a small current is used for discharge, and then a large current is used for discharge after a few seconds. The small current represents high impedance, ensuring that there will be no sparking problem during the connection process. Then, the large current is discharged while ensuring that the discharge time is fast enough, so that the DC bus capacitor is quickly discharged to avoid the safety hazard caused by high voltage. In addition, the discharge can be sampled by a constant current circuit for discharge, and the connection is made through a meter pen, without the need for manual hand-held operation, thus solving the safety hazard of manual hand-held contact discharge, and also solving the problem of sparks generated by resistor contact. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a circuit diagram of the utility model. DETAILED DESCRIPTION

[0016] In order to better understand the technical solution of the present invention, the following will be described in detail in conjunction with the relevant illustrations. It should be understood that the following specific embodiments are not intended to limit the specific implementation of the technical solution of the present invention, and are only implementations that can be adopted by the technical solution of the present invention. It should be noted that the description of the positional relationship of each component in this article, such as component A being located above component B, is based on the description of the relative positions of the components in the illustration, and is not intended to limit the actual positional relationship of the components. Example 1

[0017] See also Figure 1 , Figure 1 The circuit diagram of the utility model is drawn. As shown in the figure, the utility model involves a DC bus capacitor discharge circuit, which includes a rectifier bridge DB1, a voltage regulator tube D1, a TVS tube D2, a capacitor C1, a triode Q1, a MOS tube Q2 and an IGBT tube GB1, the rectifier bridge DB1 is connected in parallel with the DC bus capacitor, the two pins of the capacitor are respectively connected to the output ends V1 and V2 of the rectifier bridge DB1, the input end of the rectifier bridge DB1 is connected to the voltage regulator tube D1, and the stable voltage VD1 end of the voltage regulator tube D1 is connected to the gate G of the IGBT tube GB1.

[0018] In order to limit the peak voltage, the gate G of the IGBT tube GB1 is also connected to a TVS tube D2, the TVS tube D2 is connected in parallel with the voltage regulator tube D1, the emitter E of the IGBT tube GB1 is respectively connected to the base of the transistor Q1 and the resistor R21, the resistor R21 is connected to the resistor R23, and the collector C of the IGBT tube GB1 and the rectifier bridge DB1 are also connected in series with resistors R10, R11, R12, R13, R14, R15, R16, R17, R18, R19, R25 and R26; the transistor Q1 is connected in parallel with the resistor R22 and the TVS tube D2, the collector of the transistor Q1 is connected to the gate G of the IGBT tube GB1 and the resistor R22, the emitter of the transistor Q1 is connected to the drain D of the MOS tube Q2; the gate G of the MOS tube Q2 is respectively connected to the resistor R22 and one end of the capacitor C1, and the source S of the MOS tube Q2 is connected to the other end of the capacitor C1.

[0019] Ten resistors are arranged between the rectifier bridge DB1 and the gate G of the IGBT tube GB1: resistors R0 to R9 connected in series.

[0020] The resistors R10 to R15 are connected in parallel with the LED lamp D3. One end of the LED lamp D3 is connected to the resistor R10 through the current limiting resistor R20, and the other end is connected to the resistor R15.

[0021] Working principle:

[0022] Electrolytic capacitors have positive and negative poles, that is, the voltage has a direction. In order to prevent reverse connection of the input, a rectifier bridge DB1 is set up. It is necessary to consider that the conventional industrial application voltage is DC 800V or DC1000V. The IGBT tube GB1 uses a withstand voltage of 1600V, which can be compatible with applications below DC1500V.

[0023] The driving voltage of IGBT tube GB1 is usually several tens of volts. Resistors R0~R9 need to be able to withstand a DC1500V withstand voltage (compatible with DC1500V). The resistors are packaged in 1206 (single withstand voltage 200V). Considering the withstand voltage and temperature rise, margins are made and resistors R0~R9 are set, with a total of 10 resistors.

[0024] When V1 and V2 are connected to the two pins of the capacitor, the voltage regulator D1 works to stabilize the voltage VD1. The TVS tube D2 protects the IGBT's driving Vge pin in order to limit the peak voltage. The IGBT works in the variable resistance area. VGE(th) is the driving threshold voltage of the IGBT. Vge maintains the voltage difference of VD1. The voltage difference between resistors R21 and R23 is V(R21+R23)=VD1-VGE(th). The initial power-on will discharge with a small current I1. The current I1=V(R21+R23) / (R21+R23). By setting the resistance of resistors R21 and R23, the size of the first-stage discharge current I1 can be set.

[0025] Through the resistor R22 and the capacitor C1, the RC delay time T1 is set. After the delay time T1, the capacitor C1 reaches the driving threshold voltage VGE (th) of the MOS tube Q2, and the MOS tube Q2 is turned on, that is, the resistor R23 is short-circuited, and the current increases. At this time, the second stage of discharge begins, and the discharge current I2 = V (R21 + R23) / R21. The transistor Q1 has a current limiting process. When the discharge current is too large, the voltage difference of the resistor R21 becomes larger. When the voltage of the resistor R21 reaches the Vbe driving voltage of the transistor Q1, the transistor Q1 is saturated and turned on. At this time, the IGBT is current limited, and the current limit size I3 = Vbe / R21.

[0026] The two discharge stages are mainly to set the resistance of resistors R21 and R23. If the current I2 is greater than the current I3, the discharge process is to discharge with current I1 in the first stage, and then discharge with current I2 in the second stage; if the current I2 is greater than the current I3, the discharge process is to discharge with current I1 in the first stage, and then discharge with current I3 in the second stage. Resistors R10~R26 are used to share part of the voltage of the MOS tube (while considering the layout), so 7 resistors are designed. LED lamp D3 is mainly used to light up the discharge process, and resistor R20 is the current limiting resistor of LED lamp D3. During the discharge process, the light is on, and the light is off when the discharge is completed.

[0027] The above are only specific application examples of the utility model, and do not constitute any limitation on the protection scope of the utility model. Any technical solution formed by equivalent transformation or equivalent replacement falls within the protection scope of the utility model.

Claims

1. A DC bus capacitor discharge circuit, characterized in that: It includes a rectifier bridge DB1, a voltage regulator tube D1, a TVS tube D2, a capacitor C1, a triode Q1, a MOS tube Q2 and an IGBT tube GB1. The rectifier bridge DB1 is connected in parallel with a DC bus capacitor, and two pins of the capacitor are respectively connected to output terminals V1 and V2 of the rectifier bridge DB1. The input terminal of the rectifier bridge DB1 is connected to the voltage regulator tube D1, and the stable voltage VD1 terminal of the voltage regulator tube D1 is connected to the gate G of the IGBT tube GB1. In order to limit the peak voltage, the gate G of the IGBT tube GB1 is also connected to a TVS tube D2, the TVS tube D2 and the voltage regulator tube D1 are connected in parallel, the emitter E of the IGBT tube GB1 is connected to the resistor R21, the resistor R21 is connected to the resistor R23, and the resistors R10, R11, R12, R13, R14, R15, R16, R17, R18, R19, R25 and R26 are also connected in series between the collector C of the IGBT tube GB1 and the rectifier bridge DB1; the TVS tube D2 is connected in parallel with the resistor R22.

2. A DC bus capacitor discharge circuit according to claim 1, characterized in that: The emitter E of the IGBT tube GB1 is also connected to the base of the transistor Q1. The transistor Q1 is connected in parallel with the resistor R22 and the TVS tube D2. The collector of the transistor Q1 is connected to the gate G of the IGBT tube GB1 and the resistor R22. The emitter of the transistor Q1 is connected to the drain D of the MOS tube Q2.

3. A DC bus capacitor discharge circuit according to claim 2, characterized in that: The gate G of the MOS transistor Q2 is connected to the resistor R22 and one end of the capacitor C1 respectively, and the source S of the MOS transistor Q2 is connected to the other end of the capacitor C1.

4. A DC bus capacitor discharge circuit according to claim 1, characterized in that: Ten resistors are arranged between the rectifier bridge DB1 and the gate G of the IGBT tube GB1: resistors R0 to R9 connected in series.

5. A DC bus capacitor discharge circuit according to claim 1, characterized in that: The resistors R10 to R15 are connected in parallel with the LED lamp D3.

6. A DC bus capacitor discharge circuit according to claim 5, characterized in that: One end of the LED lamp D3 is connected to the resistor R10 via the current limiting resistor R20 , and the other end is connected to the resistor R15 .

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