A low-cost, high-reliability pre-charge and bus discharge composite circuit

Abstract

The utility model provides a kind of low cost, high reliable pre-charging and bus discharge composite circuit, it is related to DC bus design field, and the circuit includes: high voltage DC input circuit, pre-charging circuit, discharge circuit, control circuit and bus capacitor circuit;The pre-charging circuit, the discharge circuit, the control circuit and the bus capacitor circuit are connected in parallel on the high voltage DC input circuit;The pre-charging circuit is connected with the discharge circuit and the control circuit respectively;The discharge circuit is connected with the control circuit, and the control circuit is used to control the discharge circuit, and the control circuit is connected to the bus capacitor circuit;Wherein, the pre-charging circuit and the discharge circuit share an electric resistance, when composite circuit pre-charges, the electric resistance is used as pre-charging resistance, when composite circuit discharges, the electric resistance is used as discharge resistance.The utility model provides the circuit with the advantages of low cost, low failure probability and high reliability.

Description

Technical Field

[0001] This utility model relates to the field of DC bus design technology, and more specifically, to a low-cost, high-reliability pre-charge and bus discharge composite circuit. Background Technology

[0002] DC bus capacitors play a crucial role in power systems, often employing large electrolytic capacitors for DC bus support. However, these large capacitors also pose safety hazards. When the system is shut down, a high voltage often remains on the bus capacitors. Without a bleeder circuit, discharge is very slow, posing a danger to maintenance and user personnel. Conventional bleeder circuits, such as... Figure 1 As shown, active discharge control is achieved by software logic controlling the U1 optocoupler. However, if the software logic malfunctions and U1 remains constantly on, or if the U2 hardware fails, the discharge circuit will continue uncontrollably, causing overheating and burning of components such as the discharge resistor, posing a fire risk. Furthermore, the bus capacitor discharge circuit uses a separate discharge resistor, while charging the bus requires a different set of discharge resistors, resulting in double the power resistor cost. Utility Model Content

[0003] The embodiments of this utility model provide a low-cost, high-reliability pre-charge and bus discharge composite circuit to solve the technical problems existing in the prior art.

[0004] Other features and advantages of this invention will become apparent from the following detailed description, or may be learned in part by practice of this invention.

[0005] According to a first aspect of the present invention, a low-cost, high-reliability pre-charge and bus discharge composite circuit is provided, comprising: a high-voltage DC input circuit, a pre-charge circuit, a discharge circuit, a control circuit, and a bus capacitor circuit. The pre-charging circuit, the discharge circuit, the control circuit, and the bus capacitor circuit are connected in parallel to the high-voltage DC input circuit; The pre-charging circuit is connected to the discharge circuit and the control circuit respectively; The discharge circuit is connected to the control circuit, and the control circuit is used to control the discharge circuit. The control circuit is also connected to the bus capacitor circuit. The pre-charging circuit and the discharge circuit share a common resistor. When the composite circuit is pre-charging, the resistor is used as a pre-charging resistor, and when the composite circuit is discharging, the resistor is used as a discharge resistor.

[0006] In some embodiments of this utility model, based on the foregoing scheme, the pre-charging circuit includes: a DC main contactor, a DC pre-charging relay, and a pre-charging / discharging resistor; Pin 1 of the DC main contactor is connected to the high-voltage DC input circuit, and pin 2 is connected to the control circuit; Pin 4 of the DC precharge relay is connected to the high-voltage DC input circuit, and pin 3 is connected to the discharge circuit. The precharge / discharge resistor is connected in parallel between pin 2 of the DC main contactor and pin 3 of the DC precharge relay.

[0007] In some embodiments of this utility model, based on the foregoing scheme, the discharge circuit includes: the pre-charge / discharge resistor, the discharge power transistor, the pulse width conducting capacitor charging resistor, the pulse width conducting capacitor, the driving resistor, the pulse width conducting capacitor discharge resistor, and the discharge control optocoupler; The pre-charge / discharge resistor is connected to the emitter of the discharge power transistor. The base of the discharge power transistor is connected to the high-voltage DC input circuit; The pulse width conduction capacitor charging resistor is connected in parallel with the base and collector of the discharge power transistor; The pulse width conduction capacitor and the driving resistor are connected in series on the collector of the discharge power transistor. The driving resistor is also connected to the output terminal of the discharge control optocoupler. The input terminal of the discharge control optocoupler is connected to the control circuit. The pulse width conduction capacitor discharge resistor is connected in parallel with the base and collector of the discharge power transistor.

[0008] In some embodiments of this utility model, based on the aforementioned scheme, a Zener diode is connected in parallel with the charging resistor of the pulse width conduction capacitor.

[0009] In some embodiments of this utility model, based on the foregoing scheme, the control circuit includes: an energy storage capacitor, a driving voltage Zener diode, a lower voltage equalizing resistor, an upper voltage equalizing resistor, a balancing impedance capacitor, and a balancing Zener diode; The balancing impedance capacitor is connected in parallel with the balancing Zener diode, and the balancing Zener diode is connected in series with the upper voltage equalizing resistor and the lower voltage equalizing resistor. The lower voltage equalizing resistor is also connected to the driving voltage Zener diode. The driving voltage Zener diode is connected in parallel with the energy storage capacitor and then connected to the discharge circuit.

[0010] In some embodiments of this utility model, based on the aforementioned scheme, the bus capacitor circuit includes: an upper bus capacitor and a lower bus capacitor connected in series.

[0011] The technical solution of this utility model has the following beneficial effects: This circuit uses a shared pre-charge / discharge resistor and a shared voltage equalization resistor, reducing the cost of power resistors by 50%. The use of "pulse-width conduction capacitor charging resistor, pulse-width conduction capacitor, and pulse-width conduction capacitor discharging resistor" reduces the probability of circuit failure and improves reliability.

[0012] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit the present invention. Attached Figure Description

[0013] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments conforming to the present invention and, together with the description, serve to explain the principles of the present invention. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. In the drawings: Figure 1 A schematic diagram of a conventional bleed circuit is shown. Figure 2 A schematic diagram of a low-cost, high-reliability pre-charge and bus discharge composite circuit according to an embodiment of the present invention is shown. Figure 3 This diagram illustrates the operation of the circuit during pre-charging. Figure 4 This diagram illustrates the operation of the circuit of this invention during discharge. Figure 5 The diagram shows the operation of the circuit of this invention when waiting for the next discharge. Detailed Implementation

[0014] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided to make the present invention more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art.

[0015] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a full understanding of embodiments of the present invention. However, those skilled in the art will recognize that the technical solutions of the present invention can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., may be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of the present invention.

[0016] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this utility model, and not all of them. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0017] The following description, in conjunction with the accompanying drawings, details some embodiments of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0018] See Figure 1 The diagram shows a structural schematic of a low-cost, high-reliability pre-charge and bus discharge composite circuit according to an embodiment of the present invention.

[0019] like Figure 1 As shown in the figure, there are five parts in total, PART1 to PART5. These five parts are the high voltage DC input circuit (PART1), the pre-charge circuit (PART2), the discharge circuit (PART3), the control circuit (PART4), and the bus capacitor circuit (PART5).

[0020] The pre-charging circuit, the discharge circuit, the control circuit, and the bus capacitor circuit are connected in parallel on the high-voltage DC input circuit. The pre-charging circuit is connected to the discharge circuit and the control circuit respectively; The discharge circuit is connected to the control circuit, and the control circuit is used to control the discharge circuit. The control circuit is also connected to the bus capacitor circuit. The pre-charging circuit and the discharge circuit share a common resistor. When the composite circuit is pre-charging, the resistor is used as a pre-charging resistor, and when the composite circuit is discharging, the resistor is used as a discharge resistor.

[0021] like Figure 1 As shown, the high-voltage DC input circuit includes two terminals, BUS+ and BUS-. The pre-charging circuit (PART2), the discharge circuit (PART3), the control circuit (PART4), and the bus capacitor circuit (PART5) are all connected in parallel to the two terminals, BUS+ and BUS-.

[0022] In some feasible embodiments, based on the foregoing scheme, such as Figure 1 As shown, the pre-charging circuit includes: a DC main contactor RLY1, a DC pre-charge relay RLY2, and a pre-charge / discharge resistor R1; Pin 1 of the DC main contactor RLY1 is connected to the high-voltage DC input circuit, and pin 2 is connected to the control circuit. Pin 4 of the DC precharge relay RLY2 is connected to the high-voltage DC input circuit, and pin 3 is connected to the discharge circuit. The precharge / discharge resistor R1 is connected in parallel between pin 2 of the DC main contactor RLY1 and pin 3 of the DC precharge relay RLY2.

[0023] In some feasible embodiments, based on the foregoing scheme, such as Figure 1 As shown, the discharge circuit includes: the pre-charge / discharge resistor R1, the discharge power transistor Q1, the pulse width conducting capacitor charging resistor R5, the pulse width conducting capacitor C3, the drive resistor R4, the pulse width conducting capacitor discharging resistor R6, and the discharge control optocoupler U1. The pre-charge / discharge resistor R1 is connected to the emitter of the discharge power transistor Q1; The base of the discharge power transistor Q1 is connected to the high-voltage DC input circuit; The pulse width conduction capacitor charging resistor R5 is connected in parallel with the base and collector of the discharge power transistor Q1. The pulse width conducting capacitor C3 and the driving resistor R4 are connected in series on the collector of the discharge power transistor Q1. The driving resistor R4 is also connected to the output terminal of the discharge control optocoupler U1. The input terminal of the discharge control optocoupler U1 is connected to the control circuit. The pulse width conduction capacitor discharge resistor R6 is connected in parallel with the base and collector of the discharge power transistor Q1.

[0024] In some feasible embodiments, based on the foregoing scheme, such as Figure 1 As shown, a Zener diode ZD3 is connected in parallel with the charging resistor of the pulse width conduction capacitor.

[0025] In some feasible embodiments, based on the foregoing scheme, such as Figure 1 As shown, the control circuit includes: energy storage capacitor C4, driving voltage Zener diode ZD1, lower voltage equalization resistor R2, upper voltage equalization resistor R3, balancing impedance capacitor C1, and balancing Zener diode ZD2. The balancing impedance capacitor C1 is connected in parallel with the balancing Zener diode ZD1. The balancing Zener diode ZD1 is connected in series with the upper voltage equalizing resistor R2 and the lower voltage equalizing resistor R3. The lower voltage equalizing resistor R3 is also connected to the driving voltage Zener diode ZD2. The driving voltage regulator diode ZD2 is connected in parallel with the energy storage capacitor C4 and then connected to the discharge circuit.

[0026] In some feasible embodiments, based on the foregoing scheme, such as Figure 1As shown, the bus capacitor circuit includes an upper bus capacitor C2 and a lower bus capacitor C5 connected in series.

[0027] The circuit operates as follows: The first working process is as follows: Figure 3 As shown: When the system needs to perform pre-charge, the DC main contactor RYLY1 is open and the DC pre-charge relay RYLY2 is closed. The upper bus capacitor C2 and the lower bus capacitor C5 are charged through the pre-charge / discharge resistor R1 with current limiting. At the same time, the energy storage capacitor C4 is charged through the upper voltage equalizing resistor R2 and the lower voltage equalizing resistor R3. When the upper bus capacitor C2 and the lower bus capacitor C5 are fully charged, the DC pre-charge relay RYLY2 is opened and the DC main contactor RYLY1 is closed, and the pre-charge is completed.

[0028] The second working process is as follows: Figure 4 As shown: When the system needs to discharge the bus capacitor normally, the discharge control optocoupler U1 is turned on. The energy stored in the energy storage capacitor C4 drives the discharge power transistor Q1 to turn on through the discharge control optocoupler U1 and the drive resistor R4. The energy of the upper bus capacitor C2 and the lower bus capacitor C5 is consumed through the pre-charge / discharge resistor R1, and the pulse width conduction capacitor C3 is slowly charged through the pulse width conduction capacitor charging resistor R5. At this time, the drive voltage of the discharge power transistor Q1 is constantly decreasing. When it drops below the turn-on voltage of the discharge power transistor Q1, the discharge power transistor Q1 is turned off, and the bus capacitor discharge is completed.

[0029] The third working process is as follows: Figure 5 As shown: When the drive pulse of the discharge control optocoupler U1 disappears, the discharge control optocoupler U1 is turned off, and the energy stored in the pulse width conduction capacitor C3 is discharged through the drive resistor R4, the pulse width conduction capacitor discharge resistor R6, the Zener diode ZD3, and the pulse width conduction capacitor charging resistor R5. Only after the discharge is completed can the next bus capacitor discharge operation be performed.

[0030] Description of abnormal protection functions; such as Figure 4 As shown, during normal system operation, the DC main contactor RYLY1 is in the closed state. If the discharge control optocoupler U1 itself breaks down or any of the control front-end software or hardware malfunctions, the discharge control optocoupler U1 will be uncontrollably turned on, and the output of the discharge control optocoupler U1 will always be at a high level. The circuit will work according to the second working process. After the discharge power transistor Q1 is turned on for a designed pulse width time, the pulse width conducting capacitor C3 will always be fully charged and will always be closed. At this time, the circuit components will not burn out.

[0031] This invention incorporates a capacitor C3 connected in series in the control loop of the discharge circuit. This capacitor ensures that the discharging IGBT can only conduct for a fixed pulse width time under a single control signal. When software bugs occur or the upstream control hardware fails, a continuous on-signal is often generated. In the circuit of this patent, even a continuous on-signal can only conduct for a single pulse width time, preventing uncontrollable continuous conduction of the discharge circuit and significantly improving reliability.

[0032] This invention also achieves the sharing of the bus capacitor discharge resistor and the pre-charge resistor, reducing the cost of the power resistor by 50%. In power supplies such as inverters, there is often an upper half-bridge bus capacitor and a lower half-bridge bus capacitor. Therefore, in the passive voltage equalization circuit of the bus capacitor, resistors are often connected in parallel across the upper and lower bus capacitors. This patent utilizes the voltage equalization resistor to supply power to the bus capacitor discharge circuit without increasing the power resistor, realizing the reuse of resistors and further reducing circuit costs.

[0033] In summary, this circuit uses a shared pre-charge / discharge resistor R1 and shared voltage equalization resistors R2 and R3, reducing the cost of power resistors by 50%. The use of "pulse-width conduction capacitor charging resistor R5, pulse-width conduction capacitor C3, and pulse-width conduction capacitor discharging resistor R6" reduces the probability of circuit failure and improves reliability.

[0034] Other embodiments of the present invention will readily occur to those skilled in the art upon consideration of the specification and practice of the embodiments disclosed herein. The present invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. It should be understood that the present invention is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A low-cost, high-reliability pre-charge and bus discharge composite circuit, characterized in that, include: High-voltage DC input circuit, pre-charge circuit, discharge circuit, control circuit and bus capacitor circuit; The pre-charging circuit, the discharge circuit, the control circuit, and the bus capacitor circuit are connected in parallel to the high-voltage DC input circuit; The pre-charging circuit is connected to the discharge circuit and the control circuit respectively; The discharge circuit is connected to the control circuit, and the control circuit is used to control the discharge circuit. The control circuit is also connected to the bus capacitor circuit. The pre-charging circuit and the discharge circuit share a common resistor. When the composite circuit is pre-charging, the resistor is used as a pre-charging resistor, and when the composite circuit is discharging, the resistor is used as a discharge resistor.

2. The composite circuit according to claim 1, characterized in that, The pre-charging circuit includes: a DC main contactor, a DC pre-charge relay, and a pre-charge / discharge resistor; Pin 1 of the DC main contactor is connected to the high-voltage DC input circuit, and pin 2 is connected to the control circuit; Pin 4 of the DC precharge relay is connected to the high-voltage DC input circuit, and pin 3 is connected to the discharge circuit. The precharge / discharge resistor is connected in parallel between pin 2 of the DC main contactor and pin 3 of the DC precharge relay.

3. The composite circuit according to claim 2, characterized in that, The discharge circuit includes: the pre-charge / discharge resistor, the discharge power transistor, the pulse width conducting capacitor charging resistor, the pulse width conducting capacitor, the drive resistor, the pulse width conducting capacitor discharge resistor, and the discharge control optocoupler; The pre-charge / discharge resistor is connected to the emitter of the discharge power transistor. The base of the discharge power transistor is connected to the high-voltage DC input circuit; The pulse width conduction capacitor charging resistor is connected in parallel with the base and collector of the discharge power transistor; The pulse width conduction capacitor and the driving resistor are connected in series on the collector of the discharge power transistor. The driving resistor is also connected to the output terminal of the discharge control optocoupler. The input terminal of the discharge control optocoupler is connected to the control circuit. The pulse width conduction capacitor discharge resistor is connected in parallel with the base and collector of the discharge power transistor.

4. The composite circuit according to claim 3, characterized in that, A Zener diode is connected in parallel with the charging resistor of the pulse width conduction capacitor.

5. The composite circuit according to claim 1, characterized in that, The control circuit includes: an energy storage capacitor, a driving voltage Zener diode, a lower voltage equalizing resistor, an upper voltage equalizing resistor, a balancing impedance capacitor, and a balancing Zener diode; The balancing impedance capacitor is connected in parallel with the balancing Zener diode, and the balancing Zener diode is connected in series with the upper voltage equalizing resistor and the lower voltage equalizing resistor. The lower voltage equalizing resistor is also connected to the driving voltage Zener diode. The driving voltage Zener diode is connected in parallel with the energy storage capacitor and then connected to the discharge circuit.

6. The composite circuit according to claim 1, characterized in that, The bus capacitor circuit includes an upper bus capacitor and a lower bus capacitor connected in series.

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