Bus discharge circuit

Abstract

The application provides a bus discharge circuit, which comprises a discharge module, a driving module and a bypass module, wherein when the bus voltage is greater than a safe voltage and less than an auxiliary source shutdown voltage, the driving module drives the discharge module to start discharging; when the bus voltage is greater than the auxiliary source shutdown voltage, the bypass module bypasses the driving module to make the discharge module stop working. When the bus voltage starts to rise to above the safe voltage and less than the auxiliary source shutdown voltage, the driving module starts to work and opens the discharge module; when the bus voltage is greater than the auxiliary source shutdown voltage, the bypass module starts to bypass the driving module, and the discharge module stops working. Thus, the application only needs to be designed according to the auxiliary source shutdown voltage, and the starting voltage does not need to be considered, so that the internal heat source of the equipment can be reduced to the maximum extent, and the requirements of safety regulations and potential balance can be met at the same time. Meanwhile, the circuit omits an optocoupler and reduces the discharge resistor specifications to the maximum extent, so that the cost is lower.

Description

Technical Field

[0001] This invention relates to the field of converter discharge technology, and more particularly to a bus discharge circuit. Background Technology

[0002] Inverters are increasingly used in the generation of new energy sources, but the environment at new energy power generation sites is generally poor. Therefore, string and distributed inverters now mostly adopt protection levels of IP65 or higher.

[0003] Inverter bus voltage can reach as high as 1500V, and safety regulations require that the bus voltage drop to 36V within 60 seconds after the equipment is powered off. Inverters typically divide the bus voltage into positive and negative voltages, and these voltages are supported by a large number of electrolytic capacitors.

[0004] The traditional solution involves connecting a discharge resistor in parallel between the positive and negative busbars. By connecting a discharge equalizing resistor with a resistance value matching the busbar capacitance in parallel between the positive and negative busbars, the busbar voltage equalization effect can be achieved. However, this resistor continuously discharges during equipment operation, generating unnecessary heat. Furthermore, high protection levels often require the equipment to be sealed, making it difficult for this heat to dissipate into the environment, causing overheating inside the equipment.

[0005] To address this issue, some in the industry have proposed using an open-loop discharge mode after the equipment is shut down. This involves sending an open-loop command to the IGBT (Insulated Gate Bipolar Transistor) module when the controller detects the need to shut down, thereby consuming the bus energy through the switching of the IGBT module. However, this solution has limited energy capacity, and when the parallel capacitors on the bus reach a certain level, the solution cannot meet the discharge time requirements.

[0006] Patent application CN112994426A discloses a DC bus discharge circuit, which controls the opening and closing of the discharge circuit through a logic discharge circuit. The discharge circuit switch is controlled by a control voltage, which is generated by an auxiliary power supply drawing power from the bus. However, the auxiliary power supply's operating voltage exhibits hysteresis, meaning the initial operating voltage is higher than the shutdown operating voltage. This design has the following problems: if the discharge resistor is designed based on the initial operating voltage, discharge will occur prematurely when the bus is powered off, resulting in wasted design capacity; if designed based on the shutdown operating voltage, the discharge resistor may burn out due to overpowering during startup. Therefore, the design has low circuit utilization, and the long auxiliary power supply startup time during the power-on phase increases the risk of discharge circuit burnout.

[0007] Therefore, a new solution is needed. Summary of the Invention

[0008] The purpose of this invention is to address the aforementioned deficiencies of the prior art by providing a fast bus discharge circuit suitable for high protection levels.

[0009] This invention provides a bus discharge circuit, including a discharge module, a drive module, and a bypass module. The first input terminal of the drive module, the first input terminal of the discharge module, and the input terminal of the bypass module are connected to the system bus BUS+. The output terminal of the drive module is connected to the second input terminal of the discharge module, and the output terminal of the bypass module is connected to the second input terminal of the drive module. When the bus voltage is greater than the safe voltage and less than the auxiliary power supply shutdown voltage, the drive module drives the discharge module to start discharging. When the bus voltage is greater than the auxiliary power supply shutdown voltage, the bypass module bypasses the drive module, causing the discharge module to stop working.

[0010] In the bus discharge circuit provided by the present invention, the discharge module includes a discharge resistor R4 and a switching transistor Q1. The first end of the discharge resistor R4 is connected to the system bus BUS+, the second end of the discharge resistor R4 is connected to the first end of the switching transistor Q1, the second end of the switching transistor Q1 is connected to the system bus BUS-, and the third end of the switching transistor Q1 is connected to the anode of the second Zener diode D2.

[0011] In the bus discharge circuit provided by the present invention, the bypass module includes a first voltage divider resistor R1, a second voltage divider resistor R2, and a comparator U1. The first end of the first voltage divider resistor R1 is connected to the system bus BUS+. The second end of the first voltage divider resistor R1 is connected to the first end of the second voltage divider resistor R2 and the first end of the comparator U1. The second end of the comparator U1 is connected to the second end of the current limiting resistor R3. The second end of the second voltage divider resistor R2 and the third end of the comparator U1 are connected to the system bus BUS-.

[0012] In the bus discharge circuit provided by this invention, the resistance R4 and the power P.R4 of the discharge resistor R4 satisfy the following formula: R4 ,

[0013] Among them, T safe For the discharge time required by safety regulations, C BUS The bus capacitance value, V stop For auxiliary power supply shutdown voltage, V safe The voltage is the safety voltage, and k is the resistor power derating.

[0014] Implementing the embodiments of the present invention has the following beneficial effects: In the bus discharge circuit provided by the present invention, when the bus voltage rises above the safe voltage but is less than the auxiliary power supply shutdown voltage, the drive module starts working and turns on the discharge module; when the bus voltage is greater than the auxiliary power supply shutdown voltage, the bypass module starts bypassing the drive module, and the discharge module stops working. Therefore, the present invention only needs to be designed according to the auxiliary power supply shutdown voltage, without considering the start-up voltage. Thus, it can minimize the internal heat source of the equipment while meeting the requirements of safety regulations and potential balance. At the same time, the circuit eliminates the need for optocouplers and minimizes the specifications of the discharge resistor, resulting in lower costs. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 The diagram shown is a schematic of the bus discharge circuit provided by the present invention. Detailed Implementation

[0017] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Typical embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0019] The general idea of ​​this invention is as follows: Existing circuits that control bus discharge by building a logic discharge circuit, designed based on the auxiliary power source start-up voltage, result in significant waste; while designing based on the auxiliary power source shutdown voltage leads to the problem of discharge resistor burnout during installation. Therefore, these circuits suffer from over-design and high costs. This invention provides a bus discharge circuit comprising a discharge module, a drive module, and a bypass module. When the bus voltage is greater than the safety voltage but less than the auxiliary power source shutdown voltage, the drive module initiates the discharge module's discharge. When the bus voltage is greater than the auxiliary power source shutdown voltage, the bypass module bypasses the drive module, thus stopping the discharge module's operation. Therefore, resistor power consumption calculations only need to meet the auxiliary power source shutdown voltage, eliminating the need to consider errors caused by the auxiliary power source start-up value or start-up delay. This minimizes internal heat sources while simultaneously meeting safety regulations and potential balance requirements.

[0020] To better understand the above technical solutions, the following detailed description, in conjunction with the accompanying drawings and specific embodiments, will be provided. It should be understood that the embodiments and specific features described herein are detailed explanations of the technical solutions of this application, and not limitations thereof. Where there is no conflict, the embodiments and technical features described herein can be combined with each other.

[0021] Figure 1 The diagram shown is a circuit diagram of the bus discharge circuit provided by this invention. Figure 1 As shown, the bus discharge circuit provided by this invention includes a discharge module 10, a drive module 20, and a bypass module 30. The drive module generates a drive signal to start the discharge module when the bus voltage is greater than the safety voltage and less than the auxiliary power supply shutdown voltage. The discharge module discharges the system bus. The bypass module generates a bypass signal to bypass the drive module when the bus voltage is greater than the auxiliary power supply shutdown voltage, thereby stopping the discharge module. Simultaneously, external software starts controlling the bus potential balance through a midpoint potential balance control algorithm.

[0022] Specifically, in one embodiment of the present invention, the driving module includes a current-limiting resistor R3, a first Zener diode D1 and a second Zener diode D2, the discharge module includes a discharge resistor R4 and a switching transistor Q1, and the bypass module includes a first voltage divider resistor R1, a second voltage divider resistor R2 and a comparator U1. In this embodiment, the first end of the current-limiting resistor R3 is connected to the system bus BUS+, the second end of the current-limiting resistor R3 is connected to the cathodes of the first Zener diode D1 and the second Zener diode D2, and the anode of the first Zener diode D1 is connected to the system bus BUS-; the first end of the discharge resistor R4 is connected to the system bus BUS+, the second end of the discharge resistor R4 is connected to the first end of the switching transistor Q1, the second end of the switching transistor Q1 is connected to the system bus BUS-, and the third end of the switching transistor Q1 is connected to the anode of the second Zener diode D2; the first end of the first voltage divider resistor R1 is connected to the system bus BUS+, the second end of the first voltage divider resistor R1 is connected to the first end of the second voltage divider resistor R2 and the first end of the comparator U1, the second end of the comparator U1 is connected to the second end of the current-limiting resistor R3, and the second end of the second voltage divider resistor R2 and the third end of the comparator U1 are connected to the system bus BUS-. In a preferred embodiment of the present invention, the switching transistor Q1 can be a MOSFET, an IGBT, an IGCT, etc.

[0023] In this invention, the discharge module mainly consists of a discharge resistor R4 and a switching transistor Q1; the drive module consists of a current-limiting resistor R3, Zener diodes D1 and D2. When the bus voltage is lower than the safe voltage, the drive module does not operate; when the bus voltage is lower than the auxiliary power shutdown voltage but higher than the safe voltage, the drive module starts operating. The bus voltage provides the required leakage current for the Zener diode D2 through the current-limiting resistor R3, and simultaneously provides the drive voltage for the switching transistor Q1 through the Zener diode D1, wherein the Zener diode D1's voltage regulation value is significantly smaller than that of the Zener diode D2. After the switching transistor Q1 starts operating, the discharge resistor R4 begins to discharge to the bus. The resistance value R4 and the power P.R4 of the discharge resistor R4 satisfy the following formula: R4 ,

[0024] Among them, T safe For the discharge time required by safety regulations, C BUS The bus capacitance value, V stop For auxiliary power supply shutdown voltage, V safe The voltage is the safety voltage, and k is the resistor power derating.

[0025] Furthermore, when the bus voltage rises above the auxiliary power shutdown voltage, the bypass module starts working. The bypass module consists of voltage divider resistors R1 and R2 and comparator U1. Comparator U1 internally generates a V.ref value. When the voltage value of voltage divider resistor R2 is greater than V.ref, comparator U1 will output a high impedance; when the voltage value of voltage divider resistor R2 is less than V.ref, comparator U1 will conduct and shunt the current flowing through current limiting resistor R3, while simultaneously outputting a voltage (e.g., 2.5V). Zener diode D2 will also be clamped at this voltage value output by comparator U1. The drive voltage flowing into switching transistor Q1 through Zener diode D1 will be lower than the threshold voltage of the switching transistor, causing switching transistor Q1 to turn off, which in turn causes discharge resistor R4 to stop working.

[0026] The bus discharge circuit provided by this invention activates the drive module and turns on the discharge module when the bus voltage rises above the safe voltage but below the auxiliary power supply shutdown voltage. When the bus voltage exceeds the auxiliary power supply shutdown voltage, the bypass module bypasses the drive module, and the discharge module stops operating. Simultaneously, to control bus potential balance, a midpoint potential balance control algorithm can be used. Therefore, this invention only needs to be designed based on the auxiliary power supply shutdown voltage, without considering the start-up voltage. This minimizes internal heat sources while meeting safety regulations and potential balance requirements. Furthermore, the circuit eliminates the need for optocouplers, resulting in lower costs.

[0027] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0028] Similarly, it should be understood that, in order to simplify this disclosure and aid in understanding one or more of the various aspects of the invention, in the above description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof. However, this method of disclosure should not be construed as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as reflected in the following claims, inventive aspects lie in fewer than all features of a single foregoing disclosed embodiment. Therefore, the claims following the detailed description are hereby expressly incorporated into this detailed description, wherein each claim itself is a separate embodiment of the invention.

[0029] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of the invention and form different embodiments. For example, in the following claims, any of the claimed embodiments can be used in any combination.

[0030] It should be noted that the above embodiments are illustrative of the invention and not restrictive, and that those skilled in the art can devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention can be implemented by means of hardware comprising several different elements and by means of a suitably programmed computer. In the unit claims enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names.

Claims

1. A bus discharge circuit, characterized in that, The system includes a discharge module, a drive module, and a bypass module. The first input terminal of the drive module, the first input terminal of the discharge module, and the input terminal of the bypass module are connected to the system bus BUS+. The output terminal of the drive module is connected to the second input terminal of the discharge module, and the output terminal of the bypass module is connected to the second input terminal of the drive module. When the bus voltage is greater than the safety voltage and less than the auxiliary power supply shutdown voltage, the drive module drives the discharge module to start discharging. When the bus voltage is greater than the auxiliary power supply shutdown voltage, the bypass module bypasses the drive module, causing the discharge module to stop working. The drive module includes a current-limiting resistor R3, a first Zener diode D1, and a second Zener diode D2. The first end of the current-limiting resistor R3 is connected to the system bus BUS+, and the second end of the current-limiting resistor R3 is connected to the cathode of the first Zener diode D1, the cathode of the second Zener diode D2, and the output terminal of the bypass module. The anode of the first Zener diode D1 is connected to the system bus BUS-, and the anode of the second Zener diode D2 is connected to the second input terminal of the discharge module. The discharge module includes a discharge resistor R4 and a switching transistor Q1. The first end of the discharge resistor R4 is connected to the system bus BUS+, the second end of the discharge resistor R4 is connected to the first end of the switching transistor Q1, the second end of the switching transistor Q1 is connected to the system bus BUS-, and the third end of the switching transistor Q1 is connected to the anode of the second Zener diode D2. The bypass module includes a first voltage divider resistor R1, a second voltage divider resistor R2, and a comparator U1. The first end of the first voltage divider resistor R1 is connected to the system bus BUS+. The second end of the first voltage divider resistor R1 is connected to the first end of the second voltage divider resistor R2 and the first end of the comparator U1. The second end of the comparator U1 is connected to the second end of the current limiting resistor R3. The second end of the second voltage divider resistor R2 and the third end of the comparator U1 are connected to the system bus BUS-.

2. The bus discharge circuit according to claim 1, characterized in that, The resistance R4 and power P.R4 of the discharge resistor R4 satisfy the following formula: R4 ， Among them, T safe For the discharge time required by safety regulations, C BUS The bus capacitance value, V stop For auxiliary power supply shutdown voltage, V safe The voltage is the safety voltage, and k is the resistor power derating.

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