Circuit and method for improving electric control efficiency and electric control system

Abstract

The invention relates to a circuit and method for improving electric control efficiency and an electric control system, and the circuit comprises a peak absorption circuit which comprises a TVS second tube and a variable capacitor C1, the anode of the TVS second tube is connected with the first end of the variable capacitor C1, the second end of the variable capacitor C1 is grounded, and the cathode of the TVS second tube is used for being connected with an IGBT switch of the electric control system; the recycling circuit comprises a controller, an NMOS tube and at least one voltage dividing element, a grid electrode of the NMOS tube is connected with the controller, a source electrode of the NMOS tube passes through the at least one voltage dividing element and then is grounded, the source electrode of the NMOS tube is further connected with the controller through another connecting path, and a drain electrode of the NMOS tube is connected with the direct current bus; the controller controls the on-off state of the NMOS tube by sampling a voltage dividing signal on at least one voltage dividing element, and adjusts the capacitance value of the variable capacitor C1 according to a control signal. The efficiency of the electric control system can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electric control systems, and in particular to a circuit and method for improving electric control efficiency, and an electric control system. Background Art

[0002] In such Figure 1 In the circuit shown, the voltage spike problem generated during the shutdown process of the IGBT (insulated gate bipolar transistor) has always been a key challenge in design and optimization. This phenomenon is mainly due to the presence of stray inductance in the system (including the inherent inductance of components such as IGBT, film capacitors, and busbars). According to the inductance law V=L*di / dt, when the current change rate (di / dt) increases sharply at the moment of IGBT shutdown, it will induce a significant voltage spike. Among them, L represents stray inductance, di is the change in current, dt is the change in time, and di / dt directly reflects the current change rate at the moment of IGBT shutdown.

[0003] In order to effectively suppress this voltage spike, the traditional method focuses on changing the turn-off time (dt) by adjusting the driving resistance of the IGBT, thereby achieving the control of the voltage spike. However, although this approach can control the size of the voltage spike to a certain extent, it inevitably increases the turn-off loss, because a longer turn-off time means higher energy dissipation. It is worth noting that if the voltage spike exceeds the safety threshold, it will directly threaten the insulation performance of the IGBT and even cause the device to break down, which will seriously affect the stability and reliability of the system.

[0004] Therefore, it is necessary to develop a new circuit and method and an electric control system for improving electric control efficiency. Summary of the invention

[0005] The object of the present invention is to provide a circuit and method for improving electric control efficiency, and an electric control system, which can reduce the peak voltage, reduce the turn-off time, and reduce the turn-off loss without increasing the turn-off resistance.

[0006] In a first aspect, a circuit for improving electric control efficiency according to the present invention is characterized by comprising:

[0007] A peak absorption circuit, the peak absorption circuit comprises a TVS diode and a variable capacitor C1, wherein the anode of the TVS diode is connected to the first end of the variable capacitor C1, the second end of the variable capacitor C1 is grounded, and the cathode of the TVS diode is used to be connected to the IGBT switch of the electric control system;

[0008] A recycling circuit comprises a controller, an NMOS tube and at least one voltage divider element, wherein the gate of the NMOS tube is connected to the controller, the source of the NMOS tube is grounded after passing through the at least one voltage divider element, and the source of the NMOS tube is also connected to the controller through another connection path, and the drain of the NMOS tube is connected to a DC bus; the controller controls the switching state of the NMOS tube by sampling the voltage divider signal on the at least one voltage divider element, and adjusts the capacitance of the variable capacitor C1 according to the control signal.

[0009] Optionally, the recycling circuit includes two voltage-dividing elements, namely, resistor R1 and resistor R2. The source of the NMOS tube is grounded through resistor R1, and the source of the NMOS tube is connected to the controller through resistor R2. The controller controls the switch state of the NMOS tube by sampling the voltage-dividing signal on the resistor R1 and the resistor R2, and adjusts the capacitance of the variable capacitor C1 according to the control signal. By sampling the voltage-dividing signal on the resistor R1 and the resistor R2, the controller can accurately control the switch state of the NMOS tube, and adjust the capacitance of the variable capacitor C1 accordingly, thereby realizing effective energy recycling and utilization.

[0010] Optionally, the peak absorption circuit further includes a diode D, the anode of the diode D is connected to the anode of the TVS diode, the cathode of the diode D is connected to the first end of the variable capacitor C1, and the diode D is used to prevent the voltage from being fed back to the collector of the IGBT switch when the IGBT switch is used as a lower bridge. The provision of the diode D enhances the stability and safety of the circuit.

[0011] Optionally, the variable capacitor C1 is a voltage-controlled capacitor, and its capacitance can be adjusted according to a control signal of a controller. This design enables the circuit to flexibly adjust the capacitance of the variable capacitor according to actual working requirements, thereby achieving more precise control and management of energy.

[0012] In a second aspect, an electric control system according to the present invention comprises a plurality of IGBT switches, each of which is connected to a circuit for improving electric control efficiency according to the present invention. By connecting a circuit for improving electric control efficiency to each IGBT switch, the energy utilization efficiency of the entire electric control system is significantly improved, and it also helps to protect the circuit from damage caused by spike voltage.

[0013] In a third aspect, a method for improving electric control efficiency according to the present invention adopts the electric control system according to the present invention, and the method comprises the following steps:

[0014] a) When the IGBT switch in the electric control system generates a spike voltage, the TVS diode is broken down, and the voltage is discharged to the variable capacitor C1 through the TVS diode to absorb the spike voltage;

[0015] b) When the variable capacitor C1 is charged to a voltage close to the DC bus voltage, the controller controls the NMOS tube to turn on according to the voltage division signal on the at least one voltage division element, and adjusts the capacitance of the variable capacitor C1 to be smaller, so that the capacitor voltage increases and supplies power to the DC bus, thereby achieving rapid discharge;

[0016] c) When the capacitance of the variable capacitor C1 drops to the minimum and the capacitor voltage is discharged to close to the DC bus voltage, the controller controls the NMOS tube to turn off and increases the capacitance of the variable capacitor C1, so that the capacitor voltage drops to a preset voltage level so as to continue to absorb subsequent peak voltages. The method includes the steps of absorbing peak voltages, recycling energy, and adjusting the capacitance of capacitors. This method improves the efficiency of the electronic control system and maximizes the use of energy by precisely controlling and managing the flow of energy in the circuit. At the same time, the method also helps to extend the service life of the electronic control system and reduce maintenance costs.

[0017] Beneficial effects of the present invention:

[0018] (1) The peak absorption circuit of the present invention absorbs the peak voltage generated by the IGBT switch in the electric control system through the combination of the TVS diode and the variable capacitor C1, which helps to protect the circuit from damage by the peak voltage.

[0019] (2) The recycling circuit of the present invention realizes the recycling of energy stored in the variable capacitor C1 after charging through the combination of the controller, the NMOS tube and the voltage divider element, thereby improving the energy utilization efficiency of the electric control system.

[0020] In summary, the present invention reduces the peak voltage without increasing the resistance of the turn-off resistor, reduces the turn-off time, and reduces the turn-off loss. At the same time, the peak voltage is recovered and released into the main current loop, realizing energy recovery and further improving the efficiency of the electric control system. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a circuit diagram of the prior art;

[0022] Figure 2 is a circuit diagram of a circuit for improving electric control efficiency described in an embodiment of the present application;

[0023] Figure 3 is a schematic diagram of the connection between the circuit for improving the electric control efficiency and the IGBT switch described in the embodiment of the present application;

[0024] Figure 4 is a schematic diagram of the circuit architecture of an embodiment of the present application;

[0025] Figure 5 It is a schematic diagram of the peak voltage result of the simulation of the non-spike absorption circuit in the embodiment of the present application;

[0026] Figure 6 is a schematic diagram of the peak voltage result of the peak absorption circuit simulation in the embodiment of the present application;

[0027] Figure 7 is a schematic diagram of capacitor voltage results of a spike absorption circuit simulation in an embodiment of the present application;

[0028] Figure 8 It is a flow chart of the method for improving electric control efficiency according to an embodiment of the present application. DETAILED DESCRIPTION

[0029] The following will describe the embodiments of the present invention with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention, not for limiting the scope of protection of the present invention.

[0030] like Figure 2 and Figure 3 As shown, in an embodiment of the present application, a circuit for improving the efficiency of electric control includes a peak absorption circuit and a recycling circuit. The peak absorption circuit includes a TVS diode and a variable capacitor C1, the anode of the TVS diode is connected to the first end of the variable capacitor C1, the second end of the variable capacitor C1 is grounded, and the cathode of the TVS diode is used to connect to the IGBT switch of the electric control system. The peak absorption circuit realizes the absorption of the peak voltage generated by the IGBT switch in the electric control system through the combination of the TVS diode and the variable capacitor C1, which helps to protect the circuit from damage by the peak voltage. The recycling circuit includes a controller, an NMOS tube and at least one voltage divider element, the gate of the NMOS tube is connected to the controller, the source of the NMOS tube is grounded after passing through at least one voltage divider element, and the source of the NMOS tube is also connected to the controller through another connection path, and the drain of the NMOS tube is connected to the DC bus; the controller controls the switching state of the NMOS tube by sampling the voltage divider signal on at least one voltage divider element, and adjusts the capacitance of the variable capacitor C1 according to the control signal. The recycling circuit realizes the recycling of energy stored in the variable capacitor C1 after charging through the combination of the controller, the NMOS tube and the voltage divider element, thereby improving the energy utilization efficiency of the electric control system.

[0031] like Figure 2 and Figure 3As shown, in a possible embodiment, the recycling circuit includes two voltage-dividing elements, namely, resistor R1 and resistor R2. The source of the NMOS tube is grounded after passing through the resistor R1, and the source of the NMOS tube is also connected to the controller after passing through the resistor R2. The controller controls the switching state of the NMOS tube by sampling the voltage-dividing signal on the resistor R1 and the resistor R2, and adjusts the capacitance of the variable capacitor C1 according to the control signal. By sampling the voltage-dividing signal on the resistor R1 and the resistor R2, the controller can control the switching state of the NMOS tube according to the voltage-dividing signal, and adjust the capacitance of the variable capacitor C1 accordingly, thereby realizing effective energy recycling and utilization.

[0032] like Figure 2 and Figure 3 As shown, in a possible embodiment, the peak absorption circuit further includes a diode D, the anode of the diode D is connected to the anode of the TVS diode, the cathode of the diode D is connected to the first end of the variable capacitor C1, and the diode D is used to prevent the voltage from being fed back to the collector of the IGBT switch when the IGBT switch is used as a lower bridge. The setting of the diode D enhances the stability and safety of the circuit. The role of the diode D is to prevent the voltage from being fed back when the IGBT switch is used as a lower bridge (because the collector of the IGBT switch may have a voltage of 0 when the IGBT switch is used as a lower bridge).

[0033] In a possible embodiment, the variable capacitor C1 is a voltage-controlled capacitor, and its capacitance can be adjusted according to the control signal of the controller. This design enables the circuit to flexibly adjust the capacitance of the variable capacitor according to actual working requirements, thereby achieving more precise control and management of energy.

[0034] In an embodiment of the present application, a circuit for improving electric control efficiency works as follows:

[0035] 1. Set the breakdown voltage of the TVS diode according to the bus operating voltage of the system (the purpose is to ensure that the TVS diode does not break down during normal operation). The breakdown voltage of the TVS diode in the simulation diagram is 1000V. Generally, it needs to be set greater than the bus voltage and leave an appropriate margin.

[0036] 2. When the voltage spike exceeds the breakdown voltage of the TVS diode, it will cause the TVS diode to break down and conduct.

[0037] 3. After the TVS diode is broken down, the voltage is discharged to the variable capacitor C1 through the TVS diode. The calculation formula for the amount of charge absorbed by the variable capacitor C1 is as follows: Q=CV, where Q represents the amount of charge absorbed by the variable capacitor C1, C represents the capacitance of the variable capacitor C1, and V represents the voltage across the variable capacitor C1.

[0038] 4. Since the V (V=L*di / dt) to be absorbed each time is fixed and the capacitance C of the variable capacitor C1 is fixed, the charge amount Q absorbed each time is a fixed value and is superimposed in the IGBT switch.

[0039] 5. According to the capacitor charging formula V = Q / C, when Q gradually increases, if C remains unchanged, V will gradually increase, see Figure 7 .

[0040] 6. The controller samples the voltage of the variable capacitor C1 by means of voltage division. If the voltage reaches the bus voltage, the controller controls the NMOS tube to open and controls the capacitance C of the variable capacitor C1 to decrease. According to V=Q / C, when V and Q are constant, C decreases and V increases rapidly. Since the current flows from high potential to low potential, power is supplied to the DC bus (including the bus copper bar & bus capacitor) to achieve rapid discharge.

[0041] 7. When the voltage of the variable capacitor C1 is discharged to near the bus voltage (voltage sampling and reading), no current flows at this time, the NMOS tube is controlled to be turned off, and the capacitance of the variable capacitor C1 is increased at the same time, so that the voltage of the variable capacitor C1 is reduced to a lower level, so as to continue to absorb subsequent spike voltages.

[0042] like Figure 1 As shown, the prior art only controls the voltage spike by adjusting the driving resistance. The loss calculation formula of the IGBT switch in this circuit is as follows:

[0043]

[0044] Among them, Vce(t) is the ce voltage of the IGBT switch at time t, and Ic(t) is the current at time t. Since dt is determined by the driving resistance and Ic(t) is a fixed value, the smaller the Vce(t), the smaller the W loss, and Vce(t) can reduce the loss. However, energy recovery is not performed in the prior art, so the stray inductance current and the parasitic capacitance form LC oscillation, and the energy is eventually consumed in the path. The design of the circuit for improving the electric control efficiency described in the implementation of this application can recover and absorb part of the energy, thereby effectively solving this problem.

[0045] like Figure 5 As shown in the figure, it is the circuit simulation result without adding the peak absorption circuit. Figure 5 It can be seen that the maximum voltage is 1160V, the TVS diode voltage is 1000V, so the peak voltage is 160V.

[0046] like Figure 6 As shown in the figure, it is the circuit simulation result with the spike absorption circuit added. Figure 6It can be seen that the maximum voltage is 1090V, the TVS voltage is 1000V, so the peak voltage is 90V, that is, the peak voltage is reduced to 90V, and the improvement is 43%.

[0047] like Figure 7 As shown, the absorption capacitor can absorb the peak energy normally through simulation, and can increase the capacitor voltage and discharge electricity to the bus copper by changing (reducing) the capacitor value.

[0048] In an embodiment of the present application, an electric control system includes a plurality of IGBT switches, each of which is connected to a circuit for improving electric control efficiency as described in the embodiment of the present application. By connecting a circuit for improving electric control efficiency in the embodiment of the present application to each IGBT switch, the energy utilization efficiency of the entire electric control system is significantly improved, and it also helps to protect the circuit from damage by spike voltage.

[0049] like Figure 8 As shown, in an embodiment of the present application, a method for improving electric control efficiency adopts an electric control system as described in the present invention, and the method comprises the following steps:

[0050] a) When the IGBT switch in the electric control system generates a spike voltage, the TVS diode is broken down, and the voltage is discharged to the variable capacitor C1 through the TVS diode to absorb the spike voltage. According to the formula V = Q / C, when the charge Q is constant, the capacitor absorbs the voltage less than the bus voltage. Since the capacitor voltage is less than the spike voltage and the loop impedance is small, the voltage can be absorbed quickly.

[0051] b) When the variable capacitor C1 is charged to a voltage close to the DC bus voltage, the controller controls the NMOS tube to open according to the voltage-dividing signal on the resistors R1 and R2, and adjusts the capacitance of the variable capacitor C1 to be smaller, so that the capacitor voltage increases and supplies power to the DC bus, thereby achieving rapid discharge.

[0052] c) When the capacitance of the variable capacitor C1 drops to the minimum and the capacitor voltage is discharged to close to the DC bus voltage (voltage sampling reading), the controller controls the NMOS tube to turn off and increase the capacitance of the variable capacitor C1 to reduce the capacitor voltage to the preset voltage level so as to continue to absorb subsequent peak voltages.

[0053] The method for improving the efficiency of electric control includes the steps of absorbing peak voltage, recycling energy and adjusting the capacitance value. This method improves the efficiency of the electric control system and maximizes the utilization of energy by accurately controlling and managing the energy flow in the circuit. At the same time, this method also helps to extend the service life of the electric control system and reduce maintenance costs.

[0054] The above-mentioned embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above-mentioned embodiments. Any other changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement modes and shall be included in the protection scope of the present invention.

Claims

1. A circuit for improving electric control efficiency, characterized in that: include: A peak absorption circuit, the peak absorption circuit comprises a TVS diode and a variable capacitor C1, wherein the anode of the TVS diode is connected to the first end of the variable capacitor C1, the second end of the variable capacitor C1 is grounded, and the cathode of the TVS diode is used to be connected to the IGBT switch of the electric control system; A recycling circuit comprises a controller, an NMOS tube and at least one voltage divider element, wherein the gate of the NMOS tube is connected to the controller, the source of the NMOS tube is grounded after passing through the at least one voltage divider element, and the source of the NMOS tube is also connected to the controller through another connection path, and the drain of the NMOS tube is connected to a DC bus; the controller controls the switching state of the NMOS tube by sampling the voltage divider signal on the at least one voltage divider element, and adjusts the capacitance of the variable capacitor C1 according to the control signal.

2. The circuit for improving electric control efficiency according to claim 1, characterized in that: The recycling circuit includes two voltage-dividing elements, namely resistor R1 and resistor R2. The source of the NMOS tube is grounded through the resistor R1, and the source of the NMOS tube is also connected to the controller through the resistor R2. The controller controls the switching state of the NMOS tube by sampling the voltage-dividing signals on the resistor R1 and the resistor R2, and adjusts the capacitance of the variable capacitor C1 according to the control signal.

3. The circuit for improving electric control efficiency according to claim 1, characterized in that: The peak absorption circuit also includes a diode D, the anode of the diode D is connected to the anode of the TVS diode, the cathode of the diode D is connected to the first end of the variable capacitor C1, and the diode D is used to prevent the voltage from being fed back to the collector of the IGBT switch when the IGBT switch is used as a lower bridge.

4. The circuit for improving electric control efficiency according to claim 2, characterized in that: The variable capacitor C1 is a voltage-controlled capacitor, and its capacitance can be adjusted according to a control signal of a controller.

5. An electric control system, comprising a plurality of IGBT switches, characterized in that: Each IGBT switch is connected to a circuit for improving electric control efficiency as claimed in any one of claims 1 to 4.

6. A method for improving electric control efficiency, characterized in that: Using the electronic control system as claimed in claim 5, the method comprises the following steps: a) When the IGBT switch in the electric control system generates a spike voltage, the TVS diode is broken down, and the voltage is discharged to the variable capacitor C1 through the TVS diode to absorb the spike voltage; b) when the variable capacitor C1 is charged to a voltage close to the DC bus voltage, the controller controls the NMOS tube to turn on according to the voltage division signal on the at least one voltage division element, and adjusts the capacitance of the variable capacitor C1 to be smaller, so that the capacitor voltage increases and supplies power to the DC bus, thereby achieving rapid discharge; c) When the capacitance of the variable capacitor C1 drops to the minimum and the capacitor voltage is discharged to close to the DC bus voltage, the controller controls the NMOS tube to turn off and increase the capacitance of the variable capacitor C1 to reduce the capacitor voltage to a preset voltage level so as to continue to absorb subsequent peak voltages.

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