Suspension capacitor three-level boost converter and control method

Abstract

Disclosed in the present application are a suspension capacitor three-level Boost converter and a control method, comprising: a first end and a second end of an inductor are respectively connected to a positive input end of a Boost converter and an anode of a first diode, and an anode and a cathode of a second diode are respectively connected to a cathode of the first diode and a positive output end of the Boost converter; a first end and a second end of a first power device are respectively connected to a second end of the inductor and a first end of a second power device, and a second end of the second power device is connected to a negative input end of the Boost converter; a first end and a second end of a first switch are respectively connected to the second end of the first power device and a first end of a suspension capacitor, and a second end of the suspension capacitor is connected to the cathode of the first diode; and a controller is used for controlling the disconnection moment of the first switch to lag behind the disconnection moment of the first power device and the disconnection moment of the second power device, so as to avoid a switch device from bearing an over-voltage failure risk.

Description

A suspended capacitor three-level Boost converter and control method

[0001] This application claims priority to the Chinese patent application with application number 2023115205412 filed with the State Intellectual Property Office of China on November 13, 2023, and application name “A suspended capacitor three-level Boost converter and control method”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of power electronics technology, and in particular to a suspended capacitor three-level Boost converter and a control method thereof. Background Art

[0003] The floating capacitor three-level Boost converter is widely used in high-voltage DC-DC conversion scenarios due to its advantages such as low switching stress and small ripple current.

[0004] Figure 1 shows a typical floating capacitor three-level Boost topology, including an input capacitor Cin, an output capacitor Cout, an inductor L, a first diode D1, a second diode D2, a first switch Q1, a second switch Q2, a first switch K1, and a floating capacitor Cf.

[0005] The first switch K1 is used to prevent the second switch tube Q2 from being over-voltage and broken down due to the instantaneous power-on of the input high voltage.

[0006] Due to the delay in the shutdown signal chain of the first switch tube Q1, the second switch tube Q2 and the first switch K1 and the differences in the shutdown speed of the devices themselves, the shutdown times of Q1, Q2 and K1 are inconsistent, which will expose the switching devices to the risk of overvoltage failure.

[0007] Summary of the Invention

[0008] In view of this, the present application provides a floating capacitor three-level Boost converter and a control method to avoid the risk of overvoltage failure of switching devices.

[0009] The present application provides a suspended capacitor three-level Boost converter, comprising: a controller, an inductor, a first power device, a second power device, a first diode, a second diode, a first switch, and a suspended capacitor;

[0010] The first end and the second end of the inductor are connected to the positive input end of the Boost converter and the anode of the first diode respectively, and the anode and the cathode of the second diode are connected to the cathode of the first diode and the positive output end of the Boost converter respectively;

[0011] The first end and the second end of the first power device are respectively connected to the second end of the inductor and the first end of the second power device, and the second end of the second power device is connected to the negative input terminal of the Boost converter; the first end and the second end of the first switch are respectively connected to the second end of the first power device and the first end of the floating capacitor, and the second end of the floating capacitor is connected to the cathode of the first diode;

[0012] The controller is used to control the disconnection time of the first switch to lag behind the disconnection time of the first power device and the second power device.

[0013] Preferably, the controller is specifically configured to, upon receiving a shutdown instruction from the Boost converter or requiring a fault shutdown, first send a shutdown signal to the first power device and the second power device, and then send a shutdown signal to the first switch after a preset time interval.

[0014] Preferably, it further comprises: a delay circuit;

[0015] The controller is specifically configured to send a shutdown signal to the first power device, the second power device, and the first switch when receiving a shutdown instruction of the Boost converter or a fault shutdown is required;

[0016] The turn-off signal sent by the controller to the first switch is delayed by a preset time by the delay circuit and then output to the first switch.

[0017] Preferably, the delay circuit comprises: a first resistor and a first capacitor;

[0018] The controller sends a shutdown signal to the first switch, which is input to the first end of the first resistor. The second end of the first resistor is connected to the first end of the first capacitor. The second end of the first capacitor is grounded. The first end of the first capacitor is connected to the control end of the first switch.

[0019] Preferably, the delay circuit further comprises: a third diode;

[0020] The cathode of the third diode is connected to the first end of the first resistor, and the anode of the third diode is connected to the second end of the first resistor.

[0021] Preferably, the controller comprises: a first output terminal, a second output terminal and a third output terminal;

[0022] The first output end is connected to the control end of the first power device, the second output end is connected to the control end of the second power device, the third output end is connected to the first end of the delay circuit, and the second end of the delay circuit is connected to the control end of the first switch;

[0023] The controller sends a shutoff signal to the first output terminal, the second output terminal, and the third output terminal.

[0024] Preferably, it further comprises: a second switch and a second resistor;

[0025] The first end of the second switch is connected to the second end of the first switch, and the second end of the second switch is connected to the negative input end of the Boost converter via a second resistor.

[0026] Preferably, it further comprises: a first voltage balancing circuit and / or a second voltage balancing circuit; the first voltage balancing circuit comprises a resistor and / or a voltage stabilizing diode, and the second voltage balancing circuit comprises a resistor and / or a voltage stabilizing diode;

[0027] The first voltage balancing circuit is connected in parallel to the first terminal and the second terminal of the first power device;

[0028] The second voltage balancing circuit is connected in parallel to the first terminal and the second terminal of the second power device.

[0029] The present application provides a control method for a suspended capacitor three-level Boost converter, wherein the Boost converter includes: a controller, an inductor, a first power device, a second power device, a first diode, a second diode, a first switch, and a suspended capacitor;

[0030] The method includes:

[0031] When a shutdown instruction of the Boost converter is received or a fault shutdown is required, the disconnection time of the first switch is controlled to lag behind the disconnection time of the first power device and the second power device.

[0032] Preferably, controlling the disconnection time of the first switch to lag behind the disconnection time of the first power device and the second power device specifically includes:

[0033] First, a shutdown signal is sent to the first power device and the second power device, and then a shutdown signal is sent to the first switch after a preset time interval.

[0034] Preferably, the Boost converter further comprises: a delay circuit;

[0035] Controlling the disconnection time of the first switch to lag behind the disconnection time of the first power device and the second power device specifically includes:

[0036] A shutdown signal is sent to the first power device, the second power device and the first switch; the shutdown signal sent to the first switch is delayed for a preset time by the delay circuit and then output to the first switch.

[0037] It can be seen that this application has the following beneficial effects:

[0038] In the control method provided in the embodiment of the present application, since the disconnection moment of the first switch lags behind the first power device and the second power device, when the Boost converter shuts down and turns off the first power device and the second power device, the first diode and the second diode are turned on to continue current flow, and the maximum voltage stress of the first power device will be clamped at the floating capacitor voltage (i.e., half the bus voltage), and the maximum voltage stress of the second power device will be clamped at the difference between the bus voltage and the floating voltage (i.e., clamped at half the bus voltage), thereby effectively solving the risk of overvoltage failure of the first power device and the second power device. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 shows a typical floating capacitor three-level Boost topology;

[0040] Figure 2 is a schematic diagram of the current path when Q1 is not turned off and K1 is not turned off;

[0041] Figure 3 is a schematic diagram of the current path when Q1 is not turned off and K1 is turned off;

[0042] Figure 4 is a schematic diagram of the current path when Q2 is not turned off and K1 is not turned off;

[0043] Figure 5 is a schematic diagram of the current path when Q2 is not turned off and K1 is turned off;

[0044] FIG6 is a schematic diagram of a Boost converter provided in an embodiment of the present application;

[0045] FIG7 is a schematic diagram of a delay control provided by an embodiment of the present application;

[0046] FIG8 is a schematic diagram of a delay circuit provided in an embodiment of the present application;

[0047] FIG9 is a schematic diagram of another Boost converter provided in an embodiment of the present application;

[0048] FIG10 is a schematic diagram of another Boost converter provided in an embodiment of the present application;

[0049] FIG11 is a flow chart of a method for controlling a floating capacitor three-level Boost converter according to an embodiment of the present application. DETAILED DESCRIPTION

[0050] In order to enable those skilled in the art to better understand the technical solution provided by the embodiment of the present application, the failure path of the circuit in FIG1 is first described in detail below.

[0051] The embodiments of the present application do not specifically limit the application scenarios of the suspended capacitor three-level Boost converter. For example, it can be applied to photovoltaic systems, energy storage systems, and other power electronics scenarios.

[0052] Continuing with Figure 1, for example, during normal operation of a floating capacitor three-level boost converter, K1 is normally closed, and Q1 and Q2 operate alternately. If Q1 is on and Q2 is off immediately before shutdown, the controller sends shutdown signals to both Q1 and K1. However, due to inconsistent signal link delays and differences in device shutdown speeds, Q1 and K1 cannot shut down synchronously. If K1 shuts off first, the inductor current path switches from Q1, K1, and Cf to D1 and D2. At this point, the voltage across the series branch of Q1 and Q2 equals the DC bus voltage. However, since Q1 has not yet shut down, Q2 is subject to the DC bus voltage, causing Q2 to overvoltage and fail, as shown in Figures 2 and 3.

[0053] Similarly, if Q1 is turned off and Q2 is turned on just before shutdown, the controller will send a shutdown signal to Q2 and K1. If K1 is turned off first, the inductor current path will switch from D1, Cf, K1, and Q2 to D1 and D2. At this time, the voltage across the series branch of Q1 and Q2 is equal to the DC bus voltage. However, since Q2 has not yet been turned off, Q1 tube is subjected to the DC bus voltage, causing Q1 to fail due to overvoltage, as shown in Figures 4 and 5.

[0054] In summary, the shutdown control of Q1, Q2, and K1 during shutdown of the floating capacitor three-level Boost converter directly affects the reliability of the topology.

[0055] Therefore, in order to avoid the risk of switch failure in the suspended capacitor three-level Boost converter when the converter is shut down, the embodiment of the present application controls the disconnection time of K1 to lag behind the disconnection time of power devices Q1 and Q2 when the suspended capacitor three-level Boost converter is shut down. In this way, when Q1 and Q2 are turned off during shutdown, diodes D1 and D2 conduct and continue current flow. The maximum voltage stress of Q1 will be clamped to the floating capacitor voltage Vcf (Vbus / 2), and the maximum voltage stress of Q2 will be clamped to the difference between the bus voltage and the floating capacitor voltage, that is, Vbus-Vcf. Generally, Vbus-Vcf = Vbus / 2, thereby effectively solving the risk of overvoltage failure of Q1 and Q2.

[0056] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the embodiments of the present application are further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0057] See FIG6 , which is a schematic diagram of a floating capacitor three-level Boost converter provided in an embodiment of the present application.

[0058] The embodiment of the present application provides a floating capacitor three-level Boost converter, including: a controller 100, an inductor L, a first power device Q1, a second power device Q2, a first diode D1, a second diode D2, a first switch K1 and a floating capacitor Cf;

[0059] The first end and the second end of the inductor L are connected to the positive input end of the Boost converter and the anode of the first diode D1 respectively, and the anode and the cathode of the second diode D2 are connected to the cathode of the first diode D1 and the positive output end of the Boost converter respectively;

[0060] The first end and the second end of the first power device Q1 are respectively connected to the second end of the inductor L and the first end of the second power device Q2, and the second end of the second power device Q2 is connected to the negative input terminal of the Boost converter; the first end and the second end of the first switch K1 are respectively connected to the second end of the first power device Q1 and the first end of the floating capacitor Cf, and the second end of the floating capacitor Cf is connected to the cathode of the first diode D1;

[0061] The controller 100 is configured to control the first switch K1 to be turned off later than the first power device Q1 and the second power device Q2.

[0062] Since the disconnection moment of K1 lags behind that of Q1 and Q2, when the Boost converter shuts down and turns off Q1 and Q2, the first diode D1 and the second diode D2 are turned on to continue current flow. The maximum voltage stress of Q1 will be clamped to the voltage Vcf (Vbus / 2) of the floating capacitor, and the maximum voltage stress of Q2 will be clamped to Vbus-Vcf (Vbus / 2), thereby effectively solving the risk of overvoltage failure of Q1 and Q2.

[0063] The embodiment of the present application does not specifically limit the implementation method of the delayed shutdown of K1. The shutdown signal that lags behind the first switch tube Q1 and the second switch tube Q2 can be directly output by the control, or the shutdown signal delay can be implemented by a hardware circuit. The following analysis and examples are used for detailed introduction.

[0064] First, the shutdown signals with different timings directly output by the controller are introduced.

[0065] The controller is specifically configured to, upon receiving a shutdown instruction from the Boost converter or requiring a fault shutdown, first send a shutdown signal to the first power device and the second power device, and then send a shutdown signal to the first switch after a preset time interval. That is, the shutdown time of the first switch lags behind the shutdown times of the first and second switching devices.

[0066] The embodiment of the present application does not specifically limit the length of the preset time, as long as the preset time can ensure that the turn-off moment of the first switch lags behind the turn-off moments of the first power device and the second power device.

[0067] The following describes how to implement delay using a hardware delay circuit in conjunction with the accompanying drawings.

[0068] See FIG. 7 , which is a schematic diagram of delay control provided in an embodiment of the present application.

[0069] The Boost converter provided in the embodiment of the present application further includes: a delay circuit 200;

[0070] The controller 100 is specifically configured to send shutdown signals PWM-Q1, PWM-Q2 and PWM-K1 to the first power device Q1, the second power device Q2 and the first switch K1 respectively when receiving a shutdown instruction of the Boost converter or a fault shutdown is required.

[0071] The turn-off signal sent by the controller 100 to the first switch K1 is delayed by a preset time by the delay circuit 200 and then output to the first switch K1 .

[0072] The controller 100 includes: a first output terminal, a second output terminal and a third output terminal;

[0073] The first output terminal is connected to the control terminal of the first power device Q1, the second output terminal is connected to the control terminal of the second power device Q2, the third output terminal is connected to the first terminal of the delay circuit 200, and the second terminal of the delay circuit 200 is connected to the control terminal of the first switch K1.

[0074] The controller 100 sends shutdown signals to the first, second, and third output terminals, namely PWM-Q1, PWM-Q2, and PWM-K1, respectively. Due to the presence of the delay circuit 200, the shutdown signal received by K1 lags behind the shutdown signals of Q1 and Q2. Therefore, Q1 and Q2 are shut down first, and K1 is shut down later than Q1 and Q2. Q1 and Q2 can be shut down synchronously or asynchronously.

[0075] The following example introduces a specific implementation of a delay circuit.

[0076] See FIG8 , which is a schematic diagram of a delay circuit provided in an embodiment of the present application.

[0077] The Boost converter provided by the embodiment of the present application has a delay circuit including: a first resistor R1 and a first capacitor C1.

[0078] The shutdown signal PWM-K1 sent by the controller to the first switch K1 is input to the first end of the first resistor R1, the second end of the first resistor R1 is connected to the first end of the first capacitor C1, the second end of the first capacitor C1 is grounded, and the first end of the first capacitor C1 is connected to the control end of the first switch K1.

[0079] The delay circuit further includes a third diode D3.

[0080] A cathode of the third diode D3 is connected to the first end of the first resistor R1 , and an anode of the third diode D3 is connected to the second end of the first resistor R1 .

[0081] The delay circuit shown in Figure 8 operates as follows: when the shutdown signal PWM-K1 is high, the third diode D3 is turned off, and PWM-K1 charges C1 through R1. The voltage across C1 slowly rises, reaching the set value after a delay, at which point K1 is turned off. When the shutdown signal PWM-K1 goes low, the third diode D3 turns on, and the voltage on C1 is rapidly discharged to zero through the third diode D3.

[0082] FIG8 merely illustrates a delay circuit. In addition, the delay circuit may also be implemented by a timer or an integrated chip such as a CPLD or FPGA. This application does not specifically limit the specific implementation method of the delay circuit.

[0083] See FIG. 9 , which is a schematic diagram of another Boost converter provided in an embodiment of the present application.

[0084] The Boost converter provided in the embodiment of the present application further includes: a second switch K2 and a second resistor R2;

[0085] A first end of the second switch K2 is connected to the second end of the first switch K1 , and a second end of the second switch K2 is connected to the negative input end of the Boost converter via a second resistor.

[0086] The second switch K2 and the second resistor R2 form a pre-charging circuit for the floating capacitor Cf, which pre-charges the voltage of the floating capacitor Cf to a set value (Vbus / 2) before the Boost converter is started.

[0087] When the Boost converter is working normally, K2 is normally open, K1 is normally closed (K2 is disconnected), and Q1 and Q2 operate at high frequency.

[0088] If the Boost converter is in the Q1-on state and Q2-off state immediately before receiving a shutdown command or a fault shutdown, the controller will first turn off Q1. At this time, the first diode D1 and the second diode D2 will be turned on to continue the current. Since K1 remains in the closed state, the voltage across Q1 will be clamped to the floating capacitor voltage Vcf (Vbus / 2), and the voltage stress of Q2 will be clamped to Vbus-Vcf (Vbus / 2).

[0089] Similarly, if the Boost converter is in the Q1-off and Q2-on state (or Q1 and Q2-on state) immediately before receiving a shutdown command or a fault shutdown, the controller will first disconnect Q2 (disconnect Q1 and Q2). At this time, diodes D1 and D2 are turned on to continue the current. Since K1 remains closed, the voltage across Q1 and Q2 will be clamped to the floating capacitor voltage Vcf (Vbus / 2) and Vbus-Vcf (Vbus / 2) respectively. Therefore, the technical solution provided in the embodiment of the present application can effectively solve the risk of overvoltage failure of Q1 and Q2.

[0090] In addition, to ensure the static voltage balancing effect of Q1 and Q2 after K1 is turned off, a voltage balancing circuit can be connected in parallel across one of Q1 and Q2. It should be understood that since Q1 and Q2 are connected in series, when the voltage of one power device is clamped, the voltage of the other power device is also clamped.

[0091] See FIG. 10 , which is a schematic diagram of another Boost converter provided in an embodiment of the present application.

[0092] The Boost converter provided in the embodiment of the present application further includes: a first voltage equalizing circuit and / or a second voltage equalizing circuit; FIG10 is introduced by taking the inclusion of two voltage equalizing circuits as an example.

[0093] The first voltage balancing circuit 300 includes a resistor or a voltage stabilizing diode, and the second voltage balancing circuit 400 includes a resistor or a voltage stabilizing diode;

[0094] The first voltage balancing circuit 300 is connected in parallel to the first terminal and the second terminal of the first power device Q1;

[0095] The second voltage balancing circuit 400 is connected in parallel to the first terminal and the second terminal of the second power device Q2 .

[0096] The specific types of K1 and K2 are not specifically limited in the embodiments of the present application, and they may be, for example, relays or power semiconductor switching devices, wherein the power semiconductor devices may be IGBTs or MOSs.

[0097] Based on the suspended capacitor three-level Boost converter provided in the above embodiment, the present application further provides a control method for the suspended capacitor three-level Boost converter, which is described in detail below with reference to the accompanying drawings.

[0098] See FIG. 11 , which is a flow chart of a method for controlling a floating capacitor three-level Boost converter according to an embodiment of the present application.

[0099] The embodiment of the present application provides a control method for a suspended capacitor three-level Boost converter, wherein the Boost converter includes: a controller, an inductor, a first power device, a second power device, a first diode, a second diode, a first switch, and a suspended capacitor;

[0100] The method includes:

[0101] S1101: Determine whether a Boost converter shutdown instruction is received or a fault shutdown is required; if yes, execute S1102;

[0102] S1102: Control the first switch to be turned off later than the first power device and the second power device.

[0103] In the control method provided in the embodiment of the present application, since the disconnection moment of the first switch lags behind the first power device and the second power device, when the Boost converter shuts down and turns off the first power device and the second power device, the first diode and the second diode are turned on to continue current flow, and the maximum voltage stress of the first power device will be clamped to the voltage Vcf of the floating capacitor (i.e., half the bus voltage), and the maximum voltage stress of the second power device will be clamped to Vbus-Vcf (i.e., half the bus voltage), thereby effectively solving the risk of overvoltage failure of the first power device and the second power device.

[0104] The embodiment of the present application does not specifically limit the implementation method of the delayed shutdown of the first switch. The shutdown signal that lags behind the shutdown signal of the first switch tube can be directly output by software control, or the shutdown signal can be delayed by a hardware circuit. The following analysis and examples will provide a detailed introduction.

[0105] The software implementation method controls the disconnection time of the first switch to lag behind the disconnection time of the first power device and the second power device, specifically including: first sending a shutdown signal to the first power device and the second power device, and then sending a shutdown signal to the first switch after a preset time interval.

[0106] In hardware implementation, the Boost converter also includes: a delay circuit; controlling the disconnection time of the first switch to lag behind the disconnection time of the first power device and the second power device, specifically including: sending a shutdown signal to the first power device, the second power device and the first switch; and outputting the shutdown signal sent to the first switch to the first switch after being delayed for a preset time by the delay circuit.

[0107] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the systems or devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0108] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present application. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A suspended capacitor three-level Boost converter, It is characterized in that include: A controller, an inductor, a first power device, a second power device, a first diode, a second diode, a first switch and a suspended capacitor; The first end and the second end of the inductor are respectively connected to the positive input end of the Boost converter and the anode of the first diode, and the anode and the cathode of the second diode are respectively connected to the cathode of the first diode and the positive output end of the Boost converter; The first end and the second end of the first power device are respectively connected to the second end of the inductor and the first end of the second power device, and the second end of the second power device is connected to the negative input end of the Boost converter; the first end and the second end of the first switch are respectively connected to the second end of the first power device and the first end of the floating capacitor, and the second end of the floating capacitor is connected to the cathode of the first diode; The controller is used to control the disconnection time of the first switch to lag behind the disconnection time of the first power device and the second power device.

2. The converter according to claim 1, It is characterized in that The controller is specifically used to first send a shutdown signal to the first power device and the second power device when receiving a shutdown instruction of the Boost converter or a fault shutdown is required, and then send a shutdown signal to the first switch after a preset time interval.

3. The converter according to claim 1, It is characterized in that Also includes: Delay circuit; The controller is specifically configured to send a shutdown signal to the first power device, the second power device and the first switch when receiving a shutdown instruction of the Boost converter or a fault shutdown is required; The turn-off signal sent by the controller to the first switch is output to the first switch after being delayed by the delay circuit for a preset time.

4. The converter according to claim 3, It is characterized in that The delay circuit comprises: a first resistor and a first capacitor; The controller sends a shutdown signal to the first switch, inputting the first end of the first resistor, the second end of the first resistor is connected to the first end of the first capacitor, the second end of the first capacitor is grounded, and the first end of the first capacitor is connected to the control end of the first switch.

5. The converter according to claim 4, It is characterized in that The delay circuit further includes: a third diode; A cathode of the third diode is connected to a first end of the first resistor, and an anode of the third diode is connected to a second end of the first resistor.

6. The converter according to any one of claims 3 to 4, It is characterized in that The controller comprises: a first output terminal, a second output terminal and a third output terminal; The first output end is connected to the control end of the first power device, the second output end is connected to the control end of the second power device, the third output end is connected to the first end of the delay circuit, and the second end of the delay circuit is connected to the control end of the first switch; The controller sends a shut-off signal to the first output terminal, the second output terminal, and the third output terminal.

7. The converter according to any one of claims 1 to 5, It is characterized in that Also includes: a second switch and a second resistor; The first end of the second switch is connected to the second end of the first switch, and the second end of the second switch is connected to the negative input end of the Boost converter through the second resistor.

8. The converter according to any one of claims 3 to 4, It is characterized in that Also includes: A first voltage balancing circuit and / or a second voltage balancing circuit; the first voltage balancing circuit includes a resistor and / or a voltage regulator tube, and the second voltage balancing circuit includes a resistor and / or a voltage regulator tube; The first voltage balancing circuit is connected in parallel to the first end and the second end of the first power device; The second voltage balancing circuit is connected in parallel to the first end and the second end of the second power device.

9. A control method for a suspended capacitor three-level Boost converter. It is characterized in that The Boost converter comprises: a controller, an inductor, a first power device, a second power device, a first diode, a second diode, a first switch and a floating capacitor; The method includes: When a shutdown instruction of the Boost converter is received or a fault shutdown is required, the disconnection time of the first switch is controlled to lag behind the disconnection time of the first power device and the second power device.

10. The method according to claim 9, It is characterized in that The controlling the disconnection time of the first switch to lag behind the disconnection time of the first power device and the second power device specifically includes: First, a shutdown signal is sent to the first power device and the second power device, and then a shutdown signal is sent to the first switch after a preset time interval.

11. The method according to claim 9, It is characterized in that The Boost converter further includes: a delay circuit; The controlling the disconnection time of the first switch to lag behind the disconnection time of the first power device and the second power device specifically includes: A shutdown signal is sent to the first power device, the second power device and the first switch; the shutdown signal sent to the first switch is output to the first switch after being delayed by a preset time by the delay circuit.

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