Power conversion device

Abstract

The invention provides a power conversion device and relates to the field of power conversion. The power conversion device comprises a double-pole single-throw relay, a double-pole double-throw relay and a single-pole single-throw relay, the double-pole single-throw relay is connected between the second power supply end and the double-pole double-throw relay, and the double-pole double-throw relay is connected between the first power supply end and the power conversion circuit and between the double-pole single-throw relay and the power conversion circuit. The single-pole single-throw relay is connected between the double-pole double-throw relay and the power supply conversion circuit, the two ends of the single-pole single-throw relay are connected in parallel with a bidirectional conduction switch tube, and when switching between the first power supply end and the second power supply end is carried out, under the condition that the digital control circuit controls the power supply conversion circuit not to work and the single-pole single-throw relay is disconnected, the double-pole single-throw relay is switched off. And the digital control circuit outputs a driving signal for controlling the switching of the double-pole single-throw relay and the double-pole double-throw relay, so that zero-current switching between the two input ends is realized, and the switching speed is high.

Description

Technical Field

[0001] The present invention relates to the field of power conversion, and in particular to a power conversion device. Background Art

[0002] In order to have input redundancy, the traditional method of power conversion device generally uses two power supplies, or even uses a battery backup power supply such as an uninterruptible power supply (UPS). In actual operation, the two power supplies run in parallel and share current at the output port. However, the use of two power supplies will take up more space, resulting in increased costs.

[0003] One way to reduce costs in the industry is to implement input redundancy between two separate input voltages within a single power supply, thereby reducing the number of power supplies used in the system, wherein each input voltage can be either an AC voltage or a DC voltage.

[0004] In specific implementation, one of the input voltages is used as the main input and the other as the auxiliary input. When the main input fails, it is necessary to switch to the auxiliary input, which is also the core function of the power conversion device to implement input redundancy technology, namely Automatic Transfer Switch function (hereinafter referred to as ATS).

[0005] However, the various solutions currently used in the industry to achieve input redundancy on the same power supply still have major drawbacks. For example, the ATS switching speed is slow (more than 8ms), which requires increasing the power supply hold time and the BULK capacitor, which greatly increases the size and cost of the power supply. For example, to achieve the ATS switching function, multiple relays (such as 8 single-pole single-throw relays) need to be used in series to meet safety requirements, which greatly increases the size and cost of the power supply. If zero current switching cannot be achieved, especially when switching from DC to AC input, arc extinguishing needs to be considered, and relays with arc extinguishing devices need to be used, resulting in a large relay size, and a large interference to the internal power supply during load switching, which greatly increases the size and cost of the power supply.

[0006] Therefore, the industry is in urgent need of a fast and reliable zero-current switching method to realize the input redundancy function of the power conversion device. Summary of the invention

[0007] The present application proposes a power conversion device, including: a double-pole single-throw relay, wherein the normally open contact of the first sub-relay is used to connect the first terminal of the second power supply end; the normally open contact of the second sub-relay is used to connect the second terminal of the second power supply end; a double-pole double-throw relay, wherein the normally closed contact of the first sub-relay is used to connect the first terminal of the first power supply end, and the normally open contact is connected to the normally closed contact of the first sub-relay in the double-pole single-throw relay; the normally closed contact of the second sub-relay is used to connect the second terminal of the first power supply end, and the normally open contact is connected to the normally closed contact of the second sub-relay in the double-pole single-throw relay. Normally closed contact, the common end of the second sub-relay in the double-pole double-throw relay is connected to an input end of the power conversion circuit; a single-pole single-throw relay, the normally open contact is connected to the common end of the first sub-relay of the double-pole double-throw relay, and the normally closed contact is connected to the other input end of the power conversion circuit, wherein two ends of the single-pole single-throw relay are connected in parallel with a bidirectional conduction switch tube; a digital control circuit is used to output a drive signal for controlling the single-pole single-throw relay, the bidirectional conduction switch tube, and the power conversion circuit, and also outputs a high-voltage excitation drive signal and a rated voltage drive signal for controlling the double-pole single-throw relay and the double-pole double-throw relay.

[0008] Furthermore, the first power supply end receives alternating current or direct current; the second power supply end receives alternating current or direct current.

[0009] Furthermore, when switching between the first power supply end and the second power supply end, when the digital control circuit controls the power conversion circuit not to work and the single-pole single-throw relay is disconnected, the digital control circuit outputs a drive signal to control the switching of the double-pole single-throw relay and the double-pole double-throw relay.

[0010] Furthermore, when the power conversion device is working and the first power supply end is the main power supply end, if the first power supply input to the first power supply end loses power and the second power supply input to the second power supply end is powered normally, then when the power conversion circuit does not work and the single-pole single-throw relay is disconnected, the high-voltage excitation drive signal output by the digital control circuit is set high.

[0011] Furthermore, when the power conversion device is working and the first power supply end is the main power supply end, the following are executed: S1: the digital control circuit controls the power conversion circuit to work, the single-pole single-throw relay is closed, the bidirectional conduction switch tube is disconnected, the high-voltage excitation drive signal and the rated voltage drive signal are set low, the first detection circuit detects whether the first power supply input to the first power supply end is powered off, and the second detection circuit detects whether the second power supply input to the second power supply end is powered normally. If so, proceed to step S2; S2: the digital control circuit determines whether the duration is greater than the set time Ts. If so, proceed to step S3; S3: at time T1, the digital control circuit controls The power conversion circuit is controlled not to work, the bidirectional conduction switch tube is turned on, the single-pole single-throw relay is turned off, and the high-voltage excitation drive signal and the rated voltage drive signal are set high; S4: at time T2, the digital control circuit controls the bidirectional conduction switch tube to be turned off; S5: at time T3, switch to power supply by the second power supply end; S6: at time T4, the digital control circuit controls the bidirectional conduction switch tube to be turned on, sets the high-voltage excitation drive signal to a low level, and controls the power conversion circuit to work at the same time or later; S7: at time T5, the digital control circuit controls the single-pole single-throw relay to be closed; S8: at time T6, controls the bidirectional conduction switch tube to be turned off.

[0012] Furthermore, when the power conversion device is working and the first power supply end is the main power supply end, the following are executed: S1: the digital control circuit controls the power conversion circuit to work, the single-pole single-throw relay is closed, the bidirectional conduction switch tube is disconnected, the high-voltage excitation drive signal and the rated voltage drive signal are set low, the first detection circuit detects whether the first power supply input to the first power supply end is powered off, and the second detection circuit detects whether the second power supply input to the second power supply end is powered normally. If so, proceed to step S2; S2: the digital control circuit determines whether the duration is greater than the set time Ts. If so, proceed to step S3; S3: at time T1, the digital control circuit controls the power conversion circuit not to Working, the bidirectional conduction switch tube is turned on; S31: at T11 time, the digital control circuit controls the single-pole single-throw relay to be disconnected, and sets the high-voltage excitation drive signal and the rated voltage drive signal to high; S4: at T2 time, the digital control circuit controls the bidirectional conduction switch tube to be disconnected; S5: at T3 time, switch to power supply by the second power supply end; S6: at T4 time, the digital control circuit controls the bidirectional conduction switch tube to be turned on, sets the high-voltage excitation drive signal to low, and controls the power conversion circuit to work at the same time or afterwards; S7: at T5 time, the digital control circuit controls the single-pole single-throw relay to be closed; S8: at T6 time, controls the bidirectional conduction switch tube to be disconnected.

[0013] Furthermore, when the power conversion device is working and the first power supply end is the main power supply end, the following are executed: S1: the digital control circuit controls the power conversion circuit to work, the single-pole single-throw relay is closed, the bidirectional conduction switch tube is disconnected, the high-voltage excitation drive signal and the rated voltage drive signal are set low, the first detection circuit detects whether the first power supply input to the first power supply end is powered off, and the second detection circuit detects whether the second power supply input to the second power supply end is powered normally. If so, the process goes to step S2; S2: the digital control circuit determines whether the duration is greater than the set time Ts. If so, the process goes to step S3; S3: at time T1, the digital control circuit controls the power conversion circuit not to work, the bidirectional conduction switch is turned on, and the power conversion circuit is turned off. The switch is turned on; S31: at T11, the digital control circuit controls the single-pole single-throw relay to be turned off; S4: at T2, the digital control circuit controls the bidirectional conduction switch to be turned off; S41: at T22, the digital control circuit sets the high-voltage excitation drive signal and the rated voltage drive signal to high; S5: at T3, switching to power supply by the second power supply end; S6: at T4, the digital control circuit controls the bidirectional conduction switch to be turned on, sets the high-voltage excitation drive signal to low, and controls the power conversion circuit to work at the same time or later; S7: at T5, the digital control circuit controls the single-pole single-throw relay to be closed; S8: at T6, the bidirectional conduction switch is controlled to be turned off.

[0014] Furthermore, when the power conversion device is working and the second power supply end is the main power supply end, if the second power supply input to the second power supply end loses power and the first power supply input to the first power supply end is powered normally, then when the power conversion circuit does not work and the single-pole single-throw relay is disconnected, the rated voltage drive signal output by the digital control circuit is set to low.

[0015] Furthermore, when the power conversion device is working and the second power supply end is the main power supply end, the following are executed: S1: the digital control circuit controls the power conversion circuit to work, the single-pole single-throw relay is closed, the bidirectional conduction switch tube is disconnected, the high-voltage excitation drive signal is set low, and the rated voltage drive signal is set high, the second detection circuit detects whether the second power supply input to the second power supply end is powered off, and the first detection circuit detects whether the first power supply input to the first power supply end is powered normally. If so, the process goes to step S2; S2: the digital control circuit determines whether the duration is greater than the set time Ts. If so, the process goes to step S3; S3: at T At time T1, the digital control circuit controls the power conversion circuit not to work, the bidirectional conduction switch tube to be turned on, the single-pole single-throw relay to be turned off, and the rated voltage drive signal to be set low; S4: at time T2, the digital control circuit controls the bidirectional conduction switch tube to be turned off; S5: at time T3, switch to power supply by the first power supply end; S6: at time T4, the digital control circuit controls the bidirectional conduction switch tube to be turned on, and controls the power conversion circuit to work at the same time or later; S7: at time T5, the digital control circuit controls the single-pole single-throw relay to be closed; S8: at time T6, controls the bidirectional conduction switch tube to be turned off.

[0016] Furthermore, when the power conversion device is working and the second power supply end is the main power supply end, the following are executed: S1: the digital control circuit controls the power conversion circuit to work, the single-pole single-throw relay is closed, the bidirectional conduction switch tube is disconnected, the high-voltage excitation drive signal is set low, and the rated voltage drive signal is set high, the second detection circuit detects whether the second power supply input to the second power supply end is powered off, and the first detection circuit detects whether the first power supply input to the first power supply end is powered normally. If so, the process goes to step S2; S2: the digital control circuit determines whether the duration is greater than the set time Ts. If so, the process goes to step S3; S3: at time T1, the digital control circuit The circuit controls the power conversion circuit not to work and the bidirectional conduction switch tube to be turned on; S31: at time T11, the digital control circuit controls the single-pole single-throw relay to be turned off and sets the rated voltage drive signal to a low level; S4: at time T2, the digital control circuit controls the bidirectional conduction switch tube to be turned off; S5: at time T3, switching to power supply by the first power supply end; S6: at time T4, the digital control circuit controls the bidirectional conduction switch tube to be turned on, and controls the power conversion circuit to work at the same time or later; S7: at time T5, the digital control circuit controls the single-pole single-throw relay to be closed; S8: at time T6, controlling the bidirectional conduction switch tube to be turned off.

[0017] Furthermore, when the power conversion device is working and the second power supply end is the main power supply end, the following are executed: S1: the digital control circuit controls the power conversion circuit to work, the single-pole single-throw relay is closed, the bidirectional conduction switch tube is disconnected, the high-voltage excitation drive signal is set low, and the rated voltage drive signal is set high. The second detection circuit detects whether the second power supply input to the second power supply end is powered off, and the first detection circuit detects whether the first power supply input to the first power supply end is powered normally. If so, the process goes to step S2; S2: the digital control circuit determines whether the duration is greater than the set time Ts. If so, the process goes to step S3; S3: at time T1, the digital control circuit controls the power conversion circuit to work, the single-pole single-throw relay is closed, the bidirectional conduction switch tube is disconnected, the high-voltage excitation drive signal is set low, and the rated voltage drive signal is set high. The circuit does not work and the bidirectional conduction switch tube is turned on; S31: at time T11, the digital control circuit controls the single-pole single-throw relay to be disconnected; S4: at time T2, the digital control circuit controls the bidirectional conduction switch tube to be disconnected; S41: at time T22, the digital control circuit sets the rated voltage drive signal to a low level; S5: at time T3, switching to power supply from the first power supply end; S6: at time T4, the digital control circuit controls the bidirectional conduction switch tube to be turned on, and controls the power conversion circuit to work at the same time or afterwards; S7: at time T5, the digital control circuit controls the single-pole single-throw relay to be closed; S8: at time T6, controlling the bidirectional conduction switch tube to be disconnected.

[0018] Furthermore, it also includes a second double-pole single-throw relay, in which the normally open contact of the first sub-relay is used to connect to the first terminal of the first power supply end, and the normally closed contact is connected to the normally closed contact of the first sub-relay in the double-pole double-throw relay; the normally open contact of the second sub-relay is used to connect to the second terminal of the first power supply end, and the normally closed contact is connected to the normally closed contact of the second sub-relay in the double-pole double-throw relay.

[0019] The above is a fairly broad overview of the features and technical advantages of the present application, so that the following detailed description of the present application can be better understood. The additional features and advantages of the present application will be described below, and they form the subject matter of the claims of the present application. It will be appreciated by those skilled in the art that the disclosed concepts and specific embodiments can be easily utilized as the basis for modifying or designing other structures or processes for realizing the same purpose of the present application. It will also be appreciated by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the present application as set forth in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more fully understand the present application and its advantages, reference is now made to the following description in conjunction with the accompanying drawings:

[0021] In the figure:

[0022] Figure 1A schematic diagram of a power conversion device provided by an embodiment of the present application is shown;

[0023] Figure 2 A control waveform diagram of a power conversion device according to an embodiment of the present application is shown;

[0024] Figure 3 A control waveform diagram of a power conversion device according to another embodiment of the present application is shown;

[0025] Figure 4 A control waveform diagram of a power conversion device according to another embodiment of the present application is shown;

[0026] Figure 5 A control waveform diagram of a power conversion device according to another embodiment of the present application is shown;

[0027] Figure 6 A control waveform diagram of a power conversion device according to another embodiment of the present application is shown;

[0028] Figure 7 A control waveform diagram of a power conversion device according to another embodiment of the present invention is shown.

[0029] Figure 8 A schematic diagram of a power conversion device provided by another embodiment of the present application is shown;

[0030] Fig. 9 A schematic diagram of a power conversion device provided in another embodiment of the present application is shown.

[0031] Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated.The figures are drawn to clearly illustrate the relevant aspects of the various embodiments and are not necessarily drawn to scale. DETAILED DESCRIPTION

[0032] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in this application. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0033] One embodiment of the present application is to provide a power conversion device, which can realize the input redundancy function of fast zero current switching, and the power conversion device is small in size and low in cost. Figure 1 The power conversion device 100 is a schematic diagram of a power conversion device provided by an embodiment of the present application. The power conversion device 100 includes:

[0034] A double-pole single-throw relay Rb, wherein the normally open contact of the first sub-relay Rb1 is used to connect to the first terminal d21 of the second power supply end; wherein the normally open contact of the second sub-relay Rb2 is used to connect to the second terminal d22 of the second power supply end;

[0035] A double-pole double-throw relay Rc, wherein the normally closed contact of the first sub-relay Rc1 is used to connect to the first terminal d11 of the first power supply end, and the normally open contact is connected to the normally closed contact of the first sub-relay Rb1 in the double-pole single-throw relay Rb; wherein the normally closed contact of the second sub-relay Rc2 is used to connect to the second terminal d12 of the first power supply end, and the normally open contact is connected to the normally closed contact of the second sub-relay Rb2 in the double-pole single-throw relay Rb, and the common terminal of the second sub-relay Rc2 in the double-pole double-throw relay Rc is connected to an input terminal din1 of the power conversion circuit 110;

[0036] A single-pole single-throw relay Rm, whose normally open contact is connected to the common terminal of the first sub-relay Rc1 of the double-pole double-throw relay Rc, and whose normally closed contact is connected to the other input terminal din2 of the power conversion circuit 110, wherein two ends of the single-pole single-throw relay Rm are connected in parallel with a bidirectional conducting switch tube 210;

[0037] The digital control circuit 310 is used to output drive signals for controlling the single-pole single-throw relay Rm, the bidirectional conducting switch tube 210, and the power conversion circuit 110, and also outputs a high-voltage excitation drive signal DRVh and a rated voltage drive signal DRVn for controlling the double-pole single-throw relay Rb and the double-pole double-throw relay Rc.

[0038] The first power supply terminal receives AC power or DC power; the second power supply terminal also receives AC power or DC power. In this way, when implementing ATS, the input of the power conversion device 100 can be switched from DC power to DC power, from DC power to AC power, from AC power to AC power, and from AC power to DC power. More specifically, the first power supply terminal and the second power supply terminal receive two separate input sources within a single power supply.

[0039] In a specific embodiment, the bidirectional conductive switch 210 is an electronic switch. Figure 1 The embodiment shown includes a first bidirectional thyristor Ta and a second bidirectional thyristor Tb connected in series. Of course, the bidirectional conducting switch tube 210 can also be other electronic switches as long as it can conduct bidirectionally.

[0040] In a specific embodiment, the power conversion device 100 further includes a first detection circuit 410 and a second detection circuit 420. The first detection circuit 410 is connected to the first power supply end, and is used to detect the first power supply VacA input to the first power supply end, and output a detection signal to the digital control circuit 310. The digital control circuit 310 determines whether the first power supply VacA is powered off or powered normally according to the detection signal from the first detection circuit 410. The second detection circuit 420 is connected to the second power supply end, and is used to detect the second power supply VacB input to the second power supply end, and output a detection signal to the digital control circuit 310. The digital control circuit 310 determines whether the second power supply VacB is powered off or powered normally according to the detection signal from the second detection circuit 420.

[0041] The present application does not limit the specific structures of the first detection circuit 410 and the second detection circuit 420 .

[0042] In a specific embodiment, the power conversion device 100 further includes an EMI circuit 510 connected to the first power supply end and an EMI circuit 520 connected to the second power supply end.

[0043] In a specific embodiment, the power conversion circuit 110 may be implemented as a power conversion circuit including a PFC circuit and a cascade connection with the PFC circuit. However, the present application does not limit the specific structure of the power conversion circuit 110, as long as it can convert the input power of the first power supply terminal or the second power supply terminal into the output power of the output terminal.

[0044] In a specific embodiment, when switching between the first power supply end and the second power supply end, when the digital control circuit 310 controls the power conversion circuit 110 to not work and the single-pole single-throw relay Rm is disconnected, the digital control circuit 310 outputs a drive signal to control the switching of the double-pole single-throw relay Rb and the double-pole double-throw relay Rc to achieve zero current switching.

[0045] For example, in a specific embodiment, when the power conversion device 100 is working and the first power supply end is the main power supply end, if the first power supply source VacA input to the first power supply end loses power and the second power supply source VacB input to the second power supply end is normally powered, then when the power conversion circuit 110 is not working and the single-pole single-throw relay Rm is disconnected, the high-voltage excitation drive signal DRVh output by the digital control circuit 310 is set high, so that the two sub-relays in the double-pole single-throw relay Rb are quickly attracted, and the two sub-relays in the double-pole double-throw relay Rc are quickly switched from the normally closed contact to the normally open contact, so as to realize the switching from the first power supply source VacA to the second power supply source VacB, and zero current switching can be achieved with a fast switching speed.

[0046] In a specific implementation, the high level of the high voltage excitation drive signal DRVh is greater than the high level of the rated voltage drive signal DRVn. Then the high level of the high voltage excitation drive signal DRVh can drive the double-pole single-throw relay Rb and the double-pole double-throw relay Rc to switch quickly, the high level of the rated voltage drive signal DRVn can drive the double-pole single-throw relay Rb and the double-pole double-throw relay Rc to maintain the energized state, and the low level of the rated voltage drive signal DRVn can drive the double-pole single-throw relay Rb and the double-pole double-throw relay Rc to maintain the released state. In a specific embodiment, the high level of the high voltage excitation drive signal DRVh is a 66V DC voltage, and the high level of the rated voltage drive signal DRVn is a 12V DC voltage.

[0047] Since the power conversion circuit 110 is not working, the single-pole single-throw relay Rm is disconnected, and the first bidirectional thyristor Ta and the second bidirectional thyristor Tb are disconnected, no current flows through the double-pole single-throw relay Rb and the double-pole double-throw relay Rc, so it can achieve zero current switching. This not only allows the double-pole single-throw relay Rb and the double-pole double-throw relay Rc to select relays without arc extinguishing devices to reduce the size of the relays, but also does not need to consider the moment of switching from the first power supply VacA to the second power supply VacB, especially when switching from direct current to alternating current, it is not necessary to control it to switch at the zero-crossing point of the alternating current, so that the control is simple and the switching speed is fast.

[0048] The double-pole single-throw relay Rb and the double-pole double-throw relay Rc are driven to switch under the high-voltage excitation drive signal DRVh, so the switching speed is fast (such as less than 4ms). There is no need to increase the BULK capacitor, so the power supply size is small and the cost is greatly reduced.

[0049] In one specific embodiment, see Figure 2 The control waveform diagram of the power conversion device of an embodiment of the present application is illustrated by taking the first power supply VacA and the second power supply VacB as AC power and the bidirectional conducting switch tube 210 as a bidirectional thyristor connected in series as an example. When the power conversion device 100 is working and the first power supply end is the main power supply end, the following is executed:

[0050] S1: The digital control circuit 310 controls the power conversion circuit 110 to work, the single-pole single-throw relay Rm is closed, the bidirectional conductive switch tube 210 is disconnected, the high-voltage excitation drive signal DRVh and the rated voltage drive signal DRVn are set low, the first detection circuit 410 detects whether the first power supply VacA input to the first power supply end is powered off, and the second detection circuit 420 detects whether the second power supply VacB input to the second power supply end is powered normally. If so, enter step S2;

[0051] S2: The digital control circuit 310 determines whether the duration is greater than the set time Ts, and if so, proceeds to step S3;

[0052] S3: At time T1, the digital control circuit 310 controls the power conversion circuit 110 to not work, the bidirectional conduction switch tube 210 to turn on, the single-pole single-throw relay Rm to turn off, and the high-voltage excitation drive signal DRVh and the rated voltage drive signal DRVn to be high;

[0053] S4: At time T2, the digital control circuit 310 controls the bidirectional conductive switch 210 to be turned off;

[0054] S5: At time T3, switching to power supply from the second power supply end;

[0055] S6: At time T4, the digital control circuit 310 controls the bidirectional conductive switch 210 to be turned on, sets the high-voltage excitation drive signal DRVh to a low level, and controls the power conversion circuit 110 to work at the same time or later;

[0056] S7: At time T5, the digital control circuit 310 controls the single-pole single-throw relay Rm to close;

[0057] S8: At time T6, the bidirectional conducting switch tube 210 is controlled to be turned off.

[0058] like Figure 2 As shown, before time T0, the digital control circuit 310 controls the power conversion circuit 110 to work, that is, the driving signal DRV conv driving the power conversion circuit 110 is set high or the duty cycle is determined according to the loop control. The driving signal DRV Rm driving the single-pole single-throw relay Rm is set high, and the driving signal DRV Ta driving the first bidirectional thyristor Ta and the driving signal DRV Tb driving the second bidirectional thyristor Tb are set low, then the single-pole single-throw relay Rm is closed. The digital control circuit 310 sets the high-voltage excitation driving signal DRVh and the rated voltage driving signal DRVn low, then the driving signal DRV Rb driving the double-pole single-throw relay Rb and the driving signal DRV Rc driving the double-pole double-throw relay Rc are low, and the double-pole single-throw relay Rb and the double-pole double-throw relay Rc are in a natural release state. The first power supply VacA as the input of the main circuit to the first power supply end is used for power supply.

[0059] At time T0, the first power supply VacA loses power, the second power supply VacB still supplies power normally, and the duration to time T1 is greater than the set time Ts, then it is considered that the power supply end needs to be switched. Specifically, the set time Ts can be determined according to actual design requirements.

[0060] The switching of the power supply end starts at time T1. At this time, the digital control circuit 310 controls the power conversion circuit 110 not to work. For example, the drive signal DRV conv for driving the power conversion circuit 110 is set low or the duty cycle is 0, so that the load of the power conversion device 100 is very small or almost zero, and the drive signal DRV Ta for driving the first bidirectional thyristor Ta and the drive signal DRV Tb for driving the second bidirectional thyristor Tb are set high, then the first bidirectional thyristor Ta and the second bidirectional thyristor Tb are opened to bypass the single-pole single-throw relay Rm. Since the speed of the electronic switch is very fast, when the drive signal DRV Rm for driving the single-pole single-throw relay Rm is set low at the same time, the single-pole single-throw relay Rm can be disconnected (or released) when there is almost no load current and it is bypassed, so that it can be protected from damage by the impact current and arcing is avoided. Not only the single-pole single-throw relay Rm is protected, but also the need to use a relay with an arcing device can be avoided, and the size of the single-pole single-throw relay Rm can be reduced. Moreover, at time T1, the high-voltage excitation drive signal DRVh and the rated voltage drive signal DRVn are set high, so that the normally open contacts of the sub-relays in the double-pole double-throw relay Rc are quickly closed, and the normally open contacts of the sub-relays in the double-pole single-throw relay Rb are quickly closed, and the switching is performed when the load of the power conversion device 100 is very small or almost zero, that is, zero-current attraction is achieved to avoid arcing, and the volume of the double-pole single-throw relay Rb and the double-pole double-throw relay Rc is also reduced, thereby extending their service life.

[0061] Then, at time T2, the digital control circuit 310 controls the bidirectional conduction switch tube 210 to be disconnected, and the single-pole single-throw relay Rm is also in the disconnected state, so that the input end of the power conversion device 100 is disconnected from the power conversion circuit 110, and at time T3, the switching from the first power supply end to the second power supply end is completed. In this way, during the process of switching the power supply end, even if the power supply is AC, there is no need to consider whether the power supply is at the zero point, which makes the control simple and realizes zero current switching.

[0062] Then, at time T4, the digital control circuit 310 sets the drive signal DRV Ta for driving the first bidirectional thyristor Ta and the drive signal DRV Tb for driving the second bidirectional thyristor Tb high, and controls the power conversion circuit 110 to work at the same time or later, that is, after completing the switching of the input end, the power conversion circuit 110 is put into working state again. Then the power conversion circuit 110 is powered by the second power supply end and works normally. At this time, the high-voltage excitation drive signal DRVh is set low, and the rated voltage excitation drive signal DRVn is high, then the high-voltage fast switching process of the double-pole single-throw relay Rb and the double-pole double-throw relay Rc is ended, and the double-pole single-throw relay Rb and the double-pole double-throw relay Rc are maintained in the energized state by the rated voltage excitation drive signal DRVn. The time length from time T3 to time T4 can be set according to the product design requirements.

[0063] Then, at time T5, the digital control circuit 310 sets the driving signal DRV Rm for driving the single-pole single-throw relay Rm high, and the single-pole single-throw relay Rm is closed. Since at time T4, the first bidirectional thyristor Ta and the second bidirectional thyristor Tb have been closed to bypass the single-pole single-throw relay Rm, the single-pole single-throw relay Rm can achieve zero current switching.

[0064] Then, at time T6, the driving signal DRV Ta for driving the first bidirectional thyristor Ta and the driving signal DRV Tb for driving the second bidirectional thyristor Tb are set low, and the first bidirectional thyristor Ta and the second bidirectional thyristor Tb are disconnected, thus completing the working state of switching from the first power supply end to the second power supply end.

[0065] For better, please refer to Figure 3 The control waveform diagram of the power conversion device of another embodiment of the present application is shown in FIG. Figure 2 The difference is that in step S3: at time T1, the digital control circuit 310 controls the power conversion circuit 110 to not work and the bidirectional conduction switch tube 210 to be turned on; in step S31 after step S3: at time T11, the digital control circuit 310 controls the single-pole single-throw relay Rm to be turned off, and sets the high-voltage excitation drive signal DRVh and the rated voltage drive signal DRVn to high. This ensures that the single-pole single-throw relay Rm is turned off during the conduction period of the first bidirectional thyristor Ta and the second bidirectional thyristor Tb, thereby achieving zero current switching. Since the switching speed of the single-pole single-throw relay Rm is very fast, such as about 1 millisecond, it can be as follows Figure 3 As shown, the double-pole single-throw relay Rb and the double-pole double-throw relay Rc are controlled to switch simultaneously with the single-pole single-throw relay Rm, and zero current switching can be achieved.

[0066] For better, see Figure 4 The control waveform diagram of the power conversion device of another embodiment of the present application is shown in FIG. Figure 2The difference is that in step S3: at time T1, the digital control circuit 310 controls the power conversion circuit 110 not to work and the bidirectional conduction switch tube 210 to conduct; in step S31 after step S3: at time T11, the digital control circuit 310 controls the single-pole single-throw relay Rm to be disconnected; in step S41 after step S4: at time T22, the digital control circuit 310 sets the high-voltage excitation drive signal DRVh and the rated voltage drive signal DRVn to high. In this way, it is ensured that the single-pole single-throw relay Rm is disconnected during the conduction period of the first bidirectional thyristor Ta and the second bidirectional thyristor Tb, and zero current switching is achieved. And it is ensured that the double-pole single-throw relay Rb and the double-pole double-throw relay Rc are attracted after the power conversion circuit 110 does not work, the first bidirectional thyristor Ta and the second bidirectional thyristor Tb are disconnected, and the single-pole single-throw relay Rm is released, so that absolute zero current switching can be achieved.

[0067] As in another specific embodiment, when the power conversion device 100 is working and the second power supply end is the main power supply end, if the second power supply source VacB input to the second power supply end loses power and the first power supply source VacA input to the first power supply end is powered normally, then when the power conversion circuit 110 is not working and the single-pole single-throw relay Rm is disconnected, the rated voltage drive signal DRVn output by the digital control circuit 310 is set low, so that the sub-relays in the double-pole single-throw relay Rb and the double-pole double-throw relay Rc achieve zero current release, so as to achieve zero current switching from the second power supply source VacB to the first power supply source VacA.

[0068] In one specific embodiment, see Figure 5 The control waveform diagram of the power conversion device of another embodiment of the present application is illustrated by taking the first power supply VacA and the second power supply VacB as AC power, and the bidirectional conducting switch tube 210 as a bidirectional thyristor connected in series as an example. When the power conversion device 100 is working and the second power supply end is the main power supply end, the following is executed:

[0069] S1: The digital control circuit 310 controls the power conversion circuit 110 to work, the single-pole single-throw relay Rm is closed, the bidirectional conductive switch tube 210 is disconnected, the high-voltage excitation drive signal DRVh is set low, and the rated voltage drive signal DRVn is set high. The second detection circuit 420 detects whether the second power supply VacB input to the second power supply end is powered off, and the first detection circuit 410 detects whether the first power supply VacA input to the first power supply end is powered normally. If so, enter step S2;

[0070] S2: The digital control circuit 310 determines whether the duration is greater than the set time Ts, and if so, proceeds to step S3;

[0071] S3: At time T1, the digital control circuit 310 controls the power conversion circuit 110 to stop working, the bidirectional conduction switch tube 210 to turn on, the single-pole single-throw relay Rm to turn off, and the rated voltage drive signal DRVn to be low;

[0072] S4: At time T2, the digital control circuit 310 controls the bidirectional conductive switch 210 to be turned off;

[0073] S5: At time T3, switching to power supply from the first power supply end;

[0074] S6: At time T4, the digital control circuit 310 controls the bidirectional conductive switch 210 to be turned on, and controls the power conversion circuit 110 to work simultaneously or subsequently;

[0075] S7: At time T5, the digital control circuit 310 controls the single-pole single-throw relay Rm to close;

[0076] S8: At time T6, the bidirectional conducting switch tube 210 is controlled to be turned off.

[0077] like Figure 5 As shown, before time T0, the digital control circuit 310 controls the power conversion circuit 110 to work, drives the driving signal DRV Rm of the single-pole single-throw relay Rm to be high, drives the driving signal DRV Ta of the first bidirectional thyristor Ta and the driving signal DRV Tb of the second bidirectional thyristor Tb to be low, and sets the high-voltage excitation driving signal DRVh to be low and the rated voltage driving signal DRVn to be high. The second power supply VacB as the input of the main circuit to the second power supply end is used for power supply.

[0078] At time T0, the second power supply VacB loses power, the first power supply VacA still supplies power normally, and the duration to time T1 is greater than the set time Ts, then it is considered that the power supply end needs to be switched. Specifically, the set time Ts can be determined according to actual design requirements.

[0079] At time T1, the switching of the power supply end starts. At this time, the digital control circuit 310 controls the power conversion circuit 110 to stop working, so that the load of the power conversion device 100 is very small or almost zero, and the driving signal DRV Ta for driving the first bidirectional thyristor Ta and the driving signal DRV Tb for driving the second bidirectional thyristor Tb are set high, and Figure 2 Similarly, the single-pole single-throw relay Rm can be disconnected (or released) when there is almost no load current and it is bypassed, and the advantages are the same, which will not be repeated here. In addition, at time T1, the rated voltage drive signal DRVn is set low, so that the sub-relays in the double-pole double-throw relay Rc and the double-pole single-throw relay Rb are released, and Figure 2Similarly, the double-pole double-throw relay Rc and the double-pole single-throw relay Rb can also achieve zero current release, and the advantages are the same, which will not be repeated here.

[0080] Then, at time T2, the digital control circuit 310 controls the bidirectional conduction switch tube 210 to be disconnected, and the single-pole single-throw relay Rm is also in the disconnected state, so that the input end of the power conversion device 100 is disconnected from the power conversion circuit 110, and at time T3, the switching from the second power supply end to the first power supply end is completed. In this way, during the process of switching the power supply end, even if the power supply is AC, there is no need to consider whether the power supply is at the zero point, which makes the control simple and realizes zero current switching.

[0081] Then, at time T4, the digital control circuit 310 sets the driving signal DRV Ta for driving the first bidirectional thyristor Ta and the driving signal DRV Tb for driving the second bidirectional thyristor Tb high, and controls the power conversion circuit 110 to work at the same time or later, that is, after completing the switching of the input end, the power conversion circuit 110 enters the working state again. Then, the power conversion circuit 110 is powered by the first power supply end and works normally.

[0082] Then, at time T5, the digital control circuit 310 sets the driving signal DRV Rm for driving the single-pole single-throw relay Rm high, and the single-pole single-throw relay Rm is closed. Since at time T4, the first bidirectional thyristor Ta and the second bidirectional thyristor Tb are closed, the single-pole single-throw relay Rm is bypassed, and the single-pole single-throw relay Rm can achieve zero current switching.

[0083] Then, at time T6, the drive signal DRV Ta for driving the first bidirectional thyristor Ta and the drive signal DRV Tb for driving the second bidirectional thyristor Tb are set low, and the first bidirectional thyristor Ta and the second bidirectional thyristor Tb are disconnected, thus completing the working state of switching from power supply from the second power supply end to power supply from the first power supply end.

[0084] For better, please refer to Figure 6 The control waveform diagram of the power conversion device of another embodiment of the present application is shown in FIG. Figure 5 The difference is that in step S3: at time T1, the digital control circuit 310 controls the power conversion circuit 110 to not work and the bidirectional conduction switch tube 210 to be turned on; in step S31 after step S3: at time T11, the digital control circuit 310 controls the single-pole single-throw relay Rm to be turned off and sets the rated voltage drive signal DRVn to a low level. This ensures that the single-pole single-throw relay Rm is turned off during the conduction period of the first bidirectional thyristor Ta and the second bidirectional thyristor Tb, thereby achieving zero current switching. Similarly, since the switching speed of the single-pole single-throw relay Rm is very fast, such as about 1 millisecond, it can be as follows Figure 6As shown, the double-pole single-throw relay Rb and the double-pole double-throw relay Rc are controlled to switch simultaneously with the single-pole single-throw relay Rm, and zero current switching can be achieved.

[0085] For better, see Figure 7 The control waveform diagram of the power conversion device of another embodiment of the present application is shown in FIG. Figure 5 The difference is that in step S3: at time T1, the digital control circuit 310 controls the power conversion circuit 110 not to work and the bidirectional conduction switch tube 210 to conduct; in step S31 after step S3: at time T11, the digital control circuit 310 controls the single-pole single-throw relay Rm to be disconnected; in step S41 after step S4: at time T22, the digital control circuit 310 sets the rated voltage drive signal DRVn to a low level. In this way, it is ensured that the single-pole single-throw relay Rm is disconnected during the conduction period of the first bidirectional thyristor Ta and the second bidirectional thyristor Tb, so as to achieve zero current switching. And it is ensured that the double-pole single-throw relay Rb and the double-pole double-throw relay Rc are attracted after the power conversion circuit 110 does not work, the first bidirectional thyristor Ta and the second bidirectional thyristor Tb are disconnected, and the single-pole single-throw relay Rm is released, so as to achieve absolute zero current switching.

[0086] like Figures 2 to 7 In the embodiments, it is taken that at time T4, the digital control circuit 310 sets the driving signal DRV Ta for driving the first bidirectional thyristor Ta and the driving signal DRV Tb for driving the second bidirectional thyristor Tb high, and controls the power conversion circuit 110 to work. In actual implementation, at time T4, the digital control circuit 310 sets the driving signal DRV Ta for driving the first bidirectional thyristor Ta and the driving signal DRV Tb for driving the second bidirectional thyristor Tb high, and controls the power conversion circuit 110 to work after a slight delay (after the first bidirectional thyristor Ta and the second bidirectional thyristor Tb are fully turned on), so that the power conversion circuit 110 can be controlled to work after the bidirectional conduction switch tube is completely turned on, thereby improving the reliability of the power conversion device.

[0087] In an actual implementation example, Figure 2 The power conversion device 100 shown in FIG. 1 further includes a second double-pole single-throw relay Rd, see Figure 8The schematic diagram of the power conversion device provided by another embodiment of the present application is shown, wherein the normally open contact of the first sub-relay Rd1 is used to connect the first terminal d11 of the first power supply end, and the normally closed contact is connected to the normally closed contact of the first sub-relay Rc1 in the double-pole double-throw relay Rc; wherein the normally open contact of the second sub-relay Rd2 is used to connect the second terminal d12 of the first power supply end, and the normally closed contact is connected to the normally closed contact of the second sub-relay Rc2 in the double-pole double-throw relay Rc. In actual implementation, the second double-pole single-throw relay Rb is synchronized with the drive signal of the double-pole single-throw relay Rb.

[0088] In an actual implementation, the Figure 2 The double-pole single-throw relay Rb in the power conversion device 100 shown in FIG. Fig. 9 As shown in the schematic diagram of a power conversion device provided by another embodiment of the present application, the double-pole double-throw relay Rc needs to be a forced-guided double-pole double-throw relay.

[0089] In an actual implementation, the input current of the power conversion device 100 of the present application is between 14A and 30A, that is, a large current input. As we know, as the current level increases, the device selection space becomes smaller and the cost is higher. Figure 1 The power conversion device 100 shown can save the cost and volume of a double-pole single-throw relay compared to the power conversion device 100 with a second double-pole single-throw relay Rb. Compared to the power conversion device 100 with only a double-pole double-throw relay Rc, a low-cost double-pole double-throw relay Rc can be selected, and the optional space is larger.

[0090] As described above, the power conversion device 100 of the present application switches the relay when the power conversion circuit 110 connected to the rear stage of the relay unit is not working, so zero current switching can be achieved. More preferably, the single-pole single-throw relay Rm is switched when it is bypassed, and the double-pole single-throw relay Rb and the double-pole double-throw relay Rc are switched when the single-pole single-throw relay Rm is disconnected, so zero current switching can be achieved. The power conversion device 100 has at least one of the following advantages: reducing the interference to the internal signal of the power supply during switching, reducing the damage to the relay during switching, increasing the life of the relay, and increasing the overall life and reliability of the power supply; there is no need to consider the zero-crossing point of the input source, and the control is simple; the double-pole single-throw relay Rb and the double-pole double-throw relay Rc are driven by short-time high-voltage pulses to achieve fast switching (less than 4ms), so the holding time of the power conversion device 100 can be shorter, the power conversion device 100 can be made smaller, and the power density is higher; because ATS zero-current switching is achieved, the problem of arc extinguishing of the relay is solved, and there is no need to use a relay with an arc extinguishing device, and ordinary relays can be used to achieve related functions, which greatly reduces the cost and the internal space occupied by the power conversion device 100, improves the power density of the power supply, and can solve the design requirements of safety regulations on electrical clearance and single-point failure, reducing costs and improving the internal space occupied by the power supply.

[0091] In actual implementation, the power conversion device 100 also includes a driving circuit for converting the signal output by the digital control circuit 310 into a driving signal suitable for driving a switch tube or a relay, which is not shown in detail in this application.

[0092] Although the embodiments of the present application and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the application as defined by the appended claims.

[0093] In addition, the scope of the present application is not limited to the specific embodiments of the processes, machines, manufactures, material compositions, modes, methods, and steps described in this specification. Those skilled in the art will readily understand from the disclosure of the present application that, according to the present application, currently existing or later to be developed processes, machines, manufactures, material compositions, modes, methods, or steps that perform substantially the same functions or achieve substantially the same results as the corresponding embodiments described herein may be utilized. Therefore, it is intended that the appended claims include such processes, machines, manufactures, material compositions, modes, methods, or steps within their scope.

Claims

1. A power conversion device, characterized in that: include: A double-pole single-throw relay, wherein the normally open contact of the first sub-relay is used to connect to the first terminal of the second power supply end; The normally open contact of the second sub-relay is used to connect the second terminal of the second power supply end; A double-pole double-throw relay, wherein the normally closed contact of the first sub-relay is used to connect to the first terminal of the first power supply end, and the normally open contact is connected to the normally closed contact of the first sub-relay in the double-pole single-throw relay; wherein the normally closed contact of the second sub-relay is used to connect to the second terminal of the first power supply end, and the normally open contact is connected to the normally closed contact of the second sub-relay in the double-pole single-throw relay, and the common terminal of the second sub-relay in the double-pole double-throw relay is connected to an input terminal of a power conversion circuit; A single-pole single-throw relay, wherein the normally open contact is connected to the common terminal of the first sub-relay of the double-pole double-throw relay, and the normally closed contact is connected to the other input terminal of the power conversion circuit, wherein two ends of the single-pole single-throw relay are connected in parallel with a bidirectional conducting switch tube; The digital control circuit is used to output a drive signal for controlling the single-pole single-throw relay, the bidirectional conduction switch tube, and the power conversion circuit, and also outputs a high-voltage excitation drive signal and a rated voltage drive signal for controlling the double-pole single-throw relay and the double-pole double-throw relay.

2. The power conversion device according to claim 1, characterized in that: The first power supply end receives alternating current or direct current; The second power supply end receives alternating current or direct current.

3. The power conversion device according to claim 2, characterized in that: When switching between the first power supply end and the second power supply end, when the digital control circuit controls the power conversion circuit to not work and the single-pole single-throw relay is disconnected, the digital control circuit outputs a drive signal for controlling the switching of the double-pole single-throw relay and the double-pole double-throw relay.

4. The power conversion device according to claim 3, characterized in that: When the power conversion device is working and the first power supply end is the main power supply end, if the first power supply input to the first power supply end loses power and the second power supply input to the second power supply end is powered normally, then when the power conversion circuit does not work and the single-pole single-throw relay is disconnected, the high-voltage excitation drive signal output by the digital control circuit is set high.

5. The power conversion device according to claim 4, characterized in that: When the power conversion device is working and the first power supply end is the main power supply end, executing: S1: The digital control circuit controls the power conversion circuit to work, the single-pole single-throw relay is closed, the bidirectional conduction switch is disconnected, the high-voltage excitation drive signal and the rated voltage drive signal are set low, the first detection circuit detects whether the first power supply input to the first power supply end is powered off, and the second detection circuit detects whether the second power supply input to the second power supply end is powered normally. If so, enter step S2; S2: The digital control circuit determines whether the duration is greater than the set time Ts, if so, proceeds to step S3; S3: at time T1, the digital control circuit controls the power conversion circuit to not work, the bidirectional conduction switch tube to turn on, the single-pole single-throw relay to turn off, and the high-voltage excitation drive signal and the rated voltage drive signal to be high; S4: at time T2, the digital control circuit controls the bidirectional conducting switch to be turned off; S5: At time T3, switching to power supply by the second power supply end; S6: at time T4, the digital control circuit controls the bidirectional conduction switch to conduct, sets the high-voltage excitation drive signal to low, and controls the power conversion circuit to work at the same time or afterwards; S7: At time T5, the digital control circuit controls the single-pole single-throw relay to close; S8: At time T6, the bidirectional conducting switch tube is controlled to be turned off.

6. The power conversion device according to claim 4, characterized in that: When the power conversion device is working and the first power supply end is the main power supply end, executing: S1: The digital control circuit controls the power conversion circuit to work, the single-pole single-throw relay is closed, the bidirectional conduction switch is disconnected, the high-voltage excitation drive signal and the rated voltage drive signal are set low, the first detection circuit detects whether the first power supply input to the first power supply end is powered off, and the second detection circuit detects whether the second power supply input to the second power supply end is powered normally. If so, enter step S2; S2: The digital control circuit determines whether the duration is greater than the set time Ts, if so, proceeds to step S3; S3: at time T1, the digital control circuit controls the power conversion circuit to not work and the bidirectional conduction switch tube to be turned on; S31: At time T11, the digital control circuit controls the single-pole single-throw relay to be disconnected, and sets the high-voltage excitation drive signal and the rated voltage drive signal to high; S4: at time T2, the digital control circuit controls the bidirectional conducting switch to be turned off; S5: At time T3, switching to power supply by the second power supply end; S6: at time T4, the digital control circuit controls the bidirectional conduction switch to conduct, sets the high-voltage excitation drive signal to low, and controls the power conversion circuit to work at the same time or afterwards; S7: At time T5, the digital control circuit controls the single-pole single-throw relay to close; S8: At time T6, the bidirectional conducting switch tube is controlled to be turned off.

7. The power conversion device according to claim 4, characterized in that: When the power conversion device is working and the first power supply end is the main power supply end, executing: S1: The digital control circuit controls the power conversion circuit to work, the single-pole single-throw relay is closed, the bidirectional conduction switch is disconnected, the high-voltage excitation drive signal and the rated voltage drive signal are set low, the first detection circuit detects whether the first power supply input to the first power supply end is powered off, and the second detection circuit detects whether the second power supply input to the second power supply end is powered normally. If so, enter step S2; S2: The digital control circuit determines whether the duration is greater than the set time Ts, if so, proceeds to step S3; S3: at time T1, the digital control circuit controls the power conversion circuit to not work and the bidirectional conduction switch tube to be turned on; S31: At time T11, the digital control circuit controls the single-pole single-throw relay to be disconnected; S4: at time T2, the digital control circuit controls the bidirectional conducting switch to be turned off; S41: At time T22, the digital control circuit sets the high voltage excitation drive signal and the rated voltage drive signal to high; S5: At time T3, switching to power supply by the second power supply end; S6: at time T4, the digital control circuit controls the bidirectional conduction switch to conduct, sets the high-voltage excitation drive signal to low, and controls the power conversion circuit to work at the same time or afterwards; S7: At time T5, the digital control circuit controls the single-pole single-throw relay to close; S8: At time T6, the bidirectional conducting switch tube is controlled to be turned off.

8. The power conversion device according to claim 3, characterized in that: When the power conversion device is working and the second power supply end is the main power supply end, if the second power supply input to the second power supply end loses power and the first power supply input to the first power supply end is powered normally, then when the power conversion circuit does not work and the single-pole single-throw relay is disconnected, the rated voltage drive signal output by the digital control circuit is set to low.

9. The power conversion device according to claim 8, characterized in that: When the power conversion device is working and the second power supply end is the main power supply end, executing: S1: the digital control circuit controls the power conversion circuit to work, the single-pole single-throw relay is closed, the bidirectional conductive switch is disconnected, the high-voltage excitation drive signal is set low, and the rated voltage drive signal is set high. The second detection circuit detects whether the second power supply input to the second power supply end is powered off, and the first detection circuit detects whether the first power supply input to the first power supply end is powered normally. If so, enter step S2; S2: The digital control circuit determines whether the duration is greater than the set time Ts, if so, proceeds to step S3; S3: at time T1, the digital control circuit controls the power conversion circuit to not work, the bidirectional conduction switch tube to turn on, the single-pole single-throw relay to turn off, and the rated voltage drive signal to be low; S4: at time T2, the digital control circuit controls the bidirectional conducting switch to be turned off; S5: at time T3, switching to power supply by the first power supply end; S6: At time T4, the digital control circuit controls the bidirectional conducting switch to be turned on, and simultaneously or subsequently controls the power conversion circuit to operate; S7: At time T5, the digital control circuit controls the single-pole single-throw relay to close; S8: At time T6, the bidirectional conducting switch tube is controlled to be turned off.

10. The power conversion device according to claim 8, characterized in that: When the power conversion device is working and the second power supply end is the main power supply end, executing: S1: the digital control circuit controls the power conversion circuit to work, the single-pole single-throw relay is closed, the bidirectional conductive switch is disconnected, the high-voltage excitation drive signal is set low, and the rated voltage drive signal is set high. The second detection circuit detects whether the second power supply input to the second power supply end is powered off, and the first detection circuit detects whether the first power supply input to the first power supply end is powered normally. If so, enter step S2; S2: The digital control circuit determines whether the duration is greater than the set time Ts, if so, proceeds to step S3; S3: at time T1, the digital control circuit controls the power conversion circuit to not work and the bidirectional conduction switch tube to be turned on; S31: At time T11, the digital control circuit controls the single-pole single-throw relay to be disconnected, and sets the rated voltage drive signal to a low level; S4: at time T2, the digital control circuit controls the bidirectional conducting switch to be turned off; S5: at time T3, switching to power supply by the first power supply end; S6: At time T4, the digital control circuit controls the bidirectional conducting switch to be turned on, and simultaneously or subsequently controls the power conversion circuit to operate; S7: At time T5, the digital control circuit controls the single-pole single-throw relay to close; S8: At time T6, the bidirectional conducting switch tube is controlled to be turned off.

11. The power conversion device according to claim 8, characterized in that: When the power conversion device is working and the second power supply end is the main power supply end, executing: S1: the digital control circuit controls the power conversion circuit to work, the single-pole single-throw relay is closed, the bidirectional conductive switch is disconnected, the high-voltage excitation drive signal is set low, and the rated voltage drive signal is set high. The second detection circuit detects whether the second power supply input to the second power supply end is powered off, and the first detection circuit detects whether the first power supply input to the first power supply end is powered normally. If so, enter step S2; S2: The digital control circuit determines whether the duration is greater than the set time Ts, if so, proceeds to step S3; S3: at time T1, the digital control circuit controls the power conversion circuit to not work and the bidirectional conduction switch tube to be turned on; S31: At time T11, the digital control circuit controls the single-pole single-throw relay to be disconnected; S4: at time T2, the digital control circuit controls the bidirectional conducting switch to be turned off; S41: At time T22, the digital control circuit sets the rated voltage drive signal to low; S5: at time T3, switching to power supply by the first power supply end; S6: At time T4, the digital control circuit controls the bidirectional conducting switch to be turned on, and simultaneously or subsequently controls the power conversion circuit to operate; S7: At time T5, the digital control circuit controls the single-pole single-throw relay to close; S8: At time T6, the bidirectional conducting switch tube is controlled to be turned off.

12. The power conversion device according to claim 1, characterized in that: It also includes a second double-pole single-throw relay, in which the normally open contact of the first sub-relay is used to connect to the first terminal of the first power supply end, and the normally closed contact is connected to the normally closed contact of the first sub-relay in the double-pole double-throw relay; the normally open contact of the second sub-relay is used to connect to the second terminal of the first power supply end, and the normally closed contact is connected to the normally closed contact of the second sub-relay in the double-pole double-throw relay.

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