Voltage reduction power supply system

Abstract

The utility model discloses a step-down power supply system in the technical field of converter miniaturization, and aims to solve the problems of large size, high manufacturing cost and poor power supply quality of a step-down power supply system in the prior art. A first IGBT switch module and a second IGBT switch module carry out voltage reduction chopping on high-voltage current in the mode that the two ends of the first IGBT switch module and the two ends of the second IGBT switch module are electrically connected with a first positive electrode line and a first negative electrode line respectively, voltage reduction of the single IGBT switch module is achieved by controlling connection and disconnection of the current, and the two IGBT switch modules are mutually staggered and connected in parallel and can complement each other in phase. The voltage reduction capability and the waveform quality are improved; the common-mode inductor is used for storing electric energy and providing follow current for a load when the IGBT switch or other switching devices are turned off, so that the execution of a voltage reduction function is ensured, and the power supply quality is further improved; because the purchasing cost and the volume of the IGBT switch module and the common mode inductor are lower than those of a sine inverter and an uncontrolled rectifier, the voltage reduction power supply system provided by the utility model has lower volume and cost, and is suitable for being installed on a pure electric vehicle.

Description

Technical Field

[0001] This utility model relates to a step-down power supply system and belongs to the field of converter miniaturization technology. Background Technology

[0002] There is a demand for miniaturized step-down power supply systems for electrical equipment, such as off-highway pure electric mining trucks. Taking off-highway pure electric mining trucks as an example, their control systems require a 24VDC (direct current voltage unit) power supply, and their battery pack voltage can reach up to 1000VDC. However, their step-down power supply system generally consists of an input circuit connected to a three-phase sinusoidal inverter. The voltage of the input circuit first passes through the three-phase sinusoidal inverter, which converts the DC power into three-phase 380V AC power. Then, a three-phase uncontrolled rectifier converts the 380V AC power into 540V DC power. Finally, a 24V charger reduces the 380V DC power to 24V DC power.

[0003] Because rectification is required before inversion, existing step-down power supply systems suffer from large size, high cost, and low power quality. Utility Model Content

[0004] The purpose of this application is to overcome the shortcomings of the prior art and provide a step-down power supply system that is small in size, low in cost, and provides high-quality power supply.

[0005] To achieve the above objectives, this application employs the following technical solution:

[0006] This application provides a step-down power supply system, including,

[0007] The first IGBT switching module and the second IGBT switching module are used for step-down chopping, and the two ends of the first IGBT switching module and the two ends of the second IGBT switching module are electrically connected to the first positive line and the first negative line, respectively.

[0008] A common-mode inductor for freewheeling, wherein the two input ports of the common-mode inductor are respectively electrically connected to the first IGBT switching module and the second IGBT switching module, and the two output ports of the common-mode inductor are both connected to the second positive line; the second negative line is electrically connected to the first negative line.

[0009] The first positive line and the first negative line are used to receive the current to be stepped down, and the second positive line and the second negative line are used to output the current to be stepped down.

[0010] In some embodiments of this application, an output capacitor is also included, which is electrically connected to the second positive line and the second negative line, respectively.

[0011] In some embodiments of this application, a discharge resistor is also included, which is connected in parallel across the output capacitor.

[0012] In some embodiments of this application, a pre-charge protector is also included. The pre-charge protector includes a first switch disposed on the first positive line or the first negative line and a pre-charge protection circuit electrically connected to both ends of the first switch. A second switch and a first resistor located downstream of the second switch are connected in series in the pre-charge protection circuit.

[0013] In some embodiments of this application, a filter is further included, the two ends of which are electrically connected to the first positive line and the first negative line, respectively; the filter includes a second resistor and at least one first capacitor connected in parallel with the second resistor.

[0014] In some embodiments of this application, a recorder is also included, as well as a first current collector, a second current collector, and a third current collector, all of which are electrically connected to the recorder; the first current collector and the second current collector are used to measure the current at the two input ports of the common-mode inductor, respectively, and the third current collector is used to collect the current of the first positive line.

[0015] In some embodiments of this application, a recorder is also included, as well as a first voltage acquisition device, a second voltage acquisition device, and a third voltage acquisition device, all of which are electrically connected to the recorder; the first voltage acquisition device is used to acquire the voltage of the first positive line, the second voltage acquisition device is used to acquire the voltage of the first negative line, and the third voltage acquisition device is used to acquire the voltage of the second positive line.

[0016] In some embodiments of this application, the first IGBT switch module includes a first IGBT circuit and a first IGBT switch and a second IGBT switch connected in series with the first IGBT circuit. The first IGBT circuit is connected to the first positive line and the first negative line at its two ends respectively. The first input port of the common mode inductor is electrically connected to the first IGBT circuit through the first inductor circuit. The connection point of the first inductor circuit is located between the first IGBT switch and the second IGBT switch.

[0017] Or / and, the second IGBT switching module includes a second IGBT circuit and a third IGBT switch and a fourth IGBT switch connected in series with the second IGBT circuit. The two ends of the second IGBT circuit are respectively connected to the first positive line and the first negative line. The common mode inductor has a second input port electrically connected to the second IGBT circuit through a second inductor circuit. The connection point of the second inductor circuit is located between the third IGBT switch and the fourth IGBT switch.

[0018] In some embodiments of this application, a charger for secondary step-down is also included;

[0019] The second positive wire and the second negative wire are electrically connected to the input terminal of the charger, and the output terminal of the charger is electrically connected to the secondary step-down positive wire and the secondary step-down negative wire, which are used to supply power to the electrical equipment.

[0020] In some embodiments of this application, a freewheeling diode is further included, with its two ends electrically connected to the positive and negative terminals of the secondary step-down line, respectively; upstream of the freewheeling diode, a contactor is provided on the positive terminal of the secondary step-down line; the electrical equipment is a heat exchange system, and the freewheeling diode is used to generate reverse freewheeling current when the contactor is disconnected.

[0021] Compared with the prior art, the beneficial effects achieved by this application are as follows:

[0022] The step-down power supply system provided in this application uses a first IGBT switching module and a second IGBT switching module to chop the high-voltage current by electrically connecting their two ends to a first positive line and a first negative line, respectively. A single IGBT switching module achieves step-down by controlling the conduction and turn-off of the current. The first and second IGBT switching modules are interleaved and connected in parallel to complement each other in phase, improving the step-down capability and waveform quality, exceeding the effect of the combined function of two individual IGBT switching modules. A common-mode inductor is used to store electrical energy and to provide freewheeling current to the load when the IGBT switches or other switching devices are turned off, ensuring the execution of the step-down function and further improving the power supply quality. Since the procurement cost and volume of the IGBT switching modules and common-mode inductors are lower than those of sinusoidal inverters and uncontrolled rectifiers, the step-down power supply system provided in this application has a lower volume and cost, making it suitable for installation in pure electric vehicles. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the structural topology of the step-down power supply system provided in this embodiment;

[0025] Figure 2 Yes Figure 1 A supplementary structural topology diagram;

[0026] In the picture:

[0027] 1. First IGBT switch module; 1.0 First IGBT circuit; 1.1 First IGBT switch; 1.2 Second IGBT switch;

[0028] 2. Second IGBT switch module; 2.0 Second IGBT circuit; 2.3 Third IGBT switch; 2.4 Fourth IGBT switch;

[0029] 3. Common-mode inductor; 3.1 First inductor circuit; 3.2 Second inductor circuit;

[0030] 4. Output capacitor; 5. Discharge resistor;

[0031] 6. Input circuit; 6.1 First positive line; 6.2 First negative line;

[0032] 7. Primary step-down circuit; 7.1 Second positive line; 7.2 Second negative line;

[0033] 9. Precharge protector; 9.1. First switch; 9.2. Precharge protection circuit; 9.3. Second switch; 9.4. First resistor;

[0034] 10.1 First current collector; 10.2 Second current collector; 10.3 Third current collector;

[0035] 11.1 First voltage acquisition unit; 11.2 Second voltage acquisition unit; 11.3 Third voltage acquisition unit;

[0036] 12. Filter; 12.1. Second resistor; 12.2. First capacitor;

[0037] 14. Buck chopper circuit; 15. Charger;

[0038] 16.1 Secondary step-down positive electrode line; 16.2 Secondary step-down negative electrode line;

[0039] 17. Electrical equipment; 18. Contactor; 19. Freewheeling diode. Detailed Implementation

[0040] The technical solutions of this application / the embodiments thereof will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application / the embodiments thereof, and not all embodiments thereof. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application / the application thereof or its application or use. Example 1

[0041] This embodiment provides a step-down power supply system to solve the problems of large structural volume, high cost, and urgent need to improve power supply quality in the prior art.

[0042] refer to Figure 1 The step-down power supply system provided in this embodiment includes a first IGBT switch module 1 and a second IGBT switch module 2, both used for step-down chopping. The two ends of the first IGBT switch module 1 and the two ends of the second IGBT switch module 2 are electrically connected to the first positive line 6.1 and the first negative line 6.2, respectively.

[0043] The common-mode inductor 3 is used for freewheeling. The two input ports of the common-mode inductor 3 are electrically connected to the first IGBT switching module 1 and the second IGBT switching module 2, respectively, so that the two ends of the first IGBT switching module 1 and the second IGBT switching module 2 are arranged in an alternating parallel configuration. The two output ports of the common-mode inductor 3 are merged and connected to the second positive line 7.1. In addition, the second negative line 7.2 is electrically connected to the first negative line 6.2.

[0044] Among them, the first positive line 6.1 and the first negative line 6.2 serve as high-voltage input sources to receive the current to be stepped down; while the second positive line 7.1 and the second negative line 7.2 are used to output stepped-down current to provide low-voltage power to the electrical equipment 17.

[0045] The input circuit 6, namely the first positive line 6.1 and the first negative line 6.2, inputs high-voltage current to the first IGBT switch module 1 and the second IGBT switch module 2. The first IGBT switch module 1 and the second IGBT switch module 2 respectively reduce the voltage of the high-voltage current by electrically connecting the first positive line 6.1 and the first negative line 6.2 at both ends. A single IGBT switch module reduces the voltage by controlling the conduction and turn-off of the current. The first IGBT switch module 1 and the second IGBT switch module 2 are connected in parallel and interleaved to complement each other in phase, thereby improving the voltage reduction capability and waveform quality, which is more than the effect of superimposing the functions of two individual IGBT switch modules.

[0046] The common-mode inductor 3 is used to store electrical energy and to provide freewheeling current to the load when the IGBT switch or other switching devices are turned off, ensuring the execution of the step-down function and further improving the power supply quality.

[0047] The final stepped-down current is output to the power-consuming device 17 through the primary step-down circuit 7, namely the second positive line 7.1 and the second negative line 7.2. Since the procurement cost and size of the IGBT switching module and common-mode inductor 3 are lower than those of the sinusoidal inverter and uncontrolled rectifier, the step-down power supply system provided in this embodiment has a lower size and cost, making it suitable for installation in pure electric vehicles. Example 2

[0048] This embodiment provides a step-down power supply system. This embodiment is an optimization based on Embodiment 1 to improve the technical effect and refine the technical solution. For details not described in this embodiment, please refer to Embodiment 1.

[0049] To further improve power quality and remove noise, as one embodiment, refer to Figure 1 An output capacitor 4 is electrically connected between the second positive line 7.1 and the second negative line 7.2. The output capacitor 4 serves to filter out noise.

[0050] In one embodiment, the connection position of the second negative line 7.2 and the first negative line 6.2 is located downstream of the first IGBT switching module 1 and the second IGBT switching module 2. The upstream and downstream mentioned in this embodiment are determined according to the distance from the input circuit 6 to the electrical device 17.

[0051] To protect this output capacitor 4, refer to... Figure 1 In one embodiment, the discharge resistor 5 is connected in parallel across the output capacitor 4.

[0052] Input circuit 6 may generate a large current at power-on. To further improve power supply quality, refer to... Figure 1 This embodiment also includes a pre-charge protector 9, which provides current protection upstream of the first IGBT switching module 1 and the second IGBT switching module 2. Taking the pre-charge protector 9 located on the first positive line 6.1 as an example, it includes a first switch 9.1 and a pre-charge protection circuit 9.2 electrically connected to both ends of the first switch 9.1. A second switch 9.3 and a first resistor 9.4 located downstream of the second switch 9.3 are connected in series on the pre-charge protection circuit 9.2. The first switch 9.1 and the second switch 9.3 can be used to control whether the first resistor 9.4 is connected to the first positive line 6.1 and to control the current magnitude.

[0053] To further improve power supply quality, refer to Figure 1 As one embodiment, the step-down power supply system also includes a filter 12, which is arranged upstream of the first IGBT switching module 1 and the second IGBT switching module 2 to filter noise from the input current. The two ends of the filter 12 are electrically connected to the first positive line 6.1 and the first negative line 6.2, respectively. The filter 12 includes a second resistor 12.1 and at least one first capacitor 12.2 connected in parallel with the second resistor 12.1. The first capacitor 12.2 plays the main filtering role, and the second resistor 12.1 is used for discharge protection across the first capacitor 12.2.

[0054] refer to Figure 1In one embodiment, the step-down power supply system also includes a recorder and three current acquisition units, namely a first current acquisition unit 10.1, a second current acquisition unit 10.2, and a third current acquisition unit 10.3, all electrically connected to the recorder. The first and second current acquisition units 10.1 and 10.2 are used to measure the current at the two input ports of the common-mode inductor 3, respectively, with the first and second current acquisition units 10.1 and 10.2 distributed across the first inductor circuit 3.1 and the second inductor circuit 3.2. The third current acquisition unit 10.3 is used to acquire the current of the first positive line 6.1, and its position can be selected between the pre-charge protector 9 and the filter 12. The current data collected by the first, second, and third current acquisition units 10.1, 10.2, and 10.3 can be used to optimize the parameter design of the IGBT switching module. Furthermore, the acquired current can also control the current closed-loop feedback.

[0055] Based on similar principles, refer to Figure 1 The step-down power supply system also includes a first voltage acquisition unit 11.1, a second voltage acquisition unit 11.2, and a third voltage acquisition unit 11.3, all connected to the recorder's electrical signals. The first voltage acquisition unit 11.1 acquires the voltage of the first positive line 6.1, the second voltage acquisition unit 11.2 acquires the voltage of the first negative line 6.2, and the third voltage acquisition unit 11.3 acquires the voltage of the second positive line 7.2. The voltage data collected by these three units can be used to optimize the parameter design of the IGBT switching module. The first voltage acquisition unit 11.1 can be positioned between the pre-charge protector 9 and the filter 12, the second voltage acquisition unit 11.2 upstream of the filter 12, and the third voltage acquisition unit 11.3 downstream of the output capacitor 4. Furthermore, the collected voltage can be used for voltage closed-loop feedback in the control system.

[0056] refer to Figure 1 In one embodiment, the first IGBT switch module 1 includes a first IGBT circuit 1.0 and a first IGBT switch 1.1 and a second IGBT switch 1.2 connected in series with the first IGBT circuit 1.0. The two ends of the first IGBT circuit 1.0 are respectively connected to the first positive line 6.1 and the first negative line 6.2. The first input port "11" of the common mode inductor 3 is electrically connected to the first IGBT circuit 1.0 through the first inductor circuit 3.1. The connection point of the first inductor circuit 3.1 on the first IGBT circuit 1.0 is located between the first IGBT switch 1.1 and the second IGBT switch 1.2.

[0057] Similarly, the second IGBT switch module 2 includes a second IGBT circuit 2.0 and a third IGBT switch 2.3 and a fourth IGBT switch 2.4 connected in series with the second IGBT circuit 2.0. The two ends of the second IGBT circuit 2.0 are respectively connected to the first positive line 6.1 and the first negative line 6.2. The common mode inductor 3 has its second input port "21" electrically connected to the second IGBT circuit 2.0 through the second inductor circuit 3.2. The connection point of the second inductor circuit 3.2 on the second IGBT circuit 2.0 is located between the third IGBT switch 2.3 and the fourth IGBT switch 2.4.

[0058] In one embodiment, the IGBT switch includes a gate, a collector, and an emitter. Taking the first IGBT switch module 1 as an example, the emitter of the first IGBT switch 1.1 is electrically connected to the collector of the second IGBT switch 1.2. The collector of the first IGBT switch 1.1 is electrically connected to the first positive line 6.1, and the emitter of the second IGBT switch 1.2 is electrically connected to the first negative line 6.2. The gate is used to control the switching on and off of the IGBT switch to achieve a voltage reduction effect. The second IGBT switch module 2 has a similar structure and will not be described in detail here.

[0059] Different components have different voltage requirements. Some components can directly use the current output from the primary step-down circuit 7, while others require a secondary step-down. (Reference) Figure 1 and Figure 2 In one embodiment, the step-down power supply system further includes a charger 15 for secondary step-down, which is coupled to the step-down chopper circuit 14. In another embodiment, the second positive line 7.1 and the second negative line 7.2 are electrically connected to the input terminal of the charger 15, and the output terminal of the charger 15 is electrically connected to the secondary step-down positive line 16.1 and the secondary step-down negative line 16.2, respectively. The secondary step-down positive line 16.1 and the secondary step-down negative line 16.2 are used to supply power to the electrical equipment 17.

[0060] When electrical equipment 17 is a heat exchange system, refer to Figure 2 The step-down power supply system also includes a freewheeling diode 19, which is electrically connected to the positive terminal 16.1 and the negative terminal 16.2 of the secondary step-down circuit, respectively. A contactor 18 is provided on the positive terminal 16.1 of the secondary step-down circuit upstream of the freewheeling diode 19. The electrical equipment 17 is a heat exchange system. Since the heat exchange system is an inductive load, the freewheeling diode 19 is used to generate reverse freewheeling when the contactor 18 is disconnected.

[0061] As one embodiment, the common-mode inductor 3 can be achieved by winding the first inductor circuit 3.1 and the second inductor circuit 3.2 on the same iron core in a certain pattern, and the effect mentioned above can be achieved by the mutual influence of the magnetic field inside the iron core.

[0062] In one embodiment, the input circuit 6 has a voltage of 1000VDC, the primary step-down circuit 7 has a voltage of 400~750VDC, the charger 15 is a 24V charger, and the voltage difference between the secondary step-down positive line 16.1 and the secondary step-down negative line 16.2 is 27.5V. (Reference) Figure 2 The charger 15 uses two units. One unit is responsible for supplying power to the control modules, BMS, and external battery thermal management unit inside the cabinet. The other unit is responsible for supplying power to the heat exchange system inside the cabinet, including the heat exchanger and water pump.

[0063] In summary, the step-down power supply system provided in this embodiment offers better step-down performance and higher quality power supply current compared to Embodiment 1, and also has the ability to collect data to support design optimization.

[0064] In the description of this utility model, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0065] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "connected," "linked," "located in," "equipped with," "located in," "installed," and "set up" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances. "Hinged connection" includes "rotational connection."

[0066] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present utility model, and these improvements and modifications should also be considered within the protection scope of the present utility model.

Claims

1. A step-down power supply system, characterized in that, include, The first IGBT switching module (1) and the second IGBT switching module (2) are used for step-down chopping. The two ends of the first IGBT switching module (1) and the two ends of the second IGBT switching module (2) are electrically connected to the first positive line (6.1) and the first negative line (6.2), respectively. A common-mode inductor (3) is used for freewheeling. The two input ports of the common-mode inductor (3) are electrically connected to the first IGBT switching module (1) and the second IGBT switching module (2) respectively. The two output ports of the common-mode inductor (3) are both connected to the second positive line (7.1); the second negative line (7.2) is electrically connected to the first negative line (6.2). The first positive line (6.1) and the first negative line (6.2) are used to receive the current to be stepped down, and the second positive line (7.1) and the second negative line (7.2) are used to output the current to be stepped down.

2. The step-down power supply system according to claim 1, characterized in that, It also includes an output capacitor (4), which is electrically connected to the second positive line (7.1) and the second negative line (7.2) respectively.

3. The step-down power supply system according to claim 2, characterized in that, It also includes a discharge resistor (5), which is connected in parallel across the output capacitor (4).

4. The step-down power supply system according to claim 1, characterized in that, It also includes a precharge protector (9), which includes a first switch (9.1) disposed on the first positive line (6.1) or the first negative line (6.2) and a precharge protection circuit (9.2) electrically connected to both ends of the first switch (9.1). A second switch (9.3) and a first resistor (9.4) located downstream of the second switch (9.3) are connected in series on the precharge protection circuit (9.2).

5. The step-down power supply system according to claim 1, characterized in that, It also includes a filter (12), the two ends of which are electrically connected to the first positive line (6.1) and the first negative line (6.2), respectively; the filter (12) includes a second resistor (12.1) and at least one first capacitor (12.2) connected in parallel with the second resistor (12.1).

6. The step-down power supply system according to claim 1, characterized in that, It also includes a recorder and a first current collector (10.1), a second current collector (10.2) and a third current collector (10.3), all of which are electrically connected to the recorder; the first current collector (10.1) and the second current collector (10.2) are used to measure the current at the two input ports of the common mode inductor (3), respectively, and the third current collector (10.3) is used to collect the current of the first positive line (6.1).

7. The step-down power supply system according to claim 1, characterized in that, It also includes a recorder and a first voltage acquisition unit (11.1), a second voltage acquisition unit (11.2), and a third voltage acquisition unit (11.3), all of which are electrically connected to the recorder; the first voltage acquisition unit (11.1) is used to acquire the voltage of the first positive line (6.1), the second voltage acquisition unit (11.2) is used to acquire the voltage of the first negative line (6.2), and the third voltage acquisition unit (11.3) is used to acquire the voltage of the second positive line (7.1).

8. The step-down power supply system according to claim 1, characterized in that, The first IGBT switch module (1) includes a first IGBT circuit (1.0) and a first IGBT switch (1.1) and a second IGBT switch (1.2) connected in series with the first IGBT circuit (1.0). The first IGBT circuit (1.0) is connected to the first positive line (6.1) and the first negative line (6.2) respectively. The first input port of the common mode inductor (3) is electrically connected to the first IGBT circuit (1.0) through the first inductor circuit (3.1). The connection point of the first inductor circuit (3.1) is located between the first IGBT switch (1.1) and the second IGBT switch (1.2). Or / and, the second IGBT switch module (2) includes a second IGBT circuit (2.0) and a third IGBT switch (2.3) and a fourth IGBT switch (2.4) connected in series with the second IGBT circuit (2.0). The two ends of the second IGBT circuit (2.0) are respectively connected to the first positive line (6.1) and the first negative line (6.2). The common mode inductor (3) has its second input port electrically connected to the second IGBT circuit (2.0) through the second inductor circuit (3.2). The connection point of the second inductor circuit (3.2) is located between the third IGBT switch (2.3) and the fourth IGBT switch (2.4).

9. The step-down power supply system according to claim 1, characterized in that, It also includes a charger (15) for secondary step-down. The second positive line (7.1) and the second negative line (7.2) are electrically connected to the input terminal of the charger (15), and the output terminal of the charger (15) is electrically connected to the secondary step-down positive line (16.1) and the secondary step-down negative line (16.2), respectively. The secondary step-down positive line (16.1) and the secondary step-down negative line (16.2) are used to supply power to the electrical equipment (17).

10. The step-down power supply system according to claim 9, characterized in that, It also includes a freewheeling diode (19), the two ends of which are electrically connected to the secondary step-down positive line (16.1) and the secondary step-down negative line (16.2), respectively; upstream of the freewheeling diode (19), the secondary step-down positive line (16.1) is provided with a contactor (18); the electrical equipment (17) is a heat exchange system, and the freewheeling diode (19) is used to generate reverse freewheeling when the contactor (18) is disconnected.

Images