Contactor and power supply method thereof

Abstract

The present disclosure relates to a contactor and a power supply method thereof that can generate an auxiliary voltage with low power consumption and low cost. The contactor includes: a coil unit, including a coil and a coil power supply unit, wherein the coil power supply unit receives an input voltage of an input power line and provides a coil voltage lower than the input voltage to the coil; a control unit for controlling the coil power supply unit; a first power supply unit for receiving the input voltage and outputting a first output voltage for the control unit; and a second power supply unit for receiving the coil voltage on the coil and outputting a second output voltage for the control unit, wherein after the second power supply unit outputs the second output voltage, the first power supply unit stops outputting power.

Description

Technical Field

[0001] The present disclosure relates to a contactor and a power supply method for the contactor, and in particular to a contactor for generating an auxiliary voltage and a power supply method for the contactor. Background Art

[0002] Contactors are often used in industry to control the opening and closing of circuits. Contactors generate a magnetic field by injecting current into a coil to control the movement of the contactor contacts, thereby controlling the opening and closing of circuits through the contact and opening of the contacts.

[0003] In order to control the voltage or current applied to the coil, the contactor often requires a control circuit. Therefore, the design of the contactor needs to consider the power supply of the control circuit. Since the voltage of the control circuit is relatively low, if the high input voltage is directly stepped down to generate an auxiliary voltage for the control circuit, the requirements for the step-down module and components are high, and it often generates greater power consumption and heat. Summary of the invention

[0004] The present disclosure relates to a contactor capable of generating an auxiliary voltage with low power consumption and low cost, and a power supply method thereof.

[0005] According to one aspect of the present disclosure, a contactor is provided, comprising: a coil unit, comprising a coil and a coil power supply unit, wherein the coil power supply unit receives an input voltage of an input power line and provides a coil voltage lower than the input voltage to the coil; a control unit, for controlling the coil power supply unit; a first power supply unit, for receiving the input voltage and outputting a first output voltage for the control unit; and a second power supply unit, for receiving the coil voltage on the coil and outputting a second output voltage for the control unit, wherein after the second power supply unit outputs the second output voltage, the first power supply unit stops outputting power.

[0006] According to another aspect of the present disclosure, a power supply method for a contactor is provided, the contactor comprising a coil, a coil power supply unit and a control unit, the power supply method comprising: outputting a first output voltage after stepping down an input voltage to supply power to the control unit; the coil power supply unit providing a coil voltage to the coil under the control of the control unit; and outputting a second output voltage after stepping down the coil voltage to supply power to the control unit, and stopping supplying power to the control unit through the first output voltage.

[0007] According to the embodiment of the present disclosure, the first power supply unit that converts the high input voltage into the low auxiliary voltage only works for a short time at the beginning of the contactor power-on, thereby avoiding large power consumption and heat generation, and reducing the device requirements and costs of the first power supply unit. At the same time, the second power supply unit that is mainly used to supply power to the control unit converts the lower coil voltage into the auxiliary voltage, thereby having good power consumption, low device requirements and costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The aspects, features and advantages of the present disclosure will become clearer and easier to understand through the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0009] Figure 1 A schematic circuit module diagram of a contactor according to an embodiment of the present disclosure is shown;

[0010] Figure 2 A schematic circuit module diagram of a contactor according to another embodiment of the present disclosure is shown;

[0011] Figure 3 A schematic circuit diagram of a contactor according to an embodiment of the present disclosure is shown;

[0012] Figure 4 A schematic circuit diagram of a coil unit according to an embodiment of the present disclosure is shown;

[0013] Figure 5 A flow chart showing a method for powering a contactor according to an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0014] The present disclosure will be described in detail below with reference to exemplary embodiments of the present disclosure. However, the present disclosure is not limited to the embodiments described herein, and it can be implemented in many different forms. The described embodiments are only used to make the present disclosure thorough and complete, and to fully convey the concept of the present disclosure to those skilled in the art. The features of the various embodiments described can be combined or replaced with each other, unless explicitly excluded or should be excluded according to the context.

[0015] For contactors with high input voltage, it is often necessary to use complex and expensive methods to obtain low voltage for the control unit. For example, for situations where the input voltage is above 200V, in order to obtain a low voltage of about 15V for the control unit, it is usually necessary to use a high-rated power insulated gate bipolar transistor (IGBT) with an additional heat sink for voltage reduction. Such a structure is expensive, occupies a large space, and is limited by isolation.

[0016] The present disclosure proposes a scheme for generating an auxiliary voltage for a control unit from the coil voltage of a contactor. The coil voltage is usually much lower than the input voltage, for example, 20V. Therefore, when the auxiliary voltage is generated from the coil voltage, the requirements for the device are low, and no excessive power consumption and heat will be generated, so that the auxiliary voltage can be provided at low cost and low power consumption. According to an embodiment of the present disclosure, the auxiliary voltage for the control unit is not always generated by directly stepping down the input voltage, but only needs to be generated by directly stepping down the input voltage before the coil voltage of the contactor is formed, and after the coil voltage of the contactor is formed, the auxiliary voltage is generated by stepping down the coil voltage and provided to the control unit, and the direct step-down power supply from the input voltage is stopped. In this case, although it is still necessary to generate the auxiliary voltage by directly stepping down the input voltage when the relay is started, since the process is shorter, the power consumption and heat generated are smaller, and a heat dissipation system is not required, the requirements and costs of the equipment are lower.

[0017] Figure 1 1 is a schematic circuit module diagram of a contactor 100 according to an embodiment of the present disclosure. The contactor 100 includes a coil unit 101. The coil unit 101 includes a coil power supply unit 1011 and a coil 1012. The coil unit 101 is a basic component of the contactor circuit. The coil power supply unit 101 receives an input voltage Vin from an input power line Li and provides a coil voltage Vc lower than the input voltage to the coil, so that the coil power supply unit 1011 can inject current into the coil 1012 to generate a magnetic field to drive the contact to move. According to an embodiment of the present disclosure, the input voltage Vin can be a DC voltage directly received from the outside of the contactor 100; or the contactor 100 can also include a rectifier and filter unit, which receives AC power from the outside and converts it into a DC input voltage Vin. The input power line Li represents a power line connected to the coil power supply unit 1011 for transmitting the input voltage Vin. When a DC input voltage Vin is received directly from outside the contactor 100, the input power line Li is connected to a power source outside the contactor 100; when the contactor 100 includes a rectifier and filter unit, the input power line Li is connected to the rectifier and filter unit for receiving a DC input voltage from the rectifier and filter unit.

[0018] The contactor 100 also includes a control unit 102 for controlling the coil power supply unit 1011. The on, off, voltage level, etc. of the coil power supply unit 1011 supplying power to the coil 1012 can be controlled by a control signal sent by the control unit 102. The control unit 102 may include, for example, a microcontroller unit (MCU). According to an embodiment of the present disclosure, the contactor 100 also includes a first power supply unit 103 and a second power supply unit 104 for supplying power to the control unit 102. Specifically, the first power supply unit 103 receives an input voltage Vin and steps down the input voltage Vin to a first output voltage Vout1 for the control unit 102; the second power supply unit 104 receives a coil voltage Vc on the coil 1012 and steps down the coil voltage Vc to a second output voltage Vout2 for the control unit 102. The first output voltage Vout1 and the second output voltage Vout2 may be the same or different, as long as they can satisfy the requirement of supplying power to the control unit 102. In addition, depending on the specific structure and components of the control unit 102, the first output voltage Vout1 and the second output voltage Vout2 may need to be further stepped down. For example, for an MCU, the power supply voltage is typically 3.3V. Therefore, if the control unit 102 includes an MCU, the first output voltage Vout1 and the second output voltage Vout2 need to be further stepped down to approximately 3.3V to provide to the MCU.

[0019] As described above, the input voltage Vin is usually high, such as 500V, the coil voltage Vc is usually low, such as 20V, and the auxiliary voltage for the control unit is usually lower, such as 15V. The first power supply unit 103 directly converts the input voltage Vin into the first output voltage Vout1 as an auxiliary voltage. If it works for a long time, it will generate large power consumption and heat, and the device requirements are high. On the contrary, the second power supply unit 104 converts the lower coil voltage Vc into the second output voltage Vout2 as an auxiliary voltage, and the device requirements are low, and long-term work will not generate excessive power consumption and heat. Therefore, according to an embodiment of the present disclosure, after the second power supply unit 104 outputs the second output voltage Vout2, the first power supply unit 103 stops outputting power. In other words, the first power supply unit 103 will only work for a short time at the beginning of the contactor 100 powering on. Once the coil 1012 of the contactor 100 is charged to obtain the coil voltage Vc, the second power supply unit 104 can generate the second output voltage Vout2 as an auxiliary voltage to provide to the control unit, and the power supply of the first power supply unit 103 can be stopped at this time. There are various ways to stop the first power supply unit 103 from supplying power, for example, disconnecting the first power supply unit 103 from the control unit 102 through a switch, stopping the operation of the first power supply unit 103, disconnecting the power supply of the first power supply unit 103, etc.

[0020] The power supply switching between the first power supply unit 103 and the second power supply unit 104 can be performed by a control circuit, for example, by a control unit 102. In one embodiment, the control unit 102 can detect whether the second power supply unit 104 outputs the second output voltage Vout2, and when it is detected that the second power supply unit 104 outputs the second output voltage Vout2, the control unit 102 controls the first power supply unit 103 to stop outputting power after a predetermined time, for example, disconnecting the connection between the first power supply unit 103 and the control unit 102 through a switch, stopping the operation of the first power supply unit 103, disconnecting the power supply of the first power supply unit 103, etc. The predetermined time can be set by the control unit 102, which can be 0, that is, the power supply of the first power supply unit 103 is stopped immediately when the second output voltage Vout2 is detected; it can also set a smaller waiting time, for example, a few milliseconds, for stopping the power supply of the first power supply unit 103 after the second output voltage Vout2 is relatively stable.

[0021] In another embodiment, the power supply switching between the first power supply unit 103 and the second power supply unit 104 can be realized by a simple diode circuit, such as Figure 2 shown. Figure 2 is a schematic circuit module diagram of a contactor 200 according to another embodiment of the present disclosure, Figure 2 and Figure 1 The difference is Figure 2 The contactor 200 in the embodiment further includes a first diode D1 and a second diode D2. The output end of the first power supply unit 103 is connected to the anode of the first diode D1; the output end of the second power supply unit 104 is connected to the anode of the second diode D2; the cathode of the first diode D1 is connected to the cathode of the second diode D2 and is connected to the control unit 102, for providing power to the control unit 102. In addition, in the present embodiment, the second output voltage Vout2 is greater than the first output voltage Vout1, so that after the second power supply unit 104 outputs the second output voltage Vout2, the first power supply unit 103 stops outputting power. In the construction of this embodiment, when the first power supply unit 103 outputs the first output voltage Vout1 and the second power supply unit 104 does not output the second voltage Vout2, the first diode D1 is turned on and the second diode D2 is turned off, and the first power supply unit 103 supplies power to the control unit 102; when the second power supply unit 104 also outputs the second output voltage Vout2, since Vout2 is greater than Vout1, the second diode D2 is turned on and the first diode D1 is turned off, and the second power supply unit 104 supplies power to the control unit 102, while the first power supply unit 103 stops supplying power to the control unit 102.

[0022] According to the above-mentioned embodiment of the present disclosure, the first power supply unit that converts the high input voltage into the low auxiliary voltage will only work for a short time in the initial stage of the contactor power-on, thereby avoiding large power consumption and heat generation, and reducing the device requirements and costs of the first power supply unit. At the same time, the second power supply unit mainly used to supply power to the control unit converts the lower coil voltage into the auxiliary voltage, so the power consumption is small, and the device requirements and costs are low.

[0023] Each unit of the contactor disclosed in the present invention can be implemented by various specific circuits. Figure 3 FIG. 2 shows a schematic circuit diagram of a contactor 300 according to an embodiment of the present disclosure. Figure 3 The specific structures of each unit in the embodiment can be applied separately or replaced by other suitable structures.

[0024] like Figure 3 As shown, the coil unit 301 includes a coil power supply unit 3011 and a coil 3012. The coil power supply unit 3011 includes a first electronic switch T1 and a freewheeling diode FD, the first electronic switch T1 is connected between the coil 3012 and the input power line Li and is controlled by the control unit 302. The coil 3012 is connected between the first electronic switch T1 and the ground line, and the freewheeling diode FD is connected between the first electronic switch T1 and the ground line. In this embodiment, the coil power supply unit 3011 provides voltage to the coil through the electronic switch T1 controlled by the control unit 302. The electronic switch T1 has a control end, which is connected to the control unit 302. The control voltage provided by the control unit 302 can control the closing and disconnection of the electronic switch T1, that is, it can control the connection and disconnection of the input power line Li connected at both ends of the electronic switch T1 and the coil 3012, thereby controlling the current injection and voltage of the coil 3012. For example, the control unit 302 can control the first electronic switch T1 to control the coil voltage on the coil 3012 by pulse width modulation (PWM). In the case of using PWM to control the electronic switch T1, the control unit 302 may include, for example, a logic device such as an MCU to output a PWM control signal, and, if necessary, also include an electronic switch driving unit, which drives the electronic switch T1 based on the PWM control signal. There are many commonly used electronic switches, such as IGBT, GTO (gate turn-off thyristor), triode, MOS (metal oxide semiconductor) tube, etc., and technicians in this field can choose according to the actual application scenario. For example, in high-voltage and high-power applications, IGBT can be used. When the electronic switch is an IGBT, the gate of the IGBT is the control terminal, which is connected to the control unit 302, and the source and drain of the IGBT are respectively connected to the coil 3012 and the input power line Li. The freewheeling diode FD in the coil unit 301 is used together with the coil 3012 to prevent sudden changes in current and voltage and ensure the normal operation of the circuit.

[0025] Furthermore, in some applications, there may be multiple contactor coils. In this case, an electronic switch may be added to select the corresponding coil. Figure 4 FIG. 4 shows a schematic circuit diagram of a coil unit 401 according to an embodiment of the present disclosure. Figure 4 In the embodiment, the coil power supply unit 4011 may further include a second electronic switch T2 connected between the coil 3012 and the ground line. The second electronic switch T2 is used to gate the coil 3012. When the second electronic switch T2 is turned on, the coil 3012 is gated, and when the second electronic switch T2 is turned off, the coil 3012 is not gated. The second electronic switch T2 may be controlled by a control circuit, for example, by the control unit 302.

[0026] Back to Figure 3 The first power supply unit 303 includes a third electronic switch T3, a first voltage stabilizing diode ZD1, a first capacitor C1, a first resistor R1 and a second resistor R2. The first resistor R1 is connected between the control end of the third electronic switch T3 and the input power line Li. The first voltage stabilizing diode ZD1 is connected between the control end of the third electronic switch T3 and the ground line. The first capacitor C1 is connected between the first end of the third electronic switch T3 and the ground line. The third electronic switch T3 is controlled by the voltage difference between its control end and the first end. The second resistor R2 is connected between the second end of the third electronic switch T3 and the input power line Li. The first end of the third electronic switch T3 is the output end of the first power supply unit 303, which is used to output the voltage provided to the control unit 302.

[0027] The first power supply unit 303 is stepped down by the third electronic switch T3. The conduction and cutoff of the third electronic switch T3 are controlled by the voltage difference between the control end and the first end. Due to the existence of the voltage stabilizing diode ZD1, the voltage of the control end of the third electronic switch T3 is constant. At the same time, when the third electronic switch T3 is turned on, the voltage drop between the control end and the first end is also constant. Therefore, when the first power supply unit 303 has a load and the third electronic switch T3 is turned on, the voltage of the first end of the third electronic switch T3 (i.e., the output end of the first power supply unit 303) is constant. Therefore, the required auxiliary voltage can be output by selecting a voltage stabilizing diode ZD1 of a suitable voltage. For example, when the third electronic switch T3 is an IGBT, the control end of the third electronic switch T3 is the gate of the IGBT, the first end is the source, and the second end is the drain. The output end of the first power supply unit 303 is the source of the IGBT, and its output voltage is the voltage of the voltage stabilizing diode ZD1 minus the voltage drop between the gate and the drain. As described above, the first power supply unit 303 directly drops the voltage from the input voltage to the auxiliary voltage for the control unit, and the voltage drop is large. If it works for a long time, the power consumption and heat generation of the power supply unit are very large. Therefore, the contactor of the present disclosure also includes a second power supply unit.

[0028] Figure 3 The second power supply unit 304 shown includes a fourth electronic switch T4, a second voltage stabilizing diode ZD2, a second capacitor C2, a third capacitor C3, a third resistor R3 and a fourth resistor R4. The first end of the second capacitor C2, the first end of the third resistor R3 and the first end of the fourth resistor R4 are connected to the coil unit 301 for receiving the coil voltage, specifically, for example, they can be connected to the connection point between the coil 3012 and the first electronic switch T1. The second end of the second capacitor C2 is connected to the ground wire. The second capacitor C2 can smooth the coil voltage output by the coil unit 301. Optionally, in order to better filter the fluctuation of the coil voltage, the second capacitor C2, the third resistor R3 and the fourth resistor R4 can also be connected to the coil unit 3012 through an inductor L. Figure 3 The inductor L is shown in FIG. 3 , but the inductor L is optional. The second end of the third resistor R3 is connected to the control end of the fourth electronic switch T4, and the second voltage stabilizing diode ZD2 is connected between the control end of the fourth electronic switch T4 and the ground line. The third capacitor C3 is connected between the first end of the fourth electronic switch T4 and the ground line, and the fourth electronic switch T4 is controlled by the voltage difference between its control end and the first end, and the first end of the fourth electronic switch T4 is the output end of the second power supply unit 304. The second end of the fourth resistor R4 is connected to the second end of the fourth electronic switch T4.

[0029] The second power supply unit 304 is stepped down by the fourth electronic switch T4. The conduction and cutoff of the fourth electronic switch T4 are controlled by the voltage difference between the control end and the first end. The existence of the voltage stabilizing diode ZD2 makes the voltage of the control end of the fourth electronic switch T4 constant. At the same time, when the fourth electronic switch T4 is turned on, the voltage drop between the control end and the first end is also constant. Therefore, when the second power supply unit 304 has a load and the fourth electronic switch T4 is turned on, the voltage of the first end of the fourth electronic switch T4 (i.e., the output end of the second power supply unit 304) is constant. Therefore, the required voltage can be output by selecting a voltage stabilizing diode ZD2 of a suitable voltage. In addition, since the input voltage of the second power supply unit 304 is relatively low, the fourth electronic switch T4 can use a relatively low-priced triode or MOS tube. When the fourth electronic switch T4 is a triode, the control end of the fourth electronic switch T4 is the base of the triode, the first end is the emitter, and the second end is the collector. At this time, the output end of the second power supply unit 304 is the emitter of the triode, and its output voltage is the voltage of the voltage-stabilizing diode ZD2 minus the voltage drop between the base and the emitter. When the fourth electronic switch T4 is a MOS tube, the control end of the fourth electronic switch T4 is the gate of the MOS tube, the first end is the source, and the second end is the drain. At this time, the output end of the second power supply unit 304 is the source of the MOS, and its output voltage is the voltage of the voltage-stabilizing diode ZD2 minus the voltage drop between the gate and the source.

[0030] exist Figure 3 In the example shown, diodes D1 and D2 are used to implement power supply switching between the first power supply unit 303 and the second power supply unit 304. Figure 3 As shown, the output end of the first power supply unit 303 (i.e., the first end of the third electronic switch T3) is connected to the anode of the first diode D1; the output end of the second power supply unit 304 (i.e., the first end of the fourth electronic switch T4) is connected to the anode of the second diode D2; the cathode of the first diode D1 is connected to the cathode of the second diode D2 and connected to the control unit 302, which is used to provide power to the control unit 102. The second output voltage Vout2 is set to be greater than the first output voltage Vout1, so that after the second power supply unit 304 outputs the second output voltage Vout2, the first power supply unit 303 stops outputting power, for example, the second output voltage Vout2 is set to 16V, and the first output voltage Vout1 is set to 14V. Therefore, when the first power supply unit 303 outputs the first output voltage Vout1 and the second power supply unit 304 does not output the second voltage Vout2, the first diode D1 is turned on and the second diode D2 is turned off, and the first power supply unit 303 supplies power to the control unit 302; when the second power supply unit 304 also outputs the second output voltage Vout2, since Vout2 is greater than Vout1, the second diode D2 is turned on and the first diode D1 is turned off, and the second power supply unit 304 supplies power to the control unit 302, while the first power supply unit 303 stops supplying power to the control unit 302.

[0031] Of course, as mentioned above, Figure 3 In the example of FIG. 3 , the power supply switching between the first power supply unit 303 and the second power supply unit 304 may alternatively be implemented by a control circuit such as the control unit 302. For example, when the control unit 302 detects that the second power supply unit 104 outputs the second output voltage Vout2, the first power supply unit 303 is controlled to stop outputting power after a predetermined time by disconnecting the first power supply unit 303 from the control unit 302, stopping the operation of the first power supply unit 303, or disconnecting the power supply of the first power supply unit 303.

[0032] Figure 5 FIG. 5 is a flow chart showing a method 500 for powering a contactor according to an embodiment of the present disclosure. The method can be applied to a contactor including a coil, a coil power supply unit and a control unit, such as the contactor described above. Figure 1-Figure 3The contactor described. The power supply method 500 includes steps S501-S503. In step S501, the contactor outputs a first output voltage after stepping down the input voltage to supply power to the control unit; in step S502, the coil power supply unit provides a coil voltage to the coil under the control of the control unit; in step S503, the contactor outputs a second output voltage after stepping down the coil voltage to supply power to the control unit, and stops supplying power to the control unit through the first output voltage. The above steps can be performed by any suitable hardware of the contactor or hardware combined with software. For example, step S501 can be performed by the above-mentioned first power supply unit, step S502 can be performed by the above-mentioned coil power supply unit, and step S503 can be performed by the above-mentioned second power supply unit in combination with a control unit or a diode circuit.

[0033] According to the power supply method of the embodiment of the present disclosure, the conversion of the high input voltage into the low auxiliary voltage is only performed in a short period of time at the initial stage of the contactor power-on, and after the coil voltage of the contactor is formed, the auxiliary voltage is generated by stepping down the coil voltage and provided to the control unit, and the direct step-down power supply from the input voltage is stopped. In this case, although it is still necessary to directly step down the input voltage to generate the auxiliary voltage when the relay is started, since the process is shorter, the power consumption and heat generated are smaller, and no heat dissipation system is required, and the requirements and costs of the equipment are lower.

[0034] The hardware computing device described in the present disclosure may be implemented in its entirety or in parts thereof through various suitable hardware means, including but not limited to FPGA, ASIC, SoC, discrete gate or transistor logic, discrete hardware components, or any combination thereof.

[0035] The block diagrams of circuits, devices, apparatuses, equipment, and systems involved in the present disclosure are only illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As will be appreciated by those skilled in the art, these circuits, devices, apparatuses, equipment, and systems may be connected, arranged, or configured in any manner as long as the desired purpose can be achieved.

[0036] Those skilled in the art should understand that the above-mentioned specific embodiments are merely examples and not limitations, and various modifications, combinations, partial combinations and replacements may be made to the embodiments of the present disclosure according to design requirements and other factors. As long as they are within the scope of the attached claims or their equivalents, they belong to the scope of rights to be protected by the present disclosure.

Claims

1. A contactor, comprising: A coil unit, comprising a coil and a coil power supply unit, wherein the coil power supply unit receives an input voltage of an input power line and provides a coil voltage lower than the input voltage to the coil; A control unit, used for controlling the coil power supply unit; a first power supply unit, configured to receive the input voltage and output a first output voltage for the control unit; as well as a second power supply unit, configured to receive a coil voltage on the coil and output a second output voltage for the control unit, After the second power supply unit outputs the second output voltage, the first power supply unit stops outputting power.

2. The contactor according to claim 1, wherein The output end of the first power supply unit is connected to the anode of the first diode; The output end of the second power supply unit is connected to the anode of the second diode; The cathode of the first diode is connected to the cathode of the second diode for providing power to the control unit; and The second output voltage is greater than the first output voltage, so that after the second power supply unit outputs the second output voltage, the first power supply unit stops outputting power.

3. The contactor according to claim 1, wherein The control unit is further configured to detect whether the second power supply unit outputs the second output voltage, and control the first power supply unit to stop outputting power after a predetermined time when it is detected that the second power supply unit outputs the second output voltage.

4. The contactor according to claim 1, wherein The coil power supply unit includes a first electronic switch and a freewheeling diode; The first electronic switch is connected between the coil and the input power line and is controlled by the control unit; The coil is connected between the first electronic switch and the ground wire; The freewheeling diode is connected between the first electronic switch and a ground line; and The control unit controls the first electronic switch in a pulse width modulation manner to control the coil voltage on the coil.

5. The contactor according to claim 4, wherein The coil power supply unit further includes a second electronic switch connected between the coil and the ground wire.

6. The contactor according to claim 4, wherein The first electronic switch is an insulated gate bipolar transistor (IGBT).

7. The contactor according to any one of claims 1 to 6, wherein The first power supply unit includes a third electronic switch, a first voltage stabilizing diode, a first capacitor, a first resistor and a second resistor; The first resistor is connected between the control end of the third electronic switch and the input power line; The first voltage stabilizing diode is connected between the control terminal of the third electronic switch and the ground line; The first capacitor is connected between the first terminal of the third electronic switch and the ground line, and the third electronic switch is controlled by the voltage difference between the control terminal and the first terminal; The second resistor is connected between the second end of the third electronic switch and the input power line; and The first end of the third electronic switch is the output end of the first power supply unit.

8. The contactor according to any one of claims 1 to 6, wherein The second power supply unit includes a fourth electronic switch, a second voltage stabilizing diode, a second capacitor, a third capacitor, a third resistor and a fourth resistor; The first end of the second capacitor, the first end of the third resistor and the first end of the fourth resistor are connected to the coil unit to receive the coil voltage; The second end of the second capacitor is connected to the ground line; The second end of the third resistor is connected to the control end of the fourth electronic switch; The second voltage stabilizing diode is connected between the control terminal of the fourth electronic switch and the ground line; The third capacitor is connected between the first end of the fourth electronic switch and the ground line; the fourth electronic switch is controlled by the voltage difference between its control end and the first end; The second end of the fourth resistor is connected to the second end of the fourth electronic switch; and The first end of the fourth electronic switch is the output end of the second power supply unit.

9. The contactor according to claim 8, wherein The second capacitor, the third resistor and the fourth resistor are connected to the coil unit via inductance.

10. A power supply method for a contactor, the contactor comprising a coil, a coil power supply unit and a control unit, the power supply method comprising: Stepping down the input voltage to output a first output voltage to supply power to the control unit; The coil power supply unit provides a coil voltage to the coil under the control of the control unit; as well as The coil voltage is stepped down to output a second output voltage to supply power to the control unit, and the first output voltage is stopped to supply power to the control unit.

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