CN215300140U - Power supply protection circuit - Google Patents

Abstract

An embodiment of the utility model provides a power supply protection circuit belongs to power and transformer technical field. The circuit is provided on a line between a power supply and a load, and includes: the first rectification module is used for rectifying the three-phase output signals of the power supply; a switching device for controlling connection between the power source and the load based on whether both the three-phase output signal and an operating voltage of the switching device are normally output; and the first voltage identification module is connected with the switching device and used for identifying whether the three-phase output signal is normally output or not, and if not, the switching device is in a disconnected state to disconnect the connection between the power supply and the load. The utility model discloses a power supply protection circuit has increased circuit break-make protect function, can in time break off the main circuit when the power meets wrong line or trouble etc. to guarantee the safety of circuit and load.

Description

Power supply protection circuit

Technical Field

The utility model relates to a power technology and transformer technical field specifically relate to a power supply protection circuit.

Background

Industrial power supply based on a servo transformer is, for example, to convert industrial power from a 380V power source into an operating voltage required by a load (e.g., a servo system, a frequency conversion system, a stepping system, etc. of an automation device) to realize power supply. However, in the power supply process, if the power supply is connected in a wrong line, the output voltage is not adaptive, and the power supply or the transformer fails, the power supply line cannot be timely disconnected, so that the rear-end load can be damaged.

SUMMERY OF THE UTILITY MODEL

An object of the embodiments of the present invention is to provide a power supply protection circuit for at least partially solving the above technical problem.

In order to achieve the above object, an embodiment of the present invention provides a power supply protection circuit, which is disposed on a line between a power supply and a load, and includes the following modules disposed at arbitrary positions on the line between the power supply and the load: the first rectification module is used for rectifying the three-phase output signals of the power supply and supplying the three-phase output signals to the load; a switching device for controlling connection between the power source and the load based on whether both the three-phase output signal and an operating voltage of the switching device are normally output; and the first voltage identification module is connected with the switching device and used for identifying whether the three-phase output signal is normally output or not, and if not, the switching device is made to be in a disconnected state so as to disconnect the power supply and the load.

Optionally, the power supply protection circuit further comprises: a transformer power supply module disposed between the power supply and the switching device, for converting and outputting an output signal of the power supply to the operating voltage adapted to the switching device.

Optionally, the transformer power supply module comprises: the second rectification module is connected with the power supply and is used for rectifying the single-phase output signal of the power supply; the inversion module is connected with the second rectification module and used for inverting the signal rectified by the second rectification module into a pulse electric signal; and the input end of the transformer is connected with the inversion module, the output end of the transformer is connected with the switching device, and the transformer is used for converting the pulse electric signal into different output voltage signals based on different turn ratios and outputting an output voltage signal matched with the switching device to be used as the working voltage of the switching device.

Optionally, the transformer has a plurality of voltage output ports corresponding to the different output voltage signals, the plurality of voltage output ports including: a voltage output port for outputting the operating voltage to the switching device; and a voltage output port for supplying power to the load.

Optionally, the power supply protection circuit further comprises: and the second voltage identification module is arranged on a line between the output end of the transformer power supply module and the switch device and used for identifying whether the transformer power supply module normally outputs the working voltage of the switch device or not, and if not, the switch device is in a disconnection state so as to disconnect the connection between the power supply and the load.

Optionally, the first voltage identification module and the second voltage identification module are voltage sensing elements capable of sensing a voltage value in a corresponding signal, and the voltage sensing elements are one or more of a voltage dependent resistor, an optical coupler, a transformer and a single chip microcomputer.

Optionally, the first voltage identification module and the second voltage identification module are integrated into the same module having at least two input ports.

Optionally, the power supply protection circuit further comprises: the alarm module is connected with the first voltage identification module and/or the second voltage identification module and is used for giving an alarm by sound and/or light under the following conditions: the first voltage identification module identifies that the three-phase output signal is not normally output; and/or the second voltage identification module identifies that the operating voltage of the corresponding switching device is not normally output.

Optionally, the power supply protection circuit further comprises: one or more filtering modules disposed at any location on a line between the power source and the load.

Optionally, the switching device comprises a relay or a contactor.

Through the technical scheme, the utility model discloses a power supply protection circuit has increased circuit break-make protect function to appear the power and connect wrong line or trouble waiting in power supply process, can in time break off the main circuit, with the safety of assurance circuit and rear end load.

Other features and advantages of embodiments of the present invention will be described in detail in the detailed description which follows.

Drawings

The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the embodiments of the invention, but do not constitute a limitation of the embodiments of the invention. In the drawings:

fig. 1 is a schematic structural diagram of a power supply protection circuit according to an embodiment of the present invention;

fig. 2 is a block diagram of an example main circuit in an embodiment of the invention;

fig. 3 is a circuit diagram illustrating an example of a first voltage identification module applied to a main circuit for voltage identification according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of the power protection circuit in a preferred embodiment;

FIG. 5 is a schematic diagram of an exemplary transformer power module;

fig. 6 is an exemplary circuit diagram of a transformer power supply module implementing DC24V power supply in accordance with an embodiment of the present invention;

fig. 7 is an auxiliary circuit diagram of the high-frequency transformer J2 of fig. 6;

FIG. 8 is a schematic diagram of the power protection circuit of another preferred embodiment; and

fig. 9 is a circuit diagram illustrating an example of the voltage identification performed by the second voltage identification module according to the embodiment of the present invention.

Description of the reference numerals

100. A power supply protection circuit; 200. a power source; 300. a load;

110. a first rectifying module; 120. a switching device; 130. a first voltage identification module; 140. a transformer power supply module; 150. a second voltage identification module;

141. a second rectification module; 142. an inversion module; 143. transformer device

Detailed Description

The following describes in detail embodiments of the present invention with reference to the accompanying drawings. It is to be understood that the description herein is only intended to illustrate and explain embodiments of the present invention, and is not intended to limit embodiments of the present invention.

The term "connected" as used in the embodiments of the present invention is mainly used to mean "electrically connected", which is used to describe signal connection between two components, for example, through circuit connection, and the term "connected" may be direct electrical connection between two components or indirect electrical connection through other components or circuits. In addition, references to "first" and "second" in the embodiments of the present invention are only used for illustrating different elements or modules, and do not indicate the number of corresponding elements or modules.

Fig. 1 is a schematic structural diagram of a power supply protection circuit according to an embodiment of the present invention. The power supply protection circuit is disposed on a line between a power source and a load that the power source ultimately supplies. The power supply is, for example, a three-phase ac power supply, and the load may be a load circuit or a load element. For example, the power source is three-phase 380V industrial power, and the load may be a transmission system such as a servo system, a frequency conversion system, and a stepping system of an automation device, or a Programmable Logic Controller (PLC), a numerical control system, a board, an illumination, etc., as required.

As shown in fig. 1, the power supply protection circuit 100 according to the embodiment of the present invention is disposed on a line between a power source 200 and a load 300, and includes the following modules disposed at any position on the line between the power source and the load: the first rectifying module 110 is configured to rectify a three-phase output signal of the power supply 200; a switching device 120 for controlling connection between the power source and the load based on whether both the three-phase output signal and an operating voltage of the switching device 120 are normally output; and a first voltage identification module 130 connected to the switching device 120, for identifying whether the three-phase output signal is normally output, and if not, making the switching device 120 in an off state to disconnect the power supply 200 and the load 300.

The first rectifying module 110 is, for example, a plurality of rectifying diodes connected in series, connected in parallel, and/or packaged together. The switching device 120 includes, but is not limited to, a relay or a contactor, for example, an autonomously designed control switch may also be employed. Also, the power supply 200, the first rectification module 110, the switching device 120, and the load 300 constitute a power supply main circuit (hereinafter, referred to as a main circuit). For example, fig. 2 is a structural diagram of an exemplary main circuit in an embodiment of the present invention, wherein the power supply 200 employs a three-phase AC380V power supply, the first rectification module 110 employs parallel rectification diodes, the switching device 120 is a contactor or a relay with an operating voltage of +24V, and the switching device 120 is disposed at either the front end of the first rectification module 110 or the rear end of the first rectification module 110. And each port of the contactor or the relay is connected with other modules in a conventional manner, and is not described herein again. For the main circuit, the first rectification module 110 is used to convert the three-phase AC380V into Direct Current (DC) power for the load 300, and the switching device 120 may disconnect the line between the power source 200 and the load 300 when it is in the off state to perform a line protection function.

Further, on the basis of the above-mentioned main circuit, the first voltage identification module 130 is coupled to the switching device 120 for identifying whether the three-phase output signal of the power supply 200 is normally output. If not, the switching device 120 is made to be in an off state to disconnect the power supply 200 from the load 300; if so, the switching device 120 is in a closed state to conduct the connection between the power supply 200 and the load 300. The first voltage identification module 130 may be a voltage sensing element capable of sensing a voltage value in a corresponding signal, and the voltage sensing element may be, for example, one or more of a voltage dependent resistor, an optical coupler, a transformer, and a single chip. And, the first voltage identification module 130 identifies whether the three-phase output signal is normally output, specifically, identifies whether the power supply 200 has phase loss and phase error.

For example, fig. 3 is an exemplary circuit diagram of the first voltage identification module according to the embodiment of the present invention applied to a main circuit for voltage identification, wherein the main circuit structure can refer to fig. 2, so that the introduction of the main circuit in fig. 3 is simplified, and some conventional signal processing circuits, such as a filter circuit, a rectifier circuit, etc., are represented by blocks with ellipses. These conventional signal processing circuits are not the focus of the present invention and they are easily implemented by those skilled in the art, so that they are not described in detail for the purpose of simplicity of description and clarity of the drawings.

With reference to fig. 3, the basic principle of supplying power to the load when the main circuit operates normally can be described as follows: the three-phase power U, V, W passes through R1, R2 and R3 respectively; when the three-phase electric balance is realized, the potentials of the common end nodes of R1, R2 and R3 are very low, after the three-phase electric balance is processed by a diode, effective voltage difference cannot be formed between the common end nodes and a zero line N to enable an optical coupler U1 to work, so that the output end of the optical coupler U1 cannot be conducted, and switching tubes Q1 and Q2 are conducted due to +24V voltage output by the power supply protection circuit 100 to enable power supply outputs J5 and J6 of the relay/contactor to form a loop, so that the relay/contactor works to connect a main circuit for supplying power to a load by the power supply protection circuit 100.

The optocoupler U1 realizes the function of the first voltage identification module 130 here, and is used for sensing whether the power output signal is normal; the relay/contactor J5, J6 fulfill the function of the switching device 120.

Based on the basic principle that the main circuit supplies power to the load when in normal operation, the circuit protection principle under the condition of phase failure is as follows: if the U-phase is in phase loss, after passing through R1, R2 and R3, the three phases are unbalanced, the potential of a common node of R1, R2 and R3 becomes high, after passing through a diode, effective pressure difference is formed between the common node and a zero line to enable an optocoupler U1 to work, the output end of the optocoupler U1 enables switching tubes Q1 and Q2 to be incapable of working to be conducted, and therefore a loop cannot be formed by power supply outputs J5 and J6 of the relay/contactor, and the main loop is disconnected. The phase loss of the V phase and the W phase is similar to the phase loss of the U phase, and will not be described herein again.

Therefore, when the U/V/W phase electricity and the zero line N supply power, any one of the U/V/W phase electricity and the zero line N is disconnected, so that the power supply does not work, the normal work of the relay/contactor is influenced, and the relay/contactor is enabled to disconnect the corresponding main loop to play a role in circuit protection.

Further, for the phase-error condition, when one of the three phases of the U/V/W is in phase-error connection with a zero line N and passes through R1, R2 and R3, the three phases are unbalanced, the potentials of common nodes of R1, R2 and R3 are high, effective pressure difference is formed between the three phases and the zero line after the three phases are processed by a diode so that an optical coupler U1 works, the output end of the optical coupler U1 is conducted to enable switching tubes Q1 and Q2 to be not conducted, power supply outputs J5 and J6 of the relay/contactor cannot form a loop, and the relay/contactor cannot be connected with a main loop.

Therefore, according to this example, the power supply protection circuit of the embodiment of the present invention utilizes the switch device 120 and the first voltage identification module 130 to add the circuit on/off protection function to the main circuit, so that when a power source fault line or fault occurs in the power supply, the main circuit can be timely disconnected to ensure the safety of the circuit and the rear end load.

Further, as described above, the switching device 120 controls the connection between the power source 200 and the load 300 based on whether both the three-phase output signal and the operating voltage of the switching device are normally output. That is, the switching device 120 needs to satisfy its operating voltage to be normally opened or closed, thereby controlling the opening or closing of the relevant line. However, taking the switching device 120 as an example of a relay/contactor, the operating voltages required by different relays/contactors may be different, for example, the operating voltages may be DC5V, DC12V, DC24V, DC36V, DC48V, DC72V, and the like, and in fig. 2 and 3, DC24V is taken as an example.

Therefore, to enable flexible power supply to different types of switching devices 120, another power supply protection circuit is also provided in the preferred embodiment. Fig. 4 is a schematic structural diagram of the power supply protection circuit in the preferred embodiment. As shown in fig. 4, the power supply protection circuit further includes, based on fig. 1: a transformer power supply module 140 disposed between the power supply 200 and the switching device 120, for converting and outputting an output signal of the power supply 200 to an operating voltage adapted to the switching device 120.

Preferably, fig. 5 is a schematic structural diagram of an example transformer power supply module 140. In this example, the transformer power supply module 140 includes: the second rectifying module 141 is connected to the power supply and is configured to rectify a single-phase output signal of the power supply; the inversion module 142 is connected to the second rectification module and is configured to invert the signal rectified by the second rectification module into a pulse electrical signal; and a transformer 143, an input end of which is connected to the inverter module, and an output end of which is connected to the switching device, and configured to convert the pulse electrical signal into different output voltage signals based on different turn ratios, and output an output voltage signal adapted to the switching device as the working voltage of the switching device.

That is, the second rectifying module 141 and the inverting module 142 cooperate with the transformer 143 to convert a single-phase output signal (e.g., 220V voltage between the U phase and the neutral line N) of the power supply into an operating voltage suitable for the switching device. Taking the single-phase output signal of AC220V as an example, based on the transformer power supply module 140, different output voltages, such as DC5V, DC12V, DC24V, DC36V, DC48V, DC72V, etc., can be obtained by changing the turn ratio of the transformer 143, so as to meet different operating voltage requirements of different types of switching devices 120.

Fig. 6 is an exemplary circuit diagram of the transformer power supply module 140 implementing DC24V power supply according to an embodiment of the present invention. Referring to fig. 2, the input power AC220V/AC380V is rectified and filtered by a rectifier bridge B1 (corresponding to the second rectifying module 141), oscillated and inverted into pulse power by a switching tube VT1 (corresponding to the inverting module 142), and then converted into the required DC24V voltage by a high-frequency transformer J2 (corresponding to the transformer 143). Further, by changing the turn ratio of the high-frequency transformer J2, other output voltages, such as DC5V, DC12V, DC36V, DC48V, DC72V, etc., can be obtained, so as to meet the requirements of different loads. The high-frequency transformer is a power transformer with the working frequency exceeding the intermediate frequency (10 kHz).

It should be noted that the switching tube VT1 and the high frequency transformer J2 are not used as a circuit module alone, but are combined with other auxiliary components to achieve the corresponding functions better. For example, in fig. 6, the R9, R10, C4, D2 and D3 elements are auxiliary elements of the switching tube VT1, which are used to adjust the signal into the switching tube VT 1. For another example, fig. 7 is an auxiliary circuit diagram of the high-frequency transformer J2 in fig. 6, in which an input terminal is connected to an output terminal (corresponding to the interfaces 8, 9, 7, and 6 in fig. 6 and fig. 7) of the high-frequency transformer J2, and an output terminal (the terminal at which the C10 is located) is connected to a load. The auxiliary circuit of fig. 7 functions primarily as a rectifying filter (with a filter module constructed, for example, of C60) to output a more stable, accurate DC24V voltage to the load.

Accordingly, it can be seen that the transformer power supply module 140 according to the embodiment of the present invention can intelligently output multi-level voltages to be provided to different types of switching devices 120 as operating voltages.

In addition, the functional requirements of the current automation equipment on the power supply are more and more diversified, for example, elements such as a PCL, a numerical control system, a board card and lighting are different from working voltages required by transmission systems such as a servo system, a frequency conversion system and a stepping system. Therefore, by utilizing the characteristics of the multi-level voltage output of the transformer power supply module 140 of the embodiment of the present invention, power can be supplied to different power utilization components of the automation device by configuring the output interface of the transformer. For example, the configuration transformer 143 has a plurality of voltage output ports corresponding to the different output voltage signals, the plurality of voltage output ports including: a voltage output port for outputting the operating voltage to the switching device 120; and a voltage output port for supplying power to the load 300. The load 300 here refers generally to the different electrical components of the automation device mentioned above. That is, the transformer power supply module 140 of the embodiment of the present invention can provide the operating voltage to the switching device 120, and can also supply power to the power consumption component of the automation device as a power source.

Further, based on the idea of designing the first voltage identification module 130 in fig. 1, a circuit on-off protection function design is also performed for a case where the transformer power supply module 140 cannot normally output a corresponding voltage (e.g., a problem of a wrong connection of the transformer or the like). That is, fig. 8 is a schematic structural diagram of a power supply protection circuit according to another preferred embodiment, and the power supply protection circuit further includes, on the basis of fig. 4: a second voltage identification module 150, disposed on a line between the output end of the transformer power supply module 140 and the switching device 120, for identifying whether the transformer power supply module 140 outputs the working voltage of the switching device normally, and if not, making the switching device 120 in a disconnected state to disconnect the connection between the power supply and the load. The second voltage identification module 150 may be configured in the same manner as the first voltage identification module 130.

Fig. 9 is a circuit diagram illustrating an example of voltage identification performed by the second voltage identification module applied to the main circuit according to an embodiment of the present invention, which is similar to the first voltage identification module of fig. 3 in structure, but further includes a second voltage identification module 150 formed by an optical coupler U2. The input end of the optical coupler U2 is connected to the output end of C10 in fig. 7 (i.e., the voltage output end of the power supply protection circuit 100), and the output end is connected to the output end of the optical coupler U1 in fig. 3. The optical coupler U2 is used to identify whether the transformer 143 outputs a normal voltage. Specifically, referring to fig. 9, when two of the U/V/W three phases are used as power supplies, the power supplies normally operate, but one of the voltages of the transformer 143 (the high-frequency transformer J2 in fig. 2) is rectified and output through a diode, the voltage exceeds a set voltage, the optocoupler U2 operates, the optocoupler output is turned on, the switching tubes Q1 and Q2 cannot operate and turn on, and the relay/contactor power supply outputs J5 and J6 cannot form a loop, so that the corresponding main loop is disconnected. In addition, when the neutral line N is out of phase, the power supply 200 does not operate and eventually does not output the DC24V voltage, so that the relay/contactor cannot be turned on, and the main circuit is also turned off to protect the circuit.

In summary, the second voltage identification module 150 and the first voltage identification module 130 control on/off of the normally open contactor/normally open relay (corresponding to the switching device 120) in the circuit together, when the input side of the power supply or the transformer is incorrectly connected or the output voltage is not suitable, no DC24V voltage is output, and the switching devices such as the normally open contactor/normally open relay are in an off state, so as to ensure the safety of the circuit; when the input side of the power supply or the transformer is correctly connected and the output voltage is adaptive, the DC24V voltage is output, the switching devices such as a contactor/a relay and the like are closed, and the whole circuit is conducted.

In a more preferred embodiment, the first voltage identification module 130 and the second voltage identification module 150 may be integrated into the same module having at least two input ports. One input port is configured to receive a power output signal of the power output, and the other input port is configured to receive an output voltage signal of the transformer power supply module 140 (more specifically, the transformer 143).

In a more preferred embodiment, the power supply protection circuit 100 may further include an alarm module (not shown in the figure) connected to the first voltage identification module 130 and/or the second voltage identification module 150 for making an alarm by sound and/or light when: the first voltage identification module 130 identifies that the three-phase output signal is not normally output; and/or the second voltage identification module 150 identifies that the operating voltage of the corresponding switching device is not normally output.

With regard to the configuration of the alarm module, with continued reference to fig. 3 and 9, D11 and D14 are light emitting diodes, which constitute the alarm module 154, and when the main circuit is working normally, the relay/contactor J3 is closed to turn on D11 (green light), and when the main circuit is working abnormally, the relay/contactor J3 is opened to turn on D14 (red light). In other examples, for the connection situation of the U/V/W three-phase (380V for example) and the neutral line N, the corresponding fault can be displayed through different lighting situations of the configurations D11 and D12, as shown in table 1 below.

TABLE 1-lamplight alarm state table

Status of state	Red light	Green lamp	Switching device such as relay (contactor)
				U/V/W/N correct wiring	Killing rice	Bright Light (LIGHT)	Suction-in
U is not connected	Bright Light (LIGHT)	Killing rice	Disconnect
				V is not connected	Bright Light (LIGHT)	Killing rice	Disconnect
W is not connected	Killing rice	Killing rice	Disconnect
				N is not connected	Killing rice	Killing rice	Disconnect
U and N are connected inversely	Bright Light (LIGHT)	Killing rice	Disconnect
				V is connected with N reversely	Bright Light (LIGHT)	Killing rice	Disconnect
W is inversely connected with N	Bright Light (LIGHT)	Killing rice	Disconnect

It will be appreciated that the function of the alarm module, i.e. making an audible alarm, may also be implemented by means of a loudspeaker.

The working states of the alarm module and the two circuit identification modules can be synchronous according to the identification results of the two voltage identification modules, for example, one circuit is disconnected and the other circuit simultaneously alarms when the power supply is in a phase failure.

In a more preferred embodiment, the power supply protection circuit 100 may further include: one or more filtering modules disposed anywhere on the line between the power source and the load, for example, are provided at the output of power source 200 for filtering the power source output signal, or at the output of transformer 143 for filtering the transformer output voltage signal. Wherein, the filtering module may be: any one of a filter element, a magnetic ring and an RC circuit; or at least two stages of filtering units connected in series, wherein each stage of filtering unit is configured to be capable of realizing harmonic filtering. Wherein the filtering unit is, for example, any one of a filtering element, a magnetic ring and an RC circuit, or a circuit formed by connecting any two or more of the filtering element, the magnetic ring and the RC circuit in series. Note that although the filtering module is not explicitly shown in the drawings, the above description relates to the filtering, and those skilled in the art can understand the arrangement of the filtering module in combination with the circuit diagram.

To sum up, the utility model discloses power supply protection circuit 100 has increased the protect function who carries out the circuit break-make, and has increased the prompt facility of sound or light alarm to appear connecing wrong line, voltage to mismatch, power failure etc. in the power supply, can in time break off the circuit on the one hand, guarantee the safety of circuit and rear end load, on the other hand can in time remind the operation personnel to maintain. It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in the process, method, article, or apparatus that comprises the element.

The above are merely examples of the present application and are not intended to limit the present application. Various modifications and changes may occur to those skilled in the art, such as changes in the location of various blocks or elements within the lines of the figures. It should be understood that any modifications, equivalents, improvements and the like which come within the spirit and principle of the application are intended to be included within the scope of the claims of the application.

Claims (10)

1. A power supply protection circuit, characterized in that it is provided on a line between a power supply and a load, and comprises the following modules arranged at any position on the line between the power supply and the load:

the first rectification module is used for rectifying the three-phase output signals of the power supply and supplying the three-phase output signals to the load;

a switching device for controlling connection between the power source and the load based on whether both the three-phase output signal and an operating voltage of the switching device are normally output; and

and the first voltage identification module is connected with the switching device and used for identifying whether the three-phase output signal is normally output or not, and if not, the switching device is made to be in a disconnected state so as to disconnect the power supply and the load.

2. The supply protection circuit of claim 1, further comprising:

a transformer power supply module disposed between the power supply and the switching device, for converting and outputting an output signal of the power supply to the operating voltage adapted to the switching device.

3. The supply protection circuit of claim 2, wherein the transformer supply module comprises:

the second rectification module is connected with the power supply and is used for rectifying the single-phase output signal of the power supply;

the inversion module is connected with the second rectification module and used for inverting the signal rectified by the second rectification module into a pulse electric signal; and

and the input end of the transformer is connected with the inversion module, the output end of the transformer is connected with the switching device, and the transformer is used for converting the pulse electric signal into different output voltage signals based on different turn ratios and outputting an output voltage signal matched with the switching device to be used as the working voltage of the switching device.

4. The power supply protection circuit of claim 3, wherein the transformer has a plurality of voltage output ports corresponding to the different output voltage signals, the plurality of voltage output ports comprising: a voltage output port for outputting the operating voltage to the switching device; and a voltage output port for supplying power to the load.

5. The supply protection circuit of claim 2, further comprising:

and the second voltage identification module is arranged on a line between the output end of the transformer power supply module and the switch device and used for identifying whether the transformer power supply module normally outputs the working voltage of the switch device or not, and if not, the switch device is in a disconnection state so as to disconnect the connection between the power supply and the load.

6. The power supply protection circuit of claim 5, wherein the first voltage identification module and the second voltage identification module are voltage sensing elements capable of sensing voltage values in corresponding signals, and the voltage sensing elements are one or more of a voltage dependent resistor, an optical coupler, a transformer and a single chip microcomputer.

7. The power supply protection circuit of claim 5, wherein the first voltage identification module and the second voltage identification module are integrated into a same module having at least two input ports.

8. The supply protection circuit of claim 5, further comprising:

the alarm module is connected with the first voltage identification module and/or the second voltage identification module and is used for giving an alarm by sound and/or light under the following conditions: the first voltage identification module identifies that the three-phase output signal is not normally output; and/or the second voltage identification module identifies that the operating voltage of the corresponding switching device is not normally output.

9. The supply protection circuit of claim 1, further comprising: one or more filtering modules disposed at any location on a line between the power source and the load.

10. The supply protection circuit of claim 1, wherein the switching device comprises a relay or a contactor.

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