CN217656471U

CN217656471U - Electrical power supply system of automatic change-over switch

Info

Publication number: CN217656471U
Application number: CN202123228437.5U
Authority: CN
Inventors: 刘琦
Original assignee: Schneider Wingoal Tianjin Electric Equipment Co Ltd
Current assignee: Schneider Wingoal Tianjin Electric Equipment Co Ltd
Priority date: 2021-12-21
Filing date: 2021-12-21
Publication date: 2022-10-25
Anticipated expiration: 2031-12-21

Abstract

The utility model provides an automatic electrical power generating system of change over switch, including rectifier circuit, switching power supply circuit and step-down circuit, switching power supply circuit's input is connected to rectifier circuit, and switching power supply circuit's output is connected to step-down circuit's input, and step-down circuit's output termination is outside electrical apparatus. An automatic electrical power generating system of change over switch simple structure only has two-stage power supply structure, and is with low costs, efficiency under the condition of exporting same power is far higher than the automatic change over switch electrical apparatus structure among the prior art, calorific capacity is low, this electrical power generating system part is small in quantity, small.

Description

Electrical power supply system of automatic change-over switch

Technical Field

The utility model belongs to the technical field of it is electric, especially, relate to an automatic change-over switch electric electrical power supply system.

Background

An automatic transfer switching apparatus is a device used in a low-voltage distribution system and capable of putting a downstream load into a backup power system after a failure of a general power source.

The power supply system of the automatic transfer switching device which is mainstream in the market at present consists of the following parts:

1. the AC/DC conversion circuit mainly comprises two identical AC-to-DC power supply circuits, the inputs of the two identical AC-to-DC power supply circuits are respectively the AC sides of a common power supply and a standby power supply, and the DC power supplies of the two identical AC-to-DC power supply circuits are directly connected in parallel.

2. The first stage DC/DC voltage-stabilized power supply mainly reduces the voltage of the unstable DC power supply of the front stage and stabilizes the unstable DC power supply into a stable DC power supply for driving electronic parts on the circuit board.

3. The second stage DC/DC stabilized power supply mainly reduces the voltage of the more stable DC power supply of the front stage into a stable DC power supply with low ripple. The high-precision electronic chip is provided for use on a circuit board.

SUMMERY OF THE UTILITY MODEL

In view of this, the present invention provides an electrical power system for an automatic transfer switch to solve the deficiencies of the prior art.

In order to achieve the above purpose, the technical scheme of the utility model is realized like this:

an electric power system of an automatic transfer switch comprises a rectification circuit, a switch power circuit and a voltage reduction circuit, wherein the input end of the switch power circuit is connected to the rectification circuit, the output end of the switch power circuit is connected to the input end of the voltage reduction circuit, and the output end of the voltage reduction circuit is connected with an external electric appliance;

the switching power supply circuit comprises a rectifying and filtering circuit and a power supply circuit, wherein the input end of the rectifying and filtering circuit is connected to the rectifying circuit, the output end of the rectifying and filtering circuit is connected to the input end of the power supply circuit, and the output end of the power supply circuit is connected to the voltage reduction circuit.

Further, the rectification filter circuit comprises a capacitor CC1, a capacitor CC2, a resistor RC1, a resistor RC2, a resistor RC7 and a resistor RC8, one end of the capacitor CC1 and one end of the capacitor CC2 are both connected to the rectification circuit, the other end of the capacitor CC1 is connected to the other end of the capacitor CC2 and one end of the resistor RC7 respectively, one end of the resistor RC7 is connected to one end of the resistor RC2, the other end of the resistor RC7 is connected to one end of the resistor RC8, the other end of the resistor RC8 is connected to one end of the capacitor CC2, the other end of the resistor RC2 is connected to one end of the resistor RC1, and the other end of the resistor RC1 is connected to one end of the capacitor CC1 and the power circuit respectively.

Further, the power supply circuit includes a resistor RE1, a resistor RE2, a resistor RE3, a resistor RE4, a resistor RE5, a resistor RE6, a resistor RE7, a resistor RE8, a resistor RE9, a resistor RE10, a resistor RE11, a diode DE1, a diode DE4, a diode DE6, a capacitor CE5, a capacitor CE6, a MOS transistor QE1, a switching power supply chip UE2, and a transformer, one end of the resistor RE1 is respectively connected to the other end of the resistor RC1 and a pin six of the transformer, the other end of the resistor RE1 is connected to one end of the resistor RE4 through the resistor RE2 and the resistor RE3 in sequence, one end of the resistor RE4 is further connected to one end of the resistor RE5, one end of the capacitor CE5, and one end of the diode DE6, the other ends of the resistor RE5 and the capacitor CE5 are both grounded, the other end of the diode DE6 is connected to Vdc, a pin six of the switching power supply chip UE2 is connected to one end of the diode DE6, a pin six of the switching power supply chip UE2 is connected to one end of the resistor RE6 and one end of the resistor RE9, the other end of the resistor RE6 is connected with the Vdc, the other end of the resistor RE9 is grounded, the third pin of the switch power supply chip UE2 is grounded through a resistor RE10, the second pin of the switch power supply chip UE2 is grounded, the fourth pin of the switch power supply chip UE2 is respectively connected with one end of a resistor RE8 and one end of a capacitor CE6, the other end of the capacitor CE6 is grounded, the other end of the resistor RE8 is respectively connected with one end of a resistor RE11 and the source electrode of an MOS tube QE1, the other end of the resistor RE11 is grounded, the grid electrode of the MOS tube QE1 is connected with one end of a resistor RE7, the other end of the resistor RE7 is connected with the fifth pin of the switch power supply chip UE2, the drain electrode of the MOS tube QE1 is respectively connected with one end of a diode DE4 and the fourth pin of the transformer, the other end of the diode DE4 is connected with the sixth pin of the transformer through a diode DE1, the second pin of the transformer is connected with the Vdc, the first pin of the transformer is grounded, the ninth pin of the transformer is connected with the tenth pin of the transformer, the tenth pin of the Vdc, the No. twelve pin of the transformer is connected with the No. eleven pin of the transformer, and the No. seven pin of the transformer, the No. eight pin of the transformer, the No. ten pin of the transformer and the No. eleven pin of the transformer are all connected to the voltage reduction circuit.

Furthermore, the voltage reduction circuit comprises a first power supply, a second power supply and an LDO power supply, wherein the input end of the first power supply is connected to the seventh pin of the transformer and the eighth pin of the transformer, the output end of the first power supply is connected with an external electric appliance, the input end of the second power supply is connected to the tenth pin of the transformer and the eleventh pin of the transformer, and the output end of the second power supply is connected to the LDO power supply.

Further, the first power supply includes a diode DE5 and a capacitor CE4, one end of the diode DE5 is connected to the eighth pin of the transformer, the other end of the diode DE5 is connected to the positive 24V, one end of the capacitor CE4 is connected to the positive 24V, the other end of the capacitor CE4 is grounded, and the seventh pin of the transformer is connected to the other end of the capacitor CE 4.

Furthermore, the second power supply comprises a diode DE2, a diode DE3, a capacitor CE1 and a capacitor CE2, one end of the diode DE2 is connected to the pin eleven of the transformer, the pin ten of the transformer is connected to the capacitor CE1, the other end of the diode DE2 is connected to one end of the capacitor CE1 and one end of the diode DE3, the other end of the diode DE3 is connected to the LDO power supply, one end of the capacitor CE1 is further connected to the positive 5V, the other end of the capacitor CE1 is grounded, one end of the capacitor CE2 is connected to the other end of the diode DE3, and the other end of the capacitor CE2 is grounded.

Further, the LDO power supply includes LDO chip UE1 and electric capacity CE3, no. three pins of LDO chip UE1 connect diode DE3, and No. one pin of LDO chip UE1 ground connection, no. two pins of LDO chip UE1 connect the one end of electric capacity CE3, and the one end of electric capacity CE3 still is connected to positive 3.3V, and electric capacity CE3 other end ground connection.

Furthermore, the rectifying circuit comprises a common power supply rectifying circuit and a standby power supply rectifying circuit, wherein the input end of the common power supply rectifying circuit is connected to a common power supply, the output end of the common power supply rectifying circuit is connected to the input end of the rectifying and filtering circuit, the input end of the standby power supply rectifying circuit is connected to the standby power supply, and the output end of the standby power supply rectifying circuit is connected to the input end of the rectifying and filtering circuit.

Compared with the prior art, an automatic change-over switch electric power supply system have following advantage:

(1) An automatic electrical power generating system of change over switch, simple structure only has two-stage power supply structure, and is with low costs, efficiency under the condition of exporting same power is far higher than the automatic change over switch electrical apparatus structure among the prior art, calorific capacity is low, this electrical power generating system part is small in quantity, small.

Drawings

The accompanying drawings, which form a part hereof, are included to provide a further understanding 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 invention without undue limitation. In the drawings:

fig. 1 is a circuit diagram of the overall structure according to an embodiment of the present invention;

FIG. 2 is an enlarged view of A in FIG. 1;

FIG. 3 is an enlarged view of B in FIG. 1;

fig. 4 is an enlarged view of C in fig. 1.

Detailed Description

It should be noted that, in the present invention, the embodiments and features of the embodiments may be combined with each other without conflict.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are used merely for convenience of description and for simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore, should not be construed as limiting the present invention. Furthermore, the terms "first", "second", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected" and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art through specific situations.

The present invention will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.

As shown in fig. 1 to 4, an electrical power system of an automatic transfer switch includes a rectifying circuit, a switching power circuit and a voltage-reducing circuit, wherein an input end of the switching power circuit is connected to the rectifying circuit, an output end of the switching power circuit is connected to an input end of the voltage-reducing circuit, and an output end of the voltage-reducing circuit is connected to an external electrical appliance;

the switching power supply circuit comprises a rectifying and filtering circuit and a power supply circuit, wherein the input end of the rectifying and filtering circuit is connected to the rectifying circuit, the output end of the rectifying and filtering circuit is connected to the input end of the power supply circuit, and the output end of the power supply circuit is connected to the voltage reduction circuit. The power supply system has the advantages of simple structure, only two-stage power supply structure, low cost, far higher efficiency than the automatic transfer switching device structure in the prior art under the condition of outputting the same power, low heat productivity, small quantity of parts and small volume.

The rectification filter circuit comprises a capacitor CC1, a capacitor CC2, a resistor RC1, a resistor RC2, a resistor RC7 and a resistor RC8, one end of the capacitor CC1 and one end of the capacitor CC2 are both connected to the rectification circuit, the other end of the capacitor CC1 is connected to the other end of the capacitor CC2 and one end of the resistor RC7 respectively, one end of the resistor RC7 is connected to one end of the resistor RC2, the other end of the resistor RC7 is connected to one end of the resistor RC8, the other end of the resistor RC8 is connected to one end of the capacitor CC2, the other end of the resistor RC2 is connected to one end of the resistor RC1, and the other end of the resistor RC1 is connected to one end of the capacitor CC1 and the power circuit respectively. In this embodiment, the rectifying and filtering circuit is used for performing filtering processing on the rectifying circuit.

The power supply circuit comprises a resistor RE1, a resistor RE2, a resistor RE3, a resistor RE4, a resistor RE5, a resistor RE6, a resistor RE7, a resistor RE8, a resistor RE9, a resistor RE10, a resistor RE11, a diode DE1, a diode DE4, a diode DE6, a capacitor CE5, a capacitor CE6, an MOS tube QE1, a switching power supply chip UE2 and a transformer, wherein one end of the resistor RE1 is respectively connected to the other end of the resistor RC1 and a pin six of the transformer, the other end of the resistor RE1 is connected to one end of the resistor RE4 through the resistor RE2 and the resistor RE3 in sequence, one end of the resistor RE4 is also respectively connected to one end of the resistor RE5, one end of the capacitor CE5 and one end of the diode DE6, the other end of the diode DE6 is connected to Vdc, the pin six of the switching power supply chip UE2 is connected to one end of the resistor RE6 and one end of the resistor RE9, the other end of the resistor RE6 is connected with the Vdc, the other end of the resistor RE9 is grounded, the third pin of the switch power supply chip UE2 is grounded through a resistor RE10, the second pin of the switch power supply chip UE2 is grounded, the fourth pin of the switch power supply chip UE2 is respectively connected with one end of a resistor RE8 and one end of a capacitor CE6, the other end of the capacitor CE6 is grounded, the other end of the resistor RE8 is respectively connected with one end of a resistor RE11 and the source electrode of an MOS tube QE1, the other end of the resistor RE11 is grounded, the grid electrode of the MOS tube QE1 is connected with one end of a resistor RE7, the other end of the resistor RE7 is connected with the fifth pin of the switch power supply chip UE2, the drain electrode of the MOS tube QE1 is respectively connected with one end of a diode DE4 and the fourth pin of the transformer, the other end of the diode DE4 is connected with the sixth pin of the transformer through a diode DE1, the second pin of the transformer is connected with the Vdc, the first pin of the transformer is grounded, the ninth pin of the transformer is connected with the tenth pin of the transformer, the No. twelve pin of the transformer is connected with the No. eleven pin of the transformer, and the No. seven pin of the transformer, the No. eight pin of the transformer, the No. ten pin of the transformer and the No. eleven pin of the transformer are all connected to the voltage reduction circuit. In this embodiment, the power supply circuit is used to supply current to the voltage-reducing circuit.

The voltage reduction circuit comprises a first power supply, a second power supply and an LDO power supply, wherein the input end of the first power supply is connected to a seventh pin of the transformer and an eighth pin of the transformer respectively, the output end of the first power supply is connected with an external electric appliance, the input end of the second power supply is connected to a tenth pin of the transformer and an eleventh pin of the transformer respectively, and the output end of the second power supply is connected to the LDO power supply. In the embodiment, the voltage reduction circuit is divided into a plurality of stages of circuits, so that power can be supplied to electric appliances with different voltage requirements.

The first path of power supply comprises a diode DE5 and a capacitor CE4, one end of the diode DE5 is connected with a pin eight of the transformer, the other end of the diode DE5 is connected with a positive 24V, one end of the capacitor CE4 is connected with the positive 24V, the other end of the capacitor CE4 is grounded, and a pin seven of the transformer is connected to the other end of the capacitor CE 4. In this embodiment, the first power supply is used to output a positive 24V current.

The second power supply comprises a diode DE2, a diode DE3, a capacitor CE1 and a capacitor CE2, one end of the diode DE2 is connected with the pin eleven of the transformer, the pin ten of the transformer is connected with the capacitor CE1, the other end of the diode DE2 is respectively connected to one end of the capacitor CE1 and one end of the diode DE3, the other end of the diode DE3 is connected to the LDO power supply, one end of the capacitor CE1 is further connected to the positive 5V, the other end of the capacitor CE1 is grounded, one end of the capacitor CE2 is connected to the other end of the diode DE3, and the other end of the capacitor CE2 is grounded. In the embodiment, the second power supply is used for outputting a positive 5V current.

The LDO power supply comprises an LDO chip UE1 and a capacitor CE3, a pin III of the LDO chip UE1 is connected with a diode DE3, a pin I of the LDO chip UE1 is grounded, a pin II of the LDO chip UE1 is connected with one end of the capacitor CE3, one end of the capacitor CE3 is further connected to positive 3.3V, and the other end of the capacitor CE3 is grounded. In this embodiment, the LDO power supply is used to output a positive 3.3V current.

The rectifying circuit comprises a common power supply rectifying circuit and a standby power supply rectifying circuit, wherein the input end of the common power supply rectifying circuit is connected to a common power supply, the output end of the common power supply rectifying circuit is connected to the input end of the rectifying and filtering circuit, the input end of the standby power supply rectifying circuit is connected to a standby power supply, and the output end of the standby power supply rectifying circuit is connected to the input end of the rectifying and filtering circuit. In this embodiment, the rectifier circuit is divided into a common power supply rectifier circuit and a standby power supply rectifier circuit, so that the practicability of the circuit is improved.

The power supply system is characterized in that the power supply voltages of two different power supply systems are rectified and then connected in parallel to form a stable high-voltage direct current voltage. And simultaneously, a switching power supply is used for converting the high-voltage direct current voltage into two paths of direct current voltages.

Example 1

As shown in the figure, the utility model provides a pair of low-cost automatic transfer switch electrical apparatus's electrical power generating system includes: the power supply circuit comprises a rectifying circuit, a switching power supply circuit and a voltage reduction circuit.

The utility model provides a pair of automatic change-over switch electric electrical power generating system's theory of operation as follows:

a rectifier circuit: the circuit is divided into a common power supply rectifying circuit and a standby power supply rectifying circuit, the inputs of the common power supply rectifying circuit and the standby power supply rectifying circuit are a common power supply and a standby power supply respectively, the circuit has the function of rectifying alternating currents of the common power supply and the standby power supply into high-voltage direct currents respectively, and the direct currents of two paths of high-voltage direct currents are connected together through diodes. The rectification circuit also comprises a protection function, and is used for inhibiting the abnormal part of the overvoltage and protecting the stability of a back-end circuit of a power supply system when the overvoltage occurs in the power distribution system.

Switching power supply circuit: the function is to convert high-voltage direct current into a low-voltage direct current system by matching an internal rectifying and filtering circuit with an inductor and a transformer, and two paths of different voltage grades are output.

The first path of power supply: the first output of the power circuit is a stable DC power supply, and is used for internal signal indication.

The second path of power supply: the output voltage of the second output circuit is a stable direct current power supply, but due to the characteristics of the switching power supply, the ripple wave of the second output circuit is large, so that the second output circuit cannot be used for a high-precision electronic chip on a circuit board, and can only be provided for some electronic parts such as a relay.

LDO: the ripple of the stable dc power supply described in the fourth aspect is further reduced, and the stable dc power supply is provided for a high-precision electronic chip.

The above description is only a preferred embodiment of the present invention, and should not be taken as limiting the invention, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An electrical power supply system for an automatic transfer switch, comprising: the voltage-reducing circuit comprises a rectifying circuit, a switching power supply circuit and a voltage-reducing circuit, wherein the input end of the switching power supply circuit is connected to the rectifying circuit, the output end of the switching power supply circuit is connected to the input end of the voltage-reducing circuit, and the output end of the voltage-reducing circuit is connected with an external electric appliance;

2. An electrical power supply system for an automatic transfer switch as claimed in claim 1, wherein: the rectification filter circuit comprises a capacitor CC1, a capacitor CC2, a resistor RC1, a resistor RC2, a resistor RC7 and a resistor RC8, one end of the capacitor CC1 and one end of the capacitor CC2 are both connected to the rectification circuit, the other end of the capacitor CC1 is connected to the other end of the capacitor CC2 and one end of the resistor RC7 respectively, one end of the resistor RC7 is connected to one end of the resistor RC2, the other end of the resistor RC7 is connected to one end of the resistor RC8, the other end of the resistor RC8 is connected to one end of the capacitor CC2, the other end of the resistor RC2 is connected to one end of the resistor RC1, and the other end of the resistor RC1 is connected to one end of the capacitor CC1 and the power circuit respectively.

3. An automatic transfer switch electrical power supply system according to claim 2, wherein: the power supply circuit comprises a resistor RE1, a resistor RE2, a resistor RE3, a resistor RE4, a resistor RE5, a resistor RE6, a resistor RE7, a resistor RE8, a resistor RE9, a resistor RE10, a resistor RE11, a diode DE1, a diode DE4, a diode DE6, a capacitor CE5, a capacitor CE6, an MOS tube QE1, a switching power supply chip UE2 and a transformer, wherein one end of the resistor RE1 is respectively connected to the other end of the resistor RC1 and a pin six of the transformer, the other end of the resistor RE1 is connected to one end of the resistor RE4 through the resistor RE2 and the resistor RE3 in sequence, one end of the resistor RE4 is also respectively connected to one end of the resistor RE5, one end of the capacitor CE5 and one end of the diode DE6, the other end of the resistor RE5 and the other end of the capacitor CE5 are grounded, the other end of the diode DE6 is connected to the Vdc, the pin six of the switching power supply chip UE2 is connected to one end of the diode DE6, one end of the pin six of the switching power supply chip UE2 is respectively connected to one end of the resistor RE6 and one end of the resistor RE9, the other end of the resistor RE6 is connected with the Vdc, the other end of the resistor RE9 is grounded, the third pin of the switch power supply chip UE2 is grounded through a resistor RE10, the second pin of the switch power supply chip UE2 is grounded, the fourth pin of the switch power supply chip UE2 is respectively connected with one end of a resistor RE8 and one end of a capacitor CE6, the other end of the capacitor CE6 is grounded, the other end of the resistor RE8 is respectively connected with one end of a resistor RE11 and the source electrode of an MOS tube QE1, the other end of the resistor RE11 is grounded, the grid electrode of the MOS tube QE1 is connected with one end of a resistor RE7, the other end of the resistor RE7 is connected with the fifth pin of the switch power supply chip UE2, the drain electrode of the MOS tube QE1 is respectively connected with one end of a diode DE4 and the fourth pin of the transformer, the other end of the diode DE4 is connected with the sixth pin of the transformer through a diode DE1, the second pin of the transformer is connected with the Vdc, the first pin of the transformer is grounded, the ninth pin of the transformer is connected with the tenth pin of the transformer, the No. twelve pin of the transformer is connected with the No. eleven pin of the transformer, and the No. seven pin of the transformer, the No. eight pin of the transformer, the No. ten pin of the transformer and the No. eleven pin of the transformer are all connected to the voltage reduction circuit.

4. An electrical power supply system for an automatic transfer switch as claimed in claim 1, wherein: the voltage reduction circuit comprises a first power supply, a second power supply and an LDO power supply, wherein the input end of the first power supply is connected to a seventh pin of the transformer and an eighth pin of the transformer respectively, the output end of the first power supply is connected with an external electric appliance, the input end of the second power supply is connected to a tenth pin of the transformer and an eleventh pin of the transformer respectively, and the output end of the second power supply is connected to the LDO power supply.

5. An automatic transfer switch electrical power supply system according to claim 4, wherein: the first path of power supply comprises a diode DE5 and a capacitor CE4, one end of the diode DE5 is connected with the pin eight of the transformer, the other end of the diode DE5 is connected with a positive 24V, one end of the capacitor CE4 is connected with the positive 24V, the other end of the capacitor CE4 is grounded, and the pin seven of the transformer is connected to the other end of the capacitor CE 4.

6. An automatic transfer switch electrical power supply system according to claim 4, wherein: the second power supply comprises a diode DE2, a diode DE3, a capacitor CE1 and a capacitor CE2, one end of the diode DE2 is connected with a pin number eleven of the transformer, a pin number ten of the transformer is connected with the capacitor CE1, the other end of the diode DE2 is respectively connected with one end of the capacitor CE1 and one end of the diode DE3, the other end of the diode DE3 is connected with the LDO power supply, one end of the capacitor CE1 is further connected to positive 5V, the other end of the capacitor CE1 is grounded, one end of the capacitor CE2 is connected to the other end of the diode DE3, and the other end of the capacitor CE2 is grounded.

7. An automatic transfer switch electrical power supply system according to claim 4, wherein: the LDO power supply comprises an LDO chip UE1 and a capacitor CE3, a pin III of the LDO chip UE1 is connected with a diode DE3, a pin I of the LDO chip UE1 is grounded, a pin II of the LDO chip UE1 is connected with one end of the capacitor CE3, one end of the capacitor CE3 is further connected to positive 3.3V, and the other end of the capacitor CE3 is grounded.

8. An electrical power supply system for an automatic transfer switch as claimed in claim 1, wherein: the rectifying circuit comprises a common power supply rectifying circuit and a standby power supply rectifying circuit, wherein the input end of the common power supply rectifying circuit is connected to a common power supply, the output end of the common power supply rectifying circuit is connected to the input end of the rectifying and filtering circuit, the input end of the standby power supply rectifying circuit is connected to a standby power supply, and the output end of the standby power supply rectifying circuit is connected to the input end of the rectifying and filtering circuit.