CN212163163U

CN212163163U - Power supply with overvoltage and undervoltage protection input

Info

Publication number: CN212163163U
Application number: CN202020399920.6U
Authority: CN
Inventors: 李锦红; 陈钦裕; 谭超
Original assignee: Guangdong Kegu Power Co ltd
Current assignee: Guangdong Kegu Power Co ltd
Priority date: 2020-03-25
Filing date: 2020-03-25
Publication date: 2020-12-15
Anticipated expiration: 2030-03-25

Abstract

The utility model discloses an input area excessive pressure and undervoltage protection's power, include: the primary filter circuit is used for performing primary EMI filtering on input commercial power; the bridge rectifier circuit is used for rectifying the commercial power subjected to the primary EMI filtering and outputting the commercial power to the surge protection circuit; the surge protection circuit is used for realizing surge protection on the power supply and outputting direct current to the feedback protection circuit and the transformer; the transformer is used for realizing voltage transformation and outputting the transformed voltage to the secondary filter circuit and the feedback voltage to the feedback protection circuit; the feedback protection circuit is used for correcting the power factor and executing input undervoltage protection and overvoltage protection; the secondary filter circuit is used for performing secondary EMI filtering on the voltage subjected to voltage transformation and outputting the voltage to a load; through the arrangement, when the input of the power supply is in overvoltage or undervoltage, the feedback protection circuit executes overvoltage protection or undervoltage protection according to the voltage fed back by the transformer, so that the power supply is prevented from being damaged due to overvoltage or undervoltage.

Description

Power supply with overvoltage and undervoltage protection input

Technical Field

The utility model relates to a power field, in particular to LED drive power supply.

Background

The LED is a semiconductor device with sensitive characteristics and has a negative temperature characteristic, so that the LED needs to be ensured to be in a stable working state in an application process, and an LED constant-current driving power supply is usually adopted to meet the use requirement of the LED. The conventional LED driving power supply has no under-voltage and over-voltage protection function, or is additionally provided with a complex circuit to realize the protection, so that the cost is high and the stability is high. When overvoltage occurs in input, a voltage device of a power supply can be directly damaged, and short circuit can occur; when the input voltage is low, the input current is too large, and the power supply can generate heat seriously after long-time operation.

It is seen that improvements and enhancements to the prior art are needed.

SUMMERY OF THE UTILITY MODEL

In view of the foregoing disadvantages of the prior art, an object of the present invention is to provide a power supply with overvoltage and under-voltage protection for input, which aims to realize the input overvoltage protection and under-voltage protection for the power supply.

In order to achieve the purpose, the utility model adopts the following technical proposal:

a power supply with input over-voltage and under-voltage protection, comprising: the primary filter circuit is used for performing primary EMI filtering on input commercial power; the bridge rectifier circuit is used for rectifying the commercial power subjected to the primary EMI filtering and outputting the commercial power to the surge protection circuit; the surge protection circuit is used for realizing surge protection on the power supply and outputting direct current to the feedback protection circuit and the transformer; the transformer is used for realizing voltage transformation and outputting the transformed voltage to the secondary filter circuit and the feedback voltage to the feedback protection circuit; the feedback protection circuit is used for correcting the power factor and executing input undervoltage protection and overvoltage protection; and the secondary filter circuit is used for performing secondary EMI filtering on the transformed voltage and outputting the filtered voltage to a load.

The input is provided with a power supply with overvoltage and undervoltage protection, wherein the transformer comprises a primary coil, a secondary coil and a feedback coil; the primary coil is respectively connected with the surge protection circuit and the feedback protection circuit, the secondary coil is connected with the secondary filter circuit, and the feedback coil is connected with the feedback protection circuit.

The input is provided with a power supply with overvoltage and undervoltage protection, wherein the feedback protection circuit comprises a driving chip U1 and a switching MOS tube Q1; the D pole of the switching MOS tube Q1 is connected with the 1 pin of the primary coil; the G pole of the switching MOS transistor Q1 is connected with the GD end of the driving chip U1 through a resistor R17, the G pole of the switching MOS transistor Q1 is also connected with the anode of a diode D1, and the cathode of the diode D1 is connected with the GD end of the driving chip U1 through a resistor R18; the S pole of the switching MOS transistor Q1 is connected with the G pole of the switching MOS transistor Q1 through a resistor R16, and is connected with the CS end of the driving chip U1 through a resistor R15; the VCC end of the driving chip U1 is connected with the surge protection circuit through a resistor R23, a resistor R24 and a resistor R26 which are connected in series, and is connected with a high-voltage ground through a capacitor C4; the GND end of the driving chip U1 is connected with a high-voltage ground, and is connected with the COMP end of the driving chip U1 through a capacitor C9; the 5-pin of the feedback coil is connected with the ZCD end of the driving chip U1 through a resistor R21, and is connected with the VCC end of the driving chip U1 through a resistor R22 and a diode D2 which are connected in series, and the diode D2 is connected positively; the 6 feet of the feedback coil are connected with a high voltage ground.

The input is provided with a power supply with overvoltage and undervoltage protection, wherein the type of the driving chip U1 is set to be RT 7330.

The input of the power supply with overvoltage and undervoltage protection also comprises a sampling circuit, wherein the sampling circuit comprises a dial switch SW 1; a pin 1 of the dial switch is connected with a CS end of a driving chip U1 through a resistor R1 and a resistor R2 which are arranged in parallel; the 2 pins of the dial switch are connected with the CS end of a driving chip U1 through a resistor R3 and a resistor R4 which are arranged in parallel; the 3 feet of the dial switch are connected with the ZCD end of the driving chip U1 through a capacitor C10, a resistor R19 and a resistor R20 which are arranged in parallel, and are connected with the S pole of a switch MOS tube Q1 through a resistor R11, a resistor R12, a resistor R13 and a resistor R14 which are arranged in parallel; and 3 pins of the dial switch are respectively connected with 4 pins and a high-voltage ground.

The input of the power supply with overvoltage and undervoltage protection also comprises an RCD buffer circuit, and the RCD buffer circuit is respectively connected with the surge protection circuit, the feedback protection circuit and the primary coil; the RCD buffer circuit is used for buffering spike voltage and spike voltage generated by the primary coil when the switching MOS tube Q1 is switched.

The input is provided with a power supply with overvoltage and undervoltage protection, wherein the RCD buffer circuit comprises a capacitor C13, a capacitor C11, a capacitor C12, a diode D3 and a diode D4; one end of the capacitor C12 is connected with the resistor R26, the other end of the capacitor C12 is connected with the cathode of the diode D3 through the resistor R25, and the two ends of the capacitor C12 are respectively connected with the resistor R27, the resistor R28 and the resistor R29 in parallel; the diode D3, the diode D4 and the capacitor C11 are connected in parallel, the diode D3 and the diode D4 are arranged in the same direction, and the anode of the diode D3 is connected with the 2 feet of the primary coil; the 1 pin of the primary coil is connected with one end of the capacitor C12 and is connected with low-voltage ground through a Y capacitor CY 3; the 2 feet of the primary coil are connected with the surge protection circuit through a resistor R10 and a capacitor C3 which are connected in series.

The input is provided with a power supply with overvoltage and undervoltage protection, wherein the secondary filter circuit comprises a capacitor C5, a capacitor C6, a capacitor C7 and a diode D6; the 3 feet of the secondary coil are connected with a load through a diode D6, the diode D6 is positively connected, and two ends of the diode D6 are connected with a capacitor C5 and a resistor R31 which are connected in series in parallel; a capacitor C7, a resistor R30 and a resistor R34 are respectively connected to two ends of the capacitor C6 in parallel, one end of the capacitor C6 is connected with the pin 3 of the secondary coil, and the other end of the capacitor C6 is connected with a low-voltage ground; the 4 legs of the secondary winding are connected to a low voltage ground, a load, and a high voltage ground through a Y capacitor CY 4.

The input power supply with overvoltage and undervoltage protection further comprises a ripple suppression circuit, wherein the ripple suppression circuit is arranged between the secondary filter circuit and the load, and the ripple suppression circuit is used for suppressing alternating current ripple in the output current.

The input is provided with a power supply with overvoltage and undervoltage protection, wherein the ripple suppression circuit comprises a plurality of filtering MOS tubes and a conjugate coil L3, and G poles, D poles and S poles among the plurality of filtering MOS tubes are correspondingly connected; the D pole of the filtering MOS tube is connected with the cathode of a diode D6 and is sequentially connected with a resistor 32 and a capacitor C8 and a low-voltage ground, the resistor R32 is connected in parallel with a diode D5, a resistor R33 and a voltage-stabilizing diode D1 which are sequentially connected in series, the voltage-stabilizing diode D1 is reversely connected, and the diode D5 is positively connected; the G pole of the filtering MOS tube is connected with the non-grounding end of the capacitor C8 through a resistor R35; the S pole of the filtering MOS tube is connected with the G pole of the filtering MOS tube through a resistor R36 and a voltage stabilizing diode ZD2 which are arranged in parallel, and the voltage stabilizing diode ZD2 is connected in the positive direction and is connected with the 1 pin of a conjugate coil L3 through a resistor R37; pins 2 and 4 of the conjugate coil L3 are connected to a load, and pin 3 of the conjugate coil L3 is connected to a low-voltage ground.

Has the advantages that:

the utility model provides an input takes power of excessive pressure and undervoltage protection compares prior art, through setting up feedback protection circuit, when in power supply working process, when excessive pressure or the undervoltage condition appear in the input, thereby feedback protection circuit carries out overvoltage protection or undervoltage protection according to the voltage of transformer feedback, avoids the power to damage because input excessive pressure or undervoltage.

Drawings

Fig. 1 is a connection block diagram of a power supply with overvoltage and undervoltage protection for input.

Fig. 2 is a schematic diagram of a power supply with overvoltage and undervoltage protection for input.

Description of the main element symbols: 100-primary filter circuit, 200-bridge rectifier circuit, 300-surge protection circuit, 400-feedback protection circuit, 500-transformer, 600-secondary filter circuit, 700-RCD buffer circuit, 800-sampling circuit and 900-ripple suppression circuit.

Detailed Description

The utility model provides an input belt excessive pressure and undervoltage protection's power, for making the utility model discloses a purpose, technical scheme and effect are clearer, more clear and definite, and it is right that the following refers to the drawing and the embodiment is lifted the utility model discloses further detailed description. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the scope of the invention.

In the description of the present invention, it is to 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; may be mechanically connected, may be electrically connected or may be in communication with each other; either directly or indirectly through intervening media, either internally or in any other suitable relationship. The specific meaning of the above terms in the present invention can be understood according to specific situations by those skilled in the art.

Referring to fig. 1-2, the present invention provides a power supply with overvoltage and undervoltage protection for input, comprising: a primary filtering circuit 100, configured to perform primary EMI filtering on an input mains; the bridge rectifier circuit 200 is used for rectifying the mains supply subjected to the primary EMI filtering and outputting the rectified mains supply to the surge protection circuit 300; the surge protection circuit 300 is configured to implement surge protection on a power supply and output a direct current to the feedback protection circuit 400 and the transformer 500; the transformer 500 is configured to transform and output a transformed voltage to the secondary filter circuit 600 and a feedback voltage to the feedback protection circuit 400; the feedback protection circuit 400 is used for power factor correction and executing input undervoltage protection and overvoltage protection; the secondary filter circuit 600 is configured to perform secondary EMI filtering on the transformed voltage and output the filtered voltage to a load.

In practical application, by the above arrangement, the commercial power is firstly subjected to primary EMI filtering, and then rectified into direct current, and the direct current is output to the transformer 500 and the feedback protection circuit 400 through the surge protection circuit 300; the surge protection circuit 300 is used for protecting a power supply and avoiding the damage of the power supply caused by severe pulse generated by surge current or surge voltage; the feedback protection circuit 400 is used for correcting the power factor, improving the power utilization efficiency, adjusting the power factor according to the voltage fed back by the transformer 500, and realizing circuit protection when undervoltage or overvoltage occurs; after the voltage transformation by the transformer 500, the output voltage is output to the LED load after the secondary EMI filtering.

Specifically, in certain embodiments, the transformer 500 includes a primary coil, a secondary coil, and a feedback coil; the primary coil is respectively connected with the surge protection circuit 300 and the feedback protection circuit 400, the secondary coil is connected with the secondary filter circuit 600, and the feedback coil is connected with the feedback protection circuit 400.

Further, in some embodiments, the feedback protection circuit 400 includes a driving chip U1 and a switching MOS transistor Q1; the D pole of the switching MOS tube Q1 is connected with the 1 pin of the primary coil; the G pole of the switching MOS transistor Q1 is connected with the GD end of the driving chip U1 through a resistor R17, the G pole of the switching MOS transistor Q1 is also connected with the anode of a diode D1, and the cathode of the diode D1 is connected with the GD end of the driving chip U1 through a resistor R18; the S pole of the switching MOS transistor Q1 is connected with the G pole of the switching MOS transistor Q1 through a resistor R16, and is connected with the CS end of the driving chip U1 through a resistor R15; the VCC end of the driving chip U1 is connected with the surge protection circuit 300 through a resistor R23, a resistor R24 and a resistor R26 which are connected in series, and is connected with a high-voltage ground through a capacitor C4; the GND end of the driving chip U1 is connected with a high-voltage ground, and is connected with the COMP end of the driving chip U1 through a capacitor C9; the 5-pin of the feedback coil is connected with the ZCD end of the driving chip U1 through a resistor R21, and is connected with the VCC end of the driving chip U1 through a resistor R22 and a diode D2 which are connected in series, and the diode D2 is connected positively; the 6 feet of the feedback coil are connected with a high voltage ground.

Through the arrangement, when the feedback coil feeds back the current I to the ZCD end of the driving chip_ZCDWhen the threshold current of the overvoltage protection is exceeded in a few cycles, the switching MOS tube 1 is controlled to be closed so as to avoid the damage of the element due to the excessive stress on the element. When the input voltage is lower than the turn-on threshold of the driver chip U1, i.e. a brown-out occurs, the driver chip U1 turns off until the turn-on threshold is restored. By utilizing the principle, the protection of the power supply is realized during undervoltage or overvoltage protection, the normal work of the power supply is recovered until the input is recovered to be normal, and the power supply is effectively prevented from being damaged due to overvoltage or undervoltage.

Preferably, the model of the driving chip U1 is set to RT7330 of RICHTEK brand.

Further, in some embodiments, a sampling circuit is also included, the sampling circuit including a toggle switch SW 1; a pin 1 of the dial switch is connected with a CS end of a driving chip U1 through a resistor R1 and a resistor R2 which are arranged in parallel; the 2 pins of the dial switch are connected with the CS end of a driving chip U1 through a resistor R3 and a resistor R4 which are arranged in parallel; the 3 feet of the dial switch are connected with the ZCD end of the driving chip U1 through a capacitor C10, a resistor R19 and a resistor R20 which are arranged in parallel, and are connected with the S pole of a switch MOS tube Q1 through a resistor R11, a resistor R12, a resistor R13 and a resistor R14 which are arranged in parallel; and 3 pins of the dial switch are respectively connected with 4 pins and a high-voltage ground. Through the setting, the ZCD end and the CS end of the drive chip U1 are sampled, so that detection personnel can conveniently detect and maintain the power supply, or technical personnel can adjust the element parameters of the feedback protection circuit 400.

Further, in some embodiments, the apparatus further comprises an RCD buffer circuit 700, wherein the RCD buffer circuit is respectively connected with the surge protection circuit 300, the feedback protection circuit 400, and the primary coil; the RCD buffer circuit 700 is used for buffering peak voltage and peak voltage generated by the primary coil when the switch MOS tube Q1 is switched, protecting the switch MOS tube Q1 and avoiding the switch MOS tube Q1 from being damaged due to overvoltage.

Specifically, the RCD buffer circuit 700 includes a capacitor C13, a capacitor C11, a capacitor C12, a diode D3, and a diode D4; one end of the capacitor C12 is connected with the resistor R26, the other end of the capacitor C12 is connected with the cathode of the diode D3 through the resistor R25, and the two ends of the capacitor C12 are respectively connected with the resistor R27, the resistor R28 and the resistor R29 in parallel; the diode D3, the diode D4 and the capacitor C11 are connected in parallel, the diode D3 and the diode D4 are arranged in the same direction, and the anode of the diode D3 is connected with the 2 feet of the primary coil; the 1 pin of the primary coil is connected with one end of the capacitor C12 and is connected with low-voltage ground through a Y capacitor CY 3; the 2-pin of the primary coil is connected with the surge protection circuit 300 through a resistor R10 and a capacitor C3 which are connected in series.

Further, in some embodiments, the primary filter circuit 100 includes a voltage dependent resistor VR1, a voltage dependent resistor VR2, a conjugate coil L1, a fuse F1, and a thermistor NTC 1; the live wire L of the commercial power is connected with one end of a fuse F1, and the other end of the fuse F1 is connected with the 1 end of a conjugate coil L1; the zero line N of the commercial power is connected with one end of a thermistor NTC1, and the other end of the thermistor NTC1 is connected with the 3 end of a conjugate coil L1; two ends of the piezoresistor VR1 are respectively connected with the other end of the fuse F1 and the other end of the thermistor NTC 1; the two ends of the voltage dependent resistor VR1 are respectively connected with an X capacitor CX1, a resistor R5 and a resistor R6 which are connected in series; the 2 feet and the 4 feet of the conjugate coil L1 are respectively connected with a bridge rectifier circuit 200, the 2 feet of the conjugate coil L1 are also connected with a ground wire PE through a resistor R7 and a Y capacitor CY1 which are connected in series, and the 4 feet of the conjugate coil L1 are also connected with the ground wire PE through a resistor R8 and a Y capacitor CY2 which are connected in series; and two ends of the piezoresistor VR2 are respectively connected with the 2 pins and the 4 pins of the conjugate coil.

Wherein, thermistor NTC1 and fuse F1 play the effect of fuse, X electric capacity CX1 plays the effect of restraining the differential mode interference, Y electric capacity CY1, Y electric capacity CY2 play the effect of restraining common mode interference, and conjugate coil plays the effect of restraining differential mode interference and common mode interference, realizes EMI filtering through above-mentioned setting, plays the effect of protection power simultaneously.

Further, in some embodiments, the bridge rectifier circuit 200 includes a rectifier BR1, where pin 1 of the rectifier BR1 is connected to pin 2 of the yoke L1, pin 3 of the rectifier BR1 is connected to pin 4 of the yoke L1, pin 4 of the rectifier BR1 is connected to a high voltage ground, and pin 2 of the rectifier BR1 is connected to the surge protection circuit 300.

Further, in some embodiments, the surge protection circuit 300 includes an inductor L2, a varistor VR 3; one end of the inductor L2 is connected with the pin 2 of the rectifier BR1 and is connected with a high-voltage ground through a capacitor C1, the other end of the inductor L2 is connected with the pin 1 of the primary coil, and two ends of the inductor L2 are also connected with a resistor R9 in parallel; one end of the piezoresistor VR3 is connected with the other end of the inductor L2, the other end of the piezoresistor VR3 is connected with a high voltage ground, and two ends of the piezoresistor VR3 are also connected with a capacitor C2 in parallel.

Further, in some embodiments, the secondary filter circuit 600 includes a capacitor C5, a capacitor C6, a capacitor C7, and a diode D6; the 3 feet of the secondary coil are connected with a load through a diode D6, the diode D6 is positively connected, and two ends of the diode D6 are connected with a capacitor C5 and a resistor R31 which are connected in series in parallel; a capacitor C7, a resistor R30 and a resistor R34 are respectively connected to two ends of the capacitor C6 in parallel, one end of the capacitor C6 is connected with the pin 3 of the secondary coil, and the other end of the capacitor C6 is connected with a low-voltage ground; the 4 legs of the secondary winding are connected to a low voltage ground, a load, and a high voltage ground through a Y capacitor CY 4.

Further, in some embodiments, a ripple suppression circuit 900 is further included, the ripple suppression circuit 900 being disposed between the secondary filter circuit 600 and the load; the voltage is AD-DC converted and contains a large amount of ac ripple, so ac ripple in the output current is suppressed by the ripple suppression circuit 900.

Specifically, in some embodiments, the ripple suppression circuit 900 includes a plurality of filtering MOS transistors and a conjugate coil L3, and a G-pole corresponding connection, a D-pole corresponding connection, and an S-pole corresponding connection between the plurality of filtering MOS transistors; the D pole of the filtering MOS tube is connected with the cathode of a diode D6 and is sequentially connected with a resistor 32 and a capacitor C8 and a low-voltage ground, the resistor R32 is connected in parallel with a diode D5, a resistor R33 and a voltage-stabilizing diode D1 which are sequentially connected in series, the voltage-stabilizing diode D1 is reversely connected, and the diode D5 is positively connected; the G pole of the filtering MOS tube is connected with the non-grounding end of the capacitor C8 through a resistor R35; the S pole of the filtering MOS tube is connected with the G pole of the filtering MOS tube through a resistor R36 and a voltage stabilizing diode ZD2 which are arranged in parallel, and the voltage stabilizing diode ZD2 is connected in the positive direction and is connected with the 1 pin of a conjugate coil L3 through a resistor R37; pins 2 and 4 of the conjugate coil L3 are connected to a load, and pin 3 of the conjugate coil L3 is connected to a low-voltage ground. It should be noted that the filtering MOS transistors are set to Q2-Q7 in fig. 2. In application, the MOS tube is controlled to work in a constant current region, and the gate-source voltage of the MOS tube is controlled to be constant, so that the current flowing through the drain-source electrode of the MOS tube is kept constant, and the suppression of alternating current ripple in voltage is realized.

Preferably, the specification models of the piezoresistor VR1, the piezoresistor VR2 and the piezoresistor VR3 are set to be 7D 561.

It is understood that equivalent substitutions or changes can be made by those skilled in the art according to the technical solution of the present invention and the inventive concept thereof, and all such changes or substitutions shall fall within the scope of the present invention.

Claims

1. A power supply with input for over-voltage and under-voltage protection, comprising: the primary filter circuit is used for performing primary EMI filtering on input commercial power; the bridge rectifier circuit is used for rectifying the commercial power subjected to the primary EMI filtering and outputting the commercial power to the surge protection circuit; the surge protection circuit is used for realizing surge protection on the power supply and outputting direct current to the feedback protection circuit and the transformer; the transformer is used for realizing voltage transformation and outputting the transformed voltage to the secondary filter circuit and the feedback voltage to the feedback protection circuit; the feedback protection circuit is used for correcting the power factor and executing input undervoltage protection and overvoltage protection; and the secondary filter circuit is used for performing secondary EMI filtering on the transformed voltage and outputting the filtered voltage to a load.

2. The input power supply with over-voltage and under-voltage protection according to claim 1, wherein the transformer comprises a primary coil, a secondary coil and a feedback coil; the primary coil is respectively connected with the surge protection circuit and the feedback protection circuit, the secondary coil is connected with the secondary filter circuit, and the feedback coil is connected with the feedback protection circuit.

3. The input power supply with over-voltage and under-voltage protection as claimed in claim 2, wherein the feedback protection circuit comprises a driving chip U1 and a switching MOS transistor Q1; the D pole of the switching MOS tube Q1 is connected with the 1 pin of the primary coil; the G pole of the switching MOS transistor Q1 is connected with the GD end of the driving chip U1 through a resistor R17, the G pole of the switching MOS transistor Q1 is also connected with the anode of a diode D1, and the cathode of the diode D1 is connected with the GD end of the driving chip U1 through a resistor R18; the S pole of the switching MOS transistor Q1 is connected with the G pole of the switching MOS transistor Q1 through a resistor R16, and is connected with the CS end of the driving chip U1 through a resistor R15; the VCC end of the driving chip U1 is connected with the surge protection circuit through a resistor R23, a resistor R24 and a resistor R26 which are connected in series, and is connected with a high-voltage ground through a capacitor C4; the GND end of the driving chip U1 is connected with a high-voltage ground, and is connected with the COMP end of the driving chip U1 through a capacitor C9; the 5-pin of the feedback coil is connected with the ZCD end of the driving chip U1 through a resistor R21, and is connected with the VCC end of the driving chip U1 through a resistor R22 and a diode D2 which are connected in series, and the diode D2 is connected positively; the 6 feet of the feedback coil are connected with a high voltage ground.

4. The input power supply with over-voltage and under-voltage protection as claimed in claim 3, wherein the driver chip U1 is provided with model number RT 7330.

5. The input power supply with over-voltage and under-voltage protection of claim 4, further comprising a sampling circuit, wherein the sampling circuit comprises a dial switch SW 1; a pin 1 of the dial switch is connected with a CS end of a driving chip U1 through a resistor R1 and a resistor R2 which are arranged in parallel; the 2 pins of the dial switch are connected with the CS end of a driving chip U1 through a resistor R3 and a resistor R4 which are arranged in parallel; the 3 feet of the dial switch are connected with the ZCD end of the driving chip U1 through a capacitor C10, a resistor R19 and a resistor R20 which are arranged in parallel, and are connected with the S pole of a switch MOS tube Q1 through a resistor R11, a resistor R12, a resistor R13 and a resistor R14 which are arranged in parallel; and 3 pins of the dial switch are respectively connected with 4 pins and a high-voltage ground.

6. The input power supply with over-voltage and under-voltage protection according to claim 3, further comprising an RCD buffer circuit, wherein the RCD buffer circuit is respectively connected with the surge protection circuit, the feedback protection circuit and the primary coil; the RCD buffer circuit is used for buffering spike voltage and spike voltage generated by the primary coil when the switching MOS tube Q1 is switched.

7. The input power supply with over-voltage and under-voltage protection according to claim 6, wherein the RCD buffer circuit comprises a capacitor C13, a capacitor C11, a capacitor C12, a diode D3 and a diode D4; one end of the capacitor C12 is connected with the resistor R26, the other end of the capacitor C12 is connected with the cathode of the diode D3 through the resistor R25, and the two ends of the capacitor C12 are respectively connected with the resistor R27, the resistor R28 and the resistor R29 in parallel; the diode D3, the diode D4 and the capacitor C11 are connected in parallel, the diode D3 and the diode D4 are arranged in the same direction, and the anode of the diode D3 is connected with the 2 feet of the primary coil; the 1 pin of the primary coil is connected with one end of the capacitor C12 and is connected with low-voltage ground through a Y capacitor CY 3; the 2 feet of the primary coil are connected with the surge protection circuit through a resistor R10 and a capacitor C3 which are connected in series.

8. The input power supply with over-voltage and under-voltage protection as claimed in claim 2, wherein said secondary filter circuit comprises a capacitor C5, a capacitor C6, a capacitor C7 and a diode D6; the 3 feet of the secondary coil are connected with a load through a diode D6, the diode D6 is positively connected, and two ends of the diode D6 are connected with a capacitor C5 and a resistor R31 which are connected in series in parallel; a capacitor C7, a resistor R30 and a resistor R34 are respectively connected to two ends of the capacitor C6 in parallel, one end of the capacitor C6 is connected with the pin 3 of the secondary coil, and the other end of the capacitor C6 is connected with a low-voltage ground; the 4 legs of the secondary winding are connected to a low voltage ground, a load, and a high voltage ground through a Y capacitor CY 4.

9. The input power supply with over-voltage and under-voltage protection according to claim 8, further comprising a ripple suppression circuit disposed between the secondary filter circuit and the load, the ripple suppression circuit for suppressing ac ripple in the output current.

10. The input power supply with over-voltage and under-voltage protection according to claim 9, wherein the ripple suppression circuit comprises a plurality of filtering MOS transistors and a conjugate coil L3, wherein G pole corresponding connection, D pole corresponding connection and S pole corresponding connection are arranged among the plurality of filtering MOS transistors; the D pole of the filtering MOS tube is connected with the cathode of a diode D6 and is sequentially connected with a resistor 32 and a capacitor C8 and a low-voltage ground, the resistor R32 is connected in parallel with a diode D5, a resistor R33 and a voltage-stabilizing diode D1 which are sequentially connected in series, the voltage-stabilizing diode D1 is reversely connected, and the diode D5 is positively connected; the G pole of the filtering MOS tube is connected with the non-grounding end of the capacitor C8 through a resistor R35; the S pole of the filtering MOS tube is connected with the G pole of the filtering MOS tube through a resistor R36 and a voltage stabilizing diode ZD2 which are arranged in parallel, and the voltage stabilizing diode ZD2 is connected in the positive direction and is connected with the 1 pin of a conjugate coil L3 through a resistor R37; pins 2 and 4 of the conjugate coil L3 are connected to a load, and pin 3 of the conjugate coil L3 is connected to a low-voltage ground.