A switch power supply circuit against EFT

Abstract

The utility model discloses a switch power supply circuit of preventing EFT, including input module, power control module, transformer T1 and output module, the output of input module is divided into two ways, one way is connected with the primary winding of transformer T1, and the other way is connected with the input of power control module, and the output of power control module is connected with the primary winding of transformer T1, and the secondary winding of transformer T1 is connected with output module. The utility model is provided with the common mode inductance LF1 and common mode inductance LF2 of series connection in input module, the input of common mode inductance LF1 is connected with pressure sensitive resistance MOV1, when EFT interference enters from firewire L and zero line N, first is absorbed by pressure sensitive resistance MOV1, then again after passing through the high impedance filter that is formed by the series connection of common mode inductance LF1 and common mode inductance LF2, thereby inhibiting the sudden wave penetration into rectification filter circuit, improve the stability of switch power supply.

Description

Technical Field

[0001] This utility model relates to a protection circuit device, and in particular to a switching power supply circuit that prevents EFT. Background Technology

[0002] EFT, or Electrical Fast Transient Burst, is a common electromagnetic interference phenomenon, mainly manifested as fast, high-frequency, short-duration pulse group interference on the power lines or signal lines of electrical equipment. In traditional switching power supplies, to meet EFT protection requirements, multiple varistors are often added, increasing costs. Simultaneously, fuses need to be replaced with resistor fuses, but this has certain drawbacks; under certain abnormal conditions, resistor fuses are not prone to burning out, posing a risk of damage to the power supply. Utility Model Content

[0003] In order to overcome the shortcomings of the prior art, this utility model provides a switching power supply circuit that prevents EFT.

[0004] The technical solution adopted by this utility model to solve its technical problem is:

[0005] An EFT-resistant switching power supply circuit includes an input module, a power control module, a transformer T1, and an output module. The output of the input module is divided into two paths: one path is connected to the primary winding of the transformer T1, and the other path is connected to the input of the power control module. The output of the power control module is connected to the primary winding of the transformer T1, and the secondary winding of the transformer T1 is connected to the output module. The input module includes a rectifier bridge BD1. The input of the rectifier bridge BD1 is connected to the live wire L and the neutral wire N of the mains power supply. A varistor MOV1 is connected between the live wire L and the neutral wire N. A fuse F1 is connected in series with the live wire L. A common-mode inductor LF1 and a common-mode inductor LF2 are connected in series between the rectifier bridge BD1 and the mains power supply. A capacitor CX1 and a thermistor NTC4 are connected between the common-mode inductors LF1 and LF2.

[0006] The power control module includes a control chip U1. Pin 8 of the control chip U1 is connected to the input module via resistor R3, diode D1, and diode D2. Pin 5 of the control chip U1 is connected to pin 5 of transformer T1 via transistor Q1. A switching diode D4 and resistor R9 are connected between pin 1 of transistor Q1 and pin 5 of the control chip U1. Pin 2 of transistor Q1 is connected to pin 5 of transformer T1. A capacitor C10 is connected between pins 2 and 3 of transistor Q1. Pin 3 of transistor Q1 is grounded via resistor RS1. Pin 6 of the control chip U1 is connected to the auxiliary winding of transformer T1 via resistor R5 and diode D3. A resistor R7 is connected between pin 6 and pin 1 of the control chip U1. Pin 2 of the control chip U1 is connected to the optocoupler module via resistor R6.

[0007] The optocoupler module includes an optocoupler U2. The first pin of the optocoupler U2 is connected to the resistor R6, and the second pin of the optocoupler U2 is grounded. A Zener diode ZD1 and a capacitor C3 are connected in parallel between the first and second pins of the optocoupler U2. The third pin of the optocoupler U2 is connected to the second pin of the transformer T1 through a Zener diode ZD2, a resistor R14, a capacitor CY6, and a resistor R28. The fourth pin of the optocoupler U2 is connected to the first pin of the voltage reference chip U3. The second pin of the voltage reference chip U3 is divided into two paths: one path is connected to the capacitor CY6 through a resistor R15, and the other path is grounded through a capacitor C8.

[0008] A filter circuit is connected between the output terminal of the rectifier bridge BD1 and the primary winding of the transformer T1. The filter circuit includes thermistor NTC1, thermistor NTC2, electrolytic capacitor EC1, electrolytic capacitor EC2 and capacitor C1.

[0009] The 9th and 10th pins of the transformer T1 constitute the secondary winding. The output module includes a common-mode inductor LF3. The 10th pin of the transformer T1 is connected to the 1st pin of the common-mode inductor LF3 through a Schottky diode D6. The 9th pin of the transformer T1 is connected to the 2nd pin of the common-mode inductor LF3. An electrolytic capacitor EC4 is connected between the 1st and 2nd pins of the common-mode inductor LF3. A capacitor C7 and a resistor R13 for filtering are connected in parallel with the Schottky diode D6.

[0010] The beneficial effects of this utility model are as follows: This utility model has a common-mode inductor LF1 and a common-mode inductor LF2 connected in series in the input module. The input terminal of the common-mode inductor LF1 is connected to a varistor MOV1. When EFT interference enters from the live wire L and the neutral wire N, it is first absorbed by the varistor MOV1, and then passes through the high-impedance filter formed by the common-mode inductors LF1 and LF2 connected in series, thereby suppressing the surge to penetrate into the rectifier filter circuit and improving the stability of the switching power supply. Attached Figure Description

[0011] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0012] Figure 1 This is the circuit schematic diagram of this utility model. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features of the present utility model can be combined with each other.

[0014] It should be understood that these descriptions are merely exemplary and not intended to limit the scope of this invention.

[0015] The following describes some embodiments of the present invention with reference to the accompanying drawings.

[0016] Reference Figure 1An EFT-resistant switching power supply circuit includes an input module, a power control module, a transformer T1, and an output module. The output of the input module is divided into two paths: one path is connected to the primary winding of the transformer T1, and the other path is connected to the input of the power control module. The output of the power control module is connected to the primary winding of the transformer T1, and the secondary winding of the transformer T1 is connected to the output module. The input module includes a rectifier bridge BD1. The input of the rectifier bridge BD1 is connected to the live wire L and the neutral wire N of the mains power supply. A varistor MOV1 is connected between the live wire L and the neutral wire N. A fuse F1 is connected in series with the live wire L. A common-mode inductor LF1 and a common-mode inductor LF2 are connected in series between the rectifier bridge BD1 and the mains power supply. A capacitor CX1 and a thermistor NTC4 are connected between the common-mode inductors LF1 and LF2. This invention incorporates two common-mode inductors, LF1 and LF2, connected in series in the input module. A varistor MOV1 is connected to the input terminal of LF1. MOV1 is a voltage clamping device; when the voltage across it is below a predetermined voltage, it exhibits high resistance. When the transient voltage exceeds its clamping voltage, its resistance drops sharply, discharging the overvoltage energy to ground as current and clamping the voltage between the live wire (L) and neutral wire (N) at a safe level. When EFT interference enters from the live wire (L) and neutral wire (N), it is first absorbed by the varistor MOV1, and then passes through a high-impedance filter formed by the series connection of common-mode inductors LF1 and LF2, thereby suppressing surge penetration into the rectifier filter circuit and improving the stability of the switching power supply.

[0017] Specifically, the live wire L is connected to pin 1 of common-mode inductor LF1, the neutral wire N is connected to pin 2 of common-mode inductor LF1, pin 3 of common-mode inductor LF1 is connected to pin 2 of common-mode inductor LF2, pin 4 of common-mode inductor LF1 is connected to pin 1 of common-mode inductor LF2, and the thermistor NTC4 is connected in series between pin 3 of common-mode inductor LF1 and pin 2 of common-mode inductor LF2. Capacitor CX1 is connected between common-mode inductors LF1 and LF2 to filter differential-mode interference signals between the live wire L and the neutral wire N. The thermistor NTC4 has a high resistance at room temperature during circuit startup, limiting surge current. As current flows, the temperature rises, and the resistance decreases, resulting in minimal impact on current during normal operation. Pin 2 of common-mode inductor LF2 is connected to the negative power supply via capacitors CY3 and CY4, specifically, the ground wire, further filtering common-mode interference signals. In this embodiment, after the common-mode inductors LF1 and LF2 are connected in series, since the number of turns and phase of the two windings are the same, the magnetic fields generated are superimposed in the same direction, causing the common-mode inductors to exhibit a high impedance state, thereby reducing the impact of EFT.

[0018] The power control module includes a control chip U1. The 8th pin of the control chip U1 is connected to the input module through a resistor R3, a diode D1, and a diode D2. Specifically, the 8th pin is divided into two paths: one path is connected to the neutral line N through a diode D1, and the other path is connected to the live line L through a diode D2. The AC power from the mains directly provides the starting power to the control chip U1. The fifth pin of the control chip U1 is connected to the fifth pin of the transformer T1 via transistor Q1. A switching diode D4 and a resistor R9 are connected between the first pin of transistor Q1 and the fifth pin of the control chip U1. The second pin of transistor Q1 is connected to the fifth pin of the transformer T1. A capacitor C10 is connected between the second and third pins of transistor Q1. The third pin of transistor Q1 is grounded via resistor RS1. The sixth pin of the control chip U1 is connected to the auxiliary winding of the transformer T1 via resistor R5 and diode D3. A resistor R7 is connected between the sixth pin and the first pin of the control chip U1. After the transformer T1 steps down the high voltage DC power, it transmits the voltage from the auxiliary winding to the sixth pin of the control chip U1, providing the operating voltage for the control chip U1. The second pin of the control chip U1 is connected to the optocoupler module through resistor R6. The second pin of the control chip U1 is a feedback pin. The input terminal of the optocoupler module is connected to the primary winding of the transformer T1. The control chip U1 monitors the voltage on the transformer T1 in real time through the feedback pin and adjusts the high / low level output of its fifth pin according to the monitoring result, thereby accurately adjusting the output voltage of the transformer T1.

[0019] In this embodiment, the optocoupler module includes an optocoupler U2. Pin 1 of the optocoupler U2 is connected to resistor R6, and pin 2 of the optocoupler U2 is grounded. A Zener diode ZD1 and a capacitor C3 are connected in parallel between pins 1 and 2 of the optocoupler U2. Pin 3 of the optocoupler U2 is connected to pin 2 of transformer T1 via Zener diode ZD2, resistor R14, capacitor CY6, and resistor R28. Pin 4 of the optocoupler U2 is connected to pin 1 of voltage reference chip U3. Pin 2 of voltage reference chip U3 is split into two paths: one path is connected to capacitor CY6 via resistor R15, and the other path is grounded via capacitor C8. The voltage reference chip U3 samples the output voltage of transformer T1 and transmits the output voltage to the optocoupler U2 via Zener diode ZD2 and resistor R14. After receiving the signal, the optocoupler U2 feeds it back to the control chip U1.

[0020] A filter circuit is connected between the output terminal of the rectifier bridge BD1 and the primary winding of the transformer T1. This filter circuit includes thermistors NTC1 and NTC2, electrolytic capacitors EC1 and EC2, and capacitor C1. Specifically, electrolytic capacitors EC1, EC2, and C1 are connected in parallel between pins 3 and 4 of the rectifier bridge BD1. Thermistor NTC1 is connected in series with pin 3 of the rectifier bridge BD1, and thermistor NTC2 is connected in series with pin 4 of the rectifier bridge BD1. In this embodiment, the rectifier bridge BD1 converts the input AC power to DC power. Electrolytic capacitors EC1, EC2, and C1 smooth the DC voltage ripple and provide a stable DC voltage output. Thermistors NTC1 and NTC2 limit inrush current during circuit startup.

[0021] Pins 9 and 10 of transformer T1 constitute the secondary winding. The output module includes a common-mode inductor LF3. Pin 10 of transformer T1 is connected to pin 1 of common-mode inductor LF3 via Schottky diode D6. Pin 9 of transformer T1 is connected to pin 2 of common-mode inductor LF3. An electrolytic capacitor EC4 is connected between pins 1 and 2 of common-mode inductor LF3. A capacitor C7 and a resistor R13 for filtering are connected in parallel with Schottky diode D6. In this embodiment, the inclusion of a common-mode inductor LF3 in the output module can suppress common-mode interference and EFT interference, ensuring stable output voltage.

[0022] Although embodiments of the present invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A switching power supply circuit that prevents EFT, characterized in that... The system includes an input module, a power control module, a transformer T1, and an output module. The output of the input module is divided into two paths: one path is connected to the primary winding of the transformer T1, and the other path is connected to the input of the power control module. The output of the power control module is connected to the primary winding of the transformer T1, and the secondary winding of the transformer T1 is connected to the output module. The input module includes a rectifier bridge BD1. The input of the rectifier bridge BD1 is connected to the live wire L and the neutral wire N of the mains power supply. A varistor MOV1 is connected between the live wire L and the neutral wire N. A fuse F1 is connected in series with the live wire L. A common-mode inductor LF1 and a common-mode inductor LF2 are connected in series between the rectifier bridge BD1 and the mains power supply. A capacitor CX1 and a thermistor NTC4 are connected between the common-mode inductors LF1 and LF2.

2. The EFT-resistant switching power supply circuit according to claim 1, characterized in that... The power control module includes a control chip U1. Pin 8 of the control chip U1 is connected to the input module via resistor R3, diode D1, and diode D2. Pin 5 of the control chip U1 is connected to pin 5 of transformer T1 via transistor Q1. A switching diode D4 and resistor R9 are connected between pin 1 of transistor Q1 and pin 5 of the control chip U1. Pin 2 of transistor Q1 is connected to pin 5 of transformer T1. A capacitor C10 is connected between pins 2 and 3 of transistor Q1. Pin 3 of transistor Q1 is grounded via resistor RS1. Pin 6 of the control chip U1 is connected to the auxiliary winding of transformer T1 via resistor R5 and diode D3. A resistor R7 is connected between pin 6 and pin 1 of the control chip U1. Pin 2 of the control chip U1 is connected to the optocoupler module via resistor R6.

3. The EFT-resistant switching power supply circuit according to claim 2, characterized in that... The optocoupler module includes an optocoupler U2. The first pin of the optocoupler U2 is connected to the resistor R6, and the second pin of the optocoupler U2 is grounded. A Zener diode ZD1 and a capacitor C3 are connected in parallel between the first and second pins of the optocoupler U2. The third pin of the optocoupler U2 is connected to the second pin of the transformer T1 through a Zener diode ZD2, a resistor R14, a capacitor CY6, and a resistor R28. The fourth pin of the optocoupler U2 is connected to the first pin of the voltage reference chip U3. The second pin of the voltage reference chip U3 is divided into two paths: one path is connected to the capacitor CY6 through a resistor R15, and the other path is grounded through a capacitor C8.

4. The EFT-resistant switching power supply circuit according to claim 1, characterized in that... A filter circuit is connected between the output terminal of the rectifier bridge BD1 and the primary winding of the transformer T1. The filter circuit includes thermistor NTC1, thermistor NTC2, electrolytic capacitor EC1, electrolytic capacitor EC2 and capacitor C1.

5. The EFT-resistant switching power supply circuit according to claim 1, characterized in that... The 9th and 10th pins of the transformer T1 constitute the secondary winding. The output module includes a common-mode inductor LF3. The 10th pin of the transformer T1 is connected to the 1st pin of the common-mode inductor LF3 through a Schottky diode D6. The 9th pin of the transformer T1 is connected to the 2nd pin of the common-mode inductor LF3. An electrolytic capacitor EC4 is connected between the 1st and 2nd pins of the common-mode inductor LF3. A capacitor C7 and a resistor R13 for filtering are connected in parallel with the Schottky diode D6.

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