5V DC regulated power supply circuit

Abstract

The utility model relates to communication power supply technical field provides a 5V direct current stabilized power supply circuit, 5V direct current stabilized power supply circuit includes first grade DC DC conversion circuit and second grade DC DC conversion circuit, wherein: first grade DC DC conversion circuit adopts flyback conversion topology, to 48V direct current electricity as the input, exports 12V direct current electricity and +5V direct current electricity, second grade DC DC conversion circuit adopts flyback conversion topology, to first grade output's 12V direct current electricity as the input, exports -5V direct current electricity and +5V direct current electricity. The utility model has realized from 48V direct current input to 12V, +5V, -5V multiway direct current output's high -efficient voltage conversion, provides complete electrical isolation for each stage transformer, ensures positive and negative voltage output between each other independent and stable reliable, thereby has improved direct current stabilized power supply's conversion efficiency, output voltage precision and multiway power supply's security significantly.

Description

Technical Field

[0001] This utility model relates to the field of communication power supply technology, and in particular to a 5V DC regulated power supply circuit. Background Technology

[0002] In modern information society, communication power supply systems play an increasingly important role in key areas such as data transmission and network communication, and have become core equipment for ensuring the stable operation of communication infrastructure. The monitor of the communication power supply system plays a crucial control and monitoring role in the entire system. The integrated circuit chips used in it typically require multiple stable ±5V (50W) DC power supplies to ensure the normal operation of the system.

[0003] Currently, in communication power supply systems, a 48V DC bus is typically used as the main power supply. Therefore, it is necessary to efficiently convert the 48V DC voltage to the ±5V DC voltage required by integrated circuit chips. However, traditional DC regulated power supply circuits often face technical limitations in voltage stability control when implementing this function. Under complex operating conditions such as input voltage fluctuations and sudden load changes, the voltage regulation capability drops sharply, leading to a decline in output voltage quality and power supply performance, thus failing to fully utilize the power supply system's capabilities.

[0004] Chinese patent CN204290759U discloses a small single-phase AC input ultra-low ripple switching power supply. This technical solution realizes the basic voltage conversion function from single-phase AC input to 28V DC output by sequentially connecting an input filter, rectifier circuit, input energy storage circuit, power conversion circuit, rectifier filter circuit, and boost circuit. However, the device can only output a single 28V positive voltage and cannot simultaneously provide ±5V (50W) bipolar power output. In communication monitoring applications, integrated circuit chips often require ±5V (50W) bipolar power supply. The single-stage conversion structure of this device cannot meet the requirement of multiple outputs from 48V DC to ±5V. Utility Model Content

[0005] In view of this, this utility model proposes a 5V DC regulated power supply circuit to solve the problem that the existing technology can only output a single 28V positive voltage and cannot simultaneously provide ±5V (50W) bipolar power output, thus failing to meet the multi-output requirements from 48V DC to ±5V.

[0006] The technical solution of this utility model is implemented as follows: a 5V DC regulated power supply circuit, wherein the 5V DC regulated power supply circuit includes a first-stage DC-DC converter circuit and a second-stage DC-DC converter circuit, wherein: The first-stage DC-DC converter circuit adopts a flyback converter topology, with 48V DC as input and 12V DC and +5V DC as output. The second-stage DC-DC converter circuit adopts a flyback converter topology, taking the 12V DC output from the first stage as input and outputting -5V DC and +5V DC.

[0007] Based on the above technical solutions, preferably, the first-stage DC-DC converter circuit includes a first MOSFET switch and a first transformer, and the second-stage DC-DC converter circuit includes a second MOSFET switch and a second transformer; the first MOSFET switch and the second MOSFET switch are respectively used to control the on / off state of the primary side of the first transformer and the second transformer, and the first transformer and the second transformer are respectively used to perform electrical isolation and voltage transformation for each stage of the circuit.

[0008] Based on the above technical solution, preferably, both the first MOSFET switch and the second MOSFET switch operate in switching mode, and the output voltage is adjusted by adjusting the switching frequency and duty cycle; The secondary sides of the first and second transformers are respectively equipped with rectifier diodes and filter capacitors to convert pulse voltages into stable DC output voltages.

[0009] Based on the above technical solutions, preferably, the 5V DC regulated power supply circuit includes an input rectifier and filter circuit, which is electrically connected to the first-stage DC-DC converter circuit. The input rectifier and filter circuit is used to filter the 48V DC input before inputting it to the first-stage DC-DC converter circuit.

[0010] Based on the above technical solutions, preferably, the 5V DC regulated power supply circuit further includes a protection circuit, which includes an input low voltage start-up circuit, an input overvoltage and overcurrent protection circuit, and a chip failure protection circuit. The low input voltage start-up circuit is used to prevent the circuit from malfunctioning when the input voltage is too low. The input overvoltage and overcurrent protection circuit is used to prevent the circuit from being damaged when the input voltage or current is too high. The chip failure protection circuit is used to protect the circuit when the control chip fails.

[0011] Based on the above technical solutions, preferably, the input rectifier filter circuit includes a lightning protection element, a reverse current protection diode, and an EMI filter circuit. The lightning protection element includes a varistor and a discharge tube, and the EMI filter circuit includes common-mode and differential-mode filter circuits.

[0012] Based on the above technical solutions, preferably, the 5V DC regulated power supply circuit includes a first PWM signal control circuit, which is electrically connected to the first-stage DC-DC converter circuit. The first PWM signal control circuit is used to output a first PWM control signal to the first-stage DC-DC converter circuit to control and drive the MOSFET switching transistor of the first-stage DC-DC converter circuit to turn on and off.

[0013] Based on the above technical solutions, preferably, the 5V DC regulated power supply circuit includes a second PWM signal control circuit, which is electrically connected to the second-stage DC-DC converter circuit. The second PWM signal control circuit is used to output a second PWM control signal to the second-stage DC-DC converter circuit to control and drive the MOSFET switching transistor of the second-stage DC-DC converter circuit to turn on and off.

[0014] Based on the above technical solutions, preferably, the first PWM signal control circuit includes a first PWM control chip, which adjusts the duty cycle of the first PWM control signal by detecting the output voltage and current feedback signals of the first-stage DC-DC converter circuit. The second PWM signal control circuit includes a second PWM control chip, which adjusts the duty cycle of the second PWM control signal by detecting the output voltage and current feedback signals of the second-stage DC-DC converter circuit.

[0015] Based on the above technical solutions, preferably, both the first PWM control chip and the second PWM control chip are UC2843BD chips; the output voltage feedback signal of the first-stage DC-DC converter circuit is obtained through a resistor divider network, compared with a reference source, and then fed back to the first PWM control chip after optocoupler isolation; the output voltage feedback signal of the second-stage DC-DC converter circuit is obtained through a resistor divider network, compared with a reference source, and then fed back to the second PWM control chip after optocoupler isolation, so as to control the output voltage.

[0016] The 5V DC regulated power supply circuit provided by this utility model has the following advantages compared with the prior art: By organically cascading and electrically connecting the first-stage DC-DC converter circuit and the second-stage DC-DC converter circuit using a flyback converter topology, efficient voltage conversion from 48V DC input to multiple DC outputs of 12V, +5V, and -5V is achieved. This provides complete electrical isolation for each stage of the transformer, ensuring that the positive and negative voltage outputs are independent and stable, thereby significantly improving the conversion efficiency, output voltage accuracy, and safety of multiple power supplies of the DC regulated power supply. By setting PWM control chips in the first-stage DC-DC converter circuit and the second-stage DC-DC converter circuit respectively, and adopting closed-loop control with output voltage and current feedback signal detection and PWM duty cycle dynamic adjustment, the stability, adjustment accuracy and dynamic response capability of multi-channel output voltage are improved. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a system structure diagram of a 5V DC regulated power supply circuit according to the present invention; Figure 2 This is the first circuit wiring diagram of a 5V DC regulated power supply circuit according to this utility model; Figure 3 This is the second circuit wiring diagram of a 5V DC regulated power supply circuit according to this utility model. Detailed Implementation

[0019] The technical solutions of this utility model will be clearly and completely described below with reference to the embodiments of this utility model. Obviously, the described embodiments are only a part of the embodiments of this utility model, and not all of them. Based on the embodiments of this utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this utility model.

[0020] Please see Figure 1 This utility model provides a 5V DC regulated power supply circuit, which includes a first-stage DC-DC converter circuit and a second-stage DC-DC converter circuit, wherein: The first-stage DC-DC converter circuit adopts a flyback converter topology, with 48V DC as input and 12V DC and +5V DC as output. The second-stage DC-DC converter circuit adopts a flyback converter topology, taking the 12V DC output from the first stage as input and outputting -5V DC and +5V DC.

[0021] Please see Figure 2 and Figure 3The first-stage DC-DC converter circuit includes a first MOSFET switch and a first transformer, and the second-stage DC-DC converter circuit includes a second MOSFET switch and a second transformer. The first MOSFET switch and the second MOSFET switch are used to control the switching on and off of the primary side of the first transformer and the second transformer, respectively. The first transformer and the second transformer are used to provide electrical isolation and voltage conversion for each stage of the circuit.

[0022] Both the first MOSFET switch and the second MOSFET switch operate in switching mode, and the output voltage is adjusted by regulating the switching frequency and duty cycle; The secondary sides of the first and second transformers are respectively equipped with rectifier diodes and filter capacitors to convert pulse voltages into stable DC output voltages.

[0023] In a specific embodiment, the first-stage DC-DC converter circuit is composed of resistors R10, R11, R28, R44, R45, R46, R47, R48, capacitors C13, C22, C31, C32, C33, C34, C35, C36, C37, C38, C39, C40, C41, C42, diodes D3, D11, D12, D13, MOSFET Q1, current transformer CT1, and transformer T1. The working principle is as follows: A flyback first-stage DC-DC converter circuit topology is adopted, with the main circuit consisting of MOSFET Q1 and transformer T1. Resistors R10 and R11, capacitor C13, and diode D3 form a reverse energy absorption circuit to absorb the reverse energy generated by the flyback first-stage DC-DC converter circuit. Resistor R28 and capacitor C22 form an RC absorption circuit to absorb the spike noise generated by MOSFET Q1. The current transformer CT1 serves as the main current sensor in the DC-DC converter circuit. An output rectifier and filter circuit, composed of diodes D11, D12, and D13, and capacitors C32, C33, C35, C36, C38, C39, and C40, outputs 12V and two 5V DC power supplies. Resistors R44 and R46, and capacitors C31 and C34 form an RC snubber circuit to absorb spike noise from diodes D11 and D12.

[0024] In a specific embodiment, the second-stage DC-DC converter circuit consists of resistors R49, R55, R57, R58, capacitors C43, C44, C45, C50, C51, C52, C53, C54, inductors L4, L5, diodes D15, D16, D17, MOSFET Q7, and transformer T2. The working principle is as follows: A flyback second-stage DC-DC converter topology is adopted, with the main circuit consisting of MOSFET Q7 and transformer T2. Resistor R49, capacitor C45, and diode D15 form a reverse energy absorption circuit to absorb the reverse energy generated by the flyback DC-DC converter. Diodes D16 and D17, capacitors C50, C52, C53, C53, C54, and inductors L4 and L5 form an output rectifier and filter circuit, which outputs -5V and 5V DC after rectification and filtering, respectively.

[0025] Please see Figure 2 and Figure 3 The 5V DC regulated power supply circuit includes an input rectifier and filter circuit, which is electrically connected to the first-stage DC-DC converter circuit. The input rectifier and filter circuit is used to filter the 48V DC input before inputting it to the first-stage DC-DC converter circuit.

[0026] The 5V DC regulated power supply circuit also includes a protection circuit, which includes an input low voltage start-up circuit, an input overvoltage and overcurrent protection circuit, and a chip failure protection circuit. The low input voltage start-up circuit is used to prevent the circuit from malfunctioning when the input voltage is too low. The input overvoltage and overcurrent protection circuit is used to prevent the circuit from being damaged when the input voltage or current is too high. The chip failure protection circuit is used to protect the circuit when the control chip fails.

[0027] The input rectifier filter circuit includes a lightning protection element, a reverse current protection diode, and an EMI filter circuit. The lightning protection element includes a varistor and a discharge tube, and the EMI filter circuit includes common-mode and differential-mode filter circuits.

[0028] In a specific embodiment, the input rectifier filter circuit is composed of resistors R1 and R2, capacitors C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, and C12, inductors L1, L2, and L3, diodes D1 and D2, fuses F1, F2, F3, and F4, varistor RV1 and RV2, and discharge tube S1. Varistors RV1 and RV2 and discharge tube S1 form the system positive and negative line protection circuits and the battery negative terminal lightning protection circuit, effectively protecting the regulated power supply from external high-voltage lightning strikes. Diodes D1 and D2 prevent reverse current flow from the regulated power supply input. A common-mode filter L1 and capacitors C3 and C4 form a common-mode filter circuit, while capacitors C1, C2, C5, C6, and C7 form a differential-mode filter circuit, effectively suppressing EMI at the power system bus input and high-frequency noise interference generated internally. Inductor L2, capacitors C8, C9, and C10 form an LC filter circuit, which filters high-frequency noise from the input.

[0029] Please see Figure 2 and Figure 3 The 5V DC regulated power supply circuit includes a first PWM signal control circuit, which is electrically connected to the first-stage DC-DC converter circuit. The first PWM signal control circuit is used to output a first PWM control signal to the first-stage DC-DC converter circuit to control and drive the MOSFET switching transistor of the first-stage DC-DC converter circuit to turn on and off.

[0030] Please see Figure 2 and Figure 3 The DC regulated power supply circuit includes a second PWM signal control circuit, which is electrically connected to the second-stage DC-DC converter circuit. The second PWM signal control circuit is used to output a second PWM control signal to the second-stage DC-DC converter circuit to control and drive the MOSFET switching transistor of the second-stage DC-DC converter circuit to turn on and off.

[0031] The first PWM signal control circuit includes a first PWM control chip, which adjusts the duty cycle of the first PWM control signal by detecting the output voltage and current feedback signals of the first-stage DC-DC converter circuit. The second PWM signal control circuit includes a second PWM control chip, which adjusts the duty cycle of the second PWM control signal by detecting the output voltage and current feedback signals of the second-stage DC-DC converter circuit.

[0032] Both the first and second PWM control chips are UC2843BD chips. The output voltage feedback signal of the first-stage DC-DC converter circuit is obtained through a resistor divider network, compared with a reference source, and then fed back to the first PWM control chip after optocoupler isolation. The output voltage feedback signal of the second-stage DC-DC converter circuit is obtained through a resistor divider network, compared with a reference source, and then fed back to the second PWM control chip after optocoupler isolation to control the output voltage.

[0033] In a specific embodiment, the first PWM signal control circuit consists of resistors R3, R4, R5, R6, R7, R8, R9, R12, R13, R14, R15, R16, R17, R18, R19, R20, R21, R22, R23, R24, R25, R26, R27, R29, R30, R31, R32, R33, R34, R35, R36, R37, R38, R39, R40, and R41. The circuit consists of resistors R42 and R43, capacitors C14, C15, C16, C17, C18, C19, C20, C21, C23, C24, C25, C26, C27, C28, C29, and C30, diodes D4, D5, D6, D7, D8, D9, and D10, transistors Q2, Q3, Q4, Q5, and Q6, reference sources U2 and U4, optocoupler U3, and a first PWM control chip U1 (UC2843BD). Its working principle is as follows: using the first PWM control chip U1 (UC2843BD) as the core of the circuit, it generates a high-frequency PWM signal to control and drive the MOSFET Q1 of the first-stage flyback DC-DC converter circuit. The UC2843BD chip is a widely used, wide-voltage-range input, precise-control, stable, and reliable current-controlled PWM signal generator.

[0034] The power supply circuit for controlling the first PWM control chip U1 consists of resistors R3, R4, R5, R6, R7, R8, R9, R12, R13, R14, R15, R16, R17, R18, R19, R20, capacitors C14, C15, C16, C17, C18, C19, diodes D4, D5, D6, transistors Q2, Q3, Q4, reference source U2, and the primary windings T1-3 and T1-6 of transformer T1. Its working principle is as follows: When there is 48V DC power at the input terminal, resistors R7, R8, R9, and R19 reduce the voltage and current, providing an 8.5V startup power supply to the first PWM control chip U1. The first PWM control chip U1 outputs a first PWM signal, triggering MOSFET Q1 to operate, which in turn causes the primary windings T1-3 and T1-6 of transformer T1 and diode D6 to operate, providing continuous power to the power supply terminal of the first PWM control chip U1. Resistors R5, R6, R14, diode D4, and transistor Q3 form a low-voltage input startup circuit. When Zener diode D4 is working, transistor Q3 conducts. 48V DC is supplied through resistors R7, R8, and R9. Resistors R12, R13, capacitor C14, and transistor Q2 form a failure protection circuit for control chip U1. When the first PWM control chip U1 fails, +5VREFP is too low or has no voltage value, transistor Q2 conducts, shutting off the power supply to transistor Q3. Resistors R3, R4, R15, R16, R17, R18, capacitor C16, transistor Q4, and reference source U2 form an over-voltage input protection circuit. When the input voltage is too high, it is compared with the reference +5VREFP, causing reference source U2 to not work, resulting in transistor Q4 being cut off, thus shutting off the power supply to transistor Q4. Diode D5 ensures unidirectional current flow.

[0035] Resistors R30, R31, R32, and capacitors C24 and C25 form the overcurrent detection and protection circuit of the first PWM control chip U1. When the current transformer CT1 detects that the main circuit current reaches the upper limit, the first PWM control chip U1 turns off the output of the first PWM control signal, thereby turning off the MOSFET Q1.

[0036] The output voltage regulation feedback circuit, composed of resistors R33, R34, R35, R36, R37, R38, R39, R40, R41, R42, R43, capacitors C26, C27, C28, C29, C30, diodes D7 and D8, transistor Q5, reference source U4, and optocoupler U3, adjusts the 5V power supply output voltage and current feedback balance through the 2.5V reference voltage of the TL431 reference source. Then, it outputs the voltage to the COMP function terminal of the first PWM control chip U1 through optocoupler U3. At the same time, the power supply output power is fed back and adjusted by the current compensation circuit composed of resistor R29, capacitor C23, and transistor Q6 to adjust the duty cycle of the waveform of the first PWM signal output by the first PWM control chip U1, thereby adjusting and controlling the working state of MOSFET Q1, achieving the functions of output voltage regulation and improving power supply efficiency.

[0037] Resistors R25, R26, R27, and diode D9 form the gate drive circuit for MOSFET Q1. When MOSFET Q1 is off, the gate charge is rapidly discharged through diode D9, resulting in a more complete and faster turn-off, thereby reducing the internal losses of MOSFET Q1. The forward conduction circuit composed of resistors R26 and R27 matches the parameters of the drive circuit with the performance indicators of the MOSFET, such as forward switching time and input impedance, achieving a more efficient switching state for the MOSFET and improving the efficiency of the DC-DC converter circuit.

[0038] In a specific embodiment, the second PWM signal control circuit consists of resistors R50, R51, R52, R53, R54, R56, R59, R60, R61, R62, R63, R64, and R65; capacitors C46, ​​C47, C48, C49, C55, and C56; diode D14; transistor Q8; reference source U7; optocoupler U6; and the second PWM control chip U5 (UC2843BD). Its working principle is based on the second PWM control chip U5 (UC2843BD) as the core of the circuit, generating a high-frequency PWM signal to control and drive the MOSFET Q7 of the second-stage flyback DC-DC converter circuit. The 12V power supply output from the first-stage DC-DC converter circuit provides freewheeling power to the power supply terminal of the second PWM control chip U5.

[0039] The output voltage regulation feedback circuit, composed of resistors R59, R60, R61, R62, R63, R64, R65, capacitors C55 and C56, diode D14, reference source U7, and optocoupler U6, adjusts the -5V power supply output voltage and current feedback balance through the 2.5V reference voltage of the TL431 reference source. Then, it outputs the voltage to the COMP function terminal of the second PWM control chip through optocoupler U6. At the same time, the power supply output power is fed back to adjust the waveform duty cycle of the PWM signal output by the second PWM control chip through the current compensation circuit composed of resistor R56, capacitor C49, and transistor Q8, thereby adjusting and controlling the working state of MOSFET Q7, achieving the functions of output voltage regulation and improving power supply efficiency.

[0040] Resistors R52 and R54 form the gate drive circuit for MOSFET Q7, which matches the parameters of the drive circuit with the performance indicators of MOSFET such as forward switching time and input impedance, so as to achieve a more efficient switching operation of MOSFET.

[0041] This embodiment adopts a two-stage isolated flyback DC-DC converter circuit topology, which makes the output circuits of the DC power supply more stable and reliable.

[0042] The PWM signal control circuit uses the UC2843BD control chip as its core. The UC2843BD chip is a widely used, wide voltage range input, precise control, stable and reliable current-controlled PWM signal generator.

[0043] The PWM signal control circuit adjusts the output voltage and current feedback balance, and adjusts the waveform duty cycle of the PWM signal output by the control chip UC2843BD according to the output power of the DC power supply, thereby adjusting and controlling the working state of the MOSFET, achieving the functions of output voltage regulation and improving power supply efficiency.

[0044] This embodiment features low input voltage start-up, input overvoltage and overcurrent protection, and chip failure protection, effectively protecting the DC power supply for safe and stable operation.

[0045] The entire circuit features a two-stage flyback DC-DC converter, effective suppression of input EMI noise interference, multiple input protections, high output accuracy, low output ripple, and stable power supply.

[0046] The working process of a DC regulated power supply circuit in this embodiment is as follows: 48V DC power is rectified and filtered by an input rectifier and filter circuit, and then undergoes two consecutive DC-DC conversions through a first-stage and a second-stage DC-DC converter circuit to output 12V and ±5V DC power. A first PWM signal control circuit and a second PWM signal control circuit control the operation of the first-stage and second-stage DC-DC converter circuits throughout the entire process.

[0047] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A 5V DC regulated power supply circuit, characterized in that, The 5V DC regulated power supply circuit includes a first-stage DC-DC converter circuit and a second-stage DC-DC converter circuit, wherein: The first-stage DC-DC converter circuit adopts a flyback converter topology, with 48V DC as input and 12V DC and +5V DC as output. The second-stage DC-DC converter circuit adopts a flyback converter topology, taking the 12V DC output from the first stage as input and outputting -5V DC and +5V DC.

2. The 5V DC regulated power supply circuit as described in claim 1, characterized in that, The first-stage DC-DC converter circuit includes a first MOSFET switch and a first transformer, and the second-stage DC-DC converter circuit includes a second MOSFET switch and a second transformer. The first MOSFET switch and the second MOSFET switch are used to control the switching on and off of the primary side of the first transformer and the second transformer, respectively. The first transformer and the second transformer are used to provide electrical isolation and voltage conversion for each stage of the circuit.

3. The 5V DC regulated power supply circuit as described in claim 2, characterized in that, Both the first MOSFET switch and the second MOSFET switch operate in switching mode, and the output voltage is adjusted by regulating the switching frequency and duty cycle; The secondary sides of the first and second transformers are respectively equipped with rectifier diodes and filter capacitors to convert pulse voltages into stable DC output voltages.

4. The 5V DC regulated power supply circuit as described in claim 1, characterized in that, The 5V DC regulated power supply circuit includes an input rectifier and filter circuit, which is electrically connected to the first-stage DC-DC converter circuit. The input rectifier and filter circuit is used to filter the 48V DC input before inputting it to the first-stage DC-DC converter circuit.

5. A 5V DC regulated power supply circuit as described in claim 4, characterized in that, The 5V DC regulated power supply circuit also includes a protection circuit, which includes an input low voltage start-up circuit, an input overvoltage and overcurrent protection circuit, and a chip failure protection circuit. The low input voltage start-up circuit is used to prevent the circuit from malfunctioning when the input voltage is too low. The input overvoltage and overcurrent protection circuit is used to prevent the circuit from being damaged when the input voltage or current is too high. The chip failure protection circuit is used to protect the circuit when the control chip fails.

6. A 5V DC regulated power supply circuit as described in claim 4, characterized in that, The input rectifier filter circuit includes a lightning protection element, a reverse current protection diode, and an EMI filter circuit. The lightning protection element includes a varistor and a discharge tube, and the EMI filter circuit includes common-mode and differential-mode filter circuits.

7. A 5V DC regulated power supply circuit as described in claim 1, characterized in that, The 5V DC regulated power supply circuit includes a first PWM signal control circuit, which is electrically connected to the first-stage DC-DC converter circuit. The first PWM signal control circuit is used to output a first PWM control signal to the first-stage DC-DC converter circuit to control and drive the MOSFET switching transistor of the first-stage DC-DC converter circuit to turn on and off.

8. A 5V DC regulated power supply circuit as described in claim 7, characterized in that, The 5V DC regulated power supply circuit includes a second PWM signal control circuit, which is electrically connected to the second-stage DC-DC converter circuit. The second PWM signal control circuit is used to output a second PWM control signal to the second-stage DC-DC converter circuit to control and drive the MOSFET switching transistor of the second-stage DC-DC converter circuit to turn on and off.

9. A 5V DC regulated power supply circuit as described in claim 8, characterized in that, The first PWM signal control circuit includes a first PWM control chip, which adjusts the duty cycle of the first PWM control signal by detecting the output voltage and current feedback signals of the first-stage DC-DC converter circuit. The second PWM signal control circuit includes a second PWM control chip, which adjusts the duty cycle of the second PWM control signal by detecting the output voltage and current feedback signals of the second-stage DC-DC converter circuit.

10. A 5V DC regulated power supply circuit as described in claim 9, characterized in that, Both the first and second PWM control chips are UC2843BD chips. The output voltage feedback signal of the first-stage DC-DC converter circuit is obtained through a resistor divider network, compared with a reference source, and then fed back to the first PWM control chip after optocoupler isolation. The output voltage feedback signal of the second-stage DC-DC converter circuit is obtained through a resistor divider network, compared with a reference source, and then fed back to the second PWM control chip after optocoupler isolation to control the output voltage.

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