Switching power supply system based on flyback topology

Abstract

The invention discloses a switching power supply system based on flyback topology, and the system comprises an input protection and rectification module which comprises a fuse F1, an EMI filter circuit, a rectifier bridge D1 and a capacitor C3, and is used for carrying out the overcurrent protection, electromagnetic interference suppression and full-wave rectification of 220V AC signal input, and converting a filtered AC signal into a 300-400V high-voltage DC signal; the flyback power conversion module comprises a PWM (Pulse Width Modulation) controller U1, an MOS (Metal Oxide Semiconductor) tube Q1, a high-frequency transformer T, a resistor R1, a resistor R2, a diode D2 and a capacitor C4, and is used for adjusting the switching duty ratio of the MOS tube Q1 through the PWM controller U1 and controlling the energy storage and release of a primary winding of the high-frequency transformer T1; and the output rectifying and filtering module comprises a diode D3, a capacitor C5 and a filtering module and is used for rectifying and filtering signals output by the secondary side of the transformer. The system solves the problems of large ripple, insufficient power and poor reliability in the prior art.

Description

Technical Field

[0001] The present invention relates to the technical field of switching power supplies, and particularly to a switching power supply system based on a flyback topology. Background Art

[0002] Existing flyback topology power supply systems usually output DC voltage by connecting a capacitor after a transformer, and adjust the PWM duty cycle through feedback to stabilize the output voltage, as Figure 1 shown. However, such a scheme has the following defects in the discontinuous conduction mode (DCM): large ripple voltage, significant fluctuations in the output current in the DCM mode, which easily causes damage to the subsequent circuit. Power limitation, it is difficult for an ordinary DC-DC converter to stably output 24V voltage under a 90W load, and the cost is relatively high. Insufficient reliability, lacking an integrated protection mechanism for overvoltage and EMI, and the system stability is poor. Summary of the Invention

[0003] To solve the technical problems existing in the background art, the present invention proposes a switching power supply system based on a flyback topology.

[0004] The switching power supply system based on a flyback topology proposed by the present invention includes:

[0005] An input protection and rectification module, including a fuse F1, an EMI filter circuit, a rectifier bridge D1, and a capacitor C3, for performing overcurrent protection, electromagnetic interference suppression, and full-wave rectification on the 220V AC signal input, and converting the filtered AC signal into a 300 - 400V high-voltage DC signal;

[0006] A flyback power conversion module, including a PWM controller U1, a MOS transistor Q1, a high-frequency transformer T, a resistor R1, a resistor R2, a diode D2, and a capacitor C4, for adjusting the switching duty cycle of the MOS transistor Q1 through the PWM controller U1 to control the energy storage and release of the primary winding of the high-frequency transformer T1;

[0007] An output rectification and filtering module, including a diode D3, a capacitor C5, and a filtering module, for rectifying and filtering the signal output by the transformer to obtain a low-ripple 24V DC voltage.

[0008] Preferably, the EMI filter circuit specifically includes: a common-mode inductor L1, capacitors C1, C2; a capacitor C1 is connected in parallel between the input ends of the common-mode inductor L1, one end of the capacitor C1 is connected to the 220V AC input through the fuse F1, a capacitor C2 is connected in parallel between the output ends of the common-mode inductor L1, and both ends of the capacitor C2 are connected in parallel with the two AC input ends of the rectifier bridge D1. The first DC output end of the rectifier bridge D1 is grounded together with one end of the capacitor C3, and the second DC output end of the rectifier bridge D1 is electrically connected to the other end of the capacitor C3.

[0009] Preferably, the output end of the input protection and rectification module is electrically connected to one end of resistor R1, one end of resistor R1 is electrically connected to one end of capacitor C4, the other end of resistor R1 is electrically connected to the other end of capacitor C4, the other end of capacitor C4 is electrically connected to the negative electrode of diode D3, the positive electrode of diode D3 is electrically connected to the drain of MOS transistor Q1, the source of MOS transistor Q1 is electrically connected to one end of resistor R2, the other end of resistor R2 is grounded, the gate of MOS transistor Q1 is electrically connected to the output end of PWM controller U1, the P1 end of high-frequency transformer T1 is electrically connected to the drain of the MOS transistor, the P2 end of high-frequency transformer T1 is electrically connected to one end of capacitor C4, and the A1 of high-frequency transformer T1 and the PWM controller U1 share the VCC power supply terminal.

[0010] Preferably, the positive electrode of diode D3 is electrically connected to the secondary output end of high-frequency transformer T1, the negative electrode of diode D3 is electrically connected to one end of capacitor C5, the other end of capacitor C5 is grounded, and the negative electrode of diode D3 outputs a low-ripple 24V DC voltage after being processed by the filtering module.

[0011] Preferably, it further includes:

[0012] A feedback module, including a voltage sampling circuit and an optocoupler isolator, for real-time monitoring of the output voltage and adjusting the duty cycle of PWM controller U1 through feedback to achieve the stability of the output voltage;

[0013] An isolated overvoltage protection module, including a voltage comparator U4 and a relay K1, which cuts off the PWM control signal or disconnects the output circuit when it detects that the output voltage exceeds the set threshold to prevent damage to the subsequent circuit.

[0014] Preferably, the feedback module specifically includes:

[0015] The voltage sampling circuit is composed of voltage-dividing resistors R3, R4 and a reference voltage source U2 to collect the output voltage in real time; the light-emitting diode of optocoupler isolator U3 is connected in parallel with the reference voltage source U2, and the photosensitive triode outputs a feedback signal to PWM controller U1.

[0016] Preferably, the isolated overvoltage protection module includes:

[0017] A voltage comparator U4, whose non-inverting input terminal is connected to the output voltage sampling circuit and the inverting input terminal is connected to the threshold voltage; the output terminal of voltage comparator U4 drives relay K1 to cut off the VCC power supply or the output circuit of PWM controller U1.

[0018] Preferably, the PWM controller U1 adopts the peak current control mode, its operating frequency is 65kHz, and the maximum duty cycle limit is 48%.

[0019] Preferably, the filtering module is specifically a π-type LC filtering network.

[0020] In the present invention, the proposed flyback topology-based switching power supply system realizes efficient and stable output of a 90W load in the DCM mode by optimizing the transformer design, integrating LC filtering and isolation overvoltage protection. It solves the problems of large ripple, insufficient power and poor reliability in the prior art, and is applicable to fields such as industrial control and household appliances. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic diagram of the system architecture of the switching power supply system in the prior art;

[0022] Figure 2 is a schematic diagram of the system architecture of the flyback topology-based switching power supply system proposed by the present invention;

[0023] Figure 3 is a schematic diagram of the structure of the implementation process of the flyback topology-based switching power supply system proposed by the present invention;

[0024] Figure 4 is a schematic diagram of the implementation circuit structure of the flyback topology-based switching power supply system proposed by the present invention;

[0025] Figure 5 is a 24V DC voltage waveform diagram of the flyback topology-based switching power supply system proposed by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] Referring to Figure 2-5 , the flyback topology-based switching power supply system proposed by the present invention includes:

[0027] An input protection and rectification module, including a fuse F1, an EMI filtering circuit, a rectifier bridge D1 and a capacitor C3, is used for overcurrent protection, electromagnetic interference suppression and full-wave rectification of the 220V AC signal input, and converts the filtered AC signal into a 300-400V high-voltage DC signal.

[0028] In this embodiment, the EMI filtering circuit specifically includes: a common-mode inductor L1, a capacitor C1, and a capacitor C2; a capacitor C1 is connected in parallel between the input ends of the common-mode inductor L1, one end of the capacitor C1 is connected to the 220V AC input through the fuse F1, a capacitor C2 is connected in parallel between the output ends of the common-mode inductor L1, both ends of the capacitor C2 are connected in parallel with both ends of the AC input of the rectifier bridge D1, the first DC output end of the rectifier bridge D1 is grounded together with one end of the capacitor C3, and the second DC output end of the rectifier bridge D1 is electrically connected to the other end of the capacitor C3.

[0029] It should be noted that a rectifier is used to rectify and filter the input 220Vac power supply, and then a stable direct current is obtained through a filter capacitor. The withstand voltage of the rectifier can be selected as 400V, and at the same time, the overcurrent situation of the rectifier should also be considered. The filter capacitor is selected as 200uF with a withstand voltage of 400V, and it can be appropriately replaced during debugging and testing.

[0030] The flyback power conversion module includes a PWM controller U1, a MOS transistor Q1, a high-frequency transformer T, a resistor R1, a resistor R2, a diode D2, and a capacitor C4, and is used to adjust the switching duty cycle of the MOS transistor Q1 through the PWM controller U1 to control the energy storage and release of the primary winding of the high-frequency transformer T1.

[0031] In this embodiment, the output end of the input protection and rectification module is electrically connected to one end of the resistor R1, one end of the resistor R1 is electrically connected to one end of the capacitor C4, the other end of the resistor R1 is electrically connected to the other end of the capacitor C4, the other end of the capacitor C4 is electrically connected to the negative electrode of the diode D3, the positive electrode of the diode D3 is electrically connected to the drain of the MOS transistor Q1, the source of the MOS transistor Q1 is electrically connected to one end of the resistor R2, the other end of the resistor R2 is grounded, the gate of the MOS transistor Q1 is electrically connected to the output end of the PWM controller U1, the P1 end of the high-frequency transformer T1 is electrically connected to the drain of the MOS transistor, the P2 end of the high-frequency transformer T1 is electrically connected to one end of the capacitor C4, and the A1 of the high-frequency transformer T1 and the PWM controller U1 share the VCC power supply terminal.

[0032] In this embodiment, the MOS transistor Q1 can be selected as a power MOS with a withstand voltage of 650V.

[0033] The output rectification and filtering module includes a diode D3, a capacitor C5, and a filtering module, and is used to rectify and filter the signal output by the transformer to obtain a low-ripple 24V DC voltage.

[0034] In this embodiment, the positive electrode of the diode D3 is electrically connected to the secondary output end of the high-frequency transformer T1, the negative electrode of the diode D3 is electrically connected to one end of the capacitor C5, the other end of the capacitor C5 is grounded, and the negative electrode of the diode D3 outputs a low-ripple 24V DC voltage after being processed by the filtering module.

[0035] Specifically, as Figure 5 shown, the measured ripple voltage of this output 24V. It can be seen from the waveform that the ripple < 1%, and the effect is good and can be implemented. For the method of outputting a DC voltage of 24V this time, after rectifying the output voltage through the capacitor, the 220V alternating current is converted into = 310V direct current. The power designed by this design method is about 96W - 100W, so the output current Iout = Pout / Vout = 96W / 24V = 4A.

[0036] In this embodiment, the filtering module is specifically a π-type LC filtering network.

[0037] In this embodiment, the PWM controller U1 adopts the peak current control mode, with a working frequency of 65 kHz and a maximum duty cycle limit of 48%.

[0038] In this embodiment, it further includes:

[0039] A feedback module, including a voltage sampling circuit and an optocoupler isolator, is used to monitor the output voltage in real time and adjust the duty cycle of the PWM controller U1 through feedback to achieve the stability of the output voltage.

[0040] Specifically, the feedback module specifically includes:

[0041] The voltage sampling circuit is composed of voltage-dividing resistors R3, R4 and a reference voltage source U2, which collects the output voltage in real time; the light-emitting diode of the optocoupler isolator U3 is connected in parallel with the reference voltage source U2, and the photosensitive triode outputs a feedback signal to the PWM controller U1.

[0042] Specifically, the UC3842 chip, the voltage sampling circuit, the TL431, and the optocoupler together constitute the feedback part, and the triode side of the optocoupler feeds back the signal to the UC3842.

[0043] An isolated overvoltage protection module, including a voltage comparator U4 and a relay K1, when it detects that the output voltage exceeds the set threshold, cuts off the PWM control signal or disconnects the output loop to prevent damage to the subsequent circuit.

[0044] Specifically, the isolated overvoltage protection module includes:

[0045] A voltage comparator U4, whose non-inverting input terminal is connected to the output voltage sampling circuit, and the inverting input terminal is connected to the threshold voltage; the output terminal of the voltage comparator U4 drives the relay K1 to cut off the VCC power supply or the output loop of the PWM controller U1.

[0046] In the specific working process of the flyback topology-based switching power supply system of this embodiment, after the AC signal passes through the EMI filtering circuit, it is converted into a DC signal through the rectification module, and a pulsating DC signal is output through the secondary of the high-frequency transformer T1. Finally, a stable DC 24V voltage is obtained through rectification. The filtering module in the discontinuous mode makes the ripple voltage smaller and the system power supply more stable. At the same time, the feedback regulation and the isolated overvoltage protection regulation further make the system power supply more stable.

[0047] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes, shall be covered by the protection scope of the present invention.

Claims

1. A flyback topology-based switching power supply system, characterized in that, Comprising: An input protection and rectification module, including a fuse F1, an EMI filter circuit, a rectifier bridge D1, and a capacitor C3, for performing overcurrent protection, electromagnetic interference suppression, and full-wave rectification on the 220V AC signal input, and converting the filtered AC signal into a 300 - 400V high-voltage DC signal; A flyback power conversion module, including a PWM controller U1, a MOS transistor Q1, a high-frequency transformer T, a resistor R1, a resistor R2, a diode D2, and a capacitor C4, for adjusting the switching duty cycle of the MOS transistor Q1 through the PWM controller U1 to control the energy storage and release of the primary winding of the high-frequency transformer T1; An output rectification and filtering module, including a diode D3, a capacitor C5, and a filtering module, for rectifying and filtering the signal output by the transformer to obtain a low-ripple 24V DC voltage.

2. The flyback topology-based switching power supply system according to claim 1, wherein The EMI filter circuit specifically includes: a common-mode inductor L1, capacitors C1, C2; a capacitor C1 is connected in parallel between the input terminals of the common-mode inductor L1, one end of the capacitor C1 is connected to the 220V AC input through the fuse F1, a capacitor C2 is connected in parallel between the output terminals of the common-mode inductor L1, both ends of the capacitor C2 are connected in parallel with the AC input terminals of both ends of the rectifier bridge D1, the first DC output terminal of the rectifier bridge D1 is grounded together with one end of the capacitor C3, and the second DC output terminal of the rectifier bridge D1 is electrically connected to the other end of the capacitor C3.

3. The flyback topology-based switching power supply system according to claim 1, characterized in that, The output terminal of the input protection and rectification module is electrically connected to one end of the resistor R1, one end of the resistor R1 is electrically connected to one end of the capacitor C4, the other end of the resistor R1 is electrically connected to the other end of the capacitor C4, the other end of the capacitor C4 is electrically connected to the negative electrode of the diode D3, the positive electrode of the diode D3 is electrically connected to the drain of the MOS transistor Q1, the source of the MOS transistor Q1 is electrically connected to one end of the resistor R2, the other end of the resistor R2 is grounded, the gate of the MOS transistor Q1 is electrically connected to the output terminal of the PWM controller U1, the P1 terminal of the high-frequency transformer T1 is electrically connected to the drain of the MOS transistor, the P2 terminal of the high-frequency transformer T1 is electrically connected to one end of the capacitor C4, and the A1 of the high-frequency transformer T1 and the PWM controller U1 share the VCC power supply terminal.

4. The flyback topology-based switching power supply system according to claim 1, wherein The positive electrode of the diode D3 is electrically connected to the secondary output terminal of the high-frequency transformer T1, the negative electrode of the diode D3 is electrically connected to one end of the capacitor C5, the other end of the capacitor C5 is grounded, and the negative electrode of the diode D3 outputs a low-ripple 24V DC voltage after being processed by the filtering module.

5. The flyback topology-based switching power supply system according to claim 1, characterized in that Further comprising: A feedback module, including a voltage sampling circuit and an opto-isolator, for real-time monitoring of the output voltage and adjusting the duty cycle of the PWM controller U1 through feedback to achieve the stability of the output voltage; An isolated overvoltage protection module, including a voltage comparator U4 and a relay K1, when it is detected that the output voltage exceeds the set threshold, cutting off the PWM control signal or disconnecting the output loop to prevent damage to the subsequent circuit.

6. The flyback topology-based switching power supply system according to claim 5, wherein, The feedback module specifically includes: The voltage sampling circuit is composed of voltage-dividing resistors R3 and R4 and a reference voltage source U2, which real-time samples the output voltage; the light-emitting diode of the optocoupler isolator U3 is connected in parallel with the reference voltage source U2, and the photosensitive triode outputs a feedback signal to the PWM controller U1.

7. The flyback topology-based switching power supply system according to claim 5, characterized in that, The isolated overvoltage protection module includes: A voltage comparator U4, whose non-inverting input terminal is connected to the output voltage sampling circuit, and the inverting input terminal is connected to the threshold voltage; the output terminal of the voltage comparator U4 drives a relay K1, which is used to cut off the VCC power supply or the output loop of the PWM controller U1.

8. The flyback topology-based switching power supply system according to claim 1, wherein The PWM controller U1 adopts a peak current control mode, its operating frequency is 65 kHz, and the maximum duty cycle limit is 48%.

9. The flyback topology-based switching power supply system according to claim 1, characterized in that, The filtering module is specifically a π-type LC filtering network.

Images