AC-DC flyback power supply circuit

Abstract

The utility model discloses an AC-to-DC flyback power supply circuit, which comprises an input rectification filtering module, a control module, a transformer and an output rectification filtering module which are connected in sequence, the control module comprises a power supply unit and an adjusting unit, and the power supply unit is simultaneously connected with a primary winding of the transformer and the adjusting unit. The adjusting unit is connected with a secondary winding of the transformer, the switching tube is connected with the output rectifying and filtering module, the input rectifying and filtering module is used for converting input alternating current into direct current and providing the direct current for the control module, and the adjusting unit is used for adjusting a feedback signal so as to adjust the PWM duty ratio of the power supply unit. According to the utility model, the power supply voltage is adjusted through the adjusting unit and is fed back to the power supply unit, so that the PWM duty ratio of the power supply unit is adjusted, the voltage feedback mode is simple, and the cost is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of switching power supplies, in particular to an AC-to-DC flyback power supply circuit. Background Art

[0002] An IH rice cooker uses electromagnetic heating technology. This technology heats the rice by generating heat in the pot through electromagnetic induction. Traditional induction cookers, IH rice cookers, and IH pressure cookers typically use a flyback power supply to convert mains power to 18V to power the IGBT and subsequent stages when a large low-voltage load is present.

[0003] The flyback solution of the existing technology generally uses current feedback in the chip. The primary winding of the transformer is the high-voltage winding, the secondary output winding, and the auxiliary power supply winding. The voltage adjustment feedback method is the feedback chip and optocoupler feedback. The voltage feedback method is complex and the cost is relatively high. Utility Model Content

[0004] The main purpose of the utility model is to provide an AC to DC flyback power supply circuit, aiming to solve the problems of complex voltage feedback mode and relatively high cost.

[0005] To achieve the above-mentioned objectives, the present invention proposes an AC-to-DC flyback power supply circuit, comprising an input rectifier and filter module, a control module, a transformer, and an output rectifier and filter module connected in sequence, wherein the control module comprises a power supply unit and an adjustment unit, wherein the power supply unit is simultaneously connected to the primary winding of the transformer and the adjustment unit, the adjustment unit is connected to the secondary winding of the transformer, the switching tube is connected to the output rectifier and filter module, the input rectifier and filter module is used to convert the input AC power into DC power and provide the DC power to the control module, and the adjustment unit is used to adjust the supply voltage and feed the supply voltage back to the power supply unit to thereby adjust the PWM duty cycle of the power supply unit.

[0006] In one embodiment, the regulating unit includes a voltage divider unit, a first resistor, a switching tube and a first diode, the collector of the switching tube is connected to the power supply unit, the emitter of the switching tube is grounded, the base of the switching tube is connected to one end of the first resistor, the voltage divider unit is simultaneously connected to the other end of the first resistor and the positive electrode of the first diode, and the negative electrode of the first diode is connected to the output rectifier and filtering module.

[0007] In one embodiment, the voltage dividing unit includes a second resistor and a third resistor, the second resistor and the third resistor are connected in series, and the first resistor is connected between the second resistor and the third resistor.

[0008] In one embodiment, the AC-to-DC flyback power supply circuit also includes a fuse, the input rectifier and filter module includes a rectifier bridge, the AC-to-DC flyback power supply circuit is connected to the mains, the mains includes a neutral wire and a live wire, the live wire is connected to one end of the fuse, the other end of the fuse is connected to the first end of the rectifier bridge, and the neutral wire is connected to the second end of the rectifier bridge.

[0009] In one embodiment, the input rectifier and filter module further includes a first capacitor, wherein a positive electrode of the first capacitor is connected to the third terminal of the rectifier bridge, and a negative electrode of the first capacitor is connected to the fourth terminal of the rectifier bridge.

[0010] In one embodiment, the AC-to-DC flyback power supply circuit further includes a fourth resistor, a fifth resistor, and a second capacitor, one end of the fourth resistor is connected to the positive electrode of the first capacitor, the other end of the fourth resistor is connected to one end of the fifth resistor, the other end of the fifth resistor is simultaneously connected to one end of the second capacitor and the power supply unit, and the other end of the second capacitor is grounded.

[0011] In one embodiment, the AC-to-DC flyback power supply circuit further includes an RCD absorption clamping module, which is connected to the input rectifier filter module and the transformer at the same time. The RCD absorption clamping module is used to reduce the peak voltage in the AC-to-DC flyback power supply circuit.

[0012] In one embodiment, the RCD absorption clamping module includes a sixth resistor, a third capacitor, and a second diode. The sixth resistor and the third capacitor are connected in parallel. One end of the sixth resistor and one end of the third capacitor are respectively connected to the opposite-name ends of the primary winding of the transformer. The other end of the sixth resistor and the other end of the third capacitor are respectively connected to the cathode of the second diode. The anode of the second diode is connected to the same-name end of the primary winding of the transformer.

[0013] In one embodiment, the output rectifier and filter module includes a third diode and a fourth capacitor, the positive electrode of the third diode is connected to the same-name end of the secondary winding of the transformer, the negative electrode of the third diode is connected to the positive electrode of the fourth capacitor, and the negative electrode of the fourth capacitor is connected to the opposite-name end of the secondary winding of the transformer and grounded.

[0014] In one embodiment, the AC-to-DC flyback power supply circuit further includes a fourth diode, the power supply unit includes an MCU chip, the MCU chip is connected to the cathode of the fourth diode, and the anode of the fourth diode is connected to the cathode of the third diode.

[0015] The utility model connects the power supply unit with the primary winding of the transformer and the regulating unit, and the regulating unit is connected to the secondary winding of the transformer, so that the secondary winding shares the output and feedback, and the number of windings of the transformer winding is reduced. The supply voltage is adjusted by the regulating unit and the supply voltage is fed back to the power supply unit, thereby adjusting the PWM duty cycle of the power supply unit, making the voltage feedback method simple and reducing the cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0017] Figure 1 This is the module schematic diagram of the AC to DC flyback power supply circuit;

[0018] Figure 2 This is the circuit diagram of the AC to DC flyback power supply.

[0019] Description of Figure Numbers:

[0020] 10-input rectifier and filter module, 20-control module, 21-power supply unit, 22-regulation unit, 221-voltage divider unit, 30-output rectifier and filter module, 40-RCD absorption clamp module, T1-transformer, Q1-switch tube, R4-first resistor, D4-first diode, R2-second resistor, R3-third resistor, F1-fuse, DB1-rectifier bridge, ACN-neutral line, ACL-live line, C1-first capacitor, R6-fourth resistor, C4-second capacitor, R7-fifth resistor, R1-sixth resistor, C2-third capacitor, D1-second diode, D3-third diode, C3-fourth capacitor, D2-fourth diode, U1-MCU chip, R5-seventh resistor, T1A-primary winding, T1B-secondary winding.

[0021] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0023] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0024] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of such features. In addition, if the meaning of "and / or" appearing in the full text is to include three parallel schemes, taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme in which A and B are satisfied at the same time. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0025] like Figure 1 As shown, Figure 1 The schematic diagram of the AC-to-DC flyback power supply circuit is shown below. The present invention provides an AC-to-DC flyback power supply circuit, comprising an input rectifier and filter module 10, a control module 20, a transformer T1, and an output rectifier and filter module 30, which are connected in sequence. The control module 20 comprises a power supply unit 21 and a regulating unit 22. The power supply unit 21 is connected to both the primary winding T1A of the transformer T1 and the regulating unit 22. The regulating unit 22 is connected to the secondary winding T1B of the transformer T1. The switch Q1 is connected to the output rectifier and filter module 30. The input rectifier and filter module 10 is used to convert the input AC power into DC power and provide the DC power to the control module 20. The regulating unit 22 is used to regulate the supply voltage and feed the supply voltage back to the power supply unit 21, thereby adjusting the PWM duty cycle of the power supply unit 21.

[0026] The utility model connects the power supply unit 21 with the primary winding T1A of the transformer T1 and the adjustment unit 22, and the adjustment unit 22 is connected to the secondary winding T1B of the transformer T1, so that the secondary winding T1B of the transformer T1 shares the output and feedback, reducing the number of windings of the transformer T1. At the same time, the adjustment unit 22 adjusts the supply voltage and feeds the supply voltage back to the power supply unit 21, thereby adjusting the PWM duty cycle of the power supply unit 21. No feedback chip and optocoupler are required, the voltage feedback method is simple, and the cost is reduced.

[0027] like Figure 2 As shown, Figure 2 This is the circuit diagram of the AC to DC flyback power supply.

[0028] First specific embodiment

[0029] The regulating unit 22 includes a voltage divider 221, a first resistor R4, a switch Q1, and a first diode D4. The collector of the switch Q1 is connected to the power supply unit 21, the emitter of the switch Q1 is grounded, and the base of the switch Q1 is connected to one end of the first resistor R4. The voltage divider 221 is also connected to the other end of the first resistor R4 and the anode of the first diode D4. The cathode of the first diode D4 is connected to the output rectifier and filter module 30. The voltage divider 221 includes a second resistor R2 and a third resistor R3. The second resistor R2 and the third resistor R3 are connected in series, and the first resistor R4 is connected between the second resistor R2 and the third resistor R3.

[0030] Principle and Effect of the First Specific Embodiment: The voltage divider unit 221 primarily uses the second resistor R2 and the third resistor R3 to distribute the input voltage into multiple output voltages. The voltage divider unit 221 can be used to regulate the voltage signal and generate the required bias voltage to ensure the amplifier operates within the appropriate range. For example, in a transistor amplifier, the voltage divider can provide an appropriate bias voltage for the base. The voltage divider unit 221 can also provide a certain degree of overload protection. For example, when the input voltage is too high, the voltage divider can reduce the output voltage, thereby protecting subsequent circuit components from damage.

[0031] The AC-to-DC flyback power supply circuit also includes a fuse F1, the input rectifier filter module 10 includes a rectifier bridge DB1, the AC-to-DC flyback power supply circuit is connected to the mains, the mains includes a neutral wire ACN and a live wire ACL, the live wire ACL is connected to one end of the fuse F1, the other end of the fuse F1 is connected to the first end of the rectifier bridge DB1, and the neutral wire ACN is connected to the second end of the rectifier bridge DB1.

[0032] Fuse F1 protects against damage caused by overcurrent or short circuits. It automatically disconnects the circuit when the current exceeds a safe level. When the current exceeds the rated value of fuse F1, the heat generated by the internal wire melts, interrupting the circuit and preventing damage.

[0033] F1 fuses are available in various types, suitable for different voltage and current ranges, including fast-blow F1 and slow-blow F1 fuses to meet different application requirements. For example, fast-blow F1 fuses are suitable for sensitive equipment, which can quickly respond to momentary overloads. Slow-blow F1 fuses are used in situations with large current fluctuations, allowing for short-term overloads without immediately opening.

[0034] Second specific embodiment

[0035] The input rectifier and filter module 10 further includes a first capacitor C1 , wherein the positive electrode of the first capacitor C1 is connected to the third terminal of the rectifier bridge DB1 , and the negative electrode of the first capacitor C1 is connected to the fourth terminal of the rectifier bridge DB1 .

[0036] Principle and Effect of the Second Specific Embodiment: The input rectifier and filter module 10 converts AC power into DC power and smoothes the DC power. The DC power obtained after rectification still contains a certain amount of ripple (pulsating voltage). The function of filtering is to smooth out these ripples and make the output DC voltage more stable. After rectification and filtering, the DC power supply has a relatively stable voltage and small ripple, providing a reliable power supply for the circuit.

[0037] The input rectifier and filter module 10 cooperates with the fuse F1 , the first diode D4 , etc. to prevent overcurrent, overvoltage, etc. in the input power supply from causing damage to the device.

[0038] Third specific embodiment

[0039] The AC-to-DC flyback power supply circuit also includes a fourth resistor R6, a fifth resistor R7, and a second capacitor C4. One end of the fourth resistor R6 is connected to the positive electrode of the first capacitor C1, and the other end of the fourth resistor R6 is connected to one end of the fifth resistor R7. The other end of the fifth resistor R7 is also connected to one end of the second capacitor C4 and the power supply unit 21. The other end of the second capacitor C4 is grounded.

[0040] Principle and Effect of the Third Specific Embodiment: The fourth resistor R6, the fifth resistor R7, and the second capacitor C4 connected in series form a low-pass filter. After the input signal passes through the fourth resistor R6, the fifth resistor R7, and the second capacitor C4, it suppresses high-frequency signals while allowing low-frequency signals to pass. This also provides impedance matching, ensuring optimal signal transmission between the signal source and the load, and reducing reflections and losses.

[0041] Fourth specific embodiment

[0042] The AC-to-DC flyback power supply circuit further includes an RCD absorption clamping module 40 , which is connected to the input rectifier filter module 10 and the transformer T1 at the same time. The RCD absorption clamping module 40 is used to reduce the peak voltage in the AC-to-DC flyback power supply circuit.

[0043] The AC-to-DC flyback power supply circuit also includes an RCD absorption clamping module 40, which includes a sixth resistor R1, a third capacitor C2, and a second diode D1. The sixth resistor R1 and the third capacitor C2 are connected in parallel. One end of the sixth resistor R1 and one end of the third capacitor C2 are respectively connected to the opposite-name terminals of the primary winding T1A of the transformer T1. The other end of the sixth resistor R1 and the other end of the third capacitor C2 are respectively connected to the cathode of the second diode D1. The anode of the second diode D1 is connected to the same-name terminal of the primary winding T1A of the transformer T1.

[0044] Principle and effect of the fourth specific embodiment: The RCD (Resistor-Capacitor-Diode) absorption clamping circuit can limit the voltage to near a predetermined value when it reaches the value. The second diode D1 is turned on when forward biased, thereby "clamping" the excess voltage to a specific value to avoid damage to subsequent circuits or components. When transient voltages (such as electromagnetic interference or switching noise) appear in the circuit, the RCD absorption clamping module 40 can quickly respond and suppress these transient voltages to protect sensitive components from high voltage shocks; by limiting voltage spikes, the RCD absorption clamping module 40 improves the reliability of the entire circuit, reduces the risk of component damage, and extends the service life of the system; the RCD absorption clamping module 40 can reduce the generation of electromagnetic interference to a certain extent, because its absorption and clamping effects can reduce the spike voltage propagating in the circuit, thereby reducing the generation of EMI.

[0045] Fifth specific embodiment

[0046] The output rectifier and filter module 30 includes a third diode D3 and a fourth capacitor C3. The anode of the third diode D3 is connected to the same-name terminal of the secondary winding T1B of the transformer T1, the cathode of the third diode D3 is connected to the positive electrode of the fourth capacitor C3, and the cathode of the fourth capacitor C3 is connected to the opposite-name terminal of the secondary winding T1B of the transformer T1 and grounded.

[0047] The AC-DC flyback power supply circuit also includes a fourth diode D2. The power supply unit 21 includes an MCU chip U1. The MCU chip U1 is connected to the cathode of the fourth diode D2. The anode of the fourth diode D2 is connected to the cathode of the third diode D3. The first capacitor C1 and the fourth capacitor C3 are electrolytic capacitors.

[0048] Principle and effect of the fifth specific embodiment: The output rectifier filter module 30 is used to convert alternating current (AC) into direct current (DC) and smooth the output to reduce fluctuations and ripples. Electrolytic capacitors can store electrical energy and release it when needed. This makes it very important in power supply circuits, able to smooth voltage and provide instantaneous current; electrolytic capacitors are also used as filters to smooth the rectified DC voltage. By storing energy and releasing it, the ripple in the output voltage can be reduced, making the DC voltage more stable; electrolytic capacitors can also be used for decoupling to reduce high-frequency noise and electromagnetic interference and maintain the stability of the power supply.

[0049] Sixth specific embodiment

[0050] The power supply unit 21 includes a seventh resistor R5 and an MCU chip U1. The MCU chip U1 is connected to the same-name terminal of the primary winding T1A of the transformer T1. The seventh resistor R5 is connected to the MCU chip U1. It should be noted that the power supply unit 21 of the present invention is based on the prior art, and the improvement of the present invention does not lie in the technology of the power supply unit 21 itself.

[0051] The principle of the present invention is as follows: the AC to DC flyback power supply circuit is connected to the AC mains power supply, and the AC mains power supply is rectified by the rectifier bridge DB1 and filtered by the first capacitor C1 to become a DC power supply. This DC power supply provides a relatively small startup current to the MCU chip U1 through the two startup resistors, the third resistor R3 and the fourth resistor R6. After the MCU chip U1 is started, the high-frequency drive switch tube Q1 inside the MCU chip U1 causes the transformer T1 to generate a high-frequency AC, and outputs a low-voltage high-frequency AC through the secondary winding T1B of the transformer T1, which is rectified into DC by the third diode D3. The RCD absorption clamp module 40 is used to absorb the high voltage generated by the primary winding T1A of the transformer T1 after the switch tube Q1 is turned off, because the third The small current generated by the resistor R3 and the fourth resistor R6 cannot maintain the operation of the MCU chip U1. The output 18V DC is returned to the MCU chip U1VDD through the fourth diode D2 to power the MCU chip U1. At the same time, the output DC signal passes through the voltage regulator, the second resistor R2 and the third resistor R3. When the output voltage is higher than about 18V, the switch tube Q1 is strengthened and fed back to the FB pin of the MCU chip U1. The MCU chip U1 reduces the PWM duty cycle to control the internal switch tube Q1. Conversely, when it is lower than about 18V, the switch tube Q1 is weakened. After being fed back to the FB pin of the MCU chip U1, the MCU chip U1 increases the PWM duty cycle to control the internal switch tube Q1. In this embodiment, the switch tube is selected as the switch tube Q1.

[0052] The AC-to-DC flyback power supply circuit converts high-voltage AC power into low-voltage DC power. Transformer T1 provides electrical isolation to protect downstream circuits and equipment, ensuring safety. Isolation prevents interference signals in the AC power from being transmitted to the DC side, improving system stability and safety. The circuit provides a stable DC output voltage even when the input voltage or load changes. Feedback control ensures that the output voltage remains within the set value range.

[0053] The above description is merely an optional embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made by utilizing the contents of the present invention specification and drawings under the inventive concept of the present invention, or direct / indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. An AC-to-DC flyback power supply circuit, characterized in that: It includes an input rectifier and filter module, a control module, a transformer, and an output rectifier and filter module connected in sequence. The control module includes a power supply unit and an adjustment unit. The power supply unit is connected to the primary winding of the transformer and the adjustment unit at the same time. The adjustment unit is connected to the secondary winding of the transformer. The adjustment unit is connected to the output rectifier and filter module. The input rectifier and filter module is used to convert the input alternating current into direct current and provide the direct current to the control module. The adjustment unit is used to adjust the supply voltage and feed the supply voltage back to the power supply unit to thereby adjust the PWM duty cycle of the power supply unit.

2. The AC-to-DC flyback power supply circuit according to claim 1, wherein: The regulating unit includes a voltage divider unit, a first resistor, a switching tube and a first diode. The collector of the switching tube is connected to the power supply unit, the emitter of the switching tube is grounded, the base of the switching tube is connected to one end of the first resistor, the voltage divider unit is simultaneously connected to the other end of the first resistor and the positive electrode of the first diode, and the negative electrode of the first diode is connected to the output rectifier and filtering module.

3. The AC-to-DC flyback power supply circuit according to claim 2, wherein: The voltage dividing unit includes a second resistor and a third resistor, the second resistor and the third resistor are connected in series, and the first resistor is connected between the second resistor and the third resistor.

4. The AC-to-DC flyback power supply circuit according to claim 1, wherein: The AC-to-DC flyback power supply circuit also includes a fuse, the input rectifier and filter module includes a rectifier bridge, the AC-to-DC flyback power supply circuit is connected to the mains, the mains includes a neutral wire and a live wire, the live wire is connected to one end of the fuse, the other end of the fuse is connected to the first end of the rectifier bridge, and the neutral wire is connected to the second end of the rectifier bridge.

5. The AC-to-DC flyback power supply circuit according to claim 4, wherein: The input rectifier and filter module further includes a first capacitor, wherein a positive electrode of the first capacitor is connected to the third end of the rectifier bridge, and a negative electrode of the first capacitor is connected to the fourth end of the rectifier bridge.

6. The AC-to-DC flyback power supply circuit according to claim 5, wherein: The AC-to-DC flyback power supply circuit also includes a fourth resistor, a fifth resistor, and a second capacitor. One end of the fourth resistor is connected to the positive electrode of the first capacitor, the other end of the fourth resistor is connected to one end of the fifth resistor, the other end of the fifth resistor is simultaneously connected to one end of the second capacitor and the power supply unit, and the other end of the second capacitor is grounded.

7. The AC-to-DC flyback power supply circuit according to claim 1, wherein: The AC-to-DC flyback power supply circuit also includes an RCD absorption clamping module, which is connected to the input rectifier filter module and the transformer at the same time. The RCD absorption clamping module is used to reduce the peak voltage in the AC-to-DC flyback power supply circuit.

8. The AC-to-DC flyback power supply circuit according to claim 7, wherein: The RCD absorption clamping module includes a sixth resistor, a third capacitor, and a second diode. The sixth resistor and the third capacitor are connected in parallel. One end of the sixth resistor and one end of the third capacitor are respectively connected to the opposite-name ends of the primary winding of the transformer, the other end of the sixth resistor and the other end of the third capacitor are respectively connected to the negative electrode of the second diode, and the positive electrode of the second diode is connected to the same-name end of the primary winding of the transformer.

9. The AC-to-DC flyback power supply circuit according to claim 1, wherein: The output rectifier and filter module includes a third diode and a fourth capacitor. The positive electrode of the third diode is connected to the same-name end of the secondary winding of the transformer, the negative electrode of the third diode is connected to the positive electrode of the fourth capacitor, and the negative electrode of the fourth capacitor is connected to the opposite-name end of the secondary winding of the transformer and grounded.

10. The AC-to-DC flyback power supply circuit according to claim 9, wherein: The AC-to-DC flyback power supply circuit also includes a fourth diode, and the power supply unit includes an MCU chip. The MCU chip is connected to the cathode of the fourth diode, and the anode of the fourth diode is connected to the cathode of the third diode.

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