Flyback conversion circuit and electric equipment

Abstract

The utility model relates to a flyback conversion circuit and electric equipment, the flyback conversion circuit comprises a first voltage conversion circuit, a switch circuit, a control circuit, a first output circuit, a second output circuit, a first feedback circuit and a second feedback circuit, the first voltage conversion circuit outputs a first voltage through the first output circuit; the second output circuit outputs a second voltage. The control circuit outputs a first control signal based on the first feedback voltage generated by the first feedback circuit so as to control the working state of the switching circuit. And if the load is reduced or no-load, when the reduced second voltage is smaller than the preset voltage, the second feedback circuit generates a second feedback voltage, and the control circuit responds to the common input of the first feedback voltage and the second feedback voltage and outputs a second control signal with the same duty ratio as the first control signal so as to control the working state of the switching circuit. And the second voltage is kept stable, so that the flyback conversion circuit is kept stable.

Description

Technical Field

[0001] This utility model relates to the field of flyback converters, and in particular to a flyback converter circuit and electrical equipment. Background Technology

[0002] Switching power supplies are characterized by low power consumption and high efficiency, and their applications are becoming increasingly widespread, influencing the development of various industrial sectors. The flyback converter circuit is a crucial component of a switching power supply. The control circuit in the flyback converter circuit controls the operating state of the switching circuit to control the energy coupling between the primary and secondary windings of the transformer, thereby controlling the output voltage.

[0003] The flyback converter circuit can have multiple outputs, one of which is used to power the load and another is used to power the control circuit. When the flyback converter circuit switches from being under load to almost no load, the output voltage supplied to the control circuit will fluctuate, and may even drop below the undervoltage point of the control circuit, causing the control circuit to be unstable. This, in turn, causes the flyback converter circuit to keep hiccuping and restarting, resulting in unstable output. Utility Model Content

[0004] The present invention aims to provide a flyback converter circuit and an electrical device that can improve the stability of the flyback converter circuit output.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solutions:

[0006] In a first aspect, the present invention provides a flyback converter circuit, the flyback converter circuit comprising: a first voltage conversion circuit, a switching circuit, a control circuit, a first output circuit, a second output circuit, a first feedback circuit, and a second feedback circuit;

[0007] The first voltage conversion circuit is electrically connected to the first power supply, the first output circuit, and the second output circuit, respectively. The first voltage conversion circuit is configured to convert the voltage of the first power supply, output a first voltage through the first output circuit to supply power to the load, and output a second voltage through the second output circuit to supply power to the power supply terminal of the control circuit. The second voltage decreases as the first voltage increases.

[0008] The first feedback circuit is electrically connected to the feedback terminals of the first output circuit and the control circuit, respectively, and the output terminal of the control circuit is electrically connected to the control terminal of the switching circuit.

[0009] The first feedback circuit is configured to generate a first feedback voltage based on the first voltage, so that the control circuit outputs a first control signal based on the first feedback voltage to control the operating state of the switching circuit, thereby controlling the output of the first voltage or the second voltage;

[0010] The second feedback circuit is electrically connected to the feedback terminals of the second output circuit and the control circuit, respectively. The second feedback circuit is configured to generate a second feedback voltage in response to the result that the first voltage increases, causing the second voltage to decrease, and the decreased second voltage is less than a preset voltage.

[0011] The control circuit is configured to output a second control signal in response to the common input of the first feedback voltage and the second feedback voltage, so as to control the operating state of the switching circuit, wherein the duty cycle of the second control signal is the same as the duty cycle of the first control signal.

[0012] In some embodiments, the second feedback circuit includes a voltage regulation unit, a switching unit, and a voltage generation unit;

[0013] The voltage regulator unit is electrically connected to the control terminal of the second output circuit and the switching unit, respectively. The first terminal of the switching unit is electrically connected to the first terminal of the voltage generation unit and the feedback terminal of the control circuit at the first node. The second terminal of the switching unit and the second terminal of the voltage generation unit are grounded together. The voltage regulator unit is configured to control the switching unit to be in the off state in response to the result that the reduced second voltage is less than the preset voltage, so that the voltage generation unit generates the second feedback voltage.

[0014] In some embodiments, the voltage regulator unit includes a first Zener diode and a first resistor;

[0015] The cathode of the first Zener diode is used to connect to the second voltage, the anode of the first Zener diode is connected to the control terminal of the switching unit and one end of the first resistor, and the other end of the first resistor is grounded.

[0016] In some embodiments, the switching unit includes a second resistor, a first capacitor, a second capacitor, and a first transistor;

[0017] One end of the second resistor is connected to the voltage regulator unit and one end of the first capacitor, respectively. The other end of the second resistor is connected to the base of the first transistor and one end of the second capacitor, respectively. The other end of the first capacitor, the other end of the second capacitor, and the emitter of the first transistor are all grounded. The collector of the first transistor is electrically connected to the first node.

[0018] In some embodiments, the voltage generation unit includes a third resistor, which is connected to the first node and ground.

[0019] In some embodiments, the first feedback circuit includes a sampling unit and an optocoupler unit;

[0020] The sampling unit is connected to the first output circuit and the first terminal of the optocoupler unit respectively. The sampling unit is configured to sample the first voltage and generate a sampled voltage.

[0021] The voltage generation unit is electrically connected to the feedback terminal of the control circuit via the optocoupler unit, and the optocoupler unit is configured to generate the first feedback voltage based on the sampled voltage.

[0022] In some embodiments, the sampling unit includes a fourth resistor, a fifth resistor, a sixth resistor, and a second Zener diode, and the optocoupler unit includes an optocoupler and a seventh resistor;

[0023] One end of the fourth resistor is used to connect to the first voltage, and the other end of the fourth resistor is connected to the anode of the diode of the optocoupler and one end of the fifth resistor, respectively. The cathode of the diode of the optocoupler is connected to the other end of the fifth resistor and the cathode of the second Zener diode, respectively. The anode of the second Zener diode is grounded. The collector of the transistor of the optocoupler is electrically connected to the first node, and the emitter of the transistor of the optocoupler is electrically connected to the voltage generation unit.

[0024] In some embodiments, the flyback converter circuit further includes a second voltage conversion circuit;

[0025] The second voltage conversion circuit is electrically connected to the power supply terminals of the second output circuit and the control circuit, respectively. The second voltage conversion circuit is configured to generate the power supply voltage of the control circuit based on the second voltage, so as to supply power to the control circuit.

[0026] In some embodiments, the second voltage conversion circuit includes a seventh resistor, a third Zener diode, and a second transistor;

[0027] One end of the seventh resistor is connected to the collector of the second transistor to receive the second voltage. The emitter of the second transistor is electrically connected to the power supply terminal of the control circuit. The base of the second transistor is connected to the other end of the seventh resistor and the cathode of the third Zener diode. The anode of the third Zener diode is grounded.

[0028] In a second aspect, embodiments of the present invention provide an electrical device including the flyback converter circuit described above.

[0029] In various embodiments of this utility model, the flyback converter circuit includes a first voltage conversion circuit, a switching circuit, a control circuit, a first output circuit, a second output circuit, a first feedback circuit, and a second feedback circuit. The first voltage conversion circuit converts the voltage of the first power supply and outputs a first voltage via the first output circuit to supply power to the load, and outputs a second voltage via the second output circuit to supply power to the power supply terminal of the control circuit. The first feedback circuit generates a first feedback voltage based on the first voltage, causing the control circuit to output a first control signal based on the first feedback voltage. The first control signal is used to control the operating state of the switching circuit, thereby controlling the output of the first voltage or the second voltage. If the load decreases or there is no load, the first voltage increases, causing the second voltage to decrease. When the decreased second voltage is less than a preset voltage, the second feedback circuit generates a second feedback voltage, causing the control circuit to respond to the common input of the first feedback voltage and the second feedback voltage and output a second control signal with the same duty cycle as the first control signal. The second control signal controls the operating state of the switching circuit, thereby keeping the second voltage output by the first voltage conversion circuit stable, thus keeping the power supply of the control circuit stable, and keeping the flyback converter circuit stable. Attached Figure Description

[0030] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0031] Figure 1 This is a schematic diagram of the structure of one of the power supply devices provided in this utility model embodiment;

[0032] Figure 2 This is a schematic diagram of the structure of one of the flyback converter circuits provided in this embodiment of the present invention;

[0033] Figure 3 This is a waveform diagram of a first voltage and a second voltage provided in one embodiment of this utility model;

[0034] Figure 4 This is a schematic diagram of the structure of one of the flyback converter circuits provided in this embodiment of the present invention;

[0035] Figure 5 This is a schematic diagram of the structure of one of the first feedback circuits and the second feedback circuit provided in one embodiment of the present utility model;

[0036] Figure 6 This is a schematic diagram of the circuit structure of one of the flyback converter circuits provided in this embodiment of the utility model;

[0037] Figure 7This is a waveform diagram of a first voltage and a second voltage provided in one embodiment of this utility model. Detailed Implementation

[0038] 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 the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining this utility model and are not intended to limit this utility model.

[0039] Please see Figure 1 , Figure 1 This is a schematic diagram of the structure of an electrical device provided in an embodiment of this application. For example... Figure 1 As shown, the electrical equipment includes a flyback converter circuit 100, a first power supply 200, and a load 300.

[0040] The first power supply 200 is connected to the flyback converter circuit 100 and provides power to the flyback converter circuit 100. The first power supply 200 can be a DC power supply or an AC power supply. When the first power supply 200 is an AC power supply, after rectification and filtering, it provides DC power to the flyback converter circuit 100. Furthermore, the first power supply 200 can be a power supply circuit composed of any suitable discrete components. For example, in some embodiments, the first power supply 200 is a power supply circuit composed of a filter circuit, a rectifier circuit, and a voltage regulator circuit. In other examples, in some embodiments, the first power supply 200 is an integrated power chip.

[0041] The flyback converter circuit 100 processes the first power supply 200 to obtain a secondary voltage signal, which is the output voltage. The flyback converter circuit 100 is connected to the load 300 and provides the output voltage to the load 300. The load 300 implements the corresponding load control logic according to the driving of the secondary voltage signal.

[0042] like Figure 2 As shown, the flyback converter circuit 100 includes a first voltage conversion circuit 10, a switching circuit 20, a control circuit 30, a first output circuit 40, a second output circuit 50, and a first feedback circuit 60. The first voltage conversion circuit 10 is electrically connected to a first power supply, the first output circuit 40, and the second output circuit 50. The first output circuit 40 is electrically connected to a load. The second output circuit 50 is electrically connected to the power supply terminal of the control circuit 30. The first feedback circuit 60 is electrically connected to the feedback terminal of the control circuit 30 and the first output circuit 40. The output terminal of the control circuit 30 is also electrically connected to the control terminal of the switching circuit 20.

[0043] The first voltage conversion circuit 10 converts the voltage of the first power supply 200 and outputs a first voltage through the first output circuit 40. The first voltage supplies power to the load 300, and the second voltage is output through the second output circuit 50. The second voltage supplies power to the control circuit 30.

[0044] The first feedback circuit 60 samples the first voltage and generates a first feedback voltage based on it. The control circuit 30 outputs a first control signal based on the first feedback voltage. The first control signal controls the switching circuit 20 to enter either a conducting or cut-off state. This, in turn, controls the first voltage conversion circuit 10 to output either a first voltage or a second voltage based on the energy stored in the first power supply 200 when the switching circuit 20 is in the conducting state, and vice versa when the switching circuit 20 is in the cut-off state. The first feedback circuit 60 is a negative feedback circuit; the larger the first voltage, the smaller the first feedback voltage, and thus the smaller the duty cycle of the first control signal output by the control circuit 30, thereby reducing the first voltage.

[0045] The first control signal is a pulse width modulation wave (PWM wave). The duty cycle of the PWM wave determines the duration of the switching circuit 20 in the on and off states, thereby controlling the magnitude of the first voltage or the second voltage.

[0046] When the flyback converter circuit 100 switches from a loaded state to a near-unloaded state, i.e., the load 300 fluctuates and becomes almost unloaded, the first voltage rises. Due to the flyback crossover regulation, this causes the second voltage to drop. If it drops below the undervoltage point of the control circuit 30, the control circuit 30 will become unstable, leading to the flyback converter circuit 100 continuously hiccuping and restarting, resulting in unstable output. The waveforms of the first and second voltages when the flyback converter circuit 100 switches from a loaded state to a near-unloaded state are as follows: Figure 3 As shown, curve L1 represents the fluctuation curve of the first voltage, and curve L2 represents the fluctuation curve of the second voltage. Figure 3 As can be seen, when the first voltage increases, the second voltage decreases accordingly, resulting in fluctuations.

[0047] To address the aforementioned issues, this utility model provides a flyback converter circuit, which further includes a second feedback circuit. The second feedback circuit enables the control circuit to continue outputting a control signal with the same duty cycle when the first voltage increases, thereby maintaining the stable output of the flyback converter circuit.

[0048] For details, please continue reading Figure 2The flyback converter circuit 100 also includes a second feedback circuit 70, which is electrically connected to the feedback terminals of the second output circuit 50 and the control circuit 30, respectively. The second feedback circuit 70 samples the second voltage and determines the magnitude of the feedback voltage to be sent to the feedback terminal of the control circuit 30 based on the magnitude of the second voltage.

[0049] When the flyback converter circuit is working normally, if the second voltage is greater than or equal to the preset voltage, the second flyback circuit will not send the second feedback voltage to the feedback terminal of the control circuit 30. In other words, if the second feedback voltage sent to the feedback terminal of the control circuit 30 is zero, the feedback terminal of the control circuit 30 will only receive the first feedback voltage. The control circuit 30 will send the first control signal based on the received first feedback voltage to control the working state of the switching circuit 20, so that the first voltage conversion circuit 10 will continuously output the first voltage V1 and the second voltage V2.

[0050] The first voltage V1 supplies power to the load 300, and the second voltage V2 supplies power to the control circuit 30. When the load 300 fluctuates and the flyback circuit switches from being under load to almost unloaded, the first voltage V1 increases. Due to the cross-regulation of the flyback circuit, the second voltage V2 decreases, resulting in a fluctuation of ΔV. The decreased second voltage becomes V2' = V2 - ΔV. V2' may cause the control circuit 30 to operate in an undervoltage state, which in turn causes it to continuously hiccup and restart, resulting in unstable output of the flyback circuit.

[0051] The increased first voltage V1' will cause the first feedback voltage to decrease, which in turn will decrease the feedback terminal voltage of the control circuit 30. When the decreased second voltage V2' is less than the preset voltage, the second feedback circuit 70 generates a second feedback voltage and outputs the second feedback voltage to the feedback terminal of the control circuit 30. The second feedback voltage raises the feedback terminal voltage of the control circuit 30, that is, the second feedback voltage cancels out the voltage change caused by the first feedback voltage, so that the voltage at the feedback terminal of the control circuit 30 remains stable. Then the control circuit 30 outputs a second control signal with the same duty cycle as the first control signal. The switching frequency of the switching circuit 20 remains unchanged, and the first voltage conversion circuit 10 continues to output the first voltage V1 and the second voltage V2, thereby keeping the power supply terminal voltage of the control circuit 30 stable and the flyback converter circuit 100 stable.

[0052] In summary, if the load decreases or there is no load, the first voltage increases, which will cause the second voltage to decrease. When the decreased second voltage is less than the preset voltage, the second feedback circuit generates a second feedback voltage, which causes the control circuit to respond to the common input of the first feedback voltage and the second feedback voltage and output a second control signal with the same duty cycle as the first control signal. The second control signal controls the working state of the switching circuit, thereby controlling the second voltage output by the first voltage conversion circuit to remain stable, thus keeping the power supply of the control circuit stable and the flyback converter circuit stable.

[0053] Please see Figure 4 , Figure 4 This is a schematic diagram of a flyback converter circuit provided in an embodiment of the present invention, as shown below. Figure 4 As shown, the flyback converter circuit 100 also includes a second voltage conversion circuit 80, which is electrically connected to the power supply terminals of the second output circuit 50 and the control circuit 30, respectively.

[0054] The second voltage conversion circuit 80 generates a supply voltage for the control circuit 30 based on the second voltage, in order to supply power to the control circuit 30. The voltage value of the second voltage may not match the supply voltage of the control circuit 30, or when the control circuit 30 uses different control chips, the supply voltage of each control chip is different. Therefore, the second voltage conversion circuit 80 is used to convert the second voltage, such as by stepping down, to obtain a suitable supply voltage for the control circuit 30.

[0055] Please see Figure 5 , Figure 5 This is a schematic diagram of the structure of a second feedback circuit and a first feedback circuit provided in an embodiment of this utility model, as shown below. Figure 5 As shown, the second feedback circuit 70 includes a voltage regulator unit 71, a switching unit 72, and a voltage generation unit 73. The voltage regulator unit 71 is electrically connected to the control terminals of the second output circuit 50 and the switching unit 72, respectively. The first terminal of the switching unit 72 is electrically connected to the first terminal of the voltage generation unit 73 and the feedback terminal of the control circuit 30 at the first node a, respectively. The second terminal of the switching unit 72 and the second terminal of the voltage generation unit 73 are grounded together.

[0056] When the flyback converter circuit is working normally, if the second voltage is greater than or equal to the preset voltage, the voltage regulator unit 71 generates a voltage regulator signal based on the second voltage. The voltage regulator signal controls the switching circuit 20 to be in the conducting state, which in turn causes the voltage generation unit 73 to generate a zero voltage. Then, the feedback terminal of the control circuit 30 only receives the first feedback voltage (the first feedback voltage is superimposed with the zero voltage to still obtain the first feedback voltage). Based on the first feedback voltage, the first control signal is generated to control the working state of the switching circuit 20.

[0057] When the first voltage increases and the second voltage decreases, if the decreased second voltage is less than the preset voltage, the voltage regulator unit 71 stops generating the voltage regulator signal, thereby controlling the switching circuit 20 to be in the off state. This causes the voltage generation unit 73 to generate the second feedback voltage. The feedback terminal of the control circuit 30 then receives the first feedback voltage and the second feedback voltage. The first feedback voltage causes the voltage at the feedback terminal of the control circuit 30 to decrease, and the second feedback voltage causes the voltage at the feedback terminal of the control circuit 30 to increase. This causes the control circuit 30 to respond to the common input of the first feedback voltage and the second feedback voltage and output the second control signal. The duty cycle of the second control signal is the same as that of the first control signal, so the switching frequency of the corresponding switching circuit 20 is the same, and the output of the first voltage conversion circuit 10 is the same, thus keeping the output of the first voltage conversion circuit 10 stable.

[0058] Therefore, when the second voltage decreases and fluctuations occur, if the decreased second voltage is less than the preset voltage, the second feedback voltage will offset the fluctuation effect caused by the first feedback voltage, so that the feedback terminal of the control circuit 30 remains stable, thereby keeping the duty cycle of the output control signal unchanged, and thus keeping the output of the flyback converter circuit 100 stable.

[0059] In some embodiments, the second feedback circuit 70 is electrically connected to the feedback terminal of the control circuit 30 via the first feedback circuit 60, that is, the second feedback circuit 70 is electrically connected to the first node a via the first feedback circuit 60. For details, please refer to [link to relevant documentation]. Figure 5 The first feedback circuit 60 includes a sampling unit 51 and an optocoupler unit 52. The sampling unit 51 is electrically connected to the input side of the first output circuit 40 and the optocoupler unit 52, respectively. The voltage generation unit 73 is electrically connected to the feedback terminal of the control circuit 30 via the output side of the optocoupler unit 52. Specifically, as shown in the figure... Figure 5 As shown, the first node a is electrically connected to the first output terminal of the optocoupler unit 52, the second output terminal of the optocoupler unit 52 is electrically connected to the feedback terminal of the control circuit 3030, and the input terminal of the optocoupler unit 52 is electrically connected to the sampling unit 51.

[0060] The sampling unit 51 samples the first voltage and generates a sampling voltage. The optocoupler unit 52 generates a first feedback voltage based on the sampling voltage and outputs the first feedback voltage to the first node a.

[0061] If the second voltage is greater than or equal to the preset voltage, the voltage generation unit generates a zero voltage. This zero voltage acts on the output side of the optocoupler unit 52, and the optocoupler unit 52 only feeds back the first feedback voltage to the first node a.

[0062] If the second voltage is less than the preset voltage, the voltage generation unit generates a second feedback voltage. The second feedback voltage acts on the output side of the optocoupler unit 52, and the optocoupler unit 52 feeds back the first feedback voltage and the second feedback voltage to the first node a.

[0063] Please see Figure 6 , Figure 6 This is a schematic diagram of the circuit structure of a second feedback circuit and a second voltage conversion circuit provided in an embodiment of this utility model, as shown below. Figure 6 As shown, the voltage regulator unit 71 includes a first Zener diode DZ1 and a first resistor R1. The cathode of the first Zener diode DZ1 is used to connect to the second voltage, and the anode of the first Zener diode DZ1 is connected to the control terminal of the switching unit 72 and one end of the first resistor R1. The other end of the first resistor R1 is grounded to AGND.

[0064] The switching unit 72 includes a second resistor R2, a first capacitor C1, a second capacitor C2, and a first transistor Q1. One end of the second resistor R2 is connected to the voltage regulator unit 71 and one end of the first capacitor C1, respectively. The other end of the second resistor R2 is connected to the base of the first transistor Q1 and one end of the second capacitor C2, respectively. The other ends of the first capacitor C1, the other ends of the second capacitor C2, and the emitter of the first transistor Q1 are all grounded to AGND. The collector of the first transistor Q1 is electrically connected to the first node a.

[0065] The voltage generation unit 73 includes a third resistor R3, which is connected to the first node a and ground AGND.

[0066] The sampling unit 51 includes a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, and a second Zener diode DZ2. The optocoupler unit 52 includes an optocoupler U201 and a seventh resistor R7. One end of the fourth resistor R4 is connected to the first voltage V1. The other end of the fourth resistor R4 is connected to the anode of the diode of the optocoupler U201 and one end of the fifth resistor R5. The cathode of the diode of the optocoupler U201 is connected to the other end of the fifth resistor R5 and the cathode of the second Zener diode DZ2. The anode of the second Zener diode DZ2 is grounded to AGND. The collector of the transistor of the optocoupler U201 is electrically connected to the first node a. The emitter of the transistor of the optocoupler U201 is electrically connected to the voltage generation unit AGND. The emitter of the transistor of the optocoupler U201 is connected to the collector of the first transistor Q1 and the third resistor R3.

[0067] In some embodiments, the first feedback circuit 60 further includes a filter capacitor and a voltage divider resistor, etc. The filter capacitor is used for filtering, and the voltage divider resistor is used for dividing the first voltage V1 to generate a voltage divider signal. The voltage divider signal is applied to the control electrode of the second Zener diode DZ2 to adjust the Zener voltage value of the second Zener diode DZ2.

[0068] The second voltage conversion circuit 80 includes a seventh resistor R7, a third Zener diode DZ3, and a second transistor Q2. One end of the seventh resistor R7 is connected to the collector of the second transistor Q2 to receive the second voltage. The emitter of the second transistor Q2 is electrically connected to the power supply terminal of the control circuit 30. The base of the second transistor Q2 is connected to the other end of the seventh resistor R7 and the cathode of the third Zener diode DZ3. The anode of the third Zener diode DZ3 is grounded to AGND.

[0069] In this embodiment, the control circuit 30 includes a control chip U202 and peripheral circuitry. The peripheral circuitry includes components such as capacitors, resistors, and diodes, ensuring that the control chip U202 can operate normally. The power supply pin (pin 5) of the control chip U202 is the power supply terminal of the control circuit 30, the feedback pin (pin 2) of the control chip U202 is the feedback terminal of the control circuit 30, and the transmit pin (pin 6) of the control chip U202 is used to transmit a first control signal or a second control signal.

[0070] The first voltage V1 conversion circuit 10, the switching circuit 20, the first output circuit 40, and the second output circuit 50 can all be conventional circuits in the art. For example, the first voltage V1 conversion circuit 10 includes a transformer, a rectifier diode, and an energy storage capacitor; the first output circuit 40 includes a secondary winding, a diode, and an energy storage capacitor; the second output circuit 50 also includes a secondary winding, a diode, and an energy storage capacitor; and the switching circuit 20 includes a power switch. When the power switch is in the on state, the voltage of the first power supply 200 is applied to the primary winding of the transformer, causing the primary winding to begin storing energy. At this time, the diode in the first output circuit 40 is reverse biased, the secondary winding does not output current, and the load 300 relies on the output capacitor to maintain power supply. Once the switch is turned off, the energy stored in the primary winding begins to be released, and the secondary winding in the first output circuit 40 generates an induced voltage. The diode turns on, providing the first voltage V1 to the load 300 and simultaneously charging the output capacitor. Similarly, once the switching transistor is turned off, the energy stored in the primary winding begins to be released, and the secondary winding in the second output circuit 50 generates an induced voltage. The diode turns on, providing a second voltage to the control chip U202 and simultaneously charging the output capacitor. The specific composition and connection relationship of each circuit will not be described in detail here.

[0071] Combination Figure 6 The working principle of the flyback converter circuit 100 can be described as follows:

[0072] The control chip U202 outputs a first control signal, causing the first voltage V1 conversion circuit 10 to output the first voltage V1 via the first output voltage and the second voltage V2 via the second output circuit 50. The first voltage V1 supplies power to the load 300, and the second voltage V2 turns on the third Zener diode DZ3, which in turn turns on the second transistor Q2. Based on the second voltage V2 and the regulated voltage of the third Zener diode DZ3, a supply voltage Vcp_Vcc is generated to supply power to the control chip U202 so that it can work normally.

[0073] When the second voltage V2 is greater than or equal to the preset voltage, the first Zener diode DZ1 breaks down in reverse and is in a conducting state, making the base voltage of the first transistor Q1 high. The first transistor Q1 conducts, grounding the emitter of the transistor in optocoupler U201 to AGND, without affecting the operation of the first feedback circuit 60. The first voltage V1, through the fourth resistor R4, the fifth resistor R5, and the sixth resistor R6, causes the second Zener diode DZ2 to break down in reverse and be in a conducting state. Consequently, the cathode voltage of the diode in optocoupler U201 is the regulated voltage of the second Zener diode DZ2, and the anode voltage of the diode in optocoupler U201 is the voltage divided by the sixth resistor R6 and the second Zener diode DZ2 across the first voltage V1. The diode in optocoupler U201 conducts, and consequently, the transistor in optocoupler U201 conducts. Optocoupler U201 converts the first voltage V1 into a first feedback voltage and feeds it back to the feedback pin of the control chip U202.

[0074] If the first output circuit 40 is switched from a loaded state to almost unloaded state, the first voltage V1 transiently rises to V1'. The anode voltage of the diode in optocoupler U201 is the sampling voltage. The larger the first voltage V1, the larger the sampling voltage, the brighter the diode in optocoupler U201, and the stronger the conduction of the transistor in optocoupler U201. Since there is a pull-up resistor and a reference source in the control chip U202, the pull-up resistor and the seventh resistor R7 are connected in series to the reference source. The common connection point of the first resistor R1 and the pull-up resistor is the feedback pin of the control chip U202. Due to the increased conduction of the transistor in optocoupler U201, the current flowing from the reference source to the feedback pin and then to the seventh resistor R7 increases. As a result, the voltage at the feedback pin of the control chip U202 decreases. That is, the first feedback circuit 60 is a negative feedback circuit. The larger the current flowing through the seventh resistor R7, the smaller the first feedback voltage received at the feedback pin of the control chip U202, which causes the voltage at the feedback pin of the control chip U202 to decrease transiently.

[0075] Furthermore, the transient increase in the first voltage V1 causes the transient decrease in the second voltage. When the decreased second voltage V2' is less than the preset voltage, the first Zener diode DZ1 is cut off, the first transistor Q1 is cut off, and a second feedback voltage is generated across the third resistor R3. This raises the voltage at the feedback pin of the control chip U202 to offset the fluctuations caused by the first feedback voltage at the feedback pin of the control chip U202, thus keeping the pin voltage of the control chip U202 stable. Consequently, the control chip U202 outputs a second control signal with the same duty cycle as the first control signal to suppress the drop in the second voltage and control the first voltage V1 conversion circuit 10 to output a stable first voltage V1 and a second voltage V2.

[0076] right Figure 6 Steady-state testing was performed on the flyback converter circuit 100. The waveforms of the first voltage V1 and the second voltage are shown in the figure. Figure 7 As shown, Figure 7 The L1 curve in the diagram represents the waveform of the first voltage V1, and the L2 curve represents the waveform of the second voltage. Figure 7 As can be seen, both the first voltage V1 and the second voltage remain stable. In this embodiment, the first voltage V1 is raised to 11.88V and remains stable, while the drop in the second voltage is suppressed. The second voltage drops to 15.1V and remains stable. Neither the first voltage V1 nor the second voltage exhibits any oscillation.

[0077] In summary, if the load decreases or there is no load, the first voltage increases, which will cause the second voltage to decrease. When the decreased second voltage is less than the preset voltage, the second feedback circuit generates a second feedback voltage, which causes the control circuit to respond to the common input of the first feedback voltage and the second feedback voltage and output a second control signal with the same duty cycle as the first control signal. The second control signal controls the working state of the switching circuit, thereby controlling the second voltage output by the first voltage conversion circuit to remain stable, thus keeping the power supply of the control circuit stable and the flyback converter circuit stable.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it; under the concept of this utility model, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of this utility model as described above, which are not provided in detail for the sake of brevity; although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A flyback converter circuit, characterized in that, The flyback converter circuit includes: a first voltage conversion circuit, a switching circuit, a control circuit, a first output circuit, a second output circuit, a first feedback circuit, and a second feedback circuit; The first voltage conversion circuit is electrically connected to the first power supply, the first output circuit, and the second output circuit, respectively. The first voltage conversion circuit is configured to convert the voltage of the first power supply, output a first voltage through the first output circuit to supply power to the load, and output a second voltage through the second output circuit to supply power to the power supply terminal of the control circuit. The second voltage decreases as the first voltage increases. The first feedback circuit is electrically connected to the feedback terminals of the first output circuit and the control circuit, respectively, and the output terminal of the control circuit is electrically connected to the control terminal of the switching circuit. The first feedback circuit is configured to generate a first feedback voltage based on the first voltage, so that the control circuit outputs a first control signal based on the first feedback voltage to control the operating state of the switching circuit, thereby controlling the output of the first voltage or the second voltage; The second feedback circuit is electrically connected to the feedback terminals of the second output circuit and the control circuit, respectively. The second feedback circuit is configured to generate a second feedback voltage in response to the result that the first voltage increases, causing the second voltage to decrease, and the decreased second voltage is less than a preset voltage. The control circuit is configured to output a second control signal in response to the common input of the first feedback voltage and the second feedback voltage, so as to control the operating state of the switching circuit, wherein the duty cycle of the second control signal is the same as the duty cycle of the first control signal.

2. The flyback converter circuit according to claim 1, characterized in that, The second feedback circuit includes a voltage regulation unit, a switching unit, and a voltage generation unit; The voltage regulator unit is electrically connected to the control terminal of the second output circuit and the switching unit, respectively. The first terminal of the switching unit is electrically connected to the first terminal of the voltage generation unit and the feedback terminal of the control circuit at the first node. The second terminal of the switching unit and the second terminal of the voltage generation unit are grounded together. The voltage regulator unit is configured to control the switching unit to be in the off state in response to the result that the reduced second voltage is less than the preset voltage, so that the voltage generation unit generates the second feedback voltage.

3. The flyback converter circuit according to claim 2, characterized in that, The voltage regulation unit includes a first Zener diode and a first resistor; The cathode of the first Zener diode is used to connect to the second voltage, the anode of the first Zener diode is connected to the control terminal of the switching unit and one end of the first resistor, and the other end of the first resistor is grounded.

4. The flyback converter circuit according to claim 2, characterized in that, The switching unit includes a second resistor, a first capacitor, a second capacitor, and a first transistor; One end of the second resistor is connected to the voltage regulator unit and one end of the first capacitor, respectively. The other end of the second resistor is connected to the base of the first transistor and one end of the second capacitor, respectively. The other end of the first capacitor, the other end of the second capacitor, and the emitter of the first transistor are all grounded. The collector of the first transistor is electrically connected to the first node.

5. The flyback converter circuit according to claim 2, characterized in that, The voltage generation unit includes a third resistor, which is connected to the first node and ground.

6. The flyback converter circuit according to claim 2, characterized in that, The first feedback circuit includes a sampling unit and an optocoupler unit; The sampling unit is connected to the first output circuit and the first terminal of the optocoupler unit respectively. The sampling unit is configured to sample the first voltage and generate a sampled voltage. The voltage generation unit is electrically connected to the feedback terminal of the control circuit via the optocoupler unit, and the optocoupler unit is configured to generate the first feedback voltage based on the sampled voltage.

7. The flyback converter circuit according to claim 6, characterized in that, The sampling unit includes a fourth resistor, a fifth resistor, a sixth resistor, and a second Zener diode; the optocoupler unit includes an optocoupler and a seventh resistor. One end of the fourth resistor is used to connect to the first voltage, and the other end of the fourth resistor is connected to the anode of the diode of the optocoupler and one end of the fifth resistor, respectively. The cathode of the diode of the optocoupler is connected to the other end of the fifth resistor and the cathode of the second Zener diode, respectively. The anode of the second Zener diode is grounded. The collector of the transistor of the optocoupler is electrically connected to the first node, and the emitter of the transistor of the optocoupler is electrically connected to the voltage generation unit.

8. The flyback converter circuit according to claim 1, characterized in that, The flyback converter circuit also includes a second voltage conversion circuit; The second voltage conversion circuit is electrically connected to the power supply terminals of the second output circuit and the control circuit, respectively. The second voltage conversion circuit is configured to generate the power supply voltage of the control circuit based on the second voltage, so as to supply power to the control circuit.

9. The flyback converter circuit according to claim 8, characterized in that, The second voltage conversion circuit includes a seventh resistor, a third Zener diode, and a second transistor; One end of the seventh resistor is connected to the collector of the second transistor to receive the second voltage. The emitter of the second transistor is electrically connected to the power supply terminal of the control circuit. The base of the second transistor is connected to the other end of the seventh resistor and the cathode of the third Zener diode. The anode of the third Zener diode is grounded.

10. An electrical appliance, characterized in that, Includes the flyback converter circuit as described in any one of claims 1-9.

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