Power supply unit and its operating method

Abstract

This invention provides a power supply unit and a method for operating it. [Solution] The power supply unit includes an AC-DC converter, a feedback circuit, an undervoltage protection circuit, a control signal generation circuit, a voltage anomaly protection circuit, and an auxiliary undervoltage detection circuit. The AC-DC converter converts AC voltage to DC voltage. The feedback circuit generates a corresponding feedback signal based on the DC voltage. The control signal generation circuit sets the AC-DC converter to convert AC voltage to DC voltage. The auxiliary undervoltage detection circuit detects that the AC voltage has been below a predetermined voltage for a longer period than a predetermined time, and changes the signal value of the first feedback signal, causing the voltage anomaly protection circuit to cause the control signal generation circuit to perform a soft-start operation on the AC-DC converter.

Description

[Technical Field]

[0001] This disclosure relates to a power supply and a method of operating the same, and more particularly to a power supply and a method of operating the same that are applicable when the input power supply is unstable. [Background technology]

[0002] To reduce the inrush current that occurs when a power converter starts up, soft-start control is usually used to gradually increase the output voltage of the power converter from the initial voltage value to a predetermined voltage. However, in environments where the AC input power supply is unstable, power supply voltage shortages or power outages occur frequently. If a power supply voltage shortage or power outage continues for a short period of time (hereinafter referred to as a momentary interruption), and the power supply unit continues to operate without detecting the interruption, an inrush current will occur in the power converter, which may cause malfunction or damage to the load or the power converter. [Overview of the project]

[0003] Therefore, how to propose a power supply that solves the above problems is an important issue in this field. One aspect of this disclosure provides a power supply. The power supply is used to supply power to a load based on an AC power source. The power supply includes an AC-DC converter, a feedback circuit, an undervoltage protection circuit, a control signal generation circuit, a voltage anomaly protection circuit, and an auxiliary undervoltage detection circuit. The AC-DC converter is used to be coupled to the AC power source to convert an AC voltage to a DC voltage. The feedback circuit is coupled to the AC-DC converter to generate a first feedback signal correspondingly based on the DC voltage. The undervoltage protection circuit is used to be coupled to the AC power source. The control signal generation circuit is coupled to the undervoltage protection circuit and the feedback circuit and is used to set the AC-DC converter to convert an AC voltage to a DC voltage. The voltage anomaly protection circuit is coupled to the feedback circuit and the control signal generation circuit. The auxiliary undervoltage detection circuit is coupled to the voltage anomaly protection circuit and is used to be coupled to the AC power source. The auxiliary undervoltage detection circuit, when it detects that the AC voltage is lower than the second predetermined voltage for a period longer than the second predetermined time, changes the signal value of the first feedback signal so that the voltage abnormality protection circuit causes the control signal generation circuit to perform a soft start operation on the AC-DC converter.

[0004] Another aspect of the present disclosure provides a method for operating a power supply. The power supply is used to supply power to a load based on an AC power source. The power supply includes an AC-DC converter, a feedback circuit, an undervoltage protection circuit, a control signal generation circuit, a voltage anomaly protection circuit, and an auxiliary undervoltage detection circuit. The AC-DC converter is used to be coupled to an AC power source. The feedback circuit is coupled to the AC-DC converter. The undervoltage protection circuit is used to be coupled to an AC power source. The control signal generation circuit is coupled to the undervoltage protection circuit and the feedback circuit. The voltage anomaly protection circuit is coupled to the feedback circuit and the control signal generation circuit. The auxiliary undervoltage detection circuit is coupled to the voltage anomaly protection circuit. The method of operation includes the following steps: The control signal generation circuit controls the AC-DC converter to convert the AC voltage to a DC voltage. The feedback circuit generates a corresponding first feedback signal based on the DC voltage. The auxiliary undervoltage detection circuit, when it detects that the AC voltage is lower than the second predetermined voltage for a period longer than the second predetermined time, changes the signal value of the first feedback signal, causing the voltage abnormality protection circuit to cause the control signal generation circuit to perform a soft-start operation on the AC-DC converter.

[0005] As described above, the power supply unit of this disclosure uses an auxiliary undervoltage detection mechanism in addition to the controller's undervoltage protection mechanism, thereby enabling the power supply unit to ensure power supply stability and device safety in various power supply environments. [Brief explanation of the drawing]

[0006] To make the above and other purposes, features, advantages, and examples of this disclosure clearer and easier to understand, the accompanying drawings are described below. [Figure 1] This is a schematic diagram showing a power supply according to some embodiments of the present disclosure. [Figure 2] This is a schematic diagram showing one embodiment of the subcircuit in Figure 1. [Figure 3] This is a schematic diagram showing the output voltage and control signal in soft-start control according to some embodiments of the present disclosure. [Modes for carrying out the invention]

[0007] The following embodiments will be described in detail with reference to the accompanying drawings, but the embodiments provided are not intended to limit the scope covered by this disclosure, nor are the descriptions of structural operation limited to their execution order, and any device having equivalent effects resulting from a rearranged structure of elements is within the scope covered by this disclosure. Furthermore, the drawings are for illustrative purposes only and are not drawn to actual dimensions. For ease of understanding, identical or similar elements will be denoted by the same reference numerals in the following description.

[0008] Terms used in this specification and in the claims have their ordinary meanings in the art, in the content of this disclosure, and in specific contexts, unless otherwise noted. Terms used herein, such as “including,” “equipped,” “having,” and “containing,” are all open terms meaning “including, but not limited to.” “And / or” used herein includes any one or more of the relevant enumerated items and all combinations thereof.

[0009] Please refer to Figure 1. Figure 1 is a schematic diagram showing a power supply 100 according to some embodiments of the present disclosure. As shown in Figure 1, the power supply 100 includes an AC-DC converter 104, a feedback circuit 106, a controller 110, and an auxiliary undervoltage detection circuit 120.

[0010] The AC-DC converter 104 is electrically coupled to the AC power supply PWR, thereby converting the AC voltage Vac into an output voltage Vout, and further supplying the output voltage Vout to the load 108. The load 108 may be a terminal load or may include other circuit elements such as other power converters. The AC-DC converter 104 may employ a power conversion circuit with an appropriate configuration, such as a boost converter, a buck converter, or a buck-boost converter, and may include one or more switches. The controller 110 is electrically coupled to the AC-DC converter 104, thereby providing one or more control signals CTRL to the AC-DC converter 104, controlling the operating states of the one or more switches, such as conduction time and switching frequency, and further converting the AC voltage Vac into an output voltage Vout. For example, the controller 110 may employ a control signal CTRL in an appropriate signal format such as a pulse width modulation signal (PWM) or a pulse frequency modulation signal (PFM).

[0011] The feedback circuit 106 is electrically coupled to the output terminal of the AC-DC converter 104 and the controller 110 to provide one or more feedback signals based on the output voltage Vout and / or output current of the AC-DC converter 104. In this embodiment, the feedback circuit 106 provides two feedback signals FB1 and FB2, which may each employ an appropriate signal format such as voltage, current, optical signal, or magnetic signal. For example, the feedback circuit 106 may include one or more voltage divider circuits that divide the output voltage Vout into feedback signals FB1 and FB2 of appropriate voltage levels and output them to the controller 110. In this embodiment, the feedback signals FB1 and FB2 include an output voltage detection signal Vfb, and the output voltage detection signal Vfb is positively correlated with the output voltage Vout, for example, Vfb = A x Vout, where A is an appropriate value less than 1 and greater than 0. In other embodiments, the feedback signals FB1 and FB2 may include an output current detection signal. In another embodiment, the feedback circuit 106 may transmit the same feedback signal as feedback signals FB1 and FB2 to the voltage abnormality protection circuit 118 and the control signal generation circuit 116.

[0012] The controller 110 includes an undervoltage protection circuit 111, a voltage anomaly protection circuit 118, and a control signal generation circuit 116. The undervoltage protection circuit 111 includes a voltage detection circuit 112 and a first timer circuit 114. The undervoltage protection circuit 111 is coupled to the input terminal of the AC-DC converter 104, the voltage anomaly protection circuit 118 is coupled to the feedback circuit 106 and the auxiliary undervoltage detection circuit 120, and the control signal generation circuit 116 is coupled to the undervoltage protection circuit 111 and the voltage anomaly protection circuit 118. The controller 110 is used to generate a corresponding control signal CTRL based on the AC voltage Vac and feedback signals FB1 and FB2.

[0013] The undervoltage protection circuit 111 includes a voltage detection circuit 112 and a first timer circuit 114, the voltage detection circuit 112 being coupled to the AC power supply PWR and the first timer circuit 114. The voltage detection circuit 112 may be implemented by methods such as a comparator circuit, and is used to detect whether the AC voltage Vac is lower than a first predetermined voltage. The first timer circuit 114 may be implemented by methods such as an oscillator circuit or a counter circuit.

[0014] The voltage detection circuit 112 and the first timer circuit 114, when they detect that the duration for which the AC voltage Vac is lower than a first predetermined voltage is longer than a first predetermined time, respectively generate an undervoltage signal Iuv to the control signal generation circuit 116 (for example, by setting the undervoltage signal Iuv to a high potential) so that the control signal generation circuit 116 causes the AC-DC converter 104 to perform a soft start operation. At least one of the voltage detection circuit 112 and the first timer circuit 114 may generate the undervoltage signal Iuv. For example, if the voltage detection circuit 112 detects that the AC voltage Vac is lower than a first predetermined voltage, it causes the first timer circuit 114 to start timing, and if the first timer circuit 114 calculates that the duration for which the voltage is lower than the first predetermined voltage is longer than a first predetermined time, it generates an undervoltage signal Iuv to the control signal generation circuit 116 accordingly. In another embodiment, if the voltage detection circuit 112 detects that the AC voltage Vac is lower than a first predetermined voltage, the voltage detection circuit 112 calculates the duration for which the AC voltage Vac is lower than the first predetermined voltage based on the timing signal of the first timer circuit 114. If the duration for which the AC voltage Vac is lower than the first predetermined voltage is longer than the first predetermined time, the voltage detection circuit 112 accordingly generates an undervoltage signal Iuv to the control signal generation circuit 116.

[0015] The voltage anomaly protection circuit 118 is coupled to the feedback circuit 106 and the auxiliary undervoltage detection circuit 120 and is used to receive the feedback signal FB1 provided by the feedback circuit 106. If the feedback signal FB1 indicates an abnormality in the output voltage, the voltage anomaly protection circuit 118 correspondingly generates a voltage anomaly signal Abn to the control signal generation circuit 116, causing the control signal generation circuit 116 to perform a soft start operation on the AC-DC converter 104. In one embodiment, the voltage anomaly protection circuit 118 includes a comparator circuit used to compare the feedback signal FB1 with a first reference voltage and to determine whether the feedback signal FB1 is lower than the first reference voltage. In another embodiment, the voltage anomaly protection circuit 118 includes two comparator circuits used to compare the feedback signal FB1 with first and second reference voltages, respectively, to determine whether the feedback signal FB1 is lower than the first reference voltage or higher than the second reference voltage, where the first and second reference voltages are the lower and upper limits of a predetermined range. The voltage abnormality protection circuit 118, after the feedback signal FB1 exceeds a predetermined range, sets the control signal generation circuit 116 to generate a corresponding control signal CTRL, thereby causing the AC-DC converter 104 to perform a soft start operation. In one embodiment, when the AC-DC converter 104 is made to perform a soft start operation by detecting the feedback signal FB1 by the voltage abnormality protection circuit 118, the response speed is faster than when the AC-DC converter 104 is made to perform a soft start operation by detecting the AC voltage Vac by the undervoltage protection circuit 111.

[0016] In one embodiment, the control signal generation circuit 116 generates a control signal CTRL correspondingly based on the feedback signal FB2, the voltage abnormality signal Abn, and the undervoltage signal Iuv, thereby generating the output voltage Vout and / or output current required for the AC-DC converter 104.

[0017] The auxiliary undervoltage detection circuit 120 includes an input voltage detection circuit 121, a second timer circuit 123, and a trigger signal circuit 125. The input voltage detection circuit 121 is used to be coupled to the AC power supply PWR to detect whether the AC voltage Vac is lower than a second predetermined voltage. The input voltage detection circuit 121 may be implemented in a manner such as a comparator circuit to detect whether the AC voltage Vac is lower than a second predetermined voltage. The second predetermined voltage may be set to be equal to the first predetermined voltage or to any other appropriate voltage value.

[0018] The second timer circuit 123 is electrically coupled to the input voltage detection circuit 121 and may be implemented in the form of an oscillation circuit, a counting circuit, or the like. The input voltage detection circuit 121 and the second timer circuit 123 may be used to calculate whether the period during which the AC voltage Vac is lower than a second predetermined voltage is longer than a second predetermined time, thereby determining whether a momentary interruption has occurred in the AC power supply PWR. The second predetermined time is shorter than the first predetermined time. The second predetermined time can be set based on the period of the AC voltage Vac. For example, if the AC voltage Vac is a 50 Hz or 60 Hz AC voltage, the second predetermined time can be set to one period (1 / 50 second or 1 / 60 second), respectively.

[0019] The trigger signal circuit 125 is electrically coupled to the input voltage detection circuit 121 and the second timer circuit 123, and based on the outputs of the input voltage detection circuit 121 and / or the second timer circuit 123, changes the signal value of the feedback signal FB1 to trigger the controller 110 to cause the AC-DC converter 104 to execute a soft start function. The operating modes of the input voltage detection circuit 121 and the second timer circuit 123 are similar to those of the voltage detection circuit 112 and the first timer circuit 114. The trigger signal circuit 125 is set by at least one of the input voltage detection circuit 121 and the second timer circuit 123 to change the signal value of the feedback signal FB1. For example, when the period during which the AC voltage Vac is lower than the second predetermined voltage is longer than the second predetermined time, at least one of the input voltage detection circuit 121 and the second timer circuit 123 activates the trigger signal circuit 125, whereby the trigger signal circuit 125 correspondingly changes the signal value of the feedback signal FB1, and further triggers the controller 110 to cause the AC-DC converter 104 to execute a soft start function.

[0020] FIG. 2 is a schematic diagram showing an embodiment of a partial circuit of the power supply 100. As shown in the embodiment of FIG. 2, the trigger signal circuit 125 includes a resistor R3 and a switch S1, and the feedback circuit 106 includes resistors R1 and R2. The feedback circuit 106 divides the output voltage Vout into a feedback signal FB1 at an appropriate voltage level by the resistors R1 and R2.

[0021] In the embodiment of FIG. 2, when the control terminal of switch S1 does not receive the enable signal EN, switch S1 is correspondingly set to non-conductive. When the period during which the AC voltage Vac is lower than the second predetermined voltage is longer than the second predetermined time, at least one of the input voltage detection circuit 121 and the second timer circuit 123 correspondingly generates the enable signal EN. When the control terminal of switch S1 receives the enable signal EN, switch S1 is correspondingly turned on. When switch S1 is turned on, resistors R2 and R3 are connected in parallel, and the signal value of the feedback signal FB1 decreases from the divided voltage value Vout*R2 / (R1+R2) of the original output voltage Vout to Vout*(R2 / / R3) / (R1+R2 / / R3). When the feedback signal FB1 exceeds the predetermined range of the voltage abnormal protection circuit 118, the control signal generation circuit 116 generates the corresponding control signal CTRL by the voltage abnormal protection circuit 118 to cause the AC-DC converter 104 to perform a soft start operation.

[0022] In the above embodiment, when an interruption occurs, the trigger signal circuit 125 rapidly changes the feedback signal FB1 to be lower than the predetermined range of the voltage abnormal protection circuit 118. In other embodiments, when an interruption occurs, the trigger signal circuit 125 rapidly changes the feedback signal FB1 to be higher than the predetermined range of the voltage abnormal protection circuit 118, thereby triggering the controller 110 to cause the AC-DC converter 104 to perform soft start control.

[0023] FIG. 3 is a schematic diagram showing the output voltage Vout and the control signal CTRL in the soft start control according to some embodiments of the present disclosure. In the embodiment of FIG. 3, the control signal generation circuit 116 generates a control signal CTRL in PWM format to control the conduction state of the switch in the AC-DC converter 104. Here, the switch control signal S which is one of the control signals CTRL is described, and the switch control signal among the control signals CTRL can also be implemented in the same or similar manner. When the control signal generation circuit 116 causes the AC-DC converter 104 to perform a soft start operation, the switch control signal S G is described, and the switch control signal among the control signals CTRL can also be implemented in the same or similar manner. When the control signal generation circuit 116 causes the AC-DC converter 104 to perform a soft start operation, the switch control signal S GThe frequency is gradually decreased, and the output voltage Vout is gradually increased from an initial voltage (e.g., 0V) to a predetermined output voltage value Vs. However, in time slots 301 to 303, the switch control signal S G Switching frequency F SW is F max From frequency F startup1 It decreases to, and further the frequency F startup2 It decreases to [value]. Also, when the control signal generation circuit 116 causes the AC-DC converter 104 to perform a soft start operation, the controller uses the switch control signal S G The duty cycle can be kept constant, gradually increased, or gradually decreased, thereby gradually increasing the output voltage Vout from the initial voltage to a predetermined output voltage value Vs, and further preventing damage to elements in the power supply 100 due to the generation of inrush current. In the embodiment shown in Figure 3, when the control signal generation circuit 116 causes the AC-DC converter 104 to perform a soft start operation, the control signal generation circuit 116 maintains a constant duty cycle of the control signal and gradually decreases the frequency of the switch control signal, thereby gradually increasing the output voltage Vout from the initial voltage to a predetermined output voltage value Vs. In another embodiment, when the control signal generation circuit 116 causes the AC-DC converter 104 to perform a soft start operation, the control signal generation circuit 116 maintains a constant frequency of the control signal and gradually increases the duty cycle of the switch control signal, thereby gradually increasing the output voltage Vout from the initial voltage to a predetermined output voltage value Vs. In another embodiment, when the control signal generation circuit 116 causes the AC-DC converter 104 to perform a soft-start operation, the control signal generation circuit 116 gradually decreases the frequency of the control signal and gradually increases the duty cycle of the switch control signal, thereby gradually increasing the output voltage Vout from an initial voltage to a predetermined output voltage value Vs.

[0024] In one embodiment, the undervoltage protection circuit 111, the control signal generation circuit 116, and the voltage abnormality protection circuit 118 are located in the same integrated circuit, while the auxiliary undervoltage detection circuit 120 is located outside the integrated circuit.

[0025] As described above, the power supply 100 of this disclosure has a monitoring mechanism for AC voltage Vac and output voltage Vout, which enables soft-start control when various voltage abnormalities occur. Furthermore, the power supply of this disclosure can be adapted to various different application environments. Therefore, in areas where the input power is unstable, if the AC power is momentarily interrupted, the auxiliary undervoltage detection circuit 120 helps the controller 110 to determine the occurrence of a momentary interruption of the AC power, and causes the AC-DC converter 104 to perform a soft-start operation, thereby preventing malfunction or damage to the load or power converter and further improving the stability of the power supply 100.

[0026] Although the present disclosure has been disclosed as described above by the embodiments, the above embodiments are not limiting to the present disclosure, and those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure; therefore, the scope of protection of the present disclosure is as defined by the appended claims. [Explanation of symbols]

[0027] To make the above and other purposes, features, advantages, and examples of this disclosure clearer and easier to understand, the attached reference numerals are explained below. 100: Power supply 104: AC-DC converter 106: Feedback Circuit 108: Load 110: Controller 111: Undervoltage protection circuit 112: Voltage detection circuit 114: First Timer Circuit 116: Control signal generation circuit 118: Voltage abnormality protection circuit 120: Auxiliary undervoltage detection circuit 121: Input voltage detection circuit 123: Second Timer Circuit 125: Trigger signal circuit 301, 302, 303: Time slots Vac: AC voltage Vout: Output voltage FB1, FB2: Feedback signal Abn: Voltage abnormal signal EN: Enable signal PWR: AC power supply Iuv: Under-voltage signal S1: Switch R1~R3: Resistor F SW : Switching frequency F max 、F startup1 、F startup2 : Frequency Vs: Preset output voltage value CTRL: Control signal S G : Switch control signal

Claims

1. A power supply device for supplying power to a load based on an AC power source, An AC-DC converter is coupled to the AC power supply to convert an AC voltage to a DC voltage, A feedback circuit coupled to the AC-DC converter generates a first feedback signal corresponding to the DC voltage, A low voltage protection circuit for coupling to the aforementioned AC power supply, A control signal generation circuit is coupled to the undervoltage protection circuit and the feedback circuit, which controls the AC-DC converter to convert the AC voltage to the DC voltage, A voltage abnormality protection circuit coupled to the feedback circuit and the control signal generation circuit, An auxiliary undervoltage detection circuit coupled to the AC power supply and the voltage abnormality protection circuit, Includes, The auxiliary undervoltage detection circuit detects that the time during which the AC voltage is lower than a second predetermined voltage is longer than a second predetermined time, and changes the signal value of the first feedback signal, thereby causing the voltage abnormality protection circuit to cause the control signal generation circuit to perform a soft start operation on the AC-DC converter.

2. The power supply according to claim 1, wherein the undervoltage protection circuit detects that the time for which the AC voltage is lower than a first predetermined voltage is longer than a first predetermined time, the control signal generation circuit causes the AC-DC converter to perform the soft start operation, and the first predetermined time is longer than a second predetermined time.

3. The auxiliary undervoltage detection circuit is, An input voltage detection circuit for coupling to the aforementioned AC power supply, A timer circuit coupled to the input voltage detection circuit, A trigger signal circuit coupled to the input voltage detection circuit and the timer circuit, It further includes, The power supply according to claim 1, wherein the input voltage detection circuit and the timer circuit detect that the time during which the AC voltage is lower than the second predetermined voltage is longer than the second predetermined time, the trigger signal circuit changes the signal value of the first feedback signal, and the voltage abnormality protection circuit causes the control signal generation circuit to perform the soft start operation on the AC-DC converter.

4. The feedback circuit includes a voltage divider circuit for dividing the DC voltage into the first feedback signal. The trigger signal circuit includes a switch and a resistor, The power supply according to claim 3, wherein when the input voltage detection circuit and the timer circuit detect that the time during which the AC voltage is lower than the second predetermined voltage is longer than the second predetermined time, at least one of the input voltage detection circuit and the timer circuit turns on the switch, thereby connecting the resistor in parallel with the voltage divider circuit and changing the signal value of the first feedback signal.

5. The power supply according to any one of claims 1 to 4, wherein the control signal generation circuit generates a switch control signal, and when the AC-DC converter performs the soft start operation, the control signal generation circuit performs at least one of gradually decreasing the switching frequency of the switch control signal and gradually increasing the duty cycle of the switch control signal.

6. A method for operating a power supply that supplies power to a load based on an AC power source, wherein the power supply includes an AC-DC converter, a feedback circuit, an undervoltage protection circuit, a control signal generation circuit, a voltage anomaly protection circuit, and an auxiliary undervoltage detection circuit, wherein the AC-DC converter is coupled to the AC power source, the feedback circuit is coupled to the AC-DC converter, the undervoltage protection circuit is coupled to the AC power source, the control signal generation circuit is coupled to the undervoltage protection circuit and the feedback circuit, the voltage anomaly protection circuit is coupled to the feedback circuit and the control signal generation circuit, the auxiliary undervoltage detection circuit is coupled to the voltage anomaly protection circuit, and the method for operating the power supply is: The steps include: controlling the AC-DC converter so that the control signal generation circuit converts the AC voltage to a DC voltage; The feedback circuit comprises the steps of generating a first feedback signal correspondingly based on the DC voltage, The auxiliary undervoltage detection circuit, when it detects that the AC voltage is lower than the second predetermined voltage for a period of time longer than the second predetermined time, changes the signal value of the first feedback signal, and the voltage abnormality protection circuit causes the control signal generation circuit to perform a soft start operation on the AC-DC converter. Instructions for operating a power supply unit, including the power supply unit itself.

7. The undervoltage protection circuit further includes the step of causing the control signal generation circuit to perform the soft-start operation on the AC-DC converter if it detects that the AC voltage has been below a first predetermined voltage for a longer period of time than a first predetermined time. The operation method according to claim 6, wherein the first predetermined time is longer than the second predetermined time.

8. The auxiliary undervoltage detection circuit further includes an input voltage detection circuit coupled to the AC power supply, a timer circuit coupled to the input voltage detection circuit, and a trigger signal circuit coupled to the input voltage detection circuit and the timer circuit, and in the operation method, The operating method according to claim 6, further comprising the step that when the input voltage detection circuit and the timer circuit detect that the time during which the AC voltage is lower than the second predetermined voltage is longer than the second predetermined time, the trigger signal circuit changes the signal value of the first feedback signal, and the voltage abnormality protection circuit causes the control signal generation circuit to perform the soft start operation on the AC-DC converter.

9. The feedback circuit includes a voltage divider circuit, the trigger signal circuit includes a switch and a resistor, and the operation method is The voltage divider circuit performs the steps of dividing the DC voltage into the first feedback signal, The operating method according to claim 8, further comprising the steps of: when the input voltage detection circuit and the timer circuit detect that the time during which the AC voltage is lower than the second predetermined voltage is longer than the second predetermined time, at least one of the input voltage detection circuit and the timer circuit turns on the switch to connect the resistor in parallel with the voltage divider circuit and change the signal value of the first feedback signal.

10. The control signal generation circuit generates a switch control signal, When the AC-DC converter performs the soft-start operation, the control signal generation circuit performs at least one of the following steps: gradually lowering the switching frequency of the switch control signal and gradually increasing the duty cycle of the switch control signal. The operating method according to any one of claims 6 to 9, further comprising:

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