TWI449315B - Fly back power supply apparatus and digital control circuit and driving method thereof - Google Patents

Description

Digital control circuit and driving method for flyback power supply device

The present invention relates to a flyback power supply device, and more particularly to a digital control circuit and a driving method for a flyback power supply device.

At present, as a power supply device for AC/DC conversion, it is mainly divided into two types of linear and switched power supply devices. The linear power supply device uses a large current transformer, which is bulky and heavy, and cannot be directly It is mounted on the board and has low conversion efficiency. Due to the advancement of the process technology of the power switching device and the change of various converter circuit topologies, the switching power supply has become the main technology of the power supply. In particular, today's computer, electrical equipment and electronic equipment, etc., continue to innovate, all require the stability, high efficiency and low cost of the power supply, making the switching power supply the mainstream of the power supply technology, the common switching power supply The device has a push pull type, a fly back type, and the like.

Wherein, the front end of the traditional Fly-Back power supply circuit is a pulse width modulation signal generated by a Pulse Width Modulation IC (PWM IC) to control the transformer of the latter stage, wherein the pulse The width modulation signal determines the duty cycle of the frequency generated by the resistor and capacitor. The control signal generated by this method not only has a frequency that is not very accurate, but usually the working cycle can only reach about 50%, which causes the reverse power supply circuit to fail to output a high voltage that meets the actual application requirements.

The invention provides a flyback power supply device and a digital control circuit and a driving method thereof, which can enable a flyback power supply device to output a high voltage that meets practical application requirements.

The invention provides a digital control circuit for a flyback power supply device, comprising a cycle counting unit, a first comparison unit, a second comparison unit and a control signal generation unit. The loop counting unit repeatedly counts from a minimum preset value to a maximum preset value to generate a loop count value. The first comparison unit is coupled to the loop counting unit to determine whether the current loop count value of the loop counting unit is equal to an activation setting value to obtain a first comparison result. The second comparison unit is coupled to the cycle counting unit to determine whether the current cycle count value of the cycle counting unit is equal to a duty cycle setting value to obtain a second comparison result. The control signal generating unit is coupled to the first comparing unit and the second comparing unit, and outputs a control signal according to the first comparison result and the second comparison result to control the conductive state of the power switching element of one of the flyback power supply devices.

The invention further provides a flyback power supply device comprising a transformer, a power switching element, a rectifying diode, a capacitor and a digital control circuit. The transformer has a primary side coil and a secondary side coil, and the first end of the primary side coil is coupled to an input voltage. The power switching element is coupled between the second end of the primary side coil and a ground. The anode and the cathode are respectively coupled to the first end of the secondary side coil and the output end of the flyback power supply device, and the second end of the secondary side coil is coupled to the ground. The capacitor is coupled between the output of the flyback power supply device and the ground. The digital control circuit is coupled to the power switching element. The digital control circuit includes a loop counting unit, a first comparing unit, a second comparing unit, and a control signal generating unit. The loop counting unit repeatedly counts from a minimum preset value to a maximum preset value to generate a loop count value. The first comparison unit is coupled to the loop counting unit to determine whether the current loop count value of the loop counting unit is equal to an activation setting value to obtain a first comparison result. The second comparison unit is coupled to the cycle counting unit to determine whether the current cycle count value of the cycle counting unit is equal to a duty cycle setting value to obtain a second comparison result. The control signal generating unit is coupled to the first comparing unit and the second comparing unit, and outputs a control signal according to the first comparison result and the second comparison result to control the conductive state of the power switching element of one of the flyback power supply devices.

In an embodiment of the invention, the control signal generating unit further detects whether the duty cycle set value is changed. If the duty cycle set value is changed, the duty cycle set value is updated to the changed duty cycle set value.

In an embodiment of the invention, when the current cycle count value of the cycle counting unit is equal to the startup set value, the power switching element is controlled by the control signal, and the current cycle count value of the cycle counting unit is equal to the duty cycle set value. When the power switching element is controlled by the control signal, it is turned off.

In an embodiment of the present invention, the digital control circuit of the flyback power supply device further includes a temporary storage unit coupled to the second comparison unit and the control signal generating unit for temporarily storing the duty cycle setting value. .

The invention also proposes a driving method of the flyback power supply device, which comprises the following steps. The repetition is counted from a minimum preset value to a maximum preset value to generate a cycle count value. It is determined whether the current cycle count value is equal to the minimum preset value-starting set value to obtain a first comparison result. It is determined whether the current cycle count value is equal to a duty cycle set value to obtain a second comparison result. And outputting a control signal according to the first comparison result and the second comparison result to control an on state of the power switching element of one of the flyback power supply devices.

In an embodiment of the present invention, the driving method of the flyback power supply device further includes detecting whether the duty cycle setting value is changed, and if the duty cycle setting value is changed, updating the duty cycle setting value to change. The duty cycle setting afterwards.

In an embodiment of the invention, the step of outputting the control signal according to the first comparison result and the second comparison result to control the conduction state of the power switching element includes the following steps. It is judged whether the current cycle count value is equal to the startup set value or equal to the duty cycle set value. If the current cycle count value is equal to the start setpoint, the power switch element is turned on by the control signal. If the current cycle count value is equal to the duty cycle set value, the power switch element is turned off by the control signal.

In an embodiment of the invention, the working cycle setting value is greater than a minimum preset value and less than a maximum preset value.

In an embodiment of the invention, the minimum preset value is 0, and the maximum preset value is 100.

Based on the above, the present invention determines the duty cycle of the control signal according to the duty cycle setting value input by the user and the cycle count value of the cycle counting unit count, thereby adjusting the output voltage of the flyback power supply device, so that the flyback power supply device It is possible to output a high voltage that meets the needs of the actual application.

The above described features and advantages of the present invention will be more apparent from the following description.

FIG. 1 is a schematic diagram of a flyback power supply device according to an embodiment of the invention. Referring to FIG. 1 , the flyback power supply device 100 includes a transformer 102 , a power switching component 104 , a rectifying diode D1 , a capacitor C1 , and a digital control circuit 106 . The transformer 102 has a primary side coil 102A and a secondary side coil 102B. The first end and the second end of the primary side coil 102A are respectively coupled to an input voltage Vin and a power switching element 104. The first end and the second end of the secondary side coil 102B are respectively coupled to the anode of the rectifying diode D1 and the ground GND, and the cathode of the rectifying diode D1 is coupled to the output end of the flyback power supply device 100. The capacitor C1 is coupled between the output end of the flyback power supply device 100 and the ground GND. In addition, the power switching element 104 is further coupled to the digital control circuit 106 and the ground GND. The power switching element 104 can be implemented, for example, by a Bipolar Junction Transistor (BJT) or a Field Effect Transistor (FET), but is not limited thereto.

The digital control circuit 106 is configured to generate an adjustable period of control signal S1 according to a duty cycle setting value X input by the user to control the conduction state of the power switching element 104. The duty cycle of the control signal S1 varies depending on the value of the duty cycle setting value X input by the user. For example, it can be designed that when the value of the input duty cycle setting value X is Y, the duty cycle of the control signal S1 is Y%, where Y is a natural number and 1≦Y≦99.

The primary side coil 102A of the transformer 102 has the functions of isolation, voltage transformation and energy storage. When the power switching element 104 is in the conducting state, the voltage will be supplied to the primary side coil 102A, and the primary side coil 102A will sense and store energy while being at In the non-conducting state, the stored energy is transferred to the secondary side coil 102B. The rectifying diode D1 is configured to convert the voltage of the secondary side coil 102B into a direct current, and then filter the chopping component through the capacitor C1 to output the current I1 to an output load (not shown), and the flyback power supply device 100 The output produces an output voltage Vout. When the power switching element 104 is in the on state, the amount of induced current change ΔI ⁺ on the primary side coil 102A can be as follows:

Where L is the inductance value of the primary side coil 102A (also equal to the inductance value of the secondary side coil 102B), and T ₁ is the conduction time of the power switching element 104. Further, when the power switching element 104 is in a non-conducting state, the induced current variation on the secondary side coil 102B △ I ^- may be as shown in the following equation:

Where T ₂ is the non-conduction time of the power switching element 104. Since the induced current variation of the primary side coil 102A △ I ⁺ will equal the amount of change in the induced current on the secondary side coil 102B △ I ^-, and therefore the output voltage Vout can be derived as shown in the following formula:

Where D represents the duty cycle of the control signal S1. It can be seen that the output voltage Vout of the flyback power supply device 100 can be adjusted by adjusting the duty cycle of the control signal S1. That is to say, the user can adjust the output voltage Vout of the flyback power supply device 100 by adjusting the duty cycle setting value X of the input digital control circuit 106. For example, suppose the value of the input voltage Vin is 110 volts (V), and the duty cycle setting value X input by the user is 99. At this time, the duty cycle of the control signal S1 is adjusted to 99%, that is, D The value is equal to 0.99, and the value of the output voltage Vout is 10890V. As described above, in the embodiment, by inputting the duty cycle setting value X of the digital control circuit 106, the duty cycle of the control signal S1 can be arbitrarily adjusted, thereby adjusting the output voltage Vout of the flyback power supply device 100, and improving the conventional technology. When the pulse width modulation signal is used as the power switching element 104 control signal, it is impossible to output a high voltage that meets the practical application requirements.

In detail, the implementation of the digital control circuit 106 can be as shown in FIG. 2. FIG. 2 is a schematic diagram of a digital control circuit according to an embodiment of the present invention. Referring to FIG. 2, in the embodiment, the digital control circuit 106 includes a loop counting unit 202, a first comparing unit 204, a second comparing unit 206, and a control signal generating unit 208. The loop counting unit 202 is coupled to the first comparing unit 204 and the second comparing unit 206. The control signal generating unit 208 is coupled to the first comparing unit 204 and the second comparing unit 206. The loop counting unit 202 is configured to count from a minimum preset value to a maximum preset value according to a reset signal SR1 and a clock signal CLK to generate a loop count value. For example, in this embodiment, the minimum preset value is 0, and the maximum preset value is 100, that is, the loop counting unit 202 can count from 0 to 100, and then return to 0 to start counting again, so that the loop is continuously circulated. Repeat the count. In addition, the period of the above-mentioned clock signal CLK can be determined, for example, by a quartz oscillator. In addition, the first comparison unit 204 receives an activation set value W, and the second comparison unit 206 receives a duty cycle set value X input by the user. The startup set value W is generated by the digital control circuit 106 itself. In this embodiment, the startup setting value is equal to the minimum preset value, that is, the startup setting value is 0 in the embodiment, but the actual application is not limited thereto, and the user can set the size of the startup setting value according to the actual situation.

The first comparison unit 204 is configured to compare the current cycle count value of the loop counting unit 202 with the startup set value W to determine whether the current cycle count value of the loop counting unit 202 is equal to the startup set value W, and obtain a first comparison result. The second comparison unit 206 is configured to compare the current cycle count value of the cycle counting unit 202 with the duty cycle set value X input by the user to determine whether the current cycle count value of the cycle counting unit 202 is equal to the duty cycle input by the user. Set the value X to get a second comparison result. In addition, the control signal generating unit 208 outputs the control signal S1 to the power switching element 104 according to the first comparison result and the second comparison result to control the conduction state of the power switching element 104.

When the current cycle count value of the cycle counting unit 202 is equal to the startup set value W, the control signal generating unit 208 outputs a digital high logic level at the next cycle count value (ie, when the next clock signal CLK comes). The control signal S1, the power switching element 104 will thus be controlled by the control signal S1, and when the current cycle count value of the cycle counting unit 202 is equal to the duty cycle setting value X input by the user, the control signal generating unit 208 At the next cycle count value (i.e., when the next clock signal CLK comes), a digital low logic level control signal S1 is output, and the power switching element 104 is thus controlled to be disconnected by the control signal S1. In other words, when the cycle count value is greater than the startup set value W and less than or equal to the duty cycle set value X, the power switching element 104 is turned on, and when the cycle count value is greater than the duty cycle set value X and less than or equal to the maximum preset value, Power switching element 104 is open. Since the duty cycle of the control signal S1 is less than 100%, the duty cycle setting value X input by the user must be greater than the minimum preset value and less than the maximum preset value. In other words, the duty cycle setting value X must be greater than 0 and less than 100. That is, the value of 1≦X≦99 can be received by the digital control circuit 106, otherwise X will be regarded as an invalid value and is not accepted by the digital control circuit 106. In addition, after each control signal generating unit 208 outputs the control signal S1 according to the first comparison result and the second comparison result, the control signal generating unit 208 detects whether the duty cycle setting value X input by the user changes, if the work The cycle set value X is changed, and the control signal generating unit 208 updates the duty cycle set value X received by the second comparing unit 206 to the changed duty cycle set value X to cause the output voltage Vout of the flyback power supply device 100. It can be changed according to the change of the duty cycle setting value X, and the user can adjust the output voltage Vout of the flyback power supply device 100 at any time according to actual needs.

FIG. 3 is a schematic diagram showing the waveform of the loop count value and the control signal S1 in the embodiment of FIG. 2. Referring to FIG. 3, for example, it is assumed that the duty cycle setting value X input by the user in the embodiment of FIG. 2 is 6, and the power switching element 104 is in an on state when the control signal is at the high logic level. When the current cycle count value of the loop counting unit is 0, since it is equal to the startup set value W, the control signal S1 will output a digit when the next clock signal CLK comes (that is, when the loop count value is equal to 1). The logic level is as shown in FIG. 3. When the loop count value is equal to 1, the control signal S1 outputs a digital high logic level, that is, the power switching element 104 is controlled to be turned on. Similarly, when the loop counting unit counts to 6, since the current loop count value is equal to the duty cycle set value X, the control signal S1 will be output when the next clock signal CLK comes (that is, when the loop count value is equal to 7), the output A digital low logic level, as can be seen from FIG. 3, when the cycle count value is equal to 7, the control signal S1 outputs a digital low logic level, that is, the power switching element 104 is controlled to be off. It can be seen that during the period from 0 to 100 in each cycle counting unit 202, the control signal S1 is at a high logic level during the period of 1 to 6, that is, the duty cycle of the control signal S1 is 6%. Similarly, if the user changes the duty cycle setting value X to another value (for example, 78), the duty cycle of the control signal S1 also changes to the corresponding duty cycle (78%).

4 is a schematic diagram of a digital control circuit according to another embodiment of the present invention. Referring to FIG. 4, the digital control circuit 400 of the present embodiment is different from the digital control circuit 106 of FIG. 2 in that the digital control circuit 400 of the present embodiment further includes a temporary storage unit 402 coupled to the second comparison unit. 206 and control signal generating unit 208. The temporary storage unit 402 is configured to store the duty cycle setting value X input by the user, the second comparison unit 206 obtains the duty cycle setting value X from the temporary storage unit 402, and the first comparison unit 204 receives a startup setting value W to perform the current A comparison between the cycle count value, the start setpoint value W, and the duty cycle setpoint value X. The startup set value W is generated by the digital control circuit 400 itself. In this embodiment, the startup set value W is from the loop counting unit 202 and is equal to the minimum preset value, that is, the startup setting value is 0 in this embodiment. In addition, the control signal generating unit 208 also determines whether the duty cycle setting value X input by the user is changed by detecting the duty cycle setting value X stored in the temporary storage unit 402 to change the work used by the second comparing unit 206. The cycle set value X is updated to the duty cycle set value X after the change. In addition to the above differences, the operation of the digital control circuit 400 is similar to the operation of the digital control circuit 106. Those skilled in the art should be able to infer the operation of the digital control circuit 400 by the teachings of the above embodiments, and therefore Let me repeat.

FIG. 5 is a flow chart showing a driving method of a flyback power supply device according to an embodiment of the present invention. Referring to FIG. 5, in summary, the driving method of the flyback power supply device may include the following steps. First, the counting from a minimum preset value to a maximum preset value is repeated to generate a loop count value (step S502). Next, the current cycle count value and a start set value are compared to determine whether the current cycle count value is equal to the start set value, and a first comparison result is obtained (step S504). The startup set value is equal to the minimum preset value. Then, the current cycle count value is compared with a duty cycle set value input by the user to determine whether the current cycle count value is equal to the duty cycle set value input by the user, and a second comparison result is obtained (step S506). The work cycle set value is greater than the minimum preset value and less than the maximum preset value. Then, a control signal is output according to the first comparison result and the second comparison result to control the conduction state of the power switching element of one of the flyback power supply devices (step S508). Then, returning to step S504, a comparison between the current cycle count value and the startup set value is performed.

In detail, the step of step S508 includes the following steps. First, it is judged that the current cycle count value is equal to the startup set value (state A), or equal to the duty cycle set value (state B) (step S510), and if the current cycle count value is equal to the startup set value, then in the next cycle The count value (that is, when the next clock signal CLK comes) starts to set the power switching element to the on state (step S512), and returns to step S504 to perform a comparison between the current cycle count value and the startup set value; If the current cycle count value is equal to the duty cycle set value, the power switch element is set to the non-conduction state at the next cycle count value (ie, when the next clock signal CLK comes) (step S514), and proceeds to step S504. , a comparison between the current cycle count value and the start set value.

6 is a flow chart showing a driving method of a flyback power supply device according to another embodiment of the present invention. Referring to FIG. 6 , the driving method of the flyback power supply device of the embodiment is different from the driving method of the flyback power supply device of the embodiment of FIG. 5 in that the embodiment further performs step S602 after step S508. , that is, whether the detection duty cycle setting value is changed (step S602), if the duty cycle setting value is not changed, then returning to step S504, performing a comparison between the current cycle count value and the startup setting value; When the set value is changed, the duty cycle set value is updated to the changed duty cycle set value (step S604), and the process returns to step S504 to perform a comparison between the current cycle count value and the start set value. In this way, the output voltage of the flyback power supply device changes with the change of the set value of the duty cycle, so that the user can adjust the output voltage of the flyback power supply device at any time according to actual needs.

In summary, the present invention utilizes the first and second comparison units to compare the startup set value, the user-entered duty cycle set value, and the loop count value of the loop count unit count, and determines the logic of the control signal based on the comparison result. The level is adjusted to adjust the duty cycle of the control signal, so that the flyback power supply device can output a high voltage that meets the actual application requirements.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the invention, and any one of ordinary skill in the art can make some modifications and refinements without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims.

100. . . Flyback power supply device

102. . . transformer

104. . . Power switching element

106, 400. . . Digital control circuit

102A. . . Primary side coil

102B. . . Secondary side coil

202. . . Cycle counting unit

204. . . First comparison unit

206. . . Second comparison unit

208. . . Control signal generating unit

402. . . Staging unit

D1. . . Rectifier diode

C1. . . capacitance

Vin. . . Input voltage

GND. . . Ground

S1. . . Control signal

X. . . Work cycle setting

Vout. . . The output voltage

SR1. . . Reset signal

CLK. . . Clock signal

S502~S514, S602~S604. . . Driving method steps of the flyback power supply device

FIG. 1 is a schematic diagram of a flyback power supply device according to an embodiment of the invention.

2 is a schematic diagram of a digital control circuit according to an embodiment of the invention.

FIG. 3 is a schematic diagram showing the waveform of the loop count value and the control signal S1 in the embodiment of FIG. 2.

4 is a schematic diagram of a digital control circuit according to another embodiment of the present invention.

FIG. 5 is a flow chart showing a driving method of a flyback power supply device according to an embodiment of the present invention.

6 is a flow chart showing a driving method of a flyback power supply device according to another embodiment of the present invention.

106. . . Digital control circuit

202. . . Cycle counting unit

204. . . First comparison unit

206. . . Second comparison unit

208. . . Control signal generating unit

S1. . . Control signal

X. . . Work cycle setting

SR1. . . Reset signal

CLK. . . Clock signal

Claims (20)

A digital control circuit for a flyback power supply device includes: a cycle counting unit that repeats counting from a minimum preset value to a maximum preset value to generate a cycle count value; a first comparison unit coupled to the a loop counting unit, comparing the current loop count value of the loop counting unit with a starting set value to obtain a first comparison result; a second comparing unit coupled to the loop counting unit, comparing the current loop counting unit a cycle count value and a duty cycle set value to obtain a second comparison result; and a control signal generating unit coupled to the first comparison unit and the second comparison unit, based only on the first comparison result and the second The comparison result outputs a control signal to control the conduction state of the power switching element of one of the flyback power supply devices. The digital control circuit of the flyback power supply device of claim 1, wherein the control signal generating unit further detects whether the duty cycle setting value is changed, and if the duty cycle setting value is changed, The duty cycle set value is updated to the duty cycle set value after the change. The digital control circuit of the flyback power supply device of claim 1, wherein the control signal generating unit further determines that the current cycle count value is equal to the start according to the first comparison result and the second comparison result. The set value is also equal to the set value of the duty cycle to output the control signal, wherein the current cycle count value of the loop counting unit, etc. When the set value is started, the power switching element is controlled by the control signal and is turned on at the next cycle count value. When the current cycle count value of the cycle counting unit is equal to the set value of the duty cycle, the power switch The component is controlled by the control signal and is turned off at the next cycle count value. The digital control circuit of the flyback power supply device of claim 1, wherein the duty cycle set value is greater than the minimum preset value and less than the maximum preset value. The digital control circuit of the flyback power supply device of claim 4, wherein the minimum preset value is 0, and the maximum preset value is 100. The digital control circuit of the flyback power supply device of claim 1, wherein the startup setting value is equal to the minimum preset value. The digital control circuit of the flyback power supply device of claim 1, further comprising: a temporary storage unit coupled to the second comparison unit and the control signal generating unit for temporarily storing the duty cycle setting value . A flyback power supply device includes: a transformer having a primary side coil and a secondary side coil, the first end of the primary side coil being coupled to an input voltage; and a power switching element coupled to the primary a second end of the side coil and a ground; a rectifying diode, wherein the anode and the cathode are respectively coupled to the first end of the secondary side coil and the output end of the flyback power supply device, the secondary side The second end of the coil is coupled to the ground; a capacitor coupled between the output end of the flyback power supply device and the ground; and a digital control circuit coupled to the power switching element, the digital control circuit comprising: a cycle counting unit, repeating from a minimum The preset value is counted to a maximum preset value to generate a loop count value; a first comparison unit is coupled to the loop count unit, and compares the current loop count value of the loop count unit with an activation set value to obtain a first comparison result; a second comparison unit coupled to the cycle counting unit, comparing the current cycle count value of the cycle counting unit with a duty cycle set value to obtain a second comparison result; and a control signal generation The unit is coupled to the first comparison unit and the second comparison unit, and outputs a control signal according to the first comparison result and the second comparison result to control conduction of one of the power switching elements of the flyback power supply device. status. The flyback power supply device of claim 8, wherein the control signal generating unit further detects whether the duty cycle setting value is changed, and if the duty cycle setting value is changed, setting the duty cycle The value is updated to the set value of the duty cycle after the change. The control signal generating unit further determines, according to the first comparison result and the second comparison result, that the current cycle count value is equal to the startup setting value, as in the flyback power supply device of claim 8 Or equal to the set value of the duty cycle to output the control signal, wherein the current cycle count value of the loop counting unit is equal to the startup set value When the power switching element is controlled by the control signal and is turned on at the next cycle count value, when the current cycle count value of the cycle counting unit is equal to the duty cycle set value, the power switch element is controlled by the The control signal is turned off at the next cycle count value. The flyback power supply device of claim 8, wherein the duty cycle setting value is greater than the minimum preset value and less than the maximum preset value. The flyback power supply device of claim 11, wherein the minimum preset value is 0, and the maximum preset value is 100. The flyback power supply device of claim 8, wherein the startup setting value is equal to the minimum preset value. The flyback power supply device of claim 8, further comprising: a temporary storage unit coupled to the second comparison unit and the control signal generating unit to store the duty cycle setting value. A driving method of a flyback power supply device includes: repeating counting from a minimum preset value to a maximum preset value to generate a cycle count value; comparing the current cycle count value with a start set value to obtain a first comparison result; comparing the current cycle count value with a duty cycle set value to obtain a second comparison result; outputting a control signal according to the first comparison result and the second comparison result to control the flyback The conduction state of the power switching element of one of the power supply devices. The driving method of the flyback power supply device of claim 15, further comprising: detecting whether the working cycle setting value is changed, and if the working cycle setting value is changed, setting the working cycle setting value Updated to the duty cycle setting after the change. The driving method of the flyback power supply device according to claim 15, wherein the step of outputting the control signal according to the first comparison result and the second comparison result to control the conduction state of the power switching element comprises: Determining, according to the first comparison result and the second comparison result, that the current cycle count value is equal to the startup setting value, or equal to the duty cycle setting value; if the current cycle counting value is equal to the startup setting value, The power switching element is initially set to an on state at a next cycle count value; and if the current cycle count value is equal to the duty cycle set value, the power switching element is initially set to a non-conducting state at a next cycle count value. The driving method of the flyback power supply device according to claim 15, wherein the duty cycle setting value is greater than the minimum preset value and less than the maximum preset value. The driving method of the flyback power supply device according to claim 18, wherein the minimum preset value is 0, and the maximum preset value is 100. The driving method of the flyback power supply device according to claim 15, wherein the startup setting value is equal to the minimum preset value.