Power supply method, power supply circuit, and isolated switching power supply using the same

Abstract

The application discloses a power supply method, a power supply circuit and an isolation type switching power supply applying the same. The technical scheme of the embodiment of the application detects the drain voltage on the drain pin of the secondary side control chip and the power supply voltage range on the power supply pin, and controls the power supply voltage to change according to the drain voltage and the power supply voltage range, so as to realize self-power supply, reduce power supply loss and improve system efficiency.

Description

Technical Field

[0001] This invention relates to power electronics technology, specifically to power supply methods, power supply circuits, and isolated switching power supplies using the same. Background Technology

[0002] The widespread application of isolated switching power supplies in power electronics has driven the rapid development of various control chips. For isolated switching power supplies, the power supply method of the secondary-side control chip is crucial, such as secondary-side synchronous rectification control chips and secondary-side protocol control chips. In existing technologies, the secondary-side control chip is directly powered by the output voltage of the isolated switching power supply. However, this power supply method is inflexible, as the secondary-side control chip can only be connected to the lower level of the secondary side of the isolated switching power supply, limiting its application range. Alternatively, the secondary-side control chip can be powered by pulsed supply, allowing it to be connected to either the upper or lower level of the secondary side of the isolated switching power supply. However, this power supply method suffers from high losses and low efficiency. Summary of the Invention

[0003] In view of this, embodiments of the present invention provide a power supply method and power supply circuit for isolated switching power supplies to reduce power supply losses and improve system efficiency.

[0004] According to a first aspect of the present invention, a power supply method for an isolated switching power supply is provided. The isolated switching power supply includes a secondary-side control chip, the secondary-side control chip including a drain pin, a power supply pin, and a reference ground pin. The power supply method includes:

[0005] Detect the drain voltage on the drain pin and the power supply voltage on the power supply pin;

[0006] When the secondary control chip is in normal startup state, the range of the power supply voltage is determined; and

[0007] The power supply voltage is controlled to vary according to the range of the drain voltage and the power supply voltage, so as to supply power to the secondary control chip.

[0008] Preferably, when the supply voltage is not greater than the first threshold, the supply voltage is controlled to be boosted.

[0009] Preferably, when the supply voltage is greater than a first threshold and less than a second threshold, the supply voltage is controlled to be boosted during the period when the drain voltage is not greater than the drain reference value.

[0010] Preferably, when the supply voltage reaches the second threshold, the supply voltage reaches its maximum value and remains unchanged.

[0011] Preferably, the power supply pin is coupled to the reference ground pin via a first capacitor.

[0012] Preferably, the secondary-side control chip includes a rectifier diode, the drain pin is coupled to the drain of the rectifier diode, and the power supply pin and the reference ground pin are coupled to the source of the rectifier diode.

[0013] According to a second aspect of the present invention, a power supply circuit is provided for use in an isolated switching power supply, the isolated switching power supply including a secondary-side control chip, the secondary-side control chip including a drain pin, a power supply pin, and a reference ground pin. The power supply circuit is configured to detect the drain voltage on the drain pin and the power supply voltage on the power supply pin, and determine the range of the power supply voltage; when the secondary-side control chip is in a normal startup state, the power supply circuit controls the power supply voltage to vary according to the range of the power supply voltage to supply power to the secondary-side control chip.

[0014] Preferably, when the supply voltage is not greater than the first threshold, the control circuit controls the supply voltage to be boosted.

[0015] Preferably, when the supply voltage is greater than a first threshold and less than a second threshold, the control circuit controls the supply voltage to be boosted during the period when the drain voltage is not greater than the drain reference value.

[0016] Preferably, when the power supply voltage reaches the second threshold, the power supply circuit controls the power supply voltage to remain unchanged.

[0017] Preferably, when the drain voltage reaches the drain reference value, the supply voltage is not increased.

[0018] Preferably, the secondary-side control chip includes a first capacitor, with a first end coupled to the power supply pin and a second end coupled to the reference ground pin.

[0019] Preferably, the power supply circuit includes:

[0020] Linear voltage regulator circuit, and

[0021] A switch is coupled between the output terminal of the linear regulator circuit and the power supply pin to control the linear regulator circuit to generate the power supply voltage.

[0022] According to a third aspect of the present invention, an isolated switching power supply is provided, comprising:

[0023] A transformer, comprising a primary winding and at least one secondary winding; and

[0024] The secondary-side control chip includes a drain pin, a power supply pin, and a reference ground pin; and

[0025] Any of the power supply circuits described in the first aspect, wherein the power supply circuit is integrated within the secondary control chip.

[0026] Preferably, the isolated switching power supply includes a rectifier diode, with a first end coupled to the secondary winding and a second end coupled to a high-potential terminal of the output of the isolated switching power supply, wherein the drain pin is coupled to the second end of the rectifier diode, the power supply pin is coupled to the reference ground pin through a first capacitor, and the reference ground pin is coupled to the first end of the rectifier diode.

[0027] Preferably, the isolated switching power supply includes a rectifier diode, with a first end coupled to the secondary winding and a second end coupled to a low-potential terminal of the output terminal of the isolated switching power supply, wherein the drain pin is coupled to the first end of the rectifier diode, the power supply pin is coupled to the reference ground pin through a first capacitor, and the reference ground pin is coupled to the second end of the rectifier diode.

[0028] The technical solution of this invention detects the drain voltage on the drain pin of the secondary control chip and the power supply voltage range on the power supply pin, and controls the power supply voltage to change according to the drain voltage and the power supply voltage range, so as to achieve self-powering, reduce power supply loss, and improve system efficiency. Attached Figure Description

[0029] The above and other objects, features and advantages of the present invention will become clearer from the following description of embodiments of the invention with reference to the accompanying drawings, in which:

[0030] Figure 1 This is a circuit block diagram of the secondary control chip according to the first embodiment of the present invention;

[0031] Figure 2 This is a circuit block diagram of an isolated switching power supply according to the first embodiment of the present invention;

[0032] Figure 3 This is a circuit block diagram of an isolated switching power supply according to a second embodiment of the present invention;

[0033] Figure 4 This is a circuit diagram of the power supply circuit according to an embodiment of the present invention;

[0034] Figure 5 This is a waveform diagram of the power supply circuit according to the first embodiment of the present invention;

[0035] Figure 6 This is a waveform diagram of the power supply circuit according to the second embodiment of the present invention;

[0036] Figure 7 This is a waveform diagram of the power supply circuit according to the third embodiment of the present invention;

[0037] Figure 8 This is a flowchart of a power supply method according to an embodiment of the present invention. Detailed Implementation

[0038] The present invention is described below based on embodiments, but the invention is not limited to these embodiments. In the detailed description of the invention below, certain specific details are described in detail. Those skilled in the art will fully understand the invention even without these details. To avoid obscuring the essence of the invention, well-known methods, processes, flows, elements, and circuits are not described in detail.

[0039] Furthermore, those skilled in the art should understand that the accompanying drawings provided herein are for illustrative purposes only and are not necessarily drawn to scale.

[0040] Furthermore, it should be understood that in the following description, "circuit" refers to a conductive loop consisting of at least one element or sub-circuit connected by electrical or electromagnetic connections. When an element or circuit is said to be "connected" to another element or "connected" between two nodes, it can be directly coupled or connected to another element, or there may be intermediate elements. The connection between elements can be physical, logical, or a combination thereof. Conversely, when an element is said to be "directly coupled to" or "directly connected" to another element, it means that there are no intermediate elements between them.

[0041] Unless the context explicitly requires it, the words "comprising," "including," and similar terms throughout the specification and claims should be interpreted as encompassing rather than being exclusive or exhaustive; that is, meaning "including but not limited to."

[0042] In the description of this invention, it should be understood that the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0043] Figure 1 This is a circuit block diagram of the secondary-side control chip according to the first embodiment of the present invention. Figure 1As shown, the secondary-side control chip 100 is applied to an isolated switching power supply and includes a drain pin (DRAIN), a power supply pin (VDD), and a reference ground pin (GND). For example, the secondary-side control chip 100 can be a synchronous rectification control chip used to drive and control the switching on or off of the synchronous rectification power in the isolated switching power supply. The secondary-side control chip 100 can also be a protocol control chip used to realize communication between the power system and the terminal device to be charged, so as to realize different voltage and current outputs and protection controls of the power system according to the charging protocol requirements of the terminal device. It should be understood that the above functional description of the secondary-side control chip 100 is merely exemplary, and corresponding functional modules can be added or removed adaptively according to the application environment.

[0044] In this embodiment, the secondary-side control chip 100 includes a power supply circuit 11. The power supply circuit 11 is configured to detect the drain voltage V on the drain pin DRAIN. DRAIN and the supply voltage V on the power supply pin VDD S When the secondary-side control chip 100 is in normal startup state, the power supply circuit 11 is configured to determine the range of the power supply voltage and, based on the drain voltage V... DRAIN The power supply voltage is controlled within a range to vary and power the secondary control chip. In this embodiment, when the drain voltage V... DRAIN When the voltage is greater than the turn-on voltage, it indicates that the secondary control chip is in a normal startup state.

[0045] In this embodiment, when the supply voltage is not greater than the first threshold, the power supply circuit 11 is configured to control the supply voltage V on the power supply pin VDD. S The voltage is boosted to power the secondary-side control chip 100. When the supply voltage is greater than a first threshold and less than a second threshold, the power supply circuit 11 detects the drain voltage V. S And during the period when the drain voltage is at resonance, that is, when the drain voltage V S The supply voltage V on the control power supply pin VDD is less than the drain reference value during the period. S The voltage is boosted. When the supply voltage reaches the second threshold, it reaches its maximum value. The power supply circuit 11 maintains the supply voltage constant, and the secondary control chip 100 completes self-powering and begins to implement control functions. For example, when the secondary control chip 100 is configured as a synchronous rectification control chip, after self-powering, the synchronous rectification control chip begins to drive the synchronous rectification power in the isolated switching power supply to turn on or off. In this embodiment, the power supply circuit adopts drain-side self-powering. When the supply voltage is very low, the supply voltage is directly boosted. When the supply voltage is greater than the first threshold, power is only drawn during the period when the drain voltage is at resonance, resulting in a low power draw voltage. Compared to drawing power when the drain voltage reaches its maximum value (e.g., when the drain voltage reaches a plateau), the power supply method of the present invention has low power loss and high power supply circuit efficiency.

[0046] Figure 2 This is a circuit block diagram of an isolated switching power supply according to the first embodiment of the present invention. This embodiment uses a synchronous rectification control chip as an example for explanation, wherein the secondary-side control chip is connected to the upper part of the secondary side of the isolated switching power supply. Figure 2 As shown, the isolated switching power supply includes a transformer T1, a rectifier diode QS, a secondary control chip 100, and an output capacitor CS2. The transformer T1 includes a primary winding N... P and secondary winding N S Primary winding N P It is connected to the input terminal of the switching power supply to receive the input voltage. The rectifier diode QS includes a first terminal (e.g., the source) connected to the secondary winding N. S The second terminal (e.g., the drain terminal) is connected to the output voltage V. OUT The high potential terminal. Output capacitor CS2 is connected to the output terminal of the switching power supply to generate an output voltage V across its terminals. OUT The secondary-side control chip 100 includes a power supply pin VDD, a drain pin DRAIN, a reference ground pin GND, and a drive pin GATE. The power supply pin VDD is connected to the reference ground pin GND through a first capacitor CS1. The reference ground pin GND is connected to the first terminal of the rectifier diode QS. The drain pin DRAIN is connected to the second terminal of the rectifier diode QS, which is the high-potential terminal of the isolated switching power supply output. The drive pin GATE is connected to the control terminal of the rectifier diode QS to control whether the rectifier diode QS is turned on or off.

[0047] Figure 3 This is a circuit block diagram of an isolated switching power supply according to a second embodiment of the present invention. This embodiment uses a synchronous rectification control chip as an example for explanation, wherein the secondary-side control chip is connected to the lower part of the secondary side of the isolated switching power supply. Figure 3 As shown, the isolated switching power supply includes a transformer T1, a rectifier diode QS, a secondary control chip 100, and an output capacitor CS2. The transformer T1 includes a primary winding N... P and secondary winding N S Primary winding N P It is connected to the input terminal of the switching power supply to receive the input voltage. The rectifier diode QS includes a first terminal (e.g., the drain terminal) connected to the secondary winding N. S The second terminal (e.g., the source) is connected to the output voltage V. OUT The low potential terminal. Output capacitor CS2 is connected to the output terminal of the switching power supply to generate an output voltage V across its terminals. OUTThe secondary-side control chip 100 includes a power supply pin VDD, a drain pin DRAIN, a reference ground pin GND, and a drive pin GATE. The power supply pin VDD is connected to the reference ground pin GND through a first capacitor CS1. The reference ground pin GND is connected to the second terminal of the rectifier diode QS, which is the low-potential terminal of the isolated switching power supply output. The drain pin DRAIN is connected to the first terminal of the rectifier diode QS, which is the secondary winding N. S The drive pin GATE is connected to the control terminal of the rectifier diode QS to control whether QS is turned on or off. It should be understood that the above functional description of the secondary-side control chip 100 is merely exemplary, and corresponding pins can be added or removed adaptively according to the application environment.

[0048] Figure 4 This is a circuit diagram of the power supply circuit according to an embodiment of the present invention. (For example...) Figure 4 As shown, the secondary-side control chip 100 includes a power supply pin VDD, a drain pin DRAIN, a reference ground pin GND, and a power supply circuit 11. The power supply pin VDD is connected to the reference ground pin GND through a first capacitor CS1.

[0049] Power supply circuit 11 includes a linear regulator circuit LDO and a switching circuit S1. Switching circuit S1 is connected between the output of the linear regulator circuit LDO and the power supply pin VDD. Power supply circuit 11 operates according to the supply voltage VDD on the power supply pin. S The range of variation and the voltage V on the drain pin DRAIN DRAIN The control switch circuit S1 is turned on or off to control the linear voltage regulator circuit LDO to generate the supply voltage V. S .

[0050] The power supply circuit 11 also includes a first comparator U1 and a second comparator U2, used to determine the power supply voltage V. S The range of variation. The first input terminal (e.g., the non-inverting input terminal) of the first comparator U1 receives the first threshold V. DD_L The second input terminal (e.g., the inverting input terminal) receives the supply voltage V. S The first input terminal (e.g., the non-inverting input terminal) of the second comparator U2 receives the supply voltage V. S The second input (e.g., the inverting input) receives the second threshold V. DD_H The power supply circuit 11 includes a third comparator U3, whose first input (e.g., the non-inverting input) receives a drain reference value V. DR_Ref The second input terminal (e.g., the inverting input terminal) receives the drain voltage V. DRAINTo determine the magnitude of the drain voltage. When the secondary-side control chip 100 is in normal startup state, the power supply circuit 11 is configured to control the switching circuit S1 to turn on or off according to the drain voltage and the range of the supply voltage, so as to control the linear regulator circuit LDO to generate the supply voltage V. S .

[0051] In this embodiment, the power supply circuit 11 further includes an inverter U4, an AND gate U5, and an OR gate U6. The first terminal of the AND gate U5 receives the output signal of the second comparator U2 after being inverted by the inverter U4, and the second terminal receives the output signal of the third comparator U3. The first terminal of the OR gate U6 receives the output signal of the first comparator U1, and the second terminal receives the output signal of the AND gate U5. The output signal of the OR gate U6 is used to control the switching circuit S1 to be turned on or off.

[0052] When the supply voltage is not greater than the first threshold V DD_L When the switching circuit S1 is turned on, the linear voltage regulator circuit LDO controls the voltage on the power supply pin VDD to boost the voltage to power the secondary control chip 100. When the power supply voltage exceeds the first threshold V... DD_L During this period, the power supply circuit 11 has a drain voltage V DRAIN Control supply voltage V during resonance period S The change occurs. For example, when the supply voltage V... S Greater than the first threshold V DD_L And less than the second threshold V DD_H At that time, power supply circuit 11 detects the drain voltage V. DRAIN And the drain voltage V DRAIN Less than the leak level reference value V DR_Ref During this period, the switching circuit S1 is turned on, and the linear voltage regulator circuit LDO controls the supply voltage V on the power supply pin VDD. S The voltage is boosted. When the supply voltage reaches the second threshold V... DD_H When the switch circuit S1 is turned off, the supply voltage V... S When the maximum value is reached, the power supply circuit 11 maintains the supply voltage V. S It remains unchanged.

[0053] In this embodiment, the power supply circuit 11 also includes a diode D1 to isolate noise between the drain pin DRAIN and the linear regulator circuit LDO.

[0054] Figure 5 This is a waveform diagram of the power supply circuit according to the first embodiment of the present invention. Figure 4 Taking the power supply circuit as an example, when the power supply voltage V S When the value is small, i.e. not greater than the first threshold V DD_L During this period, the operating waveform of the power supply circuit is as follows: Figure 5 As shown. At time t1, the drain voltage VDRAIN Greater than the turn-on voltage V DD_TH The secondary control chip is in normal startup mode. At this time, the supply voltage V... S Less than the first threshold V DD_L The first comparator U1 and OR gate U6 generate an effective level (e.g., high level), the switching circuit S1 is turned on, the output of the linear regulator circuit LDO is connected to the power supply pin VDD, and the current I... DRAIN Charge the first capacitor CS1 so that the supply voltage V S Boost voltage. At time t2, the supply voltage Vs is greater than the first threshold voltage V. DD_L Less than the second threshold V DD_H However, the drain voltage V DRAIN Less than the threshold voltage V DD_TH The secondary control chip is in a standby state. The outputs of the first comparator U1 and the OR gate U6 switch from an active level (e.g., high level) to an inactive level (e.g., low level), and the current I... DRAIN The voltage across the first capacitor CS1 is zero, which is also the supply voltage V. S It remains essentially unchanged. At time t3, the drain voltage V... DRAIN Greater than the turn-on voltage V DD_TH The supply voltage Vs is greater than the first threshold V DD_L Less than the second threshold V DD_H And the drain voltage V DRAIN Less than the drain reference value V DR_Ref When gate U6 generates an active level, switch circuit S1 is turned on, and current I... DRAIN Charge the first capacitor CS1 so that the supply voltage V S Boost voltage. At time t4, the drain voltage V DRAIN Reaching the drain reference value V DR_Ref When switch S1 is turned off, the current I... DRAIN The voltage across the first capacitor CS1 is zero, which is also the supply voltage V. S It remains essentially unchanged. In the next cycle, the drain voltage VDRAIN is again in the resonant period, and the power supply circuit 11 continues to control the supply voltage to rise until the supply voltage reaches its maximum value. It should be understood that the first capacitor CS1 will discharge during the turn-off period of the switching circuit S1, and the supply voltage V S It will decrease slightly, but the decrease will be very small, therefore the supply voltage V S The basics remain unchanged.

[0055] Figure 6 This is a waveform diagram of the power supply circuit according to the second embodiment of the present invention. Figure 4 Taking the power supply circuit as an example, when the power supply voltage V S Greater than the second threshold V DD_H At that time, the operating waveform of the power supply circuit is as follows Figure 6 As shown. At time t1, the drain voltage V DRAIN Greater than the turn-on voltage V DD_TH The secondary control chip is in normal startup mode. At this time, the supply voltage V... S Greater than the first threshold V DD_L Less than the second threshold V DD_H And the drain voltage V DRAIN Less than the drain reference value V DR_Ref When AND gate U5 and OR gate U6 generate an effective level (e.g., high level), switching circuit S1 is turned on, and the output of linear voltage regulator circuit LDO is connected to the power supply pin VDD, and the current I... DRAIN Charge the first capacitor CS1 so that the supply voltage V S Boost voltage. At time t2, the drain voltage V DRAIN Less than the threshold voltage V DD_TH The secondary control chip is in a standby state. The outputs of AND gate U5 and OR gate U6 switch from an active level (e.g., high level) to an inactive level (e.g., low level). Switching circuit S1 is turned off, and current I... DRAIN The voltage across the first capacitor CS1 is zero, which is also the supply voltage V. S It remains essentially unchanged. At time t3, the drain voltage V... DRAIN Greater than the turn-on voltage V DD_TH The supply voltage Vs is greater than the first threshold V DD_L Less than the second threshold V DD_H And the drain voltage V DRAIN Less than the drain reference value V DR_Ref Inverter U4, AND gate U5, and OR gate U6 generate an effective level (e.g., high level), switching circuit S1 is turned on, and the output of linear regulator circuit LDO is connected to the power supply pin VDD, with current I... DRAIN Charge the first capacitor CS1 so that the supply voltage V S Continue increasing the voltage. At time t4, the supply voltage Vs reaches the second threshold V. DD_H When the second comparator U2 generates an effective level (e.g., high level), the switching circuit S1 is turned off, and the current I... DRAIN The voltage across the first capacitor CS1 is zero, which is also the supply voltage V. S When the maximum value is reached, the power supply circuit completes self-powering.

[0056] Figure 7 This is a waveform diagram of the power supply circuit according to the third embodiment of the present invention. Figure 4 Taking the power supply circuit as an example, when the power supply voltage V S Greater than the first threshold V DD_L Less than the second threshold V DD_H At that time, the operating waveform of the power supply circuit is as follows Figure 7As shown. At time t1, the drain voltage V DRAIN Greater than the turn-on voltage V DD_TH The secondary control chip is in normal startup mode. At this time, the supply voltage V... S Greater than the first threshold V DD_L Less than the second threshold V DD_H And the drain voltage V DRAIN Less than the drain reference value V DR_Ref That is, the drain voltage V DRAIN During resonance, the third comparator U3, inverter U4, AND gate U5, and OR gate U6 generate an effective level (e.g., high level), the switching circuit S1 is turned on, and the output of the linear regulator circuit LDO is connected to the power supply pin VDD, and the current I... DRAIN Charge the first capacitor CS1 so that the supply voltage V S Boost voltage. At time t2, the drain voltage V DRAIN Less than the threshold voltage V DD_TH The secondary control chip is in a standby state. The outputs of the third comparator U3, inverter U4, AND gate U5, and OR gate U6 switch from an active level (e.g., high level) to an inactive level (e.g., low level). Switching circuit S1 is turned off, and current I... DRAIN The voltage across the first capacitor CS1 is zero, which is also the supply voltage V. S It remains essentially unchanged. At time t3, the drain voltage V... DRAIN Greater than the turn-on voltage V DD_TH The supply voltage Vs is greater than the first threshold V DD_L Less than the second threshold V DD_H And the drain voltage V DRAIN Less than the drain reference value V DR_Ref The third comparator U3, inverter U4, AND gate U5, and OR gate U6 generate an effective level (e.g., high level), the switching circuit SI is turned on, and the output of the linear regulator circuit LDO is connected to the power supply pin VDD, with current I... DRAIN Charge the first capacitor CS1 so that the supply voltage V S Continue boosting the voltage. At time t4, the drain voltage V... DRAIN Reaching the drain reference value V DR_Ref When switch S1 is turned off, the current I... DRAIN The voltage across the first capacitor CS1 is zero, which is also the supply voltage V. S It remains essentially unchanged. In the next cycle, the drain voltage V... DRAIN During the resonant period again, the power supply circuit 11 continues to control the power supply voltage to increase until the power supply voltage reaches its maximum value.

[0057] This invention provides a power supply method for an isolated switching power supply, the isolated switching power supply including a secondary-side control chip, the secondary-side control chip including a drain pin, a power supply pin, and a reference ground pin. The power supply method includes the following steps.

[0058] S100: Detects the drain voltage V on the drain pin. DRAIN This is to determine whether the secondary-side control chip is in a normal startup state. When the drain voltage V DRAIN Greater than the turn-on voltage V DD_TH If the signal is positive, it indicates that the secondary control chip is in a normal startup state; otherwise, it is in a standby startup state.

[0059] S200: Detects the power supply voltage V on the power supply pin S And determine the supply voltage V S The range.

[0060] S201: When the supply voltage V S Not greater than the first threshold V DD_L At that time, the power supply voltage is increased.

[0061] S202: When the supply voltage V S Greater than the first threshold V DD_L and less than the second threshold V DD_H The magnitude of the drain voltage is determined. Further, this includes S2021: [The text abruptly shifts to a different topic] ...the drain voltage V... DRAIN Not greater than the reference value V at the drain end DR_Ref During this period, control the power supply voltage V S Perform a boost; and S2022: at the drain voltage V DRAIN Greater than the leak reference value V DR_Ref During this period, the supply voltage V is not... S Increase the pressure.

[0062] S203: When the supply voltage V S Greater than the second threshold V DD_H At that time, the supply voltage V S It reaches its maximum value and remains unchanged, thus completing self-powered operation.

[0063] The technical solution of this invention detects the drain voltage on the drain pin of the secondary control chip and the power supply voltage range on the power supply pin, and controls the power supply voltage to change according to the drain voltage and the power supply voltage range, so as to achieve self-powering, reduce power supply loss, and improve system efficiency.

[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. For those skilled in the art, the present invention can be modified and varied in various ways. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of protection of the present invention.

Claims

1. A power supply method for an isolated switching power supply, the isolated switching power supply including a secondary-side control chip, the secondary-side control chip including a drain pin, a power supply pin, and a reference ground pin, characterized in that, The power supply method includes: Detect the drain voltage on the drain pin and the power supply voltage on the power supply pin; determine whether the secondary control chip is in a normal startup state based on the drain voltage. When the secondary control chip is in normal startup state, the range of the power supply voltage is determined; and The power supply voltage is controlled to vary according to the range of the drain voltage and the power supply voltage in order to supply power to the secondary control chip; Specifically, when the supply voltage is not greater than a first threshold, the supply voltage is controlled to be boosted; when the supply voltage is greater than the first threshold, power is drawn only when the drain voltage is in resonance.

2. The power supply method according to claim 1, characterized in that, include: When the supply voltage is greater than a first threshold and less than a second threshold, the supply voltage is controlled to be boosted during the period when the drain voltage is not greater than the drain reference value.

3. The power supply method according to claim 2, characterized in that, When the supply voltage reaches the second threshold, the supply voltage reaches its maximum value and remains unchanged.

4. The power supply method according to claim 1, characterized in that, When the drain voltage reaches the drain reference value, the supply voltage is controlled not to increase.

5. The power supply method according to claim 1, characterized in that, The power supply pin is coupled to the reference ground pin via a first capacitor.

6. The power supply method according to claim 1, characterized in that, The secondary-side control chip includes a rectifier diode, the drain pin is coupled to the drain of the rectifier diode, and the power supply pin and the reference ground pin are coupled to the source of the rectifier diode.

7. A power supply circuit applied to an isolated switching power supply, the isolated switching power supply including a secondary-side control chip, the secondary-side control chip including a drain pin, a power supply pin, and a reference ground pin, characterized in that, The power supply circuit is configured to detect the drain voltage on the drain pin and the power supply voltage on the power supply pin, and determine the range of the power supply voltage; and determine whether the secondary control chip is in a normal startup state based on the drain voltage. When the secondary control chip is in normal startup state, the power supply circuit controls the power supply voltage to change according to the range of the power supply voltage in order to supply power to the secondary control chip; Specifically, when the supply voltage is not greater than the first threshold, the power supply circuit controls the supply voltage to be boosted; when the supply voltage is greater than the first threshold, the power supply circuit draws power only during the period when the drain voltage is in resonance.

8. The power supply circuit according to claim 7, characterized in that, When the supply voltage is greater than a first threshold and less than a second threshold, the power supply circuit controls the supply voltage to be boosted during the period when the drain voltage is not greater than the drain reference value.

9. The power supply circuit according to claim 8, characterized in that, When the power supply voltage reaches the second threshold, the power supply circuit controls the power supply voltage to remain unchanged.

10. The power supply circuit according to claim 7, characterized in that, When the drain voltage reaches the drain reference value, the supply voltage does not increase.

11. The power supply circuit according to claim 7, characterized in that, The secondary control chip includes a first capacitor, with its first end coupled to the power supply pin and its second end coupled to the reference ground pin.

12. The power supply circuit according to claim 7, characterized in that, include: Linear voltage regulator circuit, and A switch is coupled between the output terminal of the linear regulator circuit and the power supply pin to control the linear regulator circuit to generate the power supply voltage.

13. An isolated switching power supply, comprising: A transformer, comprising a primary winding and at least one secondary winding; as well as The secondary-side control chip includes a drain pin, a power supply pin, and a reference ground pin; as well as The power supply circuit as described in any one of claims 7-12, wherein the power supply circuit is integrated within the secondary control chip.

14. The isolated switching power supply according to claim 13, characterized in that, include: The rectifier includes a first end coupled to the secondary winding and a second end coupled to the high-potential end of the output terminal of the isolated switching power supply, wherein the drain pin is coupled to the second end of the rectifier, the power supply pin is coupled to the reference ground pin through a first capacitor, and the reference ground pin is coupled to the first end of the rectifier.

15. The isolated switching power supply according to claim 13, characterized in that, include: The rectifier includes a first end coupled to the secondary winding and a second end coupled to a low-potential terminal of the output of the isolated switching power supply, wherein the drain pin is coupled to the first end of the rectifier, the power supply pin is coupled to the reference ground pin through a first capacitor, and the reference ground pin is coupled to the second end of the rectifier.

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