Power adapter for supplying power to electronic device

Abstract

The invention provides a power adapter for supplying power to an electronic device. The power adapter comprises a power conversion circuit and a control circuit. The power conversion circuit receives input power. The power conversion circuit comprises a power switch. The control circuit communicates with the electronic device to obtain a power supply demand of the electronic device. When the electronic device is connected with the power adapter and provides a power supply demand, the control circuit controls the power switch by using the first switching frequency, so that the power conversion circuit converts the input power supply into the first output power supply. When the power supply demand of the electronic device is not received, the control circuit controls the power switch by using the second switching frequency, so that the power conversion circuit converts the input power supply into the second output power supply. The second switching frequency is lower than the first switching frequency.

Description

Technical Field

[0001] The invention relates to a power adapter, and in particular to a power adapter for supplying power to an electronic device. Background Art

[0002] Generally speaking, a power adapter receives input power and provides output power according to the input power. Once the power adapter is connected to an electronic device, the power adapter will supply power to the electronic device according to the power supply requirement of the electronic device.

[0003] However, based on the need to save power, when the electronic device is in a dormant state or the electronic device is not connected to the electronic device, the power adapter will not receive a power supply request from the electronic device. Therefore, the power adapter will be required to reduce power consumption and continue to provide output power. It can be seen that when no power supply request is received, how to reduce power consumption while continuing to provide output power for the power adapter is one of the research focuses of those skilled in the art. Summary of the invention

[0004] The invention provides a power adapter for supplying power to an electronic device. When no power supply demand is received, the power adapter can effectively reduce power consumption while continuously providing output power.

[0005] The power adapter of the present invention includes a power conversion circuit and a control circuit. The power conversion circuit receives input power. The power conversion circuit includes a power switch. The control circuit is coupled to the power conversion circuit. The control circuit communicates with the electronic device to obtain the power supply demand of the electronic device. When the electronic device is connected to the power adapter and the electronic device makes a power supply demand, the control circuit uses a first switching frequency to control the power switch so that the power conversion circuit converts the input power into a first output power. When the power supply demand of the electronic device is not received, the control circuit uses a second switching frequency to control the power switch so that the power conversion circuit converts the input power into a second output power. The second switching frequency is lower than the first switching frequency.

[0006] Based on the above, when the power supply demand of the electronic device is not received, the control circuit reduces the switching frequency to control the power switch. Therefore, when the power supply demand of the electronic device is not received, the switching energy loss of the switching state of the power switch can be greatly reduced. In this way, when the power supply demand is not received, the power adapter can effectively reduce power consumption while continuously providing output power. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a schematic diagram of a power adapter according to an embodiment of the present invention;

[0008] Figure 2 is an operation schematic diagram shown according to an embodiment of the present invention;

[0009] Figure 3 is a voltage waveform diagram of a first output power source and a second output power source according to an embodiment of the present invention;

[0010] Figure 4 is a circuit diagram of a power adapter according to an embodiment of the present invention.

[0011] Description of Reference Numerals

[0012] 100, 200: Power adapter

[0013] 110, 210: Power conversion circuit

[0014] 120, 220: Control circuit

[0015] 211: Primary circuit

[0016] 212: Secondary circuit

[0017] 221: Optical coupling circuit

[0018] 222: Primary side controller

[0019] 223: Secondary side controller

[0020] 2231: Judgment circuit

[0021] BT: Battery

[0022] CC, CF, CI, CL, CO: Capacitors

[0023] D1: Rectifier diode

[0024] DL: diode

[0025] DP: light emitting diode

[0026] ED: Electronic Device

[0027] F1: First switching frequency

[0028] F2: Second switching frequency

[0029] I1: operating current

[0030] I2: Current

[0031] L: Light signal

[0032] LP: Primary winding

[0033] LS: Secondary winding

[0034] Q1: Power switch

[0035] Q2: Control switch

[0036] R1, RF, RS, RL: resistors

[0037] REQ: Power supply requirement

[0038] RV1, RV2: Ripples

[0039] S110~S150: Steps

[0040] SC: Control signal

[0041] SS: Operation signal

[0042] TR: Transformer

[0043] VCC: Reference high voltage

[0044] VFB: Feedback voltage

[0045] VIN: Input power

[0046] VO1: First output power supply

[0047] VO2: Second output power supply

[0048] VSH: Set peak value

[0049] VSL: Set valley value

[0050] VSPH: High voltage value

[0051] VSPL: Low specification voltage value

[0052] VSS: Reference low voltage

[0053] W1, W2: Voltage waveform DETAILED DESCRIPTION

[0054] Some embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The component symbols cited in the following description will be regarded as the same or similar components when the same component symbols appear in different drawings. These embodiments are only part of the present invention and do not disclose all possible implementation methods of the present invention. More specifically, these embodiments are only examples in the claims of the present invention.

[0055] Please refer to Figure 1 , Figure 11 is a schematic diagram of a power adapter according to an embodiment of the present invention. In this embodiment, the power adapter 100 is used to power the electronic device ED. The power adapter 100 includes a power conversion circuit 110 and a control circuit 120. The power conversion circuit 110 receives an input power source VIN. The power conversion circuit 110 includes a power switch Q1. The power conversion circuit 110 can operate based on the switching state of the power switch Q1, thereby converting the input power source VIN into one of a first output power source VO1 and a second output power source VO2.

[0056] In the present embodiment, the control circuit 120 is coupled to the power conversion circuit 110. The control circuit 120 communicates with the electronic device ED to obtain a power demand REQ from the electronic device ED. The power demand REQ may be a signal or a state value (such as a voltage value). When the electronic device ED is connected to the power adapter 100 and the electronic device ED raises a power demand REQ, the control circuit 120 receives the power demand REQ and controls the power switch Q1 using the first switching frequency F1. Therefore, the power conversion circuit 110 converts the input power VIN into the first output power VO1. In other words, the power switch Q1 switches the switch state based on the first switching frequency F1, so that the power conversion circuit 110 will provide the first output power VO1 and power the electronic device ED.

[0057] In this embodiment, when the power supply demand REQ of the electronic device ED is not received, the control circuit 120 uses the second switching frequency F2 to control the power switch Q1. Therefore, the power conversion circuit 110 converts the input power VIN into the second output power VO2. In this embodiment, the second switching frequency F2 is lower than the first switching frequency F1.

[0058] It is worth mentioning that when the power supply demand REQ of the electronic device ED is not received, the control circuit 120 reduces the switching frequency to control the power switch Q1. Therefore, when the power supply demand REQ of the electronic device ED is not received, the switching energy loss of the switching state of the power switch Q1 can be greatly reduced. In this way, when the power supply demand REQ is not received, the power adapter 100 can effectively reduce power consumption while continuously providing output power (i.e., the second output power VO2).

[0059] In this embodiment, the electronic device ED may be a wearable device, a mobile phone, a laptop computer, a tablet computer, etc. (but the present invention is not limited thereto). The power conversion circuit 110 may be any type of flyback converter, LLC converter, boost converter, or buck converter (but the present invention is not limited thereto).

[0060] Please also refer to Figure 1 as well as Figure 2 , Figure 2 It is an operation diagram according to an embodiment of the present invention. In this embodiment, the power adapter 100 can, for example, use USB TYPE-C to communicate with the electronic device ED and power the electronic device ED. The power adapter 100 determines whether it is connected to the electronic device ED in step S110. When the electronic device ED is connected to the power adapter 100 and the electronic device ED is in a normal state, the electronic device ED sends a power supply request REQ. Therefore, the control circuit 120 uses the first switching frequency F1 to control the power switch Q1 in step S120. The power conversion circuit 110 converts the input power VIN into a first output power VO1. The power conversion circuit 110 uses the first output power VO1 to power the electronic device ED.

[0061] In step S130, when the electronic device ED is connected to the power adapter 100 and is in a dormant state, the electronic device ED does not send a power supply request REQ. The control circuit 120 controls the power switch Q1 using the second switching frequency F2. Therefore, the power conversion circuit 110 converts the input power VIN into the second output power VO2.

[0062] Similarly, in step S130, when the electronic device ED is connected to the power adapter 100 and the battery BT of the electronic device ED is in a fully charged state, the electronic device ED will not send a power supply request REQ. The control circuit 120 uses the second switching frequency F2 to control the power switch Q1. Therefore, the power conversion circuit 110 converts the input power VIN into the second output power VO2.

[0063] In step S140, when the electronic device ED is awakened and in a normal state and / or the battery BT of the electronic device ED is not in a fully charged state, the electronic device ED sends a power supply request REQ. The control circuit 120 controls the power switch Q1 using the first switching frequency F1. Therefore, the power conversion circuit 110 converts the input power VIN into the first output power VO1.

[0064] Therefore, when the power supply demand REQ is not received, the power conversion circuit 110 provides the second output power VO2 based on the second switching frequency F2. Once the power supply demand REQ is received, the power conversion circuit 110 provides the first output power VO1 based on the first switching frequency F1. Once the power supply demand REQ is received, the power conversion circuit 110 changes the second output power VO2 to the first output power VO1. Therefore, the power conversion circuit 110 does not require an additional voltage rise time length. The power conversion circuit 110 can output the first output power VO1 in real time.

[0065] In step S110, when the electronic device ED is not connected to the power adapter 100, the power adapter 100 does not receive the power supply requirement REQ of the electronic device ED. Therefore, the control circuit 120 uses the second switching frequency F2 to control the power switch Q1 in step S150. Therefore, the power conversion circuit 110 converts the input power VIN into the second output power VO2.

[0066] Please also refer to Figure 1 as well as Figure 3 , Figure 3 FIG. 4 is a voltage waveform diagram of a first output power source and a second output power source according to an embodiment of the present invention. Figure 3 The voltage waveform W1 of the first output power source VO1 and the voltage waveform W2 of the second output power source VO2 are shown. In this embodiment, based on the first switching frequency F1, the voltage waveform W1 of the first output power source VO1 has a first voltage ripple. In other words, the voltage waveform W1 has a ripple fluctuation RV1 of the first switching frequency F1. Based on the second switching frequency F2, the voltage waveform W2 of the second output power source VO2 has a second voltage ripple. In other words, the voltage waveform W2 has a ripple fluctuation RV2 of the second switching frequency F2.

[0067] In this embodiment, the ripple fluctuation RV2 of the second voltage ripple is greater than the ripple fluctuation RV1 of the first voltage ripple.

[0068] Further, when a specific load (such as medium load or heavy load) is connected, the power conversion circuit 110 provides a first output power VO1. Based on the first switching frequency F1, the voltage waveform W1 of the first output power VO1 has a very small ripple RV1. In the case of light load or no load, the power conversion circuit 110 provides a second output power VO2. Based on the second switching frequency F2, the voltage waveform W2 of the second output power VO2 has a larger ripple RV2. It should be noted that the voltage waveform W1 and the voltage waveform W2 are controlled between a high specification voltage value VSPH and a low specification voltage value VSPL. The high specification voltage value VSPH and the low specification voltage value VSPL are the specification voltage values ​​set by the industry, respectively.

[0069] In this embodiment, the set peak value VSH and the set valley value VSL of the second voltage ripple of the voltage waveform W2 are set. The set peak value VSH of the second voltage ripple is lower than the high standard voltage value VSPH and higher than the peak value of the first voltage ripple. The set valley value VSL of the second voltage ripple is higher than the low standard voltage value VSPL and lower than the valley value of the first voltage ripple. The set peak value VSH is slightly lower than the high standard voltage value VSPH. The set valley value VSL is slightly higher than the low standard voltage value VSPL. Therefore, although the second voltage ripple of the voltage waveform W2 has a larger ripple fluctuation RV2, it is still controlled between the high standard voltage value VSPH and the low standard voltage value VSPL.

[0070] In this embodiment, the control circuit 120 receives the second output power VO2. When the voltage value of the second output power VO2 rises to a set peak value VSH, the control circuit 120 controls the power switch Q1 to be in a first switching state. Therefore, the voltage value of the second output power VO2 starts to decrease from the set peak value VSH. For example, when the voltage value of the second output power VO2 rises to the set peak value VSH, the control circuit 120 turns on (or turns off) the power switch Q1. When the voltage value of the second output power VO2 drops to a set valley value VSL, the control circuit 120 controls the power switch Q1 to be in a second switching state. The second switching state is opposite to the first switching state. Therefore, the voltage value of the second output power VO2 starts to rise from the set valley value VSL. For example, when the voltage value of the second output power VO2 drops to the set valley value VSL, the control circuit 120 turns off (or turns on) the power switch Q1. Therefore, the ripple RV2 of the voltage waveform W2 of the second output power VO2 is equal to the set difference between the set peak value VSH and the set valley value VSL. In addition, the duty cycle of the control signal for controlling the power switch Q1 may be determined by the rising time of the voltage value of the second output power source VO2 and the falling time of the voltage value of the second output power source VO2 .

[0071] It can be seen that the second switching frequency F2 is associated with the set peak value VSH and the set valley value VSL. The smaller the set difference between the set peak value VSH and the set valley value VSL, the smaller the second voltage ripple of the voltage waveform W2, and the higher the second switching frequency F2. The larger the set difference between the set peak value VSH and the set valley value VSL, the larger the second voltage ripple of the voltage waveform W2, and the lower the second switching frequency F2. The lower the second switching frequency F2, the lower the switching energy loss of the switching state of the power switch Q1.

[0072] Please refer to Figure 4 , Figure 41 is a circuit diagram of a power adapter according to an embodiment of the present invention. In this embodiment, the power adapter 200 includes a power conversion circuit 210 and a control circuit 220. The power conversion circuit 210 includes a transformer TR, a primary side circuit 211 and a secondary side circuit 212. The primary side circuit 211 is coupled to the primary side winding LP of the transformer TR. The primary side circuit 211 includes a power switch Q1. The secondary side circuit 212 is coupled to the secondary side winding LS of the transformer TR.

[0073] The control circuit 220 includes an optical coupling circuit 221, a primary-side controller 222, and a secondary-side controller 223. The optical coupling circuit 221 is controlled to provide an optical signal L, and according to the optical signal L, provides an operating current I1.

[0074] The secondary side controller 223 is coupled to the secondary side circuit 212 and the optical coupling circuit 221. The secondary side controller 223 controls the optical signal L provided by the optical coupling circuit 221 according to the voltage value of one of the first output power source VO1 and the second output power source VO2. The primary side controller 222 is coupled to the power switch Q1 and the optical coupling circuit 221. The primary side controller 222 controls the power switch Q1 according to the operating current I1.

[0075] Further, taking this embodiment as an example, the primary side circuit 211 also includes capacitors CI, CL, resistors RS, RL and a diode DL. The first end of the capacitor CI is coupled to the input end of the primary side circuit 211 and the first end (or the same name end) of the primary side winding LP. The second end of the capacitor CI is coupled to the ground end corresponding to the primary side circuit 211. The first end of the power switch Q1 is coupled to the second end (or the opposite name end) of the primary side winding LP. The control end of the power switch Q1 is coupled to the primary side controller 222. The resistor RS is coupled between the second end of the power switch Q1 and the ground end corresponding to the primary side circuit 211. The anode of the diode DL is coupled to the second end of the primary side winding LP. The resistor RL is coupled between the first end of the primary side winding LP and the cathode of the diode DL. The capacitor CL is coupled between the first end of the primary side winding LP and the cathode of the diode DL.

[0076] The capacitor CL, the resistor RL and the diode DL can together form a leakage inductance absorption circuit of the primary side circuit 211. When the power switch Q1 is turned off, the capacitor CL, the resistor RL and the diode DL absorb the leakage inductance from the transformer TR. Therefore, the stress damage of the power switch Q1 caused by the leakage inductance can be reduced. The life of the power switch Q1 can be improved.

[0077] The first end (or the same-name end) of the secondary winding LS is coupled to the ground end corresponding to the secondary circuit 212. The secondary circuit 212 includes a rectifier diode D1, a capacitor CO, and a resistor R1. The anode of the rectifier diode D1 is coupled to the second end (or the opposite-name end) of the secondary winding LS. The cathode of the rectifier diode D1 is coupled to the output end of the secondary circuit 212. The capacitor CO is coupled between the output end of the secondary circuit 212 and the ground end corresponding to the secondary circuit 212.

[0078] The optical coupling circuit 221 includes a light emitting diode DP and a phototransistor TP. The anode of the light emitting diode DP is coupled to the output terminal of the secondary side circuit 212 through the resistor R1. The cathode of the light emitting diode DP is coupled to the secondary side controller 223. The first terminal of the phototransistor TP is coupled to the primary side controller 222. The second terminal of the phototransistor TP is coupled to the ground terminal corresponding to the primary side circuit 211. The control terminal of the phototransistor TP receives the light signal L provided by the light emitting diode DP, and generates the operating current I1 according to the light signal L.

[0079] In this embodiment, the load of the power adapter 200 can be based on the power supply requirements (such as Figure 1 When the power supply demand is received, the load of the power adapter 200 is greater than or equal to the predetermined load. In other words, the power adapter 200 is in a medium load state or a heavy load state. Therefore, when the load of the power adapter 200 is greater than or equal to the predetermined load, the judgment circuit 2231 uses the operation signal SS to control the optical coupling circuit 221 to provide an operation current I1 having a first operation current value. The primary side controller 222 controls the power switch Q1 using the first switching frequency F1 in response to the first operation current value.

[0080] When no power supply demand is received, the load of the power adapter 200 is less than the predetermined load. In other words, the power adapter 200 is in a light load state. Therefore, when the load of the power adapter 200 is less than the predetermined load, the judgment circuit 2231 uses the operation signal SS to control the optical coupling circuit 221 to provide an operation current I1 having a second operation current value. The primary side controller 222 controls the power switch Q1 using the second switching frequency F2 in response to the second operation current value.

[0081] In this embodiment, the secondary side controller 223 includes a judgment circuit 2231 and a control switch Q2. The judgment circuit 2231 provides an operation signal SS according to the load state of the power adapter 200. The first end of the control switch Q2 is coupled to the optical coupling circuit 221. The second end of the control switch Q2 is coupled to the rise time of the voltage value of the second output power source VO2 of the reference low voltage VSS. The control end of the control switch Q2 receives the operation signal SS.

[0082] The control switch Q2 of this embodiment is implemented by, for example, an N-type field effect transistor (FET), but the present invention is not limited thereto. In some embodiments, the control switch Q2 can be implemented by an NPN bipolar transistor (BJT).

[0083] The primary side controller 222 includes a resistor RF. The resistor RF is coupled between the reference high voltage VCC and the first terminal of the photo transistor TP. In addition, a capacitor CF is provided. The capacitor CF is coupled between the first terminal of the photo transistor TP and the ground terminal corresponding to the primary side circuit 211.

[0084] Taking this embodiment as an example, when the load of the power adapter 200 is greater than or equal to the predetermined load, the output current value at the output end of the secondary side circuit 212 will increase. The output voltage value at the output end of the secondary side circuit 212 will decrease. Therefore, the voltage value of the operation signal SS provided by the judgment circuit 2231 will decrease. The on-resistance of the control switch Q2 increases, thereby reducing the current value of the current I2 flowing through the light-emitting diode DP. Therefore, the intensity of the light signal L will also decrease. The current value of the operation current I1 flowing through the phototransistor TP will decrease to the first operation current value. Therefore, the feedback voltage VFB at the first end of the phototransistor TP can be charged to a higher first voltage level. Therefore, the primary side controller 222 will respond to the feedback voltage VFB with the first voltage level to provide a control signal SC with a first switching frequency F1. The primary side controller 222 uses the control signal SC with the first switching frequency F1 to control the power switch Q1. Therefore, the power conversion circuit 210 converts the input power VIN into the first output power VO1. In addition, the primary-side controller 222 receives a sense voltage value VS at the second end of the power switch Q1. The sense voltage value VS is associated with the state of the first output power source VO1. The primary-side controller 222 fine-tunes the first switching frequency F1, the duty cycle of the control signal SC, and / or the voltage value of the feedback voltage VFB according to the sense voltage value VS.

[0085] When the load of the power adapter 200 is less than the predetermined load, the output current value at the output end of the secondary side circuit 212 will decrease. The output voltage value at the output end of the secondary side circuit 212 will increase. Therefore, the voltage value of the operation signal SS provided by the judgment circuit 2231 will increase. The on-resistance of the control switch Q2 is reduced, so that the current value of the current I2 flowing through the light-emitting diode DP increases. Therefore, the intensity of the light signal L will also increase. The current value of the operation current I1 flowing through the phototransistor TP will increase to the second operation current value. Therefore, the feedback voltage VFB at the first end of the phototransistor TP can be charged to a lower second voltage level. Therefore, the primary side controller 222 will respond to the feedback voltage VFB with the second voltage level to provide a control signal SC with a second switching frequency F2. The primary side controller 222 uses the control signal SC with the second switching frequency F2 to control the power switch Q1. Therefore, the power conversion circuit 210 converts the input power VIN into the second output power VO2.

[0086] In addition, the primary side controller 222 receives a sense voltage value VS at the second end of the power switch Q1. The sense voltage value VS is associated with the state of the second output power source VO2. The primary side controller 222 fine-tunes the second switching frequency F2 and / or the duty cycle of the control signal SC according to the sense voltage value VS.

[0087] In this embodiment, the determination circuit 2231 is implemented by, for example, a comparator or an analog-to-digital converter (ADC). The optical coupling circuit 221 is implemented by, for example, an optical coupling component PC817.

[0088] In this embodiment, the capacitor CC is coupled between the output terminal of the secondary side circuit 212 and the ground terminal corresponding to the secondary side circuit 212, but the invention is not limited thereto. In some embodiments, the capacitor CC may be omitted.

[0089] In summary, when the power adapter does not receive the power supply demand of the electronic device, the control circuit of the power adapter reduces the switching frequency to control the power switch in the power conversion circuit. Therefore, when the power supply demand of the electronic device is not received, the switching energy loss of the switching state of the power switch can be greatly reduced. In this way, when the power supply demand is not received, the power adapter can effectively reduce power consumption while continuously providing output power.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A power adapter for supplying power to an electronic device, characterized in that: The power adapter comprises: a power conversion circuit configured to receive an input power source, wherein the power conversion circuit comprises a power switch; and A control circuit is coupled to the power conversion circuit and is configured to communicate with the electronic device to obtain a power supply requirement of the electronic device, wherein: When the electronic device is connected to the power adapter and the electronic device puts forward the power supply demand, the control circuit uses the first switching frequency to control the power switch, so that the power conversion circuit converts the input power into the first output power, and When the power supply demand of the electronic device is not received, the control circuit uses a second switching frequency to control the power switch, so that the power conversion circuit converts the input power into a second output power. The second switching frequency is lower than the first switching frequency.

2. The power adapter according to claim 1, characterized in that: When the electronic device is connected to the power adapter and is in a normal state, the control circuit uses the first switching frequency to control the power switch so that the power conversion circuit converts the input power into the first output power.

3. The power adapter according to claim 1, characterized in that: When the electronic device is connected to the power adapter and is in a dormant state, the control circuit uses the second switching frequency to control the power switch so that the power conversion circuit converts the input power into the second output power.

4. The power adapter according to claim 1, characterized in that: When the electronic device is connected to the power adapter and / or the battery of the electronic device is in a fully charged state, the control circuit uses the second switching frequency to control the power switch so that the power conversion circuit converts the input power into the second output power.

5. The power adapter according to claim 1, characterized in that: When the electronic device is not connected to the power adapter, the control circuit uses a second switching frequency to control the power switch, so that the power conversion circuit converts the input power into the second output power.

6. The power adapter according to claim 1, characterized in that: The voltage waveform of the first output power source has a first voltage ripple, The voltage waveform of the second output power has a second voltage ripple, and The fluctuation of the second voltage ripple is greater than the fluctuation of the first voltage ripple.

7. The power adapter according to claim 6, characterized in that: The voltage values ​​of the first output power supply and the second output power supply are regulated between a high regulated voltage value and a low regulated voltage value. The set peak value of the second voltage ripple is lower than the high specification voltage value and higher than the peak value of the first voltage ripple, and A set valley value of the second voltage ripple is higher than the low specification voltage value and lower than a valley value of the first voltage ripple.

8. The power adapter according to claim 7, characterized in that: The control circuit receives the second output power, When the voltage value of the second output power source rises to the set peak value, the control circuit controls the power switch to be in the first switch state, and When the voltage value of the second output power source drops to the set valley value, the control circuit controls the power switch to be in a second switching state opposite to the first switching state.

9. The power adapter according to claim 8, characterized in that: The second switching frequency is associated with the set peak value and the set valley value.

10. The power adapter according to claim 7, characterized in that: The power conversion circuit further includes: A transformer, comprising a primary winding and a secondary winding; a primary side circuit coupled to the primary side winding and comprising the power switch; and The secondary side circuit is coupled to the secondary side winding.

11. The power adapter according to claim 10, characterized in that: The control circuit comprises: An optical coupling circuit controlled to provide an optical signal and to provide an operating current according to the optical signal; a secondary-side controller coupled to the secondary-side circuit and the optical coupling circuit, and configured to control the optical signal provided by the optical coupling circuit according to a voltage value of one of the first output power source and the second output power source; and The primary-side controller is coupled to the power switch and the optical coupling circuit, and is configured to control the power switch according to the operating current.

12. The power adapter according to claim 11, characterized in that: The secondary side controller comprises: a determination circuit configured to provide an operation signal according to a load state of the power adapter; and A control switch, wherein a first end of the control switch is coupled to the optical coupling circuit, a second end of the control switch is coupled to a reference low voltage, and a control end of the control switch receives the operation signal.

13. The power adapter according to claim 12, characterized in that: When the load of the power adapter is greater than or equal to a predetermined load, the judgment circuit uses an operation signal to control the optical coupling circuit to provide the operation current having a first operation current value, and The primary-side controller controls the power switch using the first switching frequency in response to the first operating current value.

14. The power adapter according to claim 12, characterized in that: When the load of the power adapter is less than a predetermined load, the judgment circuit uses an operation signal to control the optical coupling circuit to provide the operation current having a second operation current value, and The primary-side controller controls the power switch using the second switching frequency in response to the second operating current value.

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