TWM652334U - Power adapter for supplying power to electronic device - Google Patents

Abstract

A power adapter for supplying power to an electronic device is provided. The power adapter includes a power conversion circuit and a control circuit. The power conversion circuit receives an input power. The power conversion circuit includes a power switch. The control circuit communicates with the electronic device to obtain a power requirement of the electronic device. When the electronic device is connected to the power adapter and the electronic device requests power supply, 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 requirement from 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.

Description

Power adapter for powering electronic devices

The invention relates to a power adapter, and in particular to a power adapter that supplies power to electronic devices.

Generally speaking, a power adapter receives input power and provides output power based on the input power. Once the power adapter is connected to the electronic device, the power adapter will power the electronic device according to the power supply requirements of the electronic device.

However, due to the need to save power, when the electronic device is in a sleep state or the electronic device is not connected to the electronic device, the power adapter does not receive the power supply demand from the electronic device. Therefore, the power adapter is required to reduce power consumption and continuously provide output power. It can be seen from this that when no power supply demand is received, how to reduce the power consumption of the power adapter while continuously providing output power is one of the research focuses of those skilled in the art.

This new creation provides a power adapter that supplies power to electronic devices. When no power demand is received, the power adapter can effectively reduce power consumption while continuously providing output power.

The power adapter created in the present invention includes a power conversion circuit and a control circuit. The power conversion circuit receives input power. Power conversion circuits include power switches. The control circuit is coupled to the power conversion circuit. The control circuit communicates with the electronic device to obtain power requirements of the electronic device. When the electronic device is connected to the power adapter and the electronic device requests power supply, 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. When no power supply demand from the electronic device is received, 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. The second switching frequency is lower than the first switching frequency.

Based on the above, when no power supply demand from the electronic device is 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 no power supply demand is received, the power adapter can effectively reduce power consumption while continuously providing output power.

Some embodiments of the present invention will be described in detail 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 invention and do not disclose all possible implementation modes of the invention. Rather, these embodiments are merely examples within the scope of the patent application for this novel creation.

Please refer to FIG. 1 , which 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 . Power conversion circuit 110 receives input power VIN. Power conversion circuit 110 includes power switch Q1. The power conversion circuit 110 may operate based on switching of the switching state of the power switch Q1 to convert the input power VIN into one of the first output power VO1 and the second output power VO2.

In this 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 the power supply requirement REQ from the electronic device ED. The power supply requirement REQ can be a signal or a status value (such as a voltage value). When the electronic device ED is connected to the power adapter 100 and the electronic device ED puts forward a power supply request REQ, the control circuit 120 receives the power supply request 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 switching 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.

In this embodiment, when the power supply requirement 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.

It is worth mentioning here that when the power supply request 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 request 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 requirement REQ is not received, the power adapter 100 can effectively reduce power consumption while continuously providing output power (ie, the second output power VO2).

In this embodiment, the electronic device ED may be a wearable device, a mobile phone, a notebook computer, a tablet computer, or other devices (but the 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 invention is not limited thereto).

Please refer to Figure 1 and Figure 2 at the same time. Figure 2 is a schematic diagram of an operation according to an embodiment of the present invention. In this embodiment, the power adapter 100 may, for example, use USB TYPE-C to communicate with the electronic device ED and provide power to 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 will send a power supply request REQ. Therefore, the control circuit 120 controls the power switch Q1 using the first switching frequency F1 in step S120. The power conversion circuit 110 converts the input power VIN into the first output power VO1. The power conversion circuit 110 uses the first output power VO1 to power the electronic device ED.

In step S130, when the electronic device ED is connected to the power adapter 100 and the electronic device ED is in a sleep state, the electronic device ED does not send the 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.

Also 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 the 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.

In step S140, when the electronic device ED is awakened and is 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.

Therefore, when the power supply requirement 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 requirement 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 request REQ is received, the power conversion circuit 110 changes the second output power supply VO2 to the first output power supply VO1. Therefore, the power conversion circuit 110 does not require additional voltage rise time length. The power conversion circuit 110 can instantly output the first output power VO1.

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 request 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.

Please refer to FIG. 1 and FIG. 3 at the same time. FIG. 3 is a voltage waveform diagram of the first output power supply and the second output power supply according to an embodiment of the present invention. FIG. 3 shows the voltage waveform W1 of the first output power supply VO1 and the voltage waveform W2 of the second output power supply VO2. In this embodiment, based on the first switching frequency F1, the voltage waveform W1 of the first output power supply VO1 has a first voltage ripple. In other words, the voltage waveform W1 has ripple fluctuations RV1 of the first switching frequency F1. Based on the second switching frequency F2, the voltage waveform W2 of the second output power supply VO2 has a second voltage ripple. In other words, the voltage waveform W2 has the ripple fluctuation RV2 of the second switching frequency F2.

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

Furthermore, when a specific load (eg, medium load, heavy load) is connected, the power conversion circuit 110 provides the first output power VO1. Based on the first switching frequency F1, the voltage waveform W1 of the first output power supply VO1 has extremely small ripple fluctuations RV1. Under light load or no load conditions, the power conversion circuit 110 provides the second output power VO2. Based on the second switching frequency F2, the voltage waveform W2 of the second output power supply VO2 has a large ripple fluctuation RV2. It should be noted that the voltage waveform W1 and the voltage waveform W2 are controlled between the high specification voltage value VSPH and the low specification voltage value VSPL. The high standard voltage value VSPH and the low standard voltage value VSPL are standard voltage values set by the industry.

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 specification 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. Set the peak value VSH slightly lower than the high specification voltage value VSPH. Set the valley value VSL slightly higher than the low specification 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.

In this embodiment, the control circuit 120 receives the second output power VO2. When the voltage value of the second output power supply VO2 rises to the set peak value VSH, the control circuit 120 controls the power switch Q1 to be in the first switching state. Therefore, the voltage value of the second output power supply VO2 starts to decrease from the set peak value VSH. For example, when the voltage value of the second output power supply 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 supply VO2 drops to the set valley value VSL, the control circuit 120 controls the power switch Q1 to be in the second switching state. The second switching state is opposite to the first switching state. Therefore, the voltage value of the second output power supply VO2 starts to rise from the set valley value VSL. For example, when the voltage value of the second output power supply VO2 drops to the set valley value VSL, the control circuit 120 turns off (or turns on) the power switch Q1. Therefore, the ripple fluctuation RV2 of the voltage waveform W2 of the second output power supply 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 supply VO2 and the falling time of the voltage value of the second output power supply VO2.

It can be seen from this that the second switching frequency F2 is associated with the set peak value VSH and the set bottom 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 greater the set difference between the set peak value VSH and the set valley value VSL, the greater the second voltage ripple of the voltage waveform W2, and the lower the second switching frequency F2. The lower the second switching frequency F2 is, the lower the switching energy loss of the switching state of the power switch Q1 is.

Please refer to FIG. 4 , which is a schematic 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 circuit 211 is coupled to the primary winding LP of the transformer TR. Primary circuit 211 includes power switch Q1. The secondary circuit 212 is coupled to the secondary winding LS of the transformer TR.

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 the optical signal L, and to provide the operating current I1 according to the optical signal L.

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 supply VO1 and the second output power supply 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.

Furthermore, 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 circuit 211 and the first end (or the same end) of the primary winding LP. The second terminal of the capacitor CI is coupled to the ground terminal corresponding to the primary circuit 211 . The first terminal of the power switch Q1 is coupled to the second terminal (or called the opposite terminal) of the primary winding LP. The control terminal of the power switch Q1 is coupled to the primary side controller 222 . The resistor RS is coupled between the second terminal of the power switch Q1 and the ground terminal corresponding to the primary circuit 211 . The anode of the diode DL is coupled to the second end of the primary winding LP. The resistor RL is coupled between the first end of the primary winding LP and the cathode of the diode DL. The capacitor CL is coupled between the first end of the primary winding LP and the cathode of the diode DL.

The capacitor CL, the resistor RL and the diode DL may jointly form a leakage inductance absorption circuit of the primary 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 caused by the leakage inductance of the power switch Q1 can be reduced. The life of power switch Q1 can be improved.

The first end (or the same 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 terminal (or the opposite terminal) of the secondary winding LS. The cathode of the rectifier diode D1 is coupled to the output terminal of the secondary side circuit 212 . The capacitor CO is coupled between the output terminal of the secondary side circuit 212 and the ground terminal corresponding to the secondary side circuit 212 .

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 end of the photoelectric crystal 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.

In this embodiment, the load of the power adapter 200 may be determined based on the power supply requirement (power supply requirement REQ as shown in FIG. 1 ). When a power supply demand is received, the load of the power adapter 200 is greater than or equal to the predetermined load. That is, 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 the operation current I1 with the 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 operating current value.

When no power supply demand is received, the load of the power adapter 200 is less than the predetermined load. That is, 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 determination circuit 2231 uses the operation signal SS to control the optical coupling circuit 221 to provide the operation current I1 with the 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 operating current value.

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

The control switch Q2 in this embodiment is implemented by, for example, an N-type field effect transistor (FET), but the invention is not limited to this. In some embodiments, the control switch Q2 may be implemented by an NPN bipolar transistor (BJT).

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

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 terminal 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 causing the current value of the current I2 flowing through the light-emitting diode DP to decrease. Therefore, the intensity of the optical signal L also decreases. The current value of the operating current I1 flowing through the photoelectric transistor TP will drop to the first operating current value. Therefore, the feedback voltage VFB located at the first terminal of the phototransistor TP can be charged to a higher first voltage level. Therefore, the primary side controller 222 responds to the feedback voltage VFB having the first voltage level to provide the control signal SC having the first switching frequency F1. The primary side controller 222 controls the power switch Q1 using the control signal SC having the first switching frequency F1. 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 the sensing voltage value VS located at the second terminal of the power switch Q1. The sensing voltage value VS will be related to the state of the first output power supply VO1. The primary side controller 222 will fine-tune 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 sensed voltage value VS.

When the load of the power adapter 200 is less than the predetermined load, the output current value at the output terminal of the secondary side circuit 212 will decrease. The output voltage value at the output terminal 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, thereby increasing the current value of the current I2 flowing through the light-emitting diode DP. Therefore, the intensity of the optical signal L also increases. The current value of the operating current I1 flowing through the photoelectric transistor TP will rise to the second operating current value. Therefore, the feedback voltage VFB located at the first terminal of the phototransistor TP can be charged to a lower second voltage level. Therefore, the primary side controller 222 responds to the feedback voltage VFB with the second voltage level to provide the control signal SC with the second switching frequency F2. The primary side controller 222 controls the power switch Q1 using the control signal SC having the second switching frequency F2. Therefore, the power conversion circuit 210 converts the input power VIN into the second output power VO2.

In addition, the primary side controller 222 receives the sensing voltage value VS located at the second terminal of the power switch Q1. The sensing voltage value VS will be related to the state of the second output power supply VO2. The primary side controller 222 will fine-tune the second switching frequency F2 and/or the duty cycle of the control signal SC according to the sensing voltage value VS.

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

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, capacitor CC may be omitted.

To sum up, 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 no power supply demand is received, the power adapter can effectively reduce power consumption while continuously providing output power.

Although the embodiments of the present invention have been disclosed above, they are not intended to limit the invention. Anyone with ordinary knowledge in the technical field can make some modifications and changes without departing from the spirit and scope of the invention. Therefore, the scope of protection of this new creation shall be determined by the scope of the patent application attached.

100, 200: Power adapter 110, 210: Power conversion circuit 120, 220: Control circuit 211: Primary side circuit 212:Secondary side circuit 221: Optical coupling circuit 222: Primary side controller 223: Secondary side controller 2231:Judgement circuit BT: battery CC, CF, CI, CL, CO: Capacitor D1: Rectifier diode DL: Diode DP: light emitting diode ED: electronic device F1: first switching frequency F2: Second switching frequency I1: operating current I2: current L: light signal LP: primary winding LS: secondary side winding Q1: Power switch Q2:Control switch R1, RF, RS, RL: resistors REQ: power supply demand RV1, RV2: ripples S110~S150: steps SC: control signal SS: operation signal TR: Transformer VCC: Reference high voltage VFB: feedback voltage VIN: input power VO1: first output power supply VO2: Second output power supply VSH: set peak value VSL: Set valley value VSPH: high specification voltage value VSPL: low specification voltage value VSS: reference low voltage W1, W2: voltage waveform

FIG. 1 is a schematic diagram of a power adapter according to an embodiment of the present invention. Figure 2 is a schematic diagram of an operation according to an embodiment of the present invention. FIG. 3 is a voltage waveform diagram of the first output power supply and the second output power supply according to an embodiment of the present invention. FIG. 4 is a schematic circuit diagram of a power adapter according to an embodiment of the present invention.

100:Power adapter

110:Power conversion circuit

120:Control circuit

BT: battery

ED: electronic device

F1: first switching frequency

F2: Second switching frequency

Q1: Power switch

REQ: power supply demand

VIN: input power

VO1: first output power supply

VO2: Second output power supply

Claims (14)

A power adapter for supplying power to electronic devices, including: a power conversion circuit configured to receive input power, wherein the power conversion circuit includes a power switch; and a control circuit coupled to the power conversion circuit and configured to communicate with the electronic device to obtain the power supply requirements of the electronic device, wherein: When the electronic device is connected to the power adapter and the electronic device makes the power supply request, the control circuit uses the first switching frequency to control the power switch so that the power conversion circuit converts the input power into 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. The power adapter of claim 1, wherein when the electronic device is connected to the power adapter and the electronic device is in a normal state, the control circuit uses the first switching frequency to control the power switch, The power conversion circuit is caused to convert the input power into the first output power. The power adapter of claim 1, wherein when the electronic device is connected to the power adapter and the electronic device is in a sleep state, the control circuit uses the second switching frequency to control the power switch, The power conversion circuit is caused to convert the input power into the second output power. The power adapter according to claim 1, wherein 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 enables the power conversion circuit to convert the input power into the second output power. The power adapter of claim 1, wherein 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 The input power is converted into the second output power. A power adapter as described in request item 1, wherein: The voltage waveform of the first output power supply has a first voltage ripple, The voltage waveform of the second output power supply has a second voltage ripple, and The fluctuation of the second voltage ripple is greater than the fluctuation of the first voltage ripple. A power adapter as described in request item 6, wherein: The voltage values of the first output power supply and the second output power supply are regulated between a high standard voltage value and a low standard 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 The set valley value of the second voltage ripple is higher than the low standard voltage value and lower than the valley value of the first voltage ripple. A power adapter as described in request item 7, wherein: the control circuit receives the second output power supply, When the voltage value of the second output power supply rises to the set peak value, the control circuit controls the power switch to be in the first switching state, and When the voltage value of the second output power supply 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. The power adapter of claim 8, wherein the second switching frequency is associated with the set peak value and the set valley value. The power adapter as described in claim 7, wherein the power conversion circuit further includes: Transformer, including primary winding and secondary winding; a primary circuit coupled to the primary winding and including the power switch; and A secondary side circuit is coupled to the secondary side winding. The power adapter according to claim 10, wherein the control circuit includes: An optical coupling circuit controlled to provide an optical signal and provide an operating current according to the optical signal; a secondary side controller, coupled to the secondary side circuit and the optical coupling circuit, configured to control the voltage value of one of the first output power supply and the second output power supply. the optical signal provided by an optical coupling circuit; and A primary-side controller coupled to the power switch and the optical coupling circuit is configured to control the power switch according to the operating current. The power adapter according to claim 11, wherein the secondary side controller includes: a judgment circuit configured to provide an operating signal according to the load status of the power adapter; and Control switch, the first end of the control switch is coupled to the optical coupling circuit, the second end of the control switch is coupled to the reference low voltage, and the control end of the control switch receives the operation signal. A power adapter as claimed in claim 12, wherein: 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 with 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. A power adapter as claimed in claim 12, wherein: 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 with 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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