Power adapter

Abstract

The present disclosure provides a power adapter. The power adapter comprises a chopper circuit, a transformer and a rectifier circuit. The chopper circuit comprises a control circuit and a high-speed electronic switch controlled by the control circuit, the high-speed electronic switch chops the alternating current power under the control of the control circuit; the transformer has a primary winding and a secondary winding; the alternating current power chopped by the high-speed electronic switch is input to the primary winding; the input end of the rectifier circuit is connected with the secondary winding to rectify the alternating current power output by the secondary winding into direct current power output for charging electronic devices. The circuit structure of the power adapter of the present disclosure makes the power adapter have a smaller size.

Description

Technical Field

[0001] This disclosure relates to the field of charging electronic devices, and particularly to a power adapter. Background Technology

[0002] The circuitry inside a power adapter typically first rectifies and filters the input AC power before it is input to the primary side of the transformer. A PWM modulation chip controls the switching of the MOSFET to chop the power on the primary side, thereby obtaining the required voltage on the secondary side of the transformer.

[0003] However, the operating frequency of the rectifier circuit and the MOSFET are limited, so the chopping frequency cannot be very high. This means that small-sized components such as transformers, capacitors, and inductors related to energy conversion cannot be used, which is not conducive to the miniaturization of adapters.

[0004] The information disclosed in the background section is only intended to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] One objective of this disclosure is to provide an adapter with a smaller size.

[0006] To solve the above-mentioned technical problems, the present disclosure adopts the following technical solution:

[0007] According to one aspect of this disclosure, a power adapter is provided, comprising:

[0008] A chopper circuit includes a control circuit and a high-speed electronic switch controlled by the control circuit, wherein the high-speed electronic switch chops the AC power supply under the control of the control circuit.

[0009] A transformer having a primary winding and a secondary winding; AC power, after being chopped by the high-speed electronic switch, is input to the primary winding;

[0010] A rectifier circuit, wherein the first terminal of the rectifier circuit is connected to the secondary winding to rectify the AC power output from the secondary winding into DC power output for charging electronic devices.

[0011] According to one embodiment of this disclosure, there are at least four high-speed electronic switches, which are electrically connected to form a full-bridge circuit to chop the positive half-cycle and negative half-cycle electrical energy of the AC power supply, respectively.

[0012] According to one embodiment of this disclosure, the high-speed electronic switch is a GaN switch, and at least four GaN switches form a GaN full-bridge circuit;

[0013] The first terminal of the GaN full-bridge circuit is connected to an AC power source, and the second terminal of the GaN full-bridge circuit is connected to the primary winding.

[0014] According to one embodiment of this disclosure, the power adapter further includes an LLC resonant circuit, one end of which is connected to the output terminal of the GaN full-bridge circuit, and the primary winding serves as the resonant inductor of the LLC resonant circuit.

[0015] According to one embodiment of this disclosure, the control circuit is further configured to detect the voltage of the AC power supply, and the control circuit is configured to control the chopping frequency of the GaN full-bridge circuit according to the voltage of the AC power supply.

[0016] According to one embodiment of the present disclosure, the GaN full-bridge circuit includes two GaN half-bridge power driver chips, and each GaN half-bridge power driver chip integrates two GaN switching devices.

[0017] The GaN half-bridge power driver chip has a first terminal, a second terminal, and a controlled terminal; the controlled terminals of both GaN half-bridge power driver chips are connected to the control circuit; the first terminals of the two GaN half-bridge power driver chips are respectively connected to the live wire and neutral wire of the AC power supply; the second terminals of both GaN half-bridge power driver chips are connected to the primary winding.

[0018] According to one embodiment of this disclosure, the power adapter further includes a synchronous rectification circuit, which has at least two switching transistors. The control circuit controls the two switching transistors to conduct alternately according to the timing of the positive and negative alternation of the voltage on the secondary winding, so as to synchronously rectify the AC power on the secondary winding.

[0019] According to one embodiment of this disclosure, the synchronous rectification circuit includes a first switching transistor and a second switching transistor; the secondary winding has a first end, a second end, and a tap end located between the first end and the second end of the secondary winding;

[0020] The first switching transistor is connected to the first end of the secondary winding and ground, and is controlled by the control circuit;

[0021] The second switching transistor is connected to the second terminal of the secondary winding and ground, and is controlled by the control circuit;

[0022] The tap terminal is the output terminal of the synchronous rectifier circuit.

[0023] According to one embodiment of this disclosure, the power adapter further includes a step-down circuit connected to the second terminal of the rectifier circuit to step down the DC power output by the rectifier circuit.

[0024] According to one embodiment of this disclosure, the power adapter further includes a voltage control chip;

[0025] The voltage control chip controls the operation of the buck circuit so that the voltage output by the buck circuit matches the desired charging voltage of the electronic device.

[0026] According to one embodiment of this disclosure, the buck circuit includes at least two different types of power conversion circuits to expand the input voltage range allowed by the buck circuit.

[0027] According to one embodiment of this disclosure, the power adapter further includes a boost circuit, which is connected in parallel between the input terminal of the buck circuit and ground;

[0028] The voltage boosting includes a third switching transistor and a voltage boosting capacitor; the third switching transistor is connected between the output terminal of the rectifier circuit and the input terminal of the buck circuit, and is controlled by the control circuit;

[0029] When the voltage at the input terminal of the buck circuit is lower than the first preset voltage value, the control circuit controls the third switch to turn on so that the voltage-raising capacitor stores energy, thereby increasing the voltage at the input terminal of the buck circuit.

[0030] According to one embodiment of this disclosure, the secondary side of the transformer further includes a feedback winding coupled to the primary winding; the control circuit has a power supply terminal;

[0031] The power adapter also includes an auxiliary power supply, the input terminal of which is connected to the feedback winding, and the output terminal of which is connected to the power supply terminal of the control circuit.

[0032] The feedback winding is used to charge the auxiliary power supply so that the auxiliary power supply can supply power to the control circuit.

[0033] The embodiments disclosed herein are based on high-speed electronic switches for chopping. By utilizing the high switching frequency of the high-speed electronic switches, the chopping frequency can be increased, thereby reducing the size of devices related to energy conversion and thus reducing the overall size of the power adapter.

[0034] Furthermore, since the high-speed electronic switch can chop the positive and negative half-cycles of the AC power supply respectively, this embodiment can place the rectifier circuit on the secondary side. Since the voltage on the secondary winding of the transformer is much lower than the voltage on the primary winding, placing the rectifier circuit on the secondary side can reduce the power requirements of the devices, thereby enabling the use of smaller, lower voltage-rated devices, which is beneficial for reducing costs.

[0035] In summary, the technical solution disclosed herein reduces the size of the power adapter, which is beneficial for miniaturizing the power adapter.

[0036] According to another aspect of this disclosure, a power adapter is also provided, comprising:

[0037] A chopper circuit includes a control circuit and a high-speed electronic switch controlled by the control circuit, wherein the high-speed electronic switch chops the AC power supply under the control of the control circuit.

[0038] A transformer having a primary winding and a secondary winding; AC power, after being chopped by the high-speed electronic switch, is input to the primary winding;

[0039] A step-down circuit, connected to the secondary winding, is used to step down the voltage output from the secondary winding; the step-down circuit includes at least two different types of power conversion circuits to expand the range of input voltages allowed by the step-down circuit.

[0040] A rectifier circuit is disposed on the primary side of the transformer and connected between the chopper circuit and the AC power supply; or the rectifier circuit is disposed on the secondary side of the transformer and connected between the secondary winding and the step-down circuit.

[0041] According to one embodiment of this disclosure, the step-down circuit includes at least a charge pump circuit and a BUCK circuit connected in series.

[0042] According to one embodiment of this disclosure, the step-down circuit is a step-down chip, and the difference between the upper and lower limits of the input voltage range of the step-down chip is greater than or equal to 40V.

[0043] The embodiments disclosed herein are based on high-speed electronic switches for chopping. By utilizing the high switching frequency of the high-speed electronic switches, the chopping frequency can be increased, thereby reducing the size of devices related to energy conversion and thus reducing the overall size of the power adapter.

[0044] Furthermore, in this embodiment, the step-down circuit connected to the secondary side of the transformer includes at least two different types of power conversion circuits to expand the allowable input voltage range of the step-down circuit. Therefore, the step-down circuit in this embodiment allows a wider voltage input range, which can effectively address the problem of a large voltage range on the secondary winding caused by using a transformer with fewer turns, thereby ensuring the reliability of the power adapter.

[0045] In summary, the embodiments disclosed herein reduce the size of the power adapter while ensuring the reliability of its operation.

[0046] It should be understood that the above general description and the following detailed description are merely exemplary and do not limit this disclosure. Attached Figure Description

[0047] The above and other objects, features and advantages of this disclosure will become more apparent from a detailed description of exemplary embodiments thereof with reference to the accompanying drawings.

[0048] Figure 1 This is a circuit structure block diagram of a power adapter as shown in the example;

[0049] Figure 2 This is a circuit block diagram of a power adapter according to another example;

[0050] Figure 3 This is a schematic diagram of the circuit structure of a power adapter according to an example;

[0051] Figure 4 This is a schematic diagram of the circuit structure on the primary side of the transformer in a power adapter, as illustrated by an example.

[0052] Figure 5 This is a circuit structure block diagram of a power adapter as illustrated in another example.

[0053] The annotations in the attached figures are explained as follows:

[0054] 10. Chopper circuit; 101. GaN full-bridge circuit; 102. Power control chip; H1. First GaN switching device; H2. Second GaN switching device; H3. Third GaN switching device; H4. Fourth GaN switching device; 1011. GaN half-bridge power driver chip;

[0055] 20. Transformer; L1. Primary winding; L2. Secondary winding; L3. Feedback winding; 30. Rectifier circuit; 40. Buck circuit; 50. LLC resonant circuit; Q1. First switch; Q2. Second switch; Q3. Third switch; C1. Pulse-up capacitor; 60. Pulse-up circuit; 70. Auxiliary power supply; 80. Voltage control chip; 90. Microwave isolation circuit. Detailed Implementation

[0056] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, they are provided to make this disclosure more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art. The drawings are merely illustrative of this disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted.

[0057] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this disclosure, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0058] The preferred embodiments of this disclosure will be further described in detail below with reference to the accompanying drawings.

[0059] This disclosure discloses a power adapter, which is a power conversion device that can convert the voltage of mains power or other AC / DC power sources into a charging voltage acceptable to electronic devices, thereby charging the electronic devices. When charging electronic devices, the power adapter disclosed herein can output a fixed voltage, or it can output a voltage matching the desired charging voltage fed back by the electronic device after a communication handshake between the power adapter and the electronic device.

[0060] The power adapter disclosed herein reduces its size by changing its internal circuit architecture, which is beneficial for the miniaturization of power adapters.

[0061] Figure 1 This is a circuit structure block diagram of a power adapter according to an example. In one embodiment, the power adapter includes a chopper circuit 10, a transformer 20, and a rectifier circuit 30 connected in sequence. The chopper circuit 10 includes a control circuit 104 and a high-speed electronic switch 103 controlled by the control circuit 104. The high-speed electronic switch 103 chops the AC power supply under the control of the control circuit 104. The transformer has a primary winding and a secondary winding; the AC power chopped by the high-speed electronic switch 103 is input to the primary winding; the input terminal of the rectifier circuit is connected to the secondary winding to rectify the AC power output from the secondary winding into DC power for charging electronic devices.

[0062] Furthermore, when the input power is AC power, at least four high-speed electronic switches 103 can be set and electrically connected to form a full-bridge circuit to chop the positive half-cycle and negative half-cycle power of the AC power respectively.

[0063] Here, high-speed electronic switch 103 refers to an electronic switch with a very high switching frequency, reaching 300 kHz or higher, such as a GaN switch. In the following embodiments, a GaN switch is used as an example to illustrate the high-speed electronic switch 103.

[0064] In one specific embodiment, the high-speed electronic switch 103 is a GaN switch, and at least four GaN switches form a GaN full-bridge circuit; the first terminal of the GaN full-bridge circuit is connected to an AC power supply, and the second terminal of the GaN full-bridge circuit is connected to the primary winding. The control circuit 104 is illustrated using a power control chip 102 as an example.

[0065] The control circuit 104 can be a power control chip 102, an MCU, or a chip dedicated to PWM modulation management, etc. Depending on the specific power control chip 102 selected, its pin names and numbers will vary. In one example, the power control chip 102 has multiple control terminals for outputting control signals. Four of these control terminals are used to switch the four arms of the GaN full-bridge circuit 101 on and off, thereby regulating the duty cycle of the output voltage of the GaN full-bridge circuit 101. It is understood that four separate power control chips 102 can also be used to control the alternating switching of the four arms of the GaN full-bridge circuit 101.

[0066] In the following embodiments, the control circuit 104 is illustrated using the power control chip 102 as an example.

[0067] Please see Figure 2 , Figure 2 This is a circuit block diagram of a power adapter according to another example. Specifically, the chopper circuit 10 includes a power control chip 102 and a GaN full-bridge circuit 101 controlled by the power control chip 102. The first terminal of the GaN full-bridge circuit 101 is connected to an AC power supply. The GaN full-bridge circuit 101 includes multiple GaN switching devices and is used to chop the AC power supply. The transformer 20 has a primary winding L1 and a secondary winding L2. The primary winding L1 is connected to the second terminal of the GaN full-bridge circuit 101. The first terminal of the rectifier circuit 30 is connected to the secondary winding L2 to rectify the AC power output by the secondary winding L2.

[0068] Furthermore, the power adapter may also include a buck circuit 40 or a boost circuit. The buck circuit 40 is connected to the second terminal of the rectifier circuit 30 to step down the DC power output by the rectifier circuit 30. The boost circuit is connected to the second terminal of the rectifier circuit 30 to boost the DC power output by the rectifier circuit 30.

[0069] Please see Figure 3 , Figure 3 This is a circuit diagram of a power adapter as shown in one example. See also: Figure 3 , Figure 3There are four GaN switching devices in total, forming the upper left bridge arm, lower left bridge arm, upper right bridge arm, and lower right bridge arm, respectively. The four GaN switching devices are connected to the control terminals of the power control chip 102. The upper left bridge arm and lower left bridge arm are connected to the live wire L and neutral wire P of the AC power supply, respectively.

[0070] Here, the GaN switching devices include a first GaN switching device H1 (corresponding to the upper left bridge arm), a second GaN switching device H2 (corresponding to the lower left bridge arm), a third GaN switching device H3 (corresponding to the upper right bridge arm), and a fourth GaN switching device H4 (corresponding to the lower right bridge arm). The gates of all four GaN switching devices are connected to the power control chip 102. The source of the first GaN switching device H1 is connected to the drain of the second GaN switching device H2, and the drain of the first GaN switching device H1 is connected to the live wire L. The source of the second GaN switching device H2 is grounded. The source of the third GaN switching device H3 is connected to the drain of the fourth GaN switching device H4, and the drain of the third GaN switching device H3 is connected to the neutral wire P. The source of the fourth GaN switching device H4 is grounded.

[0071] Here, we take AC mains power as an example. During the positive half-cycle of the mains power, the power control chip 102 controls the GaN switching devices on the upper left and lower right bridge arms to conduct; during the negative half-cycle of the mains power, the power control chip 102 controls the GaN switching devices on the lower left and upper right bridge arms to conduct. In this way, the GaN full-bridge circuit 101 achieves chopping of the positive and negative half-cycles of the mains power.

[0072] In this embodiment, compared to the related art where a single switch is used to modulate the electrical energy on the primary winding L1 of transformer 20, the voltage fluctuation amplitude on the primary winding L1 is large. Therefore, when the voltage on the primary winding L1 is too low to meet the switching conditions, the switch cannot conduct, resulting in energy not being able to be conducted to the negative terminal of transformer 20. The accumulated energy is then converted into heat, causing transformer 20 to overheat. Here, the interval where the voltage on the primary winding L1 is too low to maintain the operation of the switch is called the dead zone. Therefore, in the related art, the voltage dead zone is relatively large during the chopping process of the electrical energy on the primary winding L1.

[0073] In this embodiment, the upper left bridge arm and the lower left bridge arm form a push-pull structure; and the upper right bridge arm and the lower right bridge arm also form a push-pull structure. The push-pull structure reduces the dead zone, thereby improving the efficiency of energy conversion from the primary winding L1 to the secondary winding L2, increasing energy utilization, and effectively reducing heat generation. Equally important, the reduction in dead zone improves the accuracy of PWM modulation of the electrical energy, thus improving the accuracy of the adapter's output voltage.

[0074] Please see Figure 4 , Figure 4 This is a schematic diagram of the circuit structure of a power adapter according to an example. In one example, the GaN full-bridge circuit 101 includes two GaN half-bridge power driver chips 1011, each GaN half-bridge power driver chip 1011 integrating two GaN switching devices; the GaN half-bridge power driver chip 1011 has a first terminal, a second terminal, and a controlled terminal; the controlled terminals of both GaN half-bridge power driver chips 1011 are connected to the power control chip 102; the first terminals of the two GaN half-bridge power driver chips 1011 are respectively connected to the live wire L and the neutral wire P of the AC power supply; the second terminals of both GaN half-bridge power driver chips 1011 are connected to the primary winding L1.

[0075] A specific GaN half-bridge power driver chip 1011 has an overall size of only 9mm x 9mm x 1mm. It integrates two GaN switching devices and the driving circuit for turning the GaN switching devices on and off. By inputting a driving signal from the outside, the GaN switching devices can be driven to work. Therefore, there is no need to configure a driving circuit outside the GaN half-bridge power driver chip 1011, thus reducing the size of the power adapter.

[0076] In some embodiments, the power control chip 102 is further configured to detect the voltage level of the AC power supply, and the power control chip 102 controls the chopping frequency of the GaN full-bridge circuit 101 based on the voltage level of the AC power supply. In a specific example, the voltage level of the AC power supply reflects the region and country.

[0077] For example, when the power control chip 102 detects an AC power supply voltage of 220V, it indicates that the AC mains power is from China. Since the voltage amplitude of the Chinese AC mains power is relatively large, more energy can be utilized. Therefore, the power control chip 102 adjusts the chopping frequency of the GaN full-bridge circuit 101 to increase the duty cycle of the chopped power waveform, thereby outputting a larger power, such as 120W. When the power control chip 102 detects an AC power supply voltage of 110V, it indicates that the AC power is from the United States. In this case, if it still outputs 120W of energy, it will affect the overall conversion efficiency of the circuit, causing the adapter to overheat and generating harmonic interference to the power grid. Therefore, the power control chip 102 controls the chopping frequency of the GaN full-bridge circuit 101 to output a lower power.

[0078] Please continue reading. Figure 3 In some embodiments, the power adapter further includes an LLC resonant circuit 50, one end of which is connected between the second ends of the two GaN half-bridge power driver chips 1011; the LLC resonant circuit 50 includes an inductor coupled to the primary winding L1.

[0079] The resonant elements in the LLC resonant circuit 50 mainly consist of the three resonant elements mentioned above: the resonant capacitor Cs, the inductor Ls, and the magnetizing inductor. The magnetizing inductor is the primary winding L1. By selecting an appropriate resonant capacitor Cs and an inductor with suitable inductance, the LLC resonant circuit 50 can operate in a resonant state within the operating frequency range of the GaN full-bridge circuit 101. When the LLC resonant circuit 50 operates in a resonant state, the reverse input current when the GaN switching device is turned off can be reduced, further reducing the energy loss of the GaN switching device during switching, which is beneficial for improving switching efficiency and reducing the heat generated by energy loss.

[0080] Furthermore, as mentioned above, the chopper circuit 10 in the above embodiment is based on a GaN switching device, which is a high electron mobility transistor (HEMT). Compared to traditional MOSFETs, GaN switching devices have a higher operating frequency, reaching 500kHz-1MHz during chopping. This increased operating frequency reduces the requirement for the inductance of the transformer 20 windings, allowing for a reduction in the number of turns in the transformer 20, thereby reducing its size.

[0081] In some embodiments, the transformer 20 is a planar transformer 20. A planar transformer 20 is characterized by high frequency, low profile, small height, and high operating frequency, which helps reduce the thickness of the power adapter. For example, a printed circuit board (PCB) type transformer 20 can be used. This eliminates the need for a winding frame, increases the heat dissipation area, and reduces eddy current losses caused by the skin effect and proximity effect at high frequencies. In one example, a 16T:2T:2T PCB type transformer 20 is used, and its size is only about 20mm x 20mm, which is very compact.

[0082] Furthermore, in this embodiment, the power adapter also includes a rectifier circuit 30. The first terminal of the rectifier circuit 30 is connected to the secondary winding L2 to rectify the AC power output from the secondary winding L2. In contrast to related technologies, the rectifier circuit 30 is always located on the primary side of the transformer 20; in this embodiment, the rectifier circuit 30 is located on the secondary side of the transformer 20. Since the voltage on the secondary winding L2 of the transformer 20 is significantly lower than the voltage on the primary winding, placing the rectifier circuit 30 on the secondary side reduces the power requirements of the devices, thereby allowing the use of smaller, lower voltage-rated devices, which helps to reduce costs.

[0083] Furthermore, by placing the rectifier circuit 30 on the secondary side, the power control chip 102 only needs to control the GaN full-bridge circuit 101 on the primary side. The rectifier circuit 30 on the secondary side can be controlled by a dedicated control chip, thereby reducing the control burden on the power control chip 102. This allows the power control chip 102 to more accurately and effectively control the operation of the GaN full-bridge circuit 101. Therefore, this embodiment is beneficial to improving the working stability and reliability of the power adapter.

[0084] It should be noted that the above-mentioned beneficial effects are achieved because the GaN full-bridge circuit 101 is used on the primary side of the embodiment to chop the positive and negative half-cycles of the AC power supply, respectively. This eliminates the need to set up a rectifier circuit 30 on the primary side of the transformer 20, and the rectifier circuit 30 can be set on the secondary side of the transformer 20.

[0085] In one embodiment, the rectifier circuit 30 is a synchronous rectifier circuit 30. The synchronous rectifier circuit 30 has at least two switching transistors, and the power control chip 102 controls the two switching transistors to be turned on alternately according to the timing of the positive and negative alternation of the voltage on the secondary winding, so as to synchronously rectify the AC current on the secondary winding.

[0086] Since the power adapter in this embodiment is relatively small, compared with the diode rectifier circuit 30, synchronous rectification can reduce the heat generated by the fixed voltage drop caused by diode rectification, thereby helping to reduce the requirements of the heat dissipation structure inside the power adapter, and thus further reducing the size of the adapter.

[0087] The power adapter also includes a microwave isolation circuit 90, and the control signal issued by the power control chip 102 is sent to the switching transistor in the rectifier circuit 30 through the microwave isolation circuit 90.

[0088] The microwave isolation circuit 90 includes a transmitter and a receiver. The transmitter is connected to the power control chip 102, and the receiver is connected to the switching transistor in the rectifier circuit 30. The transmitter is used to convert the control signal emitted by the power control chip 102 into a microwave signal and send it to the receiver. The receiver is used to convert the microwave signal into the control signal to control the corresponding switching transistor to turn on or off.

[0089] Because the isolation microwave unit 90 has a fast response speed, its transmitting end can convert the control signal into a microwave signal and quickly transmit it to the receiving end. Therefore, even if the dead time of the control signal is set to be short, the switching transistor can be turned on or off quickly, which can improve efficiency and avoid crosstalk in the circuit. On the other hand, since microwave transmission does not rely on medium transmission, the distance between the transmitting end and the receiving end of the microwave unit can be set to be farther. This can further avoid circuit crosstalk and also avoid mis-turning of the switching transistor.

[0090] In one example, the synchronous rectification circuit 30 includes a first switch Q1 and a second switch Q2; the secondary winding L2 has a first end, a second end, and a tap located between the first end and the second end of the secondary winding L2; the first switch Q1 is connected to the first end of the secondary winding L2 and ground, and is controlled by the power control chip 102; the second switch Q2 is connected to the second end of the secondary winding L2 and ground, and is controlled by the power control chip 102; the tap is connected to the input of the buck circuit 40.

[0091] In this example, the first switch Q1 and the second switch Q2 can be MOSFETs. The taps are used to output a positive voltage. The first switch Q1 and the second switch Q2 are grounded alternately, thereby rectifying the secondary winding L2 of transformer 20. The synchronous rectification circuit 30 in this example uses a logic high level to directly drive the rectifier MOSFET, eliminating the need for a bootstrap circuit, thus saving components and simplifying the circuit structure.

[0092] As mentioned earlier, due to the use of GaN switching devices for chopping, the high switching frequency of GaN switching devices allows transformer 20 to use fewer turns. When the number of turns in transformer 20 decreases, the transformation ratio of transformer 20 will be larger; that is, the voltage variation range on the secondary winding L2 of transformer 20 will be wider. Furthermore, for printed circuit board (PCB) transformer 20, the multilayer PCB board is sandwiched between the magnetic cores. During the manufacturing process, the air gap is not easily controlled, which can easily cause a deviation between the actual transformation ratio and the design transformation ratio of PCB transformer 20. This deviation may further increase the voltage range on the secondary winding L2 of transformer 20.

[0093] Based on this, in this embodiment, the step-down circuit 40 connected to the secondary side of the transformer 20 includes a charge pump circuit and a buck circuit connected in series. The charge pump circuit allows for a wider voltage input range, while the buck circuit has higher energy conversion efficiency. Therefore, the step-down circuit 40 in this embodiment allows for a wider voltage input range, which can effectively address the problem of a large voltage range on the secondary winding L2 caused by using a transformer 20 with fewer turns.

[0094] In one embodiment, a buck converter chip that allows for a wide input voltage range can be directly used. The difference between the upper and lower limits of the buck converter chip's input voltage range is greater than or equal to 40V, for example, it can be 5V to 60V. The use of a buck converter chip can further reduce the size of the power adapter.

[0095] In some embodiments, the buck converter chip can be directly controlled by the power control chip 102. In other embodiments, the buck converter chip is controlled by a voltage control chip 80 located on the secondary side of the transformer 20. The voltage control chip 80 can be an MCU. The voltage control chip 80 outputs a PWM wave with an adjustable duty cycle and controls the switching of the switch inside the buck converter chip through a MOS switch (which can be built into or external to the voltage control chip 80), thereby achieving the purpose of regulating the output voltage of the buck converter chip.

[0096] In addition, the voltage adapter also includes a charging interface through which the electronic device to be charged connects to the voltage adapter to receive the power ultimately output by the step-down chip. The charging interface can be a Type-C interface, a USB 2.0 interface, a Micro USB interface, etc.

[0097] When the voltage adapter is connected to the electronic device to be charged, the voltage control chip 80 is also used for communication handshake with the electronic device to determine the desired output voltage and desired output current of the electronic device. Then, the power control chip 102 adjusts the duty cycle of the output PWM based on the desired output voltage and desired output current, thereby controlling the output voltage and output current of the buck circuit 40.

[0098] In this embodiment, a power control chip 102 is used on the primary side of transformer 20 to control the chopping frequency of the GaN full-bridge circuit 101, enabling wide-range voltage transformation of the AC power supply according to the desired output voltage. On the secondary side of transformer 20, a voltage control chip 80 is used to further refine the voltage output by the final step-down chip, thereby improving the matching between the power adapter's output voltage and the desired output voltage. Therefore, this embodiment improves the accuracy of the power adapter's on-demand output voltage.

[0099] The voltage on the secondary winding L2 of transformer 20 is rectified by synchronous rectifier circuit 30 to form a wave. The voltage of the wave changes over time. When the voltage drops to a certain level, it exceeds the operating threshold of buck circuit 40, causing buck circuit 40 to be unable to convert the energy in this low-voltage range, resulting in energy waste.

[0100] Please continue reading. Figure 3 And see Figure 5 ,in, Figure 5This is a circuit structure block diagram of a power adapter according to another exemplary embodiment. In one embodiment, the power adapter further includes a voltage boosting circuit 60, which is used to raise the input voltage of the buck circuit 40, so that the buck circuit 40 can operate normally even when the output voltage of the synchronous rectifier circuit 30 is low, enabling the buck circuit 40 to perform energy conversion on electrical energy in the low voltage range, thereby improving the energy conversion efficiency.

[0101] Specifically, the boost circuit 60 is connected in parallel between the input terminal of the buck circuit 40 and ground; the boost voltage includes the third switch Q3 and the boost capacitor C1; the third switch Q3 is connected between the tap terminal and the input terminal of the buck circuit 40 and is controlled by the power control chip 102; when the voltage at the input terminal of the buck circuit 40 is lower than the first preset voltage value, the power control chip 102 controls the third switch Q3 to turn on, so that the boost capacitor C1 stores energy, thereby increasing the voltage at the input terminal of the buck circuit 40.

[0102] The third switch Q3 can be a MOSFET. When an NMOS transistor is used, its gate can be connected to the power control chip 102 or other control chips. The drain of the MOSFET is connected to a capacitor, and its source is grounded. It should also be understood that multiple capacitors can be connected in parallel to increase the voltage boost effect.

[0103] When the output voltage of the synchronous rectifier circuit 30 is in the low voltage range of the swirl wave, the power control chip 102 controls the third switch Q3 to turn on. At this time, the capacitor is gradually charged and has voltage. The voltage on the capacitor is applied to the input terminal of the buck circuit 40, thereby raising the voltage at the input terminal of the buck circuit 40 to ensure that the electrical energy in the low voltage range of the swirl wave can be effectively utilized.

[0104] The operation of the voltage boosting circuit 60 is controlled by the power control chip 102. The power control chip 102 can send control signals to the switching transistors within the voltage boosting circuit 60 via the microwave isolation circuit 90. For a specific embodiment of the microwave isolation circuit 90, please refer to the above embodiments.

[0105] It should be understood that the power control chip 102 can send control signals to the switching transistors in the rectifier circuit 30 and the boost circuit 60 respectively via different microwave isolation circuits 90 to avoid signal crosstalk.

[0106] In this embodiment, the voltage boosting circuit 60 is only connected in parallel to the circuit when the output voltage of the rectifier circuit 30 is low, in order to raise the input voltage of the buck circuit 40. This allows the use of a smaller capacitor to meet the operating requirements of the buck circuit 40. A smaller capacitor results in a smaller overall size, which helps to further reduce the size of the adapter. Therefore, the voltage boosting circuit 60 in this embodiment is designed to meet the operating requirements of the buck circuit 40 while contributing to a further reduction in adapter size.

[0107] In some embodiments, the secondary side of transformer 20 further includes a feedback winding L3, which is coupled to the primary winding L1; the power control chip 102 has a power supply terminal; the power adapter further includes an auxiliary power supply 70, the input terminal of which is connected to the feedback winding L3, and the output terminal of which is connected to the power supply terminal of the power control chip 102; at the initial operation of the power adapter, the weak electrical energy on the primary side of transformer 20 can be fed to the feedback winding L3, so the feedback winding L3 charges the auxiliary power supply 70, and after the auxiliary power supply 70 is charged, it supplies power to the power control chip 102 to start the power control chip 102 from working.

[0108] In one example, the auxiliary power supply 70 is a linear regulator. Specifically, a modified linear regulator chip can also be used to output a stable supply voltage to the power control chip 102.

[0109] The feedback winding L3 is also used to detect the voltage on the feedback winding L3 and feed this voltage back to the power control chip 102, thereby enabling the power control chip 102 to adjust the GaN full-bridge circuit 101 according to the feedback voltage. In one example, the auxiliary power supply 70 may include a voltage divider sampling circuit, which may specifically be formed by at least two resistors connected in series.

[0110] In some embodiments, the compatibility of the power adapter is improved by configuring multiple charging protocols within the power adapter. These charging protocols can be PD, QC, SCP, VOOC, etc.

[0111] The embodiments disclosed herein are based on a GaN full-bridge circuit 101 for chopping. By utilizing the higher switching frequency of GaN switching devices, the chopping frequency can be increased, thereby reducing the size of devices related to energy conversion and thus reducing the overall size of the power adapter.

[0112] Furthermore, since the GaN full-bridge circuit 101 can chop the positive and negative half-cycles of the AC power supply respectively, the rectifier circuit 30 is placed on the secondary side in this embodiment. Since the voltage on the secondary winding L2 of the transformer 20 is much lower than the voltage on the primary winding, placing the rectifier circuit 30 on the secondary side can reduce the power requirements of the devices, thereby enabling the use of smaller devices with lower withstand voltage values, which is beneficial to reducing costs.

[0113] In summary, the technical solution disclosed herein reduces the size of the power adapter, which is beneficial for miniaturizing the power adapter.

[0114] The embodiments disclosed herein are based on a GaN full-bridge circuit 101 for chopping. By utilizing the higher switching frequency of GaN switching devices, the chopping frequency can be increased, thereby reducing the size of devices related to energy conversion and thus reducing the overall size of the power adapter.

[0115] Furthermore, in this embodiment, the step-down circuit 40 connected to the secondary side of the transformer 20 includes a charge pump circuit and a buck circuit connected in series. The charge pump circuit allows for a wider voltage input range, while the buck circuit has high energy conversion efficiency. Therefore, the step-down circuit 40 in this embodiment allows for a wider voltage input range, which effectively addresses the problem of a large voltage range on the secondary winding L2 caused by using a transformer 20 with fewer turns, thereby ensuring the reliability of the power adapter.

[0116] In summary, the embodiments disclosed herein reduce the size of the power adapter while ensuring the reliability of its operation.

[0117] Although this disclosure has been described with reference to several typical embodiments, it should be understood that the terminology used is descriptive and exemplary, and not restrictive. Because this disclosure can be embodied in many forms without departing from the spirit or essence of the invention, it should be understood that the above embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope defined by the appended claims. Therefore, all variations and modifications falling within the scope of the claims or their equivalents should be covered by the appended claims.

Claims

1. A power adapter, characterized by, The power adapter comprises: a chopper circuit comprising a control circuit and high-speed electronic switches controlled by the control circuit, the high-speed electronic switches chopping an alternating current power supply under the control of the control circuit; a transformer having a primary winding and a secondary winding, the chopped alternating current power being input to the primary winding through the high-speed electronic switches; a rectifier circuit having an input end connected to the secondary winding to rectify alternating current power output by the secondary winding into direct current power for charging electronic devices; the power adapter further comprises a voltage-lowering circuit and a voltage-raising circuit; the voltage-lowering circuit is connected to a second end of the rectifier circuit to lower the direct current power output by the rectifier circuit; the voltage-lowering circuit comprises a charge pump circuit and a BUCK circuit connected in series; the voltage-raising circuit is connected in parallel between an input end of the voltage-lowering circuit and the ground; the voltage-raising circuit comprises a third switch tube and a voltage-raising capacitor; the third switch tube is connected between an output end of the rectifier circuit and the input end of the voltage-lowering circuit and is controlled by the control circuit; when the voltage on the input end of the voltage-lowering circuit is lower than a first preset voltage value, the control circuit controls the third switch tube to be turned on to enable the voltage-raising capacitor to store energy, thereby increasing the voltage on the input end of the voltage-lowering circuit.

2. The power adapter of claim 1, wherein, The high-speed electronic switches are at least four in number and are electrically connected to form a full-bridge circuit to chop positive half-cycle power and negative half-cycle power of the alternating current power supply respectively.

3. The power adapter of claim 2, wherein, The high-speed electronic switches are GaN switches, and at least four GaN switches form a GaN full-bridge circuit. A first end of the GaN full-bridge circuit is connected to an alternating current power supply, and a second end of the GaN full-bridge circuit is connected to the primary winding.

4. The power adapter of claim 3, wherein, The power adapter further comprises an LLC resonant circuit, one end of the LLC resonant circuit being connected to an output end of the GaN full-bridge circuit, and the primary winding being a resonant inductor of the LLC resonant circuit.

5. The power adapter of claim 3, wherein, The control circuit is further configured to detect the voltage of the alternating current power supply, and the control circuit is configured to control the chopping frequency of the GaN full-bridge circuit according to the voltage of the alternating current power supply.

6. The power adapter of claim 3, wherein, The GaN full-bridge circuit comprises two GaN half-bridge power drive chips, and each GaN half-bridge power drive chip has two GaN switch devices integrated therein. The GaN half-bridge power drive chip has a first end, a second end, and a controlled end; the controlled ends of the two GaN half-bridge power drive chips are connected to the control circuit; the first ends of the two GaN half-bridge power drive chips are connected to live and neutral lines of the alternating current power supply respectively; and the second ends of the two GaN half-bridge power drive chips are connected to the primary winding.

7. The power adapter of claim 1, wherein, The power adapter further comprises a synchronous rectifier circuit having at least two switch tubes, and the control circuit controls the two switch tubes to be turned on alternately according to the positive and negative alternating time of the voltage on the secondary winding to synchronously rectify the alternating current on the secondary winding.

8. The power adapter of claim 7, wherein, The synchronous rectification circuit comprises a first switch tube and a second switch tube; the secondary winding has a first end, a second end and a tap end between the first end and the second end; The first switch tube is connected to the first end of the secondary winding and the ground, and is controlled by the control circuit; The second switch tube is connected to the second end of the secondary winding and the ground, and is controlled by the control circuit; The tap end is an output end of the synchronous rectification circuit.

9. The power adapter of claim 7, wherein, The power adapter further comprises a microwave isolation circuit, and the control signal sent by the control circuit is sent to the switch tube in the rectification circuit through the microwave isolation circuit; The microwave isolation circuit comprises a transmitting end and a receiving end, the transmitting end is connected with the control circuit, the receiving end is connected with the switch tube in the rectification circuit, the transmitting end is used for converting the control signal sent by the control circuit into a microwave signal and sending the microwave signal to the receiving end, and the receiving end is used for converting the microwave signal into the control signal to control the conduction or turn-off of the corresponding switch tube.

10. The power adapter of claim 1, wherein, The power adapter further comprises a voltage control chip; The voltage control chip controls the operation of the voltage reduction circuit, so that the voltage output by the voltage reduction circuit matches the charging voltage expected by the electronic device.

11. The power adapter of claim 1, wherein, The voltage reduction circuit comprises at least two different types of electric energy conversion circuits to expand the voltage range allowed to be input by the voltage reduction circuit.

12. The power adapter of claim 1, wherein, The secondary side of the transformer further comprises a feedback winding coupled with the primary winding; the control circuit has a power supply end; The power adapter further comprises an auxiliary power supply, the input end of the auxiliary power supply is connected with the feedback winding, and the output end of the auxiliary power supply is connected with the power supply end of the control circuit; The feedback winding is used for charging the auxiliary power supply to supply power to the control circuit.

13. A power adapter, characterized by It comprises: a chopper circuit comprising a control circuit and a high-speed electronic switch controlled by the control circuit, the high-speed electronic switch chops the alternating power supply under the control of the control circuit; a transformer having a primary winding and a secondary winding; the alternating power energy chopped by the high-speed electronic switch is input to the primary winding; a voltage reduction circuit connected with the secondary winding for reducing the voltage output by the secondary winding; the voltage reduction circuit comprises at least two different types of electric energy conversion circuits to expand the voltage range allowed to be input by the voltage reduction circuit; wherein, the two different types of electric energy conversion circuits comprise a charge pump circuit and a BUCK circuit connected in series; a rectification circuit arranged on the primary side of the transformer and connected between the chopper circuit and the alternating power supply; or the rectification circuit is arranged on the secondary side of the transformer and connected between the secondary winding and the voltage reduction circuit; The power adapter further comprises a voltage lifting circuit; The voltage lifting circuit is connected in parallel between the input end of the voltage reduction circuit and the ground. The voltage-boosting voltage comprises a third switch tube and a voltage-boosting capacitor; the third switch tube is connected between an output end of the rectifier circuit and an input end of the voltage-reducing circuit and is controlled by the control circuit; When the voltage on the input end of the voltage-reducing circuit is lower than a first preset voltage value, the control circuit controls the third switch tube to be turned on, so that the voltage-boosting capacitor stores energy, thereby increasing the voltage on the input end of the voltage-reducing circuit.

14. The power adapter of claim 13, wherein, The voltage-reducing circuit is a voltage-reducing chip, and a difference between an upper limit value and a lower limit value of an input voltage range of the voltage-reducing chip is greater than or equal to 40 V.

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