TWI879622B - Power supply device for suppressing electromagnetic interference - Google Patents

Abstract

A power supply device for suppressing EMI (Electromagnetic Interference) includes a switch circuit, a transformer, a first resonant capacitor, an output stage circuit, a tunable capacitive element, a feedback compensation circuit, and a detection and control circuit. The output stage circuit generates an output voltage. The feedback compensation circuit generates a feedback voltage according to an input voltage. The detection and control circuit includes an NTC (Negative Temperature Coefficient) resistor disposed adjacent to the first resonant capacitor. The NTC resistor provides a temperature dependent voltage. The detection and control circuit selectively enables or disables the tunable capacitive element according to the output voltage, the feedback voltage, and the temperature dependent voltage.

Description

Power supply for suppressing electromagnetic interference

The present invention relates to a power supply, and more particularly to a power supply capable of suppressing electromagnetic interference.

Power supplies are indispensable components in the field of laptop computers. However, if the electromagnetic interference (EMI) of the power supply is too severe, it is easy to cause the overall operating performance of the related laptop to decline. In view of this, it is necessary to propose a new solution to overcome the difficulties faced by previous technologies.

In a preferred embodiment, the present invention provides a power supply for suppressing electromagnetic interference, comprising: a switching circuit, which generates a switching potential according to an input potential, a first driving potential, and a second driving potential; a transformer, which comprises a main coil, a first secondary coil, and a second secondary coil, wherein the transformer has a built-in leakage inductor and an excitation inductor, and the main coil receives the switching potential through the leakage inductor; a first resonant capacitor, which is coupled to the excitation inductor; an output stage circuit, which is coupled to the first secondary coil and the second secondary coil. A coil and generates an output potential; an adjustable capacitance element coupled to the excitation inductor; a feedback compensation circuit that generates a feedback potential according to the input potential; and a detection and control circuit that generates the first drive potential and the second drive potential and includes a negative temperature coefficient resistor adjacent to the first resonant capacitor, wherein the negative temperature coefficient resistor provides a temperature-dependent potential; wherein the detection and control circuit selectively enables or disables the adjustable capacitance element according to the output potential, the feedback potential, and the temperature-dependent potential.

In some embodiments, the switching circuit includes: a first transistor having a control end, a first end, and a second end, wherein the control end of the first transistor is used to receive the first driving potential, the first end of the first transistor is coupled to a first node to output the switching potential, and the second end of the first transistor is coupled to an input node to receive the input potential; and a second transistor having a control end, a first end, and a second end, wherein the control end of the second transistor is used to receive the second driving potential, the first end of the second transistor is coupled to a ground potential, and the second end of the second transistor is coupled to the first node.

In some embodiments, the leakage inductor has a first end and a second end, the first end of the leakage inductor is coupled to the first node to receive the switching potential, the second end of the leakage inductor is coupled to a second node, the main coil has a first end and a second end, the first end of the main coil is coupled to the second node, the second end of the main coil is coupled to a third node, the excitation inductor has a first end and a second end, the first end of the excitation inductor is coupled to the second node, the second end of the excitation inductor is coupled to the third node, The first resonant capacitor has a first end and a second end, the first end of the first resonant capacitor is coupled to the third node, and the second end of the first resonant capacitor is coupled to the ground potential. The first secondary coil has a first end and a second end, the first end of the first secondary coil is coupled to a fourth node, and the second end of the first secondary coil is coupled to a common node. The second secondary coil has a first end and a second end, the first end of the second secondary coil is coupled to the common node, and the second end of the second secondary coil is coupled to a fifth node.

In some embodiments, the output stage circuit includes: a first diode having an anode and a cathode, wherein the anode of the first diode is coupled to the fourth node, and the cathode of the first diode is coupled to an output node to output the output potential; a second diode having an anode and a cathode, wherein the anode of the second diode is coupled to the fifth node, and the cathode of the second diode is coupled to the output node; and a first capacitor having a first end and a second end, wherein the first end of the first capacitor is coupled to the output node, and the second end of the first capacitor is coupled to the common node.

In some embodiments, the adjustable capacitance element includes: a third transistor having a control terminal, a first terminal, and a second terminal, wherein the control terminal of the third transistor is used to receive an amplified potential, the first terminal of the third transistor is coupled to the ground potential, and the second terminal of the third transistor is coupled to a sixth node; a fourth transistor having a control terminal, a first terminal, and a second terminal, wherein the control terminal of the fourth transistor is used to receive a control potential, the first terminal of the fourth transistor is coupled to the sixth node, and the The second end of the fourth transistor is coupled to a seventh node; a fifth transistor having a control end, a first end, and a second end, wherein the control end of the fifth transistor is used to receive the output potential, the first end of the fifth transistor is coupled to the seventh node, and the second end of the fifth transistor is coupled to an eighth node; and a second resonant capacitor having a first end and a second end, wherein the first end of the second resonant capacitor is coupled to the third node, and the second end of the second resonant capacitor is coupled to the eighth node.

In some embodiments, the feedback compensation circuit includes: a first resistor having a first end and a second end, wherein the first end of the first resistor is coupled to the input node to receive the input potential, and the second end of the first resistor is coupled to a ninth node; a second resistor having a first end and a second end, wherein the first end of the second resistor is coupled to the ninth node, and the second end of the second resistor is coupled to the ground potential; a linear optical coupler including a light emitting diode and a bipolar junction transistor, wherein the light emitting diode The diode has an anode and a cathode, the anode of the light-emitting diode is coupled to the ninth node, the cathode of the light-emitting diode is coupled to the ground potential, the bipolar junction transistor has a collector and an emitter, the collector of the bipolar junction transistor is used to output the feedback potential, and the emitter of the bipolar junction transistor is coupled to a tenth node; and a second capacitor has a first end and a second end, wherein the first end of the second capacitor is coupled to the tenth node, and the second end of the second capacitor is coupled to the common node.

In some embodiments, the detection and control circuit further includes: an amplifier that amplifies the feedback potential by a gain factor to generate the amplified potential; and an AND gate having a first input terminal, a second input terminal, and an output terminal, wherein the first input terminal of the AND gate is used to receive the amplified potential, the second input terminal of the AND gate is used to receive the output potential, and the output terminal of the AND gate is used to output a logic potential.

In some embodiments, the detection and control circuit further includes: a microcontroller, which generates the first driving potential and the second driving potential, and outputs a fixed current, wherein the fixed current flows through the negative temperature coefficient resistor; wherein the negative temperature coefficient resistor has a first end and a second end, the first end of the negative temperature coefficient resistor is coupled to the common node, and the second end of the negative temperature coefficient resistor is used to output the temperature-dependent potential to the microcontroller.

In some embodiments, if the temperature-dependent potential is lower than or equal to a reference potential, the microcontroller will output the control potential with a high logic level, and if the temperature-dependent potential is higher than the reference potential, the microcontroller will output the control potential with a low logic level.

In some embodiments, the distance between the negative temperature coefficient resistor and the first resonant capacitor is less than or equal to 3 mm.

In order to make the purpose, features and advantages of the present invention more clearly understood, specific embodiments of the present invention are specifically listed below and described in detail with reference to the accompanying drawings.

Certain terms are used in the specification and patent application to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different terms to refer to the same component. This specification and patent application do not use differences in names as a way to distinguish components, but use differences in the functions of components as the criterion for distinction. The words "include" and "including" mentioned throughout the specification and patent application are open terms and should be interpreted as "including but not limited to". The word "substantially" means that within an acceptable error range, those skilled in the art can solve the technical problem within a certain error range and achieve the basic technical effect. In addition, the word "coupled" in this specification includes any direct and indirect electrical connection means. Therefore, if a first device is described herein as being coupled to a second device, it means that the first device may be directly electrically connected to the second device, or may be indirectly electrically connected to the second device via other devices or connection means.

FIG. 1 is a schematic diagram showing a power supply 100 according to an embodiment of the present invention. For example, the power supply 100 can be applied to a desktop computer, a laptop computer, or an all-in-one computer. As shown in FIG. 1, the power supply 100 includes: a switching circuit 110, a transformer 120, a first resonant capacitor CR1, an output stage circuit 130, an adjustable capacitance element 140, a feedback compensation circuit 150, and a detection and control circuit 160. It should be noted that, although not shown in FIG. 1, the power supply 100 may further include other components, such as: a voltage regulator or (and) a negative feedback circuit.

The switching circuit 110 can generate a switching potential VW according to an input potential VIN, a first drive potential VG1, and a second drive potential VG2. For example, the input potential VIN can be a DC potential, and its potential level can be between 360V and 440V, but it is not limited to this. The transformer 120 includes a main coil 121, a first sub-coil 122, and a second sub-coil 123. The transformer 120 can further have a built-in leakage inductor LR and an excitation inductor LM, wherein the leakage inductor LR, the excitation inductor LM, and the main coil 121 can all be located on the same side of the transformer 120, and the first sub-coil 122 and the second sub-coil 123 can all be located on the opposite side of the transformer 120. The main coil 121 can receive the switching potential VW via the leakage inductor LR, and the first sub-coil 122 and the second sub-coil 123 can operate in response to the switching potential VW. The first resonant capacitor CR1 is coupled to the magnetizing inductor LM. For example, the leakage inductor LR, the magnetizing inductor LM, and the first resonant capacitor CR1 can together form a resonant tank of the power supply 100.

The output stage circuit 130 is coupled to the first sub-coil 122 and the second sub-coil 123, and can generate an output potential VOUT. For example, the output potential VOUT can be a DC potential, and its potential level can be between 18V and 22V, but is not limited thereto. The adjustable capacitance element 140 is coupled to the excitation inductor LM. The feedback compensation circuit 150 can generate a feedback potential VF according to the input potential VIN. The detection and control circuit 160 can generate a first driving potential VG1 and a second driving potential VG2, and includes a negative temperature coefficient (NTC) resistor RN adjacent to the first resonant capacitor CR1, wherein the negative temperature coefficient resistor RN can provide a temperature-dependent potential VT. In addition, the detection and control circuit 160 can also selectively enable or disable the adjustable capacitor element 140 according to the output potential VOUT, the feedback potential VF, and the temperature-dependent potential VT. According to actual measurement results, the addition of the adjustable capacitor element 140 helps to fine-tune the quality factor of the power supply 100, so that the electromagnetic interference (EMI) related to the power supply 100 can be greatly reduced. It must be noted that the term "adjacent" or "adjacent" in this specification may refer to the distance between the two corresponding elements being less than a predetermined distance (for example: 5mm or shorter), but usually does not include the situation where the two corresponding elements are directly in contact with each other (that is, the aforementioned distance is shortened to 0).

The following embodiments will introduce the detailed structure and operation of the power supply 100. It must be understood that these drawings and descriptions are only examples and are not intended to limit the scope of the present invention.

FIG. 2 is a circuit diagram of a power supply 200 according to an embodiment of the present invention. In the embodiment of FIG. 2, the power supply 200 has an input node NIN and an output node NOUT, and includes: a switching circuit 210, a transformer 220, a first resonant capacitor CR1, an output stage circuit 230, an adjustable capacitance element 240, a feedback compensation circuit 250, and a detection and control circuit 260. The input node NIN of the power supply 200 can receive an input potential VIN from a boost converter (not shown), and the output node NOUT of the power supply 200 can be used to output an output potential VOUT to an external device, such as a laptop (not shown).

The switching circuit 210 includes a first transistor M1 and a second transistor M2. For example, the first transistor M1 and the second transistor M2 may each be an N-type metal oxide semi-conductor field effect transistor. The first transistor M1 has a control end (e.g., a gate), a first end (e.g., a source), and a second end (e.g., a drain), wherein the control end of the first transistor M1 is used to receive a first driving potential VG1, the first end of the first transistor M1 is coupled to a first node N1 to output a switching potential VW, and the second end of the first transistor M1 is coupled to the input node NIN. The second transistor M2 has a control end (e.g., a gate), a first end (e.g., a source), and a second end (e.g., a drain), wherein the control end of the second transistor M2 is used to receive a second driving potential VG2, the first end of the second transistor M2 is coupled to a ground potential VSS (e.g., 0V), and the second end of the second transistor M2 is coupled to the first node N1.

The transformer 220 includes a main coil 221, a first secondary coil 222, and a second secondary coil 223, wherein the transformer 220 further has a built-in leakage inductor LR and an excitation inductor LM. The leakage inductor LR and the excitation inductor LM can be inherent components generated when the transformer 220 is manufactured, and they are not external independent components. The leakage inductor LR, the main coil 221, and the excitation inductor LM can all be located on the same side of the transformer 220 (for example: the primary side), and the first secondary coil 222 and the second secondary coil 223 can both be located on the opposite side of the transformer 220 (for example: the secondary side, which can be isolated from the primary side). The leakage inductor LR has a first end and a second end, wherein the first end of the leakage inductor LR is coupled to the first node N1 to receive the switching potential VW, and the second end of the leakage inductor LR is coupled to a second node N2. The main coil 221 has a first end and a second end, wherein the first end of the main coil 221 is coupled to the second node N2, and the second end of the main coil 221 is coupled to a third node N3. The excitation inductor LM has a first end and a second end, wherein the first end of the excitation inductor LM is coupled to the second node N2, and the second end of the excitation inductor LM is coupled to the third node N3. The first resonant capacitor CR1 has a first end and a second end, wherein the first end of the first resonant capacitor CR1 is coupled to the third node N3, and the second end of the first resonant capacitor CR1 is coupled to the ground potential VSS. For example, the leakage inductor LR, the excitation inductor LM, and the first resonant capacitor CR1 can together form a resonant slot of the power supply 200. The first sub-coil 222 has a first end and a second end, wherein the first end of the first sub-coil 222 is coupled to a fourth node N4, and the second end of the first sub-coil 222 is coupled to a common node NCM. For example, the common node NCM can provide a common potential, which can be regarded as another ground potential and can be the same as or different from the aforementioned ground potential VSS. The second sub-coil 223 has a first end and a second end, wherein the first end of the second sub-coil 223 is coupled to the common node NCM, and the second end of the second sub-coil 223 is coupled to a fifth node N5.

The output stage circuit 230 includes a first diode D1, a second diode D2, and a first capacitor C1. The first diode D1 has an anode and a cathode, wherein the anode of the first diode D1 is coupled to the fourth node N4, and the cathode of the first diode D1 is coupled to the output node NOUT. The second diode D2 has an anode and a cathode, wherein the anode of the second diode D2 is coupled to the fifth node N5, and the cathode of the second diode D2 is coupled to the output node NOUT. The first capacitor C1 has a first end and a second end, wherein the first end of the first capacitor C1 is coupled to the output node NOUT, and the second end of the first capacitor C1 is coupled to the common node NCM.

The adjustable capacitance element 240 includes a third transistor M3, a fourth transistor M4, a fifth transistor M5, and a second resonant capacitor CR2. For example, the third transistor M3, the fourth transistor M4, and the fifth transistor M5 can each be an N-type metal oxide semi-conductor field effect transistor. The third transistor M3 has a control terminal (e.g., a gate), a first terminal (e.g., a source), and a second terminal (e.g., a drain), wherein the control terminal of the third transistor M3 is used to receive an amplified potential VA, the first terminal of the third transistor M3 is coupled to the ground potential VSS, and the second terminal of the third transistor M3 is coupled to a sixth node N6. The fourth transistor M4 has a control terminal (e.g., a gate), a first terminal (e.g., a source), and a second terminal (e.g., a drain), wherein the control terminal of the fourth transistor M4 is used to receive a control potential VC, the first terminal of the fourth transistor M4 is coupled to the sixth node N6, and the second terminal of the fourth transistor M4 is coupled to a seventh node N7. The fifth transistor M5 has a control terminal (e.g., a gate), a first terminal (e.g., a source), and a second terminal (e.g., a drain), wherein the control terminal of the fifth transistor M5 is used to receive the output potential VOUT, the first terminal of the fifth transistor M5 is coupled to the seventh node N7, and the second terminal of the fifth transistor M5 is coupled to an eighth node N8. The second resonant capacitor CR2 has a first end and a second end, wherein the first end of the second resonant capacitor CR2 is coupled to the third node N3, and the second end of the second resonant capacitor CR2 is coupled to the eighth node N8. The capacitance value of the second resonant capacitor CR2 may be greater than the capacitance value of the first resonant capacitor CR1. For example, the capacitance value of the second resonant capacitor CR2 may be 2 to 3 times the capacitance value of the first resonant capacitor CR1, but is not limited thereto.

In some embodiments, the feedback compensation circuit 250 includes a linear optical coupler 252, a second capacitor C2, a first resistor R1, and a second resistor R2.

The first resistor R1 has a first end and a second end, wherein the first end of the first resistor R1 is coupled to the input node NIN, and the second end of the first resistor R1 is coupled to a ninth node N9. The second resistor R2 has a first end and a second end, wherein the first end of the second resistor R2 is coupled to the ninth node N9, and the second end of the second resistor R2 is coupled to the ground potential VSS. For example, the first resistor R1 and the second resistor R2 can form a voltage divider circuit. In some embodiments, the potential V9 at the ninth node N9 can be determined roughly according to the following method (1):

………………………………(1)Wherein, “V9” represents the level of the potential V9 at the ninth node N9, “VIN” represents the level of the input potential VIN, “R1” represents the resistance value of the first resistor R1, and “R2” represents the resistance value of the second resistor R2.

In some embodiments, the linear optical coupler 252 is implemented by a PCX electronic component. In detail, the linear optical coupler 252 includes a light emitting diode DL and a bipolar junction transistor Q6 (e.g., NPN type). The light emitting diode DL has an anode and a cathode, wherein the anode of the light emitting diode DL is coupled to the ninth node N9, and the cathode of the light emitting diode DL is coupled to the ground potential VSS. The bipolar junction transistor Q6 has a collector and an emitter, wherein the collector of the bipolar junction transistor Q6 is used to output a feedback potential VF, and the emitter of the bipolar junction transistor Q6 is coupled to a tenth node N10.

In addition, the second capacitor C2 has a first end and a second end, wherein the first end of the second capacitor C2 is coupled to the tenth node N10, and the second end of the second capacitor C2 is coupled to the common node NCM. It should be noted that the potential V10 at the tenth node N10 is associated with the aforementioned feedback potential VF. In some embodiments, the potential V10 at the tenth node N10 can be almost equal to the aforementioned feedback potential VF.

The detection and control circuit 260 includes an amplifier 262, an AND gate 264, a microcontroller unit (MCU) 266, and a negative temperature coefficient resistor RN.

The amplifier 262 can amplify the feedback potential VF by a gain factor K to generate the aforementioned amplified potential VA. For example, the gain factor K can be between 7 and 9, but is not limited thereto. In some embodiments, the amplified potential VA can be determined roughly according to the following formula (2):

…………………………………………(2) “VA” represents the level of the amplified potential VA, “K” represents the gain factor K, and “VF” represents the level of the feedback potential VF.

The AND gate 264 has a first input terminal, a second input terminal, and an output terminal, wherein the first input terminal of the AND gate 264 is used to receive the amplified potential VA, the second input terminal of the AND gate 264 is used to receive the output potential VOUT, and the output terminal of the AND gate 264 is used to output a logic potential VL. For example, if both the amplified potential VA and the output potential VOUT are high logic levels (i.e., logic "1"), the AND gate 264 will output a logic potential VL with a high logic level; conversely, if either the amplified potential VA or the output potential VOUT is a low logic level (i.e., logic "0"), the AND gate 264 will output a logic potential VL with a low logic level.

The microcontroller 266 can generate a first driving potential VG1 and a second driving potential VG2. For example, the first driving potential VG1 and the second driving potential VG2 can have complementary logic levels, wherein each of the first driving potential VG1 and the second driving potential VG2 can have a switching frequency FS. In addition, the microcontroller 266 can also output a fixed current IX, wherein the fixed current IX can flow through the negative temperature coefficient resistor RN.

In some embodiments, the negative temperature coefficient resistor RN is disposed adjacent to the first resonant capacitor CR1 to monitor an operating temperature of the first resonant capacitor CR1. For example, the distance DS between the negative temperature coefficient resistor RN and the first resonant capacitor CR1 may be less than or equal to 3 mm, but is not limited thereto. The negative temperature coefficient resistor RN has a first end and a second end, wherein the first end of the negative temperature coefficient resistor RN is coupled to the common node NCM, and the second end of the negative temperature coefficient resistor RN is used to output a temperature-dependent potential VT to the microcontroller 266. In some embodiments, if the common potential at the common node NCM is set to 0V, the temperature-dependent potential VT may be determined roughly according to the following method (3):

…………………………………………(3)Wherein, “VT” represents the level of the temperature-dependent potential VT, “IX” represents the magnitude of the fixed current IX, and “RN” represents the resistance value of the negative temperature coefficient resistor RN.

For example, if the operating temperature of the first resonant capacitor CR1 decreases, the resistance value of the negative temperature coefficient resistor RN will increase and the temperature-dependent potential VT will increase; conversely, if the operating temperature of the first resonant capacitor CR1 increases, the resistance value of the negative temperature coefficient resistor RN will decrease and the temperature-dependent potential VT will decrease.

In response, the microcontroller 266 may continuously monitor the temperature-dependent potential VT from the negative temperature coefficient resistor RN, and may compare the temperature-dependent potential VT with a reference potential VR. For example, the reference potential VR may be between 1V and 1.5V, but is not limited thereto. For example, if the temperature-dependent potential VT is lower than or equal to the reference potential VR, the microcontroller 266 may output a control potential VC with a high logic level; conversely, if the temperature-dependent potential VT is higher than the reference potential VR, the microcontroller 266 may output a control potential VC with a low logic level.

In some embodiments, the operating principle of the power supply 200 can be described as follows. Generally speaking, after the power supply 200 enters a stable state, the amplified potential VA and the output potential VOUT are both high enough to enable the third transistor M3 and the fifth transistor M5. At the beginning, when the operating temperature of the first resonant capacitor CR1 is relatively low, the microcontroller 266 will output a control potential VC with a low logic level to disable the fourth transistor M4 (or disable the adjustable capacitance element 240). At this time, the total resonant capacitance value of the resonant tank of the power supply 200 can be roughly determined according to the following method program (4):

……………………………………………(4)Wherein, “CT” represents the total resonant capacitance value of the resonant tank of the power supply 200, and “CR1” represents the capacitance value of the first resonant capacitor CR1.

After a period of time, when the operating temperature of the first resonant capacitor CR1 is relatively high, the microcontroller 266 will output a control potential VC with a high logic level to enable the fourth transistor M4 (or enable the adjustable capacitance element 240), so that the second resonant capacitor CR2 will be coupled in parallel with the first resonant capacitor CR1. At this time, the total resonant capacitance value of the resonant tank of the power supply 200 can be roughly determined according to the following method (5):

……………………………………(5)Wherein, “CT” represents the total resonant capacitance value of the resonant tank of the power supply 200, “CR1” represents the capacitance value of the first resonant capacitor CR1, and “CR2” represents the capacitance value of the second resonant capacitor CR2.

It must be understood that the quality factor of the power supply 200 is inversely proportional to the square root of the total resonant capacitance of the resonant tank of the power supply 200. In other words, if the total resonant capacitance of the resonant tank of the power supply 200 increases, the corresponding quality factor will decrease, and if the total resonant capacitance of the resonant tank of the power supply 200 decreases, the corresponding quality factor will increase.

FIG. 3 is a diagram showing the operating characteristics of the power supply 200 according to an embodiment of the present invention, wherein the horizontal axis represents the switching frequency FS of the power supply 200, and the vertical axis represents the gain value of the power supply 200. For example, the gain value of the power supply 200 may refer to the ratio of the output potential VOUT to the input potential VIN. In some embodiments, the switching frequency FS of the power supply 200 may be between a first frequency F1 and a second frequency F2, and it may generally be temporarily set to the second frequency F2. As shown in FIG. 3, a first curve CC1 represents the operating characteristics of the power supply 200 at the initial stage, and a second curve CC2 represents the operating characteristics of the power supply 200 after entering a stable state. Under the proposed design, the power supply 200 has a relatively large quality factor (e.g., 2) at the beginning, and the power supply 200 operating in a stable state has a relatively small quality factor (e.g., 0.5). It can be assumed here that the power supply 200 wants to provide a target gain value GT. Initially (refer to the first curve CC1), because the operating temperature of the first resonant capacitor CR1 is relatively low, the switching frequency FS of the power supply 200 must be reduced from the second frequency F2 to a first required frequency FA, with a first frequency difference. After the power supply 200 enters the stable state (refer to the second curve CC2), because the operating temperature of the first resonant capacitor CR1 is relatively high, the switching frequency FS of the power supply 200 only needs to drop from the second frequency F2 to a second required frequency FB, with a second frequency difference It must be noted that due to the second frequency difference Obviously higher than the first frequency difference Therefore, the power supply 200 operating in a stable state can provide the aforementioned target gain value GT only by using a very small frequency change. According to the measurement results of FIG. 3 , the electromagnetic interference associated with the power supply 200 can be greatly reduced.

The present invention proposes a novel power supply with an adjustable quality factor. According to actual measurement results, the electromagnetic interference associated with the power supply using the above design can be effectively suppressed, so it is very suitable for application in various types of devices.

It is worth noting that the potential, current, resistance, inductance, capacitance, and other component parameters described above are not limiting conditions of the present invention. Designers can adjust these settings according to different needs. The power supply of the present invention is not limited to the states shown in Figures 1-3. The present invention may only include any one or more features of any one or more embodiments of Figures 1-3. In other words, not all of the features shown in the diagrams need to be implemented in the power supply of the present invention at the same time. Although the embodiments of the present invention use metal oxide semi-conductor field effect transistors as an example, the present invention is not limited to this. People in the technical field can use other types of transistors, such as junction field effect transistors, or fin field effect transistors, etc., without affecting the effects of the present invention.

Ordinal numbers in this specification and the scope of the patent application, such as "first", "second", "third", etc., have no sequential relationship with each other, and are only used to mark and distinguish two different components with the same name.

Although the present invention is disclosed as above with the preferred embodiments, it is not intended to limit the scope of the present invention. Anyone skilled in the art can make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the attached patent application.

100,200: Power supply 110,210: Switching circuit 120,220: Transformer 121,221: Main coil 122,222: First secondary coil 123,223: Second secondary coil 130,230: Output stage circuit 140,240: Adjustable capacitor element 150,250: Feedback compensation circuit 160,260: Detection and control circuit 252: Linear optocoupler 262: Amplifier 264: AND gate 266: Microcontroller C1: First capacitor C2: Second capacitor CC1: First curve CC2: Second curve CR1: First resonant capacitor CR2: Second resonant capacitor D1: First diode D2: Second diode DL: Light-emitting diode DS: Spacing F1: First frequency F2: Second frequency FA: First desired frequency FB: Second desired frequency FS: Switching frequency GT: Target gain value IX: Fixed current K: Gain multiplier LM: Excitation inductor LR: Leakage inductor M1: First transistor M2: Second transistor M3: Third transistor M4: Fourth transistor M5: Fifth transistor N1: First node N2: Second node N3: Third node N4: Fourth node N5: Fifth node N6: Sixth node N7: Seventh node N8: Eighth node N9: Ninth node N10: Tenth node NCM: Common node NIN1: First input node NIN2: Second input node NOUT: Output node Q6: Bipolar junction transistor R1: First resistor R2: Second resistor RN: Negative temperature coefficient resistor V9, V10: Potential VA: Amplification potential VC: Control potential VF: Feedback potential VG1: First drive potential VG2: Second drive potential VIN: Input potential VL: Logic potential VOUT: Output potential VR: Reference potential VSS: Ground potential VT: Temperature dependent potential VW: Switching potential ΔA: First frequency difference ΔB: Second frequency difference

FIG. 1 is a schematic diagram showing a power supply according to an embodiment of the present invention. FIG. 2 is a circuit diagram showing a power supply according to an embodiment of the present invention. FIG. 3 is an operating characteristic diagram showing a power supply according to an embodiment of the present invention.

100: Power supply

110: Switching circuit

120: Transformer

121: Main coil

122: First coil

123: Second coil

130: Output stage circuit

140: Adjustable capacitor element

150: Feedback compensation circuit

160: Detection and control circuit

CR1: First resonant capacitor

DS: Spacing

LM: Magnetizing inductor

LR: Leakage Inductor

RN: Negative temperature coefficient resistor

VF: Feedback potential

VG1: first driving potential

VG2: Second driving potential

VIN: input voltage

VOUT: output voltage

VT: Temperature dependent potential

VW: Switching potential

Claims (10)

A power supply for suppressing electromagnetic interference, comprising: A switching circuit, generating a switching potential according to an input potential, a first driving potential, and a second driving potential; A transformer, comprising a main coil, a first sub-coil, and a second sub-coil, wherein the transformer has a built-in leakage inductor and an excitation inductor, and the main coil receives the switching potential through the leakage inductor; A first resonant capacitor, coupled to the excitation inductor; An output stage circuit, coupled to the first sub-coil and the second sub-coil, and generating an output potential; An adjustable capacitance element, coupled to the excitation inductor; A feedback compensation circuit, generating a feedback potential according to the input potential; and A detection and control circuit generates the first driving potential and the second driving potential, and includes a negative temperature coefficient resistor adjacent to the first resonant capacitor, wherein the negative temperature coefficient resistor provides a temperature-dependent potential; wherein the detection and control circuit selectively enables or disables the adjustable capacitance element according to the output potential, the feedback potential, and the temperature-dependent potential. A power supply as described in claim 1, wherein the switching circuit comprises: a first transistor having a control terminal, a first terminal, and a second terminal, wherein the control terminal of the first transistor is used to receive the first driving potential, the first terminal of the first transistor is coupled to a first node to output the switching potential, and the second terminal of the first transistor is coupled to an input node to receive the input potential; and a second transistor having a control terminal, a first terminal, and a second terminal, wherein the control terminal of the second transistor is used to receive the second driving potential, the first terminal of the second transistor is coupled to a ground potential, and the second terminal of the second transistor is coupled to the first node. A power supply as described in claim 2, wherein the leakage inductor has a first end and a second end, the first end of the leakage inductor is coupled to the first node to receive the switching potential, the second end of the leakage inductor is coupled to a second node, the main coil has a first end and a second end, the first end of the main coil is coupled to the second node, the second end of the main coil is coupled to a third node, the excitation inductor has a first end and a second end, the first end of the excitation inductor is coupled to the second node, the second end of the excitation inductor is coupled to the third node. The first resonant capacitor has a first end and a second end, the first end of the first resonant capacitor is coupled to the third node, the second end of the first resonant capacitor is coupled to the ground potential, the first secondary coil has a first end and a second end, the first end of the first secondary coil is coupled to a fourth node, the second end of the first secondary coil is coupled to a common node, the second secondary coil has a first end and a second end, the first end of the second secondary coil is coupled to the common node, and the second end of the second secondary coil is coupled to a fifth node. A power supply as described in claim 3, wherein the output stage circuit comprises: a first diode having an anode and a cathode, wherein the anode of the first diode is coupled to the fourth node, and the cathode of the first diode is coupled to an output node to output the output potential; a second diode having an anode and a cathode, wherein the anode of the second diode is coupled to the fifth node, and the cathode of the second diode is coupled to the output node; and a first capacitor having a first end and a second end, wherein the first end of the first capacitor is coupled to the output node, and the second end of the first capacitor is coupled to the common node. A power supply as described in claim 4, wherein the adjustable capacitance element comprises: A third transistor having a control terminal, a first terminal, and a second terminal, wherein the control terminal of the third transistor is used to receive an amplified potential, the first terminal of the third transistor is coupled to the ground potential, and the second terminal of the third transistor is coupled to a sixth node; A fourth transistor having a control terminal, a first terminal, and a second terminal, wherein the control terminal of the fourth transistor is used to receive a control potential, the first terminal of the fourth transistor is coupled to the sixth node, and the second terminal of the fourth transistor is coupled to a seventh node; a fifth transistor having a control terminal, a first terminal, and a second terminal, wherein the control terminal of the fifth transistor is used to receive the output potential, the first terminal of the fifth transistor is coupled to the seventh node, and the second terminal of the fifth transistor is coupled to an eighth node; and a second resonant capacitor having a first terminal and a second terminal, wherein the first terminal of the second resonant capacitor is coupled to the third node, and the second terminal of the second resonant capacitor is coupled to the eighth node. A power supply as described in claim 5, wherein the feedback compensation circuit comprises: a first resistor having a first end and a second end, wherein the first end of the first resistor is coupled to the input node to receive the input potential, and the second end of the first resistor is coupled to a ninth node; a second resistor having a first end and a second end, wherein the first end of the second resistor is coupled to the ninth node, and the second end of the second resistor is coupled to the ground potential; A linear optical coupler includes a light-emitting diode and a bipolar junction transistor, wherein the light-emitting diode has an anode and a cathode, the anode of the light-emitting diode is coupled to the ninth node, the cathode of the light-emitting diode is coupled to the ground potential, the bipolar junction transistor has a collector and an emitter, the collector of the bipolar junction transistor is used to output the feedback potential, and the emitter of the bipolar junction transistor is coupled to a tenth node; and a second capacitor, having a first end and a second end, wherein the first end of the second capacitor is coupled to the tenth node, and the second end of the second capacitor is coupled to the common node. The power supply as described in claim 5, wherein the detection and control circuit further comprises: an amplifier, which amplifies the feedback potential by a gain factor to generate the amplified potential; and an AND gate, which has a first input terminal, a second input terminal, and an output terminal, wherein the first input terminal of the AND gate is used to receive the amplified potential, the second input terminal of the AND gate is used to receive the output potential, and the output terminal of the AND gate is used to output a logic potential. A power supply as described in claim 7, wherein the detection and control circuit further comprises: A microcontroller, generating the first driving potential and the second driving potential, and outputting a fixed current, wherein the fixed current flows through the negative temperature coefficient resistor; wherein the negative temperature coefficient resistor has a first end and a second end, the first end of the negative temperature coefficient resistor is coupled to the common node, and the second end of the negative temperature coefficient resistor is used to output the temperature-dependent potential to the microcontroller. A power supply as described in claim 8, wherein if the temperature-dependent potential is lower than or equal to a reference potential, the microcontroller will output the control potential with a high logic level, and if the temperature-dependent potential is higher than the reference potential, the microcontroller will output the control potential with a low logic level. A power supply as described in claim 1, wherein the distance between the negative temperature coefficient resistor and the first resonant capacitor is less than or equal to 3 mm.

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