TWI736491B - Low-noise power supply device - Google Patents

Abstract

A low-noise power supply device includes a bridge rectifier, a boost inductor, a DC (Direct Current) converter, a power switch circuit, a transformer, an output stage circuit, a feedback circuit, a detection and control circuit, and a fan element. The bridge rectifier generates a rectified voltage according to a first input voltage and a second input voltage. The boost inductor receives the rectified voltage. A first current flows through the boost inductor. A magnetizing inductor is built in the transformer. A second current flows through the magnetizing inductor. The output stage circuit generates an output voltage. The fan element is supplied by the feedback circuit. The detection and control circuit detects the first current and the second current, and controls the rotation speed of the fan element according to the first current and the second current.

Description

Low noise power supply

The present invention relates to a power supply, and particularly relates to a low-noise power supply.

With the evolution of computer technology, the power required by the power supply will become larger and larger. However, the fan of the traditional power supply often has the problem of excessive noise. In view of this, it is necessary to propose a new solution to overcome the difficulties faced by the previous technology.

In a preferred embodiment, the present invention provides a low-noise power supply, including: a bridge rectifier that generates a rectified potential based on a first input potential and a second input potential; and a boost inductor that receives the A rectified potential, in which a first current flows through the boost inductor; a DC converter, coupled to the boost inductor, and generates a DC potential; a power switching circuit, which generates a switching according to the DC potential Potential; a transformer, including a main coil, a first auxiliary coil, and a second auxiliary coil, wherein the main coil is used to receive the switching potential, the transformer built-in an excitation inductor, and a second current system Flows through the magnetizing inductor; an output stage circuit, coupled to the first auxiliary coil and the second auxiliary coil, and generates an output potential and an output current; a feedback circuit generates a supply according to the output current Potential; a detection and control circuit that detects the first current and the second current, and generates a control pulse width modulation potential based on the first current and the second current; and a fan element; wherein the The fan element is powered by the supply potential, and the rotation speed of the fan element is determined according to the duty cycle of the control pulse width modulation potential.

In order to make the purpose, features and advantages of the present invention more comprehensible, specific embodiments of the present invention are listed below, with the accompanying drawings, and detailed descriptions are as follows.

Certain vocabulary is used to refer to specific elements in the specification and the scope of the patent application. Those skilled in the art should understand that hardware manufacturers may use different terms to refer to the same component. This specification and the scope of the patent application do not use differences in names as a way to distinguish elements, but use differences in functions of elements as a criterion for distinguishing. The terms "including" and "including" mentioned in the entire specification and the scope of the patent application are open-ended terms and should be interpreted as "including but not limited to". The term "approximately" 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 term "coupling" includes any direct and indirect electrical connection means in this specification. Therefore, if it is described in the text that a first device is coupled to a second device, it means that the first device can be directly electrically connected to the second device, or indirectly electrically connected to the second device through other devices or connection means. Two devices.

FIG. 1 is a schematic diagram of a power supply 100 according to an embodiment of the invention. For example, the power supply 100 can be applied to a desktop computer, a notebook computer, or an integrated computer. As shown in Figure 1, the power supply 100 includes: a bridge rectifier 110, a boost inductor LU, a DC converter 120, a power switching circuit 130, a transformer 140, an output stage circuit 150, and a feedback Circuit 160, a detection and control circuit 170, and a fan element 180. It should be noted that although not shown in Figure 1, the power supply 100 may further include other components, such as a voltage regulator or (and) a negative feedback circuit.

The bridge rectifier 110 can generate a rectified potential VR according to a first input potential VIN1 and a second input potential VIN2. Both the first input potential VIN1 and the second input potential VIN2 can come from an external input power source, wherein an AC voltage having any frequency and any amplitude can be formed between the first input potential VIN1 and the second input potential VIN2. For example, the frequency of the AC voltage can be about 50Hz or 60Hz, and the root mean square value of the AC voltage can be 90V to 264V, but it is not limited to this. The boost inductor LU can receive the rectified potential VR, and a first current I1 can flow through the boost inductor LU. The DC converter 120 is coupled to the boost inductor LU and can generate a DC potential VE. The power switching circuit 130 can generate a switching potential VW according to the DC potential VE. The transformer 140 includes a primary winding 141, a first secondary winding 142, and a second secondary winding 143, and the transformer 140 has a built-in magnetizing inductor LM. Both the main coil 141 and the exciting inductor LM can be located on the same side of the transformer 140, and the first secondary coil 142 and the second secondary coil 143 can both be located on the opposite side of the transformer 140. The main coil 141 can receive the switching potential VW, and a second current I2 can flow through the magnetizing inductor LM. The output stage circuit 150 is coupled to the first auxiliary coil 142 and the second auxiliary coil 143, and can generate an output potential VOUT and an output current IOUT. For example, the output potential VOUT may be approximately a DC potential, and its level may be about 19V, but it is not limited to this. The feedback circuit 160 can generate a supply potential VS according to the output current IOUT. The detection and control circuit 170 can detect the first current I1 and the second current I2, and can generate a control pulse width modulation potential VMC according to the first current I1 and the second current I2. The shape and type of the fan element 180 are not particularly limited in the present invention. The fan element 180 can be powered by the supply potential VS, and the rotation speed of the fan element 180 is determined according to the duty cycle of controlling the pulse width modulation potential VMC. Under this design, the fan element 180 can be enabled when the output power of the power supply 100 is relatively large, and its rotation speed can be fine-tuned according to the aforementioned output power. Therefore, the efficiency and service life of the fan element 180 can be maximized, and the noise of the fan element 180 can also be minimized.

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 used to limit the scope of the present invention.

FIG. 2 is a schematic diagram of the power supply 200 according to an embodiment of the invention. In the embodiment of Figure 2, the power supply 200 has a first input node NIN1, a second input node NIN2, and an output node NOUT, and includes: a bridge rectifier 210, a boost inductor LU, The current converter 220, a power switching circuit 230, a transformer 240, an output stage circuit 250, a feedback circuit 260, a detection and control circuit 270, and a fan element 280. The first input node NIN1 and the second input node NIN2 of the power supply 200 can receive a first input potential VIN1 and a second input potential VIN2 from an external input power source, respectively, and the output node NOUT of the power supply 200 can be used for Output an output potential VOUT to an electronic device (not shown).

The bridge rectifier 210 includes a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4. The anode of the first diode D1 is coupled to the first input node NIN1, and the cathode of the first diode D1 is coupled to a first node N1 to output a rectified potential VR. The anode of the second diode D2 is coupled to the second input node NIN2, and the cathode of the second diode D2 is coupled to the first node N1. The anode of the third diode D3 is coupled to a ground potential VSS (for example, 0V), and the cathode of the third diode D3 is coupled to the first input node NIN1. The anode of the fourth diode D4 is coupled to the ground potential VSS, and the cathode of the fourth diode D4 is coupled to the second input node NIN2.

The first end of the boost inductor LU is coupled to the first node N1 to receive the rectified potential VR, and the second end of the boost inductor LU is coupled to a second node N2. A first current I1 can flow through the boost inductor LU.

The detection and control circuit 270 includes a first resistor R1, a first slope detector 271, and a first peak detector 272. The first end of the first resistor R1 is coupled to the second node N2, and the second end of the first resistor R1 is coupled to a third node N3. The first slope detector 271 can detect the slope of the first current I1 (that is, the differential value of the first current I1 with respect to time), and then generate a first slope potential VL1 accordingly. For example, the first slope potential VL1 may be proportional to the slope of the first current I1. The first peak detector 272 can detect the maximum value of the first current I1 (that is, the peak value of the first current I1 in a predetermined time interval), and then generate a first peak potential VP1 accordingly. For example, the first peak potential VP1 may have a proportional relationship with the maximum value of the first current I1.

The DC converter 220 includes a fifth diode D5 and a first capacitor C1. The anode of the fifth diode D5 is coupled to the third node N3, and the cathode of the fifth diode D5 is coupled to a fourth node N4 to output a DC potential VE. The first terminal of the first capacitor C1 is coupled to the fourth node N4, and the second terminal of the first capacitor C1 is coupled to the ground potential VSS.

The power switching circuit 230 includes a first pulse width modulation integrated circuit 231, a second pulse width modulation integrated circuit 232, a first transistor M1, a second transistor M2, and a third transistor M3 . The first pulse width modulation integrated circuit 231 can generate a first pulse width modulation potential VM1. The second pulse width modulation integrated circuit 232 can generate a second pulse width modulation potential VM2 and a third pulse width modulation potential VM3. For example, the second pulse width modulation potential VM2 and the third pulse width modulation potential VM3 may have complementary logic levels, and the first pulse width modulation potential VM1 and the second pulse width modulation potential VM2 may have complementary logic levels. It has the same logic level as one of the third pulse width modulation potential VM3. The first transistor M1, the second transistor M2, and the third transistor M3 can each be an N-type MOSFET. The first transistor M1 has a control terminal (for example: a gate), a first terminal (for example: a source), and a second terminal (for example: a drain), wherein the control of the first transistor M1 The terminal can receive the first pulse width modulation potential VM1, the first terminal of the first transistor M1 is coupled to the ground potential VSS, and the second terminal of the first transistor M1 is coupled to the third node N3. The control terminal of the second transistor M2 can receive the second pulse width modulation potential VM2, the first terminal of the second transistor M2 is coupled to a fifth node N5 to output a switching potential VW, and the second transistor M2 The second terminal of M2 is coupled to the fourth node N4 to receive the DC potential VE. The control terminal of the third transistor M3 can receive the third pulse width modulation potential VM3, 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 the fifth node N5.

The transformer 240 includes a primary winding 241, a first secondary winding 242, and a second secondary winding 243, and the transformer 240 further includes a leakage inductor LR and a magnetizing inductor LM. Both the leakage inductor LR and the magnetizing inductor LM may be inherent components produced when the transformer 240 is manufactured, and they are not external independent components. The main coil 241, the leakage inductor LR, and the exciting inductor LM can all be located on the same side of the transformer 240, and the first secondary coil 242 and the second secondary coil 243 can be located on the opposite side of the transformer 240. A second current I2 can flow through the magnetizing inductor LM. In some embodiments, the inductance value of the magnetizing inductor LM is substantially equal to the inductance value of the boost inductor LU. The first terminal of the leakage inductor LR is coupled to the fifth node N5 to receive the switching potential VW, and the second terminal of the leakage inductor LR is coupled to a sixth node N6. The first end of the magnetizing inductor LM is coupled to a sixth node N6, and the second end of the magnetizing inductor LM is coupled to a seventh node N7. The first end of the main coil 241 is coupled to the sixth node N6, and the second end of the main coil 241 is coupled to an eighth node N8. The first end of the first auxiliary winding 242 is coupled to a ninth node N9, and the second end of the first auxiliary winding 242 is coupled to a common node NCM. The common node NCM can be regarded as another ground potential of the power supply 200, which may be the same as or different from the aforementioned ground potential VSS. The first end of the second auxiliary coil 243 is coupled to the common node NCM, and the second end of the second auxiliary coil 243 is coupled to a tenth node N10.

The detection and control circuit 270 can further include a second resistor R2, a second capacitor C2, a second slope detector 273, and a second peak detector 274. The first end of the second resistor R2 is coupled to the seventh node N7, and the second end of the second resistor R2 is coupled to the eighth node N8. The first terminal of the second capacitor C2 is coupled to the ground potential VSS, and the second terminal of the second capacitor C2 is coupled to the eighth node N8. The second slope detector 273 can detect the slope of the second current I2 (that is, the differential value of the second current I2 with respect to time), and then generate a second slope potential VL2 accordingly. For example, the second slope potential VL2 may be proportional to the slope of the second current I2. The second peak detector 274 can detect the maximum value of the second current I2 (that is, the peak value of the second current I2 in a predetermined time interval), and then generate a second peak potential VP2 accordingly. For example, the second peak potential VP2 may be in a proportional relationship with the maximum value of the second current I2.

The output stage circuit 250 includes a sixth diode D6, a seventh diode D7, a third capacitor C3, and a fourth capacitor C4. The anode of the sixth diode D6 is coupled to the ninth node N9, and the cathode of the sixth diode D6 is coupled to the output node NOUT. The anode of the seventh diode D7 is coupled to the tenth node N10, and the cathode of the seventh diode D7 is coupled to the output node NOUT. The first end of the third capacitor C3 is coupled to the output node NOUT, and the second end of the third capacitor C3 is coupled to the common node NCM. The first end of the fourth capacitor C4 is coupled to the output node NOUT, and the second end of the fourth capacitor C4 is coupled to an eleventh node N11 to output an output current IOUT.

The feedback circuit 260 includes a third resistor R3, a fourth resistor R4, a fifth resistor R5, a linear optical coupler 261, and an amplifier 262. The first end of the third resistor R3 is coupled to the common node NCM, and the second end of the third resistor R3 is coupled to the eleventh node N11 to receive the output current IOUT. The fourth resistor R4 has a first end and a second end, wherein the first end of the fourth resistor R4 is coupled to a twelfth node N12, and the second end of the fourth resistor R4 is coupled To the eleventh node N11. In some embodiments, the linear optical coupler 261 is implemented by a PC817 electronic component. The linear optical coupler 261 includes a light emitting diode DL and a dual carrier junction transistor Q4. The anode of the light emitting diode DL is coupled to the twelfth node N12, and the cathode of the light emitting diode DL is coupled to the common node NCM. The collector of the two-carrier junction transistor Q4 is used to output a feedback potential VF, and the emitter of the two-carrier junction transistor Q4 is coupled to a thirteenth node N13. The first end of the fifth resistor R5 is coupled to the thirteenth node N13, and the second end of the fifth resistor R5 is coupled to the ground potential VSS. The amplifier 262 can be used to amplify a positive gain ratio of the feedback potential VF, and then generate a supply potential VS accordingly.

The detection and control circuit 270 may further include a first error amplifier 275, a second error amplifier 276, an AND Gate 277, a microcontroller 278, a fifth capacitor C5, and a sixth resistor R6.

The first input terminal of the first error amplifier 275 is coupled to a fourteenth node N14 to receive the first slope potential VL1, and the second input terminal of the first error amplifier 275 is coupled to a fifteenth node N15 to receive The second slope potential VL2, and the output terminal of the first error amplifier 275 is used to output a first control potential VC1. For example, if the second slope potential VL2 is exactly equal to the first slope potential VL1, the first control potential VC1 will be at a high logic level (that is, logic "1"); on the contrary, if the second slope potential VL2 is not equal to the first slope potential VL1 A slope potential VL1, the first control potential VC1 will be a low logic level (ie, logic "0"). The first end of the fifth capacitor C5 is coupled to the fourteenth node N14, and the second end of the fifth capacitor C5 is coupled to the fifteenth node N15. The addition of the fifth capacitor C5 helps to eliminate the differential error of the first error amplifier 275.

The first input terminal of the second error amplifier 276 is coupled to a sixteenth node N16 to receive the first peak potential VP1, and the second input terminal of the second error amplifier 276 is coupled to a seventeenth node N17 to receive The second peak potential VP2, and the output terminal of the second error amplifier 276 is used to output a second control potential VC2. For example, if the second peak potential VP2 is exactly equal to the first peak potential VP1, the second control potential VC2 will be at a high logic level; on the contrary, if the second peak potential VP2 is not equal to the first peak potential VP1, the second control potential The potential VC2 will be at a low logic level. The first end of the sixth resistor R6 is coupled to the sixteenth node N16, and the second end of the sixth resistor R6 is coupled to the seventeenth node N17. The addition of the sixth resistor R6 helps to eliminate the integration error of the second error amplifier 276.

The first input terminal of the gate 277 is used to receive the first control potential VC1, the second input terminal of the gate 277 is used to receive the second control potential VC2, and the output terminal of the gate 277 is used to output an integrated control Potential VCM. For example, if both the first control potential VC1 and the second control potential VC2 are at high logic levels, the integrated control potential VCM will be at a high logic level; otherwise, in other cases (for example, the first control potential VC1 and Any one of the second control potential VC2 is a low logic level), and the integrated control potential VCM is all a low logic level.

The microcontroller 278 can generate a control pulse width modulation potential VMC according to the integrated control potential VCM. For example, if the integrated control potential VCM is at a low logic level, the microcontroller 278 can maintain the duty cycle (Duty Cycle) of the control pulse width modulation potential VMC unchanged; on the contrary, if the integrated control potential VCM is at a high logic level If it is correct, the microcontroller 278 can update the duty cycle of controlling the pulse width modulation potential VMC. In other words, only when the maximum value of the second current I2 is exactly equal to the maximum value of the first current I1 and the slope of the second current I2 is exactly equal to the slope of the first current I1, the duty cycle of the pulse width modulation potential VMC is controlled Will be updated and adjusted. In detail, when the integrated control potential VCM is at a high logic level, the duty cycle of the control pulse width modulation potential VMC can be adjusted according to the first peak potential VP1 and the second peak potential VP2. For example, if the first peak potential VP1 and the second peak potential VP2 become higher, the duty cycle of the pulse width modulation potential VMC will become larger; on the contrary, if the first peak potential VP1 and the second peak potential VP2 become lower, Then the duty cycle of the pulse width modulation potential VMC will be reduced.

The fan element 280 is powered by the supply potential VS of the feedback circuit 260. For example, if the supply potential VS is higher than or equal to a critical potential, the fan element 280 will be enabled; conversely, if the supply potential VS is lower than the aforementioned critical potential, the fan element 280 will be disabled. In some embodiments, if the output power of the power supply 200 is higher than or equal to a critical power, the fan element 280 will be enabled; conversely, if the output power of the power supply 200 is lower than the aforementioned critical power, then The fan element 280 will be disabled. Therefore, the fan element 280 will stop operating when the output power of the power supply 200 is relatively low, so as to reduce the overall noise level. When the fan element 280 is enabled, the rotation speed of the fan element 280 can be determined according to the duty cycle of the control pulse width modulation potential VMC. For example, if the duty cycle of controlling the pulse width modulation potential VMC becomes larger, the speed of the fan element 280 will be increased; conversely, if the duty cycle of controlling the pulse width modulation potential VMC becomes smaller, the speed of the fan element 280 will be reduced. Will become slower. In other words, the rotation speed of the fan element 280 can be dynamically adjusted according to the output power of the power supply 200 to improve the overall operating efficiency.

Fig. 3 shows a signal waveform diagram of the power supply 200 according to an embodiment of the present invention, in which the horizontal axis represents time, and the vertical axis represents the potential level or current value of each signal. According to the measurement results in Figure 3, when the first current I1 and the second current I2 become larger, the duty cycle of controlling the pulse width modulation potential VMC can also become larger; on the contrary, when the first current I1 and the second current I2 become larger When the second current I2 becomes smaller, the duty cycle of controlling the pulse width modulation potential VMC may also become smaller accordingly.

Figure 4 is a diagram showing the operating characteristics of the power supply 200 according to an embodiment of the present invention, where the horizontal axis represents the duty cycle (%) of the control pulse width modulation potential VMC, and the vertical axis represents the fan element 280 Rotation speed (revolutions per minute, RPM). In the embodiment of FIG. 4, the duty cycle of controlling the pulse width modulation potential VMC is between 20% and 80%, and the revolutions per minute of the fan element 280 is between 1200 and 1800. For example, every time the duty cycle of controlling the pulse width modulation potential VMC increases by 10%, the revolutions per minute of the fan element 280 will increase by 100. It must be understood that the above numerical range can also be adjusted according to different needs.

In some embodiments, the component parameters of the power supply 200 may be as described below. The inductance value of the boost inductor LU may be between 324 μH and 396 μH, preferably 360 μH. The inductance value of the leakage inductor LR may be between 43.2 μH and 52.8 μH, and preferably may be 48 μH. The inductance value of the magnetizing inductor LM may be between 324 μH and 396 μH, preferably 360 μH. The capacitance value of the first capacitor C1 may be between 544 μF and 816 μF, preferably 680 μF. The capacitance value of the second capacitor C2 may be between 42.3 nF and 51.7 nF, preferably 47 nF. The capacitance value of the third capacitor C3 may be between 376 μF and 564 μF, preferably 470 μF. The capacitance value of the fourth capacitor C4 may be between 376 μF and 564 μF, preferably 470 μF. The capacitance value of the fifth capacitor C5 may be between 1.425 nF and 1.575 nF, preferably 1.5 nF. The resistance value of the first resistor R1 may be between 0.99Ω and 1.01Ω, and preferably may be 1Ω. The resistance value of the second resistor R2 may be between 0.99Ω and 1.01Ω, and preferably may be 1Ω. The resistance value of the third resistor R3 may be between 4.95Ω and 5.05Ω, and preferably may be 5Ω. The resistance value of the fourth resistor R4 may be between 19Ω and 21Ω, preferably 20Ω. The resistance value of the fifth resistor R5 may be between 9.5KΩ and 10.5KΩ, and preferably may be 10KΩ. The resistance value of the sixth resistor R6 may be between 7.2Ω and 8.8Ω, preferably 8Ω. The ratio of the number of turns of the primary coil 241 to the first secondary coil 242 can be between 1 and 100, and preferably can be 20. The ratio of the number of turns of the main coil 241 to the second auxiliary coil 243 can be between 1 and 100, and preferably can be 20. The maximum output power of the power supply 200 can be greater than 500W. The critical power of the power supply 200 can be set to 60W. That is, when the output power of the power supply 200 is less than 60W, the fan element 280 can be disabled. The above parameter range is based on the results of many experiments, which helps to minimize the overall noise of the fan element 280 of the power supply 200.

The present invention proposes a novel power supply. According to the actual measurement results, the use of the aforementioned power supply design can greatly reduce the noise of the fan component, while effectively improving the efficiency and service life of the fan component, so it is very suitable for use in various types of devices.

It is worth noting that the above-mentioned potential, current, resistance value, inductance value, capacitance value, and other component parameters are not limitations of the present invention. The designer can adjust these settings according to different needs. The power supply of the present invention is not limited to the state shown in Figures 1-4. The present invention may only include any one or more of the features of any one or more of the embodiments in FIGS. 1-4. In other words, not all the features shown in the figures need to be implemented in the power supply of the present invention at the same time. Although the embodiment of the present invention uses metal oxide half field effect transistors as an example, the present invention is not limited to this. Those skilled in the art can use other types of transistors, such as junction field effect transistors or fins. Type field effect transistors, etc., without affecting the effect of the present invention.

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

100,200: power supply 110, 210: Bridge rectifier 120, 220: DC converter 130, 230: Power switching circuit 140,240: Transformer 141,241: main coil 142,242: The first secondary coil 143,243: The second secondary coil 150, 250: output stage circuit 160,260: feedback circuit 170,270: detection and control circuit 180,280: Fan element 231: The first pulse width modulation integrated circuit 232: Second pulse width modulation integrated circuit 261: Linear Optocoupler 262: Amplifier 271: The first slope detector 272: The first peak detector 273: The second slope detector 274: Second Peak Detector 275: first error amplifier 276: second error amplifier 277: and the gate 278: Microcontroller C1: The first capacitor C2: second capacitor C3: third capacitor C4: The fourth capacitor C5: Fifth capacitor D1: The first diode D2: The second diode D3: The third diode D4: The fourth diode D5: Fifth diode D6: The sixth diode D7: seventh diode DL: Light-emitting diode I1: first current I2: second current IOUT: output current LM: Magnetizing inductor LR: Leakage inductor LU: Boost inductor M1: The first transistor M2: second transistor M3: third transistor N1: the first node N2: second node N3: third node N4: Fourth node N5: fifth node N6: sixth node N7: seventh node N8: The eighth node N9: Ninth node N10: Tenth node N11: The eleventh node N12: Twelfth node N13: Thirteenth node N14: Fourteenth node N15: Fifteenth node N16: Sixteenth node N17: Seventeenth node NCM: Common Node NIN1: the first input node NIN2: second input node NOUT: output node Q4: Two-carrier junction transistor R1: first resistor R2: second resistor R3: third resistor R4: Fourth resistor R5: fifth resistor R6: sixth resistor VC1: The first control potential VC2: second control potential VCM: Integrated control potential VE: DC potential VF: feedback potential VIN1: the first input potential VIN2: second input potential VL1: first slope potential VL2: second slope potential VM1: first pulse width modulation potential VM2: second pulse width modulation potential VM3: third pulse width modulation potential VMC: control pulse width modulation potential VOUT: output potential VP1: first peak potential VP2: second peak potential VR: Rectified potential VS: supply potential VSS: Ground potential VW: Switching potential

Fig. 1 is a schematic diagram of a power supply according to an embodiment of the invention. FIG. 2 is a schematic diagram of the power supply according to an embodiment of the invention. Fig. 3 shows a signal waveform diagram of the power supply according to an embodiment of the present invention. Figure 4 is a diagram showing the operating characteristics of the power supply according to an embodiment of the present invention.

100: power supply

110: Bridge rectifier

120: DC converter

130: Power switching circuit

140: Transformer

141: main coil

142: The first secondary coil

143: The second secondary coil

150: output stage circuit

160: feedback circuit

170: Detection and control circuit

180: fan element

I1: first current

I2: second current

IOUT: output current

LM: Magnetizing inductor

LU: Boost inductor

VE: DC potential

VIN1: the first input potential

VIN2: second input potential

VMC: control pulse width modulation potential

VOUT: output potential

VR: Rectified potential

VS: supply potential

VW: Switching potential

Claims (10)

A low-noise power supply, including: A bridge rectifier that generates a rectified potential according to a first input potential and a second input potential; A boost inductor receiving the rectified potential, wherein a first current flows through the boost inductor; A DC converter, coupled to the boost inductor, and generates a DC potential; A power switching circuit generates a switching potential according to the DC potential; A transformer includes a main coil, a first auxiliary coil, and a second auxiliary coil, wherein the main coil is used to receive the switching potential, the transformer has a built-in magnetizing inductor, and a second current flows through The magnetizing inductor; An output stage circuit, coupled to the first auxiliary coil and the second auxiliary coil, and generates an output potential and an output current; A feedback circuit generates a supply potential according to the output current; A detection and control circuit for detecting the first current and the second current, and generating a control pulse width modulation potential according to the first current and the second current; and A fan element; The fan element is powered by the supply potential, and the rotation speed of the fan element is determined according to the duty cycle of the control pulse width modulation potential. The power supply according to claim 1, wherein the bridge rectifier includes: A first diode has an anode and a cathode, wherein the anode of the first diode is coupled to a first input node to receive the first input potential, and the first diode of the The cathode is coupled to a first node to output the rectified potential; A second diode has an anode and a cathode, wherein the anode of the second diode is coupled to a second input node to receive the second input potential, and the second diode of the The cathode is coupled to the first node; A third diode having an anode and a cathode, wherein the anode of the third diode is coupled to a ground potential, and the cathode of the third diode is coupled to the first input Node; and A fourth diode having an anode and a cathode, wherein the anode of the fourth diode is coupled to the ground potential, and the cathode of the fourth diode is coupled to the second input node; The boost inductor has a first terminal and a second terminal, the first terminal of the boost inductor is coupled to the first node to receive the rectified potential, and the second terminal of the boost inductor The terminal system is coupled to a second node; The inductance value of the magnetizing inductor is equal to the inductance value of the boost inductor. The power supply according to claim 2, wherein the detection and control circuit includes: A first resistor has a first end and a second end, wherein the first end of the first resistor is coupled to the second node, and the second end of the first resistor is coupled Connected to a third node; A first slope detector, which detects the slope of the first current, and generates a first slope potential accordingly; and A first peak detector detects the maximum value of the first current, and then generates a first peak potential accordingly. The power supply according to claim 3, wherein the DC converter includes: A fifth diode having an anode and a cathode, wherein the anode of the fifth diode is coupled to the third node, and the cathode of the fifth diode is coupled to a fourth node Node to output the DC potential; and A first capacitor has a first terminal and a second terminal, wherein the first terminal of the first capacitor is coupled to the fourth node, and the second terminal of the first capacitor is coupled to the Ground potential. The power supply according to claim 4, wherein the power switching circuit includes: A first pulse width modulation integrated circuit to generate a first pulse width modulation potential; A second pulse width modulation integrated circuit, generating a second pulse width modulation potential and a third pulse width modulation potential; A first transistor has a control terminal, a first terminal, and a second terminal, wherein the control terminal of the first transistor is used to receive the first pulse width modulation potential, and the first transistor The first end of the crystal is coupled to the ground potential, and the second end of the first transistor is coupled to the third node; A second transistor has a control terminal, a first terminal, and a second terminal, wherein the control terminal of the second transistor is used to receive the second pulse width modulation potential, and the second transistor The first terminal of the crystal is coupled to a fifth node to output the switching potential, and the second terminal of the second transistor is coupled to the fourth node to receive the DC potential; and A third transistor has a control terminal, a first terminal, and a second terminal, wherein the control terminal of the third transistor is used to receive the third pulse width modulation potential, and the third transistor The first end of the crystal is coupled to the ground potential, and the second end of the third transistor is coupled to the fifth node. The power supply of claim 5, wherein the transformer further has a built-in leakage inductor, the leakage inductor has a first end and a second end, and the first end of the leakage inductor is coupled to the The fifth node receives the switching potential, the second end of the leakage inductor is coupled to a sixth node, the magnetizing inductor has a first end and a second end, and the first end of the magnetizing inductor Is coupled to the sixth node, the second end of the magnetizing inductor is coupled to a seventh node, the main coil has a first end and a second end, and the first end of the main coil is coupled Connected to the sixth node, the second end of the main coil is coupled to an eighth node, the first auxiliary coil has a first end and a second end, the first end of the first auxiliary coil Is coupled to a ninth node, the second end of the first auxiliary coil is coupled to a common node, the second auxiliary coil has a first end and a second end, and the second auxiliary coil has a The first end is coupled to the common node, and the second end of the second secondary coil is coupled to a tenth node. The power supply according to claim 6, wherein the detection and control circuit further includes: A second resistor has a first end and a second end, wherein the first end of the second resistor is coupled to the seventh node, and the second end of the second resistor is coupled Connected to the eighth node; A second capacitor has a first terminal and a second terminal, wherein the first terminal of the second capacitor is coupled to the ground potential, and the second terminal of the second capacitor is coupled to the first terminal Eight nodes A second slope detector, which detects the slope of the second current, and generates a second slope potential accordingly; and A second peak detector detects the maximum value of the second current, and then generates a second peak potential accordingly. The power supply according to claim 7, wherein the output stage circuit includes: A sixth diode having an anode and a cathode, wherein the anode of the sixth diode is coupled to the ninth node, and the cathode of the sixth diode is coupled to an output node To output the output potential; A seventh diode having an anode and a cathode, wherein the anode of the seventh diode is coupled to the tenth node, and the cathode of the seventh diode is coupled to the output node ； A third capacitor has a first terminal and a second terminal, wherein the first terminal of the third capacitor is coupled to the output node, and the second terminal of the third capacitor is coupled to the common Node; and A fourth capacitor has a first terminal and a second terminal, wherein the first terminal of the fourth capacitor is coupled to the output node, and the second terminal of the fourth capacitor is coupled to a first terminal Eleven nodes to output the output current. The power supply according to claim 8, wherein the feedback circuit includes: A third resistor has a first end and a second end, wherein the first end of the third resistor is coupled to the common node, and the second end of the third resistor is coupled To the eleventh node to receive the output current; A fourth resistor has a first end and a second end, wherein the first end of the fourth resistor is coupled to a twelfth node, and the second end of the fourth resistor is Coupled to the eleventh node; A linear optical coupler includes a light-emitting diode and a bi-carrier junction transistor, wherein the light-emitting diode has an anode and a cathode, and the anode of the light-emitting diode is coupled to the tenth Two nodes, the cathode of the light-emitting diode is coupled to the common node, the two-carrier junction transistor has a collector and an emitter, and the collector of the two-carrier junction transistor is used A feedback potential is output, and the emitter of the bi-carrier junction transistor is coupled to a thirteenth node; A fifth resistor has a first end and a second end, wherein the first end of the fifth resistor is coupled to the thirteenth node, and the second end of the fifth resistor is Coupled to the ground potential; and An amplifier amplifies the feedback potential, and then generates the supply potential accordingly. The power supply according to claim 9, wherein the detection and control circuit further includes: A first error amplifier has a first input terminal, a second input terminal, and an output terminal, wherein the first input terminal of the first error amplifier is coupled to a fourteenth node to receive the first Slope potential, the second input terminal of the first error amplifier is coupled to a fifteenth node to receive the second slope potential, and the output terminal of the first error amplifier is used to output a first control potential ； A fifth capacitor has a first terminal and a second terminal, wherein the first terminal of the fifth capacitor is coupled to the fourteenth node, and the second terminal of the fifth capacitor is coupled to The fifteenth node; A second error amplifier has a first input terminal, a second input terminal, and an output terminal, wherein the first input terminal of the second error amplifier is coupled to a sixteenth node to receive the first Peak potential, the second input terminal of the second error amplifier is coupled to a seventeenth node to receive the second peak potential, and the output terminal of the second error amplifier is used to output a second control potential ； A sixth resistor has a first end and a second end, wherein the first end of the sixth resistor is coupled to the sixteenth node, and the second end of the sixth resistor is Coupled to the seventeenth node; A and gate 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 first control potential, and the second input of the and gate The terminal is used to receive the second control potential, and the output terminal of the gate is used to output an integrated control potential; and A microcontroller generates the control pulse width modulation potential according to the integrated control potential, wherein the duty cycle of the control pulse width modulation potential is determined according to the first peak potential and the second peak potential.

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