TWI442677B - Power supply and controller thereof - Google Patents

Description

Power supply and its controller

The present invention refers to a power supply controller and its associated power supply, and more particularly to a low cost, single circuit chip power controller with high power factor and its associated power supply.

Power supplies are an integral part of electrical products, such as Light Emitting Diode (LED) lighting applications. The ideal power supply should have Power Factor Correction (PFC) to ensure that the AC current is consistent with the voltage phase and eliminates non-ideal harmonics to increase power factor.

The power supply should maintain the output voltage, current or power within a stable range to ensure the safety and efficiency of the operation of the electronic device. Therefore, the power supply typically utilizes a feedback path from one of its outputs to maintain the output voltage, current, or power within a particular range. Furthermore, based on safety considerations, conventional power supplies typically isolate the primary and secondary sides of a transformer from each other.

Please refer to FIG. 1 , which is a schematic diagram of a conventional power supply 10 . The power supply 10 is a Fly-back Switching Mode Power Supply (SMPS), and includes a transformer (Transformer) 100, a transistor 102, and a pulse width modulation (Pulse Width). Modulation, PWM) control unit 104, a feedback control unit 106, a diode 108 (as a rectification function) and a capacitor C1. The transformer 100 includes a primary side winding (N _P ) and a secondary side winding (N _S ). The feedback control unit 106 includes resistors R1 R R4 , a capacitor C2 , a photocoupler 110 , and a three-terminal Shunt Regulator 112 .

The power conversion function of the power converter 10 is realized by controlling the transistor 102 through the pulse width modulation control unit 104. The pulse width modulation control unit 104 generates a corresponding one of the control signals V _PWM according to a feedback signal V _F from the feedback control unit 106 to control the turning on and off of the transistor 102. When the transistor 102 is turned on, the electrical energy is stored in the primary side winding N _P , at which time the rectifier 108 is not turned on due to the reverse bias, and the electrical energy required for the load of the power converter 10 is supplied by the capacitor C1; when the transistor 102 is turned off The electric energy stored in the primary side winding N _P is transferred to the secondary side winding N _S , at which time the rectifier 108 is turned on and the electric energy is transferred to the load. As shown in FIG. 1, the feedback signal V _F is generated by the three-terminal shunt regulator 112 driving the optical coupler 110. When the output voltage V _{OUT of the} power converter 10 rises or falls, the feedback signal V _F changes accordingly, thereby changing the duty cycle of the control signal V _PWM to adjust the power output to the load and make the output The voltage V _OUT remains stable. The three-terminal shunt regulator 112 must be matched with its peripheral components to achieve its function, wherein resistors R1 and R2 are used to divide the output voltage V _OUT to generate a reference voltage, and resistor R3 and capacitor C2 are used to provide three-terminal shunt regulation. The loop compensation required by the device 112.

However, such a secondary feedback control mechanism increases circuit area and increases power loss, and requires high cost components to isolate the primary side from the secondary side, such as an optocoupler and a three-terminal shunt regulator. . Furthermore, to accommodate high power output applications, the circuit requires two independent controller ICs, the PFC controller and the PWM controller. As a result, not only will the circuit design complexity increase, but also the production cost.

Accordingly, it is a primary object of the present invention to provide a power supply that is low cost, single wafer, and has high power factor.

The invention discloses a controller for a power supply, the power supply comprises a secondary winding, a primary winding and an auxiliary winding, the auxiliary winding can generate an output corresponding to the secondary winding a control signal for changing the current, the controller includes a power switch, including a first end coupled to the primary side winding, a second end, and a third end for receiving according to the second end a modulation signal, controlling the conduction of the electrical connection between the first end and the third end, and generating a current sensing signal from the third end; a certain current block, according to the feedback signal and the The current sensing signal generates a first current signal; and a control unit is configured to generate the first current signal, the feedback signal, the current sensing signal, and a voltage signal from the power supply The signal is modulated to control the power switch.

The invention further discloses a power supply comprising a transformer comprising a secondary winding for providing a secondary current; a primary winding for providing a primary winding a side current; and an auxiliary winding for generating a feedback signal corresponding to a change in an output current of the secondary winding, the ratio of the secondary current to the primary current being a constant value; The controller includes a power switch, including a first end coupled to the primary side, a second end, and a third end, configured to receive a modulation signal according to the second end, and control the first end Conducting a positive connection with the third end, and generating a current sensing signal from the third end; a current block for generating a first current according to the feedback signal and the current sensing signal And a control unit configured to generate the modulation signal according to the first current signal, the feedback signal, the current sensing signal, and a voltage signal from the power supply to control the power switch.

Please refer to FIG. 2, which is a schematic diagram of a power supply 20 according to an embodiment of the present invention. The power supply 20 is used to provide an output voltage V _o and an output current I _o to a load 214, such as a plurality of light emitting diodes. The power supply 20 includes a transformer 200, a power switch Q1, a constant current block 206, a certain voltage block 208, a control unit 210, and a current sensing resistor R _S . An AC input voltage ACin line after a bridge rectifier circuit 222 rectifies 224 generates a primary-side voltage signal V _i transmitted through a voltage divider. The transformer 200 includes a primary winding (N _P ) and a secondary winding (N _S ) for providing a primary side current I _P and a secondary side current I _{S , respectively} . Among them, the ratio of the secondary side current I _S to the primary side current I _P is a constant value. The transformer 200 further includes an auxiliary winding (N _A ), and a feedback signal V _FB corresponding to the change of the output current I _o of the secondary winding can be generated through a feedback node AUX. The auxiliary winding N _A is inductively coupled to the primary side winding N _P and the secondary side winding N _S such that one of the inductor currents I _L on the auxiliary winding N _A can be mapped to the secondary side current change on the secondary side winding N _S . As a result, the feedback signal V _FB generated from the node AUX corresponds to the change of the output current I _o . Since the feedback signal V _FB is from the primary side of the power supply 20, this feedback mechanism is called a primary side feedback control architecture. One of the advantages of primary-side feedback control over secondary-side feedback control is that it does not require the use of high-cost components, such as optocouplers, and reduces production costs.

The power switch Q1 is used to turn on or off the primary side current I _P on the primary side winding N _P according to a received modulation signal V _Mod . When the power switch Q1 is turned off, the primary side current I _P falls to zero, and the electric energy is transferred to the secondary side. When the power switch Q1 is turned on, the primary side current I _P flows through the current sensing resistor R _S and generates a current sensing signal CS corresponding to the primary side current I _P . Preferably, the power switch Q1 can be an N-type metal-oxide-semiconductor (NMOS), and the drain is coupled to the primary winding N _{P of the} transformer 200 (ie, the primary side of the power supply 20). The gate is coupled to the control unit 210 to receive the modulation signal V _Mod , and the source is coupled to the current sensing resistor R _S to generate the current sensing signal CS.

Therefore, by controlling the on or off of the power switch Q1, the power transmitted from the primary side of the power supply 20 to the secondary side can be controlled, thereby controlling its output power. The modulation signal V _{Mod is} preferably a pulse width modulation signal for turning on or off the power switch Q1, thereby regulating the output current I _o . Any other signal that can control the on/off state of the power switch Q1 is applicable to the power supply 20 of the present invention. In detail, the control unit 210 determines the energy of the primary side winding N _{P of the} transformer 200 to the secondary side winding N _S by changing the duty cycle of the pulse width modulation signal V _Mod and further Ground control output current I _o .

When the modulation signal V _Mod is switched from a low potential to a high potential, the power switch Q1 is turned on, and the primary side current I _P through the primary side winding N _P and the current sensing resistor R _S is gradually increased. The current sense resistor R _S senses the primary side current I _P , thus generating a current sense signal CS to the constant current block 206. The electric energy generated by the input voltage ACin is stored in the primary side winding N _P , and at this time, one of the secondary side rectifier 226 and one of the primary side diodes 216 are not turned on due to the reverse bias, so the current passing through the secondary side winding N _S I _S is zero. When the modulation signal V _Mod causes the power switch Q1 to be turned off, the electric energy stored in the primary side winding N _P is transmitted to the secondary side winding N _S , resulting in an increase in the current I _S passing through the secondary side winding N _S . Since the auxiliary winding N _A can map the change of I _S , the inductor current I _L also increases synchronously.

Please refer to FIG. 3, which is a schematic diagram of a constant current block 206 according to a second embodiment of the present invention. The constant current block 206 includes a waveform detecting unit 302, an arithmetic unit 304, an error amplifier 306, and a comparing unit 308. The waveform detecting unit 302 is coupled to the current sensing resistor R _S and used to detect a waveform of the current sensing signal CS to generate a capture signal V _P . The waveform detecting unit 302 detects the primary side current I _P on the current sensing resistor R _S to obtain the waveform of the current sensing signal CS.

The computing unit 304 is coupled to the waveform detecting unit 302 and configured to divide the buffering signal V _P to generate a selection voltage V _X . The operation unit 304 is configured to detect one of the discharge periods T _{dis of the} feedback signal V _FB (ie, the secondary side current I _S on the secondary winding N _S is decremented to one of the discharge periods of zero) and the feedback signal V _FB One cycle T, and a time factor Tf is generated. The time factor Tf can be expressed as [(T _{d system} / T) * K], where K is a constant. The arithmetic unit 304 generates the selection voltage V _X based on the time factor Tf and the capture signal V _P . Selecting the voltage V _X is a partial pressure of the signal V _P , which can be expressed as: The voltage selection unit 304 is preferably a digital-to-analog converter.

The selection voltage V _X is proportional to the output current Io of the power supply 20, and the derivation details can be known from the Republic of China Patent Application No. 099123938 (the same applicant and inventor as the present invention), and the selection voltage V _X can be expressed as:

That is to say, the constant current block 206 can obtain the selection voltage V _X proportional to the output current I _o according to the waveform detecting unit 302 and the arithmetic unit 304. Briefly, the output current I _o line selection voltage V _X by the control.

The error amplifier 306 includes two input terminals respectively coupled to the selection voltage V _X and a reference voltage V _ref4 , which can limit the maximum value of one of the selection voltages V _X to the fourth reference voltage V _ref4 . Thus, one of the output current I _{o I} oMAX maximum output current may be limited to a stable value associated with one of the fourth reference voltage _ref4 V. According to the Republic of China patent application number 099123938, it can be further derived that I _oMAX can be expressed as . Thus, if the power supply voltage V _o the output 20 of more than tolerable voltage, output current I _o can be limited to a fixed value, to protect the circuit of the power supply 20 will not be damaged. In addition, the stable output current I _o can be applied to related constant current circuits, such as LED illumination.

The comparing unit 308 is configured to compare one of the first comparison signal COMPI and the first reference voltage V _ref1 outputted by the error amplifier 306, and generate the first current signal I _i to the control unit 210. A voltage storage unit 312 is used to store the first comparison signal COMPI output by the error amplifier 306. A comparator 310 is used to turn on or off a first switch SW1 to generate a first current signal I _i . The comparator 310 includes a first positive input coupled to the first comparison signal COMPI, a second positive input coupled to the first reference voltage V _ref1 , and a negative input coupled to the first node A. When the voltage of one of the two positive input terminals is higher than the negative input terminal (ie, when one of the first comparison signal COMPI or the first reference voltage V _{ref1 is} higher than the voltage of the first node A), the comparator 310 outputs A high level voltage is applied to turn on the first switch SW1. When the first switch SW1 is turned on, a current source C1 outputs the first current signal I _i to the control unit 210. A resistor (as a load) is coupled between the first node A and a ground, and when a current from the current source C1 flows through the load, the voltage of the first node A increases. When the voltage of the first node A and the negative input of the comparator 310 are higher than the voltages of the two positive inputs, the comparator 310 outputs a low voltage level to turn off the first switch SW1. The first switch SW1 is a three-terminal component, and is preferably an N-type MOSFET. The drain is coupled to the current source C1, and the gate is coupled to the comparator. The device 310 and the source are coupled to the first node A.

As for the implementation method of the operation unit 304, it is possible to have a general knowledge in the field. Referring to the Republic of China Patent Application No. 099123938, (the same application and inventor as the present invention) utilizes a counter and a plurality of switches to implement the arithmetic unit 304. Therefore, the present invention can realize the constant current block 206 without using complicated or expensive components (for example, integrators), thereby reducing the production cost of the power supply 20.

Power supply 20 can optionally include a voltage block 208 to provide circuit over-voltage protection. A method for realizing the voltage block 208 in the Republic of China Patent Application No. 099125126 (the same applicant and inventor of the present invention) can be further referred to by those having ordinary knowledge in the art. Please refer to FIG. 4, which is a schematic diagram of the constant voltage block 208. The constant voltage block 208 can generate a second current according to one knee voltage of the feedback signal V _FB (ie, a voltage on the auxiliary winding N _A when the current I _{S of the} secondary winding N _S drops to zero) The signal includes a peak detecting unit 402 for generating a peak voltage signal V _e according to a knee voltage of the feedback signal V _FB . The peak detecting unit 402 is composed of a voltage tracking unit 414 and a sample holding unit 416. The voltage tracking unit 414 is configured to track the feedback signal V _FB to output a first voltage signal V _tr and a first control signal V. _The sample holding unit 416 is coupled to the voltage tracking unit 414 for sampling the first voltage signal V _tr to generate a peak voltage signal V _e .

Briefly, when the current flowing through the secondary side winding N _S is decremented to zero, one of the knee point voltages generated on the feedback signal V _FB is tracked by the voltage tracking unit 414. The sample hold unit 416 samples the knee point voltage of the voltage tracking unit 414 and generates a peak voltage signal V _e . The constant voltage block also generates a corresponding second current signal I _v , so that the control unit 210 generates the modulation signal V _Mod to control the power switch to be turned on or off, thereby controlling the conversion power of the power supply 20 . Therefore, when the load of the power supply 20 changes and causes the output voltage _{Vo to} fluctuate (for example, when one of the LEDs of the load 214 is burned or short-circuited), the knee voltage of the feedback signal V _FB also changes accordingly. Subsequently, the peak detecting unit 402 generates corresponding to the knee voltage of the feedback signal V _{FB is} a peak of the signal voltage V _E, thereby enabling the control unit 210 according to the feedback signal V _FB, generating an appropriate one of the modulation signal having a duty cycle V _Mod . The control signal V _Mod is used to control the transistor 204 and regulate the different power supplies delivered to the secondary side for power supply to different loads. The operation of error amplifier 406 and comparison unit 408 is similar to constant current block 206 and will not be described herein.

Please refer to FIG. 5, which is a schematic diagram of an embodiment of the control unit 210 of the power supply 20 in FIG. The control unit 210 includes a setting unit 502, a reset unit 504, and an SR flip-flop 506. The setting unit 502 is configured to generate a setting signal V _set , the reset unit 504 is configured to generate a reset signal V _reset , and the SR flip-flop 506 generates the modulation signal V according to the setting signal V _set and the reset signal V _reset . _Mod .

The setting unit 502 includes a zero current detector 518 for detecting one of the zero currents of the feedback signal V _FB and generating the setting signal V _set . In detail, when the inductor current I _{L of the} auxiliary winding N _{A is} decremented to zero, the zero current detector 518 detects a zero current and outputs the set signal V _set to the SR flip-flop 506. The SR flip-flop 506 further sets the modulation signal V _Mod to a high voltage level "1" to turn on the power switch Q1.

The reset unit 504 includes a current adding unit 508, an input voltage unit 510, an error amplifier 512, a multiplier 514, and a comparator 516. The current summing unit 508 adds the first current signal I _i and the second current signal I _v from the constant current block 206 and the constant voltage block 208 to generate a current sum I _sum . The input voltage unit 510 generates an inverted voltage signal V _inv according to the current sum I _sum . The error amplifier 512 can limit the inverted voltage signal V _inv not to exceed the first reference voltage V _ref1 and generate a comparison signal COMP. The multiplier 514 pairs of signal COMP to compare the power supply from the voltage signal V _i 20 of the multiplication, and generating a voltage product V _m. The comparator 516 compares the voltage product V _m with the current sense signal CS and generates a reset signal V _reset . In detail, once the power switch Q1 is turned on, the primary side current I _P rises, and the voltage of the current sense resistor R _s of the source of the power switch Q1 also rises. The error amplifier 512 compares the reference voltage V _ref1 with the inverted voltage signal V _inv (which corresponds to the sum of the current from the first current signal I _{i of the} constant current block 206 and the second current signal I _v from the constant voltage block 208 I _sum ) and generate a comparison signal COMP. Next, the multiplier 514 multiplies the comparison signal COMP with a primary voltage signal V _i (corresponding to the rectified DC input voltage of the power supply 20) that divides the input voltage from the power supply 20, and generates a voltage product. V _m . Next, the comparator 516 compares the voltage product V _m with the current sense signal CS. If the current signal CS is higher than the voltage product V _m , the comparator 516 outputs the reset signal V _reset to the SR flip-flop 506 to generate a low voltage level modulation signal V _Mod , thereby cutting the power switch Q1. FIG. 6B is a schematic diagram of the voltage modulation product V _m and the current sensing signal CS being compared to generate a modulation signal V _Mod .

Briefly, by alternately setting or resetting the SR flip-flop 506 according to the modulation signal V _Mod to turn the power switch Q1 on or off, the waveform of the average current I _{p_avg} of the primary side current I _P will follow the direct current. input voltage V _i of the fluctuation waveform, the primary-side current I _P reaches and DC input voltage V _i between the phase, and therefore to obtain a high power factor, and improve power conversion efficiency. As shown in FIG. 6A, FIG. 6A is a schematic diagram of related signal waveforms of the power supply 20. In Figure 6A, the inductor current rises when the modulation signal V _Mod is at the high voltage level and reaches a peak inductor current determined by the voltage product V _m . When the power switch Q1 is turned off, the inductor current drops. One of the inductor currents, zero current, causes the power switch Q1 to turn on again, so that the average input current I _{p_avg of the} waveform and the same phase of V _m can be obtained. Therefore, the average input current I _{p_avg is} also in phase with the input voltage V _i , so the power supply 20 has a high power factor. The control unit 210 can also cut off the power switch Q1 when the first current signal I _i (corresponding to the output current I _o ) or the second current signal I _v (corresponding to the output voltage V _o ) is too high, so the power supply 20 Provides stable output current and output voltage. Thus, the power supply 20 can be used in a variety of constant current applications, such as light emitting diode sources and the like. Moreover, the power supply 20 has an overvoltage protection mechanism, so that different output powers can be output to different loads. Please refer to FIG. 7, for example, the power supply output voltage V _o 20 a schematic diagram of an output current I _o of a seventh embodiment of the present invention graph. In Fig. 7, when the output voltage V _{o is} between V _f and 0, the output current I _o gradually decreases. When the output voltage Vo falls between V _f and nV _f , the output current I _o is controlled to a constant current value I1. Preferably, the voltage Vf is a tolerable level of the output voltage V _o of the single light-emitting diode in a light-emitting diode lighting circuit, and nV _f is one output when the n light-emitting diodes are connected in series. Voltage. When the output voltage V _o exceeds the voltage V _f , the output current I _o of the power supply is limited to a stable current value I1 . As a result, it is possible to prevent the power supply from outputting excessive power and damaging internal or external circuits.

Therefore, when the output voltage V _O exceeds a tolerable level, the power supply 20 can provide a stable output current I _OMax for related applications requiring a constant current and avoid excessive damage of the power supply 20 due to excessive output current. In short, the constant current block can pass through the waveform detecting unit 302 and the arithmetic unit 304 to obtain the selection voltage V _X proportional to the output current I _o and limit the selection voltage V _X to the reference voltage V _ref4 so that the maximum The output current I _OMax is limited to a certain value for the application of the constant current.

In summary, the present invention can achieve a power supply with high power factor, and can pass through the primary side feedback mechanism to avoid the use of expensive and complex components (such as optical coupler to achieve primary and secondary side isolation of the power supply) ), thereby reducing costs. At the same time, the present invention can provide adjustment of output power through constant current blocks and constant voltage blocks without using complex or expensive circuit components (such as integrators, three-terminal shunt regulators, etc.). Furthermore, according to the present invention, functions such as power factor correction, pulse width modulation (PWM), and power adjustment control can be realized by a single circuit chip, thereby reducing circuit area, reducing unnecessary power consumption, and reducing manufacturing cost. .

The above are only the preferred embodiments of the present invention, and all changes and modifications made to the scope of the present invention should be within the scope of the present invention.

10, 20‧‧‧Power supply

100, 102‧‧‧ transformer

104‧‧‧ Pulse width modulation control unit

106‧‧‧Responsible control unit

110‧‧‧Optocoupler

112‧‧‧Three-terminal shunt regulator

200‧‧‧Transformer

204‧‧‧Optoelectronics

206‧‧‧Constant current block

208‧‧ ‧ constant voltage block

210‧‧‧Control unit

214‧‧‧ load

216‧‧ ‧ diode

222‧‧‧Bridge rectifier circuit

224‧‧ ‧pressure unit

226‧‧‧Rectifier

302‧‧‧ Waveform detection unit

304‧‧‧ arithmetic unit

306, 406, 512‧‧‧ error amplifier

308, 408‧‧‧ comparison unit

310, 410, 516‧‧‧ comparator

402‧‧‧Crest detection unit

414‧‧‧Voltage tracking unit

416‧‧‧Sampling unit

502‧‧‧Setting unit

504‧‧‧Reset unit

506‧‧‧SR positive and negative

508‧‧‧current summing unit

510‧‧‧Input voltage unit

514‧‧‧Multiplier

518‧‧‧ zero current detector

V _FB ‧‧‧Response signal

CS‧‧‧current sensing signal

N _P ‧‧‧ primary winding

N _S ‧‧‧secondary winding

N _A ‧‧‧Auxiliary winding

V _o ‧‧‧output voltage

I _o ‧‧‧Output current

V _Mod ‧‧‧ modulated signal

V _set ‧‧‧Set signal

V _reset ‧‧‧Reset signal

V _m ‧‧‧voltage product

I _sum ‧‧‧current sum

Figure 1 is a schematic diagram of a conventional power supply.

FIG. 2 is a schematic diagram of a power supply according to an embodiment of the present invention.

Fig. 3 is a schematic view showing a constant current block in Fig. 2 of the embodiment of the invention.

Figure 4 is a schematic diagram of a constant voltage block in Figure 2 of the embodiment of the present invention.

Figure 5 is a schematic diagram of a control unit in Figure 2 of the embodiment of the present invention.

6A and 6B are schematic views showing waveforms of a power supply device in Fig. 2 of the embodiment of the present invention.

Figure 7 is a schematic diagram showing the output voltage versus output current of the power supply of the embodiment of the present invention.

20‧‧‧Power supply

200‧‧‧Transformer

204‧‧‧Optoelectronics

206‧‧‧Constant current block

208‧‧ ‧ constant voltage block

210‧‧‧Control unit

214‧‧‧ load

216‧‧ ‧ diode

222‧‧‧Bridge rectifier circuit

224‧‧ ‧pressure unit

226‧‧‧Rectifier

V _FB ‧‧‧Response signal

CS‧‧‧current sensing signal

N _P ‧‧‧ primary winding

N _S ‧‧‧secondary winding

N _A ‧‧‧Auxiliary winding

V _o ‧‧‧output voltage

I _o ‧‧‧Output current

V _Mod ‧‧‧ modulated signal

Claims (32)

A controller for a power supply, the power supply comprising a secondary winding, a primary winding and an auxiliary winding, the auxiliary winding generating a change corresponding to an output current of the secondary winding a controller, the controller includes: a power switch including a first end coupled to the primary side winding, a second end, and a third end for receiving one of the second ends a modulation signal, controlling conduction between the first end and the third end, and generating a current sensing signal from the third end; a current block for determining the feedback signal and the current The sensing signal generates a first current signal; and a control unit is configured to generate the tone according to the first current signal, the feedback signal, the current sensing signal, and a voltage signal from the power supply A variable signal to control the power switch. The controller of claim 1, wherein the power switch is an N-type metal oxide semiconductor field effect transistor, the first end is a drain, the second end is a gate, and the third end As a source. The controller of claim 1, wherein the constant current block comprises: a waveform detecting unit for detecting a waveform of the current sensing signal and generating a signal; and a calculating unit for Generate a selection based on the captured signal and the feedback signal The voltage selection includes: a time factor unit for detecting a discharge period of the feedback signal according to the feedback signal, and generating a time factor; and a voltage selection unit coupled to the time factor unit and The waveform detecting unit is configured to divide the captured signal according to the time factor to generate the selected voltage; an error amplifier coupled to the calculating unit to limit a maximum value of the selected voltage to not exceed one a fourth reference voltage, and a first comparison signal is generated through an output terminal according to the selection voltage and the fourth reference voltage; and a comparison unit is configured to generate the first comparison signal according to the first comparison signal and a first reference voltage The first current signal. The controller of claim 3, wherein the comparing unit comprises: a voltage storage unit comprising a resistor and a capacitor connected in series between the output end of the error amplifier and a ground to store the first a comparator signal includes a first positive input coupled to the voltage storage unit, a second positive input coupled to the first reference voltage, and a negative input coupled to the first node And an output; a load is disposed between the first node and the ground; a current source is configured to be turned on according to a first switch to generate the first current signal; and a first switch is used To turn on or cut according to the signal of the output of the comparator Broken between one of the current source and the first node. The controller of claim 4, wherein when the voltage of one of the first positive input terminal or the second positive input terminal is higher than the negative input terminal, the comparator outputs a high-level voltage through the output terminal to The first switch causes the first switch to turn on the connection between the current source and the first node. The controller of claim 5, wherein when the voltage of one of the first positive input terminal or the second positive input terminal is lower than the negative input terminal, the comparator outputs a low level voltage through the output terminal to The first switch causes the first switch to cut off the connection between the current source and the first node. The controller of claim 6, wherein the current source generates the first current signal when the first switch turns on the connection between the current source and the first node. The controller of claim 1, wherein the control unit comprises: a setting unit for generating a setting signal; a reset unit for generating a reset signal; and an SR flip-flop comprising a setting The terminal is coupled to the setting unit, a reset terminal is coupled to the resetting unit, and an output terminal is configured to generate the modulation signal according to the setting signal and the reset signal. The controller of claim 8, wherein the reset unit comprises: a current adding unit for adding the first current signal and a second current signal, and generating a current sum result; an input voltage unit And generating an inverting voltage signal according to the sum of the currents; an error amplifier for generating a comparison signal according to a first reference voltage and the inverted voltage signal; and a multiplier for using the comparison signal The voltage signal from the power supply is multiplied and generates a voltage product; and a comparator coupled to the reset terminal of the SR flip-flop for comparing the voltage product and the current Sensing the signal and generating the reset signal. The controller of claim 8, wherein the setting unit comprises: a zero current detector for detecting a zero current of the feedback signal and generating the setting signal. The controller of claim 1, further comprising a voltage block for generating a second current signal according to a knee voltage of the feedback signal, the constant voltage block comprising: a peak detecting unit, The peak detecting signal is used to generate a peak voltage signal according to the knee voltage of the feedback signal. The peak detecting unit includes: a voltage tracking unit for tracking the feedback signal to output a first voltage signal, and outputting a First control signal; a sample-and-hold unit coupled to the voltage tracking unit for sampling the first voltage signal to generate the peak voltage signal; an error amplifier coupled to the sample and hold unit for limiting the peak voltage signal One of the maximum values does not exceed a third reference voltage, and a second comparison signal is generated through an output terminal according to the peak voltage signal and the third reference signal; and a comparison unit is configured to use the second comparison signal and A first reference voltage is generated to generate the second current signal. The controller of claim 11, wherein the comparing unit comprises: a voltage storage unit, comprising a resistor and a capacitor connected in series between the output end of the error amplifier and a ground for storing the a second comparison signal; a comparator comprising a first positive input coupled to the voltage storage unit, a second positive input coupled to the first reference voltage, and a negative input coupled to a second node And an output; a load is disposed between the second node and the ground; a current source is configured to generate the second current signal according to a conduction condition of a second switch; and a second switch And for electrically connecting or disconnecting between the current source and the first node according to the signal of the output of the comparator. The controller of claim 14, wherein the comparator transmits the voltage when the voltage of one of the first positive input terminal or the second positive input terminal is higher than a voltage of the negative input terminal The output terminal outputs a high level voltage to the second switch, so that the second switch conducts a connection between the current source and the second node. The controller of claim 15, wherein when the voltage of one of the first positive input terminal or the second positive input terminal is lower than a voltage of the negative input terminal, the comparator outputs a low level through the output terminal The bit voltage is applied to the second switch such that the second switch cuts off the connection between the current source and the second node. The controller of claim 16, wherein the current source generates the second current signal when the second switch conducts the connection between the current source and the second node. The controller of claim 1, wherein the voltage signal is proportional to an input voltage of the power supply after rectification. A power supply comprising: a transformer comprising: a secondary winding for providing a secondary current; a primary winding for providing a primary current; and an auxiliary winding for Generating a feedback signal corresponding to a change in the output current of the secondary winding, a ratio between the secondary current and the primary current is a fixed value; and a controller comprising: A power switch includes a first end coupled to the primary side, a second end, and a third end, configured to receive the first modulation signal and the third end according to the second end receiving a modulation signal The electrical connection between the terminals is turned on, and a current sensing signal is generated by the third terminal; a certain current block is configured to generate a first current signal according to the feedback signal and the current sensing signal; and The control unit is configured to generate the modulation signal according to the first current signal, the feedback signal, the current sensing signal, and a voltage signal from the power supply to control the power switch. The power supply of claim 17, wherein the power switch is an N-type metal oxide semiconductor field effect transistor, the first end is a drain, the second end is a gate, and the third The end is a source. The power supply device of claim 17, wherein the constant current block comprises: a waveform detecting unit for detecting a waveform of the current sensing signal and generating a signal; and a calculating unit And generating, according to the captured signal and the feedback signal, a selection voltage, comprising: a time factor unit, configured to detect a discharge period of the feedback signal according to the feedback signal, and generate a time factor; And a voltage selection unit coupled to the time factor unit and the waveform detection unit for dividing the capture signal according to the time factor to produce Generating the selected voltage; an error amplifier coupled to the calculating unit for limiting a maximum value of the selected voltage not exceeding a fourth reference voltage, and transmitting an output according to the selected voltage and the fourth reference voltage Generating a first comparison signal; and a comparing unit for generating the first current signal according to the first comparison signal and a first reference voltage. The power supply device of claim 19, wherein the comparing unit comprises: a voltage storage unit, comprising a resistor and a capacitor connected in series between the output end of the error amplifier and a ground for storing the The first comparison signal includes a first positive input coupled to the voltage storage unit, a second positive input coupled to the first reference voltage, and a negative input coupled to the first node And an output; a load is disposed between the first node and the ground; a current source is configured to be turned on according to a first switch to generate the first current signal; and a first switch, And connecting, according to the signal of the output end of the comparator, a connection between the current source and the first node. The power supply of claim 19, wherein the comparator outputs a high-level voltage through the output terminal when the voltage of the first positive input terminal or the second positive input terminal is higher than the negative input terminal Up to the first switch, causing the first switch to turn on the current The link between the source and the first node. The power supply device of claim 21, wherein when the voltage of one of the first positive input terminal or the second positive input terminal is lower than the negative input terminal, the comparator outputs a low level voltage through the output terminal Up to the first switch, the first switch cuts off the connection between the current source and the first node. The controller of claim 6, wherein the current source generates the first current signal when the first switch turns on the connection between the current source and the first node. The power supply device of claim 17, wherein the control unit comprises: a setting unit for generating a setting signal; a reset unit for generating a reset signal; and an SR flip-flop comprising a The setting end is coupled to the setting unit, a reset end is coupled to the resetting unit, and an output end is configured to generate the modulation signal according to the setting signal and the reset signal. The power supply device of claim 24, wherein the reset unit comprises: a current adding unit for adding the first current signal and a second current signal, and generating a current sum result; an input voltage a unit for generating an inverted voltage signal according to the sum of the currents; An error amplifier for generating a comparison signal according to a first reference voltage and the inverted voltage signal; a multiplier for multiplying the comparison signal and the voltage signal from the power supply, And generating a voltage product; and a comparator coupled to the reset terminal of the SR flip-flop for comparing the voltage product and the current sensing signal, and generating the reset signal. The power supply device of claim 24, wherein the setting unit comprises: a zero current detector for detecting a zero current of the feedback signal and generating the setting signal. The power supply device of claim 17, further comprising a voltage block for generating a second current signal according to a knee voltage of the feedback signal, the constant voltage block comprising: a peak detecting unit And generating a peak voltage signal according to the knee voltage of the feedback signal, the peak detecting unit includes: a voltage tracking unit for tracking the feedback signal to output a first voltage signal, and outputting a a first control signal; and a sample and hold unit coupled to the voltage tracking unit for sampling the first voltage signal to generate the peak voltage signal; an error amplifier coupled to the sample and hold unit The maximum value of one of the peak voltage signals is not more than a third reference voltage, and a second is generated through an output terminal according to the peak voltage signal and the third reference signal. Comparing the signal; and a comparing unit, configured to generate the second current signal according to the second comparison signal and a first reference voltage. The power supply device of claim 27, wherein the comparing unit comprises: a voltage storage unit comprising a resistor and a capacitor connected in series between the output end of the error amplifier and a ground for storing the a second comparison signal; a comparator comprising a first positive input coupled to the voltage storage unit, a second positive input coupled to the first reference voltage, and a negative input coupled to a second node And an output; a load is disposed between the second node and the ground; a current source is configured to generate the second current signal according to a conduction condition of a second switch; and a second switch And for electrically connecting or disconnecting between the current source and the first node according to the signal of the output of the comparator. The power supply of claim 28, wherein when the voltage of one of the first positive input terminal or the second positive input terminal is higher than a voltage of the negative input terminal, the comparator outputs a high output through the output terminal The level voltage is applied to the second switch to turn on the connection between the current source and the second node. The power supply of claim 29, wherein the comparator is transparent when a voltage of one of the first positive input or the second positive input is lower than a voltage of the negative input The output terminal outputs a low level voltage to the second switch, so that the second switch cuts off the connection between the current source and the second node. The power supply of claim 30, wherein the current source generates the second current signal when the second switch conducts the connection between the current source and the second node. The power supply of claim 17, wherein the voltage signal is proportional to an input voltage of the power supply after rectification.