TW201128891A - Power converter device and power converter integrated circuit - Google Patents

Abstract

A power converter device and a power converter integrated circuit (IC) are provided. The power converter device includes a power converter inductor and the power converter IC. The power converter inductor generates a driving power according to an input power. One pin of the power converter IC receives the driving power. The power converter IC includes an over voltage protection circuit, a power switch, and a control circuit. The over voltage protection circuit and the power switch are electrically connected to the pin. The over voltage protection circuit generates an over-voltage protection signal according to the driving power and a reference signal. The control circuit generates a pulse width modulation (PWM) signal according to the over-voltage protection signal to control the power switch.

Description

201128891 ITPT-09-014 3311 Otwf. doc/n VI. Description of the invention: [Technical field to which the invention belongs] - Recording is (4) in a kind of power supply, and the system is related to the power conversion of the type of overvoltage protection function. Wafer. L flawless technology] The emitted electronic products are gradually opened by 1 θ including a variety of integrated circuits and different loads, and its voltage does not have to be fully matched with a power supply, and the power is tied to the production.彺 雷 ( (4) Γ conversion onverter) 'to convert a fixed level of electric dust into the operating voltage required for each integrated circuit. The source converter is a lightning pressure conversion circuit that uses an inductor and a capacitor to alternately charge. The power converter has a voltage buck for mutual charge, and an inverted iinvet wood structure such as a rising type (b, fiyba〇k).i« (^ In the prior art, in order to bring pressure, usually Will design over voltage protection circuit electricity / value ^ main = out of the large voltage protection circuit designed for electricity _ = plant 5 疋, if it will be increased - independent sensing pin (pinB) \ 'electric conversion chip must The overvoltage protection circuit is used. The above sensing pin is only used to supply voltage. The above method may not only affect the load end but also affect the wafer area. The area of the wafer is greatly increased, the range. Application for limiting power conversion wafers 201128891 ITPT-09-014 3311〇twf.doc/n [Summary of the Invention] The 曰 Γ Γ Γ 装置 ' ' ' 即使 即使 即使 即使 即使 即使 即使 即使 即使 即使 即使 即使 即使 即使 即使 即使 即使 即使 即使 即使 即使 即使 即使 即使 即使The invention provides a power conversion chip, which can share the same -m road WM with the power switch, so that the effect of over-current (four) protection can be achieved without increasing the number of pins.

This hair service it}- (four) turn riding, which includes surface conversion inductors and two power conversion chips. The electric conversion inductor can be driven according to the input power of the input power source. The power conversion includes an overvoltage protection circuit, a power switch, and a control circuit. The overvoltage protection circuit is electrically connected to the above pin, and the overvoltage protection signal can be generated according to the driving power source and the reference signal. The electric connection is electrically connected to the above-mentioned pins, and the power can be borrowed according to the pulse width modulation domain. The control circuit is electrically connected to the power switch, and the pulse width signal can be generated according to j = to control the power switch. In an embodiment of the invention, the overvoltage protection circuit includes a circuit, a peak rectification circuit, and a ripple! . The partial voltage is connected to the pin, and the second is divided according to the driving power source. The peak rectification circuit _divide' can generate a rectification signal according to the voltage division signal. The comparator is electrically connected to the rectifier circuit'. The voltage divider circuit includes a first-dividing resistor and a second voltage-dividing resistor. In one embodiment of the invention, the voltage dividing circuit includes a first-divider resistor and a second voltage-dividing resistor. The first end of the first-divider resistor is electrically connected to the above-mentioned pin. The first end of the second voltage dividing resistor is electrically connected to the second of the first voltage dividing resistor. 201128891 ΙΤΡΤ-09-014 3311 Otwf.doc/n terminal. The second end of the second voltage dividing resistor is electrically connected to the ground. In an embodiment of the invention, the peak rectification circuit comprises a rectifying diode and a rectifying capacitor. The rectifier diode is electrically connected to the voltage divider circuit and the anode of the body can receive the voltage division signal. The first end of the rectifying capacitor is electrically connected to the cathode of the pole body and the first wheel of the comparator. The second = of the rectifying capacitor is connected to the ground. In the case of a separate towel, the peak rectifier circuit is further equipped with a f discharge switch. The discharge switch is electrically connected between the first end of the rectifying capacitor and the ground end, and the rectifying capacitor can be discharged according to the discharge signal. In another embodiment, the overvoltage protection circuit further includes reference to ^^. The reference field produces a second input with comparison 11 with a peak recording current axis _ multi-station. The above components can be set to provide a reference signal to the second input of the comparator, and the power supply 11 further includes an error prevention switch. The output of the comparator is controlled according to the discharge signal, and the output of the anti-protection signal is determined. In an embodiment of the invention, the power supply further includes a rectifying two-pole switching capacitor. The anode of the rectifying diode receives the driving power and is electrically connected to the load. The first end of the power conversion capacitor is electrically connected to the cathode and the load of the body. The second end of the power conversion capacitor is applicable to the degree of application. The present invention proposes a power conversion chip which can be used as a power conversion device for the conversion inductor. Power conversion inductor pin. The human source generates a driving power source and supplies it to the power conversion wafer. Power conversion crystal includes over-current protection circuit, power switch and control 201128891 ΓΓΡΊ-09-014 3311 Otwf.doc/n ^ circuit. The electric power protection circuit is electrically connected to the above surface, and the overvoltage signal can be generated according to the source and the reference position. The power of the power switch determines whether or not to conduct according to the pulse width modulation signal, so that the power is driven by the electric: === system. The control circuit is electrically connected to the power switch, and can be turned off and the pulse width modulation signal is generated, so as to control the power supply. Based on the above, the power conversion chip of the present invention, the circuit and the power switch share the same-support condition. Achieved the effect of relying on. The characteristics of the pin Γ (4) The above characteristics and advantages can be (4) (4) understand, the following is a special example, and the following is a detailed description. Wente [Embodiment] Set -===== placed in the power conversion chip, need to increase the use of = practice may limit the power _ change "circuit body and power conversion ΐ; =; power conversion inductance, rectifier two-pole inductance. Whole, ά __ whole ~ pole body anode electrical connection power conversion power conversion crystal 7 package two = connected power conversion capacitor and load. Protection circuit including Lili ===, voltage protection circuit. Over voltage protection through power conversion Β曰片红正·circuit and comparator. Power switch pole, can be used to connect the chip It-pin to the rectifier power supply conversion inductor and power conversion capacitor misplacement energy, 201128891 nr ι-υ^- Υχ 4 33110twf.d〇c/n and then provide the output power to drive the load. It is worth noting that the overvoltage protection circuit can share the same pin with the power switch. The voltage dividing circuit can be divided according to the voltage of the above pin. In order to generate a voltage division signal, the peak rectifier circuit can rectify the voltage division signal to generate a rectified signal. The peak rectifier circuit can generate a DC output voltage equal to the peak value of the input AC signal. The rectification signal generated by the value rectification circuit can simulate the output power source for driving the load. The comparator can determine whether the voltage of the output power source is too high according to the rectified signal and the reference signal, and if so, generate an overvoltage protection signal to indirectly control the power switch. Embodiments of the present invention will be described in detail with reference to the accompanying drawings, in which FIG. Schematic diagram of the device and the power conversion chip. Referring to the figure, the power conversion device 1 can be used to drive the load 20. In the present embodiment, the load 2 is described by taking a plurality of LEDs in series as an example, but The invention is not limited thereto. In other embodiments, the load 20 may be other components. The power conversion device 10 includes a power conversion inductor 4A and a power conversion wafer 80. The power conversion device 1〇 may also include an input capacitor, a rectification The diode 50, the power conversion capacitor 60 and the current detecting resistor 70. The first end of the input capacitor 3〇 is electrically connected to the input The source Vin, the first end of the power conversion inductor 4〇, and the pin VIN of the power conversion transistor 80. The first end of the input capacitor 30 is electrically connected to the ground end. The second end of the power conversion inductor 4〇 is electrically connected to the rectifying diode The anode of the body 50 and the pin sw of the power conversion wafer 8〇. Rectifier 2 201128891 ιιη-υ>.〇ΐ4 33110twf.d〇c/n The first end of the cathode electrical connection 20 of the polar body 50. The load is 2〇, The 苐-end of the electric command 60 and the second end of the load carrier 20 are electrically connected to the output power supply V_. The first end of the negative current detecting resistor 70 is connected to the ground of the chip 8〇 and the electrical connection ground 舆 power supply Second, the second end of the resistor 70, such as the connection source, includes a power switch 9. And the control circuit _ and the SW and the control circuit 100, the circuit 110 can electrically connect the voltage of the pin-reference signal to determine whether the wheel voltage is higher than the wish condition, and the power switch 90 can be generated according to whether the power failure occurs. Available transistor ^ : Control the power switch 9 〇. Connected with the thyristor: the electrical connection f is the entangled conversion inductor 40 and the power conversion capacitor 6 〇 is used for storage. More specifically, the control circuit 1G is stored therein.

Control power switch 9 〇 conduction or Gong Guang see modulation signal PWM No, power conversion inductance 40 and 3 electric switch ^ switch 90 conduction and by means _ power v_ = interactive storage energy; Ϊ source conversion inductor 40 will store energy, capacitance 60 will release the second. When the power switch 90 is turned on, the capacitor 60 will store the comb amount. "Converting money 4G will release energy, rectification =: ^=_ line filtering. Reverse DP ^ rectification, and can prevent the rotation of power supply vout and drive power Dp mutual 201128891 nr y-\jy'\ji4 33110twf.doc/n

interference. The current sense resistor 70 can be used to measure the flow rate by 2 〇 small. More specifically, when the current flowing through the load 2 变 becomes larger, the electric house of the pin machine will also rise, and the power conversion chip 8 〇 can be tested according to the B electric dust. Handa, private foot 2: protect two other 'pin FB' can also be used to:: Vout疋 is too big. It should be noted that the power of the power supply pin FB will be pulled to the grounded ink supply conversion = the situation is wrong (four) the output of the v_ face is too low resistance = 80 will be the voltage of the power supply Vout. - Hold,, 'only pull up the wheel out of this, in this embodiment, the over-current pin SW is lightly connected to the first end of the load 20 is 0, the pass ho does not need to pass the load 20 to test the round = House protection power If the load 20 is disconnected, the voltage may be misjudged. The electric protection circuit U 0 is not worthwhile. It is worth mentioning that the overvoltage protection 90 shares the same pin sw together. This method 0 and the power switch The wafer changer 80 does not need to be added only for overvoltage protection. The advantage is that the power supply is turned to a separate pin. In general, the area of the wafer used in the power conversion wafer shame is greatly increased, or the size of the chip may be caused by the singer. Therefore, in the present embodiment, the overvoltage=change and the lowering of the application 90 share the same pin sw, and not only the reachable path 110 and the power supply load 20 turnaround, but also the misjudgment and the voltage health effect, and the connection must be added. Limit the range of applications. The conversion of the wafer 80 is also not described in more detail. Overvoltage protection network 201128891 ITPT-09-014 33110twf.doc/n Undertake the above-mentioned Tian Yuying power protection circuit 丨丨〇 is used to detect whether the voltage of the power supply Vout is too high, and the output power v〇ut If the voltage β is too high, it will be directly related to the voltage of the driving power source DP. Therefore, it is necessary to make some judgments on the signal of the pin SW (in this embodiment, the driving power source Dp is taken as an example), for example, whether the voltage of the pin sw is a line-reference signal voltage can be used indirectly to judge the turn-out' Whether the voltage of the second is too high. If the voltage of the pin sw is greater than the reference fresh output voltage V〇Ut, the voltage can be turned off. The right pin SW's small conversion test signal voltage, the voltage from V _ is in the normal range, t source _ 9 〇 can be normally transported - the source although the above implementation has been converted to electricity: the film depicts a possible The type of technology, but belongs to the technical field : = : Knowledge should know that 'the various manufacturers for the power conversion load fish;: : energy type. In other words, as long as it is the power conversion chip = 1 circuit and the electrical switch to share the power conversion chip, it is in line with the spirit of the present invention. In the following, there are several areas in which the ITF (4) is more advanced - the way to implement the present invention. 1 EMBODIMENT OF THE INVENTION The overvoltage protection circuit shown in Fig. 1 is exemplified by the present invention. Familiarity: The choice of implementation changes the architecture of the electric dust protection circuit. (4) The power conversion device of the other embodiment can be modified according to its requirements: electricity = in accordance with the present invention. Referring to Figures i and 2, the electric/original conversion device η of the lightning = conversion wafer is similar to the power conversion device 10 of Fig. 1 of 201128891 ΠΚ1-υν-υι4 3311〇twf.d〇c/n. It should be noted that in the present embodiment, the overvoltage protection circuit U1 includes a voltage dividing circuit 120, a comparator 130, and a peak rectifying circuit 14A. The voltage dividing circuit 120 includes a voltage dividing resistor 12, and the peak rectifying circuit includes a rectifying diode 150 and a rectifying capacitor 160. The first end of the voltage dividing resistor 121 is electrically connected to the pin sw. The second end of the voltage dividing resistor 121 is electrically connected to the anode of the voltage dividing resistor 122 and the anode of the rectifying diode 150. The second end of the voltage dividing resistor 122 is electrically connected to the ground. The peak rectifying circuit 14A is disposed between the voltage dividing circuit 120 and the comparator 130. Anode receiving of rectifier diode 150

For the pressure signal DS. The first end of the cathode electrical connection 160 of the rectifier diode 15 is coupled to the first input of the comparator 13A. The second end of the rectifying capacitor is electrically connected to the ground. In another embodiment, the rectifying diode 150 can also be implemented with a transistor. The first input of the comparator 13 is electrically connected to the cathode of the rectifier diode 15 and the first end of the rectifying capacitor 16A. The second input of the vehicle state 130 receives the reference signal REF. The control circuit 100 is electrically connected to the U output terminal. The overvoltage protection circuit 110 is used to detect whether the output power supply Vout is at a high voltage or not, and whether the voltage of the output power supply 〇泔 is too high, and the voltage of the driving power supply ^ is directly related. Therefore, as long as the pin ^= number (in the present embodiment, the driving power source Dp is taken as an example), the one-month J processing is performed to improve the accuracy of determining whether the output power source and the voltage are too high. In this embodiment, the voltage dividing circuit 120 can be used to divide and drive the driving power supply p to provide a voltage dividing signal DS peak rectifying circuit 12 201128891 ah x-wy-014 33110twf.doc/n HO. This prevents excessive voltage input to the back-end circuitry. In this embodiment, the peak rectifying circuit 140 rectifies the divided voltage signal Ds to provide a rectified signal FS to the first input of the comparator 130. The peak rectifying circuit 140 can record the voltage peak of the voltage dividing signal DS, and can convert the high frequency alternating current signal into a lower frequency direct current signal, thereby providing the rectifying signal FS to the first input end of the comparator 130. In this way, the comparator 130 does not need to use a comparator with a high reaction speed, and a comparator with a lower reaction speed can be selected. Next, the comparator 130 compares whether the voltage of the rectified signal fs is greater than the voltage of the reference signal REF. If yes, the voltage representing the output power v〇ut is too high, and the comparator 130 can provide the overvoltage protection signal 〇vPS to the control circuit 100. By way of control, the power switch 90 is turned off; if not, the voltage representing the output power source Vout is within a safe range, and the power switch 9 〇 can maintain normal operation. In addition, in this embodiment, the rectifying diode 150 and the rectifying capacitor 160 of the peak rectifying circuit 140 are designed to cooperate with the rectifying diode 50 and the power converting capacitor 60. More specifically, the voltage division signal DS has a waveform similar to that of the driving power source DP. The driving power source DP can be converted into an output power source Vout after being processed by the rectifying diode 50 and the power converting capacitor 60. Similarly, after the voltage division signal DS is processed by the rectifying diode 15 and the rectifying capacitor 160, a rectifying signal FS similar to the waveform of the output power supply can be generated. In other words, after the processing by the peak rectifying circuit 14A, the rectification signal FS can simulate the waveform of the output power source Vout. In this way, the comparator 130 can more accurately determine whether the voltage of the output power source v〇ut 13 201128891 ιιπ-υ^-υι4 33110twf.doc/n is too high through the rectified signal FS. Further, FIG. 3 is a schematic diagram of a power conversion device and a power conversion wafer in accordance with still another embodiment of the present invention. Referring to Figures 2 and 3 in combination, the power conversion device 12 of Figure 3 is similar to the power conversion device 11 of Figure 2 . The difference is that the overvoltage protection circuit 112 in the power conversion chip 82 of the power conversion device 12 further includes a reference signal generator 180 and an error prevention switch 190. In addition, the peak rectifying circuit 141 further includes a discharge switch 170. Since the rectifying capacitor 160 is overcharged, the 0.7V dropout between the rectifying diode 15〇 anode and the cathode gradually disappears, which may cause the comparator 130 to misjudge. Therefore, the rectifying grid 160 can be periodically discharged by the discharge switch 17 , to prevent the comparator 13 from being misjudged. The discharge switch 170 is, for example, a transistor, and the first end and the second end thereof are electrically connected to the first end of the rectifying capacitor 160 and the ground end, respectively. The gate of the discharge switch 17A can receive the discharge number DIS and discharge the rectifying capacitor 16? For example, the discharge signal DIS can turn on the discharge switch 17 每隔 every 32 clock cycles, thereby discharging the rectifying capacitor 160. However, the present invention is not limited thereto, and those skilled in the art can change the discharge signal according to the needs thereof. DIS. It should also be noted that the components in the peak rectification circuit 141 are subject to environmental influences, such as changes in ambient temperature, and the rectified signal FS supplied to the comparator 130 also changes. If the reference signal ref does not change with the rectification signal FS, the comparator 130 may also generate a false positive. In order to avoid interference with the peak rectifying circuit 141 by factors such as the environment, the reference signal generator 180 can be designed to have the same element 14 201128891 nt*i-uy-014 33110 twf.doc/n as the peak rectifying circuit 141. 4 is a schematic diagram of a reference signal generator in accordance with FIG. Referring to FIG. 3 and FIG. 4 together, in the present embodiment, the reference signal generator 18A includes a rectifying diode 150, a rectifying capacitor 160, and a discharging switch 17A. Since the reference signal generator 180 has the same components as the peak rectifying circuit mi, when the peak rectifying circuit 141 is disturbed by environmental factors, etc., and the rectified signal FS having an error is generated, the reference signal REF also has a rectification signal 5 FS A similar error 'as a result can reduce the chance of misjudgment. Further, in the present embodiment, since the discharge switch 17 is disposed, when the discharge switch 170 discharges the rectifying capacitor 160, the comparator 130 may be misjudged. In view of this, when the discharge switch 17 放电 discharges the rectifying capacitor 16 ’ , the operation of the comparator 130 can be disabled or the output of the over-voltage protection signal OVPS can be stopped to avoid the misjudgment of the comparator 130 . In the present embodiment, when the discharge switch 170 discharges the rectifying capacitor 160, the error preventing switch 190 is turned on, but the present invention is not limited thereto. It will be appreciated by those skilled in the art that the power conversion wafer disclosed above can also be applied to various types of power conversion devices. The power conversion device 10 of Figure 1 is merely an alternative embodiment. The power conversion chip can be applied to various types of power conversion devices such as boost type, step down, inversion, and transformer flyback. The pin SW of the power conversion chip 80 is also not limited to being electrically connected to the second end of the power conversion inductor 40 and the anode of the rectifying diode 50. Those skilled in the art can change the pin SW of the power conversion chip 80 according to the needs thereof. Coupling relationship. In summary, the power conversion chip proposed by the present invention has an overvoltage of 15 201128891 nr i-uy-ui4 33110twf.doc/n and 5 switches and power switches can also be used in the case of feet. 'Therefore, it does not have the effect of adding the following effects. In addition, the actual overvoltage protection circuit of the present invention is disposed on the load receiving and outputting power source - ^ to avoid (4) occurrence of a false occurrence of the slew and the wire voltage circuit. The over-circuit circuit can be configured to record circuits, which can lead to excessive voltage signals. The sigh of the pressure-changing circuit can be configured with a quasi-rectifier circuit to convert the high-frequency signal into a low-frequency reduction, so that the whistle of the Wei Du New can be selected. The components of the peak recording circuit can be matched with the components of the power conversion and the similar configuration of the configuration relationship, so that the peak rectifier circuit can be supplied with the waveform of the output power source (4) to rectify the signal to the comparator. 5. The reference signal generator can be configured with a similar architecture in accordance with the components of the peak rectifier circuit and its configuration relationship, and the noise caused by the low environment. The singular value rectification circuit and the reference signal generate 11 configurable discharge switches periodically discharge the rectifying capacitors, and (4) the rectifying capacitors are overcharged to cause a misjudgment of the comparison state. 7. When the rectifier capacitor is discharged, the comparator can be used to output the overvoltage protection signal to avoid misjudgment of the comparator.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and those skilled in the art can make some changes and refinements without departing from the spirit and scope of the present invention. The scope of the invention is defined by the scope of the appended claims. X 33110twf.doc/n 201128891 1 ±j. ι-υ^-014 [Simplified Schematic] FIG. 1 is a schematic diagram of a power conversion device and a power conversion wafer according to an embodiment of the present invention. 2 is a schematic diagram of a power conversion device and a power conversion wafer in accordance with another embodiment of the present invention. Fig. 3 is a schematic illustration of a power conversion device and a power conversion wafer in accordance with still another embodiment of the present invention. 4 is a schematic diagram of a reference signal generator in accordance with FIG. [Main component symbol description] 10~12: Power conversion device 20: Load 30: Input capacitor 40: Power conversion inductor 50, 150: Rectifier diode 60: Power conversion capacitor 70: Current detection resistor 80 to 82: Power conversion Wafer 90: power switch 100: control circuit 110 to 112: overvoltage protection circuit 120: voltage dividing circuit 121, 122: voltage dividing resistor 130: comparator 17 33110twf.doc/n 201128891 1 ir i-\J7-uι4 140 141: Peak rectification circuit 160: rectification capacitor 170: discharge switch 180: reference signal generator 190: anti-error switch VIN, SD, SW, FB, GND: pin DP: drive power

Vout: output power

Vin : Input power FS : Rectifier signal PWM : Pulse width modulation signal DS : Voltage division signal DIS : Discharge signal REF : Reference signal OVPS : Over voltage protection signal 18

Claims (1)

201128891 ιιπ-υ7-014 33ll〇twf.doc/n VII. Patent application scope: I A power conversion device, including: and - power conversion inductor 'generates a driving power source according to one round of power supply; - electricity == protection;: : Receiving the driving power supply, including: dynamic power supply and - reference signal generation - over-talking "depending on the power switch of the drive, the electrical connection is not connected" - through the power conversion inductance control: over-electricity = · The power supply of the first item of the first item, wherein the branching circuit is electrically connected to the pin, and according to the _ power source, a 1==:^ laydown (four) way is generated, according to the brain pressure dividing signal-comparator, Electrically connecting the peak rectification mask to the reference signal generating surface t 峨. The power supply device of the second aspect of the machine information distribution range, wherein: ί , the first end thereof is electrically connected to the pin; and the knife r resistance is electrically connected to the first end thereof. The second end of the first resistor of the resistor 201128891 /i4 33110 twd dcc / n is electrically connected - the ground end. The learned value rectifier circuit, comprising the power supply of item 2, wherein the anode receives the partial pressure The rectifying diode is connected to the grounding end of the rectifying diode electrically connected to the rectifying diode. The second end of the rectifying capacitor is electrically connected to the peak 4 excision source _, which is The first end of the rectifying capacitor is discharged with the connection and the rectifying capacitor, such as the second rectifying capacitor. The overvoltage protection circuit, and the power supply including the fourth item, wherein the end, Ιίίίί Zhao 11, The connection diagram of the new connection is more correct: the peak rectification circuit has: and the wheel is input to the ί terminal, and the reference signal is provided to the = comparison: the first: 7: as described in claim 6 The power supply, more packaged by the signal: =: === round-off end 'according to the release t 8. If the patent application scope 1 The power supply, further includes 20 201128891 nr 1-U7-014 33110twf.doc / n the whole machine - the pole body 'the pole is integrated with the cathode electrically connected to a load; and (4) - the polarization_electric_replacement capacitor 'The first impurity is connected to the cathode of the whole red body and the load, and the second end of the power conversion capacitor is electrically connected to a ground. 9. The power conversion chip is suitable for the __ power conversion inductor - The power conversion device f, the power supply power system--the input power source generates a driving power source and is provided to the electric_transformer_-pin, the marriage conversion chip comprises: an overvoltage protection circuit, electrically connected a pin, according to the driving power source and a reference signal to generate an overvoltage protection signal; a power switch, electrically connected to the pin, according to a pulse width modulation signal to determine whether to conduct, thereby controlling the driving power through the power conversion inductor And a control circuit electrically connected to the power switch, and generating the pulse width modulation signal according to the over-voltage protection signal, thereby controlling the power switch.