TWI443946B - Over power protection (opp) compensation circuit and flyback power supply - Google Patents
Over power protection (opp) compensation circuit and flyback power supply Download PDFInfo
- Publication number
- TWI443946B TWI443946B TW099125022A TW99125022A TWI443946B TW I443946 B TWI443946 B TW I443946B TW 099125022 A TW099125022 A TW 099125022A TW 99125022 A TW99125022 A TW 99125022A TW I443946 B TWI443946 B TW I443946B
- Authority
- TW
- Taiwan
- Prior art keywords
- circuit
- switch
- coupled
- compensation
- feedback
- Prior art date
Links
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
Landscapes
- Dc-Dc Converters (AREA)
Description
本發明是有關於一種具有過功率保護功能的返馳式電源，且特別是有關於一種採用寬範圍輸入電壓且採用過功率保護補償的返馳式電源。The present invention relates to a flyback power supply having an overpower protection function, and more particularly to a flyback power supply that employs a wide range of input voltages and employs overpower protection compensation.
圖1為一種現有的返馳式(flyback)電源的電路圖。請參見圖1，返馳式電源1採用寬範圍交流電壓Vac輸入。寬範圍交流電壓Vac通過電磁干擾(ElectroMagnetic Interference，簡稱EMI)濾波器11濾除EMI雜訊，再通過橋式整流器12的整流及電容C3的濾波而轉換成寬範圍輸入電壓Vin。寬範圍交流電壓Vac通常採用90Vrms-264Vrms，使得寬範圍輸入電壓Vin約為120V-370V。寬範圍輸入電壓Vin通過由變壓器T1、開關Q1及輸出整流濾波電路13所組成的返馳式直流至直流轉換電路轉換成輸出電壓Vout提供到負載。返馳式電源1通過回饋電路14取樣輸出電壓Vout以產生與負載量對應的回饋電流Ic，再通過脈寬調變(Pulse-Width Modulation，簡稱PWM)控制器U1根據其回饋端FB接收的與回饋電流Ic對應的回饋電壓Vfb，從其驅動端GATE輸出PWM信號Vgate控制開關Q1的切換，進而調整輸出電壓Vout。1 is a circuit diagram of a conventional flyback power supply. Referring to Figure 1, the flyback power supply 1 uses a wide range of AC voltage Vac inputs. The wide range AC voltage Vac filters the EMI noise through the Electromagnetic Interference (EMI) filter 11, and then converts it into a wide range of input voltage Vin through the rectification of the bridge rectifier 12 and the filtering of the capacitor C3. The wide range AC voltage Vac typically uses 90Vrms-264Vrms, making the wide range of input voltage Vin approximately 120V-370V. The wide range input voltage Vin is supplied to the load by a flyback DC-to-DC conversion circuit composed of a transformer T1, a switch Q1, and an output rectifying and filtering circuit 13 to be converted into an output voltage Vout. The flyback power supply 1 samples the output voltage Vout through the feedback circuit 14 to generate a feedback current Ic corresponding to the load amount, and then receives the pulse received by the pulse width modulation (PWM) controller U1 according to the feedback end FB thereof. The feedback voltage Vfb corresponding to the current Ic is fed, and the PWM signal Vgate is outputted from the drive terminal GATE to control the switching of the switch Q1, thereby adjusting the output voltage Vout.
為了確保輸出超載或短路時電源零件不受損壞或不產生安全隱患問題，電源通常設計有過功率保護(Over Power Protection，簡稱OPP)功能。返馳式電源1通過檢測電阻Rs及PWM控制器U1來提供OPP功能。檢測電阻Rs檢測流過開關Q1的電流Ip以產生與電流Ip對應的檢測電壓Vcs。檢測電壓Vcs通常需要通過由電阻R1及電容C1所組成的低通濾波電路來濾除因開關Q1切換所產生的高頻雜訊，以避免PWM控制器U1誤動作。PWM控制器U1根據其檢測端CS接收的濾波後的檢測電壓Vcs1，判斷電流Ip的最大值是否有達到OPP保護點來決定是否要停止從驅動端GATE輸出PWM信號Vgate，即停止電源轉換而關閉返馳式電源1。返馳式電源1設計用來提供固定的輸出電壓Vout到負載，故輸出功率與輸出電流有關，而輸出電流與流過變壓器T1次級繞組Ns1的次級電流有關，進而與流過變壓器T1初級繞組Np1的初級電流(即流過開關Q1的電流Ip)有關，因此可通過PWM控制器U1檢測並限制初級電流Ip的最大值來限制輸出功率，即提供OPP功能。In order to ensure that the power supply parts are not damaged or pose a safety hazard when the output is overloaded or short-circuited, the power supply is usually designed with Over Power Protection (OPP) function. The flyback power supply 1 provides an OPP function by detecting the resistor Rs and the PWM controller U1. The detection resistor Rs detects the current Ip flowing through the switch Q1 to generate the detection voltage Vcs corresponding to the current Ip. The detection voltage Vcs usually needs to filter the high-frequency noise generated by the switching of the switch Q1 through a low-pass filter circuit composed of the resistor R1 and the capacitor C1 to prevent the PWM controller U1 from malfunctioning. The PWM controller U1 determines whether the maximum value of the current Ip reaches the OPP protection point according to the filtered detection voltage Vcs1 received by the detection terminal CS to determine whether to stop outputting the PWM signal Vgate from the driving end GATE, that is, to stop the power conversion and turn off. Flyback power supply 1. The flyback power supply 1 is designed to provide a fixed output voltage Vout to the load, so the output power is related to the output current, and the output current is related to the secondary current flowing through the secondary winding Ns1 of the transformer T1, and thus flows through the transformer T1 primary. The primary current of the winding Np1 (i.e., the current Ip flowing through the switch Q1) is related, so the output power can be limited by the PWM controller U1 detecting and limiting the maximum value of the primary current Ip, that is, providing the OPP function.
PWM控制器U1提供的OPP保護點大小主要與輸入電壓Vin有關，即與交流電壓Vac有關。例如，在輸入90Vrms的交流電壓Vac或120V的輸入電壓Vin時，OPP保護點設計在40W，則在輸入264Vrms的交流電壓Vac或370V的輸入電壓Vin時，OPP保護點變為60W。由於輸入寬範圍電壓Vin(或Vac)導致OPP保護點的漂移，返馳式電源1對其變壓器T1、開關Q1等元件要有足夠的設計裕度，以便輸出超載或短路時，在變壓器T1還未達到飽合且流過開關Q1的電流Ip還未達到其規格最大值之前，PWM控制器U1就會開始進行OPP，以確保電源零件不受損壞或不產生安全隱患。而增加設計裕度除了可能增加電源設計成本之外，還可能增加電源設計難度。The size of the OPP protection point provided by the PWM controller U1 is mainly related to the input voltage Vin, that is, related to the AC voltage Vac. For example, when an AC voltage Vac of 90 Vrms or an input voltage Vin of 120 V is input, the OPP protection point is designed to be 40 W, and when an AC voltage Vac of 264 Vrms or an input voltage Vin of 370 V is input, the OPP protection point becomes 60 W. Since the input wide-range voltage Vin (or Vac) causes the drift of the OPP protection point, the flyback power supply 1 has sufficient design margin for its transformer T1, switch Q1 and other components, so that when the output is overloaded or short-circuited, the transformer T1 is also The PWM controller U1 will start OPP before the saturation current and the current Ip flowing through the switch Q1 have reached the maximum value of the specification to ensure that the power supply parts are not damaged or pose a safety hazard. Increasing the design margin may increase the difficulty of power supply design in addition to increasing the power supply design cost.
圖2為圖1所示返馳式電源1採用OPP補償的電路圖。請參見圖2，返馳式電源2即是在圖1所示返馳式電源1中加入補償電阻Rc，補償電阻Rc兩端分別耦接電容C3正端和PWM控制器U1的檢測端CS。輸入電壓Vin落於電阻Rc、R1和Rs上而產生一補償電流Irc，Irc=Vin/(Rc+R1+Rs)，此補償電流Irc通過電阻R1和Rs產生一電壓疊加到檢測端CS對OPP保護點的漂移做補償(下稱OPP補償)。例如，在輸入90Vrms的交流電壓Vac或120V的輸入電壓Vin(下稱輸入90Vrms)時，在檢測端CS會得到較小的OPP補償，在輸入264Vrms的交流電壓Vac或370V的輸入電壓Vin(下稱輸入264Vrms)時，在檢測端CS會得到較大的OPP補償，使得輸入90Vrms-264Vrms的交流電壓Vac或120V-370V的輸入電壓Vin(下稱輸入90Vrms-264Vrms)的高低兩端OPP保護點更接近。2 is a circuit diagram of the flyback power supply 1 shown in FIG. 1 using OPP compensation. Referring to FIG. 2, the flyback power supply 2 is added with a compensation resistor Rc in the flyback power supply 1 shown in FIG. 1. The two ends of the compensation resistor Rc are respectively coupled to the positive terminal of the capacitor C3 and the detection terminal CS of the PWM controller U1. The input voltage Vin falls on the resistors Rc, R1 and Rs to generate a compensation current Irc, Irc=Vin/(Rc+R1+Rs), and the compensation current Irc generates a voltage superimposed on the detection terminal CS to the OPP through the resistors R1 and Rs. The drift of the protection point is compensated (hereinafter referred to as OPP compensation). For example, when inputting 90Vrms AC voltage Vac or 120V input voltage Vin (hereinafter referred to as input 90Vrms), CS will get smaller OPP compensation at the detection terminal CS, input 264Vrms AC voltage Vac or 370V input voltage Vin (under When the input is 264Vrms), CS will get a large OPP compensation at the detection terminal, so that the input voltage of 90Vrms-264Vrms or the input voltage Vin of 120V-370V (hereinafter referred to as input 90Vrms-264Vrms) OPP protection point Closer.
圖3為圖2所示返馳式電源2的OPP補償的實驗數據。請參見圖3，通過調整補償電阻Rc電阻值可發現：補償電阻Rc電阻值在小於630KΩ時，輸入90Vrms-264Vrms的高低兩端OPP保護點差值較大，且OPP保護點在輸入264Vrms時反而比輸入90Vrms時大得多，OPP補償過度。補償電阻Rc電阻值在630KΩ-1MΩ時，輸入90Vrms-264Vrms的高低兩端OPP保護點差值較小，OPP補償效果較好，但此時損耗在補償電阻Rc上的功耗約為136mW-201mW，無法應用到要求低待機功耗的電子產品上。補償電阻Rc電阻值在2.2MΩ以上時，輸入90Vrms-264Vrms的高低兩端OPP保護點差值較大，OPP補償不足，且補償電阻Rc電阻值越大則OPP補償效果越差。補償電阻Rc電阻值無窮大或開路時，相當於返馳式電源1未加入補償電阻Rc的情況，此時無OPP補償。FIG. 3 is experimental data of OPP compensation of the flyback power supply 2 shown in FIG. 2. Referring to FIG. 3, by adjusting the resistance value of the compensation resistor Rc, it can be found that when the resistance value of the compensation resistor Rc is less than 630KΩ, the difference between the high and low OPP protection points of the input 90Vrms-264Vrms is large, and the OPP protection point is at the input of 264Vrms instead. It is much larger than when inputting 90Vrms, and OPP compensation is excessive. When the resistance of the compensation resistor Rc is 630KΩ-1MΩ, the difference between the high and low OPP protection points of the input 90Vrms-264Vrms is small, and the OPP compensation effect is good, but the power consumption of the loss on the compensation resistor Rc is about 136mW-201mW. Cannot be applied to electronic products that require low standby power consumption. When the resistance value of the compensation resistor Rc is 2.2 MΩ or more, the difference between the high and low OPP protection points of the input 90Vrms-264Vrms is large, the OPP compensation is insufficient, and the larger the compensation resistance Rc resistance value is, the worse the OPP compensation effect is. When the resistance value of the compensation resistor Rc is infinite or open, it corresponds to the case where the flyback power supply 1 is not added with the compensation resistor Rc, and there is no OPP compensation at this time.
本發明的目的就是在提出一種過功率保護(OPP)補償電路，適用於返馳式電源，可補償因輸入寬範圍電壓所導致的OPP保護點漂移問題，且可在例如待機模式的輕載或空載情況下關閉OPP補償電路。The object of the present invention is to propose an over-power protection (OPP) compensation circuit suitable for a flyback power supply, which can compensate for the OPP protection point drift problem caused by inputting a wide range of voltages, and can be light load in, for example, standby mode or The OPP compensation circuit is turned off under no load conditions.
本發明的另一目的就是在提出一種返馳式電源，採用OPP補償電路，可補償因輸入寬範圍電壓所導致的OPP保護點漂移問題，且可在例如待機模式的輕載或空載情況下關閉OPP補償電路。Another object of the present invention is to provide a flyback power supply that uses an OPP compensation circuit to compensate for OPP protection point drift caused by inputting a wide range of voltages, and can be used, for example, in a light or no load condition in standby mode. Turn off the OPP compensation circuit.
本發明提出一種OPP補償電路，適用於返馳式電源。返馳式電源包括變壓器、開關、輸出整流濾波電路、回饋電路及脈寬調變(PWM)控制器。其中，變壓器包括設在其初級側的初級繞組及設在其次級側的次級繞組。初級繞組打點端耦接以接收寬範圍輸入電壓且其非打點端耦接開關第一端。開關第二端接地。次級繞組打點端接地且其非打點端耦接輸出整流濾波電路輸入端。輸出整流濾波電路輸出端提供輸出電壓到負載。回饋電路取樣輸出電壓以產生與負載量對應的回饋信號。PWM控制器具有檢測端及回饋端，通過檢測端檢測流過開關的電流以提供OPP，且通過回饋端接收回饋信號以控制開關的切換。The invention provides an OPP compensation circuit suitable for a flyback power supply. The flyback power supply includes a transformer, a switch, an output rectification filter circuit, a feedback circuit, and a pulse width modulation (PWM) controller. Among them, the transformer includes a primary winding disposed on a primary side thereof and a secondary winding disposed on a secondary side thereof. The primary winding dot end is coupled to receive a wide range of input voltages and the non-tapping end is coupled to the first end of the switch. The second end of the switch is grounded. The secondary winding dot is grounded and its non-injected terminal is coupled to the output rectifier filter circuit input. The output of the output rectification filter circuit provides an output voltage to the load. The feedback circuit samples the output voltage to generate a feedback signal corresponding to the amount of load. The PWM controller has a detecting end and a feedback end. The detecting end detects the current flowing through the switch to provide an OPP, and the feedback end receives the feedback signal to control the switching of the switch.
OPP補償電路包括補償繞組、整流濾波電路、補償電阻及開關電路。其中，補償繞組設在變壓器初級側，補償繞組打點端耦接整流濾波電路輸入端且其非打點端接地。補償電阻第一端耦接檢測端，補償電阻第二端耦接開關電路第二端。開關電路第一端耦接整流濾波電路輸出端，開關電路控制端耦接回饋端。當回饋信號表示負載量小於預定值時，開關電路關斷，當回饋信號表示負載量大於預定值時，開關電路導通。The OPP compensation circuit includes a compensation winding, a rectification and filtering circuit, a compensation resistor, and a switching circuit. The compensation winding is disposed on the primary side of the transformer, and the compensation winding end is coupled to the input end of the rectifying and filtering circuit and the non-tapping end is grounded. The first end of the compensation resistor is coupled to the detection end, and the second end of the compensation resistor is coupled to the second end of the switch circuit. The first end of the switch circuit is coupled to the output end of the rectifying and filtering circuit, and the control end of the switch circuit is coupled to the feedback end. When the feedback signal indicates that the load amount is less than the predetermined value, the switch circuit is turned off, and when the feedback signal indicates that the load amount is greater than the predetermined value, the switch circuit is turned on.
本發明另提出一種返馳式電源，包括上述的變壓器、開關、輸出整流濾波電路、回饋電路、PWM控制器及OPP補償電路。The invention further provides a flyback power supply, comprising the above transformer, switch, output rectification and filtering circuit, feedback circuit, PWM controller and OPP compensation circuit.
本發明因採用補償繞組來感應出與寬範圍輸入電壓對應的電壓，此感應電壓再通過整流濾波電路、開關電路及補償電阻在PWM控制器的檢測端提供一個偏壓補償因輸入寬範圍電壓所導致的OPP保護點漂移問題，且在例如待機模式的輕載或空載情況下(即負載量小於預定值時)，通過開關電路的關斷來關閉OPP補償電路，故可應用到要求低待機功耗的液晶顯示產品返馳式電源當中。The invention adopts a compensation winding to induce a voltage corresponding to a wide range of input voltages, and the induced voltage further provides a bias compensation at the detection end of the PWM controller through a rectification filter circuit, a switching circuit and a compensation resistor. The OPP protection point drift problem is caused, and in the case of, for example, a light load or no load condition in the standby mode (ie, when the load amount is less than a predetermined value), the OPP compensation circuit is turned off by the shutdown of the switch circuit, so that it can be applied to the required low standby. Power consumption of liquid crystal display products in the flyback power supply.
為讓本發明之上述和其他目的、特徵和優點能更明顯易懂，下文特舉較佳實施例，並配合所附圖式，作詳細說明如下。The above and other objects, features and advantages of the present invention will become more <RTIgt;
圖4為依照本發明一實施例的採用寬範圍輸入電壓且採用OPP補償的返馳式電源的電路圖。請參見圖4，返馳式電源4即是在圖1所示返馳式電源1中加入OPP補償電路，其中OPP補償電路包括補償繞組Np2、整流濾波電路41、開關電路42及補償電阻Rc。因此，返馳式電源4包括EMI濾波器11、橋式整流器12、電容C3、返馳式直流至直流轉換電路(其包括變壓器T1、開關Q1及輸出整流濾波電路13)、回饋電路14、PWM控制器U1、檢測電阻Rs、低通濾波電路(其包括電阻R1及電容C1)及OPP補償電路。返馳式電源4採用寬範圍交流電壓Vac輸入。寬範圍交流電壓Vac通過EMI濾波器11濾除EMI雜訊，再通過橋式整流器12的整流及電容C3的濾波而轉換成寬範圍輸入電壓Vin。寬範圍交流電壓Vac通常採用90Vrms-264Vrms，使得寬範圍輸入電壓Vin約為120V-370V。4 is a circuit diagram of a flyback power supply employing a wide range of input voltages and employing OPP compensation, in accordance with an embodiment of the present invention. Referring to FIG. 4, the flyback power supply 4 is an OPP compensation circuit added to the flyback power supply 1 shown in FIG. 1. The OPP compensation circuit includes a compensation winding Np2, a rectification and filtering circuit 41, a switching circuit 42, and a compensation resistor Rc. Therefore, the flyback power supply 4 includes an EMI filter 11, a bridge rectifier 12, a capacitor C3, a flyback DC to DC conversion circuit (which includes a transformer T1, a switch Q1, and an output rectification filter circuit 13), a feedback circuit 14, and a PWM. The controller U1, the detecting resistor Rs, the low-pass filter circuit (which includes the resistor R1 and the capacitor C1), and the OPP compensation circuit. The flyback power supply 4 uses a wide range of AC voltage Vac input. The wide range AC voltage Vac filters the EMI noise through the EMI filter 11, and is converted into a wide range of input voltage Vin by the rectification of the bridge rectifier 12 and the filtering of the capacitor C3. The wide range AC voltage Vac typically uses 90Vrms-264Vrms, making the wide range of input voltage Vin approximately 120V-370V.
寬範圍輸入電壓Vin通過返馳式直流至直流轉換電路轉換成輸出電壓Vout提供到負載。變壓器T1包括設在其初級側的初級繞組Np1和補償繞組Np2及設在其次級側的次級繞組Ns1。初級繞組Np1打點端耦接電容C3正端以接收寬範圍輸入電壓Vin且其非打點端耦接開關Q1第一端。開關Q1第二端通過檢測電阻Rs接地(初級側地)。補償繞組Np2打點端耦接整流濾波電路41輸入端且其非打點端接地(初級側地)。次級繞組Ns1打點端接地(次級側地)且其非打點端耦接輸出整流濾波電路13輸入端。輸出整流濾波電路13輸出端提供輸出電壓Vout到負載。在本實施例中，輸出整流濾波電路13包括整流二極體及由兩電容與一電感所組成的CLC低通濾波器。The wide range of input voltage Vin is converted to an output voltage Vout through a flyback DC to DC conversion circuit to the load. The transformer T1 includes a primary winding Np1 and a compensation winding Np2 provided on the primary side thereof and a secondary winding Ns1 provided on the secondary side thereof. The primary winding Np1 dot end is coupled to the positive terminal of the capacitor C3 to receive the wide range of input voltage Vin and the non-injecting end is coupled to the first end of the switch Q1. The second end of the switch Q1 is grounded (primary side ground) through the sense resistor Rs. The tapping end of the compensation winding Np2 is coupled to the input end of the rectifying and filtering circuit 41 and its non-tapping end is grounded (primary side ground). The secondary winding Ns1 is grounded (secondary side) and its non-injected end is coupled to the input of the output rectifying and filtering circuit 13. The output of the output rectification filter circuit 13 provides an output voltage Vout to the load. In this embodiment, the output rectification and filtering circuit 13 includes a rectifying diode and a CLC low-pass filter composed of two capacitors and an inductor.
回饋電路14取樣輸出電壓Vout以產生與負載量對應的回饋信號Ic。在本實施例中，回饋電路14包括電阻R2～R5、電容C2、光耦合器U2及並聯穩壓器U3，其中光耦合器U2包括發光二極體IR及光電晶體PT，並聯穩壓器U3具有陽極端A、陰極端K及參考端R，並聯穩壓器U3例如是型號TL431積體電路，其內部電路示意圖如圖5所示。請同時參見圖4及圖5，回饋電路14通過電阻R3和R4取樣輸出電壓Vout，取樣後的輸出電壓Vout1輸入到並聯穩壓器U3的參考端R。並聯穩壓器U3通過其內部運算放大器OP1將取樣後的輸出電壓Vout1和其內部參考電壓源所提供的參考電壓Vref1兩者的差異放大並輸出對應的基極電流Ib驅動其內部電晶體Q4，進而產生對應的流過電晶體Q4的電流If，因此電流If大小對應於負載量。電流If通過光耦合器U2的發光二極體IR在其光電晶體PT產生對應的集極電流Ic，因此電流Ic大小對應於負載量，可作為回饋信號來調整開關Q1的切換，進而調整輸出電壓Vout。另外，電阻R5及電容C2串接於並聯穩壓器U3輸入的參考端R及輸出的陰極端K之間，提供負回饋電路做頻率補償。The feedback circuit 14 samples the output voltage Vout to generate a feedback signal Ic corresponding to the amount of load. In this embodiment, the feedback circuit 14 includes resistors R2 R R5, a capacitor C2, an optocoupler U2, and a shunt regulator U3. The photocoupler U2 includes a light emitting diode IR and a phototransistor PT, and a shunt regulator U3. It has an anode terminal A, a cathode terminal K and a reference terminal R. The shunt regulator U3 is, for example, a model TL431 integrated circuit, and its internal circuit schematic is shown in FIG. 5. Referring to FIG. 4 and FIG. 5 simultaneously, the feedback circuit 14 samples the output voltage Vout through the resistors R3 and R4, and the sampled output voltage Vout1 is input to the reference terminal R of the shunt regulator U3. The shunt regulator U3 amplifies the difference between the sampled output voltage Vout1 and the reference voltage Vref1 provided by its internal reference voltage source through its internal operational amplifier OP1 and outputs the corresponding base current Ib to drive its internal transistor Q4. Further, a corresponding current If flowing through the transistor Q4 is generated, so that the magnitude of the current If corresponds to the amount of load. The current If generates a corresponding collector current Ic in the photodiode PT through the light-emitting diode IR of the photocoupler U2, so the magnitude of the current Ic corresponds to the load amount, and can be used as a feedback signal to adjust the switching of the switch Q1, thereby adjusting the output voltage. Vout. In addition, the resistor R5 and the capacitor C2 are connected in series between the reference terminal R input from the shunt regulator U3 and the cathode terminal K of the output, and provide a negative feedback circuit for frequency compensation.
PWM控制器U1具有檢測端CS、回饋端FB及驅動端GATE。PWM控制器U1通過檢測端CS耦接檢測電阻Rs以檢測流過開關Q1的初級電流Ip，進而提供變壓器T1初級側過電流保護(Over Current Protection，簡稱OCP)，即提供變壓器T1次級側輸出的OPP。PWM控制器U1通過回饋端FB將電流形式的回饋信號(下稱回饋電流)Ic轉換成對應的電壓形式的回饋信號(下稱回饋電壓)Vfb。在檢測端CS檢測到初級電流Ip未達到OCP保護點時，PWM控制器U1根據檢測端CS接收的檢測電壓Vcs/Vcs1及回饋端FB接收的回饋電壓Vfb，從驅動端GATE輸出PWM信號Vgate控制開關Q1的切換，進而調整輸出電壓Vout。在檢測端CS檢測到初級電流Ip達到OCP保護點時PWM控制器U1，停止從驅動端GATE輸出PWM信號Vgate，即停止電源轉換而關閉返馳式電源1，輸出電壓Vout為零。The PWM controller U1 has a detection terminal CS, a feedback terminal FB and a drive terminal GATE. The PWM controller U1 is coupled to the detection resistor Rs through the detection terminal CS to detect the primary current Ip flowing through the switch Q1, thereby providing the transformer T1 primary side over current protection (OCP), that is, providing the secondary side output of the transformer T1. OPP. The PWM controller U1 converts a feedback signal (hereinafter referred to as a feedback current) Ic in the form of a current into a feedback signal (hereinafter referred to as a feedback voltage) Vfb in a corresponding voltage form via the feedback terminal FB. When the detection terminal CS detects that the primary current Ip does not reach the OCP protection point, the PWM controller U1 outputs a PWM signal Vgate control from the driving end GATE according to the detection voltage Vcs/Vcs1 received by the detection terminal CS and the feedback voltage Vfb received by the feedback terminal FB. The switching of the switch Q1 further adjusts the output voltage Vout. When the detection terminal CS detects that the primary current Ip reaches the OCP protection point, the PWM controller U1 stops outputting the PWM signal Vgate from the driving terminal GATE, that is, stops the power conversion and turns off the flyback power supply 1, and the output voltage Vout is zero.
PWM控制器U1例如是型號LD7576積體電路，其內部電路示意圖如圖6所示。請參見圖6，PWM控制器U1包括上拉電阻Rfb及PWM比較器CMP1，其中上拉電阻Rfb第一端耦接供電電壓Vbias，上拉電阻Rfb第二端耦接回饋端FB且通過兩二極體及兩電阻耦接PWM比較器CMP1負輸入端，因此回饋端FB接收的回饋電壓Vfb通過兩二極體及兩電阻取樣後產生電壓Vfb2輸入PWM比較器CMP1負輸入端，電壓Vfb2對應於回饋電壓Vfb。另外，檢測端CS接收的濾波後的檢測電壓Vcs1通過領先前緣屏蔽(Leading Edge Blanking，簡稱LEB)模組將檢測電壓Vcs1波形前緣屏蔽一小段時間以避免開關Q1切換所產生的高頻雜訊造成PWM控制器U1誤動作，LEB模組處理後的檢測電壓Vcs2再通過與內部一斜率補償電壓Vslope疊加後產生電壓Vcs3輸入PWM比較器CMP1正輸入端。The PWM controller U1 is, for example, a model LD7576 integrated circuit, and its internal circuit schematic is shown in FIG. 6. Referring to FIG. 6, the PWM controller U1 includes a pull-up resistor Rfb and a PWM comparator CMP1, wherein the first end of the pull-up resistor Rfb is coupled to the power supply voltage Vbias, and the second end of the pull-up resistor Rfb is coupled to the feedback terminal FB and passes through two or two. The pole body and the two resistors are coupled to the negative input terminal of the PWM comparator CMP1. Therefore, the feedback voltage Vfb received by the feedback terminal FB is generated by the two diodes and the two resistors, and the voltage Vfb2 is input to the negative input terminal of the PWM comparator CMP1, and the voltage Vfb2 corresponds to The voltage Vfb is fed back. In addition, the filtered detection voltage Vcs1 received by the detection terminal CS shields the leading edge of the detection voltage Vcs1 by a Leading Edge Blanking (LEB) module for a short period of time to avoid the high frequency miscellaneous generated by the switch Q1 switching. The signal causes the PWM controller U1 to malfunction. The detection voltage Vcs2 processed by the LEB module is superimposed with the internal slope compensation voltage Vslope to generate a voltage Vcs3 input to the positive input terminal of the PWM comparator CMP1.
PWM控制器U1還包括OCP比較器CMP2，其中OCP比較器CMP2正輸入端通過LEB模組耦接檢測端CS，OCP比較器CMP2負輸入端耦接參考電壓Vref2，因此通過LEB模組處理後的檢測電壓Vcs2輸入OCP比較器CMP2正輸入端。PWM比較器CMP1及OCP比較器CMP2的輸出通過或閘OR1的或運算處理後，再與內部時脈信號Vclk一起通過PWM產生模組產生從驅動端GATE輸出的PWM信號Vgate。The PWM controller U1 further includes an OCP comparator CMP2, wherein the positive input end of the OCP comparator CMP2 is coupled to the detection terminal CS through the LEB module, and the negative input end of the OCP comparator CMP2 is coupled to the reference voltage Vref2, and thus processed by the LEB module. The detection voltage Vcs2 is input to the positive input terminal of the OCP comparator CMP2. The output of the PWM comparator CMP1 and the OCP comparator CMP2 is processed by OR operation of the OR gate OR1, and then the PWM signal Vgate outputted from the driving terminal GATE is generated by the PWM generation module together with the internal clock signal Vclk.
圖7為圖4所示返馳式電源在不同負載量的控制時序圖。請同時參見圖6及圖7，當PWM控制器U1內部時脈信號Vclk傳送一個觸發信號Vp時，PWM控制器U1從驅動端GATE輸出的PWM信號Vgate此時為高準位而控制開關Q1導通。此時流過開關Q1的初級電流Ip開始增加，使檢測電壓Vcs及Vcs1開始上升，進而使電壓Vcs3開始上升。當電壓Vcs3大於電壓Vfb2時，PWM控制器U1從驅動端GATE輸出的PWM信號Vgate此時為低準位而控制開關Q1關斷。此時流過開關Q1的初級電流Ip為零，使檢測電壓Vcs及Vcs1為零，進而使電壓Vcs3為零。當電壓Vcs2大於參考電壓Vref2時，表示檢測到變壓器T1初級側有過電流問題，即變壓器T1次級側輸出會有過功率問題，因此PWM控制器U1停止從驅動端GATE輸出PWM信號Vgate，關閉返馳式電源4。當電壓Vcs2小於參考電壓Vref2時，表示沒有過電流及過功率問題，PWM控制器U1從驅動端GATE輸出PWM信號Vgate。FIG. 7 is a timing chart of control of the flyback power supply shown in FIG. 4 at different load amounts. Please also refer to FIG. 6 and FIG. 7. When the internal clock signal Vclk of the PWM controller U1 transmits a trigger signal Vp, the PWM signal Vgate outputted by the PWM controller U1 from the driving end GATE is at a high level and the control switch Q1 is turned on. . At this time, the primary current Ip flowing through the switch Q1 starts to increase, and the detection voltages Vcs and Vcs1 start to rise, and the voltage Vcs3 starts to rise. When the voltage Vcs3 is greater than the voltage Vfb2, the PWM signal Vgate output from the driving terminal GATE by the PWM controller U1 is at a low level and the control switch Q1 is turned off. At this time, the primary current Ip flowing through the switch Q1 is zero, and the detection voltages Vcs and Vcs1 are zero, and the voltage Vcs3 is made zero. When the voltage Vcs2 is greater than the reference voltage Vref2, it indicates that there is an overcurrent problem on the primary side of the transformer T1, that is, the secondary side output of the transformer T1 has an over-power problem, so the PWM controller U1 stops outputting the PWM signal Vgate from the driving end GATE, and turns off. Flyback power supply 4. When the voltage Vcs2 is less than the reference voltage Vref2, indicating that there is no overcurrent and overpower problem, the PWM controller U1 outputs the PWM signal Vgate from the driving terminal GATE.
請再參見圖4，OPP補償電路包括補償繞組Np2、整流濾波電路41、開關電路42及補償電阻Rc。其中，補償繞組Np2設在變壓器T1初級側，其打點端耦接整流濾波電路41輸入端且其非打點端接地(初級側地)。補償電阻Rc第一端耦接PWM控制器U1的檢測端CS，補償電阻Rc第二端耦接開關電路42第二端422。開關電路42第一端421耦接整流濾波電路41輸出端，開關電路42控制端423耦接PWM控制器U1的回饋端FB。當回饋信號表示負載量小於預定值時，開關電路42關斷，當回饋信號表示負載量大於預定值時，開關電路42導通，其中本例回饋信號採用回饋電壓Vfb。Referring to FIG. 4 again, the OPP compensation circuit includes a compensation winding Np2, a rectification and filtering circuit 41, a switching circuit 42, and a compensation resistor Rc. The compensation winding Np2 is disposed on the primary side of the transformer T1, and the dot end is coupled to the input end of the rectifying and filtering circuit 41 and its non-tapping end is grounded (primary side ground). The first end of the compensation resistor Rc is coupled to the detection terminal CS of the PWM controller U1, and the second end of the compensation resistor Rc is coupled to the second end 422 of the switch circuit 42. The first end 421 of the switch circuit 42 is coupled to the output end of the rectifying and filtering circuit 41, and the control end 423 of the switch circuit 42 is coupled to the feedback end FB of the PWM controller U1. When the feedback signal indicates that the load amount is less than the predetermined value, the switch circuit 42 is turned off. When the feedback signal indicates that the load amount is greater than the predetermined value, the switch circuit 42 is turned on, wherein the feedback signal of the present example uses the feedback voltage Vfb.
直流輸入電壓Vin通過開關Q1的切換在初級繞組Np1上產生一交流電壓Vnp1，並在補償繞組Np2上感應產生一交流電壓(下稱感應電壓) Vnp2，Vnp2=Vnp1×Np2/Np1，此感應電壓Vnp2再通過整流濾波電路41的整流濾波後產生一直流電壓Vnp2’。由於直流電壓Vnp2’與寬範圍輸入電壓Vin有關，因此可模仿先前技術的做法，在開關電路42導通時，直流電壓Vnp2’落於電阻Rc、R1和Rs上而產生一補償電流Irc，Irc=Vnp2’/(Rc+R1+Rs)，此補償電流Irc通過電阻R1和Rs產生一電壓疊加到檢測端CS做OPP補償。The DC input voltage Vin generates an AC voltage Vnp1 on the primary winding Np1 through the switching of the switch Q1, and induces an AC voltage (hereinafter referred to as an induced voltage) Vnp2, Vnp2=Vnp1×Np2/Np1, the induced voltage is generated on the compensation winding Np2. Vnp2 is further subjected to rectification and filtering by the rectifying and filtering circuit 41 to generate a DC voltage Vnp2'. Since the DC voltage Vnp2' is related to the wide range of input voltage Vin, it can be imitated in the prior art. When the switch circuit 42 is turned on, the DC voltage Vnp2' falls on the resistors Rc, R1 and Rs to generate a compensation current Irc, Irc= Vnp2' / (Rc + R1 + Rs), this compensation current Irc generates a voltage superimposed on the detection terminal CS through the resistors R1 and Rs for OPP compensation.
在本實施例中，整流濾波電路41包括整流二極體D1及電容C4，整流二極體D1陽極端耦接整流濾波電路41輸入端，整流二極體D1陰極端耦接電容C4第一端及整流濾波電路41輸出端，電容C4第二端接地。開關電路42包括第一型開關Q2及第二型開關Q3，其中第一型開關Q2控制端收到高準位信號時導通且在收到低準位信號時關斷，而第二型開關Q3控制端收到低準位信號時導通且在收到高準位信號時關斷。第一型開關Q2第一端耦接第二型開關Q3控制端，第一型開關Q2第二端接地(初級側地)，第一型開關Q2控制端耦接開關電路42控制端423。第二型開關Q3第一端耦接開關電路42第一端421，第二型開關Q3第二端耦接開關電路42第二端422。In this embodiment, the rectifying and filtering circuit 41 includes a rectifying diode D1 and a capacitor C4. The anode end of the rectifying diode D1 is coupled to the input end of the rectifying and filtering circuit 41, and the cathode end of the rectifying diode D1 is coupled to the first end of the capacitor C4. And the output end of the rectifying and filtering circuit 41, the second end of the capacitor C4 is grounded. The switch circuit 42 includes a first type switch Q2 and a second type switch Q3, wherein the control terminal of the first type switch Q2 is turned on when receiving the high level signal and is turned off when the low level signal is received, and the second type switch Q3 is turned off. The control terminal turns on when it receives the low level signal and turns off when it receives the high level signal. The first end of the first type switch Q2 is coupled to the control end of the second type switch Q3, the second end of the first type switch Q2 is grounded (primary side ground), and the control end of the first type switch Q2 is coupled to the control end 423 of the switch circuit 42. The first end of the second type switch Q3 is coupled to the first end 421 of the switch circuit 42 and the second end of the second type switch Q3 is coupled to the second end 422 of the switch circuit 42.
在本實施例中，第一型開關Q2由N通道場效應電晶體所實現，但亦可由NPN雙載子接面電晶體所實現。第二型開關Q3由PNP雙載子接面電晶體所實現，但亦可由P通道場效應電晶體所實現。開關電路42因此還包括電阻R6和R7以便在第一型開關Q2導通時可分壓提供第二型開關Q3導通所需的偏壓，另外還包括電阻R8和R9以便取樣回饋電壓Vfb，取樣後的回饋電壓Vfb1控制第一型開關Q2導通或關斷，電容C5用以濾除高頻雜訊。另外，補償繞組Np2圈數較佳為一圈，因為補償繞組Np2圈數越多則成本越高，且補償繞組Np2感應出來電壓Vnp2越高，損耗在補償電阻Rc上的功耗可能會增加。In the present embodiment, the first type switch Q2 is implemented by an N-channel field effect transistor, but can also be realized by an NPN double carrier junction transistor. The second type of switch Q3 is implemented by a PNP bipolar junction transistor, but can also be implemented by a P-channel field effect transistor. The switch circuit 42 thus further includes resistors R6 and R7 to provide a bias voltage required for the second type switch Q3 to be turned on when the first type switch Q2 is turned on, and a resistor R8 and R9 for sampling the feedback voltage Vfb, after sampling. The feedback voltage Vfb1 controls the first type switch Q2 to be turned on or off, and the capacitor C5 is used to filter out high frequency noise. In addition, the number of turns of the compensation winding Np2 is preferably one turn, because the higher the number of turns of the compensation winding Np2, the higher the cost, and the higher the voltage Vnp2 induced by the compensation winding Np2, the power consumption of the loss on the compensation resistor Rc may increase.
請同時參見圖4及圖7，在t1期間，輸出負載量不變，返馳式電源4輸出電流不變，此時變壓器T1輸出功率等於電源4輸出功率，輸出電壓Vout為一個穩定的電壓，光耦合器U2的電流If及Ic為一個穩定的電流。Please refer to FIG. 4 and FIG. 7 simultaneously. During t1, the output load is unchanged, and the output current of the flyback power supply 4 is unchanged. At this time, the output power of the transformer T1 is equal to the output power of the power supply 4, and the output voltage Vout is a stable voltage. The currents If and Ic of the photocoupler U2 are a stable current.
在t2期間，輸出負載量突然變大，返馳式電源4輸出電流變大，此時變壓器T1輸出功率小於電源4輸出功率，輸出電壓Vout瞬間下降，電流If及Ic開始下降，由於PWM控制器U1的回饋端FB內接上拉電阻Rfb，電流If及Ic開始下降會使在回饋端FB上的回饋電壓Vfb開始上升，因此PWM控制器U1從驅動端GATE輸出的PWM信號Vgate的責任週期(duty cycle)開始增大，使變壓器T1輸出功率開始增大，進而使輸出電壓Vout上升。During t2, the output load suddenly becomes larger, and the output current of the flyback power supply 4 becomes larger. At this time, the output power of the transformer T1 is smaller than the output power of the power supply 4, the output voltage Vout drops instantaneously, and the currents If and Ic start to decrease due to the PWM controller. The feedback terminal FB of U1 is internally connected with a pull-up resistor Rfb, and the currents If and Ic start to decrease, so that the feedback voltage Vfb on the feedback terminal FB starts to rise, so the duty cycle of the PWM signal Vgate outputted by the PWM controller U1 from the driving terminal GATE ( The duty cycle starts to increase, so that the output power of the transformer T1 starts to increase, and the output voltage Vout rises.
在t3期間，輸出電壓Vout上升到t1期間的準位，電流If及Ic開始保持較低的準位不變，使回饋電壓Vfb開始保持較高的準位不變，因此PWM控制器U1輸出的PWM信號Vgate開始保持較大的責任週期不變，使變壓器T1輸出功率等於電源4輸出功率。During t3, the output voltage Vout rises to the level during t1, and the currents If and Ic start to remain at the lower level, so that the feedback voltage Vfb starts to maintain a higher level, so the PWM controller U1 outputs The PWM signal Vgate begins to maintain a large duty cycle, so that the output power of the transformer T1 is equal to the output power of the power supply 4.
在t4期間，輸出負載量突然變小，返馳式電源4輸出電流變小，此時變壓器T1輸出功率大於電源4輸出功率，輸出電壓Vout瞬間上升，電流If及Ic開始上升，使回饋電壓Vfb開始下降，因此PWM控制器U1輸出的PWM信號Vgate的責任週期開始減小，使變壓器T1輸出功率開始減小，進而使輸出電壓Vout下降。During t4, the output load suddenly becomes smaller, and the output current of the flyback power supply 4 becomes smaller. At this time, the output power of the transformer T1 is greater than the output power of the power supply 4, the output voltage Vout rises instantaneously, and the currents If and Ic start to rise, so that the feedback voltage Vfb Starting to fall, the duty cycle of the PWM signal Vgate output by the PWM controller U1 starts to decrease, so that the output power of the transformer T1 starts to decrease, and the output voltage Vout is lowered.
在t5期間，輸出電壓Vout下降到t1期間的準位，電流If及/Ic開始保持較高的準位不變，使回饋電壓Vfb開始保持較低的準位不變，因此PWM控制器U1輸出的PWM信號Vgate開始保持較小責任週期不變，使變壓器T1輸出功率等於電源4輸出功率。During t5, the output voltage Vout drops to the level during t1, and the current If and /Ic start to maintain a high level, so that the feedback voltage Vfb starts to remain at a lower level, so the PWM controller U1 outputs The PWM signal Vgate begins to maintain a small duty cycle, so that the output power of the transformer T1 is equal to the output power of the power supply 4.
由此可知，當輸出負載量變大時，回饋電壓Vfb上升，當輸出負載量變小時，回饋電壓Vfb下降，OPP補償電路利用了輕重載變化引起回饋電壓Vfb變化的特性來設計開關電路42控制OPP補償電路的導通或關斷。例如，設計輸出負載量小於預定值時，返馳式電源4必然工作在待機模式而為輕載或空載，此時電流Ic會在較高的準位不變，使回饋電壓Vfb在較低的準位不變，因此可設計回饋電壓Vfb取樣後的電壓Vfb1將使第一型開關Q1關斷，進而使開關電路42關斷，不再進行OPP補償，即此時OPP補償電路幾乎沒有功耗，故可應用到要求低待機功耗的液晶顯示產品返馳式電源當中。而輸出負載量大於預定值時，返馳式電源4必然工作在正常模式而為重載，此時電流Ic會在較低的準位不變，使回饋電壓Vfb在較高的準位不變，因此可設計回饋電壓Vfb取樣後的電壓Vfb1將使第一型開關Q1導通，進而使開關電路42導通，故補償繞組Np2的感應電壓Vnp2可通過導通的開關電路42及補償電阻Rc在檢測端CS提供一個偏壓補償OPP保護點的漂移。It can be seen that when the output load amount becomes large, the feedback voltage Vfb rises, and when the output load amount becomes small, the feedback voltage Vfb decreases, and the OPP compensation circuit utilizes the characteristic that the light-heavy load change causes the feedback voltage Vfb to change to design the switch circuit 42 to control the OPP compensation. The circuit is turned on or off. For example, when the designed output load is less than the predetermined value, the flyback power supply 4 must work in the standby mode and be light or no load. At this time, the current Ic will remain at a higher level, so that the feedback voltage Vfb is lower. The level of the switch is unchanged, so the voltage Vfb1 after the sampling voltage Vfb is sampled will turn off the first type switch Q1, so that the switch circuit 42 is turned off, and the OPP compensation is no longer performed, that is, the OPP compensation circuit has almost no work. It can be applied to a liquid crystal display product that requires low standby power consumption. When the output load is greater than the predetermined value, the flyback power supply 4 must work in the normal mode and be heavy. At this time, the current Ic will be unchanged at a lower level, so that the feedback voltage Vfb is unchanged at a higher level. Therefore, the voltage Vfb1 after the sampling of the feedback voltage Vfb can be designed to turn on the first type switch Q1, thereby turning on the switching circuit 42. Therefore, the induced voltage Vnp2 of the compensation winding Np2 can pass through the switching circuit 42 and the compensation resistor Rc at the detecting end. The CS provides a bias to compensate for the drift of the OPP protection point.
圖8為圖4所示返馳式電源4的OPP補償的實驗數據，其是在補償繞組Np2圈數為1圈且開關電路42導通為前提下的量測結果。請參見圖8，通過調整補償電阻Rc電阻值可發現：補償電阻Rc電阻值在3.9KΩ以下時，輸入90Vrms-264Vrms的高低兩端OPP保護點差值較大，且OPP保護點在輸入264Vrms時反而比輸入90Vrms時大得多，OPP補償過度。補償電阻Rc電阻值在4.3KΩ-5.6KΩ時，輸入90Vrms-264Vrms的高低兩端OPP保護點差值很小，OPP補償效果很好，且此時損耗在補償電阻Rc上的功耗約為9.78mW-12.73mW。補償電阻Rc電阻值在9.1KΩ以上時，輸入90Vrms-264Vrms的高低兩端OPP保護點差值較大，OPP補償不足，且補償電阻Rc電阻值越大則OPP補償效果越差。補償電阻Rc電阻值無窮大或開路時，相當於返馳式電源1未加入補償電阻Rc的情況，此時無OPP補償。8 is experimental data of OPP compensation of the flyback power supply 4 shown in FIG. 4, which is a measurement result under the premise that the number of turns of the compensation winding Np2 is one turn and the switch circuit 42 is turned on. Referring to Figure 8, by adjusting the resistance value of the compensation resistor Rc, it can be found that when the resistance value of the compensation resistor Rc is below 3.9KΩ, the difference between the high and low OPP protection points of the input 90Vrms-264Vrms is large, and the OPP protection point is 264Vrms at the input. Instead, it is much larger than when 90Vrms is input, and OPP compensation is excessive. When the resistance value of the compensation resistor Rc is 4.3KΩ-5.6KΩ, the difference between the high and low OPP protection points of the input 90Vrms-264Vrms is small, the OPP compensation effect is very good, and the power consumption of the loss on the compensation resistor Rc is about 9.78. mW-12.73mW. When the resistance value of the compensation resistor Rc is above 9.1KΩ, the difference between the high and low OPP protection points of the input 90Vrms-264Vrms is large, the OPP compensation is insufficient, and the larger the resistance value of the compensation resistor Rc is, the worse the OPP compensation effect is. When the resistance value of the compensation resistor Rc is infinite or open, it corresponds to the case where the flyback power supply 1 is not added with the compensation resistor Rc, and there is no OPP compensation at this time.
由於本發明的OPP補償電路在補償繞組Np2圈數為1圈且補償電阻Rc電阻值可適度補償OPP的設計下，損耗在補償電阻Rc上的功耗僅為10mW左右，因此，對於待機功耗要求較不嚴格(如低於0.5W)的液晶顯示產品，其OPP補償電路設計可以考慮不增加開關電路42以降低成本。若不增加開關電路42，則將整流濾波電路41輸出端改成直接耦接補償電阻Rc第二端。但是，對於待機功耗要求較嚴格(如低於0.3W或甚至更低)的液晶顯示產品，其OPP補償電路設計則需要增加開關電路42，以便在待機模式下關閉OPP補償電路，此時OPP補償電路幾乎沒有功耗，使低於0.3W或甚至更低的待機功耗較容易實現。Since the OPP compensation circuit of the present invention has a design in which the number of turns of the compensation winding Np2 is one turn and the resistance value of the compensation resistor Rc can be appropriately compensated for the OPP, the power consumption of the loss on the compensation resistor Rc is only about 10 mW, and therefore, for standby power consumption. For liquid crystal display products that are less stringent (such as less than 0.5W), the OPP compensation circuit design can be considered without increasing the switching circuit 42 to reduce the cost. If the switching circuit 42 is not added, the output end of the rectifying and filtering circuit 41 is changed to directly couple the second end of the compensating resistor Rc. However, for liquid crystal display products with strict standby power requirements (such as less than 0.3W or even lower), the OPP compensation circuit design needs to increase the switching circuit 42 to turn off the OPP compensation circuit in the standby mode, at this time OPP The compensation circuit has almost no power consumption, making standby power consumption below 0.3W or even lower easier to implement.
綜上所述，本發明因採用補償繞組來感應出與寬範圍輸入電壓對應的電壓，此感應電壓再通過整流濾波電路、開關電路及補償電阻在PWM控制器的檢測端提供一個偏壓補償因輸入寬範圍電壓所導致的OPP保護點漂移問題，且在例如待機模式的輕載或空載情況下(即負載量小於預定值時)，通過開關電路的關斷來關閉OPP補償電路，故可應用到要求低待機功耗的液晶顯示產品返馳式電源當中。In summary, the present invention uses a compensation winding to induce a voltage corresponding to a wide range of input voltages, and the induced voltage provides a bias compensation factor at the detection end of the PWM controller through a rectification filter circuit, a switching circuit, and a compensation resistor. The OPP protection point drift problem caused by inputting a wide range voltage, and in the case of light load or no load in the standby mode (for example, when the load amount is less than a predetermined value), the OPP compensation circuit is turned off by the shutdown of the switch circuit, so It is applied to a liquid crystal display product that requires low standby power consumption.
雖然本發明已以較佳實施例揭露如上，然其並非用以限定本發明，任何熟習此技藝者，在不脫離本發明之精神和範圍內，當可作些許之更動與潤飾，因此本發明之保護範圍當視後附之申請專利範圍所界定者為準。While the present invention has been described in its preferred embodiments, the present invention is not intended to limit the invention, and the present invention may be modified and modified without departing from the spirit and scope of the invention. The scope of protection is subject to the definition of the scope of the patent application.
1、2、4．．．返馳式電源1, 2, 4. . . Flyback power supply
11．．．EMI濾波器11. . . EMI filter
12．．．橋式整流器12. . . Bridge rectifier
13．．．輸出整流濾波電路13. . . Output rectification filter circuit
14．．．回饋電路14. . . Feedback circuit
41．．．整流濾波電路41. . . Rectifier filter circuit
42．．．開關電路42. . . Switch circuit
421．．．開關電路的第一端421. . . First end of the switching circuit
422．．．開關電路的第二端422. . . Second end of the switching circuit
423．．．開關電路的控制端423. . . Control terminal of the switching circuit
C1～C5．．．電容C1 ~ C5. . . capacitance
CMP1．．．PWM比較器CMP1. . . PWM comparator
CMP2．．．OCP比較器CMP2. . . OCP comparator
D1．．．整流二極體D1. . . Rectifier diode
OP1．．．運算放大器OP1. . . Operational Amplifier
OR1．．．或閘OR1. . . Gate
Q1．．．開關Q1. . . switch
Q2．．．第一型開關Q2. . . Type 1 switch
Q3．．．第二型開關Q3. . . Second type switch
Q4．．．電晶體Q4. . . Transistor
R1～R9．．．電阻R1 ~ R9. . . resistance
Rc．．．補償電阻Rc. . . Compensation resistor
Rfb．．．上拉電阻Rfb. . . Pull-up resistor
Rs．．．檢測電阻Rs. . . Sense resistor
T1．．．變壓器T1. . . transformer
Np1．．．初級繞組Np1. . . Primary winding
Np2．．．補償繞組Np2. . . Compensation winding
Ns1．．．次級繞組Ns1. . . Secondary winding
U1．．．PWM控制器U1. . . PWM controller
CS．．．PWM控制器的檢測端CS. . . PWM controller detection terminal
FB．．．PWM控制器的回饋端FB. . . Feedback terminal of PWM controller
GATE．．．PWM控制器的驅動端GATE. . . Drive terminal of PWM controller
U2．．．光耦合器U2. . . Optocoupler
IR．．．發光二極體IR. . . Light-emitting diode
PT．．．光電晶體PT. . . Photoelectric crystal
U3．．．並聯穩壓器U3. . . Shunt regulator
A．．．並聯穩壓器的陽極端A. . . Anode end of shunt regulator
K．．．並聯穩壓器的陰極端K. . . Cathode terminal of shunt regulator
R．．．並聯穩壓器的參考端R. . . Reference terminal of shunt regulator
Ib．．．電晶體的基極電流Ib. . . Base current of the transistor
Ic．．．光電晶體的集極電流Ic. . . Collector current of photoelectric crystal
If．．．發光二極體的正向電流If. . . Forward current of light-emitting diode
Ip．．．初級電流Ip. . . Primary current
Irc．．．補償電流Irc. . . Compensation current
Vac．．．寬範圍交流電壓Vac. . . Wide range AC voltage
Vbias．．．供電電壓Vbias. . . Supply voltage
Vclk．．．時脈信號Vclk. . . Clock signal
Vcs．．．檢測電壓Vcs. . . Detection voltage
Vcs1．．．濾波後的檢測電壓Vcs1. . . Filtered detection voltage
Vcs2．．．OCP比較器正輸入端電壓Vcs2. . . OCP comparator positive input voltage
Vcs3．．．PWM比較器正輸入端電壓Vcs3. . . PWM comparator positive input voltage
Vfb．．．回饋電壓Vfb. . . Feedback voltage
Vfb1．．．取樣後的回饋電壓Vfb1. . . Sampled feedback voltage
Vfb2．．．PWM比較器負輸入端電壓Vfb2. . . PWM comparator negative input voltage
Vgate．．．PWM信號Vgate. . . PWM signal
Vin．．．寬範圍輸入電壓Vin. . . Wide range input voltage
Vnp1．．．初級繞組上的交流電壓Vnp1. . . AC voltage on the primary winding
Vnp2．．．補償繞組上的感應電壓Vnp2. . . Compensation voltage on the winding
Vnp2’．．．整流濾波後的感應電壓Vnp2’. . . Rectified filtered induced voltage
Vout．．．輸出電壓Vout. . . The output voltage
Vout1．．．取樣後的輸出電壓Vout1. . . Sampled output voltage
Vp．．．觸發信號Vp. . . Trigger signal
Vref1、Vref2．．．參考電壓Vref1, Vref2. . . Reference voltage
Vslope．．．斜率補償電壓Vslope. . . Slope compensation voltage
t1～t5．．．期間T1~t5. . . period
圖1為一種現有的採用寬範圍輸入電壓但不採用OPP補償的返馳式電源的電路圖。Figure 1 is a circuit diagram of a conventional flyback power supply that uses a wide range of input voltages but does not employ OPP compensation.
圖2為圖1所示返馳式電源採用OPP補償的電路圖。FIG. 2 is a circuit diagram of the OPP compensation of the flyback power supply shown in FIG. 1.
圖3為圖2所示返馳式電源的OPP補償的實驗數據。FIG. 3 is experimental data of OPP compensation of the flyback power supply shown in FIG. 2.
圖4為依照本發明一實施例的採用寬範圍輸入電壓且採用OPP補償的返馳式電源的電路圖。4 is a circuit diagram of a flyback power supply employing a wide range of input voltages and employing OPP compensation, in accordance with an embodiment of the present invention.
圖5為圖4所示並聯穩壓器的內部電路示意圖。FIG. 5 is a schematic diagram of an internal circuit of the shunt regulator shown in FIG. 4.
圖6為圖4所示PWM控制器的內部電路示意圖。FIG. 6 is a schematic diagram of an internal circuit of the PWM controller shown in FIG. 4.
圖7為圖4所示返馳式電源在不同負載量的控制時序圖。FIG. 7 is a timing chart of control of the flyback power supply shown in FIG. 4 at different load amounts.
圖8為圖4所示返馳式電源的OPP補償的實驗數據。FIG. 8 is experimental data of OPP compensation of the flyback power supply shown in FIG. 4.
4．．．返馳式電源4. . . Flyback power supply
11．．．EMI濾波器11. . . EMI filter
12．．．橋式整流器12. . . Bridge rectifier
13．．．輸出整流濾波電路13. . . Output rectification filter circuit
14．．．回饋電路14. . . Feedback circuit
41．．．整流濾波電路41. . . Rectifier filter circuit
42．．．開關電路42. . . Switch circuit
421．．．開關電路的第一端421. . . First end of the switching circuit
422．．．開關電路的第二端422. . . Second end of the switching circuit
423．．．開關電路的控制端423. . . Control terminal of the switching circuit
C1～C5．．．電容C1 ~ C5. . . capacitance
D1．．．整流二極體D1. . . Rectifier diode
Q1．．．開關Q1. . . switch
Q2．．．第一型開關Q2. . . Type 1 switch
Q3．．．第二型開關Q3. . . Second type switch
R1～R9．．．電阻R1 ~ R9. . . resistance
Rc．．．補償電阻Rc. . . Compensation resistor
Rs．．．檢測電阻Rs. . . Sense resistor
T1．．．變壓器T1. . . transformer
Np1．．．初級繞組Np1. . . Primary winding
Np2．．．補償繞組Np2. . . Compensation winding
NS1．．．次級繞組NS1. . . Secondary winding
U1．．．PWM控制器U1. . . PWM controller
CS．．．PWM控制器的檢測端CS. . . PWM controller detection terminal
FB．．．PWM控制器的回饋端FB. . . Feedback terminal of PWM controller
GATE．．．PWM控制器的驅動端GATE. . . Drive terminal of PWM controller
U2．．．光耦合器U2. . . Optocoupler
IR．．．發光二極體IR. . . Light-emitting diode
PT．．．光電晶體PT. . . Photoelectric crystal
U3．．．並聯穩壓器U3. . . Shunt regulator
A．．．並聯穩壓器的陽極端A. . . Anode end of shunt regulator
K．．．並聯穩壓器的陰極端K. . . Cathode terminal of shunt regulator
R．．．並聯穩壓器的參考端R. . . Reference terminal of shunt regulator
Ic．．．光電晶體的集極電流Ic. . . Collector current of photoelectric crystal
If．．．發光二極體的正向電流If. . . Forward current of light-emitting diode
Ip．．．初級電流Ip. . . Primary current
Irc．．．補償電流Irc. . . Compensation current
Vac．．．寬範圍交流電壓Vac. . . Wide range AC voltage
Vcs．．．檢測電壓Vcs. . . Detection voltage
Vcs1．．．濾波後的檢測電壓Vcs1. . . Filtered detection voltage
Vfb．．．回饋電壓Vfb. . . Feedback voltage
Vfb1．．．取樣後的回饋電壓Vfb1. . . Sampled feedback voltage
Vgate．．．PWM信號Vgate. . . PWM signal
Vin．．．寬範圍輸入電壓Vin. . . Wide range input voltage
Vnp1．．．初級繞組上的交流電壓Vnp1. . . AC voltage on the primary winding
Vnp2．．．補償繞組上的感應電壓Vnp2. . . Compensation voltage on the winding
Vnp2’．．．整流濾波後的感應電壓Vnp2’. . . Rectified filtered induced voltage
Vout．．．輸出電壓Vout. . . The output voltage
Vout1．．．取樣後的輸出電壓Vout1. . . Sampled output voltage
Claims (10)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| TW099125022A TWI443946B (en) | 2010-07-29 | 2010-07-29 | Over power protection (opp) compensation circuit and flyback power supply |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| TW099125022A TWI443946B (en) | 2010-07-29 | 2010-07-29 | Over power protection (opp) compensation circuit and flyback power supply |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| TW201206034A TW201206034A (en) | 2012-02-01 |
| TWI443946B true TWI443946B (en) | 2014-07-01 |
Family
ID=46761825
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| TW099125022A TWI443946B (en) | 2010-07-29 | 2010-07-29 | Over power protection (opp) compensation circuit and flyback power supply |
Country Status (1)
| Country | Link |
|---|---|
| TW (1) | TWI443946B (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9325246B1 (en) | 2015-01-20 | 2016-04-26 | Chicony Power Technology Co., Ltd. | Flyback apparatus with voltage superposition circuit and overpower protection |
| CN105871184A (en) * | 2015-11-12 | 2016-08-17 | 成都启臣微电子有限公司 | Ultrahigh-precision overpower compensating circuit |
| TWI556564B (en) * | 2015-09-18 | 2016-11-01 | 強弦科技股份有限公司 | Converter control system |
| TWI568119B (en) * | 2014-10-09 | 2017-01-21 | 群光電能科技股份有限公司 | Power supply apparatus with over power protection function |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111900783B (en) * | 2019-05-05 | 2022-05-03 | 宏碁股份有限公司 | Over-power protection circuit, charger and over-power protection method |
| CN111884512A (en) * | 2020-03-18 | 2020-11-03 | 深圳市航嘉驰源电气股份有限公司 | Switching power supply, power adapter and charger |
| TWI786589B (en) * | 2021-04-07 | 2022-12-11 | 全漢企業股份有限公司 | Function trigger circuit of power conversion device, function trigger method and power conversion device thereof |
| TWI784755B (en) * | 2021-10-18 | 2022-11-21 | 通嘉科技股份有限公司 | Controller applied to a flyback power converter and operational method thereof |
| TWI826072B (en) * | 2022-10-26 | 2023-12-11 | 宏碁股份有限公司 | Power supply device with high output stability |
-
2010
- 2010-07-29 TW TW099125022A patent/TWI443946B/en not_active IP Right Cessation
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| TWI568119B (en) * | 2014-10-09 | 2017-01-21 | 群光電能科技股份有限公司 | Power supply apparatus with over power protection function |
| US9325246B1 (en) | 2015-01-20 | 2016-04-26 | Chicony Power Technology Co., Ltd. | Flyback apparatus with voltage superposition circuit and overpower protection |
| TWI556564B (en) * | 2015-09-18 | 2016-11-01 | 強弦科技股份有限公司 | Converter control system |
| US9847726B2 (en) | 2015-09-18 | 2017-12-19 | Joint Power Exponent, Ltd. | Converter control system |
| CN105871184A (en) * | 2015-11-12 | 2016-08-17 | 成都启臣微电子有限公司 | Ultrahigh-precision overpower compensating circuit |
| CN105871184B (en) * | 2015-11-12 | 2018-06-29 | 成都启臣微电子股份有限公司 | A kind of superhigh precision Overpower compensating circuit |
Also Published As
| Publication number | Publication date |
|---|---|
| TW201206034A (en) | 2012-02-01 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| TWI443946B (en) | Over power protection (opp) compensation circuit and flyback power supply | |
| TWI580161B (en) | Off-line power converter and integrated circuit suitable for use in same | |
| US7881077B2 (en) | PWM controller with output current limitation | |
| US9991812B2 (en) | Variable blanking frequency for resonant converters | |
| JP5170117B2 (en) | Switching control circuit and switching power supply device | |
| JP5526857B2 (en) | Semiconductor integrated circuit for power control and isolated DC power supply | |
| TWI483524B (en) | A system and method for adjusting a power conversion system | |
| US20140078789A1 (en) | Switching power converter with secondary-side dynamic load detection and primary-side feedback and control | |
| JP6075008B2 (en) | Switching power supply | |
| TWI466426B (en) | Method and circuit for changing power consumption | |
| JP5056395B2 (en) | Switching power supply | |
| US20140140107A1 (en) | Isolated power converter, inverting type shunt regulator, and operating method thereof | |
| JP6554888B2 (en) | Switching power supply | |
| US20080291709A1 (en) | Switching power supply apparatus | |
| TWI425757B (en) | Power converter and method thereof | |
| TW202002494A (en) | Power conversion system | |
| US20080037296A1 (en) | Green-mode flyback pulse width modulation apparatus | |
| TWM457343U (en) | Circuit for inhibiting switching power supply outputting overshoot voltage at startup | |
| TW201401923A (en) | Driving circuit for driving light source and controller for controlling converter | |
| KR20070090529A (en) | Switching mode power supply | |
| JP2015216763A (en) | Switching power supply circuit | |
| US10306717B1 (en) | Flicker-free LED driving apparatus and voltage regulating method thereof | |
| JP2012253900A (en) | Switching power supply device and led lighting apparatus using the same | |
| CN220570463U (en) | Load adjustable circuit, power supply circuit, circuit board and electronic equipment | |
| JP5633535B2 (en) | Switching control circuit and switching power supply device |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MM4A | Annulment or lapse of patent due to non-payment of fees |