本發明涉及電路領域，更具體地涉及一種開關電源電路。The invention relates to the field of circuits, and more particularly to a switching power supply circuit.
第1圖示出了傳統的反激開關電源電路的電路圖。第2圖示出了第1圖所示的脈寬調變控制晶片(Pulse Width Modulation integrated circuit,PWM IC)的結構框圖。這裡，為了說明的目的，第1圖所示的反激開關電源電路被實現為帶同步整流的反激電流模式的脈寬調變(PWM)恒壓系統。FIG. 1 shows a circuit diagram of a conventional flyback switching power supply circuit. FIG. 2 shows a structural block diagram of a pulse width modulation control circuit (Pulse Width Modulation Integrated Circuit, PWM IC) shown in FIG. 1. Here, for the purpose of explanation, the flyback switching power supply circuit shown in FIG. 1 is implemented as a pulse width modulation (PWM) constant voltage system with a flyback current mode with synchronous rectification.
如第1圖所示，在變壓器T1的二次側，分壓電阻對輸出電壓VO進行分壓得到輸出電壓表徵信號，並將輸出電壓表徵信號傳送到TL431；TL431基於輸出電壓表徵信號和其內部的基準電壓生成誤差放大信號，並經由光耦將誤差放大信號傳送到位於變壓器T1的一次側的PWM IC的FB端子。As shown in Figure 1, on the secondary side of the transformer T1, the voltage dividing resistor divides the output voltage VO to obtain an output voltage characterization signal, and transmits the output voltage characterization signal to the TL431; the TL431 is based on the output voltage characterization signal and its internal The reference voltage is used to generate an error amplification signal, and the error amplification signal is transmitted to the FB terminal of the PWM IC located on the primary side of the transformer T1 via an optical coupler.
如第2圖所示，在位於變壓器T1的一次側的PWM IC中，基於經由FB端子接收的誤差放大信號和經由CS端子接收的表徵變壓器T1的儲能狀態的儲能狀態表徵信號生成PWM控制信號，然後基於PWM控制信號生成閘極驅動信號，用於驅動連接在變壓器T1的一次繞組和電流取樣電阻Rs之間的功率開關M1的導通與關斷。As shown in FIG. 2, in the PWM IC located on the primary side of the transformer T1, the PWM control is generated based on the error amplification signal received through the FB terminal and the energy storage state characteristic signal representing the energy storage state of the transformer T1 received through the CS terminal. The signal is then used to generate a gate drive signal based on the PWM control signal, which is used to drive the on and off of the power switch M1 connected between the primary winding of the transformer T1 and the current sampling resistor Rs.
進一步地，如第1圖所示，在變壓器T1的二次側，同步整流控制晶片(Synchronous Rectifier,SR IC)通過VD端子感測變壓器T1是否處於續流狀態(即，將變壓器T1中儲存的能量釋放到反激開關電源電路的輸出端的狀態)；如果SR IC感測到變壓器T1處於續流狀態，則控制功率開關M2導通；如果SR IC感測到變壓器T1續流結束或功率開關M1導通，則控制功率開關M2關斷。Further, as shown in FIG. 1, on the secondary side of the transformer T1, a synchronous rectification control chip (Synchronous Rectifier, SR IC) senses whether the transformer T1 is in a freewheeling state through the VD terminal (that is, the transformer T1 stores the The state of energy release to the output of the flyback switching power supply circuit); if the SR IC senses that the transformer T1 is in a freewheeling state, the power switch M2 is controlled to be turned on; if the SR IC senses that the transformer T1 is freewheeling or the power switch M1 is on , The control power switch M2 is turned off.
由於位於變壓器T1的一次側的PWM IC和位於變壓器T1的二次側的SR IC分別獨立控制功率開關M1和M2的導通與關斷，所以在某些條件下(例如，動態負載切換或者短路等條件下)，位於變壓器T1的一次側的功率開關M1和位於變壓器T1的二次側的功率開關M2有可能在短時間內同時導通，導致瞬間峰值電流非常大而損壞功率開關或者引起炸機問題。Since the PWM IC on the primary side of the transformer T1 and the SR IC on the secondary side of the transformer T1 independently control the on and off of the power switches M1 and M2, under certain conditions (for example, dynamic load switching or short circuit, etc.) Under the conditions), the power switch M1 located on the primary side of the transformer T1 and the power switch M2 located on the secondary side of the transformer T1 may be simultaneously turned on in a short period of time, resulting in a very large instantaneous peak current that damages the power switch or causes problems with the bomber .
鑒於以上所述的一個或多個問題，本發明提供了一種新穎的開關電源電路。In view of one or more of the problems described above, the present invention provides a novel switching power supply circuit.
根據本發明實施例的一種開關電源電路，包括變壓器、位於變壓器的一次側的第一控制晶片、位於變壓器的二次側的第二控制晶片、連接在變壓器的一次繞組與第一電阻之間並經由第一電阻連接到參考地的第一功率開關、以及連接在變壓器的二次繞組與地之間的第二功率開關，其中：第一控制晶片通過對變壓器的輔助繞組上的電壓進行取樣來生成表徵開關電源電路的輸出電壓的第一輸出電壓表徵信號，通過對第一電阻上的電壓進行取樣來生成表徵變壓器的儲能狀態的儲能狀態表徵信號，並根據第一輸出電壓表徵信號和儲能狀態表徵信號來控制第一功率開關的導通與關斷；第二控制晶片通過對開關電源電路的輸出電壓進行取樣來生成表徵開關電源電路的輸出電壓的第二輸出電壓表徵信號，通過對第二功率開關的汲極電壓進行取樣來生成表徵變壓器的退磁狀態的退磁狀態表徵信號，並根據第二輸出電壓表徵信號和退磁狀態表徵信號來控制第二功率開關的導通與關斷。A switching power supply circuit according to an embodiment of the present invention includes a transformer, a first control chip located on a primary side of the transformer, a second control chip located on a secondary side of the transformer, and connected between a primary winding of the transformer and a first resistor and A first power switch connected to a reference ground via a first resistor, and a second power switch connected between a secondary winding of the transformer and the ground, where the first control chip samples the voltage on the auxiliary winding of the transformer to sample Generate a first output voltage characterization signal that characterizes the output voltage of the switching power supply circuit, and sample the voltage on the first resistor to generate a storage state characterization signal that characterizes the energy storage state of the transformer, and according to the first output voltage characterization signal and The energy storage status characterization signal controls the on and off of the first power switch; the second control chip generates a second output voltage characterization signal characterizing the output voltage of the switching power supply circuit by sampling the output voltage of the switching power supply circuit, The drain voltage of the second power switch is sampled to generate a Characterized demagnetized magnetic state signal, and a signal indicative of a second output voltage according to a signal indicative of the state of demagnetization and to control the second power switch is turned on and off.
根據本發明實施例的開關電源電路無需使用TL431和光耦器件即可使得位於變壓器的二次側的第二控制晶片與位於變壓器的一次側的第一控制晶片協同工作，因此節省了系統成本。The switching power supply circuit according to the embodiment of the present invention enables the second control chip located on the secondary side of the transformer to cooperate with the first control chip located on the primary side of the transformer without using a TL431 and an optocoupler device, thereby saving system cost.
T1‧‧‧變壓器T1‧‧‧Transformer
vref_cv、vref_cc‧‧‧參考閾值vref_cv, vref_cc‧‧‧ reference threshold
VO‧‧‧輸出電壓VO‧‧‧Output voltage
CMP1、cmp2‧‧‧比較器CMP1, cmp2‧‧‧ comparator
M1、M2‧‧‧功率開關M1, M2‧‧‧ Power Switch
RS‧‧‧觸發器RS‧‧‧Trigger
AC IN‧‧‧交流輸入電壓AC IN‧‧‧ AC input voltage
demag‧‧‧退磁狀態表徵信號demag‧‧‧Signal for demagnetization status
Rst‧‧‧啟動電阻Rst‧‧‧Starting resistance
R1、R2‧‧‧分壓電阻R1, R2‧‧‧‧Voltage Divider
Cd‧‧‧電容Cd‧‧‧Capacitor
Vref‧‧‧基準電壓Vref‧‧‧reference voltage
Pri_IC、Sec_IC‧‧‧控制晶片Pri_IC, Sec_IC‧‧‧control chip
Vramp‧‧‧斜坡電壓Vramp‧‧‧Ramp voltage
Vcs‧‧‧電壓Vcs‧‧‧Voltage
R5‧‧‧外接電阻R5‧‧‧External resistor
Rs、R3、R4‧‧‧電阻Rs, R3, R4‧‧‧ resistance
Gm_cc、Gm_cv‧‧‧誤差放大器Gm_cc, Gm_cv‧‧‧ Error Amplifier
Vthocp‧‧‧閾值Vthocp‧‧‧threshold
CC‧‧‧恒流CC‧‧‧Constant Current
DC‧‧‧直流電源DC‧‧‧DC Power Supply
CV‧‧‧恒壓CV‧‧‧constant voltage
R0、Rs、R3、R4‧‧‧電阻R0, Rs, R3, R4‧‧‧ resistance
Na‧‧‧變壓器T1輔組繞組匝數Na‧‧‧Transformer T1 auxiliary windings
Ns‧‧‧變壓器T1副邊輸出繞組匝數Ns‧‧‧Transformer T1 secondary side output winding turns
Np‧‧‧變壓器T1原邊繞組匝數Np‧‧‧Transformer T1 primary winding turns
VFB‧‧‧Sec_IC輸出電壓檢測端子VFB‧‧‧Sec_IC output voltage detection terminal
VD‧‧‧Sec_IC續流狀態感測端子VD‧‧‧Sec_IC freewheeling state sensing terminal
FB‧‧‧光耦回饋電壓檢測端子FB‧‧‧Photocoupler feedback voltage detection terminal
CS‧‧‧CS Pri_IC電流檢測端子CS‧‧‧CS Pri_IC current detection terminal
GATE‧‧‧Pri_IC功率開關驅動端子GATE‧‧‧Pri_IC power switch drive terminal
VDD‧‧‧IC供電端子VDD‧‧‧IC power supply terminal
COMP‧‧‧Sec_IC電壓環路補償端子COMP‧‧‧Sec_IC voltage loop compensation terminal
DRV‧‧‧Sec_IC功率開關驅動端子DRV‧‧‧Sec_IC Power Switch Drive Terminal
INV‧‧‧Pri_IC輸出電壓和退磁時間檢測端子INV‧‧‧Pri_IC output voltage and demagnetization time detection terminal
從下面結合附圖對本發明的具體實施方式的描述中可以更好地理解本發明，其中：1圖示出了傳統的返馳變換器電源電路的電路圖。The present invention can be better understood from the following description of specific embodiments of the present invention with reference to the accompanying drawings, wherein: FIG. 1 shows a circuit diagram of a conventional flyback converter power circuit.
圖2圖示出了圖1圖所示的脈寬調變控制晶片的結構框圖。FIG. 2 illustrates a structural block diagram of the pulse width modulation control chip shown in FIG. 1.
第3圖示出了根據本發明實施例的開關電源電路的電路圖。FIG. 3 shows a circuit diagram of a switching power supply circuit according to an embodiment of the present invention.
第4圖示出了第3圖所示的控制晶片Sec_IC的結構框圖。FIG. 4 is a block diagram showing the structure of the control chip Sec_IC shown in FIG. 3.
第5圖示出了第3圖所示的控制晶片Pri_IC的結構框圖。FIG. 5 shows a block diagram of the control chip Pri_IC shown in FIG. 3.
第6圖示出了第4圖和第5圖所示的晶片內部以及晶片端子處的一些信號的時序圖。Fig. 6 shows a timing chart of some signals inside the wafer and at the wafer terminals shown in Figs. 4 and 5.
第7圖示出了根據本發明實施例的開關電源電路的應用示例的電路圖。FIG. 7 is a circuit diagram showing an application example of a switching power supply circuit according to an embodiment of the present invention.
第8圖和第9圖分別示出了第7圖所示的控制晶片Sec_IC的示例結構框圖。8 and 9 are block diagrams showing an example structure of the control chip Sec_IC shown in FIG. 7, respectively.
下面將詳細描述本發明的各個方面的特徵和示例性實施例。在下面的詳細描述中，提出了許多具體細節，以便提供對本發明的全面理解。但是，對於本領域技術人員來說很明顯的是，本發明可以在不需要這些具體細節中的一些細節的情況下實施。下面對實施例的描述僅僅是為了通過示出本發明的示例來提供對本發明的更好的理解。本發明決不限於下面所提出的任何具體配置和演算法，而是在不脫離本發明的精神的前提下覆蓋了元素、部件和演算法的任何修改、替換和改進。在附圖和下面的描述中，沒有示出公知的結構和技術，以便避免對本發明造成不必要的模糊。Features and exemplary embodiments of various aspects of the invention will be described in detail below. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it is obvious to a person skilled in the art that the present invention can be implemented without the need for some of these specific details. The following description of the embodiments is merely for providing a better understanding of the present invention by showing examples of the present invention. The invention is by no means limited to any specific configuration and algorithm proposed below, but covers any modification, replacement and improvement of elements, components and algorithms without departing from the spirit of the invention. In the drawings and the following description, well-known structures and techniques are not shown in order to avoid unnecessarily obscuring the present invention.
第3圖示出了根據本發明實施例的開關電源電路的電路圖。第4圖示出了第3圖所示的控制晶片Sec_IC的結構框圖。第5圖示出了第3圖所示的控制晶片Pri_IC的結構框圖。下面結合第3圖至第5圖，詳細描述根據本發明實施例的開關電源電路的工作原理。FIG. 3 shows a circuit diagram of a switching power supply circuit according to an embodiment of the present invention. FIG. 4 is a block diagram showing the structure of the control chip Sec_IC shown in FIG. 3. FIG. 5 shows a block diagram of the control chip Pri_IC shown in FIG. 3. The working principle of the switching power supply circuit according to the embodiment of the present invention is described in detail below with reference to FIGS. 3 to 5.
如第3圖所示，根據本發明實施例的開關電源電路包括變壓器T1、位於變壓器T1的一次側的控制晶片Pri_IC、位於變壓器T1的二次側的控制晶片Sec_IC、連接在變壓器T1的一次繞組與電流取樣電阻Rs之間並經由電流取樣電阻Rs連接到參考地的功率開關M1、以及連接在變壓器T1的二次繞組與地之間的功率開關M2。As shown in FIG. 3, the switching power supply circuit according to the embodiment of the present invention includes a transformer T1, a control chip Pri_IC on the primary side of the transformer T1, a control chip Sec_IC on the secondary side of the transformer T1, and a primary winding connected to the transformer T1. A power switch M1 connected to the current sampling resistor Rs and connected to the reference ground via the current sampling resistor Rs, and a power switch M2 connected between the secondary winding of the transformer T1 and the ground.
在第3圖所示的開關電源電路中，控制晶片Pri_IC通過對變壓器T1的輔助繞組上的電壓進行取樣來生成表徵開關電源電路的輸出電壓VO的第一輸出電壓表徵信號，通過對電流取樣電阻Rs上的電壓Vcs進行取樣來生成表徵變壓器T1的儲能狀態的儲能狀態表徵信號，並根據第一輸出電壓表徵信號和儲能狀態表徵信號來控制功率開關M1的導通與關斷。In the switching power supply circuit shown in FIG. 3, the control chip Pri_IC samples the voltage on the auxiliary winding of the transformer T1 to generate a first output voltage characterization signal characterizing the output voltage VO of the switching power supply circuit, and the current sampling resistor The voltage Vcs on Rs is sampled to generate an energy storage state characterizing signal representing the energy storage state of the transformer T1, and control the on and off of the power switch M1 according to the first output voltage characterizing signal and the energy storage state characterizing signal.
在第3圖所示的開關電源電路中，控制晶片Sec_IC通過對開關電源電路的輸出電壓VO進行取樣來生成表徵開關電源電路的輸出電壓VO的第二輸出電壓表徵信號，通過對功率開關M2的汲極電壓進行取樣來生成表徵變壓器T1的退磁狀態的退磁狀態表徵信號，並根據第二輸出電壓表徵信號和退磁狀態表徵信號來控制功率開關M2的導通與關斷。這裡，控制晶片Sec_IC將第1圖所示的SR IC和TL431集成在一起，並且集成了PWM控制功能。In the switching power supply circuit shown in FIG. 3, the control chip Sec_IC generates a second output voltage characterizing signal that characterizes the output voltage VO of the switching power supply circuit by sampling the output voltage VO of the switching power supply circuit. The drain voltage is sampled to generate a demagnetization state characterization signal representing the demagnetization state of the transformer T1, and control the on and off of the power switch M2 according to the second output voltage characterization signal and the demagnetization state characterization signal. Here, the control chip Sec_IC integrates the SR IC and TL431 shown in Figure 1, and integrates the PWM control function.
當交流輸入電壓(AC IN)接入第3圖所示的開關電源電路時，電磁干擾(Electromagnetic Interference,EMI)濾波器對交流輸入電壓進行濾波，整流橋將經過濾波的交流輸入電壓整流成直流輸入電壓；該直流輸入電壓通過啟動電阻Rst對電容Cd充電；當電容Cd上的電壓(即，控制晶片Pri_IC的VDD端子處的電壓)高於控制晶片Pri_IC的欠壓-保護(Under Voltage Lock Out,UVLO)電壓時，控制晶片Pri_IC開始工作。When the AC input voltage (AC IN) is connected to the switching power supply circuit shown in Figure 3, an electromagnetic interference (EMI) filter filters the AC input voltage, and the rectified bridge rectifies the filtered AC input voltage into DC Input voltage; the DC input voltage charges capacitor Cd through the startup resistor Rst; when the voltage on capacitor Cd (ie, the voltage at the VDD terminal of the control chip Pri_IC) is higher than the under voltage lock out of the control chip Pri_IC , UVLO) voltage, the control chip Pri_IC starts to work.
當控制晶片Pri_IC的VDD端子處的電壓超過控制晶片Pri_IC的UVLO電壓時，控制晶片Pri_IC中的振盪器開始工作，觸發控制晶片Pri_IC中的RS觸發器的輸出置“1”，控制晶片Pri_IC的GATE端子處的電壓為高電平，功率開關M1導通，變壓器T1儲能，電流取樣電阻Rs上的電壓Vcs(即，控制晶片Pri_IC的CS端子處的電壓或儲能狀態表徵信號)逐漸增大。當控制晶片Pri_IC的CS端子處的電壓Vcs達到閾值Vthocp時，控制晶片Pri_IC中的比較器CMP1輸出高位準，觸發控制晶片Pri_IC中的RS觸發器的輸出置“0”，控制晶片Pri_IC的GATE端子處的電壓為低位準，功率開關M1關斷，變壓器T1中儲存的能量釋放到開關電源電路的輸出端。上述過程一直重複，開關電源電路的輸出電壓VO逐漸升高。When the voltage at the VDD terminal of the control chip Pri_IC exceeds the UVLO voltage of the control chip Pri_IC, the oscillator in the control chip Pri_IC starts to work, the output of the RS trigger that triggers the control chip Pri_IC is set to "1", and the GATE of the control chip Pri_IC is set The voltage at the terminal is high, the power switch M1 is turned on, the transformer T1 stores energy, and the voltage Vcs on the current sampling resistor Rs (that is, the voltage at the CS terminal of the control chip Pri_IC or the energy storage state characterization signal) gradually increases. When the voltage Vcs at the CS terminal of the control chip Pri_IC reaches the threshold Vthocp, the comparator CMP1 in the control chip Pri_IC outputs a high level, the output of the RS trigger that triggers the control chip Pri_IC is set to "0", and the GATE terminal of the control chip Pri_IC Voltage at low level, power switch M1 is turned off, and energy stored in transformer T1 is releasedTo the output of the switching power supply circuit. The above process is repeated all the time, and the output voltage VO of the switching power supply circuit gradually increases.
當開關電源電路的輸出電壓VO超過控制晶片Sec_IC的UVLO電壓時，控制晶片Sec_IC開始工作。這裡，控制晶片Pri_IC通過感測其INV端子處的電壓(即，第一輸出電壓表徵信號)可以判斷開關電源電路的輸出電壓VO是否超過控制晶片Sec_IC的UVLO電壓。當控制晶片Pri_IC感測到開關電源電路的輸出電壓VO超過控制晶片Sec_IC的UVLO電壓時(即，控制晶片Sec_IC開始工作)，使得控制晶片Pri_IC中的振盪器停止工作從而控制功率開關M1關斷。當控制晶片Pri_IC感測到開關電源電路的輸出電壓VO沒有超過控制晶片Sec_IC的UVLO電壓時，按照上述程序控制功率開關M1的導通與關斷。這裡，控制晶片Pri_IC的INV端子處的電壓是分壓電阻R3和R4對變壓器T1的輔助繞組上的電壓進行分壓得到的。When the output voltage VO of the switching power supply circuit exceeds the UVLO voltage of the control chip Sec_IC, the control chip Sec_IC starts to work. Here, the control chip Pri_IC can determine whether the output voltage VO of the switching power supply circuit exceeds the UVLO voltage of the control chip Sec_IC by sensing the voltage at its INV terminal (ie, the first output voltage characterization signal). When the control chip Pri_IC senses that the output voltage VO of the switching power supply circuit exceeds the UVLO voltage of the control chip Sec_IC (ie, the control chip Sec_IC starts to work), the oscillator in the control chip Pri_IC is stopped to control the power switch M1 to be turned off. When the control chip Pri_IC senses that the output voltage VO of the switching power supply circuit does not exceed the UVLO voltage of the control chip Sec_IC, it controls the on and off of the power switch M1 according to the above procedure. Here, the voltage at the INV terminal of the control chip Pri_IC is obtained by dividing the voltage on the auxiliary winding of the transformer T1 by the voltage dividing resistors R3 and R4.
當控制晶片Sec_IC的VDD端子處的電壓超過控制晶片Sec_IC的UVLO時，控制晶片Sec_IC開始工作。控制晶片Sec_IC經由其VD端子感測功率開關M2的汲極電壓來生成表徵變壓器T1的退磁狀態的退磁狀態表徵信號。在變壓器T1處於退磁狀態時，退磁狀態表徵信號demag為高位準，控制晶片Sec_IC的DRV端子處的電壓為高位準，功率開關M2導通，同時退磁狀態表徵信號demag的上升沿重定控制晶片Sec_IC中的斜坡生成器。在變壓器T1不處於退磁狀態時，控制晶片Sec_IC根據退磁狀態表徵信號和控制晶片Sec_IC經由其VFB端子接收的分壓電阻R1和R2對開關電源電路的輸出電壓VO進行分壓得到的電壓(即，第二輸出電壓表徵信號)來控制功率開關M2的導通與關斷。具體地，在變壓器T1不處於退磁狀態時，控制晶片Sec_IC中的gm誤差放大器基於控制晶片Sec_IC的VFB端子處的電壓和晶片內部的基準電壓Vref生成誤差放大信號；控制晶片Sec_IC中的比較器將該誤差放大信號和晶片內部的斜坡電壓Vramp進行比較生成PWM/Pulse Frequency Modulation,PFM(脈衝頻率調變)控制信號；退磁狀態表徵信號demag為低位準，當晶片內部的斜坡電壓Vramp上升到控制晶片Sec_IC的COMP端子處的電壓(即，控制晶片Sec_IC中的gm誤差放大器生成的誤差放大信號)時，比較器cmp的輸出為“1”，觸發RS觸發器的輸出置“1”，RS觸發器的輸出通過oneshot產生固定寬度(例如，300ns)的pwm-on信號，功率開關M2導通。這裡，在變壓器T1退磁結束時，在沒有生成pwm-on信號的時段中，功率開關M2關斷。When the voltage at the VDD terminal of the control chip Sec_IC exceeds the UVLO of the control chip Sec_IC, the control chip Sec_IC starts to work. The control chip Sec_IC senses the drain voltage of the power switch M2 via its VD terminal to generate a demagnetization state characterization signal that characterizes the demagnetization state of the transformer T1. When the transformer T1 is in a demagnetized state, the demagnetization state characterization signal demag is at a high level, the voltage at the DRV terminal of the control chip Sec_IC is high level, the power switch M2 is turned on, and at the same time, the rising edge of the demagnetization state characterization signal demag resets the control chip Sec_IC. Ramp generator. When the transformer T1 is not in the demagnetized state, the control chip Sec_IC divides the output voltage VO of the switching power supply circuit according to the demagnetization state characterization signal and the voltage dividing resistors R1 and R2 received by the control chip Sec_IC via its VFB terminal (that is, the voltage A second output voltage characterization signal) to control the on and off of the power switch M2. Specifically, when the transformer T1 is not in a demagnetized state, the gm error amplifier in the control chip Sec_IC generates an error amplification signal based on the voltage at the VFB terminal of the control chip Sec_IC and the reference voltage Vref inside the chip; the comparator in the control chip Sec_IC will The error amplification signal is compared with the ramp voltage Vramp inside the chip to generate a PWM / Pulse Frequency Modulation, PFM (Pulse Frequency Modulation) control signal; the demagnetization state characterization signal demag is at a low level. When the ramp voltage Vramp inside the chip rises to the control chip Power at COMP terminal of Sec_ICWhen pressing (ie, the error amplification signal generated by the gm error amplifier in the control chip Sec_IC), the output of the comparator cmp is "1", the output of the triggering RS trigger is set to "1", and the output of the RS trigger is fixed by oneshot With a pwm-on signal (for example, 300 ns), the power switch M2 is turned on. Here, at the end of the demagnetization of the transformer T1, the power switch M2 is turned off in a period in which a pwm-on signal is not generated.
第6圖示出了第4圖和第5圖所示的晶片內部以及晶片端子處的一些信號的時序圖。如第6圖所示，控制晶片Sec_IC的DRV端子處的固定時間脈衝，會在變壓器T1的一次側的控制晶片Pri_IC的INV端子上激勵出一個相同時間寬度的退磁信號。如第6圖所示，在真實的退磁結束後，如果控制晶片Pri_IC通過其INV端子感測到一個固定時間的退磁信號，則在此固定時間的退磁信號結束後將其GATE端子的輸出置“1”以控制功率開關M1導通；當感測到功率開關M1流過的電流超過一定值後，即CS端子處的電壓Vcs超過閾值Vthocp時，控制晶片Pri_IC將其GATE端子的輸出置“0”以控制功率開關M1關斷。Fig. 6 shows a timing chart of some signals inside the wafer and at the wafer terminals shown in Figs. 4 and 5. As shown in Figure 6, a fixed time pulse at the DRV terminal of the control chip Sec_IC will excite a demagnetization signal of the same time width at the INV terminal of the control chip Pri_IC on the primary side of the transformer T1. As shown in Figure 6, after the actual demagnetization is over, if the control chip Pri_IC senses a demagnetization signal at a fixed time through its INV terminal, then set the output of its GATE terminal to " 1 "to control the power switch M1 to be turned on; when the current flowing through the power switch M1 is sensed to exceed a certain value, that is, the voltage Vcs at the CS terminal exceeds the threshold Vthocp, the control chip Pri_IC sets the output of its GATE terminal to" 0 " To control the power switch M1 to turn off.
通過以上方式，在變壓器T1的二次側實現了同步整流控制，並且通過控制功率開關M2的導通與關斷將恒壓模式PWM/PFM控制信號傳遞到變壓器T1的一次側，變壓器T1的一次側接收到PWM/PFM控制信號後開通一次側的功率開關M1來傳遞能量，從而實現了二次側控制恒壓模式功能。也就是說，根據本發明實施例的開關電源電路無需使用TL431和光耦器件即可使得控制晶片Pri_IC與控制晶片Sec_IC協同工作，因此節省了系統成本。In the above manner, the synchronous rectification control is realized on the secondary side of the transformer T1, and the constant voltage mode PWM / PFM control signal is transmitted to the primary side of the transformer T1 and the primary side of the transformer T1 by controlling the on and off of the power switch M2. After receiving the PWM / PFM control signal, the power switch M1 on the primary side is turned on to transfer energy, thereby realizing the function of constant voltage mode control on the secondary side. That is, the switching power supply circuit according to the embodiment of the present invention can make the control chip Pri_IC and the control chip Sec_IC work together without using the TL431 and the optocoupler device, thereby saving the system cost.
在根據本發明實施例的開關電源電路中，功率開關M1在功率開關M2關斷後才導通，因此確保了功率開關M1和功率開關M2不會同時導通，解決了傳統的反激開關電源電路中一次功率開關和二次功率開關在某些條件下(比如，動態負載切換或者短路條件下)共通問題引起的功率管損壞或者炸機問題。In the switching power supply circuit according to the embodiment of the present invention, the power switch M1 is turned on only after the power switch M2 is turned off. Therefore, it is ensured that the power switch M1 and the power switch M2 are not turned on at the same time, which solves the problem in the conventional flyback switching power supply circuit. Under certain conditions (such as dynamic load switching or short-circuit conditions), the common problem of the primary power switch and the secondary power switch is the damage of the power tube or the problem of the bomber.
第7圖示出了根據本發明實施例的開關電源電路的應用示例的電路圖。如第7圖所示，控制晶片Sec_IC的CC端子通過外接電阻R5用於調節恒流點大小，控制晶片Sec_IC的ICOMP端子通過外接電容用於恒流(CC)環路補償，控制晶片Sec_IC的VCOMP通過外接電容用於恒壓(CV)環路補償。FIG. 7 is a circuit diagram showing an application example of a switching power supply circuit according to an embodiment of the present invention. As shown in Figure 7, the CC terminal of the control chip Sec_IC is used to adjust the size of the constant current point through an external resistor R5, and the ICOMP terminal of the control chip Sec_IC is used for an external capacitor.For constant current (CC) loop compensation, VCOMP of the control chip Sec_IC is used for constant voltage (CV) loop compensation through an external capacitor.
第8圖示出了第7圖所示的控制晶片Sec_IC的示例結構框圖。當第8圖所示的控制晶片Sec_IC工作在CV模式時，誤差放大器Gm_cc的輸出電壓(即，控制晶片Sec_IC的ICOMP端子處的電壓)為“0”，比較器cmp2的輸出電壓一直為“1”。因此，第8圖所示的控制晶片Sec_IC的工作模式和第4圖所示的控制晶片Sec_IC相同，負載越大，第8圖所示的控制晶片Sec_IC的VCOMP端子處的電壓越低，系統工作頻率越高，負載越小，第8圖所示的控制晶片Sec_IC的VCOMP端子處的電壓越高，系統工作頻率越低；當第8圖所示的控制晶片Sec_IC工作在CC模式時，誤差放大器Gm_cv的輸出電壓(即，控制晶片Sec_IC的VCOMP端子處的電壓)為“0”，比較器cmp1的輸出電壓一直為“1”，因此控制晶片Sec_IC的ICOMP端子處的電壓大小決定了系統工作頻率。FIG. 8 is a block diagram showing an example structure of the control chip Sec_IC shown in FIG. 7. When the control chip Sec_IC shown in FIG. 8 operates in the CV mode, the output voltage of the error amplifier Gm_cc (that is, the voltage at the ICOMP terminal of the control chip Sec_IC) is "0", and the output voltage of the comparator cmp2 is always "1" ". Therefore, the operation mode of the control chip Sec_IC shown in FIG. 8 is the same as that of the control chip Sec_IC shown in FIG. 4. The larger the load, the lower the voltage at the VCOMP terminal of the control chip Sec_IC shown in FIG. 8, and the system works. The higher the frequency, the smaller the load. The higher the voltage at the VCOMP terminal of the control chip Sec_IC shown in Figure 8, the lower the system operating frequency. When the control chip Sec_IC shown in Figure 8 works in CC mode, the error amplifier The output voltage of Gm_cv (that is, the voltage at the VCOMP terminal of the control chip Sec_IC) is "0", and the output voltage of the comparator cmp1 is always "1". Therefore, the voltage at the ICOMP terminal of the control chip Sec_IC determines the system operating frequency .
第9圖示出了第7圖所示的控制晶片Sec_IC的另一示例結構框圖。在第9圖所示的控制晶片Sec_IC中，通過DP/DN端子或者CC1/CC2端子和負載設備溝通來改變參考閾值vref_cv或者vref_cc的大小，從而改變開關電源電路的輸出電壓VO的大小或者輸出恒流值大小來實現快沖模式。FIG. 9 shows a block diagram of another example of the control chip Sec_IC shown in FIG. 7. In the control chip Sec_IC shown in Figure 9, the DP / DN terminal or CC1 / CC2 terminal is used to communicate with the load device to change the reference threshold value vref_cv or vref_cc, thereby changing the output voltage VO of the switching power supply circuit or the output constant. Stream size to achieve fast burst mode.
應該理解的是，上述控制方式並不僅限於返馳變換器電源電路，也可以應用於FORWARD、BUCK、BOOST等架構的開關電源電路。It should be understood that the above-mentioned control method is not limited to the flyback converter power circuit, but can also be applied to switching power supply circuits of FORWARD, BUCK, BOOST and other architectures.
本發明可以以其他的具體形式實現，而不脫離其精神和本質特徵。例如，特定實施例中所描述的演算法可以被修改，而系統體系結構並不脫離本發明的基本精神。因此，當前的實施例在所有方面都被看作是示例性的而非限定性的，本發明的範圍由所附權利要求而非上述描述定義，並且，落入權利要求的含義和等同物的範圍內的全部改變從而都被包括在本發明的範圍之中。The present invention may be implemented in other specific forms without departing from the spirit and essential characteristics thereof. For example, the algorithms described in particular embodiments may be modified without the system architecture departing from the basic spirit of the invention. Therefore, the present embodiments are to be considered in all respects as illustrative and not restrictive, the scope of the present invention is defined by the appended claims rather than the above description, and falls within the meaning and equivalents of the claims. All changes within the scope are thus included in the scope of the present invention.
| Application Number | Priority Date | Filing Date | Title |
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| ??201810035547.3 | 2018-01-15 | ||
| CN201810035547.3ACN108173434B (en) | 2018-01-15 | 2018-01-15 | Switching power supply circuit |
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| TWI642265B TWI642265B (en) | 2018-11-21 |
| TW201933752Atrue TW201933752A (en) | 2019-08-16 |
| Application Number | Title | Priority Date | Filing Date |
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| TW107106023ATWI642265B (en) | 2018-01-15 | 2018-02-22 | Switching power supply circuit |
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| TW (1) | TWI642265B (en) |
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