TWM505122U - Primary-side regulated flyback converter and power control circuit thereof - Google Patents
Primary-side regulated flyback converter and power control circuit thereof Download PDFInfo
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本新型係關於一種反馳式轉換器的技術,更進一步來說,本新型係關於一種一次側回授控制之反馳式轉換器及其使用之電源控制電路。The present invention relates to a technique of a flyback converter, and further, the present invention relates to a flyback converter for primary side feedback control and a power supply control circuit therefor.
返馳式轉換器因具有架構簡單、生產成本低廉,廣泛地應用在低壓電源供應市場上。一般的返馳式轉換器回授電路必須使用昂貴的光耦合器與TL431穩壓積體電路,以達成電器隔離之功效。如此一來不僅增加了電路成本,也增加了電路體積與功率消耗。一次側回授控制返馳式轉換器藉由偵測輔助繞組電壓,完成穩定輸出電壓之功效。因偵測輔助繞組與脈波寬度調變電源控制積體電路皆位於一次側,避免了使用到昂貴的元件,對整體返馳式轉換器成本、效率、體積都有助益。The flyback converter is widely used in the low voltage power supply market due to its simple structure and low production cost. A general flyback converter feedback circuit must use an expensive optocoupler and a TL431 stabilized integrated circuit to achieve electrical isolation. This not only increases the circuit cost, but also increases the circuit volume and power consumption. The primary side feedback control flyback converter achieves the effect of stabilizing the output voltage by detecting the auxiliary winding voltage. Since the detection auxiliary winding and the pulse width modulation power supply integrated circuit are located on the primary side, the use of expensive components is avoided, which is beneficial to the overall cost, efficiency and volume of the flyback converter.
假設一次側回授控制的反馳式轉換器操作於不連續導通模式(Discontinuous Conduction Mode,DCM)。然而,當輸入的線電壓(Line Voltage)過低時,會導致所輸出的脈波寬度調變(Pulse Width Modulation,PWM)訊號之責任週期過大,並且會增加電感電流。此情況將導致反馳式轉換器由非連續導通模式進入連續導通模式(Continuous Conduction Mode,CCM),回授的補償機制將會被破壞。因此,一次側回授控制之反馳式轉換器需要有一偵測機制,避免上述情況發生。Assume that the flyback converter of the primary side feedback control operates in discontinuous conduction mode (Discontinuous Conduction mode) Mode, DCM). However, when the input line voltage is too low, the duty cycle of the output Pulse Width Modulation (PWM) signal is too large and the inductor current is increased. This situation will cause the flyback converter to enter the Continuous Conduction Mode (CCM) from the discontinuous conduction mode, and the feedback compensation mechanism will be destroyed. Therefore, the flyback converter of the primary side feedback control needs a detection mechanism to avoid the above situation.
本新型的一目的在於提供一種一次側回授控制之反馳式轉換器及其使用之電源控制電路,藉由在原本一次側的回授端部分,增加一輸入電壓檢測機制。當輸入電壓過低時,將電源控制電路進入保護模式。An object of the present invention is to provide a flyback converter for primary side feedback control and a power supply control circuit therefor, by adding an input voltage detection mechanism to the feedback portion of the primary side. When the input voltage is too low, the power control circuit enters the protection mode.
有鑒於此,本新型提供一種一次側回授控制之反馳式轉換器,此一次側回授控制之反馳式轉換器包括一變壓器、一開關元件、一分壓電路以及一電源控制積體電路。變壓器包括一次側繞組、一二次側繞組以及一輔助繞組。開關元件包括一第一端、一第二端以及一控制端,其中,開關元件的第一端耦接該變壓器的一次側繞組之第二端,開關元件的第二端耦接一共接電壓。分壓電路包括一輸入端以及一輸出端,其中,分壓電路的輸入端耦接輔助繞組的第一端,分壓電路的輸出端輸出一分壓電壓。電源控制積體電路包括一開關控制端以及一回授端,其中,電源控制積體電路的開關控制端耦接開關元件的控 制端,電源控制積體電路的回授端耦接分壓電路的輸出端。In view of this, the present invention provides a flyback converter with primary side feedback control. The flyback converter of the primary side feedback control includes a transformer, a switching element, a voltage dividing circuit and a power control product. Body circuit. The transformer includes a primary side winding, a secondary side winding, and an auxiliary winding. The switching element includes a first end, a second end, and a control end, wherein the first end of the switching element is coupled to the second end of the primary winding of the transformer, and the second end of the switching element is coupled to a common voltage. The voltage dividing circuit includes an input end and an output end, wherein the input end of the voltage dividing circuit is coupled to the first end of the auxiliary winding, and the output end of the voltage dividing circuit outputs a divided voltage. The power control integrated circuit includes a switch control end and a feedback end, wherein the switch control end of the power control integrated circuit is coupled to the control of the switch element The terminal end of the power control integrated circuit is coupled to the output end of the voltage dividing circuit.
當開關元件截止時,電源控制積體電路的回授端接收分壓電壓,以調節開關控制端所輸出的一脈波寬度調變信號之責任週期。當開關元件導通時,電源控制積體電路的回授端輸出一固定電流,並接收分壓電壓,當分壓電壓大於一參考電壓,電源控制積體電路進入一保護模式。When the switching element is turned off, the feedback terminal of the power control integrated circuit receives the divided voltage to adjust the duty cycle of a pulse width modulation signal outputted by the switch control terminal. When the switching element is turned on, the feedback terminal of the power control integrated circuit outputs a fixed current and receives the divided voltage. When the divided voltage is greater than a reference voltage, the power control integrated circuit enters a protection mode.
本新型另外提供一種電源控制積體電路,適用於一次側回授控制之反馳式轉換器,此一次側回授控制之反馳式轉換器包括一變壓器、一開關元件以及一分壓電路。變壓器包括一次側繞組、一二次側繞組以及一輔助繞組。開關元件包括一第一端、一第二端以及一控制端,其中,開關元件的第一端耦接變壓器的一次側繞組之第二端,開關元件的第二端耦接一共接電壓。分壓電路包括一輸入端以及一輸出端,其中,分壓電路的輸入端耦接輔助繞組的第一端,分壓電路的輸出端輸出一分壓電壓。The present invention further provides a power control integrated circuit suitable for a flyback converter of primary side feedback control, the reverse side converter of the primary side feedback control comprises a transformer, a switching element and a voltage dividing circuit . The transformer includes a primary side winding, a secondary side winding, and an auxiliary winding. The switching element includes a first end, a second end, and a control end, wherein the first end of the switching element is coupled to the second end of the primary winding of the transformer, and the second end of the switching element is coupled to a common voltage. The voltage dividing circuit includes an input end and an output end, wherein the input end of the voltage dividing circuit is coupled to the first end of the auxiliary winding, and the output end of the voltage dividing circuit outputs a divided voltage.
本新型的電源控制積體電路包括一開關控制端、一回授端、一脈波寬度調變電路、一回授電路、一電流提供電路以及一電壓檢測電路。開關控制端耦接開關元件的控制端。回授端耦接分壓電路的輸出端。脈波寬度調變電路耦接開關控制端,用以輸出一脈波寬度調變訊號。回授電路耦接回授端,其中,當開關元件截止時,用以根據分壓電壓,決定脈波寬度調變電路的責任週期。電 流提供電路耦接回授端。當開關元件導通時,電流提供電路輸出一固定電流給分壓電路的輸出端。電壓檢測電路耦接回授端。當該開關元件導通時,電壓檢測電路接收分壓電壓,當分壓電壓大於一參考電壓,致能一保護訊號。當保護訊號致能時,電源控制積體電路進入一保護模式。The power control integrated circuit of the present invention comprises a switch control terminal, a feedback terminal, a pulse width modulation circuit, a feedback circuit, a current supply circuit and a voltage detection circuit. The switch control end is coupled to the control end of the switching element. The feedback end is coupled to the output of the voltage dividing circuit. The pulse width modulation circuit is coupled to the switch control end for outputting a pulse width modulation signal. The feedback circuit is coupled to the feedback terminal, wherein when the switching element is turned off, the duty cycle of the pulse width modulation circuit is determined according to the divided voltage. Electricity The flow providing circuit is coupled to the feedback end. When the switching element is turned on, the current supply circuit outputs a fixed current to the output terminal of the voltage dividing circuit. The voltage detection circuit is coupled to the feedback terminal. When the switching element is turned on, the voltage detecting circuit receives the divided voltage, and when the divided voltage is greater than a reference voltage, a protection signal is enabled. When the protection signal is enabled, the power control integrated circuit enters a protection mode.
依照本新型較佳實施例所述之一次側回授控制之反馳式轉換器及電源控制積體電路,上述電源控制積體電路包括一固定電流源以及一第一開關。固定電流源用以提供上述固定電流。第一開關的第一端耦接固定電流源,第一開關的第二端耦接電源控制積體電路的回授端。當開關元件導通時,第一開關導通,固定電流由第一開關的第一端流向第一開關的第二端,以提高上述分壓電壓。在一較佳實施例中,當分壓電壓大於一參考電壓之次數大於N次,電源控制積體電路進入保護模式,且電源控制積體電路停止輸出脈波寬度調變信號,其中,N為大於1之自然數。According to the first-side feedback control of the flyback converter and the power control integrated circuit according to the preferred embodiment of the present invention, the power control integrated circuit includes a fixed current source and a first switch. A fixed current source is used to provide the above fixed current. The first end of the first switch is coupled to the fixed current source, and the second end of the first switch is coupled to the feedback end of the power control integrated circuit. When the switching element is turned on, the first switch is turned on, and the fixed current flows from the first end of the first switch to the second end of the first switch to increase the divided voltage. In a preferred embodiment, when the voltage dividing voltage is greater than a reference voltage for more than N times, the power control integrated circuit enters the protection mode, and the power control integrated circuit stops outputting the pulse width modulation signal, wherein N is A natural number greater than 1.
依照本新型較佳實施例所述之一次側回授控制之反馳式轉換器及電源控制積體電路,上述電壓檢測電路包括一取樣保持電路以及一比較電路。取樣保持電路包括一第二開關以及一取樣電容。第二開關包括一第一端以及一第二端,其中,第二開關的第一端耦接固定電流源。取樣電容的第一端耦接第二開關的第二端,取樣電容的第二端耦接共接電壓。比較電路包括一第一輸入端、一第二輸入端以及一輸出端,其中,比較電路的第一輸入 端耦接該取樣電容的第一端,比較電路的第二輸入端耦接一參考電壓,比較電路的輸出端輸出一比較信號。According to the first-side feedback control of the flyback converter and the power control integrated circuit according to the preferred embodiment of the present invention, the voltage detecting circuit includes a sample and hold circuit and a comparison circuit. The sample and hold circuit includes a second switch and a sampling capacitor. The second switch includes a first end and a second end, wherein the first end of the second switch is coupled to the fixed current source. The first end of the sampling capacitor is coupled to the second end of the second switch, and the second end of the sampling capacitor is coupled to the common voltage. The comparison circuit includes a first input terminal, a second input terminal, and an output terminal, wherein the first input of the comparison circuit The terminal is coupled to the first end of the sampling capacitor, the second input of the comparison circuit is coupled to a reference voltage, and the output of the comparison circuit outputs a comparison signal.
依照本新型較佳實施例所述之一次側回授控制之反馳式轉換器及電源控制積體電路,上述電源控制積體電路更包括一計數電路。此計數電路包括一輸入端以及一輸出端。計數電路的輸入端耦接比較電路的輸出端。計數電路用以計算計數電路的輸入端的電壓由第一邏輯電壓轉為第二邏輯電壓的次數,作為一計數值。每一預設時間,計數電路的計數值被重置為一預設計數值。當計數值大於一預設值,電源控制積體電路進入保護模式,並停止輸出脈波寬度調變信號。According to the first-side feedback control of the flyback converter and the power control integrated circuit according to the preferred embodiment of the present invention, the power control integrated circuit further includes a counting circuit. The counting circuit includes an input and an output. The input end of the counting circuit is coupled to the output of the comparison circuit. The counting circuit is configured to calculate the number of times the voltage at the input end of the counting circuit is changed from the first logic voltage to the second logic voltage as a count value. At each preset time, the count value of the counting circuit is reset to a pre-designed value. When the count value is greater than a predetermined value, the power control integrated circuit enters the protection mode and stops outputting the pulse width modulation signal.
本新型的精神在於利用一次側的回授電路,檢測輸入電壓。當主開關截止時,進行一般的輸出電壓的回授。當主開關導通時,輔助繞組的線圈反映出輸入電壓,然此電壓為負電壓。此時,電源控制電路對回授端輸出一固定電流,並檢測此回授電壓。當此回授電壓維持負值,表示輸入電壓足夠。當此電壓因為上述固定電流而轉為正電壓,且大於晶片內部的參考電壓,就表示輸入電壓不足。此時,電源控制電路便可以及時進入保護模式,避免損壞。The spirit of the present invention lies in the use of a feedback circuit on the primary side to detect the input voltage. When the main switch is turned off, the general output voltage is fed back. When the main switch is turned on, the coil of the auxiliary winding reflects the input voltage, but the voltage is a negative voltage. At this time, the power control circuit outputs a fixed current to the feedback terminal and detects the feedback voltage. When this feedback voltage is maintained at a negative value, it indicates that the input voltage is sufficient. When this voltage is converted to a positive voltage due to the above fixed current and larger than the reference voltage inside the wafer, it indicates that the input voltage is insufficient. At this point, the power control circuit can enter the protection mode in time to avoid damage.
為讓本新型之上述和其他目的、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 apparent and understood.
101‧‧‧變壓器101‧‧‧Transformer
102‧‧‧開關元件102‧‧‧Switching elements
103‧‧‧分壓電路103‧‧‧voltage circuit
104‧‧‧電源控制積體電路104‧‧‧Power Control Integrated Circuit
105‧‧‧二次側整流電路105‧‧‧Secondary side rectifier circuit
106‧‧‧輔助繞組整流電路106‧‧‧Auxiliary winding rectifier circuit
RHV ‧‧‧高壓電阻R HV ‧‧‧ high voltage resistor
RCS ‧‧‧電流感測電阻R CS ‧‧‧current sense resistor
HV‧‧‧高壓啟動端HV‧‧‧High-voltage starter
GND‧‧‧共接電壓端GND‧‧‧Common voltage terminal
SW‧‧‧開關控制端SW‧‧‧Switch control terminal
FB‧‧‧回授端FB‧‧‧reporting end
LP ‧‧‧一次側繞組L P ‧‧‧ primary winding
LS ‧‧‧二次側繞組L S ‧‧‧ secondary winding
LAUX ‧‧‧輔助繞組L AUX ‧‧‧Auxiliary winding
VCC ‧‧‧電源控制積體電路104的操作電壓V CC ‧‧‧ Operating voltage of the power control integrated circuit 104
VFB ‧‧‧分壓電壓V FB ‧‧‧voltage voltage
VO ‧‧‧二次側繞組LS 的電壓V O ‧‧‧voltage of the secondary winding L S
VAUX ‧‧‧輔助繞組LAUX 的電壓V AUX ‧‧‧Auxiliary winding L AUX voltage
VOUT ‧‧‧輸出電壓V OUT ‧‧‧ output voltage
D1‧‧‧二極體D1‧‧‧ diode
201‧‧‧脈波寬度調變電路201‧‧‧ Pulse width modulation circuit
202‧‧‧回授電路202‧‧‧Return circuit
203‧‧‧電壓檢測電路203‧‧‧Voltage detection circuit
204‧‧‧電流提供電路204‧‧‧ Current supply circuit
PWM‧‧‧脈波寬度調變訊號PWM‧‧‧ pulse width modulation signal
ILS ‧‧‧固定電流I LS ‧‧‧fixed current
205‧‧‧固定電流源205‧‧‧Fixed current source
SW1、SW2‧‧‧開關SW1, SW2‧‧‧ switch
RFB1 、RFB2 ‧‧‧分壓電路的兩個電阻R FB1 , R FB2 ‧ ‧ two resistors for the voltage divider circuit
VIN ‧‧‧輸入電壓V IN ‧‧‧ input voltage
LVS‧‧‧保護訊號LVS‧‧‧ protection signal
301‧‧‧比較器301‧‧‧ comparator
302‧‧‧取樣電容302‧‧‧Sampling capacitor
Vref ‧‧‧參考電壓V ref ‧‧‧reference voltage
303‧‧‧計數電路303‧‧‧Counting circuit
第1圖繪示為本新型一較佳實施例的一次側回授控制之反馳式轉換器之電路圖。FIG. 1 is a circuit diagram of a flyback converter of a primary side feedback control according to a preferred embodiment of the present invention.
第2圖繪示為本新型一較佳實施例的部分一次側回授控制之反馳式轉換器以及部分電源控制積體電路之電路圖。2 is a circuit diagram of a flyback converter and a partial power control integrated circuit of a partial primary side feedback control according to a preferred embodiment of the present invention.
第3圖繪示為本新型一較佳實施例的部分一次側回授控制之反馳式轉換器以及部分電源控制積體電路之電路圖。FIG. 3 is a circuit diagram of a flyback converter and a partial power control integrated circuit of a partial primary side feedback control according to a preferred embodiment of the present invention.
第1圖繪示為本新型一較佳實施例的一次側回授控制之反馳式轉換器之電路圖。請參考第1圖,此一次側回授控制之反馳式轉換器包括一變壓器101、一開關元件102、一分壓電路103、一電源控制積體電路104、二次側整流電路105、輔助繞組整流電路106、高壓電阻RHV 以及電流感測電阻RCS 。電源控制積體電路104包括、高壓啟動端HV、共接電壓端GND、開關控制端SW以及回授端FB,變壓器101包括一次側繞組LP 、一二次側繞組LS 以及一輔助繞組LAUX 。此輔助繞組整流電路106主要是用以將輔助繞組LAUX 的電壓整流後,並供應電源控制積體電路104的操作電壓VCC 。分壓電路103是由兩個電阻構成,用以將輔助繞組107的電壓進行分壓,並輸出分壓電壓VFB 。FIG. 1 is a circuit diagram of a flyback converter of a primary side feedback control according to a preferred embodiment of the present invention. Referring to FIG. 1 , the primary side feedback control of the flyback converter includes a transformer 101 , a switching element 102 , a voltage dividing circuit 103 , a power control integrated circuit 104 , and a secondary side rectifying circuit 105 . Auxiliary winding rectification circuit 106, high voltage resistor R HV and current sense resistor R CS . The power supply control integrated circuit 104 includes high voltage to start the HV side, the GND common voltage terminal, a control terminal of the switch SW and the FB feedback terminal, the transformer 101 includes a primary winding P L, S L a secondary winding and an auxiliary winding L AUX . The auxiliary winding rectifying circuit 106 is mainly used to rectify the voltage of the auxiliary winding L AUX and supply the operating voltage V CC of the power control integrated circuit 104. The voltage dividing circuit 103 is composed of two resistors for dividing the voltage of the auxiliary winding 107 and outputting the divided voltage V FB .
由於此電路為一次側回授控制的反馳式轉換器,因此,電源控制積體電路104需要檢測上述分壓電壓VFB 作為輸出電壓的參考。當此一次側回授控制之反馳式轉換器的開關元件102截止時,變壓器101釋放所儲存的能量至二次側繞組LS 以及輔助繞組LAUX 。此時,二次側繞組LS 的電壓VO 與輔助繞組LAUX 的電壓VAUX 成圈數比關係(VAUX =VO ×NAUX /NS )。藉此,電源控制積體電路104只要檢測分壓電壓VFB 便可以得知輸出電壓VOUT 之變化。一般來說,分壓電壓VFB 的大小並不能完全表示輸出電壓VOUT 。由於二次側整流電路105,在輸出電流大小不同時,二極體D1的跨壓會跟著變動,因此,一次側回授控制的反馳式轉換器還需對此做補償。Since this circuit is a flyback converter controlled by the primary side feedback, the power supply control integrated circuit 104 needs to detect the above-mentioned divided voltage V FB as a reference for the output voltage. When the switching element 102 of the flyback converter of this primary side feedback control is turned off, the transformer 101 releases the stored energy to the secondary side winding L S and the auxiliary winding L AUX . In this case, the secondary winding voltage V O L S and the auxiliary winding L AUX voltage V AUX relation to the turns ratio (V AUX = V O × N AUX / N S). Thereby, the power supply control integrated circuit 104 can know the change of the output voltage V OUT as long as the divided voltage V FB is detected. In general, the magnitude of the divided voltage V FB does not fully represent the output voltage V OUT . Due to the secondary side rectifying circuit 105, when the magnitude of the output current is different, the voltage across the diode D1 will fluctuate accordingly. Therefore, the flyback converter of the primary side feedback control needs to compensate for this.
另外,當此一次側回授控制之反馳式轉換器的開關元件102導通時,輸入電流流過變壓器101,對變壓器101進行儲存能量,此時,輔助繞組LAUX 的電壓約為(VAUX =-VIN ×NAUX /NS )。控制電路便可藉由檢測分壓電壓VFB 進行輸入電壓VIN 是否足夠的檢查。然而,對於本身不帶負電壓的電源控制積體電路104,檢測負電壓是一個問題。以下實施例,說明本新型如何檢測此負電壓以判斷輸入電壓是否足夠的資訊。In addition, when the switching element 102 of the flyback converter of the primary side feedback control is turned on, the input current flows through the transformer 101 to store energy for the transformer 101. At this time, the voltage of the auxiliary winding L AUX is approximately (V AUX =-V IN ×N AUX /N S ). The control circuit can be detected by the divided voltage V FB input voltage V IN to check whether or not sufficient. However, detecting the negative voltage is a problem for the power supply control circuit 104 which does not have a negative voltage itself. The following embodiment illustrates how the novel detects this negative voltage to determine if the input voltage is sufficient.
第2圖繪示為本新型一較佳實施例的部分一次側回授控制之反馳式轉換器以及部分電源控制積體電路之電路圖。請參考第2圖,此電源控制積體電路包括脈波寬度調變電路201、回授電路202、電壓檢測電路 203以及電流提供電路204。上述脈波寬度調變電路201、回授電路202、電壓檢測電路203以及電流提供電路204之耦接關係如圖所示。脈波寬度調變電路201用以輸出一脈波寬度調變訊號PWM。在開關元件102截止時,回授電路202用以根據分壓電壓VFB ,決定脈波寬度調變電路201所輸出的脈波寬度調變訊號PWM的責任週期。2 is a circuit diagram of a flyback converter and a partial power control integrated circuit of a partial primary side feedback control according to a preferred embodiment of the present invention. Referring to FIG. 2, the power control integrated circuit includes a pulse width modulation circuit 201, a feedback circuit 202, a voltage detection circuit 203, and a current supply circuit 204. The coupling relationship of the pulse width modulation circuit 201, the feedback circuit 202, the voltage detection circuit 203, and the current supply circuit 204 is as shown. The pulse width modulation circuit 201 is configured to output a pulse width modulation signal PWM. When the switching element 102 is turned off, the feedback circuit 202 determines the duty cycle of the pulse width modulation signal PWM outputted by the pulse width modulation circuit 201 based on the divided voltage V FB .
電流提供電路204用以在開關元件102導通時,提供一固定電流ILS
給分壓電路103。在此實施例中,電流提供電路204包括一固定電流源205以及一開關SW1。在此實施例中,開關SW1是用脈波寬度調變電路201所輸出的脈波寬度調變訊號PWM控制。換句話說,開關元件102被脈波寬度調變訊號PWM導通時,開關SW1也同時導通。此時,固定電流ILS
輸出給分壓電路103。分壓電壓VFB
可以數學表示如下:
其中,電阻RFB1 與RFB2 為分壓電路的兩個電阻;ILS 表示上述固定電流;VIN 表示輸入電壓。電壓檢測電路203則是用以檢測上述分壓電壓VFB ,當分壓電壓過高VFB 時,表示輸入電壓VIN 過低,此時,電壓檢測電路203輸出一保護訊號LVS,電源控制積體電路104跟著進入保護模式而關閉並停止輸出脈波寬度調變訊號 PWM。Wherein, the resistors R FB1 and R FB2 are two resistors of the voltage dividing circuit; I LS represents the above fixed current; V IN represents the input voltage. The voltage detecting circuit 203 is configured to detect the divided voltage V FB . When the divided voltage is too high V FB , the input voltage V IN is too low. At this time, the voltage detecting circuit 203 outputs a protection signal LVS, and the power control product The body circuit 104 is turned off in the protection mode and stops outputting the pulse width modulation signal PWM.
第3圖繪示為本新型一較佳實施例的部分一次側回授控制之反馳式轉換器以及部分電源控制積體電路之電路圖。請參考第3圖,在此實施例中,電壓檢測電路203包括一比較器301、一取樣電容302以及一開關SW2。同樣的道理,開關SW2是用脈波寬度調變電路201所輸出的脈波寬度調變訊號PWM控制。換句話說,開關元件102被脈波寬度調變訊號PWM導通時,開關SW2也同時導通。電容302與開關SW2構成了一取樣保持電路。當開關元件102被脈波寬度調變訊號PWM導通時,開關SW2導通,此時,電容302取樣分壓電壓VFB 。比較器301的正輸入端接收上述分壓電壓VFB ,比較器301的負輸入端接收參考電壓Vref 。FIG. 3 is a circuit diagram of a flyback converter and a partial power control integrated circuit of a partial primary side feedback control according to a preferred embodiment of the present invention. Referring to FIG. 3, in this embodiment, the voltage detecting circuit 203 includes a comparator 301, a sampling capacitor 302, and a switch SW2. By the same token, the switch SW2 is controlled by the pulse width modulation signal PWM outputted by the pulse width modulation circuit 201. In other words, when the switching element 102 is turned on by the pulse width modulation signal PWM, the switch SW2 is also turned on at the same time. Capacitor 302 and switch SW2 form a sample and hold circuit. When the switching element 102 is turned on by the pulse width modulation signal PWM, the switch SW2 is turned on. At this time, the capacitor 302 samples the divided voltage V FB . The positive input terminal of the comparator 301 receives the above-mentioned divided voltage V FB , and the negative input terminal of the comparator 301 receives the reference voltage V ref .
一般來說,固定電流ILS 輸出給分壓電路103,分壓電壓VFB 因此被提高。然而,當輸入電壓VIN 足夠高時,即使有固定電流ILS 存在,分壓電壓VFB 仍然為負值。此時,比較器301輸出邏輯低電壓。當輸入電壓VIN 下降時,分壓電壓VFB 會由負電壓轉為正電壓。當分壓電壓VFB 小於參考電壓Vref ,表示輸入電壓VIN 仍然足夠高,此時,比較器301輸出邏輯低電壓。當輸入電壓VIN 過低時,分壓電壓VFB 會大於參考電壓Vref 。此時,比較器301輸出邏輯高電壓。In general, the fixed current I LS is output to the voltage dividing circuit 103, and the divided voltage V FB is thus increased. However, when the input voltage V IN is sufficiently high, the divided voltage V FB is still negative even if a fixed current I LS is present. At this time, the comparator 301 outputs a logic low voltage. When the input voltage V IN drops, the divided voltage V FB turns from a negative voltage to a positive voltage. When the divided voltage V FB is smaller than the reference voltage V ref , it indicates that the input voltage V IN is still sufficiently high, and at this time, the comparator 301 outputs a logic low voltage. When the input voltage V IN is too low, the divided voltage V FB will be greater than the reference voltage V ref. At this time, the comparator 301 outputs a logic high voltage.
然而,在此實施例中,瞬間的輸入電壓過低,並不會立即讓電源控制積體電路104進入保護模 式。若僅是一時電壓不穩,就使得整個電源供應器進入保護,將會造成使用者的不便。電源不穩的情況下,一般會瞬間恢復。因此,在此實施例中,配置了一計數電路303。計數電路303用以計數當開關元件102被脈波寬度調變訊號PWM導通時,比較器301輸出邏輯高電壓的次數。若此次數大於一預設次數,例如10次或20次,表示輸入電壓VIN 不穩定狀態持續發生。此時,計數電路303便輸出保護訊號LVS,電源控制積體電路104跟著進入保護模式而關閉並停止輸出脈波寬度調變訊號PWM。However, in this embodiment, the instantaneous input voltage is too low and the power control integrated circuit 104 is not immediately brought into the protection mode. If the voltage is unstable for a while, the entire power supply will be protected, which will cause inconvenience to the user. When the power supply is unstable, it will generally recover instantaneously. Therefore, in this embodiment, a counting circuit 303 is configured. The counting circuit 303 is configured to count the number of times the comparator 301 outputs a logic high voltage when the switching element 102 is turned on by the pulse width modulation signal PWM. If the number of times is greater than a predetermined number of times, for example, 10 or 20 times, it indicates that the unstable state of the input voltage V IN continues to occur. At this time, the counting circuit 303 outputs the protection signal LVS, and the power control integrated circuit 104 is turned off in the protection mode and stops outputting the pulse width modulation signal PWM.
另外,此計數電路303會在每一段預設時間便進行重置。此時,計數電路303所計算的比較器301輸出邏輯高電壓的次數會被歸零。換句話說,若在一段時間內,輸入電壓VIN 沒有持續過低,分壓電壓VFB 沒有持續大於參考電壓Vref ,電源控制積體電路104便不會進入保護模式,避免使用者感覺到電源供應器不明原因被關閉。In addition, the counting circuit 303 resets every preset time. At this time, the number of times the comparator 301 calculated by the counting circuit 303 outputs the logic high voltage is reset to zero. In other words, if the input voltage V IN does not continue to be too low for a period of time, and the divided voltage V FB does not continue to be greater than the reference voltage V ref , the power control integrated circuit 104 does not enter the protection mode, thereby preventing the user from feeling The power supply was turned off for unknown reasons.
綜上所述,本新型的精神在於利用一次側的回授電路,檢測輸入電壓。當主開關截止時,進行一般的輸出電壓的回授。當主開關導通時,輔助繞組的線圈反映出輸入電壓,然此電壓為負電壓。此時,電源控制電路對回授端輸出一固定電流,並檢測此回授電壓。當此回授電壓維持負值,表示輸入電壓足夠。當此電壓因為上述固定電流而轉為正電壓,且大於晶片內部的參考電壓,就表示輸入電壓不足。此時,電源控制電路便可以及時進入 保護模式,避免損壞。In summary, the spirit of the present invention is to detect the input voltage by using a feedback circuit on the primary side. When the main switch is turned off, the general output voltage is fed back. When the main switch is turned on, the coil of the auxiliary winding reflects the input voltage, but the voltage is a negative voltage. At this time, the power control circuit outputs a fixed current to the feedback terminal and detects the feedback voltage. When this feedback voltage is maintained at a negative value, it indicates that the input voltage is sufficient. When this voltage is converted to a positive voltage due to the above fixed current and larger than the reference voltage inside the wafer, it indicates that the input voltage is insufficient. At this point, the power control circuit can enter in time. Protect the mode from damage.
在較佳實施例之詳細說明中所提出之具體實施例僅用以方便說明本新型之技術內容,而非將本新型狹義地限制於上述實施例,在不超出本新型之精神及以下申請專利範圍之情況,所做之種種變化實施,皆屬於本新型之範圍。因此本新型之保護範圍當視後附之申請專利範圍所界定者為準。The specific embodiments set forth in the detailed description of the preferred embodiments are merely used to facilitate the description of the technical scope of the present invention, and are not intended to limit the present invention narrowly to the above embodiments, without departing from the spirit of the present invention and the following claims. The scope of the scope and the implementation of various changes are within the scope of this new model. Therefore, the scope of protection of this new type is subject to the definition of the scope of the patent application.
201‧‧‧脈波寬度調變電路201‧‧‧ Pulse width modulation circuit
202‧‧‧回授電路202‧‧‧Return circuit
203‧‧‧電壓檢測電路203‧‧‧Voltage detection circuit
204‧‧‧電流提供電路204‧‧‧ Current supply circuit
205‧‧‧固定電流源205‧‧‧Fixed current source
ILS ‧‧‧固定電流I LS ‧‧‧fixed current
LVS‧‧‧保護訊號LVS‧‧‧ protection signal
PWM‧‧‧脈波寬度調變訊號PWM‧‧‧ pulse width modulation signal
RFB1 、RFB2 ‧‧‧分壓電路的兩個電阻R FB1 , R FB2 ‧ ‧ two resistors for the voltage divider circuit
SW1‧‧‧開關SW1‧‧‧ switch
VFB ‧‧‧分壓電壓V FB ‧‧‧voltage voltage
VIN ‧‧‧輸入電壓V IN ‧‧‧ input voltage
Claims (10)
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Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
TWI562525B (en) * | 2014-08-15 | 2016-12-11 | Eosmem Corp | Primary-side regulated flyback converter and power control integrated circuit thereof |
CN113726132A (en) * | 2020-05-22 | 2021-11-30 | 万国半导体国际有限合伙公司 | Flyback converter for controlling change of conduction time |
TWI829374B (en) * | 2022-06-02 | 2024-01-11 | 大陸商昂寶電子(上海)有限公司 | Flyback power converter based on primary side feedback |
TWI832463B (en) * | 2022-07-22 | 2024-02-11 | 大陸商昂寶電子(上海)有限公司 | Flyback power converter based on primary side feedback |
-
2014
- 2014-08-15 TW TW103214536U patent/TWM505122U/en unknown
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
TWI562525B (en) * | 2014-08-15 | 2016-12-11 | Eosmem Corp | Primary-side regulated flyback converter and power control integrated circuit thereof |
CN113726132A (en) * | 2020-05-22 | 2021-11-30 | 万国半导体国际有限合伙公司 | Flyback converter for controlling change of conduction time |
TWI829374B (en) * | 2022-06-02 | 2024-01-11 | 大陸商昂寶電子(上海)有限公司 | Flyback power converter based on primary side feedback |
TWI832463B (en) * | 2022-07-22 | 2024-02-11 | 大陸商昂寶電子(上海)有限公司 | Flyback power converter based on primary side feedback |
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