TWI817321B - Multi-mode hybrid control DC-DC power conversion circuit and control method - Google Patents
Multi-mode hybrid control DC-DC power conversion circuit and control method Download PDFInfo
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Abstract
一種多模式混合控制的直流-直流電源轉換電路,包含一切換式電源轉換器與一微控制器,該切換式電源轉換器包含一變壓器及一切換開關,該微控制器根據該切換式電源轉換器的輸入電壓設定多個回授電壓門檻值,並判斷該切換式電源轉換器的回授電壓與各該回授電壓門檻值之間的大小關係,以根據其判斷結果執行一變頻控制模式、一定頻控制模式或一跳週期控制模式;該微控制器輸出一驅動信號至該切換開關,該微控制器根據所執行的模式對應調整該驅動信號的頻率,讓該切換式電源轉換器從輕載到滿載獲得最佳的效率曲線。A multi-mode hybrid controlled DC-DC power conversion circuit includes a switching power converter and a microcontroller. The switching power converter includes a transformer and a switching switch. The microcontroller converts power according to the switching power supply. Set multiple feedback voltage thresholds for the input voltage of the converter, and determine the relationship between the feedback voltage of the switching power converter and each of the feedback voltage thresholds, so as to execute a frequency conversion control mode based on the judgment results. Fixed frequency control mode or one-hop period control mode; the microcontroller outputs a driving signal to the switch, and the microcontroller adjusts the frequency of the driving signal according to the executed mode, so that the switching power converter can easily Load to full load to obtain the best efficiency curve.
Description
本發明涉及直流-直流(DC to DC)電源轉換電路,特別是指多模式混合控制的直流-直流電源轉換電路與控制方法。The present invention relates to a DC-to-DC power conversion circuit, and in particular to a multi-mode hybrid control DC-to-DC power conversion circuit and control method.
習知直流-直流電源轉換電路包含一切換式電源轉換器與一微控制器,其中,返馳式(Flyback)電源轉換器是該切換式電源轉換器的一種電路架構,該返馳式電源轉換器的電源輸出端供連接一負載,該返馳式電源轉換器基本上包含一變壓器,該變壓器的一次側繞組串聯一電晶體,該電晶體常見的是金氧半場效電晶體(MOSFET),該微控制器及其控制迴路連接該切換式電源轉換器的電源輸入端、電源輸出端和該電晶體的閘極。A conventional DC-DC power conversion circuit includes a switching power converter and a microcontroller. Among them, a flyback power converter is a circuit architecture of the switching power converter. The flyback power converter The power output end of the converter is used to connect a load. The flyback power converter basically includes a transformer. The primary winding of the transformer is connected in series with a transistor. The transistor is usually a metal oxide semi-field effect transistor (MOSFET). The microcontroller and its control loop are connected to the power input terminal, the power output terminal of the switching power converter and the gate of the transistor.
藉此,使用該微控制器來控制,可偵測該切換式電源轉換器的輸入電壓和回授電壓以判斷該切換式電源轉換器所連接之該負載的負載量,並根據該負載量產生一驅動信號(PWM)給該電晶體,該電晶體根據該驅動信號實施導通/關閉(ON/OFF)的作動方式。Thereby, using the microcontroller to control, the input voltage and feedback voltage of the switching power converter can be detected to determine the load amount of the load connected to the switching power converter, and generate a signal based on the load amount. A driving signal (PWM) is given to the transistor, and the transistor implements an ON/OFF action mode according to the driving signal.
一般而言,該微控制器係執行一準諧振控制模式(QR mode),該準諧振模式的功能是當偵測到的該負載量越低,該驅動信號的頻率越高。然而,該負載量的態樣多元,至少包含重載與輕載等態樣,舉例來說,在滿載時,該驅動信號的頻率可為120kHz;但當該負載量降低為輕載(例如滿載的30%),該驅動信號的頻率可能提升為400kHz。由此可見,當該負載量為輕載或更低,甚至於空載,該驅動信號的頻率將維持在較高的頻率,致使該驅動開關實施較高頻率的導通/關閉的切換,衍生高頻雜訊、高頻切換損失和電路板線路上的電磁干擾等問題。Generally speaking, the microcontroller implements a quasi-resonant control mode (QR mode). The function of the quasi-resonant mode is that when the detected load is lower, the frequency of the driving signal is higher. However, the load has various forms, including at least heavy load and light load. For example, when the load is full, the frequency of the driving signal can be 120kHz; but when the load is reduced to a light load (such as full load) 30%), the frequency of the driving signal may be increased to 400kHz. It can be seen that when the load is light load or lower, or even no-load, the frequency of the drive signal will be maintained at a higher frequency, causing the drive switch to perform on/off switching at a higher frequency, resulting in high Frequency noise, high-frequency switching losses and electromagnetic interference on circuit board lines and other issues.
有鑒於此,本發明的主要目的是提供一種多模式混合控制的直流-直流電源轉換電路與控制方法,以期改善習知直流-直流電源轉換電路在準諧振控制模式(QR mode)下,當負載量為輕載或更低,所衍生高頻雜訊、高頻切換損失和電路板線路上的電磁干擾等問題。In view of this, the main purpose of the present invention is to provide a multi-mode hybrid control DC-DC power conversion circuit and control method, in order to improve the performance of the conventional DC-DC power conversion circuit when the load is in the quasi-resonant control mode (QR mode). The load is light load or lower, resulting in problems such as high-frequency noise, high-frequency switching loss and electromagnetic interference on the circuit board lines.
本發明的多模式混合控制的直流-直流電源轉換電路包含: 一切換式電源轉換器,包含: 一變壓器;及 一切換開關,串聯於該變壓器的一次側繞組且具有一控制端;以及 一微控制器,連接該切換式電源轉換器以及該切換開關的控制端,該微控制器根據該切換式電源轉換器的輸入電壓設定多個回授電壓門檻值,以及判斷該切換式電源轉換器的一回授電壓與各該回授電壓門檻值之間的大小關係,以根據其判斷結果執行一變頻控制模式、一定頻控制模式或一跳週期控制模式;該微控制器輸出一驅動信號至該切換開關,並根據所執行的該變頻控制模式、該定頻控制模式或該跳週期控制模式對應調整該驅動信號的頻率。 The multi-mode hybrid controlled DC-DC power conversion circuit of the present invention includes: A switching power converter containing: a transformer; and A switch is connected in series to the primary winding of the transformer and has a control terminal; and A microcontroller is connected to the control terminal of the switching power converter and the switching switch. The microcontroller sets a plurality of feedback voltage thresholds according to the input voltage of the switching power converter, and determines the conversion of the switching power supply. The relationship between a feedback voltage of the device and each feedback voltage threshold is used to execute a variable frequency control mode, a constant frequency control mode or a skip cycle control mode according to the judgment result; the microcontroller outputs a driving signal to the switch, and correspondingly adjust the frequency of the driving signal according to the executed frequency conversion control mode, the fixed frequency control mode or the skip cycle control mode.
本發明的多模式混合控制的直流-直流電源轉換電路的控制方法係於一微控制器執行,該微控制器連接一切換式電源轉換器與一切換開關,該控制方法包含以下步驟: (a) 偵測該切換式電源轉換器的一輸入電壓和一回授電壓; (b) 根據該切換式電源轉換器的該輸入電壓設定多個回授電壓門檻值; (c) 判斷該切換式電源轉換器的該回授電壓與各該回授電壓門檻值之間的大小關係;以及 (d) 根據步驟(c)的判斷結果執行一變頻控制模式、一定頻控制模式或一跳週期控制模式,其中,該微控制器輸出一驅動信號至該切換開關,並根據所執行的該變頻控制模式、該定頻控制模式或該跳週期控制模式對應調整該驅動信號的頻率。 The control method of the multi-mode hybrid control DC-DC power conversion circuit of the present invention is executed by a microcontroller, and the microcontroller is connected to a switching power converter and a switch. The control method includes the following steps: (a) detecting an input voltage and a feedback voltage of the switching power converter; (b) setting multiple feedback voltage thresholds based on the input voltage of the switching power converter; (c) Determine the relationship between the feedback voltage of the switching power converter and each feedback voltage threshold; and (d) Execute a frequency conversion control mode, a constant frequency control mode or a skip cycle control mode according to the judgment result of step (c), in which the microcontroller outputs a drive signal to the switch, and executes the frequency conversion control mode according to the executed frequency conversion control mode. The control mode, the fixed frequency control mode or the skip cycle control mode correspondingly adjusts the frequency of the driving signal.
根據本發明的多模式混合控制的直流-直流電源轉換電路與控制方法,所謂多模式即例如包含該變頻控制模式、該定頻控制模式和該跳週期控制模式,該微控制器即時監測該切換式電源轉換器的輸入電壓和回授電壓,其中,該切換式電源轉換器的回授電壓可反映該直流-直流電源轉換電路所連接之一負載的負載量,該微控制器所設定的該些回授電壓門檻值係作為評估該負載量的判斷基準值。According to the multi-mode hybrid control DC-DC power conversion circuit and control method of the present invention, the so-called multi-mode includes, for example, the frequency conversion control mode, the fixed frequency control mode and the skip cycle control mode, and the microcontroller monitors the switching in real time The input voltage and feedback voltage of the switching power converter, where the feedback voltage of the switching power converter can reflect the load of a load connected to the DC-DC power conversion circuit, the microcontroller sets the These feedback voltage thresholds are used as judgment reference values for evaluating the load.
當該微控制器判斷出該負載量為重載,執行該變頻控制模式;當該微控制器判斷出該負載量為輕載或更低,執行該定頻控制模式或該跳週期控制模式,在該定頻控制模式或該跳週期控制模式下,該驅動信號的頻率維持在定值而不隨著負載量變輕而提高,如此一來,有效改善先前技術所述該負載量為輕載或更低所衍生高頻雜訊、高頻切換損失和電路板線路上的電磁干擾等問題,並讓該切換式電源轉換器從輕載到滿載獲得最佳的效率曲線。When the microcontroller determines that the load is heavy load, the variable frequency control mode is executed; when the microcontroller determines that the load is light load or lower, the fixed frequency control mode or the cycle skip control mode is executed. In the fixed frequency control mode or the skip cycle control mode, the frequency of the driving signal is maintained at a constant value without increasing as the load becomes lighter. In this way, the load is effectively improved when the load is light or light as described in the prior art. It reduces the problems caused by high-frequency noise, high-frequency switching losses and electromagnetic interference on the circuit board lines, and allows the switching power converter to obtain the best efficiency curve from light load to full load.
本發明多模式混合控制的直流-直流電源轉換電路包含一切換式電源轉換器與一微控制器(MCU),或可進一步包含一主動箝位電路,其中,該切換式電源轉換器是以一返馳式(Flyback)電源轉換器為例,需說明的是,該返馳式電源轉換器的工作原理並非本發明特徵所在,僅概略敘述而容不詳述。The multi-mode hybrid controlled DC-DC power conversion circuit of the present invention includes a switching power converter and a microcontroller (MCU), or may further include an active clamping circuit, wherein the switching power converter is based on a Taking a flyback power converter as an example, it should be noted that the working principle of the flyback power converter is not a feature of the present invention and is only briefly described without going into detail.
請參考圖1,該切換式電源轉換器10包含一變壓器20、一切換開關Q1與一輸出電路30。該變壓器20的一次側繞組21及二次側繞組22未共地,該一次側繞組21的一第一端連接該切換式電源轉換器10的電源輸入端11以供接收直流的一輸入電壓V
I,該切換開關Q1串聯於該一次側繞組21且具有一控制端,本發明的實施例中,該切換開關Q1可為一電晶體,例如為金氧半場效電晶體(MOSFET),其閘極作為該控制端,其汲極連接該一次側繞組21的一第二端,其源極供接地,該切換開關Q1由此連接結構與該一次側繞組21形成串聯。該輸出電路30連接該二次側繞組22且包含用以連接一負載的電源輸出端12,由電源輸出端12提供一輸出電壓V
O給該負載。該微控制器40的一信號輸入端連接該切換式電源轉換器10,該微控制器40的一信號輸出端連接該切換開關Q1的控制端,該微控制器40能輸出一驅動信號S1至該切換開關Q1,以控制該切換開關Q1的作動(即:導通/關閉),其中,該驅動信號S1可為脈波寬度調變(PWM)信號,該微控制器40可設定及調整該驅動信號的脈波寬度與頻率。
Please refer to FIG. 1 , the
本發明的實施例中,該微控制器40的一第一信號輸入端透過一隔離回授電路50連接該切換式電源轉換器10的電源輸出端12,以從該隔離回授電路50接收一回授電壓V
FB,該回授電壓V
FB能反映該切換式電源轉換器10的輸出電壓V
O,也就是說,當該切換式電源轉換器10連接一負載時,該回授電壓V
FB的大小能反映該負載提供的一負載量,例如滿載、重載、輕載、極輕載或空載。需說明的是,利用一隔離回授電路50取得回授電壓V
FB以偵測該負載量是電源電路技術領域中的通常知識,該隔離回授電路50的工作原理並非本發明特徵所在,僅概略敘述而容不詳述,該隔離回授電路50的詳細電路可參考圖2,該隔離回授電路50基本上可包含一光耦合器51,該光耦合器51包含兩輸入端、一第一輸出端與一第二輸出端,該兩輸入端分別連接該切換式電源轉換器10的電源輸出端12,該第一輸出端連接一電壓源Vcc與該微控制器40的該第一信號輸入端,藉此使該微控制器40能從該隔離回授電路50接收該回授電壓V
FB,該光耦合器51的第二輸出端供接地,其中,該電壓源Vcc可取自該一次側繞組21,舉例而言,該一次側繞組21可耦合一輔助繞組(圖中未示)或連接一分壓電路(圖中未示),該光耦合器51連接該輔助繞組或該分壓電路以獲得該電壓源Vcc。
In the embodiment of the present invention, a first signal input terminal of the
該微控制器40儲存多個回授電壓門檻值,該些回授電壓門檻值為可調整預設值,該些回授電壓門檻值作為評估該負載之負載量的判斷基準值。該微控制器40係判斷該回授電壓V
FB與各該回授電壓門檻值之間的大小關係,以根據其判斷結果執行多個回授控制模式當中之一者,該微控制器40根據所執行的回授控制模式而對應調整輸出至該切換開關Q1的該驅動信號S1的脈波寬度及/或頻率。
The
本發明的實施例中,該些回授控制模式包含一變頻控制模式、一定頻控制模式與一跳週期控制模式(Pulse Skipping Mode, PSM)。在該負載量為滿載或重載時,該微控制器40執行該變頻控制模式,顧名思義,該微控制器40使該驅動信號S1的頻率隨著負載量而改變,一般而言,隨著該負載量越低,該驅動信號S1的頻率越高,相對的,隨著該負載量越高,該驅動信號S1的頻率越低,此亦為電源電路技術領域中的通常知識,舉例而言,該變頻控制模式可為準諧振變頻控制模式(Quasi-Resonant mode, QR mode)。在該負載量為輕載時,該微控制器40執行該定頻控制模式,顧名思義,該微控制器40使該驅動信號S1的頻率為固定頻率。在該負載的負載量為極輕載或空載時,該微控制器40執行該跳週期控制模式,以使該驅動信號S1的頻率呈現「零」與「非零」的交替變化,「非零」的頻率是指該定頻控制模式的該固定頻率,容後說明。在該變頻控制模式中,當該負載的負載量為滿載時,該驅動信號S1的頻率定義為一滿載頻率,該滿載頻率例如約為120kHz;在該定頻控制模式和該跳週期控制模式中,該驅動信號S1的頻率為該滿載頻率的二分之一以上。In embodiments of the present invention, the feedback control modes include a variable frequency control mode, a constant frequency control mode and a pulse skipping mode (PSM). When the load is full or heavy, the
該微控制器40的一第二信號輸入端能偵測該切換式電源轉換器10的輸入電壓V
I,以圖1為例,該微控制器40的該第二信號輸入端可透過一分壓電路13連接該切換式電源轉換器10的電源輸入端11以偵測該輸入電壓V
I。該微控制器40根據該切換式電源轉換器10的輸入電壓V
I設定該些回授電壓門檻值。本發明的實施例中,該些回授電壓門檻值包含一第一回授電壓門檻值V
LL與一第二回授電壓門檻值V
SK,且V
LL大於V
SK。當該微控制器40判斷出該回授電壓V
FB大於該第一回授電壓門檻值V
LL,該微控制器40執行該變頻控制模式,以對應該負載量為滿載或重載;當該微控制器40判斷出該回授電壓V
FB小於或等於該第一回授電壓門檻值V
LL並且大於該第二回授電壓門檻值V
SK,該微控制器40執行該定頻控制模式,以對應該負載量為輕載;當該微控制器40判斷出該回授電壓V
FB小於或等於該第二回授電壓門檻值V
SK,該微控制器40執行該跳週期控制模式,以對應該負載量為極輕載或空載。
A second signal input terminal of the
以上已說明該切換式電源轉換器10與該微控制器40的電路架構與功能,以下配合波形圖說明該微控制器40所執行的多模式混合控制方法,該控制方法的流程圖可參考圖3。The circuit architecture and functions of the switching
步驟S01:偵測該切換式電源轉換器10的輸入電壓V
I和回授電壓V
FB。如前所述,該微控制器40可透過該分壓電路13偵測該切換式電源轉換器10的輸入電壓V
I,另透過該隔離回授電路50接收該回授電壓V
FB,該回授電壓V
FB反映該切換式電源轉換器10的輸出電壓V
O,該輸出電壓V
O反映所連接之該負載的負載量,故能利用該回授電壓V
FB偵測該負載的負載量。
Step S01: Detect the input voltage V I and the feedback voltage V FB of the switching
步驟S02:根據該切換式電源轉換器10的輸入電壓V
I設定多個回授電壓門檻值。如前所述,該些回授電壓門檻值包含該第一回授電壓門檻值V
LL與該第二回授電壓門檻值V
SK,且V
LL大於V
SK。本發明的實施例中,該微控制器40儲存多個回授電壓門檻參考值、一第一比例值R1與一第二比例值R2,該些回授電壓門檻參考值分別對應於該切換式電源轉換器10的不同的輸入電壓V
I的大小,該第一比例值大於該第二比例值,即R1大於R2,例如該第一比例值可為55%,該第二比例值可為10%,但不以此為限。該微控制器40選擇與該切換式電源轉換器10的輸入電壓V
I相對應的其中之一回授電壓門檻參考值,再將被選的回授電壓門檻參考值乘以該第一比例值而設定為該第一回授電壓門檻值V
LL,即V
LL=被選的回授電壓門檻參考值×R1,以及將被選的回授電壓門檻參考值乘以該第二比例值而設定為該第二回授電壓門檻值V
SK,即V
SK=被選的回授電壓門檻參考值×R2。下表記載一範例,但不以此範例為限,也就是說,當該微控制器40偵測出該切換式電源轉換器10的輸入電壓V
I為9V,即選擇2.32V的回授電壓門檻參考值以供計算該第一回授電壓門檻值V
LL和該第二回授電壓門檻值V
SK,依此類推。
Step S02: Set multiple feedback voltage thresholds according to the input voltage VI of the switching
原則上,該回授電壓門檻參考值、該第一比例值R1和該第二比例值R2會以較優化的輕載效率及空載低功耗為目的進行設計,以決定該微控制器40進入該定頻控制模式和該跳週期控制模式的時機。本發明的實施例中,透過該第一比例值R1的設定,於該負載的負載量為半載時(即:滿載的一半)開始實施該定頻控制模式,使該驅動信號S1的頻率為該滿載頻率的二分之一以上。In principle, the feedback voltage threshold reference value, the first proportional value R1 and the second proportional value R2 are designed for the purpose of more optimized light load efficiency and low no-load power consumption to determine the
步驟S03:判斷該切換式電源轉換器10的回授電壓V
FB與各該回授電壓門檻值之間的大小關係。本發明的實施例中,該微控制器40是先後判斷該回授電壓V
FB與該第一回授電壓門檻值V
LL和該第二回授電壓門檻值V
SK之間的電壓大小,容後說明。
Step S03: Determine the relationship between the feedback voltage V FB of the switching
步驟S04:根據步驟S03的判斷結果執行一變頻控制模式、一定頻控制模式或一跳週期控制模式,其中,該微控制器40輸出一驅動信號S1至該切換開關Q1,並根據所執行的該變頻控制模式、該定頻控制模式或該跳週期控制模式對應調整該驅動信號S1的電壓大小、脈波寬度及/或頻率。該切換式電源轉換器10的輸出電流I
O與輸出電壓V
O、該回授電壓V
FB和該驅動信號S1的波形可參考圖4A至圖4D,其中,圖4A顯示該切換式電源轉換器10的輸出電流I
O的波形,該輸出電流I
O在時間t0為一最大電流並隨著時間而遞減,故從時間t0開始能依序呈現滿載、重載、輕載、極輕載與空載的負載量。
Step S04: Execute a variable frequency control mode, a constant frequency control mode or a skip period control mode according to the judgment result of step S03, in which the
在步驟S03中,該微控制器40判斷該回授電壓V
FB是否小於或等於該第一回授電壓門檻值V
LL(步驟S031),若在步驟S031判斷為否,進入步驟S04執行該變頻控制模式,使該驅動信號S1的頻率隨著該負載的負載量而改變。若在步驟S031判斷為是,該微控制器40進一步判斷該回授電壓V
FB是否小於或等於該第二回授電壓門檻值V
SK(步驟S032),若在步驟S032判斷為否,進入步驟S04以執行該定頻控制模式,使該驅動信號S1的頻率為固定頻率。
In step S03, the
若在步驟S032判斷為是,該微控制器40進入步驟S04以執行該跳週期控制模式,在該跳週期控制模式中,該微控制器40判斷該回授電壓V
FB是否回升而大於或等於該第二回授電壓門檻值V
SK(步驟S041);若在步驟S041判斷為是,該微控制器40執行該定頻控制模式以使該驅動信號S1的頻率為該固定頻率並再回到步驟S031;若在步驟S041判斷為否,該微控制器40停止輸出該驅動信號S1至該切換開關Q1。
If it is determined to be yes in step S032, the
綜合圖4A至圖4D來看,該微控制器40在時間t1判斷出V
FB≦V
LL而進入該定頻控制模式,也就是說,時間t0至t1代表該負載量為滿載或重載,故該微控制器40在時間t0至t1執行該變頻控制模式,且可見該切換式電源轉換器10在時間t0至t1的輸出電流I
O較高且輸出電壓V
O較穩定。該微控制器40在時間t2判斷出V
FB≦V
SK而進入該跳週期控制模式,也就是說,時間t1至t2代表該負載量為輕載,且可見該微控制器40從該變頻控制模式進入該定頻控制模式後,係降低該驅動信號S1的頻率。時間t2至t4代表該負載量為極輕載或空載,故該微控制器40在時間t2至t4執行該跳週期控制模式,其中,該微控制器40於時間t2至t3判斷出V
FB≦V
SK而停止輸出該驅動信號S1(即:0V,且頻率為0 Hz),並於時間t3判斷出V
FB≧V
SK而執行該定頻控制模式,故使該驅動信號S1的頻率在時間t2至t4之間呈現「零」與「非零」的交替變化。
Based on Figures 4A to 4D, the
該切換式電源轉換器10的輸出電壓V
O在時間t2至t4的波形起伏現象是該跳週期控制模式的現象,配合參考圖2與圖4A至4D,當該驅動信號S1從時間t2開始暫時為0V,該切換式電源轉換器10的輸出電壓V
O開始遞減,該微控制器40從該隔離回授電路50接收的該回授電壓V
FB則遞增(基於該光耦合器51的第一輸出端所連接的電壓源Vcc),隨著時間推進,該微控制器40在時間t3判斷出V
FB≧V
SK而執行該定頻控制模式,故於時間t3至t4輸出該定頻控制模式下的驅動信號S1給該切換開關Q1,該切換式電源轉換器10的輸出電壓V
O開始遞增,該微控制器40從該隔離回授電路50接收的該回授電壓V
FB則遞減,在時間t4之後,依此類推,該微控制器40可再次判斷出V
FB≦V
SK而停止輸出該驅動信號S1,並週而復始,使該驅動信號S1的頻率在該跳週期控制模式中呈現「零」與「非零」的交替變化。
The waveform fluctuation phenomenon of the output voltage V O of the switching
請參考圖1與圖2,本發明中的該主動箝位電路60連接該變壓器20的一次側繞組21,該主動箝位電路60可為自激式主動箝位電路,包含一箝位開關Q2、一第一電容C1、一第二電容C2、一電阻R,也可以進一步包含一個二極體D。以返馳式電源轉換器的電路架構來看,該箝位開關Q2可為高側開關(high-side switch),該切換開關Q1可為低側開關(low-side switch)。Please refer to Figures 1 and 2. The
該箝位開關Q2的一端連接該第一電容C1的一端,該第一電容C1的另一端連接該變壓器20的一次側繞組21的第一端與該切換式電源轉換器10的電源輸入端11;該箝位開關Q2的另一端連接該第二電容C2的一端,該第二電容C2的另一端連接該變壓器20的一次側繞組21的第二端與該切換開關Q1的一端,故使該箝位開關Q2串聯在該第一電容C1及該第二電容C2之間;另外,該箝位開關Q2還具有一控制端。本發明的實施例中,該箝位開關Q2為一電晶體,例如為金氧半場效電晶體(MOSFET),其閘極作為該控制端,其汲極連接該第一電容C1,其源極連接該第二電容C2,其閘極和源極之間存在一寄生電容C3。One end of the clamp switch Q2 is connected to one end of the first capacitor C1 , and the other end of the first capacitor C1 is connected to the first end of the primary winding 21 of the
該電阻R的一端連接該箝位開關Q2的控制端,該電阻R的另一端連接該變壓器20的一次側繞組21的第二端與該切換開關Q1的一端。該二極體D的陽極連接該箝位開關Q2的控制端,該二極體D2的陰極連接該變壓器20的一次側繞組21的第二端與該切換開關Q1的一端,也就是說,該電阻R跨接在該二極體D的陽極與陰極。One end of the resistor R is connected to the control end of the clamp switch Q2, and the other end of the resistor R is connected to the second end of the primary winding 21 of the
該主動箝位電路60應用於一電流臨界模式,以下簡稱為BCM模式(Boundary Current Mode),其相關電壓波形請參考圖5A至5H,各波形圖的縱軸標示電壓值(V),橫軸則表示時間;以下進一步說明該主動箝位電路60的電路動作。The
T0時段:在BCM模式下,該變壓器20一次側繞阻21的電壓V
P逐漸下降為0V,該第二電容C2兩端的電壓V
C2也降至0V,該寄生電容C3的電壓經由該二極體D快速放電至0V,使該箝位開關Q2的閘極電壓低於導通臨界電壓(Vgs-th),該箝位開關Q2即轉為關閉狀態(OFF),此時,該切換開關Q1的汲極-源極電壓V
Q1-DS隨同Vp由原本的高準位逐漸降至0V,在該切換開關Q1的閘極電壓V
Q1-G開始送出一高準位訊號,該切換開關Q1的控制模式亦達到零電壓切換(ZVS)。
T0 period: In the BCM mode, the voltage V P of the primary side winding 21 of the
T1時段:該切換開關Q1導通,即該切換開關Q1即將由原本的關閉狀態(OFF)轉換至導通狀態(ON),該變壓器20的一次側繞阻21的電壓Vp由0V上升至V
I。
Period T1: The switch Q1 is turned on, that is, the switch Q1 is about to switch from the original off state (OFF) to the on state (ON), and the voltage Vp of the primary winding 21 of the
T2時段:當該切換開關Q1的閘極電壓V
Q1-G降低至低準位時(即PWM信號的低準位),切換開關Q1成為關閉狀態(OFF)。因為該切換開關Q1從導通狀態轉為關閉狀態,因此在該變壓器20的一次側繞阻21會產生一反向電壓,因此圖5H所示的一次側繞阻電壓V
P顯示負值。如圖6所示,該電壓V
P經由該箝位開關Q2的本體二極體(body diode)往該第二電容C2及該第一電容C1充電,該第二電容C2及該第一電容C1充電在充電期間同時也會吸收該變壓器20漏感所產生的突波(spike),此時該第二電容C2及該第一電容C1會漸漸充電至穩態,該箝位開關Q2的汲極-源極電壓V
Q2-DS也因為本體二極體先導通,而在給驅動信號前先降下來至約該本體二極體的順向電壓(VF),如波形圖上標示S的位置。該第二電容C2在充電過程中亦會經由該電阻R對該寄生電容C3充電,當該寄生電容C3的電壓達到該箝位開關Q2的導通臨界電壓(Vgs-th),該箝位開關Q2即轉為導通狀態,實現零電壓切換(ZVS)以及吸收突波。其中,該電阻R作為一延遲(delay)元件,在充電時透過該電阻R以及該寄生電容C3決定的延遲時間,讓該箝位開關Q2的閘極電壓V
Q2-G在該箝位開關Q2的汲極-源極電壓V
Q2-DS降至約為本體二極體(body diode)的順向電壓(VF)時,才達到導通臨界電壓(Vgs-th),可讓該箝位開關Q2的驅動控制符合零電壓切換的要求。
Period T2: When the gate voltage V Q1-G of the switch Q1 decreases to a low level (ie, the low level of the PWM signal), the switch Q1 becomes closed (OFF). Because the switch Q1 changes from the on state to the off state, a reverse voltage is generated on the primary winding 21 of the
T3時段:在BCM模式下,該變壓器20一次側繞阻21的電壓V
P會漸漸降為零,該第二電容C2兩端的電壓V
C2也降至0V,該寄生電容C3的電壓經由該二極體D快速放電至0V(參考圖7所示),使該箝位開關Q2的閘極電壓V
Q2-G低於導通臨界電壓(Vgs-th),該箝位開關Q2即轉為關閉狀態(OFF),因為該箝位開關Q2可快速關閉,可降低該箝位開關Q2的切換損失,該切換開關Q1的汲極-源極電壓V
Q1-DS由原本的高準位漸降至0V,重複T0時段的動作。
Period T3: In the BCM mode, the voltage V P of the primary winding 21 of the
T4時段:此時該切換開關Q1導通,如圖7所示,重複T1時段的動作。T4 period: At this time, the switch Q1 is turned on, as shown in Figure 7, and the action of the T1 period is repeated.
在一較佳實施例中,為了使該箝位開關Q2導通時的導通電阻(R
DS)最小、損耗最低,該箝位開關Q2的閘極應維持在一較理想的驅動電壓值,約為一較佳值10V左右。該第一電容C1及該第二電容C2的電壓總和(V
C1+V
C2)約等於一次側繞阻21在釋能時的電壓(即V
P為反向電壓),此時的V
P電壓值與變壓器20的一次側繞阻21的匝數N
P、二次側繞阻22的匝數N
S有關,即V
P=[(N
S/N
P)×V
O]。在實際設計電源轉換裝置時,因為有不同的輸入/輸出需求,V
P受限於匝數比而無法接近該較佳值10V,本發明便可選用適當的該第二電容C2的值,令該第一電容C1與該第二電容C2分壓後,在該第二電容C2上得到接近該較佳值10V的電壓,即可使該箝位開關Q2的閘極具有較佳的驅動電壓值,達到較理想的驅動效果。
In a preferred embodiment, in order to minimize the on-resistance (R DS ) and the lowest loss when the clamp switch Q2 is turned on, the gate of the clamp switch Q2 should be maintained at a more ideal driving voltage value, which is about A better value is about 10V. The sum of the voltages of the first capacitor C1 and the second capacitor C2 (V C1 + V C2 ) is approximately equal to the voltage of the primary winding 21 when releasing energy (that is, VP is the reverse voltage). The VP voltage at this time The value is related to the number of turns N P of the primary side winding 21 and the number of turns N S of the secondary side winding 22 of the
綜上所述,本發明具備以下功效:To sum up, the present invention has the following effects:
1、該微控制器40即時監測該切換式電源轉換器10的輸入電壓V
I和回授電壓V
FB,該回授電壓V
FB可反映該負載量,該微控制器40實施多模式混合控制,所謂多模式即例如包含該變頻控制模式、該定頻控制模式和該跳週期控制模式,以實現效率曲線最佳化的電源轉換特性。
1. The
舉例而言,當本發明所連接的負載為滿載或重載時,該微控制器40執行該變頻控制模式。隨著該負載量變輕,輸出至該切換開關Q1的驅動信號S1的頻率越高,為避免該切換開關Q1在輕載、極輕載或空載時實施高頻切換所導致的高頻雜訊、切換損失和電路板線路上的電磁干擾等問題,該微控制器40可即時切換到該定頻控制模式,另於極輕載或空載時即時切換到該跳週期控制模式,致使該驅動信號S1的頻率維持在定值而不再提高,藉以最佳化電源轉換效率,有效改善如前所述高頻雜訊、切換損失和電路板線路上的電磁干擾等問題。For example, when the load connected to the present invention is fully loaded or heavily loaded, the
2、透過該主動箝位電路60的設置,其不需要額外增設驅動電路,而可根據該一次側繞組21的電壓V
P極性自己控制該箝位開關Q2的導通/關閉。該主動箝位電路60不僅可以達到吸收突波的功能,也可藉由適當挑選的該第二電容C2而使該箝位開關Q2的閘極獲得一理想的驅動電壓,在該箝位開關Q2導通時呈現較小的導通電阻(R
DS)並使損耗降低。
2. Through the arrangement of the
10:切換式電源轉換器 11:電源輸入端 12:電源輸出端 13:分壓電路 20:變壓器 21:一次側繞組 22:二次側繞組 30:輸出電路 40:微控制器 50:隔離回授電路 51:光耦合器 60:主動箝位電路 Q1:切換開關 Q2:箝位開關 C1:第一電容 C2:第二電容 C3:寄生電容 R:電阻 D:二極體 V I:輸入電壓 V O:輸出電壓 Vcc:電壓源 V FB:回授電壓 V LL:第一回授電壓門檻值 V SK:第二回授電壓門檻值 V P:一次側繞組的電壓 I O:輸出電流 S1:驅動信號 10: Switching power converter 11: Power input terminal 12: Power output terminal 13: Voltage dividing circuit 20: Transformer 21: Primary side winding 22: Secondary side winding 30: Output circuit 40: Microcontroller 50: Isolated return Feeding circuit 51: Optocoupler 60: Active clamping circuit Q1: Switch Q2: Clamp switch C1: First capacitor C2: Second capacitor C3: Parasitic capacitance R: Resistor D: Diode V I : Input voltage V O : Output voltage Vcc: Voltage source V FB : Feedback voltage V LL : First feedback voltage threshold V SK : Second feedback voltage threshold V P : Voltage of primary winding I O : Output current S1: Drive signal
圖1:本發明多模式混合控制的直流-直流電源轉換電路的實施例的電路示意圖(一)。 圖2:本發明多模式混合控制的直流-直流電源轉換電路的實施例的電路示意圖(二)。 圖3:本發明的控制方法的流程示意圖。 圖4A:本發明的實施例中,切換式電源轉換器的輸出電流I O波形圖。 圖4B:本發明的實施例中,回授電壓V FB的波形圖。 圖4C:本發明的實施例中,驅動信號S1的波形圖。 圖4D:本發明的實施例中,切換式電源轉換器的輸出電壓V O波形圖。 圖5A:本發明的實施例中,切換式電源轉換器的輸出電壓V O細部波形圖。 圖5B:本發明的實施例中,第二電容C2兩端的電壓V C2波形圖。 圖5C:本發明的實施例中,第一電容C1兩端的電壓V C1波形圖。 圖5D:本發明的實施例中,箝位開關Q2的汲極-源極之間的電壓V Q 2 -DS波形圖。 圖5E:本發明的實施例中,箝位開關Q2的閘極-源極之間的電壓V Q2-G波形圖。 圖5F:本發明的實施例中,切換開關Q1的汲極-源極之間的電壓V Q1-DS波形圖。 圖5G:本發明的實施例中,切換開關Q1的閘極電壓V Q1-G波形圖。 圖5H:本發明的實施例中,變壓器的一次側繞組兩端之間的電壓V P波形圖。 圖6:本發明的實施例中,切換開關Q1關閉、箝位開關Q2導通時的電路動作示意圖。 圖7:本發明的實施例中,切換開關Q1導通、箝位開關Q2關閉時的電路動作示意圖。 Figure 1: Circuit schematic diagram (1) of an embodiment of a multi-mode hybrid controlled DC-DC power conversion circuit of the present invention. Figure 2: Circuit schematic diagram (2) of an embodiment of the multi-mode hybrid controlled DC-DC power conversion circuit of the present invention. Figure 3: Schematic flow chart of the control method of the present invention. Figure 4A: In an embodiment of the present invention, the output current I O waveform diagram of the switching power converter. Figure 4B: Waveform diagram of feedback voltage V FB in the embodiment of the present invention. Figure 4C: Waveform diagram of the driving signal S1 in the embodiment of the present invention. Figure 4D: Waveform diagram of the output voltage V O of the switching power converter in an embodiment of the present invention. Figure 5A: Detailed waveform diagram of the output voltage V O of the switching power converter in an embodiment of the present invention. Figure 5B: In the embodiment of the present invention, the waveform diagram of voltage V C2 across the second capacitor C2. Figure 5C: In the embodiment of the present invention, the waveform diagram of voltage V C1 across the first capacitor C1. Figure 5D: In the embodiment of the present invention, the voltage V Q 2 -DS waveform diagram between the drain and the source of the clamp switch Q2. Figure 5E: In the embodiment of the present invention, the voltage V Q2-G waveform between the gate and the source of the clamp switch Q2. Figure 5F: In the embodiment of the present invention, the voltage V Q1-DS between the drain and the source of the switch Q1 is a waveform diagram. Figure 5G: In the embodiment of the present invention, the gate voltage V Q1-G waveform diagram of the switch Q1. Figure 5H: In the embodiment of the present invention, the voltage V P waveform between the two ends of the primary winding of the transformer. Figure 6: In the embodiment of the present invention, the circuit operation diagram is shown when the switch Q1 is turned off and the clamp switch Q2 is turned on. Figure 7 is a schematic diagram of the circuit operation when the switch Q1 is turned on and the clamp switch Q2 is turned off in the embodiment of the present invention.
10:切換式電源轉換器 11:電源輸入端 12:電源輸出端 13:分壓電路 20:變壓器 21:一次側繞組 22:二次側繞組 30:輸出電路 40:微控制器 50:隔離回授電路 60:主動箝位電路 V I:輸入電壓 V O:輸出電壓 V FB:回授電壓 V P:一次側繞組的電壓 I O:輸出電流 S1:驅動信號 Q1:切換開關 10: Switching power converter 11: Power input terminal 12: Power output terminal 13: Voltage dividing circuit 20: Transformer 21: Primary side winding 22: Secondary side winding 30: Output circuit 40: Microcontroller 50: Isolated return Feed circuit 60: Active clamping circuit V I : Input voltage V O : Output voltage V FB : Feedback voltage V P : Voltage of primary winding I O : Output current S1: Drive signal Q1: Switch
Claims (10)
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