TWI446695B - Isolation conversion circuits and methods, and lamps using isolated conversion circuits - Google Patents
Isolation conversion circuits and methods, and lamps using isolated conversion circuits Download PDFInfo
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Description
本發明涉及電子電路,更具體地說,本發明涉及用於發光元件的電子電路。This invention relates to electronic circuits and, more particularly, to electronic circuits for light emitting elements.
發光二極體(Light Emitting Diode,LED)由於無污染、長壽命、耐振動等諸多優點,在照明領域備受關注,並且已經得到了一定的應用。Light Emitting Diode (LED) has attracted much attention in the field of lighting due to its many advantages such as no pollution, long life and vibration resistance, and it has been applied.
LED的發光亮度通常由流過其上的平均電流決定,因此精確控制流過LED的平均電流尤為重要。在現有LED電子電路中,通常採用一與LED串聯的採樣電阻採樣流過LED的電流,通過電路後續控制器的控制,實現精確控制流過LED的平均電流。如圖1所示的隔離變換電路100,為一典型採用馳回拓撲的LED電子電路。隔離變換電路100從牆上插座(電網)獲得交流輸入電壓,通過一整流橋將該交流電壓轉換為一直流電壓,並通過馳回電路將該直流電壓轉換為所需的直流供電電壓。The brightness of an LED is usually determined by the average current flowing through it, so it is especially important to accurately control the average current flowing through the LED. In the existing LED electronic circuit, a sampling resistor connected in series with the LED is generally used to sample the current flowing through the LED, and the average current flowing through the LED is accurately controlled by the control of the subsequent controller of the circuit. The isolation conversion circuit 100 shown in FIG. 1 is an LED electronic circuit that typically uses a reversing topology. The isolation conversion circuit 100 obtains an AC input voltage from a wall outlet (grid), converts the AC voltage into a DC voltage through a rectifier bridge, and converts the DC voltage to a desired DC supply voltage through a flyback circuit.
具體來說,隔離變換電路100包括整流橋101、輸入電容CIN 、變壓器T、主開關M、第一採樣電阻RS 、二極體D、輸出電容CO 、負載採樣電阻R、控制器102、零交叉檢測器103以及隔離回饋電路110。其中變壓器T為儲能元件,包括原邊繞組T1 、副邊繞組T2 和第三繞組T3 。整流橋101接收交流輸入電壓VIN ,並將其轉換成一不控直流電壓。輸入電容CIN 並聯至整流橋101的兩端,即輸入電容CIN 的一端耦接至變壓器T原邊繞組T1 的一端,另一端接原邊參考接地。變壓器T的原邊繞組T1 、主開關M、二極體D、變壓器T的次級繞組T2 以及輸出電容CO 的耦接方式構成典型馳回拓撲。其耦接方式是本領域技術人員的熟知方式,這裏不再詳述。第一採樣電阻RS 與主開關M串聯耦接、負載採樣電阻R與LED串聯耦接。隔離回饋電路110的輸入端耦接至負載採樣電阻R和LED的串聯耦接點,其輸出端耦接至控制器102的一個輸入端。零交叉檢測器103的輸入端耦接至第三繞組T3 的一端,其輸出端耦接至控制器102的另一個輸入端。第三繞組T3 的另一端耦接至接地。控制器102的第三輸入端耦接至第一採樣電阻RS 和主開關的串聯耦接點,以及;控制器102的輸出端耦接至主開關M的控制端。Specifically, the isolation conversion circuit 100 includes a rectifier bridge 101, an input capacitor C IN , a transformer T, a main switch M, a first sampling resistor R S , a diode D, an output capacitor C O , a load sampling resistor R, and a controller 102. The zero crossing detector 103 and the isolation feedback circuit 110. The transformer T is an energy storage component, and includes a primary winding T 1 , a secondary winding T 2 and a third winding T 3 . The rectifier bridge 101 receives the AC input voltage V IN and converts it into an uncontrolled DC voltage. The input capacitor C IN is connected in parallel to both ends of the rectifier bridge 101, that is, one end of the input capacitor C IN is coupled to one end of the primary winding T 1 of the transformer T, and the other end is connected to the ground reference ground. The coupling of the primary winding T 1 of the transformer T, the main switch M, the diode D, the secondary winding T 2 of the transformer T, and the output capacitor C O constitutes a typical reversing topology. The manner of coupling is well known to those skilled in the art and will not be described in detail herein. The first sampling resistor R S is coupled in series with the main switch M, and the load sampling resistor R is coupled in series with the LED. The input end of the isolation feedback circuit 110 is coupled to the series coupling point of the load sampling resistor R and the LED, and the output end is coupled to an input end of the controller 102. The input of the zero-crossing detector 103 is coupled to one end of the third winding T 3 , and the output of the zero-crossing detector 103 is coupled to the other input of the controller 102 . The other end of the third winding T 3 is coupled to ground. The third input end of the controller 102 is coupled to the series coupling point of the first sampling resistor R S and the main switch, and the output end of the controller 102 is coupled to the control end of the main switch M.
因為負載採樣電阻R和LED串聯耦接,因此,負載採樣電阻R兩端電壓反映了流過LED的電流。而第一採樣電阻RS 和主開關M串聯耦接,因此,第一採樣電阻RS 兩端電壓反映了流過主開關M的電流,即第一採樣電阻RS 兩端電壓為電流採樣信號Isense 。Since the load sampling resistor R and the LED are coupled in series, the voltage across the load sampling resistor R reflects the current flowing through the LED. The first sampling resistor R S and the main switch M are coupled in series. Therefore, the voltage across the first sampling resistor R S reflects the current flowing through the main switch M, that is, the voltage across the first sampling resistor R S is a current sampling signal. I sense .
當隔離變換電路100運行時,流過LED的電流通過負載採樣電阻R和隔離回饋電路110被輸送至控制器102,流過主開關M的電流通過第一採樣電阻RS 被輸送至控制器102。經過零交叉檢測器103的共同作用,流過LED的平均電流可得到控制。因其控制方式為本領域技術人員所熟知,為敍述簡明,這裏不再詳述。When the isolation conversion circuit 100 is operated, the current flowing through the LED is sent to the controller 102 through the load sampling resistor R and the isolation feedback circuit 110, and the current flowing through the main switch M is sent to the controller 102 through the first sampling resistor R S . . Through the interaction of the zero crossing detector 103, the average current flowing through the LED can be controlled. Since the manner of control is well known to those skilled in the art, for brevity of description, it will not be described in detail herein.
然而,這種控制方式需要額外的負載採樣電阻來採樣流過LED的電流,增大了損耗,降低了效率。而隨著電子技術的發展和環保要求的提高,效率已成為電源變換器至關重要的設計因素。並且這種控制方式需要採用隔離回饋電路來回饋負載的狀態,使電路結構複雜化。However, this type of control requires an additional load sampling resistor to sample the current flowing through the LED, increasing losses and reducing efficiency. With the development of electronic technology and the improvement of environmental protection requirements, efficiency has become a crucial design factor for power converters. And this control method needs to use the isolation feedback circuit to feed back the load state, which complicates the circuit structure.
因此,有必要提出一種無需負載採樣電阻和隔離回饋電路即可實現對諸如LED之類發光元件的電流採樣,從而控制其平均電流的電路和方法。Therefore, it is necessary to propose a circuit and method for controlling current sampling of a light-emitting element such as an LED without using a load sampling resistor and an isolation feedback circuit to control the average current.
因此,本發明的目的在於解決傳統隔離變換電路需要負載採樣電阻採樣輸出電流,需要隔離回饋電路回饋所採樣的輸出電流,從而造成電路結構複雜化和電路低效率的問題。Therefore, the object of the present invention is to solve the problem that the conventional isolation conversion circuit needs the load sampling resistor to sample the output current, and the isolation feedback circuit needs to feed back the sampled output current, thereby causing the circuit structure to be complicated and the circuit low efficiency.
基於上述目的,本發明提出了一種電路,包括:變壓器,所述變壓器包括原邊繞組、副邊繞組和第三繞組,所述原邊繞組用以接收所述隔離變換電路的輸入信號,所述副邊繞組用以提供驅動信號至被驅動元件;主開關,耦接至所述原邊繞組,根據開關驅動信號被導通和斷開;輸出電流計算器,根據所述主開關導通期間流過所述主開關的電流和所述開關驅動信號,計算流過所述被驅動元件的電流的等效值;零交叉檢測器,根據所述第三繞組兩端的電壓,提供零交叉檢測信號;控制器,根據所述等效值、零交叉檢測信號、所述主開關導通期間流過所述主開關的電流和一參考信號,提供所述開關驅動信號。Based on the above object, the present invention provides a circuit comprising: a transformer comprising a primary winding, a secondary winding and a third winding, the primary winding for receiving an input signal of the isolation conversion circuit, a secondary winding for providing a driving signal to the driven component; a main switch coupled to the primary winding, being turned on and off according to the switching driving signal; and an output current calculator flowing through the main switch during the conduction period a current of the main switch and the switch drive signal, calculating an equivalent value of a current flowing through the driven component; a zero-crossing detector, providing a zero-cross detection signal according to a voltage across the third winding; And providing the switch drive signal according to the equivalent value, a zero-cross detection signal, a current flowing through the main switch during the on-time of the main switch, and a reference signal.
基於上述目的,本發明還提出了一種電路,包括:變壓器,所述變壓器包括原邊繞組和副邊繞組,所述原邊繞組用以接收所述隔離變換電路的輸入信號,所述副邊繞組用以提供驅動信號至被驅動元件;主開關,耦接至所述原邊繞組,根據開關驅動信號被導通和斷開;零交叉檢測電容,一端耦接至所述原邊繞組和所述主開關的串聯耦接點,另一端耦接至零交叉檢測器的輸入端;輸出電流計算器,根據所述主開關導通期間流過所述主開關的電流和所述開關驅動信號,計算流過被驅動元件的電流的等效值;所述零交叉檢測器,根據流過所述零交叉檢測電容的電流,提供零交叉檢測信號;控制器,根據所述等效值、零交叉檢測信號、所述主開關導通期間流過所述主開關的電流和一參考信號,提供所述開關驅動信號。Based on the above object, the present invention also provides a circuit comprising: a transformer comprising a primary winding and a secondary winding, the primary winding for receiving an input signal of the isolation conversion circuit, the secondary winding Providing a driving signal to the driven component; a main switch coupled to the primary winding, being turned on and off according to the switch driving signal; and a zero-crossing detecting capacitor coupled to the primary winding and the main end at one end a series coupling point of the switch, the other end being coupled to the input end of the zero-crossing detector; an output current calculator calculating the flow according to the current flowing through the main switch and the switch driving signal during the main switch being turned on An equivalent value of the current of the driven component; the zero-crossing detector provides a zero-crossing detection signal according to a current flowing through the zero-crossing detection capacitor; the controller, according to the equivalent value, the zero-crossing detection signal, The current flowing through the main switch and a reference signal during the main switch being turned on provide the switch drive signal.
基於上述目的,本發明還提出了一種燈具。該燈具使用本發明的上述電路。Based on the above object, the present invention also proposes a lamp. The luminaire uses the above described circuit of the present invention.
基於上述目的,本發明還提出了一種用於一電路的方法,所述電路包括:變壓器,所述變壓器包括原邊繞組、副邊繞組和第三繞組,所述原邊繞組用以接收所述隔離變換電路的輸入信號,所述副邊繞組用以提供驅動信號至被驅動元件;和主開關,耦接至所述原邊繞組,根據開關驅動信號被導通和斷開,所述方法包括步驟:根據所述主開關導通期間流過所述主開關的電流和所述開關驅動信號,計算流過所述被驅動元件的電流的等效值;根據所述第三繞組兩端的電壓,提供零交叉檢測信號;根據所述等效值、零交叉檢測信號、所述主開關導通期間流過所述主開關的電流和一參考信號,提供所述開關驅動信號。Based on the above object, the present invention also provides a method for a circuit, the circuit comprising: a transformer comprising a primary winding, a secondary winding and a third winding, the primary winding for receiving the An input signal of the isolation conversion circuit, the secondary winding is configured to provide a driving signal to the driven component; and a main switch coupled to the primary winding and turned on and off according to the switching driving signal, the method comprising the steps : calculating an equivalent value of a current flowing through the driven element according to a current flowing through the main switch during the conduction of the main switch and the switch driving signal; providing zero according to a voltage across the third winding And a cross-detection signal; the switch drive signal is provided according to the equivalent value, a zero-cross detection signal, a current flowing through the main switch during the on-time of the main switch, and a reference signal.
本發明提出的上述電路、方法和使用該電路的燈具,無需負載採樣電阻和隔離回饋電路即可採樣輸出電流,從而簡化了電路結構。The above-mentioned circuit, method and lamp using the same can sample the output current without load sampling resistor and isolation feedback circuit, thereby simplifying the circuit structure.
如圖2所示,為根據本發明一個實施例的隔離變換電路200。此實施例用於AC-DC變換電路中。但是本領域的技術人員應該意識到,隔離變換電路可以用於其他電路,如DC-DC變換電路。隔離變換電路200與隔離變換電路100相同部分採用相同的附圖標記,與圖1所示的隔離變換電路100相比,隔離變換電路200的不同之處在於,隔離變換電路200無需負載採樣電阻和隔離回饋電路,而是用輸出電流計算器104實現對LED負載的電流採樣及回饋。其中輸出電流計算器104輸出的等效輸出電流IEQ 反映了副邊電流。As shown in FIG. 2, there is an isolation conversion circuit 200 in accordance with one embodiment of the present invention. This embodiment is used in an AC-DC conversion circuit. However, those skilled in the art will appreciate that the isolation conversion circuit can be used in other circuits, such as DC-DC conversion circuits. The same portion of the isolation conversion circuit 200 and the isolation conversion circuit 100 are given the same reference numerals. The isolation conversion circuit 200 is different from the isolation conversion circuit 100 shown in FIG. 1 in that the isolation conversion circuit 200 does not require a load sampling resistor and The feedback circuit is isolated, and the current sampling and feedback of the LED load is implemented by the output current calculator 104. The equivalent output current I EQ output by the output current calculator 104 reflects the secondary current.
具體來說,隔離變換電路200包括整流橋101、輸入電容CIN 、變壓器T(包括原邊繞組T1 、副邊繞組T2 和第三繞組T3 )、主開關M、第一採樣電阻RS 、二極體D、輸出電容CO 、LED。其耦接方式與隔離變換電路100相同,為敍述簡明,這裏不再詳述。隔離變換電路200還包括零交叉檢測器103,其輸入端耦接至第三繞組T3 的一端,以檢測第三繞組T3 兩端電壓VT3 ,並根據第三繞組T3 兩端電壓VT3 的零交叉情況,提供零交叉檢測信號ZDET 至控制器102的第一輸入端;輸出電流計算器104,其第一輸入端耦接至第一採樣電阻RS 和主開關M的串聯耦接點,以接收電流採樣信號Isense ,其第二輸入端耦接至控制器102的輸出端,以接收開關驅動信號CTR ,並根據電流採樣信號Isense 和開關驅動信號CTR ,提供等效輸出電流IEQ 至控制器102;控制器102,其第一輸入端耦接至零交叉檢測器103,以接收零交叉檢測信號ZDET ,其第二輸入端耦接至輸出電流計算器104的輸出端,以接收等效輸出電流IEQ ,其第三輸入端耦接至第一採樣電阻RS 和主開關M的串聯耦接點,以接收電流採樣信號Isense ,其第四輸入端接收參考信號REF ,從而根據等效輸出電流IEQ 、零交叉檢測信號ZDET 、電流採樣信號Isense 和參考信號REF ,提供開關驅動信號CTR 至輸出電流計算器104和主開關M的控制端,以控制輸出電流計算器104和主開關M的導通與斷開。Specifically, the isolation conversion circuit 200 includes a rectifier bridge 101, an input capacitor C IN , a transformer T (including a primary winding T 1 , a secondary winding T 2 , and a third winding T 3 ), a main switch M, and a first sampling resistor R. S , diode D, output capacitor C O , LED. The coupling manner is the same as that of the isolation conversion circuit 100, and the description is concise and will not be described in detail herein. Insulating converter circuit 200 further includes a zero crossing detector 103, an input terminal coupled to the third winding end T 3, T 3 to detect a third voltage V across winding T3, and a third voltage V across the winding T 3 The zero-crossing condition of T3 provides a zero-crossing detection signal Z DET to the first input of the controller 102; the output current calculator 104 has a first input coupled to the series coupling of the first sampling resistor R S and the main switch M a contact to receive the current sampling signal I sense , the second input end coupled to the output end of the controller 102 to receive the switch drive signal C TR , and to provide according to the current sampling signal I sense and the switch drive signal C TR The output current I EQ is output to the controller 102. The first input end of the controller 102 is coupled to the zero-crossing detector 103 to receive the zero-crossing detection signal Z DET , and the second input end is coupled to the output current calculator 104 . output terminal to receive the equivalent output current I EQ, which third input terminal coupled to the first sampling resistor coupled in series point of R S and M of the main switch to receive the current sense signal I sense, its fourth input receiving a reference signal R EF, so that the root Equivalent output current I EQ, zero-cross detection signal Z DET, I sense a current sensing signal and the reference signal R EF, provides a control terminal of the switch driving signal C TR calculator 104 and to the output current of the main switch M to control the output current calculating The switch 104 and the main switch M are turned on and off.
在一個實施例中,二極體D可用整流管代替。主開關M可以是任何可控半導體開關器件,例如金屬氧化物半導體場效應電晶體(MOSFET)、絕緣閘雙極電晶體(IGBT)等。In one embodiment, the diode D can be replaced with a rectifier. The main switch M can be any controllable semiconductor switching device such as a metal oxide semiconductor field effect transistor (MOSFET), an insulated gate bipolar transistor (IGBT), or the like.
在電路實際應用中,現有技術的隔離變換電路100中的隔離回饋電路110通常需要多個週邊分立元件實現。而本實施例的隔離變換電路200無需隔離回饋電路,因此,隔離變換電路200相對隔離變換電路100不僅降低了損耗,還簡化了週邊電路。下面闡述隔離變換電路200的工作原理。In circuit practical applications, the isolation feedback circuit 110 of the prior art isolation conversion circuit 100 typically requires multiple peripheral discrete components to be implemented. However, the isolation conversion circuit 200 of the present embodiment does not need to isolate the feedback circuit. Therefore, the isolation conversion circuit 200 not only reduces the loss but also simplifies the peripheral circuit with respect to the isolation conversion circuit 100. The operation of the isolation conversion circuit 200 will be described below.
電路200運行時,當控制器102提供一高電平開關驅動信號CTR 給主開關M的控制端,主開關M被閉合導通,交流輸入電壓VIN 經整流橋101、輸入電容CIN 、原邊繞組T1 、主開關M、第一採樣電阻RS 至接地。流過主開關M的電流IM 在原邊繞組T1 激磁電感的作用下,線性上升。隨之第一採樣電阻RS 兩端電壓也線性上升。當流過主開關M的電流上升到設定的峰值電流IPK 時,控制器102輸出的開關驅動信號CTR 變低。相應地,主開關M被斷開。此時,第三繞組T3 兩端電壓極性為上正下負,即電壓VT3 為正,副邊繞組T2 兩端電壓極性也為上正下負,二極體D導通,流過二極體D的電流ID 開始線性下降。若變壓器T的原邊繞組T1 和副邊繞組T2 的變壓器匝比為n:1,則二極體D的峰值電流為n×IPK 。即流過二極體D的電流ID 從n×IPK 開始線性下降。當其下降至零時,原邊繞組T1 的激磁電感和主開關M的寄生電容(未圖示)產生振盪。該振盪第一次零交叉,即電壓VT3 第一次為零時,零交叉檢測器103檢測到該零交叉現象,輸出相應的零交叉檢測信號ZDET 至控制器102。控制器102接收該零交叉檢測信號ZDET ,輸出高電平開關驅動信號CTR ,從而將主開關M閉合導通。隔離變換電路200進入一個新週期,如前所述工作。When the circuit 200 is running, when the controller 102 provides a high level switch drive signal C TR to the control terminal of the main switch M, the main switch M is closed and turned on, and the AC input voltage V IN is passed through the rectifier bridge 101, the input capacitor C IN , and the original The side winding T 1 , the main switch M, and the first sampling resistor R S are grounded. The current I M flowing through the main switch M rises linearly under the action of the magnetizing inductance of the primary winding T 1 . Accordingly, the voltage across the first sampling resistor R S also rises linearly. When the current flowing through the main switch M rises to the set peak current I PK , the switch drive signal C TR outputted by the controller 102 goes low. Accordingly, the main switch M is turned off. At this time, the polarity of the voltage across the third winding T 3 is positive and negative, that is, the voltage V T3 is positive, and the voltage polarity across the secondary winding T 2 is also positive and negative, and the diode D is turned on and flows through two. The current I D of the polar body D begins to decrease linearly. If the transformer turns ratio of the primary winding T 1 and the secondary winding T 2 of the transformer T is n: 1, the peak current of the diode D is n × I PK . That is, the current I D flowing through the diode D linearly decreases from n × I PK . When it falls to zero, the magnetizing inductance of the primary winding T 1 and the parasitic capacitance (not shown) of the main switch M oscillate. The first zero crossing of the oscillation, that is, when the voltage V T3 is zero for the first time, the zero crossing detector 103 detects the zero crossing phenomenon and outputs a corresponding zero crossing detection signal Z DET to the controller 102. The controller 102 receives the zero-cross detection signal Z DET and outputs a high-level switch drive signal C TR to turn the main switch M off. The isolation converter circuit 200 enters a new cycle and operates as previously described.
圖3示出根據本發明的輸出電流計算器的工作原理流程圖300,即計算隔離變換電路副邊輸出電流的方法。如圖3所示,該方法包括:步驟301,開始,即週期導通和斷開隔離變換電路原邊繞組的主開關M;步驟302,判斷主開關M是否為導通狀態,若主開關M為導通狀態,進入步驟303,採樣流過主開關M的電流,等效輸出電流IEQ 置零;若主開關M為斷開狀態,進入步驟304,保持主開關M的峰值電流並作為主開關M斷開時間間隔內的等效輸出電流IEQ ;步驟305,提供等效輸出電流IEQ 。也就是說,計算隔離變換電路副邊輸出電流的方法包括:週期導通和斷開隔離變換電路原邊繞組的主開關M;在主開關M被導通的時間間隔內,採樣流過主開關M的電流,等效輸出電流IEQ 置零;在主開關M被斷開的時間間隔內,保持主開關M的峰值電流並作為主開關M斷開時間間隔內的等效輸出電流IEQ 。Figure 3 is a flow chart 300 showing the operation of the output current calculator in accordance with the present invention, i.e., a method of calculating the output current of the secondary side of the isolation converter circuit. As shown in FIG. 3, the method includes: Step 301, starting, that is, periodically turning on and off the main switch M of the primary winding of the isolation conversion circuit; Step 302, determining whether the main switch M is in an on state, if the main switch M is conducting. State, proceeding to step 303, sampling the current flowing through the main switch M, the equivalent output current I EQ is set to zero; if the main switch M is in the off state, proceeding to step 304, maintaining the peak current of the main switch M and acting as the main switch M The equivalent output current I EQ during the on time interval; step 305, provides the equivalent output current I EQ . That is, the method for calculating the output current of the secondary side of the isolation conversion circuit includes: periodically turning on and off the main switch M of the primary winding of the isolation conversion circuit; sampling the flow through the main switch M during the time interval when the main switch M is turned on The current, the equivalent output current I EQ is set to zero; during the time interval in which the main switch M is turned off, the peak current of the main switch M is maintained and serves as the equivalent output current I EQ in the main switch M off time interval.
圖4示出根據本發明一個實施例採用圖3所示計算隔離變換電路副邊輸出電流方法的隔離變換電路400。隔離變換電路400的電路模組與隔離變換電路200的相同部分採用相同的附圖標記。為敍述簡明,這裏不再詳述相同部分的電路耦接方式。如圖4所示,輸出電流計算器104包括:第一開關S1 ,一端耦接至第一採樣電阻RS 和主開關M的串聯耦接點,以接收電流採樣信號Isense ;第一電容C1 ,耦接在第一開關S1 的另一端和原邊參考接地之間;第二開關S2 ,一端耦接至第一開關S1 和第一電容C1 的耦接點;第三開關S3 ,耦接在第二開關S2 的另一端和原邊參考接地之間。第一開關S1 、第二開關S2 和第三開關S3 的控制端耦接至控制器102的輸出端,並且當開關驅動信號CTR 為高電平時,第一開關S1 和第三開關S3 閉合導通,第二開關S3 斷開;當開關驅動信號CTR 為低電平時,第一開關S1 和第三開關S3 斷開,第二開關S2 閉合導通。4 illustrates an isolation conversion circuit 400 employing the method of calculating the secondary side output current of the isolation conversion circuit of FIG. 3, in accordance with one embodiment of the present invention. The circuit module of the isolation conversion circuit 400 and the same portion of the isolation conversion circuit 200 are given the same reference numerals. For the sake of brevity, the circuit coupling method of the same part will not be described in detail herein. As shown in FIG. 4, the output current calculator 104 includes: a first switch S 1 , one end coupled to the series coupling point of the first sampling resistor R S and the main switch M to receive the current sampling signal I sense ; the first capacitor C 1, a first switch coupled between the other end of the primary side S 1 and the ground reference; a second switch S 2, a first end coupled to a switch S 1 is a first capacitor C and a coupling point; a third The switch S 3 is coupled between the other end of the second switch S 2 and the primary side reference ground. The control ends of the first switch S 1 , the second switch S 2 and the third switch S 3 are coupled to the output of the controller 102, and when the switch drive signal C TR is at a high level, the first switch S 1 and the third closing the switch S 3 is turned on, turned off the second switch S 3; when the switch drive signal C TR is low, the first switch S 1 is turned off and the third switch S 3, S 2 is closed the second switch is turned on.
假定開始時開關驅動信號CTR 為高電平,則第一開關S1 和第三開關S3 被閉合導通,第二開關S2 被斷開,同時該高電平的開關驅動信號CTR 將主開關M閉合導通。此時等效輸出電流IEQ 被置零,即IEQ =0。如前所述,交流輸入電壓VIN 經整流橋101、輸入電容CIN 、原邊繞組T1 、主開關M、第一採樣電阻RS 至接地。流過主開關M的電流在原邊繞組T1 激磁電感的作用下,線性上升,第一採樣電阻RS 兩端電壓,即電流採樣信號Isense 也線性上升。而此時由於第一開關S1 閉合導通,因此,電容C1 兩端電壓即為電流採樣信號Isense 。也就是說,在該段時間內,電容C1 兩端電壓線性上升。當其上升到設定的峰值電流IPK 時,開關驅動信號CTR 變為低電平。相應地,第一開關S1 和第三開關S3 被斷開,第二開關S2 被閉合導通;主開關M被斷開。此時,等效輸出電流IEQ 為電容C1 兩端電壓,即IEQ =IPK ×RRS ,其中RRS 為第一採樣電阻RS 的電阻值。When assuming the switch drive start signal C TR is high, and the first switch S 1 is closed the third switch S 3 is turned on, the second switch S 2 is turned off, while the high level of the switch drive signal C TR The main switch M is closed and turned on. At this time, the equivalent output current I EQ is set to zero, that is, I EQ =0. As described above, the AC input voltage V IN is passed through the rectifier bridge 101, the input capacitor C IN , the primary winding T 1 , the main switch M, and the first sampling resistor R S to ground. The current flowing through the main switch M rises linearly under the action of the exciting inductance of the primary winding T 1 , and the voltage across the first sampling resistor R S , that is, the current sampling signal I sense also rises linearly. At this time, since the first switch S 1 is turned on, the voltage across the capacitor C 1 is the current sampling signal I sense . That is to say, during this period of time, the voltage across the capacitor C 1 rises linearly. When it rises to the set peak current I PK , the switch drive signal C TR becomes a low level. Accordingly, the first switch S 1 and the third switch S 3 are turned off, the second switch S 2 is turned off; the main switch M is turned off. At this time, the equivalent output current I EQ is the voltage across the capacitor C 1 , that is, I EQ =I PK ×R RS , where R RS is the resistance value of the first sampling resistor R S .
開關驅動信號CTR 、流經主開關M的電流IM 、流經二極體D的電流ID ,第三繞組T3 的電壓VT3 以及等效輸出電流IEQ 的波形如圖5所示。The waveforms of the switch drive signal C TR , the current I M flowing through the main switch M, the current I D flowing through the diode D , the voltage V T3 of the third winding T 3 , and the equivalent output current I EQ are as shown in FIG. 5 . .
由圖5可得,等效輸出電流IEQ 在一個開關週期內的平均值為As can be seen from Figure 5, the average value of the equivalent output current I EQ in one switching cycle is
流經二極體的電流ID 在一個週期內的平均值ID(AVE) 為The average value I D (AVE) of the current I D flowing through the diode in one cycle is
其中TON 為一個週期內主開關M的閉合導通時間,TOFF 為一個週期內主開關M的斷開時間。Where T ON is the closed on-time of the main switch M in one cycle, and T OFF is the off-time of the main switch M in one cycle.
由上述等式(1)和等式(2)可得,Obtained by the above equations (1) and (2),
由等式(3)可以看到,當第一採樣電阻RS 的阻值RRS 給定後,等效輸出電流IEQ 的平均值與流經二極體D的電流ID 的平均值成正比。而由於流過輸出電容CO 的直流電流為零,因此,流經二極體D的電流ID 的平均值等於流經LED的平均電流。因此,等效輸出電流IEQ 的平均值與流經LED的平均電流成正比,等效輸出電流IEQ 為流經LED的平均電流即輸出電流的等效值。輸出電流計算器104實現了對副邊LED的原邊採樣。It can be seen from equation (3) that when the resistance value R RS of the first sampling resistor R S is given, the average value of the equivalent output current I EQ and the average value of the current I D flowing through the diode D become Just proportional. Since the direct current flowing through the output capacitor C O is zero, the average value of the current I D flowing through the diode D is equal to the average current flowing through the LED. Thus, the equivalent output current proportional to the average value of the average current flowing through the LED I EQ, the equivalent output current I EQ is the average current through the LED output that is the equivalent value of the current. The output current calculator 104 implements sampling of the primary side of the secondary side LED.
圖6示出根據本發明一個實施例的隔離變換電路600。隔離變換電路600的電路模組與隔離變換電路200的相同部分採用相同的附圖標記。與隔離變換電路200不同的是,隔離變換電路600具體示出了控制器102的一種實現結構。然而本領域的技術人員應該認識到,控制器102的電路結構不限於圖6所示的電路結構。如圖6所示,控制器102包括:誤差放大器UA ,其一輸入端(反相輸入端)耦接至輸出電流計算器104的輸出端,以接收輸出電流計算器104提供的等效輸出電流IEQ ,其另一輸入端(同相輸入端)接收參考信號REF ,以根據等效輸出電流IEQ 和參考信號REF 提供誤差放大信號,即設定的峰值電流IPK 至比較器UC 的反相輸入端;比較器UC ,其一輸入端(反相輸入端)耦接至誤差放大器UA 的輸出端,以接收誤差放大信號,其另一輸入端(同相輸入端)耦接至第一採樣電阻RS 和主開關M的串聯耦接點,以接收電流採樣信號Isense ,以根據誤差放大信號和電流採樣信號Isense 提供比較信號SCMP 至邏輯電路;邏輯電路,一端接收比較信號SCMP ,另一端接收零交叉檢測信號ZDET ,以根據比較信號SCMP 和零交叉檢測信號ZDET 提供開關驅動信號CTR 來控制主開關M的閉合導通與斷開。在本實施例中,邏輯電路為RS觸發器,其置位端R耦接至比較器UC 的輸出端,以接收比較信號SCMP ;其復位端耦接至零交叉檢測器103的輸出端,以接收零交叉檢測信號ZDET ;其輸出端Q耦接至主開關M的控制端,以提供開關驅動信號CTR 。在本實施例中,誤差放大器UA 的輸出端和原邊參考接地之間還耦接一補償電路ZC 。在一個實施例中,補償電路ZC 可以是電容補償網路,也可以是電阻、電容補償網路,其結構為本領域技術人員所熟知。為敍述簡明,這裏不再詳述補償電路ZC 的電路結構。FIG. 6 shows an isolation conversion circuit 600 in accordance with one embodiment of the present invention. The circuit module of the isolation conversion circuit 600 and the same portion of the isolation conversion circuit 200 are given the same reference numerals. Unlike the isolation conversion circuit 200, the isolation conversion circuit 600 specifically illustrates an implementation structure of the controller 102. However, those skilled in the art will recognize that the circuit configuration of the controller 102 is not limited to the circuit configuration shown in FIG. As shown in FIG. 6, the controller 102 includes an error amplifier U A having an input (inverting input) coupled to the output of the output current calculator 104 to receive an equivalent output provided by the output current calculator 104. The current I EQ , the other input (non-inverting input) receives the reference signal R EF to provide an error amplification signal according to the equivalent output current I EQ and the reference signal R EF , ie the set peak current I PK to the comparator U C Inverting input terminal; comparator U C , an input terminal (inverting input terminal) coupled to the output end of the error amplifier U A to receive the error amplification signal, and the other input end (in-phase input terminal) coupled a series coupling point of the first sampling resistor R S and the main switch M to receive the current sampling signal I sense to provide a comparison signal S CMP to the logic circuit according to the error amplification signal and the current sampling signal I sense ; the logic circuit receives at one end the comparison signal S CMP, and the other end receiving a zero cross detection signal Z DET, to provide a switch in accordance with the comparison signal S CMP and the zero-cross detection signal Z DET driving signal C TR to control the main switch M is closed and is turned OFF. In this embodiment, the logic circuit is an RS flip-flop, and the set terminal R is coupled to the output end of the comparator U C to receive the comparison signal S CMP ; the reset end is coupled to the output end of the zero-cross detector 103 . To receive the zero-cross detection signal Z DET ; its output terminal Q is coupled to the control terminal of the main switch M to provide the switch drive signal C TR . In this embodiment, a compensation circuit Z C is coupled between the output of the error amplifier U A and the primary reference ground. In one embodiment, the compensation circuit Z C is the capacitance of the compensation network may be, may be resistance, capacitance compensation network, the structure of those skilled in the art. For the sake of brevity, the circuit structure of the compensation circuit Z C will not be described in detail herein.
如圖6所示,由於誤差放大器UA 的該耦接方式,設定的峰值電流IPK ,即誤差放大信號由等效輸出電流IEQ 和參考信號REF 決定。而由等式(3)可知,等效輸出電流IEQ 與流經LED的平均電流成正比,並且參考信號REF 為給定信號,因此,設定的峰值電流IPK 由流經LED的平均電流決定。在主開關M被閉合導通的時間段內,當採樣電流Isense 達到設定的峰值電流IPK 時,比較器輸出的比較信號SCMP 變高,進而復位RS觸發器的輸出,開關驅動信號CTR 被重設為低,從而將主開關M斷開。因此,流經LED的平均電流決定了設定的峰值電流IPK ,也即設定了主開關M被控制斷開的時間點。當主開關M被斷開後,當零交叉檢測器檢測到第三繞組T3 的電壓VT3 為零時,輸出高電平的零交叉檢測信號ZDET ,從而置位元RS觸發器的輸出,使得開關驅動信號CTR 變高。相應地,主開門M被閉合導通,隔離變換電路600進入一個新的工作週期。As shown in FIG. 6, due to the coupling mode of the error amplifier U A , the set peak current I PK , that is, the error amplification signal is determined by the equivalent output current I EQ and the reference signal R EF . From equation (3), the equivalent output current I EQ is proportional to the average current flowing through the LED, and the reference signal R EF is a given signal. Therefore, the set peak current I PK is the average current flowing through the LED. Decide. When the sampling current I sense reaches the set peak current I PK during the period in which the main switch M is turned on, the comparison signal S CMP outputted by the comparator goes high, thereby resetting the output of the RS flip-flop, and the switch driving signal C TR It is reset to low to disconnect the main switch M. Therefore, the average current flowing through the LED determines the set peak current I PK , that is, the time point at which the main switch M is controlled to be turned off. When the main switch M is turned off, when the zero-crossing detector detects that the voltage V T3 of the third winding T 3 is zero, the high-level zero-cross detection signal Z DET is output, thereby setting the output of the meta-RS flip-flop , causing the switch drive signal C TR to go high. Accordingly, the main open door M is closed and turned on, and the isolation conversion circuit 600 enters a new duty cycle.
圖7示出根據本發明另一個實施例的隔離變換電路700。隔離變換電路700的電路模組與隔離變換電路400的相同部分採用相同的附圖標記。為敍述簡明,這裏不再詳述兩者相同部分的耦接方式。與隔離變換電路400不同的是,為了在實際應用中避免因輸出電流計算器104中的電容C1 電容值不夠大,而不能實現阻抗匹配,隔離變換電路700的輸出電流計算器104在電容C1 和第二開關S2 之間耦接有緩衝器U1 。即輸出電流計算器104包括:第一開關S1 ,一端耦接至第一採樣電阻RS 和主開關M的串聯耦接點;第一電容C1 ,耦接在第一開關S1 的另一端和原邊參考接地之間;緩衝器U1 ,其輸入端耦接至第一開關S1 和第一電容C1 的耦接點;第二開關S2 ,耦接至緩衝器U1 的輸出端;第三開關S3 ,耦接在第二開關S2 的另一端和接地之間。第一開關S1 、第二開關S2 和第三開關S3 的控制端耦接至控制器102的輸出端,並且開關驅動信號CTR 為高電平時,第一開關S1 和第三開關S3 閉合導通,第二開關S3 斷開;當開關驅動信號CTR 為低電平時,第一開關S1 和第三開關S3 斷開,第二開關S2 閉合導通。本領域技術人員應該認識到,隔離變換電路700的工作過程與隔離變換電路400相同,為敍述簡明,這裏不再詳述。FIG. 7 shows an isolation conversion circuit 700 in accordance with another embodiment of the present invention. The circuit module of the isolation conversion circuit 700 and the same portion of the isolation conversion circuit 400 are given the same reference numerals. For the sake of brevity, the coupling of the same parts will not be described in detail here. And isolation of different conversion circuit 400, in order to avoid output current calculator 104. 1 C is the capacitance value of the capacitance is not large enough, the impedance matching can not be achieved, the isolation circuit 700 converting the output current of the capacitance C in the calculator 104 in practical applications A buffer U 1 is coupled between 1 and the second switch S 2 . That is, the output current calculator 104 includes: a first switch S 1 , one end coupled to the series coupling point of the first sampling resistor R S and the main switch M; the first capacitor C 1 coupled to the first switch S 1 Between the one end and the primary side reference ground; the buffer U 1 , the input end of which is coupled to the coupling point of the first switch S 1 and the first capacitor C 1 ; the second switch S 2 , coupled to the buffer U 1 The third switch S 3 is coupled between the other end of the second switch S 2 and the ground. The control ends of the first switch S 1 , the second switch S 2 and the third switch S 3 are coupled to the output end of the controller 102, and when the switch drive signal C TR is at a high level, the first switch S 1 and the third switch S 3 is closed is turned on, turned off the second switch S 3; when the switch drive signal C TR is low, the first switch S 1 is turned off and the third switch S 3, S 2 is closed the second switch is turned on. Those skilled in the art should appreciate that the operation of the isolation conversion circuit 700 is the same as that of the isolation conversion circuit 400. For the sake of brevity, it will not be described in detail herein.
圖8示出根據本發明又一實施方式的隔離變換電路800。隔離變換電路800的電路模組與隔離變換電路200相似,並且隔離變換電路800中與隔離變換電路200相同的部分採用相同的附圖標記。為敍述簡明,這裏不再詳述兩者相同部分的耦接方式。與隔離變換電路200不同的是,隔離變換電路800省略第三繞組T3 ,取而代之的是,隔離變換電路800採用一零交叉檢測電容C2 。並且零交叉檢測電容C2 的一端耦接至零交叉檢測器103的輸入端。零交叉檢測電容C2 的另一端耦接至主開關M和原邊繞組T1 的串聯耦接點。當主開關M被斷開後,流過二極體D的電流ID 開始從n×IPK 下降,當其下降至零,原邊繞組T1 的激磁電感和主開關M的寄生電容(未圖示)產生振盪。該振盪第一次零交叉時,流過零交叉檢測電容C2 的電流反向,零交叉檢測器103檢測到此反向電流,輸出高電平零交叉檢測信號ZDET ,從而使控制器102輸出高電平開關驅動信號CTR ,將主開關M閉合導通。隔離變換電路800進入一個新的工作週期。隔離變換電路800的其餘工作原理與前述隔離變換電路200相同,為敍述簡明,這裏不再詳述。FIG. 8 shows an isolation conversion circuit 800 in accordance with yet another embodiment of the present invention. The circuit module of the isolation conversion circuit 800 is similar to the isolation conversion circuit 200, and the same portions of the isolation conversion circuit 800 as the isolation conversion circuit 200 are given the same reference numerals. For the sake of brevity, the coupling of the same parts will not be described in detail here. The insulating converter circuit 200 except that the insulating converter circuit 800 will be omitted third winding T 3, instead, the insulating converter circuit 800 employs a zero-crossing detector capacitance C 2. And one end of the zero-crossing detecting capacitor C 2 is coupled to the input end of the zero-crossing detector 103. The other end of the zero-crossing detecting capacitor C 2 is coupled to the series coupling point of the main switch M and the primary winding T 1 . When the main switch M is turned off, the current I D flowing through the diode D starts to fall from n × I PK , and when it falls to zero, the magnetizing inductance of the primary winding T 1 and the parasitic capacitance of the main switch M (not The illustration shows an oscillation. When the oscillation is zero crossing for the first time, the current flowing through the zero-cross detecting capacitor C 2 is reversed, the zero-crossing detector 103 detects the reverse current, and outputs a high-level zero-crossing detection signal Z DET , thereby causing the controller 102 The high level switch drive signal C TR is output to turn the main switch M closed. The isolation converter circuit 800 enters a new duty cycle. The remaining working principle of the isolation conversion circuit 800 is the same as that of the isolation conversion circuit 200 described above, and is not described in detail herein.
圖8所示的隔離變換電路800中雖然沒有示出輸出電流計算器105的具體結構,在一個具體實施例中,輸出電流計算器105可以是圖4或圖7中所示的結構;在另一個具體實施例中,還可以在上述基礎上附加如圖6中所示的補償電路ZC 。Although the specific structure of the output current calculator 105 is not shown in the isolation conversion circuit 800 shown in FIG. 8, in one specific embodiment, the output current calculator 105 may be the structure shown in FIG. 4 or FIG. 7; In a specific embodiment, the compensation circuit Z C as shown in FIG. 6 can also be added on the basis of the above.
雖然上面以LED元件作為被驅動元件的例子來描述本發明的思想,但是本領域的普通技術人員應該理解,本發明實施例也可以應用於對其他類型的驅動元件,例如電流源。Although the idea of the present invention has been described above with LED elements as driven components, those of ordinary skill in the art will appreciate that embodiments of the present invention are also applicable to other types of drive components, such as current sources.
以上公開內容僅涉及較佳實施例或實施例,可產生許多修改方案而不脫離所附申請專利範圍提出的本發明的精神和範圍,不應解釋為對本發明保護範圍的限定。本說明書所描述的特定實施例僅用於說明目的,本領域技術人員在本發明的精神和原理內,可得出多種修改、等同方案。本發明涵蓋的保護範圍以所附申請專利範圍為準。因此落入權利要求或其等效範圍內的全部變化和改型都應為隨附申請專利範圍所涵蓋。The above disclosure is only intended to be a preferred embodiment or embodiment, and many modifications may be made without departing from the spirit and scope of the invention as set forth in the appended claims. The specific embodiments described herein are for illustrative purposes only, and various modifications and equivalents can be made by those skilled in the art in the spirit and scope of the invention. The scope of protection encompassed by the present invention is subject to the scope of the appended claims. All changes and modifications that come within the scope of the claims and their equivalents should be covered by the appended claims.
100‧‧‧隔離變換電路100‧‧‧Isolation conversion circuit
101‧‧‧整流橋101‧‧‧Rectifier Bridge
102‧‧‧控制器102‧‧‧ Controller
103‧‧‧零交叉檢測器103‧‧‧Zero cross detector
104‧‧‧輸出電流計算器104‧‧‧Output current calculator
110‧‧‧隔離回饋電路110‧‧‧Isolated feedback circuit
200‧‧‧隔離變換電路200‧‧‧Isolation conversion circuit
400‧‧‧隔離變換電路400‧‧‧Isolation conversion circuit
600‧‧‧隔離變換電路600‧‧‧Isolation conversion circuit
700‧‧‧隔離變換電路700‧‧‧Isolation conversion circuit
800‧‧‧隔離變換電路800‧‧‧Isolation conversion circuit
T‧‧‧變壓器T‧‧‧Transformer
M‧‧‧主開關M‧‧‧ main switch
T1 ‧‧‧原邊繞組T 1 ‧‧‧ primary winding
T2 ‧‧‧副邊繞組T 2 ‧‧‧ secondary winding
T3 ‧‧‧第三繞組T 3 ‧‧‧third winding
S1 ‧‧‧第一開關S 1 ‧‧‧first switch
S2 ‧‧‧第二開關S 2 ‧‧‧second switch
S3 ‧‧‧第三開關S 3 ‧‧‧third switch
C1 ‧‧‧第一電容C 1 ‧‧‧first capacitor
U1 ‧‧‧緩衝器U 1 ‧‧‧buffer
UA ‧‧‧誤差放大器U A ‧‧‧Error Amplifier
UC ‧‧‧比較器U C ‧‧‧ comparator
ZC ‧‧‧補償電路Z C ‧‧‧compensation circuit
圖1示出傳統隔離變換電路100。FIG. 1 shows a conventional isolation conversion circuit 100.
圖2示出根據本發明一個實施例的隔離變換電路200。FIG. 2 illustrates an isolation conversion circuit 200 in accordance with one embodiment of the present invention.
圖3示出根據本發明的輸出電流計算器的工作原理流程圖300。Figure 3 shows a flow chart 300 of the operation of an output current calculator in accordance with the present invention.
圖4示出根據本發明一個實施例採用圖3所示計算隔離變換電路副邊輸出電流方法的隔離變換電路400。4 illustrates an isolation conversion circuit 400 employing the method of calculating the secondary side output current of the isolation conversion circuit of FIG. 3, in accordance with one embodiment of the present invention.
圖5示出圖4所示隔離變換電路400中開關驅動信號、流經主開關的電流、流經二極體的電流,第三繞組的電壓以及等效輸出電流的波形。5 shows the waveforms of the switching drive signal, the current flowing through the main switch, the current flowing through the diode, the voltage of the third winding, and the equivalent output current in the isolation conversion circuit 400 shown in FIG.
圖6示出根據本發明一個實施例的具體示出控制器一種實現結構的隔離變換電路600。FIG. 6 illustrates an isolation conversion circuit 600 that specifically illustrates an implementation of a controller in accordance with one embodiment of the present invention.
圖7示出根據本發明另一個實施例的隔離變換電路700。FIG. 7 shows an isolation conversion circuit 700 in accordance with another embodiment of the present invention.
圖8示出根據本發明又一個實施例的隔離變換電路800。FIG. 8 shows an isolation conversion circuit 800 in accordance with yet another embodiment of the present invention.
101...整流橋101. . . Rectifier bridge
102...控制器102. . . Controller
103...零交叉檢測器103. . . Zero crossing detector
104...輸出電流計算器104. . . Output current calculator
200...隔離變換電路200. . . Isolated conversion circuit
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