M411756 技術，是業者需要積極研發的方向。 【新型内容】 本創作提供一種發光二極體（lighy emitting diode, LED)的定電流驅動電路，其能使通過發光二極體的電流 實質上維持在固定值。M411756 technology is the direction that the industry needs to actively develop. [New content] The present invention provides a constant current driving circuit for a lighy emitting diode (LED) which can substantially maintain a current through a light emitting diode at a fixed value.
本創作提供一種光源裝置，其能提供穩定亮度的發光 二極體光源。 本創作提出一種發光二極體的驅動電路，其包括一控 制單元、一降壓轉換器（buck converter)以及一補償單元。 控制單元具有_第—輸人端與—第一輸出端，且控制單元 透過第-輸出端輸出-控制信號。降壓轉換器输入 ，源’且_於控制單元之第—輸出端與—發光二極體串 (lght emmmg diode string, LED string)之間。補償 發t二極體串與控制單元的第—輸人端之間，並中 第一輸入端接收補償單元的-補償信號’: 在本創作之一實施例中，上述之 降壓轉換器的-第—端與―第二端之間。—°體串輕接於 在本創作之-實施例中，上述之補償單元 第:輸出端。第二輸入端_轉換;G 一編且第—輪出端轉接控制單元 》 制單元的第-輪入端之間。第-電二=:= 5 接地端之間。 從10在歐一=例中’上述之補償電阻的電阻值為 U k姆（Ohm，Ω )到50萬歐姆。 在本創作之-實施例中’上述之補償單元更包括一遽 電阻。濾波電阻耦接於補償電阻與第一電阻之間。 從]^創作之一實施例中’上述之補償電阻的電阻值為 处14歐姆到9千萬歐姆。 波dt:實施例中，上述之補償單元更包括一濾 谷濾波電谷耦接於濾波電阻與接地端之間。 路更實施例中，發光二極體的定電流驅動電 灵匕括一電谷。電容耦接於發光二極體串的兩端。 極體在之—實施例中，上述之降壓轉換器包括-二 極Ξ虫電感以及—開關。二極體搞接輸人電源與發光二 串。電感減於二極體與發光二極體串之間，其 二二極體形成一迴圈。開關的-端轉接 體，、電感，且另一端耦接補償單元。 ，本創作之-實施例中’上述之㈣單元包括一時脈The present invention provides a light source device that provides a light-emitting diode source that stabilizes brightness. The present invention proposes a driving circuit for a light emitting diode comprising a control unit, a buck converter and a compensation unit. The control unit has a _first-input terminal and a first output terminal, and the control unit outputs a control signal through the first-output terminal. The buck converter inputs the source 'and _ between the first output of the control unit and the lght emmmg diode string (LED string). Compensating between the t-diode string and the first-input terminal of the control unit, and the first input receiving the compensation signal of the compensating unit': In an embodiment of the present invention, the buck converter described above - between the first end and the second end. - ° body string lightly connected in the present embodiment - the above compensation unit: output. The second input _ conversion; G and the first-round output control unit 》 between the first-input of the unit. The first - electric two =: = 5 between the ground. From 10 in the EU = example, the resistance value of the above-mentioned compensation resistor is U k (Ohm, Ω) to 500,000 ohms. In the present invention, the compensation unit described above further includes a resistor. The filter resistor is coupled between the compensation resistor and the first resistor. In the embodiment of the invention, the resistance value of the above-mentioned compensation resistor is 14 ohms to 90 million ohms. Wave Dt: In the embodiment, the compensation unit further includes a valley filter electric valley coupled between the filter resistor and the ground. In a further embodiment, the constant current drive of the light emitting diode includes a valley. The capacitor is coupled to both ends of the LED string. In the embodiment, the buck converter described above includes a - diode aphid inductor and a switch. The diode is connected to the power supply and the two strings. The inductance is reduced between the diode and the LED string, and the diode forms a loop. The switch's - terminal adapter, the inductor, and the other end are coupled to the compensation unit. In the present invention - the above-mentioned (four) unit includes a clock
正反^接:正反$ (SR fllP fl〇P)以及一比較器。SR 反接於時脈產生器與降_換器之間。sr正反 有一设定端以及一會署*山 ^ - 辦。比較考且古一 Έ * 並透過飫疋端接收一時脈信 儿 °八有一正端、一負端以及一第三輪出端。正 搞接補償單元，負端接收—參考電壓，且第 至SR正反器之重置端。 叫耦接 除此之外，本創作還提出—種光源裝置，其包括—發 M411756 光二極體串與一定電流驅動電路。定電流驅動電路耦接發 光二極體串’且包括上述之控制單元、降壓轉換器以及補 償單元。 基於上述，本創作所之實施例藉由將補償單元耦接於 發光二極體串與控制單元的第一輸入端之間，以提供一會 隨輸入電源與發光二極體跨壓變化而自行調整的補償信 號，故能使通過發光二極體的電流實質上維持在固定值， 而較不會被發光二極體跨壓的變化或延遲時間因素與工作 頻率的變化所影響，從而能提供穩定亮度的發光二極體光 源。 為讓本創作之上述特徵和優點能更明顯易懂，下文特 舉實施例’並配合所附圖式作詳細說明如下。 【實施方式】 第一實施例 圖1為本創作第一實施例之光源裝置的示意圖。請參 照圖1，光源裝置100包括發光二極體串（light emitting diode string，LED string) 110以及定電流驅動電路12〇。發 光二極體串110例如由多個串接在一起的發光二極體ιΐ2 (圖1不意地繪示三個）所組成。定電流驅動電路12〇耦 接發光二極體串110’並適於驅動發光二極體串11〇，其中 本實施例之定電流驅動電路12〇能使通過發光二極體串 110的電流，在發光二極體串110之工作頻率發生變化的 狀態下實質上仍維持在固定值。 7 M411756 如圖1所示，定電流驅動電路120包括控制單元122、 降壓轉換器（buck converter) 124以及補償單元126。控 制單元122具有輸入端ίρι與輸出端〇ρι，控制單元122 透過輸出鸲ορι輸出控制信號sctl。降壓轉換器124耦接 輸入電源vin，且降壓轉換器124耦接於控制單元122之輸 出端0P1與發光二極體串11〇之間。另外，補償單元126 耦接於發光二極體串110與控制單元122的輸入端Ipl之 間，其中控制單元122透過輸入端IP1接收補償單元126 的補偵t號scmp。除此之外，發光二極體串輕接於降 壓轉換器124的第一端E1與第二端拉之間。補償單元126 具有輸入端IP2與輸出端〇P2，其中輸入端汗2耦接降壓 轉換器124的第二端E2,且輸出端OP2耦接控制單元122 的輸入端IP1。 詳細而言，本實施例的降壓轉換器124包括二極體 D1、電感L1以及開關Qi。如圖i所示，二極體D1耦接 輸入電源兄„與發光二極體串11〇。電感u耦接於二極體 D1與發光二極體串11〇之間，其中發光二極體串11〇、電 感L1與二極體D1形成一迴圈。開關Q1的一端耦接二極 體D1與電感L1，且其另一端耦接補償單元126。 另一方面，控制單元122包括時脈產生器122a、SR 正反器（SR flip-flop) 122b以及比較器122c。SR正反器 122b耦接於時脈產生器122a與降壓轉換器124之間。sr 正反器122b具有設定端s、重置端R以及輸出端Q，SR 正反122b透過設定端s接收時脈信號Scik，並透過輸出 M411756 ，Q輸ih控輸號Setl。比較器122e具有正端e 收:t輸Λ端0P3，其中正端EP耗接補償單元126以接 負端EN接收參考電壓Vref，且輸出端 0P3耦接至SR正反态122b之重置端汉。在Positive and negative: positive and negative $ (SR fllP fl〇P) and a comparator. The SR is connected between the clock generator and the down converter. Sr positive and negative has a setting end and a meeting * mountain ^ - do. Compare the test and the ancient one Έ * and receive a clock letter through the terminal. There is a positive end, a negative end and a third round out. The compensation unit is being connected, and the negative terminal receives the reference voltage and the reset terminal of the SR to the flip-flop. In addition to this, the author also proposes a light source device comprising - a M411756 optical diode string and a certain current drive circuit. The constant current drive circuit is coupled to the light emitting diode string' and includes the above described control unit, buck converter, and compensation unit. Based on the above, the embodiment of the present invention couples the compensation unit between the LED string and the first input end of the control unit to provide a change with the input power and the LED across the voltage. The adjusted compensation signal enables the current through the light-emitting diode to be substantially maintained at a fixed value, and is less affected by the change in the voltage across the LED or the delay time factor and the change in the operating frequency, thereby providing A light-emitting diode source that stabilizes brightness. To make the above-described features and advantages of the present invention more comprehensible, the following detailed description is made in conjunction with the accompanying drawings. [Embodiment] First Embodiment Fig. 1 is a schematic view showing a light source device of a first embodiment of the present invention. Referring to FIG. 1, the light source device 100 includes a light emitting diode string (LED string) 110 and a constant current driving circuit 12A. The light-emitting diode string 110 is composed of, for example, a plurality of light-emitting diodes ι 2 (three are not shown in Fig. 1) connected in series. The constant current driving circuit 12 is coupled to the LED string 110' and is adapted to drive the LED string 11 〇. The constant current driving circuit 12 of the embodiment can enable the current through the LED string 110. The value is substantially maintained at a fixed value in a state where the operating frequency of the LED string 110 changes. 7 M411756 As shown in FIG. 1, the constant current drive circuit 120 includes a control unit 122, a buck converter 124, and a compensation unit 126. The control unit 122 has an input terminal ίρι and an output terminal 〇ρι, and the control unit 122 outputs a control signal sctl through the output 鸲ορι. The buck converter 124 is coupled to the input power source vin, and the buck converter 124 is coupled between the output terminal OP1 of the control unit 122 and the LED string 11〇. In addition, the compensation unit 126 is coupled between the LED array 110 and the input terminal Ipl of the control unit 122, wherein the control unit 122 receives the compensation signal tmp of the compensation unit 126 through the input terminal IP1. In addition, the light emitting diode string is lightly connected between the first end E1 of the down converter 124 and the second end pull. The compensation unit 126 has an input terminal IP2 and an output terminal 〇P2, wherein the input terminal K2 is coupled to the second terminal E2 of the buck converter 124, and the output terminal OP2 is coupled to the input terminal IP1 of the control unit 122. In detail, the buck converter 124 of the present embodiment includes a diode D1, an inductor L1, and a switch Qi. As shown in Figure i, the diode D1 is coupled to the input power source „ 发光 发光 发光 发光 〇 〇 〇 〇 〇 〇 〇 〇 〇 〇 〇 〇 〇 〇 〇 〇 〇 〇 〇 〇 〇 〇 〇 〇 〇 〇 〇 〇 〇 〇 〇 〇 〇 〇 〇 The circuit 11 is connected to the diode D1 and the inductor L1, and the other end of the switch Q1 is coupled to the compensation unit 126. On the other hand, the control unit 122 includes the clock. The generator 122a, the SR flip-flop 122b, and the comparator 122c. The SR flip-flop 122b is coupled between the clock generator 122a and the buck converter 124. The sr flip-flop 122b has a set terminal s, reset terminal R and output terminal Q, SR forward and reverse 122b receives the clock signal Scik through the set terminal s, and through the output M411756, Q inputs the ih control number Setl. The comparator 122e has a positive end e: t input The terminal 0P3, wherein the positive terminal EP consumption compensation unit 126 receives the reference voltage Vref with the negative terminal EN, and the output terminal OP3 is coupled to the reset terminal of the SR positive and negative state 122b.
=元m例如為一控制晶片，且控制晶片包括上述之 =除=’補償單元126包括補償電阻、以及 一 劾電阻％_於發光二極體串110與控制 =122的輸入端IP1之間’且節點奶的電壓為輸入電 源Vln與發光二極體串110之跨壓、的差值 — =))。另外，電阻R1 _於補償電阻％與接地端°之 圖2為圖丨之發光二極體串之電流^隨時間變 ^的示意圖。請同時參照圖i與圖2，詳細而言，圖ι之 日生器1223負責提供時脈信號SdkJ*SR正反器122b 之叹疋端s，以於每次時脈脈衝時觸發SR正反器12沘之 設定端s，從而使得降壓轉換器124的開關φ導通。當 開關Q1於圖2之期間τ〇η導通時，流經發光二極體串11〇 的電流iled會沿圖1之路徑P1傳送，並依序通過電感、 開關Q1到達接地端，其中流經發光二極體串及電感 L1的電流Iled會隨時間逐漸增加（如圖2所示），從而使得 電上的跨壓隨之增力口。當發光二極體帛110的電流 加到Ipeak使電阻R1上的跨壓（即補償信號semp)超 ref時（例如為IV)，比較器122c會觸發SR正反器122b 的重置端R以使降壓轉換器124的開關Q1截止。接著， 9 M411756 田開關Q1於期間Toff截止時，發光二極體串n〇的電流 lied會在由發光二極體串UG、電感u以及二極體D1形成 的迴圈中沿路徑P2循環，並且電流Iied會隨發光二極體串 11 〇之能源逸散而逐漸降低至Imin，朗下—次時脈脈衝產 生。因此，如圖2所示，發光二極體串110的電流iled會 呈現-個週期㈣織波形，且大致上為定的電流平 均值iav。 “ 。值得-提的是，由於在期間TQff流經電感L1的電流 可表不為 IL off = VledxToff / L，且由圖 2 可知，Iav = Ipeak — / 2) ’故電流lled的平均值可表示為l = ^ — (I# off/2L)。因此，由上式可知，只要藉由調整電流峰值 間Taff的大小，便能使通過發光二極體串ho的電流 平均值Iav維持在固定的大小，從而能達到定電流控制的效 ，。另外’在本實施例巾’假設期帛Toff皆為固定因此 若要達到定電流控制的功效，則必須使電流峰值t幸旦 維持固定，以下將對此作詳細介紹。 P kint里 圖3A至圖3C為不同頻率下之補償信號與參考電壓隨 時間變化的比較示意圖’其中tl為信號在一般晶片内傳遞 所需要的時間，亦即從晶片偵測到電流異常到真正使關閉 戴止之間的延遲時間（delaytime)。請參照圖3A，如前所 述，當通過發光二極體串110的電流增加到使補償信號 Scmp高於參考電麈^時，開關Q1會被截止，以避免 發光二極體串110的電流丨㈣持續上升。然而，如圖3八所 示，由於信號的傳遞需要固定的時間tl，故等到開關Q1 真正被截止時，補償信號Semp實際上已超過參考恭 -相當的量cU。為方便說明，以下將工作頻率= 時所對應的電流峰值設為Ipeaki。 8 應注意的是’由於發光二極體串11()的卫作週 cyclOD = Vled/ Vin，其中Vied為發光二極體串ιι〇的跨壓， 且發光二極體串11〇的工作頻率Fs = D / L = (1d) / T。汗， 故發光二極體串11G的:^作解很容易受到輸人電壓。％ 與跨壓Vled的影響，從而使得電流峰值w發生變化。詳n 細來說，如圖3Β所示，在延遲時間u固定的情況下，當 ，光二極體串110的工作頻率Fs&5〇KHz增加到ι〇〇κΗβζ 時（即補償信號Scmp的斜率增加），由於信號的傳遞依舊 需要固定，故當光源裝置UK)沒有麵單it 126的 It况下’等到圖1之P· Qi真正被截止時，補償信號Scmp 實際上已超過參考電壓Vref一相當的量d2，且d2>dl。如 此一來，將會發光二極體串11〇的電流峰值從增為 Ipeak2 ’其中Ipeak2為工作頻率& = 1〇〇KHz時所對應的電流 峰值。類似地，當發光二極體串的工作頻率h從 ΙΟΟΚΗζ增加到150KHz時（即補償信號Scmp的斜率更 大），由於信號的傳遞仍舊需要固定時間tl，等到開關Q1 真正被截止時，補償信號&叫實際上已超過參考電壓Vref 一相當的量d3，且d3 > d2。如此一來，將會發光二極體 串no的電流峰值從Ipeak2增為Ipeak3，其中Ipeak3為工作頻 率Fs = 150KHz時所對應的電流峰值。由上述可知，一旦 工作頻率Fs因輸入電源Vin或跨壓vied改變而發生變化 M411756 時，將會使得發光二極體串110的電流峰值‘^發生變動 (亦即從Ipeakl增為I—2或從1_增為Ipeak3)，從而無法 使通過發光一極體串110的電流平均值Iav維持在固定的大 /J、〇 有鑑於此，在本實施例之定電流驅動電路100的補償 單元126便是用來解決上述問題。圖4A至圖4B為圖i之 不同頻率下之補償信號與參考電壓隨時間變化的比較示意 圖。請參照m ’在本實施中，補償單元m的電阻％ 係耦接於發光二極體串110與控制單元122的輸入端Ιρι # ^間。由於節點N1的電壓為(Vin —Vied)，故節點N2的電 壓可表不為(Vin-Vled)XRl/(R1+Rcmp)(即補償信號U。 其中電阻R1的電阻值例如小於或等於1〇歐姆⑽瓜， Ω)，補償電阻Rcmp的電阻值例如是從1〇歐姆到5〇萬歐 ，因此如圖4A與圖4B所示，一旦輸入電源Vin與發 光二極體串110之跨壓Vied的差值變大（例如輸人電源Vin 上升或跨壓、下降或二者皆有），導致發光二極體串110 的工作週期〇下降，從而使工作頻率Fj ΙΟΟΚΗζ上升翁 150KHz時，節點N2的電壓（即補償信號s_)亦會隨差 升而上升。如此一來’即便工作頻率Fs上升，使補 償信號S，的斜率增加，但由於補償信號％正比於上述 差值’而能提供更高的補償值dcmp3 (dcmp3 > dcmp2)，故相 較於圖4B，圖4C的補償信f虎Scmp會提前超過參考電壓 vref使^關φ提早截止。基此，便能避免發光二極體串 11〇的電流持續上升，從而能使圖4C與圖4B的電流峰值 12 M411756 dcmpl 〜dcrnp3 :補償值 Res ·遽波電阻 Ccs ·;慮波電容 Cl :電容 19The element m is, for example, a control chip, and the control chip includes the above-mentioned = division = 'compensation unit 126 includes a compensation resistor, and a resistor %_ between the LED string 110 and the input IP1 of the control=122' And the voltage of the node milk is the difference between the input voltage Vln and the voltage across the LED string 110 - ()). In addition, the resistor R1_ is at the compensation resistor % and the ground terminal °. FIG. 2 is a schematic diagram of the current ^ of the LED string of FIG. Please refer to FIG. 2 and FIG. 2 at the same time. In detail, the generator 1223 of FIG. 1 is responsible for providing the sigh terminal s of the clock signal SdkJ*SR flip-flop 122b to trigger the SR flip-flop every time pulse pulse. The set terminal s of 12 turns, so that the switch φ of the buck converter 124 is turned on. When the switch Q1 is turned on during the period of FIG. 2, the current iled flowing through the LED string 11〇 is transmitted along the path P1 of FIG. 1, and sequentially passes through the inductor and the switch Q1 to reach the ground, where the flow passes through. The current Iled of the LED string and the inductor L1 will gradually increase with time (as shown in FIG. 2), so that the voltage across the power increases. When the current of the LED 帛110 is applied to Ipeak such that the voltage across the resistor R1 (ie, the compensation signal semp) exceeds ref (eg, IV), the comparator 122c triggers the reset terminal R of the SR flip-flop 122b. The switch Q1 of the buck converter 124 is turned off. Then, when the 9 M411756 field switch Q1 is turned off during the period Toff, the current LED of the LED string n〇 circulates along the path P2 in the loop formed by the LED string UG, the inductor u, and the diode D1. And the current Iied will gradually decrease to 1 min with the energy dissipation of the LED string 11 ,, and the sub-clock pulse will be generated. Therefore, as shown in Fig. 2, the current iled of the LED string 110 exhibits a period (four) weave waveform and is substantially a constant current average value iav. “It is worth mentioning that since the current flowing through the inductor L1 during the period TQff can be expressed as IL off = VledxToff / L, and as can be seen from Fig. 2, Iav = Ipeak — / 2) 'The average value of the current lled can be It is expressed as l = ^ - (I# off/2L). Therefore, as can be seen from the above equation, the current average value Iav passing through the light-emitting diode string ho can be maintained at a fixed level by adjusting the magnitude of the Taff between the current peaks. The size can be adjusted to achieve the effect of constant current control. In addition, in the case of the present embodiment, the Toff is fixed. Therefore, if the effect of the constant current control is to be achieved, the current peak value t must be maintained constant. This will be described in detail. P kint, Figure 3A to Figure 3C are schematic diagrams of the comparison of the compensation signal and the reference voltage with time at different frequencies, where t1 is the time required for the signal to be transmitted in a general wafer, that is, from the wafer. The delay time between the abnormality of the current and the actual closing of the wear is detected. Referring to FIG. 3A, as described above, when the current through the LED string 110 is increased to make the compensation signal Scmp higher than the reference power麈^, open The Q1 will be turned off to prevent the current 丨(4) of the LED string 110 from rising continuously. However, as shown in Fig. 38, since the signal transmission requires a fixed time t1, the compensation is waited until the switch Q1 is actually turned off. The signal Semp has actually exceeded the reference K-equivalent amount cU. For convenience of explanation, the current peak corresponding to the operating frequency = is set to Ipeaki. 8 It should be noted that 'because of the LED string 11 () Week cyclOD = Vled/ Vin, where Vied is the cross-voltage of the light-emitting diode string ιι〇, and the operating frequency of the light-emitting diode string 11〇 Fs = D / L = (1d) / T. Khan, so the light two The polar body string 11G: ^ is easy to be affected by the input voltage. % and the voltage across the voltage Vled, so that the current peak w changes. Detailed, in detail, as shown in Figure 3, fixed at the delay time u In the case, when the operating frequency Fs & 5 〇 KHz of the optical diode string 110 is increased to ι 〇〇 Η Η ζ (that is, the slope of the compensation signal Scmp is increased), since the signal transmission still needs to be fixed, when the light source device UK) is not In the case of the face single 126, 'wait until the P· Qi Zhen of Figure 1. When it is cut off, the compensation signal Scmp has actually exceeded the reference voltage Vref by a certain amount d2, and d2 > dl. As a result, the current peak value of the light-emitting diode string 11〇 is increased from Ipeak2 'where Ipeak2 is working The current peak corresponding to the frequency & = 1 〇〇 KHz. Similarly, when the operating frequency h of the LED string is increased from ΙΟΟΚΗζ to 150 kHz (ie, the slope of the compensation signal Scmp is larger), the signal is still transmitted. A fixed time t1 is required, and when the switch Q1 is actually turned off, the compensation signal & call has actually exceeded the reference voltage Vref by an amount d3, and d3 > d2. As a result, the current peak of the LED string no is increased from Ipeak2 to Ipeak3, where Ipeak3 is the current peak corresponding to the operating frequency Fs = 150KHz. It can be seen from the above that when the operating frequency Fs changes M411756 due to the change of the input power source Vin or the voltage across the vied, the current peak value of the LED string 110 will be changed (i.e., from Ipeakl to 1-2 or From 1_ to Ipeak3), the current average value Iav passing through the light-emitting monopole string 110 cannot be maintained at a fixed large value /J, and in view of this, the compensation unit 126 of the constant current drive circuit 100 of the present embodiment. It is used to solve the above problems. 4A-4B are schematic diagrams showing the comparison of the compensation signal and the reference voltage with time at different frequencies of FIG. Please refer to m ′. In the present embodiment, the resistance % of the compensation unit m is coupled between the LED array 110 and the input terminal Ιρι # ^ of the control unit 122. Since the voltage of the node N1 is (Vin_Vied), the voltage of the node N2 can be expressed as (Vin-Vled)XR1/(R1+Rcmp) (ie, the compensation signal U. wherein the resistance value of the resistor R1 is, for example, less than or equal to 1 〇 ohm (10) melon, Ω), the resistance value of the compensation resistor Rcmp is, for example, from 1 〇 ohm to 50,000 ohms, so as shown in FIG. 4A and FIG. 4B, once the input power source Vin and the light-emitting diode string 110 are pressed The difference of Vied becomes larger (for example, the input power Vin rises or crosses, drops, or both), causing the duty cycle of the LED string 110 to drop, thereby causing the operating frequency Fj ΙΟΟΚΗζ to rise at 150 KHz, the node The voltage of N2 (ie, the compensation signal s_) will also rise with the rise. In this way, even if the operating frequency Fs rises, the slope of the compensation signal S increases, but since the compensation signal % is proportional to the above difference ', a higher compensation value dcmp3 (dcmp3 > dcmp2) can be provided, as compared with 4B, the compensation signal f tiger Scmp of FIG. 4C will exceed the reference voltage vref in advance to make the ^off φ early. Therefore, the current of the LED string 11〇 can be prevented from continuously rising, so that the current peaks of FIG. 4C and FIG. 4B can be 12 M411756 dcmpl to dcrnp3: compensation value Res · chopper resistance Ccs ·; Capacitor 19