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1、如何采用固定導(dǎo)通時(shí)間控制器進(jìn)行設(shè)計(jì) How to Design with a Fixed On-Time Controller 您優(yōu)化輕載能效的關(guān)鍵所在Your Key to Optimizing Light Load Efficiency,議程Agenda,當(dāng)前水準(zhǔn)：準(zhǔn)諧振和固定頻率 State of the art: quasi resonant and fixed frequency 用于反激的固定導(dǎo)通時(shí)間(FON)控制介紹 Introduction to the fixed on time control for flybacks 固定頻率、準(zhǔn)諧振和固定導(dǎo)通時(shí)間比較 Fixed fre

2、quency, quasi resonant, and fixed on time comparison 設(shè)計(jì)方法學(xué)及示例 Design methodology and example 將您的固定頻率適配器更新為固定導(dǎo)通時(shí)間模式 Update your fixed frequency adapter to fixed on time 增添額外功能性的技巧與決竅 Tips and tricks to add additional functionality 面向快速簡(jiǎn)單的固定導(dǎo)通時(shí)間設(shè)計(jì)的資源 Resources for quick and easy fixed on time designs,

3、議程Agenda,當(dāng)前水準(zhǔn)：準(zhǔn)諧振和固定頻率 State of the art: quasi resonant and fixed frequency 用于反激的固定導(dǎo)通時(shí)間(FON)控制介紹 Introduction to the fixed on time control for flybacks 固定頻率、準(zhǔn)諧振和固定導(dǎo)通時(shí)間比較 Fixed frequency, quasi resonant, and fixed on time comparison 設(shè)計(jì)方法學(xué)及示例 Design methodology and example 將您的固定頻率適配器更新為固定導(dǎo)通時(shí)間模式 Update

4、 your fixed frequency adapter to fixed on time 增添額外功能性的技巧與決竅 Tips and tricks to add additional functionality 面向快速簡(jiǎn)單的固定導(dǎo)通時(shí)間設(shè)計(jì)的資源 Resources for quick and easy fixed on time designs,準(zhǔn)諧振和固定頻率 Quasi Resonant and Fixed Frequency,必須提升寬輸出負(fù)載范圍下的能效 Must improve the efficiency for a wide output load range 必須改善

5、待機(jī)能耗 Must improve the standby,議程Agenda,當(dāng)前水準(zhǔn)：準(zhǔn)諧振和固定頻率 State of the art: quasi resonant and fixed frequency 用于反激的固定導(dǎo)通時(shí)間(FON)控制介紹 Introduction to the fixed on time control for flybacks 固定頻率、準(zhǔn)諧振和固定導(dǎo)通時(shí)間比較 Fixed frequency, quasi resonant, and fixed on time comparison 設(shè)計(jì)方法學(xué)及示例 Design methodology and exampl

6、e 將您的固定頻率適配器更新為固定導(dǎo)通時(shí)間模式 Update your fixed frequency adapter to fixed on time 增添額外功能性的技巧與決竅 Tips and tricks to add additional functionality 面向快速簡(jiǎn)單的固定導(dǎo)通時(shí)間設(shè)計(jì)的資源 Resources for quick and easy fixed on time designs,固定導(dǎo)通時(shí)間(FOT)工作原理 Fixed On Time (FOT) Principle of Operation,峰值電流保持恒定，而開(kāi)關(guān)頻率則會(huì)變化(改變關(guān)閉時(shí)間)，以提供必需

7、的輸出功率：The peak current is constant, switching frequency changes (Off time gets longer) to deliver the necessary output power: 頻率最高時(shí)提供的功率最大 Maximum Power is delivered at maximum frequency,峰值電流保持恒定，可用用戶選擇 Constant peak current, user selectable,Pout1 Pout2,固定導(dǎo)通時(shí)間(FOT)工作原理 Fixed On Time (FOT) Principle

8、of Operation,峰值電流通過(guò)控制器來(lái)保持恒定 the peak current is kept constant by the controller 頻率發(fā)生變化以滿足上述等式 the frequency varies to satisfy the above equations 缺少環(huán)路控制(短路，啟動(dòng))時(shí)， Fsw被(Ct針對(duì)NCP1351進(jìn)行)鉗位 in lack of loop control (short-circuit, startup), Fsw is clamped (by Ct for the NCP1351),開(kāi)關(guān)頻率由反饋回路進(jìn)行控制 The FB loop c

9、ontrols the switching frequency,固定導(dǎo)通時(shí)間(FOT) 可變開(kāi)關(guān)頻率 FOT Variable Switching Frequency,(時(shí)序電容電壓 Timing capacitor voltage),Load,Ct,Fsw 鉗位clamp,在正常操作模式，回路固定著頻率，而非Ct ！In normal operation, the loop fixes the frequency, NOT Ct! 輕載條件下，峰值電流減小，開(kāi)關(guān)頻率下降。這就限制了可聽(tīng)噪聲問(wèn)題。In light load conditions, Ipeak reduces and Fsw g

10、oes down. This limits audible noise problems. 滿載條件下，開(kāi)關(guān)頻率增加，直至其碰到Ct鉗位：故障 In full load conditions, Fsw increases until it hits the Ct clamp: fault,固定導(dǎo)通時(shí)間(FOT) 開(kāi)關(guān)損耗 FOT Switching Losses,由于頻率可變，與開(kāi)關(guān)頻率相關(guān)的損耗減少：As the frequency is variable, Fsw related losses decrease: Coss和門(mén)電荷損耗 Coss and gate charge losses

11、 泄漏感抗損耗 Leakage inductance losses,FOT大幅提高輕載能效 FOT dramatically improves light load efficiency,議程Agenda,當(dāng)前水準(zhǔn)：準(zhǔn)諧振和固定頻率 State of the art: quasi resonant and fixed frequency 用于反激的固定導(dǎo)通時(shí)間(FON)控制介紹 Introduction to the fixed on time control for flybacks 固定頻率、準(zhǔn)諧振和固定導(dǎo)通時(shí)間比較 Fixed frequency, quasi resonant, and

12、 fixed on time comparison 設(shè)計(jì)方法學(xué)及示例 Design methodology and example 將您的固定頻率適配器更新為固定導(dǎo)通時(shí)間模式 Update your fixed frequency adapter to fixed on time 增添額外功能性的技巧與決竅 Tips and tricks to add additional functionality 面向快速簡(jiǎn)單的固定導(dǎo)通時(shí)間設(shè)計(jì)的資源 Resources for quick and easy fixed on time designs,控制拓?fù)浣Y(jié)構(gòu)比較 Control Topology C

13、omparison,固定導(dǎo)通時(shí)間(FOT)：適合極寬輸出功率范圍，是您改善待機(jī)能耗和優(yōu)化工作能效的關(guān)鍵！FOT : your key to improve standby and optimize efficiency for a wide output power range !,議程Agenda,當(dāng)前水準(zhǔn)：準(zhǔn)諧振和固定頻率 State of the art: quasi resonant and fixed frequency 用于反激的固定導(dǎo)通時(shí)間(FON)控制介紹 Introduction to the fixed on time control for flybacks 固定頻率、準(zhǔn)

14、諧振和固定導(dǎo)通時(shí)間比較 Fixed frequency, quasi resonant, and fixed on time comparison 設(shè)計(jì)方法學(xué)及示例 Design methodology and example 新的NCP1351固定導(dǎo)通時(shí)間控制器 The new NCP1351 FOT controller 設(shè)計(jì)方法學(xué) Design methodology 設(shè)計(jì)示例 Design example 將您的固定頻率適配器更新為固定導(dǎo)通時(shí)間模式 Update your fixed frequency adapter to fixed on time 增添額外功能性的技巧與決竅 Ti

15、ps and tricks to add additional functionality 面向快速簡(jiǎn)單的固定導(dǎo)通時(shí)間設(shè)計(jì)的資源 Resources for quick and easy fixed on time designs,NCP1351是一款瞄準(zhǔn)總成本極為重要的低功率離線反激開(kāi)關(guān)電源(SMPS)應(yīng)用的電流模式控制器 The NCP1351 is a current-mode controller targeting low power off-line flyback Switched Mode Power Supplies (SMPS) where total cost is of

16、 utmost importance,準(zhǔn)固定導(dǎo)通時(shí)間，可變關(guān)閉時(shí)間Quasi fixed Ton, variable Toff 帶峰值電流壓縮的頻率反走Frequency foldback with Peak Current Compression 短路保護(hù)(閉鎖A&C或自動(dòng)恢復(fù)B&D)Short circuit protection,適應(yīng)大輸出功率瞬態(tài)現(xiàn)象(打印機(jī)) Accommodates large output power transients (printers) 初級(jí)端或次級(jí)端穩(wěn)壓 Primary or secondary side regulation 閂鎖輸入 Latch in

17、put 低啟動(dòng)電流 Low start-up current 固有的頻率抖動(dòng) Natural frequency jittering 帶可編程電流感測(cè)電阻的負(fù)電流感測(cè)功能 Negative current sensing with programmable current sense resistor 擴(kuò)展的Vcc范圍：28 V Extended Vcc range: 28 V,NCP1351XDR2G: SOIC8 X = A, B, C ,D,Others Features,Ordering & Package Information,Market & Applications,NCP13

18、51 固定導(dǎo)通時(shí)間、可變關(guān)閉時(shí)間控制器 Fixed On Time Variable Off Time Controller,O, DW,適配器 Adapters 離線電池充電器 Offline battery chargers 輔助電源 Auxiliary power supplies,簡(jiǎn)單而緊湊的設(shè)計(jì) Simple and compact design,固有的頻率反走 Natural frequency foldback 無(wú)噪聲，輕載能效提高 Noise free & improved efficiency in light load 獨(dú)立于輔助繞組 Independent of the

19、aux. winding,Value Proposition,Unique Features,Benefits,Application Data,NCP1351 輸入輸出功率和功能描述 NCP1351 Pinout and Function Description,FB: 在此引腳注入電流，降低頻率Injecting current in this pin reduces the frequency,Ct: 沒(méi)有反饋電流時(shí)設(shè)定最大開(kāi)關(guān)頻率 sets the maximum switching frequency at no feedback current,CS: 感測(cè)初級(jí)端電流 Senses

20、 the primary current,Timer: 設(shè)定故障確認(rèn)前的持續(xù)時(shí)間 Sets the time duration before fault validation,Latch: 高于5 V的正電壓完全閂鎖控制器 A positive voltage above 5 V fully latches off the controller,Vcc: 為控制器提供高達(dá)28伏電壓 Supplies the controller up to 28 V,DRV: 驅(qū)動(dòng)脈沖至功率MOSFET Driving pulses to the power MOSFET,NCP1351 峰值電流壓縮 NCP

21、1351 Peak Current Compression,FB current,Vds light load,Ioffset,大負(fù)載時(shí)峰值電流恒定 Constant peak current at high load 輕載時(shí)峰值電流下降 Reduced peak current at light load,沒(méi)有飽和 No saturation 沒(méi)有可聽(tīng)噪聲 No Audible noise,峰值電流從100%降至26% Peak current reduction from 100% to 26%,NCP1351 負(fù)電流感測(cè) NCP1351 Negative Current Sensing,

22、ICS x Roffset產(chǎn)生正偏置(如1 V) ICS x Roffset generates a positive offset (e.g. 1 V) 電流流過(guò)時(shí)， Vsense 為負(fù)值 Vsense is negative when current flows 兩路信號(hào)的和接近零時(shí)，MOSFET關(guān)閉 When the sum of both signal reaches 0, MOSFET is off,不用擔(dān)心！ Do not be afraid !,NCP1351 負(fù)電流感測(cè) NCP1351 Negative Current Sensing,想要降低感測(cè)電阻的功率耗散？Want to

23、 reduce Rsense power dissipation? 選擇Select Vsense = 0. 5 V Roffset = 0.5 / 270u = 1.8 k,潔凈的電壓圖像：沒(méi)有開(kāi)啟尖峰，更好的噪聲免疫性 Clean voltage image: no turn-on spikes, better noise immunity 一種微調(diào)最大感測(cè)電壓的途徑 A way to fine tune the maximum sense voltage,如何計(jì)算感測(cè)電阻和偏置電阻？ How to calculate Rsense and Roffset ?,NCP1351 過(guò)載/短路保

24、護(hù) NCP1351 Overload / Short-Circuit Protection,過(guò)載檢測(cè)僅依賴于反饋?zhàn)兓疧verload detection only dependent of FB variation 2個(gè)選項(xiàng)：閂鎖或自動(dòng)恢復(fù) 2 options: latched or auto recovery,過(guò)載OVERLOAD 輸出電壓減小 Vout decreases,反饋電流減小Less FB current,500mV,D2,Vcc,V,OUT,C,TIMER,NCP1351 過(guò)載定時(shí)器 Overload Timer,適應(yīng)大輸出功率瞬態(tài)現(xiàn)象Accommodates large ou

25、tput power transients,適合于打印機(jī)應(yīng)用Suitable for printers,Vout,故障定時(shí)器啟動(dòng) Fault timer starts,輸出負(fù)載Output load,最大輸出功率Max output power,Vout,故障定時(shí)器啟動(dòng)Fault timer starts,輸出負(fù)載Output load,最大峰值功率Max peak power,過(guò)載Over load,過(guò)載Over load,瞬態(tài)峰值功率Transient peak power,輸出仍在穩(wěn)壓 Output still in regulation,最大直流功率Max DC power,A&B版本

26、 versions,C&D版本 versions,對(duì)MOSFET的BVdss降額后定義變比Define turn ratio after derating the BVdss of the MOSFET:,NCP1351 設(shè)計(jì)方法學(xué) Design Methodology,(僅對(duì)非連續(xù)導(dǎo)電模式有效 valid for DCM only),計(jì)算最大占空比 Calculate maximum duty cycle:,在功率最大期間輸入電壓最低時(shí)選擇最大開(kāi)關(guān)頻率Choose the maximum switching frequency Fsw at Vin,min during power peak

27、s.,然后通過(guò)下列公式計(jì)算初級(jí)端感抗值：Then calculate the primary inductance value by:,kc: 鉗位系數(shù)clamp coefficientVclamp / Vr Vds,max = 85% BVdss,推導(dǎo)初級(jí)端最大峰值電流 Deduce the maximum primary peak current: 最后通過(guò)下列公式估計(jì)時(shí)序電容值 Finally estimate the timing capacitor value by: MOSFET、整流器、電感和緩沖器根據(jù)平均輸出功率(非峰值功率)來(lái)計(jì)算,NCP1351 設(shè)計(jì)方法學(xué) NCP1351

28、Design Methodology,(僅對(duì)非連續(xù)導(dǎo)電模式有效 valid for DCM only) (設(shè)計(jì)示例中將涉及連續(xù)導(dǎo)電模式 design example will cover CCM),時(shí)序電容的正常值為 Normalized values for CT are: - 65 kHz: 270 pF - 100 kHz: 180 pF,MOSFET, rectifiers, inductors and snubbers are designed according to the average delivered power (not the peak),NCP1351 設(shè)計(jì)示例NC

29、P1351 Design Example,輸出電壓 Output voltage: 19 V 57 W 輸入電壓 Input voltage: 90 265 Vrms 待機(jī)能耗(空載) Standby power (no-load) 200 mW 自動(dòng)恢復(fù)過(guò)載保護(hù) Auto-recovery overload protection 閂鎖過(guò)壓保護(hù)(OVP) Latched over-voltage protection (OVP) 工作頻率 Operating frequency: 65 kHz,在輸入電壓為85 Vac及滿載時(shí)， Cbulk 選擇為100 Vdc的最低等級(jí) Cbulk sele

30、cted for min level of 100 Vdc at Vin = 85 Vac, full load,NCP1351 設(shè)計(jì)示例NCP1351 Design Example,減小MOSFET最大的BVdss Derate maximum MOSFET BVdss:,針對(duì)最大高電壓來(lái)選擇鉗位電壓 For a maximum bulk voltage, select the clamping voltage :,選擇鉗位系數(shù)的變比為1.6 Select turn ratio for a kc of 1.6:,計(jì)算最大占空比 Calculate maximum duty-cycle:,BV

31、dss,Vds,max,鉗位電壓Vclamp,Vbulk,max,15%降額derating,NCP1351 設(shè)計(jì)示例NCP1351 Design Example,對(duì)于通用的主設(shè)計(jì)而言，選擇K = 0.8 For a universal mains design, select K = 0.8,NCP1351 設(shè)計(jì)示例NCP1351 Design Example,用它作為導(dǎo)電損耗 Use it for conduction losses,NCP1351 設(shè)計(jì)示例NCP1351 Design Example,使用200 V的二極管 Use a 200 V diode,通過(guò)270 pF的Ct 電容

32、來(lái)選定65 kHz頻率 The 65 kHz selection is made via Ct capacitor of 270 pF,如果我們想要VCS = 0.5 V而非1 V If we want VCS = 0.5 V instead of 1 V,NCP1351 設(shè)計(jì)示例NCP1351 Design Example,NCP1351 設(shè)計(jì)示例NCP1351 Design Example,Pin 空載no-load = 143 mW, Vin = 230 Vrms Pin 空載no-load = 112 mW, Vin = 100 Vrms,Above 80 %,盡管負(fù)載變化，但效 率仍

33、維持在較高水平 Efficiency is kept good despite load variations.,高于80% Above 80%,Vout 1 mV / div.,Vds 200 V / div.,Vout 1 mV / div.,Vds 200 V / div.,NCP1351 設(shè)計(jì)示例NCP1351 Design Example,5 W負(fù)載，小輸出紋波 5 W load, small output ripple,空載，小輸出紋波 No load, small output ripple,NCP1351 設(shè)計(jì)示例NCP1351 Design Example,Vout 50 m

34、V / div.,瞬態(tài)響應(yīng)，高線，低線 Transient response, high line, low line,議程Agenda,當(dāng)前水準(zhǔn)：準(zhǔn)諧振和固定頻率 State of the art: quasi resonant and fixed frequency 用于反激的固定導(dǎo)通時(shí)間(FON)控制介紹 Introduction to the fixed on time control for flybacks 固定頻率、準(zhǔn)諧振和固定導(dǎo)通時(shí)間比較 Fixed frequency, quasi resonant, and fixed on time comparison 設(shè)計(jì)方法學(xué)及示例

35、 Design methodology and example 將您的固定頻率適配器更新為固定導(dǎo)通時(shí)間模式 Update your fixed frequency adapter to fixed on time 增添額外功能性的技巧與決竅 Tips and tricks to add additional functionality 面向快速簡(jiǎn)單的固定導(dǎo)通時(shí)間設(shè)計(jì)的資源 Resources for quick and easy fixed on time designs,將您的固定頻率適配器更新為固定導(dǎo)通時(shí)間模式！ Update Your Fixed Frequency Adapter to

36、 FOT!,提升輕載條件下的能效，但沒(méi)有紋波 Improved efficiency in light load conditions without ripple 輕載條件下輸出紋波更少 Less output ripple in light load conditions 易于應(yīng)用過(guò)載保護(hù)(非耗散型) Ease of OPP implementation (non dissipative) 基于定時(shí)器的保護(hù)與輔助電壓監(jiān)控對(duì)比 Timer-based protection versus auxiliary voltage monitoring,僅用于非連續(xù)導(dǎo)電模式 DCM onlyDSS -

37、 無(wú)輔助繞組 DSS - No auxiliary winding 通用主電源 Universal mains,將您的固定頻率適配器更新為固定導(dǎo)通時(shí)間模式！ Update Your Fixed Frequency Adapter to FOT!,采用NCP1200的12 V/24 W適配器原理圖 12 V / 24 W adapter schematic with NCP1200,開(kāi)關(guān)頻率為65 kHz Switching frequency: 65 kHz 內(nèi)部固定短路保護(hù) Internal fixed short circuit protection,開(kāi)關(guān)頻率65 kHz Switchin

38、g frequency 65 kHz 選擇choose Ct = 270 pF NCP1200的最大電流設(shè)定點(diǎn)為1 V Maximum current setpoint of NCP1200 is 1 V 選擇choose VCS= 1 V，并計(jì)算Roffset : 無(wú)須修改感測(cè)電阻 No need to modify Rsense 光耦合器配置 Optocoupler configuration,NCP1200: 共發(fā)射極 common emitter,NCP1351: 共集電極 common collector,將您的固定頻率適配器更新為固定導(dǎo)通時(shí)間模式！ Update Your Fixe

39、d Frequency Adapter to FOT!,2.4 k,采用NCP1351的12 V/24 W適配器原理圖 12 V / 24 W adapter schematic with NCP1351,將您的固定頻率適配器更新為固定導(dǎo)通時(shí)間模式！ Update Your Fixed Frequency Adapter to FOT!,將您的固定頻率適配器更新為固定導(dǎo)通時(shí)間模式！ Update Your Fixed Frequency Adapter to FOT!,輸入電壓為230 Vrms時(shí)的效率和空載能耗 Efficiency and no-load power consumption

40、 at Vin = 230 Vrms,動(dòng)態(tài)自供電功率耗散！DSS power dissipation !,輸出紋波比較 Output ripple comparison,NCP1200, 空載 No load,NCP1351, 空載 No load,NCP1351的輸出紋波要小10倍 The output ripple is 10 times smaller with NCP1351,將您的固定頻率適配器更新為固定導(dǎo)通時(shí)間模式！ Update Your Fixed Frequency Adapter to FOT!,議程Agenda,當(dāng)前水準(zhǔn)：準(zhǔn)諧振和固定頻率 State of the art

41、: quasi resonant and fixed frequency 用于反激的固定導(dǎo)通時(shí)間(FON)控制介紹 Introduction to the fixed on time control for flybacks 固定頻率、準(zhǔn)諧振和固定導(dǎo)通時(shí)間比較 Fixed frequency, quasi resonant, and fixed on time comparison 設(shè)計(jì)方法學(xué)及示例 Design methodology and example 將您的固定頻率適配器更新為固定導(dǎo)通時(shí)間模式 Update your fixed frequency adapter to fixed

42、on time 增添額外功能性的技巧與決竅 Tips and tricks to add additional functionality 面向快速簡(jiǎn)單的固定導(dǎo)通時(shí)間設(shè)計(jì)的資源 Resources for quick and easy fixed on time designs,啟動(dòng)技巧與決竅 Start-Up Tip & Trick,傳統(tǒng)配置 Classical configuration,改善的啟動(dòng)耗散 Improved startup dissipation,啟動(dòng)電阻可被任意連接 The startup resistor can either be connected: 至帶啟動(dòng)電阻的大

43、電容 To the bulk capacitor with Rstartup 至半波 對(duì)于相似的充電電流，選擇Rstartup/pi To the half-wave for a similar charging current, take Rstartup/pi 半波提供最佳的閂鎖恢復(fù)時(shí)間 Half-wave gives the best latch recovering time,啟動(dòng)技巧與決竅 Start-Up Tip & Trick,輕載條件下，Vcc崩潰 In light load conditions, Vcc collapses: 增加Vcc電容，減小啟動(dòng)電阻 Increase

44、Vcc capacitor degrades startup 將Vcc分解為兩個(gè)電容 Split Vcc with two capacitors Cvcc單獨(dú)正常啟動(dòng)(D1) CVcc starts-up normally alone (D1) Creser在待機(jī)時(shí)維持Vcc工作狀態(tài) Creser keeps Vcc alive in standby,4.7 F,47 F,啟動(dòng)電壓調(diào)節(jié) Startup Voltage Adjustment,極低的啟動(dòng)電流/大啟動(dòng)電阻值 Extremely low start-up current / High start-up resistors values

45、,啟動(dòng)電阻 Start-up resistors,最小啟動(dòng)電壓調(diào)節(jié)Minimum voltage start-up adjustment,工作時(shí)固定最小高電壓 Fix the minimum bulk voltage for operation,門(mén)驅(qū)動(dòng)技巧與決竅 Gate Drive Tip & Trick,采用小型PNP來(lái)提高驅(qū)動(dòng)能力 Improve drive capability with a small PNP 更好的傳播延遲 better propagation delay 改進(jìn)故障電流控制 improves current control in fault,No PNP,with

46、PNP,200 ns / div,200 ns / div,過(guò)載保護(hù) Over Power Protection,只需數(shù)量很少的外部元件 Requires limited number of external components 兼容于現(xiàn)有輔助繞組 Compatible with existing Aux winding,二極管避免C3被反激充電 The diode avoids C3 charged by flyback,在任意電壓條件下控制最大輸出功率 Control the maximum output power under any voltage condition,非耗散型！ N

47、on dissipative!,頻率抖動(dòng)技巧與決竅 Frequency Jittering Tip & Trick,注入一些全波或半波紋波來(lái)增加固有頻率抖動(dòng) Inject some full-wave or half-wave ripple to increase the natural frequency jittering,注入全波紋波至CS引腳 Inject full wave ripple into CS pin,注入半波紋波至CS引腳 Inject half wave ripple into CS pin,閂鎖輸入技巧與決竅Latch Input Tip & Trick,NTC,參考

48、電壓 Reference voltage,與閂鎖引腳一起提供簡(jiǎn)單的過(guò)壓保護(hù)和過(guò)溫度保護(hù)Combined with the latch pin gives easy OVP and OTP protection.,在FB引腳插入齊納二極管，造就更便宜的參考 Inserting zener with FB pin, creates cheap reference.,欠壓 Brown Out,欠壓關(guān)閉BO off,欠壓導(dǎo)通BO on,斜波補(bǔ)償Ramp Compensation,斜坡補(bǔ)償1：正向斜坡補(bǔ)償至FB引腳，以降低峰值 Ramp compensation 1 : a positive ramp

49、into the FB pin reduces the peak,斜波補(bǔ)償Ramp Compensation,斜坡補(bǔ)償2：負(fù)電流在導(dǎo)通時(shí)間將Ct維持在低位 Ramp compensation 2 : a negative current keeps Ct low during ton,接近Ct引腳 Close to the Ct pin,軟啟動(dòng) Soft Start,軟啟動(dòng)(如果有必要) Soft Start (if necessary),在電源開(kāi)啟期間通過(guò)軟啟動(dòng)序列來(lái)限制應(yīng)力 Limit the stress at power-on via a soft-start sequence.,VC

50、S,t,將NCP1351與其他控制器相連接 Interfacing NCP1351 with Other Controllers,NCP1351怎樣能夠與其它控制器共享接地信號(hào)？(將負(fù)電流和正電流感測(cè)混合在一起) How NCP1351 can share ground signal with other controller? (mixing negative and positive current sensing),NCP1351接地 NCP1351 ground,主接地 Main ground,主接地 Main ground,布線建議 Layout Suggestions,Rsense

51、,Roffset,22 pF,為了改善噪聲免疫性，需要將元件布置在臨近控制器的位置 To improve the noise immunity, keep components close to the controller,低阻抗點(diǎn) Low impedance point,Vcc,改變最大開(kāi)關(guān)頻率Changing the Maximum Switching Frequency,保持Lp值不變 Keep Lp value 保持Rsense值不變 Keep Rsense,修改偏置電阻值Roffse以設(shè)定新的峰值電流Ipeak2 Modify Roffset value to set new pe

52、ak current,計(jì)算磁芯磁通量 Calculate core flux,B Bsat ?,修改變壓器參數(shù) Modify transformer,保持變壓器參數(shù) Keep transformer,減小開(kāi)關(guān)頻率FSW? FSW decreases ?,否no,否no,是yes,是yes,計(jì)算新的峰值電流Ipeak Calculate new Ipeak,(僅適用于非連續(xù)導(dǎo)電模式DCM only),開(kāi)始START,結(jié)束 END,否no,改變最大輸出功率Changing the Maximum Output Power,查看反饋噪聲 Look out for FB noise 使用平均模型來(lái)穩(wěn)定

53、電源 Use the averaged model to stabilize the power supply,是否穩(wěn)定Stable ?,是yes,檢查回路響應(yīng) VCheck loop response,計(jì)算提供Pout2所需的開(kāi)關(guān)頻率Fsw Calculate needed Fsw to deliver Pout2,(適適用于非連續(xù)導(dǎo)電模式DCM only),改變最大開(kāi)關(guān)頻率 Change the maximum switching frequency:,最大輸出功率Pout,max增加= 最大開(kāi)關(guān)頻率Fsw,max增加 Pout,max increases = Fsw,max increa

54、ses 最大輸出功率Pout,max減小= 最大開(kāi)關(guān)頻率Fsw,max減小Pout,max decreases = Fsw,max decreases,議程Agenda,當(dāng)前水準(zhǔn)：準(zhǔn)諧振和固定頻率 State of the art: quasi resonant and fixed frequency 用于反激的固定導(dǎo)通時(shí)間(FON)控制介紹 Introduction to the fixed on time control for flybacks 固定頻率、準(zhǔn)諧振和固定導(dǎo)通時(shí)間比較 Fixed frequency, quasi resonant, and fixed on time com

55、parison 設(shè)計(jì)方法學(xué)及示例 Design methodology and example 將您的固定頻率適配器更新為固定導(dǎo)通時(shí)間模式 Update your fixed frequency adapter to fixed on time 增添額外功能性的技巧與決竅 Tips and tricks to add additional functionality 面向快速簡(jiǎn)單的固定導(dǎo)通時(shí)間設(shè)計(jì)的資源 Resources for quick and easy fixed on time designs,NCP1351 設(shè)計(jì)資源 Collaterals,應(yīng)用筆記 Application not

56、es: 40 W打印機(jī)電源設(shè)計(jì)AND8278 Design of a 40 W Printer PSU AND8278 50 W適配器電源設(shè)計(jì)AND8263 Design of a 57 W Adapter PSU AND8263 12 W適配器電源設(shè)計(jì)AND8288 Design of a 12 W Adapter PSU AND8288 使用脈寬調(diào)制(PWM)開(kāi)關(guān)技術(shù)建模：AND8280 Modeling Using the PWM Switch Technique: AND8280 評(píng)估板 Evaluation board: 40 W額定/80瓦峰值功率打印機(jī)板 40 W nominal

57、/ 80 W peak printer board 57 W適配器板 57 W adapter board 參考設(shè)計(jì) Reference design: 40 W打印機(jī)電源：TND320/D 40 W Printer Power Supply: TND320/D 設(shè)計(jì)與開(kāi)發(fā) Design & Development: NCP1351電感計(jì)算數(shù)據(jù)表 NCP1351 inductor calculation Spreadsheet 仿真工具：Simulations tools: Spice模型(PSPICE和ISPICE) Spice model (PSPICE and ISPICE),謝謝！如有問(wèn)題，敬請(qǐng)?zhí)岢觯?Thank You! Any Questions?,