PWM電源介紹及故障分析

..PWM電源的工作原理1.死區(qū)時(shí)間,上管下管均截止+3VALWPPQ24&PQ26Turn-off@T0~T1-[1]B++PC374.7UF_1210_25V5678PC36HiDDDDPC324.7UF_1210_25V0.1UF_0805_25VPQ24SI4800GSSSPQ24ONVgs(PQ24)OUT2_UPR4604321LowPL6210V10UH_SPC_1205P_1005678T0T1T2T3T4T5DDDDT0T1PQ26SI4810DYOUT2_DGSSSHi4321PC41Vgs(PQ26)PQ26ON@1000PF0VFB2IM2DeadTime:T0~T1,T2~T3,T4~T5(T0~T1)PR7433.2K_1%PR73330+3VALWPPC76PC70PR782204700P112200P++PD23PC80+PZD3BYS10-45@150UF_D_6.3VRLZ4.3BPR772211.5K_1%PC82PC86@150UF_D_6.3V150UF_D_6.3V+3.3V:Ipeak=6.66A~10A此時(shí)上下管驅(qū)動信號均為低電平 ,兩管均截止2.T1-T2時(shí)間段,上管驅(qū)動信號為高電平 ,下管驅(qū)動信號為低電平 ,此時(shí)上管導(dǎo)通,c..下管截止.公共點(diǎn)電壓經(jīng)上管 D-S。向PL6流過負(fù)載,最終流向地,當(dāng)電池流經(jīng)電感時(shí),在電感上產(chǎn)生左正右負(fù)的感應(yīng)電壓。+3VALWPPQ24-ON,PQ26-OFF@T1~T2-[2]B++PC374.7UF_1210_25V5678PC36HiDDDDPC324.7UF_1210_25V0.1UF_0805_25VPQ24SI4800GSSSPQ24ONVgs(PQ24)PR4604321OUT2_U+--LowPL6210VT0T1T2T3T4T5T0T1HiVgs(PQ26)PQ260VONDeadTime:T0~T1,T2~T3,T4~T5(T0~T1)

10UH_SPC_1205P_1005 67 8DDDDPQ26SI4810DYGS SSOUT2_D4 32 1PC41@1000PFFB2 IM2PR7433.2K_1%PR73330+3VALWPPC76PC70PR784700P112202200P++PD23PC80+PZD3BYS10-45@150UF_D_6.3VRLZ4.3BPR772211.5K_1%PC82PC86@150UF_D_6.3V150UF_D_6.3V+3.3V:Ipeak=6.66A~10A3.T2-T3時(shí)間段,死區(qū)時(shí)間此時(shí)上下管驅(qū)動信號均為低電平 ,上下管均截止,流經(jīng)電感 PL6的電流突然消c..失,由于電感的感應(yīng)效應(yīng),電感兩端反產(chǎn)生一個(gè)反向的電壓,此電壓方向?yàn)橛艺筘?fù)+3VALWPPQ24&PQ26Turn-off@T2~T3-[3]B++PC374.7UF_1210_25V5678PC36HiDDDDPC324.7UF_1210_25V0.1UF_0805_25VPQ24SI4800GSSSPQ24ONVgs(PQ24)OUT2_UPR4604321Low+PL6--120V10UH_SPC_1205P_1005678--+T0T1T2T3T4T5DDDDT0T1PQ26SI4810DYOUT2_DGSSSHi4321PC41Vgs(PQ26)PQ26ON@1000PF0VFB2IM2DeadTime:T0~T1,T2~T3,T4~T5(T0~T1)PR7433.2K_1%PR73330+3VALWPPC76PC70PR782204700P112200P++PD23PC80+PZD3BYS10-45@150UF_D_6.3VRLZ4.3BPR772211.5K_1%PC82PC86@150UF_D_6.3V150UF_D_6.3V+3.3V:Ipeak=6.66A~10A流經(jīng)電感的電流不能突變,如流經(jīng)電感的電流突然消失,電感會產(chǎn)生反向的感應(yīng)電壓來抑制這個(gè)電流的減少4.T3-T4 時(shí)間段,此時(shí)上管驅(qū)動為低電平 ,下管驅(qū)動為高電平 .于是上管截止 ,下管導(dǎo)通,電感上感應(yīng)出的右正左負(fù)的感應(yīng)電壓經(jīng)過PL6的1腳過負(fù)載,過下管S-D流向電壓的負(fù)端,即PL6的2腳c..+3VALWPPQ24-OFF,PQ26ON@T3~T4 -[4]B++PC374.7UF_1210_25VHi5678PC36DDDDPC324.7UF_1210_25V0.1UF_0805_25VPQ24PQ24ONSI4800GSSSVgs(PQ24)LowOUT2_UPR4604321PL60V2110UH_SPC_1205P_100T0T1T2T3T4T55678--+T0T1DDDDPQ26HiSI4810DYOUT2_DGSSSVgs(PQ26)PQ260VONPC414321DeadTime:T0~T1,T2~T3,T4~T5(T0~T1)@1000PFFB2IM2PR7433.2K_1%PR73330+3VALWPPC76PC70PR782204700P112200P++PD23PC80+PZD3BYS10-45@150UF_D_6.3VRLZ4.3BPR772211.5K_1%PC82PC86@150UF_D_6.3V150UF_D_6.3V+3.3V:Ipeak=6.66A~10Ac..以MAX8734A為例針腳定義:空腳PGOOD輸出3.ON33V開啟信號4.ON55V開啟信號ILIM33V限流調(diào)節(jié)腳SHDN-總開啟信號7.FB33V反饋輸入8.REF2V參考電壓輸出9.FB55V電壓反饋輸入10.PRO過壓/欠壓保護(hù)開關(guān)此腳接VCC時(shí),關(guān)閉過壓/欠壓保護(hù),及輸出放電模式此腳接GND時(shí),打開過壓/欠壓保護(hù)以及輸出放電模式11.ILIM55V限流調(diào)節(jié)腳12.SKIP-此腳接地時(shí)工作在跳脈沖模式接VCC時(shí)工作在PWM模式接REF或懸空時(shí)工作在超聲模式(跳脈沖,最小25KHZ)13.TON頻率選擇輸入,接VCC時(shí)PWM頻率為200/300KHZ接GND時(shí)工作在400/500KHZ14.BST55V自舉升壓15.LX55V輸出相位檢測腳16.DH55VPWM上管驅(qū)動17.VCCPWM核的模擬電壓輸入LDO55V線性電壓輸出DL55VPWM下管驅(qū)動c..20.V+電源電壓輸入21.OUT55V輸出電壓檢測22.OUT33V輸出電壓檢測23.GND模擬及功率地24.DL33VPWM下管驅(qū)動25.LDO33V線性電壓輸出26.DH33VPWM上管驅(qū)動27.LX33V輸出相位檢測腳28.BST33V自舉升壓腳由于IC電源芯片本身的驅(qū)動能力有限，在這樣的高頻率的工作條件下它不能通過 DH5端直接驅(qū)動外部 MOS管，所以為了提高IC的驅(qū)動能力并簡化電路，幾乎所有的 PWM電路都采用了自舉升壓電路來提高驅(qū)動器的驅(qū)動能力，MAX8734在引腳BST5與LX5之間跨接了一個(gè) 0.1UF的自舉電容，在DH5為低電平時(shí)關(guān)閉高端驅(qū)動門驅(qū)動信號， 此時(shí)下管低端驅(qū)動門驅(qū)動信號為高電平， 低端驅(qū)動管（下管）導(dǎo)通，上管截止，下管導(dǎo)通，這樣就把輸出的 LX5端強(qiáng)拉到地，此時(shí)，MAX8734內(nèi)部本體產(chǎn)生的線性電壓 +5VALWAYSON 電壓通過一個(gè)二極管給自舉電容充電。在高端門驅(qū)動管打開時(shí)，低端門驅(qū)動管就關(guān)閉，上管導(dǎo)通，下管截止，自舉電容通過 BST5向DH5放電，此時(shí)由于 DH5的瞬間電壓比輸入19V電壓還大，高端驅(qū)動門驅(qū)動管很快就進(jìn)入飽和導(dǎo)通狀態(tài)，這樣大大提高了 DH5驅(qū)動信號的驅(qū)動能力，使外部的MOS管能正常的工作。c..1．芯片V+ VCC供電正常,2．芯片8腳輸出2V參考電壓3．當(dāng)REF達(dá)到穩(wěn)定后,LDO3上電可為外部負(fù)載提供 100m