本(ben)文將(jiang)對開關電源(yuan)中恒(heng)電流源(yuan)電路的(de)工(gong)作原理(li)及特點(dian)等進行分(fen)析(xi)，供(gong)讀者。

　　一、開關電源恒流源電路的(de)(de)(de)(de)構成(cheng)(cheng)及工(gong)(gong)作(zuo)原(yuan)理由分(fen)立元件(jian)組成(cheng)(cheng)的(de)(de)(de)(de)開(kai)(kai)關(guan)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)(yuan)中(zhong)的(de)(de)(de)(de)恒(heng)(heng)(heng)流(liu)(liu)(liu)(liu)(liu)(liu)源(yuan)(yuan)(yuan)(yuan)(yuan)電(dian)(dian)(dian)(dian)(dian)(dian)路由分(fen)立元件(jian)組成(cheng)(cheng)的(de)(de)(de)(de)開(kai)(kai)關(guan)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)(yuan)采用恒(heng)(heng)(heng)流(liu)(liu)(liu)(liu)(liu)(liu)源(yuan)(yuan)(yuan)(yuan)(yuan)電(dian)(dian)(dian)(dian)(dian)(dian)路的(de)(de)(de)(de)彩(cai)電(dian)(dian)(dian)(dian)(dian)(dian)有：長虹NC-2、NC- 3、A6等機心(xin)系列(lie)闈電(dian)(dian)(dian)(dian)(dian)(dian)。另外，東芝2929DH/DXH彩(cai)3開(kai)(kai)關(guan)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)(yuan)基(ji)(ji)本(ben)相同(tong)(tong)，也(ye)是(shi)采用恒(heng)(heng)(heng)流(liu)(liu)(liu)(liu)(liu)(liu)源(yuan)(yuan)(yuan)(yuan)(yuan)電(dian)(dian)(dian)(dian)(dian)(dian)揠。，是(shi)這(zhe)種開(kai)(kai)關(guan)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)(yuan)中(zhong)的(de)(de)(de)(de)振蕩(dang)和恒(heng)(heng)(heng)流(liu)(liu)(liu)(liu)(liu)(liu)源(yuan)(yuan)(yuan)(yuan)(yuan)原(yuan)理圖。振蕩(dang)‘路由-⑨繞組是(shi)振蕩(dang)電(dian)(dian)(dian)(dian)(dian)(dian)路的(de)(de)(de)(de)反饋支路。恒(heng)(heng)(heng)流(liu)(liu)(liu)(liu)(liu)(liu)源(yuan)(yuan)(yuan)(yuan)(yuan)由VQ820、R822、VD820、C821、R823、T803⑦~⑧和⑦⑨繞組構成(cheng)(cheng)。其(qi)工(gong)(gong)作(zuo)原(yuan)理是(shi)：在VQ83截止期(qi)間，T803的(de)(de)(de)(de)⑧端(duan)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)為(wei)正，⑨端(duan)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)為(wei)負(fu)。⑨端(duan)的(de)(de)(de)(de)負(fu)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)經R823加(jia)到VQ820的(de)(de)(de)(de)基(ji)(ji)極，使VQ820截止。T803⑧端(duan)的(de)(de)(de)(de)正電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)通(tong)過(guo)VD820向C821充電(dian)(dian)(dian)(dian)(dian)(dian)，C821上充得的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)就(jiu)成(cheng)(cheng)為(wei)VQ820導(dao)通(tong)時(shi)(shi)所需(xu)的(de)(de)(de)(de)工(gong)(gong)作(zuo)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)。VQ83導(dao)通(tong)時(shi)(shi)，T803⑧端(duan)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)變負(fu)，⑨端(duan)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)由負(fu)變正。⑧端(duan)的(de)(de)(de)(de)負(fu)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)加(jia)到VD820正極使其(qi)截止，⑨端(duan)的(de)(de)(de)(de)正電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)經R823加(jia)到VQ820基(ji)(ji)極使其(qi)導(dao)通(tong)。VQ820導(dao)通(tong)后，流(liu)(liu)(liu)(liu)(liu)(liu)經VQ820集-射之間的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)(liu)(liu)便(bian)成(cheng)(cheng)為(wei)VQ83的(de)(de)(de)(de)基(ji)(ji)極注人電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)(liu)(liu)。VQ820的(de)(de)(de)(de)導(dao)通(tong)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)(liu)(liu)不(bu)受交流(liu)(liu)(liu)(liu)(liu)(liu)輸人電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)波(bo)動(dong)的(de)(de)(de)(de)影(ying)響(xiang)，其(qi)大(da)小取決于C821上的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)和電(dian)(dian)(dian)(dian)(dian)(dian)阻R822的(de)(de)(de)(de)大(da)小，所以，VQ83的(de)(de)(de)(de)基(ji)(ji)極電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)(liu)(liu)同(tong)(tong)樣(yang)不(bu)受交流(liu)(liu)(liu)(liu)(liu)(liu)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)波(bo)動(dong)的(de)(de)(de)(de)影(ying)響(xiang)，這(zhe)就(jiu)展寬了開(kai)(kai)關(guan)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)(yuan)對(dui)交流(liu)(liu)(liu)(liu)(liu)(liu)輸入電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)的(de)(de)(de)(de)適應范圍。

　　恒流(liu)(liu)源(yuan)電(dian)(dian)(dian)(dian)路6333等。采用STR-S6309組成開(kai)關電(dian)(dian)(dian)(dian)源(yuan)的(de)彩電(dian)(dian)(dian)(dian)有：康佳06系(xi)列(lie)），夏普25N42-E2、29FN1、29AW1及寬屏W288、W328，熊貓C64P2、2919，長城G8173MF、G8263、G8363，創維(wei)CTV-8259、CTV-8298.厚膜電(dian)(dian)(dian)(dian)路STR-S6308與STR-S6309內部電(dian)(dian)(dian)(dian)路結構基本相同(tong)，恒流(liu)(liu)源(yuan)電(dian)(dian)(dian)(dian)路和(he)原(yuan)理完(wan)全相同(tong)。下(xia)面(mian)以STR-S6308厚膜電(dian)(dian)(dian)(dian)路組成的(de)開(kai)關電(dian)(dian)(dian)(dian)源(yuan)為例說明其恒流(liu)(liu)源(yuan)工作原(yuan)理。

　　是STR-6308厚(hou)膜(mo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)組(zu)成的(de)(de)(de)(de)開關電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)中的(de)(de)(de)(de)振蕩和恒流(liu)(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)原理(li)圖(tu)。圖(tu)中，IC801內部(bu)的(de)(de)(de)(de)Q1是開關管，R803、R804是振蕩啟動電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)，C812、R807、T803①-②繞組(zu)是振蕩電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)的(de)(de)(de)(de)反饋支路(lu)(lu)。恒流(liu)(liu)源(yuan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)由(you)IC801內部(bu)的(de)(de)(de)(de)Q3、R2、R3、D2及外部(bu)的(de)(de)(de)(de)C814、D803、R806和T803①-②繞組(zu)構成。其(qi)恒流(liu)(liu)源(yuan)工(gong)作(zuo)原理(li)為(wei)(wei)(wei)：在(zai)（1截(jie)止期間(jian)，T803②端(duan)(duan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)為(wei)(wei)(wei)正(zheng)，①端(duan)(duan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)為(wei)(wei)(wei)負。T803②端(duan)(duan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)通(tong)(tong)過IC801內部(bu)的(de)(de)(de)(de)D2向C814充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)，其(qi)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)路(lu)(lu)徑為(wei)(wei)(wei)：T803②④一814-803-803①。C814上(shang)充得(de)的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)就(jiu)成為(wei)(wei)(wei)Q3導(dao)(dao)(dao)通(tong)(tong)時所(suo)需要的(de)(de)(de)(de)工(gong)作(zuo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)。在(zai)Q1導(dao)(dao)(dao)通(tong)(tong)時，T803②端(duan)(duan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)由(you)正(zheng)變負，①端(duan)(duan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)由(you)負變正(zheng)。②端(duan)(duan)的(de)(de)(de)(de)負電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)加到(dao)D2的(de)(de)(de)(de)正(zheng)極(ji)(ji)(ji)使其(qi)截(jie)止，①端(duan)(duan)的(de)(de)(de)(de)正(zheng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)加到(dao)IC801的(de)(de)(de)(de)⑤腳，再通(tong)(tong)過其(qi)內部(bu)R3加到(dao)Q3的(de)(de)(de)(de)基(ji)(ji)極(ji)(ji)(ji)使其(qi)導(dao)(dao)(dao)通(tong)(tong)。Q3導(dao)(dao)(dao)通(tong)(tong)后，C814通(tong)(tong)過Q3放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)，其(qi)放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)路(lu)(lu)徑為(wei)(wei)(wei)：C814正(zheng)極(ji)(ji)(ji)->IC801dH3ce極(ji)(ji)(ji)->Qlbe極(ji)(ji)(ji)―IC801②―R806->C814負極(ji)(ji)(ji)。Q3導(dao)(dao)(dao)通(tong)(tong)后，流(liu)(liu)過Q3集射之間(jian)的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)便成為(wei)(wei)(wei)（1的(de)(de)(de)(de)基(ji)(ji)極(ji)(ji)(ji)注人電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)。因為(wei)(wei)(wei)Q3的(de)(de)(de)(de)導(dao)(dao)(dao)通(tong)(tong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)不受交(jiao)(jiao)流(liu)(liu)輸(shu)人電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)波動的(de)(de)(de)(de)影響，只取決于(yu)C814上(shang)的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)和電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)R806的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)大小，所(suo)以，開關管Q1的(de)(de)(de)(de)基(ji)(ji)極(ji)(ji)(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)同(tong)樣不受交(jiao)(jiao)流(liu)(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)波動的(de)(de)(de)(de)影響，這就(jiu)展(zhan)寬了開關電(dian)(dian)(dian)(dian)(dian)(dian)(dian)海對(dui)交(jiao)(jiao)流(liu)(liu)輸(shu)人電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)的(de)(de)(de)(de)適(shi)應范圍(wei)。

　　二、開(kai)關中楦流(liu)(liu)源電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)的(de)(de)特(te)點1.含(han)(han)(han)恒(heng)(heng)(heng)流(liu)(liu)源的(de)(de)開(kai)關電(dian)(dian)(dian)(dian)(dian)(dian)源與不含(han)(han)(han)恒(heng)(heng)(heng)流(liu)(liu)源的(de)(de)開(kai)關電(dian)(dian)(dian)(dian)(dian)(dian)源的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)區(qu)別通過對含(han)(han)(han)恒(heng)(heng)(heng)流(liu)(liu)源開(kai)關電(dian)(dian)(dian)(dian)(dian)(dian)源和(he)(he)不含(han)(han)(han)恒(heng)(heng)(heng)流(liu)(liu)源開(kai)關電(dian)(dian)(dian)(dian)(dian)(dian)源的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)對比，就會發現，這(zhe)兩類電(dian)(dian)(dian)(dian)(dian)(dian)源的(de)(de)振(zhen)蕩(dang)(dang)反(fan)(fan)饋(kui)(kui)(kui)(kui)支(zhi)路(lu)的(de)(de)阻(zu)抗是不同的(de)(de)（反(fan)(fan)饋(kui)(kui)(kui)(kui)支(zhi)路(lu)主(zhu)要由電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)和(he)(he)電(dian)(dian)(dian)(dian)(dian)(dian)容串聯(lian)組成(cheng)）。附(fu)表(biao)是這(zhe)兩類電(dian)(dian)(dian)(dian)(dian)(dian)源幾(ji)種機心彩電(dian)(dian)(dian)(dian)(dian)(dian)反(fan)(fan)饋(kui)(kui)(kui)(kui)電(dian)(dian)(dian)(dian)(dian)(dian)容和(he)(he)反(fan)(fan)饋(kui)(kui)(kui)(kui)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)的(de)(de)統(tong)計表(biao)。從統(tong)計表(biao)中可以看出：含(han)(han)(han)恒(heng)(heng)(heng)流(liu)(liu)源的(de)(de)開(kai)關電(dian)(dian)(dian)(dian)(dian)(dian)源振(zhen)蕩(dang)(dang)反(fan)(fan)饋(kui)(kui)(kui)(kui)電(dian)(dian)(dian)(dian)(dian)(dian)容小，阻(zu)抗大，反(fan)(fan)饋(kui)(kui)(kui)(kui)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)小；不含(han)(han)(han)恒(heng)(heng)(heng)流(liu)(liu)源的(de)(de)開(kai)關電(dian)(dian)(dian)(dian)(dian)(dian)源振(zhen)蕩(dang)(dang)反(fan)(fan)饋(kui)(kui)(kui)(kui)電(dian)(dian)(dian)(dian)(dian)(dian)容大，阻(zu)抗小，反(fan)(fan)饋(kui)(kui)(kui)(kui)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)大。

　　2.失效(xiao)后(hou)機器的(de)(de)(de)故障表現開(kai)(kai)關電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)中(zhong)的(de)(de)(de)恒(heng)流電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)失效(xiao)后(hou)，注人(ren)開(kai)(kai)關管的(de)(de)(de)基極電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流僅(jin)有(you)(you)振蕩反(fan)饋(kui)支路(lu)一路(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流，只能(neng)維持開(kai)(kai)關管處(chu)于弱振蕩狀態，開(kai)(kai)關電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)的(de)(de)(de)負載能(neng)力將會大(da)(da)大(da)(da)降(jiang)低。遙控(kong)彩(cai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)在待電(dian)(dian)(dian)(dian)(dian)(dian)(dian)子世界老式(shi)(shi)彩(cai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)加裝哞(mou)技討嫡t媒(mei)葙(xiang)f鯰改良方鉉李超2.記錄(lu)數據安(an)裝前測量并記錄(lu)彩(cai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)各模(mo)擬(ni)量的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓調節板±的(de)(de)(de)運放。農彩(cai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)中(zhong)模(mo)擬(ni)量控(kong)制電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓的(de)(de)(de)兩個指標(biao)彩(cai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)中(zhong)有(you)(you)音量、亮度等模(mo)擬(ni)量控(kong)制電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)，它們(men)一般用調節電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓的(de)(de)(de)方式(shi)(shi)進行控(kong)制。在這種(zhong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)中(zhong)，控(kong)制電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓有(you)(you)兩個指標(biao)。

　　調(diao)節范圍(wei)設電位(wei)器調(diao)到上、下極限(xian)時，對(dui)應(ying)的觸(chu)頭(tou)電位(wei)分別(bie)為Vh、Vl，則(ze)控制(zhi)電壓調(diao)節范圍(wei)AV=VH―VL.一(yi)般來說厶V越大控制(zhi)范圍(wei)越寬。但(dan)是(shi)，過大的AV會使調(diao)節精度(du)下降，影響圖像或伴(ban)音質量(liang)，嚴重時彩電不能正(zheng)常(chang)工作。

　　平均電(dian)位(wei)平均電(dian)位(wei)丫=丫11一￥1/2.丫的大(da)小(xiao)直接影響控(kong)(kong)制效果。如飽和度(du)控(kong)(kong)制中，V過小(xiao)會(hui)造成圖(tu)像飽和度(du)調(diao)不起來，色彩很(hen)淡。所以在加(jia)裝遙控(kong)(kong)時，AV和V應盡可能調(diao)整到設計水(shui)平。如有困難，以適當偏高為宜。

　　改良方法的(de)基本(ben)構想1.模擬(ni)量(liang)(liang)控制(zhi)電(dian)(dian)路的(de)特點老(lao)式彩電(dian)(dian)一(yi)般有(you)四(si)個(ge)模擬(ni)量(liang)(liang)，如遙控板上(shang)(shang)有(you)四(si)個(ge)相應的(de)模擬(ni)量(liang)(liang)輸出(chu)(chu)(chu)電(dian)(dian)路，各由三只電(dian)(dian)阻(zu)(zu)：輸出(chu)(chu)(chu)電(dian)(dian)阻(zu)(zu)，上(shang)(shang)、下(xia)偏(pian)置(zhi)電(dian)(dian)阻(zu)(zu)組成，在中相應的(de)電(dian)(dian)阻(zu)(zu)分別(bie)是R17、R18、R19.其中，輸出(chu)(chu)(chu)電(dian)(dian)阻(zu)(zu)主要控制(zhi)調節范圍，上(shang)(shang)、下(xia)偏(pian)置(zhi)電(dian)(dian)阻(zu)(zu)主要控制(zhi)平均電(dian)(dian)位。

　　2.現行的(de)調整(zheng)方法(fa)及(ji)改良安裝說明書及(ji)一(yi)般(ban)資料(liao)上介紹(shao)的(de)方法(fa)是，廢(fei)除(chu)彩電原有的(de)分壓(ya)調節電路，對遙控板(ban)上的(de)電阻(zu)進行調整(zheng)。這樣須(xu)調整(zheng)的(de)電阻(zu)一(yi)般(ban)有12只。在實際工作(zuo)中(zhong)要選(xuan)定并找到相應的(de)電阻(zu)并不容易，調整(zheng)起(qi)來反反復復，耗時多，精度差。

　　從上(shang)面的(de)分析中，我們不難發現：如(ru)果保留彩電(dian)上(shang)的(de)分壓電(dian)路就可(ke)以省掉遙(yao)控板上(shang)的(de)分壓電(dian)路，這(zhe)樣(yang)需調(diao)整(zheng)(zheng)的(de)電(dian)阻由(you)12只減為4只，大(da)大(da)減少了工作量，有(you)利于提高調(diao)整(zheng)(zheng)精度。

　　實例(li)-1803PD（S）彩(cai)(cai)(cai)電(dian)(dian)安裝卓(zhuo)異(yi)Z9831遙控(kong)器為(wei)例(li)，現介紹如(ru)下(xia)：1.準(zhun)備(bei)材(cai)料(liao)找51kn、200kfl可調電(dian)(dian)阻各(ge)一只，按(an)連接(jie)，引線長(chang)約30cm.備(bei)1/8W電(dian)(dian)阻若干。機狀態(tai)，行(xing)、場掃描電(dian)(dian)路停止(zhi)工作，開(kai)(kai)(kai)關電(dian)(dian)源(yuan)(yuan)處于(yu)輕(qing)負(fu)荷狀態(tai)，即使恒流有問題也(ye)看不出它的故障表現。當電(dian)(dian)視(shi)機處于(yu)正常收視(shi)狀態(tai)，特別(bie)是電(dian)(dian)視(shi)屏幕比較亮時，行(xing)、場掃描系統(tong)要消耗(hao)較大的功率，恒流源(yuan)(yuan)失效了的開(kai)(kai)(kai)關電(dian)(dian)源(yuan)(yuan)難以負(fu)擔(dan)這(zhe)一重(zhong)(zhong)任，開(kai)(kai)(kai)關電(dian)(dian)源(yuan)(yuan)將會停止(zhi)工作。開(kai)(kai)(kai)關電(dian)(dian)源(yuan)(yuan)停止(zhi)工作后，行(xing)、場掃描電(dian)(dian)路因(yin)失去供電(dian)(dian)也(ye)自然停止(zhi)工作，這(zhe)時開(kai)(kai)(kai)關電(dian)(dian)源(yuan)(yuan)因(yin)失去負(fu)載又開(kai)(kai)(kai)始起(qi)振工作，行(xing)、場掃描又得到(dao)供電(dian)(dian)再度工作，開(kai)(kai)(kai)關管(guan)負(fu)擔(dan)加重(zhong)(zhong)又停止(zhi)工作，周而(er)復(fu)始，范(fan)圍，留作調試(shi)標(biao)準(zhun)。實測(ce)數據為(wei)：亮度：7.4彩(cai)(cai)(cai)電(dian)(dian)電(dian)(dian)路改動關掉彩(cai)(cai)(cai)電(dian)(dian)電(dian)(dian)源(yuan)(yuan)拔下(xia)插頭(tou)，將各(ge)模擬量的控(kong)制端由電(dian)(dian)位器的中心抽頭(tou)改接(jie)到(dao)電(dian)(dian)位器的高電(dian)(dian)位端，并與遙控(kong)板(ban)上(shang)相應模擬量的輸出引線庫接(jie)，如(ru)所示。

　　4遙控(kong)板調(diao)(diao)(diao)整拔下遙控(kong)板上(shang)各(ge)模擬量輸(shu)出端的(de)上(shang)下偏置(zhi)電(dian)阻(zu)共(gong)8只，在(zai)其(qi)它加(jia)裝(zhuang)工作已完成的(de)情況下，對各(ge)模擬量的(de)輸(shu)出電(dian)阻(zu)進行調(diao)(diao)(diao)整。以亮度(du)控(kong)制為例，具體步驟(zou)如(ru)下：⑴拔下輸(shu)出電(dian)阻(zu)R17，將51M1可調(diao)(diao)(diao)電(dian)阻(zu)焊(han)上(shang)，通(tong)電(dian)并用遙控(kong)將亮度(du)調(diao)(diao)(diao)到最小。如(ru)果熒光(guang)屏不(bu)亮，可用萬用表監(jian)測亮度(du)控(kong)制電(dian)壓，下降(jiang)到不(bu)動為止。

　　（2）調(diao)(diao)整(zheng)(zheng)51kfi可調(diao)(diao)電(dian)(dian)阻(zu)(zu)使亮度控(kong)制電(dian)(dian)壓為(wei)7.4V.關機焊下(xia)可調(diao)(diao)電(dian)(dian)阻(zu)(zu)的一端，測得其阻(zu)(zu)值為(wei)37kfl.⑶重新焊上可調(diao)(diao)電(dian)(dian)阻(zu)(zu)并開機，用(yong)遙控(kong)器將(jiang)(jiang)亮度調(diao)(diao)到(dao)最(zui)大。調(diao)(diao)整(zheng)(zheng)可調(diao)(diao)電(dian)(dian)阻(zu)(zu)使亮度控(kong)制電(dian)(dian)壓為(wei)7.9V，關機焊下(xia)可調(diao)(diao)電(dian)(dian)阻(zu)(zu)，測得其阻(zu)(zu)值為(wei)40kft.在步驟⑵、⑶中(zhong)。如(ru)果(guo)調(diao)(diao)整(zheng)(zheng)可調(diao)(diao)電(dian)(dian)阻(zu)(zu)達不到(dao)所需(xu)電(dian)(dian)壓，就將(jiang)(jiang)可調(diao)(diao)電(dian)(dian)阻(zu)(zu)由(you)51kfl換(huan)成200M1后(hou)重試。

　　⑷一般來(lai)說，選(xuan)擇偏小(xiao)的輸出電(dian)阻(zu)(zu)使調(diao)節范圍適當擴大為宜，這里選(xuan)R17=36kft.經(jing)測試亮度控制電(dian)壓為7.3~8.IV，效(xiao)果很理(li)想。如(ru)果選(xuan)R17=33kft，效(xiao)果也(ye)不錯。其它三個模擬量輸出電(dian)阻(zu)(zu)的選(xuan)擇方法與此相同，這里不再贅(zhui)述。

　　從上面(mian)(mian)的(de)(de)(de)介紹中不(bu)(bu)難發現(xian)這(zhe)種(zhong)方法(fa)有三個優點：（1）不(bu)(bu)需(xu)對電(dian)路(lu)(lu)(lu)進(jin)(jin)行太(tai)多分析和(he)了解(jie)。⑵需(xu)要調整電(dian)阻(zu)由12只(zhi)(zhi)(zhi)變成4只(zhi)(zhi)(zhi)，減少了工作(zuo)(zuo)量(liang)。⑶調整精度便(bian)于控(kong)(kong)制，有利(li)于提高圖(tu)(tu)像(xiang)質量(liang)。必須(xu)說明的(de)(de)(de)是(shi)，這(zhe)里(li)介紹的(de)(de)(de)；1一般(ban)性的(de)(de)(de)方法(fa)，在(zai)實際工作(zuo)(zuo)中應靈活運用(yong)(yong)。例如(ru)，在(zai)對本例的(de)(de)(de)音量(liang)控(kong)(kong)制電(dian)路(lu)(lu)(lu)進(jin)(jin)行連接時(shi)，可將遙(yao)控(kong)(kong)板上的(de)(de)(de)三只(zhi)(zhi)(zhi)電(dian)阻(zu)R11、R12、R13拔(ba)掉，將電(dian)視機(ji)(ji)中的(de)(de)(de)R302移到遙(yao)控(kong)(kong)板上R11的(de)(de)(de)位置(zhi)，如(ru)所示，則音量(liang)控(kong)(kong)制電(dian)壓(ya)為(wei)0~5.6V，效果(guo)不(bu)(bu)錯(cuo)。對于控(kong)(kong)制電(dian)壓(ya)為(wei)0~12V的(de)(de)(de)電(dian)路(lu)(lu)(lu)，如(ru)夏普(pu)NC-2T的(de)(de)(de)色度和(he)對比度控(kong)(kong)制電(dian)路(lu)(lu)(lu)，可將遙(yao)控(kong)(kong)板輸出端的(de)(de)(de)上、下(xia)偏置(zhi)電(dian)阻(zu)拔(ba)掉，將輸出電(dian)阻(zu)換成l~2kft即可使用(yong)(yong)。這(zhe)時(shi)輸出電(dian)阻(zu)僅(jin)起限流作(zuo)(zuo)用(yong)(yong)，以(yi)保護(hu)遙(yao)控(kong)(kong)開(kai)關(guan)電(dian)源(yuan)只(zhi)(zhi)(zhi)能(neng)處(chu)于間歇振蕩狀態。表現(xian)在(zai)電(dian)視屏(ping)幕上的(de)(de)(de)故障(zhang)現(xian)象是(shi)：電(dian)視屏(ping)幕亮(liang)(liang)度高時(shi)，光柵(zha)(zha)會(hui)不(bu)(bu)斷地(di)收縮(suo)。或者當電(dian)視畫面(mian)(mian)較(jiao)暗(an)時(shi)，圖(tu)(tu)像(xiang)尚能(neng)穩(wen)定(ding)住。當電(dian)視畫面(mian)(mian)較(jiao)亮(liang)(liang)時(shi)，就(jiu)會(hui)出現(xian)“光柵(zha)(zha)不(bu)(bu)停地(di)收縮(suo)――展開(kai)一收縮(suo)”。這(zhe)時(shi)你測量(liang)+B115V電(dian)壓(ya)，在(zai)光柵(zha)(zha)收縮(suo)瞬(shun)間會(hui)降至(zhi)70V左右。該電(dian)視機(ji)(ji)在(zai)調機(ji)(ji)進(jin)(jin)行搜(sou)(sou)索時(shi)，搜(sou)(sou)索到的(de)(de)(de)圖(tu)(tu)像(xiang)比較(jiao)暗(an)時(shi)，可以(yi)正常搜(sou)(sou)索并存儲。搜(sou)(sou)索到的(de)(de)(de)圖(tu)(tu)像(xiang)較(jiao)亮(liang)(liang)時(shi)，光柵(zha)(zha)來回(hui)閃動，圖(tu)(tu)像(xiang)不(bu)(bu)穩(wen)定(ding)，或同步不(bu)(bu)良(liang)，電(dian)視頻(pin)道不(bu)(bu)能(neng)存儲。

                                                                                                                   本(ben)文摘自于中(zhong)國鋰(li)電網