Bi 4 - Phn tch bnh - Bt cng tc, mn hnh sng ln 2-3 giy ri tt

Bnh 1 - Bt cng tc ngun, mn hnh sng ln c 2 - 3 giy ri tt Hin tng:

____________________________________________________________________________ Nguyn nhn:- Do hng khi cao p hoc chy bng cao p, xc nh ng nguyn nhn bn cn xc nh b cao p ca my thuc dng no sau y ?------------------------------------------------------------------------------------------------------ Dng 1 - Cao p c mch h p:

S khi ca b cao p c mch h p

S nguyn l ca b cao p c mch h p

B cao p c mch h p th c cc cun dy

Phn tch:- cc b cao p c mch h p, thng thng c hai v, mi v iu khin mt bng cao p- in p ra ca b cao p sau khi i qua bng cao p trn ng thot v mass, chng c trch ly mt phn in p a v chn hi tip (IN+) ca IC, bt k mt nguyn nhn no dn n lm mt in p hi tip th IC cng s ngt dao ng c hai v sau khi hot ng c vi giy.- V vy, vi b cao p c mch h p th nguyn nhn ca bnh: Bt cng tc mn sng ln ri tt c th do cc nguyn nhn sau:* Mt dao ng ra t mt v ca IC* Hng n Mosfet thun (Q4 hoc Q6 s trn)* Hng cc n cng sut (Q7, Q8 hoc Q9, Q10 s trn)* Chy mt bng cao p

Kim tra:

Bn hy kim tra nh sau:- o kim tra cc n Mosfet thun- o kim tra cc n cng sut BCE (rt hay hng), nu hng cc n BCE ny bn c th thay bngC5707- Nu cc n Mosfet thun tt, cc n cng sut BCE tt th bn cp ngun v o kim tra in p ra sau mch h p (o ti chn cun dy hoc chn D mosfet thun) xem c in p ra khong 8 n 10V ko ?, nu n mosfet tt, cc n cng sut tt m khng c in p ra th do hng IC dao ng (c th hng 1 v ca IC dao ng).

* Ghi ch: Bn c th u tt D-S ca n mosfet thun th s hot ng ca mch cng sut, nhng bn lu trng hp bn u tt mosfet th s b nng cc n cng sut, do vy bn ch nn th trong khong 30 giy thi.

* Kim tra in p ra cp cho cc bng:

- Chnh ng h v thang 1000V AC- t sn que o vo chn rc cm ra bng cao p- Bt cng tc my v quan st in p

Nu: => C in p ra 1000V AC th chng t mch cao p chy, nu khng sng l do chy bng cao p

Nu: => Khng c in p ra th chng t mch cao p khng hot ng, bn cn kim tra mch h p v cp n cng sut

--------------------------------------------------------------------------------------------------- Dng 2 - Cao p khng c mch h p:

Phn tch:- Vi b cao p khng c mch h p, do c hai v cng sut u tham gia iu khin bin th cao p, v vy trng hp hng mt v s dn n mt ton b cao p v s khng c nh sng trn mn hnh.- V vy trng hp ln mn sng vi giy ri tt dng my ny ch yu l do chy mt bng cao p- Khi bng cp p chy, in p ra b hng ti v tng cao, in p ny s theo mch bo v qu p a v chn OVP ca IC v IC s ngt dao ng sau khi hot ng vi giy.

Vi mch cao p khng c mch h p th hin tng bt cng tc ngun, mn hnhsng ln 2 - 3 giy ri tt ch yu l do chy mt bng cao p- Cc trng hp hng IC dao ng hay hng 1 v cng sut thng dn n hintng mn hnh khng sngCu hi v gii p1. Cu hi 1- Nguyn nhn ca hin tng; khi bt cng tc ngun, mn hnh sng ln c 2 - 3 giy ri tt l g ?

Tr li:- Nguyn nhn l do hng b cao p hoc n cao p, c th l do hng nhng linh kin g th cn ph thuc vo kiu cao p ca my, cao p c s dng kiu mch c mch h p kt hp vi mch cng sut t dao ng hay kiu IC iu khin trc tip cc n cng sut .

2. Cu hi 2 -Lm sao nhn bit khi cao p c mch h p hay khng ?

Tr li:

- Khi cao p c mch h p th bn lun nhn thy l chng c cc cun dy (nh hnh trn)- Cc n cng sut ca khi cao p ny s dng cc n BCE, chng hot ng theo nguyn tc dao ng i xng, IC dao ng trn b cao p ny ch iu khin mch h p ch khng iu khin cc n cng sut.

- Khi cao p khng c mch h p ta thy khng c cun dy, n cng sut l Mosfet kp c hai n Mosfet thun v Mosfet ngc c tch hp trong mt linh kin 8 chn

3. Cu hi 3 -Nu khi cao p c mch h p th hin tng ln mn sng 2 - 3 giy ri tt l do nhng nguyn nhn g ?

Tr li:- Khi cao p c mch h p th bt k hng mt linh kin no khin cho mt in p hi tip ca mt v n s sinh ra hin tng trn,V d:- Hng mt n Mosfet thun- Hng mt v cng sut- Chy mt bng cao p- IC dao ng hng mt mt v

Hng cc n cng sut BCE ca mt v cng sinh ra hin tng sng mn hnh 2 - 3 giy ri tt

Hng mt n Mosfet thun ca mt v hoc IC b mtmt v dao ng cng dn n hin tng trn

Chy mt bng cao p cng s dn n hin tng mn hnh sng ln 2 - 3 giy ri tt4. Cu hi 4 -Nu IC dao ng cht mt v m kng c IC thay th c cch no khc phc

Tr li:C th khc phc c m khng phi thay IC, cch lm nh sau:

- Bn ct mch t chn dao ng ra n cc n khuch i m i (ca v b hng)- Cu mch t v dao ng cn sng cho chng iu khin c hai mch h p ng thi

Cu mch t mt v dao ng cn sng chng iu khin c hai mch hp trong trng hp IC hng mt v dao ng, bn s khng phi thay IC5. Cu hi 5 -Nu khi cao p khng c mch h p th hin tng ln mn sng 2 - 3 giy ri tt l do nhng nguyn nhn g ?

Tr li:

Cc my c khi cao p khng c mch h p th hin tng mn hnh sng ln 2 - 3 giy ri tt thng do chy bng cao p, hin tng ny cng ch sy ra trn cc my c t 2 n 4 bng cao p, khi chy mt bng n s sinh hin tng trn.

- Cc trng hp nh hng IC dao ng hay hng mt n Mosfet kp th thng s dn n hin tng mt hon ton nh sng trn mn hnh.

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