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4-6 Oaclllatlng circuit, control circuit and drive circuit
The osc i l lati n g , contro l , and d rive ci rcui ts comp rise mai n ly IC602.
The IC602 has a bui lt-i n osc i l lator of which frequency is determi n ed by R61 4, C61 3 a n d R61 3
9,
co n n ected to p i ns
1 0 an d 1 1 respect ively. In this c i rcuit, ho rizontal sync. s i g n a l is i n put to p i n 1 1
so that the osc i l lation cyc le is synchron ous with ho rizontal scann i n g cyc le.
On the other hand, the output of d etect i o n erro r amp l ifier ci rcuit is fed back to the control ci rcuit
8
from pin
via PC601 to cont ro l the duty of 0601 so that output voltage is kept constant.
4-7 Overvoltage protection
The voltage of aux i l iary wind ing ri ses p roportiona l l y to the output vo ltage if a fault occurs in the
ci rcuit and output voltage then rises.
That voltage is detected at IC602 pin 6, and the protection circuit bui lt in the IC602 sto ps
osc i l lati on.
IC602
&
Fig. 6 Osc i l lating
Control C i rcuits
0604
Fig. 7 Ove rvo ltage Protection C i rcuit
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