Service manual

CB-2
CB CIRCUIT DESCRIPTIONS
briefly drop. However, as the regulator begins to operate, it drives the chopper, and power derived from
pin 13 of the transformer is drawn through DX3407 to maintain the voltage on CX3410. Overload and
over-voltage protection are both internal to the regulator IC, and sensed through pin 4. Should either of
these conditions occur, and latch will deactivate the oscillator inside ICX3412, thus eliminating any power
supplied by the chopper.
ICX3412
TX3401
B+VDC
RX3416
To Rectifier Ckt
LX3410
LX3417
PROV
LX3402
CX3412
CX3409 CX3418
PROV
CX3408
CX3411
DX3406
DX3407
DX3408
PROV
C3413
PROV
RX3405
RX3403 RX3404
RX3415
PROV
RX3406
RX3407
CX3410
1
23
4
ICX3403
Secondary
Side, SMPS
To Secondary
Feedback Ckt.
16
13
11
18
1
2
3
4
5
<<Figure CB-2>>
Pin 1 of the regulator IC allows feedback input for voltage regulation. Control voltage is supplied to this pin
via ICX3403, an opto-isolator that receives output information from the secondary side of the chopper,
particularly from the regulated B+. This feedback is accomplished by the programmable reference device,
ICX3406. The output from this IC is fed to the opto-isolator, which then communicates this signal back to
the switch mode regulator circuit. The output voltage error derived from ICX3403 puts a DC bias across
RX3405 and a drain current ramp on RX3403. The net effect of both the output voltage error and drain
OCP/FB Comp
INH Comp
4
1
3
5 2
OCP/FB
GND
Vin
Source
Drain
DRV
221-00060-03
ICX3412
DRV Bias
OVP
TSDBias
UVLO Latch
Oscillator
<<Figure CB-3>>