Quick Charging Voltage Tripler Circuit; External Power Circuit - Canon 580EXII Service Manual

. Quick Charging Voltage Tripler Circuit

Quick Flash, which triples the main capacitor voltage operates as follows.
<Negative Tripler Flash Circuit>
(1) The C22 capacitor multiplies the voltage to the flash circuit. It is charged along with the
main capacitor C14.
It is charged from the top of C14 through R28 and D22W and connected to ground by
D14.
(2) When the Xenon lamp is triggered, IT1 is turned on through SCR1 and IT1. This
effectively puts the plusside of C22 at ground level which places the minus end at a
minus voltage equivalent to the main capacitors positive voltage.
(3) At this time the base of Q14 is connected through R40 and the emitter is connected
directly to the minus side of C22 turning on Q14.
(4) With Q14 on, the (+) side of C88W becomes a negative voltage.
(5) Because the same voltage as the main capacitor is charged to C88W beforehand through
R28 and D29W, the (-) side of C88W becomes twice the negative voltage.
The voltage is applied to the negative terminal of the Xe lamp through Q24W, R139W,
and R32W.
Therefore, a voltage three times the main capacitor voltage will be applied to the Xe
tube.

. External Power Circuit

(1) Recharging by external power
During regular operation, 4.8V from E1 power is output to SHE through R1, which
activates the external power converter. If pin 113 of IC107S outputs, FET5 turns on,
FET4 turns on through R310 and R309, and then recharging by the external power
starts. If output from pin 113 of SHE and IC107S is set to "L" at the time of power-off or
reset so external power is being blocked off.
(2) Detecting operation
If pin 51(A/D detection terminal) of IC107S detects the external power that has been
applied across R113S, R114S, R118S and R115, voltage regulation setting (detected
from pin 47 of IC107S) for the main capacitor is switched from 330V to 320V.
(3) Operation when abnormal voltage is detected
If pin 51(A/D detection terminal) of IC107S detects the external power that has been
applied across R113S, R114S, R118S and R115 and also voltage detected from the main
capacitor (detected from pin 47 of IC107S) is 340V or higher, output from pin 113 of
IC107S is set to "L", FET4 turns off, and external power is blocked off.

Technical Information