Canon 580EX - Speedlite II - Hot-shoe clip-on..., Service Manual, Page: 25 / 97

Technical Information
(Recharging Stop)
(4) When the main capacitor's voltage becomes about 350V or higher, it passes through
ZD2 and R203 and turns on Q34. CPU is reset to stop the recharging.
(This is a safety circuit that stops charging in case the MPU malfunctions.)
(5) If any of the following conditions occurs, IC107S pin 114 outputs "L" turning off
FET6 and FET7 to stop the recharging. Then if all of the following conditions are met,
recharging starts again.
* IC107S pin 47 (A-D detection terminal) input voltage is 2.4V or higher (when it is lower
than 2.3875V at the restart of recharging).
(Hysteresis = 0.0125V)
* IC106s pin 3 input voltage is 2.5V or lower.
(An input voltage of 2.5V is equivalent to a voltage of 5V at IC15 pin 3.)
* ZOOM is operating
* PD1, PD2 or PD9 (AF-assist light) is on.
* A flash is being fired.
(Prevents CPU misoperation due to a battery voltage decrease.)
<Operation Sequence>
(1) → (2) → (3) →
↑ ↑
(4) → (5)
Repeats until Main capicator reaches 330V
(Recharging suspension due to heating)
If the temperature of B PCB (converter PCB) is 124 degrees or higher, divided voltage over
the resistance value of TH2 (Posister) that becomes over 4.7ohm and R13 (4.7K ohm) makes
input from pin 8 and 9 of IC304 become "L", and recharging will stop.
If the temperature of B PCB increases, recharging will restart automatically.
. Flash-Ready Indicator
(1) When IC107S pin 47 (A-D detection terminal) input voltage becomes 1.56V or higher,
IC107S pin 12 is set to "H" and RQ28 green pilot lamp (PD3) is lit to indicate that quick
flash is ready to fire.
When IC107S pin 47 (A-D detection terminal) input voltage becomes 1.96V or higher,
IC107S pin 12 is set to "H" and PD3 (green) is turned off. IC107S pin 13 is set to "L" and
the red pilot lamp (PD3) is lit.
(2) When IC107S pin 47 (A-D detection terminal) input voltage becomes 1.94V or lower,
C107S pin 13 is set to "H" and PD3 (red) is turned off.
(An input voltage of 1.94V is equivalent to 266.6V on the main capacitor.)
<Operation Sequence>
(1) → (2)