NEC AccuSync LCD72VM User Manual page 124

Commute and filter output circuit:
When PIN 8 of IC901 sends a high pulse, current passes through Q903 and produces a current in the primary
coil of T901 (pin 1 +, pin 3 -). This produces a reverse electromotive force (EMF) in the secondary coil.
Energy is stored in the secondary coil because D910, and D912 are closed. When PIN 8 of IC901 sends a low
pulse, Q903 is closed.
When the primary coil produces a reverse current EMF, the secondary coil will produce a reverse EMF. At that
time D910, D911 conducts with a voltage output of 12V is filtered through C922, C923. The RC circuit R920,
C920 will absorb the surge voltage produced by D910, and R921 and C921 will absorb the surge voltage
produced by D911.
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