Surge Absorber - Epson LQ-1050 Technical Manual

I (A)
t
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1 0 3 5
1 0 -
o
Fig. 2-13. Waveforms at Primary and
Secondary Sides of T1

2.2.4.2 Surge Absorber

When switching transistor Q1 is turned off, a large opposite-polarity surge voltage is produc~to
amplify the collector voltage of Q 1. The power of this surge voltage is first stored by capacitor C8 via
diode D 1, and converted into DC, then dissipated in resistor R3. This is called a snubber circuit.
When the switching transistor is turned off, the generated surge current flows through
back electromotive force in T1l-s as another surge current. This current amplifies the GND level of the
a
main switching section and is applied to coil
of the input coil temporarily increases
up. Then the emitter voltage at Q3 exceeds the normal level and Q3 is turned on because the base
of Q3 is stabilized by Q5.
Correspondingly, Q2 is also turned on to shoti the base of Q1 to main switching GND, and remains
off until the surge voltage is dissipated through GND.
I )
L P
AVERAGE
Fig. 2-14. RCC System Switching Operation
fry-wheel diode D6. At this time, the resistance
so that the induced power in TM-E accordingly 9oes
2-15
( A )
of Q 1
REV.-A