TM
11-6625-3041-30/TO
33A1-8-908-12
1-24. MULTI VDC (A1) START (CONT)
Start/Run
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With the Run Ref low, the positive input to the Start/Run
Sens at U5-7 is low. Since the negative input at U5-6 is high,
Sens
the output from the Start/Run Sens at U5-1 is low.
150V Lo
The 150V Supply continues to rise towards 150V and
shortly reaches 100V. The voltage to the positive input of
Sens
the 150V Lo Sens at U5-9 becomes slightly more positive than
that at the negative input at U5-8. The positive input takes
control and sets the output of the 150V Lo Sens at U5-14 high.
Auto Start
The high-level Sens Sum output at U5-13 is applied through
R69 in the Auto Start circuit to C64 and, through CR3, to C66.
Both capacitors begin to charge positive.
After 100 ms, C64 and C66 have charged sufficiently to
provide a voltage at the positive input to the Start/Run
Sens at U5-7 that is more positive than the negative input at
U5-6. The output of the Start/Run Sens then goes high.
Sens Sum
All three Sens outputs are now high and C62 at the nega-
tive input to the Sens Sum circuit at U5-10 begins to charge
through R51.
C62 eventually changes sufficiently to cause the negative
input to the Sens Sum circuit at U5-10 to be more positive than
the +5V at the positive input. This sets the output of the
Sens Sum circuit at U5-13 low.
Clock
When the Sens Sum output at U5-13 goes low, C64 begins to
discharge through R68 and CR1 and C66 begins to discharge through
R67. The low-level Sens Sum output also enables the Clock, which
produces a 22 kHz (nominal) output that drives the Switcher.
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