Publication 700-AT001A-EN-E June 2002
Considerations When Designing SSR Control Systems
2-3
Input Conditions
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When there is a ripple in the input control voltage, ensure that the
peak voltage of the ripple is lower than the maximum operating SSR
voltage and the root voltage is above the SSR minimum operating
voltage.
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When the SSR input circuit is powered by a transistor output, the SSR
reset voltage may be insufficient due to leakage current of the
transistor during power OFF. To counteract this, connect a bleeder
resistance R as shown in the diagram below and set the resistance so
that the voltage applied to both ends of the resistance is less than half
of the reset voltage of the SSR.
The bleeder resistance R can be obtained in the way shown below.
E: Voltage applied at both ends of the bleeder resistance = half of the
reset voltage of the SSR
I
L
: Leakage current of the transistor
I: Reset current of the SSR
The actual value of the reset current is not given in the datasheet and
so when calculating the value of the bleeder resistance, use the
following formula:
Peak voltage
Root voltage
0 V
Bleeder resistance
R
5
(
,
/
−
,
≤
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