SP646
1 Form A
Solid State Relay
PERFORMANCE DATA
SP646
Maximum Load Current vs. Temperature
SP646
Typical Blocking Voltage Distribution
N = 100, Ambient Temperature = 25°C
Load Current (mA)
1500
1000
500
0
-40
-20
0
20
40
60
80
Tem perature (C)
60
50
40
30
20
10
0
425 450 475 500 525 550 575 600
Blocking Voltage (V)
ZERO-VOLT SWITCHING
This solid state relay has been designed with a driver circuit that controls the operation of two back-to-back silicon controlled rectifiers
(SCRs), each responsible for one half of the AC cycle. If an AC signal is examined, the turn on, turn off and zero-volt switching can be seen.
Figure 1 shows a typical 60 Hz, 120Vac signal with a corresponding relay input signal:
1
Relay Input Signal is
Turned On.
5
Relay Input Signal is
Turned Off.
Input Signal
2
SCR #1 Turns On when
5V threshold is reached.
Device Count
6
SCR #1 and Relay Turn
Off at Zero Volts.
5V
Threshold
3
SCR #1 Turns Off,
SCR #2 Turns On
at Zero Volts.
4
SCR #2 Turns Off,
SCR #1 Turns On
at Zero Volts.
Figure 1 shows the sequence of zero-volt switching operation. At Stage 1, an input signal is applied to the relay. The relay will not turn on
until the threshold voltage of 5V is reached. Once this point is reached (Stage 2), SCR #1 (designated as the SCR which controls positive
AC voltage) turns on. However, SCR #1 only conducts for an instant, as the cycle quickly crosses zero. At this point (Stage 3), SCR #1 will
turn off and SCR #2 (negative AC voltage) turns on. Likewise, at the next zero cross (Stage 4), SCR #2 will turn off and SCR #1 conducts
again. Even though the input signal is terminated at Stage 5, the relay will continue to conduct (typical SCR behavior) until Stage 6, when
SCR #1 crosses zero and ceases to conduct. Please note that turn on can likewise begin on the negative phase of the AC cycle with a -5V
threshold, though only the positive phase is shown here.
© 2004 Solid State Optronics • San José, CA
www.ssousa.com • +1.408.293.4600
Page 3 of 5
SP646
rev 1.40 (10/25/2004)
SSOUSA [ SOLID STATE OPTRONIC ]
