TD3082
Zero-Volt Switching
Triac Driver
PERFORMANCE DATA
0
10
20
30
40
50
800 810 820 830 840 850 860 870
Blocking Voltage (V)
TD3082
Typical Blocking Voltage Distribution
N = 100, Ambient Temperature = 25°C
0
20
40
60
80
100
120
-40
-20
0
20406080
Tem perature (C)
TD3082
Typical Load Current vs. Temperature
5 V
Threshold
Input Signal
SCR #1 Turns On when
5V threshold is reached.
SCR #1 Turns Off,
SCR #2 Turns On
at Zero Volts.
SCR #2 Turns Off,
SCR #1 Turns On
at Zero Volts.
SCR #1 and Relay Turn
Off at Zero Volts.
5
4
2
6
3
1
Relay Input Signal is
Turned On.
Relay Input Signal is
Turned Off.
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:
ZERO-VOLT SWITCHING
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.
rev 1.0
Solid State Optronics, Inc.
1.888.377.4776
www.ssousa.com