MOC3051 Datasheet, PDF (3/8 Pages) Motorola, Inc – 6-Pin DIP Random-Phase Optoisolators Triac Drivers

TYPICAL ELECTRICAL CHARACTERISTICS
MOC3051 MOC3052
TA = 25°C
1.6
IFT versus Temperature (normalized)
NORMALIZED TO
This graph shows the increase of the trigger current when
1.4
TA = 25°C
the device is expected to operate at an ambient temperature
below 25°C. Multiply the normalized IFT shown on this graph
with the data sheet guaranteed IFT.
1.2
Example:
TA = – 40°C, IFT = 10 mA
1
IFT @ – 40°C = 10 mA x 1.4 = 14 mA
0.8
0.6
– 40 – 30 – 20 –10 0 10 20 30 40 50 60 70 80
TA, AMBIENT TEMPERATURE (°C)
Figure 3. Trigger Current versus Temperature
25
NORMALIZED TO:
20
PWin ≥ 100 µs
15
10
5
0
1
2
5
10
20
50
100
PWin, LED TRIGGER PULSE WIDTH (µs)
Figure 4. LED Current Required to Trigger
versus LED Pulse Width
AC SINE
0°
180°
LED PW
LED CURRENT
LED TURN OFF MIN 200 µs
Figure 5. Minimum Time for LED Turn–Off to Zero
Cross of AC Trailing Edge
Phase Control Considerations
LED Trigger Current versus PW (normalized)
Random Phase Triac drivers are designed to be phase
controllable. They may be triggered at any phase angle with-
in the AC sine wave. Phase control may be accomplished by
an AC line zero cross detector and a variable pulse delay
generator which is synchronized to the zero cross detector.
The same task can be accomplished by a microprocessor
which is synchronized to the AC zero crossing. The phase
controlled trigger current may be a very short pulse which
saves energy delivered to the input LED. LED trigger pulse
currents shorter than 100 µs must have an increased ampli-
tude as shown on Figure 4. This graph shows the dependen-
cy of the trigger current IFT versus the pulse width t (PW).
The reason for the IFT dependency on the pulse width can be
seen on the chart delay t(d) versus the LED trigger current.
IFT in the graph IFT versus (PW) is normalized in respect to
the minimum specified IFT for static condition, which is speci-
fied in the device characteristic. The normalized IFT has to be
multiplied with the devices guaranteed static trigger current.
Example:
Guaranteed IFT = 10 mA, Trigger pulse width PW = 3 µs
IFT (pulsed) = 10 mA x 5 = 50 mA
Minimum LED Off Time in Phase Control Applications
In Phase control applications one intends to be able to
control each AC sine half wave from 0 to 180 degrees. Turn
on at zero degrees means full power and turn on at 180 de-
gree means zero power. This is not quite possible in reality
because triac driver and triac have a fixed turn on time when
activated at zero degrees. At a phase control angle close to
180 degrees the driver’s turn on pulse at the trailing edge of
the AC sine wave must be limited to end 200 µs before AC
zero cross as shown in Figure 5. This assures that the triac
driver has time to switch off. Shorter times may cause loss of
control at the following half cycle.
Motorola Optoelectronics Device Data
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