MOC3052M Datasheet, PDF (7/11 Pages) Fairchild Semiconductor – 6-PIN DIP RANDOM-PHASE OPTOISOLATORS TRIAC DRIVERS (600 VOLT PEAK)

6-PIN DIP RANDOM-PHASE
OPTOISOLATORS TRIAC DRIVERS
(600 VOLT PEAK)
MOC3051-M
MOC3052-M
APPLICATIONS GUIDE
Basic Triac Driver Circuit
The new random phase triac driver family MOC3052-M and
MOC3051-M are very immune to static dv/dt which allows
snubberless operations in all applications where external
generated noise in the AC line is below its guaranteed dv/dt
withstand capability. For these applications a snubber circuit is
not necessary when a noise insensitive power triac is used.
Figure 11 shows the circuit diagram. The triac driver is directly
connected to the triac main terminal 2 and a series Resistor R
which limits the current to the triac driver. Current limiting
resistor R must have a minimum value which restricts the
current into the driver to maximum 1A.
R = Vp AC/I_TM max rep. = Vp AC/1A
The power dissipation of this current limiting resistor and the
triac driver is very small because the power triac carries the
load current as soon as the current through driver and current
limiting resistor reaches the trigger current of the power triac.
The switching transition times for the driver is only one micro
second and for power triacs typical four micro seconds.
Triac Driver Circuit for Noisy Environments
When the transient rate of rise and amplitude are expected to
exceed the power triacs and triac drivers maximum ratings a
snubber circuit as shown in Figure 12 is recommended. Fast
transients are slowed by the R-C snubber and excessive
amplitudes are clipped by the Metal Oxide Varistor MOV.
Triac Driver Circuit for Extremely Noisy Environments, as
specified in the noise standards IEEE472 and IEC255-4.
Industrial control applications do specify a maximum transient
noise dv/dt and peak voltage which is superimposed onto the
AC line voltage. In order to pass this environment noise test a
modified snubber network as shown in Figure 13 is recom-
mended.
VCC RLED ^{TRIAC DRIVER}
POWER TRIAC
CONTROL
Q
AC LINE
R
LOAD
RET.
RLED = (VCC - V _F LED - V _sat Q)/IFT
R = Vp AC line/ITSM
Figure 11. Basic Driver Circuit
VCC RLED ^{TRIAC DRIVER}
POWER TRIAC
CONTROL
RET.
RS
R
MOV ^{AC LINE}
CS
LOAD
Typical Snubber values RS = 33 Ω, CS = 0.01 µF
MOV (Metal Oxide Varistor) protects triac and
driver from transient overvoltages >VDRM max.
Figure 12. Triac Driver Circuit for Noisy Environments
POWER TRIAC
VCC RLED ^{TRIAC DRIVER}
R
CONTROL
RET.
RS
MOV ^{AC LINE}
CS
LOAD
Recommended snubber to pass IEEE472 and IEC255-4 noise tests
RS = 47 W, CS = 0.01 mF
Figure 13. Triac Driver Circuit for Extremely Noisy
Environments
© 2004 Fairchild Semiconductor Corporation
Page 7 of 11
9/2/04