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

MOC3051-M
Figure 9. Delay Time, t(d), and Fall Time, t(f),
vs. LED Trigger Current
100
10
t(d)
1
t(f)
0.1
10
20
30
40
50
60
I_FT, LED TRIGGER CURRENT (mA)
+400
Vdc
PULSE
INPUT
RTEST
R = 1 kΩ
MERCURY
WETTED
RELAY
CTEST
D.U.T.
X100
SCOPE
PROBE
6-PIN DIP RANDOM-PHASE
OPTOISOLATORS TRIAC DRIVERS
(600 VOLT PEAK)
MOC3052-M
t(delay), t(f) versus I_FT
The triac driver’s turn on switching speed consists of a turn on
delay time t(d) and a fall time t(f). Figure 9 shows that the delay
time depends on the LED trigger current, while the actual
trigger transition time t(f) stays constant with about one micro
second.
The delay time is important in very short pulsed operation
because it demands a higher trigger current at very short
trigger pulses. This dependency is shown in the graph I_FT
versus LED PW.
The turn on transition time t(f) combined with the power triac’s
turn on time is important to the power dissipation of this
device.
ISOL. TRANSF.
AC
SCOPE
IFT
VTM
t(d)
t(f)
ZERO CROSS
DETECTOR
EXT. SYNC
FUNCTION
GENERATOR
Vout
115 VAC
PHASE CTRL.
PW CTRL.
PERIOD CTRL.
Vo AMPL. CTRL.
VTM
IFT
10 kΩ
DUT
100 Ω
APPLIED VOLTAGE
WAVEFORM
0 VOLTS
252 V
τ_RC
Vmax = 400 V
dv/dt = ^{0.63 V}
τ_RC
=_τ
Figure 10. Static dv/dt Test Circuit
1. The mercury wetted relay provides a high speed repeated
pulse to the D.U.T.
2. 100x scope probes are used, to allow high speeds and
voltages.
3. The worst-case condition for static dv/dt is established by
triggering the D.U.T. with a normal LED input current, then
removing the current. The variable R_TEST allows the dv/dt to
be gradually increased until the D.U.T. continues to trigger
in response to the applied voltage pulse, even after the LED
current has been removed. The dv/dt is then decreased
until the D.U.T. stops triggering. τ_RC is measured at this
point and recorded.
© 2004 Fairchild Semiconductor Corporation
Page 6 of 11
9/2/04