CA3059 Intersil, CA3059 Datasheet - Page 6

• Manufacturer Part Number: CA3059
• Description: ZERO VOLTAGE CROSSING SWITCH
• Manufacturer: Intersil

Specifications of CA3059

• Rohs Status: RoHS non-compliant

Half Cycling Effect
The method by which the zero-voltage switch senses the
zero crossing of the AC power results in a half cycling
phenomenon at the control point. Figure 10 illustrates this
phenomenon. The zero-voltage switch senses the zero-
voltage crossing every half cycle, and an output, for example
pulse No. 4, is produced to indicate the zero crossing.
During the remaining 8.3ms, however, the differential
amplifier in the zero-voltage switch may change state and
inhibit any further output pulses. The uncertainty region of
the differential amplifier, therefore, prevents pulse No. 5 from
triggering the triac during the negative excursion of the AC
line voltage.
When a sensor with low sensitivity is used in the circuit, the
zero-voltage switch is very likely to operate in the linear
FIGURE 8. OPERATION OF THE ZERO-VOLTAGE SWITCH
FIGURE 9. DC SUPPLY VOLTAGE AS A FUNCTION OF EXTER-
120VRMS
ALL RESISTANCE
VALUES ARE IN
6.5
6.0
5.5
5.0
4.5
4.0
3.5
60Hz
0
120V
R
S
10K
FROM AN EXTERNAL DC POWER SUPPLY CON-
NECTED BETWEEN TERMINALS 2 AND 7.
NAL LOAD CURRENT FOR SEVERAL VALUES
RMS
1
, 50-60Hz OPERATION
12
7
2
EXTERNAL LOAD CURRENT (mA)
3
3
R
5
ZVS
S
R
8
R
= 5K (PULSE MODE)
S
S
2
9
= 10K (INHIBIT MODE)
4
= 10K (PULSED MODE)
10
V
13
11
CC
5K
R
S
5
= 5K (INHIBIT MODE)
100 F
6
6K
4
Application Note 6182
TO
THYRISTOR
GATE
7
8
6
120V
mode. In this mode, the output trigger current may be
sufficient to trigger the triac on the positive going cycle, but
insufficient to trigger the device on the negative going cycle
of the triac supply voltage. This effect introduces a half
cycling phenomenon, i.e., the triac is turned on during the
positive half cycle and turned off during the negative half
cycle.
Several techniques may be used to cope with the half cycling
phenomenon. If the user can tolerate some hysteresis in the
control, then positive feedback can be added around the dif-
ferential amplifier. Figure 11 illustrates this technique. The
tabular data in the figure lists the recommended values of
resistors R1 and R2 for different sensor impedances at the
control point.
FIGURE 11. CA3059 ON-OFF CONTROLLER WITH HYSTERESIS
If a significant amount (greater than
hysteresis is required, then the circuit shown in Figure 12
may be employed. In this configuration, external transistor
Q
TRIGGER
FIGURE 10. HALF CYCLING PHENOMENON IN THE ZERO-
60Hz
VOLTAGE
PULSES
1
OUT OF
CA3059
AC
can be used to provide an auxiliary timed delay function.
LOAD
+
-
100 F
15V
V
0.001
L
DC
F
VOLTAGE SWITCH
R
NTC
SENSOR
P
1/2W
1/2W
1
8.3ms
R
R
THERMISTOR
1
2
2
14
13
2
8
7
3
10K
2W
4
5
9
CA3059
8.3ms
10
6
5
10%) of controlled
11
100K 200K 18K
1
NTC
12K 68K
5K
6
3
12
12K
7
R1
4
R
8
L
G
12K
12K
R2
MT
MT
2
1