CA3059 Intersil, CA3059 Datasheet - Page 8

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

Specifications of CA3059

• Rohs Status: RoHS non-compliant

applied to terminal 13 of the zero-voltage switch, and
triggers the triac on.
“Proportional Control” Systems
The on/off nature of the control shown in Figure 1 causes
some overshoot that leads to a definite steady state error.
The addition of hysteresis adds further to this error factor.
However, the connections shown in Figure 15A. can be used
to add proportional control to the system. In this circuit, the
sense amplifier is connected as a free running multivibrator.
At balance, the voltage at terminal 13 is much less than the
voltage at terminal 9. The output will be inhibited at all times
until the voltage at terminal 13 rises to the design differential
voltage between terminals 13 and 9; then proportional con-
trol resumes. The voltage at terminal 13 is as shown in Fig-
ure 15B). When this voltage is more positive than the
threshold, power is applied to the load so that the duty cycle
is approximately 50 percent. With a 0.1M
ues of R
period greater than 3 seconds is achieved. This period
should be much shorter than the thermal time constant of
the system. A change in the value of any of these elements
changes the period, as shown in Figure 16. As the resis-
tance of the sensor changes, the voltage on terminal 13
moves relative to V
tive direction. The triac is on for a larger portion of the pulse
cycle and increases the average power to the load.
FIGURE 15. USE OF THE CA3059 IN A TYPICAL HEATING CON-
120V
60Hz
AC
+
-
V
100 F
15V
P
DC
= 01.M , R
TROL WITH PROPORTIONAL CONTROL: A.
TRIAC
OFF
R
NTC
SENSOR
P
9
. A cooling sensor moves V
C
10 F
1/2W
EXT
R
2
FIGURE 15A.
FIGURE 15B.
2
= 10,000 , and C
TRIAC
ON
t
14
13
2
8
7
10K
2W
5
9
CA3059
10
6
11
V
1
9
sensor and val-
THRESHOLD
VOLTAGE
3
EXT
Application Note 6182
12
13
= 10 F, a
in a posi-
4
R
L
G
MT
MT
2
1
8
As in the case of the hysteresis circuitry described earlier,
some special applications may require more sophisticated
systems to achieve either very precise regions of control or
very long periods.
Zero-voltage switching control can be extended to applications
in which it is desirable to have constant control of the
temperature and a minimization of system hysteresis. A closed
loop top burner control in which the temperature of the cooking
utensil is sensed and maintained at a particular value is a good
example of such an application; the circuit for this control is
shown in Figure 17. In this circuit, a unijunction oscillator is
outboarded from the basic control by means of the internal
power supply of the zero-voltage switch. The output of this
ramp generator is applied to terminal 9 of the zero-voltage
switch and establishes a varied reference to the differential
amplifier. Therefore, gate pulses are applied to the triac
whenever the voltage at terminal 13 is greater than the voltage
at terminal 9. A varying duty cycle is established in which the
load is predominantly on with a cold sensor and predominantly
off with a hot sensor. For precise temperature regulation, the
time base of the ramp should be shorter than the thermal time
constant of the system but longer than the period of the 60Hz
line. Figure 18, which contains various waveforms for the
system of Figure 17, indicates that a typical variance of 0.5
might be expected at the sensor contact to the utensil.
Overshoot of the set temperature is minimized with approach,
FIGURE 16. EFFECT OF VARIATIONS IN TIME CONSTANT ELE-
15
12
SCHEMATIC DIAGRAM, AND B. WAVEFORM OF
VOLTAGE AT ERMINAL 13
MENTS ON PERIOD
9
5
3
0
0
FIRING RATE (FLASHED/MINUTE)
20
R
G
, R
40
P
100K
130K
= 82K
60
C
EXT
80
= 10 F
100
120
o
C