CA3059 Intersil, CA3059 Datasheet - Page 19

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

Specifications of CA3059

• Rohs Status: RoHS non-compliant

FIGURE 37. SCHEMATIC DIAGRAM OF BASIC OVEN CONTROL
Integral Cycle Temperature Controller (No half cycling)
If a temperature controller which is completely devoid of half
cycling and hysteresis is required, then the circuit shown in
Figure 38 may be used. This type of circuit is essential for
applications in which half cycling and the resultant DC com-
ponent could cause overheating of a power transformer on
the utility lines.
In the integral cycle controller, when the temperature being
controlled is low, the resistance of the thermistor is high, and
an output signal at terminal 4 of zero volts is obtained. The
SCR (Y
gered directly from the line on positive cycles of the AC
voltage. When Y
R
When the AC line swings negative, capacitor C discharges
through the triac gate to trigger the triac on the negative half
cycle. The diode-resistor-capacitor “slaving network” triggers
the triac on negative half cycle to provide only integral cycles
of AC power to the load.
When the temperature being controlled reaches the desired
value, as determined by the thermistor, then a positive volt-
age level appears at terminal 4 of the zero-voltage switch.
The SCR then starts to conduct at the beginning of the posi-
tive input cycle to shunt the trigger current away from the
gate of the triac. The triac is then turned off. The cycle
repeats when the SCR is again turned OFF by the zero-volt-
age switch.
The circuit shown in Figure 39 is similar to the configuration
in Figure 38 except that the protection circuit incorporated in
the zero-voltage switch can be used. In this new circuit, the
NTC sensor is connected between terminals 7 and 13, and
transistor Q
the phase reversal introduced by the SCR (Y
power supply of the zero-voltage switch supplies bias current
to transistor Q
Of course, the circuit shown in Figure 39 can readily be con-
verted to a true proportional integral cycle temperature
L1
L2
L
220 V
, capacitor C is charged to the peak of the input voltage.
AC
SW1
SENSOR
1
), therefore, is turned off. The triac (Y
NTC
P1
OFF
0
inverts the signal output at terminal 4 to nullify
0
.
2
is triggered and supplies power to the load
14
13
2
8
7
3
ZVS
9
10
11
5
5K
8 W
BROILER
4
OVEN
1
Application Note 6182
). The internal
2
) is then trig-
19
VOLT.
REF.
6.2K
ADJ
controller simply by connection of a positive going ramp
voltage to terminal 9 (with terminals 10 and 11 open), as
previously discussed in this Note.
Thermocouple Temperature Control
Figure 40 shows the CA3080A operating as a preamplifier
for the zero-voltage switch to form a zero-voltage switching
circuit for use with thermocouple sensors.
Thermocouple Temperature Control with Zero-Voltage
Load Switching
Figure 41 shows the circuit diagram of a thermocouple tem-
perature control system using zero-voltage load switching. It
should be noted that one terminal of the thermocouple is
connect to one leg of the supply line. Consequently, the ther-
mocouple can be “ground referenced”, provided the
appropriate leg of the AC line is maintained at ground. The
comparator, A
of potential provided by the zero-voltage switch (ZVS) circuit
(a CA3079). The ZVS, in turn, is powered off-line through a
series dropping resistor R
trigger pulses to the gate of the load switching triac in
response to an appropriate control signal at terminal 9.
10K
FIGURE 40. THERMOCOUPLE TEMPERATURE CONTROL
FIGURE 41. THERMOCOUPLE TEMPERATURE CONTROL
20K
R
1
6.2K
Hysteresis = R3/R4 x 6.4V = 1K/5.1M x 6.4V = 1.25mV
150K
2K
0.1 F
200K
THERMO-
100K
COUPLE
R
R
1K
R
2K
2
2
3
2
3
WITH ZERO-VOLTAGE SWITCHING
WITH ZERO-VOLTAGE SWITCHING
IN914
IN914
+
THERMO-
2
3
-
1
COUPLE
1
A1
COMPARATOR
CA3130
(a CA3130), is powered from a 6.4V source
100K
5.1M
R
R
CA
3080A
-
+
4
4
7
5
5
5
R
7
4
F
50K
6
100 F
. Terminal 4 of the ZVS provides
10V
6
6
+
13
-
6
+
-
100 F
All Resistors 1/2W,
Unless Otherwise Specified
+6.4V
9
8
2
7
ZVS
CA3079
2
7
ZVS
8
10
3
10
5
9
4W
5K
4W
5K
11
R
11
6
13
5
6
TRIAC
4
G
LOAD
LOAD
MT
MT
120VAC
60Hz
2
1
VAC
120