CA3059 Intersil, CA3059 Datasheet - Page 5

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

Specifications of CA3059

• Rohs Status: RoHS non-compliant

low temperatures, the high resistance of the sensor causes ter-
minal 13 to be positive with respect to terminal 9 so that the thy-
ristor fires on every half cycle, and power is applied to the load.
As the temperature increases, the sensor resistance decreases
until a balance is reached, and V
point, the transistor pair Q
pulses. The controlled temperature is adjusted by variation of
the value of the potentiometer R
positions of R
and 13 may be interchanged.
The low bias current of the sensing amplifier permits opera-
tion with sensor impedances of up to 0.1M
without introduction of substantial error (i.e., greater than 5
percent). The error may be reduced if the internal bridge ele-
ments, resistors R
with resistances which equal the sensor impedance. The
minimum value of sensor impedance is restricted by the cur-
rent drain on the internal power supply. Operation of the
zero-voltage switch with low impedance sensors is dis-
cussed later under Special Application Considerations. The
voltage applied to terminal 13 must be greater than 1.8V at
all times to assure proper operation.
Protection Circuit
A special feature of the CA3059 zero-voltage switch is the
inclusion of an interlock type of circuit. This circuit removes
power from the load by interrupting the thyristor gate drive if
the sensor either shorts or opens. However, use of this cir-
cuit places certain constraints upon the user. Specifically,
effective protection circuit operation is dependent upon the
following conditions:
1. The circuit configuration of Figure 1 is used, with an inter-
2. The value of potentiometer R
3. The ratio of sensor resistance and R
The protective feature may be applied to other systems
when operation of the circuit is understood. The protection
circuit consists of diodes D
Diode D
in Figure 1 shorts or its resistance drops too low in value, as
follows: Transistor Q
junction of diodes D
mately 2V) above terminal 7. As long as V
or only 0.15 volt negative with respect to that point, diode
D
the voltage at terminal 14 drops to 1 volt, the anode of diode
D
not flow through diodes D
thyristor then turns off.
The actual threshold is approximately 1.2V at room tempera-
ture, but decreases 4mV per degree C at higher
12
8
nal supply, no external load on the supply, and terminal 14
connected to terminal 13.
tance must be between 2000 and 0.1M .
than 0.33 and less than 3.0 for all normal conditions. (If ei-
ther of these ratios is not met with an unmodified sensor,
a series resistor or a shunt resistor must be added to avoid
undesired activation of the circuit.)
can have a potential of only 1.6 to 1.7V, and current does
does not conduct, and the circuit operates normally. If
1
activates the protection circuit if the sensor shown
P
and the sensor may be reversed or terminals 9
4
6
and R
8
is on during an output pulse so that the
and D
2
-Q
5
8
, are not used, but are replaced
4
12
and D
turns on and inhibits any further
12
P
. For cooling service, either the
and D
is 3 diode drops (approxi-
P
13
9
and of the sensor resis-
and transistor Q
approaches V
15
and transistor Q
P
14
must be greater
is more positive
Application Note 6182
at balance
9
. At this
6
. The
10
.
5
temperatures. As the sensor resistance increases, the volt-
age at terminal 14 rises toward the supply voltage. At a
voltage of approximately 6V, the zener diode D
down and turns on transistor Q
sistor Q
0.2 volt more positive than the breakdown voltage of diode
D
this reason, loading the internal supply may cause this circuit
to malfunction, as may the selection of the wrong external
supply voltage. Figure 7 shows a guide for the proper opera-
tion of the protection circuit when an external supply is used
with a typical integrated circuit zero-voltage switch.
Special Application Considerations
As pointed out previously, the Intersil integrated circuit zero-
voltage switches (CA3059 and CA3079) are exceptionally
versatile units than can be adapted for use in a wide variety
of power control applications. Full advantage of this versatil-
ity can be realized, however, only if the user has a basic
understanding of several fundamental considerations that
apply to certain types of applications of the zero-voltage
switches.
Operating Power Options
Power to the zero-voltage switch may be derived directly
from the AC line, as shown in Figure 1, or from an external
DC power supply connected between terminals 2 and 7, as
shown in Figure 8. When the zero-voltage switch is operated
directly from the AC line, a dropping resistor R
10,000
the current in the switch circuit. The optimum value for this
resistor is a function of the average current drawn from the
internal DC power supply, either by external circuit elements
or by the thyristor trigger circuits, as shown in Figure 9. The
chart shown in Figure 1 indicates the value and dissipation
rating of the resistor R
230, and 277V.
15
FIGURE 7. OPERATING REGIONS FOR BUILT-IN PROTECTION
, activation of the protection circuit is not possible. For
7
6
5
4
3
2
1
0
-50
6
and the thyristor. If the supply voltage is not at least
must be connected in series with terminal 5 to limit
-25
CIRCUITS OF A TYPICAL ZERO-VOLTAGE SWITCH.
0
AMBIENT TEMPERATURE (
S
25
for AC line voltages 24, 120, 208 to
50
10
, which then turns off tran-
75
THYRISTOR TURN-OFF
AREA OF NORMAL
OPERATION
THYRISTOR TURN-OFF
AREA OF UNCERTAIN
OPERATION
AREA OF UNCERTAIN
OPERATION
o
C)
S
of 5,000 to
15
breaks