CA3059

Manufacturer Part NumberCA3059
DescriptionZERO VOLTAGE CROSSING SWITCH
ManufacturerIntersil
CA3059 datasheet
 


Specifications of CA3059

Rohs StatusRoHS non-compliant  
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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
approaches V
13
point, the transistor pair Q
-Q
turns on and inhibits any further
2
4
pulses. The controlled temperature is adjusted by variation of
the value of the potentiometer R
. For cooling service, either the
P
positions of R
and the sensor may be reversed or terminals 9
P
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
and R
, are not used, but are replaced
4
5
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-
nal supply, no external load on the supply, and terminal 14
connected to terminal 13.
2. The value of potentiometer R
and of the sensor resis-
P
tance must be between 2000 and 0.1M .
3. The ratio of sensor resistance and R
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.)
The protective feature may be applied to other systems
when operation of the circuit is understood. The protection
circuit consists of diodes D
and D
12
15
Diode D
activates the protection circuit if the sensor shown
1
in Figure 1 shorts or its resistance drops too low in value, as
follows: Transistor Q
is on during an output pulse so that the
6
junction of diodes D
and D
is 3 diode drops (approxi-
8
12
mately 2V) above terminal 7. As long as V
or only 0.15 volt negative with respect to that point, diode
D
does not conduct, and the circuit operates normally. If
12
the voltage at terminal 14 drops to 1 volt, the anode of diode
D
can have a potential of only 1.6 to 1.7V, and current does
8
not flow through diodes D
and D
and transistor Q
8
9
thyristor then turns off.
The actual threshold is approximately 1.2V at room tempera-
ture, but decreases 4mV per degree C at higher
Application Note 6182
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
. At this
sistor Q
and the thyristor. If the supply voltage is not at least
9
6
0.2 volt more positive than the breakdown voltage of diode
D
, activation of the protection circuit is not possible. For
15
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.
at balance
7
6
5
4
3
2
1
0
-50
-25
FIGURE 7. OPERATING REGIONS FOR BUILT-IN PROTECTION
CIRCUITS OF A TYPICAL ZERO-VOLTAGE SWITCH.
Special Application Considerations
As pointed out previously, the Intersil integrated circuit zero-
voltage switches (CA3059 and CA3079) are exceptionally
must be greater
P
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
and transistor Q
.
10
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
is more positive
14
directly from the AC line, a dropping resistor R
10,000
must be connected in series with terminal 5 to limit
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
. The
6
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.
5
breaks
15
, which then turns off tran-
10
THYRISTOR TURN-OFF
AREA OF UNCERTAIN
OPERATION
AREA OF NORMAL
OPERATION
AREA OF UNCERTAIN
OPERATION
THYRISTOR TURN-OFF
0
25
50
75
o
AMBIENT TEMPERATURE (
C)
of 5,000 to
S
for AC line voltages 24, 120, 208 to
S