CA3059

Manufacturer Part NumberCA3059
DescriptionZERO VOLTAGE CROSSING SWITCH
ManufacturerIntersil
CA3059 datasheet
 


Specifications of CA3059

Rohs StatusRoHS non-compliant  
1
2
3
4
5
6
7
8
9
10
11
Page 11
12
Page 12
13
Page 13
14
Page 14
15
Page 15
16
Page 16
17
Page 17
18
Page 18
19
Page 19
20
Page 20
21
22
23
24
25
26
27
28
29
30
31
Page 17/31

Download datasheet (595Kb)Embed
PrevNext
that, though the gate pulse V
of triac Y
G
Y
is switched on by the current through R
2
ing current of the sensitive gate triac results in dissipation of
only 2W in R
, as opposed to 10 to 20W when devices that
L1
have high latching currents are used.
Electric Heat Application
For electric heating applications, the 40A triac and the zero-
voltage switch constitute an optimum pair. Such a combina-
tion provides synchronous switching and effectively replaces
the heavy-duty contactors which easily degrade as a result
of pitting and wear-out from the switching transients. The
salient features of the 40A triac are as follows:
1. 300A single surge capability (for operation at 60Hz).
2. A typical gate sensitivity of 20mA in the I(+) and III(+) modes.
3. Low on state voltage of 1.5V maximum at 40A.
4. Available V
equal to 600V.
DROM
Figure 35 shows the circuit diagram of a synchronous
switching heat staging controller that is used for electric
heating systems. Loads as heavy as 5kW are switched
sequentially at zero-voltage to eliminate RFI and prevent a
dip in line voltage that would occur if the full 25kW were to be
switched simultaneously.
Transistor Q
and Q
are used as a constant current source
1
4
to charge capacitor C in a linear manner. Transistor Q
as a buffer stage. When the thermostat is closed, a ramp
voltage is provided at output E
. At approximately 3 second
O
intervals, each 5kW heating element is switched onto the
power system by its respective triac. When there is no fur-
ther demand for heat, the thermostat opens, and capacitor C
discharges through R1 and R2 to cause each triac to turn off
in the reverse heating sequence. It should be noted that
some half cycling occurs before the heating element is
switched fully on. This condition can be attributed to the
inherent dissymmetry of the triac and is further aggravated
by the slow rising ramp voltage applied to one of the inputs.
The timing diagram in Figure 36 shows the turn-on and turn-
off sequence of the heating system being controlled.
Seemingly, the basic method shown in Figure 35 could be
modified to provide proportional control in which the number
of heating elements switched into the system, under any
given thermal load, would be a function of the BTU’s
required by the system or the temperature differential
between an indoor and outdoor sensor within the total sys-
tem environment. That is, the closing of the thermostat
would not switch in all the heating elements within a short
time interval, which inevitable results in undesired tempera-
ture excursions, but would switch in only the number of
heating elements required to satisfy the actual heat load.
Application Note 6182
has elapsed, triac
1
. The low latch-
L1
4
3
2
3
1
3
FIGURE 36. RAMP VOLTAGE WAVEFORM FOR THE HEAT
STAGING CONTROLLER
Oven/Broiler Control
Zero-voltage switching is demonstrated in the oven control
circuit shown in Figure 37. In this circuit, a sensor element is
included in the oven to provide a closed loop system for
accurate control of the oven temperature.
As shown in Figure 37, the temperature of the oven can be
adjusted by means of potentiometer R
with the sensor, as a voltage divider at terminal 13. The volt-
age at terminal 13 is compared to the fixed bias at terminal 9
acts
which is set by internal resistors R
2
is cold and the resistance of the sensor is high, transistors
Q
and Q
are off, a pulse of gate current is applied to the
2
4
triac, and heat is applied to the oven. Conversely, as the
desired temperature is reached, the bias at terminal 13 turns
the triac off. The closed loop feature then cycles the oven
element on and off to maintain the desired temperature to
approximately
noted, external resistors between terminals 13 and 8, and 7
and 8, can be used to vary this temperature and provide hys-
teresis. In Figure 11, a circuit that provides approximately 10
percent hysteresis is demonstrated.
In addition to allowing the selection of a hysteresis value, the
flexibility of the control circuit permits incorporation of other
features. A PTC sensor is readily used by interchanging ter-
minals 9 and 13 of the circuit shown in Figure 37 and
substituting the PTC for the NTC sensor. In both cases, the
sensor element is directly returned to the system ground or
common, as is often desired. Terminal 9 can be connected
by external resistors to provide for a variety of biasing, e.g.,
to match a lower resistance sensor for which the switching
point voltage has been reduced to maintain the same sensor
current.
To accommodate the self-cleaning feature, external switch-
ing, which enables both broiler and oven units to be
paralleled, can easily be incorporated in the design. Of
course, the potentiometer must be capable of a setting such
that the sensor, which must be characterized for the high,
self-clean temperature, can monitor and establish control of
the high temperature, self-clean mode. The ease with which
this self-clean mode can be added makes the overall solid
state systems cost competitive with electromechanical sys-
17
3
3
2
3
10
5
TIME (s)
, which acts, together
1
and R
. When the oven
4
5
o
2
C of the set value. Also, as has been