
Application Notes
AN1003
2002 Teccor Electronics
Thyristor Product Catalog
AN1003 - 5
http://www.teccor.com
+1 972-580-7777
Figure AN1003.13
Precision Proportional Temperature Control
Several speed control and light dimming (phase) control circuits
have been presented that give details for a complete 120 V appli-
cation circuit but none for 240 V. Figure AN1003.14 and Figure
AN1003.15 show some standard phase control circuits for 240 V,
60 Hz/50 Hz operation along with 120 V values for comparison.
Even though there is very little difference, there are a few key
things that must be remembered. First, capacitors and triacs con-
nected across the 240 V line must be rated at 400 V. Secondly,
the potentiometer (variable resistor) value must change consider-
ably to obtain the proper timing or triggering for 180° in each half-
cycle.
Figure AN1003.14 shows a simple single-time-constant light dim-
mer (phase control) circuit, giving values for both 120 V and
240 V operation.
Figure AN1003.14
Single-time-constant Circuit for Incandescent Light
Dimming, Heat Control, and Motor Speed Control
The circuit shown in Figure AN1003.15 is a double-time-constant
shown in Figure AN1003.14. This circuit uses an additional RC
network to extend the phase angle so that the triac can be trig-
gered at small conduction angles. The additional RC network
also minimizes any hysteresis effect explained and illustrated in
Figure AN1003.10 and
Figure AN1003.11.
Figure AN1003.15
Double-time-constant Circuit for Incandescent Light
Dimming, Heat Control, and Motor Speed Control
Load
120 V
(60 Hz)
R2
R6
R7
R3
R4
R8
D2
D1
D6
D3
R1
D5
TR5
T
T1
C1
Q1
D4
Q2
Triac
"Gain"
0
Ramp
Time
Cool
Hot
UJT Triggering Level
Pedestal
UJT Emitter Voltage
R1, R2 = 2.2 k, 2 W
R3 = 2.2 k, 1/2 W
R4 = Thermistor, approx. 5 k
at operating temperature
R5 = 10 k Potentiometer
R6 = 5 M Potentiometer
R7 = 100 k, 1/2 W
R8 = 1 k, 1/2 W
Q1 = 2N2646
Q2 = Q2010L5
T1 = Dale PT 10-101
or equivalent
D1-4 = 200 V Diode
D5 = 20 V Zener
D6 = 100 V Diode
C1 = 0.1
μ
F, 30 V
0.1 μF 200 V
0.1 μF 400 V
AC
Input
Voltage
120 V ac
60 Hz
240 V ac
50/60 Hz
12 A
3 A
250 k
500 k
Q2015L9
Q4004L4
100 μH
200 μH
R1
Q1
L1
C1, C3
R1
R2
3.3 k
C1
HT-32
AC
Input
C2
D1
Q1
L1
R3 *
100
C3 *
Load
Note: L1 and C1 form an
RFI filter that may be eliminated
* dv/dt snubber network
when required
0.1 μF
100 V
AC
Load
Current
0.1 μF 200 V
0.1 μF 400 V
0.1 μF 400 V
AC
Input
Voltage
120 V ac
60 Hz
240 V ac
50 Hz
240 V ac
60 Hz
8 A
6 A
6 A
250 k
500 k
500 k
Q2010L5
Q4008L4
Q4008L4
100 μH
200 μH
200 μH
R2
Q1
L1
C1, C2, C4
R2
R1
3.3 k
C1
HT-32
AC
Input
C2
D1
Q1
L1
R4 *
100
C4 *
Note: L1 and C1 form an
* dv/dt snubber network
when required
R3
0.1 μF
100 V
15 k
1/2 W
C3
Load
AC
Load
Current