tca280b Hendon Semiconductors, tca280b Datasheet - Page 19

• Manufacturer Part Number: tca280b
• Description: General Purpose Triggering Circuit
• Manufacturer: Hendon Semiconductors

Integrated Electronic Solutions, Hendon, South Australia
10.4
Fig. 13 shows the circuit diagram of
the current source of the difference
amplifier (TR14, R9, D13, D14). If the
current flowing. through pin 3 is
positive, the current source of the
difference amplifier is supplied via
D11: if the current is negative, supply
is via TR8 and TR9. The amplifier is
inhibited by cutting off the current
supply to pin 3, so that TR14 is cut off.
This stage is needed for single-pulse
phase control. When controlling
inductive loads, it serves to delay the
trigger pulse until the voltage on
2002 Nov 08
General purpose triggering circuit
Inhibiting stage
+
−
11
16
Fig.13 Connection of the difference amplifier
terminal 2 of the triac is restored when
the trigger angle is adjusted to be
smaller than the phase angle
between the load current and the load
voltage. Thus the load receives
maximum power. The inhibiting stage
blocks TR14 as long as the triac
keeps conducting. Not until the
voltage on pin 3 is restored. by the
triac switching off, will the current
source be switched on again. thus
starting the (delayed) trigger pulse.
QC−
IC−
6
7
TR8
R8
10.1
kΩ
RX1
3
D11
TR9
D12
18
TR10
TR12
D13
D14
TR14
R9
2.4
kΩ
TR11
TR13
4
5
QC+
IC+
feedback from
amplifier
−
Fig-13-circuit
10.5
The difference amplifier (Fig. 13)
consists of transistors TR12 and
TR13 forming a long-tail pair. Any
current through pin 3 exceeding
10 A activates the current source,
and thus the difference amplifier. In all
cases where the inhibiting stage is not
used, pin 3 must receive current via a
resistor connected to the supply
voltage to keep the difference
amplifier at standby for operation.
TR10 and TR11 are the output stages
of the difference amplifier.
−
+
Difference amplifier
TCA280B
Data Sheet