tca280b Hendon Semiconductors, tca280b Datasheet - Page 15

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

Integrated Electronic Solutions, Hendon, South Australia
10 APPLICATION INFORMATION
The reliability of modern thyristors
and triacs has given a strong impetus
to the introduction of electronic power
control in industrial as well as
non-industrial areas. Because of the
low cost of these devices and
simplification in trigger circuitry,
electronic power control now enjoys a
host of applications such as electronic
household cookers, panel radiators,
fans, hobby tools, and even vacuum
cleaners.
The monolithic integrated trigger
circuit TCA280B, referred to as a
trigger module, supplies the pulses
for triggering these thyristors and
triacs. This module can be connected
to the mains via a dropping resistor
and, in most cases, no trigger
transformer is needed.
The TCA280B is an inexpensive,
versatile trigger module and, being a
monolithic IC in 16-pin dual in-line
package, it takes up hardly any space
at all. It is ideally suited for
applications such as:
1. On/off control: static switch.
2002 Nov 08
General purpose triggering circuit
On/off control is a method of
power control where triggering.
should preferably occur
symmetrically with respect to the
zero crossing of the triac current
to avoid r.f. interference. That is,
triggering must start before the
current has dropped to the
holding value, and must continue
2. Phase control: single phase and
3. Time proportional control:
until the current has risen again
above the latching level. Under
these conditions radio
interference is kept at a minimum.
three phase control (half cycle
and full cycle).
Phase control is stepless control
of output power by varying the
conduction angle of the triac or
thyristor, 180 degree conduction
corresponding to full output
power. Step changes in thyristor
voltage and current during
turn-on give rise to r.f.
interference, so that phase
control is limited to a few hundred
watts if the regulations on
interference are to be complied
with. It should be noted that
phase control is not permitted for
heating purposes.
temperature and motor. speed
control.
Time proportional control is on/off
control with a fixed repetition rate
of load switching. The system is
called time proportional because
the power in the load averaged
over the repetition period is
varied. This system provides
more accurate temperature
control, avoiding the overshoot
which is inherent in on/off control.
Triggering conditions are the
same as for on/off control.
14
10.1
Fig.10 shows the circuit diagram of
the TCA280B. It comprises the
following circuit sections:
d.c. supply fed from the mains via a
dropping resistor and diode;
zero-crossing detector for
synchronization of the trigger
pulses;
difference amplifier passing a
signal from a sensor, or indication
of a potentiometer setting or switch
position, etc.;
inhibiting stage rendering the
difference amplifier immune to
sensor signals, etc.;
ramp function generator operating
as the sawtooth oscillator in time
proportional control;
output amplifier amplifying the
trigger pulses and feeding the triac
(or thyristor) gate.
The TCA280B circuit
TCA280B
Data Sheet