tca280b Hendon Semiconductors, tca280b Datasheet - Page 20

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

Integrated Electronic Solutions, Hendon, South Australia
10.6
Fig 14 shows the circuit diagram of
the ramp function generator which
consists of the voltage reference
diode D15, the current source TR18,
the unijunction transistor
TR15 TR16, and the inverting
amplifier TR17. The unijunction
transistor starts to conduct when the
2002 Nov 08
General purpose triggering circuit
Ramp function generator
Vref from
D8 and D9
Fig.14 Connection of the ramp function (sawtooth) generator
+
−
16
11
voltage between pins 14 and 16
exceeds the voltage across D15 plus
the base-emitter threshold voltage of
TR15, and cuts off again when its
current drops below the holding level.
This level is determined by R12.
With a time-proportional switch, the
sawtooth voltage produced by the
ramp function generator serves to
C2
QS 15
IS
14
R13
TR15
19
9.5
kΩ
R10
2.75
kΩ
TR16
1.9 kΩ
15 kΩ
R12
R11
TR17
R14
6.8
kΩ
TR18
D15
D16
TR19
TR21
D17
TR20
Fig-14-circuit
D18
provide the repetition frequency of
load switching that can be adjusted
with the control voltage.
In phase control with trigger burst, the
flyback of the sawtooth is used as the
drive signal for generating the trigger
pulse. During flyback, TR17 is
conducting.
+
−
TCA280B
Data Sheet