tca785_ph_ctrl

Semiconductor Group

7

         TCA 785

Pulse Extension versus Temperature

Ramp capacitance

Triggering point

Charge current

The minimum and maximum values of I10
are to be observed

min

max

tTr =

C10

500 pF

1

 µF1)

2)

I10 =

2)

V11

× R9 × C10

VREF

× K

VREF

× K

R9

V10 max = VS – 2 V V10 =

VREF

× K × t

R9

 × C10

2)

Ramp voltage

Application Hints for External Components

1) Attention to flyback times
2) K = 1.10

± 20 %

Semiconductor Group

8

         TCA 785

Supply Current versus Supply Voltage

Output Voltage measured to + VS

Semiconductor Group

9

         TCA 785

Test Circuit 1

It is necessary for all measurements to adjust the ramp with
the aid of C10 and R 9 in the way that 3 V

≤ Vramp max ≤ V S – 2 V

e.g. C10 = 47 nF; 18 V: R 9 = 47 k

Ω; 8 V: R 9 = 120 kΩ

Semiconductor Group

10

         TCA 785

Test Circuit 2

Test Circuit 3

The remaining pins are connected as in test circuit 1

The remaining pins are connected as in test circuit 1

Semiconductor Group

11

         TCA 785

Test Circuit 4

Remaining pins are connected as in test circuit 1
The 10

 µF capacitor at pin 5 serves only for test purposes

Test Circuit 5

Test Circuit 6

Semiconductor Group

12

         TCA 785

Inhibit 6

Long Pulse 13

Pulse Extension 12

Reference Voltage 8

Semiconductor Group

13

         TCA 785

A phase control with a directly controlled triac is shown in the figure. The triggering angle of
the triac can be adjusted continuously between 0˚ and 180˚ with the aid of an external
potentiometer. During the positive half-wave of the line voltage, the triac receives a positive
gate pulse from the IC output pin 15. During the negative half-wave, it also receives a positive
trigger pulse from pin 14. The trigger pulse width is approx. 100

 µs.

Application Examples
Triac Control for up to 50 mA Gate Trigger Current

Semiconductor Group

14

         TCA 785

Shown is the possibility to trigger two antiparalleled thyristors with one IC TCA 785. The trigger
pulse can be shifted continuously within a phase angle between 0˚ and 180˚ by means of a
potentiometer. During the negative line half-wave the trigger pulse of pin 14 is fed to the
relevant thyristor via a trigger pulse transformer. During the positive line half-wave, the gate of
the second thyristor is triggered by a trigger pulse transformer at pin 15.

Fully Controlled AC Power Controller
Circuit for Two High-Power Thyristors

Semiconductor Group

15

         TCA 785

Half-Controlled Single-Phase Bridge Circuit with Trigger Pulse Transformer and Direct
Control for Low-Power Thyristors

Semiconductor Group