6

4766B–INDCO–10/05

U2010B

3.7

Load-current Compensation

The circuit continuously measures the load current as a voltage drop at resistance R

uation and use of both half waves results in a quick reaction to load-current change. Due to the

voltage at resistance R

difference controls the internal current source, whose positive current values are available at

pins 5 and 6. The output current generated at pin 5 contains the difference from the load-current

detection and from the mains voltage compensation, see Figure 1-2 on page 2.

The efficient impedance of the set-point network generates a voltage at pin 4. A current, flowing

out of pin 5 through R

increase of control angle

α, an increase of load current results in a decrease in the control angle.

This avoids a decrease in revolution by increasing the load as well as an increase of revolution

by the increment of the mains supply voltage.

3.8

Load-current Limitation

The total output load current is available at pin 6. It results in a voltage drop across R

the potential of the load current reaches about 70% of the threshold value (V

V at pin 6, it switches the high-load comparator and opens the switch between pins 11 and 12.

By using an LED between these pins (11 and 12), a high-load indication can be realized.

If the potential at pin 6 increases to about 6.2 V (= V

The result is programmable at pin 9 (operation mode).

3.8.1

Mode Selection

a)

α

In this mode of operation, pin 13 switches to -V

(pin 10) after V

shorted and the control angle is switched to

α

until the supply voltage is switched off. The motor can be started again with the

soft-start function when the power is switched on again. As the overload condition

switches pin 13 to pin 11, it is possible to use a smaller control angle,

α

connecting a further resistance between pins 13 and 14.

b)

Auto start (pin 9 – open), see Figure 7-8 on page 12

The circuit behaves as described above, with the exception that pin 6 is not

connected to GND. If the value of V6 decreases to 25% of the threshold

value (V

c)

I

When V

pin 13 is switched to pin 8 (V

soft-start capacitor discharging at pin 7. With this mode of operation, direct

load-current control (I