Resistive loads on/off control

AN1172

10/23

Then, the average conduction and gate current losses in the ACS are given by the following

relationship:

Equation 4

Equation 5

Since the thermal impedance values at 0.18 s for TO92 and DIL20 packages are 22.5 and

8° C/W respectively, it can be said that the junction temperature elevation, at the end of the

inrush current period, is 40° C for a TO92 package and 14° C for a DIL20 package.

So, the maximal junction temperature before door lock switch-on should be at most 96° C for

For washing systems, as the door lock start may appear at the beginning of a washing cycle,

respect, both ACS devices are convenient for door lock operation.

3.3

Light bulb flashover

Another point should be highlighted when driving a light bulb with a silicon switch. Indeed, at

the lamp life time end, the filament breaks itself. This results on a flashover across the gas,

included in the bulb. Then, the overall filament can be can short circuited by the flashover,

and the load current is not limited. Figure 10. gives the typical overcurrent measured when a

Figure 10.

25 W light bulb flashover current

g

gt

RMS

0

t

2

RMS

d

av

I

V

2

2

I

V

I

r

P+

+

=

π

av

p

jo

peak

j

P

t

Zth

T

T

⋅

+

=

t = 500 µs/div

I lamp (50A/div)

250 Amp !