IXDN0036 datasheet(33/41 Pages) IXYS

33 / 41 page

Conclusion

7-34

ATAVRFBKIT / EVLD001 User Guide

7597A–AVR–02/06

The lamps are dimmed for as long as the switch is pressed or until the minimum or max-

imum dimmer setting is reached.

7.2

Appendix 2:

Capacitor

Coupled Low

Voltage Supply

Small currents for the low voltage supply can be obtained from the AC line at

low loss by means of capacitor coupling as shown in the figures below. To esti-

mate the required size of the coupling capacitor, use the following relationships

for current, charge, voltage and capacitance.

1.dQ/dt = I

Figure 7-1. Negative Line Half Cycle

Figure 7-2. Positive Line Half Cycle

1.dV = 2Vpk-Vo-2V

2.dQ = CdV or C = dQ/dV

For example, to obtain 15 ma at 20 VDC from a 220 Vrms 50 Hz line:

1.dQ/dt = (15 millijoules/sec)/(50 cycles/sec) or 0.3 millijoules / cycle.

“Negative” line half -cycle:

C1 charges to Vpk - VD with polarity shown.

Ich1

IDC

-VPK

-VC1 +

“Positive” line half -cycle:

C1 charges to Vpk - VD - Vo with polarity shown.

Ich2

IDC

+VPK

+ VC1 -

IXDN0036 Datasheet(PDF) 33 Page - IXYS Corporation