7

SR036/SR037

Applications Information, continued

1235 Bordeaux Drive, Sunnyvale, CA 94089

TEL: (408) 744-0100 • FAX: (408) 222-4895

www.supertex.com

06/13/02rev.12

©2002 Supertex Inc. All rights reserved. Unauthorized use or reproduction prohibited.

220

µF

1

µF

SR037

VN2460N8

120VAC

or

240VAC

Fuse

Logic

Control

Circuit

Unregulated Voltage

5.0V

5V Coil

Relay

Vz

5.1V

HV

IN

GND

Gate

Source

V

OUT

Figure 6: Driving 5V Relay Coils with Zener Diode Clamp

The circuit shown in Figure 6 uses the SR037 to supply a

regulated 5.0V for the logic control circuitry. A 5.1V Zener diode

is used in parallel with the 5.0V relay coil to ensure that the relay

coil’s maximum operating voltage is not exceeded. The Zener

diode also acts as the catch diode when the coil is switched to the

off state. An external series resistor is used to limit the amount

of Zener current.

220

µF

1

µF

SR036 or

SR037

TN2425N8

120VAC

Fuse

330

Ω

330

Ω

Unregulated Voltage

HV

IN

GND

Gate

Source

V

OUT

Figure 7: Driving LEDs from 120VAC

The circuit shown in Figure 7 uses the SR036 or SR037 to drive

12 high efficient red LEDs from a 120V AC line. The average LED

current is approximately 20mA.