SR036DB1
Inductorless Switching Power Supply
Introduction
The Supertex SR036 is an inductorless, dual output off-line
regulator intended for 120/240VAC line operation. The
operating principle is to activate a pass element between
line and load only when the input voltage is lower than a
certain value. Thus conduction only occurs with a low
voltage drop across the pass element, resulting in more
efficient operation compared to a standard linear regulator.
The SR036DB1 demo board contains all the circuitry
needed to supply a low-current (<40mA) load. Included are
input protection circuitry, a full wave bridge rectifier, a pass
element, and output capacitors.
Specifications
AC Input
Output Voltages
V
UNREG
V
REG
Output Current
I
UNREG
+ I
REG
Efficiency
AC
IN
=120VAC 60Hz, I
U
=40mA, I
R
=0mA
24VAC to 264VAC
40Hz to 100Hz
18V鹵20%
3.3V 鹵10%
40mA @ 120VAC
30mA @ 240VAC
40% typ
Board Layout and Connections
Q
1
Z
1
AC
IN
F
1
D
1
IC
1
C
2
C
1
GND
WARNING!!!
Do not connect to scope ground or to the ground of other
earth-grounded instruments. Doing so will short the AC line,
resulting in damage to the circuit and/or instrument. Either
use an isolation transformer on the AC line, use a differential
probe, or use a floating, battery-powered instrument to make
measurements.
V
REG
V
UNREG
WARNING!!!
No galvanic isolation. Dangerous voltages are
present when connected to the AC mains.
AC
IN
Connect to the AC line. Neutral to top, hot to bottom.
V
UNREG
The unregulated output. Nominal output voltage is 18 volts.
This output will have a certain amount of 120Hz ripple,
depending on load.
Do not connect to earth-grounded loads.
GND
Circuit common.
Note that since galvanic isolation is not provided, connecting
this point to an earth-grounded instrument (such as an
oscilloscope) will short the AC line, resulting in circuit and/or
instrument damage.
Also note that GND may be at a higher potential with respect
to earth ground, even if the AC is switched off. Use caution!
Do not connect to earth-ground.
V
REG
The regulated output. 5V nominal output voltage.
Do not connect to earth-grounded loads.
Fuse
The AC input is fused to protect against overloads. It should
be replaced with a 125mA, 250V standard 3AG fuse.
16APR02
1
1
2
