Page 1
SR036DB1
W
r
r
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.
Board Layout and Connections
Z
1
AC
IN
ARNING!!!
Do not connect to scope ground or to the ground of other
earth-grounded instruments. Doing so will short the AC line,
esulting 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
ements.
measu
AC
IN
Connect to the AC line. Neutral to top, hot to bottom.
GND
Circuit common.
Inductorless Switching Power Supply
Specifications
AC Input
Output Voltages
UNREG
REG
V
V
Output Current
+ I
I
UNREG
REG
Efficiency
ACIN=120VAC 60Hz, IU=40mA, IR=0mA
D
1
F
1
Q
1
IC
1
C
1
C
2
GND
V
REG
V
UNREG
WARNING!!!
No galvanic isolation. Dangerous voltages are
present when connected to the AC mains.
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.
24VAC to 264VAC
40Hz to 100Hz
18V±20%
3.3V ±10%
40mA @ 120VAC
30mA @ 240VAC
40% typ
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
V
REG
The regulated output. 5V nominal output voltage.
instrument damage.
Also note that GND may be at a higher potential with respect
Do not connect to earth-grounded loads.
to earth ground, even if the AC is switched off. Use caution!
Do not connect to earth-ground.
Fuse
The AC input is fused to protect against overloads. It should
be replaced with a 125mA, 250V standard 3AG fuse.
16APR02 1
Page 2
SR036DB1
AC
IN
P6KE400CA
F
1
125mA
Inductorless Switching Power Supply
SR036 Circuit
D
1
Z
1
Q
1
VN2460N8
IC
1
SR036
C
1
220µF
C
2
1µF
V
UNREG
V
REG
Parts List
Desig Description Part Number
F1 Fuse, 3AG, 125mA, 250V
Z1 Transient voltage suppressor, 400V P6KE400CA
D1 Diode bridge, 1A, 600V
IC1 HV Supply Controller Supertex SR036SG
Q1 MOSFET, 600V N-channel Supertex VN2460N8
C1 Capacitor, alum, 220µF, 35V
C2 Capacitor, cer, 1µF, 16V
Modifications
The SR036DB1 may be modified to provide higher output current. Remove Q1 and replace with a D-Pak N-channel MOSFET with
a voltage rating appropriate for the input voltage. The on resistance of the replacement FET is not as important as the gate
threshold voltage – the lower the threshold voltage, the more efficient the converter.
To reduce ripple at the higher output current, C1 may be replaced with a higher value capacitor.
16APR02 2
Loading...