Introduction:
The Supertex SR086DB1 is an inductorless switching power
supply intended for operation directly from a 120/230VAC
line. Two outputs, 12.6V and 3.3V are provided.
The operating principle is to turn on a pass transistor when
the rectified AC input is below the output voltage, and to turn
it off when the output storage capacitor is charged up to the
regulation point. Since the output capacitor charges up on
the rising edge of a sine wave, reasonable efficiencies can
be obtained without the use of magnetics.
Instructions on page 2 and 3 describe how the demoboard
may be modified to better suit applications that are not satis-
fied by the board as provided. For a full description of the
SR086, see the SR086 datasheet.
Board Layout and Connection Diagram
Connections:
V
tected by a 275V metal oxide varistor (MOV) and a 1.25A
slow-blow fuse.
Do not use a transformer on the input line. The high induc-
tance creates inductive kickback, which can overload the
MOV.
The SR086DB1 will not operate from uninterruptible power
supplies having a square wave output. This type of output is
usually referred to as “modified sine wave”.
IN
90 - 270VAC
instrument, load, and/or the SR086 circuit.
-
Use floating instruments or high voltage
Connect to a 120/230VAC line. The AC input is pro-
the AC line, resulting in damage to the
or test instruments. Doing so will short
50/60Hz
Do not connect earth-grounded loads
differential probes. Do not use a
V
Supertex inc.
IN
transformer on the AC line.
WARNING!!!
Inductorless Switching Off-line
●
Power Supply Demoboard
Terminal blocks J1 and J2 may be removed by pulling straight up.
1235 Bordeaux Drive, Sunnyvale, CA 94089
Supertex SR086DB1
Warning! No galvanic isolation.
Dangerous voltages are present.
Do not connect grounded loads
or test equipment. Do not use
a transformer on the AC line.
V
IN
F1
Z1
~ ~
-
D1
R2
R3
Notes:
GND -
vided, 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.
tion!
Specifications
Parameter
AC Input (V
Output voltages:
Output current, max:
Efficiency, typ.
Standby power, typ. (no load):
1. Adjustable from 9.0V to 50V.
2. Referenced to V
R4
V
V
I
I
REG
OUT
OUT
REG
+ I
IC1
(no load)
Circuit common. Since galvanic isolation is not pro-
REG
●
IN
Tel: 408-222-8888
):
R5
2
C5
Q1
(full load):
OUT
.
C2
C3
GND
V
V
EN
OUT
REG
●
www.supertex.com
J2
WARNING!!!
No galvanic isolation.
Dangerous voltages are
present when connect to
the AC line.
120VAC
100mA
62mW
60mA
52%
SR086DB1
90 to 270VAC
45Hz to 65Hz
V
V
ENABLE
GND
12.6V ± 8%
REG
OUT
3.3V ± 5%
230VAC
200mW
(3.3V)
Use cau-
(12.6V)
60mA
60mA
44%
Value
1