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Supertex inc.
Adjustable Off-Line Inductorless Switching Regulator
Features
Efficient operation without magnetics No high voltage capacitors Adjustable main output voltage (9V to 50V) Additional 3.3V or 5V internal regulator Up to 100mA combined output current Single BOM for 120VAC/230VAC Built-in soft start Less than 200mW standby power
SR086/SR087
Initial Release
General Description
The Supertex SR08X is an inductorless switching regulator designed to operate directly from a rectified AC line. The operating principle is to turn on a pass transistor when the rectified AC is below the output voltage, and to turn it off when the output voltage reaches a specific level. A linear regulator supplied by VOUT provides an additional fixed 3.3V output (SR086) or 5V output (SR087). Efficiencies of around 55% may be realized for loads up to 1W in 120VAC applications, with around 50% efficiencies for loads up to 800mW in 230VAC applications. A logic-level enable input allows the SR08X to be disabled - useful when the SR08X is employed as a keep-alive power supply. WARNING! Galvanic isolation is not provided. Dangerous voltages are present when connected to the AC line. It is the responsibility of the designer employing the SR08X to ensure adequate safeguards are in place to protect the end user from electrical shock.
Applications
White goods Household appliances Lighting controls Circuit breakers Keep-alive supplies
Typical Application Circuit
1.25A
90VAC to 270VAC 50/60HZ
1.0kV 1A 275V 50A
STGD5NB120SZ
1F
VOUT 9-50VDC @ 100mA - IREG
470F
390k
1.1M GATE VIN
100nF
R1 VGD VOUT FB
= R2
VOUT 1.25V
- 1
SR08X
Enable EN GND VREG 3.3V or 5V @ 60mA
100nF
R2
12.4k
NR040306
Supertex inc.
* 1235 Bordeaux Drive, Sunnyvale, CA 94089 * Tel: (408) 222-8888 * FAX: (408) 222-4895 * www.supertex.com
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SR086/SR087
Ordering Options
Device (VREG)
SR086 (3.3V) SR087 (5.0V)
Pinout
Package Options 8-Lead SOIC
SR086SG-G
GND VIN EN GATE VGD VOUT
SR087SG-G
VREG
-G indicates package is RoHS compliant (`Green')
Heat Slug
VFB
SO-8
Backside on the SO-8 package is at ground potential and may be connected to ground or left unconnected.
Pin Description Absolute Maximum Ratings
Parameter Output Voltage (VOUT) Feedback Voltage (VFB) Enable Voltage (VEN) Operating Junction Temperature Value -0.3V to 56V -0.3V to 6.5V -0.3V to 6.5V -40oC to +125oC GND VREG FB VOUT VGD GATE 3 4 5 6 7 8 Name VIN EN Pin # 1 2 Description Rectified AC input voltage Active low enable input Circuit ground
Note: circuit ground will be at the AC line potential
Absolute Maximum Ratings are those values beyond which damage to the device may occur. Functional operation under these conditions is not implied. Continuous operation of the device at the absolute rating level may affect device reliability. All voltages are referenced to device ground.
Regulated output voltage, fixed 3.3V or 5.0V Feedback input Output voltage (9.0V - 50V adj.) Gate drive supply (referenced to VOUT) Drives external IGBT pass transistor
Recommended Operating Conditions
Symbol VOUT IOUT Parameter Output voltage Load on VOUT including feedback divider and load on VREG Min 9 100 Typ Max 50 Units V A Conditions -----
Specifications
(Unless otherwise noted, TA = -40C to +85C, Voltages referenced to GND pin)
Symbol IGD IOUT(int) VGD VGATE(hi) VGATE(lo) VFB(off) VFB(hys)
Parameter Current consumption at VGD Current consumption of the lower circuitry Gate drive supply voltage1 GATE output high voltage1 GATE output low voltage
1
Min 11 11 1.18 -
Typ 13 1.25 50
Max 60 400 15 15 0.5 1.31 -
Units A A V V V V mV
Conditions --VOUT = 9-50V -----------
Feedback voltage (GATE off) Feedback voltage hysteresis
NR040306
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SR086/SR087
Specifications (cont.)
Symbol IFB VTRIP(on) VTRIP(off) VEN(on) VEN(off) tDIG(on) tDIG(off) tDFG(off) VREG IVREG VD
1
Parameter FB input current VIN trip voltage, GATE on1 VIN trip voltage, GATE off Enable voltage, on Enable voltage, off VIN - GATE turn-on delay VIN - GATE turn-off delay FB - GATE turn-off delay Regulated output voltage SR086 SR087 VREG load regulation GATE - VGD diode drop
1
Min 0 9 0.2 0 3.125 4.750 -50 -
Typ 3.300 5.000 -
Max 500 3 15 0.75 1.0 600 450 3.465 5.250 +50 800
Units nA V V V VREG s ns ns V
Conditions ----------CGATE = 1nF CGATE = 1nF CGATE = 1nF VFB = 1.5V ILOAD = 1mA, VOUT = 9V 0mA < ILOAD < 60mA, VOUT = 9V, TAmb = 25C I = 20mA
mV mV
Referenced to VOUT.
Block Diagram
1.25A 90VAC to 270VAC 50/60Hz 1.0kV 1A 275V 50A RPD
390k
STGD5NB120SZ
9VDC to 50VDC CGD 100nF COUT1 1.0F VOUT COUT 470F
RGD
1.1M
VIN
GATE
VGD
13V
R Q S
RFBhi = RFBlo
(
VOUT 1.25V
-1
)
Upper circuitry powered by VGD VOUT Lower circuitry powered by VOUT GND
level translator
FB EN 1.25V Reg VREG 3.3V/5V CREG 100nF
RFBlo 12.4k
SR08X
GND
NR040306
3
SR086/SR087
SR08X Timing
Pass Transistor on
VIN
VFB(OFF)
()
1+ RFBhi RFBlo
VOUT
not to scale
Pass Transistor is turned on when VIN falls below: VOUT +VTRIP(ON) Pass Transistor is on but not conducting since the input voltage is lower than the output voltage Pass Transistor is on and conducting
Pass Transistor is turned off once VOUT reaches the trip point
NR040306
4
SR086/SR087
Data Sheet Application Section: Typical Application Circuit
F VIN 90VAC to 270VAC 50/60Hz
1
1.00A Z1 275V 50A
D1 1.0kV 1A *R 200k *R 200k * Two resistors used in series for reasons of high voltage creepage and resistor voltage rating. EN R 100k
7 2 2 1
Q
1
STGD5NB120SZ *R C
VOUT 12.6VDC C2 1.0F C3 470F
3
1
510k *R 4 510k
1 8 7
100nF
6
VIN
GATE
VGD
VOUT FB VREG
5
R
5
EN
IC1 SR087
GND
3
113k R VREG 5VDC C
4 6
4
12.4k
100nF
Output Voltage*
VOUT may be adjusted in the range of 9V to 50V* by changing feedback resistor R5 according to the following equation. V R5 = R6 OUT - 1 1.25 V Leave R6 at 12.4k or less - it assures a minimum 100A load required for the proper operation of the SR087. Change R3 and R4 according to the R3+R4 equation below. Select C2 and C3 with appropriate voltage ratings. For C3, use a low ESR capacitor with an adequate ripple current rating (800mARMS). Use ceramic for C2. Since VREG is a linear regulator supplied from VOUT, the maximum current available from VREG is reduced as VOUT is increased due to power considerations. IREG(max) = 1 .5 W VOUT - 5 V or 60mA, whichever is less.
Input Voltage
To reduce standby power for 230VAC-only applications, or for supply voltages less than 90Vrms, R3 and R4 should be changed according to the R3+R4 equation below. R1+R2 should remain at 400k or less. Two resistors in series are employed to ensure adequate creepage distances for 230VAC operation. For 120VAC-only applications, single resistors may be employed.
Output Ripple*
Storage capacitor C3 was sized to provide about 2VP-P ripple at 100mA load (IOUT + IREG). For lighter loads, C3 may be reduced. Conversely, C3 may be increased for lower ripple. Use a low ESR capacitor with an adequate ripple current rating (800mARMS for 100mA loads). Efficiency and output current capability may drop with increased capacitance because of a smaller conduction angle associated with lower ripple. Due to feedback hysteresis, ripple cannot be reduced below 4%. VRIPPLE(P -P ) IOUT + IREG 2fINC3
*VREG requires at least 4V of headroom. Therefore, VOUT, including ripple, must not fall below 9V for the SR087, or below 7.3V for the SR086.
R3 + R4 Equation:
( R3 + R 4 ) <
2VIN2 - VX2 VX cos-1
25A
(
VX 2 VIN
)
where VX = VOUT + 15V
Use the minimum anticipated RMS value for VIN. Take resistor tolerance into account, selecting the next lower standard value. Choosing a lower value has no effect other than higher standby power.
NR040306
5
SR086/SR087
Line Transformer
During initial testing it is tempting to use an isolation transformer or a variable transformer on the AC line. However, the high inductance of the transformer (frequently in the mH's) interferes with the normal operation of the SR08X and should not be used. This is not a concern with the normal inductance of the AC line or for AC line filters.
Fuse
Although the average current drawn from the AC line is low, the RMS current is fairly high due to the current being drawn in short, high-current pulses. Since a fuse is basically a resistor with a power dissipation given by IRMS2 R, the fuse must be sized for the RMS current, not the average current. For a 1W load and 120VAC the RMS current is 700mARMS, and for a 0.5W load at 230VAC it is 360mARMS.
AC Line
SR08X & Circuitry
Transient Protection
The transient protector must be located before the bridge rectifier. The reason for this is to minimize capacitance to allow the rectified AC to fall below VOUT.
The SR08X draws current from the AC line in short, high current pulses. The transformer's high inductance tends to limit the current pulse. Furthermore, inductive kickback on the falling edge of the current pulse can create high voltage spikes which must be absorbed by the transient protector.
Since there is no capacitor to absorb AC line transients, complete transient protection must be provided by the TVS or MOV device. Since the recommended IGBT is rated at 1.2kV and the SRO8x never sees the full input voltage, the bridge EMI Capacitor rectifier becomes the limiting element when selection an MOV. If using a 1.0kV bridge, an MOV having a clamping voltage of The use of a small-value capacitor from circuit common to < 1.0kV is recommended. earth ground prevents the SR08X from operating and should not be employed.
Load
AC Line
SR08X & Circuitry
Total load on the SR08X is the total load current drawn from VOUT (IOUT) and, since the linear regulator is supplied from VOUT, it also includes the current drawn from VREG (IREG). Total load is calculated as follows: ILOAD = IOUT + IREG PLOAD = VOUT (IOUT + IREG )
earth ground
circuit common
EMI
UPS
The SR08X circuit as depicted on Page 1, (Typical Application The SR08X will not operate from uninterruptable power Circuit), meets FCC Class B and CISPR 14-1 (household supplies having a square wave output. This type of output is appliances) requirements for conducted emissions, for usually referred to as `modified sine wave' combined loads of less than 20mA (IOUT + IREG).
NR040306
6
SR086/SR087
8-LEAD SMALL OUTLINE PACKAGE WITH HEAT SLUG (SG)
0.1935 +/- 0.0035 (4.915 +/- 0.085)
Measurement Legend =
Dimensions in Inches (Dimensions in Millimeters)
0.1 +/- 0.01 (2.54 +/- 0.25)
Heat Slug
0.1535 +/- 0.0035
0.236 +/- .008
(3.9) (5.995) (+/- 0.09) (+/- 0.205)
0.0165 +/- 0.0035 (0.42 +/- 0.09) 0.14 +/- 0.01 (3.555 +/- 0.255) 0.055 +/- 0.005 (1.395 +/- 0.125)
0.0085 +/- 0.0015 (0.215 +/- 0.035)
0.05 +/- 0.01 (1.27 +/- 0.25)
0.0575 +/- 0.0065 (1.46 +/- 0.16)
0.0015 +/- .0025 (0.065 +/- 0.035)
0.033 +/- 0.017 (0.84 +/- 0.43)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to http://www.supertex.com/packaging.html.)
Supertex inc. does not recommend the use of its products in life support applications, and will not knowingly sell its products for use in such applications, unless it receives an adequate "product liability indemnification insurance agreement". Supertex does not assume responsibility for use of devices described and limits its liability to the replacement of the devices determined defective due to workmanship. No responsibility is assumed for possible omissions or inaccuracies. Circuitry and specifications are subject to change without notice. For the latest product specifications, refer to the Supertex website: http//www.supertex.com.
(c)2006 Supertex inc. All rights reserved. Unauthorized use or reproduction is prohibited.
Supertex inc.
1235 Bordeaux Drive, Sunnyvale, CA 94089 TEL: (408) 222-8888 / FAX: (408) 222-4895
Doc.# DSFP - SR086_SR087 NR040306
www.supertex.com
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