SR087DB1 Supertex inc. Inductorless Switching Off-line Power Supply Demoboard Specifications Introduction: The Supertex SR087DB1 is an inductorless switching power Parameter Value supply intended for operation directly from a 120/230VAC 90 to 270VAC AC Input (V ): line. Two outputs, 12.6V and 5.0V are provided. IN 45Hz to 65Hz Output voltages: The operating principle is to turn on a pass transistor when 1 V (no load) 12.6V 8% OUT the rectified AC input is below the output voltage, and to turn V 5.0V 5% REG it off when the output storage capacitor is charged up to the Output current, max: 120VAC 230VAC regulation point. Since the output capacitor charges up on I 60mA 60mA REG the rising edge of a sine wave, reasonable efficiencies can I + I 100mA 60mA OUT REG be obtained without the use of magnetics. 2 Efficiency, typ. (full load): 52% 44% Instructions on page 2 and 3 describe how the demoboard Standby power, typ. (no load): 62mW 200mW may be modified to better suit applications that are not satis- Notes: fied by the board as provided. For a full description of the 1. Adjustable from 9.0V to 50V. 2. Referenced to V . OUT SR087, see the SR087 datasheet. Board Layout and Connection Diagram WARNING WARNING Supertex SR087DB1 Do not connect earth-grounded loads No galvanic isolation. Warning No galvanic isolation. or test instruments. Doing so will short Dangerous voltages are Dangerous voltages are present. the AC line, resulting in damage to the present when connect to Do not connect grounded loads or test equipment. Do not use instrument, load, and/or the SR087 circuit. the AC line. Q1 a transformer on the AC line. Use floating instruments or high voltage V OUT V (12.6V) differential probes. Do not use a R2 OUT C2 F1 R3 C5 transformer on the AC line. V REG V (5.0V) - REG V R4 IN C3 D1 J2 IC1 V IN ~~ R5 ENABLE Z1 90 - 270VAC J1 EN 50/60Hz GND GND Terminal blocks J1 and J2 may be removed by pulling straight up. Doc. DSDB-SR087DB1 Supertex inc. A032014 www.supertex.com R1 + R7 R6 R8 C1 C4SR087DB1 Connections: regulates the peak output voltage, not the average, thus the V - Connect to a 120/230VAC line. The AC input is pro- IN average voltage will decrease under load. tected by a 275V metal oxide varistor (MOV) and a 1.25A slow-blow fuse. V is adjustable from 9.0 to 50V. See the modifications OUT section on page 3. A source-only external voltage may be Do not use a transformer on the input line. The high induc- applied to this output. tance creates inductive kickback, which can overload the MOV. Do not connect earth-grounded loads or instruments The SR087DB1 will not operate from uninterruptible power V - The regulated output, 5.0V nominal output voltage. supplies having a square wave output. This type of output is REG V is the output of a linear regulator internal to the SR087, usually referred to as modified sine wave. REG which in turn is supplied by V . Thus any load on V is ef- OUT REG fectively a load on V . V requires at least 4.0V of head- GND - Circuit common. Since galvanic isolation is not pro- OUT REG room to operate. Being a linear regulator, the SR087 will dis- vided, connecting this point to an earth-grounded instrument, sipate power as I is increased, up to 460mW at 60mA. (such as an oscilloscope), will short the AC line, resulting in REG circuit and/or instrument damage. Enable - A logic low (<0.2V) enables Q switching. A logic 1 high (>0.75 V ) disables Q , shutting down V and thus Also note that GND may be at a higher potential with respect REG 1 OUT V . However, if an external voltage is applied to V when to earth ground, even if the AC is switched off. Use cau- REG OUT disabled, V will continue to function and provide a 5.0V tion REG output. V - The main output. No-load output voltage is 12.6V. OUT The input has 20k pull-down. If unused, Enable should be Because the V storage capacitor (C3) recharges twice OUT left unconnected or connected to ground. per input cycle, this output will have a certain amount of 100/120Hz ripple, depending upon the load. The SR087 Schematic F 1 D Q 1.25A 1 1 V IN STGD5NB120SZ 1.0kV, 1.0A V V OUT 90 to 270VAC IN Z 1 12.6VDC 50/60Hz C C 2 3 275V R 1 1.0F 470F 50A 200k R 3 510k GND C 5 R do not 2 not installed 200k optional EMI connect to R 8 supressor earth 0 R ground C 4 1 510k 100nF R 5 113k 1 8 7 6 VIN GATE VGD VOUT FB EN EN 5 SR087 2 V REG R 6 R VREG 7 GND 5.0VDC 12.4k 4 C 20k 4 3 100nF Doc. DSDB-SR087DB1 Supertex inc. A032014 2 www.supertex.com