SR037DB1 Datasheet | Supertex Inc

SR037DB1 Inductorless Switching Power Supply Introduction The Supertex SR037 is an inductorless switching power supply controller 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 pared to a standard linear regulator. The SR037DB1 demo board contains all the circuitry needed to supply a low-current (<40m A) load. Included is input protection circuitry, a full wave bridge rectifier, a pass element, and output capacitors. Specifications AC Input Output Voltages VUNREG VREG Output Current IUNREG + IREG Efficiency ACIN=120VAC 60Hz, IU=40m A, IR=0m A 24VAC to 264VAC 40Hz to 100Hz 12V to 22V 5.0V ±10% 40m A @120VAC 30m A @ 240VAC 40% typ Board Layout and Connections Q1 Z1 ACIN F1 D1 IC1 C2 C1 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. VREG VUNREG WARNING!!! No galvanic isolation. Dangerous voltages are present when connected to the AC mains. ACIN Connect to the AC line. The AC input is protected by a 400V transient voltage suppressor and a 250m A fuse. GND Circuit mon. Note that since galvanic isolation is not provided, connecting this point to an earth-grounded instrument (such as an oscilliscope) 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. This ground must remain floating when supplied from the AC line! VUNREG The unregulated output. Nominal output voltage is 18...