Part # TA301 datasheet

Part Manufacturer: ST Microelectronics

ST Microelectronics

Part Description: STIL A NEW COMPONENT FAMILY FOR INRUSH CURRENT LIMITATION CIRCUIT (ICLC)


Part Details:

TA301 ® TECHNICAL ARTICLE STIL: a new component family forInrush Current Limitation Circuit (ICLC)Igor Bimbaud and Benoît Peron,ASDTM and Discrete Division,STMicroelectronics,Tours, France. Abstract During the start up of an AC/DC power supply, the high current can raise up to 50 times the nominal currentof the system. This inrush current can create a voltage drop in the main supply that may affect the operationof any equipment connected to the same power network and blow up the input wire fuse as well. In order to control this effect and limit the inrush current intensity, the two most commonly found solutionsare either for lower power systems, the use of stand-alone impedance before the rectifier bridge or the useof serial impedance at the input shorted by a pass element (SCR, Triac or relay). Unfortunately none of these solutions are fully acceptable and fulfill the ideal expectation of the inrush cur-rent limitation circuit (ICLC). Based on its advanced ASDTM technology, STMicroelectronics is proposing a new circuit configuration andthe associated component family, the STIL, which closely meets the requirements mentioned above. Thisarticle describes in detail this new circuit as well as the benefits brought by STIL and the ASDTM technology. 1. Introduction to the Inrush Current Limitation The immediate but not suitable design solution Circuit (ICLC) would be to oversize these serial protectiondevices; thus increasing the total system cost by All the front-ends of off-line power supplies are reducing the responsiveness of the power failure made with a bridge rectifier and a filter bulk protection circuits of the converter. capacitor as shown in figure 1. Hence, power supply designers must introduce anICLC on the front-end of the power supply to re- Fig. 1: Typical off-the-line AC/DC power supply. duce this inrush current; however this ICLC shouldnot affect the performance of the converter andshould respond to the following expectations: Mechanic a) Power losses reduction and no hot spot: Power Breaker Fuse Switch Fuse the inrush current should not degrade the global DC/DC efficiency of the power supply. It should also not Load Power converter source generate an excessive local point of heat (hot spot)on the power printed circuit that might increase theoperating temperature of the components and af- Power Filtrate Bridge converter capacitor Mains fect the reliability of the power supply. Obsolete Product(s) - Obsolete Product(s) b) Responsiveness: the circuit should be able toinstantly limit the inrush current during repetitiveon / off cycles of the mains (a.c. on / off cycling). During start up, the charge of the bulk capacitorgenerates a surge current on the mains network, c) Robustness and immunity: the ICLC should commonly called inrush current. be immune against power line disturbance thatmight be generated at turn-on of the power supply. If nothing is done to limit the level of this inrushcurrent, the protection wire fuse of the power d) Small size: the inrush current limitation circuit supply might blow up and the circuit breaker of the volume should be minimized in order to keep the main power distribution might be forced to open. power density (W/cm3) of the power supply high. October 2002 - Ed: 1


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