Fairchild FPS Series Design Manual

Fairchild FPS Series Design Manual Manual pdf 20 page image

20www.fairchildsemi.com/fpsFPS™ Design GuideExamples of Typical Application CircuitsBuck converters are ideal in low power applications where a single non-isolated power output is required. The FSDL0165RN buckcircuit was measured to have an excellent efficiency of over 77% for 15V/100mA, 15V/200mA and 15V/300mA levels over theinput voltage range. Buck circuits need a minimum load. This circuit was measured to have a power consumption of less than350mW with a 15V/10mA output load. The low 50kHz switching frequency option helps to keep the switching losses low. Voltageaccuracy was measured to be around ±6% over line, load and temperature for one board. The fully avalanche rated MOSFETprovides additional robustness against voltage transients needed in those industrial applications where buck converters are commonlyused. The current mode control simplifies the feedback control circuit which supports both discontinuous and continuous currentmodes. The device's frequency scaling helps to reduce the EMI caused by the switching.• Buck converter using FSDL0165 has high efficiency and low standby power– Ideal replacement for 50Hz transformer solutions• FSDL0165RN has a fully avalanche rated MOSFET– Robust performance under transient conditions• Current mode control maximizes operating flexibility– Low component count for feedback control circuit– Same circuit operates in DCM and CCM• Current limit may be lowered using an external resistor• Good control of start-up surge– Internal soft start feature helps• Frequency modulation helps to reduce EMI– Cost saving in external filter circuitFairchild Devices DescriptionFSDL0165RN Fairchild Power Switch (1.2A/50kHz)BZX84C15 Zener Diodes (15V)UF4004 Fast Recovery Diode (1A/400V)BC337-25 General Purpose Transistor5W Buck Converter Using FSDL0165RNTypical Application – Industrial automation, household appliances, instrumentationVout 15V/300mAVin 120Vdc-385Vdc12VStr5Drain 7Drain 8GND1Vcc 2VFB 3Drain 6ILim412C2014.7uF50V+Q200BC337-25CONN1B2P3-VHR205470R0.25WL210820uH0.3AC10422nF50VD102UF4004D20015V0.5WR1045K10.25WD210UF4004IC1FSDL0165RNC2114.7uF50V+C10122uF400V+CONN2B2P-VHR204100R0.25W