Switch Mode Power Supply

30 EE SWITCH MODE POWER SUPPLY Following the general introductions into the operation and application of switch mode power supplies in reference 0) and (2), this article discusses a practical design of a versatile, compact and highly efficient SMPSU rated at 2.5 A. The circuit described here is based around the integrated switch mode power supply controller Type L4960 from SGS. Briefly recapitulating the general introduction in reference (2), this IC has the following features: • Input voltage range: 9-50 VDC • Output voltage adjustable between 5 and 40 V. • Maximum output current: 2.5 A. • Maximum output power: 100 W. • Built-in soft start circuitry. • Stability of internal reference: ± 4%. • Requires very few external compo- nents. • Duty factor: 0-1. • High efficiency: ri up to 90%. • Built-in thermal overload protection. • Built-in current limiter for short- circuit protection. The pinning of the 3 regulators in SGS"s L496X series of switch mode regulato...