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AND8273/D Design of a 100 W Active Clamp Forward DC-DC Converter for Telecom Systems Using the NCP1562...

Prepared by Juan Carlos Pastrana ON Semiconductor INTRODUCTION...

http //onsemi.com...

APPLICATION NOTE...

The NCP1562 PWM controller contains all the features and flexibility needed to implement an active clamp forward dc-dc converter. This IC operates from an input supply up to 150 V, thus covering the input voltages usually found in telecom, datacom and 42 V automotive systems. One can also note that the NCP1562 can be used in mains related applications (e.g. desktop, server, flat TVs) as it can be supplied by an auxiliary power supply. The NCP1562 is the ideal choice for new generation isolated fixed switching frequency dc-dc converters using the active clamp topology with synchronous rectification to achieve extremely high conversion efficiency. This controller will help designers cope with their daily challenge, "small form factor highly protected module" through the following features Dual Outputs with Adjustable Overlap Delay provide design flexibility. Output 1 (OUT1) drives the main switch in a forward or flyback converter topology. Output 2 (OUT2) can be used to drive an active clamp/reset switch, a synchronous rectifier switch, or both. OUT2 has an adjustable overlap delay to prevent simultaneous conduction of the switching elements. Soft-Stop discharges the active clamp capacitor prior to turn off to eliminate unwanted oscillations. An Internal Startup Regulator provides power to the NCP1562 during startup. Once the system powers up, the regulator is disabled, thus reducing power consumption. The regulator can be powered directly from the input line. Soft-Start allows the system to turn on in a controlled manner and reduce stress on system components. Adjustable Maximum Duty Ratio allows the design to be optimized without a penalty on drain voltage. Duty ratio is controlled within 5%. Adjustable Volt-second Limit prevents transformer saturation and improve transient response. Line Feedforward adjusts the duty ratio inversely proportional to line voltage, allowing the controller to...

Semiconductor Components Industries, LLC, 2006...

respond in the same cycle to line voltage changes. It provides the controller some advantages of current-mode control, while eliminating noise susceptibility, low power jitter and the need for ramp compensation. Dual Mode Overcurrent Protection Circuit handles momentary and continuous overcur...

Document Keywords

Design of a 100 W Active info ncp1562 and8273

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