Controller provides high-voltage startup

The NCP1280 is a highly integrated, voltage mode PWM controller which is the first in the industry to offer a high-voltage (up to 700V) startup for active clamp circuits.

The NCP1280 is a highly integrated, voltage mode PWM controller which is the first in the industry to offer a high-voltage (up to 700V) startup for active clamp circuits.

Ideal applications for the device include medium- to high-power offline power supplies for synchronous rectification/active clamp designs found in applications such as computing power supplies, telecomms front-end power systems and high-end consumer equipment such as plasma or LCD TVs.

The NCP1280 provides a highly integrated solution for offline power supplies requiring high efficiency and low parts count.

This controller provides control outputs for driving a forward convertor primary mosfet and an auxiliary mosfet for active clamp circuit.

The second output with its programmable delay can also be used for driving a synchronous rectifier on the secondary or for asymmetric half bridge circuits.

Additional features include a 700V startup circuit, voltage feedforward, adjustable maximum duty cycle control, adjustable oscillator frequency up to 500kHz, line under- and overvoltage detectors, dual-mode overcurrent protection and soft start.

Compared with traditional forward convertor topologies, an active clamp solution implemented with the NCP1280 offers lower switching and conduction losses, requires a smaller output inductor and lowers the voltage across primary switches and secondary rectifiers, reducing stress on these components.

Ultimately, the device reduces board space usage and overall costs.

The NCP1280 is offered in a space-saving SOIC-16 package and priced at $1.90 per unit in 10,000 unit quantities.

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