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New PWM controllers 'solve ZVS controller shortcomings'

Posted: 15 Mar 2005 ?? ?Print Version ?Bookmark and Share

Keywords:zero-voltage switching? zvs? pwm controller? controller? intersil?

The two new low pin count, zero-voltage switching (ZVS) full-bridge PWM controllers from Intersil Corp. promise to optimize performance, cost and time-to-market for 400W and higher ac-dc switching power supplies.

According to Jeff Strang, product marketing manager for Intersil's Isolated Power Products, they focused on the two major shortcomings of existing ZVS full-bridge controllershigh price and complexityto develop their two new products. "The ISL6752 and ISL6753 solved both [shortcomings]," Strang said.

The ISL6752 PWM controller is designed for ZVS full-bridge applications requiring adjustable synchronous rectifier drive, while the ISL6753 is more suitable for applications employing conventional output rectification. Rather than phase-modulating two half-bridges, these two new devices drive the upper switches at a fixed 50 percent duty cycle while trailing-edge-modulating the lower switches. This approach yields excellent conversion efficiencies while greatly simplifying the architecture of the PWM controller, said Intersil.

Additional features of the ISL6752 and ISL6753 include an adjustable oscillator frequency up to 2MHz, internal over-temperature protection, precision dead time and resonant delay control, short propagation delays, adjustable dead time control, tight 3 percent current limit threshold, low 175?A startup current, and internal under-voltage lockout.

Meanwhile, multi-pulse suppression ensures alternating output pulses at low duty cycles where pulse skipping may otherwise occur. The ISL6753 features adjustable soft start to reduce voltage stresses and the ISL6752 includes synchronous rectifier outputs with adjustable timing.

Targeted at file server, communication infrastructure and industrial equipment applications, the ISL6752 and ISL6753 are available in a Pb-free 16-lead QSOP package. The suggested price in 1,000 unit quantities is $2.99 each.




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