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CAES Unveils Unprecedented GaN Based Single-Stage, Isolated DC-DC Converters

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Ashok Bindra
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Employing space qualified gallium nitride (GaN) FETs from a third party GaN supplier, Arlington, VA based CAES, a major provider of mission critical electronics for aerospace and defense applications, has unveiled a family of single-stage, isolated dc-dc converters for high throughput satellite payloads. Labeled SCD51028xx, the 28 V radiation-tolerant step-down converters are also the first satellite single-stage power supplies to incorporate GaN FET technology, according to Chris Clardy, CAES vice president of business development, Space Systems Division.

Designed for 28 V bus applications, the new GaN based single stage, isolated dc-dc converter family offers seven members with output voltages ranging from 0.8 V to 7.0 V, and maximum output power varying from 50 W to 75 W, respectively. The input voltage range is 20 – 38 V.

By comparison to conventional silicon-based two-stage dc-dc converters, the GaN-based single-stage converter modules increase power efficiency from approximately 80% to more than 90% while simultaneously reducing size, weight and power requirements in space applications. Per the company website table, the 0.8 V unit offers 89% efficiency and the 7 V member flaunts 93% efficiency.  By converting power straight from the power bus to the point-of-load, the new single-stage converters operate easily within the stringent voltage tolerances of today’s leading-edge processing devices, such as the deep-submicron ASICs and FPGAs used in software-defined payloads that can be reprogrammed in-orbit to extend the mission life of space applications, noted Clardy.

Senior design engineer Dan Gonzalez stated that these GaN-based dc-dc modules are fully tested off-the-shelf power conversion solutions for space applications. Besides higher performance, higher switching frequencies also improves response time to changing load currents compared to silicon-based dc-dc converters, explained Gonzalez. The switching frequency for the GaN based converters is around 400 kHz. Plus, it uses single ended forward converter design with secondary synchronous rectification. In addition, these new converters can also be used in parallel for higher-power outputs. However, for optimal performance, Gonzalez recommends using only two modules in parallel.

Designed for aerospace and high-reliability space applications, the new 28 V SCD51028xx converters have a total dose radiation tolerance of 50 krads (Si) and are available in a (2.5L x 1.5W x 0.63H inch) gull-winged power package that enables surface-mount installation and a low-impedance interconnect with the system board (Figure 1). Other features include a lightweight (50 g) design and an operating temperature of -40 ºC to +125 ºC.

GaN dc dc module
FIG 1 Radiation tolerant, single-stage isolated GaN dc-dc module is housed in a gull-winged power package. Source: CAES

CAES said that the new GaN based dc-dc converters comply with the U.S. Department of Commerce Export Administration Regulations (EAR99) and are commercially available worldwide.

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