New IC Reduces Volume of AC-DC Converters By Up To 40 Per Cent

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Significant size reduction is achieved while using fewer components and high EMI and transformer/clamp dissipation challenges are avoided

By halving the size of the high-voltage bulk electrolytic capacitors required in offline power supplies, the MinE-CAP IC by Power Integrations is suited for high power density, universal input AC-DC converters. 

This new type of IC enables a reduced adapter size (of up to 40 per cent). The MinE-CAP device also reduces in-rush current, making NTC thermistors unnecessary, increasing system efficiency and reducing heat dissipation. 

Saves Size

Conventional power conversion solutions reduce power supply size by increasing switching frequency to allow the use of a smaller transformer. The innovative MinE-CAP IC achieves just as significant overall power supply size reduction while using fewer components and avoiding the challenges of higher EMI and the increased transformer/clamp dissipation challenges associated with high-frequency designs. Applications include smart mobile chargers, appliances, power tools, lighting and automotive.

The MinE-CAP leverages the small size and low RDSon of PowiGaN gallium nitride transistors to actively and automatically connect and disconnect segments of the bulk capacitor network depending on AC line voltage conditions. Designers using MinE-CAP select the smallest high-line rated bulk capacitor required for high AC line voltages and allocate most of the energy storage to lower voltage capacitors that are protected by the MinE-CAP until needed at low AC line. This approach dramatically shrinks the size of input bulk capacitors without compromising output ripple, operating efficiency, or requiring redesign of the transformer. 

Addresses Design Challenges

“Electrolytic capacitors are physically large, occupy a significant fraction of the internal volume and often constrain form factor options – particularly minimum thickness – of adapter designs. The MinE-CAP IC allows the designer to use predominantly low voltage rating capacitors for a large portion of the energy storage, which shrinks the volume of those components linearly with voltage. USB PD has driven a major market push towards small 65 W chargers and many companies have concentrated on increasing switching frequency to reduce the size of the flyback transformer. MinE-CAP provides more volume saving than doubling the switching frequency, while actually increasing system efficiency,” said Chris Lee, product marketing director at Power Integrations.

“In India, we often design for voltages from 90 VAC to 350 VAC, with a generous surge de-rating above that. Engineers here often complain about the forest of expensive high-voltage capacitors required. MinE-CAP dramatically reduces the number of high-voltage storage components, and shields lower voltage capacitors from the wild mains voltage swings, substantially enhancing robustness while reducing system maintenance and product returns,” said Bhaskar Thiagaragan, Director of Power Integrations India Ltd.

Housed in the miniature MinSOP-16A package, the new devices work seamlessly with Power Integrations’ InnoSwitch family of power supply ICs with minimal external components. MinE-CAP MIN1072M ICs are available immediately from PI offices and franchised distributors.

Two initial design example reports (DERs) pair the MinE-CAP IC with Power Integrations’ InnoSwitch3-Pro PowiGaN IC, INN3370C-H302. A 65 W USB PD 3.0 power supply with 3.3 V – 21 V PPS output for mobile phone/laptop chargers is described in DER-626, and DER-822 describes a 60 W USB PD 3.0 power supply for USB PD/PPS power adapters using INN3379C-H302.


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