STMicroelectronics’ ‘Back-Current Circuit’ replaces SiC devices in solar inverters

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Product Briefing Outline

STMicroelectronics has released details of a patented high-efficiency circuit and dedicated optimized power components. ST’s new design, called BC2 (Back-Current Circuit) is claimed to produce cost savings while helping designers comply with the highest power-efficiency standards. The new circuit and power components are ideally suited for boost or buck converters, which are power devices that are usually used in solar inverters.


Legislation governing energy efficiency and power quality already requires many types of mains-powered equipment to be fitted with Power Factor Correction (PFC) circuitry to minimize energy loss and distortion. These PFC circuits typically combine a power MOSFET, a rectifier diode, an inductor, and a capacitor. Historically, engineers required expensive technology, such as silicon carbide (SiC) for the rectifier diode, to meet high efficiency certification levels such as 80 Plus Bronze, Silver or Gold.


This new technology now allows competitively priced silicon diodes to be used in preference to SiC devices in boost or buck converters inside solar inverters or SMPS applications such as desktop PCs, servers, telecom base stations. Where the low recovery current of a SiC boost diode helps to minimize the MOSFET switching-on losses, BC2 fully removes these losses and recycles the energy linked to the recovery of the boost diode. Compared to a standard circuit, the new topology requires one additional inductor and three optimized diodes. This approach increases the efficiency by as much as 2% at approximately half the price of a solution using SiC devices.


Used in kits, these diodes permit the design of competitive high-efficiency circuits up to 2kW.


To enable designers to implement BC2 in new power supply designs, ST has announced a family of six silicon-based rectifiers and free-wheel diodes optimized for this application: STTH8BC060D/STTH8BC065DI, STTH10BC065CT and STTH16BC065CT – 600V and 650V rectifier diodes, offering current ratings of 8A, 10A and 16A, respectively; STTH3BCF060U and STTH5BCF060 – 600V free-wheel diodes offering current ratings of 3A and 5A, respectively. ST provides full design support for the new topology, to help designers achieve the best performance and efficiency.


November 2010 onwards.

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