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Incremental advances drive growth in photovoltaic installations

Bringing greater efficiency and versatility to next generation photovoltaic designs

Solar power continues to be one of the cleanest and most reliable alternatives to the fossil fuels that we have relied on for so long. While Europe has been the leading market for solar power, demand is also increasing elsewhere, not least due to investments in countries such as China, Japan and India.

According to research firm, MarketsandMarkets (www.marketsandmarkets.com) one of the reasons behind this strong growth is the predictability of solar PV costs, when compared with volatile fossil fuel prices. However, Future Market Insights (www.futuremarketinsights.com) state that subsidies on conventional energy sources 'represent a challenge to the growth of the solar power market owing to cost issues'.

The challenge for designers is compounded as installers and users are demanding greater functionality alongside the lower costs, driving a strong requirement for new and innovative solar PV solutions.

The very latest wide bandgap materials such as GaN or SiC deliver enhanced efficiency but the cost is currently higher than silicon-based solutions. As a result, innovation in circuit technologies is required to deliver the desired performance enhancements.

While power circuits and topologies are very well established and there is little room for step-change innovation, incremental advances can make all the difference to system viability.

The half-bridge topology has been a mainstay of Solar PV inverters for some time and is a relatively efficient solution, especially when used with advanced MOSFETs with low on-resistance (RDS(ON)).

The half-bridge topology has been a mainstay of Solar PV inverters for some time and is a relatively efficient solution, especially when used with advanced MOSFETs with low on-resistance (RDS(ON)).

However, there are two switching losses that occur every cycle and are, therefore, more of a consideration in modern high-frequency designs. The first loss is related to the reverse recovery charge (Qrr) causing a peak current and the second relates to recharging the MOSFET's output capacitance (COSS).

One technique developed to address this is Synchronous Reverse Blocking (SRB). This builds on adds a second MOSFET to block the reverse current through the main MOSFET's free-wheeling diode. In this technique, the free-wheeling current is diverted to a stand-alone high-performance SiC SBD with a very low Qrr value, thereby reducing the losses found in a standard half-bridge arrangement.

To further improve the losses, a voltage source can be added to pre-charge the COSS of the main transistor prior to turning on the low-side switch. This technique, known as Advanced-SRB (A-SRB) further reduces the losses in the PV inverter and can lead to efficiency gains of up to 4%.

To download a copy of Toshiba’s A-SRB whitepaper, click here:

Click here to download the whitepaper

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·Before creating and producing designs and using, customers must also refer to and comply with the latest versions of all relevant TOSHIBA information and the instructions for the application that Product will be used with or for.