Overview
A cost-optimized driver solution is achieved using Power Integrations' highly integrated SCALE and SCALE-2 gate drivers. Compared with typical solutions based on discrete driver stages, this approach can significantly reduce component count and PCB size. Integration also improves reliability, since fewer components mean fewer potential failure points. Therefore, using SCALE and SCALE-2 gate drivers can improve system mean time between failures (MTBF).
Overvoltage Challenge in Solar Applications
One of the technical challenges for solar applications involves overvoltage protection.
During normal operation, when the load is connected at standard temperature, the DC bus voltage of solar inverters is relatively low compared with the blocking capability of the power switch. Therefore there is sufficient voltage margin to handle any overvoltages that may occur when the power switch turns off. Using an active-clamp approach can therefore provide reliable protection for these switches.
However, the open-circuit voltage of solar panels, especially at low temperatures, can cause the DC bus voltage to rise near the blocking capability of the power switch. During these periods, any conventional active-clamp circuit may inadvertently turn the power switch on. In the best case this causes additional losses and increased EMI; in the worst case it can destroy the solar converter.
Dynamic Active Clamp (DAC)
To address this, Power Integrations developed an advanced active-clamp technique called Dynamic Active Clamp (DAC), which automatically enables and disables the clamp function so solar inverters can operate safely under all conditions (see figure).
