Tool/software:
Solar power generation for the home is becoming more popular with the push and incentives for renewable energy. There are several architectures for solar power conversion including string inverters, power optimizers and microinverters. The microinverter approach is popular due to the ability to generate higher energy output and flexibility in installations.
Figure 1
The diagram in Figure 1 is a basic diagram of the solar power microinverter showing the solar panel DC-DC converter and DC-AC inverter blocks. There is a DC-DC converter to convert the 20-60V panel voltage to the 400V bus needed for the inverter for each panel. Each panel can deliver 400W to 600W for a total 4 panel power in the 1.6KW to 2.4kW range. The 20V-60V to 400V DC-DC power stage topologies include flyback, push-pull or LLC. A typical full bridge LLC power stage is shown for the DC-DC block in Figure 2.
Solar Panel DC-DC Converter DC-AC Inverter
Figure 2
The 120V half-bridge gate drivers that TI offers are a good fit for this DC-DC power stage due to being optimized for high performance converters. With a panel voltage output of 20-60V and up to 600W the average input current can be up to 20-30A. In order to keep resistive losses low to target high efficiency the power MOSFETs in the DC-DC converter must be low RDSON which will generally result in fairly high gate charge (QG). The UCC27301A, UCC27311A and UCC27211A offer high gate drive current of 3.7A/4.5A to enable driving high QG and achieve fast switching times . If the power level is more modest, the UCC27201A driver has 3A gate drive current for applications where the lower drive current is adequate. Also, an important consideration to optimize efficiency is optimizing the timing of the power train including dead time. The TI 120V gate drivers have low propagation delays in the 19 to 22nS range and very low delay matching between the low side and high side gate drive outputs of 7ns maximum. This allows the designer to optimize the power train for low switching losses and ensure there will not be large variance in production.
In order to achieve high efficiency in solar microinverter applications it is important to incorporate high performance gate drivers in the power train. TI offers several high performance 120V half-bridge gate drivers with high drive strength, low propagation delays and excellent delay matching to optimize the switching of the power stage of the DC-DC converter block in the solar microinverter.