As the United States enters the summer, I have begun to yearn for the days of holiday on the beach and barbecue by the pool. I grew up in southern Florida and now live in Texas. Hot and sunny days are familiar to me. Similarly, I’m used to paying higher electricity bills in the summer. From a positive point of view, sunny days also bring many benefits, one of which is solar energy.
Solar energy helps to reduce the costs associated with power generation. One of the hottest topics in this industry is power conversion efficiency. In order to improve the efficiency of 0.1%, solar inverter manufacturers often need to invest a lot of time. Considering the correlation between higher efficiency and increased energy, i.e. faster return on investment of photovoltaic (PV) system, it will be very important to determine the ability of inverter to convert DC of solar panel into domestic AC.
Micro inverter and solar optimizer are two fast developing architectures in the solar market. Figure 1 shows a typical block diagram of the solar micro inverter. The micro inverter converts power from a single PV module and is usually designed for a maximum output power of 250W to 400W.
To maximize the performance of PV panels, the front end of the micro inverter is DC / DC stage, in which the digital controller performs maximum power point tracking (MPPT). The most common topology is non isolated DC / DC boost converter. For a single solar panel, the rail or DC link is usually 36V; For this voltage range, you can use standard silicon metal oxide semiconductor field effect transistors (MOSFETs) for DC / DC conversion.
Given that size reduction is a priority (so micro inverters and power optimizers will be suitable for the back end of photovoltaic systems), solar inverter manufacturers are adopting gallium nitride (GAN) technology as it can switch at higher frequencies. Higher frequency reduces the size of large magnetic components in micro inverter and solar optimizer applications.
H-bridge topology is usually used in DC / AC level or secondary level; For the micro inverter, the rail voltage is about 400V. At present, the gate driver can use a variety of isolation technologies to isolate the controller and the power switch, and can drive the high frequency switch at the same time. These requirements are driven by safety standards for signal isolation.
Ti’s ucc21220 basic isolated gate driver improves these integrated advantages by providing leading performance in propagation delay and delay matching between high side and low side. These timing characteristics reduce the switch related losses because they conduct faster and minimize the on time of the bulk diode, thus improving efficiency. These parameters are also less dependent on VDD, so you can relax the voltage tolerance design margin for the rest of the system, as shown in the workbench data in Figure 2. Figure 2 also shows that ucc21220 provides faster propagation delay than competitive products.
Ucc21220 offers alternatives to solar applications, such as micro inverters and solar optimizers, where basic isolation may be sufficient. Ucc21220 adopts the second generation capacitor isolation technology, which reduces the cost by reducing the chip size. It can not only improve the efficiency by providing a typical propagation delay of 28ns, but also reduce the printed circuit board (PCB) space and system cost.
Ti’s Gan technology enables DC / DC boost and DC / AC inverter to operate at frequencies over 100 kHz. The inherent low switching loss of Gan power stage enables it to achieve 99% or higher efficiency.
Higher efficiency means not only less energy waste, but also smaller radiators, less cooling requirements, and a more compact and cost-effective design. Using the right high voltage grid driver can help you achieve higher efficiency and reduce the system cost in the design of space limited micro inverter or solar optimizer.