Power Optimizers have been introduced to the photovoltaic (PV) market in the past few years and proven that there is a viable market for distributed electronics in PV systems. As of early 2012, more than one million power optimizers from various manufacturers have been installed in all climate regions around the world overcoming the initial hesitation of the industry in using electronics in smart junction boxes or close to the PV module.
Figure 1 shows a typical mid size PV array with power optimizers deployed within each module. In every PV array the individual PV modules are operating under varying conditions that lead to a different I/V combination to generate maximum power. These mismatches can be substantial, especially when local shading occurs on part of the array. Local Maximum Power Point Tracking (MPPT) performed by DC/DC conversion in the power optimizer allows for maximum energy harvest of the overall PV system.
Cost reduction has been the driving force in the PV industry to make it a viable source of energy that can be competitive with fossil fuel power generation. Maximum harvesting of the sun’s energy also requires low cost and highly efficient power electronics. The SM72445 is the latest generation of MPPT controllers to give the power optimizer the ability to adjust to the varying conditions of each individual PV module.
The SM72445 offers the ideal compromise between flexibility, low power consumption and low cost.
The highlighted features are:
- Selection of three PWM frequencies (110, 135 and 215kHz) to optimize overall system efficiency and sizing of the magnetic components
- Panel Mode pin for optional bypass switch control, this convenient feature eliminates two FETs to reduce part count and cost
- I2C interface for communication, e.g. panel diagnostics: Voltage and Current
- Programmable maximum power point tracking, tracking speed is very fast at 0.01seconds
- Single inductor buck-boost converter control
The evaluation board for the SM72445 gives a customer a convenient and quick way to design a power optimizer with all basic features that market requires: highest efficiency, robust design that allows quick certification, field proven and low cost. This reference design has been optimized to work with the SM72295 full bridge driver and is shown in Figure 2.
The functionality of the SM72445 MPPT controller can be abstracted as an impedance matching device used in other applications as shown in Figure 3. The objective is to maximize the transfer of power from the generator to the load. In principle all applications with dynamic generator and load conditions would benefit from the functionality of the power optimizer.
Typical examples for fluctuating generator impedance are solar and wind generators. However, there are many more cases including audio (amplifier to speaker), signal transmission, motor control, etc. where dynamic generator and/or load conditions require an optimizer in the power path between source and load to minimize losses.
In order to compete with traditional energy sources solar and wind power generators have been forced to be as efficient as technically possible. Energy efficient designs are now required in most electronic designs. The MPPT capability of the SM72445 constitutes a basic building block for implementing impedance matching in a wide range of new applications in addition to its home base in the renewable energy market.
If you have any questions regarding this power solution, please feel free to list them in the comment section below.
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