The SM72442 MPPT digital controller and SM72295 photovoltaic full bridge drivers are designed to control high efficiency DC/DC conversion used in photovoltaic applications. This application note will detail the usage of those devices in a battery charging application. The reference design is meant to provide support for a wide variety of implementations, however, unless otherwise noted, this reference design system is shown charging a 12V commercial automotive lead acid battery.
If the battery voltage is very low, a slow charge current is applied and limited until the voltage rises above a pre-set threshold value Vt. The full charge current is then applied. Once full charge is detected on the voltage of the battery, the system switches to a floating charge and maintains the battery voltage at a fixed threshold. At any time, the system will run in MPPT mode if the available power is lower than the power required to achieve voltage or current regulation.