In a present-day house, most of the equipment (i.e. battery chargers, lights) require DC voltage. Renewable energy sources and storage system in a house also provide DC voltage. But due to AC distribution system inside house additional power conversion stages are required which decrease overall system efficiency and increase cost. In near future, power distribution system will be DC. An optimal voltage level for DC distribution system inside house considering lower conduction losses and safety is 48V. Solar panels and batteries are usually available with the voltage rating of 24V. This voltage difference between two voltage levels creates a need for a 24V to 48V DC converter. This converter needs to be small in size and have very high efficiency. The power rating of the converter is 200W. Estimated efficiency of the converter is 98%.
Main components contributing to the size of the converter are inductor, capacitor and heat sink. Size of the heat sink is directly related to the amount of losses occurring inside switching components. Size of the capacitor is dependant on ripple current in the output of the converter. Size of inductor depends on the amount of energy to be stored inside inductor. In order to decrease output ripple current, 2 phase interleaved boost converter is used. Both phases work with 180-degree phase difference which results in current cancellation in output, reducing output current ripple. Interleaving also reduces conduction losses in the switch. Further, the converter is operated in boundary condition mode at all load conditions which gives two benefits:1) decreased amount of energy stored in the inductor, 2) valley switch-on of the semiconductor switch. Valley switch-on of the semiconductor switch results in lower switching losses. In order to reduce diode losses, synchronous rectification is used.
Values of the input voltage, output voltage, Inductor 1 current and inductor 2 current values are fed into the microcontroller which generates 4 PWM signals for 4 switches. Inductor current sensors ensure converter is working in boundary condition mode at all time. PWM1/3 and PWM2/4 are complementary signals with sufficient dead time between them.
So, combining interleaving, boundary condition mode, valley switching and synchronous rectification will result in a converter with very high efficiency and small size.
2 TAPAS board. Total 4 switches are required in the converter. Each tapas board has 3 half bridges. In my design only bottom switch can be utilized as connection sequence of two switches is source-drain-drain-source as seen from the diagram. Whereas half bridge given on board has connection sequence of drain-source-drain-source.
this idea will get two TAPAS boards