MATLAB Examples

# Watkins-Johnson Converter

This example shows the operation of a Watkins-Johnson Converter.

## Description

The Watkins-Johnson (WJ) converter employs a tapped-inductor giving an extra-degree of freedom compared to the classical buck converter. The theoretical transfer function of the WJ converter is:

where is the Duty cycle and is the turns ratio of the tapped inductor,

Note that the above equation is valid in continuous conduction mode only. For a giving conversion ratio, the WJ converter has the advantage of employing a larger duty cycle than the traditional classical buck converter. In our example, the tapped inductor is built using the SPS mutual inductance. By double-clicking on the Tapped Inductor block, you can specify the value in henrys and the turns ratio of the tapped inductor.

## Simulation

Run the simulation and observe waveforms on Scope. The mean value of the load voltage (Vout) should be very close to the theoretical value of:

Vout = 24 * (0.857-0.75) /(0.855*(1-0.75) ) = 12.01 V