This paper addresses different aspects of design process of a power source for a mechanical respirator. It displays a detailed design procedure for an AC/DC converter boost power factor correction as a power supply for a DC/DC converter that powers the mechanical respirator. It also has an internal energy source, and an algorithm that detects the absence of a main power supply and low battery voltage. Besides, strategies and control schemes for the converter are proposed. This work also suggests a digital control and equations in difference to be implemented in a microprocessor. The system simulations are consistent with the real implementation observing proper operation.