James Mackey Fundamentals of Power Supplies

James Mackey RectifierFilterRegulator AC Input AC Rectified (Pulsating DC) Smoothed DC Smoothed & Regulated DC

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Basic Diode Circuits

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Capacitive Filtering

James Mackey Finite Charge/Discharge times of RC circuit smooths out pulsating DC from the Rectifying circuit

James Mackey The effect of a single diode rectifying circuit - called a half-wave rectifier - produces the 60 Hz pulsating DC signal that must be smoothed by the filter circuit. The action of this circuit removes 1/2 of the AC component from the Power Supply input and increases the difficulty of smoothing. The full-wave rectifier saves both halves of the AC input and makes the signal easier to smooth by the filter circuit Types of Rectifiers

James Mackey Full-Wave Rectifier AC Input Diode B Diode A

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Output waveform from Diode A - half wave rectified + cycle Output waveform from Diode B - half wave rectified - cycle Combined waveform from both + & - cycles

James Mackey The full-wave rectifier circuit requires a center tapped transformer in order to function. Transformers are usually the most expensive part of a power supply; with center tapped transformers more expensive than single transformers. For these reasons, an alternate full-wave circuit is usually used, called a full-wave bridge rectifier. Full-Wave Rectifiers

James Mackey Full-Wave Bridge Rectifier

James Mackey Full-Wave Rectifier and Filter Circuit

James Mackey Full-Wave Bridge Rectifier and Filter Circuit

James Mackey The operation of all of these circuits is based on the rectifying property of semiconductor diodes. We saw these effects in the Workbench exercise done earlier. A plot of diode voltage versus diode current is shown on the next slide.

James Mackey Scale is mA Scale is  A

James Mackey