Signal Rectifier + Low Pass Filter Using PSoC® 1

Question: How to use PSoC 1 as a Full wave rectifier / Low Pass Filter?




A rectifier converts an alternating input current (AC) to direct current (DC) signal. A full wave rectifier converts both polarities of the input signal to a positive amplitude and is more efficient than a half wave rectifier in terms of power transfer. Versatile architecture of PSoC 1 switched capacitor blocks helps in consutructing a full wave rectifier with LPF all in hardware.

In this project, a full wave rectifier is configured using the inbuilt analog resources. The analog signal is fed to a unity gain programmable gain amplifier (PGA) and to a Comparator which is configured as a Zero Crossing Detector, and a modulator. The output of the comparator is used to modulate the sign of the modulator block that converts the AC input signal to full wave rectified output.

A Low Pass filter user module is used to filter the output from the modulator block. The LPF2 User Module implements a general purpose second order low-pass filter. Any classical all-pole filter configuration (Butterworth, Bessel, and Chebyshev) can be implemented. The corner frequency can be set very accurately or adjusted by controlling the sample rate clock.

The rectified output is fed to the 2-pole low pass filter which gives a filtered DC voltage as output.