What is a chopper or PWM or what is pulse width modulation?
A PWM or chopper is a device that uses a specific technique called pulse width modulation to efficiently lower the voltage from a DC source. The result is a pulsatile waveform that has an effective (RMS) voltage that is lower than the input. The circuit can be made very efficient especially when used with lights, which require no special filtering of the output voltage. Note that a simple PWM or chopper does not regulate the voltage in any way, it merely makes the apparent voltage to the bulb lower to act as a dimmer. Also note that this is not an efficient way to dim a light bulb, as you can see from the efficiency curve in the graph in Section 6.2. A very highly efficient method of voltage regulation is possible using the PWM technique, however. By using analog or microprocessor circuits, it is possible to achieve a high degree of regulation. NiteRider’s digital lights use such a circuit. Willie Hunt has also designed such a device and made it available for sale. For more information
