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Adjusting the brightness of light emitted by a light source is then merely a matter of setting at what voltage (or phase) in the AC half-cycle the dimmer begins to provide electric current to the light source (e.g. by using an electronic switch such as a triac). In this case the PWM duty cycle is the ratio of the conduction time to the duration ...
The switch is controlled by a PWM (Pulse Width Modulation) signal, which alternately turns the switch on and off at a rapid rate. The relative proportion of off time vs. on time determines brightness. For example, if the switch is off 10% of the time, the resulting control signal would be the equivalent of 1 V produced with a variable resistor.
Fig. 2. EMI noise of output voltage for programmed switching frequency (PWM): a) Spectrum and b) Spectrogram. PWM is considered the most common deterministic technique. Considering the example of a DC-DC converter, a controlled switch is designed to “cut-off” the DC waveform into a pulse-shaped waveform.
Servo and receiver connections A diagram showing typical PWM timing for a servomotor. Servo control is a method of controlling many types of RC/hobbyist servos by sending the servo a PWM (pulse-width modulation) signal, a series of repeating pulses of variable width where either the width of the pulse (most common modern hobby servos) or the duty cycle of a pulse train (less common today ...
This circuit is called a leading-edge dimmer or forward phase dimming. Waveform of the output voltage of a thyristor dimmer set for 60 volts RMS output, with 120 V input. The red trace shows the output device switching on about 5.5 ms after the input (blue) voltage crosses zero.
For all the chopper configurations operating from a fixed DC input voltage, the average value of the output voltage is controlled by periodic opening and closing of the switches used in the chopper circuit. The average output voltage can be controlled by different techniques namely: Pulse-width modulation; Frequency modulation
Space vector modulation (SVM) is an algorithm for the control of pulse-width modulation (PWM), invented by Gerhard Pfaff, Alois Weschta, and Albert Wick in 1982. [1] [2] It is used for the creation of alternating current (AC) waveforms; most commonly to drive 3 phase AC powered motors at varying speeds from DC using multiple class-D amplifiers.
Fig. 2: Top and bottom views of an air-cooled 10kW-Vienna Rectifier (400kHz PWM). The Vienna Rectifier is useful wherever six-switch converters are used for achieving sinusoidal mains current and controlled output voltage, when no energy feedback from the load into the mains is available.