1. Thyristor dimmer: Principle – The output voltage is adjusted by controlling the phase shift at which the thyristor conducts, thereby performing AC chopping. Features – This technology is mature, reliable, and compact; however, it generates considerable noise. Thyristor dimming involves processing 50 Hz/60 Hz sine wave AC power, controlling the energy output per unit time. The current drawn from the power grid is a distorted non-sine wave with a low power factor. When the thyristor conducts, the current flowing through the lamp rises rapidly, resulting in the generation of numerous electromagnetic harmonics that cause interference. The range of these harmonic frequencies is very wide, from several hundred hertz to several thousand hertz, and in some cases even up to several megahertz. The output voltage from a thyristor dimmer contains many harmonics, primarily the 3rd, 5th, 7th, 9th, 11th, and 13th harmonic currents. The greater the load power, the higher the intensity of these higher-order harmonics, which contaminates the power grid and also interferes with audio and video equipment connected to the same network. Although the use of large specialized chokes in series with the circuit can prolong the rise time and reduce interference, it is impossible to completely eliminate all harmonic distortions. In stage lighting installations, various measures such as isolation and shielding are required, which not only increases construction and maintenance costs but also fails to fully suppress harmonic interference.
2. Sine wave electronic dimmer: Principle – This device combines pulse width modulation (PWM) with IGBT 180° timing control techniques to achieve AC-AC sine wave output voltage regulation, ensuring that both the current drawn from the power grid and the output current are pure sine waves. Features – It has a high power factor, excellent waveform quality, no interference, high efficiency, low noise, high level of intelligence, and does not require special measures for power grid management. Sine wave electronic dimming involves amplitude modulation of a pure sine wave, allowing for the adjustment of the output voltage between 0 and 220 V to drive loads. The current drawn from the power grid by this dimmer is a sine wave, which significantly reduces harmonic content in both the power grid and the output. Since it operates in a high-frequency switching mode, it allows for smaller passive filtering components, thereby reducing production costs and improving performance. Currently, sine wave electronic dimmers represent the fifth generation of dimming devices. They offer unique advantages in terms of improving the waveform of output voltage and current as well as reducing harmonics in the power supply system, which in turn leads to better suppression of external electromagnetic interference and full compliance with national standards. They feature a more sophisticated control system that is more intelligent and user-friendly. The circuit also includes overcurrent and short-circuit protection mechanisms, enhancing safety and reliability. Since the sine wave electronic dimmer adjusts the brightness by changing only the amplitude of the sine wave, it significantly reduces losses in the entire power distribution system. Moreover, as it is not limited by the characteristics of the load, it can be used to control the brightness of resistive loads such as spotlights and imaging lights, as well as to regulate the speed of motors and fans. It can also be used to dim gas discharge lamps, fluorescent lamps, and energy-saving lamps. Multiple circuits can be connected in parallel to achieve higher output powers. Sine wave electronic dimmers do not pollute the power grid, reduce losses in the power supply system and wiring, and eliminate the need for separate power transformers or isolation/shielding measures, thus saving costs.