LED dimming adjusts the current supplied to the LED light emitting tube to achieve the purpose of brightness adjustment. LED has strict requirements for power supply voltage and current, too high voltage and current will seriously reduce its service life. Better LEDs have a constant current circuit inside them, which reduces the current output and reduces the brightness. At present, the commonly used LED dimming power supply is: SCR dimming, 0/1-10V dimming power supply, PWM dimming power supply, DALI dimming and DMX dimming. The working principle of dimming is to achieve LED dimming function by controlling the output of current, voltage and frequency.
1, thyristor dimming
It has been used in incandescent lamp and energy-saving lamp dimming before, and it is also a dimming mode that is widely used in LED dimming at present.
Its working principle is to generate a tangential output voltage waveform after passing the input voltage waveform through the conduction Angle shear wave. By applying the tangential principle, the effective value of the output voltage can be reduced, thus reducing the power of the ordinary load (resistive load). SCR dimming has the advantages of high efficiency and stable performance.
2, 0/1-10V dimming
The 0-10V dimming power supply is designed with a control chip. When connected to the 0-10V dimmer, the output current of the power supply can be changed and the brightness of the light can be adjusted by changing the 0-10V voltage. For example, when the 0-10V dimmer modulates to 0V, the current drops to 0 and the brightness of the light is turned off (there is a switch function). When the 0-10V dimmer is turned up to a maximum of 10V, the output current will reach 100% of the output of the power supply and the brightness will be 100%(the output voltage is constant).
1-10V dimming principle, only the dimmer is 1-10V: when the resistance dimmer is adjusted to the minimum 1V, change the output current is also 10%, such as 10V (adjusted to the maximum), the output current will reach 100% of the output of the power supply, brightness will be 100%(the output voltage is constant). Note: 1-10V is no switch function, can not turn the lamp to the lowest off function!
3, PWM dimming
PWM dimming, also known as digital dimming, through the PWM wave on and off the LED to change the forward current conduction time, in order to achieve the effect of brightness regulation. The method is based on the human eye is not sensitive to the flicker of brightness, so the load LED is bright and dark. If the frequency of brightness and darkness is more than 100Hz, the human eye will see the average brightness, not the LED flashing. PWM adjusts brightness by adjusting the ratio of bright time to dark time. In a PWM cycle, because human eyes blink to the light within 100Hz, the perceived brightness is a cumulative process, that is, the greater the proportion of bright time in the whole cycle, the brighter human eyes will feel.