Patent ID: 6954299

Claim:
A controlling system for controlling a reflectance of an electrochromic element, including: an analog-to-digital converter reading an averaged voltage before the averaged voltage is applied on the electrochromic element, and then transforming said averaged voltage; a microcontroller provided with at least a look up table and a PWM unit for providing a PWM function, receiving a input averaging voltage transformed from the analog-to-digital converter and then determining whether an output voltage with a fixed frequency in PWM signal form is relatively generated, by way of looking up several corresponding output voltages pre-stored in the look up table for the voltage of input signal and only judging whether the input averaged voltage is less than the pre-stored output voltage; and a charging circuit capable of being disabled by the microcontroller to release overloading voltages in the electrochromic element when the input averaged voltage is in contrast of being less than the pre-stored output voltage.