Abstract: An electronic circuit for an electrochromic element. In order to improve the response time of the electrochromic element and reduce the cost and complexity, a modulated signal, such as a pulse width modulated (PWM) signal is coupled to the electrochromic element without signal averaging. In order to compensate for the compressed operating range of the reflectance characteristic under such conditions, the electronic circuit in accordance with the present invention utilizes active loading or alternatively voltage feedback of the electrochromic element to provide a reflectance response characteristic with an uncompressed linear operating range similar to a reflectance characteristic for an electrochromic element with a DC drive circuit.

Abstract: A system and method for optimizing the signal range of a photocell for all ambient lighting conditions. A switched resistor circuit is serially connected to the photocell. The duty cycle of the switched resistor circuit is controlled to provide an optimal signal range for the photocell in both light and dark ambient light conditions.