US Patent 9563097 Driver for electrochromic glass unit

A method for controlling an electrochromic device is provided. The method includes applying a constant supply current to the electrochromic device and determining an amount of charge transferred to the electrochromic device, as a function of time and current supplied to the electrochromic device. The method includes ceasing the applying the constant supply current, responsive to a sense voltage reaching a sense voltage limit and applying one of a variable voltage or a variable current to the electrochromic device to maintain the sense voltage at the sense voltage limit, responsive to the sense voltage reaching the sense voltage limit. The method includes terminating the applying the variable voltage or the variable current to the electrochromic device, responsive to the determined amount of charge reaching a target amount of charge.