Apparatus for controlling an electrochromic device

Apparatus for controlling a charge state of an electrochromic devices, said electrochromic device receiving a charging current, said apparatus comprising:

• a reference impedance, coupled to receive a reference current proportional to said charging current, said reference impedance having a known impedance relationship with said electrochromic device;
• a comparator, coupled to said reference impedance, for comparing a voltage level of said reference impedance to a threshold voltage level and producing an output signal indicative of said comparison;
• and
• control logic, coupled to said comparator, for simultaneously adapting said reference current and said charging current in response to said output signal of said comparator.

In a pair of sunglasses having a lens portion optically cooperating with an electrochromic material, apparatus for controlling a charge state of said electrochromic material, said electrochromic material receiving a charging current, said apparatus comprising:

• a reference impedance, coupled to receive a reference current proportional to said charging current, said reference impedance having a known impedance relationship with said electrochromic material;
• a comparator, coupled to said reference impedance, for comparing a voltage level of said reference impedance to a threshold voltage level and producing an output signal indicative of said comparison;
• and
• control logic, coupled to said comparator, for simultaneously adapting said reference current and said charging current in response to said output signal of said comparator.