FIELD OF THE INVENTION

The present invention relates generally to the field of interior rearview mirror assemblies for vehicles.

BACKGROUND OF THE INVENTION

It is known to provide a mirror assembly that is adjustably mounted to an interior portion of a vehicle, such as via a double ball pivot or joint mounting configuration where the mirror casing and reflective element are adjusted relative to the interior portion of a vehicle by pivotal movement about the double ball pivot configuration. The mirror casing and reflective element are pivotable about either or both of the ball pivot joints by a user that is adjusting a rearward field of view of the reflective element. The mirror reflective element may comprise a variable reflectance mirror reflective element that varies its reflectance responsive to electrical current applied to conductive coatings or layers of the reflective element.

SUMMARY OF THE INVENTION

The present invention provides an electrochromic rearview mirror assembly, such as an interior or exterior rearview mirror assembly. The mirror assembly includes a mirror reflective element sub-assembly that includes an electrochromic (EC) cell and an EC driving circuit. The EC driving circuit includes a fixed voltage switching regulator configured to provide voltage to a power input of the electrochromic (EC) cell and a drive transistor connected to an output of the fixed voltage switching regulator and configured to switch the provided voltage on and off to the EC cell. The circuit also includes a protection diode connected to the drive transistor and the EC cell and a bleach transistor connected to the power input of the EC cell and to ground. A controller is connected to the fixed voltage switching regulator, the drive transistor, and the bleach transistor, and the controller is configured to control the fixed voltage switching regulator, the drive transistor, and the bleach transistor to control the voltage provided to the EC cell.

These and other objects, advantages, purposes and features of the present invention will become apparent upon review of the following specification in conjunction with the drawings.

