Controlling transitions in optically switchable devices

A method of controlling an optical transition of an electrochromic device from a starting optical state to an ending optical state, the method comprising:

• (a) applying a drive voltage or drive current for driving the electrochromic device to transition from the starting optical state to the ending optical state, wherein the drive voltage or drive current is applied to bus bars of the electrochromic device;
• (b) detecting current or open circuit voltage in the electrochromic device;
• (c) determining whether the current or open circuit voltage detected in (b) has a characteristic indicating that the optical transition will complete within a target timeframe;
• and
• (d) if it is determined in (c) that the optical transition will not complete within the target timeframe, applying a modified drive voltage or a modified drive current, wherein the magnitude of the modified drive voltage or modified drive current is greater than the magnitude of the drive voltage or drive current, respectively, applied in (a).

A method of controlling an optical transition of an electrochromic device from a starting optical state to an ending optical state, the method comprising:

• (a) applying a drive voltage for driving the electrochromic device to transition from the starting optical state to the ending optical state, wherein the drive voltage is applied to bus bars of the electrochromic device;
• (b) before the transition is complete, reducing the magnitude of the voltage applied to the bus bars to a hold voltage;
• (c) after reducing the magnitude of voltage applied to the bus bars, detecting current or open circuit voltage in the electrochromic device;
• (d) determining whether the current or open circuit voltage detected in (c) has a characteristic indicating that the optical transition is nearly complete;
• and
• (e) if it is determined in (d) that the optical transition is nearly complete, applying the hold voltage for holding the ending optical state, wherein the magnitude of the hold voltage is lower than the magnitude of the drive voltage.