Driving thin film switchable optical devices
Controllers and control methods apply a drive voltage to bus bars of a thin film optically switchable device. The applied drive voltage is provided at a level that drives a transition over the entire surface of the optically switchable device but does not damage or degrade the device. This applied voltage produces an effective voltage at all locations on the face of the device that is within a bracketed range. The upper bound of this range is associated with a voltage safely below the level at which the device may experience damage or degradation impacting its performance in the short term or the long term. At the lower boundary of this range is an effective voltage at which the transition between optical states of the device occurs relatively rapidly. The level of voltage applied between the bus bars is significantly greater than the maximum value of the effective voltage within the bracketed range.
1. A method of transitioning an optically switchable device between two optical states, comprising:
applying a ramp function to a voltage applied to drive the optically switchable device until one or more regions of the optically switchable device achieves a predetermined voltage;
after the one or more regions of the optically switchable device achieves the predetermined voltage,
(a) reducing the voltage to generate a reduced magnitude voltage; and
(b) reducing a current delivered to the optically switchable device, wherein a profile of the current as a function of time is shaped in accordance with a profile of the reduced magnitude voltage applied to the optically switchable device.
2. The method of claim 1 , wherein the optically switchable device is provided in an insulated glass unit.
3. The method of claim 1 , wherein the optically switchable device comprises an ion conducting layer disposed between two electrically conductive layers.
4. The method of claim 3 , wherein the ion conducting layer comprises silicon.
5. The method of claim 3 , wherein the ion conducting layer comprises an oxide.
6. The method of claim 3 , wherein the two electrically conductive layers comprise a transparent conductive oxide.
7. The method of claim 6 , wherein the transparent conductive oxide comprises indium oxide, indium tin oxide, doped indium oxide, tin oxide, doped tin oxide, zinc oxide, aluminum zinc oxide, doped zinc oxide, ruthenium oxide, or doped ruthenium oxide.
8. The method of claim 1 , wherein the reduced magnitude voltage comprises a value of about one (1) Volt (V) or less.
9. A method of transitioning an optically switchable device between two optical states, comprising:
applying a ramp function to a voltage to drive the optically switchable device until one or more regions of the optically switchable device achieves a predetermined voltage; and
after the one or more regions of the optically switchable device achieves the predetermined voltage, reducing a magnitude of the voltage to generate a reduced magnitude voltage, such that a current delivered to the optically switchable device has a profile that is shaped in accordance with a profile of the reduced magnitude voltage, in which the profile is shaped as a function of time.
10. The method of claim 9 , wherein the optically switchable device is provided between two lites of an insulated glass unit.
11. The method of claim 9 , wherein the optically switchable device comprises an ion conducting layer bounded on one or more opposing sides by conductive electrode layers.
12. The method of claim 11 , wherein the ion conducting layer comprises a thickness of between about one hundredth (0.01) μm to about one (1) micrometer (μm).
13. The method of claim 11 , wherein the ion conducting layer comprises silicon.
14. The method of claim 11 , wherein the conductive electrode layers comprise a transparent oxide.
15. The method of claim 14 , wherein the transparent oxide comprises indium oxide, indium tin oxide, doped indium oxide, tin oxide, doped tin oxide, zinc oxide, aluminum zinc oxide, doped zinc oxide, ruthenium oxide, or doped ruthenium oxide.
16. The method of claim 9 , wherein the reduced magnitude voltage comprises a value of at most about one (1) Volt (V).
17. A method of transitioning between two optical states in an optically switchable device, comprising:
during a first phase, controlling current conducted to the optically switchable device;
terminating the first phase responsive to one or more regions of the optically switchable device attaining a predetermined voltage magnitude; and
after the first phase, controlling a voltage applied to the optically switchable device, wherein a profile of a current conducted to the optically switchable device is in accordance to a profile of the applied voltage.
18. The method of claim 17 , wherein the current conducted during the first phase conducts from a first conductive layer to a second conductive layer, the conducted current causing movement of ions in the optically switchable device to bring about an electrochromic phenomenon.
19. The method of claim 18 , wherein the current conducted in the first phase causes movement of one or more lithium ions.
20. The method of claim 18 , wherein the first and the second conductive layer each comprise indium oxide, indium tin oxide, doped indium oxide, tin oxide, doped tin oxide, zinc oxide, aluminum zinc oxide, doped zinc oxide, ruthenium oxide, or doped ruthenium oxide.