CONTROLLING TRANSITIONS IN OPTICALLY SWITCHABLE DEVICES

• US 20160139477A1
• Filed: 06/20/2014
• Published: 05/19/2016
• Est. Priority Date: 06/28/2013
• Status: Active Grant

• Current Assignee: View Incorporated
• Original Assignee: View Incorporated
• Inventors: Jack, Gordon, Kailasam, Sridhar K., Brown, Stephen C., Pradhan, Anshu A.
• Granted Patent: US 9,885,935 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G02F 1/163 Operation of electrochromic cells, e.g. electrodeposition cells; Circuit arrangements therefor
• CPC Class Codes: G09G 3/19 using electrochromic devices

Abstract

Aspects of this disclosure concern controllers and control methods for applying a drive voltage to bus bars of optically switchable devices such as electrochromic devices. Such devices are often provided on windows such as architectural glass. In certain embodiments, the applied drive voltage is controlled in a manner that efficiently drives an optical transition over the entire surface of the electrochromic device. The drive voltage is controlled to account for differences in effective voltage experienced in regions between the bus bars and regions proximate the bus bars. Regions near the bus bars experience the highest effective voltage.

Claims

1. A method of controlling an optical transition of an optically switchable device from a starting optical state to an ending optical state, the method comprising:

(a) applying a drive voltage for driving the optically switchable device to transition from the starting optical state to the ending optical state, wherein the drive voltage is applied to bus bars of the optically switchable device;

(b) before the transition is complete, periodically determining an open circuit voltage between the bus bars of the optically switchable device, and periodically determining a total delivered charge density supplied to the optically switchable device during the transition;

(c) determining whether the open circuit voltage determined in (b) has a magnitude greater than or equal to a magnitude of a target open circuit voltage, and determining whether a magnitude of the total delivered charge density determined in (b) is greater than or equal to a magnitude of a threshold charge density; and

(d) if it is determined in (c) that both (i) the magnitude of the open circuit voltage determined in (b) is greater than or equal to the magnitude of the target open circuit voltage, and (ii) the magnitude of the total delivered charge density determined in (b) is greater than or equal to the magnitude of the threshold charge density, applying a hold voltage for holding the ending optical state.

2. The method of claim 1, wherein the open circuit voltage is determined in (b) at a defined time after applying the drive voltage in (a).

3. The method of claim 2, wherein the defined time is at most about 120 minutes.

4. The method of claim 1, wherein the magnitude of the target open circuit voltage is between about 0-1V greater than the magnitude of the hold voltage.

5. The method of claim 4, wherein the magnitude of the target open circuit voltage is at least about 0.025V greater than the magnitude of the hold voltage.

6. The method of claim 1, wherein the magnitude of the threshold charge density is between about 1×

10<sup>−

5</sup> C/cm² and about 5 C/cm².

7. The method of claim 6, wherein the magnitude of the threshold charge density is between about 0.01-0.04 C/cm².

8. The method of claim 1, further comprising after (c) and before (d)

(i) increasing the magnitude of voltage applied to the bus bars to the drive voltage as a result of determining in (c) that either the magnitude of the open circuit voltage determined in (b) is less than the magnitude of the target open circuit voltage, or that the magnitude of the total delivered charge density determined in (b) is less than the magnitude of the threshold charge density;

and

(ii) repeating (b)-(c).

9. The method of claim 8, wherein (b)-(c) are repeated at a frequency of between about 5 seconds and 5 minutes.

10. The method of claim 1, wherein the optically switchable device is an electrochromic device.

11. The method of claim 1, wherein the bus bars are separated from one another by at least about 10 inches.

18. The apparatus of claim 11, wherein the processor is further designed or configured to, after (c) and before (d)

(i) increase the magnitude of voltage applied to the bus bars to the drive voltage as a result of determining in (c) that either the magnitude of the open circuit voltage determined in (b) is less than the magnitude of the target open circuit voltage, or that the magnitude of the total delivered charge density determined in (b) is less than the magnitude of the threshold charge density;

and

(ii) repeat (b)-(c).

19. The apparatus of claim 18, wherein the processor is further designed or configured to repeat (b)-(c) at a frequency of between about 5 seconds and 5 minutes.

20. The apparatus of claim 11, wherein the optical switchable device is an electrochromic device.

21. The apparatus of claim 11, wherein the bus bars are separated from one another by at least about 10 inches.

12. An apparatus for controlling an optical transition of an optically switchable device from a starting optical state to an ending optical state, the apparatus comprising:

a processor designed or configured to

(a) apply a drive voltage for driving the optically switchable device to transition from the starting optical state to the ending optical state, wherein the drive voltage is applied to bus bars of the optically switchable device,

(b) before the transition is complete, periodically determine an open circuit voltage between the bus bars of the optically switchable device, and periodically determine a total delivered charge density supplied to the optically switchable device during the transition,

(c) determine whether the open circuit voltage determined in (b) has a magnitude greater than or equal to a magnitude of a target open circuit voltage, and determine whether the total delivered charge density determined in (b) has a magnitude greater than or equal to a magnitude of a threshold charge density, and

(d) if it is determined in (c) that both (i) the magnitude of the open circuit voltage determined in (b) is greater than or equal to the magnitude of the target open circuit voltage, and (ii) the magnitude of the total delivered charge density determined in (b) is greater than or equal to the magnitude of the threshold charge density, apply a hold voltage for holding the ending optical state; and

a power supply for providing voltage and/or current at defined magnitudes to the optically switchable device to control the optical transition.

13. The apparatus of claim 12, wherein the processor is further designed or configured to determine the open circuit voltage and total delivered charge density in (b) at a defined time after applying the drive voltage in (a).

14. The apparatus of claim 13, wherein the defined time is at most about 120 minutes.

15. The apparatus of claim 12, wherein the magnitude of the target open circuit voltage is between about 0-1V greater than the magnitude of the hold voltage.

16. The apparatus of claim 15, wherein the magnitude of the target open circuit voltage is at least about 0.025V greater than the magnitude of the hold voltage.

17. The apparatus of claim 12, wherein the magnitude of the threshold charge density is between about 1×

10<sup>−

5</sup> C/cm² and about 5 C/cm².

22. A method of controlling an optical transition of an optically switchable device from a starting optical state to an ending optical state, the method comprising:

(a) applying a drive voltage for driving the optically switchable device to transition from the starting optical state to the ending optical state, wherein the drive voltage is applied to bus bars of the optically switchable device;

(b) before the transition is complete, periodically reducing the magnitude of the voltage applied to the bus bars of the optically switchable device to a probe voltage and detecting a current response, and periodically determining a total delivered charge density supplied to the optically switchable device during the transition;

(c) determining whether the current response detected in (b) reaches a target current, and determining whether a magnitude of the total delivered charge density determined in (b) is greater than or equal to a magnitude of a threshold charge density; and

(d) if it is determined in (c) that both (i) the current response detected in (b) reaches the target current, and (ii) the magnitude of the total delivered charge density determined in (b) is greater than or equal to the magnitude of the threshold charge density, applying a hold voltage for holding the ending optical state.

23. The method of claim 22, wherein the target current is about 0 Amps.

24. An apparatus for controlling an optical transition of an optically switchable device from a starting optical state to an ending optical state, the apparatus comprising:

a processor designed or configured to

(a) apply a drive voltage for driving the optically switchable device to transition from the starting optical state to the ending optical state, wherein the drive voltage is applied to bus bars of the optically switchable device;

(b) before the transition is complete, periodically reduce the magnitude of the voltage applied to the bus bars of the optically switchable device to a probe voltage and detect a current response, and periodically determine a total delivered charge density supplied to the optically switchable device during the transition;

(c) determine whether the current response detected in (b) reaches a target current, and determine whether a magnitude of the total delivered charge density determined in (b) is greater than or equal to a magnitude of a threshold charge density; and

(d) if it is determined in (c) that both (i) the current response detected in (b) reaches the target current, and (ii) the magnitude of the total delivered charge density determined in (b) is greater than or equal to the magnitude of the threshold charge density, apply a hold voltage for holding the ending optical state; and

a power supply for providing voltage and/or current at defined magnitudes to the optically switchable device to control the optical transition.