Electrochromic system and its supply process

• US 5,694,144 A
• Filed: 05/15/1995
• Issued: 12/02/1997
• Est. Priority Date: 05/16/1994
• Status: Expired due to Term

• Current Assignee: Saint-Gobain Vitrage
• Original Assignee: Saint-Gobain Vitrage
• Inventors: Lefrou, Christine, Ast, Marc
• Primary Examiner(s): LIANG, REGINA
• Application Number:
  US08/441,295
• Time in Patent Office: 932 Days
• Field of Search: 345/49, 345/105, 359/265, 359/267, 359/275, 359/273, 359/269, 359/270, 359/271
• US Class Current: 345/49
• CPC Class Codes: G02F 1/163 Operation of electrochromic cells, e.g. electrodeposition cells; Circuit arrangements therefor

Abstract

Electrochromic systems having a material, whose coloration state and/or the transmission in certain electromagnetic radiation wavelengths varies by performing an electrochemical reaction involving the passage of an electric current. The electric current is generated by an intensity generator able to supply a current, whose intensity obeys a reference value determined as a function of the number of charges to be transferred for switching from the initial coloration state to the desired coloration state and as a function of the time chosen for the switching. The system also relates to using a power supply in an electrochromic glazing process.

Claims

1. An electrochromic system comprising:

a material, whose coloration state or transmission in certain electromagnetic radiation wavelengths varies by performing an electrochemical reaction involving applying an electric current;

an intensity generator for supplying a variable current, the variable current having an intensity which obeys a reference value determined as a function of a number of charges to be transferred for switching from an initial coloration state to a desired coloration state and as a function of a time chosen for the switching; and

means for regulating the intensity supplied by the intensity generator, at least when a coloration change is a decoloration, in order to remain at an intensity which is below, in absolute terms, a value corresponding to at least one of a voltage and a voltage variation that gives rise to a deterioration of the system.

2. The electrochromic system according to claim 1, further comprising:

means for determining the intensity supplied by the intensity generator independent of a use temperature of the system.

3. The electrochromic system according to claim 1, wherein the means for regulating comprises at least one of a data processing means and an electronic means.

4. The electrochromic system according to either claim 1 or 3, wherein the means for regulating further comprises:

a voltage measuring means;

means for determining a second derivative with respect to time of said voltage; and

means for reducing the intensity supplied by the intensity generator when said derivative has reached a reference value.

5. The electrochromic system according to either claim 1 or 3, wherein the means for regulating further comprises:

a means for measuring the voltage or for calculating a derivative of said voltage with respect to time; and

means for reducing the intensity supplied by the intensity generator when said voltage or said derivative reaches a reference value using the measurements/calculations of the voltage or the derivative since the coloration change of the system started.

6. The electrochromic system according to claim 1, wherein the means for regulating further comprises:

a means for interrupting the intensity generator when at least one of the intensity supplied, an efficiency and the coloration state of said system reaches a reference value.

7. The electrochromic system according to claim 1, further comprising:

plural connections from plural electroconductive layers to the means for regulating, wherein the plural connections are two supply points on each of said plural conductive layers, each of the supply points supplying a conductive network in contact with respective conductive layers.

8. The electrochromic system according to claim 7, wherein the plural connections to the means for regulating comprises two conductive supply strips deposited on one edge of each of the plural conductive layers which are diametrically opposite.

9. The electrochromic system according to claim 1, further comprising:

two transparent glass sheet substrates;

two transparent, electroconductive layers covering said substrates;

an electrode formed by a layer of an electrochromic material separating the electroconductive layers;

an electrolyte; and

a counterelectrode,

wherein the intensity generator is connected to the electroconductive layers.

10. The electrochromic system according to claim 9, wherein the electroconductive layers have a square resistance exceeding 15 Ohms.

11. The electrochromic system according to claim 9, wherein the electrolyte at 20°

C. has an ion conductivity below 10^-6 Ohm^-1 ·

cm^-1.

12. The electrochromic system according to claim 1, wherein the time chosen for switching is independent of a size of the system and independent of a use temperature.

13. A method for the electrical supply of an electrochromic system, whose switching between two coloration states is obtained by applying a variable electrical current, the method comprising the steps of:

generating a regulated intensity which is a function of the number of charges to be transferred to obtain a coloration change and as a function of a coloration change time, wherein at least when the coloration change is decoloration, the regulated intensity is maintained in absolute terms below an intensity corresponding to at least one of a voltage and a voltage variation that gives rise to a deterioration of the system; and

applying the regulated intensity to an electrochromic material.

14. The method according to claim 13, wherein the step of generating generates the regulated intensity independent of a use temperature of the system.

15. The method according to claim 13, wherein the step of generating further comprises:

measuring the voltage in the circuit;

determining at a given time interval, a second derivative with respect to time of the voltage; and

reducing the regulated intensity when said second derivative reaches a reference value.

16. The method according to claim 15, wherein the step of reducing the regulated intensity further comprises:

interrupting the regulated intensity when at least one of a) the regulated intensity reaches a minimum reference value, b) the efficiency is 100% and c) the coloration state of the system has reached a reference value.

17. The method according to claim 13, wherein:

the step of generating further comprises measuring the voltage or calculating, using the measurement of the voltage, a first derivative with respect to time of the voltage, at a given time interval; and

reducing the regulated intensity when said voltage or said first derivative reaches a reference value based on the measurements/calculations of the voltage or the first derivative since the coloration change started.