Inferential temperature measurement of an electrochromic device
View Patent ↗An electrochromic device driver system having inferential temperature measurement of the electrochromic device. The inferred temperature measurements enable the system to determine the maximum but safe driving voltages to improve the speed of varying the transmissivity levels of the electrochromic device without damaging the device.
1. A process for driving an electrochromic (EC) device comprising:
applying a driving signal to bleach or color the EC device, wherein initially the driving signal has a voltage amplitude that is harmless to the EC device at any temperature;
measuring a first voltage amplitude of the driving signal applied to the EC device;
measuring a second voltage amplitude of the driving signal applied to the EC device;
measuring a first current amplitude of the driving signal applied to the EC device;
measuring a second current amplitude of the driving signal applied to the EC device;
determining a voltage amplitude difference between the first voltage amplitude and the second voltage amplitude;
determining a current amplitude difference between the first current amplitude and the second current amplitude;
determining a first resistance from the voltage amplitude difference and the current amplitude difference;
determining a second resistance by subtracting a third resistance from the first resistance, wherein the third resistance is a static resistance of the EC device that is static relative to temperature change of the EC device; and
adjusting the first and second voltage amplitudes to a maximum amplitude that is harmless to the EC device at a present temperature that is inferred from the second resistance.
2. The process of claim 1 , wherein said process is repeated upon receipt of a first or second indication signal to bleach or color, respectively.
3. The process of claim 2 , wherein:
the driving signal has a reversal of polarity for short periods of time;
the first and second voltage amplitudes are measured when the polarity is not reversed and reversed; and
the first and second current amplitudes are measured when the polarity is not reversed and reversed.
4. The process of claim 3 , wherein the reversal of the polarity of the driving signal is approximately periodic.
5. The process of claim 4 , wherein the first voltage amplitude may be equivalent to any one of several set amplitudes, each set amplitude being harmless to the EC device within a particular range of temperatures of the EC device.
6. The process of claim 5 , wherein the second voltage amplitude may be equivalent to any one of several set amplitudes, each set amplitude being harmless to the EC device within one of plurality of ranges of temperatures of the EC device.
7. The process of claim 6 , wherein the plurality of ranges of temperatures is at least three ranges of temperatures.
8. The process of claim 7 , wherein the plurality of ranges of temperatures do not necessarily overlap with one another.
9. The process of claim 8 , wherein the first and second voltage amplitudes are at a plus or minus values.
10. The process of claim 2 , wherein any temperature is the operational temperature range of the EC device.
11. The process of claim 3 , wherein the first voltage amplitude is at an amplitude that is harmless to the EC device at any temperature.
12. The process of claim 4 , wherein the second voltage amplitude is at an amplitude that is harmless to the EC device at any temperature.