Method and apparatus for controlling an electrochromic device
First Claim
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1. Apparatus for controlling a charge state of an electrochromic (EC) device, comprising:
- a controllable voltage source, for providing a charging voltage to said EC device;
a temperature sensor, for providing an indicium of a temperature proximate said EC device; and
a controller, for determining, in response to said temperature indicium, an appropriate voltage to be applied to said EC device by said controllable voltage source, said determined voltage defining a rate of charge.
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Abstract
A method and apparatus for controlling a charge/discharge voltage applied to an EC device to ensure that an appropriate voltage drop across the EC device is maintained during charge and/or discharge modes of operation. The appropriate voltage drop is determined with respect to a temperature measurement proximate the EC device. The charge level of the device is monitored using a coulomb counter circuit having a topology designed to minimize interference in the operation of the EC device.
126 Citations
17 Claims
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1. Apparatus for controlling a charge state of an electrochromic (EC) device, comprising:
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a controllable voltage source, for providing a charging voltage to said EC device;
a temperature sensor, for providing an indicium of a temperature proximate said EC device; and
a controller, for determining, in response to said temperature indicium, an appropriate voltage to be applied to said EC device by said controllable voltage source, said determined voltage defining a rate of charge. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
a charge counter, for counting charge quanta imparted to said EC device;
said controller causing said controllable voltage source to stop producing said charging voltage when said charge quanta imparted to said EC device reaches a desired level.
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3. The apparatus of claim 2, further comprising:
a polarity reversal circuit, for selectively applying said appropriate voltage produced by said controllable voltage source to said EC device as one of a charge current and a discharge voltage.
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4. The apparatus of claim 3, wherein said charge counter comprises:
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a current mirror, for producing a reference current It proportional to said charge current produced by said controllable voltage source; and
a switch, selectively coupling said reference current to a capacitor, for repeatedly causing said capacitor to be charged to a first threshold level and discharged to a second threshold level by said reference current;
wherein a pulse is provided to said controller each time said capacitor is charged to said first threshold level and each time said capacitor is discharged to said second threshold level.
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5. The apparatus of claim 4, further comprising:
a counter, said counter being incremented in response to pulses provided during a charge mode and decremented in response to pulses provided during a discharge mode, said count being indicative of a present charge level of said EC device.
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6. The apparatus of claim 5, wherein said charge level of said EC device QEC is approximately defined by the following equation:
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7. The apparatus of claim 1, wherein:
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said controllable voltage source provides a charging voltage across said EC device; and
said appropriate voltage to be produced by said controllable voltage source comprises a charging voltage bounded by a minimum charge voltage and a maximum charge voltage, said minimum and maximum charging voltages being temperature dependent.
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8. The apparatus of claim 7, wherein said maximum charge level is selected to avoid browning or bubbling of said EC device.
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9. The apparatus of claim 8, wherein said appropriate charge voltage is bounded by a minimum charge voltage and a maximum charge voltage, said minimum and maximum charging voltages being temperature dependent.
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10. The apparatus of claim 7, wherein said minimum charge level is selected to provide a minimum rate of chromatic change within said EC device.
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11. Apparatus for controlling a charge state of an electrochromic (EC) device, said electrochromic device receiving a charging current, said apparatus comprising:
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a reference resistance, coupled to receive a reference current proportional to said charging current, said reference resistance having a known resistance relationship with said electrochromic device;
a window comparator, coupled to said reference impedance, for comparing a voltage level of said reference impedance to upper and lower threshold levels and producing an output signal indicative of said comparison; and
a controller, coupled to said window comparator, for determining a charge level of said EC device using said window comparator output signal;
a temperature sensor, for determining a temperature proximate said electrochromic device;
said controller, in response to said determined temperature, determining an appropriate charging voltage for said EC device and adapting said charging voltage to said appropriate charging voltage.
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12. In eyewear having a lens portion optically cooperating with an electrochromic material, apparatus for controlling a charge state of said electrochromic material, comprising:
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a controllable current source, for providing a current to said electrochromic device;
a charge counter, for counting charge quanta imparted to said electrochromic device;
a temperature sensor, for providing an indicium of a temperature proximate said electrochromic device; and
a controller, for determining, in response to said temperature indicium, an appropriate voltage to be produced by said controllable current source;
said controller causing said current source to stop producing said current when said charge quanta imparted to said electrochromic device reaches a desired level. - View Dependent Claims (13, 14, 15, 16, 17)
a polarity reversal circuit, for selectively applying said current produced by said controllable current source to said electrochromic device as one of a charge current and a discharge current.
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14. The apparatus of claim 12, wherein said charge counter comprises:
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a current mirror, for producing a reference current proportional to said current produced by said controllable current source; and
a switch, selectively coupling said reference current to a capacitor, for repeatedly causing said capacitor to be charged to a first threshold level and discharged to a second threshold level by said reference current;
wherein a pulse is provided to said controller each time said capacitor is charged to said first threshold level and each time said capacitor is discharged to said second threshold level.
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15. The apparatus of claim 14, further comprising:
a counter, said counter-being incremented in response to pulses provided during a charge mode and decremented in response to pulses provided during a discharge mode, said count being indicative of a present charge level of said electrochromic device.
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16. The apparatus of claim 14, wherein said charge level of said electrochromic device QEC is approximately defined by the following equation:
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17. The apparatus of claim 12, wherein:
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said controllable current source induces a charging voltage across said electrochromic device; and
said appropriate current to be produced by said controllable current source comprises a current that produces a charging voltage bounded by a minimum charging voltage and a maximum charging voltage, said minimum and maximum charging voltages being temperature dependent.
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Specification