Device for driving an EC antiglare mirror

• US 5,486,952 A
• Filed: 04/06/1995
• Issued: 01/23/1996
• Est. Priority Date: 04/13/1994
• Status: Expired due to Term

• Current Assignee: Murakami Kaimedio Company Limited
• Original Assignee: Murakami Kaimedio Company Limited
• Inventors: Sato, Hidenori, Nagao, Mitsuyoshi, Hattori, Michiaki
• Primary Examiner(s): Dzierzynski, Paul M.
• Assistant Examiner(s): SIKDER, MOHAMMAD YUNUS
• Application Number:
  US08/418,062
• Time in Patent Office: 292 Days
• Field of Search: 359/603, 359/601, 359/265, 359/267, 359/884, 359/885, 359/604, 250/214 AL, 250/205, 250/201.1, 250/214 LS
• US Class Current: 359/603
• CPC Class Codes: B60R 1/088 using a cell of electrically changeable optical characteristic, e.g. liquid-crystal or electrochromic mirrors

Abstract

In a device for driving an EC antiglare mirror in which reflectivity is variably controlled by an EC element, a surrounding light quantity detection circuit detects quantity of light surrounding a vehicle. A rear light quantity detection circuit detects quantity of light in the rear of the vehicle. An oscillation circuit is constructed so that duration of an "H" level of an oscillation signal and duration of an "L" level of the oscillation signal are individually controlled. An inversion period control circuit variably controls duration of one of the "H" and "L" levels of the oscillation signal generated by the oscillation circuit in response to light quantity detected by the surrounding light quantity detection circuit and also variably controls duration of the other level in response to light quantity detected by the rear light quantity detection circuit. An EC element drive circuit inverts, in accordance with the level of the oscillation signal, the polarity of drive voltage supplied from a drive power source and applies the inverted voltage to the EC element and thereby controls the amount of coloration in accordance with duty factor of the oscillation signal.

Claims

1. A device for driving an EC antiglare mirror in which reflectivity is variably controlled by an EC element comprising:

surrounding light quantity detection means for detecting quantity of light surrounding a vehicle;

rear light quantity detection means for detecting quantity of light in the rear of the vehicle;

oscillation means for generating an oscillation signal of an "H" level and an oscillation signal of an "L" level repeatedly and alternately, said oscillation means being capable of individually controlling duration of the "H" level and duration of the "L" level;

inversion period control means for variably controlling duration of one of the "H" and "L" levels of the oscillation signal generated by said oscillation means in response to light quantity detected by said surrounding light quantity detection means and variably controlling duration of the other of the "H" and "L" levels of the oscillation signal in response to light quantity detected by said rear light quantity detection means;

a drive power source for driving the EC element; and

EC element drive means for inverting the polarity of drive voltage supplied from the drive power source in response to the "H" or "L" level of the oscillation signal generated by said oscillation means and applying the inverted drive voltage to the EC element,

said inversion period control means performs control, when said EC element drive means is so set that it drives the EC element in a color imparting direction at the one level of the oscillation signal and in a color fading direction at the other level of the oscillation signal, in such a manner that, when the surrounding light quantity is larger, the duration of the one level is shorter and, when the surrounding light quantity is smaller, the duration of the one level is longer and that, when the rear light quantity is larger, the duration of the other level is shorter and, when the rear light quantity is smaller, the duration of the other level is larger and, when said EC element drive means is so set that it drives the EC element in a color fading direction at the one level of the oscillation signal and in a color imparting direction at the other level of the oscillation signal, in such a manner that, when the surrounding light quantity is larger, the duration of the one level is longer and, When the surrounding light quantity is smaller, the duration of the one level is shorter and that, when the rear light quantity is larger, the duration of the other level is longer and, when the rear light quantity is smaller, the duration of the other level is shorter.

4. A device for driving an EC antiglare mirror as defined in claim 1 wherein the oscillation period of the oscillation means is 10 ms or below.

5. A device for driving an EC antiglare mirror as defined in claim 1 which further comprises oscillation stop means for stopping oscillation of the oscillation means through an outside operation to fix an output level of the oscillation means to a level at which the voltage of a color fading direction is applied to the EC element.

2. A device for driving an EC antiglare mirror in which reflectivity is variably controlled by an EC element comprising:

oscillation means comprising

first inversion period control means including a first photoconductive cell which receives light surrounding a vehicle and decreases its value of resistance in response to quantity of the surrounding light, first resistance and a first diode connected in series to the first photoconductive cell, and second resistance connected in parallel to the first photoconductive cell, and

second inversion period control means including a second photoconductive cell which receives light in the rear of the vehicle and decreases its value of resistance in response to quantity of the rear light, third resistance and a second diode having a direction reverse to the first diode connected in series to the second photoconductive cell, and fourth resistance connected in parallel to the second photoconductive cell,

said first inversion period control means and said second inversion period control means being arranged in parallel in a feedback loop, and, when the value of resistance of the first photoconductive cell decreases, duration of one of "H" and "L" levels of oscillation signals is shortened whereas, when the value of resistance of the second photoconductive cell decreases, duration of the other level of oscillation signals is shortened;

a drive power source for driving the EC element;

an EC element drive switching circuit which inverts the polarity of drive voltage supplied from the drive power source in accordance with the "H" or "L" level of the oscillation signal generated by the oscillation means and applies the inverted voltage to the EC element, said switching circuit applying voltage of a color imparting direction when the oscillation signal is at the one level and applying voltage of a color fading direction when the oscillation signal is at the other level.

3. A device for driving an EC antiglare mirror as defined in claim 2 wherein the EC element drive switching circuit comprises a switching element and which further comprises an energy supply restricting element which is connected in series to the switching element for restricting supply of driving energy to the EC element.