Abstract:
Provided are a method and apparatus for controlling an ECD for reducing power consumption of the ECD. In The the method for of controlling an ECD coloredcoloring and decolored discoloring of an ECD by using a coloring voltage and a discoloring voltage, does not apply the coloring voltage and the discoloring voltage are not applied to the ECD after a lapse of predetermined time is passed from the time when the coloring voltage and the discoloring voltages are applied to the ECD. The apparatus for controlling an ECD blocks the coloring voltage and the discoloring voltage applied to the ECD after a lapse of predetermined time is passed from the start of coloring and discoloring operations to reduce power consumption of the ECD.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION  
       [0001]     This application claims the benefit of Korean Patent Applications No. 10-2005-0021865, filed on Mar. 16, 2005, and No. 10-2006-0002383, filed on Jan. 9, 2006, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein in their entirety by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to an apparatus for controlling an electrochromic device (ECD), and more particularly, to a method and apparatus for reducing power consumed by the ECD.  
         [0004]     2. Description of the Related Art  
         [0005]     A room-mirror of a vehicle is attached in the front of a room of the vehicle in general in order that a driver can look at the situation in the rear of the vehicle without turning his/her head around. However, strong head-light from the vehicle in the rear can cause interference of safety operations and also aggravate a degree of fatigue of driver&#39;s eyes when it is reflected by the room-mirror because the driver feels dazed by it.  
         [0006]     Accordingly, various techniques to block glare of the light from the rear by giving the room-mirror and a side-mirror the ability to change its color have been studied.  
         [0007]     As a glare-free mirror, an ECD is mostly used, which is disclosed in U.S. Pat. Nos. 4,902,108, No. 4,204,778, No. 4,278,693, No. 5,282,077, No. 5,336,448, No. 5,448,397, No. 5,451,822 and No. 6,512,624. The ECD is a kind of display device including a material capable of bringing out achanging color according to an oxidation and reduction reaction when a voltage is applied thereto. The ECD is adapted to a smart windows, a temperature sensors, a vehicle mirrors, an optical shutters and so on to control the quantity of light.  
         [0008]      FIG. 1  is a cross-sectional view of a conventional ECD. Referring to  FIG. 1 , the ECD includes first and second glass substrates  102  and  104  arranged in parallel with each other spacing at a predetermined distance, transparent electrodes  106  and  108  respectively formed on the first and second glass substrates  102  and  104 , first and second EC layers  110  and  112  respectively formed in a predetermined thickness on the transparent electrodes  106  and  108  with predetermined thickness, and an electrolyte layer  114  formed between the first and second EC layers  110  and  112 . The first EC layer  110  uses is formed of a Wo3 layer while the second EC layer  112  uses is formed of a NiO film. The electrolyte layer  114  uses is formed of a liquid electrolyte layer, a gel-type electrolyte layer or a solid electrolyte layer.  
         [0009]      FIG. 2  illustrates the configuration of a conventional ECD controller. Referring to  FIG. 2 , the ECD controller includes a resistor  202  and a photoconductive cell (ex, CDS)  204  serially connected between a power supply voltage B+ and a ground voltage, a comparator  206  comparing a voltage applied to the photoconductive cell  204  to a predetermined reference voltage Vref and outputting a logic signal, a switch  208  opened or closed in response to the output logic signal of the comparator  206 , and an ECD  210  operated by the power supply voltage B+ when the switch  208  is closed.  
         [0010]     The resistance of the photoconductive cell  204  has a resistance varied witch varies depending on the quantity of light input thereto, for example, light from the headlight of vehicle in the rear, and thus a voltage Vsense applied to the photoconductive cell  204  is varied. The voltage applied to the photoconductive cell  204  is compared to the reference voltage Vref by the comparator  206 . The voltage Vsense applied to the photoconductive cell  204  decreases when the quantity of light input from the rear is large. When the voltage Vsense applied to the photoconductive cell  204  becomes lower than the reference voltage Vref, a negative logic signal is output from the comparator  206 . The switch  208  is closed by the negative logic signal.  
         [0011]     When the switch  208  is closed, the power supply voltage B+ is applied to the ECD  210  and the ECD  210  is colored by the power supply voltage B+. The colored ECD  210  less does not reflect as much light from the headlight of vehicle in the rear than as the uncolored ECD before colored, and thus a driver cannot be dazzled.  
         [0012]     When the quality quantity of light from the headlight of vehicle in the rear is reduced, the voltage Vsense applied to the photoconductive cell  204  is increased. When the voltage Vsense applied to the photoconductive cell  204  becomes higher than the reference voltage Vref, a positive logic signal is output from the comparator  206 . The switch  208  is opened by the positive logic signal.  
         [0013]     When the switch  208  is opened, the power supply voltage B+ is not applied to the ECD  210  and thus coloring of the ECD  210  is stopped and the ECD  210  is gradually discolored according to an oxidation/reduction operation thereof. The conventional ECD controller shown illustrated in  FIG. 2  applies a coloring voltage (the power supply voltage B+ of  FIG. 2 ) to the ECD  210  when coloring and blocks the coloring voltage when discoloring. Furthermore, the ECD controller may apply a discoloring voltage when discoloring in order to accelerate discoloring operation.  
         [0014]     The currently used ECD rearview mirror has a considerably slow response speed ranged 3 through 6 seconds and relatively large power consumption by the ECD because the coloring voltage and discoloring voltage applied to the ECD are remained after when the ECD is colored and discolored completely.  
         [0015]     When the quantity of light input from the rear becomes a normal stateis normalized, that is, the quantity of light decreases to a degree at which a driver may not be dazzled, the ECD rearview mirror should be discolored as soon as possible. If not so, it happens to occur that the driver hardly observes secure the situation in the rear of a vehiclerear view temporarily. Accordingly, a method for of reducing power consumption of the ECD rearview mirror and rapidly discoloring the ECD is required.  
       SUMMARY OF THE INVENTION  
       [0016]     The present invention provides an ECD controlling method for of reducing power consumption of an ECD.  
         [0017]     The present invention also provides an apparatus for executing the ECD controlling method.  
         [0018]     According to an aspect of the present invention, there is provided a method of controlling coloring and discoloring of an ECD using a coloring voltage and a discoloring voltage, respectively, the method including blocking the coloring voltage and the discoloring voltage the coloring voltage and the decoloring voltage are not applied to the ECD after a lapse of predetermined time from the time when the coloring voltage and the discoloring voltages are applied to the ECD.  
         [0019]     The discoloring voltage may have a polarity opposite to that of the coloring voltage to promote the discoloring operation.  
         [0020]     According to another aspect of the present invention, there is provided an apparatus for controlling coloring and discoloring of an ECD using a coloring voltage and a discoloring voltage, respectively, the apparatus including a comparator comparing a light sensing voltage corresponding to the quantity of light input to the ECD to a reference voltage for coloring the ECD; and a timer switch operated in synchronization with a logic signal output from the comparator, the timer switch applying the coloring voltage or the discoloring voltage to the ECD only for a predetermined time after the timer switch starts to operate.  
         [0021]     The apparatus may further comprise a voltage selector selectively applying the coloring voltage or the discoloring voltage to the ECD in response to the comparison result of the comparator.  
         [0022]     The voltage selector may selectively apply the coloring voltage or the discoloring voltage having a polarity opposite to that of the coloring voltage to the ECD in response to the comparison result of the comparator. The voltage selector may selectively apply the coloring voltage or the discoloring voltage obtained by inverting the coloring voltage in response to the comparison result of the comparator. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]     The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:  
         [0024]      FIG. 1  is a cross-sectional view of a conventional electrochromic device (ECD);  
         [0025]      FIG. 2  illustrates the a configuration of a conventional ECD controller;  
         [0026]      FIG. 3  illustrates the a configuration of an ECD controller according to an embodiment of the present invention;  
         [0027]      FIG. 4  illustrates the a configuration of a timer switch of  FIG. 3 ;  
         [0028]      FIG. 5  illustrates the a configuration of an ECD controller according to another embodiment of the present invention;  
         [0029]      FIG. 6  is a diagram for explaining an ECD coloring control operation of the ECD controller of  FIG. 5 ; and  
         [0030]      FIG. 7  is a diagram for explaining an ECD discoloring control operation of the ECD controller of  FIG. 5 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0031]     The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. The invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. Throughout the drawings, like reference numerals refer to like elements.  
         [0032]     The present invention blocks a voltage applied to an electrochromic device (ECD) after after a predetermined predetermined time is passed from the beginning of coloring/discoloring operation by utilizing the memory effect of an inorganic ECD, that is, the effect of maintaining a colored/discolored state even though the voltage applied to the ECD when coloring/discoloring is removed, to thereby minimize power consumption. Furthermore, the present invention applies a voltage opposite to the coloring voltage to the ECD when discoloring in order to accelerate a discoloring speed.  
         [0033]      FIG. 3  illustrates the a configuration of an ECD controller according to an embodiment of the present invention. Referring to  FIG. 3 , the ECD controller includes a comparator  310  comparing a reference voltage Vref to a light sensing voltage Vsense and outputting a logic signal, a voltage selector  312  selecting one of a coloring voltage V DD  and a discoloring voltage −V DD  in response to the logic signal output from the comparator  310 , and a timer switch  314 . The reference voltage Vref is obtained at the connection node of a first photoconductive cell  302  and a first resistor  304 , which are serially connected between a driving voltage Vdd and a ground voltage, and the light sensing voltage Vsense is obtained at the connection node of a second photoconductive cell  306  and a second resistor  318 , which are serially connected between the driving voltage Vdd and the ground voltage.  
         [0034]     The first photoconductive cell  302  detects the quantity of light input from the front of a vehicle and the second photoconductive cell  306  detects the quantity of light input from the rear of the vehicle. That is, the ECD controller of  FIG. 3  controls the coloring and discoloring of an ECD  316  according to a difference between the quantity of light input from the front of the vehicle and the quantity of light input from the rear of the vehicle.  
         [0035]     The voltage selector  312  selects one of the coloring voltage V DD  or and the discoloring voltage −V DD  in response to the logic signal output from the comparator  310  and outputs the selected one. The comparator  310  compares the reference voltage Vref to the light sensing voltage Vsense, outputs a positive logic signal when the reference voltage Vref is higher than the light sensing voltage Vsense or a negative logic signal when the reference voltage Vref is lower than the light sensing voltage Vsense. In other words, the comparator  310  outputs the a negative logic signal when the quantity of light from the rear of the vehicle is larger than the quantity of light from the front of the vehicle, that is, in a coloring condition, and outputs the a positive logic signal when the quantity of light from the front of the vehicle is larger than the quantity of light from the rear of the vehicle, that is, in a discoloring condition.  
         [0036]     The timer switch  314  operates in synchronization with the a rising or falling edge of the output signal of the comparator  310 . The timer switch  314  maintains its turned-on state only for a predetermined time after started starting to operate and is then turned off.  
         [0037]     On the coloring condition, the comparator  310  outputs the negative logic signal. Then, the voltage selector  312  selects and outputs the coloring voltage V DD . The timer switch  314  is started to operatestarts operating at the time t 0  when the coloring condition is satisfied, maintains its turned-on state turned on only for a predetermined time T and is then turned off. Accordingly, the coloring voltage V DD  is applied to the ECD  316  at the time t 0  when the coloring condition is satisfied to color the ECD  316 . The coloring voltage V DD  is blocked after a lapse of the predetermined time T. The ECD  316  maintains its colored state due to its memory effect.  
         [0038]     On the discoloring condition, the comparator  310  outputs the positive logic signal. Then, the voltage selector  312  selects the discoloring voltage −V DD . The timer switch  314  is turned on only for a predetermined time T from the time t 1  when the discoloring condition is satisfied and is then turned off. Accordingly, the discoloring voltage −V DD  is applied to the ECD  316  at the time t 1  when the discoloring condition is satisfied to discolor the ECD  316 . The discoloring voltage −V DD  is blocked after a lapse of the predetermined time T. The ECD  316  maintains its discolored state by its memory effect.  
         [0039]      FIG. 4  illustrates the a configuration of the timer switch  314  of  FIG. 3 . Referring to  FIG. 4 , the timer switch  314  includes a first pulse generator  402  operated at the negative edge of the logic signal output from the comparator  310 , a second pulse generator  404  operated at the positive edge of the logic signal output from the comparator  310 , an OR gate  406  performing a logic OR operation on ORing the output signals of the first and second pulse generators  402  and  404 , and a switch  408  controlled by the OR gate  406 .  
         [0040]     When the comparator  310  outputs the negative logic signal, the first pulse generator  402  is operated to generate a first pulse signal maintaining a positive state for the predetermined time T. When the comparator  310  outputs the positive logic signal, the second pulse generator  404  is operated to generate a second pulse signal maintaining a positive state for the predetermined time T. Accordingly, the timer switch  314  provides the coloring voltage V DD  or the discoloring voltage −V DD , output from the voltage selector  312  only for the time T from the time when the coloring or discoloring condition is satisfied by the operations of the first and second pulse generators  402  and  404 , to the ECD  316 .  
         [0041]      FIG. 5  illustrates the a configuration of an ECD controller according to another embodiment of the present invention. Referring to  FIG. 5 , the ECD controller includes a comparator  510  comparing a reference voltage Vref to a light sensing voltage Vsense, an inverter  512  performing an inverting operation in response to the an output signal of the comparator  510 , a first timer  514  operated in synchronization with the a negative edge of the output signal of the comparator  510 , a second timer  516  operated in synchronization with the a positive edge of the output signal of the comparator  510 , and four switches  518 ,  520 ,  522  and  524  opened and closed by the first and second timers  514  and  516 .  
         [0042]     The reference voltage Vref is obtained at the connection node of a first photoconductive cell  502  and a first resistor  504 , which are serially connected between a driving voltage Vdd and a ground voltage, and the light sensing voltage Vsense is obtained at the connection node of a second photoconductive cell  506  and a second resistor  518 , which are serially connected between the driving voltage Vdd and the ground voltage.  
         [0043]     The first photoconductive cell  502  detects the quantity of light input from the front of a vehicle and the second photoconductive cell  506  detects the quantity of light input from the rear of the vehicle.  
         [0044]     The 4 switches  518 ,  520 ,  522  and  524  constructs form a bridge circuit having an ECD  526  as a common path. The  4  switches  518 ,  520 ,  522  and  524  are paired into a first switch pair of switches  518  and  524  and a second switch pair of switches  520  and  522  which respectively determine two different paths of the bridge circuit in diagonal directions. The first switch pair of switches  518  and  524  and the second switch pair of switches  520  and  522  are switched to form one of the two different paths in response to the comparison result of the comparator  510 .  
         [0045]     The inverter  512  outputs a ground voltage GND and a coloring voltage V DD  through first and second output terminals P 1  and P 2  in response to a logic signal output from the comparator  510 . Specifically, the inverter  512  outputs the coloring voltage V DD  through the first output terminal P 1  and outputs the ground voltage GND through the second output terminal P 2  when the comparator  510  outputs a negative logic signal. On the contrary, the inverter  512  outputs the ground voltage GND through the first output terminal P 1  and outputs the coloring voltage V DD  through the second output terminal P 2  when the comparator  510  outputs a positive logic signal.  
         [0046]     The 4 switches  518 ,  520 ,  522  and  524  are operated in pairs. That is, the first timer  514  controls the first and fourth switches switch pair having the first switch  518  and the fourth switch  524  while are controlled in a pair by the first timer  514  the second timer  516  controls the second and third switchesswitch pair having the second switch  520  and the third switch  522  are controlled in a pair by the second switch  516 . When the first timer  514  is operated, the coloring voltage V DD  and the ground voltage GND are respectively applied to top and bottom terminals of the ECD  526 . When the second timer  516  is operated, the ground voltage GND and the coloring voltage V DD  are respectively applied to the top and bottom terminals of the ECD  526 .  
         [0047]      FIG. 6  is a diagram for explaining an ECD coloring control operation of the ECD controller of  FIG. 5 . The comparator  510  outputs the a negative logic signal when the quantity of light input from the read rear of a vehicle is larger than the quantity of light input from the front of the vehicle, that is, when a coloring condition is satisfied. Accordingly, the inverter  512  respectively outputs the coloring voltage V DD  and the ground voltage GND through the first and second output terminals P 1  and P 2 , respectively.  
         [0048]     The first timer  514  outputs the first pulse signal maintaining a positive state for a predetermined time T 1  in synchronization with the negative edge of the output signal of the comparator  510 . The first and fourth switches  518  and  524  controlled by the first timer  514  are turned on for the time  1 i in response to the first pulse signal. Consequently, the coloring voltage V DD  and the ground voltage GND are respectively applied to the top and bottom terminals of the ECD  526 . Accordingly, the ECD  526  is colored for the predetermined time T 1  and then maintains its colored state by its memory effect.  
         [0049]      FIG. 7  is a diagram for explaining an ECD discoloring control operation of the ECD controller of  FIG. 5 . The comparator  510  outputs the a positive logic signal when the quantity of light input from the front of the vehicle is larger than the quantity of light input from the rear of the vehicle, that is, when a discoloring condition is satisfied. Accordingly, the inverter  512  respectively outputs the ground voltage GND and the coloring voltage V DD  through the first and second output terminals P 1  and P 2 , respectively.  
         [0050]     The second timer  516  outputs the second pulse signal maintaining a positive state for a predetermined time T 2  in synchronization with the positive edge of the output signal of the comparator  510 . The second and third switches  520  and  522  controlled by the second timer  516  are turned on for the time T 2  in response to the second pulse signal. Consequently, the ground voltage GND and the coloring voltage V DD  are respectively applied to the top and bottom terminals of the ECD  526 . Accordingly, the ECD  526  is discolored for the predetermined time T 2  and then maintains its discolored state by its memory effect. The ground voltage GND and the coloring voltage V DD  are respectively applied to the top and bottom terminals of the ECD  526  in  FIG. 7  while the coloring voltage V DD  and the ground voltage GND are respectively applied to the top and bottom terminals of the ECD  526  in  FIG. 6 .  
         [0051]     The ECD controllers of  FIGS. 3 and 5  apply the voltage, obtained by inverting the voltage applied to the ECDs  326  and  526  to color the ECDs  326  and  526 , to the ECDs  316  and  526  to discolor the ECDs  326  and  526 , to thereby accelerate a discoloring operation speed. This uses is achieved by utilizing an the oxidation/reduction operation of the ECD  526 .  
         [0052]     The ECD controllers of  FIGS. 3 and 5  block the coloring voltage and the discoloring voltage applied to the ECDs  326  and  526  after a predetermined predetermined time is passed from when coloring and discoloring operations are started. Even though the coloring voltage and the discoloring voltage are blocked, the ECDs  326  and  526  maintain colored and discolored states by their memory effect. Accordingly, the ECDs  326  and  526  require small power consumption because they perform the coloring and discoloring operations only for a predetermined time.  
         [0053]     The ECD controllers of  FIGS. 3 and 5  carry out the coloring and discoloring operations only for a predetermined time and then maintain the colored and discolored states by their memory effect to extend the life spans of them.  
         [0054]     The ECD controller of  FIG. 5  is more effective when the coloring and discoloring operations are rapidly switched. This is because the coloring and discoloring operations can be carried out at any time irrespective of the state of the ECD  526  since the coloring voltage and the discoloring voltage are respectively applied to the ECD  526  through different paths.  
         [0055]     As described above, the ECD controller according to the present invention reduces power consumption of the ECD by blocking coloring and discoloring voltages applied to the ECD after after a lapse of predetermined time is passed from the start of coloring and discoloring operations. Furthermore, the ECD controller according to the present invention accelerates a discoloring operation speed by applying a voltage obtained by inverting the coloring voltage to the ECD.  
         [0056]     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.