Driver circuit for electrochromic display device

• US 4,117,475 A
• Filed: 11/26/1976
• Issued: 09/26/1978
• Est. Priority Date: 12/01/1975
• Status: Expired due to Term

• Current Assignee: Citizen Watch Co Limited (Citizen Electronics Company Limited)
• Original Assignee: Citizen Watch Co Limited (Citizen Electronics Company Limited)
• Inventors: Ebihara, Heihachiro, Sekiya, Fukuo
• Primary Examiner(s): Moskowitz, Nelson
• Assistant Examiner(s): Goodwin, Lawrence
• Application Number:
  US05/745,138
• Time in Patent Office: 669 Days
• Field of Search: 340/336, 340/324 EC, 340/324 M, 340/166 EL, 350/160 R, 350/332, 315/169 R, 315/169 TV
• US Class Current: 345/105
• CPC Class Codes: G04G 9/0047 electrical, e.g. selection or application of the operating voltage
• CPC Class Codes: G09G 3/16 by control of light from an independent source

Abstract

In an electro-optical display device having a persistence property, a driving voltage is immediately applied to each display element after both electrodes of the display element are short-circuited in anticipation of a driving operation intended to reverse the state of a display.

Claims

1. A driver circuit for an electro-chromic display device having a persistence effect and a plurality of display elements adapted to display information in response to display information signals, comprising:

means for generating first and second drive signals in response to a change of each display information signal for thereby driving said each display element; and

means for generating control signals just prior to said drive signals in response to said change of said each display information signal for thereby short-circuiting said each display element just prior to driving said each display element;

said first and second drive signals having a narrow pulse width, whereby said each display element is driven only for predetermined short time intervals and maintained in its open state during time intervals other than said predetermined short time intervals to display said information due to its persistence effect.

2. A driver circuit for an electro-chromic display device having a persistence effect and a plurality of display elements adapted to display information in response to display information signals, comprising:

means for generating first and second drive signals in response to a change of each display information signal for thereby driving said each display element, said drive signal generating means including a latch circuit for storing said each display information signal and generating a first output delayed in phase with respect to said each display information signal, first gate means for generating a second output in response to said each display information signal and said first output, said second output representing said change of said each display information signal, second gate means for generating a third output having a narrow pulse width in response to said second output and a clock pulse having a pulse width equal to said narrow pulse width, third gate means for generating said first drive signal in response to said each display information signal and said third output, and fourth gate means for generating said second drive signal in response to said third output and an inverted value of said each display information signal; and

means for generating control signals just prior to said drive signals in response to said change of said each display information signal for thereby short-circuiting said each display element just prior to driving said each display element, said control signal generating means including gate means for generating said control signals just prior to said first and second drive signals in response to said second output and said clock pulse whereby said each display element is driven just after an electrical charge stored in said each display element has been discharged;

said first and second drive signals having a narrow pulse width, whereby said each display element is driven only for predetermined short time intervals and maintained in its open state during time intervals other than said predetermined short time intervals to display said information due to its persistence effect.

3. A driver circuit for an electro-chromic display device having a persistence effect and a plurality of display elements adapted to display information in response to display information signals, comprising:

means for generating first and second drive signals in response to a change of each display information signal for thereby driving said each display element;

means for generating control signals just prior to said drive signals in response to said change of each said display information signal for thereby short-circuiting said each display element just prior to driving said each display element said control signal generating means including gate means for generating said control signals prior to said first and second drive signals in response to said change of display information signal and a clock pulse having a narrow pulse width; and

means for applying regenerative timing signals to said drive signal generating means whereby said drive signal generating means generates auxiliary drive signals to regeneratively drive said each display element to maintain said each display element in its first and second display states;

said first and second drive signals having a pulse width equal to said narrow pulse width, whereby said each display element is driven only for predetermined short time intervals and maintained in its open state during time intervals other than said predetermined short time intervals to display said information due to its persistence effect.

4. A driver circuit for an electro-chromic display device having a persistence effect and a plurality of display elements adapted to display information in response to display information signals, comprising:

a source of first and second clock pulses, said first clock pulse having a frequency higher than that of said second clock pulse;

means for storing each of said display information signals and generating a first output delayed in phase from said each display information signal in response to said second clock pulse;

means for generating a second output in response to said each display information signal and said first output;

means for generating first and second drive signals in response to said first clock pulse and said second output;

electronic switching means responsive to said first and second drive signals for driving each of said display elements; and

means for generating a control signal just prior to each of said first and second drive signals in response to said second output and said first clock pulse for short-circuiting said each display element to discharge an electrical charge stored in said each display element just prior to driving said each display element;

said first and second drive signals having a pulse width equal to said first clock pulse, whereby said each display element is driven only for predetermined short time intervals and maintained in an open state during time intervals other than said predetermined short time intervals to display said information due to its persistence effect.

5. A driver circuit according to claim 4, in which said storing means comprises a latch circuit having a data input terminal adapted to receive said each display information signal, a clock input terminal responsive to said second clock pulse.

6. A driver circuit according to claim 4, in which said second output generating means comprises an Exclusive OR gate having one input adapted to receive said first output and another input adapted to receive said each display information signal.

7. A driver circuit according to claim 4, in which said drive signal generating means comprises a first gate responsive to said second output and said first clock pulse to generate third output, a second gate responsive to said display information signal and said third output to generate said first drive signal, and a third gate responsive to said third output and an inverted value of said display information signal to generate said second drive signal.

8. A driver circuit according to claim 4, further comprising first switching means responsive to said first drive signal to apply an electric current to said each display element in a direction to induce a first display state, second switching means responsive to said second drive signal to apply an electric current in a direction to induce a second display state, and third switching means responsive to said control signal to cause said each display element to be short-circuited.

9. A driver circuit according to claim 8, in which each of said switching means comprises a semiconductor field effect transistor.

10. A driver circuit according to claim 4, further comprising means for applying regenerative timing signals to said drive signal generating means whereby said drive signal generating means generates auxiliary drive signals to regeneratively drive said each display element to maintain said each display element in its first and second display states, respectively.

11. A driver circuit according to claim 10, in which said timing signal applying means comprises means for generating an output signal at a predetermined frequency, and gate means for generating said regenerative timing signals in response to said output signal.