Power supply device, liquid crystal display device, and method of supplying power

• US 5,627,457 A
• Filed: 07/18/1994
• Issued: 05/06/1997
• Est. Priority Date: 07/21/1993
• Status: Expired due to Term

• Current Assignee: JohnsonDiversey, Inc
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Ishiyama, Hisanobu, Aoki, Shigeki
• Primary Examiner(s): Hecker, Stuart N.
• Application Number:
  US08/276,470
• Time in Patent Office: 1,023 Days
• Field of Search: 323/318, 345/94
• US Class Current: 323/318
• CPC Class Codes: G05F 3/24 wherein the transistors are of the field-effect type only G05F3/205, G05F3/26, G05F3/30 take precedence
• CPC Class Codes: G09G 2320/041 Temperature compensation
• CPC Class Codes: G09G 2320/0606 Manual adjustment
• CPC Class Codes: G09G 2320/066 for control of contrast
• CPC Class Codes: G09G 3/3674 Details of drivers for scan electrodes
• CPC Class Codes: G09G 3/3696 Generation of voltages supplied to electrode drivers

Abstract

An objective of the present invention is to provide a power supply device, a liquid crystal display device, and a method of supplying power that can enable designs with lower power consumptions and can also enable higher display qualities. A first voltage Vx, which is a constant voltage, is generated by a first voltage generation portion in a voltage regulation portion. A second voltage Vy having a value independent of that of Vx is generated by a second voltage generation portion, and Vx and Vy are added by an adder portion to generate a regulated voltage Vreg. A control portion provides variable control of Vy within a voltage regulation range that is defined to include Vx. The regulated voltage Vreg is divided by a voltage divider portion within a multi-value voltage generation portion. The impedances of voltages V2 and V4 are converted by first impedance conversion portions (n-type OP-amps), and the impedances of voltages V1 and V3 are converted by second impedance conversion portions (p-type OP-amps).

Claims

1. A power supply device comprising a voltage regulation means and configured to supply a supply voltage that has been regulated by said voltage regulation means to an object to be driven, wherein:

said voltage regulation means comprises an operational amplifier which has first and second input terminals and an output terminal for outputting an output voltage based on voltages input to said first and second input terminals;

a reference voltage source electrically connected to said first input terminal;

a first resistor electrically connected at one end to said second input terminal of said operational amplifier and at the other end to a fixed potential;

a second resistor electrically connected at one end to said second input terminal of said operational amplifier and at the other end to said output terminal of said operational amplifier;

variably controlling means for variably controlling a current which flows through said second resistor.

2. A power supply device according to claim 1, wherein:

a reference voltage output from said reference voltage source and said current controlled by said variably controlling means have a temperature characteristic which compensates for a temperature characteristic of said object to be driven.

3. A power supply device according to claim 1, wherein:

said current controlled by said variably controlling means is fixed at a predetermined value during the initial operation of the device.

4. A power supply device according to claim 1, wherein:

said variably controlling means comprises a constant-current source and means for variably controlling a current output from said constant-current source.

5. A power supply device according to claim 4, wherein:

a reference voltage output from said reference voltage source and said current controlled by said variably controlling means have a temperature characteristic which compensates for a temperature characteristic of said object to be driven.

6. A power supply device according to claim 4, wherein:

said current controlled by said variably controlling means is fixed at a predetermined value during the initial operation of the device.

7. A power supply device according to claim 4, wherein:

said reference voltage source and said constant-current source comprise MOS transistors, and a reference voltage from said reference voltage source and a constant current from said constant-current source are generated by using the threshold voltages of said MOS transistors.

8. A power supply device comprising a multi-value voltage generation means for supplying multi-value driving supply voltages, wherein:

said multi-value voltage generation means comprises a voltage divider means for generating divided voltages at divider terminals thereof, and at least three impedance conversion means connected between said divider terminals and capacitive objects to be driven for converting the impedances of said divided voltages generated at said divider terminals;

said impedance conversion means includes at least one first impedance conversion means having a drive portion that is capable of drawing in a greater amount of positive charge than a negative charge and at least one second impedance conversion means having a drive portion that is capable of drawing in a greater amount of negative charge than a positive charge, said first impedance conversion means being connected to a first type object to be driven, the polarity of the charge that should be transferred from said first type object to be driven to said first impedance conversion means during the drive period being positive in total, and said second impedance conversion means being connected to a second type object to be driven, the polarity of the charge that should be transferred from said second type object to be driven to said second impedance conversion means during the drive period being negative in total.

9. A power supply device according to claim 8, wherein:

each of said first and second impedance conversion means is formed of a voltage-follower connected operational amplifier comprising a differential portion and a drive portion;

the drive portion of said first impedance conversion means comprises a constant-current source or resistor connected at one end to a high-potential power-source side and at the other end to an output-terminal side, and an n-channel drive transistor connected at one end to a low-potential power-source side and at the other end to said output-terminal side; and

the drive portion of said second impedance conversion means comprises a p-channel drive transistor connected at one end to said high-potential power-source side and at the other end to said output-terminal side, and a constant-current source or resistor connected at one end to said low-potential power-source side and at the other end to said output-terminal side.

10. A power supply device according to claim 9, further comprising:

a control means for controlling one or a plurality of multi-value driving supply voltages generated by said multi-value voltage generation means, in such a manner that said voltage or voltages reach predetermined levels within a predetermined period immediately after the power is turned on.

11. A power supply device according to claim 10, wherein:

a voltage in a transient state from said multi-value driving power source is controlled such that it is not applied to said object to be driven during said predetermined period.

12. A power supply device according to claim 9, further comprising:

a control means for controlling said one or a plurality of multi-value driving supply voltages generated by said multi-value voltage generation means, in such a manner that said voltage or voltages reach predetermined levels within a predetermined period immediately after the power is turned on;

wherein said control means comprises means for increasing the current flowing into said low-potential power-source side of the drive portion of said second impedance conversion means during said predetermined period, when said high-potential power source acts as a fixed-potential power source and said low-potential power source is turned on.

13. A power supply device according to claim 12, wherein:

a voltage in a transient state from said multi-value driving power source is controlled such that it is not applied to said object to be driven during said predetermined period.

14. A power supply device according to claim 9, further comprising:

a control means for controlling one or a plurality of multi-value driving supply voltages generated by said multi-value voltage generation means, in such a manner that said voltage or voltages reach predetermined levels within a predetermined period immediately after the power is turned on;

wherein said control means comprises means for increasing the current flowing from said high-potential power-source side of the drive portion of said first impedance conversion means during said predetermined period, when said low-potential power source acts as a fixed-potential power source and said high-potential power source is turned on.

15. A power supply device according to claim 14, wherein:

a voltage in a transient state from said multi-value driving power source is controlled such that it is not applied to said object to be driven during said predetermined period.

16. A power supply device according to claim 8, further comprising:

a control means for controlling one or a plurality of multi-value driving supply voltages generated by said multi-value voltage generation means, in such a manner that said voltage or voltages reach predetermined levels within a predetermined period immediately after the power is turned on.

17. A power supply device according to claim 16, wherein:

a voltage in a transient state from said multi-value driving power source is controlled such that it is not applied to said object to be driven during said predetermined period.

18. A power supply device comprising a multi-value voltage generation means and configured to supply multi-value driving supply voltages from said multi-value voltage generation means, wherein:

said multi-value voltage generation means comprises a voltage divider means for generating divided voltages at divider terminals thereof;

a plurality of impedance conversion means connected between said divider terminals and said objects to be driven for converting the impedances of said divided voltages generated at said divider terminals, thus generating multi-value driving supply voltages intended for capacitive objects to be driven; and

means for controlling said impedance conversion means;

said impedance conversion means is formed of a voltage-follower connected operational amplifier comprising a differential portion and a drive portion; and

said drive portion comprises a constant-current source or resistor connected at one end to a first power-source side and at the other end to an output-terminal side, and a drive transistor connected at one end to a second power-source side and at the other end to an output-terminal side; and

said means for controlling said impedance conversion means controls a current to flow through said constant-current source or said resistor of said impedance conversion means only during a fixed period immediately after the rise or fall of the reference clock that is used in driving said object to be driven.

19. A power supply device according to claim 18, wherein:

said drive portion comprises a constant-current source or resistor that is controlled by said means for controlling said impedance conversion means, and another constant-current source or resistor that is not controlled by said control means.

20. A power supply device comprising a multi-value voltage generation means and configured to supply multi-value driving supply voltages from said multi-value voltage generation means, wherein:

said multi-value voltage generation means comprises a voltage divider means for generating divided voltages at divider terminals thereof;

a plurality of impedance conversion means connected between said divider terminals and said objects to be driven for converting the impedances of said divided voltages generated at said divider terminals, thus generating multi-value driving supply voltages intended for capacitive objects to be driven; and

means for controlling said impedance conversion means;

said impedance conversion means is formed of a voltage-follower connected operational amplifier comprising a differential portion and a drive portion; and

said drive portion comprises a constant-current source or resistor connected at one end to a first power-source side and at the other end to an output-terminal side, and a drive transistor connected at one end to a second power-source side and at the other end to an output-terminal side; and

when a frame signal for driving an object to be driven is at a predetermined level, said means for controlling said impedance conversion means puts limitations on a current that flows through said constant-current source or said resistor of said impedance conversion means.

21. A power supply device according to claim 20, wherein:

said drive portion comprises a constant-current source or resistor that is controlled by said means for controlling said impedance conversion means, and another constant-current source or resistor that is not controlled by said control means.

22. A power supply device comprising a voltage regulation means and a multi-value voltage generation means, and configured to supply multi-value driving supply voltages generated by said multi-value voltage generation means from a regulated voltage generated by said voltage regulation means, wherein:

said voltage regulation means comprises an operational amplifier which has first and second input terminals and an output terminal for outputting an output voltage based on voltages input to said first and second input terminals;

a reference voltage source electrically connected to said first input terminal;

a first resistor electrically connected at one end to said second input terminal of said operational amplifier and at the other end to a fixed potential;

a second resistor electrically connected at one end to said second input terminal of said operational amplifier and at the other end to said output terminal of said operational amplifier;

variably controlling means for variably controlling a current which flows through said second resistor;

said multi-value voltage generation means comprises a voltage divider means for generating divided voltages at divider terminals thereof, and at least three impedance conversion means connected between said divider terminals and capacitive objects to be driven for converting the impedances of said divided voltages generated at said divider terminals;

said impedance conversion means includes at least one first impedance conversion means having a driven portion that is capable of drawing in a greater amount of positive charge than a negative charge and at least one second impedance conversion means having a drive portion that is capable of drawing in a greater amount of negative charge than a positive charge, said first impedance conversion means being connected to a first type object to be driven, the polarity of the charge that should be transferred from said first type object to be driven to said first impedance conversion means during the drive period being positive in total, and said second impedance conversion means being connected to a second type object to be driven, the polarity of the charge that should be transferred from said second type object to be driven to said second impedance conversion means during the drive period being negative in total.

23. A power supply device according to claim 22, wherein:

each of said first and second impedance conversion means is formed of a voltage-follower connected operational amplifier comprising a differential portion and a drive portion;

the drive portion of said first impedance conversion means comprises a constant-current source or resistor connected at one end to a high-potential power-source side and at the other end to an output-terminal side, and an n-channel drive transistor connected at one end to a low-potential power-source side and at the other end to said output-terminal side; and

the drive portion of said second impedance conversion means comprises a p-channel drive transistor connected at one end to said high-potential power-source side and at the other end to said output-terminal side, and a constant-current source or resistor connected at one end to said low-potential power-source side and at the other end to said output-terminal side.

24. A liquid crystal display device comprising a voltage regulation means, wherein supply voltages for driving liquid crystal elements are regulated by said voltage regulation means, thus regulating contrast for a liquid crystal display, and wherein:

said voltage regulation means comprises an operational amplifier which has first and second input terminals and an output terminal for outputting an output voltage based on voltages input to said first and second input terminals;

a reference voltage source electrically connected to said first input terminal;

a first resistor electrically connected at one end to said second input terminal of said operational amplifier and at the other end to a fixed potential;

a second resistor electrically connected at one end to said second input terminal of said operational amplifier and at the other end to said output terminal of said operational amplifier;

variably controlling means for variably controlling a current which flows through said second resistor.

25. A liquid crystal display device according to claim 24, wherein:

said variably controlling means comprises a constant-current source and means for variably controlling a current output from said constant-current source.

26. A liquid crystal display device characterized in comprising a multi-value voltage generation means configured to use a 6-level drive method to drive a liquid crystal element that is an object to be driven, on the basis of multi-value driving supply voltages generated by said multi-value voltage generation means wherein:

said multi-value voltage generation means comprises a voltage divider means for generating divided voltages at divider terminals thereof;

a plurality of impedance conversion means connected between said divider terminals and said objects to be driven for converting the impedances of said divided voltages generated at said divider terminals, thus generating multi-value driving supply voltages intended for said objects to be driven; and

supply voltages for driving liquid crystal elements by using said 6-level drive method, said supply voltages termed driving supply voltages at a zero level, a first level, a second level, a third level, a fourth level, and a fifth level from a high-potential side, each of said second and fourth levels of driving supply voltage is generated by a first impedance conversion means having a drive portion that is capable of drawing in a greater amount of positive charge than a negative charge from said object to be driven to said first impedance conversion means, and each of said first and third levels of driving supply voltage is generated by a second impedance conversion means having a drive portion that is capable of drawing in a greater amount of negative charge than a positive charge from said object to be driven to said second impedance conversion means wherein each of said first and said second impedance conversion means is formed of a voltage follower connected operational amplifier comprising a differential portion and a drive portion.

27. A liquid crystal display device according to claim 26, wherein:

each of said first and second impedance conversion means is formed of a voltage-follwer connected operational amplifier comprising a differential portion and a drive portion;

the drive portion of said first impedance conversion means comprises a constant-current source or resistor connected at one end to a high-potential power-source side and at the other end to an output-terminal side, and an n-channel drive transistor connected at one end to a low-potential power-source side and at the other end to said output-terminal side; and

the drive portion of said second impedance conversion means comprises a p-channel drive transistor connected at one end to said high-potential power-source side and at the other end to said output-terminal side, and a constant-current source or resistor connected at one end to said low-potential power-source side and at the other end to said output-terminal side.

28. A power supply method for supplying electrical power with respect to an object to be driven such that voltage division is performed and the resultant divided voltages are subjected to impedance conversion and are supplied as multi-value (at least five values) driving supply voltages, wherein:

performing impedance conversion in such a manner that a greater amount of positive charge than a negative charge is drawn in from said object to be driven when the polarity of the charge that must be transferred from said object to be driven during the drive period is positive in total, and performing impedance conversion in such a manner that a greater amount of negative charge than a positive charge is drawn in from said object to be driven when the polarity of the charge that must be transferred from said object to be driven during the drive period is negative in total.

29. A power supply device comprising a multi-value voltage generation means for supplying multi-value driving supply voltages wherein:

said multi-value voltage generation means comprises a voltage divider means for generating divided voltages at divider terminals thereof, a plurality of impedance conversion means connected between said divider terminals and capacitive objects to be driven for converting the impedances of said divided voltages generated at said divider terminals;

wherein a current-supply capability of a drive portion of at least one of said impedance conversion means is increased based on a control signal.

30. A power supply device according to claim 29, wherein:

at least one of said impedance conversion means is controlled by said control signal in such a manner that at least one of said multi-value driving supply voltage reaches predetermined level within a predetermined period immediately after the power is turned on.

31. A power supply device according to claim 30, wherein:

said impedance conversion means includes at least one first impedance conversion means having a drive portion that is capable of drawing in a greater amount of positive charge than a negative charge and at least one second impedance conversion means having a drive portion that is capable of drawing in a greater amount of negative charge than a positive charge, said first impedance conversion means being connected to a first type object to be driven, the polarity of the charge that should be transferred from said first type object to be driven to said first impedance conversion means during the drive period being positive in total, and said second impedance conversion means being connected to a second type object to be driven, the polarity of the charge that should be transferred from said second type object to be driven to said second impedance conversion means during the drive period being negative in total.

32. A power supply device according to claim 30, wherein:

a voltage in a transient state from said multi-value driving power source is controlled such that it is not applied to the object to be driven during said predetermined period.

33. A power supply device according to claim 29, wherein:

at least one of said impedance conversion means is controlled by said control signal in such a manner that at least one of said multi-value driving supply voltage reaches predetermined level within a predetermined period immediately after the power is turned on,

a current flowing into a low-potential power-source side of the drive portion of said at least one impedance conversion means is increased during said predetermined period, when a high-potential power-source acts as a fixed-potential power source and a low potential power source is turned on.

34. A power supply device according to claim 29, wherein:

at least one of said impedance conversion means is controlled by said control signal so that at least one of said multi-value driving supply voltage reaches predetermined level within a predetermined period immediately after the power is turned on;

a current flowing from a high-potential power-source side of the drive portion of said at least one impedance conversion means is increased during said predetermined period, when a low-potential power-source acts as a fixed-potential power source and a high potential power source is turned on.

35. A power supply according to claim 29, wherein:

said control signal is supplied based on reference clock for driving the object to be driven.

36. A power supply device according to claim 35, wherein:

a current-supply capability of the drive portion of at least one of said impedance conversion means is increased during a period immediately after at least one of a rising edge and a falling edge of said reference clock.

37. A power supply device according to claim 29, wherein:

each of said impedance conversion means is formed of a voltage-follower connected operational amplifier comprising a differential portion and said drive portion;

the drive portion comprises a first constant-current source or first resistor and a drive transistor controlled by output of said differential portion and an output terminal;

said first constant-current source or first resistor and said drive transistor are connected in serial between a high-potential power-source and a low-potential power-source;

said output terminal is connected to a connection point between said first constant-current source or first resistor and said drive transistor.

38. A power supply device according to claim 37, wherein:

said drive portion comprises a second constant-current source or second resistor which is connected in parallel with said first constant-current source or first resistor;

a current supplied by said second constant-current source or second resistor into said output-terminal is controlled by said control signal.

39. A power supply device according to claim 38, wherein:

at least one of said impedance conversion means is controlled by said control signal so that at least one of said multi-value driving supply voltage reaches predetermined level within a predetermined period immediately after the power is turned on.

40. A power supply device according to claim 38, wherein:

a current-supply capability of the drive portion is increased during a period immediately after at least one of a rising edge and a falling edge of a reference clock for driving the object to be driven.

41. A power supply device according to claim 29, wherein:

a current flowing through a constant-current source of the drive portion of at least one of said impedance conversion means is put on limitation, when a frame signal for driving the object to be driven is at a predetermined level.