Control circuit of liquid crystal display device, liquid crystal display device, and electronic device including liquid crystal display device

• US 9,135,880 B2
• Filed: 08/04/2011
• Issued: 09/15/2015
• Est. Priority Date: 08/16/2010
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Koyama, Jun
• Primary Examiner(s): Sitta, Grant
• Application Number:
  US13/197,823
• Publication Number:
  US 20120038618A1
• Time in Patent Office: 1,503 Days
• Field of Search: 345/204, 345/87, 345/212, 345/100
• US Class Current: 1/1
• CPC Class Codes: G09G 2320/106 Determination of movement vectors or equivalent parameters within the image
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 3/3688 suitable for active matrices only

Abstract

A current that flows through a common source amplifier circuit provided in a current amplifier circuit of an operational amplifier in displaying a moving image is made to be different from that in displaying a still image. Specifically, in one embodiment of the present invention, current source circuits which are provided in the current amplifier circuit in the operational amplifier operate by switching the current source circuit used for displaying a moving image and the current source circuit used for displaying a still image. The current amplitude in the common source amplifier circuit is controlled by switching the current source circuits, whereby low power consumption in the power supply circuit is achieved. The switching of the current source circuit in the operational amplifier is performed by a display control circuit for controlling a liquid crystal display panel in order to switch moving image display and still image display.

Claims

1. A control circuit of a liquid crystal display device comprising:

a display control circuit configured to control a liquid crystal display panel, the liquid crystal display panel configured to display a moving image in a first period and a still image in a second period; and

a power supply circuit electrically connected to the display control circuit, the power supply circuit comprising an operational amplifier comprising;

a differential amplifier circuit;

a current amplifier circuit electrically connected to the differential amplifier circuit; and

a source follower circuit electrically connected to the current amplifier circuit,

wherein the current amplifier circuit comprises a first transistor and a second transistor,

wherein the first transistor is turned on and the second transistor is turned off during the first period,

wherein the first transistor is turned off and the second transistor is turned on during the second period,

wherein a current supply capability of the operational amplifier is changeable depending on an amount of current flowing through the current amplifier circuit in the first period and an amount of current flowing through the current amplifier circuit in the second period, and

wherein the amount of current flowing through the current amplifier circuit in the first period is different from the amount of current flowing through the current amplifier circuit in the second period.

2. The control circuit of the liquid crystal display device according to claim 1,

wherein the liquid crystal display panel comprises a liquid crystal element including a pixel electrode and a counter electrode,

wherein the operational amplifier is configured to control a potential of the counter electrode.

3. The control circuit of the liquid crystal display device according to claim 2 further comprising a gate driver and a source driver electrically connected to the display control circuit,

wherein the gate driver and the source driver are configured to control a potential of the pixel electrode.

4. The control circuit of the liquid crystal display device according to claim 1, wherein the display control circuit comprises a memory circuit, a comparison circuit, a control signal output circuit, and a selection circuit.

5. The control circuit of the liquid crystal display device according to claim 1,

wherein the liquid crystal display panel comprises a liquid crystal element and a transistor, and

wherein a semiconductor film of the transistor is an oxide semiconductor.

6. An electronic device provided with the liquid crystal display device according to claim 1.

27. The control circuit of the liquid crystal display device according to claim 1, wherein a channel width of the first transistor and a channel width of the second transistor are different from each other.

7. A control circuit of a liquid crystal display device comprising:

a display control circuit configured to control a liquid crystal display panel, the liquid crystal display panel configured to display a moving image in a first period and a still image in a second period; and

a power supply circuit electrically connected to the display control circuit, the power supply circuit comprising an operational amplifier comprising;

a differential amplifier circuit;

a current amplifier circuit electrically connected to the differential amplifier circuit, the current amplifier circuit comprising;

a first current source circuit; and

a second current source circuit; and

a source follower circuit electrically connected to the current amplifier circuit,

wherein the current amplifier circuit comprises a first transistor and a second transistor,

wherein the first transistor is turned on and the second transistor is turned off during the first period,

wherein the first transistor is turned off and the second transistor is turned on during the second period,

wherein a current supply capability of the operational amplifier is changeable depending on an amount of current flowing through the first current source circuit in the first period and an amount of current flowing through the second current source circuit in the second period, and

wherein the amount of current flowing through the first current source circuit in the first period is different from the amount of current flowing through the second current source circuit in the second period.

8. The control circuit of the liquid crystal display device according to claim 7, further comprising a control circuit electrically connected to the first current source circuit and the second current source circuit,

wherein the control circuit is configured to operate the first current source circuit in the first period and the second current source circuit in the second period.

9. The control circuit of the liquid crystal display device according to claim 7,

wherein the liquid crystal display panel comprises a liquid crystal element including a pixel electrode and a counter electrode,

wherein the operational amplifier is configured to control a potential of the counter electrode.

10. The control circuit of the liquid crystal display device according to claim 9 further comprising a gate driver and a source driver electrically connected to the display control circuit,

wherein the gate driver and the source driver are configured to control a potential of the pixel electrode.

11. The control circuit of the liquid crystal display device according to claim 7, wherein the display control circuit comprises a memory circuit, a comparison circuit, a control signal output circuit, and a selection circuit.

12. The control circuit of the liquid crystal display device according to claim 7,

wherein the liquid crystal display panel comprises a liquid crystal element and a transistor, and

wherein a semiconductor film of the transistor is an oxide semiconductor.

13. An electronic device provided with the liquid crystal display device according to claim 7.

28. The control circuit of the liquid crystal display device according to claim 7, wherein a channel width of the first transistor and a channel width of the second transistor are different from each other.

14. A control circuit of a liquid crystal display device comprising:

a display control circuit configured to control a liquid crystal display panel, the liquid crystal display panel configured to display a moving image in a first period and a still image in a second period; and

a power supply circuit electrically connected to the display control circuit, the power supply circuit comprising an operational amplifier comprising;

a differential amplifier circuit;

a first transistor;

a second transistor;

a third transistor;

a fourth transistor; and

a fifth transistor,

wherein a gate of the first transistor is electrically connected to an output terminal of the differential amplifier circuit,

wherein one of a source and a drain of the first transistor is directly connected to a high power supply voltage side terminal,

wherein the other of the source and the drain of the first transistor is electrically connected to one of a source and a drain of the second transistor and one of a source and a drain of the third transistor,

wherein the other of the source and the drain of the first transistor is directly connected to a gate of the fourth transistor,

wherein the other of the source and the drain of the second transistor and the other of the source and the drain of the third transistor are directly connected to a low power supply voltage side terminal,

wherein one of a source and a drain of the fourth transistor is directly connected to the high power supply voltage side terminal,

wherein the other of the source and the drain of the fourth transistor is directly connected to one of a source and a drain of the fifth transistor,

wherein the other of the source and the drain of the fifth transistor is directly connected to the low power supply voltage side terminal,

wherein a current supply capability of the operational amplifier is changeable depending on an amount of current flowing through the second transistor in the first period and an amount of current flowing through the third transistor in the second period, and

wherein the amount of current flowing through the second transistor in the first period is different from the amount of current flowing through the third transistor in the second period.

15. The control circuit of the liquid crystal display device according to claim 14, further comprising a control circuit electrically connected to a gate of the second transistor and a gate of the third transistor.

16. The control circuit of the liquid crystal display device according to claim 14,

wherein the liquid crystal display panel comprises a liquid crystal element including a pixel electrode and a counter electrode,

wherein the operational amplifier is configured to control a potential of the counter electrode.

17. The control circuit of the liquid crystal display device according to claim 16, further comprising a gate driver and a source driver electrically connected to the display control circuit,

wherein the gate driver and the source driver are configured to control a potential of the pixel electrode.

18. The control circuit of the liquid crystal display device according to claim 14, wherein the display control circuit comprises a memory circuit, a comparison circuit, a control signal output circuit, and a selection circuit.

19. The control circuit of the liquid crystal display device according to claim 14,

wherein the liquid crystal display panel comprises a liquid crystal element and a transistor, and

wherein a semiconductor film of the transistor is an oxide semiconductor.

20. An electronic device provided with the liquid crystal display device according to claim 14.

29. The control circuit of the liquid crystal display device according to claim 14, wherein a channel width of the second transistor and a channel width of the third transistor are different from each other.

21. A liquid crystal display device comprising:

a liquid crystal display panel configured to display a moving image in a first period and a still image in a second period;

a display control circuit configured to control the liquid crystal display panel; and

a power supply circuit electrically connected to the display control circuit, the power supply circuit comprising an operational amplifier comprising;

a differential amplifier circuit;

a current amplifier circuit electrically connected to the differential amplifier circuit; and

a source follower circuit electrically connected to the current amplifier circuit,

wherein the current amplifier circuit comprises a first transistor and a second transistor,

wherein the first transistor is turned on and the second transistor is turned off during the first period,

wherein the first transistor is turned off and the second transistor is turned on during the second period,

wherein a current supply capability of the operational amplifier is changeable depending on an amount of current flowing through the current amplifier circuit in the first period and an amount of current flowing through the current amplifier circuit in the second period, and

wherein the amount of current flowing through the current amplifier circuit in the first period is different from the amount of current flowing through the current amplifier circuit in the second period.

22. The liquid crystal display device according to claim 21,

wherein the liquid crystal display panel comprises a liquid crystal element including a pixel electrode and a counter electrode,

wherein the operational amplifier is configured to control a potential of the counter electrode.

23. The liquid crystal display device according to claim 22 further comprising a gate driver and a source driver electrically connected to the display control circuit,

wherein the gate driver and the source driver are configured to control a potential of the pixel electrode.

24. The liquid crystal display device according to claim 21, wherein the display control circuit comprises a memory circuit, a comparison circuit, a control signal output circuit, and a selection circuit.

25. The liquid crystal display device according to claim 21,

wherein the liquid crystal display panel comprises a liquid crystal element and a transistor, and

wherein a semiconductor film of the transistor is an oxide semiconductor.

26. An electronic device provided with the liquid crystal display device according to claim 21.

30. The liquid crystal display device according to claim 21, wherein a channel width of the first transistor and a channel width of the second transistor are different from each other.