Series drive circuit

• US 5,956,012 A
• Filed: 04/02/1997
• Issued: 09/21/1999
• Est. Priority Date: 04/02/1997
• Status: Expired due to Term

• Current Assignee: Gentex Corporation
• Original Assignee: Gentex Corporation
• Inventors: Vanderwel, Peter William, Bauer, Frederick Thomas, Turnbull, Robert Ralph
• Primary Examiner(s): Zimmerman, Mark K.
• Assistant Examiner(s): Kovalick, Vincent E.
• Application Number:
  US08/825,768
• Time in Patent Office: 902 Days
• Field of Search: 345/105, 345/211, 345/212, 345/49, 349/16, 359/265-279, 327/108, 327/109, 327/309, 327/327, 327/328, 327/331, 327/540, 327/541
• US Class Current: 345/105
• CPC Class Codes: G02F 1/163 Operation of electrochromic cells, e.g. electrodeposition cells; Circuit arrangements therefor

Abstract

A series drive circuit for driving a plurality of serially-connected electronic elements, such as electrochromic elements. The series drive circuit maintains a accurately controlled voltage across each of the electronic elements, while reducing power consumption and current consumption. A constant voltage is applied to the serially-connected electronic elements that is the sum of the required voltage for each of the electronic elements. In order to prevent excess voltage across any of the elements, shunts are connected in parallel with each of the elements. In order to reduce excess voltage across any of the elements, the voltage across each of the elements is monitored and used to control the shunts to maintain a accurately controlled voltage across each of the serially-connected electronic elements.

Claims

1. A series drive circuit for driving a plurality of serially-connected predetermined electronic elements, the series drive circuit comprising:

a power transistor connected to said serially-connected electronic elements for providing a first predetermined voltage equal to the voltages across the serially-connected electronic elements;

a power transistor feedback loop for said power transistor for controlling said power transistor to maintain said predetermined voltage across said serially-connected electronic elements;

a plurality of shunt devices, each shunt device connected across one of said serially-connected electronic elements; and

a feedback loop for each of said shunt devices for controlling the voltage across each of said serially-connected electronic devices.

2. The series drive circuit as recited in claim 1, wherein said power transistor feedback loop includes a difference amplifier for comparing said first predetermined voltage applied across said serially-connected electronic elements with a second predetermined voltage in order to control said drive transistor to maintain said first predetermined voltage.

3. The series drive circuit recited in claim 1, further including means for maintaining an equal voltage across each of the serially-connected electronic elements.

4. The series drive circuit as recited in claim 1, further including means for maintaining the voltage across said serially-connected electronic elements as a predetermined fraction of said first predetermined voltage.

5. The series drive circuit as recited in claim 1, further including means for preventing said plurality of shunt devices from operating at the same time during predetermined conditions.

6. The series drive circuit as recited in claim 1, further including means for shunting all of said serially-connected electronic devices under the control of a predetermined control signal.

7. A series drive circuit for driving a plurality of serially-connected electronic elements, the series drive circuit comprising:

means for providing a first predetermined voltage across all of said serially-connected electronic elements; and

means for controlling the voltage across each of said serially-connected electronic devices.

8. The series drive circuit as recited in claim 7, wherein said controlling means includes a plurality of shunt devices configured such that a shunt device is connected across each of said serially-connected electronic devices.

9. The series drive circuit as recited in claim 7, wherein said controlling means includes means for controlling the voltage across each of said predetermined serially-connected electronic to be a predetermined fraction of said first predetermined voltage.

10. A series drive circuit for driving a plurality of serially-connected predetermined electronic elements including a first element and a second element, the series drive circuit comprising:

means for providing a predetermined overall voltage across said plurality of serially connected elements; and

means for controlling the voltage across said first electronic element to be a predetermined fraction of said predetermined overall voltage.

11. The series drive circuit as recited in claim 10, wherein said controlling means includes means for maintaining the voltages across each of said plurality of serially connected electronic elements to be equal.

12. The series drive circuit as recited in claim 10, wherein said controlling means includes means for maintaining the voltage across one of said plurality of serially connected elements to be different than another one of said serially connected electronic elements.

13. The series drive circuit as recited in claim 10, wherein said controlling means includes one or more shunts.

14. The series drive circuit as recited in claim 13, wherein at least one of said one or more shunts is connected in parallel across one of said serially connected electronic elements.

15. The series drive circuit as recited in claim 10, wherein at least one of said serially connected electronic elements is an electrochromic element.

16. The series drive circuit as recited in claim 15, wherein said electrochromic element is an electrochromic mirror.

17. The series drive circuit as recited in claim 15, wherein said electrochromic element is electrochromic glass with variable transmissivity.