Systems and methods for multi-state switch networks

• US 8,432,102 B2
• Filed: 12/20/2007
• Issued: 04/30/2013
• Est. Priority Date: 01/05/2007
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Terlizzi, Jeffrey, Kalayjian, Nicholas R.
• Primary Examiner(s): VU, JIMMY T
• Application Number:
  US11/961,836
• Publication Number:
  US 20080164825A1
• Time in Patent Office: 1,958 Days
• Field of Search: 315/185.R, 315/209.R, 315/225, 315/291, 315/307, 315/308, 315/312
• US Class Current: 315/209.R
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/37 Converter circuits
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

Systems and methods for multi-state switch networks and multi-state LED networks are provided. Systems and methods for maintaining the brightness of LEDs in multi-state LED networks are also provided. The multi-state networks contain control circuitry that can output a single control signal that is able to drive a pair of diodes in three different states. In a network of 2*N diodes, N wires are sufficient to drive the diodes in 3^N different states. The control circuitry may also include a pulse-width modulator that controls the perceived brightness of the LEDs in a multi-state LED network in response to a voltage level of the power source.

Claims

1. A multi-state switch network comprising:

a serially-connected diode pair that receives a single control signal at a control node;

wherein the single control signal is operative to drive the serially-connected diode pair to one of at least three different states; and

wherein the single control signal is operative to alternatively;

turn ON a first diode of the diode pair and turn OFF a second diode of the diode pair when the single control signal is in a first state;

turn OFF the first diode and turn ON the second diode when the single control signal is in a second state; and

turn OFF the first diode and turn OFF the second diode when the single control signal is in a third state, wherein the third state comprises a high impedance state.

2. The multi-state switch network of claim 1, wherein the serially-connected diode pair comprises a pair of LEDs.

3. The multi-state switch network of claim 2, comprising a pulse-width modulator that modulates the single control signal to control a perceived brightness level of the pair of LEDs.

4. The multi-state switch network of claim 3, wherein the pulse-width modulator is operative to adjust a duty cycle of the single control signal based on a monitored voltage level.

5. The multi-state switch network of claim 4, wherein the pulse-width modulator is operative to increase the duty cycle of the single control signal based on a decrease in the monitored voltage level.

6. The multi-state switch network of claim 4, wherein the pulse-width modulator is operative to decrease the duty cycle of the single control signal based on an increase in the monitored voltage level.

7. The multi-state switch network of claim 1, wherein the serially-connected diode pair is operative to control a pair of switches.

8. The multi-state switch network of claim 1, wherein:

the first state comprises a higher voltage state; and

the second state comprises lower voltage state.

9. The multi-state switch network of claim 1, wherein the serially-connected diode pair consists essentially of two diodes and two resistors in serial communication.

10. The multi-state switch network of claim 1, comprising a tri-state buffer that provides the control signal.

11. A plurality of serially-connected diode pairs as defined in claim 1, each of the serially-connected diode pairs controlled by a single control signal.

12. The multi-state switch network of claim 1, wherein the second state comprises a high voltage state.

13. The multi-state switch network of claim 1, wherein the first state comprises a low voltage state.

14. The multi-state switch network of claim 1, comprising:

a power source;

a ground source; and

a control node, wherein;

a first diode of the diode pair is serially coupled between the power source and the control node;

a second diode of the diode pair is serially coupled between the control node and the ground source; and

the diode pair receives the single control signal at the control node.

15. The multi-state switch network of claim 14, comprising:

a first resistor; and

a second resistor, wherein;

the first resistor is serially coupled between the first diode and the control node; and

the second resistor is serially coupled between the second diode and the control node.

16. The multi-state switch network of claim 14, comprising a first switch node serially coupled between the first diode and the control node.

17. The multi-state switch network of claim 16, comprising a first switch coupled to the first switch node.

18. The multi-state switch network of claim 17, wherein the first switch comprises one of a transistor switch, a buffer, and a logic circuit.

19. The multi-state switch network of claim 17, comprising:

a second switch node serially coupled between the second diode and the control node; and

a second switch coupled to the first switch node.

20. A method of controlling a multi-state switch network comprising first and second diodes, the method comprising:

receiving a single control signal at a control node;

in response to the single control signal, alternatively;

turning ON the first diode and turning OFF the second diode when the single control signal is in a first state;

turning OFF the first diode and turning ON the second diode when the single control signal is in a second state; and

turning OFF the first diode and turning OFF the second diode when the single control signal is in a third state, wherein the third state comprises a high impedance state.

21. The method of claim 20, wherein the first diode and the second diode are LEDs.

22. The method of claim 21, comprising pulse-width modulating the single control signal to control a perceived brightness level of the LEDs.

23. The method of claim 22, comprising:

monitoring a voltage level of a power source; and

adjusting a duty cycle of the control signal based on the monitored voltage level.

24. The method of claim 20, comprising:

switching a first switch in response to turning ON the first diode; and

switching a second switch in response to turning ON the second diode.