Charge recovery scheme
View Patent ↗Shuttering eyewear (or shutter glasses) may be used to enable stereoscopic 3D and to provide different images to two viewers using a single display, known as Dual View. The shuttering eyewear may utilize charge recovery circuits. The charge recovery circuits may achieve high charge recovery efficiencies on the order of 80 to 90 percent resulting in a dramatic reduction in power supply battery operating current and a resulting increase in operating time. The charge recovery circuits may utilize switch mode boost conversion to recover most of the charge from a shutter that is being closed to one that is to be opened. Further, a charge recovery method for utilizing energy stored on a capacitive storage device may include closing a first active shutter, moving charge to a converter in buck mode to a capacitor, and pulling charge from the capacitor to open a second shutter.
1. A charge recovery method utilizing energy stored on a capacitive storage device, comprising:
closing a first switch (SLR), which allows a first liquid crystal cell to charge a first inductor;
increasing the voltage on a first capacitor by alternately opening and closing a second switch (SREC) until the voltage is discharged from the first liquid crystal cell; and
closing a third switch (SLG) to maintain an approximately zero voltage on the first liquid crystal cell.
2. The charge recovery method of claim 1 , further comprising limiting output current from the first liquid crystal cell by alternately opening and closing the second switch (SREC).
3. The charge recovery method of claim 2 , further comprising charging the first inductor when the second switch SREC closes.
4. The charge recovery method of claim 3 , further comprising transferring, at least in part, current in the first inductor to a diode.
5. The charge recovery method of claim 4 , further comprising increasing the voltage incrementally on the first capacitor.
6. The charge recovery method of claim 1 , further comprising detecting the voltage on the first liquid crystal cell with a zero-crossing detector.
7. The charge recovery method of claim 1 , further comprising closing a third switch (SLG).
8. The charge recovery method of claim 7 , wherein closing the third switch (SLG) further comprises holding the voltage on the first liquid crystal cell at approximately zero volts.
9. The charge recovery method of claim 8 , wherein holding the voltage on the first liquid crystal cell at approximately zero volts further comprises closing the first liquid crystal cell.
10. The charge recovery method of claim 9 , further comprising opening the first switch (SLR).
11. A charge recovery method for utilizing energy stored on a liquid crystal capacitive storage device, comprising:
closing at least a first switch to allow charge to flow from the capacitive storage device to a first inductor;
charging the first inductor for a first charge time;
closing at least a second switch to allow charge to flow from the first inductor to a first capacitor; and
charging the first capacitor for a first discharge time.
12. The charge recovery method of claim 11 , wherein the capacitive storage device is a liquid crystal shutter.
13. The charge recovery method of claim 11 , further comprising detecting the voltage on the capacitive storage device with a zero-crossing detector.
14. The charge recovery method of claim 13 , further comprising closing a third switch when the voltage on the capacitive storage device is approximately zero.
15. The charge recovery method of claim 14 , wherein closing the third switch further comprises holding the voltage on the capacitive storage device at approximately zero volts.
16. The charge recovery method of claim 15 , wherein the capacitive storage device is a liquid crystal shutter, further wherein holding the voltage at approximately zero volts on the liquid crystal shutter further comprises closing the liquid crystal shutter.
17. The charge recovery method of claim 12 , further comprising closing the first liquid crystal shutter when the voltage on the first liquid crystal shutter is approximately zero.
18. The charge recovery method of claim 17 , further comprising moving charge from a converter in buck mode, to the first capacitor.
19. The charge recovery method of claim 18 , further comprising pulling charge from the first capacitor to open a second liquid crystal shutter.
20. A charge recovery method for utilizing energy stored on a capacitive storage device, comprising:
closing a first active liquid crystal shutter;
moving charge to a converter in buck mode to a capacitor; and
pulling charge from the capacitor to open a second shutter.