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 circuit utilizing energy stored on a capacitive storage device, comprising: a first switch (SLR) operable to selectively allow a first liquid crystal cell to charge a first inductor; a first capacitor operable to receive charge from the first liquid crystal cell by alternately opening and closing a second switch until the voltage is substantially discharged from the first liquid crystal cell; and a third switch operable to selectively maintain an approximately zero voltage on the first liquid crystal cell.
2. The charge recovery circuit of claim 1 , wherein the first liquid crystal cell limits the output current by alternately opening and closing a second switch (SREC).
3. The charge recovery circuit of claim 2 , wherein the first inductor charges when the second switch (SREC) closes.
4. The charge recovery circuit of claim 2 , wherein current in the first inductor transfers to a diode when the second switch (SREC) opens.
5. The charge recovery circuit of claim 4 , wherein the diode allows the voltage on the first capacitor to incrementally increase.
6. The charge recovery circuit of claim 1 , further comprising a zero-crossing detector operable to detect the voltage on the first liquid crystal cell.
7. The charge recovery circuit of claim 1 , further comprising a third switch (SLG) operable to close after the voltage on the first liquid crystal cell is approximately zero.
8. The charge recovery circuit of claim 7 , wherein closing the third switch (SLG) holds the voltage on the first liquid crystal cell at approximately zero volts.
9. The charge recovery circuit 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.