Inductorless electroactive lens driver and system
View Patent ↗An electroactive lens driver comprises a voltage generator generating a high alternating current voltage signal for application to an electroactive lens in response to a low direct current voltage signal. The voltage generator does not include an inductor or a transformer.
1. A circuit for supplying a drive voltage to an electroactive lens, comprising:
an input terminal for coupling to a low voltage direct current supply;
an output terminal for coupling to said electroactive lens;
a high voltage power supply for producing a DC output, said high voltage power supply including a plurality of charge pump circuits coupled between said input terminal and said output terminal; and
a switching circuit coupled to said output terminal for alternating polarity of said DC output at said output terminal;
wherein each charge pump of the plurality of charge pump circuits comprises:
a first diode having a first terminal coupled to a first output of said charge pump circuit for preventing discharge of said first output;
a first capacitor having a first terminal coupled to a first phase of a clock and further having a second terminal coupled to a second terminal of said first diode for charging said output through said first diode;
a second diode having a first input coupled to said second terminal of said first diode; and
a second capacitor having a first terminal coupled to a second phase of a clock input and further having a second terminal coupled to a second output of second diode.
2. The circuit of claim 1 , further comprising an oscillator coupled to said high voltage power supply for controlling switching of said plurality of charge pump circuits.
3. The circuit of claim 2 , wherein said circuit includes four external terminals comprising:
a first terminal for coupling to a first terminal of said electroactive lens;
a second terminal for coupling to a second terminal of said electroactive lens;
a third terminal for coupling to an input power supply; and
a fourth terminal for coupling to an input power supply return.
4. The circuit of claim 1 , wherein the plurality of charge pumps is cascaded in series.
5. The circuit of claim 4 , wherein a first charge pump of said plurality of charge pumps generates a first voltage that is approximately twice an input voltage of said circuit, and wherein a second charge pump of said plurality of charge pumps comprises a plurality of stacked switched capacitor circuits for producing said DC output from said first voltage.
6. The circuit of claim 5 , wherein said first charge pump circuit comprises a switched transistor voltage doubler.
7. The circuit of claim 1 , further comprising a feedback circuit coupled to plurality of charge pump circuits that disables the plurality of charge pump circuits when a predetermined voltage level is generated.
8. The circuit of claim 1 , wherein said circuit has exactly four external terminals comprising:
a first terminal for coupling to a first terminal of said electroactive lens;
a second terminal for coupling to a second terminal of said electroactive lens;
a third terminal for coupling to an input power supply; and
a fourth terminal for coupling to an input power supply return.
9. The circuit of claim 1 , wherein said switching circuit comprises a full bridge transistor circuit for switching said DC output alternatively with ground to said output terminal.
10. The circuit of claim 1 , further comprising a variable regulator interposed between said high voltage supply and said switching circuit, whose input is coupled to the DC output of said high voltage DC supply, and the regulator output is coupled to the input of said switching circuit, for providing a variable amplitude AC signal at said output terminals.
11. The circuit of claim 10 where the electroactive lens is a liquid lens.
12. The circuit of claim 10 where the electroactive lens is a liquid crystal lens.
13. The circuit of claim 10 where the variable regulator is a digital to analog converter.
14. The circuit of claim 13 where the electroactive lens is a liquid lens.
15. The circuit of claim 13 where the electroactive lens is a liquid crystal lens.
16. The circuit of claim 10 where the variable regulator is a digital to analog converter coupled to a serial digital interface.
17. The circuit of claim 16 where the electroactive lens is a liquid lens.
18. The circuit of claim 16 where the electroactive lens is a liquid crystal lens.
19. A method for driving an electroactive lens, said method comprising:
providing a circuit for supplying a drive voltage to said electroactive lens, comprising:
coupling an input terminal to a low voltage direct current supply;
coupling an output terminal to said electroactive lens;
producing a DC output using a high voltage power supply including a plurality of charge pump circuits coupled between said input terminal and said output terminal; and
alternating polarity of said DC output at said output terminal using a switching circuit;
wherein each charge pump of the plurality of charge pump circuits comprises:
a first diode having a first terminal coupled to a first output of said charge pump circuit for preventing discharge of said first output;
a first capacitor having a first terminal coupled to a first phase of a clock and further having a second terminal coupled to a second terminal of said first diode for charging said output through said first diode;
a second diode having a first input coupled to said second terminal of said first diode; and
a second capacitor having a first terminal coupled to a second phase of a clock input and further having a second terminal coupled to a second output of second diode.
20. The method of claim 19 , further comprising doubling an input supply voltage to produce said supply voltage for said charging.
21. The method of claim 19 , further comprising coupling a variable regulator said high voltage supply and said switching circuit, coupling an input of the variable regulator to the DC output of said high voltage DC supply, and coupling an output of the variable regulator to the input of said switching circuit, for providing a variable amplitude AC signal at said output terminals.
22. The method of claim 21 where the electroactive lens is a liquid lens.
23. The method of claim 21 where the electroactive lens is a liquid crystal lens.
24. The method of claim 21 wherein the variable regulator is a digital to analog converter.
25. The method of claim 24 wherein the electroactive lens is a liquid lens.
26. The method of claim 24 wherein the electroactive lens is a liquid crystal lens.
27. The method of claim 21 wherein the variable regulator is a digital to analog converter coupled to a serial digital interface.
28. The method of claim 27 wherein the electroactive lens is a liquid lens.
29. The method of claim 27 wherein the electroactive lens is a liquid crystal lens.