# US 5,347,383 A · High speed, low power driving circuit for liquid crystal shutter > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,347,383 A - Document ID: US5347383A - Status: Granted - Kind: A - Application number: 07/943,994 - Filed: 1992-09-11 - Granted: 1994-09-13 - Earliest claimed: 1989-06-12 - Assignees: OSD Envizion Company - Inventors: John D. Fergason - Web page: https://patentgrep.com/patent/US5347383A ## CPC - G02F 1/13306: {Circuit arrangements or driving methods for the control of single liquid crystal cells (G02F1/132, G02F1/133382 take precedence)} - G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS ## Abstract A driving circuit for a liquid crystal shutter or for other devices that reduces the power drain on the portable power supply and has the characteristic of fast response time. Accurate voltage regulation also is provided by referencing an accurate reference voltage supplied by a diode. ## Claims ### Claim 1 A power supply for a liquid crystal shutter, comprising input means for providing an input representative of an optical characteristic of such shutter, output means for supplying an electrical driving signal to such shutter to cause such optical characteristic thereof, power circuit means for selectively supplying to such output means a drive signal of selected power as a function of the input from said input means, and AC control signal means for selectively supplying an AC driving control signal at a frequency selected between two or more different, non-zero frequencies as a function of the input from said input means, to said output means to deliver such electrical driving signal according to the characteristics of such AC driving control signal. ### Claim 2 (depends on 1) The power supply of claim 1, said power circuit means comprising means for supplying both relatively high and relatively low amplitude drive signals. ### Claim 3 (depends on 2) The power supply of claim 2, said power circuit means comprising switch means for providing such relatively high amplitude power signal in response to such input representative of a desired characteristic of such shutter. ### Claim 4 A power supply for a liquid crystal shutter, comprising input means for providing an input representative of an optical characteristic of such shutter, output means for supplying an electrical driving signal to such shutter to cause such optical characteristic thereof, power circuit means for selectively supplying to such output means a drive signal of selected power as a function of the input from said input means, AC control signal means for supplying an AC driving control signal to said output means to deliver such drive signal according to the characteristics of such AC driving control signal, and said power circuit means including a transistor amplifier, and further comprising speed up means coupled to said transistor amplifier to speed the operative response thereof. ### Claim 5 (depends on 4) The power supply of claim 4, said transistor amplifier comprising a drive transistor and an output transistor, and said speed up means comprising a speed up capacitor coupled between said drive and output transistors. ### Claim 6 (depends on 5) The power supply of claim 5, wherein said transistor amplifier comprises a second output transistor, and said output transistors are configured as a Darlington pair. ### Claim 7 (depends on 1) The power supply of claim 1, said input means comprising a photosensitive diode. ### Claim 8 A power supply for a liquid crystal shutter, comprising input means for providing an input representative of an optical characteristic of such shutter, output means for supplying an electrical driving signal to such shutter to cause such optical characteristic thereof, power circuit means for selectively supplying to such output means a drive signal of selected power as a function of the input from said input means, AC control signal means for supplying an AC driving control signal to said output means to deliver such drive signal according to the characteristics of such AC driving control signal, and said input means comprising oscillator means for producing AC signals at two different frequencies as a function of the amplitude of the desired characteristic of such shutter. ### Claim 9 (depends on 8) The power supply of claim 8, wherein such shutter is a liquid crystal shutter presenting a capacitive load to such output means, and said oscillator means comprises means for providing a relatively low frequency output to cause a relatively low frequency driving signal to such liquid crystal shutter at relatively high power and a relatively higher frequency drive signal to such liquid crystal shutter at relatively low power to achieve a prescribed operational characteristic of such liquid crystal shutter. ### Claim 10 A liquid crystal optical shutter apparatus, comprising a liquid crystal shutter means for producing a prescribed optical characteristic as a function of a prescribed input thereto, and a power supply for driving said liquid crystal shutter means, said power supply comprising input means for providing an input representative of an optical characteristic of said shutter means, output means for supplying an electrical driving signal to said shutter means to cause such optical characteristic thereof, power circuit means for selectively supplying to such output means a drive signal of selected power as a function of the input from said input means, and AC control signal means for selectively supplying an AC driving control signal at a frequency selected between two or more different, non-zero frequencies as a function of the input from said input means, to said output means to deliver such electrical driving signal according to the characteristics of such AC driving control signal. ### Claim 11 (depends on 10) The shutter of claim 10, said power circuit means including a transistor amplifier, and further comprising speed up means coupled to said transistor amplifier to speed the operative response thereof. ### Claim 12 A liquid crystal optical shutter apparatus, comprising a liquid crystal shutter means for producing a prescribed optical characteristic as a function of a prescribed input thereto, and a power supply for driving said liquid crystal shutter means, said power supply comprising input means for providing an input representative of an optical characteristic of said shutter means, output means for supplying an electrical driving signal to said shutter means to cause such optical characteristic thereof, power circuit means for selectively supplying to such output means a drive signal of selected power as a function of the input from said input means, and AC control signal means for supplying an AC driving control signal to said output means to deliver such drive signal according to the characteristics of such AC driving control signal, and said input means comprising oscillator means for producing AC signals at two different frequencies as a function of the amplitude of the desired characteristic of said shutter means. ### Claim 13 (depends on 12) The shutter of claim 12, wherein said shutter means is a liquid crystal shutter presenting a capacitive load to such output means, and said oscillator means comprises means for providing a relatively low frequency output to cause a relatively low frequency drive signal to said liquid crystal shutter at relatively high power and a relatively higher frequency drive signal to such liquid crystal shutter at relatively low power to achieve a prescribed operational characteristic of said liquid crystal shutter. ### Claim 14 (depends on 10) The power supply of claim 10, said input means comprising a photosensitive diode. ### Claim 15 A power supply circuit for selectively charging a storage device from a power source, comprising a free running circuit means for developing an oscillatory signal, a power means for responding to such free running circuit means to charge such storage device from such power means, and a comparator means for comparing a first signal representative of the voltage level of such storage device with a reference signal and preventing operation of said power means to charge such storage device when adequate charge is contained in such storage device. ### Claim 16 (depends on 15) The circuit of claim 15, wherein said comparator is operative to maintain a substantially constant charge on such storage device even with a variable input voltage from such power source. ### Claim 17 (depends on 16) The circuit of claim 16, further comprising a diode means for providing such reference signal. ### Claim 18 (depends on 1) The power supply of claim 1, wherein the frequency of said AC driving control signal remains non-zero during operation. ### Claim 19 A power supply for a liquid crystal shutter, comprising: input means for providing an input signal representative of a desired optical characteristic of such shutter, output means for supplying an electrical driving signal to such shutter to cause such optical characteristic thereof, power circuit means for selectively supplying to such output means a power signal of selected power as a function of the input signal from said input means, AC control signal means for selectively supplying to said output means an AC control signal of selected frequency as a function of the input signal from said input means; and wherein said output means delivers such electrical driving signal according to the characteristics of such power signal and such AC control signal, and wherein at least one of the magnitude and frequency of such electrical driving signal remains non-zero during operation. ### Claim 20 (depends on 19) The power supply of claim 19, wherein the magnitude of said electrical driving signal remains non-zero. ### Claim 21 (depends on 20) The power supply of claim 20, wherein the frequency of said electrical driving signal remains non-zero. ### Claim 22 (depends on 1) The power supply of claim 1, wherein said input means comprises a photosensitive sensor which provides a signal representative of the intensity of light in the area of said shutter. ### Claim 23 (depends on 1) The power supply of claim 1, wherein said input means comprises a photosensitive sensor that detects the intensity of light emitted from a welding arc. ### Claim 24 (depends on 1) The power supply of claim 1, said input means comprising a detector for detecting an input thereto, and wherein a characteristic of such input represents a desired light transmitting characteristic of such shutter. ### Claim 25 (depends on 1) The power supply of claim 1, said power circuit means comprising a circuit for selectively charging a storage device from a power source, including a free running circuit means for developing an oscillatory signal, a power means for responding to such free running circuit means to charge such storage device from such power means, and a comparator means for comparing a first signal representative of the voltage level of such storage device with a reference signal and preventing operation of said power means to charge such storage device when adequate charge is contained in such storage device. ### Claim 26 (depends on 10) The apparatus of claim 10, wherein said input means comprises a photosensitive sensor which provides a signal representative of the intensity of light in the area of said shutter. ### Claim 27 (depends on 10) The apparatus of claim 10, wherein said input means comprises a photosensitive sensor that detects the intensity of light emitted from a welding arc. ### Claim 28 (depends on 10) The apparatus of claim 10, said input means comprising a detector for detecting an input thereto, and wherein a characteristic of such input represents a desired light transmitting characteristic of such shutter. ### Claim 29 (depends on 10) The apparatus of claim 10, said power circuit means comprising a circuit for selectively charging a storage device from a power source, including a free running circuit means for developing an oscillatory signal, a power means for responding to such free running circuit means to charge such storage device from such power means, and a comparator means for comparing a first signal representative of the voltage level of such storage device with a reference signal and preventing operation of said power means to charge such storage device when adequate charge is contained in such storage device. ### Claim 30 (depends on 10) The apparatus of claim 10, wherein said liquid crystal shutter means is operative to produce an optical characteristic as different conditions of optical transmission as a function of the input thereto. ### Claim 31 (depends on 12) The apparatus of claim 12, wherein said liquid crystal shutter means is operative to produce an optical characteristic as different conditions of optical transmission as a function of the input thereto. ### Claim 32 (depends on 15) The circuit of claim 15, wherein said power means comprises a power transistor. ### Claim 33 (depends on 32) The circuit of claim 32, wherein said power means further comprises an inductor connected in series with said power transistor. ### Claim 34 (depends on 19) The power supply of claim 19, wherein said input means comprises a photosensitive sensor which detects the intensity of light in the area of said shutter. ### Claim 35 (depends on 19) The power supply of claim 19, wherein said input means comprises a photosensitive sensor that detects the intensity of light emitted from a welding arc. ### Claim 36 (depends on 19) The power supply of claim 19, said input means comprising a detector for detecting an input thereto, and wherein a characteristic of such input represents a desired light transmitting characteristic of such shutter. ### Claim 37 (depends on 19) The power supply of claim 19, said power circuit means comprising a circuit for selectively charging a storage device from a power source, including a free running circuit means for developing an oscillatory signal, a power means for responding to such free running circuit means to charge such storage device from such power means, and a comparator means for comparing a first signal representative of the voltage level of such storage device with a reference signal and preventing operation of said power means to charge such storage device when adequate charge is contained in such storage device.