Drive circuit with reduced kickback voltage for liquid crystal display
First Claim
1. A drive circuit for an active liquid crystal display comprising:
- voltage signal generating means for boosting a supply voltage signal to generate a voltage signal during a scanning time;
drop signal generating means for modifying the voltage signal during a portion of the scanning time to generate a drop signal; and
signal mixing means for combining the voltage signal and the drop signal to generate a composite signal.
2 Assignments
0 Petitions
Accused Products
Abstract
A drive circuit and method for driving a thin film transistor liquid crystal display which reduce kickback voltage by generating a gate drive signal that has a reduced on voltage during a drop portion of the horizontal scanning time. The circuit includes a voltage signal generating circuit for receiving both a common electrode signal and an inverting common electrode signal and generating voltage signals, a drop signal generating circuit for generating drop signals, and a signal mixer circuit for combining the voltage signals and the drop signals and generating a composite output signal. The voltage signal generating circuit and the drop signal generating circuits both include a series of boost stages comprised of diode voltage multipliers. The signal mixing circuit includes a series of switches that are controlled by the drop signals. The length of the drop portion of the horizontal scan time can be controlled by a period control signal.
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Citations
17 Claims
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1. A drive circuit for an active liquid crystal display comprising:
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voltage signal generating means for boosting a supply voltage signal to generate a voltage signal during a scanning time; drop signal generating means for modifying the voltage signal during a portion of the scanning time to generate a drop signal; and signal mixing means for combining the voltage signal and the drop signal to generate a composite signal. - View Dependent Claims (2, 3, 4)
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5. A drive circuit for an active liquid crystal display comprising:
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voltage signal generating means for boosting a supply voltage signal to generate a voltage signal during a scanning time; drop signal generating means for modifying the voltage signal during a portion of the scanning time to generate a drop signal; and signal mixing means for combining the voltage signal and the drop signal to generate a composite signal; wherein the voltage signal generating means includes a boost stage for receiving the supply voltage signal and generating the voltage signal responsive to an inverting common electrode signal. - View Dependent Claims (6, 7, 8)
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9. A drive circuit for an active liquid crystal display comprising:
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voltage signal generating means for boosting a supply voltage signal to generate a first voltage signal during a scanning time; drop signal generating means for modifying the first voltage signal during a portion of the scanning time to generate a drop signal; and signal mixing means for combining the first voltage signal and the drop signal to generate a composite signal; wherein the drop signal generating means includes a drop signal generator for receiving the first voltage signal and generating a drop signal responsive to a control signal; and wherein the drop signal generator includes a diode and a capacitor, the anode of the diode coupled to the first voltage signal, one terminal of the capacitor coupled to the cathode of the diode, the other terminal of the capacitor coupled to the control signal. - View Dependent Claims (10)
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11. A drive circuit for an active liquid crystal display comprising:
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voltage signal generating means for boosting a supply voltage signal to generate a first voltage signal during a scanning time; drop signal generating means for modifying the first voltage signal during a portion of the scanning time to generate a drop signal; and signal mixing means for combining the first voltage signal and the drop signal to generate a composite signal; wherein the voltage signal generating means generates second, third and fourth voltage signals, the drop signal generating means generates first, second and third drop signals, and the signal mixing means includes; a first switch for receiving the second voltage signal and generating a first portion of the composite signal responsive to the first drop signal; a second switch for receiving the third voltage signal and generating a second portion of the composite signal responsive to the second drop signal; a third switch for receiving the third voltage signal and generating a third portion of the composite signal responsive to the second drop signal; and a fourth switch for receiving the fourth voltage signal and generating a fourth portion of the composite signal responsive to the third drop signal. - View Dependent Claims (12, 13)
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14. A drive circuit for an active liquid crystal display comprising:
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a voltage generating circuit having a supply terminal for receiving a supply signal, and a plurality of output terminals, the voltage generating circuit generating voltage signals at its output terminals; a drop signal generating circuit having a plurality of input terminals coupled to the output terminals of the voltage generating circuit to receive the voltage signals, and a plurality of output terminals, the drop signal generating circuit modifying the voltage signals during a portion of a scanning time, thereby generating drop signals at its output terminals; and a signal mixing circuit having a plurality of source input terminals coupled to the output terminals of the voltage generating circuit to receive the voltage signals, a plurality of gate input terminals coupled to the output terminals of the drop signal generating circuit to receive the drop signals, and an output terminal, the signal mixing circuit generating a composite signal at its output terminal.
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15. A drive circuit for an active liquid crystal display comprising:
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a voltage generating circuit having a supply terminal for receiving a supply signal, and a plurality of output terminals, the voltage generating circuit generating voltage signals at its output terminals; a drop signal generating circuit having a plurality of input terminals coupled to the output terminals of the voltage generating circuit to receive the voltage signals, and a plurality of output terminals, the drop signal generating circuit generating drop signals at its output terminals; and a signal mixing circuit having a plurality of source input terminals coupled to the output terminals of the voltage generating circuit to receive the voltage signals, a plurality of gate input terminals coupled to the output terminals of the drop signal generating circuit to receive the drop signals, and an output terminal, the signal mixing circuit generating a composite signal at its output terminal; wherein the voltage generating circuit further includes; an electrode terminal for receiving an electrode signal; an inverting electrode terminal for receiving an inverting electrode signal; a first diode having an anode coupled to the supply terminal and a cathode coupled to a first output terminal; a second diode having an anode coupled to the first output terminal and a cathode coupled to a second voltage output terminal; a third diode having an anode coupled to the second output terminal and a cathode coupled to a third output terminal; a fourth diode having an anode coupled to the third output terminal and a cathode coupled to a fourth output terminal; a first capacitor having a first terminal coupled to the cathode of the first diode and a second terminal coupled to the inverting electrode terminal; a second capacitor having a first terminal coupled to the cathode of the second diode and a second terminal coupled to the electrode terminal; a third capacitor having a first terminal coupled to the cathode of the third diode and a second terminal coupled to the inverting electrode terminal; and a fourth capacitor having a first terminal coupled to the cathode of the fourth diode and a second terminal coupled to the electrode terminal.
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16. A drive circuit for an active liquid crystal display comprising:
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a voltage generating circuit having a supply terminal for receiving a supply signal, and a plurality of output terminals, the voltage generating circuit generating voltage signals at its output terminals; a drop signal generating circuit having a plurality of input terminals coupled to the output terminals of the voltage generating circuit to receive the voltage signals, and a plurality of output terminals, the drop signal generating circuit generating drop signals at its output terminals; and a signal mixing circuit having a plurality of source input terminals coupled to the output terminals of the voltage generating circuit to receive the voltage signals, a plurality of gate input terminals coupled to the output terminals of the drop signal generating circuit to receive the drop signals, and an output terminal, the signal mixing circuit generating a composite signal at its output terminal; wherein the drop signal generating circuit further includes; a control terminal for receiving a control signal; a first diode having an anode coupled to a first input terminal and a cathode coupled to a first output terminal; a second diode having an anode coupled to a second input terminal and a cathode coupled to a second output terminal; a third diode having an anode coupled to a third input terminal and a cathode coupled to a third output terminal; a first capacitor having a first terminal coupled to the cathode of the first diode and a second terminal coupled to the control terminal; a second capacitor having a first terminal coupled to the cathode of the second diode and a second terminal coupled to the control terminal; and a third capacitor having a first terminal coupled to the cathode of the third diode and a second terminal coupled to the control terminal.
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17. A drive circuit for an active liquid crystal display comprising:
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a voltage generating circuit having a supply terminal for receiving a supply signal, and a plurality of output terminals, the voltage generating circuit generating voltage signals at its output terminals; a drop signal generating circuit having a plurality of input terminals coupled to the output terminals of the voltage generating circuit to receive the voltage signals, and a plurality of output terminals, the drop signal generating circuit generating drop signals at its output terminals; and a signal mixing circuit having a plurality of source input terminals coupled to the output terminals of the voltage generating circuit to receive the voltage signals, a plurality of gate input terminals coupled to the output terminals of the drop signal generating circuit to receive the drop signals, and an output terminal, the signal mixing circuit generating a composite signal at its output terminal; wherein the signal mixing circuit further includes; a first transistor having a source coupled to a first source input terminal, a gate coupled to a first gate input terminal, and a drain coupled to the output terminal; a second transistor having a source coupled to a second source input terminal, and a gate coupled to a second gate input terminal; a third transistor having a source coupled to the second source input terminal, and a gate coupled to the second gate input terminal; a fourth transistor having a source coupled to a third source input terminal, a gate coupled to a third gate input terminal, and a drain coupled to the output terminal; a first diode having a cathode coupled to the drain of the second transistor and an anode coupled to the output terminal; and a second diode having an anode coupled to the drain of the third transistor and a cathode coupled to the output terminal.
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Specification