PWM controller with automatic low battery power reduction circuit and lighting device incorporating the controller
First Claim
1. A control circuit for a load, comprising:
- a square wave generator producing a square wave output, a duty cycle of the square wave output being controllable by a control input of the square wave generator, the square wave output being coupled to the load, wherein the square wave generator comprises a comparator circuit having a threshold level set by the control input;
a low voltage detection circuit for monitoring a voltage level of a power source and providing a control signal to the control input of the square wave generator, to thereby decrease the duty cycle of the square wave output when the voltage level of the power source decreases below a predetermined level; and
a triangular wave oscillator producing a triangle wave signal, wherein the triangle wave signal is provided as input to the square wave generator for comparison to the threshold level by the comparator circuit.
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Accused Products
Abstract
A controller for controlling a voltage applied to a load from a power source includes a square wave producing circuit for connection in the circuit with the battery and the lamp. The square wave producing circuit produces a variable duty cycle square wave for controlling application of power to the load in accordance with the duty cycle of the square wave. The square wave producing circuit has a control input for varying the duty cycle of the square wave in response to a voltage at the control input. A voltage varying circuit is connected to the power source for producing a selectively variable voltage that is fed to the control input of the square wave producing circuit for selectively adjusting the duty cycle of the square wave. A low voltage detection circuit is connected to the power source and coupled to the control input of the square wave producing circuit for automatically producing a voltage that decreases the duty cycle of the square wave when the battery voltage decreases to or below a predetermined level.
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Citations
41 Claims
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1. A control circuit for a load, comprising:
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a square wave generator producing a square wave output, a duty cycle of the square wave output being controllable by a control input of the square wave generator, the square wave output being coupled to the load, wherein the square wave generator comprises a comparator circuit having a threshold level set by the control input;
a low voltage detection circuit for monitoring a voltage level of a power source and providing a control signal to the control input of the square wave generator, to thereby decrease the duty cycle of the square wave output when the voltage level of the power source decreases below a predetermined level; and
a triangular wave oscillator producing a triangle wave signal, wherein the triangle wave signal is provided as input to the square wave generator for comparison to the threshold level by the comparator circuit.
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2. A control circuit for a load, comprising:
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a square wave generator producing a square wave output, a duty cycle of the square wave output being controllable by a control input of the square wave generator, the square wave output being coupled to the load; and
a low voltage detection circuit for monitoring a voltage level of a power source and providing a control signal to the control input of the square wave generator, to thereby decrease the duty cycle of the square wave output when the voltage level of the power source decreases below a predetermined level; and
manual control means for varying the control signal input to the control input of the square wave generator. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A control circuit for a load, comprising:
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a square wave generator producing a square wave output, a duty cycle of the square wave output being controllable by a control input of the square wave generator, the square wave output being coupled to the load; and
a low voltage detection circuit for monitoring a voltage level of a power source and providing a control signal to the control input of the square wave generator, to thereby decrease the duty cycle of the square wave output when the voltage level of the power source decreases below a predetermined level, wherein the low voltage detection circuit comprises a control transistor, wherein the control transistor is gradually turned off as the voltage level of the power source decreases below the predetermined level.
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13. A control circuit for a load, comprising:
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a square wave generator producing a square wave output, a duty cycle of the square wave output being controllable by a control input of the square wave generator, the square wave output being coupled to the load; and
a low voltage detection circuit for monitoring a voltage level a power source and providing a control signal to the control input of the square wave generator, to thereby decrease the duty cycle of the square wave output when the voltage level of the power source decreases below a predetermined level; and
a transistor coupled to the square wave generator and arranged so as to permit and shut off input to the square wave generator. - View Dependent Claims (14, 15, 16)
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17. A control circuit for a load, comprising:
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a square wave generator producing a square wave output, a duty cycle of the square wave output being controllable by a control input of the square wave generator, the square wave output being coupled to the load, wherein the square wave generator comprises a timer circuit; and
a low voltage detection circuit for monitoring a voltage level of a power source and providing a control signal to the control input of the square wave generator, to thereby decrease the duty cycle of the square wave output when the voltage level of the power source decreases.
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18. A method of controlling a load, comprising the steps of:
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producing a controllable variable duty cycle square wave for controlling application of power to the load in accordance with the duty cycle of the square wave;
detecting when the voltage of a power source decreases to a predetermined level and upon such detection automatically producing a voltage that decreases the duty cycle of the square wave used for controlling application of power to the load; and
manually controlling the duty cycle of the square wave to control the intensity of the load.
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19. A method of controlling a load, comprising the steps of:
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producing a controllable variable duty cycle square wave for controlling application of power to the load in accordance with the duty cycle of the square wave; and
detecting when the voltage of a power source decreases to a predetermined level and upon such detection automatically producing a voltage that decreases the duty cycle of the square wave used for controlling application of power to the load, wherein the step of producing the controllable variable duty cycle square wave comprises the steps of;
providing a fixed frequency triangular wave; and
comparing the triangular wave to a threshold voltage, thereby producing the square wave. - View Dependent Claims (20, 21)
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22. A pulse-width modulation (PWM)-based lamp control circuit comprising:
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a square wave generator for producing a square wave output, a duty cycle of the square wave output being controllable by a control input of the square wave generator, the square wave output being coupled to the lamp, wherein the square wave generator comprises a comparator circuit having a threshold level set by the control input;
a low voltage detection circuit for monitoring a voltage level of a power source and providing a control signal to the control input of the square wave generator, to thereby decrease the duty cycle of the square wave output when the voltage level of the power source decreases below a predetermined level; and
a triangular wave oscillator producing a triangle wave signal, wherein the triangle wave signal is provided as input to the square wave generator for comparison to the threshold level by the comparator circuit.
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23. A pulse-width modulation (PWM)-based lamp control circuit comprising:
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a square wave generator for producing a square wave output, a duty cycle of the square wave output being controllable by a control input of the square wave generator, the square wave output being coupled to the lamp;
a low voltage detection circuit for monitoring a voltage level of a power source and providing a control signal to the control input of the square wave generator, to thereby decrease the duty cycle of the square wave output when the voltage level of the power source decreases below a predetermined level; and
manual control means for varying the control signal input from the low voltage detection circuit to the control input of the square wave generator. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32)
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33. A pulse-width modulation (PWM)-based lamp control circuit comprising:
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a square wave generator for producing a square wave output, a duty cycle of the square wave output being controllable by a control input of the square wave generator, the square wave output being coupled to the lamp;
a low voltage detection circuit for monitoring a voltage level of a power source and providing a control signal to the control input of the square wave generator, to thereby decrease the duty cycle of the square wave output when the voltage level of the power source decreases below a predetermined level, wherein the low voltage detection circuit comprises a control transistor, wherein the control transistor is gradually turned off as the voltage level of the power source decreases below the predetermined level.
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34. A pulse-width modulation (PWM)-based lamp control circuit comprising:
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a square wave generator for producing a square wave output, a duty cycle of the square wave output being controllable by a control input of the square wave generator, the square wave output being coupled to the lamp;
a low voltage detection circuit for monitoring a voltage level of a power source and providing a control signal to the control input of the square wave generator, to thereby decrease the duty cycle of the square wave output when the voltage level of the power source decreases below a predetermined level; and
a transistor coupled to the square wave generator and arranged so as to permit and shut off input to the square wave generator. - View Dependent Claims (35, 36, 37)
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38. A pulse-width modulation (PWM)-based lamp control circuit composing:
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a square wave generator for producing a square wave output, a duty cycle of the square wave output being controllable by a control input of the square wave generator, the square wave output being coupled to the lamp, wherein the square wave generator comprises a timer circuit;
a low voltage detection circuit for monitoring a voltage level of a power source and providing a control signal to the control input of the square wave generator, to thereby decrease the duty cycle of the square wave output when the voltage level of the power source decreases below a predetermined level.
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39. A control circuit for a load, comprising:
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a square wave generator producing a square wave output, a duty cycle of the square wave output being controllable by a control input of the square wave generator, the square wave output being coupled to the load; and
a low voltage detection circuit for monitoring a voltage level of a power source and providing a control signal to the control input of the square wave generator, to thereby decrease the duty cycle of the square wave output when the voltage level of the power source decreases below a predetermined level, wherein said predetermined level is less than or equal to about 80%.
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40. A method of controlling a load, comprising the steps of:
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producing a controllable variable duty cycle square wave for controlling application of power to the load in accordance with the duty cycle of the square wave;
detecting when a voltage of a power source decreases to a predetermined level and upon such detection automatically producing a voltage that decreases the duty cycle of the square wave used for controlling application of power to the, wherein said predetermined level is less than or equal to about 80%.
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41. A pulse-width modulation (PWM)-based lamp control circuit comprising:
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a square wave generator for producing a square wave output, a duty cycle of the square wave output being controllable by a control input of the square wave generator, the square wave output being coupled to the lame, wherein the square wave generator comprises a comparator circuit having a threshold level set by the control input;
a low voltage detection circuit for monitoring a voltage level of a power source and providing a control signal to the control input of the square wave generator, to thereby decrease the duty cycle of the square wave output when the voltage level of the power source decreases below a predetermined level, wherein said predetermined level is less than or equal to about 80%.
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Specification