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, the square wave output being coupled to a load; and
a low voltage detection circuit for monitoring the voltage level of a power source and providing a control signal to the control input of the square wave oscillator, 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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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
53 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, the square wave output being coupled to a load; and
a low voltage detection circuit for monitoring the voltage level of a power source and providing a control signal to the control input of the square wave oscillator, to thereby decrease the duty cycle of the square wave output when the voltage level of the power source decreases below a predetermined level. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. 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. - View Dependent Claims (26, 27, 28, 29)
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30. 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, the square wave output being coupled to the lamp; and
a low voltage detection circuit for monitoring the voltage level of a power source and providing a control signal to the control input of the square wave oscillator, to thereby decrease the duty cycle of the square wave output when the voltage level of the power source decreases below a predetermined level. - View Dependent Claims (31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53)
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Specification