Line ripple reducer
AssigneeSemiconductor Components Industries, LLC
InventorHyunchul EUM
Life of this patent
Estimating the term…
Abstract
A circuit includes a power supply circuit and a ripple reduction circuit. The power supply circuit supplies a Direct Current (DC) lighting current to a light emitting circuit. The lighting current has a ripple current at a ripple frequency. The ripple reduction circuit receives the lighting current, and performs, based on the received lighting current, Pulse Width Modulation (PWM) of the lighting current at a PWM frequency. The PWM frequency is higher than the ripple frequency. By performing the PWM, the ripple reduction current reduces variations in a magnitude of the lighting current at the ripple frequency. The PWM frequency may be higher than a frequency at which variations in the magnitude of the light produced by the lighting circuit have a harmful effect on the human eye.
Claims20
A circuit comprising:
- a power supply circuit to supply a lighting current to a light emitting circuit, the lighting current having a ripple current at a ripple frequency;
- and
- a ripple reduction circuit to:
- receive the lighting current, and
- perform, based on the received lighting current, Pulse Width Modulation (PWM) of the lighting current at a PWM frequency to reduce variations in a magnitude of the lighting current at the ripple frequency by performing the PWM,
- wherein the PWM frequency is higher than the ripple frequency.
A circuit comprising:
- a ripple reduction circuit to receive a lighting current flowing through a light emitting circuit, the lighting current having a ripple current, the ripple current having a ripple frequency, the ripple reduction circuit comprising:
- a switching device to control the lighting current according to a Pulse Width Modulation (PWM) signal,
- a Current Sense (CS) circuit to produce a CS signal according to a magnitude of the lighting current,
- a CS integrator to generate, by integrating the CS signal over a duration, an integrated CS signal, and
- a PWM signal generation circuit to generate, according to a PWM clock signal and the integrated CS signal, the PWM signal,
- wherein the ripple reduction circuit operates to reduce a magnitude of the ripple current at the ripple frequency.
A method for reducing an effect of a ripple current having a ripple frequency in a current, the method comprising:
- performing, using a clock signal, Pulse Width Modulation (PWM) of the current so that an average current during a cycle of the clock signal is equal to a target value,
- wherein a frequency of the clock signal is greater than the ripple frequency, and
- wherein the current is a current through a light emitting circuit.
Dependencies are inferred from the claim text.