METHOD AND APPARATUS FOR DETERMINING A TARGET LIGHT INTENSITY FROM A PHASE-CONTROL SIGNAL

摘要

A dimmable ballast circuit for a compact fluorescent lamp controls the intensity of a lamp tube in response to a phase-control voltage received from a dimmer switch. The ballast circuit comprises a phase-control-to-DC converter circuit that receives the phase-control voltage, which is characterized by a duty cycle defining a target intensity of the lamp tube, and generates a DC voltage representative of the duty cycle of the phase-control voltage. Changes in the duty cycle of the phase-control voltage that are below a threshold amount are filtered out by the converter circuit, while intentional changes in the duty cycle of the phase-control voltage are reflected in changes in the target intensity level and thereby the intensity level of the lamp tube.

主权项

1. A circuit for controlling an intensity level of a lighting load, the load control circuit configured to receive a phase-control voltage characterized by a duty cycle, the load control circuit comprising:
a load regulation circuit adapted to be coupled to the lighting load for control of the intensity level of the lighting load; and a control circuit configured to determine a target intensity level for the lighting load in response to the duty cycle of the phase-control voltage, the control circuit configured to receive an actual-intensity signal representative of an actual intensity level of the lighting load, the control circuit configured to control the load regulation circuit to adjust the actual intensity level of the lighting load towards the target intensity level; wherein the control circuit is configured to adjust the target intensity level for the lighting load using a first time constant in response to changes in the duty cycle of the phase-control voltage that are less than a threshold amount, and to adjust the target intensity level of the lighting load using a second time constant less than the first time constant in response to changes in the duty cycle of the phase-control voltage that are greater than the threshold amount.