CIRCUIT AND METHOD FOR CONTROLLING PULSE WIDTH MODULATION OF A CURRENT SUPLY FOR A LOAD

摘要

A circuit comprising a controller (2) for controlling a pulse width modulated input signal, and a driver (4) configured to supply current to a load (6) based on the input signal, wherein over the on time of each pulse width modulation period the driver (4) supplies current to the load (6) with a second frequency that is greater than the first frequency. The controller (2) is configured to control the duty cycle to set the output of the load (6) to a desired output level, and to dither the duty cycle about a point corresponding to the desired output level.

主权项

1. A circuit comprising:
A driver; and a controller for controlling a pulse width modulated input signal applied to the driver, the input signal having a period comprising an on time and on off time with said period repeating at a first frequency, and the controller being configured to control a duty cycle of the input signal being a proportion of the on time relative to the period or off time; wherein the driver is configured to supply current to a load based on the input signal, wherein over the off time of each period the driver withholds supply of current from a power supply to the load, and over the on time of each period the driver supplies current from the power supply to the load but with a second frequency that is greater than the first frequency, the load thus generating an output at a level dependent on the duty cycle; wherein the controller is configured to control the duty cycle to set the output of the load to a desired output level, and to dither the duty cycle about a point corresponding to the desired output level; and wherein the circuit further comprises a feedback channel from the driver to the controller for measuring the second frequency, wherein the controller is configured to adapt the dithering of the duty cycle in dependence on the second frequency as measured via said feedback channel.