Patent ID: 8059141

Claim:
A display brightness control circuit, wherein, in where a drive circuit for a display device in which display brightness is switched based on an illuminance signal outputted by an external light sensor which measures environmental illuminance, there exists a case where the illuminance signal has a linear relationship with incident light and a case where the illuminance signal has a logarithmic relationship with incident light, the display brightness control circuit comprising: a converting circuit for converting the illuminance signal having the logarithmic relationship with incident light into a linear signal, where the converting circuit subjects the illuminance signal to exponential processing in the case where the illuminance signal has a logarithmic relationship with incident light, wherein, in the case where the illuminance signal has a linear relationship with incident light, the illuminance signal is not converted by preventing the illuminance signal from passing through the converting circuit and is directly used for display brightness control in the display brightness control circuit, wherein, in the case where the illuminance signal has a logarithmic relationship with incident light, the illuminance signal is converted by passing the illuminance signal through the converting circuit and is then used for display brightness control in the display brightness control circuit, wherein a signal inputted into the display brightness control circuit in a linear mode is the illuminance signal or in a logarithmic mode is a signal outputted by the converting circuit, and switching between the linear mode and the logarithmic mode can be performed externally, wherein the linear mode is separate from the logarithmic mode, and wherein the exponential processing to which the illuminance signal is subjected by the converting circuit is adjustable.