Method and apparatus for measuring forward voltage drop of light emitting element, light source apparatus, and thermal printer

摘要

An optical fixing device is provided with a light emitting element array that consists of a plural number of LEDs connected in a matrix. The LEDs are connected in serial to each other in each column, and the LED columns are connected in parallel to each other. Transistors are connected in serial to the LED columns respectively, so as to turn the associated LED columns ON or OFF. A capacitor is connected in parallel to the LED columns. After the capacitor is charged by turning a switch ON, selected one of the LED columns is turned ON, to discharge the capacitor through the selected LED column. Based on a voltage across the capacitor at the completion of discharging, a forward voltage VFL across the selected LED column is measured.