| 摘要 |
Light emitting diodes (LEDs) are commonly used to backlight liquid crystal display screens for mobile telephones and other display devices. It may be desirable for the LEDs to be gradually dimmed and this can result in noise being emitted by the components of the driving circuit, along with other undesirable effects. A device for driving a circuit element is provided, comprising a voltage source (6, 7, 8) for generating a pulse width modulated (PWM) output voltage signal, a capacitor (9) arranged to filter the PWM output voltage signal; and a switching element (13) characterized in that the switching element (13) is synchronized with the PWM output voltage signal such that when the PWM output voltage signal is at a minimum, the switching element (13) isolates the capacitor (9) and so prevents the capacitor (9) from discharging. |
