초록 ▼

An automatic backlight turns on before a user hits a key, but only in dark lighting conditions. A capacitive proximity sensor detects active handling of the device and the backlight itself is used as a light sensor. The circuit requires only a single additional capacitor and three free I/O pins to i

An automatic backlight turns on before a user hits a key, but only in dark lighting conditions. A capacitive proximity sensor detects active handling of the device and the backlight itself is used as a light sensor. The circuit requires only a single additional capacitor and three free I/O pins to implement on typical microprocessor-based systems (such as remote controls). Because the system uses the current backlight LED as a sensor, devices can often be upgraded to include this feature without changing the existing packaging.

대표청구항 ▼

1. An automatic backlight, comprising: an LED coupled in series with a resistor; a micro-processor having a first I/O pin connected to the LED and a second I/O pin coupled to the resistor; means for periodically driving the LED in forward bias to emit light; means for periodically driving the

1. An automatic backlight, comprising: an LED coupled in series with a resistor; a micro-processor having a first I/O pin connected to the LED and a second I/O pin coupled to the resistor; means for periodically driving the LED in forward bias to emit light; means for periodically driving the LED in reverse bias; means for discharging the LED after driving the LED in reverse bias to measure a level of ambient light; and means for adjusting a level of the emitted light according to a level of measured ambient light. 2. The automatic backlight of claim 1 wherein the level of emitted light is on or off. 3. The automatic backlight of claim 1 further comprising: means for measuring a capacitive coupling with a user, and only driving the LED when there is a capacitive coupling with the user. 4. The automatic backlight of claim 1 further comprising: means for measuring a capacitive coupling with a user. 5. The automatic backlight of claim 4 wherein the LED is driven only when the capacitive coupling with the user exceeds a predetermined threshold. 6. The automatic backlight of claim 4 wherein a standby signal is transmitted to a controlled device when the capacitive coupling with the user exceeds a threshold. 7. A method for operating an automatic backlight, comprising: coupling an LED in series with a resistor; connecting a first I/O pin of a microprocessor to the LED and a second I/O pin to the resistor; periodically driving the LED in forward bias to emit light; periodically driving the LED in reverse bias; discharging the LED after driving the LED in reverse bias to measure a level of ambient light; and adjusting a level of the emitted light according to a level of measured ambient light.