Controlling transmission power in an IrDA/RC transmitter circuit
View Patent ↗An infrared LED of an IrDA transceiver module is usable to transmit IrDA signals as well as RC control signals. When making an IrDA transmission, the IrDA LED is driven with a lower amount of current. When making an RC transmission, the IrDA LED is driven with an increased amount of current such that infrared emissions received by an RC receiver are of adequate power to be received as RC control signals. A current-limiting circuit allows more LED current to flow the longer current is allowed to flow through the IrDA LED. By controlling the durations of infrared bursts in the RC transmission, the average LED current during infrared bursts of RC transmissions is controlled. Using this technique allows the IrDA module to be used to transmit RC signals at different transmission power settings. To reduce power consumption, the minimum transmission power necessary to engage in RC communications is used.
1. A handheld infrared remote control (RC) device, the remote control device comprising:
an infrared transmitter circuit that emits an infrared remote control signal that controls an electronic consumer device, wherein the infrared transmitter circuit transmits the remote control signal to the electronic consumer device at a plurality of transmission power settings; and
a microcontroller that determines which one of the plurality of transmission power settings will be used.
2. The handheld infrared remote control (RC) device of claim 1 , wherein the infrared transmitter circuit comprises:
an infrared light emitting diode (LED);
a passive current-limiting circuit that limits an LED drive current flowing through the infrared LED to a first average current value if the remote control signal is transmitted with bursts having a shorter first duration, whereas the passive current-limiting circuit limits the LED drive current flowing to a second average current value if the remote control signal is retransmitted with bursts having a longer second duration; and
a switch for switching the LED drive current on and off.
3. The handheld infrared remote control (RC) device of claim 2 , wherein the remote control signal has a lower transmission power setting when transmitted with bursts having the shorter first duration and has a higher transmission power setting when retransmitted with bursts having the longer second duration.
4. The handheld infrared remote control (RC) device of claim 1 , wherein the remote control signal has bursts of infrared energy, wherein each of the bursts has a burst duration, and wherein the microcontroller changes the transmission power setting at which the bursts of the remote control signal are transmitted by changing the burst duration.
5. The handheld infrared remote control (RC) device of claim 1 , wherein the handheld infrared RC device does not have an IrDA communication capability.
6. A method, comprising:
(a) transmitting an infrared remote control (RC) signal that includes a plurality of infrared bursts from an infrared light emitting diode (LED) of a remote control device during a key press condition using a first transmission power setting; and
(b) determining that the key press condition has exceeded a predetermined duration, and in response to said determining changing a burst duration to change the transmission power setting to a second transmission power setting, wherein the second transmission power setting is a higher transmission power setting than the first transmission power setting.
7. The method of claim 6 , wherein the changing of the transmission power setting in (b) involves increasing the burst duration.
8. The method of claim 6 , wherein both the first transmission power setting and the second transmission power setting are sufficient to communicate the RC signal from the remote control device to an electronic consumer device.
9. The method of claim 6 , wherein the first transmission power setting is achieved by limiting an LED drive current that flows through the LED by using an inductor.
10. The method of claim 9 , wherein the inductor does not saturate when the LED drive current flows through the inductor during the second transmission power setting.
11. The method of claim 6 , wherein the remote control device does not have an IrDA communication capability.
12. The method of claim 6 , wherein the first transmission power setting is insufficient to communicate the RC signal from the remote control device to an electronic consumer device, and wherein the second transmission power setting is sufficient to communicate the RC signal from the remote control device to the electronic consumer device.
13. A handheld infrared remote control device, the remote control device comprising:
an infrared light emitting diode (LED) through which a burst of LED drive current flows;
an infrared transmitter that emits an infrared remote control signal that controls an electronic consumer device, wherein the infrared transmitter transmits the remote control signal to the electronic consumer device at a plurality of transmission power settings; and
a microcontroller that selects at which of the plurality of transmission power settings the remote control signal is emitted by selecting how long the burst of LED drive current flows through the infrared LED.
14. The handheld infrared remote control device of claim 13 , wherein the plurality of transmission power settings at which the remote control signal is transmitted includes a first power setting in which the burst of LED drive current flows through the infrared LED during a longer first duration and a second power setting in which the burst of LED drive current flows through the infrared LED during a shorter second duration, and wherein the burst of LED drive current during the shorter second duration is sufficient to communicate the remote control signal from the remote control device to the electronic consumer device.
15. The handheld infrared remote control device of claim 13 , wherein the plurality of transmission power settings at which the remote control signal is transmitted includes a first power setting in which the burst of LED drive current flows through the infrared LED during a longer first duration and a second power setting in which the burst of LED drive current flows through the infrared LED during a shorter second duration, and wherein both the first power setting and the second power setting are sufficient to communicate the remote control signal from the remote control device to the electronic consumer device.
16. The handheld infrared remote control device of claim 13 , wherein the microcontroller includes a switch that is conductive during a mark time of the remote control signal.