Field of the Invention
The invention relates to an electronic device having an operating mode and an energy saving standby mode, and to a method for switching between the two modes.
The field of the present invention preferably covers receivers and transmitter/receivers (transceivers) that are supplied with voltage by a battery. Devices and methods for energy saving are used to prevent the batteries in these appliances from quickly becoming dead or empty. In order to save electrical energy in states in which there is no need for the electronic device to be operated, this appliance can be switched from a normal operating mode to an energy saving standby mode. In this case, all those parts of the appliance that result in a high current draw are generally switched off. The only parts that remain active are those used for switching back to the operating mode. This switching-back process is generally carried out automatically by identifying a valid external signal. This drastically reduces the overall current draw of the electronic device. Since, in the case of battery-powered electronic devices, the time in the standby mode is generally many times longer than the time in the operating mode, it is desirable for the appliance to have a very sparing current draw in the standby mode, in order to maximize the useful life of the battery.
An electronic device of this generic type is known from Issued European Patent EP 0 554 386 B1. The receiver includes an input-side antenna element for receiving a signal carrying information, in this case in the form of an RF (radio frequency) radio signal.
For the purposes of the present invention, the term antenna element is defined as an input-side element of the electronic device, which converts radiation energy to energy carried by cables for the receiving unit. In principle, radiowaves, microwaves, lightwaves or waves in some other frequency spectrum that is suitable for transporting information can be received by the antenna element as radiation energy. By way of example, the “antenna element” may thus also be a photoelement in order to receive lightwaves. If energy supplied by cables is already available on the input side, then it may even be possible to dispense entirely with the antenna element, replacing it by a suitable interface—for example by a socket arrangement.
In the case of the present receiver, a receiving unit that is connected downstream from the antenna element has a demodulator for recovering the AF (audio frequency) radio signal as basic information that has been modulated on the RF signal in accordance with the modulation method used at the transmitter end. An optical indication for the operating parameters, various control elements for manually adjusting the receiver, as well as a loudspeaker for emitting the AF radio signal are controlled by a central controller, which controls their interaction. A battery is provided as the voltage supply unit for providing the supply voltage required for operating the receiver. In order to achieve a long battery life, the receiver has an operating mode and a standby mode. Switching devices for switching between the two modes are integrated into the central controller.
Switching from the operating mode to the standby mode is carried out automatically when a noise switching-off signal is present. In the standby mode, the receiver is not ready to operate. The system is woken up from the standby mode by periodically switching on the operating mode at defined time intervals. A timer, whose time consumption is as low as possible, runs in the standby mode for this purpose. When the receiver is ready to operate, the controller thus very quickly checks whether a valid RF radio signal is being received on the input side. If a noise switching-off signal is present instead of this, then the receiver returns to the standby mode again. This method has the disadvantage that the process of switching on the operating mode on a sample, time-controlled basis, which is often unsuccessful, results in quite a high current draw. Attempts have been made to minimize the current draw by identifying the presence of a signal on the input side as quickly as possible, in order to make it possible to return to the energy saving standby mode as quickly as possible where necessary. With this method, when information is not transmitted continuously, that is to say it is transmitted in a pulsed form, it is still possible for a problem to occur when the transmitter is transmitting during a time in which the receiver is not ready to operate, so that the receiver cannot reliably receive the signal carrying the information. In order to preclude this problem, it is necessary either for the transmitter to transmit for a long enough period, or for the time intervals between the waking-up processes to be matched to the transmitted pulse length.
A method for waking up from the standby mode is also generally known, in which the problems discussed above are avoided by ensuring that the electronic device is ready to operate all of the time, despite being in a standby mode with restricted functionality. In this case, circuit components whose current draw is high are switched off in the standby mode. The only circuit components which are kept in operation are those which are used for monitoring the status of devices on the input side, such as receivers, sensors, detectors. In this way, it is possible to confirm when there is once again a requirement to switch on the other circuit components whose current draw is high, in order to initiate the process of waking up from the standby mode to the operating mode.
By way of example, the receiver sensitivity can be reduced in the standby mode. The receiver can then distinguish only roughly between the system's own signals and external signals, but draws less current in the process. As soon as a signal arrives which overrides the selection to maintain the standby mode, the receiver changes fully or partially to the operating mode in order to check the validity of the signal. In comparison with the method described initially, the transmitter may admittedly transmit signals in a pulse manner in this method; however, since it is necessary for the circuit components to be permanently active, the current draw is generally greater. In this case, owing to the reduced sensitivity, it is also difficult to distinguish between disturbances and the system's own signals, which leads to spurious changes to the operating mode. This results in a disadvantageous increase in the energy consumption.