Circuit configuration for controlling the transmitting power of a battery-operated transceiver
View Patent ↗A circuit configuration is provided for controlling the transmitting power of a battery-operated transceiver. A high transmitting power of a mobile transceiver generates a high voltage drop across an internal impedance of the battery which can lead to the device switching off. A reduction in the transmitting power in dependence on the battery voltage is therefore proposed. The battery voltage is thus compared with a reference voltage and a signal representing a nominal transmitting power is correspondingly corrected. The circuit can be integrated in a simple manner with analog components in an IC.
1. A circuit configuration for controlling the transmitting power of a battery-operated transceiver, the circuit configuration comprising:
a battery for providing a supply voltage;
a power stage for controllable amplification of a radio-frequency signal, said power stage having a gain;
a comparison device, said comparison device having an input side for receiving a reference signal and a signal coupled to the supply voltage, said comparison device having an output aide for supplying a difference signal, said comparison device:
outputting the difference signal with a zero-amplitude, when an amplitude of the signal coupled to the supply voltage is above an amplitude of the reference signal;
outputting the difference signal with an amplitude different from the zero-amplitude of the difference signal in the positive direction, when the amplitude of the signal coupled to the supply voltage lies below the amplitude of the reference signal;
a control device for controlling the gain of said power stage in dependence on the difference signal; and
a digitally operating functional unit supplied by the supply voltage, said functional unit generating a switching-off signal in dependence on the supply voltage for switching off the transceiver.
2. The circuit configuration according to claim 1 , wherein said control device includes a logic element for generating a difference between the difference signal and a further reference signal, said logic element having an output for supplying a control signal to be supplied to said power stage for controlling the gain of said power stage.
3. The circuit configuration according to claim 1 , including a voltage divider having an input side connected between terminals for the supply voltage and an output side connected to an input of said comparison device.
4. The circuit configuration according to claim 2 , wherein said control device includes a measuring device for measuring power of a signal output by said power stage and a further comparison device, said further comparison device having an input side coupled to an output of said measuring device and to the output of maid logic element, and said further comparison device having an output side for supplying the control signal for controlling power of said power stage.
5. The circuit configuration according to claim 4 , wherein said measuring device includes a directional coupler having a coupling element coupled to an output of said power stage, an element connected to said coupling element for detecting a radio-frequency amplitude, and a resistor connected between said coupling element and an input of said further comparison device.
6. The circuit configuration according to claim 5 , wherein said coupling element detects a wave moving away from said power stage and has a gate, and said element detecting the radio-frequency amplitude is a Schottky diode connected to the gate of said coupling element.
7. A circuit configuration for controlling the transmitting power of a battery-operated transceiver in a mobile telephone for operation in a cellular telephone network, the circuit configuration comprising:
a battery for providing a supply voltage;
a power stage for controllable amplification of a radio-frequency signal, said power stage having a gain;
a comparison device, said comparison device having an input side for receiving a reference signal and a signal coupled to the supply voltage, and said comparison device having an output side for supplying a difference signal, said comparison device:
outputting the difference signal with a zero-amplitude, when an amplitude of the signal coupled to the supply voltage is above an amplitude of the reference signal;
outputting the difference signal with an amplitude different from the zero-amplitude of the difference signal in the positive direction, when the amplitude of the signal coupled to the supply voltage lies below the amplitude of the reference signal;
a control device for controlling the gain of said power stage in dependence on the difference signal; and
a digitally operating functional unit supplied by the supply voltage, said functional unit generating a switching-off signal in dependence on the supply voltage for switching off the transceiver.