Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
1998-12-17
2001-12-11
Chang, Vivian (Department: 2682)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C455S343200, C455S572000
Reexamination Certificate
active
06330463
ABSTRACT:
CROSS-REFERENCE TO THE INVENTION
Not Applicable
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a voltage supply apparatus, in particular for a radio telephone in a motor vehicle.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 AND 1.98
A radio telephone which is permanently installed in a motor vehicle is normally supplied with power from the vehicle electrical system. It is thus connected to the vehicle electrical system such that the operating current for the radio telephone is supplied from the vehicle battery or from the generator, depending on the operating state of the vehicle electrical system. In this case, the supply voltage or supply voltages for the radio telephone, that is to say for the transmission radio-frequency amplifier and the rest of the telephone electronics, is or are taken from an appropriate power supply unit or a voltage matching circuit, on which the vehicle electrical system voltage from about 10 V to 16 V, if the rated voltage is 12 V, is present.
If the connection between the radio telephone and the vehicle electrical system is interrupted or if the vehicle battery is disconnected from the vehicle electrical system, then the voltage supply for the radio telephone thus fails, and telephoning is no longer possible.
Particularly if the vehicle electrical system fails as a result of an accident, in which the vehicle battery is ripped out or destroyed, it is desirable for the radio telephone still to be operable, at least for a certain time, in order to make an emergency call.
Proceeding from this, the invention is based on the object of providing a voltage supply apparatus for a radio telephone, in particular in a motor vehicle, which still allows telephone calls to be made, at least for a certain time, even in the event of failure of a main voltage source.
BRIEF SUMMARY OF THE INVENTION
This object is achieved by the voltage supply apparatus according to claim
1
.
Thus, according to the invention, a main voltage source and an auxiliary voltage source are provided for a voltage supply apparatus, in particular for a voltage supply apparatus for a radio telephone, the auxiliary voltage source being disconnected from the rest of the circuit by means of a switch during normal operation, so that it makes no contribution to the voltage supply. In order to ensure uninterrupted operation of the radio telephone in the event of failure of the main voltage source, a voltage monitoring circuit is provided which monitors the voltage supplied by the main voltage source and, if this fails, that is to say if it falls below a predetermined value, causes the auxiliary voltage source to be connected in order to supply voltage.
It is particularly advantageous in this case if the voltage matching circuit comprises a first voltage converter which outputs a first supply voltage at its output, and a second voltage converter which supplies a second supply voltage which is less than the first supply voltage, the output of the first voltage converter being connected to the input of the second voltage converter, in order to simplify the circuit.
Thus, according to the invention, the voltage supplied by the main voltage source or, possibly, by the auxiliary voltage source is initially used to derive from said voltage a first, relatively high supply voltage which is used in particular to supply the transmission radio-frequency amplifier and from which a second, relatively low supply voltage is preferably derived for the rest of the telephone electronics.
A development of the invention preferably provides for the first voltage converter to have a voltage-raising circuit in addition to a filter circuit. In this case, in order to allow even batteries with a relatively low output voltage to be used, in particular, for the auxiliary voltage source, which is intended for emergencies, the auxiliary voltage source can be connected via the controllable switch to the input of the voltage matching circuit. This therefore makes it possible to use a battery whose output voltage is, for example, 5 V, preferably a non-rechargeable primary cell, as the auxiliary voltage source, even if the voltage supply apparatus according to the invention is used in a motor vehicle having a vehicle electrical system with a rated voltage of 12 V.
The use of primary cells has the advantage that they have a high energy density, that is to say occupy little space, and at the same time are mechanically very robust in comparison with a vehicle battery, normally a lead-acid accumulator, so that, even in an emergency, for example in the event of a dangerous vehicle impact in an accident, they are not damaged and thus have high operational reliability. Furthermore, primary cells, such as LiMnO
2
batteries, have a low self-discharge rate, so that they remain serviceable even over a period of several years.
According to a further refinement of the invention, it is also expediently possible to provide the capability for the auxiliary voltage source to be connected via the controllable switch to one input of the second voltage converter of the voltage matching circuit. This refinement is particularly expedient if the auxiliary voltage source is an emergency battery which supplies a relatively high voltage, for example a no-load voltage of 18 V, since the auxiliary voltage source in this arrangement is not additionally loaded by the first voltage converter during emergency operation.
In order to ensure continuous operation of the radio telephone even while switching over from the main voltage source to the auxiliary voltage source, and in particular to an auxiliary voltage source with a lower voltage than that of the main voltage source, the invention provides for the voltage-raising circuit to be controllable as a function of the voltage of the main voltage source when the radio telephone is switched on or when the ignition is switched on. This makes it possible for the voltage-raising circuit to be switched on even before the auxiliary voltage source is switched on, while the main voltage source is still supplying a voltage whose value is, however, less than the minimum value of the first supply voltage.
A drop in the voltage supplied by the main voltage source also occurs, for example, if the main voltage source is destroyed or is at least disconnected from the vehicle electrical system, and thus also from the input of the voltage matching circuit. The voltage-raising circuit, which is required when the radio telephone is being operated by means of the auxiliary voltage source, prevents an interruption in the voltage supply for the radio telephone.
The voltage supply apparatus operates particularly reliably if the voltage-raising circuit has a control input which is connected to the output of the first voltage converter, in order to keep the supply voltage at a stabilized value independently of the voltage which is present at the input.
When the voltage supply apparatus according to the invention is used for a radio telephone in a motor vehicle, to ensure that the telephone electronics in the radio telephone, excluding the radio-frequency amplifier, are continuously supplied with voltage without unnecessarily loading the connecting voltage sources, the invention provides for the second voltage converter to comprise a first, continuously operating, voltage-reducing circuit and, in parallel with this, a second voltage-reducing circuit, which can be switched on and off, the first voltage-reducing circuit being a linear regulator and the second voltage-reducing circuit being a DC/DC voltage converter, which is switched on whenever the ignition and/or the radio telephone are/is switched on.
Thus, in the situation when the ignition and the radio telephone are switched off, the voltage is supplied entirely via a linear regulator, which is preferably designed as an integrated transistor circuit, while, when the radio telephone is switched on and/or the ignition is switched on, the voltage supply for the telephone electronics is ensured by a DC/DC voltage conver
Chang Vivian
Nokia Mobile Phones Limited
Perman & Green LLP
Ramos-Feliciano Eliseo
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