Miscellaneous active electrical nonlinear devices – circuits – and – External effect – Temperature
Reexamination Certificate
1997-11-07
2001-05-29
Callahan, Timothy P. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
External effect
Temperature
C327S540000, C379S412000
Reexamination Certificate
active
06239648
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method and a device for diverting waste power in an electric device.
STATE OF THE ART
When connecting for example an electric circuit with a variable load, problems can occur with overheating of certain of the constituent components in the electric circuit. This problem is known and a number of technical solutions have been developed in order to take care of this.
In many solutions it is accepted that waste power occurs in the circuit. Other solutions use a DC/DC-converter for each load, the output voltage of which is continually controlled in order to be adapted according to the actual load. Another alternative is, if there is access to two or more supply voltages in the circuit, to reduce the waste power in the circuit through switching between them for the lowest adequate supply voltage for the occasion, which is described in SE Patent 9403876-7.
U.S. Pat. No. 5,428,682 describes a technique for conducting away heat in a telephone circuit. This consists of two line supply amplifiers, one for each exiting telephone line, which outputs are connected to earth respectively the supply voltage by a pair of switches and two external resistances. The switches permit a pole reversal of a DC-supply to the telephone line. In the external resistances the undesired heat can be given off and the heat generation in the telephone circuit remains at an acceptable level.
SE Patent 8003419-2 describes a technique with connection of an external resistance for heat diversion, which resembles greatly the technique in the above mentioned U.S. Pat. No. 5,428,682.
GB Patent 2 050 115 A describes a technique where a resistance is connected into the final stage of an amplifier which has a certain output line current. The generated power in the final stage transistors is reduced through a part of the output line current passing through the resistance, and in this way the generated heat in the final stage is held at an acceptable level.
FR Patent 2 690 537 describes a technique where a current regulator in a line supply circuit limits an output current through the connection of a resistance.
DISCLOSURE OF THE INVENTION
A circuit, for example a line circuit comprising a final stage and a voltage regulator, which is to drive a balanced two-wire transmission with both an AC-signal and a DC-current, has a DC-supply characteristic which means that the line voltage and the DC-current is a function of a combined resistance in the line and load of the circuit. With the line open, the line is supplied with the maximal line voltage at the same time as the DC-current is zero, and furthermore the final stage of the circuit must have access to a drive voltage which is somewhat greater than the required line voltage. The drive voltage is obtained from the output of the voltage regulator which in turn is supplied from the drive voltage of the circuit.
When the line is loaded the line voltage will drop and the DC-current will rise depending on the resistance of the line and the load and on the supply characteristic of the line circuit. A so-called regulator voltage, which is the difference between the supply voltage of the circuit and the drive voltage of the final stage, is generated in this case over the voltage regulator at the same time as the DC-current flows through it, which leads to an undesirable power generation in the voltage regulator.
The undesired power generation can be difficult to lead away so that the temperature of the circuit is held at a safe level.
The power generation in the circuit, more closely defined that over the voltage regulator, is greatest in short lines, i.e. when the total resistance of the line and the load has a low value, as both the regulator voltage and the DC-current through the voltage regulator are large.
The present invention tackles a problem with diverting waste power in a circuit through emitting it in an outer component.
Another problem is to obtain the above described function with the smallest possible interference in an existing circuit.
The object of the present invention is, through diverting a part of the waste power of a circuit to an outer component, to increase the life length of the circuit and to reduce its thermal effects.
The above problem is solved through connecting an external component, e.g. a resistance, in parallel with the voltage regulator of the circuit, which leads to that all or part of the waste power of the circuit being emitted in the external component.
An electric device, e.g. a subscriber line circuit, comprises a user with a variable voltage requirement and a voltage-regulating circuit, e.g. a voltage regulator. The voltage requirement of the user is fed back via a reference signal to an input on the voltage regulator, which supplies the user with a drive voltage adapted to the value of the reference signal. Over the voltage regulator there is formed a voltage drop from the difference between the drive voltage and the supply voltage of the circuit. The size of the voltage drop depends on the value of the varying drive voltage. When the voltage regulator is connected in parallel with an external component, e.g. a resistance, the electric circuit is relieved when all or part of the user's supply current is led to the external resistance and then all or part of the waste power of the voltage regulator is emitted.
An advantage of the suggested invention is that only one resistance is required in order to take care of waste power in the circuit. Another advantage is that there is no longer need for any switches for pole reversing of the DC-supply of the two-wire transmission.
Yet another advantage is that the invention is easy to implement without large changes to an already existing circuit solution.
The invention will now be described more closely with the help of the preferred embodiment and with reference to the appended drawing.
REFERENCES:
patent: 4150411 (1979-04-01), Howell
patent: 4800589 (1989-01-01), Siligoni et al.
patent: 5381113 (1995-01-01), Kimura
patent: 5428682 (1995-06-01), Apfel
patent: 5475323 (1995-12-01), Harris et al.
patent: 5519775 (1996-05-01), Lagana et al.
patent: 5596637 (1997-01-01), Pasetti et al.
patent: 5929616 (1999-07-01), Perraud et al.
patent: 0 622 943 A1 (1994-11-01), None
patent: 2 690 537 (1993-10-01), None
patent: 2 050 115 (1980-12-01), None
patent: 446 798 (1980-12-01), None
patent: 503 646 (1996-07-01), None
Emericks Anders
Hellberg Henrik
Israelsson Mattias
Malmgren Carl-Henrik
Burns Doane Swecker & Mathis L.L.P.
Callahan Timothy P.
Englund Terry L.
Telefonaktiebolaget LM Ericsson (publ)
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