DE3820624A1 - Device for supplying power to equipment - Google Patents

Abstract

The invention relates to an ancillary telephone equipment power supply from the telephone line, comprising an energy converter and a start-up circuit which are inserted into the current loop of the telephone line, two switching elements which, in the inactive condition, have a high forward resistance in one current flow direction and a low forward resistance in the opposite current flow direction but which can be switched through in the active condition being connected in series in the opposite direction in one current path and the voltage supply (UV) being extractable at the connection point of these controllable switching elements and at the connection point of two diodes whose other terminal is connected to the input or output of the looped-in power supply.

Description

The invention relates to a device for energy supply of devices by drawing current from the current loop of a Communication line into which an energy converter is inserted is.

Additional devices for telephone connections, e.g. automatic Changeover switches (so-called AWADO) or fee counters become very often trained to ge from the telephone line are fed and therefore on an external supply via a network connecting devices or batteries.

A parallel supply of the additional devices from the telecommunications Final line is problematic because, on the one hand, at rest due to connection conditions of private telephone companies companies or public postal administrations (especially the German Bundespost) for this purpose only an extremely small one Electricity may be drawn from the telephone line network or on the other hand the activation criterion, e.g. "Loop current flows "or" fork switch operated ", very often missing.

For example, the one specified by the Deutsche Bundespost Conditions for a current draw from a telecommunications connection Conditions specified in the loop are:

• a) Increased resistance of the loop 20 ohms, newer thing 10 ohms in the loop current range, one Loop current from 17 to 60 mA a voltage drop from 0.34 to 1.2 V (at 20 ohms) or 0.17 to 0.6 V (at 10 ohms);
• b) functions independent of polarity;  
• c) Resistance between the wires ( 1 a ) and ( 1 b ) of the telecommunication connection cable 6M ohms.

The previously common power supply circuits for additional telephony devices from the current loop of a Fernmeldean connection line can not yet meet the above-mentioned conditions of the German Bundespost, such as those in the "Auxiliary Book for Interference Suppressors", published by Verlag für Wissenschaft und Leben, Georg Heidecker, Bad Winzheim / Mittel Franconia, 1977, p. 508, shown and described circuit of the header fee indicator 68 v shows. In this 16 kHz meter, as shown in FIG. 5, the circuit around the rectifier bridge ( Gr 1 ) and the switching transistor ( T 3 ) forms an energy converter which is fed by the loop current, but which is not able to meet the above condition ( a ) to be met. This can easily be seen from the fact that the operation of the circuit requires at least 2 diode forward voltages and a base-emitter voltage. This means that depending on the technology used (silicon, silicon Schottky, germanium) of the semiconductor components mentioned, the operating voltage must exceed approximately 2.1 V to 0.6 V before energy can be converted at all. The loop resistance introduced at a loop current of 17 mA is therefore higher than 123 ohms or 35 ohms, which, for example, clearly exceeds the above-mentioned condition of the Deutsche Bundespost for increasing the resistance of the loop by 20 or 10 ohms.

The invention has therefore set itself the task Specify power supply solution for telephone accessories, which the energy for the operation of the additional circuits takes from the loop current of the telecommunication connection line and nevertheless, the very difficult to implement demands Coordinated postal administrations, especially the German Confederation post, met.  

This object of the invention is achieved by the main claim specified characteristics.

The use of the properties of a MOS-FET transistor as active element in a converter circuit saves under the Be conditions of the input voltage less than diode passage voltage the rectifier bridge and solves for the first time ever and, in addition, the postal code in a very economical way conditions.

Advantageous refinements and developments of the counter state of the invention can be found in the dependent claims.

The advantage of the present invention is thus achieved that telephone accessories from the loop current of the official battery can be fed remotely without the aforementioned restrictive regulations of the telecommunications network operator violated will.

In the following the invention with reference to drawings explained embodiment described in more detail. It shows

Fig. 1 is a block diagram for illustrating the principle of the invention,

Fig. 2 and 3 are block diagrams illustrating the operation of the invention in opposite flow directions of the loop current,

Fig. 4 is an illustration of a circuit arrangement practical embodiment of the invention,

Fig. 5 shows the circuit of a telephone apparatus and

Fig. 6 is an illustration of the circuit of a known telephone accessory (17 kHz charge indicator).

In the circuit arrangement shown in Fig. 1, the energy required for the operation of a telephone auxiliary device is taken from the loop current of the telecommunication line ( 1 b ). It could just as well be taken from line ( 1 a ).

An energy converter ( 1 ) and two MOS-FET transistors ( 2 and 3 ) of the enrichment type, each provided with integrated diodes, are connected in series in the line ( 1 b ). If, for example, by lifting the handset of a connected telephone set, for example the telephone set shown in Fig. 5, the line ( 1 a '') with the line ( 1 a ') and the line ( 1 b '') with the line ( 1 b ') is connected, the hook switch ( U ) in Fig. 5 is closed, then a loop current begins to flow. In the first moment, the transistors ( 2 and 3 ; Fig. 1) are conductive, and the energy converter ( 1 ) represents a very low resistance. Depending on the current direction, one of the diodes integrated with the transistor ( 2 or 3 ) conducts, and each other transistor blocks.

In the direction of the loop current shown in FIG. 2, the loop current ( IS ) charges a storage capacitor ( 6 ) via a diode ( 4 ) when transistor ( 3 ) is conductive and transistor ( 2 ) is blocked. The capacitor ( 6 ) is charged until the voltage ( UV ) has reached the value required for the operation of a control circuit ( 7 ), for example 3 or 5 V. This will typically be the case after fractions of a second. During this extremely short period of time, the circuit has a higher resistance than the required 10 to 20 ohms. However, this is permitted for the short switch-on torque.

If the loop current ( IS ) flows in the other direction, as shown in Fig. 3, then with a conductive transistor ( 2 ) and a blocked transistor ( 3 ) the capacitor ( 6 ) is charged via the diode ( 5 ) . It is charged again until the operating voltage ( UV ) of the control circuit ( 7 ) has reached 3 or 5 V. Since, in this case, too, analogously to the case described above, the additional loop resistance was greater than 10 to 20 ohms, again no problems arise because of the short duration of this state.

When the control circuit ( 7 ) starts operating by reaching its operating voltage ( UV ) of 3 to 5 V, it controls the transistor ( 3 ) into a conductive state by means of a signal on line ( 9 ) and transmits it via line ( 8 ) to the transistor ( 2 ) a square wave signal with a frequency suitable for the operation of the energy converter ( 1 ), which can usually be between 10 and 100 kHz. The energy converter ( 1 ) now feeds the control circuit ( 7 ) via the line ( 11 ), the storage capacitor ( 6 ) having to be dimensioned in such a way that it peaks in the current of the auxiliary telephone device or brief interruptions in the loop, for example through the dialing impulses of the number plate by means of the pulse contact ( nsi ) in the telephony apparatus according to FIG. 5.

As transistors ( 2 and 3 ) MOS-FET transistors of the on-type fuse with very low forward resistances are used, so that a large proportion of the energy taken from the loop is available for the conversion and supply of the control circuit and thus the additional telephone function. The proper function of the energy conversion in both current directions is achieved by the bipolarity and low operating voltage of the MOS-FET transistors. To suppress disturbing effects of voltages of the converter frequency and their harmonic African on the phone line, an interference filter ( 10 ) can be connected in parallel to the series circuit of energy converter ( 1 ) and transistor ( 2 ).

Fig. 4 now shows a practical embodiment of the energy converter circuit, which uses a transformer ( 110 ) designed for a converter frequency of 25 kHz as the energy converter. Together with the rectifier diodes ( 111 and 112 ), it forms a power supply with full-wave rectification for the control circuit ( 170 ). The diodes ( 140 and 150 ), which correspond to the diodes ( 4 and 5 ) in FIGS. 1 to 3, serve to charge the storage capacitor ( 160 ) at startup, which is the storage capacitor ( 6 ) in FIGS. 1 to 3 corresponds and has the task of absorbing both short-term current demand peaks of the connected auxiliary telephone device and short loop interruptions.

The control circuit ( 170 ) contains a microprocessor (not shown) which, in addition to its usual functions and specific applications, activates the transistor ( 130 ) after its activation, ie after the start-up process has ended. The converter control voltage, preferably a square-wave voltage of 25 kHz, is made available by the clock of the microprocessor according to frequency division known per se.

Claims (8)

1. Energy converter, which voltages of either polarity and having an amplitude smaller than usual Diodendurchlaß voltages into voltages for the power supply of devices converts, characterized in that in series to a known energy converter (1) comprises two MOS FET transistors (2 3 ) are connected with integrated diodes, very low operating voltage and with low forward and high blocking resistance. 2. Device for supplying energy to devices by drawing current from the current loop of a communication line into which an energy converter according to claim 1 is inserted, characterized in that in a line (eg 1 a or 1 b ) the energy converter ( 1 ) and a Start-up circuit ( 2 to 6 ) are looped in, the latter having two switching elements ( 2 , 3 ) connected in series in the current path and controllable in the active state, which in the inactive state have a high forward resistance in one current direction and a low in the opposite direction, whereby at the connection point ( V 1 ) of the controllable switching elements and at the connection point ( V 2 ) two diodes ( 4 , 5 ), of which one ( 4 ) with its other connection ( V 3 ) with the input (e.g. 1 b ) the looped device and the other ( 5 ) with its other connection ( V 4 ) with the output (z. B. 1 b ' ) of the looped device is connected, the supply voltage ( UV ) f is removable for the device. 3. Device according to claim 1 and / or 2, characterized in that the device in the inactive state (for example during startup) in a current direction ( IS ) has a low and in the other current direction (- IS ) has a high forward resistance. 4. Device according to one or more of claims 1 to 3, characterized in that the controllable switching elements ( 2 , 3 ) after exceeding a predetermined value (eg 3 or 5 V) of the supply voltage ( UV ) in a low-resistance state in both current directions be switched. 5. Device according to one or more of claims 1 to 4, characterized in that the supply voltage ( UV ) by means of a capacitor ( 6 ) between the connection points ( V 1 , V 2 ) of the diodes ( 4 , 5 ) and the controllable switching elements ( 2 , 3 ) is switched, is smoothed. 6. Device according to one or more of claims 1 to 5, characterized in that a control circuit ( 7 ) is provided which is fed by the supply voltage ( UV ) and generates the control signals for the controllable switching elements ( 2 , 3 ) and via control lines ( 8 , 9 ) applies electrodes to their control. 7. Device according to one or more of claims 1 to 6, characterized in that a known energy converter with self-excitation is used as the energy converter ( 1 ). 8. Device according to one or more of claims 1 to 6, characterized in that the energy converter ( 1 ) is used with external excitation, the excitation voltage is a square wave voltage of a certain frequency, preferably 25 kHz, by frequency division from the clock Control of a microprocessor in the controller ( 7 ) is generated.