Electricity: power supply or regulation systems – Input level responsive – Using a linearly acting final control device
Patent
1997-10-03
1999-05-04
Wong, Peter S.
Electricity: power supply or regulation systems
Input level responsive
Using a linearly acting final control device
323273, 307 44, 307 60, G05F 500, G05F 140, H02J 110, H02J 104
Patent
active
059007249
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The method relates to the parallel connection of power supplies.
2. Description of the Related Art
In order to achieve a tolerance to power drop, it has been found that parallel connection of a plurality of identically designed power supplies is expedient in power supply units. In order to achieve a longer life, it is necessary in this case to ensure that, in normal operation, the two power supplies contribute approximately the same proportion and are thus also loaded with only half the load (in the case of two power supplies).
To this end, a method is disclosed in German Patent Specification DE 33 20 885 C2, in which an additional cable is used, by means of which the power supply units regulate their output voltage to a small extent, so that the proportions are approximately equal.
However, this additional cable is not always available, particularly when parallel connection is intended to be carried out in existing wiring.
SUMMARY OF THE INVENTION
An object of the present invention is thus to connect power supplies in parallel in such a manner that they supply approximately equal proportions of the load and, apart from the necessarily connected input cables of the primary supply and the output cables, have no further connections.
This and other objects and advantages of the invention achieved in that an output characteristic is produced which has a small but defined voltage drop at half (or the envisaged proportion) of the maximum output load.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings,
FIG. 1 shows an schematic circuit diagram for the voltage supply according to the invention,
FIG. 2 shows an schematic circuit diagram for use in the invention in a switch-mode power supply,
FIG. 3 shows a graph of an output characteristics of the circuit according to FIG. 1,
FIG. 4 shows the resultant overall characteristic.
FIG. 5 is a schematic block diagram of two power supplies connected in parallel to a load.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an schematic circuit for a voltage supply which allows parallel connection. An unregulated DC voltage Ubatt is used as the source of the supply, and is regulated by any desired control element, this being illustrated here for the sake of clarity as a transistor Q1, and is provided as Uout. This control element Q1 is controlled by an operational amplifier U1B, which mainly compares the output voltage Uout across the load with a reference voltage Uref and, in the form of a linear regulator, minimizes the error between the output voltage Uout and the reference voltage Uref. The output voltage Uout is applied, via a resistor R4, to the inverted input. The input current of the amplifier U1B does not cause any significant voltage drop across the resistor R4.
A current measuring resistor R2 is connected in the supply line to the control element T1. The voltage dropped across it is a direct measure of the current which the circuit supplies to the load. For explanation purposes only, it is assumed that the maximum current is 10 A and the reference current 5 A, that is to say that two current supplies, each providing 5 A, supply a load current of 10 A. Thus, in the desired normal case, the intention is that a current of 5 A will flow through the current measuring resistor R2, and a voltage of 0.1V will thus be dropped across it. This voltage across the resistor R2 is applied, via the resistor R3, to the inverting input of a second operational amplifier 1 A. The normal measures, known to the person skilled in the art, for suppressing oscillations, for example by frequency compensation, are not illustrated.
A comparison voltage is applied to the non-inverted input of the second amplifier U1A, this comparison voltage having been obtained by voltage division by means of the resistors R1 and R6 from the supply voltage Ubatt and, in the present example, being equal to the nominal voltage of 0.1V across the current measuring resistor R2. If the current through the current measuring resistor R2 is less than th
REFERENCES:
patent: 3521150 (1970-07-01), Bates
patent: 4476399 (1984-10-01), Yoshida et al.
patent: 4580090 (1986-04-01), Bailey et al.
patent: 4611162 (1986-09-01), Erratico et al.
patent: 5570004 (1996-10-01), Shibata
Pollmeier Werner
Weidner Ernst
Siemens Nixdorf Informationssysteme Aktiengesellschaft
Vu Bao Q.
Wong Peter S.
LandOfFree
Method of splitting a power supply does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of splitting a power supply, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of splitting a power supply will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1871611