Electricity: power supply or regulation systems – Output level responsive – Using a three or more terminal semiconductive device as the...
Patent
1990-04-21
1991-09-03
Stephan, Steven L.
Electricity: power supply or regulation systems
Output level responsive
Using a three or more terminal semiconductive device as the...
323285, 323351, G05F 1575
Patent
active
050457713
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The present invention relates to a method and device suitable for preventing transients from hampering the operation of a switching regulator (buck cell).
BACKGROUND OF INVENTION
Switching regulators based on the principle of the buck cell are known, for example, from Patent WO 84/00085 or EP/O 111 493. Such switching regulators have a power switch that opens and closes according to a predetermined pattern, whereby energy is periodically fed to a choke and through the latter both to a capacitor and a load switched in parallel thereto.
The principle of the switching regulator is very simple and its construction is sturdy. The switching regulator can, however, be damaged under extreme operating conditions, especially its power switch can be damaged. Such conditions occur primarily in the event of short-circuits at the output and during turning the regulator on. In general, the conventional switching regulator reacts too slowly and is not able to handle rapid changes, that is, so-called transients.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a simple and effective method by which the conventional switching regulator can be safeguarded against the above-described extreme operating conditions and thus protect against damage or even destruction during operation.
The proposed solution is characterized by the optimal functioning of the switching regulator under all operating conditions. Deleterious short switching intervals are completely eliminated. In addition, the excessive currents caused by transients, as well as long-lasting perturbations, are prevented from occurring.
There is more particularly provided in accordance with the present invention a method for preventing transients from damaging a switching regulator, which includes at least a switch, a recovery diode, a choke, a capacitor, comprising the steps of providing a switch control that actuates the switch throughout a continuous series of period intervals (T) of variable length for a time period (t) in each of such period intervals that is virtually constant, and determining prior to the beginning of each switch-on interval (t) whether or not the current flowing through the choke will surpass a predetermined maximum value (i.sub.max), and, in the event of such excess, holding the switch open until, at the end of the finally initiated switch-on interval (t), maximum current (i.sub.max) is reached but not exceeded.
Further, in accordance with the present invention, a circuit arrangement is provided for preventing transients from damaging a switching regulator which includes at least a switch, a recovery diode, a choke, a capacitor and a switch control for the switch, wherein the switch control includes a monostable multivibrator whose switch-on interval (t) is inversely proportional to an input voltage (e), and a voltage/frequency converter suitable for sending switch-on signals to the multivibrator. The switch control also includes a priority loop suitable for releasing the greater of any one of two given voltages (u.sub.1, u.sub.2) to said voltage/frequency converter, a controller capable of generating one of the input voltages to the priority loop by comparing prevalent actual voltage (U.sub.ist) to a reference voltage (U.sub.soll), and an emergency control unit suitable for generating the other of the input voltage (u.sub.1) to the priority loop.
For a better understanding of the present invention, reference is made to the following description and accompanying drawings while the scope of the invention will be pointed out in the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is illustrated by way of example in the accompanying drawings wherein:
FIG. 1 is a schematic circuit diagram of a buck-type regulator;
FIG. 2 is a schematic circuit diagram of a control circuit unit;
FIG. 3 is a schematic circuit diagram of an emergency control unit;
FIG. 4A is a waveform of the current in the choke following a short circuit;
FIG. 4B is a waveform of the output voltage of the regulator
REFERENCES:
patent: 3585491 (1971-06-01), Peterson
patent: 3733540 (1973-05-01), Hawkins
patent: 3736469 (1973-05-01), Baugher et al.
patent: 4712169 (1987-12-01), Albach
patent: 4719552 (1988-01-01), Albach et al.
Ascom Hasler AG
Stephan Steven L.
Sterrett Jeffrey
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