Electricity: power supply or regulation systems – Output level responsive – Using a three or more terminal semiconductive device as the...
Patent
1991-09-09
1993-03-09
Stephan, Steven L.
Electricity: power supply or regulation systems
Output level responsive
Using a three or more terminal semiconductive device as the...
323282, G05F 140
Patent
active
051929066
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a method according to the and arrangement for a switching regulator.
Such a switching regulator is disclosed in Electronics, Nov. 8, 1971, Vol. 44, No. 23, page 79.
Switching regulator are often equipped with current limiting devices which switch off the switching regulator actuator if the load currents are too high, see, for example, DE 3,402,479.A1. In the switching regulator according to DE 3,402,479.A1 a voltage corresponding to the load current is formed in the load circuit and rots in a controlling manner on the pulse frequency modulator. In the switching regulator according to EP 27,847.A1 a signal is picked up which is a function of the current through the actuator and this signal is employed together with a signal that is proportional to the load current to control the pulse width modulator.
SUMMARY OF THE INVENTION
In the switching regulator according to Electronics, see above, a current limiting device is provided which detects the current through the actuator and blocks the actuator by way of a control input of the pulse width modulator if an actual current value signal derived from the current through the actuator exceeds a reference value that serves as current limiting value.
U.S. Pat. No. 4,771,357 discloses a driver circuit for a switching transistor including current limiting means. However, this arrangement does not operate as a switching regulator.
It is an object of the invention to provide a method and arrangement wherein the current limitation operates precisely with respect to its response value. This is accomplished by obtaining a reference current value from control pulses.
The invention has the following advantages:
By evaluating the actuator control pulses for the current limitation, it becomes possible to quickly switch off the actuator under a sudden change of load. For this reason, the method/arrangement according to the invention is suitable for high switching frequencies. Due to the direct evaluation of the current through the actuator, this fast reaction is further supported. Delays caused by a current evaluation on the secondary as, for example, in the switching regulator according to DE 3,402,479.A1, do not occur. With the invention, it is possible at little expense to realize a switching regulator having a reversing characteristic. For switching regulators with potential separation (transformer between supply source and load) the invention can be employed advantageously since the current limitation can take place solely in the primary circuit. Load proportional signals need not be transmitted into the primary circuit for current limitation. The invention can also be used to advantage if a precise response value is required for the current limitation, that is, an exactly reproducible value for the reversal point of the reversing characteristic. For switching regulators having a constant energy discharge time--DE 3,402,479.A1, EP 205,630.A1--the invention can be employed very advantageously.
BRIEF DESCRIPTION OF THE DRAWINGS
An embodiment of the invention will now be described in greater detail with reference to the drawing figures. In which:
FIG. 1 shows a basic circuit diagram for a switching regulator according to the invention; and
FIG. 2 shows a circuit diagram for the current limiting device.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
The basic circuit diagram of FIG. 1 represents a switching regulator with pulse width control. The direct voltage source QE at the input, which has an input voltage UE, is connected in series with the actuator, here configured as a bipolar power switching transistor TS, and with the switching regulator inductance LS. In the illustrated example, the switching regulator is configured as a buck converter. An idling diode DF lies in the load circuit together with the load RL. The capacitor CG is a smoothing capacitor at the output. The output voltage UA appearing at the load RL is picked up by a voltage divider R1, R2. The voltage divider tap is connected with the comp
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Olla, "Comparator Logic Limits Switching Regulator Current," Electronics/Nov. 8, 1971, vol. 44, No. 23, p. 79.
ANT Nachrichtentechnik GmbH
Stephan Steven L.
Sterrett Jeffrey
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