US 5,490,054 AGranted

Ringing generator and method for converting DC to AC having continuously adjustable amplitude

AssigneeFerro Magnetics Corporation

InventorLawrence E. Hanebrink, Jr.

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Abstract

A ringing generator and a method for converting a DC input voltage signal from a DC source to an AC output voltage and supplying this output voltage to a variable load, The output signal has a continuously adjustable amplitude so as to continuously adapt to the current demanded by the load, A power supply converts the DC input voltage to variable DC supply voltages. A linear amplifier then converts these variable supply voltages to an AC output voltage using a precision sine wave oscillator as a reference. A load current sensor senses and measures the output current being supplied to the load and then a control circuit is employed to automatically and continuously adjust the amplitude of the output voltage to maintain the maximum output current that can be safely supplied to the load by the linear amplifier. An output voltage sensor senses and measures the output voltage being supplied to the load and then a control circuit is employed to automatically and continuously adjusts the amplitude of the variable DC supply voltages based upon the output voltage so as to guarantee that at any instant in time the variable DC supply voltages are slightly greater in magnitude than the output voltage at the same instant in time. The ringing generator also includes a fault monitor for continually monitoring multiple critical locations in the ringing generator for any anomaly that would affect the output voltage of the unit and thereby degrade the performance of the ringing generator. Ringing generators may be connected in parallel for increased capacity without any additional external equipment.

Claims30

Dependent claims

A ringing generator for converting a DC input voltage signal from a DC source having positive and negative output terminals to an AC output voltage at one of output terminals of said ringing generator, said AC output voltage being connected to a variable load and having a continuously adjustable amplitude so as to continuously adapt to the current demanded by said load, said ringing generator including:

a power supply for converting said DC input voltage to variable DC supply voltages, said power supply having positive and negative input terminals connected to said positive and negative output terminals of said DC source respectively and having a plurality of output terminals including positive, negative and common output terminals;
a linear amplifier for converting said variable DC supply voltages to said AC output voltage, said linear amplifier having a plurality of input terminals including positive, negative and common input terminals which are operatively connected to said positive, negative and common output terminals of said power supply, said linear amplifier having a plurality of output terminals including output terminals which are connected to said output terminals of said ringing generator;
control circuitry for automatically and continuously adjusting the amplitude of said variable supply voltages based upon said output voltage being supplied to said load so as to guarantee that at any instant in time said variable supply voltages are slightly greater in magnitude than said output voltage at that instant in time, said control circuitry having a plurality of input terminals including an input terminal connected to one of said output terminals of said linear amplifier, said control circuitry having a plurality of output terminals including positive, negative and common output terminals which are operatively connected to said positive, negative and common input terminals of said linear amplifier respectively, at least one of said plurality of output terminals of said control circuitry also being connected to one of input terminals of said power supply;
a reference oscillator having an output terminal for generating a reference signal at said output terminal, said reference oscillator output terminal being connected to one of input terminals of said linear amplifier;
and
a load current sensor being connected between said load and one of input terminals of said control circuitry.

3 more elements

A method for converting a DC input voltage to an AC output voltage having a continuously adjustable amplitude comprising the steps of:

converting said DC input voltage to variable DC supply voltages;
converting said supply voltages to said output voltage by using a linear amplifier including a plurality of power transistors;
supplying said output voltage to a variable load;
adjusting said supply voltages continuously so that at any instant in time said supply voltages are slightly greater in magnitude than said output voltage;
generating a reference voltage which corresponds to the maximum safe operating level for said power transistor;
continuously monitoring said output voltage to determine if said output voltage exceeds said maximum safe operating voltage;
reducing the magnitude of said supply voltages if an excessive output voltage is detected so as to guarantee said output voltage will return to the safe operating level;
continually monitoring said linear amplifier for an overload condition such that if an overload condition is detected, said supply voltages to the linear amplifier are reduced to remain only slightly larger in magnitude than the corresponding reduced AC output voltage of the linear amplifier;
and
further protecting said power transistors by limiting the current inherent in the design of the linear amplifier so as to further reduce the power dissipation to a safe level for all overload conditions.

7 more elements

Dependencies are inferred from the claim text.