Electricity: power supply or regulation systems – In shunt with source or load – Using choke and switch across source
Reexamination Certificate
2000-08-16
2001-07-24
Berhane, Adolf Deneke (Department: 2838)
Electricity: power supply or regulation systems
In shunt with source or load
Using choke and switch across source
C323S282000
Reexamination Certificate
active
06265854
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a converter for converting a terminal voltage of a battery connected between an input terminal and a reference terminal into an output voltage across a load connected between an output terminal and said reference terminal, comprising switching means for controlling the value of the output voltage to the value of a reference voltage, and a control circuit for controlling the switching means.
Such a converter is known from the prior art. Controlling the value of the output voltage takes place by means of pulse width modulation and/or frequency modulation of the switching means.
A disadvantage of the known converter is that it is not provided with a simple and at the same time accurate indicator for supplying a signal indicating that the battery is almost empty.
The load may be, for example, a hearing aid. An accurate indicator for supplying a signal indicating that the battery is almost empty is highly desirable here because in the absence thereof either the hearing aid may fail in an uncontrolled manner (i.e. unexpectedly), or a battery which is not nearly empty yet is replaced.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a converter with a simple and at the same time accurate indicator for supplying an indicator signal signifying that the battery is almost exhausted.
According to the invention, the converter mentioned in the opening paragraph is for this purpose characterized in that the converter comprises comparison means for making a comparison of the output voltage with the reference voltage and for providing a start signal to the control circuit in response to said comparison so as to initiate a energy transport from the battery to the load; frequency detection means for determining the frequency of the start signal; and indication means coupled to the frequency detection means for providing an indication signal when the frequency of the start signal has exceeded a certain limit.
The invention is based on the recognition that the number of times per unit time an energy transfer is to take place from the battery to the load is dependent on the terminal voltage supplied by the battery.
Whenever an energy transfer is to take place, this fact is transmitted by the comparison means to the control circuit of the converter by means of the start signal. The frequency of the start signal is thus directly proportional to the number of energy transfers per unit time. The frequency of the start signal is as a result dependent on the terminal voltage of the battery, and is thus also a measure for the condition of the battery (i.e. how full the battery still is). The frequency detection means determine the frequency of the start signal and pass it on to the indication means. If the limit mentioned above is chosen such that it corresponds to an almost (but not completely) empty battery, the indication signal will give a warning at the correct moment that the battery is to be replaced. The indication signal may be, for example, a pulsatory bleep tone.
An embodiment of a converter according to the invention is characterized in that the converter comprises a coil with a first and a second terminal; and in that the switching means comprise a first switch of which a control electrode is coupled to the control circuit for receiving a first control signal and a second switch of which a control electrode is coupled to the control circuit for receiving a second control signal; and in that the first terminal of the coil is coupled to the input terminal; and in that the first switch is connected between the second terminal of the coil and the reference terminal; and in that the second switch is connected between the second terminal of the coil and the output terminal.
A simple implementation of a converter according to the invention is obtained in this manner. The converter is a so-called inductive converter, i.e. it has a coil which serves to store energy from the battery and to release energy to the load again. The use of the inductive converter implies that the frequency of the start signal rises in proportion as the battery becomes more exhausted.
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patent: 5736841 (1998-04-01), Gucyski
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Berhane Adolf Deneke
Biren Steven R.
U.S. Philips Corporation
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