Voltage dividing circuit

• US 4,578,772 A
• Filed: 09/14/1982
• Issued: 03/25/1986
• Est. Priority Date: 09/18/1981
• Status: Expired due to Term

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Fujii, Shigeru
• Primary Examiner(s): Fleming, Michael R.
• Application Number:
  US06/418,008
• Time in Patent Office: 1,288 Days
• Field of Search: 364/811, 364/850, 307/498, 307/264, 307/284, 328/141, 357/42, 357/48, 357/51, 357/86, 357/89, 338/48, 338/163, 338/164, 338/184, 338/199, 338/217, 323/281, 363/62, 363/204, 363/60, 320/1
• US Class Current: 708/844
• CPC Class Codes: H03H 7/24 Frequency- independent attenuators
• CPC Class Codes: H03M 1/74 Simultaneous conversion

Abstract

The present invention relates to a voltage dividing circuit comprising capacitors or resistors. In the case of a voltage dividing circuit comprising capacitors, the capacitors are connected at one end to an output terminal and at the other end connected alternately to two power sources through changeover switches. The switches are selectively operated so that the capacitors divide the source voltages into fractions of the voltage. The average of the fractions of voltage is used an output voltage. The averaging of the fractions of voltage cancels out the characteristic difference among the capacitors. The fractions of voltage are changed by varying the time during which each capacitor is connected to either power source. Similarly, in the case of a voltage dividing circuit comprising resistors, the resistors divide a voltage into fractions. The average of the fractions of voltage is used as an output voltage. The voltage dividing circuit according to the present invention may employ the method used in the known voltage dividing circuits which comprise capacitors or resistors. In this case, the circuit can divide a voltage into smaller fractions of voltage than the known voltage dividing circuits. In other words, the circuit of the present invention can enhance the resolution of the analog output signal.

Claims

1. A voltage dividing circuit, comprising:

first power source means for providing a first voltage;

second power source means for providing a second voltage;

an output terminal;

a plurality of capacitance elements of substantially the same capacitance each operatively and continuously connected to the output terminal; and

switching means, operatively connected to each of said capacitance elements, individually, and to said first and second power source means, for alternately connecting said capacitance elements to said first power source means and said second power source means using simultaneous connection changes, whereby an output voltage, generated by dividing the first and second voltages into fractions by means of the capacitance elements, is generated at the output terminal as an average of periods during which each of said capacitance elements is connected to one of said first power source means and said second power source means.

2. A voltage dividing circuit according to claim 1, wherein each of said capacitance elements is connected alternately to the first and second power source means for the same period of time, thereby cancelling out a capacitance error of each capacitance element and providing an accurate output voltage.

3. A voltage dividing circuit according to claim 1, wherein each of said capacitance elements is connected alternately to said first and second power source means for different periods of time, thereby dividing the first and second voltages with a ratio of one period to the other period and providing different fractions of voltage.

4. A voltage dividing circuit according to claim 1, wherein said switching means comprises:

switching signal generating means for generating a switching signl indicating the periods during which each capacitance element is connected; and

connecting means, operatively connected to said switching signal generating means and each of said capacitance elements, for connecting said capacitance elements to said first and second power source means in dependence upon the switching signal.

5. A voltage dividing circuit, comprising:

first and second power source means for providing reference voltages;

an output terminal;

a plurality of resistor elements operatively connected to form a series circuit, forming junction points between connected resistor elements and which series circuit is connected at one end to said first power source means and at the other end to said second power source means;

switch control means for supplying a switch control signal; and

a changeover switch circuit, operatively connected to the output terminal and different junction points of the series circuit, for selectively supplying fractions of voltage defined by said resistor elements, the fractions of voltage being supplied for periods of time defined by the switch control signal, whereby an output voltage is generated as a function of the average of the periods of time during which said changeover switch circuit supplies the fractions of voltage.

6. A voltage dividing device, comprising:

first and second power source means for supplying voltages;

capacitors having respective first electrodes, commonly connected second electrodes and capacitance values which are substantially equal; and

control means operatively connected to said first and second power source means and the first electrodes of said capacitors, for connecting the first electrodes of said capacitors repeatedly to one and then the other of said first and second power source means for periods of time, thereby providing an output at the commonly connected second electrodes of said capacitors which has a value that is determined by the capacitance values and the periods of time that said capacitors are connected to said first and second power source means.

7. A voltage dividing device as set forth in claim 6,

wherein said capacitors are connected in parallel, and

wherein said control means alternately connects all the capacitors to said first power source means then to said second power source means.

8. A voltage dividing device as set forth in claim 6,

wherein said capacitors are divided into first and second groups, and

wherein said control means connects the first group to said first power source means and said second group to the second power source means for a first connection time, and then connects said first group to the second power source means and the second group to said first power source means for a second connection time.

9. A voltage dividing device, comprising:

first power supply means for supplying a first voltage;

second power supply means for supplying a second voltage lower than the first voltage;

resistors connected in a series network forming connection points therebetween, said series network operatively connected to said first and second power supply means; and

control means, operatively connected to said first and second power supply means and said series network, for generating an output voltage greater than or equal to the second voltage and less than or equal to the first voltage by supplying one of the first voltage, the second voltage and a third voltage generated by repeatedly switching between at least two of the connection points in said series network.

10. A voltage dividing device as set forth in claim 9, wherein said control means comprises:

input terminals each connected to a different connection point;

an output terminal; and

switching means, operatively connected to said input terminals and said output terminal, for connecting the output terminal to different input terminals for an amount of time and providing the output voltage at the output terminal, the output voltage having a level which is determined by the amount of time each input terminal is connected to the output terminal.

11. A voltage dividing device as set forth in claim 10, wherein the output voltage is determined by which of said input terminals is connected and the amount of time each input terminal is connected.