Method and apparatus for digitizing a voltage

• US 6,949,903 B2
• Filed: 11/18/2002
• Issued: 09/27/2005
• Est. Priority Date: 12/22/2001
• Status: Expired due to Fees

• Current Assignee: Ebm-Papst St Georgen GmbH & Company KG (Ebm-Papst Mulfingen GmbH & Company KG)
• Original Assignee: Ebm-Papst St Georgen GmbH & Company KG (Ebm-Papst Mulfingen GmbH & Company KG)
• Inventors: Berroth, Hansjorg, Kuner, Arnold, Schondelmaier, Hans-Dieter
• Primary Examiner(s): Martin, David
• Assistant Examiner(s): MCCLOUD, RENATA D
• Application Number:
  US10/298,332
• Publication Number:
  US 20030117098A1
• Time in Patent Office: 1,044 Days
• Field of Search: 341/172, 341/120, 341/128, 341/166, 341/126, 341154-158, 341/118, 318/471, 318/268, 318/440, 318/700, 318/254, 318/439, 318/599, 701/99
• US Class Current: 318/440
• CPC Class Codes: H03M 1/145 the steps being performed sequentially in series-connected stages H03M1/141, H03M1/143, H03M1/16 take precedence
• CPC Class Codes: H03M 1/34 Analogue value compared with reference values H03M1/48 takes precedence
• CPC Class Codes: H03M 1/54 Input signal sampled and held with linear return to datum

Abstract

When digitizing a voltage, a capacitor is charged, through an impedance, to a voltage value (Um) dependent on the voltage to be digitized. The limits of that one of a plurality of voltage ranges in which said voltage value (Um) lies, are ascertained, and the two limits of that voltage range are defined as a first limit and second limit; the voltage at the capacitor is modified to the first limit by a charge modification circuit containing an impedance, and a first time interval needed therefor is identified; the voltage at the capacitor is modified to the second limit; the voltage at the capacitor is modified from the second to the first limit via the charge modification circuit. A seond time interval needed therefor is identified. Based on values of the first time interval and second time interval, a digital value is calculated, which serves as an indication of how much the voltage value (Um) at the capacitor differs from one of said two limits.

Claims

1. A method of digitizing a voltage, comprising the steps of

providing a capacitor (80) and an impedance,

charging said capacitor, through said impedance, to a voltage value (Um) which is a function of the voltage to be digitized;

ascertaining within which one of a plurality of voltage ranges said voltage value (Um) lies, each voltage range being defined by a respective first limit and respective second limit;

providing a charge modification circuit containing an impedance,

modifying, by means of said charge modification circuit, the voltage at the capacitor to the first limit, and ascertaining a first time interval needed therefor;

modifying, by means of the charge modification circuit, the voltage at the capacitor from the first limit to the second limit, and ascertaining a second time interval needed therefor;

calculating, based on the first time interval and second time interval, a digital value which serves as an indication of how much the voltage value (Um) at the capacitor differs from one of the two limits of the ascertained voltage range;

further providing a resistor chain in the form of a series circuit of resistors connected via a connecting point, applying a substantially constant voltage to said resistor chain,

successively comparing the respective potentials at the connecting points to the voltage value (Um) at the capacitor, in order to determine the first limit and the second limit of one of said voltage ranges,

providing a resistor (94) for connection in parallel with said capacitor (80),

testing whether the voltage value (Um) at the capacitor is greater than the potentials at all the connecting points of the resistor chain and, if so, completing a circuit path (78, 94, 96, 54) including said resistor in parallel with the capacitor (80), in order to reduce the voltage value at said capacitor; and

thereafter again comparing the potentials at the connecting points to the voltage value (Um) at the capacitor, in order to determine the first limit and the second limit.

2. The method of claim 1, wherein said step of charging said capacitor comprises

connecting an impedance converter, having an input and an output, to a voltage source and

using an output signal of said impedance converter to charge said capacitor.

3. In a method of digitizing a voltage, comprising the steps of

providing a capacitor and an impedance, charging said capacitor through said impedance to a voltage value (Um) which is a function of the voltage to be digitized;

ascertaining within which one of a plurality of voltage ranges said voltage value (Um) lies, each voltage range being defined by a respective first limit and respective second limit;

providing a charge modification circuit containing an impedance,

modifying, by means of said charge modification circuit, the voltage at the capacitor to the first limit, and ascertaining a first time interval needed therefor;

modifying, by means of the charge modification circuit, the voltage at the capacitor from the first limit to the second limit, and ascertaining a second time interval needed therefor;

calculating, based on the first time interval and second time interval, a digital value which serves as an indication of how much the voltage value (Um) at the capacitor differs from one of the two limits of the ascertained voltage range,

further providing a routine whose program steps are adapted to control an electric motor, and

executing said routine between said step of ascertaining the first time interval and said step of ascertaining the second time interval.

4. A method of digitizing a voltage, comprising the steps of

providing a capacitor and an impedance,

charging said capacitor, through said impedance, to a voltage value (Um) which is a function of the voltage to be digitized;

ascertaining within which one of a plurality of voltage ranges said voltage value (Um) lies, each voltage range being defined by a respective first limit and respective second limit;

providing a charge modification circuit containing an impedance,

modifying, by means of said charge modification circuit, the voltage at the capacitor to the first limit, and ascertaining a first time interval needed therefor;

modifying, by means of the charge modification circuit, the voltage at the capacitor from the first limit to the second limit, and ascertaining a second time interval needed therefor;

calculating, based on the first time interval and second time interval, a digital value which serves as an indication of how much the voltage value (Um) at the capacitor differs from one of the two limits of the ascertained voltage range;

further providing a routine adapted for controlling an electric motor, and

executing, between said ascertaining of said second time interval and said calculating based on the first time interval and the second time interval, said motor controlling routine.

5. An arrangement for digitizing a voltage, said arrangement comprising:

a capacitor;

a charging circuit having an input connected to a voltage to be digitized, said charging circuit including an impedance which charges said capacitor to a voltage value (Um) which is a function of the voltage to be digitized;

a microprocessor for coarse classification of said voltage value (Um) into one of a plurality of voltage ranges, which voltage ranges are each defined by a respective first limit and a respective second limit;

a charge modification apparatus for modifying the voltage at the capacitor to the first limit of the voltage range identified by said coarse classification and for measuring a first time interval needed for such modification;

a charge modification apparatus for modifying the voltage at the capacitor to the second limit of the voltage range identified;

a charge modification apparatus for modifying the voltage at the capacitor from the second limit to the first limit and for measuring a second time interval needed therefor; and

a calculation apparatus for calculating a second digital value, based upon values of the first time interval and the second time interval, and for calculating, from a digital value obtained by coarse classification and from the second digital value, a combined digital value that has a greater accuracy than the value obtained by coarse classification.

6. The arrangement according to claim 5,

wherein the microprocessor serves to control at least one charge modification apparatus.

7. The arrangement according to claim 5,

wherein a measurement range switchover apparatus, controlled by the microprocessor, is provided, and is activated if the voltage value (Um) at the capacitor is outside the available voltage ranges.

8. The arrangement according to claim 5,

wherein there is provided, in the charging circuit of the capacitor, an impedance converter which is controllable on an input side thereof by a voltage source whose analog voltage is to be transformed into a digital signal.

9. The arrangement according to claim 5, further comprising

means (184), coupled to an output of said calculation apparatus (190), for temperature-dependent control of the rotation speed of a fan.

10. The arrangement according to claim 9, wherein

said capacitor voltage value for digitization represents a temperature, and

an output signal of said arrangement for digitizing serves for temperature-dependent control of the rotation speed of a fan.

11. The arrangement according to claim 9,

wherein the means (184) for rotation speed control is controlled (166) by the instantaneous position (164) of the rotor of a motor driving the fan.

12. An arrangement for digitizing a voltage, said arrangement comprising:

a capacitor;

a charging circuit having an input connected to a voltage to be digitized, said charging circuit including an impedance which charges said capacitor to a voltage value (Um) which is a function of the voltage to be digitized;

an electric motor;

a microprocessor for coarse classification of said voltage value (Um) into one of a plurality of voltage ranges, which voltage ranges are each defined by a respective first limit and a respective second limit, and for controlling commutation of said electric motor;

a program for execution by the microprocessor, said program comprising a plurality of program calls for the digitization process, each program call being adapted for executing part of the digitization process;

a charge modification apparatus for modifying the voltage at the capacitor to the first limit of the voltage range identified by said coarse classification and for measuring a first time interval needed for such modification;

a charge modification apparatus for modifying the voltage at the capacitor to the second limit of the voltage range identified;

a charge modification apparatus for modifying the voltage at the capacitor from the second limit to the first limit and for measuring a second time interval needed therefor; and

a calculation apparatus for calculating a second digital value, based upon values of the first time interval and the second time interval.