METHOD AND APPARATUS FOR DETECTING SLOW AND SMALL CHANGES OF ELECTRICAL SIGNALS INCLUDING THE SIGN OF THE CHANGES, AND CIRCUIT ARRANGEMENT FOR THE EXACT DETECTION OF THE PEAK VALUE OF AN ALTERNATING VOLTAGE

• US 6,628,125 B1
• Filed: 01/10/2002
• Issued: 09/30/2003
• Est. Priority Date: 07/15/1999
• Status: Expired due to Fees

• Current Assignee: Andras Fazakas
• Original Assignee: Andras Fazakas
• Inventors: Fazakas, Andras
• Primary Examiner(s): Le, N.
• Assistant Examiner(s): He, Amy
• Application Number:
  US10/031,106
• Time in Patent Office: 628 Days
• Field of Search: 324/678, 324/676, 324/677, 324/710, 324/711, 324/432, 324/433, 320/127, 320/166, 320/152, 320/148
• US Class Current: 324/678
• CPC Class Codes: G01R 19/0053 Noise discrimination; Analog sampling; Measuring transients measuring characteristics of individual pulses G01R29/02; digital sampling G01R19/2509; measuring noise figure G01R29/26
• CPC Class Codes: G01R 19/16542 for batteries charge condition monitoring in G01R31/36
• CPC Class Codes: G01R 31/3835 involving only voltage measurements

Abstract

Apparatus for detecting slow and small changes of electrical signals including the sign of the changes, the apparatus includes: a controlled switch (2); a capacitor (3) charged to the voltage of a signal to be detected; an amplifier (5) for generating a pulse signal corresponding to the charge or discharge current of the capacitor (3) having corresponding proper sign; a window comparator (7) for indicating whether the output signal of the amplifier (5) lies in the range defined by the window or it has been crossed in negative or positive directions; storage and logic units each having first and second storage devices (8, 11); a pulse generator (9) connected to the controlled switch (2) to make.it closed for periodically repeated sampling periods; a first storage device storing the logical state of the window comparator (7) with proper sign, and a predetermined section of each pulse of the pulse generator reading such stored values of the first storage device into a second storaged device.

Claims

1. Apparatus for detecting slow and small changes of electrical signals including the sign of the changes, comprising:

a controlled switch (2) connected in the path of the signal to be detected;

a capacitor (3) connected with a first terminal to the switch and charged to the voltage of said signal;

an amplifier (5) with an input connected to second terminal of the capacitor (3) and generating a pulse signal corresponding to the charge or discharge current of the capacitor having corresponding proper sign;

a window comparator (7) having first and second reference voltages (+U_K, −

U_K) determining a window, and a signal input connected to output of the amplifier (5) for indicating whether the output signal of the amplifier lies in the range defined by the window or it has been crossed in negative or positive directions;

storage and logical units each having first and second storage means (8, 11); and

a pulse generator (9) connected to control input of the controlled switch (2) to make it closed for periodically repeated sampling periods, and also connected to the storage and logical units,

wherein said first storage means storing the logical state of the window comparator (7) taken during said pulse signal with proper sign, and a predetermined section of each pulse of said pulse generator reading such stored values of said first storage means into said second storage means.

2. The apparatus as claimed in claim 1, wherein said pulse generator (9) has pulses with variable period time.

3. The apparatus as claimed in claim 1, wherein the amplifier (5) comprises RC feedback elements complementing each of said charging or discharging pulse with a respective pulse of opposite sign, and the time of these pulses being in the same order of magnitude.

4. The apparatus as claimed in claim 1, wherein the voltage window of said window comparator (7) being adjustable to be symmetric relative to the base level of the output signal of the amplifier (5).

5. The apparatus as claimed in claim 1, wherein said first storage means being a pair of bistables (8a, 8b), having inputs gated by the inverted output of the other one in the pair, furthermore said bistables being reset by the leading edges of the sampling pulses of the pulse generator (9).

6. The apparatus as claimed in claim 1, wherein said second storage means being a pair of bistables (11a, 11b), and the storage therein occurring under the effect of the rear edges of said sampling pulses of the pulse generator (9).

7. A method for detecting slow and small changes of electrical signals including the sign of the changes, comprising the steps of switching the signal to be detected periodically to a capacitor (3) and changing thereby its charge state taken in the previous period, examining the extent and sign of a decaying current pulse caused when said capacitor (3) has been forced to take the new charge state, if the extent of this decaying current pulse is higher than a predetermined threshold limit, storing this fact and the sign of the change till the next period, characterized by the steps of generating a single alternating wave in response to every change in the charge state of said capacitor (3) so that the DC average of the alternating wave is zero and the amplitude of first half wave being proportional to said decaying current pulse, in said examining step examining directly said first half wave of said alternating wave as a signal representing said decaying current pulse, wherein the duration of said switching step being longer than the period time of said single alternating wave, which itself being longer than said decaying current pulse.

8. The method as claimed in claim 7, wherein depending on the accuracy how the steepness of the changes of the electrical signal should be determined, the time elapsed between subsequent sampling periods being adjusted, wherein said adjustment being unrelated to the transient processes that take place during said switching step.

9. The method as claimed in claim 7, wherein the signal to be examined being the voltage of a battery when being charged.