Test circuit including a power supply with a current transformer to monitor capacitor output current

• US 5,789,934 A
• Filed: 05/23/1996
• Issued: 08/04/1998
• Est. Priority Date: 05/23/1996
• Status: Expired due to Fees

• Current Assignee: Agilent Technologies, Inc.
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Gallo, James S., Kolkowski, John
• Primary Examiner(s): BROWN, GLENN WARNER
• Application Number:
  US08/652,746
• Time in Patent Office: 803 Days
• Field of Search: 324/522, 324/537, 324/555, 324/713, 324/763, 324/771, 324/111
• US Class Current: 324/764.01
• CPC Class Codes: G01R 19/0092 measuring current only all subgroups of G01R19/00 take precedence

Abstract

A measurement system is provided for the measurement of current supplied from a power source, wherein the power source provides a time-varying current, with certain portions thereof being supplied by discharge of an output capacitor. The measurement system includes a circuit for providing a supply voltage between a first terminal and a second terminal, with a sense resistor connected to the first terminal. A capacitor is coupled between the sense resistor and the second terminal and a current sensing circuit is coupled to the capacitor for sensing current flow therein and providing a first signal which is indicative thereof. At least one operational amplifier is coupled to the sense resistor and provides a signal that is indicative of voltage drop as a result of current flow therethrough. A summing amplifier is coupled to the current sense circuit and the operational amplifier and provides an output that is indicative of a sum of the first and second signals, thereby providing an indication of both power source output current and capacitor discharge current to a load connected between the first terminal and the second terminal.

Claims

1. A system for measuring a dc power supply output current into a load when the current includes capacitive discharge components, said system comprising:

means for providing a supply current between a first terminal and a second terminal;

sense resistor means connected to said first terminal;

capacitor means coupled between said first terminal and said second terminal;

current sense means coupled to said capacitor means for sensing current flow therein and for providing a first signal indicative thereof;

amplifier means coupled to said sense resistor means for providing a second signal indicative of a current flow-induced voltage across said sense resistor means; and

summing means coupled to said current sense means and said amplifier means for providing an output that is indicative of a sum of said first signal and second signal.

2. The system as recited in claim 1 wherein said current sense means comprises a current transformer having an output connected to a second amplifier means which, in turn, provides an output to said summing means.

3. The system as recited in claim 2 further comprising:

calibration means for adjusting a gain of said current sense means to assure equal circuit gains are applied to signals input to said summing means.

4. The system as recited in claim 3 wherein said sense resistor means comprises a resistor connected in series to a return current path from a device under test.

5. The system as recited in claim 4, further comprising:

microprocessor means coupled to said summing means for storing a time series of outputs therefrom that are indicative of summed current sensed by said current sense means and said sense resistor means.