D.C. monitoring circuit

• US 4,181,842 A
• Filed: 09/13/1976
• Issued: 01/01/1980
• Est. Priority Date: 09/13/1976
• Status: Expired due to Term

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Inventors: Elias, Jack, Bozarth, Theodore B.
• Primary Examiner(s): Rubinson, Gene Z.
• Assistant Examiner(s): Indyk, Eugene S.
• Application Number:
  US05/722,785
• Time in Patent Office: 1,205 Days
• Field of Search: 307/64, 307/66, 307/23
• US Class Current: 307/66
• CPC Class Codes: G01R 19/16538 in AC or DC supplies G01R19/16519 and G01R19/16528 take precedence
• CPC Class Codes: H02J 9/061 for DC powered loads

Abstract

A power supply structure for an electronic system includes a primary power source and a stand-by or secondary power source. The secondary power source is ground circuit isolated from the primary source. A monitoring circuit, which is energized from the secondary source is connected to monitor the primary source for incipient failure, then to produce an output signal which may be used to trigger an alarm and/or switch the secondary power source into energizing connection with respect to the electronic system.

Claims

1. A power supply structure for a utilization system comprising

a primary power supply means and a secondary power supply means,

said primary power supply means being connected in energizing relation with said utilization system,

said secondary power supply means being arranged in circuit ground isolation with respect to said primary power supply means,

sampling means for sampling the voltage across said primary power supply means,

a voltage monitoring circuit connected to be energized by said secondary power supply means,

said voltage monitoring circuit including a voltage-to-current converter connected to produce a current signal proportional to the voltage sample provided by said sampling means,

said voltage monitoring circuit further including a current-to-voltage converter connected to produce a voltage signal proportional to said proportional current signal, and

comparator means connected to compare said proportional voltage signal with a fixed reference signal to produce an output signal representative of said comparison.

2. A power supply structure for a utilization system comprising

a primary power supply means and a secondary power supply means,

said primary power supply means being connected in energizing relation with said utilization system,

said secondary power supply means being arranged in circuit ground isolation with respect to said primary power supply means,

sampling means for sampling the voltage across said primary power supply means,

a voltage monitoring circuit connected to be energized by said secondary power supply means,

said voltage monitoring circuit including a voltage-to-current converter connected to produce a current signal proportional to the voltage sample provided by said sampling means,

said voltage monitoring circuit further including a current-to-voltage converter connected to produce a voltage signal proportional to said proportional current signal,

a comparator means connected to compare said proportional voltage signal with a fixed reference signal to produce an output signal representative of said comparison, and

means responsive to a change of state of said output signal to connect said secondary power supply means in energizing relation with said utilization system.

3. The power supply structure as set forth in claim 2 wherein said sampling means comprises a voltage divider connected across said primary power supply means.

4. The power supply structure as set forth in claim 3 wherein said voltage monitoring circuit comprises means to detect an incipient failure of said primary power supply means.

5. The power supply structure as set forth in claim 4 wherein said means responsive to said change of state of said output signal includes switch means operable to effect the connection of said secondary power supply means to said utilization system.

6. A power supply structure for a utilization system comprising

a primary power supply means and a secondary power supply means,

said primary power supply means being connected in energizing relation with said utilization system,

said secondary power supply means being arranged in circuit ground isolation with respect to said primary power supply means,

sampling means for sampling the voltage across said primary power supply neans, said sampling means including a first and a second resistor serially connected across said primary power supply means as a voltage divider,

a voltage monitoring circuit connected to be energized by said secondary power supply means, said voltage monitoring circuit including a first amplifier having a first input terminal connected to the junction between said first and second resistor, said first amplifier having an output terminal connected to the base electrode of a transistor, the emitter of said transistor being connected through a third resistor to the positive lead of said secondary power supply means, the collector of said transistor being connected through a fourth resistor to the negative lead of said secondary power supply means, a feedback connection from said emitter of said transistor to a second input terminal of said first amplifier, said first amplifier and said transistor comprising a voltage-to-current converter for producing a current signal through said transistor which is proportional to said sampled voltage at said junction between said first and second resistors,

said voltage monitoring circuit further including a comparator amplifier having a first input terminal connected to the junction between said collector of said transistor and said fourth resistor, said fourth resistor comprising a current to-voltage converter for producing a voltage signal at said first input terminal of said comparator amplifier which is proportional to the current through said transistor, said comparator amplifier having a second input terminal connected to a reference voltage means whereby to compare said proportional voltage with said reference voltage to produce a change of state of an output signal from said comparator indicative of an incipient failure of said primary power supply means, and

means including switch means responsive to said change in said output signal to connect said secondary power supply means in energizing relation with said utilization system.