EP0196802A2
Expired / Lapsed
EP
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Method and apparatus for controlling the operation of a DC load
Assignee: Wickes Manufacturing Co
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Filing: 1986-03-10
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Granted: —
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Expires: 2006-03-10
Abstract
Abstract A control circuit and method for using the same in operating a power switch such as a relay, FET, etc., having conductive and nonconductive conditions and adapted to direct a high magnitude driving current from a power supply through an electric load circuit when the power switch is in the conductive condition. Such a power switch can be used to control small motors used extensively in motor vehicles. This control circuit comprises testing means for directing a low magnitude, low duty cycle testing current through the load or motor circuit while the power switch is in the nonconductive condition, sensing means for creating a control signal indicative of a predetermined electrical characteristic, such as current flow, in the load circuit, means for shifting the power switch into the conductive condition for energizing the load when the control signal from the sensing means has a predetermined value, i.e. exceeds a preselected level, and load protecting means for interrupting the high magnitude driving current passing through the load circuit when the driving current exceeds the preselected value. Preferably, the protective means involves no extemal resetting or time delay in operation.
Inventors
- 👤 George P. Lambropoulos
- 👤 Ben J. Charboneau
- 👤 David H. Eilola
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 07:14
CPC Classifications
H; H02; H02P; H02P1/00; H02P1/02; H02P1/04; H02H; H02H3/00; H02H3/08; H02H3/087
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
151 words
A control circuit for operating a power switch 30 having nonconductive and conductive conditions and adapted to direct a normal driving current from a power supply 12 through an electric load circuit 14 when the switch is in its conductive condition, said control circuit comprising: testing means (72, 70, 42) for directing a testing current through said load circuit 14 while said switch 30 is in said nonconductive condition, said testing current having a magnitude substantially less than said normal driving current, sensing means 100 for creating a control signal with a value indicative of a predetermined electrical characteristic in said load circuit 14, shifting means 142 for shifting said switch 30 into said conductive condition only when said value of said control signal has a preselected value, and protecting means 152,160 for interrupting said driving current flowing through said load circuit when said driving current exceeds a preselected current level.
Claim 2
Dependent Claim
151 words
A control circuit for operating a power switch 30 having nonconductive and conductive conditions and adapted to direct a normal driving current from a power supply 12 through an electric load circuit 14 when the switch is in its conductive condition, said control circuit comprising: testing means (72, 70, 42) for directing a testing current through said load circuit 14 while said switch 30 is in said nonconductive condition, said testing current having a magnitude substantially less than said normal driving current, sensing means 100 for creating a control signal with a value indicative of a predetermined electrical characteristic in said load circuit 14, shifting means 142 for shifting said switch 30 into said conductive condition only when said value of said control signal has a preselected value, and protecting means 152,160 for interrupting said driving current flowing through said load circuit when said driving current exceeds a preselected current level.
Claim 3
Dependent Claim
22 words
A control circuit as defined in claim 1 wherein said testing current is a series of pulses created by said power supply.
Claim 4
Dependent Claim
47 words
A control circuit as defined in claim wherein said testing means (70, 72, 42) includes a switch means Q1 connecting said load circuit 14 with said power supply 12 through a current limiting resistor 40 and means 72 for actuating said switch means at a high frequency.
Claim 5
Dependent Claim
46 words
A control circuit as defined in claim 3 wherein said switch means is a transistor 21 and said actuating means includes an oscillator means 72 for creating a high frequency control signal and means 70 for gating said transistor 21 by said high frequency control signal.
Claim 6
Dependent Claim
69 words
A control circuit as defined in claim 4 including gating means for applying said control signal to said transistor for a selected time, including a bistable oscillator 74 having a first condition applying said control signal to said transistor 21 for a first period matching said selected time and a second condition isolating said control signal from said transistor 21 for a second period greater than said selected time.
Claim 7
Dependent Claim
78 words
A control circuit as defined in any of the preceding claims wherein said sensing means 100 includes a capacitor connected between a selected location in said load circuit 14 and to ground, means 102,104 for charging said capacitor to an average voltage indicative of current flow in said load circuit 14 at least when said testing current is applied through said load circuit 14 and means for creating said control signal by the charged voltage on said capacitor.
Claim 8
Dependent Claim
27 words
A control circuit as defined in any of the preceding claims including means Q2 for deactivating said testing means in response to actuation of said shifting means.
Claim 9
Dependent Claim
69 words
A control circuit as defined in any of the preceding claims wherein said shifting means 142 includes a comparator means 130 having an output 140 and means for setting said output to a given condition when said control signal VC exceeds a reference signal and means 1 4 2,3 4 for shifting said power switch 30 in response to said output 1 40 being set to said given condition.
Claim 10
Dependent Claim
125 words
A control circuit as defined in any of the preceding claims wherein said load circuits is a DC motor circuit 14 and said control signal of said sensing means 100 is a variable voltage signal created by flow of said testing current in said motor circuit 14 and having a relatively low value below said preselected value when said motor circuit 14 has a high current indicative of a stall of a motor in said motor circuit 14 or a short in said motor circuit 14 and said shifting means 142 includes a comparator means 130 for comparing said variable voltage signal with reference voltage signal and said preselected value of said control signal occurring when said variable voltage signal exceeds said reference voltage signal.
Claim 11
Dependent Claim
105 words
A control circuit as defined in claim 9 wherein said variable voltage signal created by flow of said testing current in said motor circuit 14 has a relatively high value above said preselected value when said motor circuit 14 has low current indicative of an open circuit or a disconnected motor in said motor circuit 14 and said shifting means includes a second comparator means for comparing said variable voltage signal with a second reference voltage and said preselected value of said control signal occurring when said variable voltage signal exceeds said first mentioned reference voltage signal and is less than said second reference voltage.
Claim 12
Dependent Claim
72 words
A control circuit as defined in claim 1 wherein said control signal of said sensing means is a variable voltage created by flow of said testing current in said load circuit 14 and said shifting means 142 includes a comparator means 130 for comparing said variable voltage signal with a reference voltage signal and said preselected value of said control signal occurring when said variable voltage signal exceeds said reference voltage signal.
Claim 13
Dependent Claim
20 words
A control circuit as defined in claim 1 including means 300 for increasing said testing current as ambient temperature decreases.
Claim 14
Independent Claim
117 words
A method of sensing a stalled or short condition in a motor circuit including the winding of an electric motor to be driven by a relatively high current from a D.C. power supply, said method comprising the steps of: (a) passing a low magnitude testing current through said motor circuits; (b) measuring the average voltage across the motor of said motor circuit during a testing cycle of a given time length while only said testing current is flowing through said motor circuit; (c) comparing said average voltage with a reference signal; and, (d) passing said high current through said motor circuit when said comparison is at a given relationship of the average voltage and the reference signal.
Claim 15
Independent Claim
117 words
A method of sensing a stalled or short condition in a motor circuit including the winding of an electric motor to be driven by a relatively high current from a D.C. power supply, said method comprising the steps of: (a) passing a low magnitude testing current through said motor circuits; (b) measuring the average voltage across the motor of said motor circuit during a testing cycle of a given time length while only said testing current is flowing through said motor circuit; (c) comparing said average voltage with a reference signal; and, (d) passing said high current through said motor circuit when said comparison is at a given relationship of the average voltage and the reference signal.
Claim 16
Dependent Claim
24 words
A method as defined in claim 13 including the further step of: (e) adjusting said testing current in accordance with changes in ambient temperature.
References Cited (Backward Citations)
No citation records indexed.
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