Apparatus for limiting current through a plurality of parallel transistors
First Claim
1. Apparatus for controlling current through a load, comprising:
- a plurality of current control stages, each current control stage including first, second and third terminals, and means for conducting current between the first and second terminals in response to a control signal present at the third terminal;
minimum circuit means, responsive to first and second input signals, for generating the minimum of the first and second input signals to thereby establish the control signal;
sensing means for determining a value that is a function of the current flow through the load;
feedback means, responsive to said sensing means, for generating the first input signal such that the first input signal is indicative of a desired level of current through the load; and
limit circuit means for generating the second input signal, to thereby establish a maximum current flow through the current control stages.
1 Assignment
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Accused Products
Abstract
Disclosed is an electrical control circuit (10) for controlling current through a furnace coil or other resistive load (14). The control circuit includes a plurality of current control stages (12(1), 12(2), . . . 12(N)), a minimum circuit (16), and a control system (22) which provides feedback from the load. The control circuit utilizes a signal conditioner (20) and a sensor (18) to provide information regarding the load to the minimum circuit. The minimum circuit provides the minimum of inputs from the control system and a limit circuit (24) to the current control stages, thereby controlling the current that is drawn through the load. Each current control stage includes an operational amplifier (30), a pass transistor (34), a sense resistor (Rs), and a feedback resistor (Rf). The sense resistors ensure that there is current sharing through each of the current control stages. The operational amplifiers are a pre-drive to the pass transistors to allow smaller sense resistors to be used. The feedback resistors (Rf) provide degenerative feedback to the operational amplifiers.
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Citations
13 Claims
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1. Apparatus for controlling current through a load, comprising:
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a plurality of current control stages, each current control stage including first, second and third terminals, and means for conducting current between the first and second terminals in response to a control signal present at the third terminal; minimum circuit means, responsive to first and second input signals, for generating the minimum of the first and second input signals to thereby establish the control signal; sensing means for determining a value that is a function of the current flow through the load; feedback means, responsive to said sensing means, for generating the first input signal such that the first input signal is indicative of a desired level of current through the load; and limit circuit means for generating the second input signal, to thereby establish a maximum current flow through the current control stages. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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Specification