| 摘要 |
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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