| 摘要 |
An improved electric shift transfer case system (10) and electronic control circuit (16) therefor utilizes a microprocessor (73), interface circuit (72), and motor drive circuit (70) to control energization of a direct current electric shift motor (58) that is used to switch between drive modes in the transfer case (14) of a full or part-time four wheel drive vehicle. The motor drive circuit (70) includes four switching elements, such as transistors (74-77). The first and second switching elements connect respective first and second ones of the two motor terminals (58a,58b) to a supply voltage and the third and fourth switching elements connect the first and second motor terminals (58a,58b), respectively, to ground. The switching elements (74-77) each have a conductive state and non-conductive state selectable by a command input that is coupled to and controlled by data outputs of the microprocessor (73). The interface circuit (72) is connected between the microprocessor (73) and motor drive circuit (70) and is used to prevent the microprocessor (73) from commanding the motor drive circuit (70) into a short circuit condition or any other operating mode that involves an undesirable combination of conductive and non-conductive states of the switching elements (74-77). <IMAGE>
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