Gm Global Technolgoy Operations, Inc.

Robert W Campbell

Donald O Ruff

David W Caldwell

A high DC voltage power supply includes a three-phase autotransformer and a three-phase full-wave rectifier applied to the usual motor vehicle electrical system of the low DC voltage type. The low three-phase AC voltage of the usual system is transformed by the autotransformer to obtain a high three-phase AC voltage which is then rectified by the rectifier to provide a high DC voltage. The load energized by the high DC voltage is ungrounded to reduce the voltage available for inadvertent discharge from either load terminal to ground. Switching apparatus is provided for selectively applying the low three-phase AC voltage to the autotransformer only when it is desired to energize the load thereby avoiding at all other times the energy losses that would otherwise be associated with energization of the autotransformer. In one embodiment, the load is windshield heater element and the autotransformer has multiple sets of input taps to provide deice and defog modes of operation, respectively. The tapping of the autotransformer on the input or primary side yields efficiencies in the construction and operation of the autotransformer. In another embodiment, a current transformer is provided for measuring the AC current through one of the input and output leads of the autotransformer as an indication of the DC current through the load thereby to detect an abnormally low load current condition.

High DC voltage power supply for motor vehicle electrical system

A high DC voltage power supply includes a three-phase autotransformer and a three-phase full-wave rectifier applied to the usual motor vehicle electrical system of the low DC voltage type. The low three-phase AC voltage of the usual system is transformed by the autotransformer to obtain a high three-phase AC voltage which is then rectified by the rectifier to provide a high DC voltage. The load energized by the high DC voltage is ungrounded to reduce the voltage available for inadvertent discharge from either load terminal to ground. Switching apparatus is provided for selectively applying the low three-phase AC voltage to the autotransformer only when it is desired to energize the load thereby avoiding at all other times the energy losses that would otherwise be associated with energization of the autotransformer. In one embodiment, the load is a windshield heater element and the autotransformer has multiple sets of input taps to provide deice and defog modes of operation, respectively. The tapping of the autotransformer on the input or primary side yields efficiencies in the construction and operation of the autotransformer. The engine driven generator of the vehicle electrical system is excited from a voltage source independent of the low three-phase AC voltage put out by the generator, at least during any period that the generator is overloaded, thereby to prevent a degenerative collapse in the generator output voltage.

A windshield heater element for an automotive vehicle is controlled to provide a maximum power deice mode of operation and a reduced power defog mode of operation. The deice mode of operation is initiated in response to an operator actuated deice command and is terminated in response to the first to occur of expiration of a predetermined time period after initiation, or an operator actuated off command. The defog mode of operation is initiated in response to termination of a preceding deice mode of operation provided that such termination was not in response to an operator actuated off command, or an operator actuated defog command. The defog mode of operation is terminated in response to the first to occur of expiration of a predetermined time period after initiation provided that such initiation was not in response to an operator actuated defog command, or an operator actuated off command. Further, the deice mode of operation is permitted only when the vehicle transmission is in the park or neutral state, and the idle speed of the engine is raised above the normal idle speed to ensure that the power produced by the engine driven generator is adequate to meet the combined power requirement of the windshield heater element and other vehicle loads during the deice mode of operation. Additionally, the energization of the heater element is terminated or prohibited in response to detection of an abnormally high windshield temperature condition, an abnormally low battery voltage condition, an abnormally low heater current condition, or vehicle ignition shut-off.

Dual mode windshield heater control

A multivoltage electrical system for a motor vehicle that has a pair of storage batteries which, in a first charging mode are charged in series from the direct voltage output terminals of a bridge rectifier connected to an alternating current generator. In a second charging mode, only one of the batteries is charged and this takes place when a plurality of controlled rectifiers connecting the generator and a common junction of the batteries are gated conductive. The switching between modes is a function of the voltage of one of the batteries and the voltage of a triangular voltage waveform generator operating at a fixed frequency. The system is maintained in the second mode when generator speed is below a predetermined value.

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Anderson, IN, United States of America

Robert W Campbell