| 摘要 |
A reasonably priced power supply circuit for a motor vehicle with two different load voltages, viz. the normal vehicle supply system voltage and a voltage higher than this for operation of a window heating glazing with a thin-film heating resistor. A generator is designed for the higher voltage, which corresponds at least to the voltage required for operation of the window heating glazing. With the window heating glazing switched off, the voltage supplied by the generator is adjusted to the vehicle supply system voltage by a controller. With the window heating glazing switched on, the vehicle supply system voltage is derived from the higher voltage. To ensure a safe operating condition, a time switch for the temporary reduction of the exciter current for the generator during change-over of the load switch, a main timer for limitation of the heating time and a threshold voltage switch for limitation of the generator voltage are provided as additional monitoring elements.
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