| 摘要 |
The amount of time required to produce a luminant output signal at the rear of a vehicle in response to the application of a brake is reduced by preheating the filament of the brake lamp and applying an overvoltage thereto when a brake switch is closed in response to the application of the brake. In accordance with the invention, preheating of the filament is achieved by switching a transistor in series with the filament at a fairly high frequency. The duty cycle of the switching operation can be adjusted to conduct a preheat signal through the lamp which results in little or no radiation of light from the filament. This corresponds to a filament temperature of approximately 2000 DEG K., and an increase in temperature of only approximately 800 DEG 0 K., is required to produce a normal steady state rated illumination for the lamp. The rate of rise of temperature, and consequently of light output, is accelerated by applying an over-voltage which may correspond to energy stored in a capacitor during periods of time when the brakes are not applied, and subsequently discharged into the brake lamp upon application of the brakes. Flyback or buck-boost circuitry may be used to provide the low level preheat, normal level, and overvoltage modes of operation.
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