Vehicle instrument panel lamps, pulse width dimmer system therefor

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to FIG.
1A, this figure depicts a prior art pulse width modulated vehicle lamp dimmer system 1.
System 1 includes a 12 power supply source 2, a microcontroller (MCU) 3 that includes an A/D converter circuit with a potentiometer 3A as an input device and a pulse width modulation (PWM) circuit of which the potentiometer settings affect the PWM, a clock pulse generator 4, a gang of conventional inverters 5, a voltage doubler circuit 6, a field effect transistor (FET) driver circuit 7, a FET 8 and instrument panel lamps 9--9.
The power supply source 2 provides 12 VDC battery power (VBATT) and a regulated 5 VDC system supply voltage (VCC).
Clock pulse generator 4 produces pulses at a rate of 1/(1.
4 RC) with components selected to produce pulses at about 45 kHz.
The gang inverters 5, connected to the output of generator 4, sharpens up the pulses from generator 4 and produces approximately a 12 VDC square wave pulses with about a 50% duty cycle.
This square wave signal routes to the voltage charger circuit 6 which provides about a 24 VDC (V charge) signal used to power the FET driver circuit 7.
The FET driver circuit 7 receives the VCC input voltage, PWM signals from MCU 3 and the V charge signal from voltage doubler circuit 6 and produces at an output terminal 24 VDC pulse signals of a duration selected by the setting of potentiometer 3A to an N-channel FET 8.
The output of FET 8 controls the intensity of the lamps 9--9.
Prior art circuit 1A provides suitable variations of output voltage signals to lamps 9--9 to permit adjusting the illumination and dimming.
However, such a circuit operates at a fairly high frequency rate that in a vehicle environment generates more system noise than desirable.
In an effort to find a less noisy vehicle lamp dimmer system a search was initiated to find new approaches to provide PWM controlled lamp dimming at a much lower frequency.
That search ended with the accomplishment of an improved PWM vehicle lamp dimming system of the present invention