At 01:27 PM 3/4/2004 -0500, you wrote:

>And build a switcher so as to add to the efficiency. Any low level PIC with
>PWM and a comparator should be able to easily drive a buck regulator simply
>by setting the duty cycle on the PWM, low pass filtering the pwm output, and
>then feeding that to the comparator along with the input signal (current or
>terminal voltage) of interest. Set the comparator to drive an output with the
>results. Tie that output to the switch on the switcher. The circuit should
>turn on while the voltage is to low, then self oscillate once the voltage
>reaches the regulation voltage. It should also be set and forget by picking
>which comparator, and setting the PWM voltage to the desired value.


I haven't tried this yet, but when driving the alternator field, I only
need a switch driven from the PWM output. The field is an inductor, so it
will smooth out the current pulses. I gather that most regulators for
alternators as in fact switching regulators; some just use a comparator,
and turn the field on when the battery voltage is low and off when high.

The problem with playing with an alternator on the bench is that the
alternator is on the boat! Which is 100 miles away. And it is winter, so it
is colder than anything.


Larry Bradley
Orleans (Ottawa), Ontario, CANADA

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