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I've put together several circuit for my power steering assist and I think each successive design / build get better than the last. Here's the last, hopeful final, design. I had to modify the steering wheel position sensor from the supplier,from resistive to Hall effect design and because setting the neutral point to a even 5.00 volts I made the input section adjustable to compensate. The oscillator section give me a triangular wave for use in PWM, the feed back injection is current feed back to reduce the input signal, the PWM section sets the signal for PWM by comparing the triangular wave to a set voltage. Straight line setting turns one of the upper FETs off (both upper FETs are on for Dynamic Braking) . Upper H Bridge voltage is high enough to allow me to use all NFETs because PFETs have given me a lot of failures.
The way this works is triangular wave centers on the 5 volts from the input and moves up or down with Hall effect voltage so that the triangular wave intersects with the PWM set voltage and triggers one of the lower FETs for the PWM. The Hall effect voltage has also turned one of the upper FETs off (or on if not using Dynamic Braking) and is set to function before the PWM section by the Straight line section.
The previous design used 3 quad opamps and 1 quad comp and 2 555s, so I have cut the components pretty much on half.
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