I'm wondering from a practical point of view whether or not it's possible to augment the control signal (e.g. PWM) from the internal voltage controller of a dc-dc boost converter bought from say Siemens/Altera etc. with my own controller. Obviously, this is probably achievable from a simulation POV or if the means of designing your own converter from scratch was available.
In reality though it is likely stakeholders, control systems designers etc. will buy different converters from different manufacturers, which have their own internal controllers. Is it possible to augment these controllers via the internal control signal (might be difficult to access in hardware) or would your controller have to act externally (with a slower bandwidth) and augment the reference signal of the converter?
Thanks
You need to check and understand the circuit layout of the converter before augmenting you control signal. In order not to damage the power switches
If you keep the source voltage (power supply) constant, set the current limiter quite low, like a few ampere, and use a resistive load which will limit the maximum current, it should be possible to manipulate the hardware in a safe way, while you work on the PWM signal. The voltage feed-back loop is the key to obtaining the output voltage behavior you desire. The current feed-back (usually via tiny pulse transformer) is the key to protect the power switches and also control some degree of soft start. The third kind of feed-back can be a capacitive coupling which optimizes the high frequency response, it can be used to reduce some RF ringing phenomenon around the individual power switch - or alternatively, to produce a "resonance mode" which increases efficiency.
One straight forward way of reducing the output voltage is finding the reference voltage element and replacing that, say 2.5 V, voltage source with your own D/A voltage output. Make sure your output can only be in the interval [0 .. 2.5] volts. Now you are able to (quite slowly, like a few cycles per second) ramp up and down the output voltage any time to fit your applications needs. The output voltage will be proportional to your 0 - 2.5 V signal. All other parts of the circuit will still perform optimally because you have not changed the feedback loops at all.
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