Control power through a resistive load from a DC source and achieve low current peaks

Question

I want to control the power through a resistive load from a DC source and achieve low current peaks. The use case is 0-1000VDC and 0-15kW (not for the entire voltage range). All other parameters and circuit design are changeable.

Right now I am using a transistor to switch (PWM) a mostly resistive load to control the power through it. Essentially the circuit looks like this (there are more diodes, filters etc) and uses a very low switching frequency (100Hz approximately, this can be changed if it helps the design).

^{simulate this circuit – Schematic created using CircuitLab}

Since this circuit is intended to be used for a very large voltage input range and with a large power span certain operation points leads to a very large current peak compared to the average current through the resistor. This means that the DC source needs to be able to supply very large currents despite having a relatively low average current output. That phenomenon severly limits the usefulness of the DC source for powering other applications at the same time since we might end up blowing a fuse despite drawing relatively low average current. The simplest idea I have had to solve this is to have a large capacitor that smoothes out the current draw and increase the switching frequency.

^{simulate this circuit}

This of course introduces a plethora of other issues: possible EMC issues due to switching faster, and the fact that we have large capacitor that is not being discharged if the load is turned off for longer periods of time. These problems could of course be helped by using discharge resistors and the EMC can be helped by other design choices.

Another idea is to divide the load between more resistive loads with higher individual resistance.

^{simulate this circuit}

Then only using some of them and only switching one at a time while the others are either turned of or fully conducting depeneding on the use case. This a problem since we will have a way bigger system etc.

But before I go down any of these tracks I would like to check if there are any other ideas of how to solve this issue. I want power control of a resistive load from a DC source with low current peaks compared to average current.

All input is appreciated!

Answer 1

For high power, a big slow FET (X5) with low RdsON switches the resistor directly using slow PWM, without inductor losses.

For low power, a small fast FET (X4) turns it into a buck converter. You'll need frequency above 10kHz to avoid a huge inductor though.

The load is tied to Vin so it shouldn't be too hard to add an EMI filter.

If you have other loads in the system, at low power you could switch the resistor in series with the source instead of drawing power from the supply