Testing led driver with a led load simulator is better for discovery of feedback loop problems?

[Flyback]

Hello,
We need to test our 165W, switch mode LED driver (as well as our future led drivers) and do not wish to just use a resistive load of the same power and voltage level as the led load. The led driver uses a negative feedback loop to regulate the led current. (Max LED loading = 46.4V at 3.52A)
If we just used a resistive load, then we would not be able to truly investigate the propensity of the led driver to go unstable. Thus we need a dummy led load which has a low dynamic impedance and a fast frequency response, -in other words, it must mimick the led load’s dynamic properties.
Do you believe that a switch mode led driver, as described, would be more likely to go unstable when supplying LEDs (or a LED simulator) than if supplying a resistive load?
We believe that a led load (compared to a resistive load) has a higher frequency RC output pole, and thus there tends to be more danger of going unstable…Do you agree?
Attached is a diagram if the led driver driving a led load, and also two different types of led load simulators….which led load simulator do you believe would be best at mimicking the leds?
(LTspice simulation of led load simulators also attached)

 

[ronsimpson]

Any time you build a "simulator" there is a good chance it is not correct. Just use real LEDs.

I see by circuit 2 that you know how to make a power zener using transistors. That is what I would do. You might have to add a resistor to get the voltage/current slope correct.

At 46V and 3.5A you are outside the safe operating area for one 2N3055 but you know that.
1)Use 3 or 4 transistors in parallel, like you are doing, to get in the one amp area. (back in the safe operating area)
2)Use a power resistor or (20 volts of LEDs or two car headlights (24volts)) on the 2N3055 collector to eat up 1/2 the voltage. If a power resistor ate up 20 volts then the heat sink has 1/2 the heat. Also 20V * 4A gets you back in the safe area for (maybe one) defiantly two transistors in parallel.

 

[Flyback]

Thanks, I will take care of the 3055 as you describe.

Any time you build a "simulator" there is a good chance it is not correct. Just use real LEDs.

Thanks, but we cannot use real leds...the load is 165w, and we need the load to be made of the max vf leds, and the chance of getting that is small.
So we need a variable led load simulator.
We will make the power zener adjustable by switching in/out zeners on the base, and varying the small resistance via a pot.
Also, the actual leds themselves would be very expensive, including there water cooled mounting etc...we will just use TO247's as in the schem above and fan cool them.