Request for feedback on LED PWM driver output circuitry (Part 2)

[daviegravee]

I am looking for feedback, thoughts and general input on a design I am working on. This is a follow up to my previous post: https://www.eevblog.com/forum/projects/request-for-feedback-on-led-pwm-driver-output-circuitry/

Key changes since the last post:

• Cabling inductance and capacitance has been modelled as per one user's suggestion
• Flyback diodes have been added to prevent ringing at the output (D1 and D2 in the simulation file)
• Output filtering capacitor has been added
• Ferrite beads have been added
• Gate driver IC has been added. The design will actually use the UC27444, however there is no SPICE model available for this part afaik.
• MOV has been added to the output, part not spec'd yet but will probably be the Bourns ZV60K1206121NIR1

 I have attached a screenshot of my LTSPICE file that simulates one single output stage. There will be 24 of these in total.

The key points of the current design are:

• PWM, constant voltage driver;
• Each channel must be able to handle a maximum 4A, at 48V (24V will be more common in practice);
• The design is not rated for 24 x 4A simultaneous drive, it's just that any channel used in isolation must be able to handle switching 4A at 48V;
• Needs to operate in ambient environments of up to 55C;
• Switching MOSFET is the DMNH6021SPDQ : https://www.diodes.com/assets/Datasheets/DMNH6021SPDQ.pdf; (however might be swapped to the IPG20N10S436AATMA1)
• Minimum switching frequency will be in the range 200-400Hz;
• Maximum switching frequency will be in the range of 15-20kHz;
• The only heatsinking method that will be used in this design is copper of the PCB (see page 2 of the datasheet for thermal characteristics). I’m not up to layout yet, but I will be using the 2oz copper, 1-inch square copper plate to achieve a Junction to Ambient thermal resistance of 54C/W;

Thank you in advance!

[daviegravee]

Ah, I didn't realise that LTSPICE wouldn't embed the custom symbol. Here it is (in the .zip, the .asy extension is not allowed by eevblog...)

I've also attached a simulation without the gate driver in it.