Using a MOSFET to control a Buck module

[Magnets]

I have one of these XL4005 buck modules to run an LED and want to control the module via a mosfet (RFP30N06LE).

http://www.aliexpress.com/item/High-Quality-5A-DC-to-DC-CC-CV-Lithium-Battery-Step-down-Charging-Board-Led-Power/32388356240.html

Do I need a diode across the buck to protect the mosfet or can I just run it like this with the buck in place of the bulb (3rd diagram)

http://bildr.org/2012/03/rfp30n06le-arduino/

Thanks

[Simon]

you should not have problems and not need a diode if the buck converter is made properly

[Magnets]

you should not have problems and not need a diode if the buck converter is made properly

Is there anything critical or obvious that I could observe to determine if that's the case?

Thanks

[Seekonk]

I question the need for it at all.  You could send a digital 5V signal through a diode and fake the feedback loop into thinking the output voltage is too high.  That would shut down any type  converter.  If it is anything like the 2596, pin #5  is the shutdown pin.  Raising it above ground will shut down the converter.  This pin is fast and you could PWM the converter for variable intensity.

[Magnets]

I question the need for it at all.  You could send a digital 5V signal through a diode and fake the feedback loop into thinking the output voltage is too high.  That would shut down any type  converter.  If it is anything like the 2596, pin #5  is the shutdown pin.  Raising it above ground will shut down the converter.  This pin is fast and you could PWM the converter for variable intensity.

Great point, the module actually has pads for pin 4 (EN) and ground pulled out which I never realised. It still uses 5.6ma when disabled, which I assume is the onboard LED.