Power Distribution to Greenhouse LED Lighting
You need some Power Factor Corrected circuitry to convert from AC to DC if your goal is to efficiently use your power. A "normal" AC/DC converter uses a rectifier and "storage cap" to get DC from the AC mains power, then converts that through a SMPS (AC/DC transformers do it without the SMPS, but still using the rectifier+diode.







simulate this circuit &ndash; Schematic created using CircuitLab

The problem is that the "storage capacitor" only really charges during the peaks of the AC waveform, thus "clipping" the waveform, and wasting available power during the rest of the wave.
This causes such "non-PFC" products to be unable to draw even close to theoretical max. power through a circuit breaker, and can result in punitive charges from your electricity provider.

There are ways of converting AC mains to a predetermined DC voltage while drawing power from the full AC waveform, but the designs are a bit more complex than I'm willing to put together for a free answer.
The basic premise behind (at least my designs) for these is in using a switched inductive load (rather than a capacitor) to draw charge from an entire half-wave of AC, then convert the stored inductive power to DC at your desired voltage (If you're interested in further discussing my designs, say so in comments &amp; I'll give you contact information).

Once that problem has been dealt with, your DC/DC SMPS converters sound like a logical &amp; efficient choice for converting between DC voltages, but I would suggest that you consider using higher-voltage series strings of LEDs, say 100V or so, to reduce the total current required by your system, thus reducing your cost in purchasing adequately heavy-gauge wiring to carry all those amps around.

Then it becomes a simple matter of running a single AC/DC converter to supply say 10A or so of DC at 100V, then run a buck converter to step that down to your 5.0/3.3V for your control circuitry to run your PWM dimming to each strand (either buck-style, or simply "strobing" the LEDs with PWM as many LED flashlights do).

All told, I would consider anything above 75% power efficiency as "quite good," considering the number of conversions necessary for multi-voltage DC, plus PWM controlling the brightness (and conductor ohmic heating losses).