Saturday, 5 March 2016

200W DATV power amplifier- 50V 20A power supply

200W DATV power amplifier- 50V 20A power supply


I am builder a DATV power amplifier, about 200W maximum. The power supply is unusually powerful as the amplifiers are only bout 25 per cent efficient. Commissioning such a power supply is not simple.

DATV power amplifier

I discovered through one of the Yahoo groups that it was possible to buy UHF DVB-T pallet amplifiers, broad band from 470 MHz to 900 MHz. I bought one through the Italian eBay for 400 Euro. It has a pair of BLF888A LDMOS transistors. The pallet is a pair of amplifiers with a splitter and combiner to allow single in and out. The BLF888A are each a match pair of transistors in push-pull.

Power supply

The power requirements are about 48V at 20A as the amplifiers are only about 25 percent with the ultra linear DVB-T.

I remembered that a lot of telecommunications equipment use 48V, so had a look on eBay. I managed to buy a new ELTEK Flatpack2 2000W 48V HE Power Supply for $150. These are state of the art telecom power supplies and very small for 2000W output.

The first complication is connecting wires to them. They are designed for an in-chassis slot connection of both mains and DC. I opened it up and soldered wires to the back of the connector. Not a good idea, but will do for the moment. I will make up a slot connector and have no wiring inside the power supply.

The next problem is testing the power supply. I bought four 12V headlight globes and mounted them together with wiring. The globes represent a load of about 220 W. The power supply easily achieved this. The voltage is 53V and is not easy to reduce to 48V, it has a CAN network for control.


For the first part of this project, the power supply, it seems to be working well. Next the heat sinking and testing the amplifier, then some filtering.