200W DATV power amplifier- 50V 20A power supply
IntroductionI 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 amplifierI 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 supplyThe 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.