How many output amps at 19.5vDC does the TV's power brick state?
There are many DC to DC converters out there.
Here
is a 150 watt one:
These adjustable units can be employed for battery equalization too, on limited battery capacities.
Lots of laptops work on 19.5vDC, and their 'car adapters' will have the much despised ciggy plug, and an enclosed powerbrick. Just cut off the ends and put on the right barrell plug/connector. Some of these are 60 watts max, some are 90, some are 120.
Ciggy plugs are basically good only for 60 watts or less, unless upgraded, then they might be good for 120 watts but perhaps not continuously.