Want to work out my back...but have limited work out equipment, what workouts would help?

Hello. I use to work out a lot for the past 4 years and was in great shape, however, due to a lifestyle change I now workout at home with limited equipment. I want to keep the 10 extra pounds I gained by lack of working out however this among other aspects are hampering my performance on my back exercises, namely pull ups. I know that when I was at the gym I use to do lat-pull downs which really improved the amount of times I can perform pull ups, however Since I am limited to just free weights and a pull up bar that I am installing, I do not have the luxury to put emphasis on my lats like I normally would. I have 300 pounds worth of free weights, weight bench for shoulder and chest presses, 45 pound bar, 17.5 pound EZ curl bar and a set of dumbbells that can go up to 40 pounds each. How and what exercises can I perform to help my lats get to the point where I can perform higher reps when performing pull-ups? I am aiming to build my lats up. Serious responses please, thank you!