LP works on a bit of a trailing weight to your MMR (match making rating, or ELO, which is hidden). When you win and lose it factors in your current division and LP, your MMR and your opponents MMR.
What do I mean by trailing weight? Well, your division and LP moves more slowly than your MMR in most cases. This causes your MMR to move up quickly when winning, and down when losing. If you then win 50% of your games, your Division will meet up with your MMR. To understand this you have to understand the ELO system originally developed for chess.
Anyway, the idea is that if your MMR is higher than your current division, you'll mostly be matched with players at that MMR. Since your MMR and opponents MMR are higher than your division, you are expected to lose. If you win, you gain more LP than if you lost. This is how you will gain LP by winning 50% of your games with higher MMR than your division.
The opposite will occur to correct you being in higher division than your MMR: you will lose more LP with losses than you gain with wins. The only way this changes is if you win more than half your games, or when your division matches your MMR.
It's all organic and designed to get you too your skill level division and offer measurable and achievable progress compared to the original ELO system.
Your LP gains and losses should even out to about 18 if your MMR is the same as your division. This usually occurs around 100 ranked games played. Before then, the match making system is stl mostly testing you.