Why did Philip the Good break his alliance with the English?

I'm reading at the moment Dan Jones' "Power and thrones" which general history of Middle Times in Europe, and I've just read how Burgundians sold Joan d'Arc to the English, only to break the alliance not long after her death and side with the French?
Given Philip's ambition to become a king in his own right, it seems to me supporting England would be much in his interest. So why did he do it?

I tried to google it, but couldn't find the reason, which is what interests me most.