Propagation delay balancing circuit, method and random number generating circuit using the same

A propagation delay balance circuit includes a signal generating circuit, a path switching element, and a signal change detecting element. The signal generating circuit includes delay chains for outputting delay signals respectively. The path switching element has input terminals and output terminals. Each output terminal of the path switching element is electrically connected to the input terminal of each delay chain one-to-one, and input terminals of the path switching element are electrically connected one-to-one to the output terminals of the delay chains. The path switching element is controlled by the path switching controlling signal to change the one-to-one internal electrical connection between input terminals and output terminals of the path switching element. The signal change detecting element is electrically connected to the path switching element, and generates a path switching controlling signal according to delay signals of the path switching element.