The voltage stabilizer consists of a voltage regulating circuit,a control circuit, a drive circuit, etc.. When the input voltage or the load changes, the control circuit will carry out sampling, comparison and amplification, and then the drive circuit starts working. By automatically regulating the turn ratio of coils, stabilization of the output voltage can be maintained. The voltage stabilizer with lager capacity can also work based on the principle of voltage compensation. According to practical needs, the voltage stabilizer can also enlarge its stabilization range and add necessary protection circuits for loads on it, such as over-voltage protection, under-voltage protection and delayed start-up.