A ballast includes a power unit for supplying DC, a converting unit having four switches connected to the power unit for converting DC into AC, a voltage-resistant electrocontrol switch connected to the converting unit and having at least one high-voltage diode and an electrocontrol switch, all of which are arranged in parallel, a high-voltage ignition unit connected to the voltage-resistant electrocontrol switch, a current sensor connected to the converting unit, and a control circuit connected to the converting unit, the power unit, the high-voltage ignition unit, and the voltage-resistant electrocontrol switch for manipulating the actions of the aforesaid elements, such that the ballast is in high-voltage and parallel structure. In addition, the electrocontrol switch of the voltage-resistant electrocontrol switch contains inside high-voltage-resistant insulated oil for enabling the voltage-resistant electrocontrol switch to be resistant to high voltage for AC running through.