A ballast includes a drive circuit, a half-bridge inverter, a transformer, and a filter. The drive circuit is configured for generating a drive signal on receiving a power. The half-bridge inverter is configured for generating a power AC signal according to the drive signal generated by the driver. The power AC signal is fed back to the drive circuit, for determining a non-overlap time of the drive signal. The transformer is configured for generating a high frequency signal based on the power AC signal. The high frequency signal is configured for lightening a lamp, and maintaining the lightening of the lamp. The filter is used for filtering out noise in the feedback power AC signal.