This application note describes the electronic lamp ballast for 70 W high intensity discharge (HID) metal halide lamps (MHL) used for general indoor applications. The ballast is composed of a boost converter and an inverter. The inverter is realized by a full bridge driver with a power control circuit. The booster converter for power factor correction (PFC) is controlled by the L6562A controller (U1). The inverter is a full bridge topology driven by two pairs of half bridge buck converters, L6385E (U3) and L6569 (U4), with the constant power control circuit L6562A (U2). In this note the dual-buck converter is introduced. One works in high frequency and the other works in complementarity with necessary dead time at a lower frequency.