AN2835

The selected solution

Doc ID 15073 Rev 1

5/21

2

The selected solution

2.1

The dual-buck converter topology

The fundamental application circuit in Figure 2 is composed of a PFC stage and a power

inversion stage. As the boost converter for power factor correction (PFC) is commonly used,

only the power inversion stage is introduced in this application note.

Figure 2.

The fundamental diagram for the HID lamp ballast

The full bridge inverter consists of two half bridge buck converters. This is shown in

Figure 3. Both converters have the same L2 load, C2 and lamp. One of the buck converters

(S2 and S4) works in high frequency (several tens of kHz) and the second buck converter

(S3 and S5) works in complementarity with necessary dead time at a lower frequency (a few

hundred Hertz). This kind of full bridge stage is also called dual-buck converter.

Figure 3.

The dual-buck converter

The timing diagram in Figure 4 indicates the relationship of a dual-buck converter and lamp

current.