AN3973

Power factor section

Doc ID 022164 Rev 1

5/24

2

Power factor section

The PFC section (boost converter) mainly consists of STD3N62K3 MOSFET SuperMESH3

technology and the L6562A power switching driver. The new SuperMESH3 technology is

obtained through the combination of fine tuning between standard SuperMESH and

MDMESH technology. This has resulted in the development of a new technology that

dynamic features. SuperMesh has integrated Zener diodes gate-to-source in order to

protect its gate-oxide from voltage spikes. The L6562A is a current-mode PFC controller

operating in transition mode. It has an improved performance compared to its predecessor,

the L6561.

Figure 2 shows the PFC section schematic plus the component values.

Figure 2.

PFC section, boost converter diagram

The power factor consists of the displacement factor related to phase angle and the

distortion factor related to wave shape. The displacement factor is the ratio between the real

power (transferred to the output) and the apparent power (RMS line voltage times RMS line

current) drawn from the main, while the distortion factor is the ratio between the

fundamental component of the current and the total current:

Equation 1

Therefore, the section is designed in order to minimize input current distortion and forces the

input current to be in phase with the input voltage.

This system operates in transition mode, the boundary between continuous and

discontinuous current mode. The control simplicity and the inductor size, due to the low

inductance value needed, are the main advantages of this conduction current mode.