SHINDENGEN

ELECTRIC MFG.CO.,LTD

- 7 -

2

Operating principles

2.1

Operating principles of current-critical PFC with ON range control

Fig. 4 Critical operation

Fig. 5 Waveform of a single switching cycle

This IC employs a current-critical system. As shown in Fig. 4, the choke current IL forms triangle

waves, starting and ending at 0 A repeatedly. The IC also uses an ON range control system. The

The following formulas give the currents:

IL(peak) is sinusoidal. (Formula 1)

]

A

[

)

(

　　

L

T

V

peak

IL

on



...(1)

considered constant during a single switching cycle (Fig. 5).

]

A

[

2

)

(

)

(

　　

peak

IL

ave

IL

I

in





...(2)

We substitute Formula 1 into Formula 2.

]

A

[

2

2

)

(

)

(

　　

L

T

V

peak

IL

ave

IL

I

on

in

in









...(3)

factor is improved. Fig. 6 shows waveform examples on the circuit.

Fig. 6 Waveform examples on the circuit