Diodes AP1662 Manuel d'utilisateur télécharger pdf (Page 14)

Data Sheet

HIGH PERFORMANCE POWER FACTOR CORRECTOR AP1662

Jul. 2012 Rev. 1. 3 BCD Semiconductor Manufacturing Limited

Functional Block Description

AP1662 is a high performance power factor

correction controller which operates in DCM

boundary conduction mode. The PFC converter's

switch will be turned on when the inductor current

reduces to zero and turned off when the sensed

inductor current reaches the required reference which

is decided by the output of multiplier.

Error Amplifier and Over-Voltage

Protection

The error amplifier regulates the PFC output voltage.

The internal reference on the non-inverting input of

the error amplifier is 2.5V. The error amplifier's

inverting input (INV) is connected to an external

resistor divider which senses the output voltage. The

output of error amplifier is one of the two inputs of

multiplier. A compensation loop is connected outside

between INV and the error amplifier output.

Normally, the compensation loop bandwidth is set

very low to realize high power factor for PFC

converter.

To make the over voltage protection fast, the internal

OVP function is added. If the output over voltage

happens, excess current will flow into the output pin

of the error amplifier through the feedback

compensation capacitor. (see Figure 22) The AP1662

monitors the current flowing into the error amplifier

output pin. When the detected current is higher than

40µA, the dynamic OVP is triggered. The IC will be

Figure 22. Error Amplifier and OVP Block

disabled and the drive signal is stopped. If the output

over voltage lasts so long that the output of error

amplifier goes below 2.25V, static OVP will take

place. Also the IC will be disabled until the output of

error amplifier goes back to its linear region. R1 and

R2 (see Fig. 22) will be selected as below:

5.22

−=

OVP

∆

Multiplier

The multiplier has two inputs. One (Pin 3) is the

divided AC sinusoidal voltage which makes the

current sense comparator threshold voltage vary from

zero to peak value. The other input is the output of

error amplifier (Pin 2). In this way, the input average

current wave will be sinusoidal as well as reflects the

load status. Accordingly a high power factor and

good THD are achieved. The multiplier transfer

character is designed to be linear over a wide

dynamic range, namely, 0V to 3V for Pin 3 and 2V to

5.8V for Pin 2. The relationship between the

multiplier output and inputs is described as below

equation：

MULTCOMPCS

VVkV

−

)5.2(

where V

(Multiplier output) is the reference for the

current sense, k is the multiplier gain, V

COMP

is the

voltage on pin 2 (error amplifier output) and V

MULT

the voltage on pin 3.

Current Sense/Current Sense

Comparator

The PFC switch's turn-on current is sensed through

an external resistor in series with the switch. When

the sensed voltage exceeds the threshold voltage (the

multiplier output), the current sense comparator will

become low and the external MOSFET will be turned

off. This insures a cycle-by-cycle current mode

control operation. The maximum current sense

reference is 1.8V. The max value usually happens at

startup process or abnormal conditions such as short

load.

1 2 ... 9 10 11 12 13 14 15 16 17 18

Commentaires sur ces manuels

Pas de commentaire

Diodes AP1662 Manuel d'utilisateur Page 14

Commentaires sur ces manuels

Produits connexes et manuels pour Matériel Diodes AP1662