UM0673

PFC board connection

Doc ID 15337 Rev 2

7/19

3

PFC board connection

The PFC board is manufactured ready to use.

Using jumper J3, the supply of the driver

L6563S can be connected directly to the supply generated by the auxiliary winding present

on the boost inductor or to an isolated low-voltage external supply. This option can be used

to debug or to test an inductor not equipped with an auxiliary winding. Set

jumper J3 to

position 2-3 to use the standard auxiliary power supply already present on the board. If an

external supply is used, set J3 to position 1-2 and connect a 15 V DC supply capable of at

least 100 mA to J4 (+15 on J4 pin1, ground on J4 pin2). Connect the board to the AC power

supply.

Use a suitable cable, in terms of insulation and cross-section, to be able to conduct the

current from the supply according to the load connected to the output port.

Connect the output port to the load.

Note:

Even if the system is able to start up and maintain the output voltage regulated to the target

value, also under open-load condition, the technical specification in terms of PF and THD

cannot be guaranteed.

The systems accept a minimum power load to work properly.

Supply the PFC board with a sinusoidal supply voltage with amplitude in the range of 185

Vrms to 265 Vrms. The power source has to be able to supply the power required by the

system, according to the output load the user intends to connect to the output port.

Caution:

Do not supply the system with a voltage value higher than 265 Vrms, as risk of serious

damage to the board and to property is present in this case. Do not supply the system with a

voltage below the minimum allowed, 185 Vrms, as the systems cannot start or operate

properly in this condition.

Note:

Low voltage supply and maximum output load present the worst operating conditions for the

system and sufficient cooling is mandatory.

3.1

STEVAL-ISF001V2 description

The demonstration board STEVAL-ISF001V2 developed by STMicroelectronics provides a

compact, and ready-to-use solution for the implementation of a simple PFC system able to

supply load with power close to the maximum delivered in most typical domestic

installations. For such a range of power the use of a continuous-mode PFC operation

becomes mandatory to drain from the mains a current with an rms value which does not

exceed the maximum allowed from the metering system and to have a reasonable size of

the devices involved in the system’s operations.

The use of a standard continuous-mode driver chip necessitates using a more expensive

and complex driver with all the required passive components.

STMicroelectronics has patented a solution that allows using a simple driver, designed for a

transition-mode operation, in a fixed-off-time, variable frequency, PWM modulation. This

kind of modulation gives a current on the boost inductor of the PFC that is comparable with

the current of a typical continuous-mode modulation.

Modulating T

ON

and fixing T

OFF

of the PWM signal applied to the main switch, it is possible

to maintain continuous current on the inductor around a sinusoidal envelope. As a