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AN3027

L6563H: high-voltage startup transition-mode PFC

Doc ID 16134 Rev 4

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L6563H: high-voltage startup transition-mode PFC

The L6563H is a new current-mode PFC controller operating in transition mode (TM) which

embeds the same features existing in the L6563S with the addition of a high-voltage startup.

The package and pinout of the two devices are different as shown in

Figure 17 and

Figure 18. The pin function is the same, in this paragraph a detailed description of the HV

startup system is given.

Figure 19 shows the internal schematic of the high-voltage startup generator. It is made up

of a high-voltage N-channel FET, whose gate is biased by a 15 M

Ω resistor, with a

temperature-compensated current generator connected to its source.

The HV generator is physically located on a separate chip, made with BCD off-line

technology able to withstand 700 V, controlled by a low-voltage chip, where all of the control

functions reside.

Figure 19.

High-voltage startup generator: internal schematic

With reference to the timing diagram of

Figure 20, when power is first applied to the

converter the voltage on the bulk capacitor (Vin) builds up and, at about 80 V, the HV

generator is enabled to operate (HV_EN is pulled high) so that it draws about 1 mA. This

Figure 17.

L6563H - SO16

Figure 18.

L6563S - SO14

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