L6566ATR View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'L6566ATR' PDF : 51 Pages View PDF
L6566A
Application information
If FF operation is selected:
1. FF mode from heavy to light load. The system operates exactly like a standard current
mode, at a frequency fsw determined by the externally programmable oscillator: both
DCM and CCM transformer operations are possible, depending on whether the power
that it processes is greater or less than:
Equation 1
PinT
=
⎜⎜⎝⎛
Vin VR
Vin + VR
⎟⎟⎠⎞ 2
2 fsw Lp
where Vin is the input voltage to the converter, VR the reflected voltage (i.e. the
regulated output voltage times the primary-to-secondary turn ratio) and Lp the
inductance of the primary winding. PinT is the power level that marks the transition from
continuous to discontinuous operation mode of the transformer.
2. Burst-mode with no or very light load. This kind of operation is activated in the same
way and results in the same behavior as previously described for QR operation.
The L6566A is specifically designed for flyback converters operated from front-end power
factor correction (PFC) stages in applications in compliance with EN61000-3-2 or JEITA-
MITI regulations. Pin 6 (Vcc_PFC) provides the supply voltage to the PFC control IC.
5.1
High-voltage startup generator
Figure 5 shows the internal schematic of the high-voltage startup generator (HV generator).
It is made up of a high-voltage N-channel FET, with a gate biased by a 15 MΩ resistor, with
a temperature-compensated current generator connected to its source.
Figure 5.
High-voltage startup generator: internal schematic
HV
L6566A
15 MΩ
1
Vcc_OK
HV_EN
IHV
CONTROL
3
GND
5 Vcc
I charge
Doc ID 13794 Rev 4
17/52
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