L6566A Datasheet L6566ATR, L6566A | P4-P6

List of tables L6566A

4/52 Doc ID 13794 Rev 4

List of tables

Table 1. Pin functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Table 2. Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Table 3. Thermal data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Table 4. Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Table 5. L6566A light load management features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Table 6. L6566A protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Table 7. External circuits that determine IC behavior upon OVP and OCP . . . . . . . . . . . . . . . . . . . 44

Table 8. SO16N dimentions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Table 9. Order codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Table 10. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

L6566A List of figures

Doc ID 13794 Rev 4 5/52

List of figures

Figure 1. Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Figure 2. Typical system block diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Figure 3. Pin connection (through top view) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Figure 4. Multi-mode operation with QR option active . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Figure 5. High-voltage startup generator: internal schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Figure 6. Timing diagram: normal power-up and power-down sequences . . . . . . . . . . . . . . . . . . . . 18

Figure 7. Timing diagram showing short-circuit behavior (SS pin clamped at 5 V) . . . . . . . . . . . . . . 19

Figure 8. Zero current detection block, triggering block, oscillator block and related logic . . . . . . . . 19

Figure 9. Drain ringing cycle skipping as the load is gradually reduced . . . . . . . . . . . . . . . . . . . . . . 20

Figure 10. Operation of ZCD, triggering and oscillator blocks (QR option active) . . . . . . . . . . . . . . . . 22

Figure 11. Load-dependent operating modes: timing diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Figure 12. Addition of an offset to the current sense lowers the burst-mode operation threshold . . . . 24

Figure 13. Adaptive UVLO block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Figure 14. Possible feedback configurations that can be used with the L6566A. . . . . . . . . . . . . . . . . 25

Figure 15. Externally controlled burst-mode operation by driving the COMP pin: timing diagram. . . . 26

Figure 16. Typical power capability change vs. input voltage in QR flyback converters . . . . . . . . . . . 27

Figure 17. Left: overcurrent setpoint vs. VFF voltage; right: line feedforward function block. . . . . . . . 28

Figure 18. Hiccup-mode OCP: timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Figure 19. Possible interfaces between the L6566A and a PFC controller . . . . . . . . . . . . . . . . . . . . . 31

Figure 20. Operation after latched disable activation: timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . 32

Figure 21. Soft-start pin operation under different operating conditions and settings . . . . . . . . . . . . . 33

Figure 22. OVP function: internal block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Figure 23. OVP function: timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Figure 24. Maximum allowed duty cycle vs. switching frequency for correct OVP detection. . . . . . . . 36

Figure 25. Brownout protection: internal block diagram and timing diagram . . . . . . . . . . . . . . . . . . . . 37

Figure 26. AC voltage sensing with the L6566A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Figure 27. Slope compensation waveforms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Figure 28. Typical low-cost application schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Figure 29. Typical full-feature application schematic (QR operation) . . . . . . . . . . . . . . . . . . . . . . . . . 43

Figure 30. Typical full-feature application schematic (FF operation) . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Figure 31. Frequency foldback at light load (FF operation) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Figure 32. Latched shutdown upon mains overvoltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Figure 33. Package drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Figure 34. Recommended footprint (dimensions are in mm). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Description L6566A

6/52 Doc ID 13794 Rev 4

1 Description

The L6566A is an extremely versatile current-mode primary controller IC specifically

designed for high-performance offline flyback converters operated from front-end power

factor correction (PFC) stages in applications in compliance with EN61000-3-2 or JEITA-

MITI regulations.

Both fixed-frequency (FF) and quasi-resonant (QR) operation are supported. The user can

choose either of the two depending on application needs.

The device features an externally programmable oscillator; it defines the converter's

switching frequency in FF mode and the maximum allowed switching frequency in QR

mode.

When FF operation is selected, the IC works like a standard current-mode controller with a

maximum duty cycle limited to 70% (min.).

QR operation, when selected, occurs and is achieved through a transformer

demagnetization sensing input that triggers MOSFET turn-on. Under some conditions, ZVS

(zero-voltage switching) can be achieved. The converter's power capability rise with the

input voltage is compensated by line voltage feedforward. At medium and light load, as the

QR operating frequency equals the oscillator frequency, a function (valley skipping) is

activated to prevent further frequency rise and keep the operation as close to ZVS as

possible.

With either FF or QR operation, at very light load the IC enters a controlled burst-mode

operation that, along with the built-in non-dissipative high-voltage startup circuit and a

reduced quiescent current, helps keep the consumption from the mains low and meet

energy saving recommendations.

To allow the meeting of energy saving recommendations in two-stage power-factor-

corrected systems as well, the L6566A provides an interface with the PFC controller that

enables the re-regulator to be turned off at light load.

An innovative adaptive UVLO helps minimize the issues related to fluctuations in the self-

supply voltage due to transformer parasites.

The protection functions included in this device are: not-latched input undervoltage

(brownout), output OVP (auto-restart or latch-mode selectable), a first-level OCP with

delayed shutdown to protect the system during overload or short-circuit conditions (auto-

restart or latch-mode selectable), and a second-level OCP which is invoked when the

transformer saturates or the secondary diode fails short. A latched disable input allows easy

implementation of OTP with an external NTC, while an internal thermal shutdown prevents

IC overheating.

Programmable soft-start, leading-edge blanking on the current sense input for greater noise

immunity, slope compensation (in FF mode only), and a shutdown function for externally

controlled burst-mode operation or remote ON/OFF control are all features of this device.

P1-P3 P4-P6 P7-P9 P10-P12 P13-P15 P16-P18 P19-P21 P22-P24 P25-P27 P28-P30 P31-P33 P34-P36 P37-P39 P40-P42 P43-P45 P46-P48 P49-P51 P52-P52

L6566A

Mfr. #:

Buy L6566A

Manufacturer:

STMicroelectronics

Description:

Power Factor Correction - PFC Multi Mode PWM Controller

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L6566A

L6566A

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