EVL6566A-75WES4 STMicroelectronics, EVL6566A-75WES4 Datasheet - Page 10

• Manufacturer Part Number: EVL6566A-75WES4
• Description: BOARD DEMO FOR L6563/LL6566A
• Manufacturer: STMicroelectronics
• Type: Power Factor Correctionr

Specifications of EVL6566A-75WES4

• Main Purpose: AC/DC, Primary and Secondary Side with PFC
• Outputs And Type: 1, Isolated
• Power - Output: 75W
• Voltage - Output: 19V
• Current - Output: 4A
• Voltage - Input: 90 ~ 264VAC
• Regulator Topology: Flyback
• Board Type: Fully Populated
• Utilized Ic / Part: L6563, L6566A, TSM1014
• Input Voltage: 90 V to 264 V
• Output Voltage: 19 V
• Dimensions: 78 mm x 170 mm
• Product: Power Management Modules
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Frequency - Switching: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• For Use With/related Products: L6563S, L6566A
• Other names: 497-8834

Main characteristics and circuit description
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Output voltage feedback loop
The output regulation is done by means of two control loops, a voltage and a current loop
working alternatively. A dedicated control IC, the TSM1014 (U5), has been used. It
integrates two operational amplifiers (used as error amplifiers) and a precise voltage
reference. The output signal of the error amplifiers drives an optocoupler SFH617A-4 (U3)
to get the required insulation of the secondary side and modulating the voltage on COMP
pin (#9) of the L6566A.
L6566A current mode control and voltage feed-forward function
R52 and R53 sense the Q5 MOSFET current of the flyback and the signal is fed into pin #7
(CS) connected to the PWM comparator. This signal is compared with the COMP (pin #9)
signal which is coming from the optocoupler.
The maximum power that the converter can deliver is set by a comparator limiting the peak
of the primary current, comparing the CS and an internal threshold (V
signal exceeds the threshold, the comparator limits the MOSFET duty cycle, hence the
output power is also limited.
Because the maximum transferable power depends on both the primary peak current and
the input voltage, in order to keep almost constant the overload set point that would change
according to flyback input voltage, the L6566A implements a voltage feed-forward function
via a dedicated pin. Hence, V
bulk voltage by a resistor divider. A higher voltage causes a smaller V
maximum power can be kept almost constant at any input voltage.
L6566A short-circuit protection
In case of short-circuit, an internal comparator senses the COMP pin after the soft-start at
which time the COMP pin goes high, activating an internal current source that restarts
charging the soft-start capacitor from the initial 2 V level. If the voltage on this pin reaches
5 V, the L6566A stops the operation and enters in the “hiccup mode”. The L6566A restarts
with a startup sequence when the Vcc voltage drops below the V
Because of the long time needed by the V
load operation increases, thus decreasing the power dissipation and the stress of the power
components. This sequence is repeated until the short is removed following which normal
operation of the converter is automatically resumed.
Another comparator, whose threshold is 1.5 V and dedicated to protecting the circuit in case
of transformer saturation or secondary diodes short, is also provided. If the voltage on the
CS pin (#7) exceeds this threshold two consecutive times, the IC immediately shuts down
and latches off. This is intended to prevent spurious activation of the protection in case of
temporary disturbances, for example during the immunity tests. Even in this case the IC
operation is resumed as soon as the V
mode operation is still obtained, avoiding consequent failures due to overheating of the
power components.
Overvoltage protection
Pin #11 (ZCD) is connected to the auxiliary winding by a resistor divider. It implements the
OVP against feedback network failures. When the ZCD pin voltage exceeds 5 V the IC is
shut down. This protection can be set as latched or auto-restart by the user with no
additional components. On the board it is set as latched, therefore operations can resume
after a mains recycling.
CSX
Doc ID 15447 Rev 3
is modulated by the voltage on pin #15 (V
CC
voltage drops below 5 V. In this way a hiccup
CC
capacitor to drop to 5 V, the duration of the no-
CCrestart
CS,MAX
CSX
). If the current
level (5 V).
FF
so that the
) sensing the
AN2941