STMicroelectronics EVL6562A-35WFLB evaluation board using the L6562A EVL6562A-35WFLB EVL6562A-35WFLB Hoja De Datos
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EVL6562A-35WFLB
Main characteristics and circuit description
AN2838
4/23
DocID15099 Rev 2
1
Main characteristics and circuit description
The main characteristics of the SMPS evaluation board are:
•
•
Line voltage range: 90 to 265 V
AC
•
Minimum line frequency (f
L
): 47-63 Hz
•
Regulated output voltage: 48 V
•
Rated output power: 35 W
•
Power factor (load = 50 %): 0.9 minimum
•
Minimum efficiency: 85 % at full load
•
Maximum 2 f
L
output voltage ripple: 1.5 V pk-pk / 0.39 V
RMS
(@V
IN
= 90 V
AC
, P
OUT
= 35 W)
•
Maximum ambient temperature: 50 °C
•
Conducted EMI: In acc. with EN55022 Class-B
•
Surge rejection: surge test 2.5 kV
•
Primary to secondary insulation: 4 kV
•
PCB type and size: double-sided, 35 µm, FR-4, 120 x 82 mm
The main feature of this converter is that the input current is almost in phase with the mains
voltage, therefore the power factor is close to unity. This is achieved by the L6562A
controller, which shapes the input current as a sinewave in phase with the mains voltage.
voltage, therefore the power factor is close to unity. This is achieved by the L6562A
controller, which shapes the input current as a sinewave in phase with the mains voltage.
The power supply utilizes a typical flyback converter topology, using a transformer to
provide the required insulation between the primary and secondary side. The converter is
connected after the mains rectifier and the capacitor filter, which in this case is quite small to
avoid damage to the shape of the input current. The flyback switch is represented by the
power MOSFET Q1, and driven by the L6562A.
provide the required insulation between the primary and secondary side. The converter is
connected after the mains rectifier and the capacitor filter, which in this case is quite small to
avoid damage to the shape of the input current. The flyback switch is represented by the
power MOSFET Q1, and driven by the L6562A.
At startup, the L6562A is powered by the V
CC
capacitor (C6), which is charged via resistors
R1 and R2. The TR1 auxiliary winding (pins 8-7) generates the V
CC
voltage, rectified by D4
and R4, that powers the L6562A during normal operation. R3 is also connected to the
auxiliary winding to provide the transformer demagnetization signal to the L6562A ZCD pin,
turning on the MOSFET at any switching cycle. The MOSFET used is the STP5NK80ZFP, a
standard, low-cost 800 V device housed in a TO-220FP package, and needing only a small
heat sink. The transformer is layer type, using a standard ferrite size ETD-29 and is
manufactured by Magnetica. The flyback reflected voltage is ~190 V, providing enough
room for the leakage inductance voltage spike still within the reliability margin of the
MOSFET. The rectifier D2 and the Transil D3 clamp the peak of the leakage inductance
voltage spike at MOSFET turn-off.
auxiliary winding to provide the transformer demagnetization signal to the L6562A ZCD pin,
turning on the MOSFET at any switching cycle. The MOSFET used is the STP5NK80ZFP, a
standard, low-cost 800 V device housed in a TO-220FP package, and needing only a small
heat sink. The transformer is layer type, using a standard ferrite size ETD-29 and is
manufactured by Magnetica. The flyback reflected voltage is ~190 V, providing enough
room for the leakage inductance voltage spike still within the reliability margin of the
MOSFET. The rectifier D2 and the Transil D3 clamp the peak of the leakage inductance
voltage spike at MOSFET turn-off.
The resistors R14 and R15 sense the current flowing into the transformer primary side.
Once the signal at the current sense pin has reached the level programmed by the internal
multiplier of the L6562A, the MOSFET turns off.
Once the signal at the current sense pin has reached the level programmed by the internal
multiplier of the L6562A, the MOSFET turns off.
The divider R7, R8, R9 and R6 provides to the L6562A multiplier pin with instantaneous
voltage information which is used to modulate the current flowing into the transformer
primary side.
voltage information which is used to modulate the current flowing into the transformer
primary side.
The divider R20 and R21 is dedicated to sensing the output voltage, and capacitor C16 and
diodes D7 and D8 provide a soft-start at turn-on. Output regulation is done by means of an
diodes D7 and D8 provide a soft-start at turn-on. Output regulation is done by means of an