EVL250W-ATX80PL STMicroelectronics, EVL250W-ATX80PL Datasheet - Page 15

• Manufacturer Part Number: EVL250W-ATX80PL
• Description: BOARD DEMO SMPS L6591/L6563S
• Manufacturer: STMicroelectronics
• Series: VIPer™ plusr

Specifications of EVL250W-ATX80PL

• Main Purpose: Power Supply, ATX
• Outputs And Type: 3, Isolated
• Power - Output: 250W
• Voltage - Output: 12V, 5V, 3.3V
• Current - Output: 13.5A, 12A, 8A
• Voltage - Input: 88 ~ 264VAC
• Regulator Topology: Flyback
• Frequency - Switching: 80kHz
• Board Type: Fully Populated
• Utilized Ic / Part: L6563S, L6591, L6727, VIPer27H
• Input Voltage: 88 VAC to 264 VAC
• Output Voltage: 3.3 V, 5 V, 12 V
• Maximum Operating Temperature: + 60 C
• Operating Supply Voltage: 80 VAC to 264 VAC
• Output Power: 250 W
• Product: Power Management Development Tools
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: L6563S PFC controller
• Other names: 497-10596

AN3203
Asymmetrical half bridge operation
Figure 9.
AHB secondary side key waveforms @ full load
Ch2: Q201 and Q202 drain pin (blue)
Ch3: FGND pin voltage (purple)
Ch4: Diode D13 current (green)
In order to improve the overall efficiency of the power supply, synchronous rectification has
been used. The two AHB output diodes have been replaced with two MOSFETs. A self
driven technique has been used to obtain a cheap solution. Two extra windings at the
secondary side generate the two square waves that, opportunely shifted, drive the two SR
MOSFETs gates directly. Referring to Q201, the extra winding (realized with just one turn)
starts from transformer pin 10 and ends in TON_DR_FLYWIRE. C210, D204, and R216 are
used to shift the voltage at the correct level to drive the MOSFET. R202 helps to keep the
MOSFET off if no driving signal is applied. A similar circuit drives the gate of Q202 starting
from the TOFF_DR_FLYWIRE signal.
Doc ID 17402 Rev 1
15/45