Wide Input Flyback Converter Features 5V at 2.6A Output

Wide Input Flyback Converter Features 5V at 2.6A Output

著者の連絡先情報

This reference design is for a highly efficient, flyback, 5V Class 3 powered device (PD) with a wide 9V to 57V auxiliary input. The design features the MAX5969B as its controller. The design also uses the MAX5974D, which controls current-mode PWM converters and provides frequency foldback for both the auxiliary input and power over Ethernet (PoE) applications. Using these devices, this reference design is IEEE® 802.3af/at compliant. It is also a high-performance, compact, and cost efficient solution for a Class 3 PD. The design can also support the wide auxiliary-input voltage range to provide 10W output power.

General Description

This reference design features the MAX5969B and MAX5974D. The MAX5969B controller is fully compliant with the IEEE 802.3af/at standard in a power-over-Ethernet (PoE) system. The device can also be powered from a wall adapter (WAD). The MAX5974D controls wide 9V to 57V input-voltage, active-clamped, current-mode PWM converters and provides frequency foldback. Using these devices, this reference design is IEEE 802.3af/at compliant. It is also a high-performance, compact, and costeffective solution for a Class 2 PD or a Class 3 PD.

Specifications:

  • The 5V/2.6A PD meets the following specifications:
  • Input voltage: 36V to 57V
  • WAD input voltage: 9V up to 57V
  • VOUT: 5V/2.6A
  • Output ripples: ±2%
  • Load transient VP-P: ±2% (50% step-load)
  • Line and load regulation: ±0.2%
  • Total efficiency with a load of 2.5A at 5V and a 48V input: 87.4% (not including input LAN transformer and diode bridge)

Top view of the reference design

Top view of the reference design

Bottom view of the reference design

Bottom view of the reference design

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

 

Figure 9

Transient Response

  • VIN = 40V, IOUT2 = 1A–2.5A
  • Ch1: 100mV/div, 5V output voltage
  • Ch4: 1A/div, output current
  • Time base: 2ms/div

Figure 10

Transient Response

  • VIN = 16V, IOUT2 = 1A–2.5A
  • Ch2: 200mV/div, 5V output voltage
  • Ch4: 1A/div, output current
  • Time base: 2ms/div