VIPER12A datasheet(7/11 Pages) STMICROELECTRONICS

7 / 11 page

AN1484 - APPLICATION NOTE

7/11

- The voltage variation of the primary and the

auxiliary side of the converter must be opposite. In

this design, the D3 diode has been placed on the

ground so the voltage swing is opposite on the

transition.

2.5 Transformer Specification

Lp = 2.5mH @ 50KHz

Ll =30

µH @ 50KHz

Cp = 35pF @ 1MHz

Voltages: 55V-Pri / 7.2V-Sec. / 20.0V-Aux

Isat > 400mA

Pout = 5W

Geometry: E12.5

Winding Order: Primary / Secondary / Auxiliary

Primary Winding: 180 Turns AWG 38

Auxiliary Winding: 66 Turns AWG 38

Secondary Winding: 25 Triple isolation 0.20mm

3.0 SYSTEM PERFORMANCES

3.1 Efficiency

The Power losses are distributed at 6V / 600mA

output power as follows:

- 400mW in the output diode

- 700mW in the VIPer12A

- 300mW in the transformer

- 380mW in the shunt resistor

Overall efficiency is 3.6W/ (3.6W+1.78W)=67%.

If the losses in the shunt resistor are considered as

available power, the converter efficiency becomes

3.98W/(3.98W+1.4W)=74%. This is possible using

secondary controller like STM’s TSM101.

Figure 7a: Efficiency at 100V

Figure 7b: Efficiency at 380V

3.2 Regulation

Figure 8: VOUT Vs. IOUT

3.3 Standby Consumption

The demoboard consumes less than 100mW at

100VDC and 120mW at 380VDC. This power level

is far below today regulation’s requirement.

The charts in Figure 9a/9b shows the details of the

charger standby consumption at minimum and

maximum input voltage.

The major contribution to the standby consumption

is the VIPer12A own consumption of just 35mW

and is independent from input voltage.

0.5

1.5

2.5

3.5

Pout (W)

Efficiency CV

Efficiency CC

0.5

1.5

2.5

3.5

Pout (W)

Efficiency CV

Efficiency CC

100

200

300

400

500

600

700

800

Iout (mA)

Vout (V)

100V

380V

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