MPZ2012S221A datasheet(19/56 Pages) STMICROELECTRONICS

19 / 56 page

6.2

Output voltage load regulation

Primary output load regulation

Figure 20 shows negligible primary output voltage variation (normalized to the value measured at IOUT = 0 A) over

the entire output current range for the L6983I with VOUTprim = 5 V.

Figure 20. Load regulation of the primary not isolated output voltage (VIN = 12 V, VOUT_prim = 5 V, fSW = 400

kHz)

Secondary output load regulation

Since there is no regulation loop involving the secondary output, its load regulation depends, to some extent,

on the primary load regulation and is affected by the leakage inductance (see Figure 22) of the transformer,

the voltage drops across to the Schottky diode (diode forward voltage) and the DCR of the secondary coil, as

indicated by the equation (Eq. (1)) (where only the last two contributions are considered). Minimizing all the

mentioned parameters leads to a better load regulation.

As shown in Section 6.1 , the input voltage also plays a role in the isolated output regulation, as depicted by

Figure 21.

Figure 21. Load regulation of the secondary isolated output voltage (VIN = 12 V, VOUT_prim = 5 V, fSW = 400

kHz, N = 6)

-30%

-20%

-10%

10%

20%

30%

0,1

0,2

0,3

0,4

0,5

0,6

0,7

Isolated output current [A]

Vin = 12V

Vin = 18V

Vin = 24V

L6983I

Output voltage load regulation

DS14040 - Rev 1

page 19/56

MPZ2012S221A Datasheet(PDF) 19 Page - STMicroelectronics