AN3011 datasheet(12/37 Pages) STMICROELECTRONICS

12 / 37 page

Testing the board

AN3011

12/37

Doc ID 16043 Rev 1

Figure 11.

Output voltage ripple 115 VINAC full-load

The measured output voltage ripple is around 20 mV, well below the maximum admitted

value (50 mV, see electrical specification in Table 1).

Figure 12.

Output voltage ripple 230 VINAC full-load

When the device is working in burst mode, a lower frequency ripple is present. In this

operation mode the converter does not supply continuous power to its output. It alternates

periods when the power MOSFET is kept off, and no power is processed by the converter,

and periods when the power MOSFET is switching and power flows towards the converter

output. Even no-load is present at the output of the converter, during no switching periods

the output capacitors are discharged by their leakage currents and by the currents needed

to supply the circuitry of the feedback loop present at the secondary side. During the

switching period the output capacitance is recharged. Figure 13 and 14 show the output

voltage and the feedback voltage when the converter is no-loaded. In Figure 13 the

converter is supplied with 115 VAC, and with 230 VAC in Figure 14.

AN3011 Datasheet(PDF) 12 Page - STMicroelectronics