AN2530

Full load, normal operation waveforms

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Full load, normal operation waveforms

Figure 4 shows the normal full load operation waveforms for this converter.

(upper MOSFET), is up to 370 V due to the charge pump inside the driver.

Channel 3 is the resonant current flowing through L1, measured with a hall effect probe.

There is a lack of symmetry probably caused by the hand-wound transformer and coil. The

major contributor to this should be the non-symmetric primary winding for the transformer

that imposes different loads as current flow changes direction at the primary.

Channel 4 is the resonant voltage at C18.

Figure 4.

Operating waveforms at full load

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Measurement conditions

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As previously stated in the introduction, this type of converter has some very good

characteristics, one of which is the very high efficiency, typically over 90%, that is easily

achieved with resonant, very low RF and EMI produced due to ZVS.

Figure 5 shows the efficiency curve against the output power and against input voltage

(Figure 6). Notice that there are two curves (Figure 5), the upper one is the efficiency curve

for this converter, as you can see in the schematic in Figure 3 . The other one is the same

converter connected after a PFC circuit. This one uses ST's L4981A as its primary driver,

References and is referred to in the conclusion.