MP6004—PRIMARY-SIDE REGULATED FLYBACK/BUCK 80V DCDC CONVERTER

MP6004 Rev. 1.0

www.MonolithicPower.com

16

4/14/2015

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DCM Detection

The

MP6004

regulator

operates

in

discontinuous conduction mode in both flyback

and buck modes.

In flyback mode, the MP6004 detects the falling

edge of the FB1 voltage in each cycle. The

second cycle switching will not start unless the

chip detects a 50 mV falling edge on FB1.

In buck mode, the MP6004 detects the falling

edge of the SW voltage in each cycle. The

second cycle switching will not start unless the

chip detects 0.14 V falling edge between

Over-Voltage & Open-Circuit Protection

In flyback mode, the MP6004 includes over-

voltage protection (OVP) and open-circuit

protection. If the voltage at FB1 exceeds 125

cannot be detected because the feedback

resistor is removed), immediately the MP6004

shuts off the driving signal and enters hiccup

mode by re-charging the internal capacitor. The

MP6004 resumes normal operation when the

fault is removed.

In buck mode, if the voltage at FB2 is higher

than the reference voltage, the MP6004 stops

switching immediately.

Over-Load Protection

MP6004 will always work in DCM mode for any

condition.

In flyback mode, the secondary-side diode

conduction duty cycle is limited to about 80

percent. In an over-load condition, the output

load, the output drops and the diode conduction

period becomes longer. This causes the

switching frequency to drop so that the output

energy can be limited. The MP6004 has same

protection logic for an over-load/output-short

condition.

In buck mode, the duty cycle limitation does not

apply, but the output current is limited to half of

Thermal Shutdown

When the junction temperature exceeds 150°C,

the MP6004 shuts down. Once the temperature

drops below 130°C, the part

re-starts

automatically.