MP4012 ─ HIGH-VOLTAGE, HIGH-CURRENT ACCURACY WLED CONTROLLER

MP4012 Rev. 1.12

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10

10/12/2013

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The short circuit threshold current is internally set

to 200% of the steady state current. When the

output current becomes higher than the short

circuit threshold after some delay, the short

circuit protection circuit is activated. See Figure

3. This allows the LED drive system auto-restart

in an accident short condition without having to

reset the IC.

The open load protection is achieved through

detecting the OVP pin voltage. When open load

fault occurs, the output voltage rises as the

output capacitor is still charged. The over voltage

protection turns off the MP4012 and takes

FAULT to GND when the OVP pin exceeds

4.95V. The converter turns on when the output

voltage falls below the falling OVP threshold after

a hiccup mode delay timer. MP4012 will repeat

the process until the open load fault is removed.

When recovering from the open load condition,

the output current might have some spike which

caused by the high output voltage, and trigger

the short load protection. But it can enter normal

work mode when output voltage is close to the

normal value. See Figure 4.

Short Load

5V

Output

Current

Fault

COMP

Normal Current

1V

Hiccup Time

Short Load

Recover

Figure 3 — Hiccup Mode Short Load

Protection

5V

Output

Current

Fault

COMP

Normal Current

1V

Open Load

OVP-H

Output

Voltage

OVP-L

Vout-normal

Open Load

Recover

Figure 4 — Open Load Protections