M54124L データシートの表示（PDF） - Renesas Electronics

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M54124L

Earth Leakage Current Detector

Renesas Electronics 

M54124L

Explanation of Operation

Operation is explained referring to the block diagram, an application example, and operation waveform diagrams.

• When a leakage current Ig occurs on the primary side of ZCT (the zero-phase current transformer), a leakage signal

voltage VIN appears in the secondary-side output, and is input to the input pin IN with the reference voltage pin VR

as reference.

• During the half-cycle when VIN is negative, in the interval in which VIN is below the DC trip voltage VT (DC), the

capacitor CMA connected to pin MA is charged. In this case, if the pin voltage VMA does not reach the MA turn-on

voltage, when the charging interval ends the capacitor CMA is discharged with a current greater than the charging

current. If the pin voltage VMA reaches the MA turn-on voltage, from that moment until VMA reaches the MA turn-

off voltage, CMA is discharged with a small current, to obtain the time tCO.

• During the interval of this time tCO, a similar operation is performed for the capacitor CMB, as a result of which an

output current with pulse width tOS is output from the output pin OS.

• That is, the leakage current when the interval during which the amplitude of the input voltage VIN is equal to or

greater than the DC trip voltage VT (DC) coincides with the input detection time tMA (= tMB) is the sense current for

the earth leakage breaker.

• Also, the output current turns on the thyristor, opening an external contact point to cause the breaker to operate.

Operation Waveforms

Rev.1.0, Sep.16.2003, page 3 of 9

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