M54124L
Explanation of Operation
Operation is explained referring to the block diagram, an application example, and operation waveform diagrams.
•
When a leakage current I
g
occurs on the primary side of ZCT (the zero-phase current transformer), a leakage signal
voltage V
IN
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 V
IN
is negative, in the interval in which V
IN
is below the DC trip voltage V
T
(DC), the
capacitor CMA connected to pin MA is charged. In this case, if the pin voltage V
MA
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 V
MA
reaches the MA turn-on voltage, from that moment until V
MA
reaches the MA turn-
off voltage, C
MA
is discharged with a small current, to obtain the time t
CO
.
•
During the interval of this time t
CO
, a similar operation is performed for the capacitor C
MB
, as a result of which an
output current with pulse width t
OS
is output from the output pin OS.
•
That is, the leakage current when the interval during which the amplitude of the input voltage V
IN
is equal to or
greater than the DC trip voltage V
T
(DC) coincides with the input detection time t
MA
(= t
MB
) 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
RENESAS [ RENESAS TECHNOLOGY CORP ]
