Mitsubishi M54124L Datasheet
MITSUBISHI <CONTROL / DRIVER IC>
)
M54124L
EARTH LEAKAGE CURRENT DETECTOR
DESCRIPTION
The M54124L is a semiconductor integrated circuit consisting of an
amplifier for a high-speed earth-leakage circuit breaker.
FEATURES
●Satisfies JIS C 8371
●Temperature-stable input current threshold
●High-input sensitivity (VT = 6.5mV)
●Low external component count
●Highly resistant to noise and power surges
●Low power dissipation (Pd = 5mW typ)
●Can be used at 100V and 200V
●High-density mounting eight-pin SIL package
●Wide operating temperature range (Ta = -20 – +80°C)
APPLICATION
High-speed earth-leakage circuit breakers
FUNCTION
The M54124L is a semiconductor integrated circuit for use in the
amplifier section of earth-leakage circuit breakers. It consists of a
differential amplifier, one-shot circuit, output circuit and voltage
regulator. It is connected to the secondary side of the zero-current
transformer, ZCT, and detects leakage current in both inputs of the
differential amplifier. Signals amplified by the differential amplifier
are integrated by an external capacitor, and applied to the input pin
of a one-shot multivibrator circuit having time-delay characteristics
that are suitable for high-speed earth-leakage circuit breakers
(such as specified in JIS C 8371). The one-shot multivibrator circuit
normally maintains a low output. When the input current (earthleakage) exceeds a specified level, a one-shot high pulse is output
to turn on an externally connected thyristor.
PIN CONFIGURATION(TOP VIEW
1
Input
VR
GND
OD
MA
MB
OS
V
→
2
IN
3
M54124L
←
4
→
5
→←←
6
←
7
8
S
Outline 8P5
Reference voltage
Differential amplifier output
One shot multivibrator A
One shot multivibrator B
Output
BLOCK DIAGRAM
R
V
2
1
INV
R GND OD
Reference
voltage
Input
1
0
Comparator
Differential
amplifier
output
5
4
MA
One shot
multivibrator A
One shot
multivibrator
A
VCC
Output
circuit
1
0
multivibrator B
One shot
multivibrator
B
6
MB
One shot
1
0
VR
7 83
OS
Output
Regulator
VS
OPERATION
(
)
g
)
)
)
Discussion refers to the block diagram, application example, and
operational waveform diagram.
• When an earth leakage current appears on the primary side of
zero-current transformer ZCT, leakage signal voltage VIN
appears on the secondary side and is input at IN with VR as the
reference.
• In the half cycle when VIN is negative, capacitor CMA connected
to pin MA charges until VIN reaches the trip voltage VT (DC). If
voltage VMA at pin MA does not reach the MA threshold voltage,
capacitor CMA discharges immediately at a current greater than
the charge current, when the charging current phase is
completed. When VMA reaches the MA threshold voltage,
capacitor CMA discharges at a small current for a period time tCO
during which the output of one-shot multivibrator A is high.
• During tCO, the same operation takes place again at capacitor
CMB, causing one-shot multivibrator B to trigger current pulse of
duration tOS at output pin OS.
• Earth leakage currents are detected when the amplitude of input
voltage VIN exceeds the trip voltage VT (DC) for longer than the
input detection time tMA.
• The output current is used to turn on the thyristor that opens the
breaker contacts.
MITSUBISHI <CONTROL / DRIVER IC>
M54124L
EARTH LEAKAGE CURRENT DETECTOR
OPERATING WAVEFORM DIAGRAM
Earth leakage signal VIN
IN
V
R
VR
OD
H
L
0MA
H
L
0MB
0OS
VMA
∗
MA
3ms
t
∗
tMB (3ms
Comparator
1 output
One-shot
A1 output
VT(DC)
MA “ON” voltage
MA “OFF” volta
∗
tCO (65ms
VMB
∗
t
: MA input detection time
MA
tCO
: MA detector on time
tMB
: MB input detection time
tOS
: OS output pulse width (MB detector on time)
Note. The values in the parentheses are typical values for reference only.
MB “ON” voltage
∗
tOS (95ms
e
MB “OFF” voltage
VOS
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