Secondary Control for Energy-Saving AC Adaptor MM1548
MITSUMI
Secondary Control for Energy-Saving AC Adaptor
Monolithic IC MM1548
Outline
This IC is secondary control on AC adaptors that have energy-saving mode. The energy-saving mode
function operates when charging is completed or when the set is unplugged, thus greatly reducing AC
adaptor power consumption.
When a set is connected, normal mode automatically starts and charging starts.
Compared to the conventional MM1529, this IC is smaller and has fewer external components.
Features
1. Automatic switching between energy-saving mode and normal mode
2. Current consumption (energy-saving mode)
60µA
3. Current consumption (normal mode)
1.5mA
4. Uses one photocoupler to control oscillator primary side.
5. One photocoupler is used to control rated voltage and rated current and switching between energy-saving
and normal modes.
Package
SOT-26
Pin Assignment
1
6
2
5
3
4
SOT-26
1
OUT
4
PO1
2
CNT
5
GND
3
VCC
6
CS
Secondary Control for Energy-Saving AC Adaptor MM1548
MITSUMI
Block Diagram
Load detection resistor
RLS
PC1
RLB
transformer secondary side
Primary-side switching
control
RL1
PO1
VCC
4
CNT
3
OUT
2
Photocoupler-turn-off
1
Voltage buffer
COUT
Input/output difference control
(VCC-OUT=200mV)
Load detection(current)
(115mV 200mV)
ROS1
1.25V
Reference voltage
VCC=4.6V
VCC
Load detection(voltage)
(VCC=3.5V)
Constant voltage control
(VCC=5.1V)
5k
ROS2
Over voltage
detection
(7V)
Constant current control
(CS=114.4mV)
(CS=34mV)
Reference voltage decrease (drop)
5
GND
6
RCS
Constant current detection resistor
CS
Secondary Control for Energy-Saving AC Adaptor MM1548
MITSUMI
Pin Description
Pin No.
Pin Name
1
OUT
Function
Internal equivalent circuit
Output (+) pin.
Connect Registor for load detection
1
V CC
between VCC pin, and connect collector
of PNP power transistor.
2
CNT
PNP power transistor control pin.
Connect base of PNP power transistor.
3
VCC
2
(+) power supply pin.
This pin doubles load detection pin.
3
Connect load detection resistor
between OUT pin, and connect emitter
of PNP power transistor.
4
PO1
1.25V
Photo diode drive pin of photocoupler
4
for constant-current and constantvoltage control.
Connect to cathode of diode.
5
GND
6
CS
Ground pin of this IC.
Overcurrent detection pin.
V CC
This pin doubles as output- pin.
Connect Resistor for overcurrent
detection between GND pin.
6
Secondary Control for Energy-Saving AC Adaptor MM1548
MITSUMI
Absolute Maximum Ratings
(Ta=25°C)
Item
Symbol
Ratings
Unit
Storage temperature
TSTG
–40~+125
°C
Operating temperature
TOPR
–30~+85
°C
Supply voltage
VCC max.
–0.3~+18
V
Allowable loss
Pd
150 (alone)
mW
Recommended Operating Conditions
Item
Symbol
Ratings
Unit
Operating temperature
TOPR
–30~+85
°C
Supply voltage
VOP
+2.5~+12
V
Electrical Characteristics
(unless otherwise specified, Ta=+25°C, Vcc=4.9V)
Item
Symbol
Test Conditions
Current consumption1(energy saving mode)
ICC1
VCC=4.4V, VOUT=4.4V, VCS=0V
Current consumption2(normal mode)
ICC2
VCC=5.3V, VOUT=5.0V, VCS=0V
Voltage control section
Output inversion voltage
VO
IIN=5mA, VOUT=VCC–0.3V, VCS=0V
OUT input sink current
IOUT
VCC=4.9V, VOUT=4.9V, VCS=0V
PO1 output sink current 1
IPO1
VCC=5.3V, VOUT=5.0V, VCS=0V VPO1=0.5V
Constant current control
Output inversion voltage 1
VCC=4.9V, RCS1=1kΩ, VOUT=4.6V, RCS2=40kΩ, IIN=5mA
VCS1
(Constant current control)
Output inversion voltage 2
VCC=2.0V, RCS1=1kΩ, VOUT=0V, RCS2=40kΩ, IIN=5mA
VCS2
(Constant current control drop)
CS input source current
ICS
VCC=4.9V, VOUT=4.6V, VCS=0.1V
Power supply voltage rejection ratio PSRR2
VCC=3.7V 4.4V, VCS=VCS1–10mV, RL1=5kΩ
PO1 output sink current 2
IPO2
VCC=4.9V, VOUT=4.6V, VCS=0.2V, VPO1=0.5V
Input-output difference control
Input-output difference control voltage
VLS
VCC=5.1V, RLS=4.7kΩ, RLB=100Ω, RO=5kΩ
CNT output sink current
ICNT
VCC=5.1V, VOUT=4.8V, VCS=0V, VCNT=0.8V
Load detection
Load detection voltage
VLSP1
VCC=4.9V, RL1=47kΩ, VOUT=4.9V L, VCS=0V
Energy saving detection voltage
VLSP2
VCC=4.9V, RL1=47kΩ, VOUT=L 4.9V, VCS=0V
(load detection release voltage)
3.5V undervoltage detection
VOL1
VCC=H L, RL1=10kΩ, VOUT=VCC, VCS=0V
3.5V undervoltage detection hysteresis
VOL1H
VCC=L H, RL1=10kΩ, VOUT=VCC, VCS=0V
4.6V undervoltage detection
VOL2
VCC=H L, RL1=47kΩ, VOUT=VCC, VCS=0V
PO1 output sink current 3
IPO3
VCC=4.9V, VOUT=4.6V, VCS=0V, VPO2=1.0V
VCC=4.9V, VOUT=4.9V, VCS=0V, VPO2=4.6V
PO1 output source current
IPO4
Constant current mode selection
2pin(CNT pin) disable voltage VCNTO
VCC=H L, VCNT=0.8V, VOUT=VCC–0.3V, VCS=0V, ICNT < 1mA
Constant current mode selection threshold
VCSS
VCC=4.9V, RCS1=1kΩ, VOUT=4.6V, RCS2=20kΩ, IIN=5mA, VCS < VCS min.
(between VCC and OUT)
Min. Typ. Max. Unit.
60
110
µA
1.5
3.0 mA
4.99
5
5.10
25
17
5.21
150
V
nA
mA
111.2 114.4 117.6 mV
22
34
100
60
5
5
70
17
nA
dB
mA
140
5
200
30
260
mV
mA
170
200
230
mV
85
115
145
mV
3.4
3.5
350
4.60
200
5.0
3.6
V
mV
V
µA
mA
4.47
100
1.0
mV
4.73
400
2.4
V
0.6
V
Secondary Control for Energy-Saving AC Adaptor MM1548
MITSUMI
Measuring Circuit 1
ICC1, ICC2, IOUT, ICS, IPO1, IPO2, IPO3, IPO4, ICNT
I PO1
A
4
5 GND
I CS
A
V CS
V PO1
6
3
A
CNT 2
A
OUT 1
A
PO1
CS
VCC
I CC
I CNT
I CNT
V OUT
V CNT
V CC
VCC
VOUT
VCS
VPO1
VCNT
ICC1
4.4V
4.4V
0.0V
OPEN
OPEN
ICC2
5.3V
5.0V
0.0V
OPEN
OPEN
IOUT
4.9V
4.9V
0.0V
OPEN
OPEN
ICS
4.9V
4.9V
0.1V
OPEN
OPEN
IPO1
5.3V
5.0V
0.0V
0.5V
OPEN
IPO2
4.9V
4.6V
0.2V
0.5V
OPEN
IPO3
4.9V
4.6V
0.0V
1.0V
OPEN
IPO4
4.9V
4.9V
0.0V
4.6V
OPEN
ICNT
5.1V
4.8V
0.0V
OPEN
0.8V
Measuring Circuit 2
VLSP1,
VLSP2,
VOL1,
VOL2
RL1
RL3
4
PO1
5 GND
VCC
3
CNT 2
RL2
V
6
CS
OUT 1
V
V OUT
VCC
VOUT
VCS
V CC
VPO1
VCNT
VLSP1
4.9V
4.9
4.6V
0V
RL1=47kΩ RL3=10kΩ
VLSP1
4.9V
4.6
4.9V
0V
RL1=47kΩ RL3=10kΩ
VOL1
3.7
3.3V
VCC
0V
RL1=10kΩ
OPEN
VOL2
4.8
4.4V
VCC
0V
RL2=47kΩ
OPEN
Secondary Control for Energy-Saving AC Adaptor MM1548
MITSUMI
Measuring Circuit 3
VLS
4
PO1
VCC
2SB1424
3
5 GND
V
CNT 2
100Ω
6
V CC
RLS
RLB
CS
4.7k
OUT 1
COUT
RO
5kΩ
100µF
Measuring Circuit 4
RL1
PSRR2
5kΩ
4
PO1
VCC
3
V
10kΩ
5 GND
V CC
3.7V 4.4V
CNT 2
100Ω
6
CS
OUT 1
V OUT
V CS
V CC–0.3V
Measuring Circuit 5
VO
I in
5mA
4
V
PO1
5 GND
6
CS
VCC
3
CNT 2
OUT 1
V OUT
Measuring Circuit 6
VCS1, VCS2
I in
5mA
4
PO1
VCC
3
V CC
RCS2
5 GND
CNT 2
V
6
RCS1
CS
OUT 1
V OUT
Secondary Control for Energy-Saving AC Adaptor MM1548
MITSUMI
Operation
Voltage between VCC and OUT(200mV)
Load current
RLS
Output
(+)
470Ω
CNT
VCC
200mV
PC1
200mV
RLB
100Ω
OUT
Input/output difference control
Load current detection
115mV Energy saving current detection
Energy saving mode
Normal mode
Voltage drop detection
(V=4.6V)
Voltage drop detection
(VCC=3.5V)
ROS1
REF
ROS2
Overvoltage
detection
(VCC, OUT=7V)
Constant voltage control
(VCC=5.1V)
Energy saving mode control
(3.5V :ON, 5.1V :OFF)
Load
Supply transistor
Constant current control
(CS=114.4mV)
(Io=520mA)
Photocoupler-turn-off(4.6V )
PO1 drive(Load 5kΩ)
PO1 drive
Photocoupler PC1 control
PO1
GND
RCS
0.22Ω
CS
(–)
1. Operation of Blocks
1.1 Input/output difference control
In the normal mode that a load current is detected and the system supplies the load current through the
Supply Transistor (PNP type), MM1548 controls CNT current flowing into the base of Supply Transistor to
keep the differential voltage between VCC and OUT (Vce of Supply Transistor) at 200mV.
1.2 Load current detection and Energy saving current detection
When load current increases in energy saving mode and the differential voltage between VCC and OUT
exceeds VLSP1 (200mV), MM1548 changes to the normal mode, PO1 switches from open to low mode,
and the photocoupler PC1turns on. As a result, the system switches primary-side switching operation to
normal mode from disabled.
The switching voltage has following hysteresis if load current is increasing ( VLSP1) or decreasing
( VLSP2).
( hysteresis: VLSP1 = 200mV < > VLSP2 = 115mV)
When the differential voltage between VCC and OUT falls to
VLSP2 (115mV), MM1548 changes to the
energy saving mode, and the photocoupler-turn-off circuit switches compulsory photocoupler current to
zero under the condition that load current is decreasing in normal mode and Vcc = 4.6V or more.
1.3 Voltage drop detection
When VCC voltage falls to 4.6V in the energy saving mode, MM1548 stops the photocoupler-turn-off circuit
operation to save consumption current of MM1548.
When VCC voltage falls to 3.5V in the energy saving mode, MM1548 changes to the normal mode.
As a result, Out voltage (output of secondary side) swings intermittent between 4.9V and 3.5V.
1.4 Constant current control
When load current is increasing in the normal mode, and the differential voltage between CS and GND
exceeds VCS1(114.4mV typ.), PO1 switches from open to low mode, and the photocoupler PC1 turns on. As
a result, MM1548 changes to the CC(constant current) mode, and the load current is controlled that CS
voltage keeps VCS1.
1.5 Constant voltage control
When MM1548 is in normal mode and isn't in constant current mode, it is in CV(constant voltage) mode,
and PO1 current is controlled that VCC voltage keeps 5.1V (equal to internal 1.25V: REF voltage).
Secondary Control for Energy-Saving AC Adaptor MM1548
MITSUMI
1.6 Overvoltage detection
When VCC voltage or OUT voltage exceeds 7V (overvoltage), overvoltage detection circuit turn on.
As a result, PO1 sink current is controlled to turn on the photocoupler PC1, and system is protected from
overvoltage.
This circuit also detects negative voltage applied CS pin, and when it is detected, PO1 current is turned off
for overvoltage protection.
Vo(5.1V typ.)– VLS(0.2V typ.)
Output voltage (between OUT and CS) [V]
2. Design principles for each mode
AC adaptor output is controlled by following 4 mode under usage with MM1548.
Switching of each control mode is explained as follow.
Energy saving mode
(PO1:Open)
CV MODE
(PO1:Control)
VCS(115mV typ.)
Energy saving current detection (load detection release )
Load current detection
CC MODE
(PO1:Control)
CC MODE
Drop curve
(PO1:Control)
Load current [A]
(115mV/RLS)
(200mV/RLS)
34mV/RCS
114.4mV/RCS
2.1 for Output voltage
In MM1548 series, the output voltage can't be adjusted by external resistor, because referential voltage
terminal (REF pin) for adjustment is build in the chip.
Instead of voltage adjustment, you can chose output voltage by select the rank of MM1548 series.
Output voltage is lower 0.2V (equal to in-out differential control voltage) than 5.1V(equal to the value set by
ROS1 and ROS2).
[Formula]
Output voltage
= Vo – VLS
= {1+(ROS1/ ROS2)} 1.25 – VLS
= {1+(2460k/800k)} 1.25 – 0.2
= 4.9V
(Vo = 5.1V)
( VLS = 0.2V)
Secondary Control for Energy-Saving AC Adaptor MM1548
MITSUMI
2.2 for Constant current detection (RCS adjust method)
Constant current value is set by RCS value as load detection resistor.
On the design, constant current operation changes when [load current] > 520[mA] in the case of 0.22Ω use.
[Formula]
[Constant current control] = VCS1 / RCS
[Drop curve]
= VCS2 / RCS
(VCS1 = 114.4mV)
(VCS2 = 34mV)
RCS(constant current detection resistor) - constant current control value
1200
constant current control value [mA]
1100
I= (VCS1) / RCS
1000
900
800
min.
700
typ.
600
0.22Ω
max.
500
400
300
200
0.1
1.0
RCS(constant current detection resistor) [Ω]
2.3 Description of load detection and energy saving detection (RLS adjust method)
Load detection current and energy saving detection current is set by RLS as load detection resistor.
On the design, each current changes when [current flows through RLS] > 240µA, in the case of 470Ω use.
[Formula]
[Load detection current]
= ( VLSP1 / RLS)
( VLSP1 = 200mV)
[Energy saving detection current] = ( VLSP2 / RLS)
( VLSP2 = 115mV)
RLS (Load detection resistor) - Energy saving detection current
1200
Energy saving detection current [µA]
1100
I= (
1000
VLSP2) / RLS
900
800
700
min.
600
500
typ.
470Ω
max.
400
300
200
100
0
0.1
1
RLS (Load detection resistor)
10
[kΩ]
Secondary Control for Energy-Saving AC Adaptor MM1548
MITSUMI
Timing Chart
Constant voltage control
Energy saving mode [Io<115mV / RLS]
Normal mode [Io>115mV / RLS]
VCC
VCC
5.1V
2
4.9V
VCC, OUT PIN
(secondary side output)
1
OUT
5.1V
4.9V
3.5V
0V
0V
0mA
0mA
ON
ON
OUT
3
PO1 current
(load det. + constant
voltage control output)
4
Primary side switching
OFF
OFF
Normal mode
Energy saving mode
Energy saving mode
Normal mode
Normal mode
Constant current control
Drop control [VCC<2.0V]
Normal control [VCC>2.0V]
2
1
VCC, OUT PIN
(secondary side output) 2V
VCC
200mV
OUT
0V
2V
over 0.6V
0V
OUT
3
PO1 current
(load det. + constant
voltage control output)
0mA
0mA
ON
ON
OFF
OFF
4
Primary side switching
114.4mV
5
CS terminal
(constant current
control input)
34mV
0mV
0mV
1
4
AC input
2
output
RL S
+
Rectifying
circuit
Delay circuit
Smoothing
circuit
VCC CNT OUT
MM1548
PO1 GND CS
RCS
Switching
interruption
control
Switching
circuit
5
3
Signal detection
circuit
–
Photocoupler
Secondary Control for Energy-Saving AC Adaptor MM1548
MITSUMI
Timing Chart
Load / Energy-saving detection
Load current decrease
Load current decrease
5 Load current
Load detection current
(200mV/RLS)
Energy saving current
(115mV/RLS)
0mA
VCC
5.1V
1 VCC PIN
4.9V
115mV
2 OUT PIN
200mV
OUT
0V
3 PO1 PIN
Low(Load 5kΩ)
Open
4 CNT PIN
Control
Open
Load current increase
Load current increase
5 Load current
Load detection current
(200mV/RLS)
Energy saving current
(115mV/RLS)
0mA
1 VCC PIN
2 OUT PIN
VCC
5.1V
4.9V
200mV
OUT
0V
3 PO1 PIN
Low(Load 5kΩ)
Open
4 CNT PIN
Control
Open
1
AC input
2
5
RLS
Output
+
4
Rectifying
circuit
Delay circuit
Smoothing
circuit
VCC CNT OUT
MM1548
PO1 GND
CS
RCS
Switching
interruption
control
Switching
circuit
signal detection
circuit
3
Photocoupler
–
Secondary Control for Energy-Saving AC Adaptor MM1548
MITSUMI
Application Circuit
6.8
R7
Q5
OUTPUT
+
C9
220µ
R18
100
GND CS
470
0.22µ
R17
0.22
R11
R16
10k
C5
PO1
C10
R19
10
Q6
10k
PH1
C11
2200p
DC4.9V
520mA
VCC CNT OUT
1000p
0.1µ
R14
100k
R12
C13
0.0056µ
D2
C4
3.3M
R8 100k
R13
R9
4700p
C3
R10
10k
C6
0.22µ
Q4
470
MM 1548
Q1
Q3 470
D4
1M
R2
C7 470µ
R5
1.5M
D3
470
Q2
L2
R15
270k
R4
D1
T1
R3
R1
C12
4.7µ
AC100V
C2
4.7µ
L1
2.2M
10
R20
C8 220µ
INPUT
–