MP4655
Pure, Single-Stage, LLC, LED Current
and System Voltage Controller
The Future of Analog IC Technology
DESCRIPTION
FEATURES
The MP4655 is a pure, single-stage, LLC, LED
current and system voltage controller for LED
backlighting, especially in larger TVs, and is
located on the secondary side. The MP4655
uses an LLC power stage and an extra Nchannel MOSFET to regulate both the LED
current and the system supply voltage. The
MP4655 is powered by input supplies ranging
from 9V to 35V that output two 180 degree
phase shifted driving signals for the external
LLC power stages. Its enhanced 12V gate
driver provides sufficient driving capability and
can drive the external LLC MOSFETs directly
through an external gate-driving transformer.
The MP4655 also provides a direct driving
signal to control the extra N-channel MOSFET
and regulate the system supply voltage.
•
The MP4655 incorporates both PWM dimming
and analog dimming for the LED current. A
driving signal is output to directly drive the
dimming MOSFET, which helps achieve fast
and high-contrast ratio PWM dimming. The
analog dimming can be achieved through a DC
signal on ADIM or a pulse signal on ADIMP.
•
•
The MP4655 employs smart protection
methods to protect the LED driver stage and
system power stage in the event that a fault
occurs, increasing system reliability.
•
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•
•
Full protection features for the LED include
open LED protection, short LED protection,
over-LED current protection, feedback open
loop protection, and protection for any point of
the LED string shorting to ground.
All MPS parts are lead-free, halogen-free, and adhere to the RoHS directive. For
MPS green status, please visit the MPS website under Quality
Assurance. “MPS” and “The Future of Analog IC Technology” are registered
trademarks of Monolithic Power Systems, Inc.
•
•
•
•
•
•
•
•
•
•
•
•
•
Pure, 1-Stage LLC for LED Current and
System Supply Voltage Regulation
CC/CV Frequency Control Loop and Duty
Cycle Control Loop
Audible Noise Elimination
9V to 35V Input Voltage Range
Deep and Fast PWM Dimming
Analog Dimming with DC or Pulse Input
Signal
Input Under-Voltage Lockout (UVLO)
System Supply Over-Voltage Protection
(OVP)
System Supply Short Protection
LED Open, LED Short Protection
LED String Short to GND Protection
Open Feedback Loop Protection for System
Bus Voltage and LED Driver
Capacitive Mode Protection for LLC
Soft Switching for the Extra N-Channel
MOSFET
Fault Indicator
Available in a SOIC-28 Package
APPLICATIONS
LCD TVs and Monitors
Desktop LCD Flat Panel Displays
Flat Panel Video Displays
Street Lighting
Full protection features for the system supply
voltage stage include over-voltage protection
(OVP), over-current protection (OCP), and
feedback open-loop protection. The MP4655
uses an extra individual capacitive mode
protection to protect the LLC power stage in
any condition system in the event it enters
capacitive mode. The MP4655 also employs
thermal shutdown and is available in a SOIC-28
package.
MP4655 Rev 1.0
2/2/2016
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© 2016 MPS. All Rights Reserved.
1
MP4655–PURE, SINGLE-STAGE, LLC, LED CURRENT AND SYSTEM VOLTAGE CONTROLLER
TYPICAL APPLICATION
VSystem
D5
Cb
PFC_400V
D2
D1
Cr
C1
M2
400V LLC
AUX winding,
reinforced wire
C4
D6
TM
M1
C3
DCDC
C2
D3
D4
TDrive
Drive circuit
MP4655 Rev 1.0
2/2/2016
www.MonolithicPower.com
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© 2016 MPS. All Rights Reserved.
2
MP4655–PURE, SINGLE-STAGE, LLC, LED CURRENT AND SYSTEM VOLTAGE CONTROLLER
ORDERING INFORMATION
Part Number*
MP4655GY
Package
SOIC-28
Top Marking
See Below
*For Tape & Reel, add suffix –Z (eg. MP4655GY–Z)
TOP MARKING
MPS: MPS prefix
YY: Year code
WW: Week code
MP4655: Product code of MP4655GY
LLLLLLLLL: Lot number
PACKAGE REFERENCE
TOP VIEW
VDR_DN
1
28
CFLY
GATEN
2
27
GR
SOURCE
3
26
GND
FTH_CMODE
4
25
GL
CMODE
5
24
DIMO
SS
6
23
VCC
VOCP
7
22
PS_ON
FSET
8
21
VIN
VCOMP
9
20
PWMIN
VFB
10
19
ADIM
DCOMP
11
18
ADIMP
IFB
12
17
EN_LED
ICOMP
13
16
VLED2
IOCP/FAULT
14
15
VLED1
MP####_PD01-SOIC28 -or- TSSOP28
SOIC-28
MP4655 Rev 1.0
2/2/2016
www.MonolithicPower.com
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© 2016 MPS. All Rights Reserved.
3
MP4655–PURE, SINGLE-STAGE, LLC, LED CURRENT AND SYSTEM VOLTAGE CONTROLLER
ABSOLUTE MAXIMUM RATINGS (1)
Thermal Resistance
VIN, PS_ON, PWMIN .....................-0.3V to 40V
GL, GR, VCC, DIMO, CFLY............-0.3V to 18V
SOURCE ........................................-0.3V to 30V
VDR_DN, GATEN...........................-0.3V to 48V
VDR_DN - SOURCE, GATEN - SOURCE……….
........................................................-0.3V to 18V
IOCP/FAULT, VOCP, CMODE .........-6.5V to 6V
Other pins ......................................-0.3V to 6.5V
Junction temperature ................................150°C
(2)
Continuous power dissipation (TA = +25°C)
SOIC-28 ..................................................... 2.1W
Storage temperature ................ -65°C to +150°C
Operating frequency .............................. 400kHz
SOIC-28 ................................. 60 ...... 30... °C/W
Recommended Operating Conditions
(4)
θJA
θJC
NOTES:
1) Exceeding these ratings may damage the device.
2) The maximum allowable power dissipation is a function of the
maximum junction temperature TJ (MAX), the junction-toambient thermal resistance θJA, and the ambient temperature
TA. The maximum allowable continuous power dissipation at
any ambient temperature is calculated by PD (MAX) = (TJ
(MAX)-TA)/θJA. Exceeding the maximum allowable power
dissipation produces an excessive die temperature, causing
the regulator to go into thermal shutdown. Internal thermal
shutdown circuitry protects the device from permanent
damage.
3) The device is not guaranteed to function outside of its
operating conditions.
4) Measured on JESD51-7, 4-layer PCB.
(3)
Supply voltage (VIN) ........................-0.3V to 35V
Operating frequency ............... 20kHz to 350kHz
Operating junction temp. ......... -40°C to +125°C
MP4655 Rev 1.0
2/2/2016
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© 2016 MPS. All Rights Reserved.
4
MP4655–PURE, SINGLE-STAGE, LLC, LED CURRENT AND SYSTEM VOLTAGE CONTROLLER
ELECTRICAL CHARACTERISTICS
VIN = 13V, TA = +25°C, unless otherwise noted.
Parameter
Symbol
Condition
VIN Supply
VIN supply range
Quiescent current
IQ
VVCC
PS_ON = 5V,
no gate driver
PS_ON = 1.5V
PS_ON = 0V
Igate = 20mA
Igate = 20mA
With 1nF load
With 1nF load
400
IVCC = 0mA
IVCC = 30mA
IVCC = 50mA
IVCC = 50mA, VIN = 10V
VCC rising
Voltage dropout
VCC UVLO threshold
VTH_UVLO_VCC
VCC UVLO hysteresis
VTH_VCC_HYST
Gate Driver (GATEN, for Extra MOSFET on Vsystem)
GATEN pull-down resistance
RGD
Igate = 20mA
GATEN pull-up resistance
RGU
Igate = 20mA
Output source current
ISOURCE_GATEN With 1nF load
Output sink current
ISINK_GATEN
With 1nF load
GATEN Supply Voltage (VDR_DN)
Charge pump pull-up resistor
Charge pump pull-down resistor
Charge pump frequency
fchargepump
VDR_DN upper threshold to
Detection circuit,
stop charge pump in standby
Vth_upper_STB
very small leakage
mode
VCC - 5.5 > 5V
VDR_DN valley threshold to
recover charge pump in
standby mode
Vth_valley_STB
Leakage current from SOURCE
Ilkg_SOURCE
MP4655 Rev 1.0
2/2/2016
Typ
Max
Units
35
V
1.6
1.9
mA
106
0.6
120
0.8
μA
mA
800
Ω
Ω
A
A
ns
9
Shutdown current
Ishutdown
Standby current
ISTB
Gate Driver GL, GR (LLC Power Stage)
Gate pull-down resistance
RGD
Gate pull-up resistance
RGU
Output source current
ISOURCE
Output sink current
ISINK
Dead time
tdead
Gate Driver Supply Voltage (VCC)
Voltage
Min
VCC - 5.5 < 5V
11.5
11.3
11.2
7.2
1.8
2
8
0.5 (5)
1 (5)
600
12.5
12.3
12.2
0.53
7.74
2.05
13.5
13.3
13.2
8.2
2.3
V
V
V
V
V
V
2.5
9
0.5 (5)
1 (5)
Ω
Ω
A
A
13
4
455
Ω
Ω
kHz
VCC 2.5
V
VCC 5.5
V
5
VSOURCE = 24V,
charge pump disabled
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© 2016 MPS. All Rights Reserved.
0.2
μA
5
MP4655–PURE, SINGLE-STAGE, LLC, LED CURRENT AND SYSTEM VOLTAGE CONTROLLER
ELECTRICAL CHARACTERISTICS (continued)
VIN = 13V, TA = +25°C, unless otherwise noted.
Parameter
Analog Dimming
Analog dimming full scale
Dimming linearity
Dimming linearity
Dimming linearity
Dimming linearity
ADIMP logic high
ADIMP logic low
ADIMP pull-up resistor
ADIMP disable threshold
PWM Dimming
PWM logic high threshold
PWM logic input hysteresis
Operating Frequency
Minimum frequency set voltage
Symbol
VADMAX
VIFB_ADIM
VIFB_ADIM
VIFB_ADIM
VIFB_ADIM
VADIM_PHI
VADIM_PLO
RADIM_P_UP
Condition
Min
Typ
Max
Units
VIFB = 200mV
VADIM = 1.2V
VADIM = 0.8V
VADIM = 0.3V
VADIM = 0.1V
2.32
2.39
100
66.8
25
8.5
2.46
V
mV
mV
mV
mV
V
V
MΩ
V
1.8
1.5
4.7
VTH-PWM
VTH-PWM-Hyst
VFSET
Minimum operating frequency
Fmin_op
Maximum operating frequency
Fmax_op
PWM dimming
PWM dimming
1.4
17
0.6
2
V
V
IFB = 0.1V, PWMIN = high
1.65
RFSET = RSS_FSET = 300kΩ,
IFB = 0.1V, PWMIN = high
RFSET = RSS_FSET = 300kΩ,
IFB = 0.21V, PWMIN = high
1.73
1.83
V
Output PWM Dimming Signal for LED (DIMO)
Logic high voltage
VH-DIMO
Normal operation
At fault condition,
Logic low voltage
VL-DIMO
or PWMIN is low
20mA drive source current
DIMO up-side resistance
for design
100mA drive sink current
DIMO low-side resistance
for design
LED Stage Enable (EN_LED)
EN_LED logic high threshold
VTH-EN_LED
EN_LED rising
EN_LED logic input hysteresis
VTH-ENLED-Hyst
IC Enable Signal (PS_ON)
Threshold for IC standby
Vth_PS_ON_STB
MP4655 Rev 1.0
2/2/2016
Rising edge
Vth_PS_ON
42.5
kHz
130
kHz
12.5
V
0.1
V
62
Ω
7
Ω
1.4
1.7
0.6
2
V
V
0.7
0.8
0.9
V
Vth_PS_ON_STB < VPS_ON <
Vth_PS_ON
Duration time to shut down IC
Threshold to turn on IC to
operate normally
3.5
0.9
1
1.9
2
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© 2016 MPS. All Rights Reserved.
ms
2.1
V
6
MP4655–PURE, SINGLE-STAGE, LLC, LED CURRENT AND SYSTEM VOLTAGE CONTROLLER
ELECTRICAL CHARACTERISTICS (continued)
VIN = 13V, TA = +25°C, unless otherwise noted.
Parameter
Symbol
Capacitive Mode Detection (CMODE)
CMODE detection high
Vth_Cmode_H
threshold
CMODE detection low
Vth_Cmode_L
threshold
FTH_CMODE voltage
VFth_Cmode
CMODE threshold frequency
Fth_cmode
Soft Start (SS)
Soft-start final voltage
VSS
Condition
Min
Isat_I
Units
0.97
VREF_VFB
At GR falling edge
0.03
VREF_VFB
1.15
1.2
91
1.25
2.34
2.405
2.47
150kΩ on FTH_CMODE
Normal operation after
start-up
VSS = 1V
30
Low-level clamp voltage
VICOMP_L
Normal operation
0.97
High-level clamp votlage
VICOMP_H
Normal operation
2.2
Output for System Voltage Feedback (VFB)
Reference voltage
VREF_VFB
1.17
Leakage current
Ilkg_VFB
Normal operation
Internal Voltage Loop Compensation Transconductance Op-Amp (VCOMP)
Low-level clamp voltage
VVCOMP_L
Normal operation
0.97
High-level clamp votlage
VVCOMP_H
Normal operation
2.2
Transconductance
Gm_V
Saturated output current
Isat_V
30
MP4655 Rev 1.0
2/2/2016
Max
At GL falling edge
Soft-start current
ISS
Discharge current when
VSS = 2V
ISS_Discharge
capacitive mode detected
Pull low resistor at latch-up
LED Current Feedback (IFB)
Magnitude
|VIFB|
0.188
LED short threshold for
490
VIFBS
immediate action
LED short detection delay time
TblankTdelay
LED short threshold for slow
370
VIFBSC
action
Delay time for slow action
Tdelay_IFB
400mV < VIFB < 600mV
250
Threshold for short protection
ICOMP saturated
Duration for short protection
Internal Current Loop Compensation Transconductance Op-Amp (ICOMP)
Transconductance
Gm_I
Saturated output current
Typ
V
kHz
13
μA
3
ISS
120
Ω
0.199
0.21
V
555
610
mV
6
us
415
460
mV
340
50%
1024
450
μs
VIFB_REF (6)
cycle
840
μA/V
50
70
μA
1.02
2.28
1.07
2.36
V
V
1.2
0.33
1.23
V
μA
1.02
2.28
150
50
1.07
2.36
V
V
μA/V
μA
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© 2016 MPS. All Rights Reserved.
70
7
MP4655–PURE, SINGLE-STAGE, LLC, LED CURRENT AND SYSTEM VOLTAGE CONTROLLER
ELECTRICAL CHARACTERISTICS (continued)
VIN = 13V, TA = +25°C, unless otherwise noted.
Parameter
Symbol
Condition
Min
Typ
Max
Units
Internal Voltage Loop Compensation Transconductance Op-Amp for Extra MOSFET Control (DCOMP)
Normal operation,
Low-level clamp voltage
VDCOMP_L
0.41
V
VOCP = 0V
Normal operation,
High-level clamp votlage
VDCOMP_H
2.1
V
VOCP = 0V
Transconductance
Gm_DCOMP
150
μA/V
Saturated output current
Isat_DCOMP
30
50
70
μA
Bus Voltage Stage Current Detection (VOCP)
VOCP detection threshold
VTH_VOCP
-230
-203 -176
mV
VOCP delay time
TD_VOCP
OCP < -200mV
7
µs
Over LED Voltage Protection (VLED1, VLED2)
Over LED voltage protection
2.33
2.41 2.49
V
VTH_OVP_LED
threshold
Over LED voltage delay time
Tdelay_VLED
8
μs
Gain of differential voltage
14
16.
18
protection
Internal resistance
RVLED
16
20
24
kΩ
Over LED voltage to latch up
2.85
3
3.15
V
VTH_OVP_LED_latch
LLC
Duration time to latch up
7.6
μs
Burst Mode (Pulse Skipping) Threshold at Normal Operation (VCOMP, ICOMP, VFB, IFB)
VCOMP threshold for burst
PS_ON = H,
VTH_burst_VCOMP
1.05
1.1
1.15
V
mode
VFB > 1.05VREF_VFB
VCOMP hysteresis for burst
PS_ON = H
80
100
120
mV
mode
VFB threshold for burst mode
VTH_burst_VFB
PS_ON = H
1.05
VREF_VFB
VFB reset threshold for burst
0.95
VREF_VFB
VTH_reset_burst_VFB PS_ON = H
mode
ICOMP threshold for burst
PS_ON = H,
1.05
1.12 1.18
V
VTH_burst_ICOMP
mode
VIFB > 1.08VIFB_REF
ICOMP hysteresis for burst
100
mV
mode
IFB threshold for burst mode
VTH_burst_IFB
PS_ON = H
1.08
VIFB_REF(6)
IFB reset threshold for burst
VTH_reset_burst_IFB PS_ON = H
0.92
VIFB_REF(6)
mode
MP4655 Rev 1.0
2/2/2016
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© 2016 MPS. All Rights Reserved.
8
MP4655–PURE, SINGLE-STAGE, LLC, LED CURRENT AND SYSTEM VOLTAGE CONTROLLER
ELECTRICAL CHARACTERISTICS (continued)
VIN = 13V, TA = +25°C, unless otherwise noted.
Parameter
Symbol
Condition
Burst Mode (Pulse Skipping) Threshold in Standby Mode (VCOMP, VFB)
VFB threshold to stop gate
driver
VFB threshold to recover gate
driver
PS_ON < 0.7V,
FSET voltage at standby mode
VFSET _STB
VFB = 0.8 * VREF_VFB
VSS low clamp value
VSS soft-on recovery current
VSS soft-off recovery current
System Voltage Protection (VFB)
Overbus voltage protection
VTH_OVP_VFB
threshold
Delay time
Min
VFB > 1.5V
VFB open protection threshold
VTH_Open_VFB
VCOMP saturated at PWM
Duration time for VFB open
off or DCOMP saturated at
protection
PWM ON
LED Stage Over-Current Detection (IOCP/FAULT)
IOCP threshold
VTH_IOCP
IOCP detection delay time
TD_IOCP
IOCP < -310mV
LED driver stage
IOCP duration time to latch up
protection triggered and
LLC
IOCP < -300mV
Pin floated, fault condition
Amplitude of output fault signal
VFault
ISOURCE = 10mA
Pull-up resistance at fault
condition
Source current of ICOP at
normal operation
-360
Typ
Max
1.05
VREF_VFB
0.95
VREF_VFB
2.1
V
0.91
100
100
V
µA
µA
1.25
VREF_VFB
7
µs
50%
VREF_VFB
512
cycles
-320
7
-280
270
3.2
Units
3.4
5
mV
µs
µs
3.6
V
0.3
kΩ
µA
NOTES:
5) The parameters are tested on the bench with several parts.
6) VIFB_REF is the reference voltage for IFB. Its value changes according to the ADIM signal.
MP4655 Rev 1.0
2/2/2016
www.MonolithicPower.com
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© 2016 MPS. All Rights Reserved.
9
MP4655–PURE, SINGLE-STAGE, LLC, LED CURRENT AND SYSTEM VOLTAGE CONTROLLER
TYPICAL CHARACTERISTICS
Quiescent Current vs.
Supply Voltage
6
Supply Current vs.
Operating Frequency
45
IQ (mA)
5.8
5.7
5.6
5.5
5.4
5.3
5.2
0
5
10
15
20
INPUT VOLTAGE(V)
40
35
30
25
20
15
10
5
0
25
VCC (V)
SUPPLY CURRENT (mA)
5.9
0
VDRN Drive Capability
14
1.7
12
1.65
50 100 150 200 250 300
OPERATING FREQUENCY(kHz)
Quiescent Current vs.
Temperature
0
20 40 60 80 100 120
VCC LOAD CURRENT (mA)
Shutdown Current vs.
Temperature
106
104
1.6
IQ (mA)
8
6
100
1.55
98
96
1.5
4
94
1.45
2
0
0.63
92
1.4
-50
0
10
20
30
40
VDRN LOAD CURRENT (mA)
Standby Current vs.
Temperature
7.76
0
50
90
-50
100
VCC UVLO vs.
Temperature
0.6
0.59
0.58
0.57
0.56
0.55
0.54
0.53
-50
MP4655 Rev 1.0
2/2/2016
0
50
100
100
2.13
7.74
7.72
7.7
7.68
7.66
7.64
-50
50
2.135
V_FSET_STB (V)
VCC_UVLO_RISING (V)
0.61
0
FSET Voltage at Standby
Mode vs. Temperature
0.62
I_STANDBY (mA)
11.95
11.9
11.85
11.8
11.75
11.7
11.65
11.6
11.55
11.5
11.45
11.4
102
10
VDRN (V)
VCC Drive Capability
2.125
2.12
2.115
2.11
2.105
0
50
100
2.1
-50
0
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© 2016 MPS. All Rights Reserved.
50
100
10
MP4655–PURE, SINGLE-STAGE, LLC, LED CURRENT AND SYSTEM VOLTAGE CONTROLLER
TYPICAL CHARACTERISTICS (continued)
CMODE High-Level Threshold
Voltage vs. Temperature
0.047
1.17
VTH_CMODE_L(V)
1.168
1.166
1.164
1.162
2.406
0.045
2.404
0.044
0.043
0.042
1.158
-50
0
50
ICOMP High-Level
Clamp Voltage
2.398
0
50
2.392
-50
100
VCOMP High-Level
Clamp Voltage
2.285
-0.2024
2.28
2.28
-0.2026
V_VCOMP_H(V)
2.285
2.27
2.265
2.255
-50
0
50
2.275
2.27
VLED OVP Threshold
Voltage vs. Temperature
2.26
-0.2034
1.504
2.415
50
-0.2036
-50
100
VFB OVP Threshold
Voltage vs. Temperature
-0.309
1.501
1.5
1.499
1.498
1.497
1.496
MP4655 Rev 1.0
2/2/2016
0
50
100
1.494
-50
-0.31
-0.311
-0.312
-0.313
-0.314
1.495
2.395
-50
100
-0.308
VTH_IOCP(V)
VTH_OVP_VFB(V)
2.4
50
-0.307
1.502
2.405
0
IOCP Threshold Voltage
vs. Temperature
1.503
2.41
-0.203
-0.2032
0
100
-0.2028
2.265
2.255
-50
100
50
-0.2022
2.29
2.275
0
VOCP Threshold Voltage
vs. Temperature
2.29
2.26
VTH_OVP_LED1(V)
2.4
2.394
0.04
-50
100
2.402
2.396
0.041
1.16
V_ICOMP_H(V)
0.046
VTH_VOCP(V)
VTH_CMODE_H(V)
1.172
2.408
V_SS(V)
1.174
CMODE Low-Level Threshold VSS Voltage vs.
vs. Temperature
Temperature
0
50
100
-0.315
-50
0
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50
100
11
MP4655–PURE, SINGLE-STAGE, LLC, LED CURRENT AND SYSTEM VOLTAGE CONTROLLER
TYPICAL CHARACTERISTICS (continued)
1.201
0.1995
1.2
0.199
1.199
0.1985
V_IFB(V)
VVFB_REF(V)
VFB Reference Voltage
vs. Temperature
1.198
MP4655 Rev 1.0
2/2/2016
0.198
0.1975
1.197
1.196
-50
IFB Reference Voltage
vs. Temperature
0
50
100
0.197
-50
0
50
100
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MP4655–PURE, SINGLE-STAGE, LLC, LED CURRENT AND SYSTEM VOLTAGE CONTROLLER
TYPICAL PERFORMANCE CHARACTERISTICS
Performance waveforms are tested on the evaluation board of the Design Example section.
400Vbus = 390V, VLED = 130V, ILED = 375mA*2 strings, System output = 13.5V/6.5A, TA = 25°C,
unless otherwise noted.
370.5
13.62
CC LOOP
13.61
13.54
13.6
13.535
13.59
13.58
13.56
4
6
VBUS LOAD CURRENT(A)
13.53
8
LED Current Cross
Regulation at 50% Analog
Dimming
369
368.5
368
0
0.2 0.4 0.6 0.8
1
PWM DIMMING DUTY
1.2
LED Current PWM
Dimming Linearity
800
800
700
700
600
500
400
300
200
0
1
2
3
4
5
6
VBUS LOAD CURRENT(A)
0
7
600
500
400
300
200
100
100
Standby Power Consumption
STANDBY POWER CONSUPTION
13.51
13.505
0 100 200 300 400 500 600 700 800
LED CURRENT(mA)
LED Current Analog
Dimming Linearity
LED CURRENT(mA)
LED CURRENT(mA)
369.5
13.52
13.515
13.55
13.54
2
13.53
13.525
13.57
370
367.5
VBUS Voltage Cross
Regulation at Analog
Dimming
13.545
VBUS VOLTAGE(V)
CV LOOP
VBUS Voltage Cross
Regulation at PWM
Dimming
LED CURRENT(mA)
13.62
13.61
13.6
13.59
13.58
13.57
13.56
13.55
13.54
13.53
13.52
13.51
0
VBUS VOLTAGE(V)
VBUS VOLTAGE(V)
VBUS Voltage Load
Regulation
0
0
0.5
1
1.5
2
2.5
ADIM VOLTAGE(V)
3
0
Standby Mode Opeartion
20
40
60
80
100 120
Standby Mode Opeartion
450
400
350
I OUT=14.8mA(P OUT=200mW)
300
250
200
I OUT=7.8mA(P OUT=104mW)
150
100
50
0
I OUT=0(P OUT=0)
0
MP4655 Rev 1.0
2/2/2016
100
200
AC INPUT VOLTAGE(V)
VGL
10V/div.
VGL
10V/div.
VBUS
10V/div.
VBUS
10V/div.
VSS
2V/div.
VSS
2V/div.
IPRI
2A/div.
IPRI
2A/div.
300
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MP4655–PURE, SINGLE-STAGE, LLC, LED CURRENT AND SYSTEM VOLTAGE CONTROLLER
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
Performance waveforms are tested on the evaluation board of the Design Example section.
400Vbus = 390V, VLED = 130V, ILED = 375mA*2 strings, System output = 13.5V/6.5A, TA = 25°C,
unless otherwise noted.
Normal Operation
PSON Start-Up
PWM Dimming
PWM=High
50%
VGL
10V/div.
VGL
10V/div.
VGATEN
20V/div.
VCOMP
1V/div.
VBUS
10V/div.
IPRI
2A/div.
VBUS
10V/div.
IPRI
2A/div.
Open LED Protection
VGL
10V/div.
VICOMP
1V/div.
VBUS
10V/div.
ILED
500mA/div.
Short LED+ to LED-
Short LED+ to GND
VGL
10V/div.
VGL
10V/div.
VGL
10V/div.
VFAULT
2V/div.
VBUS
10V/div.
VBUS
10V/div.
VLED
50V/div.
ILED
500mA/div.
VLED
50V/div.
ISHORT
10A/div.
VFAULT
5V/div.
ISHORT
10A/div.
VBUS OVP Protection
Short VBUS to GND
VGL
10V/div.
VGL
10V/div.
VBUS
10V/div.
VBUS
10V/div.
VFAULT
5V/div.
ISHORT
10A/div.
VFAULT
5V/div.
ILED
10A/div.
MP4655 Rev 1.0
2/2/2016
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14
MP4655–PURE, SINGLE-STAGE, LLC, LED CURRENT AND SYSTEM VOLTAGE CONTROLLER
PIN FUNCTIONS
Pin #
Name
1
VDR_DN
2
GATEN
3
SOURCE
4
5
6
7
8
9
10
11
12
Description
Drive voltage for the extra MOSFET. VDR_DN is formed by the charge pump and is
referred to SOURCE.
Gate of the extra N-channel MOSFET.
Source of the extra N-channel MOSFET.
FTH_CMODE sets the threshold frequency to shut down the LLC when capacitive
mode is detected. Its typical voltage is 1.2V. The sourcing current through
FTH_CMODE determines the threshold frequency. When capacitive mode is detected,
FTH_CMODE
the IC discharges SS and increases the operating frequency. If the operating frequency
is higher than this threshold frequency when capacitive mode is detected, the IC latches
up LLC and the IOCP/FAULT signal output is high.
Detection of capacitive mode. The secondary side winding voltage is fed back on
CMODE
CMODE for capacitive mode detection.
Soft start. SS functions as a soft start and also sets the operating frequency together
with FSET. Connect a capacitor from SS to GND to set the soft-start time. An internal
SS
10µA sourcing current charges this capacitor to 2.4V at soft start. Connect a resistor
between SS and FSET to set the operating frequency together with the resistor from
FSET to GND.
Over-current protection of the system bus voltage stage. VOCP senses the
secondary current of the system bus voltage stage. When VOCP is lower than -203mV,
VOCP
the IC triggers a bus stage protection. VOCP is also used for the inner current control
loop for the bus voltage compensation to control the extra MOSFET duty cycle.
Frequency set. Connect a resistor from FSET to GND, and another resistor between
FSET and SS. The operating frequency is determined by the sourcing current through
FSET
FSET. The voltage of FSET and the operating frequency are programmed by the
current control loop and the voltage control loop.
Feedback compensation node of the voltage control loop. Connect a compensation
VCOMP
capacitor or an R-C network from VCOMP to GND. The VCOMP voltage is internally
clamped between 1.02V and 2.28V, which limits the operating frequency range.
Bus voltage feedback. VFB feeds back the bus voltage for regulation. Its inner
reference voltage is 1.2V. VFB is also used for over-voltage protection of the bus
voltage stage. When VFB exceeds 1.5V, the over-voltage protection of the bus voltage
VFB
stage is triggered. VFB also functions as the open feedback loop protection. If VFB is
lower than 50% of its reference voltage and VCOMP or DCOMP is saturated for 512
cycles, the IC triggers the bus voltage stage protection.
Feedback compensation node of the voltage control loop. DCOMP is used to
DCOMP
program the duty cycle of the extra N-channel MOSFET. Connect a compensation
capacitor or an R-C network from DCOMP to GND.
LED current feedback input. IFB feeds back the LED current through a sensing
resistor. The internal error amplifier sinks a current from ICOMP proportional to the
absolute value of the voltage at IFB. The average voltage at IFB is regulated to the
reference voltage (controlled by the ADIM voltage, 199mV when ADIM is high). The
IFB
voltage on IFB is also used for LED over-current detection. When the voltage on IFB
rises higher than 415mV for 340μs or when the voltage rises higher than 555mV, the IC
triggers the LED stage protection. IFB also functions as the LED current open feedback
loop protection. If the IFB voltage is lower than 50% of its reference voltage and the
ICOMP is saturated for 1024 cycles, the IC triggers the LED stage protection.
MP4655 Rev 1.0
2/2/2016
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15
MP4655–PURE, SINGLE-STAGE, LLC, LED CURRENT AND SYSTEM VOLTAGE CONTROLLER
PIN FUNCTIONS (continued)
Pin #
Name
13
ICOMP
14
IOCP/FAULT
15
VLED1
16
VLED2
17
EN_LED
18
ADIMP
19
ADIM
20
PWMIN
21
VIN
Description
Feedback compensation node of the current control loop. Connect a compensation
capacitor or an R-C network from ICOMP to GND. The ICOMP voltage is internally
clamped between 1.02V and 2.28V, which limits the operating frequency range. ICOMP
also functions as the short LED to GND protection. When ICOMP is saturated and the
IFB voltage is lower than 50% of the reference current for 1024 cycles, IC uses it as the
fault condition and triggers an LED fault protection.
LED stage over-current protection and fault indicator. IOCP/FAULT feeds back the
secondary side current of the LED driver stage. When the voltage on IOCP/FAULT is
less than -320mV for 7μs, the IC disables the output of the DIMO signal. After 270μs,
the IC outputs the fault indicator. If the IOCP voltage is always lower than -320mV for
270μs, the IC latches up the LLC.
Voltage feedback of LED string 1. VLED1 and VLED2 cooperate for the protection of
the LED driver stage. The maximum voltage and the voltage difference among VLED1
and VLED2 are detected and used for LED stage protection. For 1-string applications,
connect VLED1 and VLED2; for two-string applications, feed back the LED strings
voltages to VLED1 and VLED2; for applications with more than two strings, feed back
the maximum voltage of the LED strings and the minimum voltage of the LED strings to
VLED1 and VLED2.
Voltage feedback of LED string 2.
The enable signal for the LED driver. Logic high enables the LED stage; logic low
disables the LED stage.
The pulse input signal for analog dimming. The duty cycle 0 to 100% of this pulse
signal programs the amplitude of the LED current from 0 to 100%. Place a 100nF
capacitor from ADIM to GND for this type of dimming. If this dimming is not being used,
pull it high to VCC through a 100k resistor or leave it open.
Analog dimming input with DC voltage. The LED current is set by 0~2.4V from 0 to
100%. ADIMP should be disabled if using this DC input analog dimming. If this dimming
is not being used, pull it high to VCC through a 100kΩ resistor.
PWM dimming control input. Apply a 100Hz to 2kHz PWM signal to PWMIN for PWM
dimming.
Supply input. Bypass VIN with a ceramic capacitor larger than 0.1μF.
On/off signal for the system power supply. PS_ON is the enable signal for the IC.
This signal determines the operation mode of the IC. If PS_ON is less than 0.8V, the IC
works in standby mode. IC operates in deep burst mode, and the system bus voltage is
controlled with a larger ripple voltage to decrease the power consumption. If PS_ON is
greater than 0.8V but less than 2V and this saturation lasts for 1ms, the IC shuts down.
If PS_ON is greater than 2V, the IC works in normal operation mode.
Power supply for the gate driver of the LLC MOSFETs and internal circuit. Bypass
VCC to GND with a ceramic capacitor larger than 1μF.
22
PS_ON
23
VCC
24
DIMO
Output of the driving signal for the dimming MOSFET.
25
GL
LLC driving signal output. 180 degree phase shift of GR.
26
GND
27
GR
28
CFLY
MP4655 Rev 1.0
2/2/2016
Ground reference.
LLC driving signal output. 180 degree phase shift of GL.
Output of the pulse signal for the charge pump. Connect a flying cap higher than
100nF of the charge pump to CFLY. Please refer to the typical application circuit for
connection details.
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MP4655–PURE, SINGLE-STAGE, LLC, LED CURRENT AND SYSTEM VOLTAGE CONTROLLER
BLOCK DIAGRAM
EN_IC
L for 1ms: disable IC
2V
STBI
(L: standby mode)
0.8V
PS_ON2V, normal operation mode
0.8V 2V: the IC is enabled in normal
operation mode.
2. 0.8V < PS_ON ≤ 2V for 1ms: the IC is
disabled and no circuits work.
3. PS_ON ≤ 0.8V: the IC is enabled in standby
mode.
It is very easy to set up the system connection,
whether the MP4655 is required to do so in
standby or not.
When the MP4655 is enabled and the VIN supply
is higher than its UVLO threshold, VCC is
charged up. When VCC passes its UVLO
threshold, the IC starts up. The voltage resets the
control loop for LLC frequency control, voltage
control loop for the extra N-channel MOSFET
duty cycle control, and the soft-start capacitor.
EN_LED and PWMIN control the start-up of the
LED driver stage. If either EN_LED or PWMIN
are low, the LED driver stage is disabled and
DIMO is pulled low. The system operates in
constant voltage mode, and VSystem is regulated
through the LLC frequency control. The extra Nchannel MOSFET is on in this condition. If either
EN_LED or PWMIN are high, the LED driver
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MP4655–PURE, SINGLE-STAGE, LLC, LED CURRENT AND SYSTEM VOLTAGE CONTROLLER
stage is enabled and DIMO rises high. The LED
current is regulated through the LLC frequency
control, and the VSystem is regulated through the
duty cycle control of the extra N-channel
MOSFET.
Standby Mode with Low Consumption Power
and No Audible Noise
The MP4655 features a standby mode with low
consumption power on the LLC power stage.
When PS_ON ≤ 0.8V, the MP4655 enters
standby mode, regardless of the status of the
LED driver stage control signals.
In standby mode, the LED stage is disabled,
VSystem is controlled through the LLC frequency
control, and the extra N-channel MOSFET is on.
The MP4655 takes the following actions to
decrease the system power consumption:
1. VSystem is controlled within ± 5% and the
circuit works in soft-burst mode. The VFSET
voltage is clamped at 2.1V, so the switching
frequency at burst mode is not too high.
Power consumption is decreased in this
mode. A soft burst-on time and soft burst-off
time are added to the burst mode to eliminate
audible noise (see Figure 3).
The MP4655 accurately regulates both the LED
current and the output system voltage with only
one LLC power stage.
In PWM dimming off condition, the LED stage is
not enabled (PWMIN is low, EN_LED is not
enabled, or LED stage fault detected). The
MP4655 regulates the output system voltage
through the LLC frequency control, and the extra
N-channel MOSFET is on (see Figure 4A).
In PWM dimming on condition, the MP4655
regulates the LED current through the LLC
frequency control, and regulates the output
system voltage through the duty cycle control of
the extra N-channel MOSFET. The integrated
individual control for this extra N-channel
MOSFET achieves soft switching, and there is no
voltage spike (see Figure 4B).
Figure 4A: MP4655 Control Scheme at PWM
Dimming Off
2. The charge pump for VDR_DN works in burst
mode, and VDR_DN is controlled with a
larger ripple voltage. This decreases the IC
consumption current.
3. The internal logic circuit consumption current
is decreased.
+5%
The regulation for the LED current and system
voltage at different conditions is as follows:
+5%
1. LED current regulation at PWM dimming on
(ICOMP loop)
-5%
94uA charge
First pulse GL: 50% width
Figure 4B: MP4655 Control Scheme at PWM
Dimming On
94μA discharge
First pulse GL: 50% width
Figure 3: LLC Soft-Burst Operation at Standby
Mode
For the LED current regulation loop with LLC
frequency control, the LED current is fed back to
IFB. The internal error amplifier regulates the
average value of IFB signal to the internal 199mV
reference voltage. Its output is connected to the
external current-loop compensation network on
ICOMP through an inner switch (S1).
During the PWM on interval, S1 is on, and the
output of the error amplifier is connected to the
external compensation network on ICOMP. The
LED Current and System Voltage Regulation
MP4655 Rev 1.0
2/2/2016
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MP4655–PURE, SINGLE-STAGE, LLC, LED CURRENT AND SYSTEM VOLTAGE CONTROLLER
LED current is regulated by this control loop and
the LLC operating frequency is programmed by
the ICOMP voltage.
During the PWM off interval, S1 is turned off, and
the compensation network on ICOMP is
disconnected from the error amplifier and holds
its value until the next PWM on interval.
The MP4655 integrates burst mode for the LED
current regulation. When the IFB voltage is
higher than 1.08 times its reference voltage and
the ICOMP voltage is low enough (which means
it is at its highest operating frequency), the IC
skips some switching cycles until the IFB voltage
decreases sufficiently.
2. Output system voltage regulation at PWM
dimming off (VCOMP loop)
For the system voltage regulation loop, the
output system voltage is fed back to VFB. During
the PWM off interval, the MP4655 regulates the
system voltage through the LLC frequency
control, and the extra N-channel MOSFET is on.
The internal voltage-loop error amplifier regulates
the average value of the VFB voltage to the
reference voltage (VREF). Its output is connected
to the external voltage-loop compensation
network on VCOMP through an inner switch S2.
During the PWM off interval, S2 is on, and the
output of the voltage-loop error amplifier is
connected to the external compensation network
on VCOMP. The output system voltage is
regulated by this control loop and the LLC
operating frequency is programmed by VCOMP.
During the PWM on interval, S2 is turned off, and
the compensation network on VCOMP is
disconnected from the error amplifier and holds
its value until the next PWM off interval.
The MP4655 also integrates burst mode for
voltage regulation with the LLC frequency control
through the VCOMP loop. When VFB is higher
than 1.05 times the reference voltage and
VCOMP is sufficiently low (which means a high
LLC operating frequency), the IC skips some
switching cycles until VFB voltage decreases
sufficiently.
The LLC operating frequency is controlled by the
output of the current loop error amplifier on
ICOMP at PWM dimming on and is controlled by
the voltage loop error amplifier on VCOMP at
MP4655 Rev 1.0
2/2/2016
PWM dimming off. A higher compensation output
voltage results in a lower operating frequency.
3. Output system voltage regulation at PWM
dimming on (DCOMP loop)
During the PWM on interval, the LLC frequency
control regulates the LED current, and the output
system voltage is regulated through the duty
cycle of the extra N-channel MOSFET. The
output system voltage is fed back on VFB, and
the internal error amplifier regulates its average
value to its reference voltage (VREF). The output
of this error amplifier is connected to DCOMP
through an inner switch (S3). S3 is on during the
PWM on interval, and the output of this error
amplifier is connected to the DCOMP
compensation network. Together with slope
compensation, the DCOMP voltage is compared
with the current through the output system
voltage stage, which is fed back to VOCP and
determines the duty cycle of the extra N-channel
MOSFET. The duty cycle of this extra N-channel
MOSFET can achieve a 0 to 100% range. The
MP4655 integrates individual controls on the
extra N-channel MOSFET and achieves soft
switching with no voltage spike.
During the PWM off interval, S3 is disconnected
and DCOMP holds its voltage until the next PWM
on interval. The extra N-channel MOSFET is
forced on during the PWM off interval.
Both the LED current and output system voltage
are accurately regulated at PWM dimming on
and PWM dimming off. ICOMP, VCOMP, or
DCOMP holds its voltage when its loop is not
effective. This achieves a fast transition between
different compensation loops at PWM dimming.
Together with the external dimming MOSFET,
which holds the LED output voltage during the
PWM off interval, both the LED current and
output system voltage are regulated accurately
and smoothly at PWM dimming. No voltage ripple
or LED current overshoot or undershoot is
caused by PWM dimming.
Dimming Control
The MP4655 provides two dimming methods:
PWM dimming mode and analog dimming mode.
Applying a digital PWM signal on PWMIN allows
for PWM dimming. The brightness of the LED
string is proportional to the duty cycle of the
external PWM signal. A driving signal on DIMO is
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MP4655–PURE, SINGLE-STAGE, LLC, LED CURRENT AND SYSTEM VOLTAGE CONTROLLER
output to drive the dimming MOSFET directly,
which helps achieve fast and high-contrast ratio
PWM dimming.
The MP4655 achieves a 1000:1 PWM dimming
ratio at 200Hz PWM dimming frequency (0.1%
minimum PWM dimming duty). The PWM
dimming ratio may decrease with a higher PWM
dimming frequency.
For analog dimming mode, a DC voltage on
ADIM or a pulse signal on ADIMP can be used.
For DC input analog dimming, apply a DC analog
signal from 0V to 2.4V on ADIM to dim the LED
current amplitude from 0 to 100%. ADIMP can be
left open or pulled high to VCC through a 100kΩ
resistor in this mode.
For analog dimming with a pulse input signal,
apply the pulse signal on ADIMP and a 100nF
capacitor on ADIM, depending on the frequency
of this pulse signal. The duty cycle of this pulse
signal from 0 to 100% dims the LED current from
0 to 100%.
The PWM dimming and analog dimming could be
applied to the IC simultaneously for an extra
dimming ratio.
Protection Features
The MP4655 integrates sufficient protection for
the LLC power stage, the output system voltage
stage, and the LED driver stage.
Capacitive Mode Protection for the LLC
Power Stage
The MP4655 integrates individual capacitive
mode protection for the LLC power stage by
detecting the secondary side signal. Feed back
the secondary side winding voltage to CMODE
for capacitive mode protection. When capacitive
mode is detected, the MP4655 discharges the
SS voltage and increases the LLC operating
frequency. If the capacitive mode is still detected
when the operating frequency is higher than the
threshold frequency setting by FTH_CMODE, the
IC latches up and outputs a high fault indicator.
System Voltage Stage Protection
The protections for the system voltage stage
include over-system voltage protection, short
protection, and open-feedback loop protection.
1. Over-system voltage protection
MP4655 Rev 1.0
2/2/2016
VFB senses the output system voltage for
regulation and over-voltage protection. If the VFB
voltage is higher than 1.25VREF, the MP4655
triggers the over-system voltage protection and
latches up. The fault indicator output is high.
2. System voltage stage short protection
VOCP senses the current through the output
system voltage stage for short protection of the
system voltage stage. If the voltage on VOCP is
lower than -203mV for 7µs, the MP4655 latches
up and outputs a high fault indicator.
3. System
voltage
stage
open-feedback
protection
During the PWM dimming off interval, if the VFB
voltage is lower than 50% of its reference and
VCOMP is saturated for 512 switching cycles, the
IC latches up and outputs a high fault indicator.
During the PWM dimming on interval, if the VFB
voltage is lower than 50% of its reference voltage
and DCOMP is high for 512 cycles, the IC
latches up and outputs a high fault indicator.
LED Driver Stage Protection
The fault protection for the LED driver stage
includes the open LED protection, short LED
protection, over-LED current protection, open
feedback loop protection, and protection for any
point of the LED string shorting to ground.
The voltage of the LED strings is sensed on
VLED1 and VLED2. Both the maximum value
and the difference in voltages of VLED1 and
VLED2 are used for protection. When the
maximum value of VLED1 and VLED2 rises
higher than 2.41V or the difference in the
voltages rises higher than 150mV for 8µs, the IC
triggers over-LED voltage protection (the voltage
difference can be adjusted by the external input
resistance on VLED1 or VLED2).
DIMO is pulled low, and the output system
voltage is regulated by the LLC frequency control,
the same as in PWM off condition, and the fault
indicator output is high. If the maximum value of
VLED1 and VLED2 rises higher than 3V for 7.6µs,
the MP4655 latches up and disables the LLC
power stage to avoid any damage to the LED
driver stage. The fault indicator output is high.
The secondary side current of the LED driver
stage is sensed on IOCP/FAULT. When the
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MP4655–PURE, SINGLE-STAGE, LLC, LED CURRENT AND SYSTEM VOLTAGE CONTROLLER
IOCP voltage is lower than -320mV for 7µs, the
MP4655 triggers the LED driver stage protection.
At the LED driver stage protection, the DIMO is
pulled low, and the output system voltage is
regulated by the LLC frequency control, the same
as in PWM off condition. The fault indicator
output is high after 270µs. After the LED driver
stage protection is triggered, IOCP/FAULT
continues detecting the LED driver stage current.
If the voltage on IOCP/FAULT remains lower
than -320mV for 270µs, the MP4655 latches up
and disables the LLC power stage.
The LED current feedback (IFB) is used for overLED current protection. When IFB voltage rises
higher than 415mV for 340µs or the IFB voltage
rises higher than 555mV for 6µs, the IC triggers
the LED driver stage protection.
for 1024 cycles, the IC considers this to be a
short LED to GND protection or open feedback
protection and triggers the LED driver stage
protection. The reference voltage varies
according to the analog dimming signal.
In a fault condition of the LED driver stage, the
gate driving signals for the LLC power MOSFETs
are still active and the output system voltage is
regulated, only if the LED driver stage can be
disconnected from the power stage. Therefore,
the system power supply is not influenced by the
fault protection of the LED driver stage. A
MOSFET can be used to disconnect the LED
driver stage at the LED fault condition (see
Figure 11).
Thermal protection is also integrated in the
MP4655.
If the voltage on IFB is lower than 50% of its
reference voltage, and the ICOMP is saturated
MP4655 Rev 1.0
2/2/2016
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22
MP4655–PURE, SINGLE-STAGE, LLC, LED CURRENT AND SYSTEM VOLTAGE CONTROLLER
APPLICATION INFORMATION
Frequency Set and Soft Start (SS, FSET)
The resistor on FSET and the resistor between
FSET and SS determine the operating frequency,
which can be calculated with Equation (1):
V
Vss − VFSET
f = ( FSET −
) * 11.4 * 109 (Hz) (1)
RFSET
RSS _ FSET
Where VFSET = 4.01V - VC. VC is the VCOMP
voltage at PWM dimming off and ICOMP voltage
at PWM dimming on. The VC range is clamped
from 1.02V to 2.28V. VSS is the voltage on SS,
typically 2.4V.
The minimum operating frequency can be
calculated with Equation (2):
fmin = (
1.73V 0.675V
−
) * 11.4 * 109 (Hz) (2)
RFSET RSS _ FSET
The maximum operating frequency at steady
state can be calculated with Equation (3):
fmax = (
2.99V 0.585V
+
) * 11.4 * 109 (Hz) (3)
RFSET RSS _ FSET
The LED current is set by the current sense
resistor on the cathode of LED and can be
calculated with Equation (7):
ILED =
VIREF
199mV
=
Rsense Rsense
A 2kΩ resistor is recommended between the LED
current sense resistor and IFB, considering the
possible spike voltage on the current sense
resistor when shorting the LED string.
System Output Voltage Set (VFB)
VFB feeds back the system output voltage.
Adjust the voltage divider to set the output
system voltage. See Equation (8):
Vsystem =
VREF _ VFB * (R VFBH + R VFBL )
R VFBL
=
1.2V * (R VFBH + R VFBL )
R VFBL
Vbus
RVFBH
2.99V
2.99V
=(
+
) * 11.4 * 109 (Hz) (4)
RFSET RSS _ FSET
CVFBH
VFB
RVFBL
The operating frequency at standby mode is
calculated with VFSET = 2.1V. See Equation (5):
fSTB = (
(8)
A capacitor (CVFBH) between the system output
and VFB provides a better phase margin for the
system output voltage control loop (see Figure 5).
When VSS is 0V, the soft start-up frequency is
calculated with Equation (4):
fstart
(7)
2.1V 0.305V
−
) * 11.4 * 109 (Hz) (5)
RFSET RSS _ FSET
It is recommended to set the operating frequency
in standby mode close to the LLC resonant
frequency (f0) for optimum efficiency.
The soft start-up time is determined by the
capacitor on SS and can be calculated with
Equation (6):
TSS =
2.405V * CSS
13uA
MP4655 Rev 1.0
2/2/2016
The zero composed by RVFBH and CVFBH is
recommended to be in range of one-fifth to onethird of the operating frequency. See Equation (9):
1
(6)
A 10nF capacitor on SS results in a 1.85ms softstart time.
LED Current Set (IFB)
Figure 5: Voltage Feedback Network
2π * R VFBH * CVFBH
1 1
= ( to )fop
5 3
(9)
The VFB also functions as the protection for the
over system output voltage. When VFB is 25%
higher than its reference voltage, the IC triggers
system output voltage stage protection.
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23
MP4655–PURE, SINGLE-STAGE, LLC, LED CURRENT AND SYSTEM VOLTAGE CONTROLLER
LED Current Compensation Loop (ICOMP)
ICOMP is the compensation node for the LED
current control loop. Connect a capacitor in
series with a resistor on ICOMP or an R-C-C
network (see Figure 6). The zero composed of
RICOMP and CICOMP is recommended to cancel the
pole formed by the LED output. See Equation
(10):
(10)
1
1
1
=
=
RICOMP * CICOMP R eq _ LED * COUT _ LED (10% to 20%) * VLED
* COUT _ LED
ILED
Figure 7: Compensation Network on VCOMP
CICOMP is in range of 10nF to 470nF, typically.
Select CICOMP_P to be less than one-twentieth of
CICOMP.
System Output Voltage Compensation Loop
through Duty-Controlled NMOS (DCOMP)
DCOMP is the compensation node for the
system output voltage control loop through the
duty-controlled NMOS. Connect a capacitor in
series with a resistor on DCOMP or an R-C-C
network (see Figure 8).
Figure 6: Compensation Network on ICOMP
System Output Voltage Compensation Loop
through LLC Control (VCOMP)
VCOMP is the compensation node for the system
output voltage control loop through the LLC
frequency. Connect a capacitor in series with a
resistor on VCOMP or an R-C-C network (see
Figure 7). The zero composed of the RICOMP and
CICOMP is recommended to cancel the pole
formed by the system output. See Equation (11):
(11)
1
1
1
=
=
Vbus
R VCOMP * CVCOMP R Vbus * COUT _ Vbus
* COUT _ Vbus
Iout _ full
Where CVCOMP is in the range of 10nF to 470nF,
typically.
The pole formed by RVCOMP and CVCOMP_P can be
designed to be around half of the operating
frequency. See Equation (12):
1
2π * R VCOMP * CVCOMP _ P
MP4655 Rev 1.0
2/2/2016
=
fop
2
(12)
Figure 8: Compensation Network on DCOMP
The zero composed of RDCOMP and CDCOMP is
recommended to cancel the pole formed by the
system output. See Equation (13):
(13)
1
1
1
=
=
Vbus
RDCOMP * CDCOMP R Vbus * COUT _ Vbus
* COUT _ Vbus
Iout _ full
Where CVCOMP is in the range of 4.7nF to 100nF,
typically.
The pole formed by RDCOMP and CDCOMP_P can be
designed to be around half of the operating
frequency. See Equation (14):
f
1
= op
2π * RDCOMP * CDCOMP _ P
2
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(14)
24
MP4655–PURE, SINGLE-STAGE, LLC, LED CURRENT AND SYSTEM VOLTAGE CONTROLLER
Over-Current Protection for the System
Output Stage (VOCP)
VOCP implements an over-current protection for
the system output voltage stage. The current of
the system output voltage stage is sensed on
VOCP with a negative polarity. When the voltage
on VOCP is lower than -203mV, the IC triggers
the system output voltage stage protection.
Calculate the over-bus current protection
threshold with Equation (15):
IOCP _ Bus
203mV
=
R VOCP
(15)
Typically, the protection point is around 1.5 to 3
times the normal current of the system output
voltage stage.
Over-Current Protection for the LED Driver
Stage (IOCP/FAULT)
IOCP detects the current through the LED stage
with a negative polarity. When the voltage on
IOCP falls below -320mV, the IC triggers LED
driver stage protection. Calculate the over-LED
current protection threshold with Equation (16):
IOCP _ LED =
320mV
RIOCP
(16)
The over-current protection point for the LED
stage can be set at around 1.5 to 2 times the
total current through the LED strings.
ICOP also functions as the fault indicator for the
system. When either LED driver stage protection,
system bus voltage protection, or capacitive
mode protection are triggered, the fault signal
output is high. Place a 10kΩ resistor between
IOCP and the LED stage current sense point.
Over-LED Voltage Protection and LED
Voltage Difference Protection (VLED1, VLED2)
VLED1 and VLED2 sense the LED voltages and
function as the over-LED voltage protection. The
voltage divider sets the over-voltage protection
point with Equation (17):
VOVP =
ROVPH + ROVPL
× 2.41V
ROVPL
(17)
Normally, the OVP point is set about 10% - 30%
higher than the maximum LED voltage.
MP4655 Rev 1.0
2/2/2016
The MP4655 also implements protection when
the LED string voltages are different from each
other to protect the condition in which several
LEDs in a string are shorted. This protection is
used only for multiple-string applications. The
protection point of the voltage difference between
the LED strings is set with Equation (18):
ΔVpro =
20k + Rinput
ROVPH + ROVPL
(18)
× 2.41V ×
ROVPL
16 × 20k
Where Rinput is the input resistance of VLED1 or
VLED2). Adjust the input resistance to program
the protection point.
A resistor (RX) can be added between the voltage
divider and VLED1 or VLED2 to adjust the input
resistance. See Equation (19):
R
× ROVPL
(19)
Rinput = OVPH
+ RX
ROVPL + ROVPH
Capacitive
Mode
Protection
(CMODE,
FTH_CMODE)
The MP4655 implements individual capacitive
mode protection for the LLC power stage from
the secondary side. CMODE monitors the
secondary side winding voltage and functions as
the capacitive mode protection. The winding
voltage polarity is positive (high) when GL is on.
When capacitive mode is detected, the IC
decreases the SS voltage and increases the
operating frequency to attempt to move the
power stage to inductive mode. FTH_CMODE
sets the threshold frequency to trigger capacitive
mode protection. If the operating frequency is
higher than that set by FTH_CMODE and
capacitive mode is still detected, the IC triggers
capacitive mode protection. Connect a resistor
on FTH_CMODE to set the threshold frequency.
See Equation (20):
1.2V
fth _ Cmod e = (
) * 11.4 * 109 (Hz) (20)
RFth _ Cmod e
PWM Dimming Input (PWM)
PWM is for the PWM dimming input. Apply a
PWM dimming signal with a frequency between
100Hz to 2kHz on PWM. The PWM dimming has
positive polarity.
PWM Dimming Signal Output (DIMO)
DIMO outputs a PWM dimming signal to drive the
external dimming N-channel MOSFET in series
with the LED string and achieves fast PWM
dimming. Connect a resistor in series with DIMO
to adjust the driving speed.
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25
MP4655–PURE, SINGLE-STAGE, LLC, LED CURRENT AND SYSTEM VOLTAGE CONTROLLER
Analog Dimming (ADIM, ADIMP)
The MP4655 implements either DC analog
dimming or pulse analog dimming for the LED
current (see Table 1).
For DC input analog dimming, apply a 0V to 2.4V
DC voltage on ADIM to program the LED current
from 0 to 100%. ADIMP is left open or pulled high
above 5V.
For pulse input analog dimming, apply the pulse
analog dimming signal on ADIMP and a capacitor
on ADIM. A duty cycle on the pulse analog
dimming signal from 0 to 100% dims the LED
current from 0 to 100%. A lower frequency of the
pulse analog dimming signal requires a larger
capacitor on ADIM. For a 10kHz pulse signal, a
capacitor 100nF or above on ADIM is
recommended.
If analog dimming is not required, pull ADIM high
and leave ADIMP open. Analog dimming and
PWM dimming can be applied together.
Table 1: MP4655 Dimming Connections
Items
ADIM
ADIMP
PWM
DC analog
dimming
signal 0 to
2.4V
Float or pulled
high above 5V
Pull high
Capacitor
Pulse analog
dimming signal
Pull high
Pull high
Float
PWM
PWM + DC
input analog
dimming
DC analog
dimming
signal 02.4V
Float or pull
high above 5V
PWM
PWM + pulse
analog dimming
Capacitor
Pulse analog
dimming signal
PWM
Only DC input
analog
dimming
Only pulse
input analog
dimming
Only PWM
dimming
Supply Input (VIN)
VIN is the supply input voltage of the IC. Bypass
VIN with a ceramic capacitor 0.47µF or larger.
LLC Gate Driver (VCC, GL, GR)
VCC supplies the gate drive signals GL, GR,
DIMO, and the charge pump from CFLY. Bypass
VCC with a ceramic capacitor 1µF or larger. VCC
can also be used to supply an external circuit. To
avoid noise during layout, place the VCC
capacitor directly between VCC and GND with a
short and separate wire.
MP4655 Rev 1.0
2/2/2016
GL and GR provide the driving signal for the LLC
power stage. GL and GR are 180 degree phase
shifted gate drive signals. With their enhanced
drive capability, GL and GR can directly drive the
external LLC MOSFETs in the power stage
through a gate driving transformer.
The gate driving transformer also isolates the
primary power stage and the secondary control
circuit. Place a 2.2nF Y-cap between the power
stage ground and the reference ground for the
control circuit to improve EMI performance. The
primary inductance of the gate driving
transformer influences its magnetic current,
which is also supplied by the IC. The primary
inductance should be larger than 1mH, and is
recommended to be over 2mH.
Extra NMOS Gate Driver (CFLY, VDR_DN,
GATEN, SOURCE)
GATEN and SOURCE are connected to the extra
duty-controlled NMOS’ gate and source. They
provide a floating driving signal for the dutycontrolled NMOS. A resistor on GATEN can
adjust the driving speed.
CFLY and VDR_DN provide a charge pump
supply for GATEN referred to SOURCE. Connect
a flying capacitor 100nF or above on CFLY, and
diodes on SOURCE and VDR_DN, as shown in
the typical application circuit.
LED Driver Stage Enable Signal (EN_LED)
EN_LED is connected to the enable signal for the
LED driver stage. Logic high enables the LED
driver stage and logic low disables the LED driver
stage. When the LED driver stage fault is
triggered but the IC is not latched up, toggle the
enable signal to restart the LED driver stage.
System Enable Signal (PS_ON)
PS_ON is connected to the enable signal or
standby signal. The voltage level on PS_ON
determines the operation of the IC as follows:
1. PS_ON > 2V: the IC is enabled in normal
operation mode.
2. 0.8V < PS_ON ≤ 2V for 1ms: the IC is
disabled and no circuits work.
3. PS_ON ≤ 0.8V: the IC is enabled in
standby mode.
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26
MP4655–PURE, SINGLE-STAGE, LLC, LED CURRENT AND SYSTEM VOLTAGE CONTROLLER
Figure 9: LLC Power System with External Standby Flyback
Figure 10: LLC Power System without External Standby Flyback
MP4655 Rev 1.0
2/2/2016
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© 2016 MPS. All Rights Reserved.
27
MP4655–PURE, SINGLE-STAGE, LLC, LED CURRENT AND SYSTEM VOLTAGE CONTROLLER
APPLICATION INFORMATION
VSystem
D5
Cb
PFC_400V
D2
D1
Cr
C1
M2
400V LLC
AUX winding,
reinforced wire
C4
D6
TM
M1
C3
DCDC
C2
D3
D4
TDrive
Drive circuit
Figure 11: Application Circuit without Standby Flyback
MP4655 Rev 1.0
2/2/2016
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28
MP4655–PURE, SINGLE-STAGE, LLC, LED CURRENT AND SYSTEM VOLTAGE CONTROLLER
VSystem
D5
Cb
PFC_400V
C4
D6
TM
M1
C3
D2
D1
Cr
C1
M2
400V LLC
C2
D3
D4
TDrive
Drive circuit
5V STB
STB
flyback
driver
STB flyback
5V STB
Figure 12: Application Circuit with Standby Flyback
MP4655 Rev 1.0
2/2/2016
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29
MP4655–PURE, SINGLE-STAGE, LLC, LED CURRENT AND SYSTEM VOLTAGE CONTROLLER
VSystem
D5
D2
Cb
PFC_400V
Cr
C4
D6
TM
M1
C3
DCDC
C1
D1
M2
C2
400V LLC
D3
AUX winding,
reinforced wire
D4
TDrive
Figure 13: Application Circuit without Protection MOSFET on LED Stage
MP4655 Rev 1.0
2/2/2016
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30
MP4655–PURE, SINGLE-STAGE, LLC, LED CURRENT AND SYSTEM VOLTAGE CONTROLLER
PACKAGE INFORMATION
SOIC-28
NOTICE: The information in this document is subject to change without notice. Users should warrant and guarantee that third
party Intellectual Property rights are not infringed upon when integrating MPS products into any application. MPS will not
assume any legal responsibility for any said applications.
MP4655 Rev 1.0
2/2/2016
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© 2016 MPS. All Rights Reserved.
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