EM8672G7 [EXCELLIANCE]
HV Start-up PWM Controller with Over Temperature Protection;
| 型号： | EM8672G7 |
| 厂家： | 
Excelliance MOS |
| 描述： | HV Start-up PWM Controller with Over Temperature Protection |
| 文件： | 总13页 (文件大小：285K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
EM8672
HV Start-up PWM Controller with Over Temperature Protection
General Description
Features
EM8672 is a high performance, low cost, HV
Start-up, current mode PWM controller with green
mode power saving. The EM8672 integrates
functions of Soft Start(SS), Under Voltage
Lockout(UVLO), Leading Edge Blanking(LEB),
internal Over Temperature Protection(OTP),
internal slope compensation. The EM8672 also
features more protection like Over Load
Protection(OLP) and Over Voltage Protection(OVP)
to prevent circuit damage occurred under
abnormal conditions. The EM8672 also has external
Over Temperature Protection(Latch).
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700V High Voltage Start up Circuit
Current Mode Control
Soft Start Function
Built-in Slope Compensation
Internal Leading-edge Blanking
External Over Temperature Protection
Over Voltage Protection (OVP) on VCC pin
Over Load Protection (OLP)
Cycle-by-cycle Current Limit
Feedback Open Protection
Internal Over Temperature Protection (OTP)
Constant Output Power Limit (Full AC Input
Range)
ꢀ
Excellent EMI performance
Applications
Ordering Information
ꢀ
ꢀ
LCD Monitor Power Supply
Part Number
EM8672G
Package
SOP-8
Remark
Open-Frame SMPS
EM8672G7
SOP-7
Typical Application Circuit
AC
INPUT
EMI
Filter
+
DC
OUTPUT
HV
VCC
LATCH
COMP
GATE
EM8672
CS
GꢀD
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EM8672
Pin Configuration
Pin Assignment
Pin Number
Pin Name
Pin Function
SOP-8
4
SOP-7
4
Ground.
GND
Voltage feedback pin. By connecting a photo-coupler to close the control loop and
achieve the regulation.
COMP
2
2
This pin provides an Internal sourcing current of 100uA, used for external latch
circuit. When this pin < 1.05V and after 160uS, IC is latch off. By connecting a NTC
resistor to GND, it can achieve the OTP protection function. Keep this pin floating
to disable the latch protection.
LATCH
1
1
Senses the primary current.
IC Power Supply Pin.
CS
VCC
GATE
NC
3
6
5
7
3
6
5
--
Gate drive output to drive the external MOSFET.
No Internal Connection.
For start-up, this pin is pulled high to the line input or the bulk capacitor via
resistors.
HV
8
7
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EM8672
Function Block Diagram
HV
VCC
Vbias
100uA
LATCH
LATCH
1.05V
OVP
OTP
Control
Logic
VOVP
OLP
UVLO
Vbias
16V / 10V
Green
mode
COMP
Oscillator
2R
R
Max duty
GATE
Soft
start
S
Q
Soft
Driver
-
-
PG
R
Line compensation
OCP
+
PWM
comparator
LEB
CS
Slope
Comp
GND
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EM8672
Absolute Maximum Ratings
ꢀ Supply Input Voltage, VCC ----------------------------------------------------------------------- 30V
(Note1)
ꢀ Gate pin------------------------------------------------------------------------------------------------ 30V
ꢀ HV pin--------------------------------------------------------------------------------------------------- 700V
ꢀ LATCH, COMP, CS Pin --------------------------------------------------------------------------------- - 0.3V to 6.5V
ꢀ Power Dissipation, PD @ TA = 25℃
SOP 8 --------------------------------------------------------------------------------------------------- 0.4W
SOP7 --------------------------------------------------------------------------------------------------- 0.4W
ꢀ Package Thermal Resistance
SOP 8 -------------------------------------------------------------------------------------------------- 160℃/W
SOP 7 -------------------------------------------------------------------------------------------------- 160℃/W
ꢀ Junction Temperature ----------------------------------------------------------------------------- 150℃
ꢀ Lead Temperature (Soldering, 10 sec.) -------------------------------------------------------- 260℃
ꢀ Storage Temperature Range --------------------------------------------------------------------- -65℃ to 150℃
ꢀ ESD Susceptibility
(Note2)
HBM (Human Body Mode) ------------------------------------------------------------------------ 3KV
MM (Machine Mode) -------------------------------------------------------------------------------- 250V
ꢀ Gate Output Current---------------------------------------------------------------------------------- 500mA
Recommended Operating Conditions
(Note3)
ꢀ Supply Input Voltage, VCC ----------------------------------------------------------------------- 11V to 25V
ꢀ VCC Capacitor ---------------------------------------------------------------------------------------- 4.7uF to 47uF
ꢀ Junction Temperature Range--------------------------------------------------------------------- -40℃ to 125℃
ꢀ Ambient Temperature Range-------------------------------------------------------------------- -40℃ to 85℃
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EM8672
Electrical Characteristics
(VCC=15V, TA=25℃, unless otherwise specified)
Parameter
VCC Section
Symbol
Test Conditions
Min
Typ
Max
Units
VCC OVP Protect voltage
Start up current
VOVP
25
-
27
45
16
10
8.8
1
29
65
17
11
V
uA
V
VCC=VTH-ON-0.5V
ISTART
VCC On Threshold Voltage
VCC Off Threshold Voltage
VCC Reset Threshold Voltage
Operating Supply Current 1
VTH-ON
VTH-OFF
VRESET
ICC-OP1
15
9
V
V
VCC=15V, VCOMP=0V,
-
-
2
-
mA
VCC=15V, VCOMP=3V,
CGATE=1nF
Operating Supply Current 2
Operating Supply Current 3
ICC-OP2
ICC-OP3
2.5
0.5
mA
mA
VCC=15V,
Protection triggerred
-
-
Gate Section
Rising Time
Falling Time
HV Section
TR
TF
CL = 1nF
CL = 1nF
-
-
100
30
160
60
nS
nS
VCC=VTH-ON-0.5V
VHV=50V
HV Current Source
IHV
1
1
mA
uA
VCC=VTH-ON+0.5V
VHV=700V
Off-State Leakage
Ileakage
20
Current-Sense Section
Maximum Internal Current
Setpoint
VCSLim
0.8
0.85
0.9
V
Leading Edge Blanking Time
Propagation Delay Time
Soft-Start Period
TLEB
TPD
TSS
200
300
100
2.5
400
nS
nS
mS
Internal Oscillator
Oscillation Frequency
Maximum Duty
fOSC
60
65
75
22
70
KHz
%
Dmax
Green mode minimum frequency
Frequency variation vs. VCC
KHz
%
VCC=11V to 25V
5
5
Frequency variation vs.
Temperature
-20℃ to 105℃(Note4)
%
COMP Section
COMP short to GND current
Open loop COMP voltage
ICOMP
VCOMP=0V
150
250
5.2
350
uA
V
VCOMP
COMP pin open
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EM8672
COMP voltage to CS voltage
Attenuation
Av
1 / 2.5
1 / 3
1 / 3.5 V/V
Green mode COMP Threshold
Voltage
VGreen
1.8
1.3
V
V
COMP voltage for zero duty
VCOMP-ZD
LATCH Section
Latch pin source current
Turn-off voltage
ILATCH
92
100
108
1.1
uA
V
VLATCH
1.0
1.05
Latch debounce time
TLATCH
100
160
220
uS
Protection Section
Open loop protection delay time Tdelay
56
4.0
140
mS
V
Open loop protection COMP Trip
voltage
VOLP
Internal Temperature Shutdown TSD
℃
Note 1. Stresses listed as the above “Absolute Maximum Ratings” may cause permanent damage to the device. These are for
stress ratings. Functional operation of the device at these or any other conditions beyond those indicated in the
operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended
periods may remain possibility to affect device reliability.
Note 2. Devices are ESD sensitive. Handling precaution is recommended.
Note 3. The device is not guaranteed to function outside its operating conditions.
Note 4. Guaranteed by design.
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EM8672
Typical Operating Characteristics
Temperature(℃)
Temperature(℃)
Fig1. UVLO (on) vs. Temperature
Fig2. UVLO (off) vs. Temperature
Temperature(℃)
Temperature(℃)
Fig3. Frequency vs. Temperature.
Fig4. Green Mode Frequency vs. Temperature.
Temperature(℃)
Fig5. Start Up Current vs. Temperature.
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EM8672
Temperature(℃)
Temperature(℃)
Fig6. OVP vs. Temperature.
Fig7. VOLP-Trip vs. Temperature.
Temperature(℃)
Temperature(℃)
Fig8. Comp Open Voltage vs. Temperature.
Fig9. Max Duty vs. Temperature.
VCC(V)
Fig10. Frequency vs. VCC.
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EM8672
Functional Description
UVLO
An UVLO comparator is implemented in EM8672 to
monitor the VCC pin voltage. As shown in Fig. 13, a
hysteresis is built in to prevent the shutdown from
the voltage drop during startup. The UVLO (on) and
UVLO (off) are setting at 16V and 10V, respectively.
Fig. 14
Switching Frequency
To guarantee accurate frequency, EM8672 is
trimmed to 7% tolerance. The internal oscillator
also generates slope compensation, 75% maximum
duty limit.
Fig. 13
Startup Operation
Leading Edge Blanking (LEB)
Fig. 14 shows a typical HV startup circuit and
transformer auxiliary winding for the EM8672
application. It consumes only startup current
(typical 45uA) and the startup current drawn from
the HV pin to charge the VCC capacitor (CVCC).
When VCC reaches UVLO (on) voltage, EM8672
begins switching and the HV startup current
switches off. Then, the power required is supplied
from the transformer auxiliary winding. The
hysteresis of UVLO (off) provides more holdup time,
which allows using a small capacitor for VCC.
Each time the power MOSFET turn on, the MOSFET
COSS, secondary rectifier reverse recovery current
and gate driver sourcing current comprise the
current spike. To avoid premature termination of
the switching pulse, a leading edge blanking time is
built in. During the blanking time (300nS), the
PWM comparator is off and cannot switch off the
gate driver. It is recommended to adopt a smaller
R-C filter (as show at Fig.15) for high power
application to avoid the total spike width over
300nS leading edge blanking time.
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EM8672
within a fixed period of time. Reducing switching
events leads reduction on the power loss and
conserves the energy.
The EM8672 adjusts the switching mode according
to the load condition, the COMP pin voltage drops
below burst mode threshold level. Device enters
Burst Mode Control. The Gate drive output remains
at off state to minimize the switching loss and
reduces the standby power consumption.
Protection
The EM8672 provides many protection functions
that intend to protect system from being damaged.
All the protection functions are listed as below:
Fig. 15
ꢀ Cycle-by-cycle current limit
The EM8672 has over-current protection
thresholds. It is for cycle-by-cycle current limit,
which turns off MOSFET for the remainder of
the switching cycle when the sensing voltage of
MOSFET current reaches the threshold.
Soft Start
The EM8672 has an internal soft-start circuit that
increases cycle-by-cycle current limit comparator
inverting input voltage slowly after it starts. The
typical soft-start time is 2.5mS. The pulse width to
the power MOSFET is progressively increased to
establish the correct working conditions for
transformers, rectifier diodes and capacitors. The
voltage on the output capacitors is progressively
increased with the intention of smoothly
establishing the required output voltage. It also
helps prevent transformer saturation and reduces
the stress on the secondary diode during startup.
ꢀ Over-load / Open-loop Protection (OLP)
When feedback loop is open, as shown in Fig. 16,
no current flows through the opto-coupler
transistor, the EM8672 pulls up the COMP pin
voltage to 5.2V.
When the COMP pin voltage is above 4.0V
longer than 56mS, OLP is triggered. This
protection is also triggered when the SMPS
output drops below the normal value longer
than 56mS due to the overload condition.
Slope compensation
In the conventional application, the problem of the
stability is a critical issue for current mode
controlling, when it operates in higher than 50% of
the duty cycle. The EM8672 built in saw-tooth
slope compensation. So it requires no extra
component.
Burst Mode Operation
At no load or light load condition, majority of the
power dissipation in switching power supply is
form switching loss on the power MOSFET, the
core loss of the transformer and the loss on the
snubber. The magnitude of power loss is in
proportion to the number of switching events
Fig. 16
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EM8672
ꢀ Over Voltage Protection (OVP) on VCC
The VGS ratings of the HV power MOSFETs are
often limited up to max 30V. To prevent the VGS
from the fault condition, the EM8672 are
implemented an Over-Voltage-Protection (OVP)
on VCC. Whenever the VCC voltage is higher
than the OVP threshold voltage (27V), the
output gate drive will be shutdown to shop the
switching of the power MOSFET until the next
UVLO (on).
5.2V
100uA
LATCH
1
LATCH
160uS
Debounce
1.05V
Fig. 18
ꢀ External Over-Temperature Protection (OTP)
The LATCH pin is equipped with a latch
shutdown function. (Fig. 18) By decreasing the
LATCH pin voltage to 1.05V or lower, the IC
enters the latch mode. To reset latch mode,
interrupt the input voltage, thus decreasing the
VCC voltage to the Reset Threshold Voltage or
lower. If the external latch shutdown function by
the LATCH pin is not to be used, let this pin
floating or connecting a capacitor only.
The Over-Voltage-Protection on VCC function in
EM8672 is an auto-restart type protection. If the
OVP condition is not released, the VCC will
tripped the OVP level again and re-shutdown
the gate output. The VCC is working as a hiccup
mode as shown in Fig. 17. On the other hand, if
the OVP condition is removed, the VCC level will
go back to normal level and the output will
automatically return to the normal operation.
VCC
Connect an NTC resistor to the LATCH pin to use
the over-temperature protection. (Fig. 18)
OVP level
UVLO(on)
UVLO(off)
ꢀ Internal Over-Temperature Protection (OTP)
Internal 140℃comparator will provide over
temperature protection (OTP). OTP will not
shutdown system. It stops the system from
switching until the VCC is below the UVLO (off)
threshold voltage, the system will hiccup.
t
Gate out
No Switch out
t
Fig. 17
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EM8672
Ordering & Marking Information
Device Name: EM8672G for SOP-8
EM
8672
EM8672: Device Name
ABCDEFG: Date Code
ABCDEFG
Device Name: EM8672G7 for SOP-7
EM
8672
ABCDEFG
EM8672: Device Name
ABCDEFG: Date Code
Outline Drawing
SOP-8
J
F
I
I
K
G
E
H
D
B
C
A
Dimension in mm
Dimension
A
B
C
D
E
F
G
H
I
J
K
Min.
4.70
3.70
5.80
0.33
1.20
0.08
0.40
0.19
0.25
0∘
Typ.
1.27
Max.
5.10
4.10
6.20
0.51
1.62
0.28
0.83
0.26
0.50
8∘
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EM8672
SOP-7
J
F
I
I
K
G
H
D
E
B
C
A
Dimension in mm
Dimension
Min.
A
4.70
B
3.70
C
5.80
D
0.33
E
F
1.20
G
0.08
H
0.40
I
0.19
J
0.25
K
0∘
Typ.
Max.
1.27
5.10
4.10
6.20
0.51
1.62
0.28
0.83
0.26
0.50
8∘
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