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PDF ( 数据手册 , 数据表 ) GR8837B

零件编号 GR8837B
描述 Green-Mode PWM Controller
制造商 Grenergy
LOGO Grenergy LOGO 


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GR8837B 数据手册, 描述, 功能
Preliminary GR8837B
Green-Mode PWM Controller with Protection
Features
Current Mode Control
Standby Power below 100mW
Under-Voltage Lockout (UVLO)
Non-Audible-Noise Green-Mode Control
65KHz Switching Frequency
Internal Leading-Edge Blanking
Internal Slope Compensation
Internal Soft Start
Gate Output Voltage Clamp
Jitter and Soft Driving for Reducing EMI
Over-Load Protection (OLP)-Auto Recovery
Mode
Vcc OVP Protection- Latch Mode
300mA Driving Capability
Description
The GR8837B is a highly-integrated, low startup
current, current mode PWM controller with
green-mode function. The integrated functions also
include the leading-edge blanking of the current
sensing, internal slope compensation, soft start
OLP, and OVP. These functions enable the power
supply to easily meet even the strictest power
requirements.
The GR8837B improves the performance and
reduces the cost of power supplies. It is with 8-pin
DIP and 6-pin SOT-26 package
Application
Switching AC/DC Adapter
Open Frame SMPS
Battery Charger
O
Ordering and Marking Information
DIP-8
SOT-26
Code 1 8 9 A B
GH IJ
Year 2008 2009 2010 2011
2016 2017 2018 2019
Code 2 1 2 3 4 ● ● ● 9 A B C
Month Jan. Feb. Mar. Apr.
Sep. Oct. Nov. Dec.
Grenergy OPTO Inc. reserves the right to make changes to improve reliability or manufacture ability without notice, and
advise customers to obtain the latest version of relevant information to verify before placing orders.
2011.11 Ver. C .Copyright Grenergy OPTO, Inc. www.grenergy-ic.com
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GR8837B pdf, 数据表
Preliminary GR8837B
OVP (Over Voltage Protection) on VCC
To prevent power MOSFET from being damaged,
the GR8837B is implemented an OVP function on
VCC. When the VCC voltage is higher than the OVP
threshold voltage, the output gate driver circuit will
be shut down immediately to stop the switching of
power MOSFET. The VCC pin OVP function is a
latch type protection. GR8837B is working in latch
mode as shown in Fig. 11.
The operation is shown in Fig.12.
VCC
VCC mode(off)
VCC mode(on)
UVLO(off)
LOAD
Full load
VCC mode
Burst mode
OUT
Switching
t
t
t
Fig. 12
The VCC mode function is used to prevent the
output re-start again when load changes. So never
let the system operate on the VCC mode at no load.
Fig. 11
Gate Clamp/Soft Driving
Driver is clamped to 13V by an internal clamping
circuit. A totem pole gate driver is fine tuned to meet
both EMI and efficiency requirement in low power
application. An internal pull low circuit is activated
after pretty low Vdd to prevent external MOSFET
from accidentally turning on during UVLO.
VCC Mode Operation
In order to avoid the output voltage shut down by
load changing from full to no load, the GR8837 is
built-in the VCC mode function. When the load from
full changes to no load, the output voltage will
overshoot and pull low the COMP pin by feedback
loop. Thus the duty will disappear and no power
delivers to the secondary. If there is without any
mechanism to prevent this situation, the VCC pin
voltage will down to UVLO off and the IC will re-start
again. In the GR8837B, before the VCC is down to
The system should operate on burst mode,
otherwise the input power maybe become larger.
Brownout Protection
The GR8837B programmable to set the brownout
protection point through BNO pin. The voltage
across the BNO pin is proportional to the bulk
capacitor voltage, referred as the line voltage. A
brownout comparator is implemented to detect the
abnormal line condition. As soon as the condition is
detected, it will shut down the controller to prevent
the damage . When VBNO falls below 0.80V, the
gate output will be kept off even Vcc has already
achieved UVLO(ON). It therefore makes Vcc hiccup
between UVLO(ON) and UVLO(OFF). Unless the
line voltage is large enough to pull VBNO larger
than 1.05V, the gate output will not start switching
even when the next UVLO(ON) is tripped. A
hysteresis is implemented to prevent the false
trigger during turn-on and turn-off.
UVLO off, it will force the OUT pin outputs the
specified duty to pull the VCC higher than UVLO off.
2011.11 Ver. C .Copyright Grenergy OPTO, Inc. www.grenergy-ic.com
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