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PDF LD7904JGPN Data sheet ( Hoja de datos )
| Número de pieza | LD7904JGPN | |
| Descripción | Green Mode Power Switch | |
| Fabricantes | Leadtrend Technology | |
| Logotipo |  |
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LD7904JGPN
4/25/2012
Green Mode Power Switch with BNO
REV：01
General Description
The LD7904JGPN is a green mode PWM chip integrated
with a 700V MOSFET in a DIP-6 package. It’s operating at
fixed frequency of 100KHz. With multi-functions built-in
this IC, such as high voltage startup, Burn-in/out
/OLP/OVP/OTP protection, internal current mode slope
compensation, and green-mode power-saving operation
under light load or no load condition, this highly integrated
device provides high efficiency, low external component
counts, and low cost solution for compact power
applications.
Features
Built-in 700V Power MOSFET
Built-in High Voltage startup circuit
Fixed Switching Frequency at 100KHz
Frequency Trembling for EMI improve
Internal High Voltage Startup Circuit
Under Voltage Lockout (UVLO) on VCC Pin
Current Mode Control with Slope Compensation
Green-Mode Control for Power Saving
OVP / OLP / Internal Thermal Shut Down
Applications
Switching AC/DC Adaptor
LCD TV or PC Standby Power
SMPS for LCD Monitor
Typical Application
Leadtrend Technology Corporation
LD7904JPGN-DS-01 April 2012
1
www.leadtrend.com.tw
1 page  
LD7904JGPN
Absolute Maximum Ratings
Supply Voltage VCC
COMP
S pin DC Voltage
S pin negative pulse voltage (Duration Time < 100nS)
Drain
Peak Pulse drain current
Total Maximum Power Dissipation of (25C)
Package thermal resistance (DIP-6)
θJA
θJC
Operating Junction Temperature Range
Operating Ambient Temperature Range
Storage Temperature Range
Lead temperature (Soldering, 10sec)
ESD Voltage Protection, Human Body Model (Exclusive Drain Pin)
ESD Voltage Protection, Machine Model (Exclusive Drain Pin)
-0.3V~30V
-0.3V ~7V
-0.3V ~7V
-1.5V
-0.3V~700V
4A
1.25W
80C/W
30C/W
-40C to 125C
-40C to 85C
-65C to 150C
260C
2.5KV
250 V
Caution:
Stresses beyond the ratings specified in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only
rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification
is not implied.
Recommended Operating Conditions
Item
Min.
Max.
Unit
Supply Voltage Vcc
Vcc Capacitor
11 25 V
10 47 F
COMP Capacitor Value
2.2 100 nF
Note:
1. It’s necessary to connect a capacitor with COMP pin to filter out the undesired
switching noise for more stable operation.
2. Using smaller signal components close to IC pins is preferable.
Leadtrend Technology Corporation
LD7904JPGN-DS-01 April 2012
5
www.leadtrend.com.tw
5 Page 
LD7904JGPN
threshold of the current sensing pin is Vcs_off (~0.45V).
The MOSFET peak current can be obtain from below
equation.
IPEAK(MAX)
Vcs _ off
RS
Due to integrated leading edge blanking circuit and
internal spike filter, it doesn’t need external LC filter parts.
Internal Slope Compensation
Stability is crucial for current mode control when it
operates at CCM and more than 50% of duty-cycle. To
stabilize the control loop, the slope compensation is
required in the traditional UC384X design by injecting the
ramp signal from the RT/CT pin through a coupling
capacitor. In the LD7904J, the internal slope
compensation circuit has been implemented to simplify
the external circuit design.
On/Off Control
The gate driver of LD7904J can be disabled immediately
by pulling COMP pin voltage level lower than Zero Duty
Trip Level. The disable-mode can be released when
Comp pin voltage level higher than Zero Duty Trip Level.
Voltage Feedback Loop
The voltage feedback signal is provided from the TL431 in
the secondary side through the photo-coupler to the
COMP pin of LD7904J. The input stage of LD7904J, like
the UC384X, is incorporated with 2 diodes voltage offset
circuit and a voltage divider with 1/6 ratio. Therefore,
V(PWMCOMPARATOR )
1
6
(VCOMP
2VF )
A pull-high resistor is embedded internally and thus an
external one is not required.
OVP (Over Voltage Protection) on Vcc
LD7904J is implemented an OVP function on Vcc.
When the Vcc voltage is higher than the OVP threshold
voltage, the output gate drive circuit will be shutdown and
stop the switching of the power MOSFET.
If fault condition is removed, the LD 7904 will automatic
restart at the next UVLO(on).
If the fault condition is not removed, at the next UVLO(on)
the Vcc will tripped the OVP level again and re-shutdown
the output. Then the Vcc is working as a hiccup mode.
The Figure 16 shows its operation.
Oscillator and Switching Frequency
The switching frequency of LD7904J is fixed at 100KHz to
provide the optimized operations by considering the EMI
performance, thermal treatment, component sizes and
transformer design. The Trembling frequency is internally
pre-set for 6.2KHz when incorporating with 100KHz
switching frequency.
Green-Mode Operation
By using the green-mode control, the switching frequency
can be reduced under the light load condition. This feature
helps to improve the efficiency in light load conditions.
The green-mode control is Leadtrend Technology’s own
IP.
Maximum Duty-Cycle
The maximum duty-cycle of LD7904J is limited to 75% to
avoid the transformer saturation.
Fig. 16
Over Load Protection (OLP)
To protect the circuit from being damaged under over load
condition or short circuit condition, a OLP function is
implemented in the LD7904J. The Figure 17 shows the
waveforms of the OLP operation. While OLP condition,
Leadtrend Technology Corporation
LD7904JPGN-DS-01 April 2012
11
www.leadtrend.com.tw
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LD7904JGPN.PDF ] | |
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