|
|
PDF LD7922 Data sheet ( Hoja de datos )
| Número de pieza | LD7922 | |
| Descripción | Primary-Side PWM Power Switch | |
| Fabricantes | Leadtrend Technology | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de LD7922 (archivo pdf) en la parte inferior de esta página. Total 17 Páginas | ||
|
No Preview Available !
LD7922
08/02/2012
Primary-Side PWM Power Switch with CV/CC Operation
VER. 00
General Description
The LD7922 integrates a 700V power MOSFET and a
primary-side feedback PWM controller with CV/CC
operation in a DIP-7 package. The LD7922 is designed for
low power adapter/charger and LED lighting applications.
It minimizes the components counts and is available in tiny
packages. Those make it an ideal design for low cost
applications.
The LD7922 provides constant voltage, constant current
(CV/CC) operation requiring neither photo-coupler nor
secondary control circuit. Also, the LD7922 features OTP
(Over Temperature Protection) and OVP (Over Voltage
Protection) to prevent the circuit from being damaged
under abnormal conditions.
Features
Built-in 700V Power MOSFET
Primary-side Feedback Control
Constant Current Control
Built-in Load Regulation Compensation
Built-in Primary Winding Inductance Compensation
Low Startup Current (<16A)
Current Mode Control with Cycle-by-Cycle Current
Limit
Green Mode Control
UVLO (Under Voltage Lockout)
LEB (Leading-Edge Blanking) on CS Pin
OVP (Over Voltage Protection) on Vcc
OTP (Over Temperature Protection)
Applications
AC-DC Adapter and Charger
AC-DC LED Lighting
Typical Application
AC
Input
AC
Input
EMI
Filter
FB
COMP
VCC
LD7922
Drain
GND
S
Leadtrend Technology Corporation
LD7922-DS-00 Aug. 2012
1
www.leadtrend.com.tw
1 page  
LD7922
Absolute Maximum Ratings
Supply Voltage VCC,
Drain
COMP, FB, S
Maximum Junction Temperature
Peak Pulse drain current1, TC=25°C
Total Power Dissipation of DIP-7, Ta=25°C
Package thermal resistance (DIP-7), JA
Operating Ambient Temperature
Operating Junction Temperature
Storage Temperature Range
Lead temperature (Soldering, 10sec)
ESD Voltage Protection, Human Body Model (Exclusive Drain Pin)
ESD Voltage Protection, Machine Model (Exclusive Drain Pin)
1. Repetitive rating: Pulse width limited by maximum junction temperature
2. w/o heat-sink, under natural convection
-0.3 ~29V
-0.3~700V
-0.3 ~6V
150°C
2.0A
1.2W
80°C/W2
-40°C to 85°C
-40°C to 125°C
-65°C to 150°C
260°C
2.5 KV
250 V
Caution:
Stress exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the
Recommended Operating Conditions is not implied. Extended exposure to stress above Recommended Operating Conditions may affect
device reliability
Leadtrend Technology Corporation
LD7922-DS-00 Aug. 2012
5
www.leadtrend.com.tw
5 Page 
LD7922
AC
input
EMI
Filter
Cbulk
R1
D1
C1 C2
VCC
Drain
LD7922
S
GND
Fig. 15
Principle of CV Operation
In the DCM flyback converter, the output voltage can be
sensed by the auxiliary winding. LD7922 samples the
auxiliary winding on the primary-side to regulate the
output voltage, as shown in the Fig 16. The voltage
induced in the auxiliary winding is a reflection of the
secondary winding voltage while the MOSFET is in off
state. Via a resistor divider connected between the
auxiliary winding and FB pin, the auxiliary voltage is
sampled after the sample delay time and will be hold until
the next sampling. The sampled voltage is compared with
internal reference VREF (2.5V) and the error will be
amplified. The error amplifier output COMP reflects the
load condition and controls the duty cycle to regulate the
output voltage, thus constant output voltage can be
achieved. The output voltage is given as:
VOUT
2.5V(1
Ra
Rb
)(
Ns)
Na
Vf
voltage clamp circuit to minimize the high frequency
ringing will achieve the best regulation. Fig. 17 shows the
desired drain voltage waveform in compare to Fig. 18 with
a large undershoot due to the leakage inductance induced
ring. This will cause error to the sample and inferior
performance to the output voltage regulation. A proper
selection for resistor RS, in series with the clamp diode,
may reduce any large undershoot, as shown in Fig. 19.
Vin
Np
Na
VCC
Ra
LD 7922
PWM
Vref
FB
S/H
+
-
COMP
Rb
Drain
S
Ns
Fig.16
VDS An overshoot
is acceptable
Fig.17
VDS
Where VF indicates the drop voltage of the output Diode,
Ra and Rb are values for top and bottom feedback
resistor, Ns and Na are the turns of transformer secondary
and auxiliary.
An undershoot
causes error to the
sample
Fig.18
In case that the output voltage is sensed through the
auxiliary winding; the leakage inductance will induce
ringing to affect output regulation. Optimizing the drain
Leadtrend Technology Corporation
LD7922-DS-00 Aug. 2012
11
www.leadtrend.com.tw
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet LD7922.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| LD7921 | Primary-Side PWM Power Switch | Leadtrend Technology |
| LD7922 | Primary-Side PWM Power Switch | Leadtrend Technology |
| Número de pieza | Descripción | Fabricantes |
| SLA6805M | High Voltage 3 phase Motor Driver IC. |
 Sanken |
| SDC1742 | 12- and 14-Bit Hybrid Synchro / Resolver-to-Digital Converters. |
 Analog Devices |
|
DataSheet.es es una pagina web que funciona como un repositorio de manuales o hoja de datos de muchos de los productos más populares, |
| DataSheet.es | 2020 | Privacy Policy | Contacto | Buscar |