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PDF PN8122 Data sheet ( Hoja de datos )
| Número de pieza | PN8122 | |
| Descripción | Low Standby-Power Off-line PWM converters | |
| Fabricantes | Chipown | |
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PN8122
Chipown
Low Standby-Power Off-line PWM converters
General Description
The PN8122 consists of an integrated Pulse Width Modulator (PWM) controller and power MOSFET, specifically designed for
a high performance off-line converter with minimal external components. PN8122 offers complete protection coverage with
automatic self-recovery feature including Cycle-by-Cycle current limiting (OCP), over voltage protection (OVP), over
temperature protection (OTP) and soft-start. Burst mode operation and device very low consumption helps to meet the standby
energy saving regulations. Excellent EMI performance is achieved with frequency modulation. The device consists of the high
voltage start-up circuit. The device provides an advanced platform well suited for low standby-power and cost-effective flyback
converters.
Features
■ 85v to 265v wide range AC voltage input
■ Operating Frequency(60kHz)
■ Frequency modulation for low EMI
■ Burst-mode Operation
■ Built-in Soft Start
■ Internal HV Start-up Circuit
■ Excellent Protection :
Over Current Protection (OCP)
Over Temperature Protection (OTP)
Over Voltage Protection (OVP)
Typical Application
Applications
■ Electromagnetic Oven power supplies
■ Small household application power supplies (Coffee
machine, Electric kettle, etc.)
■ LED Driver
Package/Order Information
GND
GND
COMP
VCC
DIP7
SW GND
SW GND
NC COMP
NC VCC
SO-8
SW
SW
NC
NC
Order codes
PN8122-NSC-T1
Package
DIP7
PN8122-SEC-R1
SOP8
AC
85~265V
Snubber
DC
Output
COMP
OTP
Block
Control
Block
FB
Block
VDD
SUPPLY
&UVLO
SW
HV Start
Block
PWM Switch
&Gate Driver
GND
PN8122
8/F, ChuangYuan Building No.21-1 Changjiang Road, Wuxi New Destrict Tel: +86(510)8521-7718 http://www.chipown.com.cn
Rev.A.1201 1 / 8
1 page  
PN8122
Functional Description
1. Startup
This device includes a high voltage start up current source connected on the SW of the device. As soon as a voltage
is applied on the input of the converter, this start up current source is activated and to charge the VCC capacitor as
long as VCC is lower than VSTART. When reaching VSTART, the start up current source is cut off by
UVLO&TSD and the device begins to operate by turning on and off its main power MOSFET. As the COMP pin
does not receive any current from the opto-coupler, the device operates at full current capacity and the output
voltage rises until reaching the regulation point where the secondary loop begins to send a current in the
opto-coupler. At this point, the converter enters a regulated operation where the COMP pin receives the amount of
current needed to deliver the right power on secondary side.
SW
VCC
UVLO
&TSD
Fig 1 Startup circuit
2. Soft-start up
In the process of start up, the current of drain increases to maximum limitation step by step. As a result, it can
reduce the stress of secondary diode greatly and is propity to prevent the transformer turning into the saturation
states. Typically, the duration of soft-start is 8ms.
3. Gate driver
The internal power MOSFET in PN8122 is driven by a dedicated gate driver for power switch control. Too weak
the gate driver strength results in higher conduction and switch loss of MOSFET while too strong gate drive results
in worse EMI.
A good tradeoff is achieved through the built-in totem pole gate design with proper output strength and dead time.
The good EMI system design and low idle loss is easier to achieve with this dedicated control scheme.
4. Oscillator
The switching frequency of PN8122 is internally fixed at 60 kHz. No external frequency setting components are
required for PCB design.
The frequency modulation is implemented in PN8122. So that, it minimizes the conduction band EMI and therefore
eases the system design because the tone energy could be spread out.
5. Feed-back
A feedback pin controls the operation of the device. Unlike conventional PWM control circuits which use a voltage
input, the COMP pin is sensitive to current. Figure 2 presents the internal current mode structure. The Power
MOSFET delivers a sense current which is proportional to the main current. R2 receives this current and the current
coming from the COMP pin. The voltage across R2(VR2) is then compared to a fixed reference voltage. The
8/F, ChuangYuan Building No.21-1 Changjiang Road, Wuxi New Destrict Tel: +86(510)8521-7718 http://www.chipown.com.cn
Rev.A.1201
5/8
5 Page | ||
| Páginas | Total 8 Páginas | |
| PDF Descargar | [ Datasheet PN8122.PDF ] | |
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