|
|
PDF IW1689 Data sheet ( Hoja de datos )
| Número de pieza | IW1689 | |
| Descripción | Low-Power Off-line Digital PWM Controller | |
| Fabricantes | iWatt | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de IW1689 (archivo pdf) en la parte inferior de esta página. Total 17 Páginas | ||
|
No Preview Available !
iW1689
Low-Power Off-line Digital PWM Controller
1.0 Features
• Primary-side feedback eliminates opto-isolators and
simplifies design
• Multi-mode operation for highest overall efficiency
• Very tight output voltage regulation
• No external compensation components required
• Complies with CEC/EPA/IEC no load power consumption
and average efficiency regulations
• Built-in secondary constant-current control with primary-
side feedback
• Low start-up current (8 µA typical)
• Built-in soft start
• Built-in short circuit protection
• AC line under/overvoltage and output overvoltage
protection
• Fixed switching frequency
• Available in a space-saving SOT-23 package
2.0 Description
The iW1689 is a high performance AC/DC power supply
controller which uses digital control technology to build
sensorless peak current mode PWM flyback power
supplies. The device provides high efficiency along with a
number of key built-in protection features while minimizing
the external component count and bill of material cost. The
iW1689 removes the need for secondary feedback circuitry
while achieving excellent line and load regulation. It also
eliminates the need for loop compensation components while
maintaining stability over all operating conditions. Pulse-by-
pulse waveform analysis allows for a loop response that is
much faster than traditional solutions, resulting in improved
dynamic load response. The built-in power limit function
enables optimized transformer design in universal off-line
applications and allows for a wide input voltage range.
The ultra-low start-up power and operating current at light
load ensure that the iW1689 is ideal for applications targeting
the newest regulatory standards for average efficiency and
standby power.
3.0 Applications
• Low power AC/DC adapter/chargers for cell phones,
PDAs, digital still cameras
• Standby supplies for televisions, DVDs, set-top boxes
and other consumer electronics
L
N
+
+ + VOUT
RTN
Rev 2.0
+
4 VCC
OUTPUT 3
GND 2
5 VIN
VSENSE 1
U1
iW1689
Figure 2.0.1 iW1689 Typical Application Circuit
iW1689
November 7, 2012
Page 1
1 page  
iW1689
Low-Power Off-line Digital PWM Controller
8.0 Functional Block Diagram
VCC
4
VIN
5
VCC SW
Start-up
Control
VIN SW
GND
2
20 kΩ
Reference
A/D
CC/CV
Control
VSENSE
1
1.538 V
1.700 V
0.128 V
–
+CMP
–
+CMP
–
+CMP
VFB
Real Time
Waveform
Analyzer
Digital
Error
Amp
tON
Calcuator
VCC
Output
Pulse
Control
OUTPUT
3
tOFF
Calcuator
Figure 8.0.1 iW1689 Functional Block Diagram
9.0 Theory of Operation
The iW1689 is a digital controller which uses a new,
proprietary primary-side control technology to eliminate the
opto-isolated feedback and secondary regulation circuits
required in traditional designs. This results in a low-cost
solution for low power AC/DC adapters. The core PWM
processor uses fixed-frequency Discontinuous Conduction
Mode (DCM) operation at higher power levels and switches
to variable frequency operation at light loads to maximize
efficiency. Furthermore, iWatt’s digital control technology
enables fast dynamic response, tight output regulation, and
full featured circuit protection with primary-side control.
Referring to the block diagram in Figure 8.0.1, the digital
error amplifier and tON/tOFF calculator blocks generate the
switching on-time and off-time information based on the
line voltage and the output voltage feedback signal. The
system loop is automatically compensated internally by
the digital error amplifier. Adequate system phase margin
and gain margin are guaranteed by design and no external
analog components are required for loop compensation. The
iW1689 uses an advanced digital control algorithm to reduce
system design time and improve reliability.
Furthermore, accurate secondary constant-current operation
is achieved without the need for any secondary-side sense
and control circuits.
The iW1689 uses PWM mode control at higher output power
levels and switches to PFM mode at light load to minimize
power dissipation to meet the Blue Angel specification.
Additional built-in protection features include overvoltage
protection (OVP), output short circuit protection (SCP) and
soft-start.
iWatt’s digital control scheme is specifically designed to
address the challenges and trade-offs of power conversion
design. This innovative technology is ideal for balancing new
regulatory requirements for green mode operation with more
practical design considerations such as lowest possible cost,
smallest size and high performance output control.
Rev 2.0
iW1689
November 7, 2012
Page 5
5 Page 
iW1689
Low-Power Off-line Digital PWM Controller
TON = 900V ms
VBULK (MIN )
TON = 900V ms
82V
TON = 10.9ms
From 10.8:
TRESET =85% × 25ms −10.9ms
TRESET = 10.35m s
Allowing a maximum forward voltage drop at the Schottky
diode of 0.7 V, substitute TON and TRESET into equation
(10.10):
=N =900 15.2
5.7 ×10.35
Secondary and axuiliary turn:
For a flyback converter, the MOSFET will be selected so that
VDS is higher than the switching voltage plus the reflecting
secondary and spike voltage.
VDS > VBULK (MAX ) + NVOUT + VSPIKE
(10.14)
If VSPIKE = 100V, then from equation (10.14):
VDS > 372 +15× 5.7 +100 =557V
And IDS > IPRPK = 304mA
Therefore, select a MOSFET = 600 V/0.4 A
The secondary current is a triangle of peak amplitude
ISECPK = IPRPK x N at a maximum duration of TRESET. It’s RMS
value during a period TP is:
ISECRMS=
IPRPK
×
N
3
×
TRESET
TP
(10.15)
NSEC
=
NPR
N
(10.11)
Substituting IPRPK = 304 mA into equation (10.15) yields:
NAUX = NPR ×VAUX
VOUT
(10.12)
ISECRMS= 0.304 ×15 × 10.35= 1.694 A
3 25
With NPR = 167, and N = 15, from equation 10.10:
NS=EC 1=67 11turns
15
From equation 10.11:
NAUX = 11 13V
5.7V
NAUX = 25turns
The working voltage of the rectifier diode includes the output
voltage plus margin reverse voltage during the TON period. A
20% marginal voltage is suitable for safety:
=VDIODE
120%
VBULK (MAX
N
)
+
VOUT
V=DIODE
1.2
3175=2 + 5
35V
Primary RMS current: Primary current is a triangle of peak
amplitude IPRPK at maximum duration TON. It’s RMS on a
period TP is:
IPRRMS
=
IPRPK
3
TON
TP
(10.13)
Substitute IPRPK = 304 mA into equation (10.13)
IPRRMS =304 × 10.9 =115mA
3 25
Typically, we select the rated current of a Schottky diode
rectifier that is twice the output current value. With a known
value for ISECRMS and VDIODE the rectifier diode will be selected
with ratings of 40 V and 3 A :
Diode = 3A / 40V
This maximum RMS current occurs at 130% of the
rated output load. Therefore, the wire size will based on
ISECRMS/1.3.
Selecting a switching MOSFET:
Rev 2.0
iW1689
November 7, 2012
Page 11
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet IW1689.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| IW1688 | Low Power Off Line Digital PWM Controller | iWatt |
| IW1689 | Low-Power Off-line Digital PWM Controller | iWatt |
| 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 |