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부품번호 | IW1696 기능 |
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기능 | Low-Power Off-line Digital Green-Mode PWM Controller | ||
제조업체 | iWatt | ||
로고 | |||
전체 11 페이지수
iW1696
Low-Power Off-line Digital Green-Mode PWM Controller
1.0 Features
●● Primary-side feedback eliminates opto-isolators and
simplifies design
●● Adaptive multi-mode PWM/PFM control improves
efficiency
●● Quasi-resonant operation for highest overall efficiency
●● EZ-EMI ® design to easily meet global EMI standards
●● Direct drive of low-cost BJT switch
●● Dynamic base current control
●● Very tight constant voltage and constant current
regulation with primary-side-only feedback
●● No external compensation components required
●● Complies with EPA 2.0 energy-efficiency specifications
with ample margin
●● Able to meet < 30 mW no load power consumption
●● Low start-up current (10 μA typical)
●● Built-in soft start
●● Built-in short circuit protection and output overvoltage
protection
●● Built-in current sense resistor short protection
●● No audible noise over entire operation range
2.0 Description
The iW1696 is a high performance AC/DC power supply
controller which uses digital control technology to build peak
current mode PWM flyback power supplies. The device
directly drives a power BJT and operates in quasi-resonant
mode to provide high efficiency along with a number of key
built-in protection features while minimizing the external
component count, simplifying EMI design and lowering the
total bill of material cost. The iW1696 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 overall
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 iW1696 is ideal for applications targeting
the newest regulatory standards for average efficiency.
3.0 Applications
●● Low power AC/DC adapter/chargers for cell phones,
PDAs, digital still cameras
●● Linear AC/DC replacement
L
+
N
+ VOUT
GND
U1
iW1696
1 VCC
OUTPUT 5
2 GND
3 VSENSE
ISENSE 4
Figure 3.1: iW1696 Typical Application Circuit
Rev. 2.0
iW1696
February 13, 2012
Page 1
iW1696
Low-Power Off-line Digital Green-Mode PWM Controller
7.0 Typical Performance Characteristics
5.58 12.20
5.54 12.10
5.50 12.00
5.46 11.90
5.42 11.80
5.38-50 -25 0
25 50 75 100 125
Ambient Temperature (ºC)
Figure 7.1 : VCC UVLO vs. Temperature
150
44
11.70-50 -25 0 25 50 75 100 125 150
Ambient Temperature (ºC)
Figure 7.2 : Start-Up Threshold vs. Temperature
2.010
42 2.006
40 2.002
38 1.998
36 1.994
34-50 -25 0 25 50 75 100 125 150
Ambient Temperature (ºC)
Figure 7.3 : Switching Frequency vs. Temperature1
10.0
1.990-50 -25 0 25 50 75 100 125 150
Ambient Temperature (ºC)
Figure 7.4 : Internal Reference vs. Temperature
8.0
6.0
4.0
2.0
0.00.0
3.5 7.0
VCC (V)
10.5
14.0
Figure 7.5 : VCC vs. VCC Supply Start-up Current
Notes:
Note 1. Operating frequency varies based on the load conditions, see Theory of Operation for more details.
Rev. 2.0
iW1696
February 13, 2012
Page 4
4페이지 iW1696
Low-Power Off-line Digital Green-Mode PWM Controller
( )ig _ peak t =
vg (t ) × tON
LM
(9.2)
This current represents a stored energy of:
E=g
LM
2
× ig _ peak
(t )2
(9.3)
When Q1, turns off at tO, ig(t) in LM forces a reversal of
polarities on all windings. Ignoring the communication-time
caused by the leakage inductance LK at the instant of turn-off
tO, the primary current transfers to the secondary at a peak
amplitude of:
feedback voltage VFB. The VFB signal precisely represents
the output voltage under most conditions and is used to
regulate the output voltage.
9.4 Constant Voltage Operation
After soft-start has been completed, the digital control block
measures the output conditions. It determines output power
levels and adjusts the control system according to a light
load or heavy load. If this is in the normal range, the device
operates in the Constant Voltage (CV) mode, and changes
the pulse width (TON) and off time (TOFF) in order to meet the
output voltage regulation requirements.
id =(t )
NP
NS
× ig _
peak
(t)
(9.4)
Assuming the secondary winding is master, and the auxiliary
winding is slave,
If no voltage is detected on VSENSE it is assumed that the
auxiliary winding of the transformer is either open or shorted
and the iW1696 shuts down.
9.5 Constant Current Operation
1
VAUX
=
VO
x
NAUX
NS
The constant current (CC mode) is useful in battery charging
applications. During this mode of operation the iW1696 will
regulate the output current at a constant level regardless of
the output voltage, while avoiding continuous conduction
mode.
VAUX
0V
2
VAUX
=
-VIN
x
NAUX
NP
Figure 9.3: Auxiliary Voltage Waveforms
To achieve this regulation the iW1696 senses the load
current indirectly through the primary current. The primary
current is detected by the ISENSE pin through a resistor from
the BJT emitter to ground.
VNOM
CV mode
The auxiliary voltage is given by:
=VAUX
N AUX
NS
(VO
+ ∆V)
(9.5)
and reflects the output voltage as shown in Figure 9.3.
The voltage at the load differs from the secondary voltage by
a diode drop and IR losses. Thus, if the secondary voltage is
always read at a constant secondary current, the difference
between the output voltage and the secondary voltage will
be a fixed ΔV. Furthermore, if the voltage can be read when
the secondary current is small, ΔV will also be small. With
the iW1696, ΔV can be ignored.
Output Current
IOUT(CC)
Figure 9.4: Power Envelope
The real-time waveform analyzer in the iW1696 reads this
information cycle by cycle. The part then generates a
Rev. 2.0
iW1696
February 13, 2012
Page 7
7페이지 | |||
구 성 | 총 11 페이지수 | ||
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구매 문의 | 일반 IC 문의 : 샘플 및 소량 구매 ----------------------------------------------------------------------- IGBT, TR 모듈, SCR 및 다이오드 모듈을 포함한 광범위한 전력 반도체를 판매합니다. 전력 반도체 전문업체 상호 : 아이지 인터내셔날 사이트 방문 : [ 홈페이지 ] [ 블로그 1 ] [ 블로그 2 ] |
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