IW1700 Datasheet, PDF (1/12 Pages) Dialog Semiconductor – Zero Power No-Load Off-Line Digital PWM Controller

iW1700
Zero Power No-Load Off-Line Digital PWM Controller
1.0 Features
●● Zero power consumption at no-load with lowest system
cost (< 5 mW at 230 V_ac with typical application circuit)
●● Intelligent low power management achieves ultra-low
operating current at no-load
●● Adaptive load transient detection and fast response
●● Very tight constant voltage and constant current
regulation over entire operating range
●● Primary-side feedback eliminates opto-isolators and
simplifies design
●● EZ-EMI ^® design enhances manufacturability
●● Intrinsically low common mode noise
●● Optimized 72 kHz maximum PWM switching frequency
achieves best size and efficiency
●● Active start-up scheme enables fastest possible start-up
●● Adaptive multi-mode PWM/PFM control improves
efficiency
●● Quasi-resonant operation for highest overall efficiency
●● Direct drive of low-cost BJT switch
●● No external compensation components required
●● Complies with EPA 2.0 energy-efficiency specifications
with ample margin
●● Built-in soft start
●● Built-in short circuit protection and output overvoltage
protection
●● Built-in current sense resistor short circuit protection
●● No audible noise over entire operating range
2.0 Description
The iW1700 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
together with an external active device (depletion mode
NFET or NPN BJT) provides a fast start-up meanwhile
achieving ultra-low no-load power consumption. 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 iW1700 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,
for both one-time and repetitive load transient. The built-in
power limit function enables optimized transformer design
in universal off-line applications and allows for a wide input
voltage range.
iWatt’s innovative proprietary technology ensures that power
supplies built with the iW1700 can achieve both highest
average efficiency and zero no-load power consumption,
and have fast load transient response in a compact form
factor. The active start-up scheme enables shortest possible
start-up time without sacrificing no-load power loss.
3.0 Applications
●● Compact AC/DC adapter/chargers for cell phones,
PDAs, digital still cameras
●● Linear AC/DC replacement
L
+
N
+
V_OUT
GND
U1
iW1700
1 V_CC
OUTPUT 6
2 V_SENSE
GND 5
3 ASU
I_SENSE 4
Figure 3.1: iW1700 Typical Application Circuit
(Achieving < 5 mW No-load Power Consumption. Using Depletion Mode NFET as Active Start-up Device)
Rev. 1.2
iW1700
February 13, 2012

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