IW1678 Datasheet, PDF (1/11 Pages) Dialog Semiconductor – Low-Power Off-line Digital Green-Mode PWM Controller

iW1678
Low-Power Off-line Digital Green-Mode PWM Controller
1.0 Features
2.0 Description
●● Primary-side feedback eliminates opto-isolators and
simplifies design
●● 64-kHz PWM switching frequency
●● No-load power consumption < 100 mW at 230 V_ac with
tight dynamic load transient response
●● Able to meet < 30 mW no-load power consumption with
large value pre-load resistor
●● 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
The iW1678 is a high performance AC/DC power supply
controller which uses digital control technology to build peak
current mode PWM flyback power supplies. The iW1678’s
64-kHz PWM switching frequency allows the design of ultra-
compact AC/DC adapters and chargers. 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 iW1678 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.
●● No external compensation components required
●● Complies with EPA 2.0 energy-efficiency specifications
with ample margin
●● Low start-up current (8 μA typical)
●● Built-in soft start
iWatt’s innovative proprietary technology ensures that power
supplies built with iW1678 can achieve both highest average
efficiency and less than 100 mW no-load power consumption
in a compact form factor.
3.0 Applications
●● Built-in short circuit protection and output overvoltage ●● Low power compact AC/DC adapter/chargers for cell
protection
phones, PDAs, digital still cameras
●● Built-in current sense resistor short circuit protection
●● Linear AC/DC replacement
●● No audible noise over entire operating range
L
+
N
+
V_OUT
GND
Rev. 1.1
U1
iW1678
1 V_CC
OUTPUT 5
2 GND
3 ^VSENSE
I_SENSE 4
Figure 3.1: iW1678 Typical Application Circuit
iW1678
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