ICE3BR0365 Datasheet, PDF (12/16 Pages) Infineon Technologies AG – Design Guide for Off-line Fixed Frequency DCM Flyback Converter

DCM Flyback
Design Note DN 2013-01
V1.0 January 2013
before the VCC voltage develops through the converter, while a larger value will slow down the startup time. This
capacitor should not be the cheapest type, but must have an adequate ESR and ripple current capability, just like
the output capacitor, or it will deteriorate in time. In parallel with the VCC capacitor it is always recommended to use
a 100nF ceramic capacitor placed very near to VCC pin and IC ground.
D. Feedback Loop Compensation: Feedback loop compensation is needed
to prevent oscillation. For the DCM Flyback, loop compensation is less
complicated compared to CCM, as there is no right half plane zero in the power
stage to compensate for. A simple RC (Rcomp, Ccomp) as shown in Figure 6 is
usually sufficient to make a stable loop. Typical Rcomp values can range from 1k
-20k while Ccomp would usually range from 100nF-470nF. A detailed analysis
about feedback loop can be found on reference [2].
IV. DCM Flyback Design Example
STEP 1:
Sytem Specifications and Requirements:
Figure 6: Feedback loop
compensation
STEP 2:
Choosing the right controller
considering the Pout: Referring to Table 3, we
chooses an integrated controller and MOSFET solution
using ICE3BR1065J. Other features include built in
startup cell, less than 50mW no load power and
frequency jitter and soft driving for lower EMI. Below is
the typical Flyback application using ICE3BR1765J
STEP 3:
Determining Input Capacitor Cin and
the DC input voltage range:
Maximum input power:
Using 2uF per watt of input power, the required DC capacitor, Cin, is:
> Use the standard capacitance value of 68uF/400V
With the input capacitor chosen the minimum DC input voltage (DC link capacitor voltage) is obtained by:
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