Abstract:
This paper presents the simulation model of flyback
switching DC-DC converters operating in heavy load modes, and
the application of the model in the converter design for
improving the system reliability. To derive the simulation model,
different operational modes and atomic circuit blocks (ACB) are
established first. Then, the state-machine of the system is studied.
Finally, the transfer function of each ACB is determined, and
according to the relationship among the ACBs, the complete
simulation model is built, which can be used for transient
analysis during starting, the operation in the under-voltage mode
or over-current mode. Furthermore, the heavy load simulation
model is applied to calculate the maximum steady-state power
loss of the output diode, one of the key factors for thermal
analysis which is crucial for the system reliability. The effect of
time delay is also considered. By modifying the parameters of a
physical flyback converter according to the simulation results,
the converter reliability is significantly improved. The theoretical
analysis is verified by experimental results.
