Instrumentation Course 2022

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HARDWARE-EFFICIENT PROGRAMMABLE-DEVIATION CONTROLLER FOR
INDIRECT ENERGY TRANSFER DC-DC CONVERTERS
Introduction
To lower the rate at which the components react, Switch-Mode Power Supplies (SMPS)
controllers are developed in a manner that they are highly sensitive to load transients alongside
other disturbances. Analog SMPS are predominantly preferred for power supply cases of low-to-
medium to multiply the number of watts putting into consideration the cost effectiveness as a
factor. In this instance, a relatively wide bandwidth control loop is preferred to obtain a fast
response. The current hardware digital controllers which are more efficient are in place to allow
installation of more developed nonlinear control techniques for the systems of low to medium
operations, enhancing dynamic operations and therefore minimizing the size of the output
capacitor by great percentage (Wang et al 2017).
From all the controllers, only minimum deviation and time optimal controllers have indicated
transient response composed of the lowest voltage deviation for the converters that operates on
direct transfer basis of energy like the forward and back topologies. I reality, the transient
response of the load is usually related with the lowest possible output voltage deviation resulting
into a smaller value in the output capacitance. This is however contrary as for the case of boost
converter which is an indirect energy transfer system. However, the voltage deviation that is
generated by time-optimal response is slightly higher than the minimum output voltage
deviation, and these results into an extensive current stress of the component (Monteiro 2016).
In addition to that, installation of optimal methods for the indirect systems of energy transfer
calls for an extensive use of hardware compared to converters that operate on direct transfer of

energy. This is due to the demand of the controller responsible for providing solutions to a bit
complex equations depending on the point of operation. For that reason, the currently designed
time-optimal controllers are not common in their applications for the case of converters
operating in indirect transfer of energy.
This paper mainly aims at presenting a controller for the converters that operate in indirect
transfer of energy with smaller deviations in the output voltage compared to time-optimal
converters enabling a reduction in the output values of the capacitor. This new controller is
characterized by less implementations of hardware and at the same time capable of reducing
current stress of the component. A programmable deviation controller shown in the figure below
is basically developed for reactive capacitor and inductor converters with output filters and is just
a simple enhancement of the conventional mixed-signal peak system of Current Programmed
Mode (CPM). Just as for the case of conventional systems, the inner current loop assumes an
analog structure while the outer current loop is designed in a digital manner (Peretz et al 2014).
The voltage loop generates a digital peak or valley current value reference denoted by iref [n] after
which the value is converted to analog equivalent by use of digital-analog converter (DAC). At
steady conditions, calculation of the reference is done by a PI compensator in consideration to
the signal error of the voltage loop eV[n] and a comparison is made for the DAC output and the
value obtained from the inductor current RsiL (t), using a comparator I cpm. The comparator
output is then fed into S-R latch to generate a modulated signal pulse c (t) just as in other
solutions of CPM. The enhancement on the system involves addition of two novel blocks, output
current self-tuning estimator and transient suppression block.
On detecting the load transient, the blocks assumes the operation of generating modulated signal
pulse width from the conventional controller and also offers transient response of approximately

lowest possible deviation in voltage. A new transient control system is developed by the transient
suppression block with dynamical change effects on the off and on periods of the transistor, with
regard to the induced valley/ peak current pre-set values and the highest possible pre-
programmed voltage deviation. The main role of the estimator is to offer a suppression logic with
approximate current values of the new conductor that the algorithm demands. After completion
of transient recovery, the controller assumes its original steady condition of operation.
Transient Mode Controller
Designing of the transient mode controller is facilitated by the concept of optimum deviation for
the converters that operate in the state of direct transfer of energy. For this case, a direct focus on
deviation is of interest rather than making an attempt to minimize the output voltage deviation by
reducing the period of recovery which is a direct technique. For the two-step mechanism
illustrated in the figure below, the current waveform of the conductor is modified to suit the
current steady state waveform that allows the compensator to recover the voltage at the stipulated
period of time. Though, following the complex relationships between the load currents, low
voltage deviation and the inductor, it is impossible to employ the above technique directly for
converters operating under indirect transfer of energy (Buso and Caldognetto 2014).
The programmable deviation controller presented in this paper together with the programming
reconstructions, the programming technique also involves the current value of the new inductor
(obtained by estimating the output current) and also the highest possible voltage deviation. These
values are both used to derive the estimates of the minimum possible deviation response while
the converter is operating under predetermined switching frequency range.