4 research outputs found
A New Mirroring Circuit for Power MOS Current Sensing Highly Immune to EMI
This paper deals with the monitoring of power transistor current subjected
to radio-frequency interference. In particular, a new current sensor with no connection
to the power transistor drain and with improved performance with respect to the existing
current-sensing schemes is presented. The operation of the above mentioned current sensor
is discussed referring to time-domain computer simulations. The susceptibility of the
proposed circuit to radio-frequency interference is evaluated through time-domain computer
simulations and the results are compared with those obtained for a conventional integrated
current sensor
Implementation of single phase watt hour meter using LPC2148
The LPC2148 device is the latest system-on-chip (SOC), which belongs to the ARM generation of devices. This generation of devices belongs to the powerful 32-bit ARM platform bringing in a lot of new features and flexibility to support robust single, two and 3-phase metrology solutions. This thesis however, discusses the implementation of 1-phase solution only. These devices find their application in energy calculation and have the necessary architecture to support them. Furthermore, for large scale manufacturing, the costs can become lower than those of the electromechanical meters currently in production. This device presents a totally electronic single phase energy meter for residential use, based on ARM processor. A four digit display is used to show the consumed power. A prototype has been implemented to adequate measurement up to 5A load current from a 230V (phase to neutral) voltage. Higher current capacity can be easily obtained by simply replacing the shunt resistor. And, by changing the transformer tap and the voltage divider ratio, it can be easily manipulated for use in a 220 V supply
Modeling and Design of High-Performance DC-DC Converters
The goal of the research that was pursued during this PhD is to eventually facilitate the
development of high-performance, fast-switching DC-DC converters. High-switching
frequency in switching mode power supplies (SMPS) can be exploited by reducing the
output voltage ripple for the same size of passives (mainly inductors and capacitors) and
improve overall system performance by providing a voltage supply with less unwanted
harmonics to the subsystems that they support. The opposite side of the trade-off is
also attractive for designers as the same amount of ripple can be achieved with smaller
values of inductance and/or capacitance which can result in a physically smaller and
potentially cheaper end product. Another benefit is that the spectrum of the resulting
switching noise is shifted to higher frequencies which in turn allows designers to push
the corner frequency of the control loop of the system higher without the switching
noise affecting the behavior of the system. This in turn, is translated to a system capable
of responding faster to strong transients that are common in modern systems that may
contain microprocessors or other electronics that tend to consume power in bursts and
may even require the use of features like dynamic voltage scaling to minimize the overall
consumption of the system.
While the analysis of the open loop behavior of a DC-DC converter is relatively
straightforward, it is of limited usefulness as they almost always operate in closed loop
and therefore can suffer from degraded stability. Therefore, it is important to have a
way to simulate their closed loop behavior in the most efficient manner possible. The
first chapter is dedicated to a library of technology-agnostic high-level models that can
be used to improve the efficiency of transient simulations without sacrificing the ability
to model and localize the different losses.
This work also focuses further in fixed-frequency converters that employ Peak Current
Mode Control (PCM) schemes. PCM schemes are frequently used due to their
simple implementation and their ability to respond quickly to line transients since any
change of the battery voltage is reflected in the slope of the rising inductor current
which in turn is monitored by a fast internal control loop that is closed with the help of
a current sensor.
Most existing models for current sensors assume that they behave in an ideal manner
with infinite bandwidth and ideal constant gain. These assumptions tend to be in
significant error as the minimum on-time of the sensor and therefore the settling time
requirements of the sensor are reduced. Some sensing architectures, like the ones that
approximate the inductor current with the high-side switch current, can be even more
complex to analyze as they require the use of extended masking time to prevent spike
currents caused by the switch commutation to be injected to the output of the sensor
and therefore the signal processing blocks of the control loop. In order to solve this issue,
this work also proposes a current sensor model that is compatible with time averaged
models of DC-DC converters and is able to predict the effects of static and transient
non-idealities of the block on the behavior of a PCM DC-DC converter.
Lastly, this work proposes a new 40 V, 6 A, fully-integrated, high-side current sensing
circuit with a response time of 51 . The proposed sensor is able to achieve this
performance with the help of a feedback resistance emulation technique that prevents
the sensor from debiasing during its masking phase which tends to extend the response
time of similar fully integrated sensors