Design and realization of high-performance LED drivers for automotive lighting applications
This Ph.D. program pertains to the design and monolithic realization of Light Emitting Diode (LED) drivers for automotive lighting where the imperative parameters are high power-efficiency and high reliability. The grand objectives thereto are substantial improved specifications over the state-of...
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Format: | Theses and Dissertations |
Language: | English |
Published: |
2018
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Online Access: | https://hdl.handle.net/10356/82740 http://hdl.handle.net/10220/46654 |
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Institution: | Nanyang Technological University |
Language: | English |
Summary: | This Ph.D. program pertains to the design and monolithic realization of Light
Emitting Diode (LED) drivers for automotive lighting where the imperative parameters
are high power-efficiency and high reliability. The grand objectives thereto are
substantial improved specifications over the state-of-the-art, including power-efficiency,
reliability, current driving capability, and dimming range. To achieve the said grand
objectives, the specific objectives are to decouple, and hence mitigate the following two
major design trade-offs that limit the performance of contemporary automotive LED
drivers.
The first trade-off is between high reliability and high current driving capability,
and applies to both single-phase and multi-phase LED drivers. Specifically, to achieve
high current driving capability, the contemporary single-phase LED driver typically
suffers from low reliability arising from large current ripples. On the other hand, the
multi-phase LED driver is highly advantageous to provide high current driving
capability, but suffers from low reliability because of the ensuing subharmonic
oscillation. To decouple this limiting trade-off, we propose the design and monolithic
realization of a novel Pulse-Width-Modulation (PWM)-based dual-phase LED driver in
Global Foundries (GF) 130nm BCDLite process. To achieve high current driving
capability, we adopt a dual-phase power stage. To achieve high reliability, we propose
an Average Current Control to eliminate the subharmonic oscillation by considering the
complete inductor-current profile vis-à-vis peak current adopted/reported elsewhere. To
further improve the reliability, we propose an accuracy-enhanced current sensor to
ascertain good current balance in the adopted dual-phase power stage. With
measurements on our prototype LED driver ICs embodying our aforesaid adoption and
proposed circuits, we demonstrate, to the best of our knowledge, for the first time that
the trade-off between high reliability and high current driving capability is decoupled,
i.e., an LED driver uniquely featuring high reliability, yet high current driving capability.
The second trade-off is between high power-efficiency and wide dimming range.
Specifically, a wide dimming range is derived by means of high switching frequency,
hence the ensuing reduced settling time of the LED current. This, however, in turn leads
to a degradation of the power-efficiency due to increased switching losses. To decouple
this limiting trade-off, we propose the design and monolithic realization of a novel fully
soft-switched LED driver in GF 130nm BCDLite process. We achieve wide dimming
range by operating at high switching frequencies, but the high switching does not
compromise the power-efficiency. Using a fully soft-switching approach, the ensuing
switching losses are negligible. This is achieved by a proposed Hysteretic SoftSwitching
Controller (HSSC) and proposed circuitries, i.e., a voltage detector, current
sensor, and a level shifter. The HSSC enables complete soft-switching, including zerovoltage
switching and zero-current switching, by means of turning on/off power
switches when their voltage/current is zero. The proposed voltage detector and current
sensor, featuring low power, monitor the voltage and current of the power switches. The
proposed level shifter, featuring ultra-fast speed, serves to quickly transmit the
monitored signal from the said voltage detector and current sensor to the HSSC. With
measurements on our prototype LED driver ICs embodying our proposed HSSC and
proposed circuits, we demonstrate, to the best of our knowledge, for the first time that
the trade-off between high power-efficiency and wide dimming range is decoupled, i.e.,
an LED driver uniquely featuring wide dimming range, yet high power-efficiency. |
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