DC-DC buck converters are widely used in portable applications because of their high power efficiency. However, their inherent fast switching releases electromagnetic emissions, making them prominent sources of electromagnetic interference (EMI). This paper proposes a voltage-controlled buck converter that reduces EMI by using a chaotic pulse-width modulation (PWM) technique based on a chaotic triangular ramp generator. The chaotic triangular ramp generator is constructed from a simple on-chip chaotic circuit linked with a symmetrically triangular ramp circuit. The proposed converter can thus operate in the chaotic mode reducing the EMI without requiring any EMI filters. Additionally, using the triangular ramp signal can relax the requirement for a large LC output filter in chaotic mode. The effectiveness of the proposed scheme was experimentally verified with a chaotic triangular ramp generator embedded in a voltage-mode controller buck converter using a 0.18 µm Complementary Metal Oxide Semiconductor (CMOS) process. The measurement results from a prototype showed that the EMI improvement from the proposed scheme is approximately 14.53 dB at the fundamental switching frequency with respect to the standard fixed-frequency PWM reference case.

In this letter, a new simple circuitry LED driver with current reduction is proposed, realized and experimentally validated. The proposed circuit comprises with very few components intended for making a costeffective and compact design while still shows a high performance. The circuit reduces non-conducting time of LEDs to enhance power factor (PF) and total harmonic distortion (THD). The flicker can also be relatively reduced. By using current limiter cells, lighting variation is eliminated with respect of the variation of AC input voltage. A worst case of a 4 W with only two LED-strings driver is implemented and tested by using a 1 um 650 V-BCDMOS high voltage process to verify advantageous characteristics of the suggested scheme. Experimental results demonstrate a PF of 0.97 with a THD of 24.62% and an efficiency of 87.1% at a 220 V AC supply.

This paper presents a compact and low-power-based discrete-time chaotic oscillator based on a carbon nanotube fieldeffect transistor implemented using Wong and Deng's well-known model. The chaotic circuit is composed of a nonlinear circuit that creates an adjustable chaos map, two sample and hold cells for capture and delay functions, and a voltage shifter that works as a buffer and adjusts the output voltage for feedback. The operation of the chaotic circuit is verified with the SPICE software package, which uses a supply voltage of 0.9 V at a frequency of 20 kHz. The time series, frequency spectra, transitions in phase space, sensitivity with the initial condition diagrams, and bifurcation phenomena are presented. The main advantage of this circuit is that its chaotic signal can be generated while dissipating approximately 7.8 µW of power, making it suitable for embedded systems where many chaos-signal generators are required on a single chip.

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A photosensitive chaotic oscillator which can be controlled with light illumination under various control voltage levels is proposed. The oscillator consists of a photodiode for the light input, clock switches and capacitors for the sample and hold function, a nonlinear function that creates an adjustable chaos map, and a voltage shifter that adjusts the output voltage for feedback. After optimizing the photodiode sub-circuit by using an available photodiode model in PC-based simulation program with integrated circuit emphasis to obtain a suitable output, the full chaotic circuit is verified with standard 0.6-𝜇m complementary metal oxide semiconductor parameters. Chaotic dynamics are analyzed as a function of the light intensity under different control voltage levels. The time series, frequency spectra, transitions in state spaces, bifurcation diagrams and the largest Lyapunov exponent are improved.