Analogue Pulse Width Modulation Research Articles

A new gate driver employing linearly sweep signal generated module for high‐resolution micro‐LED display with line‐by‐line pulse width modulation driving method

AbstractA new gate driver with metal oxide thin‐film transistors (MO‐TFTs) has been presented for micro‐light‐emitting diode (Micro‐LED) display. The proposed gate driver employing linearly decreasing sweep signal generated module could realize the line‐by‐line pulse width modulation (PWM) driving method, which is valuable for application in high‐resolution Micro‐LED display compared with the conventional driving method employing global sweep signal. A simple Micro‐LED pixel circuit including an inverter module driven by the analog PWM method is employed to demonstrate the feasibility of the proposed gate driver. A 10 × 10 green Micro‐LED display array has been fabricated with MO‐TFTs backplane technology. It is shown that a 10‐μs width pulse and linearly scanning sweep signal can be successfully output. Consequently, the pixel circuit array can be driven properly under analog line‐by‐line PWM driving method.

P‐23: Low Power A‐PWM μLED Pixel Circuit of Progressive‐mode Using Single Sweep Signal for Mobile Displays

An analog pulse‐width‐modulation (A‐PWM) Micro‐LED (μLED) pixel circuit based on low‐temperature‐polysilicon (LTPS) thin‐film transistors (TFTs) for mobile displays is proposed. The progressive‐emission mode is implemented using a single Sweep (SW) signal by in‐pixel logic operation circuits. By adjusting the emission time of the progressive‐emission mode, the μLED is biased with the maximum quantum efficiency (EQE). Consequently, the static power consumption of proposed pixels is reduced by 29.2%, compared with conventional schemes.

Design of High-Precision Driving Control System for Charge Management

Due to the interaction of accumulated charges on the surface of a test mass with the surrounding electric and magnetic fields, the performance of inertial sensors is affected, necessitating charge management for the test mass. Discharge technology based on Ultraviolet LEDs is internationally recognized as the optimal solution for charge management. Precision driving of Ultraviolet LEDs is considered a key technology in charge management. This paper presents the driving control system used for Ultraviolet LEDs, achieving precision pulse-width-modulation-type current output with controllable pulse width and amplitude. The system generates the pulse-width-controllable pulse voltage signal via analog pulse-width modulation, and subsequently regulates the amplitude of the PWM signal through range switching. To convert the voltage into the pulse-width-modulation-type driving current, the improved Howland current source is employed. The test results demonstrate that the driving control system can output controllable current in the range of 0.01 mA to 10 mA, with a minimum step of 0.01 mA. The accuracy of the current reaches 1%, the stability within 1 h is better than 1%, and the load regulation is better than 2%. The driving control system provides an important reference for the integration of charge management system and the precision drive control method for LEDs.

An analog PWM pixel circuit with shaping function for low grayscale display of Micro-LEDs

This paper presents a new analog pulse width modulation (PWM) micro light-emitting diode (LED) pixel circuit with a shaping function. The rising/falling time of PWM signal generated by the proposed pixel circuit can be greatly reduced to improve the low grayscale display quality of micro-LED. Metal oxide thin film transistors with the top-gate (TG) coplanar structure are used to realize the proposed pixel circuit on the glass substrate. It is shown that the pulse width of micro-LED current can be linearly modulated by the data voltage. Furthermore, the measured rising time and falling time of the PWM signal are 15.6 μs and 25.5 μs, respectively, which are much smaller than that of the PWM signal in the conventional analog PWM pixel circuits.

A New SRAM-Embedded Pixel Circuit That Modulates Accurately Gray Level for PWM-Driven Micro-LED Displays

A new analog pulse width modulation (A-PWM) pixel circuit is proposed for micro light-emitting diode (micro-LED) displays, which improves the accuracy of modulating gray level by efficient switching of its in-pixel static random access memory (SRAM). Varied gray levels are realized successfully with the integral of a constant current over corresponding designated duty for target gray. In practice, however, the imperfection of the current’s falling due to unavoidable switching delays results in nonlinear inaccuracy of displayed gray levels, undermining displaying quality. To remedy the problem, the proposed in-pixel SRAM is able to conduct faster switching than conventional pixel circuits for precise displaying of grays. The simulated results show the falling time is significantly reduced to 0.8ls from averaged 287ls of that without SRAM, obtained a near-constant gray output of 6.63nA*s/V. Based on experiments, the measured results show the DNL is improved from +0.05LSB-to-+0.78LSB to.0.09LSB-to-+0.14LSB, leading to the INL is reduced from the maximum +20.5LSB to +4.16LSB. In other words, the effectiveness offered by the proposed in-pixel SRAM in modulating accurately gray level is verified.

Hybrid Analog and Digital Control of a High Current Converter Based on an EDLC Bank for Rapidly Decreasing Input Voltage

This paper proposes unconventional control techniques for a portable power supply consisting of electric double-layer capacitors (EDLCs), a dc-dc converter, and a low-impedance load such a plasma load. Between the EDLCs and the plasma load consuming high power, a dc-dc converter is required to control the output voltage from the rapidly decreasing voltage of EDLCs. In addition, the dc-dc converter should maintain a set point by responding to arcs occurred in plasma process. This paper proposed hybrid analog and digital controls for a nonideal boost converter which was setup by theoretical analysis. The proposed system is verified with experiment and simulation. As a result, the proposed control method can maintain the constant output voltage longer than a traditional analog pulsewidth modulation control.

PWM Series Dimming for Slow-Dynamics HPF LED Drivers: the High-Frequency Approach

This paper deals with the capability of pulse width modulation (PWM) dimming operation added to the high-power factor-integrated buck-flyback converter (IBFC), which was developed in previous works for LED lighting applications. First, the two main dimming techniques will be introduced, namely, analog dimming and PWM dimming. Then, the three main PWM dimming schemes found in the literature, that is, enable dimming, series dimming, and parallel dimming, will be briefly discussed. Afterwards, the IBFC topology will be tested performing both analog and enable dimming. In addition, a new proposal is introduced: the high-frequency series PWM dimming technique, which overcomes all the challenges faced when developing PWM dimming capabilities in low slew-rate constant-current fixed-frequency-controlled converters and offers all the advantages of PWM dimming over analog dimming while maintaining good efficiency. The proposed dimming-technique control loop, as well as the laboratory tests, will be presented, discussed, and compared to analog dimming and PWM dimming, showing satisfactory results in terms of dimming ratio, input current total harmonic distortion (THDI), and power factor.

Novel analog pulse‐width‐modulated 15‐μm SiGe micromirrors

Abstract— A novel six‐electrode SiGe micromirror pixel enabling analog pulse‐width modulation (PWM) in display applications is presented. Instead of utilizing bitplanes, arbitrary duty cycles can be realized, resulting in an analog gray‐level distribution. This eliminates the posterization (contouring) effect that is typical for digital micromirrors. Moreover, the pixel design does not require the incorporation of electronic comparators and the gamma compensation can be processed externally. Two out of the six electrodes are used as landing electrodes. The other four attracting electrodes are driven by two anti‐phase saw‐tooth signals and two fixed analog voltage signals. By applying this signal scheme, the duty cycle of the mirror is modulated in an analog manner. Test vehicles were manufactured where SiGe is the microelectromechanical systems (MEMS) material. The use of SiGe as a structural layer is advantageous to build MEMS since the CMOS and MEMS layers can be deposited in a monolithic manner. Measurements using a Laser Doppier Vibrometer (LDV) have confirmed the feasibility of analog PWM for 15‐μm SiGe micromirrors.

Novel micromirror design with variable pull-in voltage

A novel micromirror is presented having a variable pull-in voltage. This allows analog Pulse Width Modulation (PWM) so that the number of grey levels is not limited by the number of subframes or bitplanes. The levels can be chosen arbitrarily, allowing less severe speed requirements for the electronic layer below the MEMS, less image processing hardware and memory. The presented design of the mirror has two attracting electrodes and one landing electrode at either side of the mirror. One electrode is used as ‘fixed’ electrode, influencing the other attracting electrode’s pull-in voltage. If we apply a general triangular waveform at the former electrode, the ‘fixed’ electrode voltage determines the duty cycle of the mirror. The mirror implements analog PWM, without needing a transistors based comparator at the CMOS level. When each ‘fixed’ electrode is connected to an active matrix cell, an active matrix display can be formed. The mirrors with variable pull-in voltage were fabricated using SiGe as the structural layer. The variable pull-in principle is demonstrated by measurements performed on these SiGe mirrors [1].

Proposed optical fiber system using pulse width and amplitude modulation for hybrid analogue/digital transmissions

The principle and design of a cost-effective optical fiber communication system are proposed to support hybrid digital/analog signal transmissions, by simultaneously using pulse-width modulation (PWM) for the analog signal and two-level pulse-amplitude modulation for the digital signal, while essentially requiring the same channel bandwidth as a conventional analog PWM system.

Digital two-level PAM and analogue PWM hybrid optical fiber transmission systems for TV and data applications

We propose a novel optical fiber transmission system for supporting both digital and analogue communications in a very cost-effective fashion. The proposed system simultaneously uses a 2-level pulse amplitude modulation (PAM) for data communications and an analogue pulse width modulation (PWM) for TV applications. The principle of the 2-level PAM and analogue PWM hybrid scheme is presented, and its some distinguishing features are explained. Moreover, this proposed technique requires the same transmission bandwidth as a conventional analogue PWM scheme. Consequently, two different types of communication services can be transmitted over a common optical fiber channel by using the 2-level PAM and analogue PWM technique, without the use of wavelength- or frequency- or time-division multiplexing.

Performance of two-level PAM and analogue PWM hybrid optical fiber transmission systems

We analyze the performance of optical fiber transmission systems using a 2-level pulse amplitude modulation (PAM) and analogue pulse width modulation (PWM) hybrid technique. The system performance is evaluated by considering the signal-to-noise ratio (SNR) of 50 dB for video communications and the bit error rate (BER) of 10/sup -9/ for digital communications as a lower bound. Optical receivers using both avalanche photodiode (APD) and PIN photodiode are considered. The minimum average optical power, which is required by an analogue-PWM signal to guarantee the 50-dB SNR at an optical receiver, is calculated, while the receiver sensitivity is analyzed for a 2-level PAM digital optical fiber system. The results show that the proposed system can perform better than the required lower bound.

Introduction of the Harmonic Distortion Determining Factor and Its Application to Evaluating Real Time PWM Inverters

The harmonic distortion determining factor (HDDF), which represents the intrinsic spectral properties of pulse-width modulation (PWM) methods, is introduced. The HDDF is almost independent of the inverter operating conditions such as the switching frequencies or load parameters if the switching frequency is 40 times greater than the output frequency. Furthermore, it is closely related to the root mean square (RMS) values of the harmonic current and motor torque ripples for induction motor drives, or the RMS values of the harmonic current and DC voltage ripples for rectifier operation. Therefore, it is useful as a common quality index for the evaluation of PWM methods. Four typical analog PWM methods and four digital PWM methods are compared and evaluated based on HDDF values. It is shown that the harmonic injected PWM for analog PWM, or the digital PWM of type C has the best characteristics. >