Design of stable active matrix organic light-emitting diode (AMOLED) displays comes with significant challenges that stem from the electrical property of the backplane materials, line parasitics in the matrix, and the opto-electronic property of the organic light-emitting diode (OLED). This paper reviews voltage and current programming schemes for AMOLEDs. Following a systematic review of pixel circuits, design considerations are examined for both current and voltage schemes with focus on stability and programming speed for both amorphous silicon (a-Si) and low temperature polysilicon (LTPS) pixel circuits. In particular, spatial parameter variations and stability, which hinder reliable operation of AMOLED display backplanes, are discussed. Analysis shows that while driving schemes reported hitherto maybe suitable for small and medium size displays, new schemes are critically needed for large-area high-resolution AMOLED displays.

Wireless power is one of the new promising technologies for IoT applications. The use of arrays for power transfer to free-moving objects has revolutionized wireless power transmission (WPT) applications. Herein, we present an extendable platform for transmitting power to a moving object receiving power from an array. The transmitter (TX) consists of two overlapping layers of square planar coils rotated 45 degrees to each other to provide the best electromagnetic flux coverage. Each layer consists of four coils to further control the power supply to the small receiver (RX) coil. This overlapping star-shaped array is stimulated automatically by a power amplifier. This smart stimulation can deliver uniform power to the receiver regardless of rotation and misalignment inconsistencies by using the geometry of the transmitter array. Moreover, by changing the direction of the current of each small square component in each array using the flower-shaped current, a receiver coil perpendicular to the transmitter’s plate can obtain power comparable with conventional structures. We use ADS-HFSS simulation to verify the fabrication and measurement results. The proposed transmitter achieves an average of 18.2% power transfer efficiency (PTE) to RX and at 90° angular misalignment, 11.5% PTE, while the conventional structure transfers no power to the perpendicular RX coil. A future application of the transmitter can be the investigation of the neurobehavioral of free-moving animals and brain–machine interface studies in medicine.

Current programmed circuits have demonstrated threshold voltage V/sub TH/ shift compensation to provide a stable drive current to the organic light-emitting diode (OLED). However, the degree of stability of drive current depends critically on the dynamic behavior of the circuit. This paper examines the dynamic behavior of a 3-TFT current programmed pixel and analyzes the impact of V/sub TH/ shift on the OLED drive current. The pixel circuit was implemented in amorphous silicon technology and lifetime tests show a 11% current degradation at 700 h.

A new voltage-programmed pixel circuit using hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) for active-matrix organic light-emitting diodes (AMOLEDs) is presented. In addition to compensating for the shift in threshold voltage of TFTs, the circuit is capable of compensating for OLED luminance degradation by employing the shift in OLED voltage as a feedback of OLED degradation

In this paper an online method of broadband battery impedance spectroscopy is proposed in which the excitation signal is injected through the inner feedback loop of a DC/DC boost converter with average current-mode control (ACMC). By deriving the average state-space model of the conventional boost converter, it is shown that an open-loop converter exhibits a resonant frequency response in regards to the injected signal, whereas the compensated current loop in ACMC produces a controllable, flat-gain closed-loop transfer function that allows broadband current excitation signals to be injected into the battery without the distortion that is seen in the open-loop configuration. In the presented method, the converter is set to discharge the battery at a constant C-rate during impedance measurement while a broadband signal is superimposed onto the loop reference current. A low-dropout regulator is then used to filter out disturbances caused in the converter output. The proposed approach is experimentally implemented and a discrete-interval binary sequence signal is utilized to measure the impedance of two 18650 lithium-ion batteries in several arbitrary frequencies at once in the 0.1Hz-1kHz range. The measured spectra are validated by a commercial impedance analyzer.