High-voltage Lead Research Articles

GaN-based high-voltage light-emitting diodes with backside reflector

High-voltage light-emitting diodes (HV-LED) withbackside reflector, including Ti3O5/SiO2 distributed Bragg reflector (DBR) or hybrid reflector combining DBR and Al or Ag metal layer, are investigated using Monte Carlo ray tracing method. The hybrid reflector leads to more enhancement of light-extraction efficiency (LEE). Moreover, the LEE can also be improved by redesigning the thicknesses of DBR. HV-LED with four redesigned DBR pairs (4-MDBR), and those with a hybrid reflector combining 4-MDBR and Al metal layer (4-MDBR-Al), are fabricated. Compared to 4-MDBR, the enhancement of light-output power induced by 4-MDBR-Al is 4.6%, which is consistent with the simulated value of 4.9%.

Failure Mechanism for GaN-Based High-Voltage Light-Emitting Diodes

We report a detailed reliability test study on GaN-based high-voltage light-emitting diodes. Under high temperature (i.e., 80°C) and high current injection (i.e., 100 mA) conditions, it was found that Al metal whiskers were formed from the sidewall of the Cr/Al/Ti/Pt/Au p-finger metal after 120-h burn-in test. It was also found that the whiskers became longer as we increased the burn-in time. Furthermore, it was found that the formation of Al whiskers is directly related to Al migration.

Stabilising current driver for high‐voltage light‐emitting diodes

High-voltage light-emitting diodes (HV LEDs) possess higher cut-in voltages and works at a high supply voltage. As the specific feature, they can be directly driven via universal utility-line voltages after appropriate rectification. This significantly simplifies the circuit structure and reduces the manufacturing cost. While HV LEDs are driven directly by half-wave rectified DC power source, which is an impure form of DC, their lumen is easily affected by changing the AC voltage source, while only constant current control is insufficient for stable lumen, thus hindering their usefulness in practical applications. This study proposes a simple, however effective, HV LED driver via a proportional and integral current control accompanied with feedforward compensation which is capable of maintaining stable lumen under changing AC voltage sources. Experimental results have demonstrated satisfactory performance in lighting.

LED Lamp Power Supply without Electrolytic Capacitors based on Integrated Double Buck-Boost Converter Operating in Full DCM

In this paper the integrated double buck-boost converter (IDBBC) operating with both stages in discontinuous conduction mode (DCM) is analyzed. The converter is intended to supply high-voltage LED lamps from the mains, typically in street lighting applications. A high input power factor is assured by operating the first stage in DCM, thus complying with current harmonic injection standards. In this work, the second stage is also operated in DCM as an option to the continuous conduction mode (CCM) that has been studied in a previous paper. The behavior of the converter with both stages in DCM is compared with that of the converter operation with the second stage in CCM. It is demonstrated that with both converters operating in DCM the filter capacitances are reduced even further, allowing for the use of long-life non-electrolytic capacitors. A laboratory prototype to supply a 70 W LED lamp with nominal voltage of 200 V from a 230 V/50 Hz mains maintaining the same design conditions as in the previous work is presented. A comparison of both prototypes is also carried out.

Ceramic-based thin-film blue LEDs with high operation voltage and unsaturated output power at 1800 W/cm2

III–nitride blue (λ = 450 nm) LEDs were fabricated on ceramic substrates using thin-film and high-voltage processes. The device, comprising sixteen cascaded sub-LEDs, exhibits excellent current spreading and thermal resilience. Under the driving power of 1800 W/cm2 (J = 450 A/cm2), the high-voltage thin-film LED delivers unsaturated output power and alleviated efficiency droop, which is not achievable with devices fabricated on Si or sapphire substrates with identical epitaxial structure.

Saga of efficiency degradation at high injection in InGaN light emitting diodes

Saga of efficiency degradation at high injection in InGaN light emitting diodes

注入电流对绿光高压LED光电特性的影响

GaN-based green high-voltage(HV) light emitting diodes(LEDs) of 12 V were designed and fabricated.The optical and electrical parameters such as forward voltage,peak of wavelength,optical power,and luminous efficiency were investigated when the injection current varied from 3 mA to 50 mA at 25 ℃.The results show that the injection current has a great effect on the optical and electrical properties of the GaN-based high-voltage LED.When the current is 20 mA,the corresponding voltage is 14 V.With the increasing of the injection current,the blue-shift of LED peak wavelength reaches 2 nm.In addition,the optical power increases approximately linearly with the current increasing.The luminous efficiency decreases 61% when the injection current increases from 3 mA to 20 mA,and decreases 39% when the injection current increases from 20 mA to 50mA.It indicates that the luminous efficiency decreases more slowly when the high-voltage LED is driven by large current.These results will have a certain reference value for the improvement and optimization of GaN-based high-voltage LEDs.

Efficiency and Droop Improvement in GaN-Based High-Voltage Flip Chip LEDs

The GaN-based high-voltage flip chip light-emitting diode (HVFC-LED) is designed and developed for the purpose of efficiency enhancement. In our design, the distributed Bragg reflector (DBR) is deposited at the bonded substrate to increase the light extraction. After the flip chip process, the general current-voltage characteristics between the flip chip sample and the traditional sample are essentially the same. With the help of great thermal conductive silicon substrate and the bottom DBR, the HVFC-LED is able to enhance the power by 37.1% when compared to the traditional high-voltage LEDs. The wall-plug efficiencies of the HVFC-LED also show good droop reduction as high as 9.9% compared to the traditional devices.

High-voltage thin-film GaN LEDs fabricated on ceramic substrates: the alleviated droop effect at 670 W/cm^2

High-voltage thin-film GaN LEDs with the emission wavelength of 455 nm were fabricated on ceramic substrates (230 W/m · K). The high-voltage operation was achieved by three cascaded sub-LEDs with dielectric passivation and metal bridges conformally deposited on the side walls. Under the driving power of 670 W/cm(2), the high-voltage LEDs exhibit much alleviated efficiency droop and the operative temperature below 80 °C. The excellent performances were attributed to the improved current spreading within each sub-LED and the superior heat sinking of the ceramic substrate.

Shock-induced failure of a Riata lead with normal electrical lead parameters and a normal fluoroscopic appearance: A case report

An 81-year-old man was scheduled for an elective implantable cardioverter defibrillator (ICD) generator exchange because of battery depletion. The Atlas™+ DR ICD (St. Jude Medical, Sylmar, CA) had been implanted in February 2007 for primary prevention. The ICD lead (Riata 1570, St. Jude Medical, Sylmar, CA) had been positioned via the left cephalic vein at the right ventricular apex. Prior to the ICD generator exchange, which took place 70 months after the initial implantation, all routine device interrogations revealed normal electrical lead parameters, and cine-fluoroscopy of the lead showed normal appearance without any apparent fracture. We attempted to conduct high-voltage shock testing, as there was concern about the possibility of silent lead malfunction. Following delivery of the first high-voltage shock, the device declared “possibility of output circuit damage.” Subsequent shocks could not be delivered. Nonetheless, other lead parameters remained stable, and high-voltage lead impedance was <20Ω. The following day, the failed generator was replaced with a new ICD generator and connected with a new ICD lead. We then tested the new device by inducing ventricular fibrillation, which was defibrillated successfully. Although electric screening in asymptomatic patients with the Riata ICD lead remains controversial, it should be remembered that there are patients with or without detected cable externalization in whom only high-voltage shock testing can disclose lead malfunction. Issues with Riata leads have not yet been elucidated in full detail.

Thermal Transient Effect and Improved Junction Temperature Measurement Method in High-Voltage Light-Emitting Diodes

The diode forward voltage method with pulsed currents was widely used for monitoring junction temperature (Tj) of light-emitting diodes (LEDs). However, a thermal transient effect (TTE) was observed by the pulsed currents and consequent errors were introduced. Thermoelectric physics was conducted to explain this phenomena and a group of experiments was used to reveal the TTE during Tj measurement for high-voltage (HV) LEDs. In addition, an improved pulse-free direct junction temperature measurement method was conducted for HV LEDs to reduce the errors and to achieve in situ Tj measurement with dc currents, simpler setups, and a less step sequence.

The higher value of high-voltage lead impedance is associated with a better clinical condition in heart failure patients with an implanted defibrillating device

Purpose: The electrical impedance measures the total resistance to the current flow. The lead impedance for implanted devices is a function of various properties of the electrode and myocardium. On the other hand, myocardium characteristics determine the patient's clinical condition. This study evaluated the relation between the high voltage (HV) lead impedance and the thoracic fluid content (TFC) as well as N-terminal pro B-type natriuretic peptide (NT-proBNP) in patients with implanted defibrillating devices. Methods: A group of 350 consecutive patients (62.9±10 years; 67 women) with an already implanted cardioverter-defibrillator or a cardiac esynchronization therapy device with defibrillating mode were studied. The HV lead impedance was measured by a telemetry during a routine device check-up. The TFC was measured at supine position after 30-minute rest by cardiac impedance (Niccomo, Medis, Germany) and plasma NT-pro-BNP was measured in venous blood samples. For the statistical purposes the NT-pro-BNP level was normalized by the natural logarithm. Patients were divided into tertiles (T1, T2 or T3) of the HV lead impedance, and the analysis of variance with the Bonferroni post-tests were applied for statistical analysis. Results: The HV lead impedance was 39.6±9.4 Ohm in T1, 49.9±2.2 Ohm in T2 and 67.2±8.8 Ohm in T3. The mean TFC was significantly decreasing for higher tertiles of HV lead impedance from 32.4±6.3 1/kOhm for T1, through 29.8±4.9 1/kOhm for T2 to 30.2±5.5 1/kOhm for T3 (ANOVA p=0.0006) and the TFC values for the T1 were significantly higher than in the T2 (p<0.001) and T3 (p<0.01). The mean NT-pro-BNP significantly decreased for higher tertiles of HV lead impedance from 7.0±1.2 pg/ml for T1, through 6.4±1.4 1pg/ml for T2 to 6.6±1.3 pg/ ml for T3 (ANOVA p=0.0028) whereas the levels of this peptide for the first tertiles were significantly higher than in the T2 (p<0.01) and T3 (p<0.05). Conclusions: The HV lead electrical impedance in patients with implanted defibrillating device is associated with worse clinical condition. As both TFC and NT-pro-BNP depend on the myocardial function, these results indicate that patients with more severe HF present with lower HV lead impedance. Further studies are required to answer the question whether the measurements of HV lead impedance might be applied for a prospective evaluation of the clinical condition and monitoring of the heart failure therapy in these patients.

Optimized Design and Performance Research of the High-Voltage LEDs Chipset

This paper introduces a technology that 16 LED chips are integrated on a substrate to form a new type of high-voltage LEDs chipset. Monte Carlo method and Finite Element Method simulation are used to optimize the structure for making the best in the luminous flux, luminous efficiency and heat dissipation. Firstly, By the comparison of three kinds of high-voltage LEDs, the vertical structure, inverted trapezoidal structure and trapezoidal structure, the results show that the luminous efficiency of the entire high-voltage LEDs chipset used trapezoidal structure is the highest, the empirical data is 41.522%, which is 2.12 times than the vertical structure; this paper introduces the heat transfer performance of three kinds of high-voltage LEDs, the empirical data are 88.374°C, 82.652°C and 93.725°C. We can see that the vertical structure is the best. This paper also optimizes the high-voltage LEDs chipset, under the circumstances of the constant chip area, we change the area of the single chips, prompting the spacing between the single chips change. We get the best single chip area and single chip change, under this circumstance, we can get the best luminous efficiency and luminous flux.

Characteristics of GaN-Based High-Voltage LEDs Compared to Traditional High Power LEDs

In this letter, GaN-based high-voltage light-emitting diodes (HV-LEDs) arrays with 16 microchips connected in series are fabricated. The light output power-current-voltage (LOP-I-V) characteristic of HV-LEDs is measured. Under input power of 1.1 W, the LOP of HV-LEDs is enhanced by 11.9% compared to traditional high power light-emitting diodes (THP-LEDs) with the same chip size. Due to the reduced metal shadow effect and better current spread, the HV-LEDs exhibit higher light extraction efficiency under the same current density, which is simulated by a 3-D ray tracing method. As a result, the luminous efficiency of HV-LEDs is 21.6% higher than that of THP-LEDs under input power of 1.1 W. Furthermore, the efficiency droop of HV-LEDs is reduced to half of that of THP-LEDs.

Clinical Experience and Procedural Outcomes Associated with the DF4 Implantable Cardioverter Defibrillator System: The SJ4 Postapproval Study

Current implantable cardioverter defibrillators (ICDs) employ two or three low- and high-voltage lead connectors, adding complexity and bulk, sometimes resulting in incorrect connections and adverse events. The SJ4 study evaluates the performance of a novel integrated single-lead DF4 connection system by characterizing lead measurements, handling characteristics, and outcomes. Patients with standard guidelines-based ICD indications were enrolled and implanted with a St. Jude Medical™ DF4 system (St. Jude Medical, Sylmar, CA, USA; right ventricular high-voltage DF4 lead models 7120Q, 7121Q, 7122Q, or 7170Q with compatible ICD). Device electrical measurements, handling characteristics, and any adverse events were collected at implant and during each scheduled 6-month follow-up. Among 1,701 patients (65 ± 13 years, 72% male, left ventricular ejection fraction 29 ± 12%) enrolled at 58 centers, there were 1,697 successful implants (99.8% implant success; ICD; n = 999, cardiac resynchronization therapy-defibrillator n = 698). Implanting physicians reported that implantation of the DF4 lead was normal or easier than normal in 94% of cases with successful implant. These patients have been followed for 1.7 ± 0.5 years with a maximum follow-up of 2.5 years. The complication rate was 0.017 per patient year of follow-up (95% confidence interval: 0.013-0.023), which included abnormal defibrillation impedance, elevated pacing thresholds, failure to detect ventricular tachycardia/ventricular fibrillation, lead dislodgement, lead fracture, loss of capture, and lead perforation. There were no set screw-related complications at implant or during follow-up. The DF4 system overall performed very well with few complications at implant and in follow-up.

Efficiency and Droop Improvement in Hybrid Warm White LEDs Using InGaN and AlGaInP High-Voltage LEDs

This study investigates the optical and electrical characteristics in hybrid warm white high-voltage light-emitting diodes (HV-LEDs). The luminous efficiency of the hybrid warm white LED in this study improved by 11% and 51%, compared to conventional cool and warm LEDs, respectively, solving the warm white gap in white LEDs. The efficiency droop of the hybrid warm white LED was reduced to 21.8% from 26.8% for the conventional cool white LED, and from 26.3% in the conventional warm white LED at 40 mA (35 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) the operated current. Furthermore, the color rendering index (CRI) and angular correlated color temperature (CCT) were analyzed, indicating a significant improvement in hybrid warm white HV-LEDs.

High-voltage lead impedance increase: How much is too much?

The shock impedance may have a difference of approximately 10–20 Ω for different implantable cardioverter-defibrillator (ICD) systems during the implantation defibrillation testing. The current ICD systems can measure impedance of the shock circuit without shock delivery. Such measured high-voltage lead impedance is usually higher than the value obtained from shock delivery. For an individual patient with a normally functioning ICD system, there is usually a mild and gradual increase in the high-voltage lead impedance within the first few weeks after implantation as the result of edema resolution and tissue fibrosis.

Defibrillation Waveform Duration Adjustment Increases the Proportion of Acceptable Defibrillation Thresholds in Patients Implanted with Single-Coil Defibrillation Leads

The aim of this study was to determine whether defibrillation waveform duration adjustment with single-coil defibrillation leads can be used to increase the proportion of patients with satisfactory defibrillation thresholds (DFTs). A retrospective analysis of the DFT levels for 105 patients with implantable cardioverter-defibrillator devices and a single-coil defibrillation lead was performed. Two groups of patients were compared: 34 patients who had undergone waveform tuning (group A) and 71 patients with a fixed-tilt waveform (group B). Additional data including demographics, etiology, New York Heart Association functional class, left ventricular ejection fraction, high-voltage lead impedance and medications were gathered to determine what effect these variables had on the DFT levels. Of the 34 patients who had undergone waveform adjustment (group A), 27 (79%) were found to have satisfactory DFTs, while 41 (58%) of the 71 patients with fixed-tilt devices (group B) had satisfactory DFTs. Waveform duration adjustment was found to significantly increase the proportion of patients with satisfactory DFTs (p = 0.03).

High thermal stability of correlated color temperature using current compensation in hybrid warm white high-voltage LEDs

This study experimentally and numerically examines the correlated color temperature (CCT) stability issue for hybrid warm white high-voltage light-emitting diodes (HV-LEDs) by using a current compensation method. This method could efficiently maintain the CCT stability factor at approximately 1.0 and yield greater color uniformity with Δu'v' values ranging from 0.017 to 0.003 in CIE 1976 chromaticity coordinates. The simulation results show that the red chip intensity drop is the primary cause of CCT instability in the hybrid warm white system when the temperature increases. Therefore, Furthermore, results indicate that the relative lumen drop improves from 21% to 15% by using a current compensation method.

Experimental investigation of the effect of the design parameters of pressboard in mineral oil on creepage discharge propagation

One of the vital causes of the failure of oil transformers is considered as the creepage discharge propagation on pressboard. The authors performed an experimental investigation under an AC step test voltage to analyse the effects of the structure, distance and gluing direction of pressboard on creepage propagation. Flat, ribbed and grooved test specimens were prepared. Further, breakdown experiments were conducted for two gluing directions, parallel and vertical with respect to the electric field. For parallel gluing, the average breakdown voltage (V BD) of the ribbed and grooved types was 1.2–1.33 times that of the flat type. For vertical gluing, the V BD of the flat type was 1.28–1.66 times that of the same type with parallel gluing, whereas the values for the ribbed and grooved types were 1.02–1.11 times the corresponding values for parallel gluing. The rib height and groove depth do not seem to contribute greatly to the breakdown strength because most of the flashover propagation appeared not on the pressboard's surface but at the glued interface. The results of this preliminary investigation may be useful for improving the dielectric creepage strength of solid insulation systems using pressboard as radial spacers, and high-voltage winding lead support parts.