Failure Analysis of Some Commercial Spotlights Based on Light Emitting Diodes

The failure mechanism of two commercial light-emitting diode (LED)-based spotlights with GU10 form factor is analyzed. Through component testing and comparison to nominal values as well as to simulations, it is found that the cause of both device failures is related to damaged components within the drive circuits rather than the LEDs themselves. Both LED heads work as normal when connected to an external direct current (DC) source. The results show that the lack of light output of one spotlight is related to the open circuit caused by damaged resistors and inductors in its drive circuit, while the flickering of the other is related to the malfunction of the integrated circuit providing constant current output. Therefore, improving the quality of the LED drive circuits is considered the most effective way for manufacturers to reduce catastrophic failures of LED spotlights.

A Novel and Cost-Effective Drive Circuit for Supplying a Piezoelectric Ceramic Actuator with Power-Factor-Correction and Soft-Switching Features

This paper proposes a novel and cost-effective drive circuit for supplying a piezoelectric ceramic actuator, which combines a dual boost AC-DC converter with a coupled inductor and a half-bridge resonant DC-AC inverter into a single-stage architecture with power-factor-correction (PFC) and soft-switching characteristics. The coupled inductor of the dual boost AC-DC converter sub-circuit is designed to work in discontinuous conduction mode (DCM), so the PFC function can be realized in the proposed drive circuit. The resonant tank of the half-bridge resonant inverter sub-circuit is designed as an inductive load, so that the two power switches in the presented drive circuit can achieve zero-voltage switching (ZVS) characteristics. A 50W-rated prototype drive circuit providing a piezoelectric ceramic actuator has been successfully implemented in this paper. From the experimental results at 110V input utility-line voltage, the drive circuit has the characteristics of high power factor and low input current total-harmonic-distortion factor, and two power switches have ZVS characteristics. Therefore, satisfactory outcomes from measured results prove the function of the proposed drive circuit.

Spice Modeling of LED Filament and its Simulation in Switch Drive Circuit

When designing the LED filament lamp device and driving circuit at the beginning, software simulation is an indispensable step. It is necessary to verify whether the circuit output results are consistent with the requirements through simulation. In this paper, first measure the volt-ampere characteristics of the actual 1W LED filament strip, and applied the six-segment linear approximation model method for Spice modeling. The simulated volt-ampere characteristics of the 1W model were consistent with the measured volt-ampere characteristics of the 1W LED filament strip. Then use the driver chip HV9910B to design the LED filament lamp switch constant current drive circuit. Combined with the piecewise linear equivalent method, 3W, 4W, 5W LED filament lamp loads are modeled, the detailed design process of the entire circuit is analyzed, and the output voltage, current, inductance output current, MOS output voltage and other parameters of the whole circuit are simulated and verified. The results show that the output voltages are 71V, 142V, 71V, and the output currents are 30.4mA, 20.7mA, 51.1mA respectively under the circuit topology of 3W, 4W, and 5W LED filament lamp. When the inductor current works in CCM mode, the duty cycle of MOS output voltage meets the requirements, and the circuit output results are consistent with the design requirements.

Carrier based PD and POD PWM Technique for MLI

This paper presents the design of gate drive circuit for controlling of multilevel inverter (MLI) with Phase Disposition (PD), Phase Opposition Disposition (POD) pulse width modulation (PWM) switching control technique.