C.S. Moo

Designing a dimmable electronic ballast with voltage control for fluorescent lamp

This paper provides a design guideline for the high-frequency dimmable electronic ballast with voltage control for fluorescent lamps. The dimming feature is accomplished by controlling the DC-link voltage of the inverter stage of the electronic ballast. Based on the power-dependent lamp model, the control equations are derived by fundamental approximation, and then the dimming characteristics of the fluorescent lamp can be calculated. Satisfied performances are achieved by properly choosing the circuit parameters under the considerations of the filament heating, the starting voltage, switching losses, circuit component stresses and the applicable DC-link voltage range. An electronic ballast with the half-bridge series-resonant parallel-load inverter for the rapid-start fluorescent lamp is used as an example for illustrating the design procedure. A laboratory circuit was built and tested. The experimental results agree well with the analytical values.

High-frequency electronic ballast with auto-tracking control for metal halide lamps

An auto-tracking control strategy is proposed for high-frequency electronic ballasts to operate the metal halide lamp at a frequency free of acoustic resonance. In case the acoustic resonance should happen, the variation in the lamp voltage is detected and then the operating frequency is changed step by step until a frequency with stable operation is located. In cooperating with the detection circuit, the control strategy is implemented on an electronic ballast with the half-bridge class-D load-resonant inverter. A prototype designed for 70 W metal halide lamps is used to illustrate the operations of the auto-tracking control.

A fluorescent lamp model for high-frequency electronic ballasts

An electrical circuit model of the fluorescent lamp for high-frequency operation is presented. The circuit model is represented by a power and temperature dependent resistance. A test system is set up to obtain the lamp arc voltage equation for a given lamp from few test data, and then the arc current and the equivalent resistance can be derived. By these lamp equations, the electrical behavior of the lamp can be described. The circuit model can be used for predicting the operating characteristics of the dimmable electronic ballast-lamp circuits with considerations on the effects of the operating power and temperature. The verification of the proposed lamp model is illustrated by implementation examples.An electrical circuit model of fluorescent lamps is derived as an aid in designing high-frequency dimmable electronic ballasts. The lamp model accounts for the effects of operating power and filament heating, describing the electrical behavior of the lamp by two voltage equations. Based on the orthogonal array methods, the variation equations of the arc and filament resistances are derived. The coefficients of the equations can be estimated from test data. The verification is performed by implementing a model of a T9-40W lamp with the experimental results. Satisfactory performance is obtained from the experimental results.

A high efficiency driver for high-brightness white LED lamp

A high efficiency driver is proposed for the high-brightness white LED lamp. The driver consists of a dc power source in series with a current regulator. The current regulation is accomplished by partially processing the power from the dc power source. The dimming feature of the LED lamp can be made by regulating the current. The detailed circuit operation stages and analysis are provided. A laboratory circuit is designed for an LED lamp which is composed of eight high-brightness LEDs. Experimental results demonstrate that a high efficiency can be achieved even at a dimmed lamp power.

Acceleration Scenarios of Metal Halide Lamps

Based on the investigation results on the starting characteristics of metal halide lamps, the time for entering the steady state is defined in a more reasonable manner. From the effects of the applied current on the generated luminance, several starting scenarios are attempted to accelerate the starting transient. Experimental evidence shows that the starting time can be effectively shortened by increasing the lamp current during the glow-to-arc transition and warm-up stage. A short interval of over-power operation during the warm-up stage enables the lamp to further enhance the production of luminance quickly and hence greatly reduce the starting transient period.

Profiling Starting Transient of Fluorescent Lamp With High-Frequency Electronic Ballast

This paper proposes a new starting profile with some modifications to the definition of American National Standards Institute to interpret the starting process of fluorescent lamps driven by high-frequency electronic ballasts. The new starting profile redefines the times of preheating, ignition, and steady state. A glow-to-arc transition is considered to account for the stage from glow discharging to a stable lamp arc. By the new definition, the glow current and the glow-to-arc current can be calculated to evaluate the lamp-starting performance. The applicability of the starting profile is confirmed experimentally by the instant-, preheat-, and rapid-starting schemes.

Investigation Into High-Frequency Operating Characteristics of Metal-Halide Lamps

Two electronic ballasts have been built to drive lamps with sinusoidal and quasi-square-wave currents, respectively, in order to investigate the high-frequency operating characteristics of small-wattage metal-halide lamps. Experiments were conducted on the tested lamps of 35, 70, and 150 W with a frequency ranging from 20 to 300 kHz. The measurements include the spectral energy, the color temperature, the acoustic resonance, and the luminous efficiency. The effects of operating frequency are discussed based on the experimental results.

Protection circuit for electronic ballasts at fluorescent lamp life-end

An approach is proposed to detect and protect the electronic ballasts from abnormal operations when fluorescent lamps are coming to their life-ends. A protection circuit is designed to identify the abnormal operation by detecting the dc component on the lamp voltage. A design example is used to illustrate the operations of the protection method. Experimental results demonstrate that the detection and protection can function effectively under various fault conditions.

Charging scenario of serial battery power modules with buck-boost converters

This paper studies the charging scenario of the battery power bank with buck-boost battery power modules (BPMs) connected in series. For the BPMs with serial connection, the charging currents to batteries can be individually scheduled by adjusting the duty-ratios of the associated power converters. During the charging process, those batteries having been completely charged can be isolated from the battery power bank without interrupting the charging operation. To fully utilize the available chargers capacity, a simple charging scenario is proposed according to the state-of-charges (SOCs) of the batteries under the limitations of the allowable chargers power and the maximum battery charging current. Experiments carried out on four buck-boost type BPMs have confirmed the efficient performance of the charging scenario.

An interleaved twin-buck converter with zero-voltage-transition

This paper proposes an interleaved twin-buck converter with zero-voltage-transition (ZVT) for low power applications. The converter comprises two identical buck conversion units employing power MOSFETs as the active power switches with an interleaved inductor. The ZVT is accomplished by resonating the currents between the interleaved inductor and the parasitic capacitances of the power MOSFETs. The detailed circuit operations and analysis are provided. A laboratory circuit rated at 50 W is designed and tested. Experimental results show that the switching losses can be effectively reduced by smoothly transiting the currents of the active power switches.