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A new low-cost and efficient cold cathode fluorescent lamp (CCFL) inverter for liquid crystal display (LCD) application is suggested in this paper. The topology of the inverter is derived from modified class E-type resonant electronic ballasts and has a dc-like input current. In addition, a new sensing circuit for lamp current and transformer volta...
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... LOW INPUT CURRENT RIPPLE Fig. 1 shows CCFL inverters with a minimum of switches and components. The inverters are modified from the electronic bal- last applied first to high intensity discharge (HID) lamps [14], [15], and they can be regarded as modified class E-type reso- nant inverters [1], [13]- [18]. By increasing the leakage of the transformer, we can simply ...
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... the main drawback of the class E-type ballast is the high switch voltage, it is inconsequential when the input voltage is low. Nonetheless, the inverters in Fig. 1 have other problems. In the case of Fig. 1(a), the input current is discontinuous with much higher peak value than the average value. The inverter can therefore adversely affect the other units that comprise the dis- play system. Fig. 1(b) shows high input reactive power, which may cause high loss. In addition, applying these inverters ...
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... the main drawback of the class E-type ballast is the high switch voltage, it is inconsequential when the input voltage is low. Nonetheless, the inverters in Fig. 1 have other problems. In the case of Fig. 1(a), the input current is discontinuous with much higher peak value than the average value. The inverter can therefore adversely affect the other units that comprise the dis- play system. Fig. 1(b) shows high input reactive power, which may cause high loss. In addition, applying these inverters to the CCFL drivers causes a proprietary ...
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... is the high switch voltage, it is inconsequential when the input voltage is low. Nonetheless, the inverters in Fig. 1 have other problems. In the case of Fig. 1(a), the input current is discontinuous with much higher peak value than the average value. The inverter can therefore adversely affect the other units that comprise the dis- play system. Fig. 1(b) shows high input reactive power, which may cause high loss. In addition, applying these inverters to the CCFL drivers causes a proprietary issue [19]. Fig. 2 shows the proposed low-cost CCFL inverter with a low input ripple current. The input current is close to a dc current with a low ripple because the input current always flows ...
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... should be zero, the voltage of equals the input voltage . Furthermore, the steady-state value of is always the same despite the varying load power under the dimming control. Therefore, by choosing sufficiently large value of and , and by assuming the voltage of is a constant voltage source, the inverter in Fig. 2 can be regarded as inverters in Fig. 1 and can be analyzed and designed similarly as in [14] and [15]. The main difference between inverters in Figs. 1 or 2 and inverters in [14] or [15] is that the resonant network in the secondary side should be considered in the design. Moreover, the resonant network includes the winding capacitance of the transformer. The principle for ...
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... Fig. 10, which shows the characteristics of the analog dim- ming control loop, we see the operating frequency of the inverter and the illuminance of the LCD panel that uses one CCFL as a backlight. The dependence of the lamp's impedance on the lamp current causes the nonlinearity of the control characteris- tics. As the lamp current decreases, ...
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... at the secondary side. This non- linear property is unavoidable in the frequency controlled CCFL inverter. However, using the current control loop for the analog dimming is still possible and useful for practical backlight units. Furthermore, the dimming range can be widened extensively by combining the LPWM dimming with the analog dimming. Fig. 11 shows the efficacy of the inverter of this work when the inverter uses the proposed sensing circuit and when the in- verter uses the conventional sensing scheme [2], [3], [5], [8], [10]- [13]. The efficacy is defined here as the ratio of the illu- minance of the lamp measured by a lux meter attached to the LCD panel and the input ...
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... the conventional sensing scheme [2], [3], [5], [8], [10]- [13]. The efficacy is defined here as the ratio of the illu- minance of the lamp measured by a lux meter attached to the LCD panel and the input power. Because the secondary side is floated, the lamp current leakage is reduced and the efficacy is increased over the entire dimming range. Fig. 12 shows the key waveforms for the open-lamp protec- tion and voltage regulation process. Prior to the slow voltage regulation loop, a fast protection circuit which was explained in Section IV suppressed the excessive voltage spikes from the transformer. Fig. 13 shows the waveforms that occurred during the LPWM dimming operations. When ...
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... current leakage is reduced and the efficacy is increased over the entire dimming range. Fig. 12 shows the key waveforms for the open-lamp protec- tion and voltage regulation process. Prior to the slow voltage regulation loop, a fast protection circuit which was explained in Section IV suppressed the excessive voltage spikes from the transformer. Fig. 13 shows the waveforms that occurred during the LPWM dimming operations. When the dimming command was ON, the lamp operated with its rating current. When the dimming command was OFF, the inverter operated at about 150 kHz which is well above the analog dimming range shown in Fig. 6. At this frequency, although the lamp current and ...
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... the current sensing signal still appeared because, as explained in Section III, the sensing circuit detected the voltage of . This characteristic, however, did not cause any error within the analog dimming range of Fig. 6. Note that and should be properly chosen not so as to cause the ringing in the current waveform at the LPWM transient region. Fig. 14 shows the soft on/off operations for the LPWM dim- ...
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Citations
... Since the introduction of the Class-E power amplifier that offers amazing advantages, the Class-E power amplifier has attracted a great deal of attention in recent years. After that, various topologies have appeared to expand the applications of class E circuit such as class E inverter [3] [14] [15] [13] [16] [17], class E DC/DC converter [14] [18] and class E rectifier [13]. Also, the class E circuits are applied to RF power amplifier [19] [20], induction heating system [20] [21], and RF powering [21] [22] [23] [24]. ...
p>This paper presents the simulation and experimental of Class-E power amplifier which consists of a load network and a single transistor. The transistor is operated as a switch at the carrier frequency of the output signal. In general, Class-E power amplifier is often used in designing a high frequency ac power source because of its ability to satisfy the zero voltage switching (ZVS) conditions efficiently even when working at high frequencies with significant reduction in switching losses. In this paper, a 10W Class-E power amplifier is designed, constructed, and tested in the laboratory. SK40C microcontroller board with PIC16F877A is used to generate a pulse width modulation (PWM) switching signal to drive the IRF510 MOSFET. To be specific, in this paper, the effect on switching and performance at 1MHz frequency are studied in order to understand the Class-E inverter behavior. Performance parameters relationships were observed and analysed in respect to the load and duty cycle. Theoretical calculations, simulation and experimental results for optimum operation using selected component values are then compared and presented.</p
... To measure this current indirectly, it is possible to use the voltage across resonant capacitor C r and differentiate it as it was offered in [8]. The development of this idea gives one more way: to use the voltage across resonant inductor L r and integrate it. ...
This paper describes two methods for the short-circuit protection of the LLC resonant converter. One of them uses the voltage across the capacitor and the other uses the voltage across the inductor of the resonant tank. These voltages can be processed (integrated or differentiated) to recover the resonant tank current. The two circuits illustrated in the described methods make it possible to develop a robust LLC converter design and to avoid using lossy current measurement elements, such as a shunt resistor or current transformer. The methods also allow measuring resonant tank current without breaking high-current paths and connecting the measuring circuit in parallel with the inductor or capacitor of the resonant tank. Practical implementations of these indirect current measurements have been experimentally tested for the short-circuit protection of the 1600 W LLC converter.
... Tu and Toumazou [4] designed a class E amplifier on integrated circuit with 1.8 GHz resonant frequency. Various topologies have appeared to expand the applications of class E circuit such as class E inverter [3,[5][6][7][8][9][10][11][12], class E DC/DC converter [5,13,14] and class E rectifier [7]. Also, the class E circuits are applied to RF power amplifier [4,15], induction heating system [11,15,16] and RF powering [16][17][18][19]. ...
In this study, an exact circuit model for the class E inverter is proposed to analyse the circuit behaviour in frequency domain without mathematical assumptions. Through this model, a close form formula is proposed to solve the load current and drain-source end voltage of metal oxide semiconductor field effect transistor at switching instants in steady-state instead of complicated numerical iteration. With these current and voltage at switching instants, the load current can be expressed with exact function and evaluated. By means of the proposed formula and current expression, the optimal and suboptimal conditions for the zero voltage switching (ZVS) operation have been expressed in terms of the shifting angle of load current with respect to drain-source voltage. Further, the ZVS and non-ZVS operation regions can be marked via calculating the shifting angle and optimal shifting angle, which are proposed in the study. To demonstrate the proposed formulas and ZVS conditions, some examples are given to examine the analysis and ZVS drifting behaviour with comparing of calculation, simulation and experiment. Good agreements from the illustrated examples have given the verification of the analysis and design for the class E inverter.
... However, the CCFL has a feature of negative incremental resistance, and hence one inverter can only drive one lamp. Accordingly, for the extra large-sized LCD TV to be considered, there are several inverters connected in parallel to drive several CCFLs, thereby causing the number of components and the power dissipation [1][2][3] to be increased. The main difference between the CCFL and the EEFL is that the electrodes of the EEFL are put outside the lamp and those of the CCFL is put inside the lamp. ...
In this paper, an asymmetric half-bridge LCC resonant inverter is presented, which is the kernel of the proposed lighting ballast that is used to drive an external electronic fluorescent lamp (EEFL). This lighting ballast contains three power stages if dimming is necessary; otherwise it contains two power stages only. The first power stage is constructed by a traditional boost converter with power factor correction (PFC), and such a converter is operated in the transient mode (TM) with the DC output voltage 390V. The second power stage is built up by a buck converter is used to control the duty cycle such that the corresponding output voltage can be changed and hence dimming of the EEFL can be achieved. The third power stage is established by an asymmetric half-bridge LCC resonant inverter operating under a fixed switching frequency with a fixed duty cycle of about 50%. Via LCC resonance, the power switches of this inverter are operated in zero voltage switching (ZVS) so as to reduce the switching loss, and at the same time, the inherent high voltage conversion characteristics make the voltage conversion gain is larger than one such that the turns ratio of transformer can be reduced. Most importantly, as the EEFL is operated on the rated conditions, i.e., without dimming, the second power stage is to be bypassed, thereby causing the corresponding efficiency to be upgraded. The basic operating principles and corresponding mathematical deductions of the proposed inverter are described, and applied to the constructed EEFL lighting ballast that is verified by some simulated and experimental results.
... + _ L To ensure zero-voltage-switching, the circuit parameters must satisfy the following relationships [19]: ...
This work presents a novel solar energy application to an illumination system that connects a photovoltaic (PV) array, battery energy storage system (BESS) and load by combining a class-E resonant inverter with a fluorescent lamp. Without a power converter between the BESS and electronic ballast stage, no power processing loss occurs between these components; therefore, the developed system reduced power losses. The proposed topology is very simple and requires a single active power switch. Carefully selected circuit parameters enable the active power switch to be driven directly by BESS and operated at zero-voltage switching, yielding high circuit efficiency. A prototype circuit that is designed for a PL-27W compact fluorescent lamp is constructed and tested to verify the theoretical predictions. The measured efficiency of the electronic ballast is as high as 94.33%. Experimental results show the functionality of the overall system and prove it to be an effective solution for numerous photovoltaic applications.
In this paper, a bi-frequency control based zero-voltage-switching push-pull driver with a wide dimming range is proposed for the cold cathode fluorescent lamp (CCFL) based back lighting of the liquid crystal display (LCD). As a result, not only the design of the driver transformer can be simplified but also the efficiency of CCFL can be improved. Finally, a prototype is constructed for verifying the effectiveness of the proposed LCD driver.
This paper compares a push-pull resonant inverter with a half-bridge resonant inverter for cold cathode fluorescent lamps. The push-pull resonant inverter is fabricated with an input inductor, a center-tapped transformer, a parallel resonant capacitor and two bipolar junction transistors, whereas the halfbridge resonant inverter comprises a series resonant capacitor, a transformer and two metal-oxide-semiconductor field-effect transistors. Nevertheless, both inverters behave zero-voltage-switching and current-output characteristics. This paper depicts the features and compares the efficiency of the inverters with experiments. The experimental results show the voltage-fed half-bridge resonant inverter exhibits a better efficiency than the current-fed push-pull resonant inverter.
In this paper, an isolated asymmetrical half-bridge LCC resonant inverter is presented, which is the kernel of the proposed lighting ballast that is used to drive an external electrode fluorescent lamp (EEFL). This lighting ballast contains three power stages if dimming is necessary; otherwise it contains two power stages only. The first power stage is constructed by a traditional boost converter with power factor correction (PFC), and such a converter operates in the critical mode (CRM). The second power stage is built up by a buck converter is used to control the duty cycle such that the corresponding output voltage can be changed and hence dimming of the EEFL can be achieved. The third power stage is established by an isolated asymmetrical half-bridge LCC resonant inverter operating under a fixed switching frequency with a fixed duty cycle. Via LCC resonance, not only the power switches of this inverter work in zero voltage switching (ZVS) so as to reduce the switching loss, but also the voltage gain is larger than one such that the turns ratio of transformer can be reduced. Most importantly, as the EEFL operates on the rated conditions, i.e., without dimming, the second power stage is to be bypassed, thereby causing the corresponding efficiency to be upgraded. The basic operating principles and corresponding mathematical deductions of the proposed inverter are described, and applied to the constructed EEFL lighting ballast that is verified by some experimental results.
This work presents a novel solar energy application to an illumination system that connects a photovoltaic (PV) array, battery energy storage system (BESS) and load by combining a class-E resonant inverter with a fluorescent lamp. Without a power converter between the BESS and electronic ballast stage, no power processing loss occurs between these components; therefore, the developed system reduced power losses. The proposed topology is very simple and requires a single active power switch. A prototype circuit that is designed for a PL-27W compact fluorescent lamp is constructed and tested to verify the theoretical predictions. The measured efficiency of the electronic ballast is as high as 94.33%. Experimental results show the functionality of the overall system and prove it to be an effective solution for numerous photovoltaic applications.
