The electronic display devices play an important role as an information display for a man-to-machine interface. With the rapid progress in the information industry, there has been a continuous increase in the demand for new electronic display devices with a large size, high resolution, and high information capacity. Among many hitherto developed display devices, an Alternating Current Plasma Display Panel (AC PDP), which features its large screen size, wide viewing angle, thinness, long life, and high contrast, has many desirable advantages over the other competing flat panel displays and is expected to be one of the most promising digital displays of the next generation.
A PDP consists of scanning (Y) and sustaining (X) electrodes covered with a dielectric layer, which produces an intrinsic capacitance Cp between these two electrodes inherently. Therefore, when applying high voltage and high frequency sustaining pulses to these electrodes without an energy recovery circuit, an excessive surge displacement current and subsequent considerable energy loss for each cycle are generated during charging or discharging transients. Furthermore, this surge current will give rise to EMI noises and increase the surge current ratings of power switches.
To relieve these problems, several prior approaches to relieve these problems have been proposed. Although they can recover most of the energy stored in Cp, they still have several serious drawbacks such as a poor energy recovery capability, complex structure, bulky system, high cost of production, considerable heat generation, large circulating current, poor efficiency, low performance, or EMI problem, which might make it difficult to produce PDP TV on a commercial scale.
To overcome these drawbacks of the several prior energy recovery circuits, six new energy recovery display drivers are proposed in the first half section of this dissertation.
First, a new SR type IGBT based cost-effective ERC for a PDP is proposed. Since it uses only two inductors and two power diodes without an auxiliary circuit to recover the energy stored in PDP, it features a simpler structure, less mass, lower cost of production, and fewer devices. Since its all power switches can be turned off under the ZCS operation and have no current tailing problem, IGBTs can be used in the proposed ERC successfully. Moreover, its experimental light waveform is very stable and uniform, proving the good quality of screen. Its overall system power consumption is generally similar to that of the conventional SR type Weber circuit, of which result is very meaningful in the sense that the proposed circuit using the small number of devices can achieve a similar efficiency and operational characteristics to the conventional circuit using a large number of devices.
Secondly, a new simple structure and low cost CR type ERC is proposed. It features a simpler structure, less mass, fewer devices, and lower cost of production. Furthermore, since all four switches are turned on with ZVS, it has a higher efficiency and lower EMI. In particular, since it compensates the plasma discharge current, it enables the panel to light at a lower voltage than the prior circuit.
Thirdly, a new SR type energy recovery circuit employing gas discharge current compensation method is proposed. The difference from the prior SR type Weber circuit is that it makes the resonant circuit be biased by $V_s$ and 0V instead of $V_s$/2 in charging and discharging $C_p$, respectively. Therefore, the panel capacitor $C_p$ can be fully charged to $V_s$ and discharged to 0V with no hard switching, which helps to achieve the ZVS of main switches M1~M4, reduce the EMI noise, and increase the energy recovery capability. Moreover, when the light is emitted from the PDP, the remaining inductor current after charging the PDP can compensate the gas discharge current and provide the turn-on timing margin. Therefore, the luminous efficiency of the proposed circuit is superior to the conventional circuit. Thanks to these favorable advantages, the proposed circuit attracts more wall charge to deposit on the dielectric layer of the electrodes, improve the operational voltage margin, and enables the PDP to light at a lower voltage (i.e. 146V) than the prior circuit (i.e. 165V).
Fourthly, a new CR type energy recovery circuit employing gas discharge current compensation method is proposed to overcome the drawbacks of prior circuits. Like the SR version of this circuit, this circuit makes the resonant circuit be biased by Vs and 0V instead of Vs/2 in charging and discharging Cp, respectively. Besides, it uses the current sources built in the inductor to recover the energy stored in the PDP and power switch output capacitors. Therefore, it can provide the ultra fast rising time of the panel polarity and ensured ZVS operation of all main power switches. In addition, since the inductor current flows for a short time, its circulating energy is very small. Therefore, it features a high efficiency and the burden on the cooling system is very light. In particular, since the inductor current compensates the gas discharge current, it can reduce the current stress of all main power switches and solve the problem of the undesirable voltage notch across the PDP, which enables the panel to light at lower voltage than the prior circuit.
Fifth, a new ZVZCS ERC for a PDP is proposed. The ZVS of all main MOSFET switches and ZCS of all auxiliary IGBT switches can be achieved and the proposed circuit can maintain the panel to light at the lower voltage with the aid of the inductor current source. Moreover, it features the simpler structure, fewer devices, lower EMI, and lower current stress.
Finally, a new high-performance and low cost single switch CR type energy recovery display driver for a PDP is proposed. Since it has only one auxiliary power switch, two small inductors, and eight diodes, it features a much simpler structure and lower cost. Its circulating energy is very small and the main power switches are all turned on with ZVS. Therefore, it features a high efficiency and the burden on the cooling system is very light. In particular, since it compensates the plasma discharge current, it could solve the problem of the undesirable voltage drop, reduce the current stress of all main switches, and improve the turn-on timing margin. Additionally, the inductor current helps to reduce the transition time of the panel polarity, which can increase the brightness. These favorable merits of the proposed circuit enable the panel to light at lower voltage than the prior circuits.
Meanwhile, the whole operation of the PDP is divided into three periods of resetting, addressing, and sustaining periods. During the resetting period, all of PDP cells are erased and prepared to carry out addressing. Then, selective write-discharges to form a required image are ignited by applying the data and scanning pulses to the addressing and scanning electrodes, respectively. Since the addressing discharge itself emits an insufficient visible light, high voltage AC square pulses are continuously applied between sustaining and scanning electrodes for the strong light emission of selective cells during the sustaining period. Therefore, to carry out these operations successfully, the PDP must be equipped with the various kinds of power modules for sustaining, erasing, addressing, scanning operations, and so on. Meanwhile, since most of the power required to drive the PDP is consumed during the sustaining period, that for sustaining operation among abovementioned power modules are mainly responsible for the overall system efficiency and size. In addition, since the recent wall hanging PDP color TV tends to require the smaller size, lighter weight, and fan-less system for the lower levels of acoustic noise and vibration, the high power density, high performance, and high efficiency become the hot issues of the PDP power module.
Therefore, in the second half section of this dissertation, five new power conversion circuits for the PDP system are proposed to overcome the drawbacks of the conventional circuits and achieve the high efficiency and good circuit performance.
First, a new high efficiency ZVS PWM asymmetrical half bridge converter is proposed. A small additional inductor, which also acts as an output filter inductor, can achieve the ZVS of power switches for the wide load range. The problem related to ringing in the secondary rectifier caused by the additional inductor can also be completely solved by employing a structure without an output filter inductor. In addition, since it has no large output inductor filter, it features a simpler structure, lower cost, less mass, and lighter weight. Moreover, since all energy stored in the additional inductor is transferred to the output side, the circulating energy problem can be effectively solved and the overall system efficiency along a wide load range is as high as above 95%.
Secondly, a new high efficiency and low device stress ZVS PWM asymmetrical half bridge converter employing VCC cell for PSPM is proposed. The large leakage inductor can achieve the ZVS of all power switches along the wide load range. The problem related to ringing voltage in the secondary rectifier caused by the large inductor can also be completely solved by employing a VCC cell. Therefore, no RC-snubber for rectifier diodes is needed and a high efficiency as well as low noise output voltage can be realized. Moreover, since all energy stored in the additional inductor is transferred to the output side, the circulating energy problem can be effectively solved and the overall system efficiency along a wide load range is as high as above 95% (Maximum efficiency: 97.3%). The measured temperatures of all components are below about 50oC except for the transformer (51oC). These results mean that the proposed converter features the high efficiency, low device stress, high reliability, and small size due to the reduced heat sink.
Thirdly, a new high efficiency and low device stress ZVS PWM full bridge converter with LDC output configuration is proposed. A small additional inductor and magnetizing inductor can achieve the ZVS of power switches along the full load range. The problem related to serious ringing in the secondary rectifier caused by the additional inductor can also be completely solved by employing a new LDC output configuration, which helps the voltages across rectifier diodes to be clamped at Vo/2=85V or Vo=170V. Therefore, no RC-snubber for rectifier diodes is needed and a high efficiency as well as low noise output voltage can be realized. Since The efficiency along a wide load range is as high as above 95%. Moreover, since both modules are operated with the 180˚ phase difference, the output voltage ripple can be considerably reduced by 50%.
Fourthly, a new ZVS TTFB PWM converter with the LDCR is proposed, which is especially suitable for high output voltage/power applications (e.g. PSPM). Since the magnetizing inductor as well as leakage inductor of two transformers contribute to the ZVS of all switches, the ZVS range of lagging leg switches can be extended to the very light load. Furthermore, the new LDCR dramatically eliminates the voltage overshoot and ringing across rectifier diodes. The clamping capacitor also helps to reduce the circulating current of the freewheeling state, which can considerably reduce the conduction loss. The prototype has been designed to prove the validity of the proposed converter. The experimental results of the prototype converter have been presented for the specifications of 385V input, 170V output, and 425W power. The measured efficiency is as high as above 94% along a wide load range and maximum efficiency comes up to 95.9% at a rated load condition, which has higher efficiency than a conventional PSFB and prior TTFB. Especially, output rectifier diodes are free from voltage overshoots and ringing by LDCR.
Finally, a new high efficiency and low cost active clamp forward converter for a PSPM is proposed. It ensures the ZVS operation of all power switches over whole load variations without the additional resonant inductor. Furthermore, since there is no large output filter inductor, it features the simpler structure, lower cost, less mass, higher efficiency, and no effective duty loss. The efficiency along a wide load range is as high as above 90%.
Therefore, it is expected that the proposed energy recovery display drivers and power converters in this dissertation are well suitable to the next generation high performance and high efficiency consumer affordable PDP TV set. Moreover, these circuit techniques are also expected to be well applied to various applications beside the PDP system.
