Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Patent
1996-03-11
1998-09-15
Pascal, Robert
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
315209R, H05B 3702
Patent
active
058084207
DESCRIPTION:
BRIEF SUMMARY
The invention is based on a generator for controlling a plasma display screen. Such a generator is disclosed in Document 92 SID DIGEST 1987, pages 92 to 95.
In the case of such a plasma display screen, every pixels represents a capacitance. An alternating voltage which periodically charges and discharges the total capacitance of the screen is required for the basic polarization of the line addressing and, initially, this means a considerable energy loss. In order to reduce the energy loss, it is known for an inductance to be connected in the charging path of the capacitance, which inductance acts in the sense of so-called energy recovery. The energy resulting from the voltage on the capacitance is in this case periodically displaced into energy in the form of current in the coil. In this way, up to 90% energy recovery can be achieved. The voltage across the capacitance reverses its polarity as a result of the resonant discharge. This means that the voltage difference across the capacitance is twice the applied operating voltage. This known circuit is also called a Weber-Wood circuit.
SUMMARY OF THE INVENTION
The invention is based on the object of modifying the described circuit such that the triggering process to excite the individual pixels to illuminate is improved.
The known generator for line control operates with two voltage values for the voltage on the total capacitance. In the case of the circuit according to the invention, a further period at a third voltage value, for example zero, is deliberately inserted between the periods at the two different voltage values for triggering and turning off, in order to delete or to neutralize the information of the respective pixel in the plasma. A transition in the form of a sinusoidal half-cycle in this case always takes place between each two different, successive voltage values. The period at the third voltage value considerably improves the deletion or so-called reset of the pixel. The two positive and negative voltage values of different magnitude allow the excitation of the pixel to be optimized. In this case, the lines and the columns can be addressed with relatively low voltages which are precisely matched, independently of one another, to the control range of the plasma. The additional addressing circuits can then receive optimum voltage values.
The total capacitance is preferably connected cyclically to earth via a third switch, such that the voltage across the capacitance has a period of the voltage zero value between periods at a positive and a negative voltage. The connection of the capacitance is preferably connected to an operating voltage via the inductance and the second switch, and to earth via the third switch. The second operating voltage is in this case preferably equal to half the first operating voltage.
An extended solution having four transitions for both polarities comprises that connection of the capacitance which is connected to the first end of the inductance being connected to earth via two parallel switches having opposite forward directions, to a positive operating voltage via a first switch and to a second operating voltage of equal magnitude via a second switch, and the second end of the inductance being connected to half the first operating voltage via two parallel switches having opposite forward directions, and to half the second operating voltage via two further switches having opposite forward directions. The switch paths having different forward directions are in this case preferably each formed by connecting a switch and a diode in series.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is explained in the following text, using a plurality of exemplary embodiments and referring to the drawing, in which:
FIG. 1 shows a simple block diagram of the circuit according to the invention for one polarity of the voltage across the capacitance,
FIG. 2 shows curves to explain the function of the circuit according to FIG. 1,
FIG. 3 shows an extended circuit for both polarities and four transitions,
FIG. 4 shows curves to exp
REFERENCES:
patent: 4070663 (1978-01-01), Kanatani et al.
patent: 4958105 (1990-09-01), Young et al.
1987 SID International Symposium--Digest of Technical Papers, vol. 18, 12 May 1987, L.F. Weber etal "Energy Recovery Sustain Circuit for the AC Plasma Display", pp. 92-95.
1976 SID International Symposium--Digest of Technical Papers, 4 May 1976, C. Suzuki etal "Character Display using Thin-Film EL Panel with Inherent Memory", pp. 50-51.
Morizot Gerard
Rilly Gerard
Deutsche Thomson Brandt GmbH
Pascal Robert
Shingleton Michael
Tripoli Joseph S.
Wein Frederick A.
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