Improved configuration of an energy recovery circuit.
Publication Date: 2002-Feb-04
The IP.com Prior Art Database
Improved configuration of an energy recovery circuit
Electroluminescent displays (EL displays) and other types like plasma displays form a
capacitive load for the drivers. Due to the combination of high driving voltages (in the
order of magnitude of 200V), and a high frequency (of 10 kHz to more than 100 kHz),
the power losses caused by charging and discharging the capacitive load is quite high.
By using resonant circuits, the energy stored in the capacitive load can be gained back.
In this way the power losses will decrease very much. This is very important,
especially for battery equipment. A well-known energy recovery circuit is a so-called
Weber circuit ("Energy Recovery Sustain Circuit for the AC Plasma Display" Larry F.
Weber and Mark B. Wood, University of Illinois at Urbana-Champaign, Urbana, IL).
However, a disadvantage of the Weber circuit is that it is necessary to drive three of
the four FETs by a driver with a floating power supply (see Fig. 1). A driver with a
floating supply can only drive one FET, therefore three drivers will be necessary. Two
of these drivers can be powered by a bootstrap (S2 and S3), the third must be
connected to a floating DC/DC converter (SI).
Another known solution is depicted in Fig. 2:
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In this solution, S2 and S3 are driven by a floating supply, powered by a bootstrap. SI
and S4 are driven by a non-floating supply. The level shifting for SI is realized by a
capacitor. The disadvantage of this solution is that the voltage of the buffer capacitor
(Vrow/2) may not fluctuate, because th...