This is a design circuit for power supply 18 V. This circuit is used by the row drivers to turn on the gate of the flat panel display’s thin film transistor (TFT). This circuit is based on LM2622 as main controller in this circuit. This is the figure of the circuit;
The charge pump works in 2 stages. First, when the switch on the LM2622 is closed, C4 charges to approximately +9.0V. When the switch is open, D2 conducts and the voltage across C5 is +9.0V. Because C5 is referenced to +9.0V node, the voltage is +18V (developed across C6) when referenced to ground. The +18V supply is unregulated, but sufficient to provide the "on" voltage for the row drivers. It is also possible to add an additional capacitor charge pump stage to bring the total generated voltage to +27V. In general, this configuration can provide either a 2x or 3x multiple of the column driver analog output voltage as the row driver "on" voltage.
[Circuit source: National Semiconductor Notes]
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