Simple Up Controlled Negative Voltage Converter Circuit Diagram

This Simple Up-Controlled Negative Voltage Converter Circuit Diagram was used to produce a variable negative voltage for contrast control of an LCD display. A 74F374 generates a square wave that is ac coupled to a rectifier and load. By using the uP clock and data from the processor bus, and properly timed load signal, the dc level generated can be controlled by the uP. 

Simple Up-Controlled Negative Voltage Converter Circuit Diagram 

 

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Build a Positive And Negative Voltage Switching Supply

Build a Positive And Negative Voltage Switching Supply. An LT1172 generates positive and negative voltages from a 5-V input. The LT1172 is configured as a step-up converter. To generate the negative output, a charge pump is used. C2 is charged by the inductor when D2 is forward-biased and discharges into C4 when LT1172`s power switch pulls the positive side of C2 to ground. 

 Positive And Negative Voltage Switching Supply  Circuit Diagram

 

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