Patent ID: 8143938
Filing Date: 2012-03-27
Classification: G09G,H02M

Abstract:
1. A boost circuit comprising: a charge pump circuit configured to boost a supply voltage by using a boost clock signal to generate a boost output voltage; and a control circuit unit configured to control said charge pump circuit, wherein said charge pump circuit comprises; a plurality of boost capacitors; and a charge switch that supplies said supply voltage to said boost capacitors, wherein said charge pump circuit is configured such that a step-up ratio thereof is variable by switching a connection relationship of said plurality of boost capacitors, wherein said control circuit unit is configured to control switching of said step-up ratio of said charge pump circuit and to select and perform any of a first operation and a second operation depending on a sum-based voltage, said first operation being to turn ON and OFF said charge switch in synchronization with said boost clock signal, said second operation being to turn OFF said charge switch irrespective of said boost clock signal, and said sum-based voltage being generated corresponding to a sum of said supply voltage and a voltage of a under-charge boost capacitor that is being charged among said plurality of boost capacitors, wherein a value of said sum-based voltage with which an operation of said charge switch is switched between said first operation and said second operation is a reference value, and wherein when switching said step-up ratio of said charge pump circuit from a first ratio to a second ratio lower than said first ratio, said control circuit unit switches said reference value from a first value that is determined corresponding to said first ratio to a second value that is determined corresponding to said second ratio, and then switches said connection relationship of said plurality of boost capacitors of said charge pump circuit.