Cholesteric liquid crystal display device including a voltage stabilization part surpressing variations in output voltage

A cholesteric liquid crystal display device in which a first step for applying a high voltage pulse to initialize a pixel to be rewritten into a planar state and a second step for applying a low voltage pulse to increase a coexistence ratio of a focal conic state to the planar state in the initialized pixel are performed and a gradation value is determined by a cumulative time during which the low voltage pulse is applied, the device comprising:

• a voltage generation circuit that outputs a predetermined voltage;
• and
• a driver circuit that generates a voltage pulse to be applied to the pixel based on the predetermined voltage supplied from the voltage generation circuit, wherein:
• the voltage generation circuit comprises:
• a step-up part that generates a step-up voltage from a power source voltage;
• a voltage switching part that generates a voltage control signal specifying a voltage value of an output voltage from the voltage generation circuit;
• and
• a voltage stabilization part that generates the predetermined voltage in accordance with the voltage control signal from the step-up voltage supplied from the step-up part;
• the voltage stabilization part is configured so as to suppress variations in output voltage with respect to variations in the step-up voltage;
• the step-up part has two step-up DC-DC converters that use one inductor each, and an output voltage of one of the two step-up DC-DC converters is higher than the pulse wave height of a high voltage pulse at the time of the first step and the other output voltage is higher than the pulse wave height of a lower voltage pulse at the time of the second step, and an output terminal of the two step-up DC-DC converters is connected to one output terminal via a diode;
• and
• the step-up part switches the step-up voltages between the first step and the second step by controlling the turning on/off of the two step-up DC-DC converters.

A method of driving a cholesteric liquid crystal display device, the device comprising:

• a voltage generation circuit that outputs a predetermined voltage;
• and
• a driver circuit that generates a voltage pulse to be applied to a pixel based on the predetermined voltage supplied from the voltage generation circuit, wherein:
• the voltage generation circuit comprises:
• a step-up part that generates a step-up voltage from a power source voltage;
• a voltage switching part that generates a voltage control signal specifying a voltage value of an output voltage from the voltage generation circuit;
• and
• a voltage stabilization part that generates the predetermined voltage in accordance with the voltage control signal from the step-up voltage supplied from the step-up part, wherein
• the voltage stabilization part is configured so as to suppress variations in output voltage with respect to variations in the step-up voltage, in the method:
• a first step for applying a high voltage pulse to initialize a pixel to be rewritten into a planar state and a second step for applying a low voltage pulse to increase a coexistence ratio of a focal conic state to the planar state in the initialized pixel are performed and a gradation value is determined by a cumulative time during which the low voltage pulse is applied;
• and
• the step-up ratios of the step-up part are switched between the first step and the second step.