Abstract: Stable control of an output voltage of a charge pump circuit is made possible by feed-back control using Pulse Width Modulation. The charge pump circuit of this invention includes a first and a second charge transfer MOS transistors connected in series, a capacitor with a first terminal connected to a connecting node between the first charge transfer MOS transistor and the second charge transfer MOS transistor, an integration circuit that generates a ramp voltage that corresponds to clocks, a comparator that compares the ramp voltage with a voltage corresponding to an output voltage from the second charge transfer MOS transistor, a divider that divides a frequency of the clocks in half and a NAND circuit that masks an output of the comparator according to an output of the divider. An output of the NAND circuit is applied to a second terminal of the capacitor.

Abstract: A driver circuit of a light emitting element is improved in efficiency. The driver circuit is to drive a white LED and includes a charge transfer device, a capacitor connected to the charge transfer device and a booster circuit that converts a power supply voltage inputted to the charge transfer device to a drive voltage of 1.5 times of the power supply voltage according to a clock applied to the capacitor. The drive voltage from the booster circuit is supplied to the white LED. The driver circuit also includes a pulse detection circuit that detects a brightness adjustment pulse BP and a switching circuit that controls a drive current to the white LED in order to adjust brightness of the white LED. The driver circuit includes a divider that reduces a frequency of the clock corresponding to a reduction in the drive current due to the brightness adjustment made by the switching circuit.

Abstract: A driver circuit to obtain a current to drive a light emitting device is reduced in a patterning area and improved in efficiency. A positive power supply voltage Vdd is applied to an agnode of a white LED, while a voltage ?0.5 Vdd from a ?0.5 Vdd generation circuit is applied to a cathode of the white LED through an N-channel type MOS transistor. The ?0.5 Vdd generation circuit generates the voltage ?0.5 Vdd according to a clock ? from a clock generation circuit. A voltage of 1.5 Vdd is applied between the anode and the cathode of the white LED, as equivalent to a prior art. Since N-channel type MOS transistors are heavily used in the ?0.5 Vdd generation circuit, the driver circuit requires less patterning area to obtain the same amount of current to drive the LED as in the prior art. In addition, a parasitic capacitance is reduced to improve efficiency of the driver circuit.

Abstract: Malfunctioning is prevented with a charge-pump circuit which boosts a voltage in increments of less than power supply voltage. The charge-pump circuit has switches S1, S2 and S3 which connect capacitors 1 and 2 to a pumping node in series or in parallel accordingly to the following control steps. {circle around (1)} The switch S2 is turned ON to connect the capacitors 1 and 2 in series while the clock CLK is at L level. {circle around (2)} The switch S2 is turned OFF. {circle around (3)} The clock CLK is changed to H level. {circle around (4)} The switches S1 and S3 are turned ON to connect the capacitors 1 and 2 in parallel. {circle around (5)} The switches S1 and S3 are turned OFF. {circle around (6)} The clock CLK is changed to L level.

Abstract: Malfunctioning is prevented with a charge-pump circuit which boosts a voltage in increments of less than power supply voltage. The charge-pump circuit has switches S1, S2 and S3 which connect capacitors 1 and 2 to a pumping node in series or in parallel accordingly to the following control steps.