US Patent No. 10,172,194

LIGHT EMITTING ELEMENT DRIVING CIRCUIT, LIGHT EMITTING DEVICE, DISPLAY DEVICE, AND LIGHT EMISSION CONTROLLING METHOD


Patent No. 10,172,194
Issue Date January 01, 2019
Title Light Emitting Element Driving Circuit, Light Emitting Device, Display Device, And Light Emission Controlling Method
Inventorship Norimasa Furukawa, Tokyo (JP)
Assignee Sony Corporation, (JP)

Claim of US Patent No. 10,172,194

1. A light emitting element driving circuit comprising:a capacitive element having a first terminal and a second terminal, in which the second terminal is fixedly grounded;
a second constant current source for supplying a first set current as a charging current steadily and constantly to the first terminal of said capacitive element;
a first constant current source stabilizing a discharging current supplied from said capacitive element to a light emitting element, in which the first constant current source is in series with the light emitting element and supplies a second set current as the discharging current from the capacitive element to the light emitting element; and
a switch in series with, and controlling ON and OFF in supplying said discharging current to, said light emitting element, in which the first constant current source, the switch and the light emitting element are connected in series in a series circuit extending from the first terminal of said capacitive element to ground and in which the first constant current source is arranged in the series circuit between the switch and the first terminal of said capacitive element,
the second constant current source supplying the charging current steadily and constantly to the first terminal of said capacitive element when said switch becomes an ON state and an OFF state,
wherein the first constant current source and the second constant current source are configured such that a product of the first set current and a scanning time period for the light emitting element is greater than or equal to a product of the second set current and a discharge time period for the capacitive element which is equal to a time period when the switch is in the OFF state and which is a portion of the scanning time period, and such that, when the switch is repetitively switched at a predetermined interval to the OFF state from the ON state and to the ON state from the OFF state synchronized with the scanning time period, a predetermined voltage at the first terminal is maintained in a predetermined range, in which the predetermined range has a maximum voltage not greater than a voltage supplied from a power source to the second constant current source,
in which the first constant current source supplies the second set current as the discharging current from the capacitive element to the light emitting element only when the switch becomes the ON state synchronized with the scanning time period.