LED drive circuit

摘要

The purpose of the present invention is to provide an LED drive circuit that is capable of ameliorating insufficient lighting and improving power utilization efficiency. This LED drive circuit is an LED drive circuit wherein the number of LEDs that are turned on varies in accordance with the voltage of a commercial alternating-current power supply, the LED drive circuit being characterized by having an LED row in which multiple LEDs are connected in series, a current detection resistor for detecting a current that flows in the LED row, a bypass circuit that is connected to an intermediate connection part of the LED row, and a current-limiting circuit that is connected to an end of the LED row, wherein the bypass circuit includes a first current-limiting component, the current-limiting circuit includes a second current-limiting component, the first current-limiting component is controlled on the basis of a voltage across the ends of the current detection resistor or a voltage that is obtained by dividing the voltage across the ends of the current detection resistor, and the second current-limiting component is controlled by the divided voltage that is obtained by dividing the current detection resistor.

主权项

1. An LED drive circuit in which the number of LEDs driven to emit light varies according to a commercial AC power supply voltage, comprising:
an LED array constructed by connecting a plurality of LEDs in series; a current detecting resistor for detecting a current flowing through said LED array; a bypass circuit connected to an intermediate connection point along said LED array; and a current limiting circuit connected to an end point of said LED array, wherein said bypass circuit includes a first current limiting device, said current limiting circuit includes a second current limiting device, and said first current limiting device is controlled based on a voltage developed across said current detecting resistor or a voltage obtained by dividing the voltage developed across said current detecting resistor, and said second current limiting device is controlled by a divided voltage obtained by voltage-dividing said current detecting resistor.