Patent ID: 9629214
Date: 2017-04-18
CPC Classifications: G09G,H05B,Y02B

Claim:
1. A method of controlling current on a light emitting device path, comprising: (a) providing a light emitting device path including one or more light emitting devices connected in series; (b) detecting the state of the light emitting device path according to a comparison between a node voltage on the light emitting device path and a predetermined reference voltage, wherein when the node voltage is lower than the predetermined reference voltage, it is determined that the light emitting device path is in a normal operation state wherein each light emitting device on the light emitting device path creates a normal voltage drop, and when the node voltage is higher than the predetermined reference voltage, it is determined that the light emitting device path is not in the normal operation state wherein the light emitting device path has a voltage drop lower than a total of the normal voltage drops; (c) conducting a relatively high current on the light emitting device path in the normal operation state, and conducting a relatively low or no current on the light emitting device path when the light emitting device path is not in the normal operation state, such that when the light emitting device path is connected to a voltage level for supplying power to the light emitting device path but the light emitting device path has a voltage drop lower than a total of the normal voltage drops, there is only low or no current on the light emitting device path; and (d) after the light emitting device path has been determined not in the normal operation state, checking whether the light emitting device path resumes to the normal operation state by determining whether the node voltage is lower than the predetermined reference voltage.