Drive circuit for at least one LED strand

• US 7,061,394 B2
• Filed: 06/10/2003
• Issued: 06/13/2006
• Est. Priority Date: 06/10/2002
• Status: Active Grant

• Current Assignee: ABL IP Holding LLC (Acuity Brands, Inc.)
• Original Assignee: Patent-Treuhand-Gesellschaft Fur Elektrische Gluhlampen mbH (Ams-Osram AG)
• Inventors: Biebl, Alois
• Primary Examiner(s): Lefkowitz, Sumati
• Assistant Examiner(s): Amadiz, Rodney
• Application Number:
  US10/457,486
• Publication Number:
  US 20030227265A1
• Time in Patent Office: 1,099 Days
• Field of Search: 345 82- 83, 315/291, 340/815.45
• US Class Current: 340/815.45
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/375 using buck topology
• CPC Class Codes: H05B 45/38 using boost topology
• CPC Class Codes: H05B 45/385 using flyback topology

Abstract

Drive circuit for at least one LED strand, with a switch being arranged in series with each LED strand and with each LED strand having a supply connection via which it can be connected to a supply voltage, in which case each switch can be driven so as to allow a current to flow in the associated LED strand, having a first control loop which is designed to drive the switch of the at least one LED strand such that an adjustable mean value is achieved for the current flowing through the LED strand, with the drive circuit also having: a second control loop which is designed to provide a supply voltage for the at least one LED strand as a function of the peak value of the current flowing through the at least one LED strand.

Claims

1. A drive circuit for at least one LED strand, with a switch being arranged in series with each LED strand and with each LED strand having a supply connection via which it can be connected to a supply voltage, in which case each switch can be driven so as to allow a current to flow in the associated LED strand, having a first control loop which is designed to drive the switch of the at least one LED strand such that an adjustable mean value is achieved for the current flowing through the LED strand, characterized in that the drive circuit also has a second control loop which is designed to provide a supply voltage for the at least one LED strand as a function of the peak value of the current flowing through the at least one LED strand, wherein the first and the second control loops are designed to determine the actual values for the mean value and the peak value of only a first LED strand, with an at least second LED strand being operated on the basis of the actual values determined for the first LED strand.

2. A drive circuit for at least one LED strand, with a switch being arranged in series with each LED strand and with each LED strand having a supply connection via which it can be connected to a supply voltage, in which case each switch can be driven so as to allow a current to flow in the associated LED strand, having a first control loop which is designed to drive the switch of the at least one LED strand such that an adjustable mean value is achieved for the current flowing through the LED strand, characterized in that the drive circuit also has a second control loop which is designed to provide a supply voltage for the at least one LED strand as a function of the peak value of the current flowing through the at least one LED strand, wherein:

the second control loop has a DC/DC converter whose output voltage is coupled to the at least one supply connection, and

the second control loop has a third comparator which is used to compare the actual value of the peak value of the current flowing through the at least one LED strand with a nominal value which can be preset, with the output signal from the third comparator being coupled to the first input of a fourth comparator, to whose second input a triangular waveform signal is applied, with the output signal from the fourth comparator being coupled to the DC/DC converter.