LED string driver arrangement with non-dissipative current balancer
View Patent ↗A solid state lighting driver arrangement exhibiting a plurality of LED strings receiving power from a single power source, the single power source providing a discontinuous current, wherein a plurality of first windings are provided, each associated with a particular LED string and coupled to provide current balancing between the various LED strings. The discontinuous current resets the windings during the off time or during a reversal period. In one particular embodiment, a second winding is magnetically coupled to each of the first windings, and the second windings are connected in a closed in-phase loop. In another particular embodiment, at least two of the first windings are magnetically coupled to each other, thus ensuring a balance between current in each LED string.
1. A solid state lighting driver arrangement comprising:
a bridge converter comprising a power transformer, a plurality of electronically controlled switches and a capacitor, the capacitor arranged in cooperation with the plurality of electronically controlled switches so as to prevent the flow of a steady state direct current through the primary winding of the power transformer, the bridge converter arranged to receive an input direct current voltage potential and provide an alternating current output across a secondary winding of the power transformer;
a plurality of light emitting diode (LED) strings, a first end of each of the plurality of LED strings coupled to the center tap of said secondary winding of said power transformer; and
a balancer transformer with a pair of magnetically coupled center tapped windings, a second end of each of the plurality of LED strings coupled to a respective end of one of the first and second windings of said balancer transformer such that power on each half cycle output by the bridge converter is balanced between the LED strings receiving power during that half cycle by said respective balancer transform winding, and that power between the half cycles output by the bridge converter is balanced between the LED strings receiving power during each half cycle by said balancer transformer,
a first end of the secondary winding of the power transformer coupled to the center tap of the first winding of said balancer transformer and a second end of the secondary winding of the power transformer coupled to the center tap of the second winding of said balancer transformer.
2. A solid state lighting driver arrangement comprising:
a bridge converter comprising a power transformer, a plurality of electronically controlled switches and a capacitor, the capacitor arranged in cooperation with the plurality of electronically controlled switches so as to prevent the flow of a steady state direct current through the primary winding of the power transformer, the bridge converter arranged to receive an input direct current voltage potential and provide an alternating current output across a secondary winding of the power transformer;
a first and a second light emitting diode (LED) string, one end of each of the first and second LED strings coupled to the center tap of said secondary winding of said power transformer, and
a balancer transformer with a first and second magnetically coupled center tapped windings, a second end of said first LED string coupled to the center tap of the first winding of said balancer transformer, a second end of said second LED string coupled to the center tap of the second winding of said balancer transformer,
the first end of the secondary winding of the power transformer coupled to a first end of the first winding of said balancer transformer and to a second end of the second winding of said balancer transformer;
the second end of the secondary winding of the power transformer coupled to a second end of the first winding of said balancer transformer and to a first end of the second winding of said balancer transformer.
3. The solid state lighting driver arrangement according to claim 2 , wherein said coupling of the first end of the secondary winding of the power transformer to the first end of the first winding of said balancer transformer and to the second end of the second winding of said balancer transformer is via respective unidirectional electronic valves.
4. A solid state lighting driver arrangement comprising:
a bridge converter comprising a power transformer, a plurality of electronically controlled switches and a capacitor, the capacitor arranged in cooperation with the plurality of electronically controlled switches so as to prevent the flow of a steady state direct current through the primary winding of the power transformer, the bridge converter arranged to receive an input direct current voltage potential and provide an alternating current output across a secondary winding of the power transformer;
a first, second, third and fourth light emitting diode (LED) string, one end of each of said first and second LED strings coupled to a first end of the secondary winding of the power transformer, one end of each of said third and fourth LED strings coupled to a second end of the secondary winding of the power transformer, and
a balancer transformer with a first and second magnetically coupled center tapped windings, a second end of each of said first, second, third and fourth LED strings coupled to a respective end of one of said first and second windings of said balancer transformer,
the center tap of each of said first and second windings of said balancer transformer coupled to the center tap of said power transformer.
5. The solid state lighting driver arrangement according to claim 4 , wherein said coupling said first, second, third and fourth LED strings to the respective end of one of said first and second windings of said balancer transformer comprises: a second end of said first LED string coupled to a first end of said first winding of said balancer transformer a second end of said second LED string coupled to a second end of said first winding of said balancer transformer; a second end of said third LED string coupled to a first end of said second winding of said balancer transformer; a second end of said fourth LED string coupled to a second end of said second winding of said balancer transformer.