LED converter with adaptive PFC and resonant converter

摘要

The invention provides an LED converter for operating a load comprising at least one LED series with at least one LED, preferably with multiple LEDs, wherein the LED converter on the primary side comprises a resonant converter supplied with a direct current voltage. Said converter has a half-bridge constructed of two reciprocally clocked switches and providing a supply voltage for the LED series through a serial/parallel resonance circuit connected to the midpoint of said bridge. The LED converter has a control unit that is arranged for adjusting the clocking frequency of the half bridge. To control or regulate the power transferred by the LED converter to the LED series, the control unit is arranged to vary the frequency of the clocking in a frequency corridor that is delimited on at least one side, and to vary the amplitude of the direct current voltage supplying the resonant converter if a change of the load and/or the change of a setpoint value for the power would lead to a frequency operating point outside the frequency corridor.

主权项

1. An LED converter (10) for operating a load comprising at least one LED string (6) having a plurality of LEDs, wherein
the LED converter (10) comprises, on the primary side, a resonant converter (1) to which a DC voltage (Vbus) is supplied, the LED converter (10) further comprises a half-bridge formed with two alternately clocked switches (S1, S2), which half-bridge provides a supply voltage for the LED string (6) via a series or parallel resonant circuit connected to a center point of said half-bridge, wherein the LED converter (10) has a control unit (2), which is configured to control or regulate the power transmitted by the LED converter (10) to the LED string (6), to vary a frequency (fsw) of the clocking in a frequency corridor (fopt) that is delimited on at least one side, and to vary the amplitude of the DC voltage (Vbus) supplying the resonant converter (1) if at least one of: a change in the load or if a variation of a setpoint value for the power (I*) would result in a frequency working point outside of the frequency corridor (fopt) and wherein the control unit (2) is configured to determine a feedback variable in the resonant converter (1) and to set the frequency (fsw) of the clocking on the basis of the feedback variable, wherein the feedback variable is a variable which reflects the power transmitted by the resonant converter (1), and wherein the feedback variable is a ratio of a current (Isense) through the resonant converter to a voltage (Vshunt) in the resonant converter (1) or an electrical parameter reflecting said current to voltage ratio.