ON Semiconductor’s parallel-to-series topology dynamically adjusts LED load voltage as the instantaneous bridge output voltage varies. While a switch-mode power supply (a buck converter) reconfigures the input voltage to match the load, this circuit reconfigures the load to match the input voltage. When the instantaneous input voltage is relatively low, the LEDs are configured in parallel. When the instantaneous input voltage is relatively high, the LEDs are configured in series.

The circuit is designed for input voltages between 100 Vac and 140 Vac. ON Semiconductor CCRs are used to provide constant LED current and to protect LEDs from over-voltage conditions. The circuit employs an additional CCR (shown as CCR2) to increase LED current at high voltages for improved PF and THD performance.