The LC series resonant converter consists of a tank circuit supplied through a full-bridge inverter. A capacitor is connected at the end of the converter output for filtering purposes. This regulating voltage (Vc) from the LC series resonant converter is added along with the bus voltage and supplied to the LED load. The cut-in voltage is supplied directly through bus voltage (Vbus) and the forward regulating current is supplied through the full-bridge LC resonant converter. This regulating current is controlled by using double pulse width modulation control. The voltage supplied by the full-bridge LC series resonant converter is very low compared to the cut-in voltage supplied directly through bus voltage. Hence, switching losses can be greatly reduced on each component, ensuring high power efficiency.
The resonant frequency of the full-bridge LC circuit is decided by the values of the resonant inductor (Lr) and capacitor (Cr) present in the tank circuit. Zero-voltage-switching (ZVS) and zero-current-switching (ZCS) can be decided by resonant frequency (fo) if the switching frequency (fs) is higher than resonant frequency (fo) ZVS can be achieved, and the switching frequency is lesser than resonant frequency ZCS can be achieved. A resonant capacitor (Cr) is added in the circuit to negotiate the impedance effect caused against the power flow due to parasitic inductance and supplying voltage with a frequency closer to resonant frequency to the tank circuit.  
2.1  Operating modes
Analysis of the circuit is simple, as the circuit is divided into two major parts. The primary part is the bus voltage (Vbus), which supplies the majority of the voltage to the load, satisfying the forward voltage drop of the LED load. The second part is the full-bridge LC series resonant converter, which supplies the control voltage, regulating the LED output current (Io). The resonant converter output (Vc) is connected in series with the bus voltage as shown in fig. \ref{644917}.