This concept was executed by using buck, boost, and buck-boost converters as the current regulator for a low power application. However, for high power applications the use of buck, boost, and buck-boost regulators is limited, since increasing load results in a reduction in switching frequency, resulting in bulky reactive components. Further, it is difficult to get zero voltage switching, and lifespan is limited due to the presence of electrolytic capacitors at load terminals. The flyback converter can be used for low power applications; however, it is not advisable to use this converter for output power above 60-70W, as it requires a large transformer which in turn reduces overall efficiency. Dimming control is often needed to control the illumination level of LED light for the human need to create a comfortable environment. Moreover, dimming operations result in reduced power consumption and produce less heat hence increasing LED lifespan and optimizing running costs. Therefore, dimming control is essential in LED lighting applications. The illumination of LED is directly related to its average current. Therefore, dimming control techniques such as amplitude modulation (AM), pulse width modulation (PWM), hybrid AM/PWM technique, integral control and double PWM control are used to regulate the average output current.
These control methods have their own merits and demerits. This work uses the two-source concept of driving LEDs; one is to supply cut-in voltage which is directly supplied through the dc bus and other is the regulating voltage supplied to the load through a full-bridge series resonant converter as current regulator. The proposed converter has several benefits such as reduced component count, compact size, and reduction of electrolytic capacitors, whereas zero voltage switching results in improved efficiency. The dimming feature was achieved by using double pulse width modulation control.
The proposed converter configuration is illustrated in fig. \ref{490782}. The bus voltage (Vbus) can be obtained through either an AC grid by using an AC-DC converter along with a filter or a battery source. A full-bridge LC series resonant converter, operating as a current regulator, is placed between the LED load and the dc voltage bus. The power to the LED load is supplied through a full-bridge LC resonant converter along with the dc bus, rather than through a resonant converter alone.