An integrated DC-AC inverter for electroluminescent lamps

An integrated DC to AC converter is proposed based on the Sinusoidal Pulse Width Modulation (SPWM) control principle in order to implement the conversion process. The proposed circuit consists of 4 stages. The first stage is a DC-DC converter to boost up the V_dd voltage. A 5-stage Dickson charge pump has been chosen in order to achieve a maximum voltage gain of 6V_dd. The second stage is an H-bridge, which receives the output voltage of the Dickson charge pump, for inverting the DC voltage to an SPWM signal. It consists of 4 MOS switches whose control is performed by the control unit, which produces two control signals. The control stage consists of two comparators; each comparator compares a sinusoidal signal with a triangular signal and produces a PWM waveform for controlling the H-bridge. The last unit is a low-pass filter, for converting the SPWM signal to an AC output voltage. The use of the output filter is very important for reducing the Total Harmonic Distortion (THD) of the DC-AC inverter output-voltage waveform. The proposed converter was designed by using a 0.35um high voltage technology, with conversion potential from V_dd=1V-5V to V_out=42,22V_P-P-311,8V_P-P (110V_RMS) at frequency f_out⁼60Hz-2000Hz for driving electroluminescent (EL) lamps. The proposed implementation of the integrated DC-AC converter exhibits lower power consumption, lower input voltage and smaller silicon area compared to previous ones, while keeping THD and output ripple at very low values.