An electrosurgical generator comprising: a power converter coupled to an electrical energy source and configured to generate electrosurgical energy, the power converter including: a boost converter configured to convert a first direct current from the electrical energy source to a second direct current; and a phase-shifted pulse width modulation (PS-PWM) resonant inverter configured to invert the second direct current to an alternating current; a plurality of sensors configured to sense voltage and current waveforms of the generated electrosurgical energy; and a controller coupled to the power converter and the plurality of sensors , the controller comprising: a signal processor configured to determine a tissue impedance based on the sensed voltage and current waveforms; and an output controller configured to select one among a plurality of output characteristics based on the determined tissue impedance, and to generate a first control signal to control the boost converter and a second control signal to control the PS-PWM resonant inverter , according to the selected output characteristic, wherein a switching frequency of the boost converter is greater than a switching frequency of the PS-PWM resonant inverter and the switching frequency of the boost converter is an integer multiple of the switching frequency of the PS-PWM resonant inverter. a power converter coupled to an electrical energy source and configured to generate electrosurgical energy, the power converter including: a boost converter configured to convert a first direct current from the electrical energy source to a second direct current; and a phase-shifted pulse width modulation (PS-PWM) resonant inverter configured to invert the second direct current to an alternating current; a boost converter configured to convert a first direct current from the electrical energy source to a second direct current; and a phase-shifted pulse width modulation (PS-PWM) resonant inverter configured to invert the second direct current to an alternating current; a plurality of sensors configured to sense voltage and current waveforms of the generated electrosurgical energy; and a controller coupled to the power converter and the plurality of sensors , the controller comprising: a signal processor configured to determine a tissue impedance based on the sensed voltage and current waveforms; and an output controller configured to select one among a plurality of output characteristics based on the determined tissue impedance, and to generate a first control signal to control the boost converter and a second control signal to control the PS-PWM resonant inverter , according to the selected output characteristic, wherein a switching frequency of the boost converter is greater than a switching frequency of the PS-PWM resonant inverter and the switching frequency of the boost converter is an integer multiple of the switching frequency of the PS-PWM resonant inverter. a signal processor configured to determine a tissue impedance based on the sensed voltage and current waveforms; and an output controller configured to select one among a plurality of output characteristics based on the determined tissue impedance, and to generate a first control signal to control the boost converter and a second control signal to control the PS-PWM resonant inverter , according to the selected output characteristic, wherein a switching frequency of the boost converter is greater than a switching frequency of the PS-PWM resonant inverter and the switching frequency of the boost converter is an integer multiple of the switching frequency of the PS-PWM resonant inverter. <EOS>