Improved performance current regulated delta modulator in series resonant inverter for induction heating application

An improved version of the current regulated delta modulator (CRDM) is proposed to obtain a high performance current controller for the zero current switched (ZCS) series resonant inverter (SRI). Especially, the induction heating applications for ZCS SRI can provide a high power density due to the near-zero switching loss and the minimized transformer rating. This inverter, however, requires the use of discrete time switching strategies. A dynamic current model of the inverter is derived and used for the current controller design. A CRDM is considered first for the discrete pulse modulated current regulator. Since the CRDM shows a nonzero steady-state error or offset, it is modified by the additional reset integrator. This reset integrator which becomes reset if the current error is larger than the predetermined error band is designed in terms of the integrator gain and error band using the concept of quasi-sliding mode. With the proposed scheme, a near-zero offset, robust response, and small overshoot are available. The performance is verified through the computer simulations