Time delay compensation of digital control for DC switchmode power supplies using prediction techniques

One of the major disadvantages of digital control is the limited control loop bandwidth due to the inherent time delay introduced by the zero-order-hold effect and the computational time delay. To alleviate this problem, two practical and straightforward predictive schemes based on linear extrapolation are proposed. With the proposed schemes, the computational time delay of the control loop is compensated and the control loop bandwidth is increased. It is shown that, using the proposed techniques, the control loop bandwidth can be increased up to two times that of the conventional digital control loop. Also, the computational overhead needed to implement these techniques is kept to the minimum. A lab prototype system of a 1 kV full bridge DC power supply was set up for the proof of concept. The prototype system operated at 10 kHz and was controlled by a TI TMS320F240 DSP (20-MHz 16-bit fixed-point). Simulation and experimental results prove the validity of the proposed techniques.