Abstract
In digital current mode controlled DC-DC converters, conventional current sensors might not provide isolation at a minimized price, power loss and size. Therefore, a current observer which can be realized based on the digital circuit itself, is a possible substitute. However, the observed current may diverge due to the parasitic resistors and the forward conduction voltage of the diode. Moreover, the divergence of the observed current will cause steady state errors in the output voltage. In this paper, an optimal current observer is proposed. It achieves the highest observation accuracy by compensating for all the known parasitic parameters. By employing the optimal current observer-based predictive current controller, a buck converter is implemented. The converter has a convergently and accurately observed inductor current, and shows preferable transient response than the conventional voltage mode controlled converter. Besides, costs, power loss and size are minimized since the strategy requires no additional hardware for current sensing. The effectiveness of the proposed optimal current observer is demonstrated experimentally.
Highlights
In recent years, predictive current control (PCC) was found to be a robust, fast and easy control strategy for digitally controlled DC-DC converters in continuous current mode (CCM)
A fast response PCC strategy is proposed by Chen et al [4], whereby the disturbance of the inductance current can be eliminated in two switching cycles, whether in the valley, peak or average current control modes
Compensation for the Sampled Voltage. It is a natural character of DC-DC converters that the output voltage contains ripples, so the sampled voltage may deviate from the average value of the output voltage, depending on the sampling point
Summary
Predictive current control (PCC) was found to be a robust, fast and easy control strategy for digitally controlled DC-DC converters in continuous current mode (CCM). The thermal drift is distinct and the accuracy could be low due to the mismatches between the filter and the power inductor [6,7] Another non-isolated current sensing technique uses the mirroring circuit, which is widely employed in integrated circuits. An easy feed forward CO was proposed in 2004 [17] It can effectively avoid the impact from the output voltage on the observed current. By employing compensations for both the observed current and the sampled voltage, the OCO-based PCC controller converges the observed current to the valley value of the inductor current, and eliminates the steady state error of the output voltage.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
