Low Cost Microcontroller Based Implementation of Robust Voltage Based Capacitor Charge Balance Control Algorithm

In this paper, a low cost microcontroller based control method utilizing the concept of capacitor charge balance is presented to achieve a near-optimal transient response for Buck converters. First, this paper presents a new derivation of practical charge balance equations based on simplified differential equations. The final implementation does not require complex calculations and accurate knowledge of the output filter LC parameter. The hardware implementation only requires the output voltage information so that no extra sensing circuitry is needed compared with voltage mode controller. Also, this algorithm can be simply extended to adaptive voltage positioning (AVP) application. Second, due to the simplicity of this algorithm, a low cost microcontroller unit (MCU) based controller can be implemented to shorten the developing period for users. Thirdly, unlike previous work, the proposed voltage based CBC (V-CBC) controller does not require accurate current sensor or fast analog-to-digital converter (ADC). Instead, to detect the critical time instant when the inductor current equals the new load current, a practical extreme voltage detector is introduced to capture the output voltage peak/valley information. Experimental prototype is built to verify the feasibility and advantage of the new method.