Final answer:
To design a buck-boost converter with specified parameters, one must perform iterative calculations to determine the switching frequency and values of inductor and capacitor, ensuring that output voltage ripple and inductor current variation are within given limits.
Step-by-step explanation:
To design a DC-DC buck-boost converter that outputs a voltage of -16 V from a 35 V source with a load current of 3 A, and has an output voltage ripple not exceeding 1% as well as an inductor current variation of no more than 1.5 A, we need to specify the switching frequency and calculate the values of the required components.
The ripple in output voltage is given by ΔV = (Vout * Ripple Percentage)/100. Assuming continuous mode operation and using the equation for the buck-boost converter we get, ΔI = (Vout * (1 - (Vout/Vin)) * D)/(L * fs), where ΔI is the inductor current ripple, D is the duty cycle, L is the inductance, and fs is the switching frequency.
By rearranging this equation and plugging in the given values, the inductor value can be obtained. Similarly, for the output voltage ripple, use the voltage ripple equation to find the capacitor value. To ensure 1.5 A current variation, the switching frequency can be adjusted. This process involves several iterative calculations and is based on the selected topology and component efficiency.