DC-DC Buck Converter Driver with Variable Off-Time Peak Current Mode Control

Power converters in automotive industries are needed to source electronic devices. DC-DC Buck converter allows to drive loads ensuring their safety operation taking the car battery voltage as an input to generate a sub-voltage or current. By means of a control loop, the system makes sure that the output variable has the desired value in each operation condition. The Peak Current Mode Control (PCMC) is used to control the output current. Whenever the current reaches the reference maximum value (by load specs), the system acts to lower it. Intrinsically over-current protection is guaranteed. The paper presents an improvement of the basic PCMC, where, instead of just controlling the peak value, the loop controls also the average, more delicate feature, resulting in a more reliable driver system. The circuit is able to source 3A average-4.5V from a 13.5V nominal battery voltage, with a peak current of 3.3A and a 0.6A maximum ripple (3 10%A). The concept has been designed and simulated on Simulink and then tested on hardware using dSpace, a Rapid Control Prototyping set-up.