Inrush current limiting method based on buck+boost topology

Abstract

A cascaded buck+boost inrush limiter is claimed where the buck converter is only allowed to switch for very short times and stays turned on, or off, during steady state operation. The inrush limiter has a control system having a digital controller and an analog comparator for controlling the buck and boost converters. The system utilizes a single loop current feedback.

What is claimed is: 
     
         1 . A cascaded buck and boost controller connected to a buck and boost converters to control the buck and boost converters so the buck converter is allowed to switch for very short times and stays turned, or off, during steady stat operation, the cascaded buck and boost control comprising:
 i) a digital controller for receiving inductor current measurements for a duty cycle command from a single loop current feedback during operation, the control system operable such that when the duty cycle command equals zero, then the converters are off and when the duty cycle command is higher than zero but less than one the boost converter stays off but the buck converter goes from 0 to 100% duty, and when the duty cycle command is between one and two the buck stays at 100% and the boost goes from 0 to 100% duty; and   ii) an analog comparator for peak current detection and during operation if a peak current is detected the buck and boost converters switches are turned off until the next pulse-width modulated period.   
     
     
         2 . A controller for a cascaded buck and boost converter, the controller comprising:
 an input bridge;   a buck converter comprising a buck switch and diode, and the buck converter connected to the input bridge;   a boost converter comprising a boost switch and diode, and the boost converter connected to the buck converter; and   common passive components shared by the buck converter and the boost converter, the common passive components comprising a inductor and a capacitor.   
     
     
         3 . A switching controller for a power converter with a power stage having an inductor, comprising:
 current control means comprising a current loop, a pulse-width modulated (PWM) generator for a buck converter and a PWM generator for a boost converter, a buck converter power stage and a boost converter poser stage, an inductor, and a switching time monitor and operating with a value of the current loop output range between about zero and two, and when the value of the current loop output range is zero, a duty cycle of a pulse-width modulated buck converter is zero percent and a duty cycle of a pulse-width modulated boost converter is zero percent, and when the value of the current loop output range is greater than zero and less than one, the duty cycle of a PWM buck converter is zero to one hundred percent and the duty cycle of a PWM boost converter is zero percent, and when the value of the current loop output range is between one and two, the duty cycle of the PWM buck converter is about one hundred percent and the duty cycle of the PWM boost converter is about one hundred percent, and when a peak current value of the inductor current measurement of the power stage is above a predetermined limit, a peak current detector output will cause the buck pulse-width modulated generator and the boost PWM generator to turn off until the next PWM period, and if a switching time sensed by the switching time monitor is above a predetermined limit, the monitor output will cause the buck PWM generator and the boost PWM generator to turn off, and the current loop switches only one of the buck converter or the boost converter at a time; and   digital control means having a voltage loop an operating so the voltage loop approximately maintains a voltage represented by a voltage setpoint.   
     
     
         4 . A current controller for a power converter with a power stage having an inductor, comprising:
 current control means comprising a switching time monitor, a buck PWM generator and a boost PWM generator for controlling current; and   if a switching time sensed by the switching time monitor is above a predetermined limit, the monitor output will cause the buck PWM generator and the boost PWM generator to turn off.   
     
     
         5 . A switch for use with a buck and boost converter configuration, the switch comprising:
 an input bridge;   a buck converter comprising a buck switch and diode, and the buck converter connected to the input bridge;   a boost converter comprising a boost switch and diode, and the boost converter connected to the buck converter;   common passive components shared by the buck converter and the boost converter, the common passive components comprising a inductor and a capacitor; and   an analog comparator for peak current detection and during operation if a peak current is detected the buck and boost converters switches are turned off until the next pulse-width modulated period.