US 2012/0268094 A1 · Analog current limit adjustment for linear and switching regulators

Abstract

Circuits and methods for dynamic adjustment of the current limit of a power management unit to avoid unwanted automatic interruption of the power flow have been disclosed. The invention can be applied to switched and linear DC-to-DC converters. The power management unit is automatically adjusted to the output resistance of a power source (including interconnect resistance). The invention maximizes the time and hence the power transferred from a power management unit to the system (including the battery, in case of battery operated systems). The input current is reduced, thus increasing the input voltage in case of a high voltage drop across the internal resistance including interconnections between power source and power management unit.

Claims13

Dependent claims

A method for dynamic adjustment of a current limit of a power management unit comprising the steps of:

(1) providing a power management unit comprising a control unit, voltage comparing means, current comparing means, and a controlled current source;
(2) connecting a power source to the power management unit;
(3) setting a maximal allowable input current limit to a default value;
(4) enabling power transfer between a power source and a load if the input voltage is higher than a threshold voltage and there is sufficient overhead between input voltage and output voltage;
(5) checking if an input voltage is lower than a defined threshold voltage Vin_low and, if so, go to step (6), else repeat step (5);
(6) checking if there is sufficient overhead between input voltage and output voltage if so, go to step (7), otherwise go to step (8);
(7) reducing input current limit and go to step (5);
and
(8) disabling the power management unit.

6 more elements

A power management unit enabled for dynamic adjustment of an input current limit comprising:

a first voltage comparator, comparing an input voltage of the power management unit with a threshold voltage, wherein its output is used by a means of setting dynamically a maximum input current limit;
a second voltage comparator, comparing an output voltage of the power management unit increased by an overhead voltage with said input voltage wherein its output is used by said means of setting dynamically a maximum input current limit;
a current comparator, comparing said input current with a reference current wherein its output is an input to said means of setting dynamically a maximum input current limit;
a means to limit said input current controlled by said means of setting dynamically a maximum input current limit;
and
said means of setting dynamically a maximum input current limit, wherein said maximum current limit depends upon the outputs of said first and second voltage comparators.

3 more elements

Dependencies are inferred from the claim text.

Analog current limit adjustment for linear and switching regulators

Life of this patent

Analog current limit adjustment for linear and switching regulators

Life of this patent

Abstract

Claims13