Automatic current limit adjustment for linear and switching regulators
AssigneeDialog Semiconductor GmbH
InventorsStefano Scaldaferri, Eric Marschalkowski, Christian Wolf
Life of this patent
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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 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.
Claims16
A method for maximizing DC power transferred by a power management unit to an electronic device comprising the steps of:
- (1) providing a power management unit comprising means to sense an input voltage and an output voltage, means to sense an input current, means to control the input current limit and means to compare voltages, and a control unit;
- (2) connecting a power source to said 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) ramping up the input current;
- (6) checking, if the input current is lower than the defined maximal allowable input current limit, and, if positive, repeat the check of step (6), otherwise go to step (7);
- (7) decreasing input current and go to step (6);
- (8) checking if an input voltage is higher than the defined input threshold voltage and, if positive go to step (9), else go to step (11);
- (9) checking, if the actual maximal allowable current limit is lower than the default value, and if negative, go to step (8), otherwise go to step (10);
- (10) increasing the maximal allowable input current limit and go to step (8);
- (11) decreasing the maximal allowable input current limit and go to step (8);
- (12) checking, if the input voltage is lower than the output voltage of the power management unit and lower than input threshold voltage, if negative, repeat step (12), otherwise go to step (13);
- and
- (13) disabling the power management unit.
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 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 a control block;
- said means of setting dynamically a maximum input current limit;
- a main input switch of the power management unit;
- and
- said control block controlling the operations of the power management unit including 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.
Dependencies are inferred from the claim text.