Power management system and method for a portable device
First Claim
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1. A power management system for a portable device, comprising:
- a power management controller that compares an input voltage provided by a battery of the portable device to a shutdown threshold and initiates a shutdown of the portable device when the input voltage falls below the shutdown threshold;
a voltage monitoring switch having an output that connects first or second inputs to the power management controller in response to a control input, the first input connected to a positive battery terminal of the battery of the portable device, the second input connected to a voltage source that is higher than the shutdown threshold, wherein the voltage monitoring switch alternately connects either the first input or the second input to the output responsive to a control signal provided to the control input;
a current sense circuit that provides the control signal to the voltage monitoring switch based on an input current through the positive battery terminal of the portable device, wherein when the input current exceeds a high current threshold, the circuit provides the control signal at a level that causes the voltage monitoring switch to connect the second input to the output, and wherein the control signal is provided to cause the voltage monitoring switch to connect the first input to the output otherwise;
a boost converter that provides a boost voltage from the battery voltage provided at the positive battery terminal;
a high voltage circuit powered by the boost converter;
a battery voltage circuit; and
a boost switch that is responsive to the control signal provided by the current sense circuit and connects the battery voltage circuit to a battery voltage provided by the positive battery terminal when the input current is below the high current threshold and connects the battery voltage circuit to the boost voltage provided by the boost converter when the input current exceeds the high current threshold.
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Abstract
A method and circuit for avoiding a low voltage shutdown in a portable device due to a low voltage falsely indicating a discharged battery employs an input current sensing circuit to determine when a high current is being drawn by the portable device. When the portable device is drawing a high current from the battery, the shutdown function is at least temporarily suppressed. If, during the high current event, the battery behavior indicates that it is actually near fully discharged, the shutdown functionality can be enabled to shut down the portable device.
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Citations
10 Claims
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1. A power management system for a portable device, comprising:
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a power management controller that compares an input voltage provided by a battery of the portable device to a shutdown threshold and initiates a shutdown of the portable device when the input voltage falls below the shutdown threshold; a voltage monitoring switch having an output that connects first or second inputs to the power management controller in response to a control input, the first input connected to a positive battery terminal of the battery of the portable device, the second input connected to a voltage source that is higher than the shutdown threshold, wherein the voltage monitoring switch alternately connects either the first input or the second input to the output responsive to a control signal provided to the control input; a current sense circuit that provides the control signal to the voltage monitoring switch based on an input current through the positive battery terminal of the portable device, wherein when the input current exceeds a high current threshold, the circuit provides the control signal at a level that causes the voltage monitoring switch to connect the second input to the output, and wherein the control signal is provided to cause the voltage monitoring switch to connect the first input to the output otherwise; a boost converter that provides a boost voltage from the battery voltage provided at the positive battery terminal; a high voltage circuit powered by the boost converter; a battery voltage circuit; and a boost switch that is responsive to the control signal provided by the current sense circuit and connects the battery voltage circuit to a battery voltage provided by the positive battery terminal when the input current is below the high current threshold and connects the battery voltage circuit to the boost voltage provided by the boost converter when the input current exceeds the high current threshold. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A portable device, comprising:
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a positive battery terminal and a negative battery terminal, wherein a battery voltage is present between the positive battery terminal and the negative battery terminal when a battery is connected to the portable device; a current sense circuit having an output that asserts a control signal when an input current through the positive battery terminal of the portable device exceeds a high current threshold; a power management controller that compares an input voltage of the battery to a shutdown threshold and initiates a shutdown of the portable device when the input voltage falls below the shutdown threshold; a voltage monitoring switch having a first input connected to the positive battery terminal, a second input connected to a voltage source that provides a voltage higher than the shutdown threshold, an output that provides the input voltage to the power management circuit, and a control input that receives the control signal, wherein the voltage monitoring switch normally connects the battery terminal as the input voltage to the power management circuit and switches the input voltage to the voltage source when the control signal is asserted; a boost converter that provides a boost voltage from a battery voltage provided at the positive battery terminal; a high voltage circuit powered by the boost converter; a battery voltage circuit; and a boost switch that is responsive to the control signal provided by the current sense circuit and connect the battery voltage circuit to a battery voltage provided by the positive battery terminal when the input current is below the high current threshold and connects the battery voltage circuit to the boost voltage provided by the boost converter when the input current exceeds the high current threshold. - View Dependent Claims (8, 9, 10)
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Specification