Charge-pump biased battery protection circuit
First Claim
1. A battery protection circuit for charging a battery from a charger and discharging said battery to a load, said circuit comprising:
- a pair of battery terminals for connecting said battery;
an input-output terminal for connecting at least one of said load and said charger;
a pass transistor having a first drain/source connection coupled to a given one of said battery terminals and a second drain/source connection coupled to said input-output terminal;
a charge-pump circuit having an output coupled to a gate of said pass transistor, wherein said charge pump circuit charges said gate of said pass transistor to a gate voltage such that a magnitude of a voltage between said gate of said pass transistor and said first drain/source connection is greater than a magnitude of a voltage across said battery terminals; and
a second charge pump having an output coupled to a body of said pass transistor, for charging said body of said pass transistor to a voltage having a polarity opposite a polarity of said gate voltage with respect to both of said drain/source terminals of said pass transistor.
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Accused Products
Abstract
A charge-pump biased battery protection circuit provides improved efficiency, reduced power dissipation, and reduced complexity in battery powered circuits. A charge pump is utilized to bias the gate of a single pass transistor such that the voltage between the pass transistor gate and the drain/source terminals of the pass transistor have a magnitude greater than the battery voltage, reducing the voltage drop across the pass transistor. The charge pump may be controlled in conformity with a sensed current through the pass transistor, so that at times of lower current loads, power is conserved. The bulk (body) of the pass transistor can be controlled using a resistor coupling a battery terminal to the bulk and a single switch coupling the bulk to a charger/load connection terminal, permitting a single pass transistor to be used for charging and discharging.
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Citations
19 Claims
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1. A battery protection circuit for charging a battery from a charger and discharging said battery to a load, said circuit comprising:
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a pair of battery terminals for connecting said battery; an input-output terminal for connecting at least one of said load and said charger; a pass transistor having a first drain/source connection coupled to a given one of said battery terminals and a second drain/source connection coupled to said input-output terminal; a charge-pump circuit having an output coupled to a gate of said pass transistor, wherein said charge pump circuit charges said gate of said pass transistor to a gate voltage such that a magnitude of a voltage between said gate of said pass transistor and said first drain/source connection is greater than a magnitude of a voltage across said battery terminals; and a second charge pump having an output coupled to a body of said pass transistor, for charging said body of said pass transistor to a voltage having a polarity opposite a polarity of said gate voltage with respect to both of said drain/source terminals of said pass transistor. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A battery protection circuit for charging a battery from a charger and discharging said battery to a load, said circuit comprising:
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a pair of battery terminals for connecting said battery; an input-output terminal for connecting at least one of said load and said charger; a pass transistor having a first drain/source connection coupled to a given one of said battery terminals and a second drain/source connection coupled to said input-output terminal; a first resistor connected between said given battery terminal and a bulk terminal of said pass transistor; a switch coupled between said input-output terminal and said bulk terminal; and a control circuit coupled to a control input of said switch, wherein said switch is set to a conducting state when a charging current is supplied to said input-output terminal to charge said battery and wherein said switch is set to a non-conducting state when a discharging current is supplied from said battery to said input-output terminal. - View Dependent Claims (9, 10)
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11. A method for protecting a battery when charging said battery from a charger and discharging said battery to a load, said method comprising:
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controlling a current passing between said battery and one of said charger and said load using a pass transistor; charging a gate of said pass transistor to a gate voltage such that a magnitude of a gate-to-drain voltage of said pass transistor is greater than a magnitude of a voltage across said battery; and charging a body of said pass transistor to a voltage having a polarity opposite a polarity of said gate voltage with respect to both drain/source terminals of said pass transistor. - View Dependent Claims (12, 13)
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14. A method for protecting a battery when charging said battery from a charger and discharging said battery to a load, said method comprising:
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controlling a current passing between said battery and one of said charger and load using a pass transistor; setting a body voltage of said pass transistor by a circuit having a first resistor coupling said body to said load and a switch coupling said body to said battery; opening said switch when said current is passing from said battery to said load; and limiting a current through said switch with a second resistor coupled in series with said switch. - View Dependent Claims (15)
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16. A battery protection circuit for charging a battery from a charger and discharging said battery to a load, said circuit comprising:
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a pair of battery terminals for connecting said battery; an input-output terminal for connecting at least one of said load and said charger; a pass transistor having a first drain/source connection coupled to a given one of said battery terminals and a second drain/source connection coupled to said input-output terminal; a charge-pump circuit having an output coupled to a gate of said pass transistor, wherein said charge pump circuit charges said gate of said pass transistor to a gate voltage such that a magnitude of a voltage between said gate of said pass transistor and said first drain/source connection is greater than a magnitude of a voltage across said battery terminals; a first resistor connected between said given battery terminal and a bulk terminal of said pass transistor; a switch coupled between said input-output terminal and said bulk terminal; and a control circuit coupled to a control input of said switch, wherein said switch is set to a conducting state when a charging current is supplied to said input-output terminal to charge said battery and wherein said switch is set to a non-conducting state when a discharging current is supplied from said battery to said input-output terminal. - View Dependent Claims (17)
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18. A method for protecting a battery when charging said battery from a charger and discharging said battery to a load, said method comprising:
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controlling a current passing between said battery and one of said charger and said load using a pass transistor; charging a gate of said pass transistor to a gate voltage such that a magnitude of a gate-to-drain voltage of said pass transistor is greater than a magnitude of a voltage across said battery; and setting a body voltage of said pass transistor by a circuit having a first resistor coupling said body to said load and a switch coupling said body to said battery; and opening said switch when said current is passing from said battery to said load.
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19. A method for protecting a battery when charging said battery from a charger and discharging said battery to a load, said method comprising:
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controlling a current passing between said battery and one of said charger and load using a pass transistor; setting a body voltage of said pass transistor by a circuit having a first resistor coupling said body to said load and a switch coupling said body to said battery; opening said switch when said current is passing from said battery to said load; and charging a body of said pass transistor to a voltage having a polarity opposite a polarity of said gate voltage with respect to both drain/source terminals of said pass transistor.
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Specification