Cable Voltage Drop Compensation For Battery Chargers
AssigneeFairchild Semiconductor Corporation
InventorHangseok CHOI
Life of this patent
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Abstract
A battery charger may be configured to charge a battery by way of a charging cable. A DC gain of a voltage control loop of the battery charger may be limited to a predetermined value to compensate for voltage drop on the charging cable. For example, a DC gain of an error amplifier on the voltage control loop may be limited to a predetermined value for cable voltage drop compensation. The error amplifier may use a reference signal that is generated as a function of the error signal. The DC gain of the error amplifier may be limited by connecting a resistor to form an RC circuit on an output node of the error amplifier.
Claims20
A battery charger comprising:
- a transformer having a primary winding and a secondary winding;
- a transistor configured to couple the primary winding to ground when the transistor is ON and to decouple the primary winding from ground when the transistor is OFF, the transistor being configured to receive an inductor current through the primary winding when the transistor is ON;
- a comparator configured to generate a control signal to control switching of the transistor by comparing a sense signal indicative of the inductor current to an error signal indicative of a level of an output voltage generated by the battery charger to charge a battery by way of a charging cable;
- and
- an error amplifier configured to generate the error signal by comparing a sampling of the output voltage to a reference voltage, the reference voltage being configured to change as a function of the error signal, the error amplifier being configured to compensate for voltage drop on the charging cable by having a predetermined and limited DC gain.
An electrical circuit for charging a battery, the circuit comprising:
- an error amplifier in a voltage control loop of a battery charger that is configured to charge a battery by way of a charging cable, the error amplifier being configured to generate an error signal by comparing a sampled output voltage indicative of an output voltage of the battery charger to a reference voltage, a DC gain of the voltage control loop being limited to a predetermined value to compensate for voltage drop on the charging cable and develop a regulated battery voltage to charge the battery;
- a reference voltage generator configured to generate the reference voltage as a function of the error signal;
- and
- a comparator configured to generate a control signal to control switching of the transistor and generation of the output voltage by comparing the error signal to a sense signal indicative of inductor current flowing through a primary winding of a transformer of the battery charger.
A method of compensating for voltage drop on a charging cable coupling a battery charger to a rechargeable battery, the method to be performed by an electrical circuit and comprising:
- sensing an output voltage of the battery charger to generate a sampled output voltage;
- comparing the sampled output voltage to a voltage reference to generate an error voltage using an error amplifier, the error amplifier having a limited DC gain;
- adjusting the voltage reference as a function of the error voltage;
- comparing the error voltage to a sense voltage indicative of inductor current on a primary winding of a transformer to control generation of the output voltage;
- and
- charging the rechargeable battery with a battery voltage presented by the output voltage through the charging cable, the DC gain of the error amplifier being configured to generate the battery voltage to compensate for voltage drop on the charging cable.
Dependencies are inferred from the claim text.