Universal battery charger
First Claim
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1. A universal battery charger for charging batteries with different number of cells connected in series, comprising:
- a power supply circuit that produces a DC output voltage, the power supply circuit including a first switch circuit to control a level of the DC output voltage;
a second switch that is connected between the power supply circuit and the battery and is turned ON to allow charging of the battery and OFF to interrupt the power supply circuit from the battery;
an output voltage detecting circuit that detects a voltage level of the DC output voltage of the power supply circuit;
a battery voltage detecting circuit that detects a voltage level across the battery;
an output voltage setting circuit that produces a predetermined number of voltages different in level;
a control unit that receives a detected signal from the battery voltage detecting circuit and sends a control signal to the output voltage setting circuit to select one of the predetermined number of voltages as a reference voltage; and
an output voltage control circuit that compares the reference voltage with the voltage level detected by the output voltage detecting circuit to produce an output signal corresponding to a difference between the reference voltage and the detected voltage level, the output signal of the output voltage control circuit being applied to the first switch to control the level of the DC output voltage of the power supply circuit;
wherein the control unit includes means for controlling the second switch to turn ON and OFF, and means for producing the control signal applied to the output voltage setting circuit to select a voltage level which is close to the detected voltage level across the battery when the second switch is turned OFF and the control unit detects that the battery is connected to the battery charger.
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Abstract
To provide a universal battery charger with low power consumption during a standby condition and a rush current suppressing capability at the time of commencement of charging, a voltage slightly larger than a battery voltage is produced and applied to the battery. Thereafter, the highest voltage is produced and applied to the battery to charge the same. When the battery is unloaded from the battery charger, the lowest voltage is produced to save power consumption.
29 Citations
15 Claims
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1. A universal battery charger for charging batteries with different number of cells connected in series, comprising:
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a power supply circuit that produces a DC output voltage, the power supply circuit including a first switch circuit to control a level of the DC output voltage; a second switch that is connected between the power supply circuit and the battery and is turned ON to allow charging of the battery and OFF to interrupt the power supply circuit from the battery; an output voltage detecting circuit that detects a voltage level of the DC output voltage of the power supply circuit; a battery voltage detecting circuit that detects a voltage level across the battery; an output voltage setting circuit that produces a predetermined number of voltages different in level; a control unit that receives a detected signal from the battery voltage detecting circuit and sends a control signal to the output voltage setting circuit to select one of the predetermined number of voltages as a reference voltage; and an output voltage control circuit that compares the reference voltage with the voltage level detected by the output voltage detecting circuit to produce an output signal corresponding to a difference between the reference voltage and the detected voltage level, the output signal of the output voltage control circuit being applied to the first switch to control the level of the DC output voltage of the power supply circuit; wherein the control unit includes means for controlling the second switch to turn ON and OFF, and means for producing the control signal applied to the output voltage setting circuit to select a voltage level which is close to the detected voltage level across the battery when the second switch is turned OFF and the control unit detects that the battery is connected to the battery charger. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of charging a battery using a universal battery charger comprising:
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a power supply circuit that produces a DC output voltage which includes a first switch circuit to control a level of the DC output voltage a second switch that is connected between the power supply circuit and a battery and is turned ON to allow charging of the battery and OFF to interrupt the power supply circuit from the battery; an output voltage detecting circuit that detects a voltage level of the DC output voltage; a battery voltage detecting circuit that detects a voltage level across the battery; an output voltage setting circuit that produces a predetermined number of reference voltages different in level, the reference voltages including a first level, a second level lower than the first level and a third level lower than the second level; a control unit that receives a detected signal from the battery voltage detecting circuit and sends a control signal to the output voltage setting circuit to select one of the reference voltages; and an output voltage control circuit that compares the selected reference voltage with the voltage level detected by the output voltage detecting circuit to produce an output signal to control the level of the DC output voltage of the power supply circuit; wherein the method comprises; first step of selecting a voltage having the third level produced by the output voltage setting circuit when the control unit detects that the second switch is rendered OFF; second step of detecting the voltage across the battery by the battery voltage detecting circuit; third step of selecting one of the first, second and third voltage levels which is higher than the detected battery voltage; and fourth step of applying the selected voltage level to the output voltage control circuit to control the level of the DC output voltage of the power supply circuit; and fifth step of controlling the second switch to turn ON. - View Dependent Claims (14, 15)
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Specification