Battery charger

• US 4,777,424 A
• Filed: 09/08/1986
• Issued: 10/11/1988
• Est. Priority Date: 09/13/1985
• Status: Expired due to Term

• Current Assignee: Asahi Matsushita Electric Works Ltd. (Panasonic Holdings Corporation)
• Original Assignee: Asahi Matsushita Electric Works Ltd. (Panasonic Holdings Corporation)
• Inventors: Sakamura, Yoshinobu, Tanimizu, Makoto
• Primary Examiner(s): Salce, Patrick R.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/904,593
• Time in Patent Office: 764 Days
• Field of Search: 320/21, 320/39, 320/40, 320/DIG. 1, 323/222, 323/906, 307/45, 363/21, 363/59
• US Class Current: 320/140
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H02J 2207/20 Charging or discharging characterised by the power electronics converter
• CPC Class Codes: H02J 7/342 The other DC source being a battery actively interacting with the first one, i.e. battery to battery charging with circuits for polarity protection H02J7/0034
• CPC Class Codes: H02M 3/1563 without using an external clock H02M3/158 takes precedence
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y10S 320/21 State of charge of battery

Abstract

An improved battery charger for charging a battery from a dc power source includes a DC-to-DC converter comprising a transformer and a switching transistor connected in series with the primary winding of the transformer. The transformer has its primary winding connected to the dc power source and has its secondary winding connected to the battery to be charged. The switching transistor is controlled to be alternately turned on and off in order to develop across the secondary winding an induce voltage which is rectified to be applied to the battery for charging the same. The secondary winding of the transformer is electrically connected to the dc voltage source in such a manner that the induced voltage of the transformer is in an additive relation with the terminal voltage of the dc voltage source.

Claims

1. In a battery charger for charging a battery from a dc voltage source which comprises a DC-to-DC voltage converter connected between the dc voltage source and the battery to be charged,

said DC-to-DC voltage converter comprising:

a transformer having a primary winding connected to the dc voltage source and having a secondary winding connected to the battery;

switching means connected in series with the primary winding of the transformer and so controlled as to be alternately turned on and off for developing across the secondary winding an induced ac voltage;

rectifying means rectifying the induced ac voltage into the dc voltage which is applied to the battery for supplying a charge current into the battery, wherein said rectifying means is a half-wave rectifier diode which is connected in circuit with an anode coupled to one end of the secondary winding of said transformer and with a cathode coupled to the positive side of the battery;

a resistor and an over-charge indicator connected in series, said over-charge indicator being a light emitting diode which is connected with its anode coupled to said resistor which is coupled to the positive side of the battery and said over-charge indicator having its cathode connected to the other end of the secondary winding of the transformer so as to produce an alarm light indicative of current drawn back to the dc power source from the battery being charged when the battery is charged up to a voltage level above a reference level determined by said resistor in series with the over-charge indicator;

said secondary winding being connected in series with the dc voltage source in such a manner that the dc voltage obtained by rectifying the ac voltage induced across the secondary winding of the transformer is in an additive relation with the terminal voltage of the dc voltage source which is applied to the battery for charging the battery.

2. In a battery charger for charging a battery from a dc voltage source which comprises a DC-to-DC voltage converter connected between the dc voltage source and the battery to be charged,

said DC-to-DC voltage converter comprising:

a transformer having a primary winding connected to the dc voltage source and having a secondary winding connected to the battery;

switching means connected in series with the primary winding of the transformer and so controlled as to be alternately turned on and off for developing across the secondary winding an induced ac voltage;

rectifying means rectifying the induced ac voltage into the dc voltage which is applied to the battery for supplying a charge current into the battery,

said secondary winding being connected in series with the dc voltage source in such a manner that the dc voltage obtained by rectifying the ac voltage induced across the secondary winding of the transformer is in an additive relation with the terminal voltage of the dc voltage source which is applied to the battery for charging the battery; and

control means for inhibiting the DC-to-DC converter in response to the terminal voltage of the dc power source being higher than the instant voltage of the battery being charged so as to allow the direct charging of the battery from the dc power source so long as the terminal voltage is higher than the instant voltage of the battery being charged.

3. In a battery charger for charging a battery from a dc voltage source which comprises a DC-to-DC voltage converter connected between the dc voltage source and the battery to be charged,

said DC-to-DC voltage converter comprising:

a transformer having a primary winding connected to the dc voltage source and having a secondary winding connected to the battery;

switching means connected in series with the primary winding of the transformer and so controlled as to be alternately turned on and off for developing across the secondary winding an induced ac voltage;

rectifying means rectifying the induced ac voltage into the dc voltage which is applied to the battery for supplying a charge current into the battery,

said secondary winding being connected in series with the dc voltage source in such a manner that the dc voltage obtained by rectifying the ac voltage induced across the secondary winding of the transformer is in an additive relation with the terminal voltage of the dc voltage source which is applied to the battery for charging the battery; and

control means for inhibiting the DC-to-DC converter in response to the terminal voltage of the dc power source being higher than the instant voltage of the battery being charged or the voltage of the battery being higher than a predetermined reference level.

4. In a battery charger for charging a battery from a dc voltage source which comprises a DC-to-DC voltage converter connected between the dc voltage source and the battery to be charged,

said DC-to-DC voltage converter comprising:

a transformer having a primary winding connected to the dc voltage source and having a secondary winding connected to the battery;

switching means connected in series with the primary winding of the transformer and so controlled as to be alternately turned on and off for developing across the secondary winding an induced ac voltage;

rectifying means rectifying the induced ac voltage into the dc voltage which is applied to the battery for supplying a charge current into the battery,

said secondary winding being connected in series with the dc voltage source in such a manner that the dc voltage obtained by rectifying the ac voltage induced across the secondary winding of the transformer is in an additive relation with the terminal voltage of the dc voltage source which is applied to the battery for charging the battery; and

control means for inhibiting the DC-to-DC converter only when the terminal voltage of the dc power source being higher than the instant voltage of the battery being charged and at the same time the charge current to the battery exceeds above a predetermined threshold level.

5. In a battery charger having a DC-to-DC converter for charging a battery from a dc voltage source, said DC-to-DC converter being connected between the dc voltage source and the battery to be charged and comprising:

a transformer having a primary winding, a secondary winding, and a feedback winding, the primary winding connected to the dc voltage source, and the secondary winding connected to the battery;

a switching transistor connected in series with the primary winding of the transformer,

an R-C network connected to the switching transistor and to the feedback winding to form a blocking oscillator by which oscillation the switching transistor is alternately turned on and off for developing an induced ac voltage across the secondary winding of the transformer; and

a rectifying diode connected in series with the secondary winding for rectifying the induced ac voltage developed across the secondary winding for supplying a charge current to the battery;

said secondary winding being connected in series with the dc voltage source in such a manner that the induced voltage of the transformer is in an additive relation with the terminal voltage of the dc voltage source;

a shunting transistor connected in the base-emitter path of the switching transistor;

a first comparator comparing the terminal voltage of the dc voltage source with the instant voltage of the battery to provide a first output when the former voltage exceeds the latter voltage;

a second comparator comparing the terminal voltage of the battery with a predetermined reference voltage to provide a second output when the former voltage exceeds the latter voltage; and

gate means connected to the first and second comparators to provide a trigger output to the base of the shunting transistor upon receiving any one of the first and second outputs, said shunting transistor being in response to the trigger output to shunt the base-emitter path of the switching transistor, inhibiting the oscillation of the DC-to-DC converter.

6. In a battery charger having a DC-to-DC converter for charging a battery from a dc voltage source, said DC-to-DC converter being connected between the dc voltage source and the battery to be charged and comprising:

a transformer having a primary winding, a secondary winding, and a feedback winding, the primary winding connected to the dc voltage source, and the secondary winding connected to the battery;

a switching transistor connected in series with the primary winding of the transformer,

an R-C network connected to the switching transistor and to the feedback winding to form a blocking oscillator by which oscillation the switching transistor is alternately turned on and off for developing an induced ac voltage across the secondary winding of the transformer; and

a rectifying diode connected in series with the secondary winding for rectifying the induced ac voltage developed across the secondary winding for supplying a charge current to the battery;

said second winding being connected in series with the dc voltage source in such a manner that the induced voltage of the transformer is in an additive relation with the terminal voltage of the dc voltage source;

a shunting transistor connected in the base-emitter path of the switching transistor;

a comparator comparing the terminal voltage of the dc voltage source with the instant voltage of the battery to provide an output to the base of the shunting transistor when the former voltage exceeds the latter voltage;

a current sensing resistor connected between the rectifier diode and the positive side of the battery;

a transistor having its emitter and base connected across the current sensing resistor so as to provide a feedback output when the current sensing resistor sees the charge current of a level exceeding a predetermined threshold level; and

gate means connected to the comparator and the transistor to provide a trigger output to base of the shunting transistor only when it receives both the output from the comparator and the feedback output from the transistor, said shunting transistor being in response to the trigger output from the gate means to shunt the base-emitter path of the switching transistor, inhibiting the oscillation of the DC-to-DC converter.