BATTERY CHARGER WITH MEANS FOR PREVENTING OVERCHARGING OF THE BATTERY

• US 3,867,682 A
• Filed: 10/23/1973
• Issued: 02/18/1975
• Est. Priority Date: 11/20/1972
• Status: Expired due to Term

• Current Assignee: Hiroyuki Yamauchi, Masahiro Ohya
• Original Assignee: Hiroyuki Yamauchi, Masahiro Ohya
• Inventors: Yamauchi, Hiroyuki, Ohya, Masahiro
• Primary Examiner(s): Miller, J. D.
• Assistant Examiner(s): Hickey, Robert J.
• Application Number:
  US05/408,536
• Time in Patent Office: 483 Days
• Field of Search: 320/39,40,20,DIG.1,DIG.2
• US Class Current: 320/139
• CPC Class Codes: H02J 7/007182 in response to battery voltage
• CPC Class Codes: H02J 7/007186 obtained with the battery disconnected from the charge or discharge circuit

Abstract

A battery charger is provided with means to prevent overcharging of the battery. The battery is connected in series with a thyristor across a pulsating voltage source. One side of the voltage source and the cathode side of the thyristor is grounded. Circuit means is provided which measures the voltage of the battery side of the thyristor with respect to ground when the pulsating voltage from the source becomes substantially zero. When the pulsating voltage from the source becomes zero, the thyristor goes off and the voltage above ground at the connection point between the battery and the thyristor is the no-load voltage of the battery. A reference voltage is provided. When the voltage at the connection point reaches the reference voltage, a control signal is supplied to the thyristor control to keep the thyristor shut off, which in turn prevents further charging of the battery.

Claims

1. A battery charger for charging a rechargeable battery comprising a pulsating voltage source, a semiconductor thyristor having an anode-cathode path connected in series with said battery across said pulsating voltage source and having a gate, a thyristor control circuit connected to said gate and having means for rendering said semiconductor thyristor conductive during a portion of each pulse from said voltage source, voltage detecting means including a reference voltage producing means, said voltage detecting means connected to the connecting point between said rechargeable battery and said semiconductor thyristor for detecting the voltage at said connecting point when the pulsating voltage source becomes substantially zero and producing an output when the detected voltage reaches the reference voltage, and means for supplying a control signal in response to the output from said voltage detecting means to said thyristor control circuit to maintain said semiconductor thyristor in a continued non-conductive state, thereby to stop the charging of said rechargeable battery, said thyristor control circuit comprises a resistor connecting said gate to said pulsating voltage source for supplying said pulsating voltage to said gate as a gate signal and switch means connected to said gate for preventing said gate signal from being supplied to said gate when said control signal is supplied to said thyristor control circuit, said switch means having a control terminal supplied with said control signal, and said thyristor control circuit also including a diode connected between the anode of said semiconductor thyristor and the control terminal of said switch means.

2. A battery charger for charging a rechargeable Battery comprising a pulsating voltage source, a semiconductor thyristor having an anode-cathode path connected in series with said battery across said pulsating voltage source and having a gate, a thyristor control circuit connected to said gate and having means for rendering said semiconductor thyristor conductive during a portion of each pulse from said voltage source, voltage detecting means including a reference voltage producing means, said voltage detecting means connected to the connecting point between said rechargeable battery and said semiconductor thyristor for detecting the voltage at said connecting point when the pulsating voltage source becomes substantially zero and producing an output when the detected voltage reaches the reference voltage, and means for supplying a control signal in respnse to the output from said voltage detecting means to said thyristor control circuit to maintain said semiconductor thyristor in a continued non-conductive state, thereby to stop the charging of said rechargeable battery, said thyristor comprising a resistor connecting said gate to said pulsating voltage source for supplying said pulsating voltage to said gate as a gate signal and switch means connected to said gate for preventing said gate signal from being supplied to said gate when said control signal is supplied to said thyristor control circuit, said switch means having a control terminal, said thyristor control circuit also including a diode connected between the anode of said semiconductor thyristor and said control terminal of said switch means.

3. A battery charger for charging a rechargeable battery comprising a pulsating voltage source, a semiconductor thyristor having an anode-cathode path connected in series with said battery across said pulsating voltage source and having a gate, a thyristor control circuit connected to said gate and having means for rendering said semiconductor thyristor conductive during a portion of each pulse from said voltage source, voltage detecting means including a reference voltage producing means, said voltage detecting means connected to the connecting point between said rechargeable battery and said semiconductor thyristor for detecting the voltage at said connecting point when the pulsating voltage source becomes substantially zero and producing an output when the detected voltage reaches the reference voltage, and means for supplying a control signal in response to the output from said voltage detecting means to said thyristor control circuit to maintain said semiconductor thyristor in a continued non-conductive state, thereby to stop the charging of said rechargeable battery, said means for supplying a control signal comprising means for generating a pulse having a predetermined width in response to the output of said detecting means and supplying said pulse to said switch means in said switch control circuit, said thyristor control circuit also including a diode connected between the anode of said semiconductor thyristor and the control terminal of said switch means.

4. A battery charger for charging a rechargeable battery comprising a pulsating voltage source, a semiconductor thyristor having an anode-cathode path connected in series with said battery across said pulsating voltage source and having a gate, a thyristor control circuit connected to said gate and having means for rendering said semiconductor thyristor conductive during a portion of each pulse from said voltage source, voltage detecting means including a reference voltage producing means, said voltage detecting means connected to the connecting point between said rechargeable battery and said semiconductor thyristor for detecting the voltage at said connecting point when the pulsating voltage source becomes substantially zero and producing an output when the detected voltage reaches the reference voltage, and means for supplying a control signal in response to the output from said voltage detecting means to said thyristor control circuit to maintain said semicondUctor thyristor in a continued non-conductive state, thereby to stop the charging of said rechargeable battery, said means for supplying a control signal comprising means for generating a pulse having a predetermined width in response to the outupt of said detecting means and supplying said pulse to said switch means in said switch control circuit, said thyristor control circuit comprising a resistor connecting said gate to said pulsating voltage source for supplying said pulsating voltage to said gate as a gate signal and switch means connected to said gate for preventing said gate signal from being supplied to said gate when said control signal is supplied to said thyristor control circuit, said switch means having a control terminal supplied with said control signal, said thyristor control circuit also including a diode connected between the anode of said semiconductor thyristor and the control terminal of said switch means.

5. A battery charger for charging a rechargeable battery according to claim 3, in which said voltage detecting means comprises a Schmitt trigger circuit provided with impedance means producing said reference voltage.

6. A battery charger for charging a rechargeable battery according to claim 5, in which said means for supplying a control signal comprises a multivibrator generating a pulse having a predetermined width in response to the output of said Schmitt trigger circuit.