JPH0431799Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention relates to the improvement of a charging circuit for a rechargeable battery.
We provide a charging circuit with an overcharge prevention mechanism that can be configured with a minimum number of parts, has low manufacturing costs, is highly reliable, can reliably prevent overcharging, and is fully equipped to prevent abnormal phenomena from occurring. It is something to do.

[Prior Art] Various methods have been proposed for charging circuits with overcharge prevention mechanisms, one of which utilizes the phenomenon in which the temperature of the battery to be charged rises rapidly just before the charging is completed, and uses this phenomenon to prevent the thermostat from overcharging. A method of opening and closing is known.

For example, the circuit shown in FIG. 1 is known as this method.

In FIG. 1, 1 is a plug and is connected to a commercial power source. The voltage of the commercial power source is dropped by transformer 2. The transformer 2 is selected to have a secondary voltage slightly larger than the rated voltage of the battery to be charged. The reduced AC voltage is full-wave rectified by the diode bridge 4. The charging power supply circuit A is configured as described above.

The charging power supply circuit A is connected in series with a battery to be charged Ba, a normally closed type thermostat Th that senses and shuts off the temperature rise of the battery to be charged, and a main thyristor SCR1. A first gate current supply path is connected to the gate of the main thyristor SCR1 by connecting resistors R1 and R2 in series from the midpoint between the charged battery Ba and the thermostat Th. A second resistor is connected between the midpoint of resistors R1 and R2 and the cathode of main thyristor
A bypass circuit in which non-contact switching elements SCR2 are connected in series is connected. A resistor R is connected to the gate of the second non-contact switching element SCR2 from the midpoint of the charged battery Ba and the thermostat Th.
4 and R3 are connected in series. A resistor R3 is connected between the gate and cathode of the second non-contact switching element SCR2.
A capacitor C is connected through the capacitor C.

The operation of this charging circuit will be explained below. A pulsating current is supplied to the output lines 5 and 6 from the charging power supply circuit.
Immediately after charging starts, thermostat Th is in a conductive state,
Thyristor SCR1 and second non-contact switching element SCR2 are in a cut-off state. In this state, the voltage of the charging power supply circuit A changes every half wave to the battery Ba to be charged.
When the charging voltage exceeds the charging voltage, a current flows to the gate of the main thyristor SCR1 via the resistors R1 and R2. At the same time, current also flows through the gate of the second non-contact switching element SCR2 via the resistors R4 and R3;
Since the capacitor C is connected between the gate and the cathode of the main thyristor SCR1, the main thyristor SCR1 becomes conductive first.

When the main thyristor SCR1 becomes conductive, charging current begins to flow. When the main thyristor SCR1 becomes conductive, the charge in the capacitor C is discharged via the thermostat Th and the main thyristor SCR1. The above operation is repeated every half wave to progress charging.

When charging is completed, the temperature of the battery to be charged rises rapidly and thermostat Th is shut off. In this state, a gate current flows through resistors R1 and R2. At the same time, a gate current to the second non-contact switching element SCR2 and a charging current to the capacitor C flow through the resistor R4. Since the capacitor C does not discharge when the thermostat is cut off, the second non-contact switching element SCR2 becomes conductive. When the second non-contact switching element SCR2 becomes conductive, the first base current supply path is bypassed via the second non-contact switching element SCR2.
When the next half-wave is supplied, the second non-contact switching element SCR2 is switched on before the main thyristor SCR1 becomes conductive due to the charging voltage of the capacitor C.
conducts, bypassing the gate current to the main thyristor. As a result, the main thyristor does not conduct. Therefore, once the battery to be charged is charged, even if the battery to be charged cools down and the thermostat Th becomes conductive, the charging current will not start flowing again.

[Problems to be solved by the invention] As described above, the conventional charging circuit operates as intended if each component is normal. However, even if, for example, the battery to be charged deteriorates and an internal short circuit occurs, the current continues to flow until the thermostat Th is turned off. As a result, the main thyristor and power supply circuit may generate heat and be damaged.

Therefore, the present invention aims to realize a charging circuit that is designed to prevent damage to the electronic components that constitute the charging circuit even in the event of an abnormality.

[Means for Solving the Problems] To achieve this, the present invention includes a charging power supply circuit, a battery to be charged, a normally closed type thermostat that senses and shuts off the temperature rise of the battery to be charged, and a main thyristor that is configured in the forward direction. The midpoint between the battery to be charged and the thermostat and the gate of the main thyristor are connected by a first gate current supply path having a resistance, and the anode is connected to the gate of the main thyristor and the cathode of the main thyristor is connected to the gate of the main thyristor. The second cathode is connected to each
A non-contact switching element is connected between the gate and cathode of the main thyristor, and a midpoint between the charged battery and the thermostat and the gate of the second non-contact switching element are connected to a second gate current supply path having a resistance. In the charging circuit, the first gate current supply path and the anode of the second non-contact switching element are connected to each other, and the gate and cathode of the second non-contact switching element are connected via a capacitor. A thermistor having a positive characteristic is thermally coupled between the charging power supply circuit, the battery to be charged, and the main thyristor and the temperature is increased by heat generation of at least one of the main thyristor. We have developed a charging circuit with an overcharge prevention mechanism that is characterized by being connected in series.

[Function] The charging circuit described above operates in the same manner as a conventional charging circuit if the power supply circuit, the battery to be charged, and the main thyristor are all at normal temperatures. However, if either of them generates abnormal heat, it becomes difficult for the gate current to flow to the main thyristor, and the second switching element becomes conductive before the main thyristor becomes conductive, thereby bypassing the gate current to the main thyristor. In other words, when abnormal heat generation occurs, the main thyristor ceases to conduct. Therefore, the conventional problem of damage to electronic components due to continued charging even in abnormal situations does not occur.

[Embodiment] FIG. 2 shows an embodiment of a charging circuit according to the present invention. In terms of circuitry, the resistor R2 in the conventional charging circuit shown in FIG. 1 is replaced with a thermistor PTH having positive characteristics. This thermistor
PTH is diode bridge 4, charged battery Ba,
They are thermally coupled so that when at least one of the main thyristors SCR1 generates heat, the temperature increases due to the heat generated.

This may be due to a short circuit between the terminals of the charger or an internal short circuit due to deterioration of the battery being charged.
When an abnormal current flows, the diode bridge 4 and the main thyristor SCR1 generate abnormal heat. Alternatively, if the charging current is not cut off even after charging is completed due to a thermostat welding accident or the like, the battery Ba to be charged abnormally generates heat. In such a case, the temperature of the thermistor PTH increases and its resistance increases rapidly. Therefore, no current is supplied to the gate of the main thyristor SCR1, and the second non-contact switching element SCR2 conducts to cut off the charging current.

As described above, in this embodiment, thorough measures are taken against the occurrence of abnormalities.

[Effects of the invention] In the charging circuit according to the invention, a thermistor is inserted in the gate current supply path of the main thyristor, and this thermistor is thermally coupled to the power supply circuit, the battery to be charged, and the main thyristor. Therefore, measures are taken to prevent the main thyristor from becoming conductive if abnormal heat generation occurs in either of them. Therefore, when an abnormality occurs, charging current does not continue to flow, preventing damage to electronic components and improving safety.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional charging circuit, and FIG. 2 is a circuit diagram of an embodiment. 4...Diode bridge, Ba...Battery to be charged, Th...Thermostat, SCR1...Main thyristor, SCR2...Second non-contact switching element, PTH...Thermistor.

Claims (1)

[Scope of Claim for Utility Model Registration] A charging power supply circuit, a battery to be charged, a normally closed type thermostat that senses and shuts off the temperature rise of the battery to be charged, and a main thyristor are connected in series in the forward direction, A midpoint between the battery to be charged and the thermostat and the gate of the main thyristor are connected by a first gate current supply path having a resistance, an anode is connected to the gate of the main thyristor, and a cathode is connected to the cathode of the main thyristor. A second non-contact switching element is connected between the gate and cathode of the main thyristor, and a midpoint between the charged battery and the thermostat and the gate of the second non-contact switching element provide a second gate current supply having a resistance. In the charging circuit, the first gate current supply path and the anode of the second non-contact switching element are connected to each other via a capacitor, and the gate and cathode of the second non-contact switching element are connected via a capacitor. A charging power supply circuit, a battery to be charged, and at least one of the main thyristors are connected between the connected point and the gate of the main thyristor.
1. A charging circuit with an overcharge prevention mechanism, characterized in that thermistors having positive characteristics and thermally coupled to each other are connected in series so that the temperature rises due to heat generated by the charging circuit.