JPH01160326A - Recharge circuit for rechargable electric cleaner and the like - Google Patents

Abstract

PURPOSE:To enable normal recharge of even a cell internal resistance of which is increased through over discharge, by decreasing or interrupting recharge current when recharge current of a secondary cell is lower than a predetermined level and voltage thereof is higher than a predetermined level. CONSTITUTION:Power is fed from a power supply circuit 11 through a recharge current control circuit 12 to a secondary cell 13 in order to recharge the secondary cell 13. When a recharge current detecting circuit 14 in a recharged state detecting circuit 16 detects that the recharging current of the secondary cell 13 is lower than a predetermined level and a voltage detecting circuit 15 detects that the voltage of the secondary circuit 13 is higher than a predetermined level, a recharge current control circuit 12 decreases or interrupts recharge current of the secondary cell 13.

Description

DETAILED DESCRIPTION OF THE INVENTION (Object of the Invention) (Industrial Application Field) The present invention relates to a charging circuit for, for example, a rechargeable vacuum cleaner.

(Prior Art) - Conventionally, this type of charging circuit has adopted the configuration shown in FIG. 6, for example.

In FIG. 6, reference numeral 1 denotes a power supply circuit consisting of, for example, a charger, and this power supply circuit 1 is connected to a secondary battery 3 via a charging current control circuit 2 that reduces or cuts off charging current. In addition, this secondary battery 3
The charging current control circuit 2 is connected to a voltage detection circuit 4 that detects the voltage of the charging current control circuit 2 and outputs the voltage to the charging current control circuit 2.

Then, pulsating power is supplied from the power supply circuit 1 to the secondary battery 3, and the secondary battery 3 is charged with a large current. Then, the minimum value of the battery voltage of the secondary battery 3, that is, the voltage when the charging current crosses zero, is detected, and when this minimum value is equal to or higher than a predetermined voltage, the charging current is reduced or cut off by the charging current III control circuit 2. do. With this configuration, even the secondary battery 3 whose internal resistance value has increased due to overdischarge due to forgetting to turn off the switch, for example, can be appropriately charged.

(Problem to be Solved by the Invention) However, in the conventional circuit described above, when the internal resistance exceeds a certain value, even when the voltage of the secondary battery 3 is at its minimum value, it exceeds the predetermined voltage. Even if the battery 3 is not charged, it is assumed that charging of the secondary battery 3 has been completed, and the charging current is reduced or cut off by a charging current control circuit 2. For this reason, the charging time becomes long, and those having a charging end indicator light have the problem of causing malfunction.

The present invention was devised in view of the above problems, and is a charging circuit for rechargeable vacuum cleaners, etc., which allows batteries with high internal resistance due to overdischarge to be charged in the same way as normal batteries without malfunctioning. The purpose is to provide

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a secondary battery, a power supply circuit that supplies power to the secondary battery, a state of charge detection circuit that detects the state of charge of the secondary battery, and a state of charge detection circuit that detects the state of charge of the secondary battery. In a charging circuit for a rechargeable vacuum cleaner or the like, which is equipped with a charging current control circuit that reduces or cuts off the charging current using the output of the charging state detection circuit, the charging state detecting circuit controls the charging current of the secondary battery. It has a charging current detection circuit for detecting and a voltage detection circuit for detecting the voltage of the secondary battery, and when the charging current of the secondary battery is below a predetermined value and the voltage of the secondary battery is above a predetermined value. The charging current control circuit reduces or cuts off the charging current.

(Function) According to the present invention, a power supply circuit supplies power to a secondary battery and charges the secondary battery with a large current.

As the charging of the secondary battery progresses, the charging current detection circuit of the charging state detection circuit detects that the charging current to the secondary battery is below a predetermined value, and the voltage detection circuit detects that the voltage of the secondary battery is at a predetermined value. In this case, the charging type 'a control circuit reduces or cuts off the charging current of the secondary battery and charges the secondary battery with a small charging current.

(Example) Hereinafter, a practical example of the charging circuit of the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral 11 denotes a power supply circuit consisting of, for example, a charger. This power supply circuit 11 is connected to a secondary battery 13 via a charging current control circuit 12 that cuts off or reduces charging current. In addition, the charging current control circuit 12
A charging current detection circuit 14 that detects the charging current of the secondary battery 13 is connected to the power transmission path between the secondary battery 13 and the secondary battery 13, and a voltage detection circuit that detects the voltage of the secondary battery 13 is connected to the secondary battery 13. 15 are connected. The charging state detection circuit 16 is composed of the charging current detection circuit 14 and the voltage detection circuit 15.
Further, these charging M flow detection circuit 14 and voltage detection circuit 15 are each connected to a charging current control circuit 12.

Next, a specific circuit example of the above embodiment will be explained with reference to FIG.

In FIG. 2, 21 is a commercial AC power supply, and this commercial AC power supply 21 step-down rectifies the power of this commercial AC power supply 21 and supplies the power to the primary winding of the step-down transformer 22 of the power supply circuit 11. It is connected to line 23.

Rectifier diodes 25 and 26 are connected to both ends of the secondary battery 24 of this transformer 22, respectively, the anodes of these diodes 25 and 26 serve as the positive pole of the power supply circuit 11, and the center of the secondary battery 24 serves as the negative pole. It has become.

A main thyristor 3, which is a switching element of the charging current control circuit 12, is connected from the positive electrode to the negative electrode of the power supply circuit 11.
1. A backflow prevention diode 32 and a secondary battery 13 are connected in series, and the main thyristor 31 has a protective resistor 33 between its anode and cathode, and a bias resistor 34 between its gate and cathode. .

Furthermore, a backflow prevention diode 35 and a smoothing capacitor 36 are connected between the positive and negative electrodes of the power supply circuit 11.

A resistor 37, an auxiliary thyristor 38 as a switching element, and a diode 39 are connected in series in parallel with this capacitor 36.

Further, a resistor 40, a resistor 41, and a diode 42 connected in series are connected in parallel with the diode 32 for preventing backflow, and a capacitor 43 is connected in parallel with the resistor 40 and the resistor 41. The operational amplifier 44 forming a comparator has a reference voltage terminal connected to a positive electrode and a negative electrode via a diode 35, a non-inverting input terminal connecting the cathode of the main thyristor 31 and a diode 32 for backflow prevention, and an inverting input terminal connected to a resistor. The connection point between 40 and resistor 41 and the output end thereof are connected to the gate of auxiliary thyristor 38 via resistor 45.

The voltage detection circuit 15 includes a resistor 4 connected in series between the positive and negative electrodes of the power supply circuit 11 via a diode 35.
5 and a Zener diode 46 for constant voltage setting, a resistor 41 connected in series, and a charging capacitor 48 are connected in parallel. The reference power terminal of the operational amplifier 49 forming the comparator is connected to the positive and negative terminals of the power supply circuit 11 via the diode 35, and the normal input terminal is connected to the connection point of the cathode of the main thyristor 31 and the anode of the diode 32, The inverting input terminal is connected to the connection point between the resistor 45 and the Zener diode 46, and the output terminal is connected to the connection point between the resistor 45 and the Zener diode 46.
1 and the connection point of the capacitor 48, and is also connected to the gate of the auxiliary thyristor 38 via the resistor 45.

A resistor 51, a diode 52, and a light emitting diode 53 are connected in series from the connection point between the diode 35 and the capacitor 36 to the connection point between the auxiliary thyristor 38 and the diode 39, and the connection point between the resistor 51 and the diode 52 and the resistance 31 and the auxiliary thyristor 38 are connected in series. A diode 54 is connected between the connection point of the resistor 31 and the diode 38, and a diode 55 is provided between the connection point of the resistor 31 and the diode 38 and the gate of the main thyristor 31.

The operation of the above embodiment will be explained.

Transformer 2 of power supply circuit 11 converts AC from commercial AC power supply 21 into
2 to step down the voltage, perform full wave rectification with diodes 25 and 26, and output a pulsating current.

When charging the secondary battery 13, since the auxiliary thyristor 38 is off, a gate current flows to the main thyristor 31, and the main thyristor 31 is turned on, so that the secondary battery 13 is charged with a large current. Furthermore, since the auxiliary thyristor 38 is off, the light emitting diode 53 is also lit.

When charging the secondary battery 13 in a normal state, the charging current is equal to or higher than the set value until the end of charging, and the voltage of the secondary battery 13 is also lower than the set value set by the Zener diode 46, so the operational amplifier 44 Since both the operational amplifier 49 and the operational amplifier 49 have low level outputs and no gate current flows through the gate of the auxiliary thyristor 38, the auxiliary thyristor 38 remains off and the main thyristor 31 is turned on.

In addition, in the case of the secondary battery 13 whose internal resistance has increased due to overdischarge due to forgetting to turn off the switch, for example, the secondary battery 13
Since the internal resistance of the secondary battery 13 is high, the voltage of the secondary battery 13 increases,
When the voltage exceeds the set voltage, the operational amplifier 47 outputs a high level output. However, since the charging current for charging the secondary battery 13 is not less than the set value, the operational amplifier 44 of the charging current detection circuit 14 has an O-level output, so no gate current flows to the auxiliary thyristor 38, and the auxiliary thyristor 38 maintains an off state, and the main thyristor 31 maintains an on state because current is applied to its gate. This results in
The secondary battery 13 is charged with a large current.

The charging current detection circuit 14 detects that if the internal resistance of the secondary battery 13 is normal, a large charging current will flow, so the voltage drop across the diode 32 for preventing backflow will be large, as shown by the solid line a in Figure 3. If the internal resistance of the secondary battery is large, the charging current will be small, so the voltage drop across the diode 32 will be small, as shown in Figure 3, broken IB. Therefore, the charging current can be estimated by detecting the voltage of the diode 32 for preventing backflow.

On the other hand, when only the charging current value is below the set value and the voltage of the secondary battery 13 is above the set voltage, the operational amplifier 44 of the charging current detection circuit 14 outputs a high level, but the operational amplifier 49 of the voltage detection circuit 15 outputs a low level. Since it is a level output, is there a gate for the gate of the auxiliary thyristor 38? fii is not applied, the auxiliary thyristor 38 remains off, and the main thyristor 31 remains on, so the secondary battery 13 is charged with a large current.

Then, as the charging of the secondary battery 13 progresses and the charging current decreases and the voltage exceeds the set value, the charging current decreases and the operational amplifier 4 of the charging current detection circuit 14
4 outputs a high level, and as the voltage of the secondary battery 13 rises above a predetermined value, the operational amplifier 49 of the voltage detection circuit 15 outputs a high level.

As a result, a gate current is applied to the gate of the auxiliary thyristor 38, the auxiliary thyristor 38 is turned on, the gate current of the main thyristor 31 is bypassed to the auxiliary thyristor 38, and the main thyristor 31 is not turned on. Therefore, with a small charging current flowing through the protective resistor 33, the secondary battery 13
is charged. Further, the current is bypassed to the auxiliary thyristor 38, so that the light emitting diode 53 is turned off.

That is, it is determined whether the charging current 1 is smaller than the set current io (Step 2), then it is determined whether the voltage 2 of the secondary battery 13 is higher than the set voltage (Step 2), and the charging current I is set. It is configured to control the charging current when the voltage V of the secondary battery 13 is smaller than the current and larger than the set voltage Vo.

Next, another embodiment will be described with reference to FIG.

The circuit shown in FIG. 5 includes a charging current detection circuit 61 that detects the charging current based on the heat generated by the diode 32 instead of the charging current detection circuit 14 that detects the charging current based on the voltage of the diode 32 shown in FIG. It's a type of thing.

This charging current detection circuit 61 includes a resistor 62, a thermistor 63, which is a resistor with a positive characteristic whose resistance value increases as the temperature rises, and a resistor 64 are connected in series from the positive pole to the negative pole of the power supply circuit 11 via a diode 35. ing. The OBE amplifier 65 forming the comparator has a reference voltage terminal connected to the positive and negative electrodes of the power supply circuit 11 via the diode 35, a normal input terminal connected to the connection point between the resistor 62 and the thermistor 63, and an inverted input terminal connected to the thermistor 63. 63
The connection point between the resistor 64 and the output terminal is connected to the gate of the auxiliary thyristor 38 via the resistor 45. Further, the thermistor 63 is disposed at a portion of the diode 32 that is easily affected by heat.

Next, the operation of the above circuit will be explained.

When the charging '1' FA current is small, the heat generation of the diode 32 is extremely small, so the resistance value of the thermistor 63 is low.
Since the voltage drop across the thermistor 63 is small, the operational amplifier 6
5 outputs high level.

On the other hand, when the charging current is large, the heat generated by the diode 32 increases the resistance value of the thermistor 63, resulting in a large voltage drop, so the operational amplifier 65 outputs a low level output.

〔Effect of the invention〕

According to the present invention, when the charging current of the secondary battery is equal to or less than a predetermined value,
In addition, when the voltage of the secondary battery exceeds a predetermined value, the charging current control circuit reduces or cuts off the charging current, so even batteries with high internal resistance due to over-discharge will not malfunction and will operate in the same way as normal batteries. can be fully charged.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing one embodiment of the present invention, Fig. 2 is a circuit diagram of the same as above, Fig. 3 is a relation between voltage and time of a backflow prevention diode, and Fig. 4 is a block diagram of the block diagram shown in Fig. 1. 5 is a circuit diagram showing another embodiment, and FIG. 6 is a circuit diagram showing a conventional example. 11...Power supply circuit, 12...Charging ff? Current control circuit, 13... Secondary battery, 14... Charging current detection circuit, 15
...Voltage detection circuit, 16...Charging state detection circuit, 32.
・Backflow prevention diode. Please be obedient.”

Claims (3)

[Claims] (1) A secondary battery, a power supply circuit that supplies power to the secondary battery, a state-of-charge detection circuit that detects the state of charge of the secondary battery, and an output of the state-of-charge detection circuit that reduces charging current. In a charging circuit for a rechargeable vacuum cleaner or the like, the charging state detection circuit includes a charging current detection circuit that detects a charging current of the secondary battery and a voltage of the secondary battery. the charging current control circuit reduces or cuts off the charging current when the charging current of the secondary battery is below a predetermined value and the voltage of the secondary battery is above the predetermined value. A charging circuit for a rechargeable vacuum cleaner, etc., characterized by the following. (2) A charging circuit for a rechargeable vacuum cleaner or the like according to claim 1, wherein the charging current detection circuit detects the charging current based on the voltage drop of a charging current backflow prevention diode. (3) A charging circuit for a rechargeable vacuum cleaner or the like according to claim 1, wherein the charging current detection circuit detects the charging current based on the temperature of an element that generates heat due to the charging current.