JPH0732545B2 - Charging circuit for rechargeable vacuum cleaners - Google Patents

Description

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

(Prior Art) As a conventional charging circuit of this type of rechargeable vacuum cleaner or the like, for example, the configuration shown in FIG. 5 is adopted.

In FIG. 5, reference numeral 1 is an AC power supply, and a step-down rectifier circuit 2 is connected to the AC power supply 1.

A main resistance thyristor 5, a diode 6 and a secondary battery 7 having a protection resistor 3 and a bias resistor 4 between the cathode and the gate are connected between the output terminals of the step-down rectifier circuit 2, and in parallel with them. A backflow preventing diode 8 and a smoothing capacitor 9 connected in series are connected. The capacitor 9 has a reference voltage terminal of an operational amplifier 10, a resistor 11 and a Zener diode 12 connected in series,
A resistor 13 and a charging capacitor 14 connected in series, and a resistor 15 and an auxiliary thyristor 16 connected in series are connected in parallel.

The non-inverted input terminal of the operational amplifier 10 is the connection point between the cathode of the thyristor 5 and the diode 6, and the inverted input terminal is the resistor 11
The zener diode 12 and the output terminal are connected to the connection point between the resistor 13 and the charging capacitor 14 and the resistor 17
Is connected to the gate of the auxiliary thyristor 16 via.

The gate of the main thyristor 5 is connected to the resistor 15 via the resistor 18.
And the thyristor 16 is connected to the connection point.

During charging, the AC of the AC power supply 1 is step-down rectified by the step-down rectifier circuit 2. When the secondary battery 7 is not sufficiently charged, the auxiliary thyristor 16 is in the off state, so the gate voltage is applied to the main thyristor 5 and the main thyristor 5
Is turned on, the secondary battery 7 is charged with a large current. When the charging voltage of the secondary battery 7 rises and the charging voltage of the secondary battery 7 rises, and the voltage of the secondary battery 7 rises above the voltage of the Zener diode 12, the operational amplifier 10 outputs a high level and the gate voltage is applied to the auxiliary thyristor 16. To do. This turns on the auxiliary thyristor 16 and bypasses the gate current of the main thyristor 5, so that the main thyristor 5 does not turn on. As a result, the secondary battery 7 is charged with a small current through the protection resistor 3.

However, if the battery is charged in a low temperature state, the battery voltage during charging becomes high, so the charging current is controlled before the battery is fully charged and the battery is not fully charged. Since the battery voltage becomes low, the battery voltage may not rise to the set voltage and overcharge may occur.

Further, the configuration shown in FIG. 2 is known to change the set voltage of the secondary battery depending on the ambient temperature. This uses a resistor 19 instead of the Zener diode 12 of FIG. 1, and sets the set voltage of the secondary battery 7 by dividing the voltage of the resistor 11 and the resistor 19.

Then, when the charging voltage of the secondary battery 7 exceeds the partial pressure set by the resistors 11 and 19, the main thyristor 5 is turned off, and the secondary battery 7 is charged with a small current.

However, since the voltage is set by dividing the voltage of the resistor 11 and the resistor 19, it is easily affected by the fluctuation of the input voltage, and it is difficult to maintain a constant voltage.

(Problems to be Solved by the Invention) As described above, in the charging circuit shown in FIG. 5, since the voltage set by the Zener diode 12 is almost constant, when the charging is performed in a low temperature state, the secondary battery being charged is charged. Since the voltage of 7 becomes high, the charging current is controlled before the battery is completely charged, and the charging current is not sufficiently charged. On the contrary, if the battery is charged at a high temperature, the voltage of the secondary battery 7 being charged reaches the set voltage. Since it does not rise, it may be overcharged by being charged even after being completely charged.

Further, the conventional charging circuit shown in FIG. 6 can change the set voltage according to the temperature to correspond to the temperature characteristic of the battery, but since the set voltage is determined by the partial voltage of the resistor, the input voltage is changed. There is a problem that it is difficult to maintain a constant voltage because it is easily affected by voltage fluctuations due to fluctuations.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a charging circuit that is not easily affected by fluctuations in input voltage and can be appropriately charged without being affected by temperature.

[Structure of Invention]

(Means for Solving Problems) A charging circuit for a rechargeable vacuum cleaner or the like according to the present invention includes a secondary battery, a charging circuit for charging the secondary battery, and a voltage for detecting the voltage of the secondary battery. In a charging circuit for a rechargeable vacuum cleaner or the like, which includes a detection circuit and a charging current control circuit that reduces or cuts off the charging current of the charging circuit according to the output of the voltage detection circuit, the voltage detection circuit increases in temperature. Then, a series circuit of a Zener diode and a resistor having a positive temperature characteristic whose resistance value increases is used, and the voltage is detected by the voltage drop of the Zener diode.

(Operation) In the present invention, the secondary battery is charged by the charging circuit. Then, the voltage of the secondary battery is detected by the voltage detection circuit, and when the charging voltage of the secondary battery is equal to or higher than the set value, the charging current control circuit reduces or cuts off the charging current of the charging circuit.

When charging is performed in a high temperature state, the resistance value of the resistor having a positive temperature characteristic increases, and the current flowing through the Zener diode decreases, so that the set voltage decreases, which prevents overcharging. On the other hand, when charging at low temperature, the resistance value of the resistor decreases and the current flowing through the Zener diode increases, so the set voltage rises.
The secondary battery is fully charged.

(Example) Hereinafter, an example of a charging circuit for a rechargeable vacuum cleaner or the like according to the present invention will be described with reference to the drawings.

In FIG. 1, 21 is a commercial AC power supply, and this commercial AC power supply 21 is connected to a step-down rectifier circuit 22. In this step-down rectification circuit 22, a primary winding 24 of a step-down transformer 23 is connected to a commercial AC power source 21, diodes 26 and 27 are connected to both ends of a secondary winding 25 of the transformer 23, and The cathodes of these two diodes 26 and 27 are the positive electrodes of the step-down rectifier circuit 22,
The middle of the secondary winding 25 forms the negative electrode of the step-down rectifier circuit 22.

A charging circuit 30 is connected between the output terminals of the step-down rectifier circuit 22. This charging circuit 30 includes a main thyristor 32 of a charging current control circuit 31, a diode 33 for preventing backflow and a secondary battery.
34 are connected in series. A protective resistor 35 is provided between the anode and cathode of the main thyristor 32, and a bias resistor 36 is provided between the gate and cathode.

A diode 37 and a capacitor 38 are connected in series at both ends of the step-down rectifier circuit 22. Further, the capacitor 38 has a reference voltage of an operational amplifier 42 forming a comparator of the voltage detection circuit 41, a thermistor 43 which is a resistor having a positive temperature characteristic in which a resistance value increases with an increase in ambient temperature connected in series, and a constant voltage. Zener diode to set voltage
44, resistor 45 connected in series and capacitor for charging
46, resistor 47 and auxiliary thyristor 48 connected in series
Are connected in parallel. Then, the non-inverting input terminal of the operational amplifier 42 is a connection point between the cathode of the thyristor 32 and the anode of the diode 33, the inverting input terminal is a connection point between the thermistor 43 and the cathode of the Zener diode 44, and the output terminal is a resistor 45.
Is connected to the connection point between the
Is connected to the gate of the auxiliary thyristor 48 via.

The gate of the main thyristor 32 is connected to the resistor 47 via the resistor 50.
And the auxiliary thyristor 48 is connected to the connection point with the anode.

Next, the operation of the above embodiment will be described.

A step-down rectifier circuit 22 rectifies the AC of the AC power supply 21 into a pulsating flow.

When the secondary battery 34 is at the set voltage or less, the auxiliary thyristor 48 is in the off state, so the main thyristor 32
Is supplied with a gate current, the main thyristor 32 is turned on, and the secondary battery 34 is charged with a large current. This secondary battery 34
The voltage at the end of charging is high at low temperature a, low at high temperature c, and intermediate at normal temperature b, as shown in FIG.

The resistance value of the thermistor 43 increases at high temperature. As a result, the current flowing into the Zener diode 44 decreases as shown in FIG. 3, and the voltage at the cathode of the Zener diode 44 decreases. On the contrary, when the temperature is low, the resistance value of the thermistor 43 decreases, which causes the voltage at the cathode of the Zener diode 44 to increase. The set voltage of the Zener diode 44 is set to V _BL at low temperature and V _BH at high temperature so that the set voltage becomes lower as the temperature becomes higher as shown in FIG. That is, the set voltage V _BL is set to be high at low temperature, the set voltage V _BH is set to be low at high temperature, and the set voltage V _BM is set to an intermediate value at room temperature. As a result, the voltage of the secondary battery 34 before the end of charging is set as the set voltage at any temperature.

When the secondary battery 34 reaches the set voltage, the operational amplifier 42
Outputs a high level and supplies a gate current to the auxiliary thyristor 48 to turn on the auxiliary thyristor 48, thereby bypassing the gate current of the main thyristor 32, stopping the gate current, and not turning on the main thyristor 32. Then, the secondary battery 34 is charged with a small current through the protection resistor 35.

Further, the thermistor 43 has a smaller rate of increase in resistance value as the temperature rises. You can use the one. Note that R is a resistance value and T is a temperature. This is because the current I-voltage V characteristic of the Zener diode 44 increases as the voltage increases, as shown in FIG. Since the voltage change is large with respect to the current change in the small current value part and the voltage change is small with respect to the current change part in the large current value, the thermistor 43
However, the characteristic of the Zener diode 44 is corrected by increasing the resistance change rate in a portion having a small resistance value and decreasing the resistance change rate in a portion having a large resistance value. As a result, the cathode voltage of the Zener diode 44 has a high set voltage V _BH at low temperatures and a low set voltage V _BL at high temperatures, as shown in FIG. 4, so that the secondary battery 34 is sufficiently charged at low temperatures. It is possible to prevent the failure or the overcharge of the secondary battery 34 at high temperature.

〔The invention's effect〕

According to the present invention, a series circuit of a resistor having a positive temperature characteristic and a Zener diode is provided, and by changing the set voltage with the resistor having a positive temperature characteristic, charging becomes insufficient at low temperature,
Since it is not overcharged at high temperature, it is difficult to obtain the influence of the fluctuation of the input voltage, and it is possible to charge properly without being affected by the temperature.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a charging circuit for a rechargeable vacuum cleaner according to the present invention, FIG. 2 is a charging characteristic graph of a secondary battery, and FIG. 3 is a current-voltage characteristic graph of a Zener diode. FIG. 4 is a graph of set voltage and temperature characteristics, and FIGS. 5 and 6 are circuit diagrams showing a conventional example. 30 …… Charging circuit, 34 …… Secondary battery, 41 …… Voltage detection circuit, 43 …… Resistance, 44 …… Zener diode.

Claims (2)

[Claims] 1. A secondary battery, a charging circuit for charging the secondary battery, a voltage detection circuit for detecting the voltage of the secondary battery, and a charging current for the charging circuit reduced according to the output of the voltage detection circuit. In a charging circuit such as a rechargeable vacuum cleaner including a charging current control circuit for shutting off, the voltage detection circuit is a series circuit of a resistor and a Zener diode having a positive temperature characteristic in which the resistance value increases as the temperature rises. A charging circuit for a rechargeable vacuum cleaner or the like, which has a voltage detection of a Zener diode. 2. A charging circuit for a rechargeable vacuum cleaner or the like according to claim 1, wherein the resistance of the positive temperature characteristic has a smaller rate of increase in resistance as the temperature rises.