JPH0683546B2 - Charging circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention relates to a charging circuit for a rechargeable handheld vacuum cleaner or other rechargeable equipment.

(Prior Art) Generally, when charging a charging battery, since the charge in the charging battery is low at the beginning of charging, it can be charged with a relatively large current, but when the charging is approaching, charging Since the electric charge in the battery for use increases, unless the current for charging is reduced, the capacity and life of the battery are reduced. Therefore, while detecting the state of charge of the charging battery,
The charging current must be controlled.

As means for detecting the state of charge, there are charging current detecting means, battery voltage detecting means for detecting the voltage of the charging battery during charging, temperature detecting means for detecting the temperature of the charging battery during charging, and the like.

Then, regarding a conventional battery voltage detection circuit for detecting the voltage of the charging battery of the means for detecting the battery voltage during charging,
It will be described with reference to the drawings.

In FIG. 4, reference numeral 1 is a rectifier circuit, and the positive output terminal of the rectifier circuit 1 is connected to the anode of a main thyristor 3 to which a protective resistor 2 is connected in parallel, and the cathode of the main thyristor 3 is the anode of a diode 4. The charging battery 5 is connected to the cathode of the diode 4, and the zener diode 6 and the resistor 7 are connected in parallel with the diode 4 and the charging battery 5.
Are connected. Further, the diode 8, the resistor 9, and the auxiliary thyristor 10 are connected in series from the positive side to the negative side of the rectifier circuit 1, and the resistor 8, the diode 12, and the light emitting diode 13 are connected in series from the diode 8, and the resistor 11, the diode
12, the capacitor 14 in parallel with the series circuit of the light emitting diode 13
Is connected to the negative side of the rectifier circuit 1.

From the connection point between the resistor 9 and the auxiliary thyristor 10, the diode 15 and the resistor 16 are connected to the connection point between the main thyristor 3 and the diode 4, and the anode of the diode 15 is connected to the gate of the main thyristor 3. . The gate of the auxiliary thyristor 10 is connected to the cathode of the Zener diode 6 with resistance.
It is connected via 17 and is connected to the negative side of the rectifier circuit 1 via the electrolytic capacitor 18. Further, a diode 19 is connected from the connection point between the resistor 11 and the diode 12 to the connection point between the resistor 9 and the auxiliary thyristor 10.

Then, the commercial alternating current is converted into a pulsating current by the rectifying circuit 1, and when the voltage of the charging battery 5 is low, the auxiliary thyristor 10 is turned off, and the gate current flows through the main thyristor 3, so that the main thyristor 3 passes through the diode 4 through the diode 4. , The charging battery 5 is charged. Then, when the charging battery 5 is charged and the voltage rises, the reverse blocking voltage of the Zener diode 6 exceeds the Zener voltage, the Zener diode 6 becomes conductive, and the resistor 7
And a gate current flows through the resistor 17 to the auxiliary thyristor 10. Then, the auxiliary thyristor 10 is turned on, and when the auxiliary thyristor 10 is turned on, the main thyristor 3 cannot be maintained in the on state and is turned off, so that the charging current flows through the charging resistor 5 to the charging battery 5. As a result, the charging current is reduced, preventing overcharging of the battery and
The current of 13 is bypassed to the diode 19 and the auxiliary thyristor 10, and the light emitting diode 13 is turned off to indicate completion of charging.

However, in the conventional charging circuit shown in FIG.
If the switch of a device (not shown) driven by the charging battery 5 is forgotten to be turned off or left uncharged for a long time, the charging battery 5 is over-discharged and the internal resistance becomes high. Further, since the charging battery 5 is charged by the pulsating voltage, the internal resistance of the charging battery 5 increases, and the voltage applied to the Zener diode 6 also forms a pulsating waveform.
At the maximum instantaneous value of this pulsating voltage, the Zener voltage is exceeded and a current flows through the Zener diode 6 to turn on the auxiliary thyristor 10, and the light emitting diode 13 is also turned off to indicate completion of charging. Since the main thyristor 3 is turned off, the charging current is charged through the protective resistor 2 without passing through the main thyristor 3, so that when charging the over-discharged charging battery 5 due to a small current, charging is performed. It takes a long time to charge the battery 5.

Further, as a structure capable of charging an over-discharged charging battery, for example, a structure described in Japanese Patent Application Laid-Open No. 60-216729 is known.

In the configuration described in JP-A-60-216729, a reverse current preventing diode and a charging capacitor are connected in parallel to the secondary battery, and based on the voltage at the connection point of the capacitor and the diode. A switching element that operates is connected.

Then, the capacitor is charged at a portion where the pulsating voltage has a high voltage value, and conversely, the capacitor is discharged at a portion having a low voltage value, which is detected as the voltage of the charging battery, and switching is controlled.

(Problems to be Solved by the Invention) However, in the configuration described in JP-A-60-216729, the capacitor is charged and discharged by the CR time constant circuit of the internal resistance value of the charging battery and the capacitor of the capacitor. Therefore, there is a problem that the switching element operates due to a change in the internal resistance value depending on the charging state of the charging battery, and the charging battery may not be sufficiently charged.

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 can reliably charge a battery having a high internal resistance as in the normal case.

[Structure of Invention]

(Means for Solving the Problems) The charging circuit of the present invention includes a rectifying circuit unit that rectifies an AC voltage, and a charging circuit unit that includes a charging battery and a series circuit of a switching element that are connected in series to the rectifying circuit unit. And the charging battery is connected to one end of the input terminal, and the connection point of the Zener diode and the resistor is connected to the other end for voltage setting, and high resistance is provided between the output terminal and the positive electrode of the rectifier circuit section, and between the negative electrode. A capacitor is connected to detect the voltage of the charging battery, and a positive output is provided when the voltage of the charging battery is above a predetermined value, and a negative output is provided when the voltage of the charging battery is below a predetermined value. A voltage detection circuit unit, and a control circuit unit for controlling the switching element by the output of the voltage detection circuit unit,
The capacitor is charged when the output of the comparator is positive and discharged when it is negative.

(Operation) The present invention charges the charging battery with the pulsating current from the rectifying circuit unit via the switching element of the charging circuit unit. At that time, the charging voltage of the charging battery connected to the comparator is compared with the voltage set by the Zener diode and the resistor, and when the charging voltage becomes high, it is detected by the voltage detection circuit unit,
The switching element is turned off by the control circuit unit. The charging current is a pulsating current, and when charging a charging battery with a high internal resistance in which the voltage of the charging radio wave is equal to or lower than a predetermined value, the positive output of the output terminal of the comparator and The high resistance charges the capacitor with a minute current, and conversely, in the low part, the negative output of the comparator discharges the charge of the capacitor. Since the capacitor repeats this charging / discharging, the voltage does not rise above a certain voltage and an erroneous output due to pulsating current is not output to the control unit. A battery with a high internal resistance can be charged in the same way as a normal battery.

(Embodiment) An embodiment of a charging circuit according to the present invention will be described below with reference to FIGS.
It will be described with reference to the drawings.

In FIG. 1, reference numeral 21 is a commercial AC power supply, to which a primary side terminal of a transformer 23 of a rectifier circuit unit 22 is connected, and a secondary side terminal of the transformer 23 has two diodes 2
The anodes of 4,25 are connected to these two diodes 24,2
The cathodes of 5 are connected together, and the conducting wire is led out from substantially the center of the secondary winding of the transformer 23. The charging circuit unit 31 is connected between the cathodes of the diodes 24 and 25 and the intermediate portion of the secondary winding of the transformer 23.
Reference numeral 31 is composed of a series circuit of a main thyristor 33 as a switching element in which a protection resistor 32 is connected in parallel, a diode 34 and a charging battery 35.

A resistor 36 is placed between the gate and anode of the main thyristor 33.
Is connected from the positive electrode to the negative electrode of the rectifier circuit section 22
37, an operational amplifier 39 as a comparator of the voltage detection circuit section 38 is connected in series, the non-inverting terminal of the operational amplifier 39 is the cathode of the main thyristor 33, and the inverting terminal is a resistor 40 and a rectifier circuit connected to the diode 37. The Zener diode 41 connected to the negative electrode of the part 22 is connected, and the output terminal of the operational amplifier 39 is connected to the diode 37.
42 and a capacitor 43 connected to the negative electrode of the rectifier circuit unit 22
Are connected.

Then, from the diode 37 to the negative electrode of the rectifier circuit unit 22, a resistor 4
4, auxiliary thyristor 46 and diode 4 of control circuit unit 45
7 are connected in series, and a diode 48 is connected to the gate of the main thyristor 33 from the connection point of the resistor 44 and the auxiliary thyristor 46.
However, a resistor 49 is connected between the gate of the auxiliary thyristor 46 and the output terminal of the operational amplifier 39. Also a diode
A resistor 50, a diode 51 and a light emitting diode 52 are connected in series from 37 to the diode 47, and a diode 53 is connected to the diode 48 from the connection point of the resistor 50 and the diode 51. Further, the capacitor 54 is connected from the diode 37 to the negative electrode of the rectifier circuit unit 22.

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

The voltage of the commercial AC power supply 21 is stepped down by the transformer 23 and the diode
Rectification is performed by the 24 and the diode 25, and a pulsating current is output by the rectification circuit unit 22.

Then, when the charge battery 35 is not sufficiently charged, since the main thyristor 33 is on, the pulsating current output by the rectifier circuit unit 22 is the main thyristor 33, the diode.
The charging battery 35 is charged via 34. When the voltage of the charging battery 35 increases as the charging progresses, and the voltage of the charging battery 35 becomes higher than the voltage set by the resistor 40 and the Zener diode 41, the voltage of the non-inverting input terminal of the operational amplifier 39 becomes the voltage of the inverting input terminal. It becomes higher than the voltage, the output of the operational amplifier 39 changes from negative to positive, the current flowing from the resistor 40 to the operational amplifier 39 is diverted to the capacitor 43 to charge the capacitor 43, and the voltage of this capacitor 43 increases, A voltage is applied to the gate of the auxiliary thyristor 46, and the auxiliary thyristor 46 turns on.

Also, since the voltage of the main thyristor 33 drops and the charging current has a moment when the current is zero due to the pulsating current, the main thyristor 33 turns off and the charging current charges the charging battery 35 with a small charging current through the protection resistor 32. To be done. And light emitting diode
The voltage of 52 drops and the light emitting diode 52 goes out.

Next, when the charging battery 35 having a high internal resistance is charged, the internal resistance of the charging battery 35 is high as shown in FIG. The voltage “a” at the non-inverting input terminal has a pulsating waveform and takes both a region higher and a region lower than the voltage “b” at the inverting input terminal of the operational amplifier 39. Therefore, the operational amplifier 39
The output of 1 repeats the positive non-inverted voltage output and the negative inverted voltage output, and the capacitor 43 repeats charging and discharging as shown in FIG.

Further, since the high resistance 42 has a high resistance value, the capacitor 43 is charged in the peak portion of one cycle of the pulsating current, and the charged electric charge is discharged through the operational amplifier 39 in the valley portion of the pulsating current.
As shown in FIG. 3, the maximum value of the capacitor 43 is set so as not to reach the gate-on voltage of the auxiliary thyristor 46. As described above, even if the internal resistance of the charging battery 35 is high, the auxiliary thyristor 46 maintains the off state, so that the main thyristor 46
33 keeps the ON state, charging battery 35 with a large charging current
Can be charged.

When the charging battery 35 is charged in this way, the charging battery 35
The voltage of 35 rises, the internal resistance becomes low and the battery is stably charged, the voltage of the non-inverting input terminal of the operational amplifier 39 is always higher than the voltage of the inverting input terminal of the operational amplifier 39, and the charging battery 35 is substantially sufficient. When charged, the capacitor 43 is also charged, and when the charging voltage of the capacitor 43 reaches the ON voltage of the auxiliary thyristor 46, the auxiliary thyristor 46 is turned on, the main thyristor 33 is turned off accordingly, and the charging current is the protective resistance. Since the current flows through 32, the charging current is reduced and the light emitting diode 52 is also turned off to indicate the completion of charging.

According to the above-described embodiment, for example, even if the battery has a high internal resistance due to over-discharging due to forgetting to turn off the switch or leaving it uncharged for a long time, it can be charged in the same manner as a battery having a low internal resistance. Is reduced.

Further, since it can be done only by adding an operational amplifier, a resistor and a diode to the conventional charging circuit, it can be formed at a low cost.

〔The invention's effect〕

According to the charging circuit of the present invention, the capacitor is charged with a small current by the positive output and high resistance of the output terminal of the comparator in the high pulsating voltage portion, and conversely, in the low portion, the negative output of the comparator output terminal is charged. The output discharges the charge of the capacitor, and the voltage of the charging battery is detected based on the voltage of the capacitor, so a charging battery with a high internal resistance can be charged in the same way as a normal charging battery, and The circuit can be constructed at low cost.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of a charging circuit of the present invention, FIG. 2 is a voltage waveform diagram of a and b above, and FIG. 3 is a relationship diagram between a voltage waveform of a capacitor and a gate-on voltage of an auxiliary thyristor. FIG. 4 is a circuit diagram of a conventional charging circuit. 22 …… Rectifier circuit section, 31 …… Charging circuit section, 33 …… Main thyristor as switching element, 35 …… Charging battery, 38
...... Voltage detection circuit section, 39 ...... operational amplifier as comparator, 40 ...... resistance, 41 ...... Zener diode, 42 ...... high resistance, 43 ...... capacitor, 45 ...... control circuit section.

Claims (1)

[Claims] 1. A rectifying circuit section for rectifying an AC voltage, a charging circuit section connected in series with the rectifying circuit section and having a series circuit of a charging battery and a switching element, and the charging battery at one end of an input terminal. , The other end is connected to a connection point of a Zener diode and a resistor for voltage setting, a high resistance is connected between the output terminal and the positive electrode of the rectifying circuit unit, and a capacitor is connected between the negative electrode, and the voltage of the charging battery is Detect and
A voltage detection circuit unit provided with a comparator that outputs a positive output when the voltage of the charging battery is a predetermined value or more and a negative output when the voltage is a predetermined value or less, and And a control circuit unit for controlling a switching element, wherein the capacitor is charged when the output of the comparator is positive and discharged when the output of the comparator is negative.