JPH0214295Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a charging device that rapidly charges a secondary battery with constant current.

[Technical background of the invention]

Generally, a charging device consists of a power supply circuit, a constant current circuit, and a secondary battery voltage detection circuit.
The secondary battery voltage detection circuit detects the voltage of the secondary battery, and when the voltage falls below the voltage at which the secondary battery should be charged, a constant current is supplied from the constant current circuit to recharge the secondary battery. When the battery is charged with a rapid constant current and the voltage reaches a voltage higher than the voltage at which charging should be terminated, the constant current charging is switched to trickle charging or the charging is stopped.

By the way, if a secondary battery is rapidly charged by passing an excessive current, the secondary battery will generate heat and expand, shortening its lifespan. Therefore, rapid constant current charging has been carried out using an appropriate current value.

[Problems with background technology]

However, when a secondary battery is being charged by the conventional charging device described above, when a load is connected to the secondary battery and a load current flows through the load, the charging current supplied to the secondary battery decreases. Therefore, there was a problem in that the charging time became long. Therefore, a method of supplying a charging current that takes into account the load current may be considered, but if the load current is not small compared to the charging current, the battery will be charged with an excessive current when the load is not connected. This results in problems such as heat generation and increased gas pressure, which shorten battery life.

[Purpose of invention]

The present invention was developed in view of the above-mentioned circumstances, and even if a load that uses the secondary battery as a power source is connected to the secondary battery while rapidly charging the secondary battery with constant current, the connected It is an object of the present invention to provide a charging device that performs rapid charging that always supplies a substantially constant current to a secondary battery even if the load is disconnected or even if the load is connected before charging.

[Summary of the idea]

Therefore, the present invention provides a first detection circuit that detects that a load is connected to the secondary battery or that the connected load is disconnected based on a sudden drop or sudden drop in the voltage of the secondary battery during charging. a second detection circuit that detects whether a load has been connected before charging starts based on the rate of increase in voltage of the secondary battery; and detection results of the first detection circuit and the second detection circuit. A current change rate control circuit is provided to gradually increase or decrease the current based on the current.

[Example of idea]

Hereinafter, the charging device according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block circuit diagram showing an embodiment of the charging device according to the present invention, and specific circuit diagrams for each block of the charging device are shown in FIGS. 2 to 7.

The charging device 1 according to the present invention includes a power supply circuit 2, a current supply circuit 3, a voltage detection circuit 4, a sudden voltage change detection circuit 5, a voltage change speed detection circuit 6, and a current change speed control circuit 7, A current is supplied to a load device 10 connected to a pair of connection terminals consisting of a terminal 8 and a ground terminal 9. The load device 10 also includes a switch 12 and a load 1 to a secondary battery 11 that is charged with a constant current by the charging device 1.
3 are connected in series. Note that since the charging device 1 and the load device 10 are connected using only one pair of connection terminals, the connection can be made extremely easily.

First, each block of the charging device 1 shown in FIG. 1 will be explained in detail.

The power supply circuit 2 outputs a constant voltage to be supplied to each part of the charging device 1 and a direct current to be supplied to the load device 10, and a detailed circuit diagram is shown in FIG. 2. In Figure 2, the constant voltage is connected to the diode 20
1,202, two power supplies are obtained: a positive voltage using a constant voltage regulator 203, etc., and a negative voltage using diodes 204, 205, a constant voltage regulator 206, etc.,
They are output from a positive voltage output terminal 207 and a negative voltage output terminal 208, respectively. Further, a direct current is obtained by diodes 209 to 212 and the like, and is outputted to a current supply circuit 3 to be described later via an output terminal 213.

The current supply circuit 3 supplies a charging current for constant-current charging the secondary battery 11, and a constant-current charging current to the secondary battery 11, depending on the state of the load device 10 under the control of a voltage detection circuit 4 and a current change rate control circuit 7, which will be described later. When the switch 12 is closed during current charging, it stably supplies either a load current to the load 13 along with the charging current, or a trickle current for trickle charging the secondary battery 11 after charging is completed. The circuit diagram is shown in Figure 3. The transistor 301 is turned on and off by a control signal applied from the voltage detection circuit 4 via the input terminal 302, which will be described later, and the transistor 303 is turned on and off in response to this.
Off state changes. In addition, the transistor 304
The on/off state of the transistor 304 changes slowly in response to a control signal applied via an input terminal 305 from a current change rate control circuit 7, which will be described later. The resistor 306 is short-circuited and opened. Both ends of the resistor 306 are open, that is, the transistor 30
4 is turned off, the DC current inputted from the input terminal 307 connected to the output terminal 213 of the power supply circuit 2 is passed through the transistor 303 as a charging current to the output terminal connected to the current supply terminal 8. 308. Also, the resistor 306
When both ends of the transistor 304 are short-circuited, that is, the transistor 304 is turned on, the base current of the transistor 303 increases, and in addition to the charging current, a load current for operating the load 13 is outputted to the output terminal 308. Further, when the transistor 301 is turned off, a trickle current is outputted to the output terminal 308 via the resistor 309. Note that transistor 3
A constant voltage is applied to the base of transistor 10 through an input terminal 311 connected to the positive voltage output terminal 207 of the power supply circuit 2, and the emitter current of the transistor 310, that is, the base current of the transistor 303 is kept constant. , the current output to the output terminal 308 is stabilized.

The voltage detection circuit 4 detects whether the voltage of the secondary battery 11 is lower than the lower limit voltage for constant current charging of the secondary battery 11 or higher than the upper limit voltage for trickle charging, and 3, and a detailed circuit diagram is shown in FIG. This voltage detection circuit 4 is constituted by a hysteresis comparator, and the voltage of the secondary battery 11 applied from the input terminal 401 via the resistor 402 and the comparison reference voltage preset by the resistor 403 are calculated by calculation. The voltage is applied to the inverting input terminal of the amplifier 404, and the operational amplifier 404 outputs a signal "1" if the voltage of the secondary battery 11 is below the lower limit voltage, and outputs a signal "0" if it is higher than the upper limit voltage to the current supply circuit. 3 input terminal 30
2 and an output terminal 405 connected to a voltage change rate detection circuit 6, which will be described later. In addition, resistance 4
03 has both ends connected to an input terminal 406 connected to the positive voltage output terminal 207 of the power supply circuit 2 and an input terminal 407 connected to the negative voltage output terminal 208, and its resistance value is varied. Therefore, the comparison reference voltage can be set to a desired value. Further, the upper limit voltage and the lower limit voltage are determined by the constant voltage diodes 408 and 409,
By changing the resistance value of the resistor 410, its size can be changed. Further, the voltage of the secondary battery 11 is applied indirectly via a delay circuit of the voltage sudden change detection circuit 5, which will be described later.
This is to prevent the voltage detection circuit 4 from malfunctioning. The voltage sudden change detection circuit 5 is connected to the switch 1
A sudden drop or a sudden drop in the voltage of the secondary battery 11 accompanying the opening/closing of the battery 2 is detected, and the current supplied to the load device 10 is increased or decreased. That is, if the switch 12 is opened or closed during constant current charging, the charging current flowing to the secondary battery 11 will decrease or increase, and the voltage of the secondary battery 11 will suddenly or suddenly drop. Charging current only,
When it is closed, a load current is supplied to the load 13 in addition to the charging current to keep the charging current constant. A detailed circuit diagram is shown in FIG. Resistor 5 from input terminal 501 connected to current supply terminal 8
The voltage of the secondary battery 11 applied to the inverting input terminal of the operational amplifier 503 via the resistor 504,
The voltage of the secondary battery 11 is compared with the voltage of the secondary battery 11 applied to the non-inverting input terminal of the operational amplifier 503 after a fixed time delay via a delay circuit composed of a capacitor 505 and an operational amplifier 506. operational amplifier 50
3 compares the voltage of the secondary battery 11 applied to the inverting and non-inverting input terminals, and if the voltage of the secondary battery 11 increases by more than a certain value than the voltage increase due to charging, it is determined as a negative voltage. When the voltage drops by a certain value or more, a positive voltage is output to the output terminal 507. In addition,
Capacitors 508 and 509 are ripple prevention capacitors, and a diode 510 and capacitor 511 are used for initial setting. Further, the voltage of the secondary battery 11 delayed by a certain period of time is applied to the input terminal 401 of the voltage detection circuit 4 via the output terminal 512.

The voltage change rate detection circuit 6 detects that a load current was already flowing through the load 13 before the constant current charging of the secondary battery 11 is started, and detects the voltage of the secondary battery 11 due to the constant current charging of the secondary battery 11. The current supply circuit 3 is controlled to detect the increase and supply the load current to the load device 10 in addition to the charging current. That is, by constant current charging, the secondary battery 11
The voltage gradually rises, but if the load 13 has been operating before the start of the constant current charging, the rate of increase in the voltage will be lower than the rate at which the load 13 is operating because a portion of the charging current flows through the load 13. It's slower than when it's not there. Therefore, if the increase in the voltage of the secondary battery 11 after a certain period of time has elapsed from the start of constant current charging is smaller than the increase in voltage when the secondary battery 11 is previously charged with the charging current, the load 13 is assumed to be operating, and the current supply circuit 3 is configured to supply a load current to the load device 10 in addition to the charging current.
A detailed circuit diagram of the control circuit is shown in FIG.
The resistor 601 and the capacitor 602 have a time constant that is a comparison reference voltage value, which is the output voltage after a certain period of time has elapsed since the positive voltage was applied through the input terminal 603 connected to the positive voltage output terminal of the power supply circuit 2. It is set in advance so that the voltage value of the secondary battery 11 due to the charging current after the certain period of time has elapsed is slightly larger than that of the charging current. Since the input terminal 604 is connected to the current supply terminal 8, when the field effect transistor (hereinafter abbreviated as FET) 605 turns on at the rise of the charging current, the voltage of the capacitor 602 becomes equal to the voltage of the secondary battery 11. be equal. Therefore, when the timer circuit, which is composed of the FET 606 and the operational amplifier 607 and starts timing at the rise of the charging current, finishes timing after the predetermined period of time (several minutes) has elapsed and turns the FET 608 on.
The operational amplifier 609 compares the comparison reference voltage with the voltage of the secondary battery 11, and outputs a signal corresponding to the comparison result to an output terminal 610 connected to a current change rate control circuit 7, which will be described later. Therefore, before starting constant current charging, if the load 13 is not operating, the voltage of the secondary battery 11 is higher than the comparison reference voltage, and if the load 13 is operating, the voltage of the secondary battery 11 is higher than the comparison reference voltage.
The voltage of 1 is lower than the comparison reference voltage, and a positive voltage or a negative voltage is output to the output terminal 610. Furthermore, the time measured by the timer circuit is
The magnitude of the voltage at the input terminal 611 connected to the output terminal 405 of the voltage detection circuit 4, the resistance 612,
It can be set by the values of capacitor 613 and resistor 614.

The current change rate control circuit 7 changes the current supplied from the current supply circuit 3 to the load device 10 under the control of the voltage change detection circuit 5 or the voltage change rate detection circuit 6 from only the charging current to the charging current together with the charging current. When changing the load current so that it flows, or conversely when changing the charging current and the load current so that only the charging current flows, the voltage change detection circuit detects the voltage change of the secondary battery due to the sudden change in current. 5 may malfunction, so in order to prevent the voltage change detection circuit 5 from malfunctioning, the current is gradually increased or decreased.
As shown in the figure. A resistor 70 is connected to an input terminal 701 connected to an output terminal 507 of the voltage sudden change detection circuit 5.
2 or an input terminal 703 connected to the output terminal 610 of the voltage change rate detection circuit 6.
Depending on the magnitude of the voltage applied to the inverting input terminal of the operational amplifier 705 via the resistor 704, the polarity of the output voltage of the operational amplifier 705 changes rapidly from positive to negative or from negative to positive. When this output voltage is directly applied to the battery supply circuit, the secondary battery 1
1 suddenly changes, causing the voltage sudden change detection circuit 5 to malfunction. Therefore, the output voltage of the operational amplifier 705 is applied to an integrating circuit composed of a resistor 706, a capacitor 707, and an operational amplifier 708, and a voltage proportional to the time integral of the output voltage is outputted to an output terminal 709.

Next, regarding the operation of the charging device according to the present invention,
This will be explained according to the operation flowchart shown in FIG.

(1) Step 100 Determine whether the voltage of the secondary battery 11 is below the minimum voltage for constant current charging or above the maximum voltage for trickle charging, and if it is below the minimum voltage, proceed to step 101 and set the maximum voltage. If above, step
Proceed to 107.

(2) Step 101 The timer circuit of the voltage change speed detection circuit 6 starts measuring time.

(3) Step 102 Simultaneously with step 101 above, a charging current is output to the secondary battery 11 to perform constant current charging.

(4) Step 103 Determine whether the voltage of the secondary battery 11 is higher than the upper limit voltage, and if it is higher than the upper limit voltage, proceed to step 103.
At step 108, if the upper limit voltage is not exceeded, the process proceeds to the next step 104.

(5) Step 104 It is determined whether or not the voltage of the secondary battery 11 has suddenly dropped. If the voltage has dropped suddenly, the process goes to step 109, and if it has not dropped suddenly, the process goes to the next step 105.

(6) Step 105 When the timer circuit that started counting in step 101 above has elapsed the preset time, it starts the next step.
The process proceeds to step 106, and if the preset time has not elapsed, the constant current charging in step 102 is continued.

(7) Step 106 Determine whether the voltage rise of the secondary battery 11 is normal or abnormal, that is, whether the load was not operating or was operating before starting constant current charging. If it was not operating, the above Continue constant current charging in step 102, and if it is working, proceed to step 109.

Note that the steps from step 103 to step 106 are not executed sequentially, but step 103 and step 104 are executed at any time during constant current charging, and steps 105 and 106 are executed immediately after a preset time has elapsed. Ru.

(8) Step 107 A trickle current is output to the secondary battery 11 to perform trickle charging. During the trickle charging, step 100 is executed at any time in the same manner as the constant current charging.

(9) Step 108 When the voltage of the secondary battery 11 exceeds the upper limit voltage during the constant current charging (see step 103 above)
stops the timer circuit and repeats the above steps.
Proceed to 107.

(10) Step 109 When the voltage of the secondary battery 11 suddenly drops during the constant current charging (see step 104 above), or when the load 13 is already operating before the constant current charging starts (step 106 above) , the timer circuit stops measuring time.

(11) Step 110 In addition to the charging current, load current is output to the load 13, and with constant current charging, the load 13 is connected to the secondary battery 1.
1, but by the charging device 1.

(12) Step 111 Determine whether the voltage of the secondary battery 11 is higher than the upper limit voltage, and if it is higher than the upper limit voltage, proceed to step 111.
At step 107, if the upper limit voltage is not exceeded, the process proceeds to the next step 112.

(13) Step 112 Determine whether or not the voltage of the secondary battery 11 has risen sharply. If it has risen sharply, proceed to step 102. If it has not risen sharply, proceed to step 110 for constant current charging and supply of load current to the load 11. Continue.

Incidentally, the above steps 111 and 112 are executed at any time similarly to the above constant current charging.

In the above embodiments, the charging device according to the present invention is configured only by an electric circuit, but it can also be configured by a microcomputer using an analog-to-digital converter and a digital-to-analog converter. In this case, by storing control data such as the voltage at which the secondary battery should be charged or the voltage at which trickle charging should be performed in the memory, various charging currents can be controlled.

[Effect of idea]

As explained above, according to the present invention, it is possible to determine whether or not a load whose power source is a secondary battery to be charged has already been connected to the secondary battery before the start of charging. By detecting whether the connected load is disconnected, rapid constant current charging of the secondary battery can be performed.

[Brief explanation of drawings]

Fig. 1 is a block circuit diagram of the charging device according to the present invention, Figs. 2 to 7 are specific circuit diagrams for each block diagram of the charging device shown in Fig. 1, and Fig. 8 is a block circuit diagram of the charging device according to the present invention. An operation flowchart of such a charging device is shown. DESCRIPTION OF SYMBOLS 1... Charging device, 2... Power supply circuit, 3... Current supply circuit, 4... Voltage detection circuit, 5... Voltage sudden change detection circuit, 6... Voltage change speed detection circuit, 7...
...Current change rate control circuit, 8...Current supply terminal,
9... Ground terminal, 10... Load device, 11... Secondary battery, 12... Switch, 13... Load, 20
1,202,204,205,209 to 21
2,510...diode, 203,206...
Constant voltage regulator, 207... Positive voltage output terminal, 208... Negative voltage output terminal, 213, 30
8,405,507,512,610,709...
...Output terminal, 301, 303, 304, 310...
...Transistor, 302, 305, 307, 31
1,401,406,407,501,603,
604, 611, 701, 703...input terminal,
306, 309, 402, 403, 410, 50
2,504,601,612,614,702,
704,706...Resistance, 404,503,50
6,607,609,705,708...operational amplifier, 408,409...constant voltage diode, 5
05,508,509,511,602,61
3,707...Capacitor, 605,606,6
08...Field effect transistor (FET).

Claims (1)

[Scope of utility model registration request] In a charging device that rapidly charges a secondary battery with a constant current, a first device detects whether a load is connected to the secondary battery or whether the connected load is disconnected based on a sudden drop or sudden drop in the voltage of the secondary battery.
a second detection circuit that detects whether a load has been connected before charging starts based on the rate of increase in voltage of the secondary battery, and the first detection circuit and the second detection circuit. Based on the detection results of
A charging device comprising: a current change rate control circuit that gradually increases or decreases current.