JP3265570B2 - Charging circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging circuit for charging a battery by controlling the charging current flowing into the battery from the temperature of the power supply section which rises by flowing the charging current when charging the battery.

[0002]

2. Description of the Related Art Conventionally, in a charging circuit of a communication device which takes measures against a power failure by a battery, the battery is often charged by a floating charging method. That is, the power supply unit of the charging circuit often simultaneously supplies power to the battery and the communication device also connected to the battery. Further, when the power supply of the power supply unit loses power or a failure occurs in the power supply unit, power supply from the power supply unit to the battery and the device is interrupted. Along with this, discharging from the battery side to the device is started without interruption.
Then, when the drive power supply is restored after the discharge from the battery side, the power supply to the battery and the device is simultaneously performed again as described above. That is, charging of the battery is restarted.

Here, a conventional charging circuit is described in Japanese Patent Application Laid-Open No. Hei 10-51972. Hereinafter, this publication will be described with reference to FIGS. In FIG. 6, reference numeral 21 denotes a pulse charging device for charging the secondary battery 22. The pulse charging device 21 includes a DC power supply 3 described later.
1, a switch circuit 32 for connecting the output of the DC power supply 31 at a predetermined cycle, and a control circuit 33 for controlling on / off of a switching element of the switch circuit 32.

In the figure, reference numeral 23 denotes current measuring means for measuring the value of the charging current supplied to the secondary battery 22;
24 is the voltage applied to the secondary battery 22 or the secondary battery 2
2 is a voltage measuring means for detecting the battery voltage. And
Reference numeral 25 denotes an internal impedance measuring unit that calculates the internal impedance of the secondary battery 22 based on the outputs from the current measuring unit 23 and the voltage measuring unit 24.

Further, in the figure, reference numeral 26 denotes a battery temperature measuring means for measuring the internal temperature of the secondary battery 22. The battery temperature measuring means 26 is configured to include a temperature detecting element such as a thermistor whose resistance changes according to the temperature. Then, the temperature sensor detects the internal temperature of the secondary battery 22 or the outer wall temperature of the secondary battery 22, and outputs a signal indicating the detected temperature.

Reference numeral 27 denotes a full charge detection device for detecting that the secondary battery 22 is in a fully charged state, that is, that charging has been completed 100%. Reference numeral 28 denotes a charging control device, which instructs the pulse charging device 21 to start charging based on the value of the internal impedance calculated by the internal impedance measuring means 25. When receiving the charging start command, the pulse charging device 21 starts the charging operation.

When the internal impedance is small, the pulse charging device 21 starts charging the secondary battery 22 by pulse charging according to a command from the charging control device 28. During this charging period, the internal impedance measuring means 2
5, the internal impedance of the secondary current 22 is calculated. In parallel with this, the battery temperature T of the secondary battery 22 is measured by the battery temperature measuring means 26.

[0008] The charge control device 28 determines whether or not the internal impedance calculated by the internal impedance measuring means 25 is equal to or more than the upper limit value. Here, the upper limit value is determined using a battery temperature detection method that determines that a full charge state is detected when the gradient of the battery temperature rise (dT / dt) is equal to or greater than a predetermined reference temperature rise gradient. Value.

Then, based on the determination, the charging control device 28 outputs a charging stop command to the pulse charging device 21 when the internal impedance is equal to or more than the upper limit value.
The pulse charging device that has received the charge stop command stops the charging operation, and the charging is completed.

Next, the control of the charging current output from the pulse charging circuit 21 will be described with reference to FIG.
In the figure, 29 is a microcomputer. The microcomputer 29 includes a CPU 91, a memory 92, an A / D converter for an output port 93 and an input port 94, and the like. A signal indicating the battery voltage, charging current and temperature of the secondary circuit 22 is A / D converted. Input to the container. The input is subjected to signal processing by the CPU 91 using software stored in the memory 92, and a control command signal is output from the output port 93 to the control circuit 33.

The control circuit 33 controls the on / off operation of the switch circuit 32 in response to a charge start / stop command output from the output port 93. For example, when a temperature of the secondary battery 22 is high and a signal of a charge stop command to stop charging is output from the charge control device 28 (not shown) because the internal impedance is equal to or higher than the upper limit value, the microcomputer 9 outputs the signal to the microcomputer 9. A signal is input.

The control circuit 3 is controlled by the above process.
3 is input to the switch circuit 32. In the switch circuit 32, the switch is turned off in accordance with the control signal, and the output of the charging current from the pulse charging device 21 to the secondary battery 22 is stopped. That is, the switch circuit 32 is turned on / off based on the temperature of the secondary battery 22 to increase the charging efficiency.

[0013]

However, the above-mentioned prior art has the following problems.

First, at the time of charging the battery, the charging current supplied from the power supply unit to the battery becomes large, and a charging current of a predetermined current value or more is output. Therefore, the temperature of the power supply unit increases. When the temperature of the power supply unit increases, the current supply amount may decrease as described later. However, in the related art, only when the temperature of the battery becomes high, the switch is turned on / off to suppress the output of the charging current, and merely increase the charging efficiency of the battery.

Further, it is necessary to lower the temperature of the power supply unit so as not to reduce the supply amount of the charging current to the battery.
Therefore, a large radiator was required in the power supply unit. Therefore, it has been difficult to reduce the size of the power supply unit.

Further, the power supply section of the charging circuit is usually provided with a protection function. This protection function is a function of reducing the output voltage of the power supply unit when the temperature of the power supply unit reaches a certain temperature or higher in order to prevent the temperature of the power supply unit from rising.
Therefore, the protection function may not be able to maintain the charging voltage. In this case, since the charging current is not output from the power supply unit, the battery cannot be sufficiently charged.

(Object of the Invention) It is an object of the present invention to provide a charging circuit capable of suppressing a rise in the temperature of a power supply unit and sufficiently charging a battery.

It is another object of the present invention to reduce the size of the power supply unit by reducing the volume of the radiator required for the power supply unit.

[0019]

SUMMARY OF THE INVENTION The present invention detects a charging current for charging a battery from a power supply unit via an opening / closing unit, and opens and closes the opening / closing unit when the charging current exceeds a predetermined current value. A charging circuit for charging the battery by keeping the opening / closing unit closed when the charging current is equal to or less than the predetermined current value, wherein the temperature of the power supply unit is detected.
And the output from the heat detecting element.
A reference voltage for controlling a reference voltage for detecting the charging current value.
A charging circuit for controlling the charging current value according to the reference voltage.
And controlling the opening / closing of the opening / closing unit based on the temperature of the power supply unit.

Further, the charging circuit of the present invention detects a charging current for charging the battery from the power supply unit via the switching unit, and opens and closes the switching unit when the charging current exceeds a predetermined current value. A charging circuit for charging the battery by keeping the opening / closing unit closed when the charging current is equal to or less than the predetermined current value, wherein a detection circuit for detecting the charging current and an output of the detection circuit are input. A flip-flop circuit for charging the battery by opening / closing the opening / closing unit by an output of the flip-flop circuit.

(Operation) The charging circuit according to the present invention includes a heat detecting element inside the power supply section, and detects the temperature rise due to the charging current of the power supply section by the heat detecting element, and controls the opening / closing of the opening / closing section.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a charging circuit according to the present invention will be described below with reference to FIG. FIG. 1 is a block diagram showing the configuration of the charging circuit of the present invention. In FIG. 1, reference numeral 1 denotes a detection circuit for detecting a charging current 2; 3, an oscillator for outputting a set oscillation cycle; and 4, a D-type flip-flop circuit (D-type) for inputting an output from the detection circuit 1 from a D input terminal. Flip Flop circuit; hereinafter, referred to as D-FF circuit.) Reference numeral 5 denotes a charging switching circuit including an opening / closing unit 53 that is opened and closed by an output from the D-FF circuit 4. Reference numeral 4 denotes a reference power supply circuit connected to a power supply input terminal, reference numeral 7 denotes a power supply unit serving as a power supply of the charging circuit, and reference numeral 8 denotes a battery for storing the charging current 2 output from the power supply unit 7.

The power supply unit 7 may adopt a floating charging system that supplies power not only to the battery 8 but also to the device.

Next, the detection circuit 1 and the like constituting the charging circuit of the present embodiment will be described with reference to the block diagram shown in FIG. In FIG. 2, a detection circuit 1 includes a resistor 10 for converting the charging current 2 into a voltage, and a comparison detector for comparing and detecting the converted voltage converted by the resistor 10 and a reference voltage generated in a reference power supply circuit 6 described later. 11 is comprised.

The D-FF circuit 4 inputs an output from the comparison detector 11 from a D input terminal. Further, the output from the oscillator 3 is input from the CLK input terminal. The oscillator 3 is composed of an astable multivibrator. In addition, D-FF
The output from circuit 4 depends on the period set in oscillator 3.

The charging and switching circuit 5 includes a driver 51 for driving the battery 8 and a relay 52 for opening and closing the contacts of an opening and closing unit 53. Further, the input unit and the output unit of the power supply unit 7 apply the voltage from the input power supply 9 to the power supply unit 7.
Alternatively, a charging device 91 for charging the battery 8 or the like is provided. The input device 91 is of a two-contact type. The input portion of the power supply 7 is a contact 91A and the output of the power supply 7 is 91B.

Further, one terminal of the opening / closing section 53 is provided with a contact 91
B is connected to one end. On the other hand, the other terminals of the opening / closing section 53 are:
It is connected to the input terminal of the battery 8 via the relay 52. The power supply unit 7 is a constant voltage power supply, and includes an overcurrent protection circuit having a function of protecting the power supply unit 7 from a temperature that rises to output a charging current. The reference power supply circuit 6 is constituted by a shunt-type stabilized power supply circuit. The internal structures of the power supply unit 7 and the reference power supply circuit 6 will be described later.

Next, the operation of this embodiment will be described. When charging the battery 8, the charging current 2 is output from the power supply unit 7. The charging current 2 flowing into the battery 8 is converted into a voltage by the resistor 10 in the detection circuit 1. The converted voltage and the reference voltage generated by the reference power supply circuit 6 are input to the comparison detector 11 to compare and detect the two.

The detection result is input to the D-FF circuit 4. As a detection result, when the above-mentioned converted voltage is higher than the reference voltage, “H” is input to the D-FF circuit 4 assuming that the charging current 2 is a current exceeding a predetermined current value. When the conversion voltage is lower than the reference voltage, the charging current 2 is a current equal to or less than the predetermined current value, and thus “L” is input to the D-FF circuit 4.

The D-FF circuit 4 further receives a clock having an oscillation cycle set in the oscillator 3 from the CLK input terminal. Then, the output from the D-FF circuit 4 depends on the oscillation cycle set in the oscillator 3,
It is input to the charge switching circuit 5 from the output terminal.

The charging switching circuit 5 includes the switching unit 5 as described above.
The opening and closing of the opening / closing section 53 is controlled by the oscillation cycle set by the oscillator 3. Specifically, when the charging current exceeds the predetermined current value, the output from the Q output terminal becomes “L”, and the closed switching unit 53 opens. That is, the charged state is released. And
The charging current 2 flowing to the detection circuit 1 is cut off.

Then, in the detection circuit 1, the charging current 2
Is not detected as a current exceeding the predetermined current value, the input signal input from the D input terminal of the D-FF circuit 4 is inverted. That is, “L” is input from the D input terminal of the D-FF circuit 4. Accordingly, when “H” is input from the CLK input terminal of the D-FF circuit 4, D-FF
The output from the Q output terminal of the FF circuit 4 becomes “H”.
Therefore, the opening / closing section 53 is closed. Thereby, the battery 8 is charged again.

In this embodiment, the configuration in which the position of the detection circuit 1 is provided on the output side of the battery 8 has been described. However, the installation position of the detection circuit 1 is provided on the input side of the battery 8 and The input charging current 2 may be detected.

Next, the temperature detection of the power supply unit 7 will be described with reference to FIG. FIG. 3 is a circuit diagram showing the internal structure of the detection circuit 1, the reference power supply circuit 6, and the power supply unit 7. A heat sink 72 is provided inside the power supply unit 7.
A power transistor for supplying power is provided on the heat sink 72, and a heat detecting element 71 such as a thermistor is disposed to measure the temperature of a part of the power transistor. The heat detecting element 71 detects the temperature of the power supply unit 7 because the temperature of the heat sink 71 increases due to the increase of the charging current 2.

Further, the reference power supply circuit 6 is provided with a shunt regulator 61. Further, resistors R1 and R2 for varying the reference voltage input to the comparison detector 11
Is also provided. The resistance R1 is connected in parallel with the heat detection element 71. As the heat detection element 71, an element having a negative temperature coefficient is used.

Next, an operation of detecting a rise in temperature of the power supply unit 7 will be described. First, when the temperature of the power supply unit 7 rises, the temperature of the heat sink 72 and the temperature of the heat detecting element 71 fixed thereto also rise. That is, when the temperature of the power supply unit 7 increases, the impedance of the heat detection element 71 decreases,
The temperature of the power supply unit 7 can be detected. Note that a positive thermistor, a negative thermistor, or the like can be used for the heat detection element 71.

The amount of current flowing from the power supply unit 7 to the reference power supply circuit 6 changes due to the change in the impedance of the heat detecting element 71. The change in the impedance of the heat detecting element 71 also changes the level of the reference voltage. That is,
The reference power supply circuit 6 detects a current output from the power supply unit 7. In addition, the control of the level of the reference voltage is performed by the rise in the temperature inside the power supply unit 7.

Further, the resistor R2 can be connected in parallel with the heat detecting element 71. In this case, a heat detecting element 71 having the opposite characteristic is used. That is, the heat detection element 7
No. 1 uses an element having a positive temperature coefficient. In addition,
Assuming that the reference voltage of the resistor R2 is Vref0 and the reference voltage which is a reference power supply input to the comparison detector 11 is Vref1, a relationship of Vref1 = (1 + R1 / R2) .Vref0 is established.

Further, the characteristics of the heat detecting element 71 can be determined by the detected temperature of the heat sink 72, the capacity of the radiator of the power supply unit 7, and the like.

Next, the operation of the above charging circuit will be described in detail with reference to a time chart shown in FIG. First, at time T ₀ , the thrower 91 is in the released state. In this case, the charging current 2 is not output from the power supply unit 7 to the battery 8. Therefore, the current flowing into the detection circuit 1 is due to the charge that has been charged in the battery 8. Therefore, the charging current 2 is not detected. Therefore, the output from the comparison detector 11 is “L”. Also,
At this time, since the output of the oscillator 3 is also “L”, DF
The output from the F circuit 4 is in the “H” state. Therefore, the opening / closing part 53 is closed.

Subsequently, when the input device 91 is closed at T ₁ , the output voltage of the power supply section 7 rises at T ₂ . Then, a charging current higher than a predetermined current is output from the power supply unit 7. Accordingly, charging of the battery 8 is started. Therefore, the output from the comparison detector 11 also rises. Then, at T ₃ in which the output of the oscillator 3 is 'H' until the battery 8 is charged. After that, the opening / closing section 53 is in the released state. Then, the battery 8 is not charged.

Next, the transition of the charge amount of the battery 8 and the temperature rise of the power supply unit 7 due to the opening and closing of the opening and closing unit 53 will be described with reference to FIG.
This will be described with reference to FIG. Figure 5 shows the temperature rise of the charge quantity of transition and the power supply unit 7 of the battery 8 from time T ₁ T _n. In the figure, the case with and without the charge switching circuit 5 will be described.

First, the dotted line shown in the figure indicates the temperature of the power supply section 7 which rises when the charging / closing circuit 5 is not provided. The bold line shown in the drawing indicates the temperature of the power supply unit 7 that rises when there is a charging circuit. The thin line shown in the figure indicates the amount of charge charged to the battery 8 when there is no charging circuit. Further, the lower part of the graph shows the opening and closing of the opening and closing part 53 described in FIG.

First, the amount of charge in the battery 8 and the temperature of the power supply 7 when no charging circuit is provided will be described. According to FIG. 5, between the times T ₁ and T _n , both the charge amount charged in the battery 8 and the temperature of the power supply unit 7 gradually rise. Since no charging circuit is provided, the output of the power supply 7 and the input of the battery 8 are directly connected. Therefore, the power supply unit 7 continues to supply the charging current 2 in a state of exceeding the predetermined current value.

Therefore, the temperature of the power supply unit 7 increases,
The temperature of the power supply unit 7 indicated as
Temperature. Then, a protection function for protecting the power supply unit 7 from heat is activated, and the output voltage of the power supply unit decreases.
Therefore, no charging current is input to the battery 8. Therefore, the stored voltage charged in the battery 8 is discharged and the charge amount is reduced.

On the other hand, the amount of charge in the battery 8 and the temperature of the power supply section 7 when the charging / closing circuit 5 is provided will be described. As described above, the switching unit 53 provided in the charging switching circuit 5 is opened and closed according to the output from the Q output terminal of the D-FF circuit 4. Therefore, the charging current 2 is intermittently output from the power supply unit 7. Accordingly, as shown as a power supply unit 7 per hour between the time T ₁ of the T _n
Temperature rise can be suppressed.

Specifically, by suppressing the rise in temperature, the power supply unit 7 does not become higher than the temperature at which the overcurrent protection circuit is turned on, so that the overcurrent protection circuit does not operate. That is, the charging voltage can be maintained. Therefore, the charging efficiency of the battery 8 can be improved.

[0048]

As described above, the charging circuit according to the present invention has the switching unit, and the opening and closing of the switching unit is controlled by the temperature of the power supply unit. The temperature of the power supply rises by outputting the charging current. Then, when the temperature of the power supply unit rises, the opening / closing unit is opened. Therefore, the power supply unit does not output the charging current. Therefore, a rise in the temperature of the power supply unit can be suppressed.

Specifically, it is possible to prevent the temperature of the power supply unit from rising to a temperature at which the overcurrent protection circuit operates. Therefore, the voltage of the power supply unit can be maintained at a charging voltage at which the battery can be charged. Therefore, the battery can be sufficiently charged.

Further, as described above, the opening and closing of the opening / closing section is controlled by the charging current output from the power supply section. When the switch is opened and closed, the charging current is intermittently output to the battery. Accordingly, the charging current output per fixed time decreases. Therefore, the temperature of the power supply unit that rises can be suppressed. Therefore, the temperature of the power supply unit does not easily rise. Therefore, the capacity of the radiator provided inside the power supply unit can be reduced. That is, the size of the power supply unit itself can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a charging circuit of the present invention.

FIG. 2 is a block diagram showing each circuit constituting the charging circuit of the present invention.

FIG. 3 shows a power supply unit and a reference power supply circuit of the charging circuit according to the present invention;
FIG. 3 is a block diagram illustrating an internal configuration of a detection circuit.

FIG. 4 is a time chart showing the operation of the charging circuit of the present invention.

FIG. 5 is a graph showing a relationship between a change in a charged amount of a battery and a rise in temperature of a power supply unit.

FIG. 6 is a block diagram illustrating a configuration of a charging circuit according to the related art.

FIG. 7 is a block diagram illustrating a configuration of a charging device of a charging circuit according to the related art.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 detection circuit 2 charging current 3 oscillator 4 D-type flip-flop circuit (D-FF circuit) 5 charging switching circuit 6 reference power supply circuit 7 power supply unit 8 battery 9 input power supply 10 resistance 11 comparison detector 21 pulse charger 22 secondary battery 23 Current measuring means 24 Voltage measuring means 25 Internal impedance measuring means 26 Battery temperature measuring means 27 Full charge detecting device 28 Charging control device 51 Driver 52 Relay 53 Opening / closing section 61 Shunt regulator 71 Heat detecting element 72 Heat sink

Claims (5)

(57) [Claims] 1. A charging current for charging a battery from a power supply unit via an opening / closing unit is detected, and when the charging current exceeds a predetermined current value, the opening / closing unit is opened and closed. A charging circuit for charging the battery by keeping the opening / closing unit closed when the temperature is equal to or less than a value, wherein the heat detecting element detects a temperature of the power supply unit;
Reference for detecting the charging current value based on the output from the element
A reference power supply circuit for controlling a voltage,
Therefore, the charging circuit detects the charging current value and controls the opening / closing of the opening / closing unit based on the temperature of the power supply unit. 2. A charging current for charging a battery from a power supply unit via an opening / closing unit is detected, and when the charging current exceeds a predetermined current value, the opening / closing unit is opened and closed. A charging circuit for charging the battery by keeping the open / close portion closed when the value is equal to or less than a value, a detection circuit for detecting the charging current, and a flip-flop circuit for inputting an output of the detection circuit. A charging circuit, wherein the battery is charged by opening and closing the opening and closing unit by an output of the flip-flop circuit. 3. The detection circuit according to claim 1, further comprising: a resistor for converting the charging current into a voltage; and a comparison detector for comparing the level of the voltage with a reference voltage controlled by the temperature of the power supply unit. The charging circuit according to claim 2 . 4. The charging circuit according to claim 3 , further comprising a heat detecting element for detecting a temperature of the power supply unit, wherein the reference voltage is changed by an output from the heat detecting element. 5. A method according to claim 2 to 4, characterized in that the switching frequency of the switching unit is determined by the characteristics of the thermal detection element
The charging circuit according to claim 1 .