JP3090461B2 - Charging circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a charging circuit for electric equipment such as a power tool and a shaver, and more particularly to a charging circuit for controlling a charging operation of a storage battery based on a temperature rise rate of the storage battery.

[0002]

[Prior art]

Conventionally, a temperature rise value per unit time of the storage battery (hereinafter referred to as a temperature rise rate ΔT) is detected simultaneously with the start of charging of the storage battery, and when the temperature rise rate ΔT exceeds a predetermined threshold value, charging of the storage battery is stopped. Such is known.

FIG. 6 is a diagram illustrating a relationship between a temperature rise rate ΔT of a storage battery and a charging time t for explaining charging control of a conventional charging circuit. In the figure, graphs A, B, and C respectively show a fully charged battery, a battery with a remaining capacity of 50%, and a battery with a remaining capacity of 0%. ΔT ₂ is a threshold value for controlling the charging stop. When the temperature rise rate ΔT of the storage battery exceeds the threshold value ΔT ₂ , the charging of the storage battery is stopped.

As shown in FIG. 1, in the case of a storage battery having a remaining capacity of 0% or 50%, when the battery is fully charged, the temperature rise rate ΔT sharply increases,
Since the threshold value ΔT ₂ is exceeded, charging is stopped when the battery is almost fully charged. On the other hand, when the storage battery is fully charged, it is preferable to stop charging immediately after the start of charging. However, the temperature rise rate ΔT does not increase rapidly due to the heat capacity of the storage battery and the like. It exceeds the threshold [Delta] T _2, has become the charging is stopped.

[0005]

[Problems to be solved by the invention]

In the conventional charging circuit, when charging the full charge of the battery, without exceeding the temperature increase rate [Delta] T immediately threshold [Delta] T _2, it takes time of about 1 minute to stop the charging. For this reason, the gas pressure in the storage battery increases due to overcharging, and a dangerous state such as explosion or liquid leakage may occur.

The present invention has been made in view of the above problems, and has a threshold value set to be small within a predetermined time after the start of charging, so that charging can be stopped in a timely manner even when a fully charged storage battery is charged. It is intended to provide a circuit.

[0007]

[Means for Solving the Problems]

In order to solve the above-described problems, the present invention provides a charging circuit that detects a temperature rise rate at the same time as the start of charging of a storage battery, and stops a charging operation when the detected temperature rise rate exceeds a predetermined threshold. Is started, a first threshold value is set as the threshold value of the temperature rise rate, and when a predetermined time set after the start of charging has elapsed, the threshold value of the temperature rise rate is larger than the first threshold value. It is provided with a threshold setting means for switching and setting to the second threshold.

According to the above configuration, the rate of temperature rise of the storage battery is detected simultaneously with the start of charging. Within a predetermined time after the start of charging, a first threshold value is set as a threshold value of the temperature rise rate, and when the temperature rise rate exceeds the first threshold value, charging of the storage battery is stopped. After a predetermined time has elapsed from the start of charging, a second threshold larger than the first threshold is set as the threshold of the temperature rise rate, and when the temperature rise rate exceeds the second threshold, charging of the storage battery is stopped. You.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION

 A charging circuit according to the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a charging circuit according to the present invention.

In FIG. 1, reference numeral 1 denotes an input filter circuit for removing a noise component contained in an AC voltage e, and 2 denotes a rectifying / smoothing circuit comprising a rectifying bridge 2a and a smoothing circuit 2b for converting the AC voltage e into a DC voltage. is there. Reference numeral 3 denotes a high-speed switching of the DC voltage generated by the rectifying and smoothing circuit 2. For example, a switching circuit composed of a power MOSFET, 4 denotes a driver circuit for driving the switching circuit 3 on and off, and 5 denotes a switching operation of the switching circuit 3. PWM that controls charging current by controlling on / off duty of
The control circuit 6 includes the driver circuit 4 and the PWM control circuit 5
Is an auxiliary power supply circuit for supplying the driving power of the power supply.

Reference numeral 7 denotes a soft start circuit for instructing a switch to gradually increase the charging current from a low level at the start of charging. When the attachment of a battery pack 11 described later is detected, a microcomputer 15 (hereinafter, referred to as a microcomputer) described later
Is input to the soft start circuit 7 via the photocoupler 19. The soft start circuit 7 receives the pack detection signal and inputs a soft start control signal to the PWM control circuit 5, and the PWM control circuit 5 receives the control signal and sets the charging current to be smaller than a predetermined charging current value. Value, and gradually increases to a predetermined charging current value after the start of charging.

T is a high-frequency transformer that steps down the high-frequency AC voltage generated on the primary side by the switching circuit 3 and supplies it to the secondary side. Reference numeral 8 denotes a rectifying / smoothing circuit including a rectifying circuit 8a and a smoothing circuit 8b, which rectifies an AC voltage supplied to the secondary side, 9 denotes a current detecting circuit that converts a charging current into a voltage, and detects the current. A constant current control circuit that amplifies the detection voltage of the detection circuit 9 and feeds it back to the PWM control circuit 5 via the photocoupler 17. PWM control circuit 5
Changes the on / off duty of the pulse signal in accordance with the voltage input from the constant current control circuit 10, and controls the charging current to be constant.

Further, 11 is a battery pack temperature sensor D _S for detecting the temperature of the battery B and the storage battery B to be charged is incorporated,
It is connected to a secondary output terminal of the charging circuit via a switch SW. The switch SW is a relay switch that is turned on and off by the microcomputer 15.

Further, 12 is an amplifier circuit for amplifying a predetermined voltage range corresponding to the detection voltage of the temperature detection range of the temperature sensor D _S, pack detection circuit for detecting the presence or absence of the battery pack 12 is 13, the 14 storage battery This is a voltage detection circuit that detects the voltage of B.

FIG. 2 shows an example of a specific circuit of the amplifier circuit 12.

The amplifier circuit 12 is composed of a differential amplifier using an operational amplifier OP, the detection voltage of the temperature sensor D _S is input via the resistor R ₃ to the inverting input terminal of the operational amplifier OP, the non-inverting input terminal A divided voltage (reference voltage) obtained by dividing a predetermined constant voltage by the dividing resistors R ₁ and R ₂ is input via the resistor R ₄ , and the operational amplifier OP
Output voltage V ₀ which is input to the A / D terminal of the microcomputer 15 through the resistor R _8. Also, the series circuit of a resistor R ₇ and the transistor Q in the split resistor R ₁ are connected in parallel, the transistor Q is adapted to be on-off controlled by a control signal from P ₀ terminal of the microcomputer 15 I have. This gives P ₀
When the control signal of the low from the terminal is output, the resistance value of the dividing resistors R ₁ side is switched from the R ₁ to R ₁ // R _7, reference voltage input to the non-inverting input terminal is split resistor R ₁ , split resistance from the divided voltages V ₁ by _{R 2 (R 1 // R 7} ), divided by R ₂ voltage V ₂ (> V
_It is switched to ₁ ). The resistor R ₅ is the feedback resistor, the resistor R ₆
Is the input resistance of the non-inverting input terminal.

In the above configuration, the output voltage 0~5v the gain of the amplifier circuit 12 for the temperature range 50 ° C. is adjusted to correspond the detected temperature is 0 ℃ temperature sensor D _S of the reference voltages V ₁ of time, it sets the output voltage V ₀ becomes 0 v, the reference when the voltage V ₂ of the temperature sensor D _S detected temperature of 50 ° C., the output voltage
V ₀ is set to 0v, and when the detected temperature is 0 to 50 ° C. by the microcomputer 15, a high signal is output from the P ₀ terminal, and when the detected temperature is 50 to 100 ° C., P ₀ is output. When control is performed so as to output a low signal from the terminal, as shown in FIG.
Two temperature detection ranges of ° C. correspond. In this way, the voltage range of 0 to 5v is 0 to 5
The measurement accuracy is doubled as compared with the case where the temperature detection range of 100 ° C. is used. That is, for example, if the output voltage of the temperature sensor is A / D-converted into 8-bit digital data and the temperature data is calculated using the digital data, the conventional value is 0.39 ° C. (100 ° C./256 bits) per bit. Thus, considering the measurement variation of about 3 bits, the temperature measurement accuracy of the storage battery is about 1.17 ° C., but in the case of this embodiment, the temperature measurement accuracy of the storage battery is improved to 0.585 ° C.
As a result, the charging control based on the temperature rise rate ΔT of the storage battery B can be performed more accurately.

Returning to FIG. 1, in the microcomputer 15, the 151 converts the voltage data of the storage battery B input from the voltage detection circuit 14 into A / A
An A / D conversion circuit 152 for performing D conversion is a cell number determination circuit that determines the number of cells of the storage battery B from the A / D converted voltage data. The number of cells of the storage battery B is, for example, the storage battery B taken in a state in which the switch SW is turned off during charging or after charging is completed, and the battery pack 11 is electrically disconnected from the charging circuit.
And is displayed on the display 16 such as an LCD.

153 is a timer circuit for measuring a charging time, and 154 is A / A for storing the temperature data of the storage battery B inputted from the amplifying circuit 12.
An A / D conversion circuit that performs D conversion, 155 is a temperature rise value per unit time of the storage battery B from the A / D converted temperature data, that is,
The temperature rise rate ΔT is calculated, and the temperature rise rate ΔT and a preset threshold value ΔT ₁ (first threshold value) or ΔT ₂ (> ΔT ₁ , second temperature
A threshold value of the battery temperature rise rate control circuit (hereinafter referred to as ΔT control circuit) 156 is an A / D
The absolute temperature protection circuit calculates the absolute temperature of the storage battery B from the converted temperature data, determines the full charge state from the absolute temperature, and prevents overcharge. Reference numeral 157 denotes an LCD driver for driving the display 16 composed of an LCD or the like.

In the above configuration, the state of charge of the storage battery B depends on the ΔT
The temperature rise rate ΔT is determined by the control circuit 155, and
Beyond _one or threshold [Delta] T _2, it is determined that a fully charged state, charging stop is instructed. In addition to the charge control by the ΔT control circuit 155, the timer circuit 153 and the absolute temperature protection circuit 156 are provided to protect the storage battery B from overcharging. When the charging time exceeds a predetermined time, the timer circuit 153 forcibly instructs the charging to stop, and the absolute temperature protection circuit 156
When the temperature of the storage battery B exceeds a predetermined value, a command is issued to forcibly stop charging. When an instruction to stop charging is issued by these circuits, a signal for switching to the terminal current is output from the microcomputer 15 to the PWM control circuit 5 via the photocoupler 18.

Next, the charging stop control of the charging circuit according to the present invention will be described with reference to the flowchart of FIG.

First, when charging is started, a threshold value ΔT ₁ is set (# 1), and temperature data of the storage battery B is read into the microcomputer 15 (# 2). Subsequently, the [Delta] T control circuit 155, a temperature increase rate [Delta] T is calculated from the temperature data, whether the temperature increase rate [Delta] T exceeds the threshold value [Delta] T ₁ is determined (# 3). If exceeds the temperature increase rate [Delta] T is the threshold value [Delta] T ₁ (YES at # 3), the process proceeds to # 8, the charging operation is stopped, if the temperature increase rate [Delta] T is less than or equal to the threshold value [Delta] T ₁ (# 3
NO), and it is further determined whether or not the charging time t has passed one minute (# 4). If the charging time t has not elapsed one minute (NO at # 4), the process returns to # 2, new temperature data is read, whether exceeds the threshold value [Delta] T ₁ for the latest temperature increase rate [Delta] T is determined (# 2, # 3). Then, when the charging time t has passed 1 minute without the temperature rise rate ΔT exceeding the threshold ΔT ₁ (YES in # 4), a threshold ΔT ₂ (> ΔT ₁ ) is set in place of the threshold ΔT _1. (#
5). Subsequently, the temperature data of the storage battery B is read (#
6), the temperature temperature increase rate [Delta] T that is calculated from the data whether it exceeds the threshold value [Delta] T ₂ is determined (#
7). If the temperature rise rate ΔT exceeds the threshold value ΔT ₂ (# 7
YES), the charging operation is stopped (# 8), and the temperature rise rate Δ
If T is the threshold value [Delta] T ₂ or less, the process returns to # 6, new temperature data is read, whether exceeds the threshold value [Delta] T ₂ for the latest temperature increase rate [Delta] T is determined (# 6, # 7), the temperature When the increase rate [Delta] T exceeds the threshold value [Delta] T ₂ (YES at # 7), the charging operation is stopped (# 8).

FIG. 5 is a diagram illustrating the relationship between the temperature rise rate ΔT per unit time and the charging time t for explaining the above-described charging control operation. In the figure, graphs A, B, and C respectively show a fully charged battery, a battery with a remaining capacity of 50%, and a battery with a remaining capacity of 0%. In the figure, the threshold ΔT ₁ is 0.5 (° C./second), and the threshold ΔT ₂ is 1.5 (° C./second).
Seconds).

As shown in FIG. 1, in the case of a storage battery having a remaining capacity of 0% or a storage battery having a storage capacity of 50%, the temperature rise rate ΔT increases after the start of charging.
Since the threshold value ΔT ₁ will not be exceeded by one minute,
Charging is continued. And with a storage battery with 0% remaining capacity,
Approximately 6 minutes after the start of charging, the battery is fully charged. Then, the temperature rise rate ΔT of the storage battery sharply increases, and the threshold ΔT ₂ approximately 6.5 minutes after the start of charging.
And charging is stopped. In the case of a storage battery with a remaining capacity of 50%, the battery is fully charged in about 3 minutes after the start of charging, and thereafter the temperature rise rate ΔT of the storage battery rapidly rises and exceeds the threshold ΔT ₂ in about 3.5 minutes after the start of charging, and charging is stopped. You. On the other hand, when the storage battery is fully charged, the temperature rise rate ΔT sharply increases after the start of charging,
The charge exceeds the threshold ΔT _{1 in} 0.5 minutes, and charging is stopped immediately.

In the above embodiment, the threshold values ΔT ₁ and ΔT ₂ are set to 0.5 (° C. /
Seconds) and 1.5 (° C./second), but any appropriate value can be set. One minute after the start of charging, the threshold Δ
Had switched T ₁ to the threshold [Delta] T _2, it is possible to set the switching timing is also appropriate time.

[0027]

【The invention's effect】

As described above, according to the present invention, the threshold value of the charge stop control based on the temperature rise rate of the storage battery is set to the first threshold value within a predetermined time after the start of charging, and is set to be lower than the first threshold value after the lapse of the predetermined time. Since the switching to the large second threshold is set, in the case of a storage battery that is not fully charged, it is possible to suitably stop charging when the storage battery is fully charged. In the case of a fully charged storage battery, charging can be stopped immediately after the start of charging, thereby preventing overcharging and preventing the capacity of the battery from deteriorating due to repeated recharging.

[Brief description of the drawings]

FIG. 1 is a block diagram of a charging circuit according to the present invention.

FIG. 2 is a diagram illustrating an example of a specific circuit of an amplifier circuit.

FIG. 3 is a diagram showing a relationship between a voltage range and a temperature detection range.

FIG. 4 is a flowchart showing a control operation for stopping charging of the charging circuit according to the present invention.

FIG. 5 is a diagram illustrating a relationship between a temperature rise rate ΔT and a charging time t for describing a control operation of stopping charging of the charging circuit according to the present invention.

FIG. 6 is a diagram illustrating a relationship between a temperature rise rate ΔT and a charging time t for describing a control operation of stopping charging in a conventional charging circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Input filter circuit 2,8 ... Rectifier smoothing circuit 3 ... Switching circuit 4 ... Driver circuit 5 ... PWM control circuit 6 ... Auxiliary power supply circuit 7 ... Soft start circuit 9 ... Current detection circuit 10 ... ... Constant current control circuit 11 ... Battery pack 12 ... Amplifier circuit 13 ... Pack detection circuit 14 ... Voltage detection circuit 15 ... Microcomputer 16 ... Display (LCD) 17-19 ... Photocoupler 151,154 A / D conversion circuit 151 …… Cell number judgment circuit 153 …… Timer circuit 155 …… ΔT control circuit 156 …… Absolute temperature protection circuit 157 …… LCD driver B …… Storage battery D _S …… Temperature sensor OP …… Op amp Q… … Transistors R _{1 to} R ₈ … Resistance SW… Switch

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-268446 (JP, A) JP-A-1-138931 (JP, A) JP-A-62-193518 (JP, A) JP-A-1 308132 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02J ^7/ 00-7/ ¹⁰

Claims (1)

(57) [Claims] 1. A charging circuit for detecting a temperature rise rate at the same time as the start of charging of a storage battery and, when the detected temperature rise rate exceeds a predetermined threshold value, in a charging circuit for stopping charging operation, when charging is started. Setting a first threshold value as the threshold value of the temperature rise rate, and when a predetermined period of time elapses after the start of charging, the threshold value of the temperature rise rate is changed to a second threshold value larger than the first threshold value. A charging circuit comprising a threshold setting means for switching and setting.