JP2001061231A - Battery protection circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress temperature rise of a battery, without turning off power from the battery. SOLUTION: The surface temperature of a battery 1 is detected by a temperature detecting part 2. The analog data detected by the temperature detecting part 2 is converted to digital temperature data by an A/D converting part 3. Based on the temperature data from this A/D converting part, a discriminating part 4 discriminates whether the temperature rises to a preset reference value or higher. If the discrimination result on the temperature is equal to or higher than the reference value, a control part 5 changes the frequency divider ratio of a clock frequency divider circuit 7, so that the frequency of a system clock is made lower than that at the normal times. Thus, the consumed current of the battery 1 is reduced, and its temperature is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to protection against temperature rise of a battery.

[0002]

2. Description of the Related Art Batteries are used in a wide variety of electronic devices. The battery generates heat when used for a long time, in an environment with a high ambient temperature, in a high environment, or when used under overload, and may cause danger. Therefore, it is necessary to prevent the temperature of the battery from rising. Conventionally, battery thermal protection usually detects the temperature of the battery and turns off the battery output (power supply) when the detected temperature exceeds a set temperature. When the power is turned off, the operation of the apparatus stops.

[0003]

As described above, conventionally, when the temperature of a battery rises above a predetermined temperature, the battery output is usually turned off and the operation of the apparatus is stopped. On the other hand, it would be advantageous if the elevated battery temperature could be reduced while maintaining operation.
SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide a battery protection circuit that reduces the temperature of a battery that has risen while maintaining the operation of the device.

[0004]

According to the present invention, there is provided an apparatus which operates using a battery as a power supply, a temperature detecting section for detecting a surface temperature of the battery, and conversion of analog data detected by the temperature detecting section into digital data. A / D
A conversion unit; a determination unit that determines whether the temperature data from the A / D conversion unit has risen to a predetermined reference value or more; and a control unit that controls the determination unit. The controller provides a battery protection circuit that changes the frequency division ratio of the clock frequency divider circuit so as to lower the frequency of the system clock when the frequency is equal to or higher than the reference value.

Alternatively, instead of changing the frequency division ratio of the clock frequency dividing circuit, the control unit may control the VCO to reduce the output signal frequency of the system clock generating VCO. As a method of frequency reduction,
Either the VCO oscillation frequency may be reduced, or the frequency division ratio of a frequency divider for dividing the frequency of the VCO oscillation signal may be increased.

[0006] The output signal frequency of the VCO may be reduced by a predetermined frequency each time the temperature of the battery rises by one degree.

Alternatively, instead of changing the frequency division ratio of the clock frequency dividing circuit, the control unit controls the backlight voltage control unit for setting the backlight of the video display LCD so as to reduce the backlight luminance. You may make it control.

Alternatively, the control unit controls the backlight voltage control unit for setting the backlight of the video display LCD so as to reduce the backlight brightness together with the change of the frequency division ratio of the clock frequency dividing circuit. You may make it.

Alternatively, instead of changing the frequency division ratio of the clock frequency dividing circuit, the control unit controls the VCO to reduce the output signal frequency of the system clock generating VCO, and controls the image display LCD. The backlight voltage control unit that sets the backlight may be controlled by the control unit to reduce the backlight luminance.

Further, the control unit may control the reduction of the backlight luminance so as to decrease by a predetermined luminance every time the temperature of the battery rises by one degree.

Alternatively, instead of changing the frequency dividing ratio of the clock frequency dividing circuit, a spare battery is provided separately from the battery.
A switching circuit for switching between the battery and the backup battery may be provided, and when the determination by the determination unit is equal to or greater than a reference value, the switching circuit may be switched to supply power from the backup battery.

Further, a display unit may be provided below the control unit, and when the determination by the determination unit is equal to or more than a reference value, the display unit displays the display value.

[0013]

Embodiments of the present invention will be described below with reference to the drawings based on embodiments. FIG. 1 is a main block diagram showing one embodiment of a battery protection circuit according to the present invention, and FIGS. 2 to 4 are main block diagrams showing another embodiment. Hereinafter, each figure will be described. In the embodiment of FIG.
Reference numeral 1 denotes a battery, which supplies power to a load circuit. Reference numeral 2 denotes a temperature detection unit that detects the surface temperature of the battery 1. For example, a thermistor is used as the temperature detecting element. Three
Denotes an A / D converter, which converts an analog detection signal from the temperature detector 2 into digital data. Reference numeral 4 denotes a determination unit that compares a signal from the A / D conversion unit 3 with a preset reference value. A control unit 5 controls the determination unit 4 and the clock frequency dividing circuit 7.

Reference numeral 6 denotes a VCO (Voltage Controlled Oscillator), and reference numeral 7 denotes a clock frequency dividing circuit, which divides the frequency into a clock signal of a predetermined frequency based on the output of the VCO and outputs it as a system clock. As an operation of the present embodiment, the output from the temperature detection unit 2 is converted into digital data by the A / D conversion unit 3.
The output of the A / D converter 3 is determined by the determiner 4 under the control of the controller 5. In the determination, when the temperature detection data from the A / D converter 3 is equal to or more than the reference value, the control unit 5 increases the system clock division ratio of the clock division circuit 7 with respect to the current division ratio, and Lower the frequency. The setting is changed so that the frequency is, for example, 又 は or ４. By changing the frequency division ratio, the current consumption of the circuit using the system clock is reduced, and the temperature of the battery 1 is thereby reduced.

Next, the embodiment of FIG. 2 will be described. FIG.
The same components as those described above are denoted by the same reference numerals, and their description is omitted (the same applies to FIGS. 3 and 4). FIG. 1 shows that the frequency dividing ratio of the frequency dividing circuit is changed when the temperature detected by the temperature detector 2 rises above a predetermined temperature, whereas FIG. 2 shows the output of the VCO 6 which is the source of the system clock. The control unit 11 controls the VCO 6 so as to lower the frequency. As a control method, for example, the battery 1
Is lowered by a predetermined frequency each time the temperature rises by one degree. As a result, the frequency of the system is reduced, the current consumption of the circuit is reduced, and the temperature of the battery 1 is reduced. Note that as a control method for lowering the output frequency of the VCO 6,
Control to lower the oscillation frequency of VCO 6 or VCO 6
There is control of changing the frequency division ratio of a frequency dividing circuit (not shown) for dividing the output of the above, but any method may be used.

Next, the embodiment of FIG. 3 will be described. Note that the same components as those in FIG. In the present embodiment, when the temperature of the battery 1 rises above a predetermined temperature, the brightness of the backlight of the LCD 22 for displaying images is reduced. As a method of lowering the brightness, the brightness is lowered by a predetermined brightness each time the temperature of the battery 1 rises by one degree. Specifically, the control unit 23 sets the backlight voltage control unit 21 for setting the backlight of the LCD 12 so as to lower the backlight as described above. Thereby, the current consumption of the present device is reduced, and the temperature of the battery 1 is reduced.

Next, the embodiment of FIG. 4 will be described. Note that the same components as those in FIG. In the present embodiment, a spare battery 31 is provided in addition to the original battery 1, and when the temperature of the battery 1 rises above a predetermined temperature, the battery is switched to the spare battery 31. Specifically, a switching circuit 32 for switching between the battery 1 and the battery 31 is provided, and the switching circuit 32 is normally set on the battery 1 side during normal operation. Switches the switching circuit 32 to the battery 31 side. As a result, the consumed current of the battery 1 whose temperature has risen disappears, and the battery 1 is protected. In the embodiments of FIGS. 1 to 4, when the temperature detected by the temperature detector 2 is equal to or higher than the reference value, a warning may be displayed on the display 8 (LED). Further, a configuration in which the configuration for lowering the luminance of the backlight (FIG. 3), a configuration for lowering the frequency of the system clock (FIG. 1), or a configuration for lowering the output frequency of the VCO 6 (FIG. 2) may be used.

[0018]

As described above, according to the present invention, in a device that operates using a battery as a power source, even if the temperature of the battery rises, the temperature of the battery that has risen in the operating state can be reduced without turning off the power. It is possible to do.

[Brief description of the drawings]

FIG. 1 is a main block diagram showing one embodiment of a battery protection circuit according to the present invention.

FIG. 2 is a main block diagram showing another embodiment of the battery protection circuit according to the present invention.

FIG. 3 is a main part block diagram showing another embodiment of the battery protection circuit according to the present invention.

FIG. 4 is a main part block diagram showing another embodiment of the battery protection circuit according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 31 Battery 2 Temperature detection part 3 A / D conversion part 4 Judgment part 5, 11, 23, 33 Control part 6 VCO 7 Clock frequency dividing circuit 8 Display part 21 Backlight voltage control part 22 LCD 32 Switching circuit

Claims (11)

[Claims] 1. An apparatus that operates using a battery as a power supply, a temperature detector that detects a surface temperature of the battery, an A / D converter that converts analog data detected by the temperature detector into digital data, A determination unit that determines whether the temperature data from the A / D conversion unit has risen above a preset reference value; and a control unit that controls the determination unit. In some cases, the control unit changes the frequency division ratio of the clock frequency dividing circuit so as to lower the frequency of the system clock. 2. The control unit controls the VCO so as to reduce the output signal frequency of a system clock generation VCO instead of changing the frequency division ratio of the clock frequency divider circuit. 2. The battery protection circuit according to 1. 3. The method according to claim 2, wherein the frequency of the output signal of the VCO is reduced.
3. The battery protection circuit according to claim 2, wherein the VCO oscillation signal frequency is reduced. 4. The output signal frequency of the VCO is reduced by:
3. The battery protection circuit according to claim 2, wherein a frequency dividing ratio of a frequency dividing circuit for dividing the frequency of the VCO oscillation signal is increased. 5. A method for reducing the output signal frequency of the VCO,
5. The battery protection circuit according to claim 2, wherein the control unit controls the temperature of the battery to decrease by a predetermined frequency each time the temperature rises by one degree. 6. A backlight voltage control unit for setting a backlight of a video display LCD instead of changing a frequency division ratio of the clock frequency dividing circuit, so that the control unit reduces the backlight luminance. The battery protection circuit according to claim 1, wherein the battery protection circuit is controlled. 7. The control unit controls a backlight voltage control unit for setting a backlight of a video display LCD so as to reduce the backlight brightness together with a change in a division ratio of the clock frequency dividing circuit. The battery protection circuit according to claim 1, wherein 8. The control section controls the VCO so as to reduce the output signal frequency of the system clock generation VCO instead of changing the frequency division ratio of the clock frequency divider circuit. 2. The battery protection circuit according to claim 1, wherein the control section controls the backlight voltage control section for setting the backlight so as to reduce the backlight luminance. 9. The control unit according to claim 6, wherein the control unit controls the reduction of the backlight luminance so as to decrease by a predetermined luminance every time the temperature of the battery rises by one degree. The battery protection circuit according to claim 7. 10. A backup battery and a switching circuit for switching between the battery and the spare battery are provided separately from the battery instead of changing the frequency division ratio of the clock frequency divider circuit. 2. The battery protection circuit according to claim 1, wherein the switching circuit is switched so as to supply power from the spare battery when the battery voltage is equal to or more than a reference value. 11. The display device according to claim 1, wherein a display unit is provided below the control unit, and when the determination by the determination unit is equal to or more than a reference value, the display is displayed on the display unit. 11. The battery protection circuit according to claim 7, claim 8, or claim 10.