JP2009106010A - Power supply system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely prevent a rise of a temperature of an AC adapter while simplifying a circuit constitution. <P>SOLUTION: This power supply system comprises the AC adapter 10 for converting an alternate current of a commercial power supply into a direct current, and an electronic apparatus 30 to which power is fed from the AC adapter 10. The AC adapter 10 comprises a temperature sensor 11 for detecting a temperature of the sensor itself, and a temperature-voltage conversion circuit 12 for changing an output voltage by using the detected temperature detected by the temperature sensor 11. The electronic apparatus 30 comprises a switching element 31 connected to an input terminal 33 in series thereto, and a control circuit 32 which detects an input voltage from the AC adapter 10, and controls the switching element 31 by using the detected input voltage. In the electronic apparatus 30, when the temperature of the AC adapter 10 rises, and the input voltage from the AC adapter 10 in the off-state of the switching element 31 is lower than a set voltage, the control circuit 32 blocks an input current from the AC adapter 10 by switching the state of the switching element 31 into the off-state. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a power supply system that supplies power to an electronic device from an AC adapter, and more particularly to a power supply system that cuts off the current of the AC adapter when the temperature of the AC adapter becomes abnormally high.

An AC adapter, which is a power supply circuit that supplies power to an electronic device, self-heats while supplying power. This is because a part of the input commercial power is consumed and a DC voltage is output. The AC adapter self-heats by consuming the difference power between the input power and the output power. The AC adapter generates heat to increase its temperature and dissipates heat to decrease its temperature. Therefore, the temperature becomes abnormally high when the amount of heat radiation becomes smaller than the amount of heat generated. The AC adapter changes its heat dissipation amount depending on the usage environment, but the heat dissipation amount cannot be larger than the heat generation amount in all usage environments of all users. For example, when the AC adapter is covered with a heat insulating sheet, the amount of heat release is extremely limited, and the temperature may rise abnormally. The temperature rise of the AC adapter causes various harmful effects. In order to prevent this problem, a technique for protecting the temperature rise of the AC adapter has been developed. (See Patent Documents 1 to 3)
JP 2005-51875 A JP 2000-209768 A JP 2000-78849 A

  Patent Document 1 has a structure in which an AC adapter can be detached from an electronic device. This AC adapter removes heat from the electronic device when the temperature rises and it is necessary to dissipate heat. When carrying, connect the AC adapter to the electronic device. Since this AC adapter is removed from the electronic device when the temperature rises, there is a disadvantage that the temperature further rises if the user cannot detect the temperature rise of the AC adapter. For this reason, there is a drawback that all users cannot use it in various usage environments with peace of mind.

  In Patent Document 2, a current fuse is connected to an input line of an AC adapter, and a temperature fuse that is short-circuited when overheated is connected in series with the current fuse. The thermal fuse is connected in parallel to the input side of the AC adapter. According to this circuit configuration, when the AC adapter is overheated and the temperature fuse is short-circuited, a current is supplied to the current fuse and blown. For this reason, when the temperature of the AC adapter becomes abnormally high, commercial power is not input to the AC adapter. For this reason, the AC adapter stops operating and does not output. Although this circuit configuration can protect the AC adapter from abnormal temperature rise, the output of the AC adapter is cut off when the temperature becomes abnormally high. It is not possible to determine whether the AC adapter is not connected or the AC adapter does not output.

  Furthermore, Patent Document 3 detects the temperature of the AC adapter on the electronic device side to which the AC adapter is connected, and transmits a status signal to the AC adapter via the bus line when the temperature is abnormally high. The AC adapter controls the output voltage and current with a status signal input from the electronic device side. In this circuit configuration, since the AC adapter and the electronic device need to be connected by a bus line, the circuit configuration becomes complicated. In particular, since the AC adapter is connected via a connector for connecting the positive and negative output terminals to the electronic device, the circuit configuration of the connector and the lead wire in the structure for connecting the bus line and the positive and negative output terminals. However, there is a disadvantage that the manufacturing cost becomes high.

The present invention has been developed for the purpose of solving the above drawbacks. An important object of the present invention is to provide a power supply system that can be used safely by all users in various usage environments and reliably preventing the temperature rise of the AC adapter.
Another important object of the present invention is to provide a power supply system that can reliably prevent the temperature rise of the AC adapter while having a simple circuit configuration.

The power supply system of the present invention has the following configuration in order to achieve the above-described object.
The power supply system according to claim 1 of the present invention includes an AC adapter 10 that converts an alternating current of a commercial power supply into a direct current of a predetermined voltage, and an electronic device 30 that is connected to the AC adapter 10 and is supplied with electric power from the AC adapter 10. With. The AC adapter 10 includes a temperature sensor 11 that detects its own temperature, and a temperature-voltage conversion circuit 12 that changes an output voltage at a temperature detected by the temperature sensor 11. The electronic device 30 includes a switching element 31 connected in series to an input terminal 33 connected to the AC adapter 10, and the switching element 31 is turned off. And a control circuit 32 that detects the input voltage and controls the switching element 31 with the detected input voltage. In the electronic device 30, when the temperature of the AC adapter 10 becomes high and the input voltage from the AC adapter 10 in the OFF state of the switching element 31 becomes lower than the set voltage, the control circuit 32 switches off the switching element 31 and turns off the AC. The input current from the adapter 10 is cut off.

  The power supply system according to claim 2 of the present invention includes an AC adapter 20 that converts an alternating current of a commercial power supply into a direct current of a predetermined voltage, and an electronic device 40 that is connected to the AC adapter 20 and is supplied with electric power from the AC adapter 20. With. The AC adapter 20 includes a temperature sensor 11 that detects its own temperature, and a temperature-current conversion circuit 22 that changes an output current at a temperature detected by the temperature sensor 11. The electronic device 40 detects the input current from the switching element 31 connected in series to the input terminal 33 connected to the AC adapter 20 and the AC adapter 20, and controls the switching element 31 with the detected input current. And a control circuit 42. In the electronic device 40, when the temperature of the AC adapter 20 becomes high and the input current from the AC adapter 20 becomes smaller than the set current, the control circuit 42 switches off the switching element 31 to generate the input current from the AC adapter 20. Cut off.

  The power supply system according to claim 3 of the present invention includes a battery 34 in which the electronic devices 30 and 40 can be charged, and a charging circuit 35 that performs pulse charging of the battery 34, and switches the switching element 31 on and off to change the battery 34. Pulse charge.

  In the power supply system according to claim 4 of the present invention, the electronic devices 30 and 40 are anchors heated by the built-in battery 34. In the power supply system according to claim 4 of the present invention, the electronic device is a battery charger.

  The power supply system of the present invention has a feature that all users can use it in various usage environments to reliably prevent the temperature rise of the AC adapter and use it safely. In the power supply system according to claim 1 of the present invention, on the AC adapter side, the output voltage is lowered when the temperature of the AC adapter increases. On the electronic device side, the switching element is switched off and the switching element is turned off. When the input voltage from the AC adapter is detected and the input voltage from the AC adapter is low in this state, it is determined that the temperature of the AC adapter is high and the switching element is turned off to cut off the AC adapter current. is there. In the power supply system according to claim 2 of the present invention, when the temperature of the AC adapter increases, the output current is reduced. On the electronic device side, the input current from the AC adapter is detected, and the AC adapter detects the input current. This is because the AC adapter temperature is determined to be high and the switching element is turned off to cut off the AC adapter current.

  Further, according to the present invention, since the temperature abnormality of the AC adapter is detected with the above-described configuration, it is not necessary to connect the AC adapter and the electronic device with a signal line such as a bus line as in the past, and the AC adapter and the electronic device Can be connected only by the positive and negative power supply lines, and the AC adapter current can be cut off when the AC adapter temperature rises abnormally. For this reason, the current of the AC adapter can be cut off with a simple circuit configuration in an abnormal temperature state.

  The power supply system according to claim 3 of the present invention cuts off the current of the AC adapter with a switching element for pulse charging the battery built in the electronic device, and thus the AC adapter is provided with an element for cutting off the current. There is no need. A switching element for pulse charging built in the electronic device can be used together to cut off the current when the temperature of the AC adapter rises abnormally. For this reason, it is not necessary to provide a dedicated switching element for interrupting the current, and the circuit configuration can be further simplified. Furthermore, when the temperature of the AC adapter is abnormally high, the current is cut off on the electronic device side. Therefore, in a state where charging of the battery is stopped, it can be determined whether the battery is fully charged or whether the AC adapter is abnormal in temperature.

  Embodiments of the present invention will be described below with reference to the drawings. However, the embodiment described below exemplifies a power supply system for embodying the technical idea of the present invention, and the present invention does not specify the power supply system as follows.

  Further, in this specification, for easy understanding of the scope of claims, numbers corresponding to the members shown in the embodiments are indicated in the “claims” and “means for solving problems” sections. It is added to the members. However, the members shown in the claims are not limited to the members in the embodiments.

  The power supply system shown in the circuit diagram of FIG. 1 includes an AC adapter 10 that converts alternating current of a commercial power source into direct current of a predetermined voltage, and an electronic device 30 that is connected to the AC adapter 10 and supplies power from the AC adapter 10. Prepare. The electronic device 30 is a battery 34 that can be charged, and a device that incorporates a charging circuit 35 for the battery 34, such as an anchor or a hood. In particular, since the anchor is used in a futon, the AC adapter connected to the anchor has a higher probability that the temperature will be higher in the futon. Therefore, the power supply system that can cut off the current when the temperature of the AC adapter becomes high is particularly effective in the power supply system using the electronic device as an anchor, and can improve safety. In addition, in a power supply system in which an electronic device is a device incorporating a battery, a switching element for pulse charging the battery can be used in combination with an element for cutting off the current of the AC adapter. There is no need to provide a dedicated element, and the circuit configuration can be greatly simplified. Moreover, in order to charge the battery in a pulse manner, the switching element is turned on and off, and the input voltage from the AC adapter can be detected in a state where the switching element is turned off. Therefore, since the power supply system of the present invention is optimal for a configuration in which an AC adapter is connected to an electronic device such as an anchor incorporating a battery, an embodiment in which the electronic device is an anchor heated by a battery will be described in detail below. To do.

  However, the power supply system of the present invention does not specify an electronic device as an anchor, nor does it specify a device that incorporates a battery, and the electronic device may be, for example, a laptop computer, an audio system, a mobile phone, or a battery. It can also be used as a charger. In an electronic device that does not incorporate a battery, the power supplied from the AC adapter is temporarily interrupted to detect the input voltage from the AC adapter in the interrupted state. The time for temporarily shutting off the power is set to a short time that does not affect the operation of the electronic device. Since this interruption time can be increased when the capacitance of the electrolytic capacitor built in the power supply circuit of the electronic device is large, it is set to 1 msec to 100 msec, for example. When the electronic device detects that the input voltage from the AC adapter is low in a state where the power of the AC adapter is cut off, that is, in a state where the AC adapter is not loaded, the electronic device cuts off the current of the AC adapter.

  The AC adapter 10 shown in FIG. 1 detects an AC / DC conversion circuit 13 that converts an input commercial power source into a direct current of a predetermined voltage, a temperature sensor 11 that detects its own temperature, and the temperature sensor 11. And a temperature-voltage conversion circuit 12 that changes the output voltage with temperature.

  The AC / DC conversion circuit 13 includes a rectifier circuit 14 including a diode 15 that rectifies input alternating current into direct current, and a smoothing capacitor 16 that is an electrolytic capacitor that smoothes the pulsating current rectified by the diode 15, and the rectifier circuit. And a DC / DC converter 17 that steps down the direct current output from 14 to a predetermined voltage. The DC / DC converter 17 stabilizes the output voltage by feeding back the output voltage to the gate of the FET 18 that is switched on and off at a predetermined cycle via the temperature-voltage conversion circuit 12. This feedback circuit shortens the ON time of the FET 18 to lower the output voltage when the output voltage becomes higher than the set voltage, and lengthens the ON time of the FET 18 to increase the output voltage when the output voltage becomes lower than the set voltage. To a constant voltage.

  The temperature sensor 11 is a thermistor. The thermistor detects the temperature by changing the electric resistance with temperature. For the temperature sensor 11, an element other than the thermistor whose electric resistance changes with temperature, such as a PTC or a varistor, can be used. The temperature sensor 11 is disposed inside the AC adapter 10 to detect the internal temperature of the case, or detects the temperature of a high-temperature element that rises in temperature, such as a diode or FET, and further detects the case temperature of the AC adapter 10. To detect the temperature of the AC adapter itself.

  The temperature-voltage conversion circuit 12 changes the output voltage by a signal input from the temperature sensor 11. The temperature-voltage conversion circuit 12 reduces the output voltage of the DC / DC converter 17 when the detected temperature detected by the temperature sensor 11 becomes higher than the set temperature. Therefore, the temperature-voltage conversion circuit 12 feeds back the signal of the temperature sensor 11 to the gate of the FET 18 that controls the output of the DC / DC converter 17 and controls the output voltage of the DC / DC converter 17. The characteristic that the temperature-voltage conversion circuit 12 changes the output voltage is shown in FIG. As shown in this figure, the temperature-voltage conversion circuit 12 controls the AC / DC conversion circuit 13 to lower the output voltage when the temperature detected by the temperature sensor 11 becomes higher than the set temperature. The AC / DC conversion circuit 13 stabilizes the output voltage at a constant voltage when the temperature sensor 11 detects a temperature lower than the set temperature, but when the detected temperature becomes higher than the set temperature, the temperature-voltage conversion circuit 12 The output voltage is lowered by the signal from. When the temperature detected by the temperature sensor 11 becomes higher than the set temperature, the temperature-voltage conversion circuit 12 controls the FET 18 to have a short ON time to reduce the output voltage. The set temperature at which the temperature-voltage conversion circuit 12 lowers the output voltage varies depending on the detection site detected by the temperature sensor 11. For example, in an AC adapter in which the temperature sensor detects the case temperature, the set temperature at which the output voltage is reduced is about 70 ° C. However, this set temperature can be set to 60 ° C. to 80 ° C. In the case of an AC adapter that detects the temperature of a diode or FET whose temperature sensor is a high temperature element, the set temperature is set higher.

  The electronic device 30 in FIG. 1 includes a switching element 31 connected in series to an input terminal 33 connected to the AC adapter 10, and the switching element 31 is turned off so that the AC adapter is turned off. And a control circuit 32 for detecting the input voltage from 10 and controlling the switching element 31 with the detected input voltage. Furthermore, the electronic device 30 shown in the figure includes a battery 34 that can be charged and a charging circuit 35 that pulse-charges the battery 34, and a switching element 31 that blocks the current of the AC adapter 10 through the switching element 36 that pulse-charges the battery 34. It is used together.

  The battery 34 is a lithium ion battery, a nickel metal hydride battery, a nickel cadmium battery, or the like, and supplies electric power to a heater 38 of a load 37 built in the case for heating. The heater 38 is a PTC and is heated by the power supplied from the battery 34 to heat a heat radiating plate (not shown) provided on the surface of the case.

  The charging circuit 35 includes a switching element 31 connected between the battery 34 and the input terminal 33, and a control circuit 32 that performs pulse charging of the battery 34 by switching the switching element 31 on and off at a predetermined cycle. When the control circuit 32 detects that the battery 34 is fully charged, the control circuit 32 switches the switching element 31 to OFF, maintains the OFF state, and stops charging the battery 34.

  Further, the control circuit 32 detects the input voltage from the AC adapter 10 when the switching element 31 is in the OFF state. The input voltage to be detected is compared with the set voltage. The control circuit 32 detects the temperature abnormality of the AC adapter 10 from the input voltage when the switching element 31 is in the OFF state.

  FIG. 3 shows a state in which the input voltage changes in a state where the switching element 31 is switched on and off. When the temperature of the AC adapter 10 is normal, the input voltage changes as indicated by the solid line in the figure. That is, when the switching element 31 is switched off, the current of the AC adapter 10 is interrupted and rises to a no-load voltage. When the switching element 31 is switched on, the voltage drops to the voltage of the battery 34 and charges the battery 34.

  When the temperature of the AC adapter 10 becomes higher than the set temperature and becomes an abnormal temperature, the AC adapter 10 decreases the output voltage. Therefore, in a state where the temperature of the AC adapter 10 is abnormally high, the input voltage at the timing when the switching element 31 is turned off, that is, the output voltage of the AC adapter 10 decreases, as shown by the chain line in FIG. From this, the control circuit 32 detects the input voltage in a state where the switching element 31 is turned off, and if the detected voltage is lower than the set voltage compared to the set voltage, the AC adapter 10 has an abnormally high temperature. After the determination, the switching element 31 is switched off to interrupt the current of the AC adapter 10. The set voltage at which the control circuit 32 switches off the switching element 31 is set to an output voltage at which the temperature of the AC adapter 10 becomes higher than the set temperature and decreases. That is, when the AC adapter 10 becomes higher than the set temperature and becomes an abnormal temperature, the output voltage is lowered. Therefore, when the control circuit 32 detects this output voltage, the set voltage is set so that the switching element 31 is switched off. Is set. In this state, the switching element 31 is held in the off state. Therefore, when the temperature of the AC adapter 10 becomes abnormally high and the current is cut off, the current is cut off. The AC adapter 10 in which the current is cut off does not generate heat and the temperature is lowered. The control circuit 32 is reset by a power switch 39 that connects the battery 34 to the heater 38, or is reset by a separate reset switch. After the control circuit 32 is reset, when the AC adapter 10 cooled below the set temperature is connected, the control circuit 32 starts pulse charging of the battery 34. When the AC adapter 10 having an abnormal temperature is connected, the voltage for turning off the switching element 31 becomes lower than the set voltage. Therefore, the switching element 31 is held off again and the current of the AC adapter 10 is cut off. To do.

Further, the power supply system of the present invention controls the output current to be small when the temperature of the AC adapter itself becomes high, and the electronic device detects the input current from the AC adapter and detects the detected input current. If the current is smaller than the set current, it is possible to determine that the temperature of the AC adapter is high and cut off the current of the AC adapter. This power supply system is shown in FIG.
In FIG. 4, the same components as those in the embodiment shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the power supply system shown in FIG. 4, the AC adapter 20 includes a temperature-current conversion circuit 22 that changes an output current at a temperature detected by the temperature sensor 11. The temperature-current conversion circuit 22 changes the output current by a signal input from the temperature sensor 11. When the detected temperature detected by the temperature sensor 11 becomes higher than the set temperature, the temperature-current conversion circuit 22 feeds back the signal of the temperature sensor 11 to the gate of the FET 18 that controls the output of the DC / DC converter 17, and the DC / DC The output current of the DC converter 17 is reduced. The characteristic that the temperature-current conversion circuit 22 changes the output current is shown in FIG. As shown in this figure, the temperature-current conversion circuit 22 controls the AC / DC conversion circuit 13 so as to lower the output current when the temperature detected by the temperature sensor 11 becomes higher than the set temperature. The AC / DC conversion circuit 13 stabilizes the output current to a constant current when the temperature sensor 11 detects a temperature lower than the set temperature. However, when the detected temperature becomes higher than the set temperature, the temperature-current conversion circuit 22. The output current is reduced by the signal from. When the temperature detected by the temperature sensor 11 becomes higher than the set temperature, the temperature-current conversion circuit 22 controls the FET 18 to have a short ON time to reduce the output current. The set temperature at which the temperature-current conversion circuit 22 decreases the output current is, for example, about 70 ° C. in an AC adapter whose temperature sensor detects the case temperature. However, this set temperature can be set to 60 ° C. to 80 ° C.

  Further, the AC adapter 20 shown in the figure includes a current detection unit 24 on the output side of the AC / DC conversion circuit 13 in order to detect the output current of the AC / DC conversion circuit 13. The current detection unit 24 shown in the figure includes a current detection resistor 25 connected in series between the AC / DC conversion circuit 13 and the output terminal 23, and the voltage at both ends of the current detection resistor 25 is expressed as a temperature − It is detected by the current conversion circuit 22. Although not shown, the current detection unit can also amplify the voltage across the current detection resistor with an amplifier, convert the output of the amplifier into a digital value with an A / D converter, and output the digital value. Since the current detection resistor 25 generates a voltage proportional to the output current, the output current can be detected by detecting the voltage generated at both ends of the current detection resistor 25. The temperature-current conversion circuit 22 detects the output current of the AC / DC conversion circuit 13 from the voltage across the current detection resistor 25 and the resistance value of the current detection resistor 25.

  The electronic device 40 detects the input current from the switching element 31 connected in series to the input terminal 33 connected to the AC adapter 20 and the AC adapter 20, and controls the switching element 31 with the detected input current. A control circuit 42 is provided. The electronic device 40 also includes a battery 34 that can be charged, and a charging circuit 35 that pulse-charges the battery 34, and a switching element 36 that pulse-charges the battery 34 is used in combination with the switching element 31 that cuts off the current of the AC adapter 20. ing. The charging circuit 35 pulse-charges the battery 34 by switching the switching element 31 on and off at a predetermined cycle by the control circuit 42. When the control circuit 42 detects full charge of the battery 34, the control circuit 42 switches the switching element 31 to OFF, maintains the OFF state, and stops charging the battery 34.

  Further, the control circuit 42 detects an input current from the AC adapter 20, compares the detected input current with a set current, and detects a temperature abnormality of the AC adapter 20 from the input current. The electronic device 40 shown in the figure includes a current detection unit 44 on the input side of the charging circuit 35 in order to detect an input current from the AC adapter 20. The current detection unit 44 shown in the figure includes a current detection resistor 45 connected in series to an input terminal 33 connected to the AC adapter 20, and the voltage across the current detection resistor 45 is detected by the control circuit 42. is doing. Although not shown, the current detection unit can also amplify the voltage across the current detection resistor with an amplifier, convert the output of the amplifier into a digital value with an A / D converter, and output the digital value. Since the current detection resistor 45 generates a voltage proportional to the input current, the input current can be detected by detecting the voltage generated at both ends of the current detection resistor 45. The control circuit 42 detects the input current from the voltage across the current detection resistor 45 and the resistance value of the current detection resistor 45.

  In the above power supply system, when the temperature of the AC adapter 20 becomes higher than the set temperature and becomes an abnormal temperature, the AC adapter 20 reduces the output current. Therefore, when the temperature of the AC adapter 20 is abnormally high, the input current from the AC adapter 20 is small. From this, the control circuit 42 compares the detected current with the set current, and if the input current is smaller than the set current, the AC adapter 20 determines that the temperature is abnormally high and switches the switching element 31 off. The current of the AC adapter 20 is cut off. The set current at which the control circuit 42 switches off the switching element 31 is set to an output current that is controlled to be small when the temperature of the AC adapter 20 is higher than the set temperature. That is, when the AC adapter 20 becomes higher than the set temperature and becomes abnormal, the output current is reduced. Therefore, when the control circuit 42 detects this output current, the set current is set so that the switching element 31 is switched off. Is set. In this state, the switching element 31 is held in the off state. Therefore, when the temperature of the AC adapter 20 becomes abnormally high and the current is cut off, the current is cut off.

  Thereafter, when the temperature of the AC adapter 20 decreases, the control circuit 42 is reset by a power switch 39 for connecting the battery 34 to the heater 38 or a reset switch provided separately. After the control circuit 32 is reset, when the AC adapter 20 cooled below the set temperature is connected, the control circuit 42 starts pulse charging of the battery 34. When the AC adapter 20 having an abnormal temperature is connected, the input current from the AC adapter 20 becomes smaller than the set current, so the switching element 31 is held off again and the current of the AC adapter 20 is cut off. .

It is a schematic block diagram of the power supply system concerning one Example of this invention. It is a graph which shows the characteristic in which a temperature-voltage conversion circuit changes an output voltage. It is a figure which shows the change of the input voltage in the state which switches a switching element on and off. It is a schematic block diagram of the power supply system concerning the other Example of this invention. It is a graph which shows the characteristic in which a temperature-current conversion circuit changes an output current.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... AC adapter 11 ... Temperature sensor 12 ... Temperature-voltage conversion circuit 13 ... AC / DC conversion circuit 14 ... Rectification circuit 15 ... Diode 16 ... Smoothing capacitor 17 ... DC / DC converter 18 ... FET
DESCRIPTION OF SYMBOLS 20 ... AC adapter 22 ... Temperature-current conversion circuit 23 ... Output terminal 24 ... Current detection part 25 ... Current detection resistor 30 ... Electronic device 31 ... Switching element 32 ... Control circuit 33 ... Input terminal 34 ... Battery 35 ... Charging circuit 36 ... Switching element 37 ... Load 38 ... Heater 39 ... Power switch 40 ... Electronic device 42 ... Control circuit 44 ... Current detection unit 45 ... Current detection resistor

Claims (5)

An AC adapter (10) for converting AC of a commercial power source into DC of a predetermined voltage, and an electronic device (30) connected to the AC adapter (10) and supplied with power from the AC adapter (10) In the power system,
The AC adapter (10) includes a temperature sensor (11) that detects its own temperature, and a temperature-voltage conversion circuit (12) that changes an output voltage at a temperature detected by the temperature sensor (11). And
The electronic device (30) includes a switching element (31) connected in series to an input terminal (33) connected to the AC adapter (10), and the switching element (31) is switched off to perform switching. A control circuit (32) for detecting an input voltage from the AC adapter (10) in an off state of the element (31) and controlling the switching element (31) with the detected input voltage;
When the temperature of the AC adapter (10) becomes high and the input voltage from the AC adapter (10) when the switching element (31) is turned off becomes lower than the set voltage, the electronic device (30) has a control circuit (32 ) Switches off the switching element (31) to cut off the input current from the AC adapter (10). An AC adapter (20) for converting AC of a commercial power source into DC of a predetermined voltage, and an electronic device (40) connected to the AC adapter (20) and supplied with power from the AC adapter (20) In the power system,
The AC adapter (20) includes a temperature sensor (11) that detects its own temperature, and a temperature-current conversion circuit (22) that changes an output current at a temperature detected by the temperature sensor (11). And
The electronic device (40) detects the input current from the switching element (31) connected in series to the input terminal (33) connected to the AC adapter (20) and the AC adapter (20), A control circuit (42) for controlling the switching element (31) with an input current to be detected,
In the electronic device (40), when the temperature of the AC adapter (20) becomes high and the input current from the AC adapter (20) becomes smaller than the set current, the control circuit (42) turns off the switching element (31). A power supply system that cuts off the input current from the AC adapter (20) by switching to.   The electronic device (30), (40) includes a battery (34) that can be charged, and a charging circuit (35) that pulse-charges the battery (34), and switches the switching element (31) on and off. The power supply system according to claim 1 or 2, wherein the battery (34) is pulse-charged.   The power supply system according to claim 1 or 2, wherein the electronic devices (30) and (40) are anchors heated by a built-in battery (34).   The power supply system according to claim 1, wherein the electronic device is a battery charger.

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