Rechargeable battery temperature detection method, power management device and electronic system

A rechargeable battery temperature detection method adapted to an electronic system includes detecting a status of a processor of the electronic system when an external power is input to a power conversion module of the electronic system; determining whether a thermistor of the electronic system is conducted to a fuel gauge or a charge control circuit according to the state of the processor such that the fuel gauge or the charge control circuit determine a temperature sensing result via the thermistor. The thermistor is disposed adjacent to a rechargeable battery and has a resistance which varies with a temperature of the rechargeable battery. The temperature sensing result is related to the resistance.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rechargeable battery temperature detection method, a power management device and an electronic system, and more particularly, to a rechargeable battery temperature detection method, a power management device and an electronic system that can switch circuits according to states of a processor in order to prevent temperature of a rechargeable battery from being out of control.

2. Description of the Prior Art

Along with the ever-increasing popularity of portable electronic devices, demand for a rechargeable battery has grown dramatically in recent years. When recharging a rechargeable battery, however, the electric current passing through will release heat (known as joule heating), which causes the rechargeable battery to become hot. If the rechargeable battery becomes too hot, it may experience thermal runaway, become damaged, or even explode. To ensure charging safety, a thermistor may be disposed in the portable electronic device in proximity to the rechargeable battery and adapted for a fuel gauge to detect temperature of the rechargeable battery. The fuel gauge determines the temperature of the rechargeable battery according to the resistance of the thermistor, and sends a temperature sensing result to the processor. The processor then transmits the temperature sensing result to the charging control circuit, which can control a magnitude of a charging current flowing from a charging circuit to the rechargeable battery to prevent thermal runaway.

The temperature sensing results detected by the fuel gauge must be ceaselessly transmitted to the charging control circuit through the processor. If the processor crashes, the charging control circuit cannot adjust the charging current according to the temperature sensing result, and charging safety will be put at risk. Moreover, in order to ensure that the charging control circuit can accurately determine the temperature of the rechargeable battery even when the portable electronic device is in a sleeping or a shutdown state, the processor must consume certain amounts of electricity to transmit the temperature sensing result to the charging control circuit. Accordingly, ensuring charging safety and saving power even when the processor is executed in different states is a main objective in the field.

SUMMARY OF THE INVENTION

Therefore, it is one of the objectives of the disclosure to provide a rechargeable battery temperature detection method, a power management device and an electronic system, which can switch circuits according to states of a processor, thereby preventing temperature of a rechargeable battery from being out of control whether the processor is operated in a working state or not.

An embodiment of the invention provides a rechargeable battery temperature detection method adapted to an electronic system. The rechargeable battery temperature detection method comprises detecting a state of a processor of the electronic system when an external power is input to a power conversion module of the electronic system; and determining whether electric currents are conducted between a thermistor of the electronic system and a fuel gauge or between the thermistor and a charging control circuit according to the state of the processor, wherein the fuel gauge or the charging control circuit determines a temperature sensing result via the thermistor; wherein the thermistor is disposed adjacent to a rechargeable battery and has a resistance which varies with a temperature of the rechargeable battery, and the temperature sensing result is related to the resistance.

An embodiment of the invention provides a power management device adapted to an electronic system. The power management device comprises a thermistor, disposed adjacent to a rechargeable battery of the electronic system and having a resistance which varies with a temperature of the rechargeable battery; a fuel gauge, configured to calculate a charge storage capacity of the rechargeable battery and determine a temperature sensing result according to the resistance of the thermistor; a charging control circuit, configured to control how a charging circuit charges the rechargeable battery and determine the temperature sensing result according to the resistance of the thermistor; and a switch module, coupled between the thermistor, the fuel gauge and the charging control circuit and configured to conduct electric currents between the thermistor and a fuel gauge or between the thermistor and a charging control circuit according to a state of a processor of the electronic system, wherein the fuel gauge or the charging control circuit determines the temperature sensing result via the thermistor.

An embodiment of the invention provides an electronic system. The electronic system comprises a power conversion module, configured to output a direct current (DC) voltage; a processor; a rechargeable battery; a charging circuit, configured to receive the DC voltage from the power conversion module and provide a charging current for the rechargeable battery; and a power management device. The power management device comprises a thermistor, disposed adjacent to the rechargeable battery and having a resistance which varies with a temperature of the rechargeable battery; a fuel gauge, configured to calculate a charge storage capacity of the rechargeable battery and determine a temperature sensing result according to the resistance of the thermistor; a charging control circuit, configured to control how the charging circuit charges the rechargeable battery and determine the temperature sensing result according to the resistance of the thermistor; and a switch module, coupled between the processor, the thermistor, the fuel gauge and the charging control circuit and configured to conduct electric currents between the thermistor and a fuel gauge or between the thermistor and a charging control circuit according to a state of the processor, wherein the fuel gauge or the charging control circuit determines the temperature sensing result via the thermistor.

DETAILED DESCRIPTION

Please refer toFIG. 1, which is a schematic diagram illustrating an electronic system10according to an embodiment of the invention. The electronic system10may be a portable electronic device or any electronic system with an independent power supply system such as a laptop, a smart phone, or a tablet. The electronic system10comprises a power conversion module102, a processor104, a rechargeable battery106, a charging circuit108and a power management device110. The power management device110comprises a thermistor112, a fuel gauge114, a charging control circuit116and a switch module118. The thermistor112is disposed adjacent to the rechargeable battery106, and resistance of the thermistor112can vary with temperature of the rechargeable battery106. The fuel gauge114is utilized to calculate charge storage capacity of the rechargeable battery106and measure the resistance of the thermistor112so as to provide the charge storage capacity of the rechargeable battery106and temperature information for the processor104. The power conversion module102can convert an external power Ext_Power (for example, an alternating current (AC) power) into a direct current (DC) power DC_Power and then provide the direct current power DC_Power to the charging circuit108. The charging control circuit116can control the charging circuit108to convert the direct current power DC_Power into a proper charging current according to the temperature of the rechargeable battery106, in order to charge the rechargeable battery106. The switch module118is coupled between the thermistor112, the fuel gauge114and the charging control circuit116. The switch module118can detect state signals STATE_1, STATE_2of the processor104by means of a pin on the processor104; the switch module118can alternately conduct electric current between the thermistor112and the fuel gauge114or between the thermistor112and the charging control circuit116according to a state of the processor104. Consequently, either the fuel gauge114or the charging control circuit116can determine the temperature sensing result RST_1or RST_2according to the resistance of the thermistor112, wherein the temperature sensing results RST_1and RST_2relate to the temperature of the rechargeable battery106.

More specifically, when an external power Ext_Power is input to the power conversion module102—for example, a charger is plugged into the power conversion module102or a socket of the power conversion module102—the switch module118conducts electric current between the thermistor112and the fuel gauge114when the switch module118detects the state signal STATE_1from the processor104and determines that the processor104is operated in a working state. The fuel gauge114can thereby determine the temperature sensing result RST_1according to the resistance of the thermistor112. The fuel gauge114then sends the temperature sensing result RST_1to the processor104, and the processor104further transmits the temperature sensing result RST_1to the charging control circuit116, such that the charging control circuit116can control how the charging circuit108charges the rechargeable battery106.

When the external power Ext_Power is input to the power conversion module102, the switch module118conducts electric current between the thermistor112and the charging control circuit116when the switch module118detects the state signal STATE_2from the processor104and determines that the processor104is not operated in a working state. The charging control circuit116can thereby determine the temperature sensing result RST_2according to the resistance of the thermistor112and accordingly control how the charging circuit108charges the rechargeable battery106. Therefore, when the electronic system10crashes, because the charging control circuit116is coupled to the thermistor112, the charging control circuit116can still obtain the temperature sensing result RST_2and accordingly control the charging circuit108, thereby assuring charging safety. In addition, when the electronic system10is operated in a sleeping or a shutdown state, because the charging control circuit116is coupled to the thermistor112, the processor104does not need to transmit the temperature sensing result from the fuel gauge114to the charging control circuit116, thereby saving power.

Via the switch module118coupled between the thermistor112, the fuel gauge114and the charging control circuit116, the power management device110can simultaneously assure charging safety and save energy. A related operation method can be summarized into a rechargeable battery temperature detection process20as shown inFIG. 2. The rechargeable battery temperature detection process20includes the following steps:

Step S202: when the external power Ext_Power is input to the power conversion module102, the switch module118detects whether the processor104is operated in a working state. If yes, go to Step204; otherwise, go to Step210.

Step S204: the switch module118conducts electric current between the thermistor112and the fuel gauge114, and the fuel gauge114determines the temperature sensing result RST_1according to the resistance of the thermistor112.

Step S206: the fuel gauge114outputs the temperature sensing result RST_1to the processor104.

Step S208: the processor104outputs the temperature sensing result RST_1to the charging control circuit116.

Step S210: the switch module118conducts electric current between the thermistor112and the charging control circuit116, and the charging control circuit116determines the temperature sensing result RST_2according to the resistance of the thermistor112.

Step S212: the charging control circuit116controls how the charging circuit108charges the rechargeable battery106to appropriately adjust charging currents flowing into the rechargeable battery106.

The rechargeable battery temperature detection process20is an operation method of the power management device110by which the switch module118can alternately conduct electric current between the thermistor112and the fuel gauge114or between the thermistor112and the charging control circuit116corresponding to different states of the processor104. When the processor104is operated in a working state, the switch module118conducts electric current between the thermistor112and the fuel gauge114, such that the fuel gauge114can determine the temperature sensing result RST_1according to the resistance of the thermistor112. The fuel gauge114sends a measured charge storage capacity of the rechargeable battery106and the temperature sensing result RST_1to the processor104, and the processor104further transmits the temperature sensing result RST_1to the charging control circuit116. Therefore, the charging control circuit116can control how the charging circuit108charges the rechargeable battery106. When the processor104is not operated in a working state, the switch module118conducts electric current between the thermistor112and the charging control circuit116, such that the charging control circuit116can determine the temperature sensing result RST_2according to the resistance of the thermistor112and accordingly control how the charging circuit108charges the rechargeable battery106. Please note that voltages of the temperature sensing results RST_1and RST_2may be the same; nevertheless, the present invention is not limited thereto and the voltages of the temperature sensing results RST_1and RST_2may differ according to system requirements or design considerations. Furthermore, when the temperature sensing results RST_1and RST_2indicate that the temperature of the rechargeable battery106is too high or too low, the charging control circuit116may force the charging circuit108to reduce the charging current flowing to the rechargeable battery106or even to stop charging the rechargeable battery106to ensure charging safety.

Please note that the electronic system10inFIG. 1or the rechargeable battery temperature detection process20inFIG. 2are embodiments of the invention; however, the present invention is not limited thereto, and those skilled in the art might make modifications or alterations accordingly. For example, the switch module118detects the state signals STATE_1, STATE_2of the processor104via a pin of the processor104so as to determine whether the processor104is operated in a working state. The state signals STATE_1and STATE_2may be different voltage levels provided on one pin of the processor104; for example, the state signals STATE_1and STATE_2may respectively be a high voltage level and a low voltage level. In the electronic system10, the thermistor106may be a negative temperature coefficient (NTC) thermistor or a positive temperature coefficient (PTC) thermistor, but is not limited herein; any component where the resistance varies with temperature can serve as a thermistor. Moreover, since the external power Ext_Power can be an AC power or a DC power, the power conversion module102can be an AC-to-DC converter or a DC-to-DC converter in order to covert the external power Ext_Power into a proper DC power DC_Power, but is not limited thereto. The rechargeable battery106can be a lithium-ion battery, a Nickel-cadmium (NiCd) battery, aNickel-metal hydride (NiMH) battery, etc., but is not limited herein; the rechargeable battery106can also be any other rechargeable battery. The processor104can be a microcontroller, a digital signal processor (DSP), a field-programmable gate array (FPGA), a complex programmable logic device (CPLD), an application specific integrated circuit (ASIC) or a central processor unit (CPU), but is not limited thereto. The electronic system10can be various electronic devices such as a smart phone, a personal digital assistant (PDA) or a laptop, but is not limited thereto.

The switch module118is utilized to switch electrical connections from a connection between the thermistor112and the fuel gauge114to a connection between the thermistor112and the charging control circuit116, and vice versa, but may be implemented in any other approach or structure. For example, the switch module118may be a double-pole double-throw (DPDT) digital switch or a dual single-pole double-throw (SPDT) digital switch and may be further modified according to different system requirements or design considerations. Please refer toFIG. 3, which is a schematic diagram illustrating the switch module118according to an embodiment of the invention. The switch module118comprises single-pole double-throw switches318aand318b, and different numerals denote different pins. Specifically, a pin11of the single-pole double-throw switch318ais electrically connected to the thermistor112. Pins2and9are electrically connected to the fuel gauge114and the charging control circuit116, respectively. Electric currents are conducted between the thermistor112and the fuel gauge114when a pin1detects the state signal STATE_1from the processor104. Alternatively, electric currents are conducted between the thermistor112and the charging control circuit116when the pin1detects the state signal STATE_2from the processor104. When a pin5of the single-pole double-throw switch318bdetects the state signals STATE_1and STATE_2, the charging control circuit116electrically connected to pin4and the fuel gauge114electrically connected to pin7are grounded through a resistor320electrically connected to a pin6. The resistor320may be omitted according to different system requirements and the pin6is thus grounded directly.

The charging control circuit116is utilized to determine the temperature sensing result RST_2according to the resistance of the thermistor112, but may be implemented in any other approach or structure. For example, please refer toFIG. 4, which is a schematic diagram illustrating the charging control circuit116according to an embodiment of the invention. The charging control circuit116comprises power sources420a,420b, resistors R, R_1-R_4, comparators430a-430cand a calculating unit440. The resistors R_1-R_4are connected in series between the power source420aof voltage value VDD1and a grounding terminal and respectively have resistances r1, r2, r3and r4. The resistors R_1-R_4, which serve as a voltage divider, can provide voltage values

r⁢⁢2+r⁢⁢3+r⁢⁢4r⁢⁢1+r⁢⁢2+r⁢⁢3+r⁢⁢4·VDD⁢⁢1,r⁢⁢3+r⁢⁢4r⁢⁢1+r⁢⁢2+r⁢⁢3+r⁢⁢4·VDD⁢⁢1,⁢r⁢⁢4r⁢⁢1+r⁢⁢2+r⁢⁢3+r⁢⁢4·VDD⁢⁢1
for positive input terminals of the comparators430a-430c, respectively. When the switch module118conducts electric current between the thermistor112and the charging control circuit116, the resistor R and the thermistor112of a negative temperature coefficient are connected in series between the power source420bof voltage value VDD2and a grounding terminal, and respectively have resistances r and r112. The resistor R and the thermistor112, which serve as another voltage divider, can provide voltage value

r⁢⁢112r+r⁢⁢112·VDD⁢⁢2
for negative input terminals of the comparators430a-430c.

The comparators430a-430csend results to the calculating unit440, and the calculating unit440transmits the calculated temperature sensing result RST_2to the charging circuit108. The voltage ratio of the resistors R_1-R_4can be adjusted according to various system requirements; for example, values

r⁢⁢2+r⁢⁢3+r⁢⁢4r⁢⁢1+r⁢⁢2+r⁢⁢3+r⁢⁢4·VDD⁢⁢1,r⁢⁢3+r⁢⁢4r⁢⁢1+r⁢⁢2+r⁢⁢3+r⁢⁢4·VDD⁢⁢1,⁢r⁢⁢4r⁢⁢1+r⁢⁢2+r⁢⁢3+r⁢⁢4·VDD⁢⁢1
may be in a ratio of 73.5:47.2:44.7. As a result, if

r⁢⁢112r+r⁢⁢112·VDD⁢⁢2
is less than

r⁢⁢4r⁢⁢1+r⁢⁢2+r⁢⁢3+r⁢⁢4·VDD⁢⁢1,
this means that the temperature of the rechargeable battery106is too high and the charging circuit108should reduce the charging current flowing into the rechargeable battery106immediately, or even stop charging the rechargeable battery106, to ensure charging safety. If

r⁢⁢112r+r⁢⁢112·VDD⁢⁢2
is within a range of

r⁢⁢4r⁢⁢1+r⁢⁢2+r⁢⁢3+r⁢⁢4·VDD⁢⁢1
to

r⁢⁢3+r⁢⁢4r⁢⁢1+r⁢⁢2+r⁢⁢3+r⁢⁢4·VDD⁢⁢1,
this means that the temperature of the rechargeable battery106is quite high and an alert signal may be output. If

r⁢⁢112r+r⁢⁢112·VDD⁢⁢2
is within a range of

r⁢⁢3+r⁢⁢4r⁢⁢1+r⁢⁢2+r⁢⁢3+r⁢⁢4·VDD⁢⁢1,
to

r⁢⁢2+r⁢⁢3+r⁢⁢4r⁢⁢1+r⁢⁢2+r⁢⁢3+r⁢⁢4·VDD⁢⁢1,
this means that the temperature of the rechargeable battery106is normal. In this case, the rechargeable battery106will still be charged, and the charging current may even increase. If

r⁢⁢112r+r⁢⁢112·VDD⁢⁢2
is greater than

r⁢⁢2+r⁢⁢3+r⁢⁢4r⁢⁢1+r⁢⁢2+r⁢⁢3+r⁢⁢4·VDD⁢⁢1,
this means that the temperature of the rechargeable battery106is low, in which case the charging circuit108can reduce the charging current flowing into the rechargeable battery106or even stop charging the rechargeable battery106. Therefore, based on the relation between the resistance of the thermistor112and the temperature of the rechargeable battery106, those skilled in the art may adjust the ratio of the resistances of the resistors R, R_1-R_4so that the charging control circuit116can accurately control the charging method of the charging circuit108.

The fuel gauge114is utilized to determine the temperature sensing result RST_1according to the resistance of the thermistor112, but may be implemented in any other approach or structure. For example, please refer toFIG. 5, which is a schematic diagram illustrating the fuel gauge114according to an embodiment of the invention. The fuel gauge114comprises power sources520a,520b, resistors R′, R_1′, a comparator530and a calculating unit540. The power source420acan provide a voltage value VDD1′ to a positive input terminal of the comparator530. When the switch module118conducts electric current between the thermistor112and the fuel gauge114, the resistor R′ and the thermistor112are connected in series between the power source520bof voltage value VDD2′ and a grounding terminal, and respectively have resistances r′ and r112. The resistor R′ and the thermistor112, which serves as another voltage divider, can provide a voltage value

r⁢⁢112r′+r⁢⁢112·VDD⁢⁢2
to a negative input terminal of the comparator530. The comparator530sends results to the calculating unit540, and the calculating unit540transmits the calculated temperature sensing result RST_1to the processor104. The temperature sensing result RST_1and the temperature of the rechargeable battery106can then be determined according to the resistance of the thermistor112.

FIGS. 3 to 5are, respectively, embodiments of the switch module118, the charging control circuit116and the fuel gauge114in the power management device110; however, the present invention is not limited to the illustrated embodiments. Those skilled in the art may adjust the implementation of the power management device110according to system requirements to alternatively connect the thermistor112to the fuel gauge114or the charging control circuit116so as to ensure charging safety and save power.

In the prior art, temperature sensing results detected by a fuel gauge must be ceaselessly transmitted to a charging control circuit through a processor. As a result, when the processor cannot be executed normally, charging safety will be put at risk. In contrast, even when the processor104of the present invention does not operate normally or even when the electronic system10is operated in a sleeping or a shutdown state, because the switch module118conducts electric currents between the thermistor112and the charging control circuit116, the charging control circuit116can still obtain the temperature sensing result RST_2and accordingly control the charging circuit108to appropriately adjust the charging current, thereby assuring charging safety and saving power.

To sum up, electric currents are conducted between the thermistor and the charging control circuit or between the thermistor and the fuel gauge according to states of the processor, thereby assuring charging safety and saving power.