Current regulation system

A current regulation system for generating a charging current curve for charging a rechargeable battery is provided, the system including a current regulation module coupled to a power converter to output a conversion current in a constant current mode and a constant voltage mode, a voltage-to-current regulation module coupled to the rechargeable battery to output a voltage conversion current in the constant voltage mode, a temperature-to-current regulation module and a resistance. The temperature-to-current regulation module outputs a temperature conversion current in the constant current mode and the constant voltage mode. The resistance is coupled to the current regulation module, the voltage-to-current regulation module and the temperature-to-current regulation module to regulate the voltage conversion current or the temperature conversion current, the conversion current is weakened by maintain a constant value so the charging current curve is regulated when the power of the rechargeable battery is full.

This application claims the benefits of the Taiwan Patent Application Serial No. 101147415 filed on Dec. 14, 2012, the subject matter of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the current regulation system and more particularly, relates to a current regulation system regulating a charging current curve of a rechargeable battery by maintaining a constant value of a voltage of a resistance.

The rapid development of electronic devices due to science and technology has improved the standard of human life greatly. As numerous electronic devices are produced nowadays, rechargeable batteries, which are very convenient and can be used repeatedly, are used in electronic devices such as laptops, PDAs, mobile phones, etc. Charging devices are utilized to recharge rechargeable batteries directly or to charge electronic devices including rechargeable batteries.

Please refer toFIG. 1, a schematic view of a conventional charging device charging a rechargeable battery and an electronic device. A charging device PA10is coupled to a switch PA20and a charging control circuit PA30; a rechargeable battery PA40is coupled to the switch PA20, the charging control circuit PA30and an electronic device PA50. When the charging device PA10charges the electronic device PA50via a charging route L1, it is deemed that the charging route L1includes the switch PA20. The conversion efficiency of charging device PA10directly charging the electronic device PA50still needs to be improved; for example, the charging efficiency for a backup battery charger to charge a smart phone is bad. Thus, solutions for this problem are offered. A linear regulator is described in Taiwan Patent No. 1221692, “Charging System Having Current Regulation and Temperature Regulation” to improve the performance of the switch PA20.

Besides, when the charging device PA10charges the rechargeable battery PA40via a charging route L2, the charging control circuit is utilized to control the charging status of the rechargeable battery PA40to have better charging performance. Relative technical features to improve the charging control circuit PA30have been provided; for example, U.S. Pat. No. 7,161,393 has described that the charging performance is enhanced by regulating output currents by judging the voltages. However, there are still problems such as a constant voltage charging mode and a constant current charging mode cannot smoothly comply with temperature regulation and thus the circuit is unstable.

SUMMARY OF THE INVENTION

In prior art, the problem of unstable loop still exists. Therefore, a current regulation system is provided according to embodiments of the present invention. The system regulates a voltage conversion current and a temperature conversion current and regulates a charging current curve of a rechargeable battery by maintaining a constant value of a voltage of a resistance in order to avoid an unstable loop.

A current regulation system is provided, the system generating a charging current curve for charging a rechargeable battery, the system coupled to a power converter and the rechargeable battery, receiving an input voltage of the power converter and outputting an output voltage to the rechargeable battery, the system including a current regulation module, a voltage-to-current regulation module, a temperature-to-current regulation module and a resistance. The current regulation module is coupled to the power converter, outputting a conversion current in a constant current mode and a constant voltage mode; the voltage-to-current regulation module is coupled to the rechargeable battery, generating a voltage conversion current according to the output voltage and a first reference voltage in the constant voltage mode.

The temperature-to-current regulation module generates and outputs a temperature conversion current according to a temperature of the rechargeable battery in the constant current mode and the constant voltage mode; a resistance is coupled to the current regulation module, the voltage-to-current regulation module and the temperature-to-current regulation module, the resistance receiving the conversion current, the voltage conversion current and the temperature conversion current, wherein the resistance includes a resistance voltage and the resistance voltage includes a constant value; when the resistance regulates the voltage conversion current or the temperature conversion current in the constant current mode and the constant voltage mode, the constant value is maintained so the conversion current is gradually weakened; the charging current curve is regulated when the power of the rechargeable battery is full.

The current regulation module includes a differential amplifier and a transistor, the differential amplifier outputting a control voltage according to the input voltage and the output voltage, the transistor controlling the conversion current generated by the power converter and flowing through the transistor. Moreover, the current regulation system is further coupled to a compensation circuit and includes an error amplifier coupled to the current regulation module, the voltage-to-current regulation module, the temperature-to-current regulation module, the resistance and the compensation circuit, the error amplifier including a second reference voltage, the error amplifier outputting an error voltage to the compensation circuit for compensation according to the second reference voltage and the resistance voltage.

When the rechargeable battery is charging in the constant current mode, all the conversion current flows through the resistance; when the output voltage reaches a first threshold value, the rechargeable battery is charging in the constant voltage mode so the voltage conversion current flows through the resistance and is gradually amplified and the conversion current is gradually weakened; when the amount of the conversion current flowing through the resistance reaches a second threshold value, the power of the rechargeable battery is full and the charging current curve is regulated. Besides, the voltage-to-current regulation module is selected from the group of linear amplifier, voltage to current circuit and operational transconductance amplifier; the temperature-to-current regulation module is selected from the group of proportional to absolute temperature circuit and complimentary to absolute temperature circuit; the temperature-to-current regulation module generates and outputs the temperature conversion current.

According to another embodiment of the present invention, when the rechargeable battery is charging in the constant current mode, all the conversion current flows through the resistance; when the output voltage reaches a first threshold value, the rechargeable battery is charging in the constant voltage mode so the voltage conversion current flows through the resistance and is gradually amplified, and the temperature-to-current module gradually amplifies the temperature conversion current according to the temperature so that the conversion current is gradually weakened; when the amount of the conversion current flowing through the resistance reaches a second threshold value, the power of the rechargeable battery is full and the charging current curve is regulated.

Compared with prior art, the current regulation system provided according to embodiments of the present invention regulates a voltage conversion current and a temperature conversion current and regulates a charging current curve of a rechargeable battery by maintaining a constant value of a voltage of a resistance; thus, regulations are performed smoothly in a constant current mode, a constant voltage mode and a temperature regulation mode without mutually interfering or suppressing which often leads to an unstable loop, and so as to improve charging efficiency.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention relates to a current regulation system. In the following description, numerous details are set forth in order to provide a thorough understanding of the present invention. It will be appreciated by one skilled in the art that variations of these specific details are possible while still achieving the results of the present invention. In other instance, well-known components are not described in detail in order not to unnecessarily obscure the present invention.

Please refer toFIG. 2toFIG. 5;FIG. 2is a schematic view of a circuit of a current regulation system according to an embodiment of the present invention;FIG. 3is a curve graph showing the current and the voltage of a rechargeable battery according to an embodiment of the present invention;FIG. 4is a graph showing a curve of a voltage-to-current regulation module according to an embodiment of the present invention; andFIG. 5is a graph showing a curve of a temperature-to-current regulation module according to an embodiment of the present invention. A current regulation system1is coupled to a power converter2, a compensation circuit3and a rechargeable battery4, receives an input voltage Vin of the power converter2, outputs an output voltage Vout to the rechargeable battery4(the output voltage Vout is also the battery voltage of the rechargeable battery4), and regulates a charging current curve100charging the rechargeable battery4. The input voltage Vin receives a power input voltage VIN and outputs to the current regulation system1via a circuit (the circuit belongs to prior art and is not mentioned redundantly here). The rechargeable battery4includes any rechargeable battery in the market; according to an embodiment of the present invention, the rechargeable battery4includes a Li battery.

The current regulation system1includes a current regulation module11, a voltage-to-current regulation module12, a resistance13, a resistance14, a temperature-to-current regulation module15, an error amplifier16and a resistance17. The current regulation module11is coupled to the power converter2and includes a differential amplifier111, a transistor112, a resistance113and a resistance114. The differential amplifier111is coupled to the transistor112(in a control end), the resistance113and the resistance114; the resistance113is coupled to the resistance114and forms a mode similar to a differential input; that is, according to an embodiment of the present invention, the input voltage Vin is located where the resistance113is coupled to the resistance114and by voltage division, the input voltage Vin performs as an input voltage (not shown) of the differential amplifier111and the output voltage Vout performs as another input voltage (not shown) of the differential amplifier111.

The voltage-to-current regulation module12is coupled to the resistance13, the resistance14and the rechargeable battery4; the resistance13is coupled to the resistance113of the current regulation module11. According to an embodiment of the present invention, the voltage-to-current module12receives an adjustable first reference voltage Vref1and receives a divided voltage VFBof the output voltage Vout in the resistance13and the resistance14. The voltage-to-current regulation module is selected from the group of linear amplifier, voltage to current circuit and operational transconductance amplifier. Any circuit that converts voltages to currents is included in the spirit of the present invention.

The temperature-to-current regulation module15is coupled to the transistor112of the current regulation module11and the voltage-to-current regulation module12; the temperature-to-current regulation module15is selected from the group of proportional to absolute temperature circuit and complimentary to absolute temperature circuit; that is, the temperature-to-current regulation module15is selected from the group of positive temperature coefficient circuit and negative temperature coefficient circuit.

The error amplifier16is coupled to the temperature-to current regulation module15, the transistor112of the current regulation module11, the voltage-to-current regulation module12and the compensation circuit13. The resistance17is coupled to the transistor112of the current regulation module11, the voltage-to-current regulation module12, the temperature-to-current regulation module15and the error amplifier16. The resistance17includes a resistance voltage that is a constant value; the error amplifier16receives an adjustable second reference voltage Vref2and the resistance voltage of the resistance17. Additionally, the resistance17includes a current-to-voltage converter according to an embodiment of the present invention. The resistance17includes other circuits according to other embodiments of the present invention. The power converter2includes a sensing module21and the compensation circuit3is electrically connected to the power converter. The compensation circuit3belongs to prior art and is not mentioned redundantly here.

The current regulation module11outputs a conversion current I1when charging in a constant current mode and a constant voltage mode. The differential amplifier111outputs a control voltage Vc according to the input voltage Vin and the output voltage Vout (more specifically, according to the divided voltage of the input voltage and according to the output voltage). The transistor112controls the conversion current I1generated by the power converter2and flowing through the transistor112, wherein the transistor112controls the volume of the conversion current I1flowing through the transistor112according to the control voltage Vc. The voltage-to-current regulation module12generates and outputs a voltage conversion current I2according to the output voltage Vout and the first reference voltage Vref1in the constant voltage mode.

The temperature-to-current regulation module15generates and outputs a temperature conversion current I3; the error amplifier16outputs an error voltage (not shown) to the compensation circuit3for compensation according to the second reference voltage Vref2and the resistance voltage. The technique of compensation belongs to prior art and is not within the scope of the present invention, and thus, it is not mentioned here. Additionally, the resistance voltage of the resistance17is a constant value in a locked loop for regulating the voltage conversion current I2or the temperature conversion current I3in the constant current mode and the constant voltage mode, and the constant value is maintained so the conversion current I1is gradually weakened so the charging current curve100is regulated when the power of the rechargeable battery4is full, wherein the sensing module21of the power converter2senses the power of the rechargeable battery4and determines whether the power is full (for example, sense that the volume of the conversion current I1is ⅕ or 1/10 lesser then its original volume); when the power is full, the constant voltage mode is switched off.

Specifically, take the regulation of voltage conversion current I2as an example by referring toFIG. 3. When the rechargeable battery4is charging in the constant current mode, all the conversion current I1flows through the resistance17; when the output voltage Vout reaches a first threshold value (e.g. A threshold voltage A of a current and voltage curve200inFIG. 3is about 4.10V, before 4.10V being the constant current mode and after 4.10V being the constant voltage mode. The value of threshold is not limited hereof), the rechargeable battery4is charging in the constant voltage mode. By the regulation of the voltage-to-current regulation module12, the voltage conversion current I2flowing through the resistance17is gradually amplified (Refer to a voltage-to-current curve300shown inFIG. 4;FIG. 4shows an embodiment of the present invention and does not comply withFIG. 3;FIG. 4does not limit the voltage-to-current curve300and can be adjusted correspondingly; the X axis is the output voltage Vout but can be the divided voltage VFBaccording to other embodiments of the present invention.) and since the resistance voltage of the resistance17must be maintained as the constant value, the conversion current I1is gradually weakened; when the amount of the conversion current I1flowing through the resistance17reaches a second threshold value (for example, the volume of the conversion current I1is 0 or ⅕ or 1/10 lesser then its original volume), the power of the rechargeable battery4is full and the charging current curve100is regulated.

Additionally, take the regulation of the temperature conversion current I3as an example by referring toFIG. 3andFIG. 5together. When the rechargeable battery4is charging in the constant current mode, all the conversion current I1flows through the resistance17; and the temperature-to-current regulation module12makes the temperature conversion current I3flow through the resistance17and gradually amplifies it (Refer to a temperature-to-current curve400inFIG. 5;FIG. 5shows an embodiment of the present invention and does not limit the temperature-to-current curve400and can be adjusted correspondingly); since the resistance voltage of the resistance17must be maintained as the constant value, the conversion current I1is gradually weakened as the temperature conversion current I3is amplified.

Additionally, take the regulation of voltage conversion current I2and the temperature conversion current I3as an example by referring toFIG. 3andFIG. 4andFIG. 5together. When the rechargeable battery4is charging in the constant current mode, all the conversion current I1flows through the resistance17; when the output voltage Vout reaches a first threshold value (e.g. A threshold voltage A of a current and voltage curve200inFIG. 3is about 4.10V, before 4.10V being the constant current mode and after 4.10V being the constant voltage mode. The value of threshold is not limited hereof), the rechargeable battery4is charging in the constant voltage mode. By the regulation of the voltage-to-current regulation module12, the voltage conversion current I2flowing through the resistance17is gradually amplified (refer to a voltage-to-current curve300shown inFIG. 4) and the temperature-to-current regulation module12makes the temperature conversion current I3flow through the resistance17and gradually amplifies it (Refer to a temperature-to-current curve400inFIG. 5;FIG. 5shows an embodiment of the present invention and does not limit the temperature-to-current curve400and can be adjusted correspondingly); since the resistance voltage of the resistance17must be maintained as the constant value, the conversion current I1is gradually weakened as the voltage conversion current I2and the temperature conversion current I3amplify; when the amount of the conversion current I1flowing through the resistance17reaches a second threshold value (for example, the volume of the conversion current I1is 0 or ⅕ or 1/10 lesser then its original volume), the power of the rechargeable battery4is full and the charging current curve100is regulated. (A three-dimensional curve graph including current, voltage and temperature can be established. Temperature is not illustrated according to the charging current curve100inFIG. 3.)

In conclusion, the current regulation system1provided according to embodiments of the present invention regulates the voltage conversion current I2and the temperature conversion current I3and regulates the charging current curve100of the rechargeable battery400by maintaining the constant value of the resistance voltage of the resistance17; thus, regulations are performed smoothly in the constant current mode, the constant voltage mode and the temperature regulation mode without mutually interfering or suppressing which often leads to an unstable loop, and so as to improve charging efficiency.