MXPA01010059A - A voltage/current regulator and method for battery charging - Google Patents

Abstract

A voltage/current regulator (1) for regulating charging of a rechargeable battery (2) in a portable apparatus (23), comprising a transistor (6), and controller means (9) coupled to said transistor (6) for controlling the charging current to the battery (2). Further the controller means (9) is capable of:determining the power dissipation in the transistor (6) of the regulator (1);determining if the power dissipation is above a maximum allowed power dissipation, if so, decreasing the charging current by a particular current step, if not, determining if the power dissipation will exceed the maximum allowed power dissipation if the charging current is increased by the current step, and if so, increasing the charging current by the current step.

Description

VOLTAGE REGULATOR / CURRENT AND METHOD FOR BATTERY CHARGING Field of the Invention The present invention relates generally to a voltage / current regulator and to a method for regulating the charging of a rechargeable battery in a portable electronic device. Description of the Prior Art Rechargeable batteries, when in a charged condition, are used to provide electric current to power a variety of electrical items, such as industrial and consumer applications, including mobile telephone devices and other similar electronic devices. However, when the battery is discharged, it needs to be charged. Battery charging usually involves applying an appropriate electric current to the battery for a certain time. The charge current required depends on what type of cells or rechargeable batteries are used, and with some types of rechargeable batteries the value of the current has to be varied during the charging process. Therefore, a charging program is used in order to regulate the current during charging.

Lithium or Li batteries are commonly used in the aforementioned items, due to their characteristics of light weight, high voltage, high electrical density, flat discharge, and long shelf life, etc. However, in some stages in the charge cycle of the Li batteries, a linear regulation of the charging current is required. Therefore, a transistor is used to control the current and during regulation has a voltage drop from the discharge to the source. Therefore, heat is generated in the transistor and energy is dissipated. Due to cost reasons and limitation of board space, you want to use a transistor that is as small as possible. However, a small transistor can handle less amount of energy dissipation. Consequently, the current must be adjusted to a low value, in order to cover all cases with respect to temperature, voltage level and load current. This means, however, that in many cases the current is unnecessarily low, resulting in longer load times. Another alternative is to apply a higher current in order to reduce the charging time for normal cases. However, in some cases the current is too high, resulting in high temperature in the transistor and in the telephone and in some cases irritates the telephone user and also reduces the useful life of the transistors. SUMMARY Therefore, an object of the present invention is to provide a voltage / current regulator and a method for charging a battery in a portable device that overcomes the aforementioned problems. This is achieved with a voltage / current regulating apparatus according to the invention, which is regulated to dissipate constant energy, where a maximum allowed current with respect to energy dissipation and temperature in the apparatus, is used in the current transistor of the device. charge on the device. An advantage of the present invention is that the charging current is dynamically adjusted to the current input voltage and the temperature inside the telephone and the battery. Consequently, the minimum charge time is always achieved even if the maximum dissipation is never exceeded. Furthermore, there is no problem in increasing the temperature in the telephone, which is important particularly with respect to very compact telephone designs, where even a small increase in temperature in the telephone is noticeable by the user. In general, an advantage of the present invention is to maintain the increase in temperature due to load, as low as possible. BRIEF DESCRIPTION OF THE DRAWINGS In order to explain the invention in more detail and the advantages and characteristics of the invention, reference is made in the following detailed description of the preferred embodiment to the accompanying drawings, wherein. Figure 1 is a block diagram illustrative of a charging environment including the voltage / current regulator according to the invention, and Figure 2 is a flow chart illustrating one embodiment of a method for voltage / current regulation according to the invention. Detailed Description of the Invention With reference to Figure 1, a voltage / current regulator 1 according to the invention is connected to a rechargeable battery pack 2 for charging and to an external charger 3. The voltage / current regulator 1 comprises a first terminal 4 intended for connection to a corresponding first terminal 5 of the charger 3. Further, the regulator 1 comprises a transistor 6 for controlling the charging current. The source 7 of the transistor having a source voltage DCIO is connected to a first terminal 8 of a controller means 9 for charge regulation and for the terminal 4. A second terminal 10 of the control means 9 is connected to the gate 11 of the transistor 6. The discharge 12 of the transistor having a discharge voltage VBAT is connected to a third terminal 13 of the controller means 9 and a first impedance terminal 14. A second terminal 16 of the impedance is connected to a fourth terminal 17 of the control means 9 and a first terminal 18 of the battery 2 via a second terminal 19 of the regulator 1. The battery 2 is also connected to ground 20 by its second terminal 21 and a third terminal 22 of the regulator 1. The control means 9 they have access to three parameters in order to control the energy dissipation: 1.

DCIO, which is the source voltage 7; 2. VBAT, which is the discharge voltage 12; and 3. Icharge, which is the charging current through the transistor to the battery pack 2. In a method according to the invention, the controlling means 9 determines the momentary energy dissipation, Pdiss, in the transistor 6 by: Pdiss = Ichange (DCIO - VBAT) in step 201. Pmax is the maximum allowed Pdiss. If Pdiss is above Pmax it is verified in step 202 and if so, Icharge is decreased by Istep in step 203, where Istep is the increase / decrease value of Icharge. If Pdiss is determined lower than Pmax in step 202, there are two alternatives available, either Icharge is increased by Istep or not changed. A temporary parameter NewPdiss is assigned (Icharge + Istep) (DCIO-VBAT) in step 203 '. Then, if NewPdiss < Pmax is verified in step 204, and if so, the first alternative is performed in step 205, i.e. Icharge is increased by Istep, otherwise Icharge is unchanged. However, if Icharge has been increased by Istep in the latter case, Pmax should have been exceeded. Again with reference to Figure 1, the regulator 1 is provided in an electrical apparatus 23, such as a mobile telephone, personal organizer, portable computer or other apparatus supplied with similar battery. When Pmax is determined, also the temperature in the apparatus 23 and in the battery 2 are taken into consideration. The temperature is detected by the temperature sensing means connected to the controller means 9. The first detector means 24 are provided in the apparatus 23 in order to detect the temperature in the apparatus and are connected to a fifth terminal 25 of the regulator 1 by a terminal 26, for transmitting a temperature signal corresponding to the controller means 9. The second sensor means 27 are provided in connection with the battery 2 in order to detect the temperature of the battery. The sensor means 27 is connected, via a third terminal 29 of the battery, to a fifth terminal 28 of the regulator 1, which is connected to the control means 9 for transmitting a corresponding temperature signal. A temperature level in the apparatus 23 or the battery 2 or both, which is considered almost high by the user, is adjusted to be a high temperature limit Tmax. Therefore, when the temperature exceeds Tmax, the charging current Icharge has to be decreased. According to the method of the invention illustrated in Figure 2, the temperature in the apparatus 23 ATemp and / or in the battery 2 BTemp, are detected in step 206. Then, if the temperature ATemp (Temp = max [ATemp, BTemp) is greater than or equal to Tmax, which is verified in step 207, Pmax is decreased by a particular value Pstep, in step 208, in order to decrease the evolution of heat in the apparatus. In another case, the temperature is quite low and the user is satisfied. When the temperature falls below another value Tmin, which is adjusted as the low temperature limit, a higher Pmax is acceptable and thus Pmax can be increased. Therefore, if the temperature is determined well below the high limit in step 207, the process proceeds to step 209, where it is determined whether the temperature is less than or equal to Tmin. If so, Pmax is increased by Pstep in step 210. Consequently, the maximum allowed power dissipation is adjusted with respect to the temperature in the apparatus. The regulation process, including temperature sensing, discharge voltage and source measurements, and the required adjustment of the current, are performed at specified time intervals that are controlled by a synchronizer in the controller means 9. No adjustments are made to current within the time interval that ensures that changes are made in the load current with a maximum controlled frequency. This is implemented by a synchronizer delay in step 211 in this embodiment of the invention. Although features and advantages of the present invention have been established in the foregoing description, it will be understood that the description is illustrative only, and that changes in detail may be made within the principles of the invention indicated by the broad general meaning of the claims.

For example, in an alternate embodiment of the invention only one temperature means is provided for temperature measurement in the apparatus.

Claims (8)

1. CLAIMS 1. A voltage / current regulator for regulating charge of a rechargeable battery in a portable device, comprising a transistor, and control means coupled to the transistor, for controlling the charge current to the battery, characterized in that the controlling means is capable of to determine the energy dissipation in the transistor of the regulator, to determine if the dissipation of energy is on a maximum tolerated energy dissipation, if so, to decrease the load current by a particular current stage, if not, to determine if the Power dissipation will exceed the maximum allowed power dissipation, if the load current is increased by the current stage, and if not, increase the load current by the current stage.
2. 2. A voltage / current regulator according to claim 1, characterized in that the controlling means are able to: detect the temperature in the apparatus and / or the battery, determine whether the temperature is greater than or equal to a temperature limit allowed maximum predetermined, if so, decrease the maximum allowed energy dissipation by a particular energy stage, in order to decrease the heat release in the apparatus, otherwise, determine if the temperature is less than or equal to a limit of minimum predetermined temperature, and if so, increase the maximum allowed energy dissipation by the energy stage.
3. 3. A battery-powered electronic device, comprising means for regulating charge of a rechargeable battery, characterized in that the means for regulating the charge are a voltage / current regulator according to any of the preceding claims.
4. 4. A battery-powered electronic device according to claim 3, characterized by temperature sensing means provided in the apparatus and connected to the controlling means, for detecting the temperature in the apparatus and transmitting a signal indicative of temperature corresponding to the controlling medium. .
5. 5. A battery-powered electronic device according to claim 3 or 4, characterized by a battery including temperature sensing means for indicating the temperature of the battery, and a terminal coupled to the sensing means and connected to the controlling means, to transmit a temperature signal corresponding to the controlling means.
6. 6. A method for voltage / current regulation in a voltage / current regulator, comprising a transistor for controlling the charging current of the regulator during charging of the battery in a portable device, characterized by the steps of: determining the dissipation of energy in the transistor of the regulator, determine if the dissipation of energy is on a maximum allowed power dissipation, and if so, decrease the load current by a particular current stage, if not, determine if the power dissipation exceed the maximum permitted power dissipation if the load current is increased by the current stage, and if not, increase the load current by the current stage.
7. 7. A method according to claim 6, characterized by the additional steps of: detecting the temperature in the apparatus, determining if the temperature is greater than or equal to a predetermined maximum allowed temperature, if so, decrease the energy dissipation allowed maximum by a particular energy stage, in order to decrease the heat release in the apparatus, if not, determine if the temperature is less than or equal to a minimum temperature, and if so, increase the energy dissipation Maximum allowed by the energy stage. A method according to claim 6 or 7, characterized in that the regulation process, including temperature sensing, discharge voltage and source measurements, and the required adjustment of the current, are performed at specified time intervals.