GB2332824A

GB2332824A - Power supply device for mobile communication terminal

Info

Publication number: GB2332824A
Application number: GB9727433A
Authority: GB
Inventors: Wan-Soo Lim
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 1997-12-29
Filing date: 1997-12-29
Publication date: 1999-06-30
Anticipated expiration: 2017-12-29
Also published as: GB9727433D0; GB2332824B; KR19990062531A

Abstract

A power supply device for use in a mobile communication terminal having a high load 13 and a low load 14 includes a first rechargeable battery 11 for providing the high load 13 with a first operating voltage, a second rechargeable battery or capacitor 17 for providing the low load 14 with a second operating voltage, a recharging circuit 18 for charging the second rechargeable battery or capacitor 17 and a power regulator 12 between the second rechargeable battery or capacitor 17 and the low load 14, for regulating the second operating voltage applied to the low load 14.

Description

POWER SUPPLY DEVICE FOR MOBILE COMMUNICATION TERMINAL BACKGROUND OF THE INVENTION The present invention relates to a power supply device for use in a TDMA (Time Division Multiple Access) communication terminal, which prevents lowering of battery efficiency due to non-uniformity of load.

Generally, mobile communication terminals use rechargeable batteries to provide a power supply voltage. A TDMA communication terminal divides a frame of a predetermined time interval into a plurality of time slots, to generate data during a selected one of the time slots. It is well known that the TDMA communication terminal consumes fifty percent of its total power requirement for the transmission time slots, which correspond to 1/8 frame cycles, during transmission of data. As a result, a voltage level of the rechargeable battery drops down below the nominal 200mV in proportion to the current consumptions. A base band processor including a microprocessor in the communication terminal must therefore be designed to operate even at the minimum voltage level of the rechargeable battery. For instance, a power regulator for providing a logic circuit with an operating voltage must maintain an input voltage which is about O.1V higher than its output voltage. To satisfy this input voltage condition, the power regulator uses a DC-to-DC converter.

Referring to Fig. 1, a conventional power supply device for use in a mobile communication terminal includes a rechargeable battery 11, a power regulator 12, a high load 13 and a low load 14. The rechargeable battery 11 provides an operating current to the high load 13 and the low load 14, in which the high load 13 may include a power amplifier and the low load 14 may include a logic circuit and a base band processor. The rechargeable battery 11 may be recharged with an external DC voltage. The power regulator 12 connected between the rechargeable battery 11 and the low load 14 regulates an operating voltage applied to the low load 14. An operational timing diagram of the power supply device of Fig. 1 is illustrated in Fig. 2.

As illustrated in Fig. 2, since a voltage V,, of the rechargeable battery 11 drops down below a threshold voltage VTN of the power regulator 12 during transmission of data, the output voltage VLN LOM of the power regulator 12 becomes unstable.

If the power supply device for the communication terminal is designed on the basis of the minimum voltage of the rechargeable battery 11, since the minimum voltage level is lower by hundreds of millivolts (mV) than the voltage level of the rechargeable battery 11, battery efficiency is lowered. This low battery efficiency is a function of the non-uniformity of the load.

SUMMARY OF THE INVENTION It is therefore an objective of the present invention to provide an improved power supply device for use in a TDMA communication terminal, which prevents lowering of battery efficiency due to non-uniformity of the load.

Accordingly, there is provided a power supply device for use in a mobile communication terminal including a high load and a low load, comprising: a first battery for providing the high load with a first operating voltage; a second, rechargeable battery for providing the low load with a second operating voltage; a recharging circuit between the first and second batteries for recharging the second battery; and a power regulator between the second battery and the low load, for regulating the second operating voltage applied to the low load.

Preferably, the first battery is a rechargeable battery.

The power supply device may further comprise a diode between the recharging circuit and the second battery, to prevent a counterflow of operating current.

Preferably, the minimum voltage of the second battery is higher than the threshold voltage of the power regulator.

The high load may comprise a power amplifier and the low load may comprise a base band processor and a logic circuit including a microprocessor.

Preferably, the capacity of the second battery is higher than the charge consumed by the low load in one frame cycle.

Preferably, the recharging circuit is adapted to charge the second battery continually while the mobile communication terminal is in operation.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will now be described by way of example with reference to the accompanying drawings in which: Fig. 1 is a block diagram of a conventional power supply device for a TDMA communication terminal; Fig. 2 is an operational timing diagram of the power supply device shown in Fig. 1; Fig. 3 is a block diagram of a power supply device for a TDMA communication terminal according to the present invention; and Fig. 4 is an operational timing diagram of the power supply device shown in Fig. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to Fig. 3, a TDMA communication terminal according to a preferred embodiment of the present invention includes a first rechargeable battery 11, a power regulator 12, a high load 13, a low load 14, a recharging circuit 18 and a second rechargeable battery 17. The first rechargeable battery 11 of a high capacity provides a first operating current to the high load 13 such as a power amplifier. The first rechargeable battery 11 may be charged with an external DC voltage. The second rechargeable battery 17 of a low capacity provides a second operating current to the low load 14 such as a base band processor and a logic circuit including a microprocessor. The low load 14 has low current consumptions and has a small variation of the current consumptions within the respective frames. The recharging circuit 18 charges the second rechargeable battery 17.

The power regulator 12 connected between the second rechargeable battery 17 and the low load 14 regulates the operating voltage applied to the low load 14. The first rechargeable battery 11 has a minimum voltage level which is higher than a threshold value Vm of the power regulator 12. A diode 19 is connected between the recharging circuit 18 and the second rechargeable battery 17, to prevent a counterflow of the operating current.

The capacity of the second rechargeable battery 17 has a value higher than the charge consumed by the low load 14 for one frame cycle. Thus, the second rechargeable battery 17 can maintain the input voltage condition of the power regulator 12 while being charged by the charging circuit 18. The charging circuit 18 continuously charges the second rechargeable battery 17, while the mobile communication terminal is in operation.

An operational timing diagram of the power supply device of Fig. 3 is illustrated in Fig. 4. As illustrated in Fig. 4, the second rechargeable battery 17 has a minimum voltage VBATT~SLAVE higher than the threshold voltage VTH of the power regulator 12 even if the minimum voltage VBTT of the first rechargeable battery 11 becomes lower than the threshold voltage VTH. Therefore, the operating voltage VAN LOB applied to the low load 14 becomes stable. As a result, the power supply device of the invention can provide the mobile communication terminal with a stable operating voltage VLN LOMT even if the voltage level of the first rechargeable battery 11 becomes lower. In this manner, it is possible to enhance the battery efficiency.

In an alternative embodiment (not shown), a capacitance capacitor and a tantalum capacitor can be utilized instead of the second rechargeable battery 17 of FIG. 3. Fig. 5 illustrates the operational waveform in the case where the capacitance capacitor and the tantalum capacitor are used.

As illustrated in FIG. 5, the power source VwSiAVE supplied to the low load 14 is shown in the form of a typical charge/discharge waveform of the capacitor. Also, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) having a comparatively low voltage drop can be used instead of the diode 19 to prevent reverse current. To use such a MOSFET, a synchronization signal is required to turning the MOSFET on/off. The synchronization signal (a signal synchronized with the control signal of the TDMA transmitter) functions to turn on the MOSFET to charge the second rechargeable battery 17 or the capacitor during times of no transmission, and functions to turn the MOSFET off during times of transmission.

Claims

CLAIMS 1. A power supply device for use in a mobile communication terminal including a high load and a low load, comprising: a first battery for providing the high load with a first operating voltage; a second, rechargeable battery for providing the low load with a second operating voltage; a recharging circuit between the first and second batteries for recharging the second battery; and a power regulator between the second battery and the low load, for regulating the second operating voltage applied to the low load.
2. A power supply device according to claim 1 in which the first battery is a rechargeable battery.
3. A power supply device according to claim 1 or claim 2, further comprising a diode between the recharging circuit and the second battery, to prevent a counterf low of operating current.
4. A power supply device according to any one of claims 1-3 in which the minimum voltage of the second battery is higher than the threshold voltage of the power regulator.
5. A power supply device according to any preceding claim in which the high load comprises a power amplifier.
6. A power supply device according to any preceding claim in which the low load comprises a base band processor and a logic circuit including a microprocessor.
7. A power supply device according to any preceding claim in which the capacity of the second battery is higher than the charge consumed by the low load in one frame cycle.
8. A power supply device according to any preceding claim in which the recharging circuit is adapted to charge the second battery continually while the mobile communication terminal is in operation.
9. A power supply device for use in a mobile communication terminal, the power supply device being substantially as described with reference to and/or as illustrated in FIGs. 3 and 4 of the accompanying drawings.