JP2001195136A - Input voltage limitation circuit in battery-driven device and method for operating the device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a pre-regulator for interrupting or minimizing voltage drop. SOLUTION: A pre-regulator circuit for holding the input of an integrated circuit at voltage matching a rated voltage is connected between a battery power supply of a cellular telephone and an integrated circuit regulator. In order to avoid a voltage drop of the pre-regulator when battery voltage is low, a breaker circuit for short-circuiting or minimizing the voltage drop of the pre-regulator is driven.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an input voltage limiting circuit and method for a battery-powered device.

[0002]

2. Description of the Related Art In order to provide a degree of design flexibility in the use of integrated circuit components, the components are housed in a circuit where under certain conditions the design limits of the integrated circuit may be exceeded. Often it is necessary. This occurs in wireless telephone applications where it is desirable to use common components across multiple production lines that may use different types of batteries. Thus, from time to time, it may not be possible to rate some components to match the full battery voltage. For example, it may be cost-effective to utilize an integrated circuit voltage regulator rated at 4 volts for a wireless telephone with a 5 volt battery power supply. In those cases, overvoltages on certain integrated circuits must be avoided.

To protect the integrated circuit voltage in the above example,
A pre-regulator is used to avoid over-voltage on the regulator. While this is somewhat straightforward at full battery voltage, as the power supply ramps down with use, the voltage drop across its pre-regulator becomes a burden. This reduces the useful life of the battery between charge cycles.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a simple system having means for interrupting or minimizing the voltage drop across a pre-regulator when battery power is at the low end of its cycle. To provide a simple pre-regulator circuit.

[0005]

SUMMARY OF THE INVENTION A pre-regulator circuit is connected between a battery power supply of a cellular telephone and an input of an integrated circuit regulator to keep the input of the integrated circuit at a voltage consistent with its rated voltage. This requires a voltage drop in the pre-regulator circuit. This voltage loss is not a problem when the battery is fully charged, but may limit the operation of the phone at the lower end of the battery charge cycle. To avoid this, a low voltage, shutoff circuit is used to limit the voltage drop in the pre-regulator circuit. The shutoff circuit is activated by a comparator that compares the battery voltage with a predetermined minimum threshold voltage. The comparator shorts the pre-regulator circuit or activates a relay or other switching means that converts its operation to minimize the voltage drop created by the pre-regulator circuit.

Next, the present invention will be described in more detail with reference to the accompanying drawings.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic components of the regulator system of the present invention are shown in the block diagram of FIG.
It includes supplying battery 1 supplying voltage (V _S) to the system. The pre-regulator circuit 2 is connected to limit the input voltage (V _IC ) to the integrated circuit 3.
Integrated circuit voltage regulator 3 provides a substantially constant voltage to microprocessor control unit 4 of a cellular telephone or other device. The pre-regulator 2 controls the voltage (V _IC ) to the integrated circuit regulator 3. This control reduces the integrated circuit regulator supply voltage V _IC ,
It is necessary to match the rated voltage of the integrated circuit 3 to ensure proper operation of the regulator 3.

In order to achieve the object of the present invention, the switch module 5 is connected to the pre-regulator 2 and the pre-regulator 2 is activated when V _S falls below a predetermined minimum threshold (V _T ). It is designed to shut off. The supply voltage is sensed by the voltage monitor 6. V
_T can be set to a voltage level just above the minimum operating voltage of the microprocessor control unit 4, taking into account the voltage drops of the IC regulator 3 and the pre-regulator 2. Although shutdown of the pre-regulator 2 can be achieved in a number of ways, for the purposes of the present invention it is specified that it is to minimize the voltage drop of the pre-regulator. This involves a short circuit as shown in the alternative embodiment shown in FIG. It effectively eliminates the negative effect of pre-regulator 2 when V _S <V _T. Thus, the operation of the cellular telephone or other device is lengthened by an additional amount of time.

Regulator 3 may be any known type of integrated circuit voltage regulator and does not form part of the present invention. Its purpose is to supply the microprocessor control unit 4 with a substantially constant voltage for the operation of the device. As is well known, the operation of the device is limited by the battery cycle, and it is important to maintain the voltage level, especially at the low end of the cycle.

As shown in FIG. 2, the system comprises:
It operates by monitoring the battery voltage V _S , comparing it to the threshold voltage V _T, and minimizing the voltage drop across the pre-regulator 2 when V _S falls below V _T. During normal operation, the pre-regulator 2 senses a voltage V _P equal to V _S (R ₂ / R ₁ + R ₂ ) indicating the input voltage V _IC to the integrated circuit 3 and _compares the reference voltage V _REF with V _P. Generates a voltage drop that compensates for the difference. The reference voltage is integrated circuit 3.
Can be set in relation to the rated operating voltage of
Variations in the operating voltage of the particular IC circuit used are generally provided appropriately by selecting the values of resistors R ₁ and R ₂ .

The pre-regulator 2 typically has an MO
Differential connected to control current through SFET 8
It is designed using the amplifier 7. MOSFET8 via
By adjusting the voltage, V_REF The voltage associated with
You. The positive terminal of the amplifier 7 is connected to a resistor R₁ And R_Two Consisting of
Connected to voltage divider. The positive terminal of the amplifier 7 is the voltage V _P 
Which is connected to a voltage dividing resistor R₁ And R_Two By
Rated voltage V for IC regulator 3_{I c}Related to
ing. The specific circuit shown is presented
Although useful in the context of the embodiment,
Without significantly affecting the invention
The pre-regulator function can be achieved in a way.

In the preferred embodiment shown in FIG.
Switching module 5 comprises a pair of MOSFs connected to adjust the bias of MOSFET 8 to convert its function to that of a low resistance switch.
Consists of ET9 and ET10. When the battery is fully charged, MOSFETs 9 and 10
The FET 8 is operated as the pre-regulator 2 in response to the differential amplifier 7. Resistors R ₁ and R ₂ are selected to provide a voltage V _IC to regulator 3 that is limited to the rated voltage of regulator 3. Although V _REF can be standardized, the resistance is varied to provide the particular IC regulator used.

The voltage monitor 6 has a pair of resistors R_Three as well as
R_Four Another connected through a voltage divider consisting of
It consists of a differential amplifier or comparator 11. Comparator 1
1 is the battery voltage V_S A resistor R indicating_Three And R_Four of
Voltage between V_S (R_Four / R _Three + R_Four ), And
To the low threshold voltage V_T Connected to compare with
ing. V_S (R_Four / R_Three + R_Four ) Is V_T Went down
At this time, the output voltage from the comparator 11
Through the switching module 5. this
Triggers MOSFETs 9 and 10 to pre-regulate
The operation of the data 2 is changed as described above. Battery
When recharged, this process is reversed and
The regulator will lower the voltage to regulator 3 again
Work.

To avoid unwanted cycling of the switch module 5 with the comparator 11, it is beneficial to design the comparator 11 with some hysteresis. Thus, comparator 11 compares the assigned battery indicator voltage to various voltage levels. When the battery voltage drops, the indicator voltage is equal to a value obtained by subtracting the hysteresis voltage from V _T. Conversely when the battery voltage is increased, the indicator voltage is a value obtained by adding the hysteresis voltage V _T.

An alternative embodiment is shown in FIG. In this embodiment, the MOSFET of the switch module 5
9 and 10 have been replaced by relays 12 driven directly from the output voltage of the differential amplifier 11. The relay is closed when the V _S is lower than the V _T, is prior to completion of the shunt 5 for short-circuiting the location regulator 2. Another alternative embodiment is shown in FIG. In this example,
The differential amplifier 11 is replaced by an A / D converter 13, and the output is processed by a microprocessor 14. Using an appropriate algorithm, the microprocessor 14 generates an activation signal for the relay 12 closing the shunt 5. Using this configuration, the MOSFET 9 in the circuit of FIG.
And 10 actions can be triggered.

In this way, the negative effect of the voltage drop caused by the pre-regulator 2 is overcome and the integrated circuit regulator 3 is protected from excessive voltages.

[Brief description of the drawings]

FIG. 1 is a block diagram showing main components of the present invention.

FIG. 2 is a flow chart of the processing steps of the method of the present invention.

FIG. 3 is a circuit diagram showing a preferred embodiment of the present invention.

FIG. 4 is a circuit diagram illustrating an alternative embodiment of the present invention.

FIG. 5 is a circuit diagram showing a second alternative embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 battery 2 pre-regulator 3 integrated circuit voltage regulator 4 microprocessor control unit 5 switch module 6 voltage monitor

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G05F 1/56 320 G05F 1/56 320C H02J 1/00 304 H02J 1/00 304E 7/00 302 7/00 302A

Claims (11)

[Claims] 1. An input voltage limiting circuit for limiting a voltage input to an integrated circuit having a rated voltage in a battery-driven device, wherein the input voltage limiting circuit is connected to an input of the integrated circuit and controls the input voltage to a predetermined reference. A pre-regulator configured to compare with a voltage and adjust the input voltage in response to the comparison; and a switch module connected to control operation of the pre-regulator, wherein the The pre-regulator is configured to be shut off when the battery voltage drops to a predetermined voltage threshold, and to sense a voltage indicative of the battery voltage and reduce the battery voltage to the predetermined minimum threshold. Comparing the switch module when the battery voltage falls below the voltage threshold. And a voltage monitor connected to operate the input voltage limiting circuit. 2. An input voltage limiting circuit for limiting a voltage input to an integrated circuit having a rated voltage in a battery-powered device, wherein the pre-regulator is operatively connected to a differential amplifier. A switch module connected to the MOSFET to adjust the bias of the MOSFET to minimize the voltage drop caused by the switch module when activated by the voltage monitor. 2. The input voltage limiting circuit according to claim 1, further comprising a circuit. 3. An input voltage limiting circuit for limiting a voltage input to an integrated circuit having a rated voltage in a battery-operated device, wherein the switch module comprises: 2. The input voltage limiting circuit of claim 1 including a relay connected in a shunt to shut off said pre-regulator when actuated. 4. An input voltage limiting circuit for limiting a voltage input to an integrated circuit having a rated voltage in a device driven by a battery, wherein the voltage monitor comprises:
The input voltage limiting circuit of claim 1, further comprising a comparator connected to compare the voltage indicative of the battery voltage to a predetermined minimum threshold voltage. 5. An input voltage limiting circuit for limiting a voltage input to an integrated circuit having a rated voltage in a battery-powered device, wherein the voltage monitor comprises:
A / is connected to sense a voltage indicative of the battery voltage and generate a digital signal accordingly.
A digital-to-analog converter, wherein the digital signal is processed by a microprocessor programmed to generate a signal to activate the switch module when the battery voltage drops to a predetermined minimum threshold. 2. The input voltage limiting circuit according to claim 1, wherein: 6. An input voltage limiting circuit for limiting a voltage input to an integrated circuit having a rated voltage in a battery-operated device, wherein the voltage reference is related to a rated voltage of the integrated circuit. The input voltage limiting circuit according to claim 1, wherein the input voltage limiting circuit is set. 7. A method for operating a limiting circuit in a battery-powered device including an input voltage limiting circuit for limiting a voltage input to an integrated circuit having a rated voltage, the method comprising: Sensing a voltage; setting a predetermined reference voltage; comparing the input voltage with the reference voltage and adjusting the input voltage in relation thereto; sensing a voltage provided by the battery Setting the predetermined minimum threshold voltage; comparing the supply voltage with the predetermined minimum threshold voltage; and controlling the input voltage limiting circuit when the supply voltage falls below the predetermined minimum threshold. Switching to a blocking state. 8. A method of operating a limiting circuit in a battery driven device including an input voltage limiting circuit for limiting a voltage input to an integrated circuit having a rated voltage, the method comprising: The method of claim 7, wherein a step reduces the voltage. 9. A method for operating a limiting circuit in a battery-powered device including an input voltage limiting circuit for limiting a voltage input to an integrated circuit having a rated voltage, wherein the switching to the cutoff state is performed. The steps are
The method of claim 7, comprising minimizing a voltage drop in the input voltage limiting circuit. 10. A method for operating a limiting circuit in a battery-powered device including an input voltage limiting circuit for limiting a voltage input to an integrated circuit having a rated voltage, the method comprising: switching to the cutoff state. The method of claim 7, wherein the step of short-circuiting comprises shorting the input voltage limiting circuit. 11. A circuit in a mobile telephone for communication in a cellular network, said telephone controlling a microprocessor control unit for operating said telephone and a voltage to said microprocessor control unit. An integrated circuit voltage regulator, the voltage regulator having a rated voltage, the circuit being an input voltage limiting circuit for limiting a voltage input to the integrated circuit, the circuit comprising: A pre-regulator connected to an input of a circuit and configured to compare the input voltage with a predetermined reference voltage and adjust the input voltage in response to the comparison; and controlling an operation of the pre-regulator. Switch module, wherein the pre-regulator reduces the battery voltage to a predetermined voltage threshold. Detecting a voltage indicating the battery voltage, comparing the battery voltage with the predetermined minimum threshold, and detecting when the battery voltage falls below the voltage threshold. And a voltage monitor connected to operate said switch module.