JP4761847B2 - Power supply device and portable information terminal having the same - Google Patents

Description

  The present invention relates to a power supply device and a portable information terminal including the same, and more particularly to a power supply device that boosts an input voltage and supplies the boosted voltage to a load and a portable information terminal including the same.

  In portable information terminals such as cellular phones and PDAs (Personal Data Assistants), LEDs (Light-Emitting Diodes) used as backlights for LCD (Liquid Crystal Display) display devices are used at voltages higher than the battery voltage of portable information terminals. Need to drive. For this reason, a general portable information terminal includes a power supply device that boosts the battery voltage using a charge pump circuit or the like and supplies it to a load such as an LED.

For example, Patent Document 1 discloses the following power supply device. That is, the selection switch is operated by an input from the external selection terminal, and the boosting capacitor corresponding to the boosting ratio of the high voltage with respect to the power supply voltage is selected. With such a configuration, the boosting ratio of the high voltage with respect to the power supply voltage can be arbitrarily switched.
Japanese Patent Laid-Open No. 6-78527

  By the way, in the power supply device described in Patent Document 1, for example, when the battery voltage is 3.5 V and the voltage to be supplied to a load such as an LED (hereinafter referred to as target voltage) is 7.0 V, the charge pump circuit. The step-up rate is set to double. However, a voltage drop may occur due to a resistance component such as an internal circuit of the power supply device, and the voltage supplied to the load may be lower than the target voltage. Also, if the boost rate of the charge pump circuit is set high in advance, the power consumption of the charge pump circuit increases as the boost rate increases, and the voltage drop value changes depending on the current consumption of the load. When the rate is set higher than necessary, the power use efficiency of the power supply device is reduced.

  In other words, in the power supply device described in Patent Document 1, it is not possible to appropriately set the step-up rate according to fluctuations in the input voltage and the magnitude of the output current.

  Therefore, an object of the present invention is to provide a power supply device capable of appropriately setting a boost rate and a portable information terminal including the power supply device.

  In order to solve the above-described problem, a power supply apparatus according to an aspect of the present invention boosts an input voltage applied to an input terminal and supplies the boosted voltage to a load, and supplies the input voltage to the load. A boosting rate setting unit that sets a boosting rate based on a target voltage value and a current flowing through the load, and the boosting circuit switches the boosting rate based on the setting.

  Preferably, the power supply device further includes a register circuit that outputs a voltage drop value based on an amount of current flowing through the load to a boost rate setting unit in a predetermined section in a path from the input terminal to the load, and the boost rate setting unit includes: The boosting rate is set based on the input voltage, the target value of the voltage supplied to the load, and the voltage drop value.

  More preferably, the register circuit notifies the boost rate setting unit of a voltage drop value in the boost circuit based on the current amount.

Preferably, the load is a light emitting element used as a backlight of an LCD display device.
A portable information terminal according to an aspect of the present invention is a portable information terminal having a power supply device. The power supply device boosts an input voltage and supplies the boosted voltage to a load, an input voltage, and a load. And a step-up rate setting unit that sets a step-up rate based on a target value of the voltage to be supplied to the current and a current flowing through the load.

  A power supply apparatus according to still another aspect of the present invention includes a voltage adjusting unit that adjusts an input voltage applied to an input terminal, a boosting circuit that boosts the adjusted voltage and supplies the boosted voltage to a load, A step-up rate setting unit for setting the step-up rate of the step-up circuit, and the step-up circuit outputs in accordance with the adjusted voltage and the setting of the step-up rate setting unit.

  Preferably, the power supply device further includes an output voltage setting unit that sets a target value of the voltage supplied to the load, and the boosting rate setting unit sets the boosting rate based on the setting of the output voltage setting unit.

  Preferably, the power supply device further includes a conversion table for storing a margin voltage corresponding to a current flowing through the load, and the boosting rate setting unit obtains a margin voltage from a voltage value obtained by multiplying the voltage adjusted by the voltage adjusting unit by the boosting rate. The voltage booster is set so that the value obtained by subtracting is not less than the target value of the voltage to be supplied to the load, and the voltage regulator adjusts the input voltage so that the output voltage of the booster circuit becomes the target value of the voltage supplied to the load Adjust.

  According to the present invention, by appropriately setting the boosting rate, it is possible to improve the power usage efficiency and to extend the usable time of the portable information terminal using this power supply device.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

[Configuration and basic operation]
FIG. 1 is a diagram showing a configuration of a power supply apparatus 100 according to an embodiment of the present invention. Referring to the figure, battery voltage Vbat from battery 500 is applied as an input voltage to input terminal t1 of power supply device 100. A load 9 that is an LED, for example, is connected to the output terminal t2 of the power supply apparatus 100. The power supply device 100 boosts the battery voltage Vbat applied to the input terminal t1, outputs the boosted voltage from the output terminal t2 as an output voltage Vout, and supplies it to the load 9.

  The power supply device 100 includes a charge pump circuit 1, a boost rate setting unit 2, a register circuit 4, an output voltage setting unit 5, a D / A (Digital / Analog) converter 6, and an A / D (Analog / Digital). Converter 8, resistors R <b> 3 to R <b> 4, constant current circuit 8, conversion table 10, and voltage adjustment unit 22 are provided.

  The voltage adjusting unit 22 includes an operational amplifier 7, resistors R1 and R2, and a P-type MOS (Metal Oxide Semiconductor) transistor M1. Hereinafter, the resistance values of the resistors R1 to R4 will be described as r1 to r4.

  The output voltage setting unit 5 generates a digital value Dset representing a voltage (target voltage) to be supplied to the load 9 based on data stored in a ROM (Read Only Memory) and data input from the outside. / A output to the converter 6 and the step-up rate setting unit 2.

  The D / A converter 6 converts the digital value Dset received from the output voltage setting unit 5 from digital to analog and outputs the analog value Vset to the operational amplifier 7 in the voltage adjustment unit 22.

  The voltage adjustment unit 22 is a regulator circuit, and reduces and adjusts the battery voltage Vbat based on the target voltage represented by the analog voltage Vset received from the D / A converter 6 and the divided value of the output voltage Vout. It outputs to the charge pump circuit 1 as Vx.

  More specifically, the operational amplifier 7 adjusts the on-resistance of the MOS transistor M1 by applying a voltage to the gate terminal of the MOS transistor M1 so that the two voltages applied to the non-inverting input terminal and the inverting input terminal are equal. To do. Here, the analog voltage Vset received from the D / A converter 6 is applied to the non-inverting input terminal of the operational amplifier 7, and the output voltage Vout is divided by the resistors R1 and R2 at the inverting input terminal. The applied voltage Vy is applied. The voltage Vy = Vout × r1 / (r1 + r2). The operational amplifier 7, the MOS transistor M1, and the charge pump circuit 1 constitute a feedback circuit, and feedback is applied so that Vset = Vy, and the on-resistance of the MOS transistor M1 is adjusted, so that Vout = Vset × (r1 + r2) The output voltage Vout converges so as to satisfy / r1. At this time, the voltage Vx applied to the input terminal of the charge pump circuit 1 converges to Vx = Vout / XCP = Vset × (r1 + r2) / r1 / XCP.

  The charge pump circuit 1 boosts the voltage Vx received from the voltage adjusting unit 22 at the boost rate XCP set by the boost rate setting unit 2, and outputs the boosted voltage to the output terminal t2. The charge pump circuit 1 can switch the step-up rate of, for example, 1 time, 1.5 times, 2 times, and 2.5 times. The voltage output to the output terminal t2 is supplied to the load 9 as the output voltage Vout. The output voltage Vout = Vx × XCP.

  The resistors R3 and R4 divide the battery voltage Vbat applied to the input terminal t1 and output the divided voltage to the A / D converter 8 as the detection voltage Vdet. Vdet = Vbat × r3 / (r3 + r4).

  The A / D converter 8 converts the detection voltage Vdet from analog to digital and outputs the digital value Ddet to the boost rate setting unit 2.

  The register circuit 4 outputs a current value to be supplied to the load 9 to the constant current circuit 8 based on a control signal received from the outside, and converts a margin voltage corresponding to the current value to be supplied to the load 9 to the conversion table. 10 and outputs the digital value Dm of the margin voltage (hereinafter also referred to as margin voltage value Dm) to the boost rate setting unit 2. The register circuit 4 is not limited to the configuration in which the current value to be supplied to the load 9 is output to the constant current circuit 8, but simply receives a measured value of the current flowing through the load 9 from the outside, It is possible to adopt a configuration in which the margin voltage corresponding to the measured value is obtained from the conversion table 10 by direct measurement.

  The constant current circuit 8 supplies current to the load 9 based on the current value received from the register circuit 4.

  FIG. 2 is a diagram illustrating an example of the conversion table 10 used by the register circuit. Iout represents the current to be supplied to the load 9.

  Referring to the figure, register circuit 4 has a margin voltage value Dm = 0.2 V when current value Iout = 0 to 50 mA to be supplied to load 9 based on a control signal received from the outside. To do. Similarly, the register circuit 4 sets the margin voltage value Dm = 0.4 V when Iout = 50 to 100 mA, and sets the margin voltage value Dm = 0.6 V when Iout = 100 to 150 mA. When Iout = 150 to 200 mA, the margin voltage value Dm = 0.8V.

  Here, the margin voltage value is a value determined by a resistance component in a predetermined section in a path from the input terminal t1 to the input of the load 9. An example of the resistance component that is dominant in the path from the input terminal t1 to the input of the load 9 is the resistance component of the charge pump circuit 1. Further, when the power supply device according to the embodiment of the present invention is a semiconductor integrated circuit, a resistance component or the like due to wire bonding, wiring on an external substrate, or the like is included in the resistance component in the path from the input terminal t1 to the load 9. . The margin voltage value can be obtained, for example, by actually measuring the voltage applied to the load 9 and calculating the difference from the theoretical value. Alternatively, the resistance value of the charge pump circuit 1 may be obtained on a desk or by experiment, and the margin voltage value based only on the resistance value of the charge pump circuit 1 may be reflected in the conversion table 10. With such a configuration using the conversion table, it is possible to flexibly cope with variations in resistance components of each circuit due to device types, manufacturing variations, and the like.

  Boost ratio setting unit 2 receives digital value Ddet received from A / D converter 8 representing the input voltage, and digital value Dset received from output voltage setting unit 5 representing the target voltage (hereinafter also referred to as target voltage value Dset). Based on the margin voltage value Dm received from the register circuit 4, the boosting rate XCP of the charge pump circuit 1 is set.

[Operation]
Next, an operation when the boost rate setting unit 2 in the power supply apparatus 100 according to the embodiment of the present invention sets the boost rate XCP will be described.

  FIG. 3 is a flowchart defining the operation procedure of power supply apparatus 100 according to the embodiment of the present invention.

  First, the register circuit 4 outputs a margin voltage value Dm corresponding to the current value to be supplied to the load 9 to the boost rate setting unit 2 (S1).

  The step-up rate setting unit 2 acquires the battery voltage Vbat, which is an input voltage, as the digital value Ddet, acquires the target voltage value Dset, and acquires the margin voltage value Dm (S2).

  Next, when the value obtained by subtracting the margin voltage value Dm from the battery voltage Vbat is equal to or greater than the target voltage value Dset, the boost rate setting unit 2 sets the boost rate XCP to 1 (YES in S3 and S6). .

  The step-up rate setting unit 2 is a case where the value obtained by subtracting the margin voltage value Dm from the battery voltage Vbat is smaller than the target voltage value Dset, and the value obtained by subtracting the margin voltage value Dm from 1.5 times the battery voltage Vbat. Is equal to or higher than the target voltage value Dset, the step-up rate XCP is set to 1.5 times (NO in S3, YES and S7 in S4).

  Similarly, the boosting rate setting unit 2 compares the value obtained by subtracting the margin voltage value Dm from twice or 2.5 times the battery voltage Vbat with the target voltage value Dset, thereby increasing the boosting rate by 2 or 2. Set to 5 times (S5, S8 and S9).

  Hereinafter, as a specific example, the battery voltage Vbat is 3.6 V, the target voltage value Dset is 7.0 V, the current value Iout to be supplied to the load 9 is 80 mA, and the register circuit 4 has the conversion table shown in FIG. The case of using will be described.

  When the register circuit 4 receives the control signal from the outside and recognizes that the current value Iout to be supplied to the load is 80 mA, the register circuit 4 refers to the conversion table 10 to set the margin voltage value Dm = 0.4 V, and sets the boost rate setting unit. Output to 2.

  Then, the boost rate setting unit 2 satisfies 3.6V × 2-0.4V <7.0V (NO in S5), and therefore supplies the target voltage to the load 9 when the boost rate XCP is 2.0 times. It is determined that it cannot be performed, and the step-up rate XCP is set to 2.5 times (S9).

  Here, when the step-up rate XCP is set to 2.5 times, the voltage supplied to the load 9 is 3.6V × 2.5−0.4V = 8.6V, and the target voltage value Dset = 7.0V. It will be bigger. However, as described above, the voltage adjustment unit 22 steps down and adjusts the battery voltage Vbat based on the target voltage represented by the analog voltage Vset received from the D / A converter 6 and the divided value of the output voltage Vout. Since the voltage Vx is output to the charge pump circuit 1, the voltage supplied to the load 9 can be set to 7.0 V that is the target voltage value.

[Portable information terminal]
FIG. 4 is a functional block diagram of a portable information terminal having the power supply device according to the embodiment of the present invention.

  With reference to the figure, the portable information terminal includes power supply devices 31 to 32, an operation unit 11, a light emitting unit 12, a processing block 13, a communication processing unit 14, and an LCD monitor 15. The light emitting unit 12 includes an LED 21 and a processing unit 22, and the processing block 13 includes a CPU (Central Processing Unit) 23 and a memory 24.

  In the following description, the portable information terminal is assumed to be a mobile phone, but the portable information terminal may be a PDA or the like.

  The communication processing unit 14 performs processing necessary for communication. That is, the communication processing unit 14 executes processing necessary for communication in a mobile communication system such as a PDC (Personal Digital Cellular System), a simple mobile phone system, a CDMA (Code Division Multiple Access), and an IrDA (Infrared Data Association) system. To do.

  The operation unit 11 includes a button for a user to input a telephone number and the like, and detects a user operation.

  The light emitting unit 12 blinks the LED 21 as an illumination when a mobile phone arrives. The processing unit 22 outputs a control signal representing a command for causing the LED 21 to blink to the LED 21. In addition, the processing unit 22 outputs a control signal representing a voltage value to be supplied to the LED 21 to the power supply device 31.

  Power supply device 31 outputs a voltage to LED 21 based on the voltage value represented by the control signal received from processing unit 22.

  The processing block 13 controls each block of the mobile phone. The LCD monitor 15 displays the telephone number of the other party with whom communication is performed, the contents of an e-mail, an image and the like. Here, the processing block 13 displays an image or the like on the LCD monitor 15 and outputs a control signal representing a voltage value to be supplied to the LED 21 to the power supply device 32. Then, power supply device 31 outputs a voltage to the backlight LED included in LCD monitor 15 based on the voltage value represented by the control signal received from processing block 13.

  By the way, in the power supply device described in Patent Document 1, the boosting rate cannot be set appropriately. However, in power supply device 100 according to the embodiment of the present invention, marginal voltage based on the current to be supplied to load 9 in addition to the input voltage of power supply device 100 and the voltage to be supplied to load 9 by boost rate setting unit 2 Based on the above, the step-up rate XCP is set. Therefore, in power supply device 100 according to the embodiment of the present invention, the boosting rate can be set appropriately, and the target voltage can be stably supplied to load 9.

  Further, in power supply apparatus 100 according to the embodiment of the present invention, boosting rate XCP is set by directly referring to battery voltage Vbat, so that an appropriate boosting rate can be set even when battery voltage Vbat varies. . As a result, the problem of setting the double boosting rate to 1.5 times is solved, so that wasteful power consumption can be prevented.

  In the light emission control circuit according to the embodiment of the present invention, the register circuit 4 outputs a current value to be supplied to the load 9 to the constant current circuit 8 based on a control signal received from the outside. 9, the margin voltage corresponding to the current value to be supplied to 9 is obtained from the conversion table 10. However, the present invention is not limited to this. The light emission control circuit does not include the register circuit 4, and the step-up rate setting unit 2 receives a measured value of the current flowing through the load 9 from the outside or directly measures the current flowing through the load 9, and a margin corresponding to the measured value The voltage can be calculated.

  In addition, the power supply device 100 according to the embodiment of the present invention is configured to include the charge pump circuit 1. However, the present invention is not limited to this, and the charge pump circuit 1 is not limited thereto. Can be substituted for

  Although only one LED is shown as the load 9, the present invention is particularly effective for a load that consumes a large current, such as a plurality of LEDs and a motor.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a figure which shows the structure of the power supply device 100 which concerns on embodiment of this invention. It is a figure which shows an example of the conversion table 10 which a register circuit uses. It is the flowchart which defined the operation | movement procedure of the power supply device 100 which concerns on embodiment of this invention. It is a functional block diagram of the portable information terminal which has the power supply device which concerns on embodiment of this invention.

Explanation of symbols

  31-32,100 Power supply device, 9 load, 1 charge pump circuit, 2 step-up ratio setting unit, 4 register circuit, 5 output voltage setting unit, 6 D / A converter, 7 operational amplifier, 8 A / D converter, 9 load DESCRIPTION OF SYMBOLS 10 Conversion table, 11 Operation part, 12 Light emission part, 13 Processing block, 14 Communication processing part, 15 LCD monitor, 21 LED, 22 Processing part, 23 CPU, 24 Memory, R1-R4 resistance, M1 MOS transistor, t1 input Terminal, t2 output terminal.

Claims (6)

A booster circuit that boosts an input voltage applied to an input terminal and supplies the boosted voltage to a load;
A step-up rate setting unit that sets a step-up rate based on the input voltage, a target value of a voltage supplied to the load, and a current flowing through the load ;
A register circuit that outputs a voltage drop value based on the amount of current flowing through the load to a step-up rate setting unit in a predetermined section in the path from the input terminal to the load ;
The booster circuit switches the boosting rate based on the setting ,
The boosting rate setting unit sets the boosting rate based on the input voltage, a target value of a voltage supplied to the load, and the voltage drop value . It said register circuit includes a power supply device according to claim 1, wherein notifying the voltage drop value in the boosting circuit based on the current amount to the boost ratio setting unit.   The power supply device according to claim 1, wherein the load is a light emitting element used as a backlight of an LCD display device. A portable information terminal having a power supply device,
The power supply device
A booster circuit that boosts an input voltage applied to an input terminal and supplies the boosted voltage to a load;
A step-up rate setting unit that sets a step-up rate based on the input voltage, a target value of a voltage supplied to the load, and a current flowing through the load ;
A register circuit that outputs a voltage drop value based on the amount of current flowing through the load to a step-up rate setting unit in a predetermined section in the path from the input terminal to the load ;
The booster circuit switches the boosting rate based on the setting ,
The step-up rate setting unit is a portable information terminal that sets the step-up rate based on the input voltage, a target value of a voltage supplied to the load, and the voltage drop value . A voltage adjustment unit for adjusting the input voltage applied to the input terminal;
A boosting circuit that boosts the adjusted voltage and supplies the boosted voltage to a load;
A boost rate setting unit for setting a boost rate of the boost circuit ;
A conversion table for storing a margin voltage corresponding to the current flowing through the load ,
The booster circuit outputs a row stomach according to the setting of the adjusted voltage and the step-up ratio setting unit,
The step-up rate setting unit is configured to prevent a value obtained by subtracting the margin voltage from a voltage value obtained by multiplying the voltage adjusted by the voltage adjusting unit by the step-up rate is less than a target value of a voltage supplied to the load. Set
The voltage adjustment unit adjusts the input voltage so that an output voltage of the booster circuit becomes a target value of a voltage supplied to the load . The power supply device further includes:
An output voltage setting unit for setting a target value of a voltage to be supplied to the load;
The power supply device according to claim 5, wherein the boost rate setting unit sets the boost rate based on the setting of the output voltage setting unit.

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