JP2002320338A - Adjusting device of voltage supplied from battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adjusting device of a voltage supplied from a battery which enables life prolongation of an operating battery of a portable device. SOLUTION: The adjusting device is a regulator of a voltage supplied from a battery to an electronic circuit and includes a low voltage regulator (6). The regulator regulates a supply voltage to an electronic device while charging is performed perfectly and a first discharge step of the battery is discharged. A battery voltage is monitored. When the battery voltage decreases down to a previously determined threshold value, a switching means 8 switches the first discharge step to a second discharge step of the battery wherein power is supplied to the electronic device through a bypass.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery-operated device, and more particularly to a voltage control device supplied from a battery for extending the life of an operating battery of a portable device.

[0002]

2. Description of the Related Art Cellular phones and PDAs (Personal Digital A)
Portable devices, such as personal digital assistants, typically use lithium ion batteries as a power source. These devices output voltages from 4.2 volts when fully charged to 3.2 volts when discharged. This is disadvantageous for digital devices that require a constant voltage of 3.3 volts, which is higher than the lowest output voltage and lower than the highest output voltage.

[0003]

In general, digital logic circuits use a nominal operating voltage of 3.3 volts. The supply voltage for these circuits is typically from a minimum of 3 volts to a maximum of 3.6 volts. Traditionally, this power has been achieved through the use of linear regulators, including low dropout regulators (hereinafter abbreviated LDO). The problem with this method is that an input voltage that is approximately 0.3 volts greater than the output voltage is required to maintain the LDO characteristic. Therefore, the input voltage must be at least 3.6 volts in order to maintain a nominal 3.3 volt supply voltage to the LDO. This limits the operating time of lithium-ion battery powered devices, and batteries are still 25%
It must be recharged when it reaches 3.6 volts, which maintains its charge capacity.

Heretofore, this problem has been achieved by using a booster converter to raise the input voltage to a higher voltage before adjusting to the required voltage. However, this method is inefficient and uneconomical in terms of component cost and component size.

It is an object of the present invention to provide a battery-supplied voltage regulator that overcomes the above-mentioned problems by using a switch to bypass the LDO for a battery-operated device.

[0006]

SUMMARY OF THE INVENTION A voltage regulator according to the present invention is a device for regulating a voltage supplied from a battery to an electronic circuit, wherein the battery is almost completely charged and the first stage of battery discharge is performed. A low dropout regulator that regulates the supply voltage to the electronic circuit during the discharge of the battery; a means for monitoring the battery voltage; and a response to a voltage drop to a predetermined threshold during the discharge of the second stage of battery discharge. Switching means for switching the electronic circuit to supply power through a bypass route.

Further, the switching means disconnects the low dropout regulator when the voltage reaches the threshold value.

The battery is a lithium ion battery.

[0009] Also, electronic circuits require operating voltages from 3 volts to 3.6 volts.

Further, the switching means switches the bypass switch to the operation when the battery voltage drops to 3.6 volts.

The preferred embodiment of the invention will be described in detail by way of example with reference to only one block diagram of a circuit embodying the invention.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention uses a simple switch that connects a battery directly to a digital power supply when the voltage drops to a desired 3.6-3.0 volt range. is there. This is shown in FIG.
Supplies the regulated output 4 via the LDO 6. The bypass switch 8 is connected in parallel with the LDO 6.

If the battery voltage is above 3.6 volts, the bypass switch is turned off and the circuit operates normally as a conventional regulator. When the battery voltage drops below 3.6 volts, the bypass switch is connected and the regulator is disconnected. The system is then powered directly from the battery. As a result, operation of the device will be fully discharged until the battery is approximately 3.2 volts.

The bypass switch is constituted by a field effect transistor (FET). This has the effect of low resistance when connected, thus saving power and being efficient.

The bypass switch can also be controlled from the voltage monitoring circuit and, fortunately, from the system microprocessor. This means that the battery voltage can be monitored to determine the remaining battery level and a bypass switch can be directly connected when a threshold of 3.6 volts is reached. This saves hardware cost and space and allows for more flexible control. This monitoring circuit is not shown, but is implemented in a direct manner found in the prior art.

In practice, it is necessary to incorporate a small amount of hysteresis into the control logic to prevent the occurrence of unwanted oscillations when the threshold to be switched is reached.

Thus, the bypass monitoring circuit turns on the bypass switch when it reaches approximately 3.6 volts,
Should be set to turn off LDO. However, in order to switch the battery voltage to reverse, it is necessary to increase this voltage to a value sufficient to absorb the oscillations assumed to occur in the battery voltage. Therefore, it must generally be switched back to 3.7 volts.

[0018]

According to the present invention, there is an effect that the life of the operating battery of the portable device can be extended by using the switch for bypassing the LDO for the device operated by the battery.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

[Explanation of symbols]

 2 Lithium ion battery 4 Control output 6 Low dropout regulator 8 Bypass switch

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Toy Banks UK, Berkshire RGS 20 TD, Reading, Imperial Way, Imperium, Level 3, NCE Technologies UK Limited F-term (reference) 5G003 BA01 DA02 DA16 5H030 AA01 AS11 BB21 FF44 5H410 FF02 FF22 LL18 5H730 AA16 AS17 BB82 BB98 CC22 DD04 EE60 FD11 FG01 FG26

Claims (5)

[Claims] 1. An apparatus for adjusting a voltage supplied from a battery to an electronic circuit, wherein the battery is almost fully charged, and the power supply voltage to the electronic circuit is adjusted during the first stage of battery discharge. A low dropout regulator; means for monitoring battery voltage; and switching to a second stage of battery discharge to power the electronic circuit through a bypass route in response to the battery voltage dropping to a predetermined threshold. A voltage regulator supplied from a battery having switching means. 2. The voltage regulator as claimed in claim 1, wherein the switching means disconnects the low dropout regulator when the voltage reaches the threshold. 3. The voltage regulator supplied from a battery according to claim 1, wherein the battery is a lithium ion battery. 4. A voltage regulator provided by a battery according to claim 1, wherein the electronic circuit requires an operating voltage of 3 volts to 3.6 volts. 5. The voltage regulator supplied from a battery according to claim 3, wherein the switching means switches the bypass switch to an operation when the battery voltage drops to 3.6 volts.