JP3261007B2 - Power circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a portable device such as a portable telephone powered by a battery, and more particularly to an improvement of a simple power supply circuit for backing up a power supply when a battery is removed.

[0002]

2. Description of the Related Art In a portable device using a battery as a power source, such as a mobile phone, it is necessary to back up the driving of functional units such as a memory and a clock circuit even when the battery is removed. Charge the backup capacitor in advance.

In such a circuit, a plurality of functional blocks such as a memory and a clock circuit may be backed up by one capacitor in terms of the number of parts and cost. Some functional blocks operate at a relatively high voltage and consume a large amount of current, such as memories, while others operate at a relatively low voltage and consume a small amount of current, such as clock circuits. It is necessary to make a backup so that the operation continues for a long period of time, so that a device having relatively large power consumption such as a memory is configured to stop the backup in a shorter time than a device which is not so.

In order to stop the power supply, a voltage detector is provided in a power supply line, a voltage lower than a threshold voltage for operating a function means such as a memory which consumes relatively large power is detected, and a power supply to the function means is detected. The supply is stopped.

[0005]

However, after the power supply to the function means having relatively large power consumption, such as a memory, is stopped, that is, after the backup is cut off, a voltage detector for detecting that the battery is mounted is used. Must be operated, and eventually the current is consumed by the voltage detector. This has a design effect on the length of backup time to a functional block that needs to be backed up at least for a long time, such as a clock circuit.

In order to solve the problems of the prior art, the present invention operates at a relatively low voltage like a clock circuit and a first functional block which consumes relatively large power such as a memory when a battery is removed. In a power supply circuit that backs up the power supply of the second functional block that consumes less current, it is unnecessary to supply power to the voltage detector after stopping the backup of the first functional block by the voltage detector. The purpose of the present invention is to provide a power supply circuit.

[0007]

According to the present invention, there is provided a voltage converter for generating a predetermined stabilized voltage from a battery, and a first converter which operates at a relatively high voltage driven by the stabilized voltage and consumes a large amount of current.
A power supply circuit including a power supply line connecting the functional block to the power supply line, wherein the power supply line includes means for preventing a backflow of current from a voltage converter side, voltage holding means charged by an output of the voltage converter, A line on / off switch for turning on / off the power supply to and from the line; and detecting a voltage equal to or higher than a predetermined voltage to maintain the on state of the line on / off switch; Line connection /
A voltage detector for turning off the disconnection switch is provided in this order, and a power supply line is drawn out between the voltage holding means and the line on / off switch, and a relatively low voltage connected to the drawn power supply line is used. A second functional block that operates and consumes a small amount of current; and a start-up line that is drawn from a power supply line between the voltage converter and the backflow prevention means and that is connected to the line on / off switch. At the time of mounting, the power supply to the second function block is started by the output voltage of the voltage converter, and the voltage turns on the line on / off switch via the start line, and the voltage detector and the first function When power supply to the block is started and the battery is removed, the power supply to the first and second functional blocks is held by the charging voltage of the voltage holding means, When the pressure detector detects that the voltage is equal to or lower than a predetermined voltage, the line on / off switch is turned off, and power supply to the voltage detector itself and the first functional block after the line on / off switch is stopped. .

[0008]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the present invention, wherein 1 is a battery, U1 is a voltage converter, D1 and D2 are diodes for preventing backflow,
Is a voltage holding circuit composed of a resistor R1 and a capacitor C1,
U2 is a voltage detector, 3 is a field effect transistor Q1, a line on / off switch composed of a transistor Q2, 4 is a first functional means (or circuit block) which operates at a relatively high voltage and consumes a large amount of current, such as a memory, Reference numeral 5 denotes a second functional means (or a circuit block) such as a clock circuit which operates at a relatively low voltage and consumes less current.

In the backup circuit, when the battery 1 is mounted, the capacitor C1 of the voltage holding means 2 is charged by the voltage detector U1, and when the battery 1 is removed, the capacitor C1 is used to connect the first functional means 4 to the first functional means 4. The second function means 5 is backed up.

That is, when the battery 1 is first mounted, the capacitor D2 is turned on with a constant output voltage of the voltage converter U1, and the transistor Q2 is turned on with the voltage. As a result, the field effect transistor Q1 is operated. The switch 3 is turned on (connected), and power supply to the first function means 4 is started. Since the voltage detector U2 has a high impedance output at a threshold voltage or higher at which the first function means 4 operates, even if the battery 1 is removed and the output voltage of the voltage converter U1 becomes 0 V, the supply voltage from the capacitor C1 is reduced. Is greater than the threshold voltage, line on / off switch 3
, The power supply to the first functional means 4 and the power supply to the voltage detector U2 itself are maintained by the capacitor C1.

When the time has elapsed since the battery 1 was removed,
Eventually, the detection voltage of the voltage detector U2 becomes equal to or lower than the Shresh voltage. At this time, the voltage detector U2 becomes an OV output, and the line on / off switch 3 is turned off (disconnected). Of the capacitor C1 is stopped. For this reason, neither the first function means 4 nor the voltage detector U2 itself operates, and the current consumption in the blocks after the line on / off switch 3 becomes zero. Therefore,
Thereafter, until the battery 1 is mounted again, the second functional unit 5
Only the operation is maintained by the voltage supply from the capacitor C1.

[0012]

According to the present invention, after stopping the backup of the power supply to the functional block which operates at a relatively high voltage and consumes a large amount of current, the operation of the voltage detector can be completely stopped. By reducing the current, the backup time of the power supply to the functional block that operates at a relatively low voltage and consumes less current can be lengthened.

[Brief description of the drawings]

FIG. 1 is a block diagram of a backup circuit showing one embodiment of the present invention.

[Explanation of symbols]

 1: Battery U1: Voltage converter 2: Voltage holding circuit U2: Voltage detector 3: Line connection / disconnection switch 4: First functional means with high current consumption 5: Second functional means with low current consumption

Claims (1)

(57) [Claims] A power supply line for connecting a voltage converter for generating a predetermined stabilized voltage from a battery and a first functional block which operates at a relatively high voltage driven by the stabilized voltage and consumes a large amount of current is provided. In the power supply circuit provided, the power supply line has a means for preventing a backflow of current from the voltage converter side, a voltage holding means charged by an output of the voltage converter, and a power supply to the rest of the power supply line. A line on / off switch to be turned on / off, and a state of detecting a predetermined voltage or more to hold an on state of the line on / off switch;
A voltage detector for detecting a voltage lower than that and turning off the line on / off switch in this order; and further, drawing out a power supply line from between the voltage holding means and the line on / off switch. A second functional block which operates at a relatively low voltage and consumes a small amount of current, connected to the connected power supply line, and which is drawn from a power supply line between the voltage converter and the backflow prevention means and connected to the line on / off switch. Connected to a start line, when the battery is installed, power supply to the second functional block is started by the output voltage of the voltage converter, and the voltage is connected / disconnected via the start line. When the switch is turned on and power supply to the voltage detector and the first functional block is started, and when the battery is removed, the first and second power sources are charged by the voltage holding means. Holding the power supply to the functional blocks, the voltage detector turns off the line contact / disconnection switch when it is detected that the predetermined voltage or lower the line tangent /
A power supply circuit for stopping power supply to a voltage detector itself and a first functional block after a disconnection switch.