JP2005137053A - Power source circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power source circuit in which the consumption of a backup power source can be suppressed certainly at a main power source voltage applying time. <P>SOLUTION: The power source circuit includes a switch circuit 22 in which a second power source voltage (Vbackup) different from a first power source voltage (Vmain) and the first power source voltage are supplied, when the first power source voltage is higher than a predetermined level, the first power source voltage is selected, and when the first power source voltage is lower than the predetermined voltage, the second power source voltage is selected, a second voltage generating circuit 23 for generating a second drive voltage V12 from the output voltage of the switch circuit, and a level setting circuit 24 for setting to a level in which the input level to the switch circuit of the second power source voltage is lower than the lower limit level of the input level of the switch circuit of the first power source voltage and which is capable of generating the second drive voltage V12 by the second voltage generating circuit. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a power supply circuit, and more particularly to a power supply circuit that generates a first drive voltage that causes a circuit to perform a main operation and a second drive voltage that causes the circuit to perform a backup operation.

  FIG. 3 shows a circuit configuration diagram of a conventional example.

  A drive power supply voltage is applied to the circuit 1 from the switch circuit 2. The switch circuit 2 includes diodes D1 and D2. In the switch circuit 2, the diode D1 is turned on when the main power supply voltage Vmain is applied, the diode D2 is turned off to supply the main power supply voltage Vmain to the circuit 1, and the diode is turned on when the main power supply voltage Vmain is disconnected. D2 is turned on and the backup power supply Vbackup is supplied to the circuit 1 (Patent Document 1).

JP 2001-231184 A

  However, in the conventional power supply circuit, when the main power supply voltage becomes smaller than the backup power supply voltage, the switch circuit 2 selects the backup power supply voltage Vbackup and supplies it to the circuit 1 even though the main power supply voltage Vmain is applied. To do. As a result, the backup battery is consumed even when it is not backed up, and the life of the backup battery is shortened.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a power supply circuit that can reliably stop consumption of a backup power supply when a main power supply voltage is applied.

  The present invention provides a power supply circuit (11) for generating a first drive voltage (V11) for causing the circuit (15) to perform a main operation and a second drive voltage (V12) for causing the circuit (15) to perform a backup operation. A first voltage generation circuit (21) for generating a first drive voltage (V11) from the first power supply voltage (Vmain), and a second power supply voltage different from the first power supply voltage (Vmain) When (Vbackup) and the first power supply voltage (Vmain) are supplied and the first power supply voltage (Vmain) is higher than a predetermined level, the first power supply voltage (Vmain) is selected and the first power supply voltage is selected. When (Vmain) is smaller than a predetermined level, the switch circuit (22) for selecting the second power supply voltage (Vbackup) and the second drive voltage (V12) for generating the second drive voltage (V12) from the output voltage of the switch circuit (22) Voltage generation circuit (23) and the second power supply voltage The input level to the switch circuit (22) of Vbackup is smaller than the lower limit level of the input level to the switch circuit (22) of the first power supply voltage (Vmain), and the second voltage generation circuit (23). And a level setting circuit (24) for setting the second driving voltage (V12) to a level that can be generated.

  The level setting circuit (24) includes one or a plurality of diodes (D21, D22) connected between the input terminal (T12) of the second power supply voltage (Vbackup) and the switch circuit (22). It is characterized by that.

  Further, the level setting circuit (24) reduces the second power supply voltage (Vbackup) by lowering the second power supply voltage (Vbackup) by the forward voltage (VF) of one or a plurality of diodes (D21, D22). The input level to the switch circuit (23) is smaller than the allowable range of the input level to the switch circuit (23) of the first power supply voltage (Vmain), and the second voltage generation circuit (23) The drive voltage (Vbackup) is set to a level that can be generated.

  The level setting circuit (24) is characterized in that the upper limit level of the second power supply voltage (Vbackup) is set to be smaller than the lower limit level of the first power supply voltage (Vmain).

  In addition, the said reference code is a reference to the last, and a claim is not limited by this.

  According to the present invention, the level setting circuit (24) generates the second drive voltage (V12) from the output voltage of the switch circuit (22), and the second power supply voltage. The input level to the switch circuit (22) of (Vbackup) is smaller than the lower limit level of the input level to the switch circuit (22) of the first power supply voltage (Vmain), and the second voltage generation circuit (23 ) Is set to a level at which the second drive voltage (V12) can be generated, and the first power supply voltage (Vmain) is reliably applied by the switch circuit (23) when the first power supply voltage (Vmain) is applied. Vmain) is selected, and the second drive voltage (V12) can be generated by the second voltage generation circuit (23) using the first power supply voltage (Vmain). Therefore, it is possible to prevent the second power supply voltage (Vbackup) from being wasted. Therefore, according to the present invention, consumption of the backup power supply can be reliably stopped when the main power supply voltage is applied.

〔System configuration〕
FIG. 1 is a circuit diagram showing an embodiment of the present invention.

In the power supply circuit 11 of this embodiment, the main power supply voltage Vmain is applied from the main battery 12 to the terminal T11 via the power switch 13, and the backup power supply voltage Vbackup is applied from the backup battery 13 to the terminal T12. The power supply circuit 11 generates a main drive voltage V11 and a backup drive voltage V12 according to the main power supply voltage Vmain when the main power supply voltage Vmain is turned on, and performs backup drive according to the backup power supply voltage Vbackup when the main power supply voltage Vmain is disconnected. A voltage V12 is generated and supplied to the signal processing circuit 15.
[Power supply circuit 11]
First, the power supply circuit 11 will be described.

The power supply circuit 11 includes regulators 21 and 23, a switch circuit 22, a level setting circuit 24, and a surge protection resistor R0.
[Regulator 21]
A voltage VB corresponding to the main power supply voltage Vmain, which is a voltage applied to the terminal T11, is applied to the regulator 21. The regulator 21 generates a voltage V11 from the voltage VB. The voltage V11 generated by the regulator 21 is output from the terminal T21 and applied to the signal processing circuit 15. The signal processing circuit 15 performs a main signal processing operation on the input signal supplied from the terminal Tin according to the voltage VB supplied from the terminal T21, and outputs it from the output terminal Tout.
[Switch circuit 22]
The switch circuit 22 includes diodes D11 and D12. The diode D11 is applied with a voltage VB corresponding to the main power supply voltage Vmain, which is the voltage applied to the terminal T11, at the anode, and outputs a voltage obtained by dropping the voltage VB from the cathode by the forward voltage VF. The diode D12 is applied with the output voltage VA of the level setting circuit 24 at the anode, and outputs a voltage obtained by dropping the voltage VA from the cathode by the forward voltage VF. The cathode of the diode D11 and the cathode of the diode D12 are connected to each other, and the connection point is applied to the regulator 23.

When the power switch 13 is turned on and the main power supply voltage Vmain is applied to the terminal T11, the switch circuit 22 turns on the diode D11, turns off the diode D12, and drops the voltage VB by the forward voltage VF of the diode D11. The applied voltage (VB−VF) is applied to the regulator 23. In the switch circuit 22, when the power switch 13 is turned off and the main power supply voltage Vmain is not applied to the terminal T11, the diode D11 is turned off, the diode D12 is turned on, and the voltage VA is changed to the forward voltage VF of the diode D12. A voltage (VA−VF) dropped by a minute is applied to the regulator 23.
[Regulator 23]
The regulator 23 generates a backup drive voltage V12 from the voltage (VA−VF) or (VB−VF) supplied from the switch circuit 22. The backup drive voltage V12 generated by the regulator 23 is supplied from the terminal T22 to the signal processing circuit 15.
[Level setting circuit 24]
The level setting circuit 24 has the input level of the backup power supply voltage Vbackup to the switch circuit 22 smaller than the lower limit level of the input level of the main power supply voltage Vmain to the switch circuit 22, and the regulator 23 generates the backup drive voltage V12. Set to a possible level.

  FIG. 2 is a diagram for explaining the operation of an embodiment of the present invention.

  In the power supply circuit 11 of the present embodiment, for example, the allowable range of the main power supply voltage Vmain is set to 3.3 ± 0.3V, and the allowable range of the backup power supply voltage Vbackup is set to 3.0 to 3.2V. .

  The backup power supply voltage Vbackup ignores the voltage drop due to the surge protection resistor R0, and when the forward voltage VF of the diodes D21 and D22 constituting the level setting circuit 24 is set to 0.35 V, the level setting circuit 24 makes about 0. 7V voltage drop. The voltage drop due to the surge protection resistor R0 is very small and negligible.

As a result, the output voltage VA of the level setting circuit 24 is
VA ≒ Vbackup-0.7
It can be expressed as At this time, since the allowable range of the backup power supply voltage Vbackup is 3.0 to 3.2 V, the output voltage VA of the level setting circuit 24 is 2.3 to 2.5 V.

The upper limit level 2.5V of the output voltage VA is smaller by ΔV = 0.3V than 3.0V which is the lower limit level of the voltage VB which is the main power supply voltage Vmain. For this reason, even if the main power supply voltage Vmain becomes the lower limit level of 3.0 V and the backup power supply voltage Vbackup reaches the upper limit level of 3.2 V, the relationship between the input voltages VA and VB to the switch circuit 22 is VB. > VA
Can be maintained. Therefore, when the main power supply voltage Vmain is applied, the diode D11 can be reliably turned on and the diode D12 can be turned off. Therefore, it is possible to prevent an operation in which the backup battery 14 is consumed even though the main power supply voltage Vmain is applied.

  In this embodiment, the backup power supply voltage Vbackup is adjusted by the forward voltage VF of the diodes D21 and D22, so that the voltage can be set accurately and the power consumption in the level setting circuit 24 is minimized. Can be suppressed to the limit.

As described above, according to the present embodiment, the backup power source is not wasted, and the life of the backup battery is extended. Therefore, the number of replacements and the number of charging can be reduced.
[Signal processing circuit 15]
The signal processing circuit 15 will be described.

The signal processing circuit 15 is, for example, a GPS (global positioning)
system), when the power switch 13 is turned on and both the main drive voltage V11 and the backup drive voltage V12 are applied from the power supply circuit 11, the main drive voltage V11 inputs the signal to the terminal Tin. The input signal is processed by the main operation process, and the positioning data is output from the terminal Tout, and the positioning data acquired by the main operation process is backed up to the built-in memory or the like by the backup drive voltage V12.

Further, when the power switch 13 is turned off and only the backup drive voltage V12 is applied from the power supply circuit 11, the signal processing circuit 15 incorporates the positioning data acquired last by the main operation process by the backup drive power supply V12. Back up to memory etc.
[Others]
In this embodiment, the example in which the main power supply voltage Vmain is set to 3.0 to 3.2 V and the backup power supply voltage Vbackup is set to 3.0 to 3.2 V has been described. However, the present invention is not limited to this. In the present invention, the relationship between the main power supply voltage Vmain and the backup power supply voltage Vbackup is Vmain <Vbackup.
This is effective when the relationship is as follows.

In this embodiment, the voltage difference ΔV between the lower limit level of the voltage VA and the upper limit level of the voltage VB is set to 0.3 V. However, the present invention is not limited to this, and VB> VA is essential.
Any setting can be used as long as it can be maintained.

It is a circuit block diagram of one Example of this invention. It is operation | movement explanatory drawing of one Example of this invention. It is a circuit block diagram of a conventional example.

Explanation of symbols

11 power supply circuit, 12 main battery, 13 power switch, 14 backup battery 15 signal processing circuit 21, 23 regulator, 22 switch circuit, 24 level setting circuit D11, D12, D21, D22 diode, R0 surge protection resistor

Claims (4)

A power supply circuit for generating a first drive voltage for causing the circuit to perform a main operation and a second drive voltage for causing the circuit to perform a backup operation,
A first voltage generation circuit for generating the first drive voltage from a first power supply voltage;
When the second power supply voltage different from the first power supply voltage and the first power supply voltage are supplied, and the first power supply voltage is higher than a predetermined level, the first power supply voltage is selected, A switch circuit for selecting the second power supply voltage when the first power supply voltage is lower than the predetermined level;
A second voltage generation circuit that generates the second drive voltage from the output voltage of the switch circuit;
An input level of the second power supply voltage to the switch circuit is smaller than a lower limit level of an input level of the first power supply voltage to the switch circuit, and the second voltage generation circuit causes the second level to be input to the switch circuit. And a level setting circuit that sets the driving voltage to a level that can be generated. The power supply circuit according to claim 1, wherein the level setting circuit includes one or a plurality of diodes connected between an input terminal of the second power supply voltage and the switch circuit. The level setting circuit lowers the second power supply voltage by a forward voltage of the one or more diodes, thereby changing the input level of the second power supply voltage to the switch circuit to the first power supply voltage. 3. The power supply according to claim 2, wherein the power supply level is set to a level that is smaller than an allowable range of an input level to the switch circuit and is capable of generating the second drive voltage by the second voltage generation circuit. circuit. 4. The level setting circuit according to claim 1, wherein an upper limit level of the second power supply voltage is set to be smaller than a lower limit level of the first power supply voltage. 5. Power supply circuit.

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