JP2002149287A - Control apparatus and method for switching its two power supply inputs - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control apparatus which can be miniaturized, whose costs are reduced by unnecessitating a capacitor for voltage drop suppression and which can improve the reliability of processing when the power is turned off by reliably securing time for the processing when the power is turned off. SOLUTION: This control apparatus has a first power supply input 1 for a normal operation mode in which an external switch (external switching means) 3 turns on or off conduction, a second power supply input 2 that is energized all the time and is for memory backup, and a controlling means (CPU) 4 for performing the processing when the power is turned off in the case the conduction of the 1st power supply input 1 is turned off. The controlling means 4 detects that the conduction of the first power supply input 1 is turned off, switches the power supply input to the controlling means 4 itself from the first power supply input 1 to the second power supply input 2 and subsequently performs the processing when the power is turned off.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device (electronic device) having two power inputs and configured to switch between the two power inputs as needed, and a method of switching the two power inputs.

[0002]

2. Description of the Related Art FIG. 3 shows a block diagram of a conventional control device. Conventionally, a control device 1 having a first power input 1 for normal operation and a second power input 2 for RAM backup
At 00, when the external switch 3 is switched from on to off (when the power is off), C
The CPU power supply 5 to be supplied to the PU 104 is switched from the first power supply input 1 for normal operation to the second power supply input 2 for RAM backup. In particular,
The voltage monitoring unit 6 monitors the voltage change of the first power supply input 1 due to the switching of the external switch 3, and the internal switch control unit 10 switches the internal switch 7 based on the output (monitoring result) of the voltage monitoring unit 6, Internal switch 7 is CPU 104
Is switched to the first power input 1 or the second power input 2. Reference numeral 14 denotes an external power supply. The logic unit 13 operates with a power supplied from the first power input 1.

FIG. 4 shows a timing chart when a power supply is turned off in a conventional control device. Conventionally, when the external switch 3 switches from the on state to the off state, the voltage of the first power supply input 1 drops. Further, until the voltage monitoring unit 6 detects this voltage drop and switches the internal switch 7, the CPU
The power supply 5 also drops in voltage. Here, if the voltage drop of the CPU power supply 5 is fast (that is, if the voltage drop of the first power supply input 1 is fast), the power supply is turned off while the voltage of the CPU power supply 5 is within the CPU operable voltage range. Processing cannot be performed (shown by a dotted line in FIG. 4). Therefore,
A large-capacity capacitor 108 is connected between the first power input 1 and the ground to suppress the voltage drop of the first power input 1.

[0004]

However, in such a conventional technique, a large-capacity voltage drop suppressing capacitor 108 such as an aluminum electrolytic capacitor is required in order to secure time for power-off processing. There is a problem that the size and cost cannot be reduced.
In addition, there is a problem that it is difficult to secure the reliability of the control device because the securing of the time of the power-off processing depends on the temperature characteristics and the reliability of the voltage drop suppressing capacitor 108.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and can reduce the size and cost by eliminating the need for a capacitor for suppressing a voltage drop. Control device capable of improving the reliability of the process at the time of power-off by securing the power supply and the second method
A method of switching power input is provided.

[0006]

A control device according to the present invention comprises a first power input for normal operation in which power is turned on or off by an external switching means, and a second power supply for memory backup which is always energized. A power supply input; and control means for executing power-off processing when power supply to the first power supply input is turned off, wherein the control means is configured to turn off power supply to the first power supply input. And switches the power input to itself from the first power input to the second power input, and then executes the power-off processing. With this configuration, it is possible to reduce the size and cost by eliminating the need for a capacitor for suppressing a voltage drop, and it is also possible to reliably secure the power-off processing time and improve the reliability of the power-off processing. You can do it.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of a control device according to the present invention. In FIG. 1, a control device (electronic device) 20 includes a first power input 1 and a second power input 2.
Monitor the voltage of the first power supply input 1 and
Is turned on, the voltage monitoring unit 6 detects that the voltage of the first power supply input 1 has increased, the internal switch control unit 10 that controls the switching of the internal switch 7, and the CPU power supply 5.
Switch 7 for switching between power supply from the first power supply input 1 and power supply from the second power supply input 2, and a control device 2 which normally receives power supply from the first power supply input 1
The control unit 20 includes a CPU 4 that controls each unit (not shown) connected to the control device 20 and a logic unit 13 that receives power supply from the first power input 1. Also, C
The PU 4 normally receives power supply from the first power supply input 1 and monitors the voltage of the first power supply input 1 to determine that the voltage of the first power supply input 1 has dropped (the first power supply input 1 When it is detected that the power supply has been turned off, the internal switch control unit 10 switches the power input to the CPU 4 itself from the first power input 1 to the second power input 2 using the power input switching request signal 9. After that, the power-off process is performed, and then the low-current-consumption state is switched by itself using the low-current-consumption switching request signal 11. In addition,
The power-off process of the CPU 4 refers to a process executed by the CPU 4 after the external switch 3 is turned off.
This is an AM save process.

FIG. 2 is a timing chart when the power is turned off in one embodiment of the control device according to the present invention. FIG.
, When the external switch 3 is switched from the ON state to the OFF state, the voltage of the first power supply input 1 drops. CP
U4 detects the voltage drop of the first power supply input 1 by itself (it detects that the power supply of the first power supply input is turned off), and sends the CPU 4 to the internal switch control unit 10 by the power supply input switching request signal 9. The internal switch 7 switches the power input from the first power input 1 to the second power input 2 which is always energized, from the first power input 1 to the second power input 2. Switch. Therefore, CP
The voltage of the U power supply 5 becomes stable. Next, CPU
Reference numeral 4 performs power-off processing. T16 is a time for performing the power-off process. When the power-off process ends, the CPU 4 switches to the low current consumption state by the low current consumption switching request signal 11.

[0010]

According to the present invention, it is possible to reduce the size and cost by eliminating the need for a capacitor for suppressing a voltage drop, and to ensure the time for power-off processing to ensure the power-off processing. It is possible to provide a control device capable of improving reliability and a method of switching between two power supply inputs.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a control device according to the present invention.

FIG. 2 is a timing chart when the power is turned off in one embodiment of the control device according to the present invention.

FIG. 3 is a block diagram of a conventional control device.

FIG. 4 is a timing chart when a power supply is turned off in a conventional control device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 first power input 2 second power input 3 external switch (external switching means) 4 CPU (control means) 5 CPU power supply 6 voltage monitoring unit 7 internal switch 9 power input switching request signal 10 internal switch control unit 11 Low current consumption switching request signal 13 Logic section 14 Power supply 20 Control device (electronic device)

Claims (2)

[Claims] 1. A first power supply input for normal operation in which power supply is turned on or off by an external switching means, a second power supply input for memory backup which is always energized, and a first power supply input for the first power supply input. Control means for executing power-off processing when power is turned off, wherein the control means detects that power supply to the first power input has been turned off, and switches the power input to itself to A control device for executing the power-off processing after switching from a first power input to the second power input. 2. A first power supply input for normal operation in which energization is turned on or off by an external switching means, a second power supply input for memory backup which is always energized, and a first power supply input for the first power supply. Control means for executing power-off processing when power is turned off, wherein the control means detects that power supply to the first power supply input has been turned off, and Power input to the first
The method of switching between two power inputs, wherein the control means executes the power-off processing after switching from the power input to the second power input.