JPH0277920A - Terminal equipment - Google Patents

Abstract

PURPOSE:To evade the destruction of programs and data at break of the power supply or at short break by detecting the drop of the supplied power supply voltage to perform the process necessary for a power OFF state and then cutting the power supply to a memory and a process means after the memory is backed up. CONSTITUTION:When the supplied power supply voltage Va drops lower than the monitor voltage level of a voltage monitor part 18, the part 18 informs a central control part 20 of an alarm signal Se. The part 20 detects the signal Se and performs the necessary processes before a power OFF state is set and validates a back-up control signal Sg. Then a power OFF signal Sf is validated after a memory is set in a back-up enable state. When the signal Sf is validated, a power supply control part 14 cuts off the output Vc and a memory part 22 can be backed up by a power supply 24. The capacity of a capacitor 16 is decided so that Td>Tef is satisfied, where the time Tef covers the detection of the signal Se performed by the part 18 through the validation of the signal Sf performed by the part 20 and the time Td assures the supply of power via the capacitor 16.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a terminal device, and particularly to a terminal device suitable for use in an in-vehicle system that uses an unstable power source such as a car battery.

[Conventional technology]

Conventionally, this type of terminal device has been configured such that when the power supply to the device is cut off, the power to the hardware is cut off at the same time.

[Problem to be solved by the invention]

In the conventional terminal device described above, if the power supply to the device is cut off while a program is being executed, the power supply is suddenly cut off, so the power supply voltage V Ce supplied to each circuit section changes from, for example, 5V to OV. Even in transient conditions, each logic circuit performs a logic operation, and as these logic circuits operate outside the voltage range that guarantees logic operation, programs and data in memory may be destroyed and the device may be reused. There was a problem where programs had to be reloaded and data had to be re-entered when the power was turned on.

The present invention was made in view of these circumstances, and
To provide a terminal device in which programs and data on a memory are not destroyed when the power supply to the device is cut off, and there is no need to reload the program and re-enter the data when the power is turned on again. The purpose is to

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention provides a terminal device that receives power from an external power source and has a memory backup function when the external power is cut off. a large-capacity capacitor, a processing means for performing various arithmetic processing,
A power supply voltage monitoring means that monitors the supply voltage from an external power supply and outputs an alarm signal when the supply voltage falls below a predetermined level, and a memory and processing means that uses the external power supply or the terminal voltage of a large capacitor as a power supply. and a power supply control means for controlling the supply/cutoff of power to the memory and the processing means, and the processing means performs necessary processing until the power supply control means cuts off the power supply to the memory and the processing means when an alarm signal is received at the detection port. and after the memory is brought into a backup-enabled state, a power-off signal is enabled, and the power control means cuts off the power supply to the processing means and the memory when the power-off signal becomes effective. It is.

According to the present invention, the power supply to the memory and processing means is cut off after detecting a voltage drop in the power supply, performing the processing necessary for powering off, and putting the memory in a backup state. Even if the power supply from the terminal device is suddenly cut off or a momentary power outage occurs, the programs and data in the memory will not be destroyed, and even if the power to the terminal device is turned on again, the program will not be reloaded or the data will be lost. There is no need for re-manpower.

〔Example〕

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

FIG. 1 shows the configuration of essential parts of an embodiment of a terminal device according to the present invention. The main parts of the terminal device according to the present invention include a power supply input section 10, a capacitor 16 for supplying current when the power supply is cut off, a diode 12 for preventing the supply current of this capacitor 16 from flowing back into the power supply input section 10, A central control unit 20, a power control unit 14 that controls the power of the central control unit 20 and the memory unit 22, and a power supply unit 10
a power supply voltage monitoring unit 18 that monitors the voltage of the memory unit 22;
and a lithium battery 24.

In the above configuration, when the power supply voltage V6 drops and the power supply voltage V becomes lower than the monitored voltage vp in the power supply voltage monitoring section 18, the power supply voltage monitoring section 18 sends an alarm signal S, as shown in FIG. The central control unit 20 is notified.

When the central control unit 20 detects the alarm signal S1, it performs the necessary processing before turning off the power, enables the backup control signal S, and after setting the memory in a state capable of backup, enables the power-off signal Sf.

When the power-off signal Sf becomes effective, the power supply control section 14 cuts off the output ve, and the memory section 22 becomes backed up by the lithium battery 24.

Here, the power supply voltage monitoring section 18 receives an alarm signal S.

After detecting the power off signal Sr, the central control unit 20
The capacitor 16
The capacitance of the capacitor 16 is determined so that the time Td during which power supply is guaranteed is T, >Tef. The capacitance of this capacitor 16 is selected to be, for example, several F for a current consumption of 100 mA. Also, the supply power voltage V
, for example, is 6V when turned on and OV when turned off, and the output voltage VC output from the power supply control section 14 is, for example, 5V when turned on.

It is OV when it is OFF. Furthermore, the alarm signal S1 and the backup control signal S are active at low level, and the power-off signal S is active at high level. Further, the monitoring voltage Vp is, for example, 5.4V,
The voltage VL at which the operation of the central control unit 20 and the memory part 22 is guaranteed is, for example, 4.5V.

〔Effect of the invention〕

As explained above, the present invention detects a voltage drop in the power supply, performs the processing necessary for powering off, puts the memory in a backup state, and then cuts off (powers off) the power supply to the processing means and the memory. I configured it so that
According to the present invention, even if the power supply is suddenly cut off or a momentary power outage occurs, the programs and data on the memory will not be destroyed.
This has the effect that there is no need to reload programs or re-enter data when the terminal device is powered on again.

In addition, in the present invention, when the power supply is cut off, the processing means turns off the power by software, so that the large capacity capacitor connected to the manual power stage of the device can be used to the extent possible within the time that the power supply is guaranteed. It is possible to temporarily terminate a business, and it also has the effect of notifying the other party of the termination if a communication business is in progress.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of essential parts of a terminal device according to the present invention, and FIG. 2 is a timing diagram showing the operating state of the terminal device shown in FIG. 1. 10...Power supply input section, 12...Diode, 14...Power control section, 16...Large capacity capacitor, 18... Power supply voltage monitoring unit, 20...Central control unit, 22...Memory unit, 24...Lithium battery.

Claims (1)

[Scope of Claims] A terminal device that receives power supply from an external power source and has a memory backup function when the external power source is cut off, comprising a large-capacity capacitor that is provided at the input stage of the external power source and is constantly charged when the external power source is supplied. , processing means for performing various arithmetic processing; power supply voltage monitoring means for monitoring the supply voltage from an external power supply and outputting an alarm signal when the supply voltage falls below a predetermined level; and the external power supply or the large capacity and a power supply control means for controlling supply/cutoff of power to the memory and processing means using the terminal voltage of the capacitor as a power supply, and the processing means controls the memory and processing by the power supply control means when an alarm signal is detected. After performing the necessary processing before cutting off the power supply to the means and making the memory ready for backup, the power-off signal is enabled, and when the power-off signal becomes effective, the power control means controls the processing means and A terminal device characterized by cutting off power supply to memory.