JP3322554B2 - Power failure detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power failure detection device,
Particularly, for example, it is used for an electric device such as a VTR which can record information such as a reserved recording time or time, and in order to prevent the stored information from being erased at the time of a power failure, a power failure is detected and the system body is shifted to a power failure mode when a power failure occurs. Power outage detection device for outputting a power outage signal for the same.

[0002]

2. Description of the Related Art Generally, an electric device having a timer function of this kind is provided with a power failure mode function that operates with lower power consumption than a normal operation when a power failure is detected. That is, when a power failure is detected by the power failure detection device, power is supplied from a capacitor or a lithium battery to the timer circuit and related circuits, and stored for a certain period of time. Can be maintained without extinction.

Conventionally, as a means for detecting a power failure (power failure detection device), conventionally, when an AC outlet is unplugged or when a power failure occurs, the voltage level of a normal power supply that cannot be supplied, and when a power failure occurs, power is supplied to the timer circuit and the like. The voltage level of the backup power source such as a capacitor or a lithium battery is compared, and if the voltage level of the normal power source falls below the voltage level of the backup power source by a predetermined level or more, it is determined that a power failure has occurred.

[0004]

However, when a power failure is detected by the power failure detection device and the mode shifts to the power failure mode,
There is a disadvantage that the microcomputer determines that a power failure has occurred, for example, during a momentary power failure of one cycle of the power supply, which should not be determined as a runaway or a power failure. That is, referring to FIG. 3, if it is set that it is determined that a power failure has occurred when the voltage level of the _commercial power supply has dropped to V _REFA , the power failure has occurred since the power supply of the system body was in the ON state. the voltage level of the backup power supply is greater than the guaranteed operating voltage V _{MI N} as shown in the point a. However, when a power failure occurs from the power off state of the system main unit, the voltage level of the backup power supply becomes lower than the operation compensation voltage V _MIN of the microcomputer as shown at point B in FIG. Will not work.

Therefore, in order to prevent the microcomputer from running out of control, the voltage level of the normal power supply for detecting a power failure is set higher (V _REFB ), and the voltage level of the backup power supply does not become lower than the operation compensation voltage V _{MIN of the} microcomputer. In this case, when a power failure occurs from the power-on state of the system main body, the power failure detection device instantaneously detects the power failure and shifts to the power failure mode.

SUMMARY OF THE INVENTION Therefore, a main object of the present invention is to provide a power failure detection device capable of setting a voltage level for power failure detection determination to an optimum value and performing stable power failure detection.

[0007]

According to the present invention, there is provided a power failure detection device including a power failure detection means for detecting a power failure by comparing a voltage of a line supplying a normal power supply with a voltage of a backup power supply. A power failure detection device comprising a grounding means for grounding a line when the voltage drops below a predetermined voltage.

[0008]

The comparing means receives the normal power supply voltage and a predetermined voltage sufficiently higher than the power failure detection level of the power failure detecting means, and compares the respective voltage levels. The comparing means outputs, for example, a low-level signal when the voltage level of the commercial power supply falls below a predetermined voltage level, that is, when a power failure occurs. As a result, the voltage of the normal power supply provided to the power failure detecting means is rapidly dropped to "0" by the grounding means. Therefore, the voltage drop speed of the normal power supply when the power is cut off from the power off state of the system main body is increased to a level substantially equal to that at the time of the power outage from the power on state of the system main body.

[0009]

According to the present invention, the voltage change of the normal power supply immediately after the occurrence of the power failure can be made substantially the same level regardless of the on / off state of the power supply of the system main body. Can be done. The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a power failure detection device 10 of this embodiment includes a power failure detection circuit 12 receiving a normal power supply and a backup power supply. In the power failure detection circuit 12, a normal (Always system) power supply which is also an original signal of power failure determination and cannot be supplied at the time of power failure, and a voltage level of a backup (backup system) power supply for compensating the power supply at the time of power failure. Are compared, and it is determined whether or not there is a power failure according to the comparison result. If it is determined that the power failure has occurred, the power failure detection circuit 12 outputs a power failure signal to the system controller 14, whereby the system controller
A command signal for shifting the entire system to the power failure mode is output.

That is, the power failure detection device 10 is mounted on, for example, a VTR 16 as shown in FIG. 2, and when a power failure is detected by the power failure detection circuit 12, the power supply circuit 18 of the VTR 16 is controlled by the system controller 14. You. That is, the power supply circuit 18 receives a control signal from the system controller 14 (VTR control unit 20), and thereby controls power supply to each circuit block included in the system body (VTR 16).

The power failure detection circuit 12 and the system controller 1
The VTR control unit 20 including the control unit 4 controls a channel selection circuit 24, a mechanism unit 26, and a display control unit 28 according to a control signal from an input control unit 22 that receives command information by remote control or key input. That is, the channel selection circuit 24 controls the tuner 30 in response to a channel request by a remote controller or key input, and a television signal received by the antenna 32 is selected as a desired channel. The video signal selected by the tuner 30 is processed by the audio circuit 34a and the video circuit 34b. And
The mechanism unit 26 records or reproduces the video signal according to a control signal from the VTR control unit 20. And
The reproduced video signal is supplied to the OSD by the display control unit 28.
Is displayed. The VTR control unit 20, the input control unit 22
The display controller 28 is generally constituted by a microcomputer 29.

Returning to FIG. 1, the VTR control unit 20 includes the power failure detection circuit 12 as described above, and the power failure detection circuit 12 receives a normal power supply and a backup power supply. That is, the power failure detection circuit 12 is supplied with a normal power supply from the power supply circuit 18 and a backup power supply for compensating the power supply of the VTR control unit 20 when a power failure occurs from the capacitor 15. The commercial power from the power supply circuit 18 is further provided to a comparator (comparing means) 36, where
The voltage level is compared with a voltage level of a predetermined reference voltage.

The reference voltage is set to a voltage level sufficiently higher than the power failure detection level of the power failure detection device 12. That is, the comparator 36 detects the power failure before the power failure detection circuit 12. Then, the comparator 36
Outputs a high-level signal when the voltage level of the commercial power supply is higher than the reference voltage, and outputs a low-level signal when the voltage level is equal to or lower than the reference voltage. The output signal of the comparator 36 turns on or off the transistor 38 connected thereto,
The normal power supply supplied to the power failure detection circuit 12 is grounded via the transistor 38 and the resistor 40.

That is, in the operation, when a power failure does not occur, the voltage level of the ordinary power supply is higher than the reference voltage, so that the comparator 36 outputs a high-level signal. Transistor 38 receives this high level signal, which turns off transistor 38. Therefore, the power failure detection circuit 12 includes the power supply circuit 18
, A predetermined level of a normal power supply voltage is applied.

On the other hand, a power failure occurs and the system main unit (VT)
When power is no longer supplied to R16), the voltage level of the commercial power supply gradually decreases as shown in FIG. When the voltage level drops below the reference voltage, a low-level signal is output from the comparator 36. As a result, the transistor 38 is turned on, and the ordinary power supplied to the power failure detection circuit 12 is grounded through the transistor 38 and the resistor 40. Therefore, the voltage drop speed of the commercial power supply shown in FIG. 3 is increased.
That is, when a power failure occurs from the power off state of the system body (VTR 16), conventionally, as shown in FIG.
The normal power supply voltage after the occurrence of the power failure gradually decreases, but by grounding via the resistor 40, this voltage change
For example, the voltage is changed to the same level as the voltage change of the ordinary power supply when a power failure occurs from the power on state shown in FIG. Therefore, regardless of whether the power supply of the system body (VTR 16) is on or off, the voltage change of the normal power supply voltage after the occurrence of the power failure can be made substantially constant. Note that the resistor 40
Is very small as compared with the current flowing through the system main unit, the voltage change of the normal power supply in the event of a power failure from the power-on state of the system main unit (VTR 16) is not affected by the presence or absence of the resistor 40 and is constant. .

As described above, the comparator 36 capable of detecting a power failure more quickly than the power failure detection circuit 12 is provided, and when the power failure is detected in the comparator 36, the power supply of the normal power supply supplied to the power failure detection circuit 12 is provided. Since the voltage is suddenly dropped to “0”, the voltage drop speed in the off state of the system body after the power failure of the commercial power supply can be increased. Therefore, the judgment reference voltage of the regular power supply as an original signal for judging a power failure can be set to an optimum value. Therefore, there is no danger that the voltage level of the backup power supply falls below the operation compensation voltage of the microcomputer, thereby causing the microcomputer to run away.
Further, it is possible to solve the problem of easily shifting to the power failure mode at the moment of a momentary power failure that is difficult to shift to the power failure mode.

[Brief description of the drawings]

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

FIG. 2 is a block diagram illustrating an example of a system main body including a VTR control unit according to the embodiment in FIG. 1;

FIG. 3 is a graph showing voltage changes of a normal power supply and a backup power supply immediately after a power failure occurs.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Power failure detection apparatus 12 ... Power failure detection circuit 14 ... Syscon 18 ... Power supply circuit 20 ... VTR control unit 36 ... Comparator 38 ... Transistor 40 ... Resistance

Claims (3)

(57) [Claims] 1. A power failure detection device including a power failure detection means for detecting a power failure by comparing a voltage of a line supplying a normal power supply with a voltage of a backup power supply, wherein the voltage of the line drops to a predetermined voltage or less. Characterized by comprising grounding means for grounding the line.
Power failure detection device. 2. The grounding means, comprising: comparing means for comparing a voltage of the line with the predetermined voltage; and being interposed between the line and the grounding means and turned on in response to an output of the comparing means. The power failure detection device according to claim 1, further comprising a switching unit that performs switching. 3. The power failure detection level of the predetermined voltage is set higher than the power failure detection level of the power failure detection means.
The power failure detection device according to the above.