JPH0358615A - Detection circuit - Google Patents

Abstract

PURPOSE:To obtain a detection circuit without malfunction by constituting a power level detection means of a constant voltage circuit to detect interruption of a power voltage accurately. CONSTITUTION:A constant voltage circuit 11 constituting a power level detection means is made up of plural diodes connected in series in the forward direction, for example, and a prescribed level VD2 is outputted to a comparator 2 in response to a change in a power voltage Vcc. When the power voltage Vcc is lowered to a prescribed level, a power detection OUT2 goes to L and when the state is kept for a long time, since the constant voltage circuit 11 is used, the relation of VD2 Vcc exists, then the relation of VD2>VC exists and the output VE2 of an inverter 3 is kept to H. Thus, the capacitor C1 is discharged and the state of VB2<VA is maintained. Thus, power interruption is detected accurately to prevent malfunction, and the detection performance of power interruption is improved.

Description

[Detailed Description of the Invention] (Summary) The purpose of this invention is to provide a detection circuit that accurately detects interruptions in the power supply voltage and does not malfunction, and whose potential changes with a predetermined response speed to the power supply voltage. A first comparing means compares the potential of the delay circuit with a power supply detection reference value to detect an interruption of the power supply, and a transistor for extracting charge is connected to the delay circuit, and the transistor is connected to the second comparing means. On/off based on the output of
The second comparison means is in a detection circuit that compares the potential of the power supply potential detection means whose voltage changes with a predetermined time constant with respect to the power supply voltage with a power supply drop reference value. It is constructed from a constant voltage circuit and is configured to output a potential according to changes in the power supply voltage.

[Industrial application field]

The present invention relates to a detection circuit, and more particularly, to a detection circuit that detects any kind of power interruption such as instantaneous power interruption or power outage.

Generally, the guaranteed operation power supply fluctuation range for semiconductors is ±5%.
This condition must be met for the power supply and power supply system as a design standard. If the fluctuation rate required of the power source is severely deviated, the power supply:JS1. In order to safely operate and maintain a system, protection functions and additional functions of the power supply system are essential elements.

[Prior Art] Under the above background, a conventional detection circuit for detecting any kind of power interruption such as interruption of power supply to a semiconductor device or power outage is as follows.
For example, there is one shown in FIG. In the same figure,
1 and 2 are converters, 3? Inharta, R, -R. is a resistor, CI and C2 are capacitors, and Q is a transistor. Also, VA is a base for power supply detection (1IH voltage (power supply detection reference value)), and power supply voltage VCC is connected to resistors R,, R
The voltage divided by Z and given by ■■ is the voltage generated by the RC delay circuit made up of resistor R3 and capacitor CI, which is the voltage from the power supply VCC.
Detection voltage for detecting the ST difference, ■0
is the power supply ■. The resistance Rs. VDI, which is given by dividing the voltage by Rs, is the voltage at the ends of resistor R7 and capacitor C2, which is related to the part provided to remove the charge from transistor Q.

In the above structure, a timing chart of the power supply detection operation is shown as shown in FIG. First, in the qui ξ ring ■, the power supply voltage VCC is O■, and each voltage V^ ・VBI
．． VC, Vwa+, VEI, o
tlL 1 + 1 = ``L''. ouL1. (hereinafter referred to as power supply detection value) is the output of converter 1, and when ouLl-H, the power supply voltage is the current planting voltage, out. 1 = L When , it indicates a power interruption, and out
Is the information on number 1 electronic? It is transmitted to the internal circuit that is supplied with the voltage VCC, for example,
) It is used for rivers, etc. to protect internal roads.

Next, at the timing, VBI>Vl1, the power supply detection value outl becomes "li", and the power supply voltage VCC becomes the specified value. Now, the timing is ■. , is I3l
? In conclusion, ■1■>V. As a result, Vl1 becomes ``H'', transistor Q1 is turned on, and the charge from capacitor C is removed, so ■8+ < V 6 and the lightning source detection value. outl becomes "L". After that, ■6. rises, capacitor C1 starts charging, and at timing ■ ■. 〉
When it becomes VA, the power supply detection value 0 11 t1 becomes "'H" again.
”.However, at timing ■, when the potential decreases to a certain constant level, < out 1 becomes “L” as described above.
However, if this state continues for a long time, capacitor C2 will be discharged at timing ①, and Vn+<V,
VEI drops to "°L"'. Therefore, capacitor C
, starts charging again and at timing ■ V s l > V
a, and in the end, OUT1 = H, but this is a malfunction, and even though VCC is interrupted, Ij
(This is the detection information that is being supplied.

(Problem to be Solved by the Invention) However, in such a conventional detection circuit, as shown in the above example, the power source spiritual pressure ■1 is kept for a long time (λ゛r or capacitor C2 is discharged). There is a problem in that if the voltage remains at a certain constant level (time), the power supply detection value O II t 1 becomes "II", causing malfunction.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a detection circuit that accurately detects the monthly analysis of the power supply voltage and does not malfunction.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the detection circuit according to the present invention uses the potential of the delay circuit whose potential changes with a predetermined response speed with respect to the power supply voltage as a power supply detection standard using the comparison means (2). In addition to detecting an interruption in the power supply by comparing the value with the value, a transistor for extracting charge is connected to the delay circuit, and the nuclear transistor is turned on/off based on the output of the second comparing means. The means detects the potential of the power supply potential detection means whose voltage changes with a predetermined time constant with respect to the power supply voltage, and the
In the detection circuit for comparing the power supply voltage with the power supply voltage, the power supply potential detection stage is constituted by a constant voltage path, and outputs a potential according to changes in the power supply voltage.

(Function) In the present invention, the power supply potential detection means is constituted by a constant voltage circuit, and the constant voltage circuit outputs a constant potential according to changes in the power supply voltage to the second comparison means.

Therefore, even if Vcc drops to a constant low potential for a long time, the potential of the delay circuit does not change, the comparison result of the first comparing means is maintained normally, and malfunctions are prevented.

? Example] Hereinafter, the present invention will be explained based on the drawings.

1 and 2 are diagrams showing an embodiment of the detection circuit according to the invention. In explaining this embodiment, the same components as those of the conventional example will be given the same reference numerals and redundant explanation will be omitted.

FIG. 1 is a circuit diagram of the detection circuit, and in this figure, l
1 is a constant voltage circuit. The constant voltage circuit 11 is provided in place of the parallel circuit of the resistor R7 and capacitor C2 in the conventional example, and corresponds to power supply potential detection means.

The constant voltage circuit 11 is constituted by, for example, a plurality of diodes (five in this embodiment) connected in series in the forward direction, and outputs a constant potential VB■ to the comparator 2 in response to changes in the power supply voltage VCC. Further, in this embodiment, the comparator 2 corresponds to the first comparison means, the comparator 2 corresponds to the second comparison means, and the resistor R3 and the capacitor CI correspond to the delay circuit 12.
1 + shioruzuru.

In the configuration below-12, the motion query ξ
If it is shown as shown in Figure 2, the tie ξ is from ■ to ■? This is the same as the Tsuchiki example, but the operation after timing ■ is different. However, in this embodiment, the difference from the conventional example is made clear by changing VBI''VRZ VDI-→VDZ VE I''VE2 ou t 1→0 11 t 2 .

That is, when VCC drops to a certain potential at timing ①, the power supply detection value out2 becomes ``L'' as described above, but if this state continues for a long time, in the conventional example, capacitor C2 is released at timing ②. Therefore, V,,<V
o, and the VEI drops to "I-". However, in this embodiment, since the constant voltage circuit 11 is used, vllz'ivcc becomes VD2>VC, and the inharter 3 The output ■1■ remains at "H". Therefore, the capacitor C1 remains discharged, and the state of ■I12<■, is maintained, and the timing ■
Even if the output voltage becomes low, output2 remains low, and malfunctions can be prevented after all.

Note that the power supply potential detection means may be constituted by a Zener diode autotoder.

〔Effect of the invention〕

According to the present invention, it is possible to accurately detect all kinds of power interruptions such as momentary power interruptions and power outages to prevent malfunctions, and it is possible to improve the detection performance of power interruptions.

As a result, a power-on reset circuit and the like can be easily constructed.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams showing an embodiment of the detection circuit according to the present invention, Figure 1 is its circuit diagram, Figure 2 is its timing chart, and Figures 3 and 4 are conventional detection circuits. FIG. 3 is its circuit diagram, and FIG. 4 is its timing chart I~. l0 1... Comparator (first comparison means) 2...
... Comparator (second comparison means) 3 ... Inheritor, Q1 ... Transistor, R1 to R7 ... Resistor, C1, C2 ... Capacitor , 11... Constant voltage circuit (power supply potential detection means) 12.
...Delay circuit. Conventional timing chart Fig. 4・182-Chart■

Claims (1)

[Scope of Claims] A potential of a delay circuit whose potential changes with a predetermined response speed with respect to a power supply voltage is compared with a power supply detection reference value by a first comparing means to detect an interruption of the power supply, etc.; A charge extraction transistor is connected to the circuit, and the transistor is turned on/off based on the output of the second comparing means, and the second comparing means changes the voltage with a predetermined time constant with respect to the power supply voltage. A detection circuit that compares the potential of a power supply potential detection means with a power supply drop reference value, characterized in that the power supply potential detection means is constituted by a constant voltage circuit, and outputs a potential according to a change in the power supply voltage. Detection circuit.