CN204287446U - A kind of power-fail detection circuit - Google Patents

Abstract

The utility model discloses a kind of power-fail detection circuit, and comprise power down voltage comparator circuit and Port detecting circuit, power down voltage comparator circuit is electrically connected with Port detecting circuit.The utility model circuit component is few, and circuit is simple, and reliability is high, directly monitor detected power vd D, is not easy the interference being subject to the external world, can change as required voltage stabilizing diode ZD1 size thus for different power down voltage, applied widely.

Description

A power failure detection circuit

technical field

The utility model relates to the field of protection circuits, in particular to a power-down detection circuit.

Background technique

At present, most power-down detection circuits adopt a method of detecting strong current to realize the purpose of detecting power-down of the detected power supply. This solution has high circuit complexity and cost, and will increase the standby power consumption of the product.

Utility model content

The utility model provides a power-down detection circuit, which has low cost, low power consumption and simple structure.

In order to achieve the above-mentioned technical purpose, the technical scheme of the utility model is as follows:

A power-down detection circuit includes a power-down voltage comparison circuit and a port detection circuit, and the power-down voltage comparison circuit is electrically connected to the port detection circuit.

Further, the power-down voltage comparison circuit includes a Zener diode ZD1, a capacitor C1, and a resistor R1-R2; the cathode of the Zener diode ZD1 is connected to the power source detected by the power-down detection circuit, and the anode of the Zener diode ZD1 is connected to the capacitor C respectively. One end of the resistor R1 is connected to one end of the resistor R2; the other end of the capacitor C1 and the other end of the resistor R1 are grounded; the other end of the resistor R2 is connected to the port detection circuit.

Further, the port detection circuit is electrically connected to include a resistor R3 and a transistor Q1; one end of the resistor R3 is connected to a backup power supply, the other end of the resistor R3 is connected to the collector of the transistor Q1, and the base of the transistor Q1 is connected to the resistor R2, The emitter of the transistor Q1 is grounded; the connection point between the resistor R3 and the transistor Q1 is used as a power-down detection port INT.

In the utility model, the detected power supply VDD is monitored through the voltage stabilizing diode ZD1. When the detected power supply VDD is powered on, the VDD voltage is higher than the voltage stabilizing voltage of the voltage stabilizing diode ZD1 so that the triode Q1 is turned on, and the INT port is low. Level, when the detected power supply VDD is powered off, the VDD voltage is lower than the regulated voltage of the Zener diode ZD1, so that the transistor Q1 is cut off, and the INT port is at a high level. In this way, by detecting the change of the high and low levels on the INT port, it is realized Brownout detection.

Further, the backup power source is a battery or a single-chip microcomputer.

Compared with the prior art, the beneficial effects of the technical solution of the utility model are:

The utility model has few circuit elements, simple circuit, high reliability, does not directly monitor the power supply VDD, and is not easy to be interfered by the outside world. The size of the voltage regulator diode ZD1 can be changed according to the needs so as to target different power-down voltages, and has a wide range of applications. .

Description of drawings

Fig. 1 is the circuit schematic diagram of the utility model.

Detailed ways

The accompanying drawings are for illustrative purposes only and cannot be construed as limiting the patent;

In order to better illustrate this embodiment, some parts in the drawings will be omitted, enlarged or reduced, and do not represent the size of the actual product;

For those skilled in the art, it is understandable that some well-known structures and descriptions thereof may be omitted in the drawings.

The technical scheme of the utility model is further described below in conjunction with the accompanying drawings and embodiments.

Example 1

As shown in FIG. 1 , a power-down detection circuit includes a power-down voltage comparison circuit and a port detection circuit, and the power-down voltage comparison circuit is electrically connected to the port detection circuit.

In this embodiment, the power-down voltage comparison circuit includes a voltage-stabilizing diode ZD1, a capacitor C1, and resistors R1-R2; the cathode of the voltage-zener diode ZD1 is connected to the power source detected by the power-down detection circuit, and the anode of the voltage-zener diode ZD1 is respectively connected to the capacitor C One end of the resistor R1 is connected to one end of the resistor R2; the other end of the capacitor C1 and the other end of the resistor R1 are grounded; the other end of the resistor R2 is connected to the port detection circuit.

The electrical connection of the port detection circuit includes a resistor R3 and a transistor Q1; one end of the resistor R3 is connected to a backup power supply, the other end of the resistor R3 is connected to the collector of the transistor Q1, the base of the transistor Q1 is connected to the resistor R2, and the emitter of the transistor Q1 ground; the connection point between the resistor R3 and the transistor Q1 is used as the power-down detection port INT.

The backup power supply is a battery or a single-chip microcomputer used to supply power to the port detection circuit.

The working principle of this circuit is as follows:

(1) When the detected power supply is powered on and normal:

When the detected power supply is powered on, when VDD rises from 0V to the regulated voltage of the zener diode ZD1, the zener diode starts to stabilize the voltage, and at this time, a current flows through the zener diode ZD1, resistors R1 and R2. When the current of R2 reaches the conduction limit of the transistor Q1, the transistor Q1 is turned on, so that the INT port obtains a low-level signal; when the detected power supply is normal, because the voltage of VDD is higher than the regulator voltage of the Zener diode ZD1, the above process remains . At this time, it is detected that the detected power supply is powered on and the detected power supply is normal.

(2) When the detected power supply is powered off:

When the detected power supply is powered off, the VDD voltage changes from high to low. When it is lower than the zener diode’s regulated voltage, the current flowing through the zener diode ZD1 and resistor R2 is less than the cut-off limit of the transistor Q1, and the transistor Q1 is cut off. , so that the INT port gets a high level signal. At this time, it is detected that the detected power supply is powered off.

The same or similar reference numerals correspond to the same or similar components;

The positional relationship described in the drawings is only for illustrative purposes and cannot be construed as a limitation to this patent;

Apparently, the above-mentioned embodiments of the present utility model are only examples for clearly illustrating the present utility model, rather than limiting the implementation manner of the present utility model. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. All modifications, equivalent replacements and improvements made within the spirit and principles of the utility model shall be included in the protection scope of the claims of the utility model.

Claims (2)

1. a power-fail detection circuit, is characterized in that, comprise power down voltage comparator circuit and Port detecting circuit, power down voltage comparator circuit is electrically connected with Port detecting circuit; Described power down voltage comparator circuit comprises voltage stabilizing diode ZD1, electric capacity C1, resistance R1-R2; The power supply that voltage stabilizing diode ZD1 negative electrode and this power-fail detection circuit detect is connected, the anode of voltage stabilizing diode ZD1 respectively with one end of electric capacity C, one end of resistance R1, one end of resistance R2 is connected; The other end of electric capacity C1, the other end ground connection of resistance R1; The other end of resistance R2 is connected with Port detecting circuit; Described Port detecting circuit electrical connection comprises resistance R3, triode Q1; One end of resistance R3 is connected with a standby power supply, and the other end of resistance R3 is connected with the collector of triode Q1, and the base stage of triode Q1 is connected with resistance R2, the grounded emitter of triode Q1; Tie point between resistance R3 and triode Q1 is as detection of power loss port INT.

2. power-fail detection circuit according to claim 1, is characterized in that, described standby power supply is battery or single-chip microcomputer.