Smoke sensing alarm capable of preventing reverse connection of battery

Abstract

The utility model discloses a smoke sensing alarm capable of preventing battery reverse connection, which comprises a battery interface, a battery reverse connection preventing circuit and a smoke sensing circuit, and is characterized in that the battery interface is used for connecting an external battery; and a battery reverse connection prevention circuit is connected between the smoke sensing circuit and the battery interface. The utility model provides a smoke alarm capable of preventing reverse connection of a battery, which can prevent damage caused by reverse connection of the battery and improve product safety.

Description

TECHNICAL FIELD

[0001] The utility model relates to alarm technology field more specifically relates to a battery reverse connection prevention smoke alarm. BACKGROUND

[0002] Smoke alarm is a kind of equipment that realizes fire prevention by monitoring the concentration of smoke, has been widely applied in important fireproof places such as family, factory, office building, hospital, school, museum etc.. The traditional smoke alarm generally uses 9V battery or 3V battery power supply, needs the user to install battery manually, if the user accidentally installs battery reversely or installs battery reversely under the condition of not knowing, will cause battery short circuit current to increase, battery heating causes fire, under serious circumstances, battery explosion can even occur, endanger personal safety. SUMMARY

[0003] In order to overcome the above-mentioned shortcomings of prior art, the utility model provides a battery reverse connection prevention smoke alarm, can prevent battery reverse connection from causing damage, improves product safety.

[0004] The utility model discloses a battery reverse connection prevention smoke alarm, including battery interface, battery reverse connection prevention circuit and smoke circuit, and the battery interface is used for connecting the battery of outside, and the smoke circuit is connected with the battery interface and has the battery reverse connection prevention circuit.

[0005] In one preferred technical solution, the smoke circuit includes a control chip, and the battery reverse connection prevention circuit is an MOS tube reverse connection protection circuit.

[0006] In one preferred technical solution, the battery reverse connection prevention circuit includes a PMOS tube, the positive pole of the battery interface is connected with the drain of the PMOS tube, the source of the PMOS tube is connected with the power supply pin of the control chip, the negative pole of the battery interface is connected with the gate of the PMOS tube, and the gate of the PMOS tube is connected with the ground pin of the control chip and grounded. The above-mentioned battery reverse connection prevention circuit utilizes the voltage relationship between the gate, source and drain of the PMOS tube to control the conduction and cut-off of the PMOS tube, thereby realizing the protection of battery reverse connection.

[0007] In one preferred technical solution, the drain and the gate of the PMOS tube are connected in parallel with a first filter capacitor.

[0008] In one preferred technical solution, the source and the gate of the PMOS tube are connected in parallel with a second filter capacitor.

[0009] In one preferred technical solution, the gate of the PMOS tube is connected in series with a voltage dividing resistor, preventing the PMOS tube from being broken down.

[0010] In a preferred technical solution, the PMOS tube is a depletion mode PMOS tube.

[0011] Via the above technical solution, compared with the prior art, the beneficial effects of the utility model are that: a battery reverse connection preventing smoke alarm, by setting up the battery reverse connection preventing circuit between the smoke circuit and the battery interface, the battery reverse connection preventing protection can be realized, the harm of battery reverse connection to the smoke circuit is avoided, and the safety of the smoke alarm product can be improved; further, the PMOS tube is used to form the battery reverse connection preventing circuit, the principle that the PMOS tube cannot be turned on by the reverse connection battery is used to realize the battery reverse connection preventing function, since the PMOS tube has the advantages of small positive connection resistance and large reverse connection resistance, the battery will not be damaged, even if the battery is reversely connected, the battery leakage will not occur, so that the rear-end equipment is protected from damage.

[0012] In addition, other advantages of the utility model will be given in the following description, some will become obvious from the following description, or be known by the practice of the utility model. BRIEF DESCRIPTION OF DRAWINGS

[0013] In order to more clearly illustrate the technical solutions of the embodiments of the utility model or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or the prior art description, obviously, the drawings in the following description are only the embodiments of the utility model, and for the ordinary skilled in the art, other drawings can be obtained without creative labor on the premise of providing the drawings.

[0014] Fig. 1 It is the structure block diagram of the smoke alarm of the utility model;

[0015] Fig. 2 It is the circuit diagram of the smoke alarm in one embodiment of the utility model;

[0016] Fig. 3 It is the circuit diagram of the smoke alarm in another embodiment of the utility model. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the utility model will be clearly and completely described in the following combined with the drawings in the embodiments of the utility model, obviously, the described embodiments are only a part of the embodiments of the utility model, not all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by the ordinary skilled in the art without creative labor are within the protection scope of the utility model.

[0018] In the description of the utility model, it is understood that the terms "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the utility model and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the utility model. In addition, in the description of the utility model, unless otherwise stated, the meaning of "a plurality of" is two or more.

[0019] Referring to Figs. 1-3 A smoke alarm for preventing battery reverse connection is described according to an embodiment of the utility model. In one embodiment, as shown in the figure, a smoke alarm for preventing battery reverse connection includes a battery interface 1, a battery reverse connection prevention circuit 2 and a smoke sensing circuit 3, the battery interface 1 is used for connecting an external battery, and the smoke sensing circuit 3 is connected with the battery interface 1 through the battery reverse connection prevention circuit 2. Figs. 1-3

[0020] Among them, the battery reverse connection prevention circuit 2 can be a diode series type reverse connection prevention protection circuit or a MOS tube reverse connection prevention protection circuit.

[0021] As an embodiment of the present embodiment, the battery reverse connection prevention circuit 2 can be a diode series type reverse connection prevention protection circuit, at this time, a forward diode is connected in series at the positive pole of the battery interface 1, and the characteristics of the diode forward conduction and reverse cut-off are used to realize the battery reverse connection prevention protection; under normal circumstances, the diode is turned on, and the smoke sensing circuit 3 works; when the battery is reversed, the diode is cut off, and the smoke sensing circuit 3 does not work, which can effectively prevent the problem of battery reverse connection.

[0022] As another embodiment of the present embodiment, the smoke sensing circuit 3 includes a control chip U1, and the battery reverse connection prevention circuit 2 is a MOS tube reverse connection prevention protection circuit. Since the conduction resistance of the MOS tube is small, the loss caused by the voltage drop and power consumption of the circuit is very small, and even negligible, therefore, selecting the MOS tube for battery reverse connection prevention protection can reduce the influence on the smoke sensing circuit 3 to a very low level. Among them, the MOS tube reverse connection prevention protection circuit can be realized by using PMOS tube or NMOS tube, the opening voltage of the PMOS tube can be 0, and the voltage difference between the drain D and the source S is small, which is more suitable for battery reverse connection prevention than the NMOS tube.

[0023] The smoke alarm for preventing battery reverse connection provided in the above embodiment can realize battery reverse connection prevention protection by setting the battery reverse connection prevention circuit 2 between the smoke sensing circuit 3 and the battery interface 1, avoid the harm of battery reverse connection to the smoke sensing circuit 3, and improve the safety of the smoke alarm product.

[0024] ​In the embodiment, as shown in Fig. 2 The battery reverse connection protection circuit 2 includes a PMOS tube Q1; the positive pole of the battery interface 1 is connected with the drain D of the PMOS tube Q1, the source S of the PMOS tube Q1 is connected with the power supply pin VDD of the control chip U1; the negative pole of the battery interface 1 is connected with the gate G of the PMOS tube Q1, and the gate G of the PMOS tube Q1 is connected with the ground pin GND of the control chip U1 and grounded.

[0025] The above battery reverse connection protection circuit 2 controls the conduction and cut-off of the PMOS tube Q1 by the voltage relationship among the gate G, the source S and the drain D of the PMOS tube Q1, thereby realizing the protection of the battery reverse connection. The specific working principle is as follows:

[0026] When the battery is normally connected, the voltage reaches the source S from the drain D of the PMOS tube Q1 through the internal body diode, and the source voltage is slightly lower than the drain voltage due to the voltage drop of the body diode. At this time, the gate G is grounded or kept at a low potential by some means or kept at a low potential by means of series connection of a voltage dividing resistor, so that the gate-source voltage Vgs is negative and less than the threshold voltage Vth of the PMOS tube Q1, thereby the PMOS tube Q1 is turned on. After the PMOS tube Q1 is turned on, the conduction voltage drop between the drain D and the source S of the PMOS tube Q1 is very small and can be ignored, so the output voltage is close to the input voltage, and the circuit works normally.

[0027] When the battery is reversely connected, the voltage originally connected to the drain D is now connected to the source S, and the gate G is still kept at a low potential or high potential relative to the source S. At this time, the gate-source voltage Vgs becomes positive and greater than the threshold voltage Vth of the PMOS tube, and the PMOS tube Q1 is in the cut-off state and cannot be turned on. Therefore, the reverse connected power supply cannot pass through the subsequent circuit, thereby protecting the rear-end device from being damaged.

[0028] The above embodiment provides a battery reverse connection protection smoke alarm, which adopts the PMOS tube Q1 to form a battery reverse connection protection circuit, and realizes the battery reverse connection protection function by using the principle that the PMOS tube Q1 cannot be turned on when the battery is reversely connected. Since the PMOS tube Q1 has the advantages of small conduction resistance when the battery is normally connected and large conduction resistance when the battery is reversely connected, the battery will not be damaged, and even if the battery is reversely connected, the battery will not be damaged, thereby protecting the rear-end device from being damaged.

[0029] In the embodiment, the first filter capacitor C1 is connected in parallel between the drain D and the gate G of the PMOS tube Q1.

[0030] The first filter capacitor C1 can play a role of soft start. At the moment when the current starts to flow, the first filter capacitor C1 is charged, and the voltage of the gate G of the PMOS tube Q1 is gradually established.

[0031] In another embodiment, as shown inFig. 3 As shown in the figure, the second filter capacitor C2 is connected in parallel between the source S and the gate G of the PMOS Q1.

[0032] In practice, the size of the filter capacitor is determined according to the specific circuit requirements, and can be 10-200nF in general; for example, for the above-mentioned smoke alarm, a 100nF capacitor can be selected as the first filter capacitor C1 and the second filter capacitor C2.

[0033] In still another embodiment, as shown in the figure, the gate G of the PMOS Q1 is connected in series with a voltage dividing resistor R1, which prevents the PMOS Q1 from being broken down. Fig. 3

[0034] In the above-mentioned various embodiments, the PMOS Q1 can be a depletion mode PMOS, which can form a conductive channel at zero gate-source voltage, realize the on state, and control is relatively simple, without the need for additional external voltage to maintain the on state.

[0035] Other configurations and operations of the smoke alarm of the battery reverse connection prevention according to the embodiments of the present application are known to those skilled in the art, and will not be described in detail here.

[0036] In the description of the present application, it should be pointed out that, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connecting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above-mentioned terms in the present application can be understood according to the specific circumstances.

[0037] In the description of the present application, the description of the terms "embodiment", "specific embodiment", "example" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are contained in at least one embodiment or example of the present application.

[0038] In the present application, the illustrative description of the above-mentioned terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined with each other in a suitable manner in any one or more embodiments or examples without interfering or contradicting.​

Claims

1. A smoke alarm with battery reverse connection protection, characterized in that: The battery interface (1) is used for connecting external battery; the battery reverse connection prevention circuit (2) is connected between the battery interface (1) and the smoke sensing circuit (3).

2. The smoke detector of claim 1, wherein: The smoke sensing circuit (3) comprises a control chip, and the battery reverse connection prevention circuit (2) is a MOS tube reverse connection prevention circuit.

3. A smoke detector as claimed in claim 2, wherein: The battery reverse connection prevention circuit (2) comprises a PMOS tube. The positive pole of the battery interface (1) is connected with the drain of the PMOS tube, the source of the PMOS tube is connected with the power supply pin of the control chip; the negative pole of the battery interface (1) is connected with the gate of the PMOS tube, and the gate of the PMOS tube is connected with the grounding pin of the control chip and grounded.

4. A smoke detector according to claim 3, wherein: The first filter capacitor is connected in parallel between the drain and the gate of the PMOS tube.

5. A smoke detector as claimed in claim 4, wherein: The second filter capacitor is connected in parallel between the source and the gate of the PMOS tube.

6. A smoke alarm of claim 5, wherein: The gate of the PMOS tube is connected with a voltage dividing resistor in series.

7. A smoke alarm of any one of claims 3 to 6 which is further characterised in that: The PMOS tube is a depletion mode PMOS tube.

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