CN105322936A

CN105322936A - PBA switch circuit with insulation blocking function

Info

Publication number: CN105322936A
Application number: CN201510875978.7A
Authority: CN
Inventors: 陶辉
Original assignee: Shanghai Aviation Electric Co Ltd
Current assignee: Shanghai Aviation Electric Co Ltd
Priority date: 2015-12-02
Filing date: 2015-12-02
Publication date: 2016-02-10

Abstract

The invention relates to a PBA switch circuit with an insulation blocking function, which comprises a lightningproof filter circuit unit, a switching circuit unit and a photocoupled circuit unit, wherein the lightningproof filter circuit unit is provided with a TVS tube, a first resistor and a first capacitor; the switching circuit unit is provided with a second resistor, a third resistor, a fourth resistor, and a field-effect tube; and the input end of the photocoupled circuit unit is connected with the output end of the lightningproof filter circuit unit, and the output end of the photocoupled circuit unit is connected with the first end of the second resistor. The PBA switch circuit disclosed by the invention has the advantages that external interference signals are isolated from internal signals, and the isolation effect is good.

Description

A kind of PBA switching circuit with insulation blocking function

Technical field

The present invention relates to a kind of PBA switching circuit with insulation blocking function.

Background technology

Band lamp push switch PBA (IlluminatedPushButtonSwitchesandAnnunciators) is indispensable a kind of electric elements in airborne equipment, is mainly used in information instruction and control inputs.Major part PBA is by its switch of airborne equipment internal signal drived control, but also some is by internal signal control PBA break-make under lamp inspection pattern, non-lamp inspection pattern is controlled by outside hard signal, and this just inevitably introduces external interference signals, must isolate with internal signal.And at present, the isolation effect of existing PBA switching circuit is poor, does not even take the quarantine measures of being correlated with.Meanwhile, thunder and lightning, as a kind of natural phenomena, happens occasionally in the flight course of aircraft, if comprise casing ground in outside hard signal, also will carry out lightning protection.Because airborne equipment has higher requirement to operational environment and security reliability aspect, and also can be subject to the restriction of the factors such as cost in circuit design, so meet above-mentioned condition still have certain difficulty simultaneously.

Summary of the invention

The object of the invention is the problem that lightning protection filtering in solution prior art, hard signal and internal signal are isolated, a kind of PBA switching circuit of novel band insulation blocking function is provided.

To achieve these goals, technical scheme of the present invention is achieved in that a kind of PBA switching circuit with insulation blocking function, includes,

Lightning protection filter circuit unit, it has TVS pipe, the first resistance and the first electric capacity, outside hard signal end connects the first end of described TVS pipe and the first end of described first resistance respectively, the first end of the first electric capacity described in second termination of described first resistance, connects the second end of described first electric capacity and the second end of described TVS pipe housing respectively;

Switching circuit unit, it has the second resistance, the 3rd resistance, the 4th resistance, field effect transistor, the first end of the second resistance described in internal drive signal termination, second end of described second resistance connects the described first end of the 3rd resistance and the grid of described field effect transistor respectively, described second end of the 3rd resistance and the source ground of described field effect transistor, the drain electrode of described field effect transistor connects the first end of described 4th resistance and the negative pole of described PBA light-emitting diode respectively, and the second end of described 4th resistance and the positive pole of described PBA light-emitting diode all connect PBA dimming power source; And,

Photoelectric coupled circuit unit, the output of lightning protection filter circuit unit described in its input termination, the first end of the second resistance described in the output termination of described photoelectric coupled circuit unit.

As a kind of preferred version of the PBA switching circuit with insulation blocking function, described TVS pipe is two-way TVS pipe.

Compared with prior art, advantage of the present invention is at least: external interference signals and internal signal are isolated, and isolation effect is good.

Accompanying drawing explanation

Fig. 1 is the structural representation of one embodiment of the invention.

Embodiment

Below in conjunction with drawings and Examples, the present invention is elaborated.

Refer to Fig. 1, shown in figure is a kind of PBA switching circuit with insulation blocking function, forms primarily of lightning protection filter circuit unit, switching circuit unit and photoelectric coupled circuit unit.

Described lightning protection filter circuit unit has TVS pipe D1, the first resistance R1 and the first electric capacity C1.Outside hard signal end connects the first end of described TVS pipe D1 and the first end of described first resistance R1 respectively, the first end of the first electric capacity C1 described in second termination of described first resistance R1, housing ground CASEGND connects described second end of the first electric capacity C1 and second end of described TVS pipe D1 respectively.Wherein, described outside hard signal end provides voltage to be 28VDC direct current signal, critical frequency in circuit, described first resistance R1 restriction enters the electric current of described photoelectric coupled circuit unit, prevents electric current excessive, plays a protective role to described photoelectric coupled circuit unit.In the present embodiment, the two-way TVS pipe of described TVS pipe D1 system.

Described switching circuit unit has the second resistance R2, the 3rd resistance R3, the 4th resistance R4, field effect transistor Q1.The first end of the second resistance R2 described in internal drive signal termination, second end of described second resistance R2 connects the described first end of the 3rd resistance R3 and the grid of described field effect transistor Q1 respectively, described second end of the 3rd resistance R3 and the source ground of described field effect transistor Q1, the drain electrode of described field effect transistor Q1 connects the first end of described 4th resistance R4 and the negative pole of described PBA light-emitting diode respectively, and second end of described 4th resistance R4 and the positive pole of described PBA light-emitting diode all connect PBA dimming power source.When only allowing to obtain small electric stream from signal source, select field effect transistor as PBA switching tube, it is advantageous that, field effect transistor is voltage controlled element, there is comparatively high input impedance and low noise and other advantages, use field effect transistor can obtain the very inaccessible performance of general transistor, such as big current small package, low-power consumption low heat emission etc. in electronic product.But field effect transistor also exists parasitic capacitance between each pole, turning on and off in process, particularly in high frequency applications, drive circuit must can carry out quick charge/discharge to its parasitic capacitance.Therefore, driving pulse should have enough steep rising and decrease speed and postpone little.Enough large instantaneous peak current can be provided when opening, make to open delay and Miller plateau time enough short, within the time required, complete the discharge and recharge to power tube input capacitance Ciss; Low-resistance discharge loop can be provided for gate charge during shutoff, improve turn-off speed.

The output of lightning protection filter circuit unit described in the input termination of described photoelectric coupled circuit unit, the first end of the second resistance R2 described in the output termination of described photoelectric coupled circuit unit.Described photoelectric coupled circuit unit forms primarily of three parts: LED drives, photoelectric current is changed and signal amplifying element.First the signal driving LED of input is converted into light signal, is then received by optical diode (PD) and produce photoelectric current, through I-V converter, photoelectric current being converted into voltage signal, then through signal amplifying element, the voltage gain needed for generation.Can find out, the transfer process of electrical-optical-electricity, reach the object of input, output signal isolation.Photoelectrical coupler also claims photoisolator, is called for short optocoupler.Optocoupler take light as the media transmission signal of telecommunication, has good buffer action to the signal of telecommunication of input, output, is widely used in various circuit.Optocoupler has transfer of unidirectional, and thus it does isolated gate by features such as magnetic interference, can not have good electrical insulation capability and antijamming capability.Again due to the low impedance element that the LED of optocoupler is current mode work, thus there is very strong common mode inhibition capacity.The advantages such as compared with isolating with transformer isolation, capacitive coupling, it is little that light-coupled isolation has volume, low price, and buffer circuit is simple, signal one-way transmission, and magnetic field antijamming capability is strong, contactless.

PBA switching circuit realizes mainly through field effect transistor Q1, cut-in voltage VGS (th) between grid and source electrode is 2V, the switching signal ON/OFFSignal of 5V can drive completely, first resistance R1 plays metering function, for limiting the electric current that drive singal charges to parasitic capacitance, in order to erasure signal ringing, but the first resistance R1 resistance size can affect the time that PBA opens and turns off, first resistance R1 less PBA opening time is shorter, otherwise it is longer, because metal-oxide-semiconductor is the electronic component of high input impedance, very easily be subject to electrostatic damage, second resistance R2 plays the protective effect to grid.Consider that leakage current and the PBA of metal-oxide-semiconductor will be luminous when small area analysis, adopt the 4th resistance R4 and PBA in parallel, to be reduced by the leakage current of PBA.It should be noted that under lamp inspection pattern, the isolation signals that outside hard signal controls is inoperative, and namely IOsignal control signal has priority.

Below only have expressed embodiments of the present invention, it describes comparatively concrete and detailed, but can not therefore be construed as limiting the scope of the patent.It should be pointed out that for the person of ordinary skill of the art, without departing from the inventive concept of the premise, can also make some distortion and improvement, these all belong to protection scope of the present invention.Therefore, the protection range of patent of the present invention should be as the criterion with claims.

Claims

1. the PBA switching circuit with insulation blocking function, is characterized in that, include,

2. a kind of PBA switching circuit with insulation blocking function according to claim 1, it is characterized in that, described TVS pipe is two-way TVS pipe.