A kind of overvoltage crowbar
Technical field
The present invention relates to protection field of circuit technology, and in particular to a kind of overvoltage crowbar.
Background technique
Sensor used in motorcycle with electronic fuel injection system automobile engine control system, such as engine load sensor, admission pressure
Sensor, temperature sensor etc., most of 0~5V analog voltage of output be using device supply voltage as reference voltage, to
Reach the requirement of engine electronic control unit, then supply voltage needed for sensor be constant 5V, if supply voltage have it is any
Deviation will all will affect the output valve of sensor.Lead to voltage overshoot since power supply in circuit may be interfered, and voltage
It is impaired that the excessive output for not only changing sensor may also lead to component.
In the prior art, most of overvoltage crowbar is that then power supply circuit disconnects more than certain threshold voltage, but in the threshold
Even if circuit is still connected, this results in output voltage to fluctuate with input voltage there are voltage fluctuation within the scope of value.And
The protection circuit input and output voltage of the prior art is identical, and such overvoltage crowbar is not suitable for needing certain constant voltage
System, such as Motorcycles Engine with EMS control system.
Summary of the invention
In view of the deficiencies of the prior art, the present invention provides a kind of overvoltage crowbar, and for solving, voltage is excessive not only to be changed
The output for becoming sensor may also lead to the impaired problem of component.
The contents of the present invention are as follows:
A kind of overvoltage crowbar, including sequentially connected division module, control module and overvoltage protective module divide mould
The input terminal of block can connect to power supply, and it further includes reference voltage module that the output end of overvoltage protective module can be connected with load, control
The output end of molding block respectively is connect with reference voltage module and overvoltage protective module, the output end of reference voltage module and over-voltage
Protective module connection, reference voltage module is for being changed into a constant reference voltage for input voltage and controlling overvoltage protection
Module carries out voltage output.
Preferably, the control module includes triode Q1, and the base stage of triode Q1 is connected to power supply by division module,
Division module is used to provide preset base voltage to triode Q1 and controls the on-off of triode Q1, the collector of triode Q1
It being connected to power supply by the first bleeder circuit, the connecting node of the collector of triode Q1 and the first bleeder circuit is node B, three
The emitter of pole pipe Q1 is grounded.
Preferably, the reference voltage module includes voltage-stablizer U1, and the input terminal of voltage-stablizer U1 is connect with node B, pressure stabilizing
The output end of device U1 is connect by the second bleeder circuit with overvoltage protective module, and the input terminal of the voltage-stablizer U1 is also connected with the
One filter circuit, the output end of voltage-stablizer U1 are also connected with the second filter circuit.
Further, the voltage-stablizer U1 uses buck regulator.
Preferably, the reference voltage module includes zener diode D2, and the cathode of zener diode D2 passes through third point
Volt circuit is connect with node B, and the cathode of zener diode D2 also passes through the second bleeder circuit and connect with overvoltage protective module, pressure stabilizing
The plus earth of diode D2.
Preferably, the overvoltage protective module includes metal-oxide-semiconductor Q2, and the grid of metal-oxide-semiconductor Q2 is connect with the second bleeder circuit,
The drain electrode of metal-oxide-semiconductor Q2 is connect with node B, and the source electrode of metal-oxide-semiconductor Q2 is connected as voltage output end and load, the metal-oxide-semiconductor Q2's
Drain electrode is also connected with third filter circuit, and the source electrode of metal-oxide-semiconductor Q2 is also connected with the 4th filter circuit.
Further, the metal-oxide-semiconductor Q2 uses grid source conducting voltage Vgs (th) < 0V field-effect tube.
The invention has the benefit that the present invention increases reference voltage module, input voltage is changed into constant reference
Voltage, both can to avoid input voltage overshoot damage component, also can solve in threshold range occur voltage fluctuation cause it is defeated
Out the problem of voltage fluctuation, achieve the effect that export constant voltage and overvoltage protection.
Detailed description of the invention
Fig. 1 show the functional block diagram of the embodiment of the present invention 1;
Fig. 2 show the circuit diagram of the embodiment of the present invention 1;
Fig. 3 show the circuit diagram of the embodiment of the present invention 2.
Specific embodiment
The above description is only an overview of the technical scheme of the present invention, in order to better understand the technical means of the present invention,
And it can be implemented in accordance with the contents of the specification, and in order to allow above and other objects, features and advantages of the invention can
It is clearer and more comprehensible, it is special below to lift preferred embodiment, and cooperate attached drawing, detailed description are as follows.
Please refer to Fig. 1, a kind of overvoltage crowbar disclosed in the present embodiment, including sequentially connected division module 1, control
Module 2 and overvoltage protective module 3, the input terminal of division module 1 connect to power supply, the output end of overvoltage protective module 3 and load
Connection, overvoltage crowbar further include reference voltage module 4, the output end of control module 2 respectively with reference voltage module 4 and mistake
Protective module 3 is pressed to connect, reference voltage module 4 is for being changed into a constant reference voltage for input voltage and controlling over-voltage
Protective module 3 carries out voltage output.Both damage component can be overshooted to avoid input voltage, also can solve in threshold range
The problem of existing voltage fluctuation causes output voltage to fluctuate achievees the effect that export constant voltage and overvoltage protection.
Embodiment 1:
Referring to figure 2., the division module 1 includes resistance R1 and resistance R2, and one end of resistance R1 connects to power supply, resistance
The other end of R1 is connect with one end of resistance R2, and the connecting node of resistance R1 and resistance R2 are node A, the other end of resistance R2
Ground connection, the control module 2 include triode Q1, and the base stage of triode Q1 is connect with node A, and the base stage of triode Q1 is by dividing
Die block 1 connects to power supply, and division module 1 is used to provide preset base voltage to triode Q1 and controls the logical of triode Q1
Disconnected, the collector of triode Q1 is connected to power supply by the first bleeder circuit 21, and the first bleeder circuit 21 includes resistance R3, three poles
The connecting node of the collector of pipe Q1 and the first bleeder circuit 21 is node B, and the emitter of triode Q1 is grounded.
The reference voltage module 4 includes voltage-stablizer U1, and the voltage-stablizer U1 of the present embodiment uses model AMS1117-3.3
Voltage-dropping type voltage stabilizing chip, the input voltage minimum value of the voltage-dropping type voltage stabilizing chip is 4.75V, the input of maximum value 12V, U1
Voltage in the range when export 3.3V constant voltage values.The input terminal of voltage-stablizer U1 is connect with node B, the output of voltage-stablizer U1
End is connect by the second bleeder circuit 43 with overvoltage protective module 3, and the second bleeder circuit 43 includes resistance R4 and resistance R5, resistance
One end of R4 is connect with the output end of voltage-stablizer U1, and the other end of resistance R4 is connect with one end of resistance R5, resistance R4 and resistance
The connecting node of R5 is node C, and the other end of resistance R5 is grounded.It is dry in order to reduce that the input and output voltage of voltage-stablizer U1 receives
Disturb signal, the input terminal of the voltage-stablizer U1 is also connected with the first filter circuit 41, the first filter circuit 41 include capacitor C1 and
Capacitor C2, capacitor C1 and capacitor C2 latter end ground connection in parallel, the other end are connect with the input terminal of voltage-stablizer U1, and voltage-stablizer U1's is defeated
Outlet is also connected with the second filter circuit 42, and the second filter circuit 42 includes capacitor C3 and capacitor C4, and capacitor C3 and capacitor C4 are simultaneously
Join latter end ground connection, the other end is connected to the output end of voltage-stablizer U1.
The overvoltage protective module 3 includes metal-oxide-semiconductor Q2, the node C company of the grid of metal-oxide-semiconductor Q2 and the second bleeder circuit 43
It connects, the drain electrode of metal-oxide-semiconductor Q2 is connect with node B, and the source electrode of metal-oxide-semiconductor Q2 is connected as voltage output end and load.The leakage of metal-oxide-semiconductor Q2
Pole is also connected with the third filter circuit 31 for protecting metal-oxide-semiconductor Q2, and third filter circuit 31 includes Transient Suppression Diode D1
With capacitor C5, transient diode D1 and capacitor C5 it is in parallel after one end connect with the drain electrode of metal-oxide-semiconductor Q2, transient diode D1 and capacitor
The other end is grounded after C5 is in parallel, and the source electrode of metal-oxide-semiconductor Q2 is also connected with the 4th filter circuit 32, and the 4th filter circuit 32 includes capacitor
C6, the one end capacitor C6 are connect with the source electrode of metal-oxide-semiconductor Q2, the other end ground connection of capacitor C6.
The working principle of the present embodiment is as follows:
The threshold voltage that the present embodiment is set is 12V, and power supply provides input voltage vin, and input voltage vin is by partial pressure mould
Block 1 gives triode Q1 offer suitable base voltage after dividing, and controls the on and off of triode Q1, in the present embodiment
Metal-oxide-semiconductor Q2 uses the field-effect tube of grid source conducting voltage Vgs (th)=- 2.5V, and when original state, triode Q1 is in cut-off shape
State, metal-oxide-semiconductor Q2 is in the conductive state, source voltage Vs=input voltage vin=0V of output voltage Vout=MOS pipe Q2;
As input voltage vin=5V, in voltage input moment, triode Q1 is in off state, and node B voltage is equal to
Input voltage vin.Metal-oxide-semiconductor Q2 is in the conductive state, the source voltage Vs=input voltage of output voltage Vout=MOS pipe Q2
Vin=5V, node B power to the drain electrode of voltage-stablizer U1 and metal-oxide-semiconductor Q2, and voltage-stablizer U1 converts voltages into the first constant electricity
Pressure, the grid voltage Vg=2.5V that first voltage provides after the second bleeder circuit 43 partial pressure to metal-oxide-semiconductor Q2, at this point, metal-oxide-semiconductor
Grid voltage Vg-metal-oxide-semiconductor Q2 source voltage Vs=2.5-5 >=metal-oxide-semiconductor Q2 grid source conducting voltage Vgs (th) of Q2 meets
The turn-on condition of metal-oxide-semiconductor Q2, metal-oxide-semiconductor Q2 is in the conductive state, the source voltage Vs=node of output voltage Vout=MOS pipe Q2
Voltage=input voltage vin=5V of B;
When input voltage vin occurs fluctuating and when 5V < input voltage vin≤12V, triode Q1 is in off state, section
Point B voltage is equal to input voltage vin.Metal-oxide-semiconductor Q2 is in the conductive state, and the source voltage Vs=of voltage Vout=MOS pipe Q2 is defeated
Enter voltage Vin, node B powers to the drain electrode of voltage-stablizer U1 and metal-oxide-semiconductor Q2, and voltage-stablizer U1 converts voltages into the first constant electricity
Pressure, the grid voltage Vg=2.5V that first voltage provides after the second bleeder circuit 43 partial pressure to metal-oxide-semiconductor Q2, at this point, metal-oxide-semiconductor
Grid voltage Vg-metal-oxide-semiconductor Q2 source voltage Vs < metal-oxide-semiconductor Q2 grid source conducting voltage Vgs (th) of Q2, is unsatisfactory for metal-oxide-semiconductor Q2
Turn-on condition, metal-oxide-semiconductor Q2 shutdown, shutdown moment metal-oxide-semiconductor source voltage Vs returns to 0V, at this time the grid voltage Vg-of metal-oxide-semiconductor Q2
Source voltage Vs >=metal-oxide-semiconductor Q2 grid source conducting voltage Vgs (th) of metal-oxide-semiconductor Q2, metal-oxide-semiconductor Q2 are connected again, so recycle, so
When input voltage vin fluctuates, and input voltage vin > 5V and when input voltage vin≤12V, metal-oxide-semiconductor Q2 is in high frequency
ON/OFF is repeated, critical unsaturated on state, the source voltage Vs=MOS pipe Q2 of output voltage Vout=MOS pipe is presented
Grid voltage Vg-metal-oxide-semiconductor Q2 grid source conducting voltage Vgs (th)=5V.
Therefore, even if input voltage fluctuates in threshold range, by the way that reference voltage module and choosing is correctly arranged
Select grid source conducting voltage Vgs (th) suitable field-effect tube, it is ensured that output voltage Vout is constant;
If triode Q1 is in the conductive state when input voltage is greater than the threshold value of 12V, node B voltage is equal to 0V, U1 not work
Make, protection load is played the role of in field-effect tube Q2 cut-off.
Embodiment 2:
Referring to figure 3., in the present embodiment, the reference voltage module 4 includes zener diode D2, zener diode D2's
Cathode is connect by third bleeder circuit 44 with node B, and the cathode of zener diode D2 also passes through the second bleeder circuit 43 and mistake
Protective module 3 is pressed to connect, the plus earth of zener diode D2.It is same as Example 1 for the part that refers in the present embodiment.
The above, only presently preferred embodiments of the present invention, the invention is not limited to above embodiment, as long as
It reaches technical effect of the invention with identical means, all should belong to protection scope of the present invention.In protection model of the invention
Its technical solution and/or embodiment can have a variety of different modifications and variations in enclosing.