Small-power EPS detecting device for output current
The utility model relates to power technique fields, in particular to a kind of small-power EPS detecting device for output current.
Emergency power supply (Emergency Power Supply, EPS) is a kind of containing battery energy storage equipment, with inverter
For the power protective equipment of formant, wherein needing to use alternating current input, and isolation detection is carried out to alternating current, exchange
Big voltage signal is processed into small voltage direct current signal and send central signal processor analog quantity sample port for central signal processor
Judgement, and issue and execute order, therefore is most important to the steady operation of power-supply system to the accuracy of exchange electro-detection.
Common detection means is, using Hall component, diode rectification, capacitor filtering, then it is appropriately processed at small
Voltage DC signal send central signal processor, and there are shortcomings for this circuit:
1, Hall component is at high cost；
2, there are threshold voltages for diode, when the small-power EPS of detection output current and voltage signals are less than threshold voltage,
Diode rectifier circuit cisco unity malfunction can not detect the output electric current of small-power EPS at this time；
3, there are nonlinearity errons for diode, will cause detection inaccuracy；
4, the temperature characterisitic of diode is poor, vulnerable to ambient temperature effect, will lead to detection inaccuracy.
Utility model content
Based on this, it is necessary to provide a kind of small-power EPS detecting device for output current, can delicately detect small
AC signal, and testing result is accurately reliable, it is not influenced by ambient temperature.
For achieving the above object, the utility model uses following technical scheme.
The utility model provides a kind of small-power EPS detecting device for output current, including sequentially connected current signal is adopted
Collector, signal amplification circuit, signal transformation circuit and voltage follower circuit, the current signal Acquisition Circuit acquire alternating current
Signal, and be input in the signal amplification circuit, the signal amplification circuit includes the first operational amplifier, for described
Ac signal amplifies, and is output in the signal transformation circuit, and the signal transformation circuit includes that the second operation is put
Big device, diode and capacitor carry out shaping for the waveform to the ac signal, and are output to the voltage follower circuit
In, the voltage follower circuit is exported for ac signal to be buffered and is isolated, and by the ac signal through one
Interface is output to operation in a processor.
Preferably, Single port protection circuit is additionally provided between the output interface and voltage follower circuit, to prevent wave
Preferably, the current signal Acquisition Circuit is made of current transformer and first resistor, the current transformer
First siding ring be connected between the phase line of alternating current and zero curve；The second siding ring both ends of the current transformer connect respectively
It is connected to the input terminal of the signal amplification circuit, the first resistor is arranged in parallel with the signal amplification circuit.
Preferably, described first siding ring the number of turns is identical as described second siding ring the number of turns.
Preferably, the signal amplification circuit includes the electricity of first operational amplifier, second, the four, the 5th and the 6th
Resistance, the negative input end of first operational amplifier connect the anode of the signal acquisition circuit by the second resistance all the way
Output end, another way are connect by the 6th resistance with output end；The positive input terminal a-road-through of first operational amplifier
The 4th resistance to be crossed to connect with the cathode output end of the signal acquisition circuit, another way passes through the 5th resistance eutral grounding,
Constitute difference amplifier.
Preferably, the second resistance is identical with the resistance value of the 4th resistance, the resistance value of the 5th resistance and the 6th resistance
It is identical.
Preferably, the signal transformation circuit includes the second operational amplifier and one second diode, and described second
The negative input end of operational amplifier is connect by the 7th resistance with the output end of the signal amplification circuit, positive input terminal ground connection,
The output end of the second operational amplifier exports outward through second diode.
Preferably, the signal transformation circuit is additionally provided with the output of three tunnels, wherein passing through the 7th resistance and one all the way
The series circuit of 8th resistance exports, and another way is exported through one the 9th resistance, also all the way through the 7th resistance, one the 1st pole
Pipe, second diode output.
Preferably, the voltage follower circuit includes third operational amplifier, the positive input of the third operational amplifier
End is connect by 1 the tenth resistance with the output end of the signal transformation circuit, negative input end and the third operational amplifier
Output end connection.
Preferably, the port protection circuit is made of third diode and the 4th diode, the anode of third diode
Ground connection, cathode connect the output interface；The anode of 4th diode connects the output interface, and cathode connects mainboard electricity
Compared to the isolation sampling apparatus that tradition uses Hall component, the utility model uses Current Mutual Inductance technology can be with
Save the cost and the volume for reducing circuit board；Due to not using diode rectifier circuit, threshold voltage is also just not present, and do not deposit
In nonlinearity erron, therefore it can detecte small AC signal, and testing result is accurately reliable.Further, since avoiding use
Diode, circuit will not be influenced by temperature, and can further improve the accuracy of testing result.
Detailed description of the invention
Fig. 1 is the electrical block diagram of the utility model embodiment middle low power EPS detecting device for output current.
Fig. 2 is the waveform diagram after shaping.
With reference to the accompanying drawing and specific embodiment is described further.
As shown in Figure 1, mainly including successively connecting the present embodiment provides a kind of small-power EPS detecting device for output current
Current signal Acquisition Circuit, signal amplification circuit, signal transformation circuit and the voltage follower circuit connect, the current signal acquisition
Circuit is input in the signal amplification circuit for acquiring ac signal；The signal amplification circuit includes the first fortune
Amplifier U1A is calculated, for being amplified to the ac signal, and is output in the signal transformation circuit；The signal
Shaping circuit includes second operational amplifier U1B, diode and capacitor, is carried out for the waveform to the ac signal whole
Shape, and be output in the voltage follower circuit；The voltage follower circuit is used to that ac signal to be buffered and is isolated,
And the ac signal is output to operation in a processor (not shown) through an output interface Uout.Processor is defeated according to institute
The ac signal entered judges whether safety, and executes corresponding alternate program.
Preferably, Single port protection electricity is additionally provided between the output interface Uout and voltage follower circuit
Processor and other electric elements are protected to prevent surge impact in road.
In the present embodiment, current signal Acquisition Circuit acquires the electric current of ac signal by the way of Current Mutual Inductance,
It is mainly made of current transformer T1 and first resistor R1, and the alternating current of EPS output is generated by inverter circuit, the inverter circuit
Phase line L connect with first siding ring one end of the current transformer T1, zero curve N is connect with the other end of the coil.Institute
The second siding ring both ends for stating current transformer T1 are connected respectively to the input terminal of the signal amplification circuit, the first resistor
R1 is arranged in parallel with the signal amplification circuit.In this way, the electricity of the output voltage of signal amplification circuit and the both ends first resistor R1
Press U3 identical.
The present embodiment, it is assumed that the turn ratio of current transformer first siding ring and secondary side is n1:n2, then the voltage of U3 is
U3=(I1 × n1)/n2 × R1, waveform are sine wave.The resistance value of first resistor R1, which can according to need, voluntarily to be selected.
Above-mentioned signal amplification circuit includes the first operational amplifier U1A, second resistance R2, the 4th resistance R4, the 5th
Resistance R5 and the 6th resistance R6, the negative input end of the first operational amplifier U1A pass through the second resistance R2 connection all the way
The cathode output end of the signal acquisition circuit, another way are connect by the 6th resistance R6 with output end；First fortune
The positive input terminal for calculating amplifier U1A passes through the 4th resistance R4 all the way and the cathode output end of the signal acquisition circuit connects
It connects, another way is grounded by the 5th resistance R5, constitutes difference amplifier.
In the present embodiment, the resistance value of the second resistance R2 and the 4th resistance R4 are identical, the 5th resistance R5 and the 6th
The resistance value of resistance R6 is identical.Voltage at U4 is U4=U3 × (R6/R2), and waveform is identical as U3's.
Above-mentioned signal transformation circuit includes the second operational amplifier U1B and one second diode D2, second fortune
The negative input end for calculating amplifier U1B is connect by the 7th resistance R7 with the output end of the signal amplification circuit, positive input termination
The output end on ground, the second operational amplifier U1B exports outward through the second diode D2.
In addition, in addition to above-mentioned outlet line, the signal transformation circuit is additionally provided with the output of three tunnels, wherein all the way by described
The output of the series circuit of 7th resistance R7 and one the 8th resistance R8, another way are exported through one the 9th resistance R9, and there are also all the way through institute
State the 7th resistance R7, a first diode D1, the second diode D2 output.
In this way, above-mentioned four road outlet line collects at U5, the voltage of U5 is U5=at this time | U3/2 |, waveform become as
Shape shown in Fig. 2.
Above-mentioned voltage follower circuit includes third operational amplifier U1C, the positive input terminal of the third operational amplifier U1C
It being connect by 1 the tenth resistance R10 with the output end of the signal transformation circuit, negative input end is connect with the output end of its own,
For being buffered and being isolated to ac voltage signal.The waveform of the output signal of the voltage follower circuit and the waveform at U5 are same
Step, really to restore current ac voltage signal, and is delivered to the processor.
In addition, the port protection circuit is made of third diode D3 and the 4th diode D4, third diode D3's
Plus earth, cathode connect the output interface Uout；The anode of the 4th diode D4 connects the output interface Uout,
Cathode connects motherboard circuit VCC.For the port protection circuit when ac voltage signal intensity is excessive, electric current can puncture the three or two pole
Pipe D3 protects output interface Uout not by surge impact to play the role of decompression protection.
It is arranged by the above circuit, whether processor can determine the ac signal that inverter circuit is exported normal,
And detection and isolation of the realization to ac signal, in order to which when occurring abnormal, processor can start corresponding spare journey in time
Sequence deactivates this EPS, so as to avoid an accident.
In conclusion the utility model can be with the volume of save the cost and reduction circuit board；Due to not using diode,
Threshold voltage is just not present, and nonlinearity erron is not present, therefore can delicately detect small AC signal, and detects knot
Fruit is accurately reliable.Further, since avoiding using diode, circuit will not be influenced by temperature, and can further improve detection
As a result accuracy.
Each technical characteristic of embodiment described above can be combined arbitrarily, for simplicity of description, not to above-mentioned reality
It applies all possible combination of each technical characteristic in example to be all described, as long as however, the combination of these technical characteristics is not deposited
In contradiction, all should be considered as described in this specification.
Above-described embodiments merely represent several embodiments of the utility model, the description thereof is more specific and detailed,
But it cannot be understood as the limitations to utility model patent range.It should be pointed out that for the common skill of this field
For art personnel, without departing from the concept of the premise utility, various modifications and improvements can be made, these are belonged to
The protection scope of the utility model.