A kind of output current of inverting welding machine testing circuit and detection method based on direct current signal
Technical field
The present invention relates to electric welding machine technology, be specifically related to electric welding machine output electric current measure technology.
Background technology
Inversion welding machine needs to detect in real time electric welding machine output current for welding current being carried out accurately control, and the general devices such as Hall current sensor or shunt that adopt detect electric welding machine output current at the output terminal of electric welding machine at present.If adopting the advantage of Hall current sensor is to realize testing circuit and main circuit isolation, but the cost of Hall current sensor is high, especially large current Hall sensor; And Hall current sensor needs Power supply, testing circuit complexity.If adopt the scheme cost of shunt low, but can not realize observation circuit and main circuit isolation, poor anti jamming capability.
For the existing problem of above-mentioned electric welding machine output electric current measure scheme, the patent No. is that 200910216856.1 Chinese patent has provided a kind of method for detecting output current of inverting welding machine, and the method is mainly to utilize voltage comparator and triode to realize the detection of electric current.But corresponding components and parts or many in the testing circuit relating in this scheme, testing circuit or more complicated cost compare is high; Be exactly to use voltage comparator in this scheme in addition, due to the response time of voltage comparator, thereby cause whole testing circuit to have the problem that the response time is long, response speed is slow.
Summary of the invention
For existing output current of inverting welding machine detection scheme, have the problems such as complex structure, cost is high, response speed is slow, first object of the present invention is to provide the output current of inverting welding machine that a kind of structure is simple in structure, the response time is short testing circuit.
As second object of the present invention, the present invention is based on above-mentioned testing circuit a kind of detection method is also provided.
In order to achieve the above object, the present invention adopts following technical scheme:
Output current of inverting welding machine testing circuit based on direct current signal, described testing circuit comprises signal sampling unit and signal processing unit, described signal sampling unit comprises current transformer,
Described signal sampling unit also comprises commutation diode D1, and described current transformer is placed in the elementary or secondary of main-transformer, and its output terminal and commutation diode D1 join, and formation is inputted corresponding DC current signal with the former limit of main-transformer DC current;
Described signal sampling unit also comprises voltage sampling circuit, and described voltage sampling circuit is connected in series and forms with circuit R1 by diode D2, and joins with the output terminal of diode D1;
Described signal processing unit comprises discharge resistance R2, capacitor C 1 and triode Q1, the base stage of described triode Q1 connects the sampled voltage of voltage collection circuit, its emitter is by capacitor C 1 ground connection, and as detection signal output terminal, described discharge resistance R2 and capacitor C 1 also connect.
In the preferred version of testing circuit, the magnitude of voltage of described voltage sampling circuit sampling is the tube voltage drop Vak of diode D2 and the voltage sum that forms in resistance R 1, and in resistance R 1 voltage and the elementary or secondary current value of main-transformer proportional.
As the second object of the present invention, method for detecting output current of inverting welding machine based on direct current signal, described detection method is utilized the conduction voltage drop of triode Q1 base stage and emitter, the principle close with the tube voltage drop of diode D2, make the proportional relation of triode Q1 emitter voltage and output current of inverting welding machine, as detection signal, export.
In the preferred version of detection method, described detection method utilizes current transformer T1 to detect the elementary or secondary of transformer, inputs corresponding DC current signal, then carry out rectification by commutation diode D1 in the output terminal formation of current transformer T1 with DC current;
This DC current forms sampled voltage through diode D2 and resistance R 1, and this sampled voltage is the tube voltage drop of diode D2 and the voltage sum that forms in resistance R 1, and in resistance R 1 voltage and primary or secondary electrical flow valuve proportional;
This sampled voltage is connected to the base stage of triode Q1, triode Q1 conducting, and power supply VCC charges to capacitor C 1 by triode Q1, triode Q1 is operated in state of saturation, the emitter voltage Ve of triode Q1 follows base voltage, equates, and export as detection signal with voltage in resistance R 1.
Further, in described detection method, the conduction voltage drop that the voltage in capacitor C 1 adds triode Q1 base stage and emitter is during higher than Q1 base voltage, and triode Q1 is in cut-off state, and in capacitor C 1, voltage discharges by resistance R 2, and the upper voltage of C1 slowly reduces.
The output current of inverting welding machine testing circuit forming according to such scheme and detection method are based on direct current signal, can in the situation that guaranteeing accuracy of detection, greatly reduce the use amount of the components and parts of testing circuit, thereby can greatly simplify the composition of circuit, reduce the cost of manufacture of circuit.
Meanwhile, abandon employing comparer, thereby greatly reduce the response time of testing circuit, improve the response speed of testing circuit.
Accompanying drawing explanation
Below in conjunction with the drawings and specific embodiments, further illustrate the present invention.
Fig. 1 is the circuit theory diagrams of the output current of inverting welding machine testing circuit based on direct current signal in the present invention.
Embodiment
For technological means, creation characteristic that the present invention is realized, reach object and effect is easy to understand, below in conjunction with concrete diagram, further set forth the present invention.
Referring to Fig. 1, it is depicted as the circuit theory diagrams of the output current of inverting welding machine testing circuit based on direct current signal provided by the invention.As seen from the figure, whole testing circuit is divided into anterior voltage signal sampling unit and signal processing unit below.
Voltage signal sampling unit mainly adopts circuit (D2, R1) to form by current transformer T1, commutation diode D1, voltage.
Wherein, current transformer T1 is placed in elementary or secondary (the former limit input direct-current electric current signal of this main-transformer) of main-transformer, detect the elementary or secondary of transformer, in the output terminal formation of current transformer T1, input corresponding DC current signal with the DC current of main-transformer.
The output terminal of commutation diode D1 and current transformer T1 joins, and the DC current signal that current transformer T1 is produced carries out rectification change.
Voltage sampling circuit is composed in series by negative pole and the resistance R 1 of diode D2, the negative pole of the positive pole of diode D2 and commutation diode D1 joins, the other end ground connection of resistance R 1, thus the DC current after diode D1 rectification is sampled and formed sampled voltage, this sampled voltage is that the tube voltage drop Vak of diode D2 and the voltage VR1 that forms in resistance R 1 are added, and in resistance R 1 voltage VR1 and primary or secondary electrical flow valuve proportional.
Signal processing unit in testing circuit mainly comprises triode Q1, discharge resistance R2, capacitor C 1.Wherein the base stage of triode Q1 connects the positive pole of diode D2 in voltage sampling circuit, and its collector directly connects power supply VCC, and emitter passes through capacitor C 1 ground connection, and as detection signal output terminal; Discharge resistance R2 and capacitor C 1 also connect.
The output current of inverting welding machine testing circuit forming thus, it is when carrying out output current of inverting welding machine detection, first the former limit input direct-current electric current of main-transformer in inversion welding machine, utilization is placed in the elementary or secondary current transformer T1 of transformer, detect the elementary or secondary of transformer, in the output terminal formation of T1, input corresponding DC current signal with DC current.
Then the DC current signal, by commutation diode D1, current transformer T1 being produced carries out rectification.
Moreover, DC current after rectification is sampled through diode D2 and R1, form sampled voltage, sampled voltage is that the tube voltage drop Vak of diode D2 and the voltage VR1 that forms on R1 are added, and wherein the upper voltage VR1 of R1 and primary (or secondary) current value are proportional.
The base stage of sampled voltage connecting triode Q1, triode Q1 conducting, power supply VCC is by triode Q1 to capacitor C 1 charging, and triode Q1 is operated in state of saturation, and the emitter voltage Ve(of triode Q1 is the signal output voltage of testing circuit) follow base voltage Vb.
Because triode Q1 emitter voltage is lower than base voltage, and difference is Q1 base stage and emitter conduction voltage drop Vbe.And triode Q1 base stage connection sampled voltage, therefore triode Q1 base voltage is identical with sampled voltage: Vb=Vak+VR1.
Thus, the emitter voltage Ve(of triode Q1 is signal output voltage)=Vb-Vbe=Vak+VR1-Vbe
Because the tube voltage drop Vak of diode D2 and triode Q1 base stage and emitter conduction voltage drop Vbe are PN junction pressure drop, so two values are approximate: Vak ≈ Vbe.
So: the emitter voltage Ve(of triode Q1 is signal output voltage)=VR1.
Because the upper voltage VR1 of R1 is proportional with primary (or secondary) current value, thereby triode Q1 emitter voltage Ve and the proportional relation of output current of inverting welding machine can be used as detection signal and export.
Wherein, the conduction voltage drop Vbe that voltage adds triode Q1 base stage and emitter in capacitor C 1 is during higher than Q1 base voltage Vb, and Q1 is in cut-off state, and in capacitor C 1, voltage discharges by resistance R 2, and the upper voltage of C1 slowly reduces.
When if input direct-current electric current signal is a series of pulse signal, when voltage VR1 that peak value of pulse produces in resistance R 1 again higher than C1 on during voltage, Q1 is by conducting again, signal output voltage=VR1 now, therefore the signal output voltage peak value that forms voltage on R1 of afterpulsing signal always during testing circuit work.
Because electric welding machine output current is proportionate relationship with the primary current peak value that flows through main-transformer, so signal output voltage and the proportional relation of output current with welding machine, the output current that both can realize butt welding machine detects.
As from the foregoing, this programme utilizes the conduction voltage drop of triode Q1 base stage and emitter, and the principle close with the tube voltage drop of diode D2 makes the proportional relation of triode Q1 emitter voltage and output current of inverting welding machine, as detection signal, exports.Thereby can adopt less components and parts both can realize output current of inverting welding machine, accurately detect, circuit is both simple, and response speed is fast again.
More than show and described ultimate principle of the present invention, principal character and advantage of the present invention.The technician of the industry should understand; the present invention is not restricted to the described embodiments; that in above-described embodiment and instructions, describes just illustrates principle of the present invention; without departing from the spirit and scope of the present invention; the present invention also has various changes and modifications, and these changes and improvements all fall in the claimed scope of the invention.The claimed scope of the present invention is defined by appending claims and equivalent thereof.