Abstract: Introduced one kind of new application in the industry vibrating spear’s frequency conversion power source, it improved the existing vibrating spear power source volume and the weight big flaw greatly, introduced in detail several important part electric circuit’s design, and through various part of analyses and the experiment showed this design has the volume to be small, the weight is light, high performance and so on various merit.
Key word: Active power factor adjustment; Is stirring up the converter; Vibrating spear; Frequency conversion velocity modulation
Introduction
Along with the electric power electronic technology, the microcomputer and large scale integrated circuit’s swift development, causes the alternating current machine frequency conversion velocity modulation system rapidly expand which is composed of the frequency changer to be mature, and obtained more and more widespread application.
The existing vibrating spear product basically is one kind of electric motor belt generator, provides the 200Hz alternating current again by the generator, leads the high speed vibrating spear electrical machinery movement active status [1]. Its prominent shortcoming is the volume and the weight is quite big, creates to the scene construction uses and moves on to be very greatly inconvenient. This article studies the key point is exchanges the frequency conversion velocity modulation technology, applies on the vibrating spear this kind of small structural purpose machinery, develops one kind of new frequency conversion power source. While realizes vibrating spear function to cause the complete machine the volume and the weight largely reduces, and enhances input end’s power factor, stable out-port’s voltage and frequency, but can also reduce the product the cost. This frequency conversion power source key property target is as follows: For vibrator’s integral asynchronous eccentric type vibrating motor’s supply frequency is 200Hz, the single-phase input, the three-phase output, electrical machinery’s line voltage is 42V, the single plane power is 350W, the request can have the movement.
1 voltage invertor’s main circuit
Not only the frequency conversion power source must realize the live pressure and the frequency conversion function, but must cause the input-output realizes the electricity to isolate, and must satisfy electrical network’s overtone request, its basic structure includes AC/DC, DC/DC and DC/AC generally and so on several important parts.
This power source main circuit before APFC the level, DC/DC and three-phase inverts 3 part constitutions. Input does not control the rectification after the entire bridge, with the Boost electric circuit as the APFC electric circuit analysis situs carries on the voltage pre-adjustment. The DC/DC part uses the single end to stir up the converter to realize the voltage dropping and the isolation function. The three-phase contravariant part uses the SPWM control mode, its basic structure as shown in Figure 1. Because has used the power factor adjustment technology, therefore the power input factor is high, the electrical network side class overtone is small, is very small to electrical network’s overtone pollution; Moreover when network voltage fluctuation or variation of load, because the DC/DC link’s control may maintain the three-phase contravariant part the direct-current side voltage regulation, thus causes system’s output voltage to be stable, but does not need to change the output voltage through the adjustment three-phase inversion part modulation depth the size, therefore, may reduce to the contravariant part’s control chip’s request, may use quite inexpensive CPU. Moreover, because is the low pressure inverts, then may use the low pressure MOS tube to take the contravariant electric circuit’s power switching valve.
2 active power factors adjust (APFC) the electric circuit
Uses the mean current control the Boost electric circuit to realize APFC, is present uses the most widespread one APFC control method in the high frequency switching power supply.
Had very many kind of integrated circuit chip using the mean current control method’s power factor adjuster’s control circuit in the market to be possible to supply the choice, American Unitrode Corporation’s UC3854 has the representative one kind very much, and obtained the widespread application in reality. In this plan, is uses Unitrode Corporation’s UC3854 chip to realize, its electric circuit schematic diagram as shown in Figure 2 [2], inputs terminal voltage electric current experimental result as shown in Figure 3. In actual voltage and chart voltage corresponding relationships for 1V∶1V, in actual electric current and chart electric current corresponding relationships for 4A∶1V.
3 are stirring up (Forward) converter’s design [2]
The vibrating spear is one kind of handhold electrically operated product, for operators’ personal safety, between the input-output must realize the electricity to isolate. Before APFC, level the input-output have not isolated, realizes the function which isolates is by the DC/DC part completes. What because uses is the high frequency DC/DC transfer network, therefore transformer’s volume may do very much slightly. Moreover, because the APFC output voltage probably is 350~400V, considered behind inverts the electric circuit switching valve’s voltage stress question, the DC/DC part should also have the voltage dropping function. Based on this kind of consideration, in this plan, what the DC/DC part uses is stirring up the transfer network (ForwardConverter). Is stirring up converter’s biggest merit is the structure is simple, the reliability was high, reduced the cost and the weight. Considered that transformer’s magnetism replacement question, this plan uses the electric circuit which as shown in Figure 4. When switching valve breakover, transformer transmission energy, when the switching valve shuts off, will output diode D1 instead not to have the energy draining return route, the magnetization energy to cause the big back pressure to add between the MOS tube’s drain electrode and the source. Uses the N2 coil the function to lie in after diode D may return the storage energy to the power source. So long as N2 and the N1 number of windings are the same, switching valve withstanding leaks - the source voltage is 2Vs. Uses method which N1 and the N2 two winding double threads and circle, may reduce the leakage inductance. In Figure 4 in electric circuit, what the power switch’s control chip uses is Unitrode Corporation’s UC3844.
4 three-phase invertor controls, actuation and protection circuit’s design
4.1 inversion control circuit’s design [3]
Because this plan inversion part does not need to change the output voltage through the adjustment modulation depth the size, only need realize the frequency conversion function to be possible, therefore the control circuit uses the chip is the INTEL 87C51FX series 8 monolithic integrated circuits, the price reduces greatly compared to the general Intel196 monolithic integrated circuit, but the performance is enough. Generally speaking, has the PWM typical usage using CPU uses the method fixed time, determines the three-phase output in the timer interruption through the inquiry way. But, this method is only suitable in outputs the PWM pulse frequency very low situation, when the output frequency is bigger than 1kHz, the interrupt query time on possible association president in the minimum output pulse width, like this to create the output pulse width fill-out or to reduce, causes the output overtone to enlarge, the three-phase between symmetric relation will also come under the influence. Compares with the ordinary 51 series monolithic integrated circuits, 87C51FX increased a programmable counter array (PCA), it is composed of a 16 timer/counter and 5 16 comparison/capture module, as shown in Figure 5, its function and Intel196 monolithic integrated circuit’s EPA are similar. The PCA 16 timer/counter takes the comparison/capture module fixed time standard, therefore, the main achievement timer use, each comparison/capture module has 4 uses, namely catches on exterior pin CEXn the power output to have the jump time, the software timer, high speed output and pulse width modulation output.
This plan uses the asymmetrical regular sampling law to produce the three-phase 6 group steering impulse. Compares in the symmetrical regular sampling law, the asymmetrical regular sampling law forms the step wave approaches in the sine wave. Will calculate the three-phase pulse width’s value saves a data sheet, takes fixed time the datum, inquires these fixed time time in the procedure to be possible to obtain 6 group steering impulses. The principle of work summary is as follows: Using the 87C51FX software timer and the high speed output mode, in 16 comparison ways, in 16 PCA timer’s counting value and in the module 16 comparison register’s pre-placed value carries on 3 comparisons in each machine cycle, if equal, then produces a match signal, causes the module work in the high speed output mode, namely when the PCA timer counting value and the module comparison register is quite equal produces a match signal, this signal causes on exterior pin CEXn the power output to have the jump, if allows also to have a PCA interrupt. Establishes on CEXn by the software the power output initial state, may cause this pin when the predetermined time achieves occurs (negative) jumps, uses this way to be possible to have 16 PWM waves.
Because the pin jump cannot complete after the CPU operation, therefore, has avoided the pulse width change which is excessively narrow as a result of the minimum pulse width creates. The procedure is mainly composed of the master routine and the interrupt service two parts. The master routine mainly carries on the initialization work, entrusts with the starting value the timer and each register. The interrupt routine mainly includes uses in producing PWM the pulse PCA interrupt service and the protection interrupt routine: In the PCA interrupt service, is mainly gives each module the next fixed time time evaluation the comparison register; The protection interrupt routine is mainly when by rights ought to place has the guard signal arrival, blocks the PWM output.
4.2 driving circuit’s design [4][5]
In this plan actuates the chip to use IR2130. The IR2130 biggest merit is may altogether move, therefore only needs a group control supply. Moreover in its 6 group output signal’s 3 roads also have the level switch function, can also actuate the low pressure side the power component, can also actuate the high-tension side the power component. IR2130 also has the electric current enlargement and the current protection function; Undervoltage locking and can instruct the undervoltage and the electric current condition function; Input end noise abatement function; Simultaneously can also have the dead time which automatically the upper side, the breast actuate to (2μs) and so on functions. In practical application’s driving circuit as shown in Figure 6.
4.3 protection circuits and main circuit’s design
Because the driving circuit part has the current protection function, therefore, the protection circuit part has only designed the voltage protection, including inputs the pressure, the undervoltage to protect and to output the pressure, the undervoltage protection. Protection circuit as shown in Figure 7. And, these kind of protection function realizes the electric circuit is similar, namely output (or input) voltage after the differential pressure delivers comparator’s opposition end, comparator’s synchronism termination assigns the voltage. Their difference lies in comparator’s output to be different, namely inputs has pressed and has output when presses, the comparator outputs the low level; When input undervoltage and output undervoltage, the comparator outputs the high level. After front 3 kind of protection circuit’s output undergoes 4011 operations, becomes “or” relations, namely, so long as has one kind of breakdown occurrence, obtains the fault signal is the high level, delivers CPU outside to interrupt the port to carry on corresponding processing. When outputs the undervoltage, the comparator outputs the high level, the light emitter diode lightens, simultaneously the buzzer sends out the sound warning.
Because the DC/DC part’s output voltage is quite low, therefore, the main circuit part uses the power switching valve is low pressure MOSFET. At the same time, to reduce in the switching process power tube’s burden, has used the cushion circuit in the main circuit part, as shown in Figure 8. And the three-phase contravariant bridge is composed of 6 MOSFET, D1~D6 was the MOSFET bringing integration quick recovery diode, R, D, C composes the cushion circuit (also to be possible to see is U, V, W three-phase cushion circuit’s equivalent circuit).
5 experiment analyses and conclusion
In this design, has carried on electric circuit’s simulation and the experiment to each part, and completes prototypical one. When normal operation the electrical machinery line voltage and electric current experiment profile like chart 9 and shown in Figure 10. This design has the volume to be small, the weight is light, the output voltage is stable and the current harmonics is small, the power factor higher merit, estimated that in overcomes stirs up the converter power switch’s voltage electric current stress question which increases after the output causes, according to this according to the design production’s product will have a higher performance-to-price ratio, has the market competitiveness.
