Structural composition and working principle Due to the variability of the electrorheological effect and the test of the electrorheological fluid performance, various performance requirements for the power supply have been increased. The power supply must provide a sufficiently high voltage that should generally not be lower than V and continuously adjustable throughout the V interval. In the study of electrorheological effect and testing of electrorheological liquid properties, it is first required to provide high electric field strength, and in order to measure the influence of electric field strength on various properties, the voltage must be continuously adjustable to ensure that a continuous structure can be established. Changing field strength.
Most high-voltage power supplies generally use multi-stage boost amplification, and then obtain high voltage output through high-voltage transformers. The disadvantages of these methods are that the power supply is bulky, the production cost is high, and the structure is complicated. As shown in the micro-controllable high-voltage power supply can make up for these shortcomings.
Structure Composition The high voltage includes two DC voltage supply circuits, a protection circuit composed of an integrated pulse width modulator and an oscillation circuit, an inverter main circuit, and a voltage doubler rectifier circuit that outputs a high voltage.
The DC voltage supply circuit includes one line of 1V. The voltage adjustment circuit is composed of a three-terminal adjustable voltage regulator. One line of 12V is supplied to the pulse width modulation controller via the output of the three-terminal regulator 7. The oscillation part of the oscillation and protection circuit is integrated. The pulse width modulator is composed by changing the resistance value of the potentiometer R, adjusting the duty cycle of the output pulse, adjusting the oscillation frequency of the circuit, limiting the flow resistance to the field effect transistor IRF control terminal G; the protection part is controlled by the relay K, Silicon composition. The main circuit of the inverter is mainly composed of a constant current inductor L, a storage capacitor C, and a field effect transistor IRF high-frequency transformer T. An end of the constant current inductor L is connected to an output terminal, and the other end is connected to a field effect transistor. The primary winding of the high-frequency transformer T is made of a 1mm enameled wire wound around 10 turns, and the secondary winding is a secondary winding of a television separate output transformer. The voltage doubler rectifier circuit consists of a small volume of high voltage capacitors and a rectifier diode with a high backpressure silicon column.
The output adjustment and R2 frequency adjustment use a digital potentiometer that is controlled by a single-chip microcomputer and has a small size, light weight, and no external circuit. Use the same bus more and adjust each other independently.
Working principle The trigger pulse generated by the pulse oscillator consisting of an integrated pulse width modulator is applied to the IRF control terminal of the FET via the current limiting resistor. G. The resistance of the potentiometer R is changed, and the duty ratio of the output pulse can be adjusted. The oscillation frequency f is determined by R2 and C41.
When the G-point trigger pulse does not arrive, the IRF is not conducting. The power supply charges the capacitor C through the constant current inductor L and stores the energy in C. After the trigger pulse arrives, the IRF is triggered to conduct. The charge on C passes through the IRF. The D pole discharges the primary winding of the high-frequency transformer T. Because the primary windings of C and T constitute an under-damped oscillation circuit, the C can be charged during the IRF conduction period, and the recoil charge is discharged through the IRF internal anti-parallel diode.
The discharge current turns off the IRF and shuts down, completing a sinusoidal oscillation. The intermittent sinusoidal voltage at the two ends of the primary winding of T is boosted by T, and the output high voltage is supplied to the load by the voltage doubler rectification. Adjust the resistance of R1 to achieve continuous adjustment of the power output voltage. R2 and C7 form a spike absorption loop, protecting IRF.R4, D42, thyristor VS, and relay K to form a power supply over-current protection circuit. When the power supply works normally, VS is in cut-off state. When the output of the high-voltage generator is discharged for some reason or the capacitance of the voltage doubler rectifier circuit and the diode is damaged, the over-current phenomenon is caused, and the primary side winding of T will instantaneously flow a large current. The potential of R4 rises, and the control pole of VS gets enough trigger voltage to turn on. K gets the electric action, its contact 12 is disconnected, the trigger pulse stops, the high voltage drop of the power output is zero, thus has protected the whole circuit. When the generator is operating normally, the voltage waveforms of the G and S poles of the IRF are as shown.
Input/Output Characteristics In order to characterize the output voltage of the high-voltage power supply, the secondary winding of T is wound with the same number of turns as the primary winding, connected to the 050V voltmeter on the front panel of the power supply, and the high voltage output is connected to the high voltage type. The passive probe is blocked and the power output voltage is measured through an oscilloscope. In order to test the performance of the power supply in a wider range, the input voltage is adjusted to 0V during the experiment. Under different voltage input conditions, the high voltage output terminal outputs different high voltages. The experimentally measured data is plotted as the input and output characteristics. .
The operating characteristic curve is a pulse width modulation controller whose frequency can be arbitrarily set. In operation, its operating frequency depends on the resistance of the timing element Rt6 externally connected to the sawtooth wave generator, that is, the oscillator, and the capacitance on the Ct5 pin. The value of its oscillation frequency. The high voltage power supply takes Ct = 20nF, Rt is continuously adjustable between 212k, so the operating frequency of the power supply is approximately in between. The experiment measured the output high voltage value of the power supply in the above operating frequency range under different input voltages, and plotted the curve as shown.
The relationship between the output high voltage and the operating frequency is not difficult to find. When the high voltage power supply is at the frequency, the high voltage output under the same conditions is higher. Therefore, when the high voltage power supply is working, you can choose to work near this frequency.
At the same time, when the input voltage is 21.V, the experimental maximum output voltage changes with different duty cycles. As shown. When the duty cycle exceeds about 46%, the power supply output voltage will be very unstable; when the duty cycle is 20.1%, the output voltage is higher, and the stability of the voltage output is better, so when the power supply is working, the best Select duty cycle 20%.
Conclusion The idea of ​​the high-voltage power production designed in this paper is different from the conventional step-by-step boost amplification, and the single-chip microcomputer controls the output of high-voltage static electricity. The voltage adjustment is rapid and accurate. In combination with the sensor input and current change control strategy, the semi-active control of the electro-hydraulic power suspension of the engine can be achieved. The high voltage power supply was tested for performance and the characteristic curve of the high voltage power supply was obtained. The high voltage power supply has a high output voltage when the duty ratio is 11% and 17kHz and the stability of the voltage output is also good. The current power supply has the characteristics of small size, light weight, simple structure, and low price in the use of electrorheological technology, and is convenient for installation and use in a limited space of a vehicle.
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