The switching power supply for electrocar based on UC3842 is designed


Posted on Feb 7, 2014    9329

The motor vehicle is the automotive of no emission at present, as the means of transportation of green, will bring the huge change to human society in the 21st century. And the direct-flow brushless electric machine relies on its fine characteristic to already become major technology and developing direction of the electrical machinery field of mo


The switching power supply for electrocar based on UC3842 is designed
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tor vehicle. The of good performance brushless electric machine system is due to the of good performance control module, and the characteristic of the control module depends on the characteristic of the electric power supply to a great extent, so the high-quality power supply power system occupies quite important position in the whole motor vehicle system. The control module of the direct-flow brushless electric machine is a numerically controlled electronic system which adopts the microcontroller. The switching power supply that is controlled on the basis of UC3842 high-performance electric current mode PWM generator is suitable for applying to this kind of system. Originally design realizing the complete segregation exported and input through the small-scale high-frequency voltage transformer, not only has raised the efficiency of the power, has simplified the peripheral circuit, also reduced cost and volume of the power. The voltage stabilization of power supply, the ripple is small, incessant, reliable performance. Single-end anti exciting type typical structure such as Fig. 1 of varying. Single-end means the magnetic core of the voltage transformer only works on the collinear side of magnetic Hysteresis; It means when the gas switching tube is turned on, the stored energy in the primary coil that anti exciting, and the secondary winding is obstructed; When the gas switching tube is shut off, the energy in the primary coil is released and supported through the secondary winding. This is a trimmer of a kind of low cost, can accomplish the partial complete segregation of Input/Output, there are better voltage percentage modulations. UC3842 chip is the products of Unitrode Company, it is a kind of high-performance single-ended output type electric current controlled pulse width modulator chip. Their functional block diagrams are shown as in Fig. 2. By 5V reference, Shaker controlling the duty ratio to set up, determines comparator, PWM latch, high gain E/A error amplifier and is suitable for the high-current push pull output circuit of the propulsion power MOSFET etc. to make up with electric current. Its leading particulars is: UC3842 chip can meet better electrical performance and lower cost at the same time, is widely used in the low-powered switching power supply of 20- 50 W. 8 feet are its internal reference voltage 5 V in the picture ; 7 feet are its end of power, the cut-in voltage of the chip work is 16V, the voltage of Under Voltage Lock Out is 10 V; 4 feet connect the resonator, produce the sawtooth wave of the required frequency, RT connects among 4, 8 feet, CT connects between 4 feet and ground. 1 and 2 feet, in order to compensate the oppisite phase input end of end and internal voltage comparator; Compare with voltage error signal of a foot from 3 foot incoming electric current feedback signals, produce one PWM puls e-width modulation The wave, from 6 feet Ausgang Output this signal, control the make-and-break of the power device. 3 feet measure the input end for the electric current. Because of set up the intersection of electric current and clamping of 1 V by the intersection of electric current and the intersection of comparator and input end, too big enabling the electric current sense resistor R13 shown as in Fig. 3 as electric current. The voltage had exceeds 1 V namely 3 foot level is greater than 1 V When, will shut off PWM pulse, thus will achieve the protective purpose of the current limiter. This text regards UC3842 as the key control unit, has designed the anti exciting type stabilized voltage s

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