Brushless dc motor current sampling and protection circuit design of the
2. 1 hall sensor
hall current sensor is a kind of advanced, can isolate the main circuit loop, and the electronic control circuit of electric detecting element. It combines all the advantages of the transformer and shunt, and overcome the disadvantages of current transformer and shunt (Transformer is only applicable to 50 Hz frequency measurement; Shunt to isolation measurement), can measure arbitrary waveform of current, high accuracy, good dynamic performance, the working frequency band width, in this paper, the hall sensor using lime (lem）The company's LF205 -S, the maximum current of type sensor measuring range is: & plusmn; Is 200 A, effective measure range & plusmn; 100 A, when measuring current such as the scope of effective output voltage is: & plusmn; 4 V, the measuring accuracy of 1%, the dynamic response time is less than 7 & mu; S, tracking speed above a / 50 di/dt & mu; s。
2. 2 TL082 dual operational amplifier
TL082 is a generic J— FET dual operational amplifier. Motor that its characteristic is: low input bias and offset currents; The output is equipped with short circuit protection; Input stage with high input impedance built-in frequency compensation circuit, the current protection in circuit design, using TL082 constitute a half-wave rectifier circuit and adder has high precision, and because TL082 for dual operational amplifier, so saved the space of the control panel, makes the design more concise and compact circuit.
2. 3 TL431 three programmable parallel zener diode
TL431 is a good thermal stability performance of three-terminal adjustable shunt reference source. Its output voltage with two resistance can be arbitrarily set to Vref (2. 5 V）Within the scope of any value (to 36 VAs shown in figure 3)。 The device of the typical dynamic impedance of 0. 2Ω, it can be used in many applications instead of zener diode, the output is a fixed voltage value, computation formula is: Vout = (R1 + R2)x2. 5 / R2
figure 1 TL431 constant voltage 5 V output circuit diagram
when the R1 value is 0, R2 can be omitted, in this article, using TI431 constant-voltage voltage source 5 V, to power a comparator.
