Dc speed control are generally USES the silicon-controlled rectifier control of the conduction angles method, this paper introduces the chopper PWM technology, applied to high accuracy of dc servo control system, Harbin HSBC electronic technology Co., LTD, a professional maintenance and design dc servo control system.

PWM, common in the small and medium-sized power system
It adopt by using a pulse width modulation technology, its work degree for principle is: through a change, "through the wide degree pulse ", make dc motor armature voltage on the "" changes than of empty, so as to change the evenness of the armature voltage values, control motor speed.
PWM speed regulation system has the following characteristics:
1. The main circuit is simple, hard work, and less component rate for open shut, so the state circuit conduction consumption is small, with high efficiency installation;
2. Open shut high, can avoid the frequency of vibration of the machine tool, for smooth; work area
3. The work rate is low to smaller motor, high speed and precision, set a
4. Low speed performance is good, steady speed high accuracy, speed surrounded wide van;
5. System wide frequency band, dynamic ring should be good, strong resistance to interference to the common PWM drive system. The main circuit of reactive rate (the amplification) tectonic model T have the H and the bipolar type by H PWM drive circuit principle for work.

Figure 1, 1-2-2-VD1, VD2 VD3, VD4, free-wheeling diode, for VT1, used to maintain, VT3, VT4 VT2 three extremely
Tube in the photo, Ub1 = Ub4 =-Ub2 =-Ub3. When Ub1 = Ub4 for timing, VT1 and VT4 conductivity, and deadlines, VT3 VT2 at UAB voltage = US; When Ub2 = Ub3 for timing, VT1 and VT4 deadline, but not immediately VT3 VT2 and conduction, because of the electric motor to existing potential AB free-wheeling, free-wheeling VD3, maintenance and VD2 flows through the four transistor, free-wheeling in this process if not get a great attenuation, and Ub1 = Ub4 stage is coming, it was VT3 no conductivity and VT2 hour; If a free-wheeling in this process have to a very large, and VT3 VT2 is attenuation conduction, at UAB voltage =-US. Obviously, Ub1 = Ub4 time and is Ub2 = Ub3 is same time at UAB uniform value = 0, electric motor state still; Ub1 = Ub4 for long in the Ub2 is in Ub3 = is when the UAB uniform, time value > 0, motor are turning the UAB motor reversal, the smaller the UAB value, the higher the speed.
Visible, need to control Ub1, Ub4, Ub2 Ub3, the pulse width, can control motor speed, and can be turned to and to a dynamic static, be helpful for positive &negative dead area to eliminate.

So the design of PWM is finished, a shortage of place please everyone for your comments. Here I will recommend all Harbin HSBC electronic technology Co., LTD. Of the web site there are many dc governor related articles, web site has a lot to learn articles for beginners, hope everybody can together with progress! .

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