1、英文原文Microcontroller-Based Single-Phase Automatic Voltage RegulatorNang Kaythi HlaingHardware Technology Department Computer University(Myanmar)nangkthi.23Abstract:This paper proposes the design and implementation of a micro controller-based single-phase automatic voltage regulator (AVR). The basic b
2、uilding blocks for this design include a PIC 16f 628 microcontroller, a triac,a step-up transformer, a zero crossing circuitry and a load voltage sensing circuitry. This design is based on the principle of phase control of ac voltage using a triac. The trigger pulse for the triac is delayed by the m
3、icrocontroller to provide the desired regulator terminal voltage. This voltage is always sensed and fed back to the microcontroller via a measuring unit to get a continuous control system. One of the intensions to develop this AVR is to use it in domestic heating and lighting controls. It can also b
4、e used as an adjustable voltage source by adjusting a variable resistor in the voltage sensing circuitry. It is also intended to introduce a compact AVR and to demonstrate the usefulness of the PIC microcontroller in power control field.Keywords:voltage regulator (AVR); PIC microcontroller; autotran
5、sformer; phase control; triacI. INTRODUCTIONThe automatic voltage regulator or A VR, as the name implies, is a device intended to regulate voltage automatically: that is to take a varying voltage level and turn it into a constant voltage level 4. Automatic voltage regulators are widely used in elect
6、rical power field to obtain the stability and good regulation of the electric system. In typical A VRs, switching is done by electromagnetic relays, or servomotor, or electronic device, which automatically selected taps in the transformer to get the required voltage to boost (add) or buck (subtract)
7、 the input voltage. Relay tapchangers have the problems such as power lost momentarily during relay change over, unstable output and relay contact damages. Servo motor types gave the disadvantages that they have low life of the contact points of the relays 5. Solidstate electronic device used AVRs c
8、an overcome most of the above problems as they do not use any moving part and the output voltage can vary from cycle to cycle 13. For microcontrollers, they have been proven their abilities to perform well in a wide range of applications 26. Nowadays, many microcontroller-based A VR can be available
9、 in markets. One of them is Sollatek AVR 7. In this paper, it is aimed to implement PIC microcontrollerbased solid sate switching automatic voltage regulator.II. OVERVIEW OF THE PROPOSED DESIGNThe basic building blocks for this design include a PIC l6f 628 microcontroller, a triac, a 400V autotransf
10、ormer, a zero crossing circuitry, and a load voltage sensing circuitry. This design is based on the principle of phase control of ac voltage using a triac, where triggering (firing) delay is determined by the PIC microcontroller. Fig. 1 shows the important com onents of our AVR.Figure 1. Block diagr
11、am of microcontroller-based automatic voltage regulatorIII. HARDW ARE IMPLEMENTATION AND OPERATION OFTHE SYSTEM COMPONENTSThe general operation of the components goes like this: line voltage is stepped up to 400V using an autotransformer. Zero crossing detection circuit provides a pulse to the PIC w
12、henever the line voltage reaches OV. After getting the zero cross pulse, the PIC determines the delay to send a gatetrigger pulse for the triac in accordance with the output of the regulator terminal voltage. Triac, here, is used to control the phase of the line voltage. The regulator terminal volta
13、ge is always sensed and fed back to the PIC via a measuring unit. AControl or Regulating Unit In control unit, PIC l6f 628 forms the heart of the unit where BTA l6(600C) triac is used as an ac switch. It is driven by PC 817 optocoupler and is triggered with a pulse sent from the PIC by taking some d
14、elay after every zero crossing of each ac main cycle. The switch is open if no trigger pulse is given to the gate. It is closed if pulses are given continuously twice every ac wave. In our design, a 16 ampere triac is used to insure an adequate margin of safety. The triac is mounted to a heat sink w
15、hich is large enough to remove the heat caused by bidirectional current flow of the triac. To suppress voltage transients a 100 resistor and a 0.1uFcapacitor is used as a snubber network across the triac. The presence of this network can improve the turn-on performance of the triac. In this control
16、unit PIC 16f 628 plus PC 817 is used as a triac gate firing circuit, which is designed with care to ensure that unwanted conduction,i.e.,loss of control,does not occur when triggering lasts too long. The gate-cathode resistor protects the device from false triggering due to noise.Fig. 2 shows the interface of PIC 16f 628 with other components contained in our AVR.Figure 2. Microcontroller interfaceBMeasuring or Feedback Uni
