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DC chopper circuit of Matlab / Simulink Simulation

Print View , by: iSee ,Total views: 122 ,Word Count: 1018 ,Date: Sun, 28 Jun 2009 Time: 5:25 AM

0 Introduction

In power electronics technology, will be a DC voltage through the power electronic converter transform to another fixed or adjustable voltage value of the transform, known as the DC-DC conversion. DC conversion circuit uses a very wide range, including the DC motor drive, switching power supply, single-phase power factor correction, as well as other areas for AC-DC power supply.

Discussed here PWM (pulse width modulation) control circuit of the step-down (Buck Chopper), and visualization applications matlab simulation tool Simulink, the buck-boost circuit and the circuit (Boost-Buck Chopper) conducted a modeling, Simulation results and analysis, not only to avoid the cumbersome process of mapping and calculating, but also try to be a kind of intuitive, efficient DC analysis of the new method of circuit transformation.

1 Working principle of DC chopper

DC step-down chopper circuit schematic in Figure 1 (a) as shown. Map with an ideal switch S on behalf of the actual power electronic switching devices; R for pure resistive load. When the switch S connected in time ton, the added load on the resistance of the voltage U. DC power supply equal to Ud. When the switch S in the off time toff, the output voltage to zero, DC transform waveform in Figure 1 (b) below.

DC chopper circuit of Matlab / Simulink Simulation

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Average output voltage as follows:

DC chopper circuit of Matlab / Simulink Simulation

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Where: ton for the chopper switch S in a cycle of on-time; toff for the chopper switch S in a cycle time of the turn-off; Ts for the chopper cycle, T = ton + t0ff; D for the duty cycle, D = ton / Ts.

This shows that the change in on-duty cycle D, Chopper will be able to control the output voltage U. Size. Because D is between 0 ~ 1, the coefficient changes, so the output voltage U. The total is less than the input voltage Ud, which is step-down output.

DC chopper 2 Modeling and Simulation

2.1 Simulation Model and Parameter Settings

(1) constituted by the IGBT DC step-down chopper circuit (Buck Chop-per) modeling and parameter setting

Figure 2, composed of the grounds of IGBT simulation model Buck DC-DC converter, IGBT according to the default parameter settings, and to remove the buffer circuit, that is, Rs = 5 ΩQ, Cs = 0; voltage source parameters from Us = 200 V, E = 80 V; load parameters R = 10 Ω, L = 5 mH.

DC chopper circuit of Matlab / Simulink Simulation

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(2) DC step-down chopper circuit simulation

Open the Simulation Parameters window, select ode23tb algorithm, relative error is set to 1e-03, the beginning of simulation time is set to O, stop the simulation time is set to O.01 s, the control pulse cycle is set to O.001 s (frequency of 1 000Hz), control 50% duty cycle pulse. After setting the parameters, start simulation, the simulation results of Figure 3.

DC chopper circuit of Matlab / Simulink Simulation

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As can be seen from Figure 3, the load on the voltage of 100 V, 160 V, 80 V, to meet the

DC chopper circuit of Matlab / Simulink Simulation

2.2 DC Buck Chopper (. Boost-Buck Chopper) Simulation

Buck Chopper average output voltage as follows:

DC chopper circuit of Matlab / Simulink Simulation

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Where: negative sign that the output voltage and input voltage RP. When D = O.5 pm, U. = Ud; when D> O.5 when, U. > Ud, for step-up transform; when D <0.5 pm, u. <Ud, for step-down transformation.

Figure 4 gives the composition of the IGBT components Buck Chopper circuit simulation model, IGBT parameters set by default and to remove the buffer circuit, load R = 50 Ω, c = 3e-05 F, slip inductance L = 5 mH. Start simulation, the simulation results of Figure 5.

DC chopper circuit of Matlab / Simulink Simulation

Picture not clear? Click here to view the image (larger).

As can be seen from Figure 5, the load on the voltage of 100 V, 33 V, 300 V, to meet the

DC chopper circuit of Matlab / Simulink Simulation

Buck chopper and with theoretical analysis.

3 Conclusion

Through the above analysis of the simulation process can be obtained the following conclusions: (1) DC Converter mainly controlled the whole power electronic devices as the switching device, by controlling the main circuit and disconnect the connection will be a constant of the DCintermittent square wave, the post-filter into a voltage adjustable DC output voltage. The use of Simulink to buck Buck Chopper Chopper and the simulation results carried out a detailed analysis, using conventional circuit analysis method has been to compare the output voltage waveform, and further verified the correctness of simulation results.


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