Implementation of One cycle control technique for Buck converter

PRESENTATION ON Implementation of One cycle control technique for Buck converter.

INTRODUCTION:

The one cycle control technique is proposed to control the duty ratio ‘d’ of a switch such that in each cycle the average value of a switched variable of the switching converter is exactly equal to or proportional to the control reference in the steady state or in a transient.

The control technique is general and applicable to all types of PWM, soft-switched switching converters for either voltage or current control in continuous or discontinuous conduction mode.

OBJECTIVE:

Our aim to control the Buck converter output by one cycle control technique.

We Apply the control technique for the following condition By Orcad simulation.

1. Rejection to Power Source Perturbation
2. Following the Control Reference
3. Variation of load.

One-Cycle Control Circuit Diagram

One-Cycle Control Theory

A switch operates according to the switch function k ( t ) at a frequency fs = l/Ts,

where T_on+ T_off= Ts.

The input signal X(t) at the input node of the switch is chopped by the switch and transferred to the output node of the switch to form a switched variable y(t).

Y(t) = k ( t ) x ( t ) (5)

Suppose the switch frequency fs Is much higher than the frequency bandwidth of either the input signal x(t) or the control reference Vref.

The switched variable y(t) at the output node of the switch is the product of the input signal x(t) and the duty-ratio d ( t ) ; therefore, the switch is nonlinear

SIMMULATION OF ONE-CYCLE CONTROL CIRCUIT DIAGRAM:

At Normal condition:

The Buck converter Output:

(1) Rejection of Input Variation

(2) Output follows the control Reference:

Variation of Load:

Normal output at load 150 ohm.

If we Change the load 150ohm to 200ohm than the output

METHODOLOGY:

1. Theoretical study and analysis of One cycle control technique .
2. Simulate the One cycle control of Buck converter circuit with ORCAD 9.2.
3. Collect the necessary components.
4. Test each portion of circuit individually.
5. Implementation the One cycle control of Buck converter circuit practically.

Experimental Setup

Opto-coupler wave Shape

Flip-flop output waveform

Inverted amplifier output

Buck Converter

Integrator output wave shape:

Comparator Output

Future Works:

The One-Cycle Control technique will be applied for the following type of Switches.

1. Constant ON-time switch.
2. Constant OFF-time switch
3. Variable switch.

CONCLUSION:

converters with One Cycle Control are capable of rejecting the power source perturbations completely the average value of the switched variable at the switch output node is able to follow the control reference within one cycle. The One-Cycle Control concept is straightforward and its implementation circuits are simple, yet it provides excellent control.

REFERENCE:

1. One-Cycle Control of Switching Converters. Keyue M. Smedley, Member, IEEE, and

Slobodan Cuk, Senior Member, IEEE.

An Integrated One-Cycle Control Buck Converter With Adaptive Output and Dual Loops for Output Error Correction. Dongsheng Ma, Member, IEEE, Wing-Hung Ki, Member, IEEE, and Chi-Ying Tsui, Member, IEEE.

One cycle control of three-phase VAR compensators and active power filters. Sandeep Bala (99007013) Department of Electrical Engineering, Indian Institute of Technology, Bombay, April 2003.

Keyue Ma Smedly. “Control Art of Switching Converter” California Institute of Technology, Pasadena, California, June 21, 1990.

Submitted by Ratan Kanti Das and Sufal Chandra Dey.