In this paper, One Cycle Control technique is implemented in the bridgeless PFC. By using one cycle control both the voltage sensing and current sensing. rectifier and power factor correction circuit to a single circuit, the output of which is double the voltage implementation of One Cycle Control required a better controller. . The figure shows a typical buck converter using PWM technique. PWM switching technique is used here as implementation of One Cycle Power Factor Correction, Bridgeless voltage Doubler, Buck Converter, One Cycle Control This problem can be solved by using bridgeless converters to reduce the.
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Options tecnhique accessing this content: As a future work the hardware circuit should be implemented using one cycle control. G1 and G2 shows the gating signals generated by the one cycle controller which is used to control the switching operation of S1 and S2. Related article at PubmedScholar Google. This circuit also act as a voltage doubler circuit whose output voltage is greater than a single buck converter. Hsing ac-dc converters has a diode bridge rectifier followed by power factor correction circuit.
The PWM control method which was already used for controlling the switching has been studied and analysed in this paper using suitable waveforms. I extend my deep sense of gratitude and hearty thanks to Prof.
When integral value Vint reaches the control reference,Vref comparator changes its state and turns the switch transistor off and the integrator is reset to zero at the same time. As long as the area under the diode-voltage waveform in each cycle is the same as the control reference signal, instantaneous control of the diode-voltage is achieved. The operation is explained for positive half cycle during which switch Q1 is operating and Q2 is off ,Vref is the reference voltage. The bridgeless voltage doubler buck converter configuration has been studied.
If the power supply voltage is changed, for example by a large step up, the rbidgeless ratio control does not see the change instantaneously since the implementztion signal must change first. This method provides greater response and rejects input voltage perturbations. At each instant the integral value is being compared with a reference Vref.
Figure shows a typical buck converter employing One Cycle control. The output of the flip flop is the required gating pulse for the switches. Each converter is operating during positive and negative half cycle respectively. The operation of an OCC controller is explained by means of the following waveforms.
Therefore, the output voltage jumps up and the typical output voltage transient overshoot will be observed at the output voltage. Any change in the input voltage must be sensed as an output voltage change and error produced in the output voltage is used to change the duty technjque to keep the output voltage constant.
The clock triggers the RS flip-flop to turn ON the transistor with a constant frequency. The results obtained are also presented in this paper. This new control method is very general and directly applicable to all switching converters.
This circuit generates the output voltage which technqiue double than a conventional buck converter since it is having two buck converters operating in a complete cycle. Beidgeless lower power levels the drawbacks of the universal-line boost PFC front-end may be overcome by implementing the PFC front-end with the buck topology . The voltage available at the output is double the voltage across each capacitor.
One Cycle Control of Bridgeless Buck Converter | Open Access Journals
Since the output voltage always follows the switched variable the output remains constant at the reference value. Therefore, one cyclw control gives an attractive solution for the bridgeless PFC circuit.
A large number of switching cycles is required before the steady-state is reached. This drop of efficiency at low line can cause increased input current that produces higher losses in semiconductors and input EMI filter components. When the integrated value of the diode-voltage becomes equal to the control reference, the transistor is turned OFF and the integration is immediately reset to zero to prepare for the next cycle.
This means that it has slow dynamic performance in regulating the output in response to the change in input voltage. Switch mode power supplies without power factor correction will introduce bridgeless content to the input current waveform which will ultimately results in a low power factor and hence lower efficiency.
One Cycle Control of Bridgeless Buck Converter
The implemnetation obtained during the hardware implementation are presented below. In this paper ,a new control method called One Cycle Control is used for controlling the buck converter during both half of supply voltage.
This PFC rectifier employs two back-to-back connected buck converters that operate in alternative halves of the line-voltage cycle. The output obtained is amplified and is fed to an integrator with reset. This technique provides fast dynamic response and good input-perturbation rejection. By using one cycle control both the voltage sensing and cotnrol sensing issues of the bridgeless PFC circuit can be solved.
The simulink model of the bridgeless buck converter is shown below. MOSFET is used as the switching device of the buck converter Usually pulse width modulation techniqye is used for switching operation and clamped current mode control is used for controlling the buck converter. The output is always influenced by the input voltage perturbation. Although the circuit structure is simple, the location of the boost inductor on the AC side makes it difficult to sense the AC line voltage and inductor current.
The hardware implementation for the prototype texhnique made for 12V dc and PWM technique is used as the switching technique.
As a result the control reference is linearly modulated into the brridgeless ratio signal. The simulation is done at a switching frequency of 65kHz. The total output obtained is the sum of voltage across each capacitor of the buck converters which are operating during positive and negative half respectively.
In PWM control, the duty ratio pulses are produced by comparing control reference signal with a saw-tooth signal. But this circuit suffers from significant conduction and switching losses due to larger number of semiconducting devices.
The simulink model of OCC controller is shown below. The output voltage V0 is fed to the integrator. At the same time, since the AC side inductor structure makes the output floating regarding the input line, the circuit suffers from high common mode noise. A bridge diode rectifier followed by a power factor correction circuit which is either a tecnnique or boost frontend is commonly used for all switched mode power supplies.
This circuit consists of two buck converters connected in parallel in series out manner.