Difference Between Time Ratio Control and Current Limit Control
Difference Between Time Ratio Control and Current Limit Control Introduction: ďƒ˜ In DC-DC converters, the average output voltage is controlled by varying the alpha (Îą) value. This is achieved by varying the Duty Cycle of the switching pulses. Duty cycle can be varied usually in 2 ways: Time Ratio Control and Current Limit Control.
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Difference Between Time Ratio Control and Current Limit Control Basic Methods Of Control There are two kinds of control strategies used in DC choppers namely • Time Ratio Control and Current • Limit Control. The average value of the o/p voltage can be changed.
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Difference Between Time Ratio Control and Current Limit Control Time Ratio Control In the time ratio control the value of the duty ratio, K =TON /T is changed. Here ‘K’ is called the duty cycle. There are two ways to achieve the time ration control, namely Variable Frequency Constant Frequency Operation.
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Difference Between Time Ratio Control and Current Limit Control Constant Frequency Operation In constant frequency control strategy operation. The ON time TON is changed. Keeping the frequency, i.e, f=1/T, or time period ‘T’ constant. This operation is also named as PWM (pulse width modulation control). Hence, the output voltage can be varied by varying ON time.
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Difference Between Time Ratio Control and Current Limit Control Constant Frequency Operation
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Difference Between Time Ratio Control and Current Limit Control Variable Frequency Operation In variable frequency control strategy operation. The frequency (f = 1/T) is changed, then the time period ‘T’ is also changed. This is also named as a frequency modulation control. In both cases, the o/p voltage can be changed with the change in duty ratio.
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Difference Between Time Ratio Control and Current Limit Control Variable Frequency Operation
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Difference between Time Ratio Control and Current Limit Control Disadvantages of Control Strategy The frequency has to be changed over an extensive range of the o/p voltage control in FM (frequency modulation). The designing of the filter for wide frequency change is quite difficult. For the duty cycle ration control. Frequency change would be varied. As such, there is a possibility of intrusion with systems by positive frequencies like telephone lines and signaling in frequency modulation (FM) technique.
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Difference between Time Ratio Control and Current Limit Control Disadvantages of Control Strategy ďƒ˜ The huge OFF time in FM (frequency modulation) technique may make the load current irregular, which is unwanted. ďƒ˜ Therefore, the constant frequency system with pulse width modulation is preferred for choppers or DC-DC converters.
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Difference between Time Ratio Control and Current Limit Control Current Limit Control In a DC to DC converter, the current value varies between the maximum as well as the minimum level of constant voltage. In this method, the DC to DC converter is turned ON & then OFF to confirm. That current is preserved constantly between the upper limits and also lower limits. When the current energies beyond the extreme point, the DC-DC converter goes OFF.
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Difference Between Time Ratio Control and Current Limit Control Current Limit Control
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Difference Between Time Ratio Control and Current Limit Control Current Limit Control While the switch is in its OFF state, current freewheels through the diode and falls in an exponential manner. Chopper is turned ON when the flow of current spreads the minimum level. This technique can be utilized either when the ON time ‘T’ is endless or when the frequency f=1/T.
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Difference Between Time Ratio Control and Current Limit Control Conclusion ďƒ˜ We can conclude that DC-DC converters or choppers are presented along with the operation and its wave forms in each case. The different control strategies used in DC choppers are discussed.. As the name suggest, here the time ratio (i.e. the duty cycle ratio Ton/T) is varied. As is obvious from its name, in this control strategy, a specific limit is applied on the current variation. This is all about the differences between time ratio control and current limit control.
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