Now, If we investigate about the efficiency, It is how much power we provide inside the circuitry and how much we get at the output. Improve efficiency of Boost Converter Circuit This is the additional circuitry, which is needed along with inductor, diodes, and capacitors. The reference feedback voltage is done using a resistor divider network. Thus simple circuitry design is achieved using the modern switching regulators. The PWM also changed to a position when the output voltage creates zero error voltage and by doing this, the closed control loop system executes the work.įortunately, Most modern Switching boost regulators have this thing inbuilt inside the IC package. Due to error voltage change, the comparator controls the PWM output. When the output voltage changes, the error voltage also affected by it. It will take a sample of the output voltage and to subtract it from a reference voltage and create a small error signal, then this error signal will be compared to an oscillator ramp signal and from the comparator output a PWM signal will operate or control the switch circuit. This circuit also uses for continuous operation in the steady state. The control circuit controls the amount of time the switch remains open or close, depending on the current drawn by the load. Most common control technic includes PWM or Pulse Width Modulation technic which is used to control the duty cycle of the circuitry. In the above image, an Error amplifier can be seen which sense the output voltage across the load using a feedback path and control the switch. So, for a complete basic boost regulator circuit, we need an additional circuitry which will vary the duty cycle and thus the amount of time the inductor receives energy from the source. So, for the duty cycle variation, we use a control circuit across the switch.
If we control the duty cycle, we can control the steady-state output of the boost converter. PWM and Duty Cycle for Boost Converter Circuit Duty Cycle (D) = Ton / (Ton + Toff)įor the boost switching regulator the Vout will be Vin / ( 1 – D )
We can also calculate the Vout using duty cycle. We can say that, Vout = Vin + Vin x (Ton / Toff) Vout = Vin x ( 1 + Ton / Toff) If we assume that the inductor charge time is Ton and the circuit has an input voltage, then there will be a specific Toff or discharge time for an output voltage.Īs the average inductor voltage is equal to zero in steady state we can construct boost circuit using following terms Vin X Ton = Toff x VL VL = Vin x (Ton / Toff)Īs the output voltage is equal to the Input voltage and average inductor voltage (Vout = Vin + VL) For this condition, the average current through the inductor is also in steady-state. When the switching regulator is in steady-state operating condition, Inductor’s average voltage is Zero during the entire switching cycle. In the above graph, the inductor current drops with time when the switch becomes off. Higher the inductor voltage, faster the current drop through the inductor. The Inductor current drop rate with time is directly proportional to the inductor voltage. The Output voltage rises until Voltage through the inductor = L * (di / dt ) is reached. When the output voltage rises, the current slope through the inductor reverses. Now, when the switch again gets off or became open, the inductor current flow through the diode and charge the output capacitor. The Current is increasing linearly with time when the switch is closed or ON. The x-axis denotes t (time) and the Y-axis denotes I (current through the inductor). In the upper graph, showing the Charging phase of the inductor. The linear current rising rate is proportional to the input voltage divided by the inductance di / dt = Voltage across Inductor / Inductance The current through the inductor rises at linearly with time. The Diode prevents the capacitor discharge through the switch to the ground. In this situation, if the switch gets close the Vin is frightened across the inductor. If we assume that the switch has been in open position for a long time, the voltage drop across the diode is negative and the voltage across the capacitor is equal to the input voltage. In case of switching boost regulators, there are two Phases, One is Inductor Charge phase or the Switch on phase (Switch is closed actually) and the other one is Discharge phase or the switch off phase (Switch is open). We will understand how the inductors transfer energy in the upcoming images and graphs.
Also, the inductor stores energy, the energy measured in Joules E = (L * I 2 / 2)
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