Filters (PDF)

FILTERS Inductor Filter Pros: Filter Circuits 1.Noise Reduction: Inductor filters are To remove the AC components or filter them...

FILTERS Inductor Filter Pros: Filter Circuits 1.Noise Reduction: Inductor filters are To remove the AC components or filter them effective at reducing high-frequency noise out in a rectifier circuit, a filter circuit is and electromagnetic interference (EMI) from used. A filter circuit is a device that is used electrical signals. They are often used in to remove the AC components of the power supplies to eliminate or reduce rectified output but allows the DC voltage spikes and ripple. components to reach the load. 2.Improved Signal Quality: By removing A filter circuit consists of passive circuit high-frequency noise and spikes, inductor elements i.e., inductors, capacitors, filters can help improve the overall quality resistors, and their combination. The filter and stability of electrical signals, making action depends on the electrical properties them suitable for sensitive applications. of passive circuit elements. 3.Energy Storage: Inductors store energy in their magnetic fields, which can be For example, an inductor allows the DC to beneficial in certain applications. They can pass through it. But it blocks AC On the act as energy reservoirs, providing other hand, a capacitor allows the AC to additional power during brief periods of high pass through it. But it blocks the DC Some demand. of the important filters are given below. 4.Simple Design: The basic design of an 1.Inductor Filter inductor filter is relatively simple, consisting 2.Capacitor Filter of only two passive components (an 3.T Filter inductor and a capacitor). This simplicity Cons: Capacitor Filter: 1.Size and Weight: Inductors tend to be physically larger and heavier than other Pros: passive components, such as resistors and 1.High-Pass Filtering: Capacitor filters capacitors. This can be a drawback in are effective at blocking low-frequency compact or lightweight electronic devices. signals while allowing high-frequency 2.Limited Frequency Range: Inductor signals to pass through. They are commonly filters are most effective at filtering high- used to eliminate ripple and provide DC frequency noise, but their effectiveness voltage in power supply applications. decreases at very low or very high 2.Compact and Lightweight: Capacitors frequencies. Choosing the right inductor and are typically smaller and lighter than capacitor values is crucial to target specific inductors, making them suitable for frequency ranges. applications where space and weight 3.Energy Loss: Inductors have resistance constraints are critical. and can dissipate some energy as heat. This 3.Low Cost: Capacitors are relatively can result in energy loss in the filter, which inexpensive and readily available, which may be a concern in energy-efficient makes them a cost-effective choice for applications. filtering applications. 4.Complex Calculations: Designing 4.Simple Design: The basic design of a inductor filters can be more complex than capacitor filter is straightforward, with only designing simple passive filters. Calculating two passive components (a capacitor and a the appropriate values for the inductor and resistor). This simplicity facilitates easy capacitor to achieve the desired filtering integration into electronic circuits effect can require expertise. Cons: Cons: 1.Voltage Droop: In capacitor filters, the 5. Complex Ripple Reduction: Achieving output voltage can experience a gradual a specific level of ripple reduction may decrease over time due to the discharge of require careful selection of resistor and the capacitor. This can be a limitation in capacitor values. Designing precise applications requiring a constant voltage capacitor filters can be more complex than output. it initially appears. 2.Limited Filtering Range: Capacitor filters are most effective at filtering low- frequency noise and ripple. They are less effective at attenuating very high-frequency noise. Additional filtering stages may be required for comprehensive noise suppression. 3.Energy Storage: Unlike inductors, capacitors do not store energy. This means that they cannot provide additional power during brief periods of high demand, which could be a drawback in certain applications. 4.Voltage Ratings: Capacitors have voltage ratings, and exceeding these ratings can lead to capacitor failure, which may result in circuit damage or safety T Filter: T Filter: Pros: Cons: 1.Simplicity: T filters have a 1.Limited Bandwidth: T filters have a straightforward design with only three limited bandwidth, meaning they are passive components, making them cost- optimized for a specific range of effective and easy to implement. frequencies. Achieving wideband filtering 2.Customizable Response: By choosing may require more complex filter designs. specific resistor and capacitor values, you 2.Energy Loss: The resistors in T filters can tailor the filter to meet your frequency introduce energy losses in the form of heat, response requirements. which can be a concern in applications 3.Versatility: T filters can be used for both requiring high efficiency. high-pass and low-pass filtering, offering 3.Component Values: Precisely designing versatility for various applications. a T filter for specific cutoff frequencies may require careful selection of resistor and capacitor values. Component tolerances can affect filter performance. LC Filter Cons: Pros: 1.Component Sizing: Properly selecting 1.Effective Filtering: LC filters are highly the values of the inductor and capacitor to effective at filtering and shaping electrical achieve the desired filtering effect can be signals, allowing you to selectively pass challenging, especially for complex filtering desired frequencies while attenuating requirements. Designing precise LC filters unwanted ones. This is crucial in can be complex. applications where signal quality is essential. 2.Limited Bandwidth: LC filters have 2.Low Power Dissipation: LC filters are limited bandwidth and may not effectively passive components, meaning they don't filter signals with frequencies far from the consume power themselves. This is cutoff frequency. They are best suited for beneficial for applications where power applications within a specific frequency efficiency is a concern. range. 3.Simple Design: They have a relatively simple design, consisting of just two passive 3. Losses: Both the inductor and capacitor components—an inductor and a capacitor. can introduce some losses into the circuit, This simplicity makes them cost-effective including resistive losses in the inductor and and easy to implement in various circuits. dielectric losses in the capacitor. This can affect overall circuit efficiency. Cons: 4. Size and Weight: Inductors can be relatively large and heavy, which can be a limitation in compact or portable electronic devices. Smaller form-factor components may be preferred in such cases. 5. Complexity for Multistage Filters: In applications requiring multiple stages filtering, managing the interaction between stages and achieving the desired overall response can be complex Pi Filter Pi Filter Pros: Cons: 1.Effective Filtering: CLC filters provide 1.Limited Bandwidth: π filters are effective filtering by combining the optimized for either high-pass or low-pass advantages of both inductive and capacitive operation, which means they are less elements. They can offer good attenuation versatile compared to CLC filters in terms of of both high and low frequencies. filtering frequency ranges. 2.Low Power Dissipation: Like other 2.Energy Loss: The resistors in π filters passive filters, CLC filters do not consume introduce energy losses in the form of heat, power themselves, which can be which can be a concern in applications advantageous for power-efficient requiring high efficiency. applications. 3.Component Values: Precisely designing 3.Simple Design: They have a relatively a π filter for specific cutoff frequencies may simple design, consisting of three passive require careful selection of resistor and components—an inductor and two capacitor values capacitors. This simplicity makes them cost- effective and easy to integrate.  FILTERS 1 CAPACITOR FILTER: A capacitor is connected at the rectifier output, and dc voltage is obtained across the capacitor. Output waveform The filtered voltage as shown in the figure below shows the waveform to have a dc level and a ripple The figure below shows the voltage as the capacitor charges and discharges. waveform across a capacitor filter. Time T1 is the time during which diodes of the full- wave rectifier conduct, charging the capacitor up to the peak rectifier voltage,. Time T2 is the time interval during which the rectifier voltage drops below the peak voltage, and the capacitor discharges through the load. The ripple voltage can be calculated from Where is in milliamperes is in microfarads is in kilo ohms Example: Example: Calculate the ripple voltage of the Calculate the ripple of a capacitor filter for a full-wave rectifier with a 100 filter peak rectified voltage of 30 V, capacitor C= capacitor connected to a load 100 uF, and a load current of 50 mA. drawing 50. Filter Capacitor Ripple DC VOLTAGE Diode Conduction Period and Peak Diode Current Recall that the diodes conduct during period T1 , during which time interval, the larger the amount of the charging current. RC FILTER: It is possible to further reduce the amount of ripple across a filter FULL –WAVE RECTIFIER AND RC FILTER: capacitor by using an additional RC filter section. The purpose of the added The operation of the filter circuit can be RC section is to pass most of the dc analyzed using superposition for the dc and component while attenuating as much ac components of signal. of the ac component as possible. DC Operation of RC Filter Section AC Operation of RC Filter Section The figure shows the equivalent circuit to The figure shows the equivalent circuit of use in analyzing the RC filter circuit. Since the RC filter section. Due to the voltage – both capacitors are open-circuit for dc divider action of the capacitor ac impedance operation, the resulting output dc voltage is and the load resistor, the ac component of the voltage resulting across the load is For a full-wave rectifier with ripple at 120 Hz, the impedance of a capacitor can be Example: load for an filter section The dc voltage across the initial filter capacitor is V. Example: Calculate the dc and ac components of the output signal across load RL in the circuit. Calculate the ripple of the output waveform. Inductor Filter L-C Filter As an inductor allows dc and vlocks ac, a A filter circuit can be constructed using both filter called Series Inductor Filter can be inductor in order to obtain a better output constructed by connecting the inductor in where the efficiencies of both inductor and series, between the rectifier and the load. capacitor can be used. The figure below shoes the circuit of a series inductor filter. The rectified output is when the inductor allows dc components ta pass through it, The rectified output when passed through blocking the AC components in the signal. this filter, the inductor blocks the AC Now from the signal, few more AC components that are present in the signal, components if any present are grounded so in order to provide a pure dc. that we get a pure dc output. The filter if also called as a Choke Input Filter as the input signal first enters the inductor. The output of this filter is better than the previous ones. Pi Filter () Pi Filter () Capacitor C1: This capacitor offers high This is another type of filter circuit which is reactance to dc and low reactance to AC very commonly used. It has a capacitor at signal. After grounding the AC components its input and hence it is also called as a present in the signal, the signal passes to Capacitor Input Filter. Here, two capacitors the inductor for further filtration. and one inductor are connected in pi shaped network. A capacitor in parallel, Inductor L: This inductor offers low then an inductor in series, followed by reactance to dc components, while blocking another capacitor in parallel makes this the AC components of any got managed to circuit.. pass through the capacitor C1. Capacitor C2: Now the signal is further smoothened using this capacitor so that it allows any AC component present in the signal, which the inductor has failed to block. In this circuit, we have a capacitor in parallel, then an inductor in series, followed by another capacitor I parallel. Diode Conduction Period and Peak Diode Current Recall that the diodes conduct during period T1 , during which time interval, the larger the amount of the charging current. Diode Conduction Period and Peak Diode Current Recall that the diodes conduct during period T1 , during which time interval, the larger the amount of the charging current. Diode Conduction Period and Peak Diode Current Recall that the diodes conduct during period T1 , during which time interval, the larger the amount of the charging current.