Bridge Diode

To understand Bridge Diode

The explanations of Bridge Diode found on the net are more or less the same. But I wonder how many common people understand. Before seeing the Bridge Diode function we see Center Tap (Transformer) type full wave rectifier, where two diode are used with a transformer.

Center Tap (Transformer) - Wiki 
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Common applications of center-tapped transformers

A full-wave rectifier using two diodes and a center tap transformer.

The above is the typical rectifier circuit by using center-tapped transformer.

 

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The sine wave is misleading as the horizontal line is time. If you think the place at the top of the secondary winding, at the left side of D1 the voltage changes 0 -> + peak -> 0 with respect to the center tap (which we can say "neutral") during the first half cycle.

Meanwhile at the same time ( the first half cycle period) if you think the place at the bottom of the secondary winding, at the left side of D2 the voltage does not change and remains change with respect to the center tap

 

Then during the 2nd half cycle if you think the place at the bottom of the secondary winding the voltage changes 0  -> + peak -> 0.

 

Then you can get the above right hand picture showing the upper part of the sine waves

 

Bridge Diode

Wiki

Rectifier

wiki 

In the diagrams below, when the input connected to the left corner of the diamond is positive, and the input connected to the right corner is negative, current flows from the upper supply terminal to the right along the red (positive) path to the output and returns to the lower supply terminal through the blue (negative) path.

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This explanation is misleading or even incorrect. The incorrect part is

the input connected to the right corner is negative,

This should be < still positive but lesser voltage than the left corner of the diamond (which is positive). The current still flows.

Please consider the polarity of diode. 

 

The input polarity changes + / - cyclically or sinusoidally.

the input connected to the left corner of the diamond is the voltage change 0 -> + peak -> 0

and then -> - peak -> 0 with time (periodically).

Meanwhile at the same time (period) what happens to the input connected to the right corner of the diamond ?

 

 

wiki

 

When the input connected to the left corner is negative, and the input connected to the right corner is positive, current flows from the lower supply terminal to the right along the red (positive) path to the output and returns to the upper supply terminal through the blue (negative) path.

sptt

 

Again this is incorrect. The incorrect part is

  (the) current flows from the lower supply terminal to the right along the red (positive) path to the output and returns to the upper supply terminal through the blue (negative) path

the blue (negative) path

This should be <still positive but lesser voltage than the right corner of the diamond (which is positive). The current still flows.

 

Again please consider the polarity of diode. 

Then you can get the full wave rectification shown above.

Anyway the above wiki explanation does not say sine wave, just simply the polarity changes at the input.

The following article is fine.

 

https://www.analog.com/en/resources/glossary/full-bridge-rectifier.html

How does a bridge rectifier work?

Since current can only flow in one direction through a diode, current must travel different paths through the diode bridge depending on the polarity of the input. In either case, the polarity of the output remains the same. When there is an AC input, the current travels one path during the positive half cycle, and the other during the negative half cycle. This creates a pulsating DC output since the signal still varies in magnitude, but no longer in direction.

Current flow in a bridge rectifier during the positive half cycle.

Current flow in a bridge rectifier during the negative half cycle.

No <negative> is shown and the polarity of diodes are OK. The current flows from Anode to cathode all the way.

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Chip Beads

<Chip Beads> or <Chip Bead> is a common or commercial name of one of the electronic component used for suppressing or absorbing Electro-Magnetic Interference (EMI) signals. Wiki describes this component as <Ferrite bead>. The name <Chip Beads> is cute.

The name of <Chip Bead> may have come from the ones shown in the photo below.

 

The black material is Ferrite. The wire transmits signals. 

Or SMT type looks more like a small bead as no lead wires. See below.

 

As ref

 
https://www.tdk.com/en/tech-mag/noise/05 (TDK)

Chip beads, which cleverly take advantage of the characteristics of ferrite, are often used as a simple and effective countermeasure for these noise problems. Chip beads are named after perforated beads used in ornaments like necklaces. This stems from the early days when conductors were actually placed through hollow ferrite material. Later, in response to the demand for miniaturization of electronic components, chip beads—with a structure in which a coil is formed inside the ferrite body using laminar fabrication techniques—came to be used. Though no longer a hollow structure, the original “bead” name was retained.

 

SMT type is a rather simple but a very clever invention.

 Structure of SMT type Chip Bead - Multilayer structure

Internal Electrode (metal like gold)

The following article explains Chip Bead very well. 

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Ferrite Beads Demystified

https://www.analog.com/en/resources/analog-dialogue/articles/ferrite-beads-demystified.html

Ferrite Bead Simplified Model and Simulation 

A ferrite bead can be modeled as a simplified circuit consisting of resistors, an inductor, and a capacitor, as shown in Figure 1a. R_DC corresponds to the dc resistance of the bead. C_PAR, L_BEAD, and R_AC are (respectively) the parasitic capacitance, the bead inductance, and the ac resistance (ac core losses) associated with the bead.

Figure 1. (a) Simplified circuit model and (b) Tyco Electronics BMB2A1000LN2 measured ZRX plot.

Ferrite beads are categorized by three response regions: inductive, resistive, and capacitive. These regions can be determined by looking at a ZRX plot (shown in Figure 1b), where Z is the impedance, R is the resistance, and X is the reactance of the bead. To reduce high frequency noise, the bead must be in the resistive region; this is especially desirable for electromagnetic interference (EMI) filtering applications. The component acts like a resistor, which impedes the high frequency noise and dissipates it as heat. The resistive region occurs after the bead crossover frequency (X = R) and up to the point where the bead becomes capacitive. This capacitive point occurs at the frequency where the absolute value of capacitive reactance (–X) is equivalent to R.

"

the bead inductance, and the ac resistance (ac core losses) associated with the bead.

can be re-written as

the ferrite coil inductance, and the ac resistance (ac core losses) associated with the ferrite material.

 

The point is that it uses or must use the ac resistive region of the ferrite material. However the

inductive region of the ferrite coil and the capacitve region of C_{PAR do have some functions.}

 

C_{PAR.is Capacitance Parasitic. See below as ref.}

 

 

 

 

 

 

 

But may not be this simple.

_{Typical XL (Coil reactance) curve}

But XL (Coil reactance) drops as the frequency becomes high (why?). 

 The above TDK article explains

https://www.tdk.com/en/tech-mag/noise/05 (TDK)

However, what differentiates a chip bead from an LPF (low-pass filter) is that it has both inductive (coil) and resistive properties. In ranges where the frequency of the noise is relatively low, a chip bead works mainly as an inductor, reflecting and blocking the noise. As the inductive component increases, so will the impedance. However, beyond a certain frequency, the impedance drops sharply and the noise reflection characteristics also diminish rapidly. The frequency at which this occurs is called the self-resonant frequency.

_{And  XC (Capacitor reactance) drops at very high frequencies.}  

 Typical XC (Capacitor reactance)

 

 

 

_{CPAR values are small.}

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