Name: single-diode ac to dc conversion
Uploaded: 2024-07-08T13:20:20.000Z
Duration: 1 min 20 s
Channel: JoVE

ダイオード整流回路は、半波または全波構成を使用してAC電圧を単方向DC電圧に変換します。
ダイオード、抵抗、および入力正弦波信号を直列に組み合わせた半波整流回路を考えてみましょう。
入力信号の正の半サイクル中に、電圧がダイオードの電圧降下を超えるか等しいと、電圧は順方向にバイアスされ、電流が流れるようになります。
次に、出力電圧は、入力電圧からダイオードの電圧降下を差し引くことによって決定されます。
逆に、負の半サイクルでは、入力電圧はダイオードの電圧降下よりも低く、ダイオードは非導電性のままであるため、出力電圧はゼロになります。
入力電圧が平均値ゼロで極性が変化するにもかかわらず、出力は整流により一貫した平均値で単方向のままです。
ピーク逆電圧は、ダイオードが損傷なく耐えることができる最大逆電圧を表します。
半波整流器では、入力電圧が負の方向にピークに達する負の半サイクル中にこれが発生します。
したがって、逆電圧のピークは入力電圧のピークと等しくなりますが、極性は逆になります。

半波整流器

半波整流器は、交流 (AC) 電圧を一方向の電圧に変換するように設計された、電子機器の基本的な回路です。最も単純な形式のダイオード整流を利用し、回路は負荷抵抗器と AC 電源に直列に接続された単一のダイオードで構成されます。

<img alt="Figure 1" src="/files/ftp_upload/15719/15719_Figure_1.svg" style="height: 150px;">

半波整流器の動作は、ダイオードが電流を一方向にのみ流すという原理に基づいています。AC 入力の正の半サイクル中、入力電圧がダイオードのしきい値を超えると、ダイオードは順方向にバイアスされます。その結果、電流が回路を流れ、負荷抵抗器の両端に出力電圧が発生します。この出力電圧は、入力電圧からダイオードの順方向電圧降下を差し引いたものです。

逆に、負の半サイクル中は、ダイオードは逆方向にバイアスされます。入力電圧はダイオード固有の電位障壁を克服するのに十分ではないため、ダイオードは非伝導状態になります。したがって、電流は流れず、出力電圧はゼロに低下します。この整流により、入力 AC 信号の正の半サイクル中にのみ流れるパルス直流 (DC) が生成されます。

整流回路のダイオードにとって重要なパラメータは、ピーク逆電圧 (PIV) です。これは、逆バイアス状態でダイオードがブレークダウンすることなく耐えられる最大電圧です。半波整流器では、PIV は基本的に入力 AC 電圧のピーク値ですが、極性が逆になります。損傷を防ぎ、回路の寿命を保証するには、選択したダイオードが予想される PIV に対応できることが重要です。

<img alt="Equation 1" src="/files/ftp_upload/15719/15719_Equation_1.svg" style="height: 30px;">

ダイオード整流回路は、半波または全波構成を使用してAC電圧を単方向DC電圧に変換します。
半波を考えてみましょう...

Education

JoVE Core

Electrical Engineering

電気工学

Unit 1

ユニット1

Diodes

ダイオード

KEY TERMS AND CONCEPTS

主要用語と概念

Half wave rectifier

single-diode ac to dc conversion

Single-diode AC to DC conversion uses a half-wave rectifier to change alternating current into a unidirectional voltage. The circuit is simple. It uses one diode in series with a load resistor and an AC power source.

The diode controls the current because it allows flow in only one direction. During the positive half-cycles of the AC input, the diode is forward-biased. When the input voltage is greater than the diode threshold, current flows and an output voltage appears across the load resistor. That output is the input voltage minus the diode's forward voltage drop.

During the negative half-cycles, the diode is reverse-biased. The input voltage cannot overcome the diode's internal barrier, so the diode does not conduct. As a result, no current flows and the output voltage falls to zero. The circuit therefore produces a pulsating DC signal that appears only during the positive half-cycles of the AC input.

Diode selection also matters in rectifier circuits because of peak inverse voltage, or PIV. PIV is the maximum reverse voltage a diode can withstand without breakdown. In a half-wave rectifier, the PIV is essentially the peak value of the input AC voltage with opposite polarity. The diode must handle this reverse voltage to avoid damage and help the circuit last longer.

Single-Diode AC to DC Conversion

the ideal diode

Ideal Diode I-V Curve and Rectification

An ideal diode is a simple model of a semiconductor diode used to show how current moves through circuits. A diode has two terminals. The anode is positive, and the cathode is negative. In this model, current can flow only in one direction. When a positive voltage is applied to the anode relative to the cathode, the diode is forward-biased. In that state, it conducts current. When the cathode is at a higher potential than the anode, the diode is reverse-biased. It then blocks current and acts...

diode: forward bias

Diode Current in Forward Bias

Diode current in forward bias depends on how the p-type and n-type regions are connected to a battery. When the p-type region is tied to the positive terminal and the n-type region to the negative terminal, the diode is forward-biased. This setup lowers the potential barrier inside the diode and lets current move easily from the p-type side to the n-type side. The current-voltage behavior of a forward-biased diode is described by its I-V characteristics. These characteristics depend on the...

diode: reverse bias

Diode Reverse Current and Breakdown

A diode in reverse bias blocks current flow and widens its depletion region. In this setup, the positive terminal of the power source connects to the n-type material, and the negative terminal connects to the p-type material. The reverse connection also raises the barrier potential, so current stays very small. The small reverse current is called leakage current. It comes mainly from minority charge carriers. At room temperature, once the reverse voltage is above the thermal voltage, the...

zener diodes

Zener Diode Voltage Regulation

Zener diodes are semiconductor devices used to hold voltage steady in reverse bias. In reverse breakdown, current flows into the cathode and makes it positive relative to the anode. This behavior is different from a conventional diode and is the reason Zener diodes are useful in voltage regulation. A Zener diode has a nearly vertical current-voltage, or I-V, curve above a threshold called the knee current. That shape lets it keep a fairly stable voltage over a wide range of currents.

modeling of diode forward characteristics

modeling-of-diode-forward-characteristics

Diode Forward Bias: I-V Curve and Models

Diode forward bias is analyzed with the current-voltage, or I-V, curve and two common circuit models. These models help describe how a diode behaves when current flows in the forward direction. They are useful for electronic circuit design and analysis. The exponential diode model is used when the source voltage rises above 0.5 volts. At that point, the diode current increases exponentially above the saturation current. The I-V curve shows this nonlinear response as the forward voltage...

small-signal diode model

Diode Bias and Small-Signal Response

Diode bias and small-signal response describe how a diode behaves when a steady DC voltage and a tiny changing signal act on the same circuit. The DC bias sets the diode’s operating point, or Q point. Around that point, the diode current and voltage follow an exponential I-V relationship. A small time-varying signal can be added on top of the DC bias to study how the diode responds to small changes. When the signal voltage is much smaller than the thermal voltage, the diode’s behavior can be...

modeling of diode reverse characteristics

modeling-of-diode-reverse-characteristics

Zener Diode Load-Line Modeling

Zener diode load-line modeling shows how a reverse-biased diode sets a steady voltage in a circuit. Zener diodes use reverse breakdown in a controlled way, so they can hold a fixed voltage across their terminals. This makes them useful for voltage regulation. When the reverse voltage rises above the Zener voltage, or VZ, the diode enters the breakdown region. In this region, the current-voltage, or I-V, curve becomes nearly vertical after the knee current, IZ, is reached. That means the...

half wave rectifier

Single-diode AC to DC conversion uses a half-wave rectifier to change alternating current into a unidirectional voltage. The circuit is simple. It uses one diode in series with a load resistor and an AC power source. The diode controls the current because it allows flow in only one direction. During the positive half-cycles of the AC input, the diode is forward-biased. When the input voltage is greater than the diode threshold, current flows and an output voltage appears across the load...

full wave rectifier

AC to DC Conversion with Full-Wave Rectifiers

A full-wave rectifier converts alternating current, or AC, into direct current, or DC. It is more efficient than a half-wave rectifier. The circuit usually uses a center-tapped transformer, two diodes, and a load resistor. The center-tapped transformer is the key part of the circuit. Its secondary winding is split into two equal voltages with opposite polarities. That split lets the rectifier use both halves of the AC input waveform. During the positive half-cycle of the AC signal, diode D1...

bridge rectifier

AC to DC Conversion with Bridge Diodes

A bridge rectifier converts alternating current (AC) into direct current (DC) using four diodes arranged in a bridge layout. It is used to turn both halves of the AC waveform into a single-direction output. That makes it an important part of many electronics circuits. During the positive half-cycle, diodes D1 and D2 conduct. Current then flows through the load resistor R. At the same time, D3 and D4 are reverse-biased, so they do not conduct. The action switches during the negative half-cycle.

clipper circuit

Dual Diode Wave Clipping

Dual diode wave clipping uses diodes and biasing batteries to reshape an AC signal. A clipper circuit is a wave-shaping device that changes waveform parts without changing the whole signal. It is commonly used in television and radar communication systems to improve waveform modulation in transmitters and receivers. A dual-clipper setup uses two ideal diodes, two biasing batteries, and a resistor connected in parallel. The circuit works by responding to the phase of the input AC signal. The...

clamper circuit

DC Restorer for Waveform Level Shifting

A clamper circuit, or DC restorer, shifts a waveform up or down by adding a DC level. It is a special form of rectifier circuit. In this setup, the output is taken across the diode instead of across the capacitor. The circuit works well with square wave inputs and other pulse signals. The diode direction lets the capacitor charge to the most negative peak of the input signal. After that, the diode stops conducting. The capacitor then holds that voltage at a steady value. As a result, the...

voltage doubler circuit

How a Voltage Doubler Raises AC Output

A voltage doubler circuit raises the output voltage by using a clamping section and a rectifier section. The clamping section includes a capacitor, C1, and a diode, D1. The rectifier section includes a second diode, D2, and a capacitor, C2. The circuit starts working when a sinusoidal input signal enters the clamping section. Under ideal conditions, this stage clamps the positive peaks at zero volts. It also lets the negative peak reach a magnitude that is twice the input amplitude. That...

schottky barrier diode

Fast Switching in Schottky Diodes

Schottky barrier diodes use a metal-semiconductor junction to control current flow. They are built by combining a metal layer with a moderately doped n-type semiconductor. This contact creates the Schottky barrier, which gives the diode its one-way current behavior. When the metal touches the semiconductor, charge transfer occurs. The Fermi levels of the two materials align, and a depletion region forms near the contact area. In an n-type semiconductor, this region contains uncompensated...

key terms and concepts

Learn how a half-wave rectifier uses one diode and a load resistor to convert AC into pulsating DC, including forward bias, reverse bias, and PIV.

Single-Diode AC to DC Conversion | JoVE K12

JoVE Core 電気工学 は、電気回路の基本概念と回路解析テクニックを網羅したアニメーションビデオシリーズです。オペアンプと回路変換および 1 次・ 2 次回路の概念を網羅しています。実験を撮影した実写動画では、設計例や現代社会での応用が含まれており、複雑な概念も分かりやすく学習いただけます。

electrical engineering

Single-Diode AC to DC Conversion

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