Name: ac to dc conversion with bridge diodes
Uploaded: 2025-05-22T09:06:19.000Z
Duration: 1 min 24 s
Channel: JoVE

ACからDCへの変換に不可欠なブリッジ整流器は、ブリッジ構成に配置された4つのダイオードで構成されています。
この配置により、波形の正と負の両方の半分を整流できます。
入力電圧の正の半サイクルの間、ブリッジ整流器はダイオードD1とD2、抵抗Rに電流を流し、ダイオードD3とD4は逆バイアスされます。
逆に、負の半サイクルでは、2次電圧は負になり、電流はダイオードD3とD4、抵抗Rを流れ、ダイオードD1とD2は逆バイアスされます。
サイクルが変化しても、電流の流れの方向は一定に保たれ、一貫して正のパルスDC出力電圧が得られます。
ピーク逆電圧は正の半サイクルで決定され、センタータップ付きトランスを備えた全波整流器の値の約半分です。
ブリッジ整流器は、変圧器の二次巻線に必要な巻数が少なくて済み、より効率的でコンパクトになります。
ブリッジ整流器の効率は、ショットキーダイオードを使用するか、コンデンサフィルタを組み込むことで向上させることができ、これにより損失が減少し、DC出力の品質が向上します。

ブリッジ整流器

ブリッジ整流器は、交流 (AC) を直流 (DC) に効率的に変換する電子機器に不可欠です。4つのダイオードをブリッジ構成で配置したこの整流器は、AC 波形の正と負それぞれの半分を効果的に処理するため、電圧調整と出力安定性の点で半波および全波センタータップ整流器よりも優れています。

ブリッジ整流器の動作では、AC 入力の各半周期中に 2 つのダイオードに電流が流れます。具体的には、正の半周期中はダイオード D_1 と D_2 が導通し、負荷抵抗器 R に電流が流れますが、ダイオード D_3 と D_4 は逆バイアスされ非導通になります。この動作は負の半周期中に逆になり、ダイオード D_3 と D_4 が導通し、D_1 と D_2 は逆バイアスされます。入力電圧が交流であるにもかかわらず、負荷抵抗器 R を流れる電流は一方向に留まり、安定した正の脈動 DC 出力が確保されます。

<img alt="Figure 1" src="/files/ftp_upload/15721/15721_Figure_1.svg" style="height: 180px;">

必要なピーク逆電圧 (PIV) は、ダイオード電圧 (V_D) を電源電圧 (V_S) から減算したもので、センタータップ付きトランスを使用した全波整流器の約半分の値になります。したがって、ブリッジ整流器はより効率的で、よりコンパクトでコスト効率の高い設計が可能になります。

<img alt="Equation 1" src="/files/ftp_upload/15721/15721_Equation_1.svg" style="height: 20px;">
<img alt="Equation 2" src="/files/ftp_upload/15721/15721_Equation_2.svg" style="height: 42px;">

さらに、ブリッジ整流器回路のトランスの二次巻線は、センタータップ付きトランス構成よりも巻数が少なくて済むため、全体的な効率が向上します。ブリッジ整流器のパフォーマンスは、順方向電圧降下が低く回復時間が速いことで知られるショットキーダイオードを統合するか、リップルを最小限に抑えるコンデンサフィルタを追加することで大幅に向上し、より高品質の DC 出力を生成することもできます。

ACからDCへの変換に不可欠なブリッジ整流器は、ブリッジ構成に配置された4つのダイオードで構成されています。
この配置により、修正することができます...

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

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. Diodes D3 and D4 conduct, while D1 and D2 are reverse-biased. Even though the input keeps alternating, the current through the load resistor still moves in one direction. The output is a steady positive pulsating DC signal.

A bridge rectifier can offer better voltage regulation and output stability than a half-wave rectifier or a full-wave center-tapped rectifier. It also needs a peak inverse voltage (PIV) of about V D subtracted from V S, which is roughly half the PIV needed in a center-tapped full-wave rectifier. This helps make the design more compact and cost-effective.

The transformer secondary in a bridge rectifier circuit also needs fewer turns than a center-tapped transformer setup. Performance can improve further with Schottky diodes, which have a low forward voltage drop and fast recovery time. A capacitor filter can also reduce ripple and produce higher-quality DC output.

AC to DC Conversion with Bridge Diodes

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

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

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 four diodes in a bridge layout convert AC to DC, why the output stays one direction, and how filtering improves the pulsating signal.

AC to DC Conversion with Bridge Diodes | 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

AC to DC Conversion with Bridge Diodes

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