# 什么是耦合电感器：工作及其应用

## What is Coupled Inductor?

Coupled inductor definition是通过电磁感应可以通过电磁感应来完成两个线圈或电感的连接。每当在整个初级线圈的交流流动时，线圈将建立连接到次级线圈的磁场并引起线圈内的电压。从一个电感到另一个电感的诱导电压的现象称为相互电感。

Coupled inductors are mainly used as essential parts fortransformers，电子电路和配电系统。一对耦合电感器可以特征在于三个参数，如L1，L2和互感等两个自体电感，如L12 = M。这耦合电感符号如下所示。

### 耦合电感器方程

In the above-coupled inductor circuit, two coils like L1 & L2 are very close to each other. Because of the ‘i1’ current flowing throughout the primary coil ‘L1’, magnetic flux can be induced, and after that, it will be transferred to the secondary coil L2.

V1 = M {di2(t)/dt}

From the above ‘V1’ equation, the mutual inductance ‘M’ is mainly responsible for the voltage which is induced mutually in two independent circuits. So, this mutual inductance (M) is the coefficient proportionality.

Similarly, for the first ‘L2’ coil, the mutually induced voltage because of mutual inductance for the ‘L2’ coil can be expressed as

v2 = m {di1（t）/ dt}

Similar to the inductance, mutual inductance (M) can also be measured in Henry. So, the highest mutual inductance value can be expressed as √L1L2. When the inductance induces voltage through the rate of change of current, mutual inductance (M) also induces a voltage which is known as mutual voltage M(di/dt). So, this mutual voltage is either positive (+ve) or negative (-ve) mainly depending on the construction of the inductor & the flow of current direction.

#### DOT公约

In the above dot convention circuit, the inductors L1 & L2 are mutually coupled. The V1 & V2 voltages are developed across the two L1 & L2 inductors which are the outcome of current flowing into the two inductors on the dotted terminals.

By assuming the two inductors mutual inductance is M, the voltage which is induced can be calculated by using the below formula,

For the primary inductor ‘L1’, the induced voltage ‘V1’ is;

V1 = L1（DI1 / DT）±M（DI2 / DT）

For the secondary inductor ‘L2’, the induced voltage ‘V2’ is;

V2 = L2（DI2 / DT）±M（DI1 / DT）

Thus, the above circuit contains two types of induced voltage like the voltage induced because of self-inductance & the voltage induced mutually because of the mutual inductance.

### 耦合电感VS变压器

 Coupled Inductor 变压器 这耦合电感器is mainly used for transmitting energy from the primary winding to the secondary through a core. A transformer is mainly used for power transmitting from the primary winding to the secondary. Coupled inductor utilizes a gapped magnetic core for changing the voltage between two coils & transmits power at time intervals which are controlled. 这transformer utilizes a non-gap magnetic core for changing the voltage in between two coils & transmits the power in real-time. 这耦合电感器includes an air gap. 这transformer doesn’t include an air gap. 在耦合电感器中，输入功率不等于现有电源。 In a transformer, the entering power is equal to the existing power from the transformer. 这storage of energy in the core can be possible in the coupled inductor. 在变压器中无法在核心中存储能量。 It is used in DC to DC converter like flyback converter to decrease the voltage from 24V DC to 5V DC. 它用于AC到AC转换，如从120VAC-24Vac的交流壁出口的电压降低。

advantages of a coupled inductorinclude the following.

• Current ripple can be reduced significantly
• Conversion of voltage.
• Circuit impedance can be changed.
• Galvanic isolation
• Switching power supplies comprise multiphase converters, SEPIC converters, galvanically isolated converters & special converter circuits that decrease the hard switching negative characteristics.

• Slightly higher losses
• Non-ideal operations within the flyback converter
• 这耦合电感器’s current specifications will change based on their windings which are connected within series or parallel.

### Applications

• Coupled inductors are used in electrical applications
• Used in power conversion-based circuits like SEPIC, flyback, ZETA, Fly-Buck, Cuk & multi-phase topologies.
• 这些电感器的性质将允许增加或减小电流和电压。
• 这些用于在整个电路中传输阻抗
• 这se can be used to isolate two circuits electrically from each other.
• 这windings of the coupled inductor can be connected in different configurations for different purposes.
• 这windings of these inductors can be connected separately to circuits to use like common mode chokes & isolation transformers.

Thus, this is all about an overview of the coupled inductor. A coupled电感用于DC到DC转换器for transferring one winding energy to another throughout the common core. These are existing in different sizes, current ratings, inductance values & shielded magnetically for low EMI (electromagnetic interference). The coupled inductor windings may have equivalent like 1:1 or un-equivalent turns ratios like 1:N. Here is a question for you, what is the function of an inductor?