设计开关模式电源（SMP） - 万博官网APP,狗万官方客户端下载,万博客户端登录

Engineers are familiar with the term Switched Mode Power Supply or SMPS. Once it is understood that what SMPS actually is, its countless applications can be easily imagined.

An SMPS is used for converting the electronic power supply efficiently. It is used to supply power to sensitive devices that require stable power supply with high efficiency. Any SMPS has some storage components which store electrical energy to supply to the load device and some switching components which turn on and off at high frequencies charging and discharging the storage components.

The power is supplied to the load device by discharge of the storage component when the switching component is in non-conduction state. The use of switching regulators makes the SMPS different from the linear regulators. The SMPS can be AC to DC, DC to DC, AC to AC or DC to AC supply. In this series on designing SMPS, AC to DC and DC to DC SMPS are dealt.

The switching regulators (like transistors) in SMPS continuously switches between their ON and OFF state. So they spend very less time in high dissipation state which reduces power dissipation of the system. In Linear regulators, all the power is dissipated in the form of heat which reduces the overall efficiency of the system. Due to use of switching components working at high frequency, SMPS can be made to deliver high efficiency up to 95%. SMPS can be used in place of any linear regulator when high efficiency and a small size, light weight power supply is required.

Fig. 1:Typical image of SMPS

In this series, SMPS are designed by using different topologies. For designing SMPS (AC to DC type) they can be categorized as follow –

Fig. 2: Image showing Different Types of SMPS

First the SMPS can be broadly categorized in two categories –

1. Non-Isolated SMPS

2. Isolated SMPS

在非分离的SMP中，输入和输出共享相同的接地，或者可以说输入和输出之间存在电连接。但是在孤立的SMP中，输入和输出通过变压器彼此隔离，该变压器通过输入电源（AC）从任何电击中提供安全性。

在非分离的SMP中，可以根据输入输出电压对SMP的基本拓扑进行分类，如下所示 -

1.增压转换器-In this SMPS, the output voltage is always greater than Input voltage.

2.Buck Converter-In this SMPS, the output voltage always less than Input voltage

3.Buck-Boost Converter-In this SMPS, the output voltage can be greater or less than the Input voltage

In Isolated SMPS, there are two topologies of SMPS which are designed in this series. They are as follows –

4. Push-pull Converter

5. Flyback Converter

现在,上述拓扑可以进一步divided into different types as follows –

1.提升转换器或降压转换器

In this series of SMPS, a Boost converter and Buck Converter is designed by four ways –

I.开放循环提升/摇滚转换器 - 在此提升转换器中，没有任何错误检测电路或任何反馈电路。因此，该增压转换器的输出电压将不受监管。

II.闭环升压/摇滚转换器 - 在此提升转换器中，将有一个错误检测电路或反馈电路。该反馈电路有助于调节输出电压。

iii。 带有可调节输出的开放循环升压/摇滚转换器 - 此增压转换器将具有可变的输出电压，但没有任何错误检测电路或反馈电路。因此，该升压转换器的输出电压将是可变但不受监管的。

IV.具有可调输出的闭环升压/摇滚转换器 - 此增压转换器将具有可变的输出电压和反馈电路。因此，该升压转换器的输出电压将是可变和调节的。

2. Buck-BoostConverter-

There will be two types of Buck-Boost Converters designed in this series –

I. Open Loop Inverting Buck –Boost Converter- In an Inverting Buck-Boost converter, the output voltage can be greater and less that the input voltage. The polarity of the output is opposite to the input voltage that’s why it is called Inverting Buck-Boost converter.

II. Open Loop Inverting Buck –带有可调节输出的增强转换器

In this Buck-Boost Converter, the output voltage can be varied from the lower voltage (voltage less than input voltage) to the higher voltage level (voltage greater than input voltage).

3. Flyback converter

飞回转换器就像一个降压转换器一样，唯一的区别是，在降压转换器中，它使用了单个电感器绕组，在飞回转换器中，电感器将电感器拆分成两个形成变压器的绕组。这给出了输入的输出的隔离。在本系列中，设计了一个飞回转换器，该转换器将降低输入电压并在输出处给出低电压。

4. Push–pull converter

An Open Loop Push-Pull converter will be designed which will be a DC to DC SMPS. This converter uses the transformer for converting one DC voltage to another level. A transformer provides the isolation between input and the output. This converter can provide either high voltage or low voltage at the output as compared to input. The number of turns of transformer and duty cycle will decide whether high voltage or low voltage is delivered at the output.

In this series, a Push-Pull converter will be designed which will step up the input voltage and give high voltage at the output

现在，让我们了解一些将用于设计SMP的基本术语 -

On the basis of output current of SMPS, it can have two modes of operation –

1. Continuous Mode

2. Discontinuous mode

1. Continuous Mode-

通常在SMPS电路中，在输入处有一个电感器，可以决定输入电流。在连续模式下，电感器中的电流在切换周期的整个周期中是连续的。因此，在连续模式下输出处获得了调节的电压。在连续模式下，输出电流有一些临界值，在此部分的一部分切换周期中，电感器电流为零，然后据说系统处于不连续模式。因此，对于连续模式的操作，输出始终大于或等同于临界电流值。

Below is the waveform which shows the inductor current in continuous mode.

Fig. 3: Graph showing Current Variation in Continuous Conduction Mode of SMPS

2. Discontinuous mode-

在此模式下，电感器中的电流是脉动的，并且在切换时间的一部分中变为零。电感器中的电流从零开始，并达到峰值电流，然后在一个开关周期完成后再次返回到零。因此，在这种模式下，不调节输出电压。因此，不连续模式需要一个错误检测块，该块调节输出电压。

Below is the waveform which shows the inductor current in discontinuous mode –

图4：显示SMP的不连续传导模式下电流变化

In this series, each circuit will be designed in both CCM and DCM Modes and there will be the standard eqautions of CCM/DCM used for calcuting the components values.

An SMPS has several advantages over Linear Regulators. Some of the main advantages which leverage SMPS over any linear regulator are as follows –

•Small size –

任何SMP都具有高频工作的开关组件。这减少了SMP的电路设计中所需的组件大小。

•Low cost-

因为小尺寸组件用于制造SMP电路，因此组装电路的成本较低。

•High efficiency up to 95%-

Due to the use of switching regulators, the efficiency of SMPS is usually very high. An SMPS can have output efficiency up to 95%. That means, around 95% of the input power can be delivered to the output load.

•Isolation between input and output-

经过using a transformer in place of inductor, the SMPS can provide good isolation. By providing the isolation between the input and output, the output load can be saved from any electrical shock or voltage fluctuation from the input supply.

The use of SMPS is not just limited to computers. They are used with most of the sensitive devices that essentially requirestable和高效的电源。他们被用作lowloss current source to drive LEDs and LED circuits. They are used in self-powered devices. They are also used as an interface between battery and components in CPU or notebooks where voltage demand is lower or higher than the battery voltage.

因此，在本系列中，将设计以下SMPS电路 -

1. Boost Converters –

a）开放循环提升转换器

b) Closed Loop Boost Converter

c) Open Loop Boost Converter with Adjustable Output

d) Closed Loop Boost Converter with Adjustable Output

2.雄鹿转换器 -

a）开放循环降压转换器

b) Closed Loop Buck Converter

c) Open Loop Buck Converter with Adjustable Output

d) Closed Loop Buck Converter with Adjustable Output

3. Buck-Boost Converters