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
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 –
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。
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
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
On the basis of output current of SMPS, it can have two modes of operation –
1. Continuous Mode
2. Discontinuous mode
1. Continuous Mode-
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-
Below is the waveform which shows the inductor current in discontinuous mode –
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 –
•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.
1. Boost Converters –
b) Closed Loop Boost Converter
c) Open Loop Boost Converter with Adjustable Output
d) Closed Loop Boost Converter with Adjustable Output
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
a) Open Loop Inverting Buck – Boost Converter
b) Open Loop Inverting Buck – Boost Converter with Adjustable Output
5. Push-Pull Converter
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