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en:iot-open:hardware2:powering:converters [2023/10/25 20:08] – pczekalski | en:iot-open:hardware2:powering:converters [2023/11/23 11:45] (current) – pczekalski | ||
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- | ==== Power conversion | + | ====== Converters for IoT Powering ====== |
+ | {{: | ||
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+ | ===== Power Conversion ===== | ||
Power sources tend to provide energy in a form that is not straightforwardly acceptable to IoT devices.\\ | Power sources tend to provide energy in a form that is not straightforwardly acceptable to IoT devices.\\ | ||
Wall sockets provide relatively high voltage alternating current (AC) that needs to be lowered and converted into DC, also stabilised as required by MCU, which is fragile for voltage variations. Common conversion flow for AC sources is present in figure {{ref> | Wall sockets provide relatively high voltage alternating current (AC) that needs to be lowered and converted into DC, also stabilised as required by MCU, which is fragile for voltage variations. Common conversion flow for AC sources is present in figure {{ref> | ||
<figure powerconversions1> | <figure powerconversions1> | ||
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<figure powerconversions2> | <figure powerconversions2> | ||
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* AC-to-DC conversion, | * AC-to-DC conversion, | ||
* filtering, | * filtering, | ||
- | * DC-DC conversion, | + | * DC-DC conversion |
- | * stabilisation. | + | |
+ | Stabilisation usually is included as a part of DC-DC or AC-DC conversion. | ||
**AC-to-AC**\\ | **AC-to-AC**\\ | ||
AC-to-AC conversion is used whenever a high-voltage source is available and is required to lower it, typically somewhere between 12V and 5V.\\ | AC-to-AC conversion is used whenever a high-voltage source is available and is required to lower it, typically somewhere between 12V and 5V.\\ | ||
- | Historically, | + | Historically, |
+ | This technique has serious drawbacks: | ||
* transformer-based converters are heavy as they use copper coils and steel cores (sample transformer in figure {{ref> | * transformer-based converters are heavy as they use copper coils and steel cores (sample transformer in figure {{ref> | ||
* the conversion rate is fixed, thus requiring different transformers in the countries with different socket voltages, | * the conversion rate is fixed, thus requiring different transformers in the countries with different socket voltages, | ||
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<figure transformer1> | <figure transformer1> | ||
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<figure transformer2> | <figure transformer2> | ||
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**AC-to-DC**\\ | **AC-to-DC**\\ | ||
- | In general, IoT devices use DC to power MCUs and peripherals. A classical AC-to-DC conversion involves a Graetz' | + | In general, IoT devices use DC to power MCUs and peripherals. A classical AC-to-DC conversion involves a Graetz' |
<figure graetz1> | <figure graetz1> | ||
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<figure graetz2> | <figure graetz2> | ||
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SMPS is used to integrate all necessary functions (including voltage stabiliser) in a single device, e.g. in figure {{ref> | SMPS is used to integrate all necessary functions (including voltage stabiliser) in a single device, e.g. in figure {{ref> | ||
<figure acdc1> | <figure acdc1> | ||
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**Filtering**\\ | **Filtering**\\ | ||
- | Proper filtering of the current interferences is essential to ensure stable MCU operation. Even when using good quality power sources, nearby communication wires, power wires, and electromagnetic fields generated by actuators can cause serious | + | Proper filtering of the current interferences is essential to ensure stable MCU operation. Even when using good quality power sources, nearby communication wires, power wires, and electromagnetic fields generated by actuators can cause severe |
- | **DC-to-DC**\\ | + | **DC-to-DC |
The DC-to-DC conversion is needed whenever the source voltage is unsuitable for an IoT device. It is also needed in the case of batteries as a second stage after AC-DC conversion. DC-DC converters involve voltage stabilisation.\\ | The DC-to-DC conversion is needed whenever the source voltage is unsuitable for an IoT device. It is also needed in the case of batteries as a second stage after AC-DC conversion. DC-DC converters involve voltage stabilisation.\\ | ||
- | Modern DC-to-DC converters are implemented with fixed output voltage or regulated to decrease (step-down) or increase (step-up) the voltage. | + | Modern DC-to-DC converters are implemented with fixed output voltage or regulated to decrease (step-down) or increase (step-up) the voltage. |
- | Former solutions include linear voltage stabilisers (only step-down), e.g. popular and still used 7805 chip (figure {{ref> | + | Former solutions include linear voltage stabilisers (only step-down), e.g. popular and still used 78xx chips. Sample 5V stabiliser |
They have several drawbacks, however: | They have several drawbacks, however: | ||
* low efficiency, | * low efficiency, | ||
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<figure 7805> | <figure 7805> | ||
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<figure 7805_2> | <figure 7805_2> | ||
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- | Modern DC-DC converters are of high efficiency, easily going over 90%. They are implemented as switching regulators rather than linear. The construction of the switching converters is quite complex. Sample device with fixed voltage regulation is present in figure {{ref> | + | Modern DC-DC converters are of high efficiency, easily going over 90%. They are implemented as switching regulators rather than linear. The construction of the switching converters is quite complex. Sample device with fixed voltage regulation is present in figure {{ref> |
<figure dcdcswitching1> | <figure dcdcswitching1> | ||
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<figure dcdcswitching2> | <figure dcdcswitching2> | ||
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+ | <figure dcdcswitching3> | ||
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