Buck Converters

A Buck Converter, also known as a Step-Down Converter, is a DC-to-DC power converter that steps down the voltage from its input to its output. A buck converter integrates the core components and circuitry needed into a single device.

Buck converters are found in countless electronic applications, where their power regulation properties are a vital component.

How does a Buck Converter work?

A Buck Converter is a type of switch-mode power supply, a class of device that incorporates a switch (e.g. typically a MOSFET) to rapidly turn the circuit on and off. This rapid switching creates a square wave. If the duty cycle of the switch is set to 50%, i.e. the switch is on 50% of the time, the average voltage will be 50% of the input.

The square wave needs to be smoothed to provide useful power, typically an inductor and capacitor are used in series to fulfil this function. This combination is called an LC low pass filter. The properties of an inductor smooth the current flow, while the capacitor resists sudden changes in voltage. The combined effect produces a relatively smooth voltage output with low ripple. For example, if the input voltage is 10V and the switch employs a duty cycle of 50%, the output voltage will be 5V.

A further necessary component of a Buck Converter is to incorporate a diode or other switch in parallel with the inductor. This is to compensate for the property of an inductor, in that the current in an inductor cannot instantly change, protecting the switching transistor from being overloaded and destroyed.

Buck Converters also incorporate additional circuitry to ensure a stable output voltage. The converter uses a closed-loop control scheme with negative feedback to monitor the voltage output and dynamically adjusts the duty cycle of the switch to regulate the output voltage.

Design considerations

  • Buck Converters are very efficient, with some devices offering efficiencies of above 95%.
  • Buck Converters can be more cost-effective than linear regulators at higher power levels, the cost of removing the heat generated by a linear regulator may be less than employing a Buck Converter.
  • The output of a Buck Converter will feature a noise, meaning the more stable output of a linear voltage regulator is better suited for application requiring low output noise.
  • Linear regulators can respond faster to input and output changes versus a buck converter.

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Description Price Maximum Output Current Maximum Output Voltage Regulator Function Minimum Output Voltage Minimum Input Voltage Maximum Input Voltage Output Type Mounting Type Series Number of Outputs Pin Count Package Type Switching Regulator Line Regulation
RS Stock No. 146-5628
Mfr. Part No.LNK304GN
MYR3.35
Each (In a Tube of 50)
units
170mA 700 V Boost, Buck, Flyback -0.3 V 85 V ac 265 V ac Fixed Surface Mount - 1 8 SMDB - -
RS Stock No. 545-5023
Mfr. Part No.LT1074CT#PBF
MYR57.16
Each
units
10A 50 V Buck Controller 2.5 V 7.3 V 45 V Adjustable Through Hole - 1 5 TO-220 Yes 0.02 %/V
RS Stock No. 533-3226
Mfr. Part No.LM2576S-5.0/NOPB
MYR15.46
Each
units
3A - Buck Controller, Inverting - 4 V 40 V Fixed Surface Mount - 1 5 D2PAK (TO-263) Yes -
RS Stock No. 146-5659
Mfr. Part No.LNK306GN
MYR4.62
Each (In a Tube of 50)
units
360mA 700 V Boost, Buck, Flyback -0.3 V 85 V ac 265 V ac Fixed Surface Mount - 1 8 SMDB - -
RS Stock No. 920-3510
Mfr. Part No.LM2576S-5.0/NOPB
MYR13.136
Each (In a Tube of 45)
units
3A - Buck Controller, Inverting - 4 V 40 V Fixed Surface Mount - 1 5 D2PAK (TO-263) Yes -
RS Stock No. 100-3978
Mfr. Part No.LM2575T-5.0/NOPB
MYR10.594
Each (In a Tube of 45)
units
1A - Buck Controller, Inverting - 4 V 40 V Fixed Through Hole - 1 5 TO-220 Yes -
RS Stock No. 533-8063
Mfr. Part No.LM2575T-5.0/NOPB
MYR12.47
Each
units
1A - Buck Controller, Inverting - 4 V 40 V Fixed Through Hole - 1 5 TO-220 Yes -
RS Stock No. 162-9288
Mfr. Part No.ADP3212MNR2G
MYR4.50
Each (On a Reel of 2500)
units
52A 1.5 V Buck Controller 0.3 V 3.3 V 22 V Adjustable Surface Mount - 2 48 QFN Yes 0.02 %
RS Stock No. 545-5859
Mfr. Part No.LT1074CT7#PBF
MYR58.38
Each
units
5A 50 V Buck Controller 2.5 V 7.3 V 45 V Adjustable Through Hole - 1 7 TO-220 Yes 0.02 %/V
RS Stock No. 533-3692
Mfr. Part No.LM2596S-5.0/NOPB
MYR26.58
Each
units
3A - Buck Controller, Inverting - 4.5 V 40 V Fixed Surface Mount - 1 5 D2PAK (TO-263) Yes -
RS Stock No. 146-5626
Mfr. Part No.LNK304PN
MYR3.384
Each (In a Tube of 50)
units
170mA 700 V Boost, Buck, Flyback -0.3 V 85 V ac 265 V ac Fixed Through Hole - 1 7 DIPB - -
RS Stock No. 920-3586
Mfr. Part No.LM2596S-5.0/NOPB
MYR22.596
Each (In a Tube of 45)
units
3A - Buck Controller, Inverting - 4.5 V 40 V Fixed Surface Mount - 1 5 D2PAK (TO-263) Yes -
RS Stock No. 533-5266
Mfr. Part No.LM2678T-12/NOPB
MYR27.02
Each
units
5A - Buck Controller - 8 V 40 V Fixed Through Hole - 1 7 TO-220 Yes -
RS Stock No. 841-7522
Mfr. Part No.MCP16301HT-E/CH
BrandMicrochip
MYR4.904
Each (In a Pack of 10)
units
600mA 15 V Step Down 2 V 4.7 V 36 V Adjustable Surface Mount - 1 6 SOT-23 Yes 0.1 %/V
RS Stock No. 920-3665
Mfr. Part No.LM2675M-5.0/NOPB
MYR20.055
Each (In a Tube of 95)
units
1A - Buck Controller - 8 V 40 V Fixed Surface Mount - 1 8 SOIC Yes -
RS Stock No. 165-4042
Mfr. Part No.MCP16301HT-E/CH
BrandMicrochip
MYR4.05
Each (On a Reel of 3000)
units
600mA 15 V Step Down 2 V 4.7 V 36 V Adjustable Surface Mount - 1 6 SOT-23 Yes 0.1 %/V
RS Stock No. 533-3743
Mfr. Part No.LM2596T-5.0/NOPB
MYR22.11
Each
units
3A - Buck Controller, Inverting - 4.5 V 40 V Fixed Through Hole - 1 5 TO-220 Yes -
RS Stock No. 100-3946
Mfr. Part No.LM2678T-12/NOPB
MYR21.43
Each (In a Tube of 45)
units
5A - Buck Controller - 8 V 40 V Fixed Through Hole - 1 7 TO-220 Yes -
RS Stock No. 533-5042
Mfr. Part No.LM2675M-5.0/NOPB
MYR23.60
Each
units
1A - Buck Controller - 8 V 40 V Fixed Surface Mount - 1 8 SOIC Yes -
RS Stock No. 920-3595
Mfr. Part No.LM2596S-ADJ/NOPB
MYR18.868
Each (In a Tube of 45)
units
3A 37 V Buck Controller, Inverting 1.2 V 4.5 V 40 V Adjustable Surface Mount - 1 5 D2PAK (TO-263) Yes -