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. 759-2916
Mfr. Part No.ADP2303ARDZ
$5.38
Each
units
3A - Step Down 0.8 V 3 V 20 V Adjustable Surface Mount - 1 8 SOIC Yes -
RS Stock No. 533-8091
Mfr. Part No.LM2576T-5.0/NOPB
$8.56
Each
units
3A - Buck Controller, Inverting - 4 V 40 V Fixed Through Hole - 1 5 TO-220 Yes -
RS Stock No. 100-3981
Mfr. Part No.LM2576T-5.0/NOPB
$6.913
Each (In a Tube of 45)
units
3A - Buck Controller, Inverting - 4 V 40 V Fixed Through Hole - 1 5 TO-220 Yes -
RS Stock No. 146-5628
Mfr. Part No.LNK304GN
$1.826
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. 146-8560
Mfr. Part No.LNK304GN
$2.27
Each
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. 686-8225
Mfr. Part No.L6902D
$5.02
Each
units
1A 34 V Buck Controller 1.235 V 8 V 36 V Adjustable Surface Mount - 1 8 SOIC Yes 10 mV
RS Stock No. 168-6454
Mfr. Part No.L6902D
$3.667
Each (In a Tube of 100)
units
1A 34 V Buck Controller 1.235 V 8 V 36 V Adjustable Surface Mount - 1 8 SOIC Yes 10 mV
RS Stock No. 920-3592
Mfr. Part No.LM2596T-3.3/NOPB
$8.955
Each (In a Tube of 45)
units
3A - Buck Controller, Inverting - 4.5 V 40 V Fixed Through Hole - 1 5 TO-220 Yes -
RS Stock No. 533-8063
Mfr. Part No.LM2575T-5.0/NOPB
$8.72
Each
units
1A - Buck Controller, Inverting - 4 V 40 V Fixed Through Hole - 1 5 TO-220 Yes -
RS Stock No. 100-3978
Mfr. Part No.LM2575T-5.0/NOPB
$6.712
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. 533-3737
Mfr. Part No.LM2596T-3.3/NOPB
$10.55
Each
units
3A - Buck Controller, Inverting - 4.5 V 40 V Fixed Through Hole - 1 5 TO-220 Yes -
RS Stock No. 545-5045
Mfr. Part No.LT1076CT#PBF
$15.86
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. 127-0676
Mfr. Part No.L4960
$8.06
Each
units
- 40 V Buck Controller 5.1 V 9 V 46 V Adjustable Through Hole - 1 7 HEPTAWATT V Yes 50 mV
RS Stock No. 686-8464
Mfr. Part No.VIPER16LN
$1.73
Each (In a Pack of 5)
units
- - - - - - - Through Hole - - 7 PDIP - -
RS Stock No. 463-050
Mfr. Part No.LM2576T-ADJG
Brandonsemi
$4.064
Each (In a Pack of 5)
units
3A 37 V Buck Controller, Inverting 1.23 V 7 V 40 V Adjustable Through Hole - 1 5 TO-220 Yes -
RS Stock No. 779-9003
Mfr. Part No.LT1076CT-5#PBF
$15.81
Each
units
2A 5 V Buck Controller - 8 V 45 V - Through Hole - 1 5 TO-220 Yes 0.1 %/V
RS Stock No. 178-1480
Mfr. Part No.VIPER16LN
$1.542
Each (In a Tube of 50)
units
- - - - - - - Through Hole - - 7 PDIP - -
RS Stock No. 100-7567
Mfr. Part No.LM2576T-ADJG
Brandonsemi
$3.404
Each (In a Tube of 50)
units
3A 37 V Buck Controller, Inverting 1.23 V 7 V 40 V Adjustable Through Hole - 1 5 TO-220 Yes -
RS Stock No. 168-5905
Mfr. Part No.L4960
$5.746
Each (In a Tube of 50)
units
- 40 V Buck Controller 5.1 V 9 V 46 V Adjustable Through Hole - 1 7 HEPTAWATT V Yes 50 mV
RS Stock No. 920-3514
Mfr. Part No.LM2576S-ADJ/NOPB
$8.272
Each (In a Tube of 45)
units
3A 37 V Buck Controller, Inverting 1.23 V 4 V 40 V Adjustable Surface Mount - 1 5 D2PAK (TO-263) Yes -