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. 102-3576
Mfr. Part No.L4973D5.1
SGD5.55
Each (In a Tube of 40)
units
3.5A - Buck Controller - 8 V 55 V Adjustable Surface Mount - 1 20 SOIC Yes 10 mV
RS Stock No. 379-921
Mfr. Part No.L5970D
SGD3.976
Each (In a Pack of 5)
units
1A 35 V Buck Controller 1.2 V 4.4 V 36 V Adjustable Surface Mount - 1 8 SOIC Yes 10 mV
RS Stock No. 379-983
Mfr. Part No.L4973D5.1
SGD6.65
Each
units
3.5A - Buck Controller - 8 V 55 V Adjustable Surface Mount - 1 20 SOIC Yes 10 mV
RS Stock No. 793-1330
Mfr. Part No.L5973D013TR
SGD4.01
Each (In a Pack of 5)
units
3.5A 35 V Buck Controller 1.235 V 4 V 36 V Adjustable Surface Mount - 1 8 HSOP Yes 10 mV
RS Stock No. 379-977
Mfr. Part No.L4973D3.3
SGD6.62
Each
units
3.5A - Buck Controller - 8 V 55 V Adjustable Surface Mount - 1 20 SOIC Yes 10 mV
RS Stock No. 265-594
Mfr. Part No.L4975A
SGD19.52
Each
units
5A 40 V Buck Controller 5.1 V 15 V 50 V Adjustable Through Hole - 1 15 MULTIWATT V Yes 30 mV
RS Stock No. 165-6598
Mfr. Part No.L5973D013TR
SGD1.994
Each (On a Reel of 2500)
units
3.5A 35 V Buck Controller 1.235 V 4 V 36 V Adjustable Surface Mount - 1 8 HSOP Yes 10 mV
RS Stock No. 168-5786
Mfr. Part No.L4973D3.3
SGD5.628
Each (In a Tube of 40)
units
3.5A - Buck Controller - 8 V 55 V Adjustable Surface Mount - 1 20 SOIC Yes 10 mV
RS Stock No. 102-3574
Mfr. Part No.L5973D
SGD2.692
Each (In a Tube of 100)
units
2A 35 V Buck Controller 1.235 V 4 V 36 V Adjustable Surface Mount - 1 8 HSOP Yes 10 mV
RS Stock No. 145-8601
Mfr. Part No.L5970D
SGD2.36
Each (In a Tube of 100)
units
1A 35 V Buck Controller 1.2 V 4.4 V 36 V Adjustable Surface Mount - 1 8 SOIC Yes 10 mV
RS Stock No. 380-034
Mfr. Part No.L5973D
SGD4.42
Each (In a Pack of 5)
units
2A 35 V Buck Controller 1.235 V 4 V 36 V Adjustable Surface Mount - 1 8 HSOP Yes 10 mV
RS Stock No. 168-5778
Mfr. Part No.L4975A
SGD16.37
Each (In a Tube of 25)
units
5A 40 V Buck Controller 5.1 V 15 V 50 V Adjustable Through Hole - 1 15 MULTIWATT V Yes 30 mV
RS Stock No. 102-3575
Mfr. Part No.L5972D
SGD2.42
Each (In a Tube of 100)
units
1.5A 35 V Buck Controller 1.235 V 4.4 V 36 V Adjustable Surface Mount - 1 8 SOIC Yes -
RS Stock No. 168-6456
Mfr. Part No.L4978D
SGD4.36
Each (In a Tube of 49)
units
2A 50 V Buck Controller 3.3 V 8 V 55 V Adjustable Surface Mount - 1 16 SOIC W Yes 10 mV
RS Stock No. 265-601
Mfr. Part No.L4977A
SGD24.55
Each
units
7A 40 V Buck Controller 5.1 V 15 V 50 V Adjustable Through Hole - 1 15 MULTIWATT V Yes 30 mV
RS Stock No. 686-8237
Mfr. Part No.L4978D
SGD5.14
Each
units
2A 50 V Buck Controller 3.3 V 8 V 55 V Adjustable Surface Mount - 1 16 SOIC W Yes 10 mV
RS Stock No. 168-5779
Mfr. Part No.L4977A
SGD17.72
Each (In a Tube of 25)
units
7A 40 V Buck Controller 5.1 V 15 V 50 V Adjustable Through Hole - 1 15 MULTIWATT V Yes 30 mV
RS Stock No. 168-6458
Mfr. Part No.L4971D
SGD4.233
Each (In a Tube of 49)
units
1.5A 50 V Buck Controller 3.3 V 8 V 55 V Adjustable Surface Mount - 1 16 SOIC W Yes 10 mV
RS Stock No. 379-993
Mfr. Part No.L5972D
SGD4.078
Each (In a Pack of 5)
units
1.5A 35 V Buck Controller 1.235 V 4.4 V 36 V Adjustable Surface Mount - 1 8 SOIC Yes -
RS Stock No. 178-1392
Mfr. Part No.L4970A
SGD17.514
Each (In a Tube of 25)
units
10A 40 V Buck Controller 5.1 V 15 V 50 V Adjustable Through Hole - 1 15 MULTIWATT V Yes 30 mV