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. 914-3109
Mfr. Part No.TPS563200DDCT
HK$9.702
Each (In a Pack of 5)
units
2A 7 V Step Down, Synchronous Voltage Converter 0.76 V 4.5 V 17 V Adjustable Surface Mount - 1 6 SOT-23 Yes -
RS Stock No. 162-9888
Mfr. Part No.TPS563200DDCT
HK$5.994
Each (On a Reel of 250)
units
2A 7 V Step Down, Synchronous Voltage Converter 0.76 V 4.5 V 17 V Adjustable Surface Mount - 1 6 SOT-23 Yes -
RS Stock No. 460-487
Mfr. Part No.LM2576HVS-ADJ/NOPB
HK$58.04
Each
units
3A 57 V Buck Controller, Inverting 1.23 V 4 V 60 V Adjustable Surface Mount - 1 5 D2PAK (TO-263) Yes -
RS Stock No. 923-2534
Mfr. Part No.LM2576HVS-ADJ/NOPB
HK$57.365
Each (In a Tube of 45)
units
3A 57 V Buck Controller, Inverting 1.23 V 4 V 60 V Adjustable Surface Mount - 1 5 D2PAK (TO-263) Yes -
RS Stock No. 533-4134
Mfr. Part No.LM2673S-5.0/NOPB
HK$55.98
Each
units
3A - Buck Controller - 8 V 40 V Fixed Surface Mount - 1 7 D2PAK (TO-263) Yes -
RS Stock No. 920-3646
Mfr. Part No.LM2673S-5.0/NOPB
HK$47.618
Each (In a Tube of 45)
units
3A - Buck Controller - 8 V 40 V Fixed Surface Mount - 1 7 D2PAK (TO-263) Yes -
RS Stock No. 422-992
Mfr. Part No.TPS54350PWP
HK$30.93
Each
units
3A - Buck Controller 0.891 V 4.5 V 20 V Adjustable Surface Mount - 1 16 HTSSOP Yes -
RS Stock No. 145-5694
Mfr. Part No.TPS54350PWP
HK$31.721
Each (In a Tube of 90)
units
3A - Buck Controller 0.891 V 4.5 V 20 V Adjustable Surface Mount - 1 16 HTSSOP Yes -
RS Stock No. 121-8929
Mfr. Part No.PTN78020WAH
HK$253.898
Each (In a Tube of 20)
units
6A - Buck Controller - - - - Through Hole - 1 7 DIP Module Yes ±10
RS Stock No. 545-7849
Mfr. Part No.PTN78020WAH
HK$226.78
Each
units
6A - Buck Controller - - - - Through Hole - 1 7 DIP Module Yes ±10
RS Stock No. 920-3517
Mfr. Part No.LM2576S-12/NOPB
HK$22.46
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. 121-8269
Mfr. Part No.LM5576MH/NOPB
HK$68.135
Each (In a Tube of 73)
units
3A - Buck Controller, Inverting - 6 V 75 V Adjustable Surface Mount - 1 20 TSSOP Yes -
RS Stock No. 920-3508
Mfr. Part No.LM2576HVT-ADJ/NOPB
HK$57.32
Each (In a Tube of 45)
units
3A 57 V Buck Controller, Inverting 1.23 V 4 V 60 V Adjustable Through Hole - 1 5 TO-220 Yes -
RS Stock No. 121-9339
Mfr. Part No.LM5017MR/NOPB
HK$29.379
Each (In a Tube of 95)
units
650mA 90 V Synchronous Buck Controller 1.25 V 7.5 V 100 V Adjustable Surface Mount - 1 8 SOIC Yes -
RS Stock No. 533-3181
Mfr. Part No.LM2576HVT-ADJ/NOPB
HK$66.49
Each
units
3A 57 V Buck Controller, Inverting 1.23 V 4 V 60 V Adjustable Through Hole - 1 5 TO-220 Yes -
RS Stock No. 920-3558
Mfr. Part No.LM2594HVN-ADJ/NOPB
HK$36.751
Each (In a Tube of 40)
units
500mA 57 V Buck Controller, Inverting 1.2 V 4.5 V 60 V Adjustable Through Hole - 1 8 MDIP Yes -
RS Stock No. 533-3541
Mfr. Part No.LM2594HVN-ADJ/NOPB
HK$46.73
Each
units
500mA 57 V Buck Controller, Inverting 1.2 V 4.5 V 60 V Adjustable Through Hole - 1 8 MDIP Yes -
RS Stock No. 533-5121
Mfr. Part No.LM2676S-ADJ/NOPB
HK$59.21
Each
units
3A 37 V Buck Controller 1.2 V 8 V 40 V Adjustable Surface Mount - 1 7 D2PAK (TO-263) Yes -
RS Stock No. 920-3510
Mfr. Part No.LM2576S-5.0/NOPB
HK$28.689
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. 921-3044
Mfr. Part No.TPS5430DDAR
HK$16.398
Each (On a Reel of 2500)
units
3A 31 V Buck 1.22 V 5.5 V 36 V Adjustable Surface Mount - 1 8 SOIC - -