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庫存編號 145-3553
製造零件編號LM2574N-12G
TWD59.00
毎管:50 個
單位
500mA - Buck Controller - - - Fixed Through Hole - 1 8 PDIP Yes -
RS庫存編號 168-6458
製造零件編號L4971D
TWD100.00
毎管:49 個
單位
1.5A 50 V Buck Controller 3.3 V 8 V 55 V Adjustable Surface Mount - 1 16 SOIC W Yes 10 mV
RS庫存編號 920-3598
製造零件編號LM2596T-12/NOPB
TWD145.80
毎管:45 個
單位
3A - Buck Controller, Inverting - 4.5 V 40 V Fixed Through Hole - 1 5 TO-220 Yes -
RS庫存編號 423-636
製造零件編號LT3505EMS8E#PBF
TWD220.00
單位
1.2A - Buck Controller 0.78 V 3.6 V 36 V Adjustable Surface Mount - 1 8 MSOP Yes 0.007 %/V
RS庫存編號 901-3260
製造零件編號LT8612EUDE#PBF
TWD410.00
單位
6A 5 V Step Down - 3.4 V 42 V Adjustable Surface Mount - 1 28 QFN Yes 0.02 %/V
RS庫存編號 779-9662
製造零件編號LT3509EDE#PBF
TWD244.00
單位
700mA 60 V Buck Controller 0.8 V 3.6 V 36 V - Surface Mount - 2 14 DFN Yes 0.01 %/V