Overview: The article reviews the efficiency, types, and advantages of switching regulators. It also discusses the working principles of buck converters, highlighting the TSR1-2450 series as a high-efficiency step-down regulator with precise output voltage control.

DC-DC converters are essential components in modern applications, providing efficient and reliable power conversion and management for various systems, such as renewable energy systems, electric vehicles, portable devices, and advanced communication systems. 

There are primarily two types of converters: 

Linear regulators, also referred to as low dropout regulators, rely on a linear passive device, like a series or shunt resistance. The output voltage can only be equal to or less than the input voltage and is solely used as a step-down converter. The linear regulators are maintained by an analog control signal with lower efficiency and a higher power loss. 

On the other hand, inductive or capacitive regulators, commonly called switching regulators, can generate an output voltage greater, lower, or inverted relative to the input voltage. These converters rely on a semiconductor-controlled switch to regulate their output. 

Switching regulators operate using the pulse width modulation principle. The duty cycle, which is a pulse-width modulated signal that controls the stable output voltage, is primarily responsible for controlling the stable output voltage. 

In addition to offering many benefits, switching regulators can mitigate the power loss that comes with linear regulators. Therefore, switching regulators are used to meet most of the power requirements.

What are switching regulators?

Switching regulators, also called DC-DC converters, are circuits that use an inductor, capacitor, power switch, and diode to convert one DC voltage into another. With variable input voltage, these regulators offer regulated output voltage. The output voltage can be greater, lesser, or inverting than the input voltage.

Switching regulators are critical components in modern electrical equipment for receiving consistent power. It consists of high-frequency switching and storage components that increase the efficiency and reduce the loss. The switching regulators consist of four key components: a switch, an inductor, a capacitor, and a diode. 

When the switch is turned on, there is no voltage across it; when it is off, no current flows through it. Thus, its power dissipation is essentially nil. Additionally, there is no power loss in the storage components, such as the inductor and capacitor, which temporarily store and deliver energy.

Advantages

  • The energy contained in the inductor can be used to step up (boost), step down (buck), and invert voltage levels, which provides extraordinary versatility in carrying out many kinds of conversions.
  • Switching regulators are more efficient than linear regulators and produce less heat, requiring fewer thermal management solutions.
  • Switching regulators have high efficiency in power conversion.

Disadvantages

  • Switching regulators can generate unwanted noise, making them unsuitable for noise-sensitive applications such as RF and sensor systems.
  • Switching regulators, which consist of multiple components, tend to be more expensive than linear regulators.
  • One of the drawbacks of these regulators is the complexity of design and component selection.

Types of Switching Regulators

The three basic switching regulator topologies are:

In the case of a buck converter, the output voltage (Vout) is smaller than (Vin), (Vout < Vin). In a boost converter, the output voltage exceeds the input voltage (Vout > Vin). In a buck-boost converter, the output voltage might be higher or lower than the input voltage (Vout >/< Vin).

This section describes how buck converters operate and provides an overview of the TSR1-2450 model performing efficiently in the market.

Buck Converter

As illustrated in Fig. 1, the fundamental workings of a buck converter consist of an inductor controlled by a switch and a diode. When the switch is turned on, current flows through an inductor, which limits and controls the flow of electric current in a circuit, decreasing the net voltage across the load. 

During the on time, the inductor temporarily stores the current as a magnetic field, and the diode is reverse-biased, and the direction of the current flow is depicted in the red line in Fig. 1.

Fig. 1  Flow of current in buck converter when the switch is in ON state. Source: Rakesh Kumar, Ph.D.

When the switch is turned off, the magnetic field collapses, and the stored energy is released in the circuit, in which the inductor works as a source. The diode is forward-biased, and current flows down the path illustrated in Fig. 2.

The capacitor smoothens the output voltage in the circuit. As a result, output voltage and current are preserved with the help of a capacitor and inductor.

Fig. 2  Flow of current in buck converter when the switch is in OFF state. Source: Rakesh Kumar, Ph.D.
 

The output voltage can be altered by altering the duty cycle or frequency of the pulse width modulated signal applied to the switch. In most instances, however, the signal's duty cycle is adjusted to produce a steady output voltage. The following equation can determine the output voltage.

Vout= D Vin

Where D is the duty cycle.

Introducing the TSR1-2450 Step-Down Switching Regulator

Made by Traco Power, the TSR1-2450 is a DC-DC step-down (buck) switching regulator. It is intended to convert a higher input voltage between 6.5 and 36 volts DC to a steady 5-volt DC output voltage that can supply up to 1 amp of current. 

The LM78XX series of three terminal regulators, which are available with a number of fixed output voltages, has been utilized in a wide variety of applications.

Fig. 3 TSR1-2450 Series. Source: oemsecrets

Advantages

With a maximum efficiency of 96% under specific circumstances, this device enables full load operation at +60° C ambient temperature without requiring heat sinks.

These TSR 1 series step-down switching regulators are a drop-in replacement for linear regulators from the LM78xx family, having comparatively lower efficiency. These regulators have pin compatibility with LM78xx and can be easily replaced without designing the circuit. 

TSR 1 is more efficient than linear regulators, with a wider input operating range, and it generates stable output with an increased precision of ±2%. Additionally, it has a lower standby current of 2 mA and a built-in filter capacitor. 

These regulators are a suitable alternative in various battery-powered applications due to their high efficiency and low standby power consumption.

Summarizing the Key Points

  • Switching regulators offer higher efficiency and versatility in power conversion than linear regulators, making them essential in modern applications.
  • Buck, boost, and buck-boost converters are key switching regulators, each serving specific voltage conversion needs.
  • The TSR1-2450 model from Traco Power is a notable DC-DC step-down regulator known for its efficiency and stable output voltage.

Reference

“Switching Regulator | Analog Devices,” n.d. https://www.analog.com/en/resources/glossary/switching_regulator.html.

Mahafzah, Khaled A., Ali Q. Al-Shetwi, M. A. Hannan, Thanikanti Sudhakar Babu, and Nnamdi Nwulu. “A New Cuk-Based DC-DC Converter with Improved Efficiency and Lower Rated Voltage of Coupling Capacitor.” Sustainability, May 24, 2023. https://doi.org/10.3390/su15118515.

“TSR 1-2450 | Traco Power,” n.d. https://www.tracopower.com/int/model/tsr-1-2450.

NPTEL-NOC IITM. “Introduction to Switching Regulators.” YouTube, October 11, 2022. https://www.youtube.com/watch?v=EhY_Vq60Zp0.

NPTEL-NOC IITM. “Linear versus Switching Regulators.” YouTube, October 12, 2022. https://www.youtube.com/watch?v=PIHxEvUEHak.