Characteristics and advantages and disadvantages analysis of linear regulated power supply

The editor below has compiled an analysis of the characteristics and advantages and disadvantages of linear regulated power supplies. It is worth knowing!

The linear regulated power supply achieves power supply regulation through transformation, rectification, filtering, and voltage stabilization.

Advantages: good stability, fast transient response, high reliability, high output voltage accuracy, and small output ripple voltage accuracy.

Disadvantages: The conversion efficiency is low, especially when the input and output voltage difference is large. If the output current is also large, there will be obvious heating, and the voltage regulator may even be burned out.

Linear regulated power supply composition:

Main parameters of low dropout linear regulator

The output voltage

Low dropout linear regulators are available in fixed output voltage and adjustable output voltage types.

Fixed output voltage regulator: The output voltage is precisely adjusted by the manufacturer, and the regulator has high accuracy.

Adjustable output voltage: The output voltage is adjusted based on the resistor across the ADJ pin of the regulator.

Maximum output current

Voltage regulators with larger output currents cost more. In order to reduce costs.

Input and output voltage difference

Under the condition of ensuring the stability of the output voltage, the lower the voltage difference, the better the performance of the linear regulator. For example, a 5.0V low-dropout linear regulator can stabilize the output voltage at 5.0V as long as the input voltage is 5.5V.

Ground current

When the output current of the series regulator tube is zero, the voltage regulator operating current provided by the input power supply. This current is sometimes also called quiescent current, load regulation

The smaller the load regulation rate of the linear regulator, the stronger the LDO's ability to suppress load interference.

power supply rejection ratio

Linear regulator input sources often have many interfering signals. PSRR reflects the linear regulator's ability to suppress these interference signals.

Notes on linear regulated power supply design:

Heat dissipation:

Due to the characteristics of the linear voltage regulator, the power consumption of the voltage difference part must be released through the heat dissipation of the chip itself. If the voltage difference and current are large, the power consumption on the device will be relatively large, and heat dissipation issues must be considered. If there is not enough space for heat dissipation during PCB design, the linear regulator chip will become hotter and hotter as the system runs. Operating in a continuously high temperature environment will seriously affect system life.

Solution:

When designing the circuit, calculate the power consumed by the linear regulator. If the power consumption is high, add a heat sink. Place vias under the regulator and cover the area with copper to connect to the ground.

Pressure difference:

There is a limit to the voltage drop that a linear voltage regulator can stabilize. When selecting a linear voltage regulator, you should consult the manual to see if the selected linear voltage regulator can meet the voltage reduction needs.

Bypass capacitor selection:

The peripheral circuit of the linear regulator is a few bypass capacitors. The selection of these capacitors should also refer to the device data sheet. Generally, 10uf and 100nf capacitors are connected to the input and output terminals. Bypass high-frequency signals and interference. When designing the schematic diagram, the 100nf capacitor should be as close as possible to the linear regulator. Used to eliminate noise generated by linear regulators.