What is Load Regulation?
Load regulation refers to the ability to maintain a constant voltage output from a power supply despite changes or variability in the input load. Typically, we express load regulation as a percentage of the max load condition, indicating how much output will vary.The information below will help you understand the components in the load regulation formula:
- Vmin indicates the output voltage under minimum load.
- Vmax indicates output voltage under maximum load.
When it comes to load regulation, the lower the percentage the better. An ideal system would vary 0 percent in response to changes in load. Of course, this ideal scenario doesn’t exist in the real world, but it’s possible to achieve load regulations of fractions of a percent with good design.
As an example, a power supply that provides 12V under minimum load and 11.5V under maximum load would have a load regulation of about 4.35 percent.
Power Supply Load Regulation
Without regulation, the output voltage will either:
- Drop suddenly when an electrical load increases, or
- Surge suddenly when the electrical load decreases.
These changes may cause problems for devices connected to the power supply (such as damaging components when voltage surges). It’s therefore crucial to the components’ health and performance that we maintain a regulated power supply.
Manufacturers typically incorporate the load regulation percentage as well as the load range in which that percentage is valid. For the safety of your components, it is critical to ensure that your power supply will operate with proper regulation in the load range you specify.
How Do We Achieve Load Regulation?
We can achieve load regulation in one of two ways: with a linear regulator or a switch-mode power supply. We’ll explore linear regulators below, but you can learn more about switch-mode power supplies here.
Linear regulators function much like variable resistors, dissipating surges in the input voltage as waste heat to ensure a constant output of voltage. Essentially, the linear regulator operates by comparing the output voltage to a reference voltage. The regulator then produces a control signal to drive the change in resistance. As a result, linear regulators can only compensate down – the output voltage must be less than the input voltage, never more. By definition, efficiency in linear regulation is limited.
When using a linear regulator, it is crucial to ensure that the input voltage will always be high enough for the regulator to function. The difference between the regulator’s output and the minimum input required to function is called the “dropout voltage.” For example, in a regulator with an output of 5V and a minimum input of 7V, the dropout voltage is 2V. In applications where the dropout will be very small, you’ll need to use low dropout regulators.