Using the voltage regulator chip 7805, 16v to 5v, what size capacitor should be used?

electricor

Using the voltage regulator chip 7805, 16v to 5v, what size capacitor should be used? [Copy link]

 

Using the voltage regulator chip 7805, 16v to 5v, what size capacitor should be used?

maychang

7805, 16V to 5V, the efficiency is too low. Unless the load current is very small (less than 20 or 30 mA), it is generally not recommended to use linear voltage regulation.

qwqwqw2088

The input and output of 78/79 should be connected with large capacitors, usually in the hundreds of uF level. Generally, the output capacitor of 78XX-79XX series IC is most suitable with 100 or 220uF, which can be adjusted according to the requirements of the power supply filtering of your own load.

chunyang

That depends on the input ripple, the load weight and its rate of change, and the requirements for the output ripple. Generally speaking, electrolytic capacitors of several hundred microfarads are selected for input and output. However, the voltage difference from 16V to 5V is large, the efficiency of the linear regulator is too low, and the heat will be obvious if the output current is large. Using a switching power supply can solve these problems and the price may not be higher.

hk6108

Although 7805 is not an LDO, its voltage difference is as high as 11V, and its power consumption is greater than its output. So a 7809 is enough to use it first.

hk6108

For the input, if it is configured at 2μF per watt, the ripple valley is believed to be no less than 8V. 16V×1.5A is 24 watts, and 47μF@16V is enough. The 78/79 series can carry a good load, so it can't be a thorn. Then, based on the input capacitance, the output capacitance of 10μ is enough, or even 1μ is also fine, and it does not need to be larger than 47μF.

eebetter

It is not recommended to use 7805 for 16V to 5V conversion. The voltage difference is too large. If the working current is large, it will be very hot and need heat dissipation. If there is a requirement for ripple, use a switching power supply + LDO to achieve it.

hk6108

eebetter posted on 2018-8-5 10:48 It is not recommended to use 7805 to convert 16V to 5V. The voltage difference is too large. If the working current is large, it will be very hot and need heat dissipation. If there is a requirement for ripple, use a switching power supply + LDO...

A module can carry 11V alone, and even water cooling may not be of much use!

qwqwqw2088

hk6108 posted on 2018-8-7 19:11 A module can handle 11V alone, even with water cooling, it may not be very useful!

In theory, this is the case. The original poster did not mention how much current the load is, such as a few hundred milliamperes. Adding a heat sink without considering the efficiency is also feasible and low cost.

2000xujian

Low cost and high cost are relative. Question: How much space does this device reserve for the power supply (16v to 5v part)? What is the allowable power supply operating efficiency? Is there enough heat dissipation space? What is the allowable operating temperature range of the device? Assume: 16v is a regulated power supply, and the load current of 5v is 0.5A, then there is 5.5w of power consumption; if the load current of 5v is 0.1A, there is 1.1w of power consumption. If the power consumption of 1.1w is converted into heat consumption, please consider how much space is needed and whether natural air cooling or forced air cooling is used?

周振宇

25v/220uf