I would like to ask about the linear voltage regulated power supply made with transformer and 7815

liushenyue

I would like to ask about the linear voltage regulated power supply made with transformer and 7815 [Copy link]

The voltage of the power supply I made drops after a while of working with load. Is it because there is no heat sink on the 7815?
Thank you

fighting

The general dual power supply (positive and negative symmetrical power supply) does not have the function of continuous adjustment, which brings inconvenience to use. Here we introduce a symmetrical connection of a 7815 and a 7915 three-terminal voltage regulator to obtain a set of positive and negative symmetrical voltage regulators, and the output voltage values can be adjusted separately or synchronously. The circuit is shown in the attached figure. The AC dual 18V voltage output by the transformer is rectified by D1~D4, and filtered by C1 and C2 to obtain a DC voltage. The center tap of the transformer dual power supply is used as the common ground terminal, and then the positive and negative poles of the DC voltage are connected to the ① pin of 7815 and the ③ pin of 7915 respectively. The ③ pin of 7815 is connected to the sliding contact "d" of potentiometer W2, and the ① pin of 7915 is connected to the sliding contact "C" of potentiometer W1. When the contact "C" is slid to the "0" end and grounded, adjusting W2, a positive variable voltage of "+6~+15V" can be obtained from the "a" end; if the contact "d" is slid to the "0" end and grounded, adjusting W1, a negative variable voltage of "-6~-15V" can be obtained at the "b" end. If W1 and W2 are replaced with coaxial potentiometers, a positive and negative symmetrical adjustable power supply will be obtained, and the output voltage value can be continuously adjusted between ±6V and ±15V, which can achieve the purpose of synchronous regulation. The 7815 and 7915 three-terminal voltage regulator blocks of this circuit should be equipped with heat sinks, and the transformer power depends on the power of the electrical appliances. See the following URL for the figure: http://www.0net.cn/electron/ShowArticle.asp?ArticleID=783 Reference: http://www.0net.cn/electron/ShowArticle.asp?ArticleID=783

dongxiahui

Hey guys, I have a power board with an output voltage of more than 40 volts, which has exceeded the maximum value of 7815. How can I use 7815 to stabilize the voltage?