Daren DIY 0 watts ranged linear DC power supply

The linear power supply is capable of stepping down the AC power and has a wide range of applications in the field of electronic design. This article will introduce a range of linear DC adjustable power supplies that can be tuned from 0V and can perform low voltage experiments.

In theory, this power supply can achieve 0-600V adjustable DC voltage output, and the components used can be fabricated using low voltage components in addition to the main filter capacitor and main regulator.

Using the panel version to build a simple circuit, successfully passed the low voltage experiment of 30V. However, the characteristics of the op amp are not very good, so the experiment was carried out with 4558, 5532, TL082, OP07, respectively, of which 07 won! Achieve continuous adjustment of 2-30V (no zero adjustment circuit, if there is a zero adjustment circuit, it should be able to adjust from 0), 5532 second, can achieve 4-30V adjustment, TL082 can also do 4- 30V adjustment, but when the potentiometer is adjusted to the minimum (that is, the potential of the positive input of the op amp is 0), the output jumps back to the maximum.

The 4558 has the worst effect, and the circuit function cannot be completed at all. The output voltage changes back and forth between 5V and 30V as the angle of the potentiometer is adjusted. If you have a CA3140 (using a zero-up circuit), the effect should be better.

This circuit is derived from the traditional series adjustable voltage regulator circuit, as shown in Figure 1.

The low-voltage test slightly simplifies the circuit. The output of the op amp does not have 8050 expansion, and the light-emitting tube of the optocoupler is directly used. The thin-plate potentiometer is 22K. The photocoupler of the optocoupler is not connected to the expansion tube, and the input voltage of the adjustment tube circuit is directly pushed. It is 30V, the sampling resistance of the sampling circuit, the upper is 12K, the lower is 1K.

The function of the coupling is to minimize the voltage of the component and to isolate it. The most common 4N35 is used.

Some people may suggest that if you use the 7805, you may be at risk. In fact, adding a first-level voltage regulator in Figure 1 can solve it. It is recommended to use a voltage regulator of about 15V for a voltage regulation and then provide it to the 7805. The reason for the birth of this circuit was that when the self-made tube measuring instrument was prepared, it was prepared for the adjustable DC voltage of the screen, so the current is expected to be between 300-500, which is not large.

There is no indication of the type of adjustment tube, just to leave a larger application space for everyone, we can freely choose according to the actual voltage and current requirements. Yesterday, the low-voltage experiment used NEC's high-power tube 2SC2750 (100V 7A 100W) Because it is only a low voltage test of 30V, there is no high back pressure pipe. If you want to use it, you can consider BU508 (1500V/5A/50W) or 2SD1403 (1500V/6A/120W) and other pipes to adjust. Of course, For example, there are actually a lot of tubes available.

This article introduces a large adjustable range linear DC adjustable power supply that can be adjusted from 0V. A detailed introduction to the circuit design and some key designs is expected. I hope that everyone can gain something after reading this article.