The purpose of this paper is to detail a variable dual lab power supply circuit which has an adjustable range from 3V, 5V, 6V, 9V, 12V, and 15V or even more at an output current rate of 1 amp.
Written By: Dhrubajyoti Biswas
双电源概念
In regard to positive volt it is preferable to use IC LM317 [-3V,-5V,-6V,-9V,-12V,-15V at 1A] and use LM337 as the negative volt. The voltage can further be controlled by S2 [+Vout] and S3 [-Vout]. The size of the transformer is set to 2A and furthermore the IC enables holding the heat sink.
However, for this development we would like to develop a dual positive power supply, ground and negative so as to experiment it in different circuits.
In addition, we can also experiment运算放大器IC - LM741, which uses the power supply voltage of +9 volts and -9 Volts. Even when we use tone control circuits or preamplifier circuit, they will use voltage supply of +15 volts and -15 volts.
Nevertheless, the circuit that we design here will be useful because a) The circuit has the capacity to enable positive voltage and even negative voltage [at 3 volts, 5 volts, 6 volts, 9 volts, 12 volts, 15 volts respectively keeping the output of the current under 1.5 amps; b)
The circuit is best to use with rotating selector switch, which will give the freedom to select the level voltage. Moreover, you won’t require any voltsmeter to measure the voltage of the output; c) The circuit is simple and the IC used for it LM317 andLM337are cheap and can be easily procured from the market.
Circuit Diagram
How the circuit works
In this dual variable power supply circuit IN4001 – D3 and D4 diode acts as the full-wave rectifier. The waveform is then filtered to ease the capacitor C1 (2, 200uF).
然后，LM317T（ICI）的输入起作用以在正模式下调节IC。此外，它还调整了1.2-37伏特的电压，并使最大电流输出提供1.5安培。
点要注意
- The output of the voltage can alter because of the value of change in Resistor R2 and further alters R3 to R8. This is accomplished by S2 selector switch and you can choose the resistance as per your need, in order to gain the voltage level from 3, 5, 6, 9, 12 and 15 volts.
- The C2 (22uF) measured with high impedance and further reduces to transient on the output of ICI-LM317T.
- The C3 (0.1uF) capacitor is used when IC1 is installed keeping distance from C1.
- The C5 (22uF) capacitor, before being amplified and as the output of the voltage goes up acts as ripple signal.
- The C9 capacitor is used to low down the ripple in the output.
——D5和D7二极管(IN4001)电路sed to protect IC1 from the discharge of C7 and C5, in situation when the input is in short circuit.
- 关于负模式，它遵循类似的原理，例如正模式。在这里，D1，D2是整流器全波的模型中的整流二极管。IC IC2-LM337T受负直流调节。
Aforesaid is the process to develop an adjustable dual power supply. However, if you need the voltage to be variable in nature [for instance, 4.5V,7.5V,13V et al], simply add the VR1 in IC1-LM317 and IC2- LM337 pin.
If a rotary switch is used instead of a potentiometer, as shown in the diagram, make sure to use a rotary switch having a "make before break " feature which will ensure that while operating the rotary switch, the output does not swing to the maximum voltage level during the split second transitional disconnection of the switch contacts. The "make before break" feature is specially designed to prevent such situations from occurring.
Calculating the Resistor Values:
The values of the various fixed resistors could be calculated either through thiscalculator softwareor using the following formula:
VO= VREF(1 + R2 / R1) + (IADJ×R2）
其中r1 = 270欧姆如图所示，r2 =与旋转开关连接的单个电阻，vREF= 1.25
For most applications IADJcould be simply ignored since it's value will be too small.
另一个LM317简单的双电源电路
The diagram above shows how a simple yet higher versatile, adjustable dual power supply circuit could be built through just a couple of LM317 ICs. The circuit will produce an adjustable dual supply of 12V, 5V, and 9V
It means, an effective variable dual supply output could be achieved by using readily available IC like LM317, which is very easily accessible in any electronic market.
The design employs a couple of identical LM317 variable regulator circuits driven through separate bridge rectifiers and AC inputs from the transformers.
This allows us to join the + and - of the two supplies to create a dual supply of our own choice as per specific requirements.
考虑到将输出电压调整为3个变量范围应该可以实现，因此，施加的电压调节器是一种可以使用少数电阻器来固定的，如电路图所示。使用公式确定输出电压
Uout = 1.25(1+R2/R1) + IadjR2, in which 1.25 signifies the reference voltage of the IC, and ladj indicates the current moving through the 'ADJ(ust)' pin of the device towards ground.
The IC LM317 has internal compartaors, which constantly analyzes portion of the output voltage, fixed by resistive divider R1/R2, with the reference voltage. In the event that Uout is required to be higher; the comparator output is switched high which forces, the internal transistors to conduct harder.
This action decreases the collector-emitter resistance, causing a boost in the Uout. This set up guarantees a practically constant Uout. Practically , the value of Iadj falls between 50 µA and 100 µA. Due to this lower value, the factor Iadj R2, could typically be removed from the formula. Therefore, the refined formula
UOUT = 1.25 [1+（1270+1280）280] = 12.19 V.
Precision Dual Voltage Power Supply
该电路具有比标准2固定电压隔板的好处，其中电压评分V：V不依赖于从中流的电流。电阻r：r1的比率确定电压比。
The OP-AMP identifies any change in this ratio via Rf并迅速执行校正。实际的签证官ltages utilized will be limited by the upper and lower operating voltages of the OP AMP. The circuit shown was developed to deliver +15 V, -15V dual supply, specifically for the operational amplifiers.
Balanced Power Supply using LM324
This stream-lined balanced power supply utilizes the 4 opamps from one LM324 IC. These are employed to stabilize the output voltage and also to control the output current. The current limiter circuit is defined at 60 mA and consists of lowest number of parts.
It has to be taken into account that under certain situations it might appear that the (input) power supply of only ±16 V is actually very low. However, the highest output voltage is determined by the specifications of the IC employed. It is far from safe to raise the input supply voltage; any kind of rise in the voltage could destroy the IC, depending on its maximum input voltage tolerating specifications.
A 5.6 V zener diode is employed for fixing the reference voltage. The zener value is not really crucial; if it is small, the output voltage is going to be a bit lower.
P1 works like the voltage adjustment pot simultaneously for controlling both the +15 and -15 supplies. Using P1, the reference voltage gets broken down and is given to the + input pinout of the (upper) opamp.
This particular opamp manages the positive output voltage by governing the base current of the series regulating transistor (BC140). The stabilization of the output voltage is influenced through a negative feedback loop through a voltage divider network composed of the 22 k and 10 k resistors.
The regulation of the negative voltage tends to be relatively more complex. The + input pinout of the lower opamp is coupled to the zero voltage '0', by means of a 6k8 resistor.
参考电压通过控制锅P1以及带有输入引脚的各种零件使用。负输出电压相对于通过33 K和10 K电阻建立的电压分隔器“ See -SAW”网络（通过修剪电路桥接在一起），相对于正参考电压平衡。
修剪预设控制器P2取消电路元件中小公差的影响，并且可以调整P2以平衡正极和负输出电压。超过当前的安全性是由IC中的几个剩余的操作员实现的。
In case the voltage difference across one of the 10 ohm resistors becomes greater than 0.6 V, the reference voltage is going to decrease to zero and, as a result, the output voltages also reduces along with it. Simultaneously the LED's illuminate to show that the protection feature of the circuit is working.
另一个简单的3V至 +15V，-15V双电源电路
下图显示了另一个简单的双电源电路，该电路可以自定义以在3V和15V之间获得任何双电压。这
By appropriately changing the values of the resistors R2, and R4 resistors it may be possible to alter the output from anywhere between 3V, 4.5V, 6V, 9V, 12V, 15V dual supplies.
对于固定的双电源，您可以使用以下配置。在这里，我们可以看到，对于正供应，使用了IC 7812，对于负供应，已使用IC 7912：
Dual Power supply circuit using IC 7815 and IC 7915
Sir Swagatam Majumdar !!!
i have simulated this circuit but it is not giving proper output voltages.
i.e when rotatory switch is connected with 3k resistance ,it gives 21.43 voltages
当旋转开关与3K电阻连接时，它给出21.34电压等，该怎么办。
Errors are expected in Simulation…have you made it on Hardware???
Asif, I have not made it practically, but the design looks very obvious and straightforward, so there's no harm in building it practically and tweaking the results with some trial and error….there's nothing in the design that might blow of or burn during the testing process…
Thanks sir.
我会尽快尝试一下。
Thanks for your informative posts.
Sharing is Caring
you are welcome!!
先生，
In circuit diagram ic LM317 output pin
direct short with Adjust pin
thanks Ubaid, it's a drawing mistake, there should be a diode there instead of a short
先生，有一个中心水龙头12-0-12变压器是否可以从每侧获得两个正12V？
if yes, kindly help me out with the circuit diagram
如果没有,我可以使用the negative (-12v) of the center tap transformer to supply circuit that requires +12
sir what I really what to do is to simply two separate circuit (that is 1. the egg Turner timer circuit and 2. the temperature control circuit) with the same center tap transformer
帕特里克（Patrick），要获得两条单独的 +12V线，您只需要使用两个单独的二极管从桥梁整流器输出分叉到一个 +12V到阳性线。那就是……为此不需要中心水龙头。
这两种 +12V线都将很常见
I found it is important to use a rotary switch that connects the next pole before disconnecting the first one. Otherwise as you rotate the control there is a brief moment where it is open circuit. This will result in a high voltage spike on the output. Possibly damaging the connected device. With a “ make before break” type there will be a brief voltage drop as you rotate. Not normally an issue.
Thanks for pointing out the issue, I will update the info in the article soon.
sir what change do i have to make to get 6 or 7 amps from the circiut will i have to wire more lm312 ic in parallel at both sides
Abioye, adding more ICs in parallel can be complex, instead you can try the following alternative design
//www.addme-blog.com/0-to-50v-0-to10amp-variable-dual-power/
Sir please am doing a project on a DC regulated power supply with voltage of 2v,6v and 9v…
I find this circuit diagram very useful but am having some doubt’s about excluding other resistors in the circuit and use the necessary ones I require.
Please its an urgent project
弗林，您可以删除不需要的开关电阻...
sir can i use lm196 or lm338 for both ic to get high current up to 10amps or are there any other ic that can replace the ones in the diagram for higher current up to 10amp
Marvin，您可以使用LM196或LM396通过在IC中添加足够的热量链接来达到10安培。
sir i hope am not disturbing you but am a little bit confused if i change the lm317 in the circiut to lm196 or lm396 what ic am i going to use to replace LM337
yes that may not be possible, because it seems there’s no negative complementary IC for LM196
Pls swag,I need a very efficient circuit that can stepdown 48v to 12 voltage.I want to use it to power a microcontroller board.
你好,约瑟夫,
您可以尝试以下概念：
//www.addme-blog.com/5v-pwm-solar-battery-charger-circuit/
Hello, I really love this idea with the switch, but I was thinking to add the 2N3055 and MJ2955 at each LMXXX IC to increase the output current. Has you designed one with this option cause sometimes 1 amp is not enough but maybe 3 or 4 amps. I would really love to hear about this. I am a Hobbyist currently working in my new Workbench Power Supply.
Thanks
Hi, yes you can add an outboard transistor for increasing the current, you can read the following article for more info on the same:
LM317带舷外电流电路
您可以考虑使用没有IC的离散零件来设计基准电源，如下所述：
用IC 741制作工作台万用表
Good day Swagatam, I would like to share with you the integration of the Bench Top Power Supply for your advice. As discussed, I used the diagram suggested by you and other diagram where the transistor were added to the LM317 and Lm337 for increasing current. I would really like to hear your advice to this respect but this plataform doesn’t allow me to send the picture.
嗨，豪尔赫，是的，不幸的是，用户本网站上没有图像上传设施，但是没问题，您可以通过评论来解释问题，我将尽力理解它并为您解决它…
Mr Swagatan
一开始，我想说的是，上帝会祝福您，您的文章真的很棒，教育
如果您可以将我引导到那儿，我会非常感谢您，这可能会为家制作的Epron程序员和读者找到一个计划
I would be awfully thankful if you may help me with this matter
Thank you for your collaboration
Jeovanny Viteri
Thank you Mr Viteri, I am sorry I do not know much about EPROMs and how they are programmed, so I can’t help you in this regard.
Very very good circuit, I really understood all thanks for all the diagrams may God bless you and give you more wisdom to analyze more circuit to us I hope to see more circuit diagrams analysis from you. Thanks
Thank you very much, and glad you liked my work!
Good evening Sir . I very often go through your page homemade -circuits . Few days ago I have visited a circuit related to smps using transistor mje13005 . But I am sorry to say that the circuit is providing very weak current. The circuit which I have assembled is capable of providing only few milliamperes of current. The same thing happened previously with other circuits. Kindly help me in building a smps 12 volt 1 ampere from 230 volt ac line voltage supply . I wish to make a led power supply with the same in low price.
嗨，Shantanu，如果您想要可靠的1AMP 12V SMP，则可以尝试以下设计：
//www.addme-blog.com/how-to-make-simple-12-v-1-amp-switch/