delabs Circuits

Showing posts with label Power-Supply-Regulators. Show all posts
Showing posts with label Power-Supply-Regulators. Show all posts

Thursday, September 28, 2017

Mains Stability and Supply Regulation

I have problem with my power supply... . The power supply uses LM317 and TIP2955 and the unstable AC net here causes the output to drop sometimes below 5V. The normally output is 13,5V. I like to look at your schematics to improve my power supply.

Mail from WV

See some circuits here ...

See the Insides of a DIY Ham Radio Power Supply

DIY Ham Radio Power Supply

You have to ensure at least a min of 15V AC to the Bridge or diodes on transformer. Only if a DC of around min 17V is available at input DC of 13.5 can be managed by this circuit. This circuit will not boost a voltage from a lower value for that you need Switching Boost Supplies.

Use AC Voltage Stabilizers or ServoStabilizers to maintain a stable AC Supply.

WorkBench Dual Power Supply
LM317 - Simple Workbench Dual Power Supply


.....I like to compare with my schematics from our power supply. We have something very strange.. the backup battery takes over and don't cause a voltage drop when I disconnect power supply from 220V AC lines.. but the backup battery can not anticipate the disturbances in the 220V AC lines and gives a very short power drop at the output..

We have sometimes very short power drops at the output of the power supply.. Do you have any idea what is wrong? The transformer is 16V AC 3A
Reply from WV

You can double the size of filter caps at input. use something like 10,000uF, if you draw 3A a 10000uf across the input rectifier may help. Or you have to use a battery of 12V after the LM317. So that the battery can supply the short outages.

But that is exactly my problem, we have a large battery after the power supply of 13,5V 5,5Ah, but it doesn't help to avoid the powerdips after the power supply..
Reply from WV

I feel you have a ground loop problem, The wires to the battery seem thin. I feel the potential across a ground wire must be lifting up when mains fluctuates.

The PCB ground plane may be thin or absent, check all ground and supply wires. Make all supply wires and Tracks thick and radiate from a center copper lug reference. Both positive, negative and ground tracks reinforce with lead or copper braids. Use decoupling caps at every stage.


Thursday, July 07, 2016

Understanding Transistor Power Dissipation

I like your page about current source circuit basic design. However, I still have Little confuse of the power dissipation calculation.

The max power dissipation of my circuit is 20.5V x 0.5A = 10.25W, but transistors I found are 2W power dissipation. But my input voltages is just varied from 18.0V to 20.5V only. Do you think the 2W power dissipation transistor is fine? Any help will be appreciated.

Mail From MT

When the Current source output is short circuited or connected to a low impedance load say 10 ohms, the full voltage of input 20V falls across the transistor but current is limited to 0.5A. which means the 2W transistor may Roast. The transistor when conducting, the watts is the volts across it and current thru it. Not your supply Voltage.

Power Electronics & Solar Energy

HeatSinks in Electronics

HeatSinks in Electronics - For all types of packages, there are heatsinks. They are mainly made of Black Anodized Aluminium. Aluminium is a good conductor of heat and Anodizing prevents any form of corrosion. Linear Regulated Supplies, RF Transmitters and Power Amplifiers have Devices that need heatsinks. Use Mica, Silpad, PolySulphone Pads for Electrical Isolation. HeatSink compound too.

Power Supplies Section

Design in such a way there is no short circuit or a a power resistor in source. But then efficiency drops. The best way is to use a switching supply design or keep the input voltage across transistor to a minimum.


Saturday, May 16, 2015

Power Supply Regulators and MOSFET Transistor

HELLO THERE ...COULD anybody pls help me with a place to get more information on the following components...cant seem to find it anywhere.

W20NB50 W8NB100 found them in a liteon power supply pack for a database supply. i just don't know what they stand for. ...saw on a web page that it is produced by ST micro electronics. i went there but no show ..can somebody pls help?

post by FP

W20NB50 ST Power MOSFET Transistors TO-247 N-Ch 500 Volt 20 Amp
W8NB100 ST Power MOSFET Transistors TO-247 N-Ch 1000 Volt 8 Amp

You  will find equivalents here - NTE Electronics - N-Channel MOSFET Selector

ST’s MOSFETs with a breakdown voltage > 650 V offer low gate charge and low on-resistance down to 0.275 Ω (850 V) in PowerFLAT 8x8 HV packages.

Junction design of a Mosfet

Junction design of a Mosfet

"The source-to-body and drain-to-body junctions are the object of much attention because of three major factors: their design affects the current-voltage (I-V) characteristics of the device, lowering output resistance, and also the speed of the device through the loading effect of the junction capacitances, and finally, the component of stand-by power dissipation due to junction leakage."

Updated - July 2013


Tuesday, February 17, 2015

Single Chip dual power supply

message: Hello, I want to know the single IC which can provide Both + V and -V from a single +Vin supply.. I need this for my dual supply opamp.Reply me as soon as possible. -  Thank u.

Mail from KM

There were chips, but now obsolete as most use a smps circuits. you can try this RS232C Level Converter it has -10 and +10 that can power low-power cmos opamps and chips.

or use LM7912 and LM7812l you will need two chips, there was a LM326 but not now. See Linear Regulated Dual Polarity Power Supply

When a Inverting Opamp Configuration is at a steady state, we say the Inverting Input is at a Virtual Ground. That means it is at 0V w.r.t to the dual power supply ground, but it cannot drive or draw any current. It is at a high impedance, but still at 0V. When you buffer this 0 V, you get a low signal ground for a opamp supply. Opamp generates Virtual Ground. See this a Isolated dual power supply from 5V

Dual Polarity Power Supply


I am very happy to see ur reply.I am appreciating ur job. Ok.. Ur information is most useful for me.. We ill meet with another problem.. Thank u..

Mail from KM