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Simple WorkBench Dual Power Supply

I will just explain part of this circuit. D9 and D10 provide a low cost -1.4 from -5 V. This is needed to reach near 0.00 for LM317 Min. setting. An LED also can be used with proper bias. Note that there is a Temperature Coefficient in ppm,  but it may not matter upto 8 bits accuracy.

TIP2955, TIP3055 (NPN), TIP2955 (PNP) Complementary Silicon Power Transistors. It is a Darlington, that means good current gain. When current in R1 10E goes more than 50mA a voltage of 50mA X 10E = 500mV is applied across Emmiter-Base junction. So lower than 500mV no bias the tap is turned off, 500mV-700mV the tap starts turning on depending on type of transistor.

Power Supplies Section

The transistor is like a water Tap. So TIP2955 carries the major current burden thru the load allowing LM317 to do the decision making when to turn-on or off. It is analog control, it is not On-Off but linear-proportional. The LM317 is very cool as the burden is passed off to TIP2955 who will need a heatsink to keep going and deliver the power you want.

WorkBench Dual Power Supply

Put the filter caps appropriately. The Hum-Noise will be filtered. The cap after the regulator should be a small guy. The main filter cap after the Bridge can be as big as your cabinet or budget.

Mains Voltage Power Transformers

If you build it and wire it without designing a PCB, then make all wiring and connection very sound. The test of this ability you can know easily, If your project stops working after the last screw of the cabinet is tightened, Then we need to improve.

PWM Control Circuit – TL494

The TL494 incorporates all the functions required in the construction of a pulse-width-modulation (PWM) control circuit on a single chip. Designed primarily for power-supply control, this device offers the flexibility to tailor the power-supply control circuitry to a specific application.

PWM Control Circuit – TL494

  • Complete PWM Power-Control Circuitry
  • Uncommitted Outputs for 200-mA Sink or Source Current
  • Output Control Selects Single-Ended or Push-Pull Operation
  • Internal Circuitry Prohibits Double Pulse at Either Output
  • Variable Dead Time Provides Control Over Total Range
  • Internal Regulator Provides a Stable 5-V Reference Supply With 5% Tolerance
  • Circuit Architecture Allows Easy Synchronization

PWM Control Circuit - TL494

The TL494 contains two error amplifiers, an on-chip adjustable oscillator, a dead-time control (DTC) comparator, a pulse-steering control flip-flop, a 5-V, 5%-precision regulator, and output-control circuits.

TL494 Related Links

SG2525 – SG3525 – PWM SMPS Regulator Chip

SG2525 – SG3525 – PWM SMPS Regulator Chip. A second generation ic switch mode controller optimized for high frequency.

100kHz Half Bridge Convertor – SG3525

The SG3525A pulse width modulator control circuit offers improved performance and lower external parts count when implemented for controlling all types of switching power supplies. The on-chip +5.1 V reference is trimmed to +/-1% and the error amplifier has an input common-mode voltage range that includes the reference voltage, thus eliminating the need for external divider resistors. Half Bridge, Push-Pull.

SG3525 usage in SMPS 500W – It was used in Parallel for Electroplating with a central Load sharing control between modules.

SG2525 - SG3525 - PWM SMPS Regulator Chip

Specs

  • 8.0 V to 35 V Operation
  • 5.1 V +/- 1.0% Trimmed Reference
  • 100 Hz to 400 kHz Oscillator Range
  • Separate Oscillator Sync Pin
  • Adjustable Deadtime Control
  • Input Undervoltage Lockout
  • Latching PWM to Prevent Multiple Pulses
  • Pulse-by-Pulse Shutdown
  • Dual Source/Sink Outputs: +/- 400 mA Peak

Circuits –

Power Electronics Section

Here are power supply, inverter, drives, chargers and high current equipment diagrams and links. There are Mosfet and Thyristor circuits too.

Power Electronics Section

Power Supplies, Inverters, UPS, Chargers, Electro Plating, Precision Welding-erosion, Coating Metals and many other Processes are made of high current circuits. Even in measurement of parameters like Micro-Ohm high currents are involved. Electronic Circuits are required in such products to give control to time, current, frequency and voltage in order to accomplish with the required precision a process or job.

Power Electronics Section - delabs
In any power equipment, efficiency and reduction of bulk is crucial so SMPS and high frequency control is an important part of this domain. These products also generate EMI-RFI. Product Safety Study is also vital.

The Power Circuits Section has been updated.

The MOSFET in Power Electronics

delabs Notes – In a Circuit Module, if all Power and Signal Polarities are reversed. All NPN to PNP, All N-Channel to P-Channel and Vice Versa. All Diodes and Caps too turned around. This Topsy Turvy or Mirror Design ought to work in Theory. It has worked for some circuits in practice too in my experience. ?

Some believe that N-Channel is more Robust than the P Type. In Bipolar Transistor NPN is more trusted for the final output stages. The NPN Transistor and N-Channel turn-on by a Positive control bias. It may be inappropriate to say this mosfet is NPN or PNP.

The MOSFET in Power Electronics

The traditional metal–oxide–semiconductor (MOS) structure is obtained by growing a layer of silicon dioxide (SiO2) on top of a silicon substrate and depositing a layer of metal or polycrystalline silicon (the latter is commonly used). As the silicon dioxide is a dielectric material, its structure is equivalent to a planar capacitor, with one of the electrodes replaced by a semiconductor.

If the MOSFET is an n-channel or nMOS FET, then the source and drain are “n+” regions and the body is a “p” region. If the MOSFET is a p-channel or pMOS FET, then the source and drain are “p+” regions and the body is a “n” region. The source is so named because it is the source of the charge carriers (electrons for n-channel, holes for p-channel) that flow through the channel; similarly, the drain is where the charge carriers leave the channel. MOSFET – Wikipedia

This application note discusses the breakdown voltage, on-resistance, transconductance, threshold voltage, diode forward voltage, power dissipation, dynamic characteristics, gate charge and dV/dt capability of the power MOSFET.
Application Note AN-1084 Power MOSFET Basics – IRF

A MOSFET is a transistor. It is a Metal Oxide Field Effect Transistor. Here are the symbols for FETs and MOSFETs: The MOSFET How the MOSFET works

The conductivity of the path from Source to drain is controlled by applying a voltage between the gate and the body of the semiconductor. N-channel enhancement MOSFET

See this simple circuit that explains everything
n-channel MOSFET switch – George Watson, Univ. of Delaware, 1996.

Power Electronics Design Methods

I first saw this practically in the Orthodox Cherokee SMPS. This is where we differentiate from Engineered Products and just Mass Production without following standards. The Cherokee SMPS was a work of art, perfect in all respects.

The Copper Desert or Isolation Land

There is a No Man’s Land in PCB. Any good power electronics designer should/will know. Product Safety and HV Isolation, Quality and Reliability all depend on this.

High Energy Circuits

Power Electronics Design Methods

These things don’t come overnight, it is a culture, learning, experience and integrity of some of these American Firms. Reliability and Product safety are important. Every human values his life very much. A manufacturer too should appreciate this.

Coming back to isolation, Keep in mind creepage distance, High energy circuits and Low voltage circuits should have clear isolation, use the best insulation. Fire and shock hazard. Mains HV transitions, spikes.

Regulated High Voltage Power Supply

Power supply faces all these, even other areas where a Human Life or Property can be endangered.

HV High Voltage Reliability and Safety

Use a Servo Stabilizer or CVT Constant Voltage Transformer or at least an Isolation Transformer. The First Defense form HV Surges, Spikes.

High Voltage Polyester & Polypropylene Metallized Capacitors in Stepdown Supplies should be Fire Retardant & Self Healing with a MOV too.

PC User Interface and Wireless Power

Wireless Charging is a Reality today, it was first conceived by me in the 90s. The first page published related to that in my netscape site.

This was conceived to get rid of cables for data and power on my desktop. I felt if we use Optics for Data and Wireless Ferrite Contact Plates to transfer power, there would be no wires at all on the desk. I even experimented with RS232 Serial Port and Ferrite Slices below thin Acrylic Plastic Sheet, it worked.

I did not patent any of my concepts, but it is offered to all humanity as an Open Design, like all my other work.

Here is a planar transformer which has PCB tracks for winding. This show that there is more scope of innovation in such ferrite transformers for short range wireless power.

PC User Interface and Wireless Power

Objects kept on a electromagnetic table must be able to draw energy from that. A Notebook or tablet can be just placed on this table to get charged.

The optic ball-less mouse is a great step in mice-tech user-interface. This mouse consumes more power, for a wireless mouse a capacitive sensor matrix based sensing may be better.

Touch Screen on PC is not common place. A combination of Touch screen and Mouse is excellent for all age-groups. Large monitors can have at least two inches of touch screen area at bottom.

Laptops, LCD Monitors make UPS (Uninterrupted Power Supply) last longer and it reduces electricity costs.

Wireless Power for Wireless Peripherals

Wireless Mouse with capacitive sensors may consume less power, no batteries works on a Supercap, Connector-less ferrite dock for recharging

Wireless mouse rechargeable battery can recharge while moving on the Mouse Pad made of Ferrite/Ceramic 1? Sq with Power Hot Spots every 3?

Flexible Ferrite, Silicone & Ferrite based Solid emulsion. Can be made as computer table mats to charge the supercaps of peripherals.

The Energy Efficient Wireless Peripherals can just be placed on this mat to draw the power without wires. Wireless power and Wireless Data.

Usability and Ergonomics Review
Aggregated Notes from 2008-12

Usability and Ergonomics of Electronic Consumer Equipment, product risks and safety are best studied with very old and very young people.

Optical Rotary Encoders, Magnetic/Eddy/Capacitive/Hall Effect based Non-Contact Joysticks, Makes Human An analog Interface with Digital Output.

For the people who type with two fingers; A Circular Keyboard is right. A Capacitive Touch Gesture Pad can replace the Mouse. Health & Ergo.

Personal Computers, Netbooks, Portable Communicating Devices, Remote Controls are where Usability Issues abound, and can be studied/remedied

delabs – 2009