LNK304 based switch mode power supply circuit

12V /120 switch mode power supply circuit

 

The circuit diagram of a practical 12V/120mA transformerless switch mode power supply is shown above. Resistor R1, capacitors C1 and C2, diodes D1 and D2 and inductor L1 forms the input stage. D1 and D2 forms the rectifier section while C1 and C2 are input filters. Resistor R1 which is a fusible resistor limits the inrush current, increases differential mode noise attenuation and also serves as an input safety fuse.

The next stage is the regulator stage which consists of IC LNK304, diodes D3 and D4, capacitors C3, C4 and C5, resistors R3, R4 and R5 and inductor L2. D3 is the freewheeling diode while L2 is the output choke. C5 is the output filter capacitor which limits the output ripple voltage to a value as low as possible. The IC LNK304 is so configured that the power supply operated in the most discontinuous mode and that’s why a fast recovery diode (UF4005) is used as the freewheeling diode (D3). UF4005 has a reverse recovery time of around 75nS and it is well enough for the given situation.

The voltage drop across diodes D3 and D4 are practically same and so the voltage across C4 tracks the output voltage and this voltage is picked by the network comprising of resistors R2, R3 and is fed to the feedback pin. R2 and R3 sets the output voltage and for 12V output the voltage at the feedback pin must be 1.65V DC. The circuit attains regulation by skipping the switching cycles. When the output voltage rise, the current at the feedback pin also rises and when the current rises above the threshold value, subsequent cycles are skipped until the current at the feedback pin goes below the threshold and thus a constant output voltage is maintained.

The IC will auto restart if no cycles are skipped during a 50mS time period and this limits the maximum output power to 6% of the maximum over load power. That’s how over load protection is attained. Resistor R4 serves as a small preload which nullifies the effects of tracking error.

12V/120mA switch mode power supply circuit.

Transformer less switch mode power supplies have become very popular these days. The circuit shown below is of a 12V/120mA output, 85 to 230V AC input transformerless switch mode power supply using LNK304 IC. Applications of a power supply based on this IC includes hand held devices, timers, small appliances, LED drivers, industrial gadgets etc.

LNK304 is a low component count, efficient off-line switcher IC that can support buck, buck-boost and flyback topologies. The IC has a built in auto start circuit for short circuit and open loop fault protection. Other features of LNK304 includes low temperature variation, thermal shut down,high break down voltage, good line & load regulation, high band width , wide input voltage range (85 to 230V AC) etc. In general the LNK304 has a better performance when compared to the many other discrete buck regulators.

 

LNK304 pin configuration and typical application

The pin configuration and the typical application diagram of LNK304 are shown above. Drain (D) pin the drain connection of the built in power MOSFET. The external by pass capacitor (0.1uF) is connected to the BYPASS (BP) terminal. FEEDBACK (FB) pin controls the switching of the built in power MOSFET. A current above than 49uA delivered to this pin will inhibit the switching. The internal power MOSFETs source is connected to the SOURCE (S) pin.

How to Save Electricity in the Winter(2)

4

Use ambient heat from appliances. If you will be in your home office for many hours of the day, and you are cooking with a slow cooker for your evening meal. Bring your slow cooker into the office. They really do put off heat. Also, be sure to bake a lot, it warms up the kitchen and there is nothing like hot baked food in the winter.

5

Use a fireplace or better yet, an indoor stove. (have one installed) Some indoor stoves generate more heat than many common homes electric furnace. Often the savings of having a stove installed is cheaper than what you would pay in electricity for the winter.

6

Install a solar heater. These are large black panels where the sun heats the air within the “box” of the panel. A small fan blows air from your home, circulating it through the panel, and will push super hot air back into your home. All this costs is the power of a small fan! The only downside to this, is that it must be moderately sunny for these to work.

7

Be sure to seal up any windows or doors with simple foam padding. Do not allow drafts to enter your home.

8

If you have windows that are not visible to the street (or do not care) pull down black window shades will heat a room dramatically. This is the same concept of a solar heater, but they will be in your home already. Naturally, the sun heats up dull black materials the best.

9

Next of course is always be cautious of your lighting. Use the “cork screw” CFL bulbs whenever you can. They are far worth the money and will ALWAYS pay themselves off. They usually use only a fifth of the power of common lighting. (Sometimes a bit less!)

Tips & Warnings

Warm Clothing goes a long way.

An electric blanket only uses around 75 Watts of power & can be subbed in with a LOW temp space heater at night.

How to Save Electricity in the Winter(1)

You are sure to save money, don’t you? Saving electricity is also an important thing to all of us in that it does well to the environment and save our money. Now winter is coming, so here are saving electricity tips for you to save electricity. It is simple to do in the winter. This article is especially for any of you with electric heat in their homes or for anybody that wants to save on their electric bill.
Steps

1

The first step is to understand that electric heat is really expensive. A small electric space heater often uses between 1000 to 1500 watts of power. This is 1KWh, or 1.5KWh’s on your electric bill. All one must do is multiply this figure by the amount of hours that they use the space heater & the current price of electricity on their electric bill (per KWH) and you can find how much that one heater costs you. Now, considering that most common bedrooms have a 15 amp breaker, and that many large scale home central heaters use TWO 60 AMP breakers and are often 15,000 watts per hour, it doesn’t take a genius to understand that a simple space heater uses far less power.

2

Learn room isolation. Shut doors of ANY room not in use. Use simple space heaters in the rooms that you are in with the doors SHUT. A common bedroom can easily be heated on a “low” setting of a space heater often just using 800W. If the door is shut, it will take less than 10 minutes for a bedroom to be warm. The question one must ask them is why heat the entire house, when just a bedroom is needed to be heated at night?

3

Dress warmly. Why do we need the entire house sitting at 80F, when we could easily have it at 60F. Some nice wool socks & sweaters can easily handle 60F indoors. Even though this step may come as simple common knowledge for some, many people do not know that wool in particular is one of the most insulated & warm materials you can wear.

 

to be continued…

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Applications :

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How to Connect Solar Panel Kits

Install solar panel kits, and this can help you save up to 90 percent on your electrical bills. Connecting a solar panel kit is a source of “green” energy. Investing in a solar panel kit protects families from blackouts and other power shortages that natural disasters can cause. Solar panel kits are widely applied in areas of tropical weather. And in fact, solar panel kits can be used in any area all over the world.

Instructions

Installation of a Solar Panel Kit

1

Attach one end of the electrical cable to the positive outlet of the solar panel. The positive sides are marked on the cable and the solar panel.

2

Attach one end of the electrical cable to the negative outlet of the solar panel. The negative sides are marked on the cable and the solar panel.

3

Attach the opposite end of the electrical cable to the positive outlet of the charge controller. The positive sides are marked on the cable and the charge controller. The charge controller prevents overcharging your power source.

4

Attach the opposite end of the electrical cable to the negative outlet of the charge controller. The positive sides are marked on the cable and the charge controller.

5

Plug the charge controller cable to a power transformer. There are no positive or negative sides to the charge controller cable. The power transformer sends electricity to your electrical items.

6

Screw the solar panel to the mount using a screwdriver. There are pre-drilled holes on the solar panel and mount.

Tips & Warnings

Do not step or put large weight directly on top of the solar panel. Solar panels actually are fragile.

Office Electronics Checklist

Every office — whether it is a business or a home office — needs a few office electronics in order to function smoothly. When you are setting up your office, use this checklist to make sure you have everything you need.

Office Electronic Essentials:

1. Computer: Whether you need a desktop computer with lots of memory or a small laptop that you can take with you to meetings, a computer is essential to business. Once you have your computer, you can look for other office electronics that will work with it.

2. Printers: You may need to print invoices, reports, letters, packaging labels and many other documents. Many printers can be found combined with fax machines and copiers. Combination printers will save space but may cost a bit more up front.

3. Fax machines: Many offices need to send and receive documents with fax machines. If you need to have forms signed, then make sure you include a fax machine in your office.

4. Copier: With a copier or scanner can make backup copies — or as many copies as you need — if you don’t have the original document saved on your computer.

5. Telephones: If you have a dedicated phone line for business and don’t have a fax machine, a simple phone will serve your purposes well. However, if you have more than one line, and you don’t always like to use your cell phone, purchase a multi-line phone. You can answer calls and receives faxes without losing business.

6. Shredders: Shredders are vital for office security. No matter what your office is for, be sure to protect your personal and business information by shredding anything you plan to dispose of that may have personal or business information on it.

7. Label makers: Keep file folders, shelves and drawers more organized by clearly labeling them.

8. Calculators: Keep your numbers balanced with a calculator. A calculator is handy to have around even if you do most of your number-crunching in a spreadsheet.

Tip:

1. Don’t forget to pick up extra ink and toner cartridges for your printers, fax machines and copiers, including both black and color ink.

X-Acto High-Volume Commercial Electric Pencil Sharpener, Beige, 1 Unit

Product Description

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• Pencil Saver prevents over-sharpening
• Thermal overload shuts off motor before overheating; Auto-Reset when cool
• 120V – North American use only