The Boost Regulator Switching

In a forward (or buck) regulator power is continuously supplied to the outlet\filter capacitor. In a boost regulator, however, energy is pumped in a cyclic manner. The filter capacitor therefore has to be of a higher value.

The boost regulator, like the flyback regulator, pumps energy into the outlet\filter capacitor in a cyclic manner, and it is therefore desirable to operate in the discontinuous mode with a fixed peak current through the inductor.

The diode conduction time in a boost regulator, unlike the flyback regulator, is not fixed, but varies with the input voltage.

Ipk = 2 x Iout,max x (Vout / Vin,min)
Tdon = (L x Ipk) / (Vout - Vin)

Output voltage is regulated by controlling the duty cycle.

Vout = ((Ton / Tdon) + 1) x Vin

Ripple voltage is directly proportional to diode conduction time.

Tdon max = (L x Ipk) / (Vout - Vin,max)

Source : http://www.hills2.u-net.com/electron/smps.htm

Switch Mode Power Supplies.

Introduction - Some Definitions.

Switch Mode Power Supplies are the current state of the art in high efficiency power supplies. Conventional series-regulated linear power supplies maintain a constant voltage by varying their resistance to cope with input voltage changes or load current demand changes. The linear regulator can, therefore, tend to be very inefficient. The switch mode power supply, however, uses a high frequency switch (in practice a transistor) with varying duty cycle to maintain the output voltage. The output voltage variations caused by the switching are filtered out by an LC filter.

SMPSs can be used to step-down a supply voltage, just as linear supplies do. Unlike a linear regulator, however, an SMPS can also provide a step-up function and an inverted output function. Typical applications are given below.

Typical application for a ste-down switching regulator:

Generation of 5V for TTL-based circuits from a 12V battery (particularly suitable if the 12V battery has limited capacity, as switching regulators are far more efficient than linear regulators).

Typical application for a step-up switching regulator:

Generation of 25V from a 5V supply in an EPROM programmer.

Typical application for an inverting switching regulator:

Generation of a double-ended supply from a single-ended for OP-AMP.

Generation of a negative bias for MOS devices eg Dynamic RAMS.

The term switch mode regulator is used to describe a circuit which takes a DC input and provides a DC output of the same or opposite polarity, and of a lower or higher voltage. Switch Mode regulators use an inductor and there is no input to output regulation.

The term switch mode converter is used to describe a circuit which takes a DC input and provides a single or multiple DC outputs, again of same or opposite polarity and lower or higher voltage. Converters use a transformer and may provide input to output isolation.

The term Switch Mode Power Supply or SMPS is used to describe switch mode regulators and converters.

Source http://www.hills2.u-net.com/electron/smps.htm

40 Hours of Play for those Long-Haul Flights

To prepare for the trip, we looked online for the biggest most long-lasting PSP battery pack we could find. Imagine our disappointment! We couldn't find any that went beyond about 8 hours of play time. This is no use on a 22-hour flight.

I found myself wondering why they didn't just make a PSP battery pack that could take normal batteries that you can buy at any airport. Sure, it would cost a bit to run on Duracells, but it would solve the problem of PSP power on a long flight once and for all. I seemed to recall that Duracell 'D' cells store about 12,000mAh (compared to the PSP internal battery's puny 1800mAh). And thus, the concept for the PSP Power Brick was born.

Read more

Electronic control and protection circuit.

SkyTronic product: Power
Electronic control and protection circuit.

Experiment 03 - Design of lightweight HV POWER SUPPLIES for EHD experiments

Experiment 03 - Design of lightweight HV POWER SUPPLIES for EHD experiments

SERIES REGULATED 4.5 TO 25 VOLT, 2.5 AMP POWER SUPPLY

SERIES REGULATED 4.5 TO 25 VOLT, 2.5 AMP POWER SUPPLY
ARRL HB 93 CHP 27 FIG 22 95HB FIG.11.32
Description: This is a variable voltage and adjustable current limit power supply project.

8 Amp Regulated Power Supply for operating mobile equipment

8 Amp Regulated Power Supply for operating mobile equipment
BR1 can be a bridge rectifier or four diodes (10A) with a 100 PIV rating.

Regulated Power Supply 13.8VDC

Regulated 13.8V DC Power Supplies.
Output short circuit protection with current limiting.
Overvoltage protection with internal fuse.

Build a 13.8V, 40A Switching Power Supply

This compact and lightweight workhorse can power your whole station!

By Manfred Mornhinweg, XQ2FOD

High Current 13.8V Power Supply

High Current 13.8V Power Supply
Rod Elliott (ESP)
There is absolutely nothing special about the circuit, except that as shown, it is quite capable of up to 20 Amps intermittently or 10A continuous.

10 Amp 13.8 Volt Power Supply

10 Amp 13.8 Volt Power Supply
source: By N1HFX
Sometimes amateurs like to home-brew their power supplies instead of purchasing one off the shelf at any of the major ham radio retail dealers.

VHF-HF TRANSVERTER

This little circuit is a transmitting and receiving converter (transverter) that converts a FT290 or similar multimode handheld transciever to the 14MHz amateur band. The project is a single board module that needs an external local oscillator, for example, the VHF harmonic oscillator (or QRP VHF FM TX) LO for transverter project. It should be a relatively simple matter of scaling coils and caps to convert other bands. You may choose to omit the TX/RX switching and the TX mixer and use this unit as a receive converter giving 14MHz - 16MHz coverage on a multimode VHF receiver.

If you choose to use the full transverter circuit then you will be pleasantly surprised at the spectral purity of the transmitted signals. All unwanted spurious signals and even oscillator breakthrough are well under -75dB at the output terminal. The HF TX output from the unit is about 2mW and will give a full ten watts from my 10-Watt HF linear amplifier. The VHF rig must be of the type that also delivers +10v DC at the antenna socket on transmit. This is true of the FT290, C58 and most multimode handportables.

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http://web.telia.com/~u85920178/conv/conv-00.htm

power supply 0-15V 5A

Here is a rather novel Power Supply Unit (PSU) for the workbench which can deliver 0-15 volts and up to 0-3 amperes. I have not shown any mains fuses as this I will leave to your own devices. You should as a minimum have a fuse in the primary and secondary of T1.

The circuit is a little cramped, but this is because I will also be posting the circuit to QRP@WW on the packet radio system. There are two resistors in the circuit marked "*see text" and these set the maximum output current limiter to a suitable value. Omit the 0R2 resistor and the PSU will deliver 100mA maximum. In this event the output TR8 can be almost any medium power transistor such as the 2N3053, BFY51 etc. It must be mounted on a heatsink no matter what output you need.

The 6R8 resistor may be an ordinary 1/4 watt resistor and is used on all versions of the PSU. The additional 0R2 (0.2 ohms) sets the maximum current limiting to about 3 amperes. If you only want a 0-1 ampere PSU then use 0.68 ohms. T1 is a simple transformer suitably rated for the output power you want and having a 15 volt secondary. This should give over 21v of DC when rectified (measured at D1 cathode - ground). The anode of D7 should also have -21 volts with respect to ground.

If you have problems getting a 15 volt transformer then you can use a 12-volt transformer and add a few extra turns to the secondary. Most transformers have enough room for you to thread another 20 turns of wire through the former to put in series with the secondary winding. By sure to use the same thickness of wire as used for the factory made secondary.

D1, D2, D3, D4, D5, D6, D7 and D8 are all 1N4001 or better for up to 500mA but 1N5401 should be used if you want up to 3 amperes. D9 and D10 may be almost any small silicon diode such as 1N4148 etc. The 1K0 potentiometer in parallel with D9 is the current set pot. The 47K pot is the output voltage pot. With the values shown you should be able to get a range of 0v to a little over 15v.

HOW IT WORKS
TR4 and TR5 compare the ground (0v) with the wiper of the 47K pot which should also be 0v. If the voltages are not equal then TR5 controls the output darlington (TR6 and TR7) until the voltages become equal. If the 47K pot is set to maximum (top) then the output voltage of the PSU must be zero in order to get a balance. If the output voltage pot is set to the bottom then the voltage balance will only occur if there is +15 volts on the top of the 47K pot; the other end of the 15K being -5v.

In the event TR7 draws too much current then the voltage drop accross the 6R8 resistor will turn on TR1 which in turn turns on TR2. TR2 sinks the 0v reference to -20 volts. The TIP41 is incapable of delivering a negative output voltage so the output remains at 0v. The base of TR1 is "lifted" by up to 0.7v due to the current flowing through D10. This overcomes the TR1 base-emitter voltage drop needed to turn it on. You can adjust the 22K resistor a little so that the current control goes all the way down to 0mA and no further. 5K6 is about the absolute minimum resistance you should use.

The power supply itself is very simple and is nothing more than a full-wave bridge rectifier. The AC from the transformer is also capacitively coupled to yet another rectifier to provide the negative voltage required to allow the PSU to be controlled down to 0 volts. TR3 regulates this to stabilise the negative reference voltage.

POSSIBLE PROBLEMS
In the event of self-oscillation of the PSU then under no circumstances put any capacitance accross any signal in the control path. This will just make the problem worse. The cure for this would be to add capacitance between the base/emitter of the controlling transistors TR4 and TR5.

SUGGESTED MODIFICATION
One modification I have thought about is to replace the 22uf in the base of TR4 with a smaller value, say 10nf, and couple audio into the base of TR4 with a large electrolytic (1uf should do it). This will allow the output voltage of the PSU to be modulated with an audio signal. This could be a very interesting modification if you are "into" AM (MW?) broadcasting.

Source : http://web.telia.com/~u85920178/use/psu2.htm

BENCH PSU
by Harry Lythall - SM0VPO

DC13.8V to DC250V easy circuit

I have done a lot of work with valves in recent years. For me valves have many advantages, least of all the price; since they are now "obsolete" it is quite easy to get hold of them for next to nothing at rally's and junk sales. I recently purchased a couple of hundred battery valves for less than SEK1 (US$ 0.15) each.

The biggest problem with valves is the PSU needed to provide +250 vDC and 6.3 vAC for the fillaments. The transformers are no-longer available at a reasonable price, but a pair of 12v-6v-0v-6v-12v mains transformers will do the job just as well. For portable use only one transformer is required together with a pair of power transistors such as 2N3055 etc.

Above is the circuit of a converter that will generate the required volrages from a 12 volt source.

Above is the circuit of a converter that will generate the required volrages from 220 volt mains.

Just one word of warning: Dont forget to put a "bleeder" 100K - 270K ohm resistor accross the 250vDC output if your equipment doesn't already have one built in. Failure to do this can be fatal because the PSU smoothing capacitors can store a lethal charge for days.

Finally if you think that there is no place for valves in QRP or portable work then think again. An "EL84" will deliver 10 watts on the lower HF bands. It draws 300mA @ 6.3v (2.1 watts) for the heater as well as + 53mA at 250vDC (about 15 watts) for the anode and screen. The DC-PSU.GIF will provide this and draw less than 2 amperes from a car battery. A 48A/H car battery will therefore last over 24 hours NONSTOP TRANSMIT !!! If you also think that valves are difficult to build with then try one. You will be surprised.

Source : http://web.telia.com/~u85920178/

OBTAINING 250vDC & 6.3vAC FOR VALVES
by Harry Lythall - SM0VPO

Zinc-Carbon Battery charger

They are cheap. The electrolyte used to leak but today they are usually much better protected. If they should leak then they will corrode all the copper in your equipment. the corrosion will travel down wires and eat its way through Printed Circuit Boards (PCBs). At high temperatures (25 degrees or more) Zinc-Carbon batteries will give up to 25% more capacity but the shelf-life will deteriorate very rapidly. Around freezing point their shelf-life can be extended by as much as 300% so one tip is to store them in the refrigerator.

Unfortunately they must be thrown away when they are exhausted. You can extend their life by up to 60% by using "Dirty-DC" to recharge them but this will also reduce the shelf-life.

Ry should be about 1.5 x greater than Rx. The resistors are determined by the charging current you want. With the circuit shown and size AA cells in a pack of ten cells, the battery voltage will be 15 volts. Discharge the battery to no less than 25%. To replace 350mA/H back into the battery over 10 hours we need to charge at 35mA.

Rx = (24 - 15 - 0.7) / (3 x 0.035) = 79 ohms

Ry = (24 - 15) / (2 x 0.035) = 128

You can also cook exhausted battery cells in the oven. About 80 degrees centigrade for five to ten minutes, no more or they may explode. This technique was demonstrated on UK TV in the series "Steptoe & Son" (h�r i Sverige i "Albert och Herbert"). I do not reccomend that you should try to sell the cells again as new batteries!

Source : http://web.telia.com/~u85920178/begin/batt-00.htm

Automatic 9-Volt Nicad Charger By IC LM339 , LM317

Click to View circuit 9-V Nicad Charger

Heat Sensor by IC 741

Click to View circuit Heat Sensor

Clock Generator by IC Digital

Click to View Circuit Clock Generator

Active Antenna for AM-FM-SW

Active Antenna for AM/FM/SW:
This simple little circuit can be used for AM, FM, and Shortwave(SW). On the shortwave band this active antenna is comparable to a 20 to 30 foot wire antenna. It is further more designed to be used on receivers that use untuned wire antennas, such as inexpensive units and car radios.

Click to View circuit

Simple Pre MIC

Click to View Circuit

Automatic 9-Volt NiCad Battery Charger

Good care given to your NiCad batteries will ensure a long life. However, they do need to be handled and charged with special care.

......

Click to View Circuit

Active Power Zener by Transistor

Click to Read More

Power Supply 0-15V / 0-3A By TIP41

Here is a rather novel Power Supply Unit (PSU) for the workbench which can deliver 0-15 volts and up to 0-3 amperes. I have not shown any mains fuses as this I will leave to your own devices. You should as a minimum have a fuse in the primary and secondary of T1.

The circuit is a little cramped, but this is because I will also be posting the circuit to QRP@WW on the packet radio system. There are two resistors in the circuit marked "*see text" and these set the maximum output current limiter to a suitable value. Omit the 0R2 resistor and the PSU will deliver 100mA maximum. In this event the output TR8 can be almost any medium power transistor such as the 2N3053, BFY51 etc. It must be mounted on a heatsink no matter what output you need.

The 6R8 resistor may be an ordinary 1/4 watt resistor and is used on all versions of the PSU. The additional 0R2 (0.2 ohms) sets the maximum current limiting to about 3 amperes. If you only want a 0-1 ampere PSU then use 0.68 ohms. T1 is a simple transformer suitably rated for the output power you want and having a 15 volt secondary. This should give over 21v of DC when rectified (measured at D1 cathode - ground). The anode of D7 should also have -21 volts with respect to ground.

If you have problems getting a 15 volt transformer then you can use a 12-volt transformer and add a few extra turns to the secondary. Most transformers have enough room for you to thread another 20 turns of wire through the former to put in series with the secondary winding. By sure to use the same thickness of wire as used for the factory made secondary.

D1, D2, D3, D4, D5, D6, D7 and D8 are all 1N4001 or better for up to 500mA but 1N5401 should be used if you want up to 3 amperes. D9 and D10 may be almost any small silicon diode such as 1N4148 etc. The 1K0 potentiometer in parallel with D9 is the current set pot. The 47K pot is the output voltage pot. With the values shown you should be able to get a range of 0v to a little over 15v.

HOW IT WORKS
TR4 and TR5 compare the ground (0v) with the wiper of the 47K pot which should also be 0v. If the voltages are not equal then TR5 controls the output darlington (TR6 and TR7) until the voltages become equal. If the 47K pot is set to maximum (top) then the output voltage of the PSU must be zero in order to get a balance. If the output voltage pot is set to the bottom then the voltage balance will only occur if there is +15 volts on the top of the 47K pot; the other end of the 15K being -5v.

In the event TR7 draws too much current then the voltage drop accross the 6R8 resistor will turn on TR1 which in turn turns on TR2. TR2 sinks the 0v reference to -20 volts. The TIP41 is incapable of delivering a negative output voltage so the output remains at 0v. The base of TR1 is "lifted" by up to 0.7v due to the current flowing through D10. This overcomes the TR1 base-emitter voltage drop needed to turn it on. You can adjust the 22K resistor a little so that the current control goes all the way down to 0mA and no further. 5K6 is about the absolute minimum resistance you should use.

The power supply itself is very simple and is nothing more than a full-wave bridge rectifier. The AC from the transformer is also capacitively coupled to yet another rectifier to provide the negative voltage required to allow the PSU to be controlled down to 0 volts. TR3 regulates this to stabilise the negative reference voltage.

POSSIBLE PROBLEMS
In the event of self-oscillation of the PSU then under no circumstances put any capacitance accross any signal in the control path. This will just make the problem worse. The cure for this would be to add capacitance between the base/emitter of the controlling transistors TR4 and TR5.

SUGGESTED MODIFICATION
One modification I have thought about is to replace the 22uf in the base of TR4 with a smaller value, say 10nf, and couple audio into the base of TR4 with a large electrolytic (1uf should do it). This will allow the output voltage of the PSU to be modulated with an audio signal. This could be a very interesting modification if you are "into" AM (MW?) broadcasting.

Source :: http://web.telia.com/~u85920178/use/psu2.htm

BENCH PSU
by Harry Lythall - SM0VPO

Power Supply 13.8V 20A by Transistor TIP3055

A heavy duty 13.8V power supply is a fine thing to have in the shack, but unless you acquire one secondhand, is an expensive little beastie to buy. This means building one should be considered, not only for the cost savings, but also because you can brag about it on air to your mates. Of course, careful consideration must be given to the properties of the completed supply, and after talking to a few of my friends who have built their own and fallen into all the traps, here are the printable ones : RF proof, easy to make, commonly available parts used, but above all CHEAP.

Well, last things first. Breaking down the construction costs of a heavy duty regulated supply, they are in order:

• The transformer (around $A80)
• The main filter electrolytics - around $A80
• The case - a metal case is well beyond the workshop capabilities of many amateurs and is quite expensive to buy (if you can).
• The meter - around $A20-$27 (either digital or analogue)
• The electronics - transistors, resistors, diodes, etc.
• All the bits - fuseholders, terminals, switches, solder tags, nuts and bolts, power cords, etc.

Dealing with these in turn, we can reduce the cost greatly by rewinding a microwave transformer (about $A5 total), scrounging old computer grade electrolytics (lots around), and designing the electronics to be so RF proof that a wooden case can be used - yes, that's right - wooden! If you are really stuck for a dollar, then good supply regulation and overload protection also allow all metering to be deleted. Finally the wooden case allows 1/4 inch bolts and washers to be substituted for expensive terminals. If you can't put the whole thing together for less than $A50 then frankly you don't even qualify for the junior scroungers league.

Moving on to the other points, manufacture is easy as no etched PCB is used. The PCB is simply made by using a hacksaw to cut through the copper overlay on the PCB material breaking it up into separate pads. Details are given in the drawings.

Keeping the supply RF proof is another matter entirely. During development, several designs were tested, based around such chips as the 723 regulator, the 3140 op amp. and a 7912 three terminal regulator with bypass transistors. In all cases, the high gain of the control amplifier forced the use of a PCB with a ground plane to which everything was heavily bypassed. This technique limits RF interference and also prevents motorboating and high frequency instability (a common problem in high current circuits such as power supplies and audio amplifiers) as the ground plane acts as both an RF shield and a single point ground.

However, for home construction, the use of a double sided PCB is undesirable and anyway, the performance of each of these circuits is totally over the top. After all, ham rigs powered from 13.8 volt are designed for use in a car where the supply voltage wanders all over the place. Two volts of variation is quite typical. Regulator circuits which hold the output voltage constant within a few millivolt for all conditions of load are simply not required. It is much more important that the output voltage is free of noise and ripple, and the published design does this very well. Noise and ripple are well under 5 millivolt peak to peak, and output regulation (no load to full load) is around 200 millivolt. A simple control circuit is used without overall feedback and the result is a cheap, very stable design. RF proofing is provided by physically earthing the heatsink, and also by using it as a ground plane. The collectors of the TIP3055s are physically earthed to the heatsink (no micas), and so a good section of the circuit is actually at earth potential. Two other advantages are easy assembly and excellent heatsinking.

Read More...
Source :: http://www.users.on.net/~endsodds/ps20.htm

Lead Acid Battery Charger with Float by LM350T , LM334

The circuit furnishes an initial charge voltage of 2.5 Volt-per-cell at 25°C to rapidly charge a Lead-Acid battery.
The charging current decreases as the battery charges, and when the current drops to about 180mA, the charging circuit reduces the output voltage to 2.35 Volt-per-cell, floating the battery in a fully charged state. This lower voltage prevents the battery from overcharging, which would shorten its life. The LM301A (U3) compares the voltage drop across R1 with an 18-mV reference set by R2. The comparator's output controls the voltage regulator, forcing it to produce the lower float voltage when the battey-charging current passing trhought R1 drops below 180mA. The 150mV difference between the charge and float voltages is set by the ratio of R10 and R12. The red and green Led's show this state of the circuit.

Read More ....
Source :: http://www.uoguelph.ca/~antoon/gadgets/labc2.htm
By Tony van Roon

Audio VU Meter 10 LED by LM324

Circuit : Matthew Hewson
Email: Matthew.Hewson@btinternet.com

Description:
This circuit uses two quad op-amps to form an eight LED audio level meter. The op-amp used in this particular circuit is the LM324. It is a popular IC and should be available from many parts stores.

VU Meter
Notes:
The 1K resistors in the circuit are essential so that the LED's turn on at different audio levels. There is no reason why you can't change these resistors, although anything above 5K may cause some of the LED's to never switch on. This circuit is easily expandable with more op-amps, and is not limited to use with the LM324. Pretty much any op-amp will work as long as you look up the pinouts and make sure everything is properly connected.

The 33K resistor on the schematic is to keep the signal input to the circuit at a low level. It is unlikely you will find a 33K resistor, so the closest you can get should do. The value of this resistor may need to be changed, so it is best you breadboard this circuit before actually constructing it on PCB. The circuit in it's current form will accept line level inputs from sources such as the aux out on a Hi-Fi, all though could be easily modified to accept speaker inputs.

The audio + is connected to the main positive rail, while the audio - is used for signal input. The 50k pot can be used to vary the sensitivity of the circuit.