DC / DC converter for USB connections

This converter is inexpensive and quick to build, it is nothing more than a DC / DC converter, its use is for USB sockets or any other device that needs a stabilized voltage 5 Volts and a maximum current of 2 amps.

With this power converter, you insert a voltage from 6 Volts to 24 Volts and have a regulated output of 5 Volts per 2 Amperes. That is, you can use a car or motorcycle battery or your vehicle's cigarette lighter as power, and you will have an outlet to charge your cell phone, camera, etc.

DC / DC converter for USB jacks

The circuit is very simple, and you may have already seen it in some project here on the site, the circuit uses only five components, a 7805 positive voltage regulator integrated circuit, a TIP42 transistor, a 5 Ohm resistor and two disk capacitors or polyester, one of .33 and the other of .1 or 330 and 100 nF.

The capacitors are filters and accompany the voltage regulator 7805. This converter works perfectly, as long as you respect a number of devices connected to it. The creator himself says it's ideal for a small USB hub that does not have large, connected devices.

DC / DC converter for USB connections Circuit

Above the electronic circuit diagram and the integrated circuit board of the converter, but because the circuit is compact, one can build the circuit without printed circuit board, ie using other ways of construction.

If you need more current, you will need to modify the circuit by adding a larger heat sink and even a more powerful transistor. The voltage regulator can be maintained since it only does the job of regulating the voltage at the base of the transistor and only a small current passes through it, requiring neither the installation of a heatsink on the 7805.

According to the creator of the project, any regulator integrated circuit of the line 78xx, 5, 6, 8 or 9 Volts can be used from a source of 12Volts.

The TIP42 was left with enough spacing around it to fit the small heat sink. The R1 resistor was calculated to maintain the maximum current through the TIP42, ie, about 2 Amperes.

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USB Converter

Does this sound familiar: you buy a small piece of equipment, such as a programming & debugging interface for a microcontroller, and you have to use a clunky AC wall adapter to supply it with power? It’s even worse when you’re travelling and there’s no mains socket anywhere in sight. Of course, you can use the USB bus directly as a power source if the supply voltage is 5 V. If you need a higher voltage, you can use the USB converter described here. This small switch-mode step-up converter can generate an output voltage of up to 15 V with a maximum output current of 150 mA.

 

The LM3578 is a general-purpose switchmode voltage converter. Figure 1 shows its internal block diagram. Here we use it as a step-up converter. The circuit diagram in Figure 2 shows the necessary components. Voltage conversion is achieved by switching on the internal transistor until it is switched off by the comparator or the current-limiting circuit. The collector current flows through coil L1, which stores energy in the form of a magnetic field. When the internal transistor is switched off, the current continues flowing through L1 to the load via diode D1. However, the voltage across the coil reverses when this happens, so it is added to the input voltage. The resulting output voltage thus consists of the sum of the input voltage and the induced voltage across the coil.

 USB Converter Circuits Diagram 1

The output voltage depends on the load current and the duty cycle of the internal transistor. Voltage divider R5/R6 feeds back a portion of the output voltage to the comparator in the IC in order to regulate the output voltage. C5 determines the clock frequency, which is approximately 55 kHz. Network R4, C2 and C3 provides loop compensation. The current-sense resistor for the current-limiting circuit is formed by three 1-Ω resistors in parallel (R1, R2 and R3), since SMD resistors with values less than 1 Ω are hard to find. The output voltage ripple is determined by the values and internal resistances of capacitors C11, C8, C7 and C6.

 
 USB Converter Circuits Diagram 2

 

The total effective resistance is reduced by using several capacitors, and this also keeps the construction height of the board low. L2, C1, C9 and C10 act as an input filter. Ensure that the DC resistance of coil L2 is no more than 0.5 Ω. Use a Type B PCB-mount USB connector for connection to the USB bus.  A terminal strip with a pitch of 5.08 mm can be used for the output voltage connector. Of course, you can also solder a cable directly to the board. Two additional holes are provided in the circuit board for this purpose. As we haven’t been able to invent a device that produces more energy than it consumes, you should bear in mind that the input current of the circuit is higher than the output current. As a general rule, you can assume that the input current is equal to the product of the output current and the output voltage divided by the input R5 and R6 for other output voltages:

6V:	R5 = 47k, R6 = 9,1k
12V:	R5 = 110k, R6 = 10k
15V:	R5 = 130k, R6 = 9,1k

voltage and divided again by 0.8. Specifically, with an output current of 100 mA at 9 V, the input current on the USB bus is approximately 225 mA. Finally, Figure 3 shows a small PCB layout for the circuit. All of the components except the connector and the terminal strip are SMDs.

Parts List:

(for UO = 9 V)

Resistors

R1,R2,R3 = 1Ω

R4 = 220kΩ

R5 = 82kΩ

R6 = 10kΩ

Capacitors

(SMD 1206)

C1 = 100nF

C2 = 2nF2

C3 = 22pF

C4 = 100nF

C5 = 1nF5

(tantalum SMD 7343)

C6 = 68μF 20V

C7 = 68μF 20V

C8 = 68μF 20V

C9 = 47μF 16V

C10 = 47μF 16V

C11 = 68μF 20V

Inductors

L1 = 820μH (SMD CD105)

L2 = 47μH (SMD 2220)

Semiconductors

D1 = SK34SMD (Schottky)

IC1 = LM3578AM (SMD SO8)

Miscellaneous

K1 = 2-way PCB terminal block, lead pitch 5mm

(optional)

K2 = USB-B connector

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Simple 6V to 12V Converter Circuit Diagram

 This inverter circuit can provide up to 800mA of 12V power from a 6V supply. For example, you could run 12V car accessories in a 6V (British?) car. The circuit is simple, about 75% efficient and quite useful. By changing just a few components, you can also modify it for different voltages.

Notes

• L1 is a custom inductor wound with about 80 turns of 0.5mm magnet wire around a toroidal core with a 40mm outside diameter.
• Different values of D3 can be used to get different output voltages from about 0.6V to around 30V. Note that at higher voltages the circuit might not perform as well and may not produce as much current. You may also need to use a larger C3 for higher voltages and/or higher currents.
• You can use a larger value for C3 to provide better filtering.
• The circuit will require about 2A from the 6V supply to provide the full 800mA at 12V.

6V to 12V Converter Circuit Diagram

Parts
R1, R4 2 2.2K 1/4W Resistor
R2, R3 2 4.7K 1/4W Resistor
R5 1 1K 1/4W Resistor
R6 1 1.5K 1/4W Resistor
R7 1 33K 1/4W Resistor
R8 1 10K 1/4W Resistor
C1,C2 2 0.1uF Ceramic Disc Capacitor
C3 1 470uF 25V Electrolytic Capcitor
D1 1 1N914 Diode
D2 1 1N4004 Diode
D3 1 12V 400mW Zener Diode
Q1, Q2, Q4 3 BC547 NPN Transistor
Q3 1 BD679 NPN Transistor
L1 1 See Notes
MISC 1 Heatsink For Q3, Binding Posts (For Input/Output), Wire, Board

Sourced By:  circuitsdiagram-lab

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300mA DC to AC converter Circuit Diagram

This is the Simple 300mA DC to AC converter Circuit Diagram. This circuit was used to provide battery backup to a device that had an AC (output)wall transformer. Due to the quasi sine-wave output and imprecise 60Hz output frequency, some devices might not work pro perly. Peak output is the DC input voltage minus about 20 ohms drop. Use bigger output MOSFETS for more current output.[link]

 Simple 300mA DC to AC converter Circuit Diagram

 

 

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Analog to Digital Converter (ADC) Circuits Diagram

Normally analogue-to-digital converter (ADC) needs interfacing through a microprocessor to convert analogue data into digital format. This requires hardware and necessary software, resulting in increased complexity and hence the total cost. The circuit of A-to-D converter shown here is configured around ADC 0808, avoiding the use of a microprocessor.

The ADC 0808 is an 8-bit A-to-D converter, having data lines D0-D7. It works on the principle of successive approximation. It has a total of eight analogue input channels, out of which any one can be selected using address lines A, B and C. Here, in this case, input channel IN0 is selected by grounding A, B and C address lines. Usually the control signals EOC (end of conversion), SC (start conversion), ALE (address latch enable) and OE (output enable) are interfaced by means of a microprocessor. However, the circuit shown here is built to operate in its continuous mode without using any microprocessor.

Therefore the input control signals ALE and OE, being active-high, are tied to Vcc (+5 volts). The input control signal SC, being active-low, initiates start of conversion at falling edge of the pulse, whereas the output signal EOC becomes high after completion of digitization. This EOC output is coupled to SC input, where falling edge of EOC output acts as SC input to direct the ADC to start the conversion. 

Analog to Digital Converter (ADC) Circuit Diagram

As the conversion starts, EOC signal goes high. At next clock pulse EOC output again goes low, and hence SC is enabled to start the next conversion. Thus, it provides continuous 8-bit digital output corresponding to instantaneous value of analogue input. The maximum level of analogue input voltage should be appropriately scaled down below positive reference (+5V) level. 

The ADC 0808 IC requires clock signal of typically 550 kHz, which can be easily derived from an astable multivibrator constructed using 7404 inverter gates. In order to visualize the digital output, the row of eight LEDs (LED1 through LED8) have been used, wherein each LED is connected to respective data lines D0 through D7. Since ADC works in the continuous mode, it displays digital output as soon as analogue input is applied. The decimal equivalent digital output value D for a given analogue input voltage Vin can be calculated from the relationship.

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Build a Converter : VGA to BNC Adapter

There are monitors which only have three BNC inputs and which use composite synchronization (‘sync on green’). This circuit has been designed with these types of monitor in mind. As can be seen, the circuit has been kept very simple, but it still gives a reasonable performance. The principle of operation is very straightforward. The RGB signals from the VGA connector are fed to three BNC connectors via AC-coupling capacitors. These have been added to stop any direct current from entering the VGA card. A pull-up resistor on the green output provides a DC offset, while a transistor (a BS170 MOSFET) can switch this output to ground. It is possible to get synchronisation problems when the display is extremely bright, with a maximum green component.

In this case the value of R2 should be reduced a little, but this has the side effect that the brightness noticeably decreases and the load on the graphics card increases. To keep the colour balance the same, the resistors for the other two colors (R1 en R3) have to be changed to the same value as R2. An EXOR gate from IC1 (74HC86) combines the separate V-sync and H-sync signals into a composite sync signal. Since the sync in DOS-modes is often inverted compared to the modes commonly used by Windows, the output of IC1a is inverted by IC1b. JP1 can then by used to select the correct operating mode. This jumper can be replaced by a small two-way switch, if required.

 

VGA to BNC adapter PCB layout

 This switch should be mounted directly onto the PCB, as any connecting wires will cause a lot of interference. The PCB has been kept as compact as possible, so the circuit can be mounted in a small metal (earthed!) enclosure. With a monitor connected the current consumption will be in the region of 30 mA. A 78L05 voltage regulator provides a stable 5 V, making it possible to use any type of mains adapter, as long as it supplies at least 9 V. Diode D2 provides protection against a reverse polarity. LED D1 indicates when the supply is present. The circuit should be powered up before connecting it to an active VGA output, as otherwise the sync signals will feed the circuit via the internal protection diodes of IC1, which can be noticed by a dimly lit LED. This is something best avoided.  

Resistors: 

R1,R2,R3 = 470Ω 

R4 = 100Ω 

R5 = 3kΩ3 

Capacitors: 

C1,C3,C5 = 47µF 25V radial 

C2,C4,C6,C7,C10 = 100nF ceramic 

C8 = 4µF7 63V radial 

C9 = 100µF 25V radial 

Semiconductors: 

D1 = LED, high-efficiency

D2 = 1N4002

T1 = BS170
IC1 = 74HC86
IC2 = 78L05

Miscellaneous:
JP1 = 3-way pinheader with jumper
K1 = 15-way VGA socket (female), PCB mount (angled pins)
K2,K3,K4 = BNC socket (female), PCB mount, 75Ω

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Build a Simple +12v to +9v converter

This little circuit uses a LM317 variable voltage regulator to adjust the input voltage down to +9 volt, or whatever else you need. Just a solid basic circuit without bells and whistles.

You can do with a 10uF capacitor for C1 if your battery is close to this circuit. If it is located more than 3 feet increase the value to 100uF or above. Without a coolrib it can easily handle 500mA. If you need more, or the maximum current (1.5A), then a good coolrib is required.

Trimmer potent meter R3 will vary the output voltage. Ceramic capacitor C2 improves frequency/transient response. Can be omitted if not needed for your application. If you want extra protection in case the adjust pin is short circuited, add an extra 1N4001 diode over the input and the output. Cathode to input. But normally only used if the output is way over 25V.

R1 and R3 determine the output voltage. You can adapt them for your own needs and applications.
Use the following formula: (((R1+R3)/R2)+1)*1.25=V-out which comes to: (((560+1000)/220)+1)*1.25 = 10.11V (assuming V-in is 12V).

Or vice-versa: ((V-out/1.25)-1)*R2=R1+R3 which comes to: ((9/1.25)-1)*220=1364. For 1364, you can make R1=560 and R3=1K, which will give plenty of play.

After dozens of emails I have included the above circuit. The parts with the red 'X' are added and act to boost the amperage. The NTE393 transistor can handle 25A with a sufficient cool rib.

Other power transistors, such as the TIP2955, or similar can be used also. The power transistor is used to boost the extra needed current above the maximum allowable current provided via the regulator. Current up to 1500mA(1.5A) will flow through the regulator, anything above that makes the regulator conduct and adding the extra needed current to the output load.

It is no problem stacking power transistors for even more current. Both regulator and power transistor must be mounted on an adequate heatsink, and if you intend to use lots of amps a fan would be nice too.

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Affordable Cost Step Down Converter

The circuit described here is mostly aimed at development engineers who are looking for an economical step-down converter which offers a wide input volt-age range. As a rule this type of circuit employs a step-down converter with integrated switching element. However, by using a more discrete solution it is possible to reduce the total cost of the step-down converter, especially when manufacturing in quantity. The TL5001A is a low-cost PWM controller which is ideal for this project.

Low Cost Step Down Converter with Wide Input Voltage Range

The input voltage range for the step-down converter described here is from 8 V to 30 V, with an output voltage of 5 V and a maximum output current of 1.5 A. 

When the input voltage is applied the PWM output of IC1 is enabled, taking one end of the voltage divider formed by R1 and R2 to ground potential. The cur-rent through the voltage divider will then be at most 25 mA: this value is obtained by dividing the maximum input voltage (30 V) minus the saturation voltage of the output driver (2 V) by the total resistance of the voltage divider (1.1 kΩ). T1 and T3 together form an NPN/PNP driver stage to charge the gate capacitance of P-channel MOSFET T2 as quickly as possible, and then, at the turn-off point, discharge it again. The base-emitter junction of T3 goes into a conducting state when the PWM output is active and a voltage is dropped across R2. T3 will then also conduct from collector to emitter and the gate capacitance of T2 will be discharged down to about 800 mV. The P-channel MOSFET will then conduct from drain to source. If the open-collector output of the controller is deactivated, a negligibly small current flows through resistor R2 and the base of T1 will be raised to the input voltage level. 

The base-emitter junction of T1 will then conduct and the gate capacitance of T2will be charged up to the input voltage level through the collector and emitter ofT1. The P-channel MOSFET will then no longer conduct from drain to source. This driver circuit constructed from discrete components is very fast, giving very quick switch-over times. 

Diodes D2 and D3 provide voltage limiting for the P-channel MOSFET, whose maximum gate-source voltage is 20 V. If the Zener voltage of diode D2 is exceeded it starts to conduct; when the forward voltage of diode D3 is also exceeded, the two diodes together clamp the gate-source voltage to approximately 19 V. The switching frequency is set at approximately 100 kHz, which gives a good compromise between efficiency and component size. 

Finally, a few notes on component selection. All resistors are 1/16 W, 1 %. Apart from electrolytic C1 all the capacitors are ceramic types. For the two larger values (C2 and C5) the following are used:

• C2 is a Murata type GRM21BR71C105KA01 ceramic capacitor, 1 µF, 16 V, X7R, 10 %;.
• C5 is a Murata type GRM32ER60J476ME20 ceramic capacitor, 47 µF, 6.3 V, X5R, 10 %.
• D1 (Fairchild type MBRS340T3) is a 40 V/3 A Schottky diode. Coil L1 is a Würth WE-PD power choke type 744771147, 47 µH, 2.21 A, 75 mΩ.
• T1 (BC846) and T3 (BC856) are 60 V, 200 mA, 310 mW complementary bipolar transistors from Vishay.
• The TL5001AID (IC1) is a low-cost PWM controller with an open-collector output from Texas Instruments. Source by Link

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How to Make 12-9 Volt DC to DC Converter BD139

This circuit is a DC voltage output from a small DC input generate large voltage.It ‘s easy and quick to do, and reducing the value of the Z-diode, the circuit can be universally adapted to other output devices of the circuit voltages. The give and all diagrams represent a DC converter with 12V battery 9 volt DC input and output.
  
12-9 Volt DC to DC Converter Circuit Diagram

With the 10V zener diode, as in the diagram, the output voltage is approximately 9.3 volts DC. The supply voltage is used, should always be at least a few volts higher than the Zener voltage. In this example, I have a 12 Volt DC battery to provide regulated 9-volt DC output. Link

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