Showing posts with label supply. Show all posts
Showing posts with label supply. Show all posts
Thursday, December 19, 2013
Solar Power Supply
This circuit delivers either 4.8 or 7.2 V regulated at 15 mA with a 3-V input from a bank of photocells. Rl should be 453 kQ for a 7.2-V output and 274 РЁ for a 4.8-Vdc output. Regulator efficiency is around 70%. This should be considered when selecting suitable solar cells.
Solar Power Supply Circuit diagram :
Solar Power Supply Circuit diagram :
Wednesday, August 7, 2013
Soft Start For Switching Power Supply
Switching power supply whose output voltage is appreciably lower than its input voltage has an interesting property: the current drawn by it is smaller than its output current. However, the input power (UI) is, of course, greater than the output power. There is another aspect that needs to be watched: when the input voltage at switch-on is too low, the regulator will tend to draw the full current. When the supply cannot cope with this, it fails or the fuse blows. It is, therefore, advisable to disable the regulator at switch-on (via the on/off input). until the relevant capacitor has been charged. When the regulator then starts to draw current, the charging current has already dropped to a level which does not overload the voltage source.
Circuit diagram:
Circuit diagram:
Soft Start Circuit For Switching Power Supply
The circuit in the diagram provides an output voltage of 5 V and is supplied by a 24 V source. The regulator need not be disabled until the capacitor is fully charged: when the potential across the capacitor has reached a level of half or more of the input voltage, all is well. This is why the zener diode in the diagram is rated at 15 V. Many regulators produced by National Semiconductor have an integral on/off switch, and this is used in the present circuit. The input is intended for TTL signals, and usually consists of a transistor whose base is accessible externally. This means that a higher switching voltage may be applied via a series resistor: the value of this in the present circuit is 22 kΩ. When the voltage across the capacitor reaches a level of about 17 V, transistor T1 comes on, whereupon the regulator is enabled.
Source: National Semiconductors
Monday, July 8, 2013
12V DC Switch Mode Power Supply Rise
Basic Of Switch Mode Power Supply
In recent years, the use of switch mode power supply (SMPS) has become more comon as more applications demand for greater power eficiency. It makes use of semiconductor (mostly MOSFET) fast switches to switch DC input that has been rectified at high frequency. The advantages of high frequency switching are that it reduces the size of inductor, capacitors & transformer used. Other advantages of switching power supply over linear power supply are :
1) High Efficiency (up to 90% and above for nice design).
2) Output can be higher than input.
3) Able to operate over a variety of input power supply.
4) Able to have over output.
3) Able to operate over a variety of input power supply.
4) Able to have over output.
The setback of using SMPS compared to linear power supply is that it generates electrical noise which contributes to electromagnetic compatibility design issues & more part count.
Buck Converter SMPS
The SMPS circuit below from Power Integration makes use of LNK304 as its high frequency switch. Take note that this circuit is non isolated type which means that the output is not electrically isolated from the input & all testing ought to be completed using an isolation transformer to provide the AC line input to the board.
Make positive that you have electrical safety knowledge & experience before you embark on doing this project.
The features of this project is as summarized below.
Input : 85-265 VAC
Output : 12 V, 120 mA, 1.44 Watt
Low Cost : Only 16 components are needed
No-load power consumption : < 0.2 Watt
Input : 85-265 VAC
Output : 12 V, 120 mA, 1.44 Watt
Low Cost : Only 16 components are needed
No-load power consumption : < 0.2 Watt
Tuesday, May 14, 2013
Variable power supply using 7805
This circuit diagram shows you how to make a 5V to 12V variable DC power supply from a fixed 5V regulator IC 7805. This is attained by adding two resistors R1 and R2 as shown in figure. When the resistors R1 and R2 are added the equation for the output voltage of 7805 becomes Vout= Vfixed + { R2 [ (V fixed/R1) + Istandby] } ,where Vfixed=5V and Istandby=Vfixed/R1.By varying the POT R2 you can adjust the output voltage between 5V and 12V.
Notes. * The circuit can be assembled on a vero board. * T1 can be a 230V primary, 9V/5A secondary stepdown transformer. * 7805 must be fitted with a heat sink. * F1 can be a 1A fuse.
Friday, April 5, 2013
0 28V 6 8A Power Supply Circuit
This is the complete design power supply circuit. This circuit has stable, clean and regulator 0-28V 6/8 Amp output voltage. This circuit is using transistor 2N3055. Although you could use this design to deliver 20 amps (with almost no modifications and with a proper transformer and a huge heat sink with a fan), it didn’t need much power. This is the figure of the circuit.
Although the 7815 power regulator will kick in on short circuit, overload and thermal overheating, the fuses in the primary section of the transformer and the fuse F2 at the output will secure your power supply. The rectified voltage of: 30 volt x SQR2 = 30 x 1.41 = 42.30 volt measured on C1. So, all the capacitors should be rated at 50 volts. Caution: 42 volt is the voltage that could be on the output if one of the transistors should blow. P1 allows you to regulate the output voltage to anything between 0 and 28 volts. The LM317 lowest voltage is 1.2 volt. To have a zero voltage on the output Ive put 3 diodes D7,D8 and D9 on the output of the LM317 to the base of the 2N3055 transistors. The LM317 maximum output voltage is 30 volts, but using the diodes D7,D8 & D9 the output voltage is approx 30v - (3x 0.6v) = 28.2volt. Calibrate your build-in voltmeter using P3 and, of course, a good digital voltmeter. P2 will allow you to set the limit of the maximum available amps at the output +Vcc. When using a 100 Ohm/1watt varistor the current is limited to approx. 3 Amps @ 47 Ohm and +- 1 Amp @ 100 Ohms.
Although the 7815 power regulator will kick in on short circuit, overload and thermal overheating, the fuses in the primary section of the transformer and the fuse F2 at the output will secure your power supply. The rectified voltage of: 30 volt x SQR2 = 30 x 1.41 = 42.30 volt measured on C1. So, all the capacitors should be rated at 50 volts. Caution: 42 volt is the voltage that could be on the output if one of the transistors should blow. P1 allows you to regulate the output voltage to anything between 0 and 28 volts. The LM317 lowest voltage is 1.2 volt. To have a zero voltage on the output Ive put 3 diodes D7,D8 and D9 on the output of the LM317 to the base of the 2N3055 transistors. The LM317 maximum output voltage is 30 volts, but using the diodes D7,D8 & D9 the output voltage is approx 30v - (3x 0.6v) = 28.2volt. Calibrate your build-in voltmeter using P3 and, of course, a good digital voltmeter. P2 will allow you to set the limit of the maximum available amps at the output +Vcc. When using a 100 Ohm/1watt varistor the current is limited to approx. 3 Amps @ 47 Ohm and +- 1 Amp @ 100 Ohms.
Subscribe to:
Posts (Atom)