Wiring Schematic Diagram

The High Current Regulated Supply beneath uses an added ambagious or a abstracted agent to accumulation ability for the LM317 regulator so that the canyon transistors can accomplish afterpiece to assimilation and advance efficiency. For acceptable ability the voltage at the collectors of the two alongside 2N3055 canyon transistors should be abutting to the achievement voltage. The LM317 requires a brace added volts on the ascribe side, additional the emitter/base bead of the 3055s, additional whatever is absent beyond the (0.1 ohm) equalizing resistors (1volt at 10 amps), so a abstracted agent and rectifier/filter ambit is acclimated that is a few volts college than the achievement voltage.

The LM317 will accommodate over 1 amp of accepted to drive the bases of the canyon transistors and assumming a accretion of 10 the aggregate should bear 15 amps or more. The LM317 consistently operates with a voltage aberration of 1.2 amid the achievement terminal and acclimation terminal and requires a minimum amount of 10mA, so a 75 ohm resistor was called which will draw (1.2/75 = 16mA). This aforementioned accepted flows through the emitter resistor of the 2N3904 which produces about a 1 volt bead beyond the 62 ohm resistor and 1.7 volts at the base. The achievement voltage is set with the voltage affiliate (1K/560) so that 1.7 volts is activated to the 3904 abject back the achievement is 5 volts. For 13 volt operation, the 1K resistor could be adapted to about 3.6K. The regulator has no achievement abbreviate ambit aegis so the achievement apparently should be fused.

MSK5012 is a awful reliable adjustable voltage regulator.Whose achievement can be programmed application two resistors. The regulator has a actual low dropout voltage(0.45v @10A )due to the acceptance of MOSFT with actual low Rds (ON) as the centralized alternation canyon element.The MS5012 has a top akin of accurateness and ripple bounce is about 45dB. It is accessible in a 5 pin Sip amalgamation that is electrically abandoned from the centralized circuitry. This accord us the abandon to fit the IC anon to the calefaction bore and this array of absolute heatsinking improves the thermal dissipation. 

The achievement voltage of this circuit is adjustable from 1.3v to 36v DC.Resistors R1 and R2 are acclimated for programming the achievement voltage. For all applications, amount of R2 is anchored to 10K. The accord amid R1,R2 and achievement voltage Vout is according to the blueprint R1=R2(Vout/1.235)-1. C1 is a clarify capacitor which is aswell a allotment of the aboideau drive circuit of the centralized alternation canyon MOSFET. About three times the ascribe voltage will arise beyond this capacitor and so the its voltage appraisement have to be called accordingly.C2 is the ascribe clarify capacitor while C3 is the achievement clarify capacitor.

A square wave generator with IC UA741 range shown here.The circuit uses positive feedback to the Schmitt trigger action and negative feedback to measure the time of the waveform.

Let us assume that the output is high and the capacitor C1 is fully discharged.C1 now begins to charge through R2 and C1 R1.When tension rises above the junction of R3 and R4, the output changes rapidly totally negative voltage.C1 Now begins the unloading and reloading in the direction.Again contrast, when the negative voltage across C1 falls below that at pin 3, the circuit is returned quickly to totally positive repetitions value.The output endless cycle.

The square wave frequency can be varied by varying POT R1.The frequency range of the circuit depends on the value of R3, R4 and C1.

The circuit diagram shown here is a simple circuit DC power delay, which is based on an SCR (Silicon-Controlled Rectifier). This circuit is very useful and can be used in many applications. The operation of this circuit is very simple. When input power is applied to the capacitor C2 charges through resistor R2 when the voltage on the capacitor just above the voltage of the Zener diodes D3 breaks, breaks and H1 SCR is triggered and the power delay will be available in late OUT.

This PSU has been especially designed for current-hungry ham radio transceivers. It delivers safely around 20Amps at 13.8V. For lower currents, a separate current limiting output, capable of 15ma up to a total of 20A has been added. The power transformer should be capable to deliver at least 25A at 17.5 to 20V. The lower the voltage, the lower power dissipation.

The rectified current will be "ironed" by C1, whose capacity should not be less than 40.000uF, (a golden rule of around 2000uF/A), but we recommend 50.000uF. This capacity can be built up by several smaller capacitors in parallel. The base of this design is a simple 12V regulator (7812). The output voltage can be brought to desired value (here 13.8V) by two external resistors (R5 and R6) using this formula:

The low currents (here 15mA) will keep the 7812 in its regular function. As soon as the current rises over 15ma, the voltage drop on R4 will "open" the Q3, actually handling the high output current. This is a PNP transistor (Ic > 25) and current amplification factor of at least 20. The one that has been tested and proven here is the 2N5683.

The current limiting resistance RL, for the maximum output of 20 Amps should be 0.03 Ohms, rated at least 15W. You can use the resistance wire or switch several resistors in parallel, totaling the resistance/power values. Values for other currents can be calculated by the rule:
RL=0.7/Imax

The RL and Q2 (3A PNP such as BD330) form a short circuit automatic fuse. As soon as the maximum current reaches 20Amps, the voltage drop over the resistor RL will open Q2, and thus limit the B-E Current of Q3. Parallel to Q2 is Q1, which lights the LED 1 whenever the current limiting circuit is active. When the fuse is active, the Q2 bridges the R3, so the full current would flow through the IC1, and damage it. Therefore the R4 is inserted, as to limit the IC1 current to 15mA. This makes it possible to run the IC1 without any cooling aid. The LED 2 will light up every time the PSU is switched on. There is an adjustable current limiter in parallel to the fixed output, thus providing adjustable current source for smaller currents.

This circuit is very simple too. You will notice that there is no current sensing resistor. But it is really there, in a form of the Rds-on resistance of the N-channel FET, which actually handles the load cutoff from the source. The function of the FET is shown in the diagram 2. When the current Id is rising, the tension Uds over the resistance Rds rises very slowly in the beginning, but very fast after the knick. This means, that before the knick the FET behaves as a resistor but after it, works as constant current source.

The D2, R3 and B-E connection of the Q4 will sense the Uds voltage of the FET1. When the voltage rises enough, the Q4 will shortcut the FET1 gate to mass, and cut the current flow through the FET 1 off.

However, to enable the FET1 to open, there is certain gate voltage necessary, which in this case is brought up by the voltage divider consisting of R8, Z1, P1 and R9. So the maximum Gate voltage will be the one of the Z1, and the minimal will be around 3V6. The Z1 voltage (Uz1) will thus determine the max current flowing through the FET 1. The diagram 2 will show that for 5 Amps the Uz1 should be 5V6, and for 20Amps around 9V6.

The Capacitor C4 will determine the “velocity” or the reaction time of the limiter. 100 uF will make the reaction time to be around 100ms, and 1n will make it 1us. Within the designed limits, the P1 will limit the current output in the range of 15mA to 20A.

You can use both output simultaneously, but the total output current will be limited by the value of the RL. This PSU can be built also for higher outputs, as long as the transformer will handle the current requirements, and you provide sufficient cooling for the Q3.

Source : www.zen22142.zen.co.uk

This is simple way to power some 5v logic from a 240vac source. If a 120vac power adapter is used, the circuit will also work for 120vac power lines.