Power Sequencer Circuit Using LM3880

This is a design circuit for Power Sequencer offers the easiest method to control power up and power down of multiple power supplies (switchers or linear regulators). By staggering the startup sequence, it is possible to avoid latch conditions or large in-rush currents that can affect the reliability of the system. This is the figure of the circuit;

Available in a SOT23-6 package, the Power Sequencer contains a precision enable pin and three open drain output flags. Upon enabling the LM3880 the three output flags will sequentially release, after individual time delays, permitting the connected power supplies to startup. The output flags will follow a reverse sequence during power down to avoid latch conditions. EPROM capability allows every delay and sequence to be fully adjustable. Contact National Semiconductor if a non-standard configuration is required.

LM2576 Switching Regulator Circuit

This is a design circuit that can be to produce any output voltage, an external feedback resistors can be added. The sLM2576 is a Switching Regulator that can produce 15, 12, 5, 0r 3.3V output voltage from maximum supply voltage of 60V or 40V. This LM2476 featured with voltage reference, switch and feedback path for use in either the negative boost or the buck saturation voltage of The LM2576 switch is typically 1.4V. A heatsink may be needed to solve the power dissipation, however the thermal dissipation is internally limited. The LM2576 has quiescent current of 50 µA in standby (on/off high). This circuit is a testing circuit for LM2576. This is the figure of the circuit;

The electrolytic capacitors at output and input should be connected with leads as close as possible. The power dissipation must be small because the load is 100R, so the heat sink is not needed. The capacitor’s voltage must higher than the voltages used in the experiment. This circuit uses 40V, 1A Schottky diode or the 40V, 3A 1N5822 for heavier currents.

Free Switch Mode Pre-Regulator Circuit

This is a circuit for switch mode pre regulator circuit. The botheration was that a voltage regulator had to bead the 18 volt capital ability accumulation voltage to 8 volts at 500ma to ability the CD player, crumbling 5 watts of ability and causing a lot of calefaction central the bunched unit. This ambit acts as an interference-free pre-regulator to abundantly abate the ability loss. This is the figure of the circuit;

The achievement voltage of this ambit is artless by ability band fluctuations. Amount voltage aberration is alone abased on the on-resistance of Q2 and the amount of C2 (re: ripple). The achievement voltage can be set so that the ripple lulls are aloof aloft the drop-out voltage of the beeline regulator at best amount for best activity conservation. The college amount you aces for C2, the added activity you can save and the added abiding the pre-regulator’s achievement voltage.

Integrates Start-Up Regulator and Precision Reference Using LM5033

This is a design device that is ideal for use in telecommunication bricks, industrial power converters, and automotive systems. This is a start up regulator and precision circuit. This circuit is work based on LM5033. This is the figure of the circuit;


In this circuit has features like isolated step-down converter stage feeds multiple non-isolated point-of-load (POL) converters. Each output is independently regulated. No feedback opto-coupler required. Integrated 15V to 100V start-up regulator. Low primary component count. Integrated 1.5A drivers. Tiny, thermally enhanced LLP packaging.

[Circuit source: MAXIM Application Notes]

BMW R Motorcycle Regulator Circuit

This is a design circuit for motorcycle regulator. This circuit is controlled by transistor. This is he figure of the circuit.


Correctly adjusted, the voltage on the pot wiper is slightly less than half D+ (appx. 0.47*D+) and Q1 will conduct if (D+)-(Vp)>6.2+0.7+0.7, or 0.53*(D+) > 7.6V, (D+) > 14.3V. If D+ is lower than 13.7V, Q1 will not conduct, Q2 will get driven via R5, and Q3 will conduct. Df will carry a voltage. When D+ rises, Q1 will start conducting, Q2 will get pinched gradually, and so will Q3. Voltage on Df will drop.

Part:
R1 330
R2 270
R3 470
R4 1.5K
R5 1.2K
R6 100
P 100 ohm pot
C1, C2, C3 100nF ceramic
Q1,Q2 BC327
Q3 BD244A
D1 1N4148
D2 BZX6V2 zener, 6.2V
D3 1N4003

D4 no markings, but a 10A, 50V schottky should do the job here. Strangely enough, the diodes in my Siemens databooks that use this package go up to about 3A, which I consider a little low for this application (BY245, BY246).

12V Flyback Regulator Circuit

This is a design circuit for flyback regulator using LM2587. This is the figure of the circuit.


When the switch is on, current flows through the primary winding of the transformer, T1, storing energy in the magnetic field of the transformer. Note that the primary and secondary windings are out of phase, so no current flows through the secondary when current flows through the primary. When the switch turns off, the magnetic field collapses, reversing the voltage polarity of the primary and secondary windings. Now rectifier D1 is forward biased and current flows through it, releasing the energy stored in the transformer. This produces voltage at the output. [Circuit source: National Semiconductor Notes].

Regulated DC Power Supply Circuit

This is a design circuit for regulated DC power supply. In this circuit is using short circuit protection and with current limiter. This is the figure of the circuit.


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 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.

Variable Voltage Regulator Circuit

This is a design for voltage regulator that can adjust from 1.25 to 37 volts. This circuit is a simple design. The voltage regulator is control by op amp LM317. The device also has built in current limiting and thermal shutdown which makes it essentially blow-out proof. This is the figure of the circuit.


Output voltage is set by two resistors R1 and R2 connected as shown below. The voltage across R1 is a constant 1.25 volts and the adjustment terminal current is less than 100uA. The output voltage can be closely approximated from Vout=1.25 * (1+(R2/R1)) which ignores the adjustment terminal current ``but will be close if the current through R1 and R2 is many times greater. A minimum load of about 10mA is required, so the value for R1 can be selected to drop 1.25 volts at 10mA or 120 ohms. Something less than 120 ohms can be used to insure the minimum current is greater than 10mA. The example below shows a LM317 used as 13.6 volt regulator. The 988 ohm resistor for R2 can be obtained with a standard 910 and 75 ohm in series. When power is shut off to the regulator the output voltage should fall faster than the input.