TREE

There are only a limited number of switching regulators designed to generate negative output voltages. In many cases, it’s thus necessary to use a switching regulator that was actually designed for a positive voltage in a modified circuit configuration that makes it suitable for generating a negative output voltage. The circuit shown in Figure 1 uses the familiar LM2575 step-down regulator from National Semiconductor (www.national.com). This circuit converts a positive-voltage step-down regulator into a negative-voltage step-up regulator. It converts an input voltage between –5 V and –12 V into a regulated –12-V output voltage. Note that the output capacitor must be larger than in the standard circuit for a positive output voltage. The switched current through the storage choke is also somewhat higher. Some examples of suitable storage chokes for this circuit are the PE-53113 from Pulse (www.pulseeng.com) and the DO3308P-153 from Coilcraft (www.coilcraft.com). The LM2575-xx is availabl...

Regulator Handles Two Input Voltages circuit in Fig 1 supplies both 3.3 and 5V to transitional circuits that employ both the new 3.3V and older 5V devices. Additionally, because the regulator accepts either 3.3 or 5V inputs, you could plug it into either a new 3.3V system or an old 5V system.The circuit consists of two sections: a dc/dc converter and a double-pole, double-throw (dpdt) switch. The dpdt switch comprises a pair of dual n-channel MOSFETs (Q2 and Q3) and their associated high-side drivers. Upon power-up, the comparator in IC2 determines the state of the circuit. The comparator’s output, IC2 pin 6, goes to the input of the MOSFET driver, IC1. The driver internally generates a gatedrive voltage 8.8V above the device’s supply voltage. This high voltage drives the appropriate MOSFETs in Q2 and Q3. IC2 is also the heart of a flying-capacitor, buck/boost dc/dc converter. Unlike other switching-regulator schemes, this topology needs no transformers. Transistor Q1 controls this se...

The circuit in Fig 1 supplies both 3.3 and 5V to transitional circuits that employ both the new 3.3V and older 5V devices. Additionally, because the regulator accepts either 3.3 or 5V inputs, you could plug it into either a new 3.3V system or an old 5V system.The circuit consists of two sections: a dc/dc converter and a double-pole, double-throw (dpdt) switch. The dpdt switch comprises a pair of dual n-channel MOSFETs (Q2 and Q3) and their associated high-side drivers. Upon power-up, the comparator in IC2 determines the state of the circuit. The comparator’s output, IC2 pin 6, goes to the input of the MOSFET driver, IC1. The driver internally generates a gatedrive voltage 8.8V above the device’s supply voltage. This high voltage drives the appropriate MOSFETs in Q2 and Q3. IC2 is also the heart of a flying-capacitor, buck/boost dc/dc converter. Unlike other switching- regulator schemes, this topology needs no transformers. Transistor Q1 controls this section’s output voltage, VS. When...

The car cigarette lighter socket does not only light cigarettes, but can be utilized as an electrical channel for powering tools to work on the car such as laptops and other electronic devices. The following circuit diagram shows a way of powering a two-way mobile radio using the LM317 T voltage regulator . The LM317 T is an adjustable 3-terminal positive voltage regulator that efficiently provides a load current of 1.5 Amps over an output range of 1.2 V and 37 V. With reference to the circuit, it can accept 14 volts without any hassle and the voltage can be controlled easily with the use of a potentiometer, a 3-terminal resister with sliding contact. The whole circuit will contain the following components:  Printed Circuit Board (PCB) Resistor 1 (R1): 270 ohms Resistor 2 (R2): 2K carbon potentiometer Capacitor 1 (C1): 100nF Capacitor 2 (C2): 1uF tantalum LM317T Voltage Regulator Heat Sink DC Power Jacks Green LED: Power Red LED: Over Voltage Zener Diode: over voltage LED switch Th...

                     Above circuit diagram is a easy, simple and cheap switching voltage regulator which has capability to deliver adjustable voltage output range of 1.8V to 32V and static electric current of 3A. This regulator use adjustable regulator IC of LM317HV and a power PNP transistor of 2N3792. The LM317HV is adjustable 3-terminal positive voltage regulators capable of supplying in excess of 1.5A over a 1.2V to 57V output range. This electronic component exceptionally easy to use and require only two external resistors to set the output voltage. Further, both line and load regulation are better than standard fixed regulators. Also, the LM317HV is packaged in standard transistor packages which are easily mounted and handled. LM317HV Features: Adjustable Output Down to 1.2V Specified 1.5A Output Current Line Regulation Typically 0.01%/V Load Regulation Typically 0.1% Current Limi...

This circuit operating with IC uA723 and add amplified with transistor  TIP31 or similiar transistor with TIP31 . Input voltage for circuit about 10 - 40 volt DC , formerly of AC voltage 220 volts or 110 volts , then lowered by the transformer voltage to 30 volts. And the supply output voltage from 1 volt to 35 volt DC  you can adjust it on potentiometer  R2 .  See this circuit power supply below : Output voltage transformer used 10 to 40 Volts . On resistor Rsc is the current limit set resistor. Its value is calculated as : Rsc = 0.65 Volt For Example : If you need current output 2.0 A Rsc = 0.65 / 2.0 = 0.32 Ohm So , you must use 0.32 Ohm to current output 2.0 A

This is the simple Systematic Negative Voltage Regulator Circuit Diagram.One v;ay to provide good negative-voltage regulation is with a low-dropout positive-voltage regulator operating from a well-isolated secondary winding of switch-mode circuit transformer. The technique works with any positive-voltage regulator, although highest efficiency occurs with low-dropout types. Under all loading conditions, the minimum voltage difference between the regulator ViN and VoUT pins must be at least 1.5 V, the LT1086`s low-dropout voltage. Systematic Negative Voltage Regulator Circuit Diagram If this requirement isn`t met, the output falls out of regulation. 1vo programming resistors, R1 and R2, set the output voltage to 12 V, and the LT1086`s servo the voltage between the output and its adjusting (ADJ) terminals to 1.25 V. Capacitor C1 improves ripple rejection, and protection diode D1 eliminates common-load problems. Since a secondary winding is galvanically isolated, a regulator`s 12 V output ...

If you have trouble locating an 8-V regulator, although they are commonly available,a 5-V unit can replace it by connecting the regulator, as is shown here.     Simple 8V From 5V Regulator Circuit Diagram