Low DC to High DC Voltage Converter

Posted by Micro System

on Monday, September 27, 2010

This is a design circuit for converting a low DC voltage into a very high DC voltage. The 555 timer IC in this circuit is configured as an astable multi vibrator, i.e., it generates a continuous signal of given frequency. This periodic signal is fed into the low-side winding of a transformer. This is the figure of the circuit;

The resulting pulsating current in the low-side winding results in a high AC voltage across the high-side winding.  The level of this voltage depends on the voltage ratio of the transformer used.  The example above uses a transformer with a voltage ratio of 6.3V:220V, which can easily generate voltages in excess of 200 volts from a 9-volt battery. The current in the output winding is rectified using a diode, and a capacitor is used to 'smoothen' the rectified voltage waveform, producing a DC voltage. R3 is required to 'bleed' the capacitor charge to ground when the circuit is not in operation. Warning: C2 can store a high voltage, so extreme care is needed when working with this circuit (e.g., the output must not be touched).

Voltage-To-Frequency Converter And Isolated Output Circuit Using LM 35

Posted by Micro System

on Friday, July 23, 2010

This is a circuit for converter circuit that can be convert from voltage to frequency. In this circuit, it can be isolated output too. This circuit is based on LM35. This is the figure of the circuit;


The LM35 series are precision integrated-circuit temperature sensors, whose output voltage is linearly proportional to the Celsius (Centigrade) temperature. The LM35 thus has an advantage over linear temperature sensors calibrated in ° Kelvin, as the user is not required to subtract a large constant voltage from its output to obtain convenient Centigrade scaling. The LM35 does not require any external calibration or trimming to provide typical accuracies of ±1⁄4°C at room temperature and ±3⁄4°C over a full −55 to +150°C temperature range. Low cost is assured by trimming and calibration at the wafer level. The LM35’s low output impedance, linear output, and precise inherent calibration make interfacing to readout or control circuitry especially easy. It can be used with single power supplies, or with plus and minus supplies. As it draws only 60 μA from its supply, it has very low self-heating, less than 0.1°C in still air. The LM35 is rated to operate over a −55° to +150°C temperature range, while the LM35C is rated for a −40° to +110°C range (−10° with improved accuracy).

[Circuit schematic source: National Semiconductor Notes]