SU1637015A1 - Voltage converter with galvanic signal isolation - Google Patents

Description

The invention relates to a pulse technique and can be used in systems for collecting and converting information with galvanic separation of signal circuits. The purpose of the invention is to improve the reliability and bandwidth conversion

body. The voltage converter with galvanic separation of signals contains a low-frequency pulse modulator 1, a controlled switch 2, a transformer 3 and a demodulator 5. Introduction to the converter of the high-frequency generator 4, the secondary circuit of the transformer 3 is included in the feedback circuit, allows to increase the frequency of the high-frequency generator and thereby expand converter bandwidth, as well as increase reliability due to simpler demodulator circuits, the design of which is determined by significant lichiem high frequency generator output signal at different positions controllable switch, Additionally, simplified isolation transformer design, thus increasing the galvanic isolation circuits. 3 il.

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The invention relates to a pulse technique and can be used in systems for collecting and transforming information with galvanic separation of signal circuits.

The purpose of the invention is to raise it. reliability and bandwidth expansion converter.

FIG. 1 shows a functional voltage converter circuit with galvanic separation of signals; in fig. 2 - time diagrams of his work; in fig. 3 is an example of a specific implementation of the Converter "15

The voltage converter with galvanic separation of signals contains a low-frequency pulse modulator 1, a controlled switch 2, a transformer 3, a high-frequency generator 20 4 and a demodulator 5, while the input of the low-frequency pulse modulator 1 is connected to the input bus of the device, and the output is connected to the control input of the controlled switch 2, the outputs of which 25 are connected to the terminals of the primary winding of the transformer 3, the secondary winding of which is included in the feedback circuit of the high-frequency generator 4 whose output is connected to the 3x0-30 house an audulator 5, the output 6 of which is connected to the output bus of the device.

FIG. 2 shows the input and output ϋ _Βχ inapryazheniya converter output voltage ^ 1, and ₅ units 1, 4 and 5, respectively.

In a particular embodiment of the converter (FIG. 3), the low-frequency pulse modulator 1 is performed on a capacitor 7, resistors 8-10, an operational amplifier 11, and performs pulse-width modulation of the input signal. In the modulator, resistors 12 and 13 form a positive feedback circuit, the circuit consisting of resistor 10 and capacitor 7 is integrating, the summation of the input signal and the signal of the integrating circuit is performed by the chokes 8 and 9. Resistor 14 and transistor 15 compose a controlled switch 2 . High-frequency generator 4 is represented by a generator with capacitive feedback. ..

Capacitors 16 and 17 and inductance 18 constitute an oscillatory circuit. Feedback is removed from the common point of the capacitors 16 and 17 and

through the secondary winding of the transformer ^{1 of the} torus 3 is fed to the transistor 19. The resistor 20 is required for the DC offset of the transistor 19, the capacitor 21 and the resistor 22 form a filter along the power circuit. The demodulator 5 is made on an unsaturated transistor switch 26 with a base 25 and a collector 27 resistors and a shunt diode 24. The demodulator 5 communicates with a high-frequency generator 4 via a coupling capacitor 23. The converter is powered by two sources with output voltages + υσ ^, - ^и ^ ^and + £ £, -and _P2, respectively. From the collector of the transistor 26, the voltage through the filter, in the simplest case containing a resistor 28 and a capacitor 29, goes to the output bus of the device.

The Converter operates as follows.

At zero input voltage υ _βχ at the output of the low-frequency pulse modulator, form “I

bipolar rectangular pulses are obtained. With one polarity of the pulse, key 2 is open and closes the primary winding of the transformer 3. In the short circuit mode, the input resistance of the transformer 3 is determined by the active resistances of the primary and secondary windings. and high-frequency oscillations of a high level, acting on the input of the demodulator 5, open it. When the other polarity of the pulse of the low-frequency pulse modulator 1 controlled key 2 is closed. The primary winding of the transformer 3 is open and the transformer goes into idle mode. In this case, the input resistance of the transformer 3 is determined by the active resistance of the secondary winding and the inductive resistance of the magnetization circuit. An increase in the resistance in the feedback circuit of the high-frequency generator 4 causes a decrease in the amplitude of its signal, and the demodulator 5 closes. Thus, the output of the demodulator 5 is restored output

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low frequency pulse modulator signal 1.

When the input voltage changes, the output ratio changes

pulses of low-frequency pulse modulator 1 and, accordingly, the duty cycle of the output demodulator pulses! 5 o The output of the demodulator filter 5 restores the original, g input signal.

In a particular embodiment, pulse-width modulation is performed at a frequency of 50 kHz at a frequency of a high-frequency generator of 10 MHz, which determines the transmission of the front of the modulator signal of at least 0.1 μs, the device bandwidth of 1 kHz with a relative error of 0.2% and a relative level of 20

output voltage ripple 0.1%. The use of an isolating transformer on an annular ferrite core with an outer diameter of 12 mm with the number of turns of the primary and secondary-25 windings equal to four, allowed to increase the level of galvanic separation to 4 kV.

Introduction to the voltage converter with galvanic separation of the signals of the high-frequency generator, the feedback circuit of which includes the secondary winding of the isolation transformer, allows, with the same element base, to increase the frequency of the high-frequency generator and, thereby, to increase the frequency bandwidth of the converter, as well as to increase reliability due to simpler demodulator circuits, the design of which is determined by the significant difference in the output signal of the high-frequency generator when different positions of the controlled key. A simplification of the design of the isolation transformer allows to increase the level of galvanic separation of signals.

Claims (1)

Claim Voltage converter with galvanic separation of signals containing a low-frequency pulse modulator, the input of which is connected to the input bus of the device, and the output of the control input of the controlled key, the outputs of which are connected to the terminals of the primary winding of the transformer, and a demodulator whose output is connected to the output bus of the device, different by the fact that, in order to increase reliability and expand the bandwidth, a high-frequency generator was additionally introduced into it, in the feedback circuit of which a second The transformer winding is identical, and the output of the high-frequency generator is connected to the input of the demodulator.