RU99254U1 - 2-PULSE CONVERTER WITH PULSE LOAD - Google Patents

Abstract

The utility model relates to converting technology and can be used in power supply systems of radio engineering, automation and computer equipment. The purpose of the utility model is to expand the field of use of a push-pull converter with a pulse load, increase the efficiency and reliability of the proposed converter, and reduce its weight and dimensions. This goal is achieved by the fact that the second secondary winding of the current transformer is connected to the input of the second rectifier, the output of which is connected to the input of the second potentiometer, the output of which is connected to the inverse terminal "IN" of the push-pull PWM controller through an isolation diode. 1 s.p. f-ly, 1 ill.

Description

The utility model relates to converting technology and can be used in power supply systems of radio engineering, automation and computer equipment.

A push-pull converter with a pulse load was adopted as a prototype (Schemes of PWM controllers (1156 EU 2, 3) Bryansk “STC SMT, 2000, 22 pages) This device is the closest in technical essence and the achieved result. In a push-pull converter with a pulsed load containing the first and second MOS transistors, a power transformer, the secondary winding of which is connected to the load of the converter through the first rectifier, filter choke, filter capacitor, the negative terminal of the filter capacitor is connected to the negative capacitor lining, the positive and negative terminals of the source power supply, push-pull PWM controller, the direct terminal “IN” of which is connected to the terminal U _REF , a current transformer whose secondary winding is connected to the input the second rectifier, terminal U _{CC of the} PWM controller is connected to an additional power source, terminal C _{T of the} PWM controller is connected to the negative side of the capacitor through a timing capacitor, to which GND and I _{LIM / stop} are also connected, terminal OUT _{A of the} PWM controller is connected to the gate of the MOS transistor, the output OUT _B - to the gate of the second MOS transistor.

Conclusion C _{T of the} PWM controller through a timing capacitor is connected to the negative capacitor plate. And the terminal R _T through the timing resistor is also connected to the negative plate of the capacitor.

The output of OUT _A PWM controller is connected to the gate of the first MOS transistor. The OUT OUT _{pin of the} PWM controller is connected to the gate of the second MOS transistor.

The secondary winding of the current transformer through the rectifier and the active-capacitive filter is connected to the terminal I _{LIM / stop of the} PWM controller.

The GND and PGND pins are connected to the negative side of the capacitor.

The prototype has the following disadvantages.

1) With a pulsed load and the maximum value of the output current of the converter, the voltage on the secondary winding of the current transformer begins to increase sharply and is fed to the output of the I _{LIM / stop} PWM controller. There is a “failure” of the logic elements of the PWM controller. Pulses of different durations are formed at the terminals OUT _A and OUT _B. The average current through the first MOS transistor will differ from the average current through the second MOS transistor. A constant current component will flow through the windings of the power transformer. This phenomenon causes the appearance of a constant component of the magnetic flux in the magnetic circuit of the power transformer. This leads to saturation of the power transformer and a short circuit in its windings. This phenomenon can be eliminated by introducing a dielectric gap in the magnetic core of the power transformer. However, this leads to a decrease in the magnetic permeability of the magnetic circuit and the need to increase the turns of the windings of the power transformer. There is a decrease in the efficiency of the power transformer, an increase in its mass and dimensions. Also there is a decrease in the efficiency of the converter, an increase in its mass and dimensions. When the transformer is saturated, the current flowing through its windings can increase to the value at which the MOS transistors fail. This reduces the reliability of the converter.

2) The presence of a pulse load can cause a mode close to the short circuit mode. In this case, the signal arriving at pin I _{LIM / stop of the} PWM controller from the current transformer causes the comparator to turn off the circuit. As a result, a logical unit is formed at its output, which, passing through the "OR" circuit of the PWM controller, turns on the transistor, which discharges the soft-start capacitor connected to the "Start" terminal. At the same time, other transistors reduce the output potential of the operational amplifier to almost zero. After the output keys are turned off, the potential at pin I _{LIM / stop is} set close to zero, the current limiting and off circuit comparators remove the ban and the soft start process begins. If the operating modes of the pulse load close to the short circuit do not disappear, the described processes are repeated and the circuit switches to the "hiccup" mode. A malfunction in the operation of the pulse load occurs. This reduces the reliability of the complex "Converter - pulse load".

The noted disadvantages limit the scope of the prototype circuit.

They are eliminated by the proposed solution.

The problem is solved of expanding the scope of the proposed push-pull converter circuit. The technical result is to increase the efficiency and reliability of the proposed converter, reducing its weight and dimensions.

An increase in efficiency and reliability, a decrease in the mass and dimensions of the converter is achieved by the fact that the current overload signal is supplied not to the I _{LIM / stop} pin of the PWM controller, but to its inverse output “IN”

This technical result is achieved in that in a push-pull converter with a pulsed load containing the first and second MOS transistors, a power transformer, the secondary winding of which is connected to the load of the converter through the first rectifier, filter choke, filter capacitor, the negative terminal of the filter capacitor is connected to the negative lining capacitor, positive and negative power supply terminals. a push-pull PWM controller, the direct IN terminal of which is connected to the U _REF terminal, a current transformer, the secondary winding of which is connected to the input of the second rectifier, the U _CC terminal of the PWM controller is connected to an additional power source, the terminal C _{T of the} PWM controller through the timing capacitor is connected to the negative capacitor plate, to which the GND and I _{LIM / stop} pins are also connected, the OUT _A PWM controller pin is connected to the gate of the MOS transistor, the OUT _B pin is connected to the gate of the second MOS transistor, the first and second series-connected MD P-transistors are connected so that the drain of the first is connected to the positive terminal of the power source, and the source of the second to its negative terminal, two recuperating diodes are connected in series, the cathode of the first diode is connected to the positive terminal of the power source, and the anode of the second diode is connected to its negative terminal , the anode of the first diode is connected to the source of the first MOS transistor, two series-connected capacitors are connected to the positive and negative terminals of the power source, their common point through the primary circuits quipment power transformer and a current transformer connected to the source of the first MIS transistor terminals OUT _A and OUT _B PWM controller through the first and second control transformer is connected to the gates of the first and second MIS transistors, respectively., entered the first and second potentiometers, a first terminal the first potentiometer is connected to the positive side of the capacitor of the inductive-capacitive filter, its second output is connected to the negative side of this capacitor, the middle terminal of the first potentiometer is connected to the inverse terminal IN The PWM controller, the output of the second rectifier is connected to the first and second terminals of the second potentiometer, the middle output of which is connected to the anode of the diode diode, the cathode of which is connected to the inverse terminal IN of the PWM controller. The diagram shows the proposed push-pull converter. The following notation is accepted:

1, 2 - positive and negative terminals of the power source;

3, 4 - the first and second MOS transistors,

5 - separation diode;

6, 7 - the first and second recovery diodes;

8, 9 - the first and second capacitors;

10 - current transformer;

11 - the second rectifier;

12 - second potentiometer;

13 - push-pull PWM controller;

14 - power transformer;

15 - first rectifier

16 - filter choke

17 - timing resistor;

18 - time-consuming capacitor;

19 - the first control transformer;

20 - the first potentiometer;

21 - second control transformer;

22 - filter capacitor;

23 - an additional power source.

24 - pulse transistor

The first 3 and second 4 series-connected MOS transistors are connected so that the drain of the first is connected to the positive terminal 1 of the power source, and the source of the second to its negative terminal 2. Two regenerative diodes 6, 7 are introduced in series. The cathode of the first diode 6 is connected to the positive terminal 1 power supply, the anode of the second diode to its negative terminal 2, the anode of the first diode 6 to the source of the first MOS transistor 3, two series-connected capacitors 8, 9 to the positive and negative terminals 1, 2 source power. Their common point through the primary windings of the power transformer 14 and current transformer 10 is connected to the source of the first MOS transistor 3. The outputs OUT _A and OUT _{B of the} PWM controllers are connected to the gates of the first 3 and second 4 MOS transistors through the first 19 and second 21 control transformers , respectively. The first 20 and second 12 potentiometers are introduced. The first output of the potentiometer 20 is connected to the positive lining of the capacitor 22 of the inductively capacitive filter, its second output to the negative lining of this capacitor. The middle terminal of the first potentiometer 20 is connected to the inverse terminal of the IN PWM controller, the output of the second rectifier 11 is connected to the first and second terminals of the second potentiometer 12, the middle terminal of which is connected to the anode of the diode 5, the cathode of which is connected to the inverse terminal of the IN PWM controller.

The principle of operation of the proposed stabilized quasi-resonant transducer is as follows.

Voltage is applied to terminals 1, 2. When the additional power supply 23 is turned on, the push-pull PWM controller 13 starts to operate. The frequency of generation of its output pulses is determined by the timing resistor 17 and capacitor 18. From its output OUT _A through the first control transformer 19 and output OUT _B through the second control transformer 21, the output pulses are fed to the gates of the MOS transistors 3, 4. The MIS transistors 3, 4 are started in turn. The soft start circuit of the Start PWM controller 13 (not indicated in FIG. 1) at the first moment of time provides the minimum Pulse duration from OUT _A and OUT _B.

When a pulse is supplied from the output OUT _{A of the} PWM controller 13 through the control transformer 19 to the gate of the MOS transistor 3, it is turned on. The current flows through the circuit: terminal 1, MIS transistor 3, the primary winding of the power transformer 14 and current transformer 10, the capacitor 9, terminal 2.

Since this circuit has an equivalent inductance of the power transformer 14 and current transformer 10, a reverse current occurs, which flows through the circuit: terminal 2, recovery diode 7, primary winding of the power transformer 14 and current transformer 10, capacitor 8, terminal 1. Energy recovery occurs. into the converter power circuit.

When a pulse is supplied from the output “OUTB” of the PWM controller 13 through the control transformer 21 to the gate of the MOS transistor 4, it is turned on. The current flows through the circuit: terminal 1, capacitor 8, the primary winding of the current transformer 10 and power transformer 14, MOS transistor 4, terminal 2.

Since this circuit has an equivalent inductance of the power transformer 14 and current transformer 10, a reverse current occurs which flows through the circuit: negative terminal 2, capacitor 9, primary winding of current transformer 10, power transformer 14 and recovery diode 6, terminal 1. Energy recovery occurs. into the converter power circuit.

As the width of the pulses from the terminals OUT _A and OUT _B increases, the voltage across the filter capacitor 22 reaches the nominal value.

Voltage feedback starts to work.

When the voltage on the capacitor 22 reaches a value higher than the nominal value, the voltage at the inverted terminal IN of the PWM controller 13 exceeds the voltage at the direct terminal IN. The pulse duration at the terminals OUT _A and OUT _B decreases and, consequently, the voltage across the capacitor 22 decreases.

When the voltage at the capacitor 22 is less than the nominal value, the voltage at the inverted terminal IN of the PWM controller 13 is less than the voltage at its direct terminal IN. The pulse duration at the terminals OUT _A and OUT _B increases and, consequently, the voltage across the capacitor 22 increases. Further, the processes are repeated.

The switching frequency of the pulse transistor 24 is much less than the operating frequency of the PWM controller 13.

When the transistor of the pulse load 24 is turned on, a partial discharge of the capacitor 22 occurs. A large current flows through the pulse load resistor 24, and a high power pulse is formed.

The converter practically works in short circuit mode. The output current of the converter increases, and therefore, the current in the primary winding of the current transformer 10. The voltage of the secondary winding of the current transformer 10 increases, at the output of the rectifier 11, at the potentiometer 12, and at the inverse terminal “IN” of the PWM controller 13. The pulse duration at its terminals OUT _A and OUT _B decreases and, consequently, the output current of the converter decreases to almost the nominal value. The converter operates in the "current cut-off" mode. In this mode, the converter is a “current source”.

After turning off the transistor of the pulse load 24, the capacitor 22 is charged.

The first stage of the charge of the capacitor 22 is produced by the "cut-off current", the value of which is determined by the potentiometer 12. In this mode, the converter is a "current source".

When the voltage on the capacitor 22 reaches a value at which the magnitude of the charge current of the capacitor is less than the value of the "cut-off current", the converter becomes a "voltage source".

The magnitude of the charge current of the capacitor 22 is limited by the equivalent resistance of the charge circuit of this capacitor. The charge will be carried out until the moment the condition is fulfilled - the voltage at the converter output is greater than the voltage at the capacitor 22. The voltage at the capacitor 22 is set by the voltage feedback potentiometer 20.

After the voltage value at the capacitor 22 becomes equal to the voltage value at the converter output, the charge current of the capacitor 22 becomes zero. Further, the converter operates in idle mode.

The duty cycle of the pulses on the pulse load resistor 24 is 1: (10 ... 20). The inclusion of the transistor pulse load 24 continues with a given frequency.

The presence of voltage feedback ensures the formation of 24 pulse voltage pulses of identical amplitude on the resistor of the pulse load.

With a pulse load of 24 and the maximum value of the output current of the converter, the voltage on the secondary winding of the current transformer 10 begins to increase sharply and is fed to the inverse terminal IN of the PWM controller. There is no “failure" of the logic elements of the PWM controller, since the signal does not pass through them.

At the terminals OUT _A and OUT _B , pulses of equal duration are formed. The average current through the first MOS transistor will be equal to the average current through the second MOS transistor. A constant current component does not flow through the windings of the power transformer. The constant component of the magnetic flux in the magnetic circuit of the power transformer is not formed. There is no saturation of the power transformer and short circuit in its windings. It is not necessary to introduce a dielectric gap in the magnetic circuit of a power transformer. There is no decrease in the magnetic permeability of the magnetic circuit, and there is no need to increase the turns of the windings of the power transformer. The efficiency of the power transformer increases, its weight and dimensions decrease. The efficiency of the converter also increases, its mass and dimensions are reduced. Since the transformer is not saturated, the current flowing through its windings cannot increase to the value at which the MOS transistors fail. The reliability of the converter increases.

The presence of a pulsed load can cause a mode close to the short circuit mode. However, in the proposed circuit, the signal from the current transformer is supplied not to the I _{LIM / stop} pin of the PWM controller, but to the inverse IN terminal, which does not cause the comparator to turn off the circuit. The I _{LIM / stop} pin of the PWM controller is connected to the “case”. As a result, the logic unit is not formed at its output, which, passing through the “OR” circuit of the PWM controller, turns on the transistor, which discharges the soft-start capacitor connected to the “Start” terminal . He decreases almost to zero the output potential of the operational amplifier. This does not start the second soft start process. If the operating modes of the pulse load close to the short circuit do not disappear, the circuit does not go into the "hiccup" mode. A malfunction in the pulse load does not occur. The reliability of the complex "Converter - pulse load" is ensured.

The main advantages of the claimed Converter in comparison with the prototype should include the following:

- there is no saturation in the power transformer, which reduces the number of turns of all its windings;

- during the operation of the “converter - pulse load” complex, there are no failures in the PWM controller caused by the operation of the pulse load.

The above listed properties provide an extension of the scope of the proposed converter, an increase in its efficiency and reliability, a decrease in mass and dimensions.

Claims (1)

A push-pull converter with a pulse load, containing the first and second MOS transistors, a power transformer, the secondary winding of which is connected to the load of the converter through the first rectifier, filter choke, filter capacitor, the negative terminal of the filter capacitor is connected to the negative capacitor lining, the positive and negative terminals of the power supply , push-pull PWM controller, a direct output of which is connected to IN terminal U _REF, a current transformer, the secondary winding of which is connected to the input a second rectifier, the output U _CC PWM controller is connected to the auxiliary power supply, the output C _T PWM controller through the timing capacitor is connected to the negative plate of the capacitor, to which are also connected terminals GND and I _{LIM / stop,} output OUT _A PWM controller is connected to MISFET gate, the output OUT _B - to the gate of the second MIS transistor, wherein the first and second series-connected MIS transistors are connected so that the first drain is connected to the positive terminal of the power source and the second source - k e about the negative terminal, two series-connected recovery diodes are introduced, the cathode of the first diode is connected to the positive terminal of the power source, and the anode of the second diode is connected to its negative terminal, the anode of the first diode is connected to the source of the first MOS transistor, two series-connected capacitors are connected to the positive and a negative power source terminals, their common point through the primary winding of a power transformer and a current transformer connected to the source of the first MIS transistor terminals OUT _a and OUT _B PWM for NTrollers through the first and second control transformers are connected to the gates of the first and second MOS transistors, respectively, the first and second potentiometers are introduced, the first output of the first potentiometer is connected to the positive lining of the capacitor of the inductive-capacitive filter, its second output is connected to the negative lining of this capacitor, the middle terminal the first potentiometer is connected to the inverse terminal IN of the PWM controller, the output of the second rectifier is connected to the first and second terminals of the second potentiometer, the middle output to which is connected to the anode of the separation diode, the cathode of which is connected to the inverse terminal IN of the PWM controller.