RU2443051C1 - Stabilized quasi-resonance converter - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: introduction into control circuit of converter power circuit MIS transistors the summation unit and new links between elements that provide for modulation of output voltage with the frequency that is less than operation frequency of quasi-resonance converter and for using discrete voltage feedback in the circuit. Due to excluding from power circuit second secondary winding of power transformer, the power loss in windings decrease, thus the efficiency of power transformer increases. Also, exclusion of second secondary winding, second rectifier, modulating MIS transistor improve mass and dimension parameters of the converter.

EFFECT: expansion of the area of application of stabilized quasi-resonance converter with dynamic voltage instability on the output filter capacity with simultaneous increase of efficiency and improvement of mass and dimension parameters.

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Description

The invention relates to a conversion technique and can be used to charge capacitive storage in electronic, electrophysical and electrotechnological installations.

Known resonant converter with pulse-width modulation, described in patent No. 2110881, RF, application No. 95114324 from 08/10/95, IPC Н02М 02/515, 7/523, V.F. Strelkov, publ. 05/10/98. It contains two series-connected recovery diodes, a resonant inductor, two series-connected resonant capacitors connected between the positive and negative terminals of the power source. The converter also contains two series-connected power circuits, each of which is formed by a series-connected charging thyristor and the primary winding of the transformer. The secondary windings of the transformer and two diodes form a rectification circuit with a midpoint connected to a load resistor. The anode of the charging thyristor of the first power circuit is connected to the end of one primary winding of the transformer, the beginning of which is connected to the positive terminal of the power source. The cathode of the charging thyristor of the first power circuit is connected to the anode of the charging thyristor of the second power circuit. The cathode of the charging thyristor of the second power circuit is connected to the end of the second primary winding of the transformer, the beginning of which is connected to the negative terminal of the power source. The connection point of the anode and cathode of the two charging thyristors through a resonant inductor is connected to a common point of the resonant capacitors. Each power circuit is shunted by connected counter-parallel modulating thyristor and a recovery diode. The anode of the first modulating thyristor is connected to the positive terminal of the power source, and the cathode is connected to the common point of the two charging thyristors and the anode of the second modulating thyristor. The cathode of the second modulating thyristor is connected to the negative terminal of the power source, the load resistor is shunted by the filter capacitor.

The disadvantage of the analog circuit is the presence in the resonant circuit of two capacitors. The spread of the nominal capacitance of these capacitors reaches ± 20%. In addition, the primary windings of the power transformer are also two and they are not identical. The noted factors lead to different magnitudes of the currents flowing during the half-cycle through each primary winding 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, which leads to saturation of the power transformer and a short circuit in its circuits. This phenomenon can be eliminated by installing a dielectric gap in the magnetic circuit of the power transformer. However, this leads to a decrease in the magnetic permeability of the magnetic circuit and the need to increase the number of turns in the windings of the power transformer. There is a decrease in the efficiency of the power transformer, an increase in its mass and dimensions, which in turn leads to a decrease in the efficiency of the entire converter, an increase in its mass and dimensions.

Thyristors, which are low-frequency semiconductor devices, are used as key elements in the analog circuit. This does not allow the creation of high-frequency converters with a power transformer and elements of the input and output filters, which have a small weight and dimensions.

In addition, three pulse transformers were used in the circuit to turn on the charging and modulating thyristors, which also complicates the circuit and increases the overall dimensions of the converter. With a small converter power, the dimensions and mass of the power and control transformers are comparable.

All of the above disadvantages limit the scope of this converter circuit.

The device adopted for the prototype is a stabilized quasi-resonant converter (patent No. 2385526, Russian Federation, application No. 2009110643 dated 03.23.09, IPC Н02М 7/53846, V.P. Kiriyenko and V.F. Strelkov, published on 03.27.10 g.). This device is the closest in technical essence and positive effect.

A stabilized quasi-resonant converter contains two series-connected regenerative diodes, the cathode of one of which is connected to the positive terminal of the power source, and the anode of the other to its negative terminal, a power transformer with two secondary windings. The first secondary winding of the power transformer is connected to the input of the first rectifier, the output of which is connected to a load resistor, which is shunted by the filter capacitor. The first output of the resonant inductor is connected to the input of the primary winding of the power transformer. The first and second series-connected charging MOS 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. The connection point of both charging MOS transistors is connected to the connection point of the recovery diodes, as well as to the first output of the resonant capacitor, the second output of which is connected to the second output of the resonant inductor. Two series-connected capacitors are connected in parallel with charging MOS transistors, their common point is connected to the output of the primary winding of the power transformer. The second secondary winding of the power transformer is connected to the input of the second rectifier, the output of which is connected to the drain-source junction of the modulating MOS transistor. The source of the modulating MOS transistor is connected to the source of the second charging MOS transistor, and the gate is connected to the inverse output “A” of a single-cycle PWM controller. The first conclusions of the timing resistor and capacitor are connected to the terminals “R” and “C” of the single-cycle PWM controller, and the second conclusions are connected to the source of the modulating MOS transistor. The “IN” input of a single-cycle PWM controller is connected to the filter capacitor via a voltage feedback circuit. The output of the SYN synchronization circuit of a single-cycle PWM controller is connected to the SYN terminal of a two-stroke PWM controller, the output “A” of which is connected through a control transformer to the gate of the first charging MOS transistor, and the output “B” is connected to the gate of the second charging MIS - transistor.

For quasi-resonant high-power converters, the placement of a second secondary winding in a transformer is not always rational:

- the presence of a second secondary winding increases the dimensions and weight of the transformer;

- during operation, when a pulse of maximum duration is supplied to the gate of the modulating MOS transistor, the transformer operates in a short circuit mode. The charging circuit current flows through the primary winding, the second secondary winding of the transformer, the second rectifier, modulating MOS transistor, i.e. power losses increase, converter efficiency decreases.

In the prototype circuit, the modulating MOS transistor begins to bypass the secondary winding of the transformer when the reverse half-wave of the current of the resonant circuit flows through it and then the direct half-wave. Therefore, regulation, while maintaining a sufficiently high stabilization coefficient, can be carried out only in a relatively small range, i.e. until the moment when the current in the secondary winding of the transformer changes direction and goes from direct to reverse.

In addition, voltage feedback is carried out by a rather complex circuit and contains many elements: a voltage divider, an adjustable stabilizer, and an optical diode. The length of the electrical connection from the voltage divider to the PWM controller is quite large. This requires a thorough PCB layout. Optodiodes at different temperatures have a large spread in transmission coefficient. For stable operation of the converter under these conditions, it is necessary to install integrating links in the correction circuits of the PWM controller. However, this reduces the performance of voltage feedback. Under these conditions, it is rather difficult to obtain a low dynamic voltage instability on the capacitor of the output filter.

A common drawback of analog and prototype circuits is the use of a modulation circuit in them, operating with a frequency equal to the operating frequency of the converter. To implement this modulation principle, additional elements are installed, such as: a second secondary winding of the power transformer, a second rectifier, a modulating MOS transistor, a complex voltage feedback circuit.

All of the above disadvantages limit the scope of these converters.

The technical result of the invention is the expansion of the scope of the quasi-resonant converter with low dynamic instability of the voltage across the capacitor of the output filter while increasing efficiency and improving its overall dimensions.

This goal is achieved by the fact that in the proposed stabilized quasi-resonant converter containing a power source, two series-connected charging MOS transistors, two series-connected recovery diodes, two series-connected capacitors, resonant capacitor and inductor, power transformer, rectifier, load resistor, key element filter capacitor, control transformer, control circuit consisting of a voltage feedback circuit, single-cycle PWM-co the controller, to the terminals «R» and "C" which are connected first terminals of timing resistor and capacitor, and a push-pull PWM controller administered key element and the adder. In this case, the drain of the first charging MOS transistor connected to the cathode of the first recovery diode and to the first output of the first capacitor is connected to the positive terminal of the power source. The source of the second charging MOS transistor, the anode of the second recovery diode, the second terminal of the second capacitor are connected to the negative terminal of the power source. The common connection point of the charging MOS transistors and recovery diodes through a resonant capacitor and inductor is connected to the input of the primary winding of the power transformer. The output of the primary winding of the power transformer is connected to a common point of connection of the capacitors. The secondary winding of the power transformer is connected to the input of the rectifier, the output of which is connected to the filter capacitor. The filter capacitor is connected with a negative terminal to the first terminal of the load resistor and with the second terminals of the timing resistor and capacitor, and with a positive terminal, through a key element, connected to the second terminal of the load resistor. The first input of the adder is connected to the “SYN” terminal of a single-cycle PWM controller, the second input is connected to the “m” terminal of a single-cycle PWM controller, and its output “U _cc ” is connected to the “U _ref ” terminal of a single-cycle PWM controller. The adder output is connected to the “SYN” terminal of the push-pull PWM controller. Pin “A” of the push-pull PWM controller is connected to the first input, and pin “B” is connected to the second input of the control transformer. The first output of the control transformer is connected to the gate of the first charging MOS transistor, and its second output is connected to the gate of the second charging MOS transistor. The voltage feedback loop is formed by a potentiometer, the input of which is connected parallel to the rectifier, and its output is connected to the “IN” terminal of a single-cycle PWM controller.

The introduction into the control circuit of MOS transistors of the power circuit of the adder converter with new connections between the elements (the adder performs pulse-width control of MIS transistors) allows modulating the output voltage with a frequency lower than the operating frequency of the quasi-resonant converter, i.e. it becomes possible to use it at a frequency of circuit of a key element of a dynamic load much lower than the operating frequency of the converter. As a key element in the proposed Converter can be used a transistor controlled by an external signal. Whereas the use of the analogues considered earlier is justified only at the frequency of the closure of the key element of the dynamic load, commensurate with the operating frequency of the converter.

In addition, the input of the adder into the circuit allows for discrete voltage feedback. In this case, corrective circuits are not required for a single-cycle PWM controller, which are necessary for analog feedback and which reduce the gain and speed of a single-cycle PWM controller. Thus, the proposed scheme of effective voltage feedback makes it possible to increase the speed of a single-cycle PWM controller and thereby obtain low dynamic voltage instability on the output filter capacitor.

Due to the fact that the second secondary winding of the power transformer is excluded from the power circuit of the converter, the power losses in the windings are reduced, therefore, the efficiency of the power transformer increases. In addition, the exclusion of the second secondary winding, the second rectifier, modulating MOS transistor improves the overall dimensions of the converter.

The figure shows a diagram of the proposed stabilized quasi-resonant transducer and the following notation:

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

3, 4 - charging MOS transistors;

5 - push-pull PWM controller;

6 - adder;

7, 8 - the first and second recovery diodes;

9, 10 - capacitors;

11 - resonant capacitor;

12 - control transformer;

13 - resonant inductor;

14 - single-cycle PWM controller;

15 - primary winding of a power transformer;

16 - power transformer;

17 - secondary winding of the power transformer;

18 - rectifier

19 - timing resistor;

20 - potentiometer;

21 - timing capacitor;

22 - filter capacitor;

23 is a key element;

24 - load resistor.

The stabilized quasi-resonant converter contains a power source (terminals 1, 2), two series-connected charging MOS transistors 3, 4, two series-connected recovery diodes 7, 8, two series-connected capacitors 9, 10, resonant capacitor 11 and inductor 13, power transformer 16, rectifier 18, filter capacitor 22, key element 23, load resistor 24, control transformer 12, control circuit consisting of a voltage feedback circuit, a single-cycle PWM controller 14, to terminals “R” and “C” of which the first leads of the timing resistor 19 and the capacitor 21, the push-pull PWM controller 5 and the adder 6 are connected. The drain of the first charging MOS transistor 3 connected to the cathode of the first recovery diode 7 and to the first terminal of the first capacitor 9 is connected to the positive terminal 1 of the power source. The source of the second charging MOS transistor 4, the anode of the second recovery diode 8, the second terminal of the second capacitor 10 are connected to the negative terminal 1 of the power source. The common connection point of the charging MOS transistors 3, 4 and the recovery diodes 7, 8, through the series-connected resonant capacitor 11 and the inductor 13, are connected to the input of the primary winding 15 of the power transformer 16, the output of which is connected to a common connection point of the capacitors 9, 10. Secondary the winding 17 of the power transformer 16 is connected to the input of the rectifier 18, the output of which is connected to the filter capacitor 22. The filter capacitor 22 is connected by a negative terminal to the first terminal of the load resistor and to the second terminals of the time delay resistor 19 and capacitor 21, and the positive output, through the key element 23, is connected to the second output of the load resistor 24. The first input of the adder 6 is connected to the terminal "SYN" of the single-ended PWM controller 14, the second input to the terminal "m" of the single-ended PWM -controller 14, and its output “U _cc ” is connected to the output “U _ref ” of the single-cycle PWM controller 14. The output of adder 6 is connected to the output “SYN” of the push-pull PWM controller 5. The output “A” of the push-cycle PWM controller 5 is connected to the first input of the control transformer 12, and the output "B" - to the second input control transformer 12. The first output of the control transformer 12 is connected to the gate of the first charging MOSFET transistor 3, and the second output to the gate of the second charging MOSFET transistor 4. The voltage feedback circuit is formed by a potentiometer 20, the input of which is connected in parallel with the rectifier 18, and its output - to the output "IN" single-cycle PWM controller 14.

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

Voltage is applied to terminals 1, 2. Power PWM controllers 5, 14 is carried out from an additional power source, not shown in the figure.

Initially, the voltage across the filter capacitor 22 and, therefore, at the output of the potentiometer 20 and at the “IN” terminal of the single-ended PWM controller 14 is zero. In this case, the voltage at terminal “m” of the single-cycle PWM controller 14 is 5 V.

The frequency of the synchronization pulses of a single-cycle PWM controller 14 (pin "SYN) is determined by the timing resistor 19 and the capacitor 21. The frequency of the synchronizing pulses should be slightly less than the natural frequency of the resonant circuit. From the output “SYN” of the single-cycle PWM controller 14, synchronizing pulses are supplied to the first input of the adder 6, and from the output “U _ref ” a voltage of 5 V is supplied to the output “U _cc ” of the adder 6.

The synchronizing pulses pass through the adder 6 and from its output are fed to the output "SYN" push-pull PWM controller 5.

At the terminals "A" and "B" of the push-pull PWM controller 5, control pulses are generated, which are alternately supplied to the first and second inputs of the control transformer 12. From the first and second outputs of the control transformer 12, the control pulses are fed to the gates of the MOS transistors 3, 4. Starts turning them on and off alternately.

When you turn on the MOS transistor 3, the direct current of the resonant circuit flows through the circuit: positive terminal 1, the drain-source of the MOS transistor 3, resonant capacitor 11, resonant inductor 13, primary winding 15 of the power transformer 16, capacitor 10, negative terminal 2.

Since the active resistance of the resonant circuit is almost zero, a reverse current arises that flows through the circuit: negative terminal 2, capacitor 10, primary winding 15 of the power transformer 16, resonant inductor 13, resonant capacitor 11, recovery diode 7, positive terminal 1. Recovery occurs. energy to the converter power circuit.

When the MIS transistor 4 is turned on, the direct current of the resonant circuit flows through the circuit: positive terminal 1, capacitor 9, primary winding 15 of the power transformer 16, resonant inductor 13, resonant capacitor 11, drain-source of the MOS transistor 4, negative terminal 2.

Since the active resistance of the resonant circuit is almost equal to zero, a reverse current flows through the circuit: negative terminal 2, recovery diode 8, resonant capacitor 11, resonant inductor 13, primary winding 15 of the power transformer 16, capacitor 9, positive terminal 1. Regeneration takes place energy to the converter power circuit.

A current flows through the primary winding 15 of the power transformer 16, which leads to an increase in the magnetic flux in the core of the power transformer 16, while the self-induction EMF is induced in the secondary winding 17 of the transformer 16. Ultimately, a voltage appears at the output of the rectifier 18. The charge of the filter capacitor 22 begins. The voltage across the filter capacitor 22 rises to the desired level. Upon reaching the voltage at the output of the potentiometer 20 and, therefore, at the “IN” terminal of the single-cycle PWM controller 14 of the set value, the voltage at the “m” terminal of the single-cycle PWM controller 14 becomes equal to zero. Clock pulses do not pass through adder 6.

In the absence of synchronizing pulses on the output "SYN" of the push-pull PWM controller 5 there are no pulses and on its conclusions "A" and "B". The inclusion of MOS transistors 3, 4 does not occur. The voltage across the filter capacitor 22 remains at the desired level.

At a given point in time, the key element 23 closes. The discharge of the filter capacitor 22 begins through the load resistor 24.

The voltage at the output of the potentiometer 20 and at the output "IN" single-ended PWM controller 14 becomes less than the specified value. The voltage at its output "m" again becomes equal to 5 V.

Thus, the synchronizing pulses again pass through the adder 6 and from its output are fed to the output "SYN" push-pull PWM controller 5.

At the terminals "A" and "B" of the push-pull PWM controller 5, control pulses are generated, which are fed to the first and second inputs of the control transformer 12. From the first and second outputs of the control transformer 12, the control pulses are fed to the gates of the MOS transistors 3, 4. It starts alternate inclusion of MOS transistors 3, 4.

The charging process of the filter capacitor 22 resumes and the filter capacitor 22 simultaneously discharges through the load resistor 24.

At a given point in time, the key element 23 opens and the discharge process of the filter capacitor 22 through the load resistor 24 stops. Only the charge of the filter capacitor 22 occurs, which continues until the voltage across the capacitor 22 of a predetermined value is reached.

Next, the processes in the quasi-resonant converter circuit are repeated.

With a short circuit in the load, the current in the resonant circuit of the converter is limited by its wave impedance.

The main advantages of the claimed quasi-resonant transducer compared to the prototype include the following:

- the introduction into the control circuit of the adder and new connections between the elements allowed the modulation of the output voltage with a frequency lower than the operating frequency of the quasi-resonant converter;

- a discrete voltage feedback circuit is used in the converter control circuit;

- the converter control circuit is quite simple: it consists of only two PWM controllers (single-cycle and push-pull) and an adder;

- the following are excluded from the power circuit of the quasi-resonant converter: the second secondary winding of the power transformer, the second rectifier, modulating the MOS transistor.

The above benefits provide:

- expanding the scope of the quasi-resonant converter;

- reducing the dynamic instability of the voltage across the capacitor of the output filter of the quasi-resonant converter;

- an increase in the efficiency of the converter, a decrease in its overall dimensions.

Claims (1)

A stabilized quasi-resonant converter containing a power source, two series-connected charging MOS transistors, two series-connected recovery diodes, two series-connected capacitors, resonant capacitor and inductor, power transformer, rectifier, load resistor, filter capacitor, control transformer, control circuit consisting of from the voltage feedback circuit, a single-cycle PWM controller, to the terminals "R" and "C" of which the first conclusions of the time are connected resistor and capacitor, and push-pull PWM controller, while the drain of the first charging MOS transistor connected to the cathode of the first recovery diode and the first output of the first capacitor is connected to the positive terminal of the power supply, and the source of the second charging MOS transistor, the anode of the second a recovery diode, the second terminal of the second capacitor is connected to the negative terminal of the power source, the common connection point of the charging MOS transistors and recovery diodes through series-connected reso The capacitor and inductor are connected to the input of the primary winding of the power transformer, the output of which is connected to a common point of connection of the capacitors, and the secondary winding of the power transformer is connected to the input of the rectifier, the output of which is connected to the filter capacitor, characterized in that the key element and the adder are introduced, the first input which is connected to the “SYN” terminal of a single-cycle PWM controller, the second input is to the “t” terminal of a single-cycle PWM controller, whose “Uref” terminal is connected to the “Dec” terminal of the adder, and the total output the ora is connected to the SYN terminal of the push-pull PWM controller, the terminal “A” of which is connected to the first input of the control transformer, and the terminal “B” - to its second input, while the first output of the control transformer is connected to the gate of the first charging MOS transistor, and the second output is to the gate of the second charging MOS transistor, the voltage feedback circuit is formed by a potentiometer, the input of which is connected parallel to the rectifier, and its output is to the “IN” terminal of a single-cycle PWM controller, the filter capacitor is a negative output connected to the first terminal of the load resistor and to the second terminals of the timing resistor and capacitor, and by a positive terminal, through a key element, connected to the second terminal of the load resistor.