UA81878U - Step-up dc converter - Google Patents

Abstract

A step-up DC converter comprises input, common and output terminals to connect to a power supply source and parallel connected capacitors of an input filter and a load, a choke, one terminal of which is connected to the input terminal, the second terminal is connected to an output lead of voltage transformer through a first diode, the start of primary winding of which is connected to the input terminal; finish of the winding through a diode is connected to the output lead, a controlled switch, one terminal of which is connected to the common terminal, the control input –to the output of control signal source, and a third diode. The second terminal of control switch is connected to the connection point of the second diode and finish of voltage transformer primary winding, start of the voltage transformer secondary winding is connected through the third diode to the output terminal, the finish - to the connection point of the choke and first diode.

Description

The useful model belongs to the field of electrical engineering, namely to conversion engineering, and can be used in the creation of secondary power sources, uninterruptible power supply units, in the conversion of energy from wind generators and solar batteries, and in other power electronics devices.

A well-known classical pulse voltage regulator of the step-up type (1|, containing input, common and output terminals for connecting the power source and load, respectively, a choke, one terminal connected to the input terminal, the other terminal through a diode to the output terminal, the output filter capacitor, included between the common and output terminals, a controlled key, one terminal is connected to the common terminal, the other terminal is connected to the point of connection of the choke and the diode. The control terminal of the key is connected to the output of the control signal source. When the key is closed, the voltage of the power supply is applied to the choke and the current in the choke increases. When the key is opened, the diode opens and the choke current is shorted through the power source, this diode to the filter capacitor and the load. At the same time, the difference between the input and output voltage is applied to the choke and the choke current decreases.

The disadvantage of such a regulator is the pulse charging of the capacitor of the output filter, which requires the use of a capacitor of large capacity and is the cause of large pulsations of the output voltage.

The closest in terms of technical essence and design features to the new technical solution, which is claimed, is the impulse voltage regulator of the step-up type |21| (Fig. 1). It contains input 1, common 2 and output Z terminals for connecting, respectively, power source 4 and load 5, choke 6, one terminal is connected to input terminal 1, the other terminal through the first diode 7 - to output terminal 2, controlled key 8, one terminal connected to the common terminal 2, the control terminal, to the output of the signal source 9 and the output filter capacitor 10, connected between the common terminal 2 and the output terminals 3. The current transformer 11, the second 12 and the third 13 diodes are additionally introduced into the regulator. Moreover, the beginning of the primary winding of the current transformer 11 is connected to the free terminal of the controlled key 8, the end - to the connection point of the choke 6 and the first diode 7. The beginning of the secondary winding of the current transformer 11 is connected to the input terminal 1, the end - through the second diode 12, turned on against the first diode 7, is connected to the output terminal C and through the third diode 13, turned on according to the second diode 12, is connected to the common terminal 2.

The known pulse voltage regulator has a reduced level of output voltage ripples due to the continuous charging current of the capacitor of the output filter 10. But the continuity of the current is achieved only under the condition of an equal number of turns of the primary and secondary windings of the current transformer 11. With a different ratio of the number of turns, the charging current of the capacitor of the output filter 10 has a power a form that is not able to provide a low level of voltage ripples at the output.

The disadvantages of the known regulator are also: - increased voltage on the open key, which exceeds the output voltage by the value of the input voltage due to the additional voltage on the primary winding of the current transformer |Z). When the operating voltage of the switches on MO5EET transistors increases, their resistance in the conducting state and corresponding power losses increase; - the remagnetization energy of the current transformer after opening the key is returned through diode 13 to the power source, instead of being transferred to the load. Such a path creates a wasteful circulation of this energy through the power source and increases power losses; - the energy accumulated in the dissipation inductance of the current transformer creates an additional increased voltage pulse when the key is opened. To suppress this impulse, you need to install a damping chain, which increases power losses; - the maximum value of the pulse filling factor in the key for the continuous mode of the output current is limited to Utakh: 0.618 |Z), and the range of adjustment by increasing the output voltage relative to the input turns out to be narrow and is within (1-1.618) times. This limitation is due to the fact that in the prototype, the core of the current transformer does not have time to remagnetize during the open state of the key.

The purpose of a useful model is to reduce power losses in the converter and expand the output voltage adjustment range.

The task is solved by the fact that the constant voltage step-up converter consists of input, common and output terminals for connecting, respectively, a power source and a parallel-connected capacitor of the output filter and load, a choke, one terminal connected to the input terminal, the second terminal through the first diode to 60 the output terminal, the voltage transformer, the beginning of the primary winding of which is connected to the input terminal, and the end through the second diode - to the output terminal, the controlled key, one terminal connected to the common terminal, and the control input - to the output of the source of control signals, and the third diode . The converter differs in that the second terminal of the controlled key is connected to the connection point of the second diode and the end of the primary winding of the voltage transformer, the beginning of the secondary winding of which is connected through the third diode to the output terminal, and the end - to the connection point of the choke and the first diode.

The achievement of a new technical result in the proposed converter is as follows: - static and dynamic power losses in the controlled key are reduced, due to the possibility of using it as a MO5EET transistor with a lower operating voltage and, accordingly, a lower resistance value in the conducting state, as well as a lower amplitude of voltage pulses ; - reduced power loss from wasted circulation through the power source of energy that accumulates in the magnetizing inductance of the voltage transformer. Most of this energy is transferred directly to the load; - the range of output voltage regulation has been expanded due to the possibility of changing the ratio of the number of turns of the primary and secondary windings of the voltage transformer without the appearance of a step form of the current that charges the capacitor of the output filter.

Based on the above, it can be concluded that the set of essential features, which is proposed in the formula of the useful model, is necessary and sufficient to achieve a new technical result.

The proposed converter (Fig. 2) consists of input 1, common 2 and output Z terminals, power source 4, parallel-connected output filter capacitor 5 and load 6, choke 7, voltage transformer 8, controlled key 9, source of control signals 10 and the first 11, the second 12 and the third 13 diodes.

Power supply 4 is connected between input 1 and common 2 terminals, and output filter capacitor 5 and load 6 - between output C and common 2 terminals.

Throttle 7 is connected with one terminal to input terminal 1, the second terminal through the first diode 11 to output terminal 3. The windings of voltage transformer 8 are connected: the beginning of the primary winding - to input terminal 1, the end of the primary winding - through the second diode 12 to output terminal 3, the beginning of the secondary winding - through the third diode 13 to the output terminal 3, and the end - to the connection point of the choke 7 and the first diode 11.

The controlled key 9 is connected by one terminal to the common terminal C, the second terminal is connected to the connection point of the second diode 12 and the end of the primary winding of the voltage transformer 8, and the control input is connected to the output of the source of control signals 10.

In fig. 1 shows a diagram of the device used as a prototype.

In fig. 2 shows the scheme of the proposed device.

In fig. 3-10 show timing diagrams explaining the operation of the proposed device:

Fig. C - signal from the output of the source of control signals 10;

Fig. 4 - the current of the controlled key 9;

Fig. 5 - voltage on the controlled key 9;

Fig. 6 - voltage on the secondary winding of voltage transformer 8;

Fig. 7 - choke current 7;

Fig. 8 - current of the third diode 13;

Fig. 9 - current of the first diode 11;

Fig. 10 - the current of the second diode 12.

The proposed converter (Fig. 2) works as follows.

The control signal source 10 turns on and off the controlled key 9 and adjusts the duty cycle of the key current pulses to maintain the set value of the voltage at the output terminal 3.

At the instant of time, the source of control signals 10 (Fig. 3) closes the controlled key 9 (Figs. 4, 5) and thereby connects the primary winding of the voltage transformer 8 to the power source 4. On the secondary winding of the voltage transformer 8 (Fig. 6) with there is a voltage with a polarity that sums up to the voltage of the power source 4. The cumulative voltage of the secondary winding of the voltage transformer 8 and the power source 4 exceeds the value of the output voltage at the terminal C and causes the increasing current of the choke 7 (Fig. 7). This current is closed in a circuit: power source 4, choke 7, secondary winding of voltage transformer 8, third diode 13 (Fig. 8), output filter capacitor 5 and load 6. At the time interval (0s), the first 11 and the second 12 diodes have a non-conducting state (Fig. 9, 10), the core of the voltage transformer 8 is magnetized by the current through its windings.

When the controlled key 9 is opened at the moment of time y: (Fig. 4, 5) the falling current of the choke 7 (Fig. 7) is closed through the first diode 11 (Fig. 9), the capacitor of the output filter 5 and the load 6 and the power source 4. In at the same time, the third diode 13 (Fig. 8) opens and the second diode 12 (Fig. 10) closes. At the time interval (i-i2), the demagnetization current of the voltage transformer core 8 is closed through the power supply 4 and the second diode 12 to the capacitor of the output filter 5 and the load 6. At the same time, the difference between the voltages at the output terminal C and the source is applied to the primary winding of the voltage transformer 8 power supply 4. After demagnetization at the moment of time yg, the core of voltage transformer 8 returns to the initial state corresponding to the moment of time yz.

In the proposed converter, the capacitor of the output filter 15 is charged both when the controlled key 9 is closed and when it is open with the same, i.e. continuous, choke current, which leads to a significant decrease in the ripples of the output voltage at terminal 3. And even in the absence of the capacitor of the output filter 5 voltage ripples on load 6 may be insignificant.

In the continuous current mode of the choke 7, the equation of the volt-second balance at the closing intervals of the controlled key 9 is determined: where E, bo. input and output voltages on outputs 1, 3; n-Mo/M transformation coefficient, that is, the ratio of the number of Me turns of the secondary winding to the number of Mi of the primary voltage transformer 8;

T,0 is the tracking period and the filling factor of key 9 control pulses.

The conversion factor M of the proposed voltage converter, as the ratio of the output voltage Sho to the input E, follows from expression (1):

M----1-p.0

E (g)

The continuous current mode of the choke 7 is possible only when timely demagnetization of the voltage transformer 8 occurs and the saturation of its core is excluded.

The time interval required for the demagnetization of the core of the Lvansfermaconductor of voltage 8 is obtained from the equation of the Volt-second balance of the primary winding 0 P in the form of the expression:

Ir- p rot y (3)

In order for the core of the voltage transformer 8 to demagnetize during the time interval of the rise to the state 1-0) of the controlled key 9, it is necessary to fulfill the inequality: c- (4)

By substituting expressions (2), (3) into the last inequality (4), we obtain the condition under which the prevention of saturation of the voltage transformer core is guaranteed: p: M (5)

Thus, if condition (5) is observed for the upper limit of the conversion factor n 2 Mulakh, then in the entire adjustment range from M-1 to M - Max, the saturation of the core of the voltage transformer 8 is excluded, and thus the continuous mode of the current of the choke 7 is preserved.

A very important feature of the proposed converter is that changing the ratio of the number of turns of the secondary M2 and the primary Mi of the windings of the voltage transformer 8 with the fulfillment of condition (5) does not lead to the appearance of a step form of the current that charges the filter capacitor, 15. This ensures minimal pulsations of the output voltage at different ratios of n and 1, i.e., as follows from expression (2), in a wide range of values of the conversion coefficient M.

The proposed converter, with the same number of circuit elements as the prototype, has the following advantages relative to it: - reduced pulse voltage on the controlled key because it is fixed at the output voltage level; - reduced power losses in individual circuit elements; - the energy accumulated in the magnetizing inductance of the voltage transformer is mainly output to the load; - minimum pulsations of the output voltage are maintained in a wide range of values of the conversion factor.

Experimental samples of the proposed constant voltage converter were manufactured at the Scientific and Production Enterprise "Impuls" (Zaporizhia). Samples with a power of 50 W and 1 kW were tested, which confirmed the functionality of the proposed scheme (Fig. 2) and the indicated advantages over the prototype.

Sources of information: 1. Meleshyn V.I. Transistor conversion technology. - M: Technosfera, 2005.-632 p. (Fig. 11. 10 on p. 235). 2. Pat. VO 2241299 C1 MPK NO2M 3/325. Pulse voltage regulator of increasing type / Krasnikov Yu.Y. Borovykov V.M. - Publ. 27.11.2004, Bull. Mo 33.

Z. Borovykov V., Krasnikov Yu. The search for "ideal" solutions in power electronics: from task statements to project implementation / Modern electronics.-2006. - Mo 8. - P. 36-42.

Claims (1)

USEFUL MODEL FORMULA A constant voltage step-up converter consisting of input, common and output terminals for connecting, respectively, a power source and a parallel-connected capacitor of the output filter and load, a choke, one terminal connected to the input terminal, the second terminal through the first diode to the output terminal , a voltage transformer, the beginning of the primary winding of which is connected to the input terminal, and the end through the second diode - to the output terminal, the controlled key, one terminal connected to the common terminal, and the control input - to the output of the source of control signals, and the third diode, which differs in that the second terminal of the controlled key is connected to the connection point of the second diode and the end of the primary winding of the voltage transformer, the beginning of the secondary winding of which is connected through the third diode to the output terminal, and the end - to the connection point of the choke and the first diode. ryh me nie an vas ef fetr zh: and Y and E and shkh and k! ей и2 ш- ны ши ЧА Э | : ; iz i ii i ; and Shy | | Z: ni p i v v Fig. 1