RU2110132C1 - Dc-to-dc voltage changer - Google Patents

Abstract

FIELD: electric power conversion. SUBSTANCE: converter has four switches connected into bridge circuit whose first pair of diagonally opposite terminals is connected to two terminals and second one, to primary winding of transformer. Novelty is that it is provided, in addition, with filter capacitors each connected through one lead to two terminals; transformer primary winding is symmetrical and center-tapped; center-tap is connected to second leads of capacitors and to third terminal. Converter functions to convert single-pole input voltage into bipolar output voltage and also to change two-fold the output voltage (to increase or decrease it) relative to input voltage. EFFECT: enlarged functional capabilities, increased efficiency of converter. 2 dwg

Description

 The invention relates to the field of conversion of electrical energy, in particular direct voltage to constant, and can be used as a device that provides both a bipolar output voltage from a unipolar input voltage and a change in output voltage by half (reduced or increased) relative to the input with high efficiency.

 Known devices using operational amplifiers with a powerful output cascade on complementary transistors [1], providing lower output voltage and the formation of a bipolar supply voltage from a unipolar voltage source. Such devices due to deep negative feedback have a high degree of symmetry. However, with an asymmetric load, the differential current flows through one of the transistors of the output stage of the stabilizer, which reduces the efficiency of the device. The efficiency of such a device is especially low if the load is connected to only one arm, for example, between the terminals + E and 0.

 Circuits with conversion of direct voltage to alternating voltage with subsequent rectification, in particular [2], have an increased efficiency, the output voltage of which (increased or lowered, depending on the need, including symmetrical) is provided at the output of a bridge rectifier powered by a medium-sized winding point transformer voltage converter.

 However, the presence of windings and diodes in the output voltage circuit leads to a certain decrease in the efficiency of the device (an additional 5-10% or even more, not counting the losses in the voltage converter itself). In addition, such a device is relatively complex, which reduces its reliability.

 The closest in purpose and technical implementation (prototype) can be recognized as a device containing four keys connected by a bridge circuit, the first diagonal of which is connected to two terminals of the power source, and the primary winding of the transformer is connected to the second diagonal [3].

 However, it is of limited use because it does not have an output with a voltage equal to half the supply voltage, for example, for supplying operational amplifiers that require bipolar voltage, or for a low-impedance load that requires half the supply voltage. In addition, it cannot provide an increase in output voltage.

 The objective of the proposed device is to provide the ability to change (decrease or increase) the output voltage by half, while increasing the efficiency of the device and forming a midpoint of the output voltage.

 This task is achieved by the fact that in a device containing four keys connected by a bridge circuit, the first diagonal of which is connected to two terminals, and the primary winding of the transformer is connected to the second diagonal, filter capacitors connected by one terminals to two terminals are additionally introduced, the primary winding of the transformer made symmetrical with a tap from the midpoint, which is connected to the second terminals of the filter capacitors and the third terminal.

 In FIG. 1 and 2 are diagrams of the proposed device.

 Here VT1 - VT4 are semiconductor (for example, transistor) switches that form a bridge voltage converter with transformer T. + E, -E - terminals to which the first diagonal of the bridge voltage converter is connected. 1-2 - the primary winding of the transformer T, included in the second diagonal of the bridge voltage Converter. The winding has a tap 3 from the midpoint, which is connected to the third terminal 0 of the device, which has a potential equal to half the voltage between the terminals + E and -E (conditional zero at the supply voltage of the device + E / -E). C1, C2 - filter capacitors connected by one output to the + E and -E terminals, and the second to the third terminal 0 of the device.

 The start-up circuits of the device are not shown, the control circuits of the device are shown conditionally in the form of windings connected between the bases and emitters of complementary pairs of transistors, since their specific performance does not affect the solution of the problem. Transformer T can be equipped with the required number of secondary windings.

 The device can operate in the mode of lowering (division) (Fig. 1) and in the mode of increasing (multiplying) voltage (Fig. 2).

 In the first mode (Fig. 1), the device operates as follows.

 When the voltage source E is connected to the + E and -E terminals of the device, two opposite switches are turned on, for example, VT1 and VT3. Moreover, at terminal 1 of the primary winding of the transformer T, the voltage is equal to + E, and at terminal 2 it is minus E. Since terminal 3 is made from the middle of the primary winding, the voltage across it is equal to half the supply voltage (conditionally equal to zero).

 After turning off the keys VT1 and VT3 and turning on the keys VT2 and VT4 at terminal 2 of the primary winding of the transformer, the voltage becomes + E, and at terminal 1 it is -E. In this case, at terminal 3, the voltage remains equal to zero. Capacitors C1 and C2 provide smoothing of AC surges that occur when switching key transistors.

 It should be noted that providing a conditional zero value at pin 3 (midpoint) of the primary winding occurs at any relative duration of the on and off states of the keys (up to the saturation of the transformer core, which does not require any special measures and is provided automatically), since it is determined only by the accuracy of winding the primary winding of the transformer T. This allows the device to be executed according to an extremely simple and, therefore, reliable circuit.

 If the device is used to power an unbalanced load connected to only one arm of the converter, for example between terminals + E and 0, then the converter works as a step-down DC voltage autotransformer with a transformation ratio of 0.5.

 The high efficiency of the device is ensured by the low output impedance of the device due to the parallel connection of the output impedance of the halves of the converter, each consisting of a key and the active resistance of the primary half-winding (as in an AC autotransformer). In addition, if a bipolar load is connected to the output of the device between the terminals -E, 0 and + E, this output resistance creates losses only for the differential current of this load, since the minimum (total) load current flows bypassing the converter.

 In the second mode, when the supply voltage is connected to terminal 0 and one of the terminals + E or -E, and the load is connected to the terminals + E and -E, the device operates as follows.

 We assume that the supply voltage is applied to the terminals 0 and - (Fig. 2) and at the first moment the keys VT1 and VT3 are turned on. In this case, the supply voltage is connected by one bus via terminal 0 to the midpoint 3 of the primary winding of the transformer T, and the second bus - through terminal -E and the public key VT3 - to terminal 2 of the primary winding of transformer T. on the second half-winding of the transformer (at terminal 1 of the winding relative to terminal 3) a voltage equal to the voltage at the first half-winding is induced, and the sign of voltage at terminal 1 is positive relative to terminal 3. Since the key VT1 is open at this moment, capacitor C1 is charged through it to a voltage equal to voltage th food. After turning off the keys VT1 and VT3 and turning on the keys VT2 and VT4, the process repeats. Moreover, the voltage across capacitor C1 is always equal to the supply voltage. If the load is connected to the + E and -E terminals, then the voltage on it becomes equal to the double value of the input voltage, i.e. the device works as a step-up autotransformer with a transformation ratio of 2. A symmetrical load can be connected to the output of the device.

 Thus, the proposed device has extensive functionality: it has the ability to lower or increase the output voltage compared to the input and in both cases to provide bipolar output voltage. In this case, the efficiency of the device is maximally high for this type of converters, since the device does not have a single extra element (winding or diode, as in the analogue [2]), through which the load current would flow and the efficiency of the device would depend on its parameters.

 The solution of the task by the device is confirmed by the layout.

 The offer can be used on the products of the enterprise.

Sources of information
1. Nesterenko B.K. Integrated Operational Amplifiers. Reference application manual. - M.: Energoizdat, 1982, p. 44, fig. 30 b

 2. Circuitry of devices based on powerful field-effect transistors. Directory. / Ed. V.P. Dykonova. - M .: Radio and communications, 1994, p. 91, fig. 4.18.

 3. In the same place, with. 184, fig. 8.14, b.

Claims (1)

 A DC / DC converter containing four keys connected in a bridge circuit, the DC diagonal of which is connected to the first and second terminals, the transformer primary winding is connected to the AC diagonal of the bridge circuit, characterized in that two capacitors are connected, connected by the first terminals respectively to the first and second terminals, the primary winding of the transformer is symmetrical with a tap from the midpoint connected to the second terminals of the capacitors and to the third terminal while one of the three terminals is for connecting one of the terminals of the voltage source, the other terminal is for connecting one of the terminals of the load, and the remaining terminal is for connecting the other terminals of the voltage source and load.

Images