RU2749280C1 - Resonant dc voltage converter with increased reliability and efficiency - Google Patents

Abstract

FIELD: electrical engineering; power converter technology.SUBSTANCE: device is a resonant DC-to-DC converter. It includes a bridge inverter, in the diagonal of which the resonant LC circuit and the primary winding of the transformer are connected in series; the secondary winding of the transformer is connected via a rectifier to the output filter and the load. In resonant converters of this type, negative processes occur during switching of key elements at non-zero values of currents (the release of voltage on the choke and the circulation of current in the resonant circuit), which leads to a decrease in the efficiency of the converter and a decrease in the reliability of its operation. To eliminate them, an additional winding is introduced into the choke of the resonant circuit, connected through a second rectifier to the output of the converter.EFFECT: proposed technical solution provides increased reliability and efficiency of the resonant DC voltage converter.1 cl, 6 dwg

Description

The invention relates to the field of electrical engineering, in particular to resonant DC-to-DC converters.

Known bridge serial resonant LC-converter with a resonant circuit included in the diagonal of the bridge [1, 2]. Due to the introduction of a resonant circuit, soft switching of key elements occurs, which makes it possible to reduce the dynamic losses of the converter. This converter consists of a resonant bridge inverter 1, a control system 2, a rectifier 3, an output filter 4 and a load 5 (Fig. 1).

The diagonal of the resonant bridge inverter 1 includes a series resonant circuit consisting of an inductance L and a capacitor C, and the primary winding of the transformer TV. The secondary winding of the TV transformer is connected to the rectifier 3.

In this topology, the resonant circuit and the primary winding of the TV transformer are a voltage divider. When the operating frequency changes, the impedance of the resonant circuit changes and, accordingly, the voltage across the transformer winding changes. Therefore, a pulse frequency modulation method is used to regulate the output voltage. The arms of the bridge inverter 1 are switched in antiphase, applying a supply voltage in direct and reverse polarity to the resonant circuit and the TV transformer, forming a "square wave" with the operating frequency of the converter determined by the control system 2. The duty cycle of the control pulses is always less than 50% to form a pause between switching arms of the bridge inverter [1].

This topology is characterized by operation in the frequency range above the resonant frequency of the LC circuit. The value of the switched current is minimum at the resonant frequency and increases with increasing operating frequency. During a pause, after turning off the transistors of one arm of the bridge inverter until the moment of switching the key elements of the rectifier, the current of the resonant circuit begins to sharply decrease to zero, while closing through the reverse diodes of the transistors of the opposite arm, while the voltage across the inductor of the resonant circuit increases sharply. In addition, during this time interval, the energy stored in the resonant circuit remains circulating in the inverter 1 circuit and is not transferred to the load. These processes lead to a decrease in efficiency and a decrease in the reliability of the converter (figure 2) [1, 2].

The closest in technical essence to the proposed invention is "Resonant bridge voltage converter" [3] (figure 3). This patent proposes to use an additional transformer, the primary winding of which is connected in parallel with the capacitor of the resonant circuit, and the secondary winding through an additional rectifier to the output filter of the converter. This technical solution makes it possible to limit the energy accumulated in the resonant circuit at a given level. If the voltage on the secondary winding does not exceed the output voltage of the converter, all diodes of the additional rectifier are closed and this circuit has practically no effect on the operation of the converter. When the specified voltage level is reached on the resonant capacitor, one of the pairs of diodes of the additional rectifier opens, depending on the polarity of the voltage across it. The voltage across the capacitor remains at a given level, and the energy of the input source is transferred to the load through an additional rectifier (Fig. 3).

However, given that the voltage across the resonant choke during a pause is always higher than the voltage across the capacitor and can exceed it by several times, in a wide range of operating modes of the converter this circuit design does not limit the circulating energy and the voltage surge across the resonant choke during the pause.

The technical result of the proposed invention is to increase the efficiency and improve the reliability of the resonant DC voltage converter.

To achieve the technical result in a resonant DC-to-DC converter (Fig. 1), which includes a bridge inverter with a control system, in the diagonal of which a resonant LC circuit consisting of a choke and a capacitor is connected in series, and the primary winding of the transformer, the secondary winding of which through the first rectifier and the output filter is connected to the output of the converter, an additional winding L: 2 is introduced into the resonant circuit inductor, connected through the second rectifier to the output of the converter (Fig. 4). The voltage on the additional winding L: 2 is proportional to the voltage on the inductor of the resonant circuit. The diodes of the second rectifier are closed until the voltage on the additional winding L: 2 exceeds the output voltage of the converter. When a predetermined voltage level is reached at the resonant choke, one of the pairs of diodes of the second rectifier 6 opens, depending on the polarity of the voltage across it. The level of the limited voltage is set in such a way that in the static mode of the converter operating interval (a pair of transistors of one arm of the bridge are fully open, the opposite one is completely closed), all diodes of the rectifier 6 are closed and all the energy is transferred to the load through the transformer TV and rectifier 3. During the pause when the current of the resonant circuit stops flowing through the key elements of the rectifier 3, the voltage across the choke L increases sharply, opening the corresponding diode pair of the rectifier 6. The voltage across the choke L remains at a given level, and the energy of the resonant circuit through the rectifier 6 enters the load. At this time, the resonant circuit current continues to decrease. At the moment when it reaches zero, the key elements of the rectifier 3 are switched, the current changes its polarity, and the energy is again transferred to the load through the TV transformer and rectifier 3. The voltage across the choke drops sharply and falls below the set value, respectively, the diodes of the rectifier 6 are closed ... The proposed circuit solution significantly reduces the level of energy circulating in the inverter circuit by transferring part of it directly to the load and reduces the voltage surge across the resonant circuit inductor (Fig. 5) during a pause, practically without affecting the operation of the converter the rest of the time. Thus, the introduction of an additional inductor winding and a second rectifier into the resonant converter circuit makes it possible to increase its efficiency and increase reliability over the entire operating range.

Made experimental prototype samples (figure 1) and the proposed converter with a power of up to 1.5 kW (figure 4), operating in the input voltage range from 105 to 160 V and stabilizing the output voltage at 100 V. Dependence of efficiency on the load current of the prototype [1] and the proposed converter [2] are presented in Fig.6.

Literature

1. Meleshin V.I. Transistor converter technology. Moscow: Technosphere, 2005.

2. Yang V. Topology investigation of front end DC / DC converter for distributed power system: PhD. Blacksburg, 2003.

3. Glebov V.A., Zhigachev V.A. Resonant bridge voltage converter, RF patent No. 2593148, BIPM No. 21 dated July 27, 2017.

Claims (1)

Resonant DC-to-DC converter, which includes a bridge inverter with a control system, in the diagonal of which a resonant LC circuit consisting of a choke and a capacitor is connected in series, and the primary winding of the transformer, the secondary winding of which is connected to the output of the converter through the first rectifier and the output filter characterized in that an additional winding is introduced into the inductor of the resonant circuit, connected through the second rectifier to the output of the converter.

Images