JPH02168857A - Resonance type power converter - Google Patents

Abstract

PURPOSE:To miniaturize a device to lighten the weight, and attenuate electromagnetic noise by connecting a reactor having the inductance of a value less than that of the self-inductance of a primary winding, to the one side at least, of the primary and secondary windings of a transformer, in parallel with each other. CONSTITUTION:To the primary winding of a transformer T, the parallel resonance circuit 1 of a resonance type capacitor Cr and a resonance reactor Lr is connected in parallel with each other. Switch elements Q1, Q2 are driven by a switch element drive circuit 2 based on a resonance type voltage detection winding Ng set on the transformer T. In the meantime, the secondary winding N2 of the transformer T is connected to a load 3. Besides, as the value of the Lr, a value sufficiently less than that of the self-inductance L1 of the whole primary winding of the transformer T is used. In this case, resonance frequency f01 is as shown by an equation (1). In this case, when the Lr is set in relation to Lr<<L1, then L' Lr is shown, and the f01 can be determined by the value of the Lr. As a result, regardless of the value of the L1, switching frequency can be converted to be high frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION [First Industrial Field] The present invention relates to a resonant type power converter, and specifically relates to a resonant type power converter suitable for a resonant type DC-DC converter and the like.

[Conventional technology]

Resonant molds and converters are used as inverters that convert direct current into alternating current using switch elements, transform this using a transformer to obtain the desired direct current voltage, and further rectify the alternating current to obtain the desired direct current. - configured as a DC converter;
In order to reduce switching losses associated with AC conversion, a capacitor is connected in parallel to a transformer to form a resonant circuit, and the above switching element is driven in synchronization with the electrical vibrations of this resonant circuit. be.

As for the conventional technology related to such a resonant power converter, Japanese Patent Application Laid-Open No. 61-277372, Magazine Transistor Technology (No. 6, 1987, pages 406-407)
The awn described in is known.

As a concrete analysis example of a DC-DC converter,
Institute of Electronics, Information and Communication Engineers Technical Research Report (PB87-26(19)
87), pages 9 to 14) are known.

Generally, the above-mentioned resonant circuit receives power from a series connection of a DC voltage and a reactor, and is composed of a self-inductance L1 between the primary winding of the transformer and a capacitor capacitance C connected in parallel with the primary winding. , is said to be voltage resonant type. In addition, as a feature of the above-mentioned resonant power converter, either the applied voltage or the current flowing through the switching element has a sinusoidal waveform, so there is little switching loss that occurs when the switching element is turned on or off. Compared to conventional non-resonant converters, this converter generates less conduction noise and radiation noise caused by wiring inductance and parasitic capacitance.

[The problem that FJA is trying to solve] However, from power,
Even in the above-mentioned resonant type conversion gain, the voltage applied to each element of the circuit varies greatly, and the current flowing through the switch element still changes sharply. For this reason, the 4% transmission and sound flowing back through the power supply line to the input power supply and the radiation noise generated from various parts of the (b) path are at a level that cannot be ignored. In order to reduce these noises, measures such as installing a noise filter on the power supply line or covering the entire conversion gain with a shield plate can be considered, but either method will increase the size of the device. Problems arise with increased weight and reduced efficiency.

Furthermore, in the above resonant transformer, a full-wave rectifying and smoothing circuit is provided on the secondary side of the transformer to supply DC power to the load, and a 5° magnetic amplifier is installed between the transformer secondary winding and the gold wave rectifying circuit. When the output is controlled by providing a filter, a new problem arises in that electromagnetic noise in a high frequency band increases.

The cause of this increase in electromagnetic noise will be explained below.

The above-mentioned resonant power converter configures a resonant circuit with the self-inductance L+ between the primary winding of the transformer and the capacitor capacitance connected in parallel with the primary winding, and generates a sinusoidal resonant voltage across both ends of the resonant circuit. Occur. In order to supply DC power to a load provided on the secondary side of a transformer, a full-wave rectifier circuit and a smoothing circuit are provided between the transformer secondary winding and the load. However, as it is, it is not possible to adjust the output according to input voltage fluctuations and load fluctuations, so it is necessary to install a magnetic booster 1191 between the secondary winding and the full-wave rectifier circuit in order to control the output. There is. Magnetic amplifiers adjust the output by controlling the phase of the resonant voltage generated in the transformer secondary winding, but due to this operation, the voltage applied to the secondary side rectifier circuit is not a sine wave, but a rising wave. The curve becomes steep. For this reason, surge currents and spike voltages are generated due to reverse recovery characteristics in the diodes used in the rectifier circuit, which significantly impairs the low noise performance of the resonant transformer.

An object of the present invention is to provide a resonant type power conversion system that can achieve compact size, light weight, and low electromagnetic noise regardless of the effects of noise filters and housing shields.

[Failure to solve the problem]

In order to achieve the above object, the resonant power converter of the present invention connects a series circuit of a DC power source and a reactor to the primary winding of a transformer via a switch element, and connects the inductance of the transformer and the inductance. A resonant circuit is formed by a capacitance connected in parallel to the transformer, and the switching element is opened and closed in synchronization with the resonant voltage to supply power to the load connected to the secondary winding of the transformer. However, the method described below was used.

(2) A reactor having an inductance equivalently smaller than the self-inductance of the primary winding is connected in parallel to at least one of the primary or secondary winding of the transformer.

, 7.

(2) Reactors connected in series with the DC power source are provided on both sides of the DC power source, and these reactors are magnetically coupled.

■Covering the outside of the transformer with a conductive material.

Further, when using a magnetic amplification gain, a full-wave rectifier circuit, and a smoothing circuit on the secondary side of the transformer, the following means are used.

(2) Provide a static shielding plate made of conductive material on the primary and secondary windings of the transformer, and connect it to one end of the load or input power source.

(2) A buffer circuit (snubber circuit) is provided in the full-wave rectifier circuit.

(2) The buffer circuit is composed of one of a resistor, a capacitor, and a reactor.

[For production]

With this configuration, according to the present invention, the object can be achieved through the following actions.

(2) When a reactor (hereinafter referred to as resonance reactor Lr) is connected in parallel to the primary winding of the transformer, the resonance frequency fo1 of the resonance circuit becomes the following equation (4).

, 8 Here, L+ + Lr In equation (4), if a resonant reactor is selected in the relationship that Lr << L+, then L'kiLr and f0+ are Lr
determined by the value of

Therefore, it is possible to set the resonance frequency f01 (switching frequency) to a high frequency regardless of the self-inductance L1 of the transformer. In other words, since Ll can be designed to a large value even when it is several hundred Kllz or more, there is no need to provide a gap in the transformer core, and the leakage magnetic flux emitted from the transformer can be reduced, reducing electromagnetic noise. do.

■If a reactor connected in series with the DC power supply is provided on both sides of the DC power supply and these are magnetically coupled, the opposite phase voltage fluctuations occurring at both ends of the reactor cancel each other out, resulting in normal mode and common mode noise. can be reduced.

(2) By covering the outside of the transformer with a conductive material (for example, copper foil), leakage magnetic flux mainly generated by gaps in the transformer core is short-circuited and leakage to the outside is prevented. Therefore, the radiation noise radiated into the space and the conduction noise induced in the circuit wiring can be reduced. ■ By providing a shielding plate between the primary and secondary windings of the transformer, the transformer It is possible to weaken the electrostatic coupling between the secondary windings and prevent the noise voltage generated on the secondary side from being conducted to the primary side.

(2) By providing a buffer circuit in the full-wave rectifier circuit, changes in the voltage applied to the rectifier diode can be made gentler when controlling the magnetic amplifier. Therefore, surge current and spike voltage generated in the diode are reduced, and electromagnetic noise can be reduced.

〔Example〕

Hereinafter, the present invention will be explained based on examples.

FIG. 1 is a block diagram of an embodiment in which the present invention is applied to a resonant DC-DC converter. As shown in the figure, a DC input power source is formed by a series circuit of a DC power source E1 and a reactor L+, and this series circuit is connected to the primary winding of a transformer T via a pair of switch elements Q1 and Q2. . A resonant circuit 1 consisting of a parallel circuit of a resonant capacitor Cr and a resonant reactor Lr is connected in parallel to the primary winding of the transformer T. The switch elements Q, , Q2 are driven by the switch element drive circuit 2 based on a resonant voltage detection winding N8 provided on the transformer T. On the other hand, the secondary winding of the transformer 6T is connected to the load 3. Further, the value of Lr is set to a value that is sufficiently lJ smaller than the self-inductance L1 of the entire primary winding of the transformer T.

Note that the switch element Q1. Q2 may be a self-extinguishing element such as a bipolar transistor, MOSFET, or GTO. With this configuration, the switching element Q
1 or Q2 is turned on, the resonant circuit 1 resonates, and the voltage Vc of the resonant capacitor Cr becomes a sinusoidal waveform υ shown in FIG. 2(a), and this voltage is applied to the switching element Q1.
Applied to Q2. In addition, the resonant current ir shown in the same figure (b)
flows. On the other hand, the switch element drive circuit 2 has a winding NI+
The voltage (resonant voltage) applied to the switching elements Q and Q is detected, and in synchronization with this, Ql and Q2 are driven to open and close alternately. The switching period at this time is different from the above-mentioned resonance frequency fi+, and is substantially unrelated to the self-inductance L1 of the transformer T.

Therefore, according to this embodiment, the switching frequency can be increased regardless of the value of Ll. Also, L
Since there is no problem even if l is large, there is no need to provide a gap in the transformer, leakage magnetic flux can be reduced, and electromagnetic noise is reduced.

FIG. 2 shows another embodiment of the invention. This example is the first
The reactors Li shown in the figure are placed at both ends of the input power source Ei, and each is magnetically coupled. In this case,
The reactor Li removes normal mode noise transmitted through the input power supply line.

FIG. 6 shows still another embodiment of the present invention.

As shown in the figure, by wrapping a foil made of conductive material such as copper around the same curve of transformer T (mainly around the gap in the iron core), the magnetic flux leaking across the gap is short-circuited, and the transformer 4 to 6 show examples in which a full-wave rectifying and smoothing circuit and a magnetic amplifier are used on the secondary side of the transformer. In the embodiment shown in FIG. 4, an electrostatic shield is provided between the transformer and the primary and secondary windings, and one end of each shield is connected to one end of the input power source or the load. In this case, the capacitive coupling between the negative and secondary windings is reduced, thereby preventing noise generated on the secondary side from being conducted to the primary side via the transformer.

In the embodiments shown in FIGS. 5 and 6, a C-R snubber circuit and a reactor are added to the secondary rectifier diode, respectively. In these cases, temporal changes in the voltage and current of the rectifier diode can be made gentler, which reduces the generation of surge currents and spike voltages, and reduces noise.

FIG. 7 shows a comparison of the measurement results of conduction noise when all of the above embodiments are used and the conventional technology.

The resonance frequency at this time was 50DKHz. From the figure, it can be seen that in the example, the noise level is reduced by a maximum of 30 dB compared to the conventional example, and the noise reduction effect of the present invention is remarkable.

In addition to the method described above, a method of detecting the resonant voltage may include detecting the current flowing through the resonant reactor Lr or the resonant capacitor Cr, but any method may be used.

In addition, in FIGS. 1 to 6, the output is transmitted to a load 6 via a transformer T, where 6 has any of resistive, capacitive, and inductive characteristics, or a combination thereof. It may be of.

〔Effect of the invention〕

As explained above, according to the present invention, a reactor having a value equivalently smaller than the self-inductance of the primary winding is connected in series to at least one of the primary or secondary winding of the transformer. Therefore, the resonant frequency can be increased regardless of the value of the transformer's self-inductance. Therefore, even when the frequency is increased, there is no need to provide a gap in the transformer core, which has the effect of reducing the generation of electromagnetic noise due to the influence of stray magnetic flux. Furthermore, by surrounding the transformer with a conductive material such as copper foil, the leakage magnetic flux can be reduced and electromagnetic noise can be reduced. In addition, by providing reactors at both ends of the input power source and magnetically coupling them, the negative phase noise components that attempt to be conducted to the input power source are canceled out, which has the effect of reducing normal mode and common mode noise. There is.

Furthermore, when a magnetic amplifier and a full-wave rectifying and smoothing circuit are provided on the secondary side of the transformer to provide a controllable DC output to the load, an electrostatic shield is provided between the transformer and the secondary winding. By connecting this one end to the input voltage or one end of the load, the capacitive coupling between the negative and secondary windings can be weakened. As a result, it is possible to prevent the voltage noise generated in the secondary circuit and the load from being conducted to the primary side, thereby reducing the conduction noise to the input power source. Additionally, by adding a buffer circuit consisting of a resistor, capacitor, or reactor to the secondary rectifier diode, it is possible to reduce surge currents and spike voltages generated in the diode, thereby reducing conduction noise and radiation noise. There is an effect that can be done.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram showing one embodiment of the present invention, FIGS. 2 to 6 are diagrams showing other embodiments of the present invention, and FIG. 7 is a circuit configuration diagram showing one embodiment of the present invention. FIG. 8 is a diagram comparing the noise measurement results obtained when carrying out the embodiment with the conventional example, and FIG. 8 is a diagram showing the conventional example. 1...Resonance circuit 2...Switch element drive circuit 6...Load 4...Full wave rectifier circuit 5
...Smoothing circuit 8...Magnetic amplifier circuit Q1. Q
2...Switch element T...Transformer a Cr...Resonance capacitor Lr...Resonance reactor Ei...DC power supply diagram

Claims (1)

[Claims] 1. A series circuit of a DC power supply and a reactor is connected to the primary winding of a transformer via a switch element, and resonance is generated by the inductance of the transformer and the capacitance connected in parallel to the inductance. A resonant power converter configured to form a circuit and open and close the switch element in synchronization with this resonant voltage to supply power to a load connected to a secondary winding of the transformer, A resonant power converter comprising a reactor having an inductance that is equivalently smaller than the self-inductance of the primary winding, connected to at least one of the primary or secondary winding of the transformer. 2. The resonant power converter according to claim 1, wherein the transformer has a coupling coefficient of 0.95 or more. 3. The resonant power converter according to claim 1 or 2, wherein the iron core of the transformer has a relative permeability of 100 or more. 4. A series circuit of a DC power source and a reactor is connected to the primary winding of a transformer via a switch element, and a resonant circuit is formed by the inductance of the transformer and the capacitance connected in parallel to the inductance. A resonant power converter configured to open and close the switch element in synchronization with a resonant voltage to supply power to a load connected to a secondary winding of the transformer, which is connected in series with the DC power source. 1. A resonant power converter comprising a reactor on both sides of the DC power supply. 5. The resonant power converter according to claim 4, wherein reactors connected to both sides of the DC power source have magnetic coupling. 6. A series circuit of a DC power source and a reactor is connected to the primary winding of a transformer via a switch element, and a resonant circuit is formed by the inductance of the transformer and the capacitance connected in parallel to the inductance. In a resonant power converter configured to open and close the switch element in synchronization with a resonant voltage to supply power to a load connected to a secondary winding of the transformer, the outside of the transformer is A resonant power converter characterized by being covered with a conductive material. 7. Claim 1, wherein the load of the transformer is a full-wave rectifier circuit.
7. The resonant power converter according to any one of 2, 3, 4, 5, or 6. 8. The resonant power converter according to claim 1, wherein the main circuit current of the full-wave rectifier circuit is controlled by a magnetic amplifier. 9. Claims 1, 2, 3, 4, 5, wherein an electrostatic shielding plate made of a conductive material is provided between the primary and secondary windings of the transformer.
9. The resonant power converter according to any one of 6, 7, and 8. 10. The resonant power converter according to claim 9, wherein the electrostatic shielding plate is connected to one end of the DC power supply or one end of the load. 11. The resonant power converter according to claim 7, wherein the full-wave rectifier circuit or the magnetic amplifier is provided with a buffer circuit. 12. The resonant power converter according to claim 11, wherein the buffer circuit is comprised of a resistance and a capacitance. 13. Claim 1, wherein the buffer circuit is constituted by a reactor.
1. The resonant power converter according to 1. 14. The resonant power converter according to claim 11, wherein the buffer circuit includes a resistor, a capacitor, and a reactor. 15. The resonant power converter according to claims 13 and 14, wherein the reactor core constituting the buffer circuit has a relative permeability of 100 or more.