JPH0438172A - current resonant converter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] In communication equipment and other devices, current resonance is used to convert an input DC voltage into a desired DC voltage using a switching current generated through a resonant circuit formed in a switching circuit. With regard to converters, the purpose is to reduce switching noise and switching loss, and one of the primary windings of the transformer is connected to a DC power supply, and the voltage applied from the DC power supply is connected to the transformer through the primary winding of the transformer. a capacitor connected in series to the secondary winding of the transformer and transmitting the obtained AC voltage to the subsequent stage; and a capacitor connected in series to the capacitor and formed between the primary and secondary sides of the transformer. A capacitor that forms a series resonant circuit with the leakage inductor and capacitor, a diode that is connected in parallel with the capacitor in a reverse direction and absorbs the charge accumulated in the capacitor, and a voltage that includes ripples depending on the alternating current voltage obtained across the capacitor. and a smoothing circuit that smoothes and outputs the smoothed signal to the load.

(Industrial Application Field) The present invention provides a current resonance device that converts an input DC voltage into a desired DC voltage using a switching current generated through a resonant circuit formed in a switching circuit in communication equipment and other devices. Concerning converters.

[Prior Art] Forward converters have less power loss due to voltage conversion than series regulators, and are widely used as high-efficiency power supplies.

FIG. 4 is a diagram showing an example of the configuration of a conventional forward converter.

In the figure, a voltage applied from a DC power source is applied to the primary winding of a transformer 41 and a switching element 42 which are connected in series, and is converted into an AC voltage by the switching operation of the switching element 42. On the secondary side of the transformer 41, the AC voltage transmitted from the primary side is rectified and smoothed by a diode 43, an inductor 44, and a capacitor 45 connected in series, and output as a predetermined DC voltage. Further, a diode 46 connected in the opposite direction to the connection point between the diode 43 and the inductor 44 supplies the energy accumulated in the inductor 44 to the load side when the switching element 42 is in the off state. Note that the switching element 42 operates according to a switching control signal given by a pulse width control method. Also, reference number 4
7 indicates a DC power supply, and reference number 48 indicates a load.

[Problem to be solved by the invention]

By the way, in a forward converter having such a conventional configuration, as shown in FIG. waveform (hereinafter referred to as "switching current waveform") 1
05 changes sharply at its rise and fall.

Therefore, the AC power generated by switching includes many harmonic components, and these harmonic components are radiated as noise. Further, since the switching current waveform and the switching voltage waveform have almost the same rise and fall times and change simultaneously, power loss occurs in the switching element.

An object of the present invention is to provide a current resonant converter that can reduce switching noise and switching loss.

[Means to solve the problem] FIG. 1 is a diagram showing the principle configuration of the present invention.

In the figure, one of the primary windings of the transformer 11 is connected to a DC power source.

The intermittent means 12 intermittents the voltage applied from the DC power source via the primary winding of the transformer 11 and converts it into an AC voltage.

A capacitor 13 is connected in series with the secondary of the transformer 11 to the line, and transmits the obtained AC voltage to the subsequent stage.

The capacitor 14 is connected in series with the capacitor 13, and forms a series resonant circuit with the leakage inductor formed between the primary side and the secondary side of the transformer 11 and the capacitor 13.

The diode 15 is connected in parallel with the capacitor 14 in a reverse direction, and absorbs the charge accumulated in the capacitor 13.

The smoothing circuit 16 smoothes a voltage including ripples corresponding to the AC voltage obtained across the capacitor 14 and outputs the smoothed voltage to a load.

[Function] According to the present invention, when the disconnection means 12 is in the on state, the transformer 1
1 is applied to the smoothing circuit 16 via the capacitor l3. Further, the electric charge of the capacitor 13 is transferred to the transformer 1 when the intermittent means 12 is turned off.
1 is discharged through the diode 15 due to the reverse voltage induced in the diode 15. The capacitor 13 repeats the above operation in response to the intermittent operation of the intermittent means 12, and transmits the AC voltage output to the secondary side of the transformer 11 to the capacitor 14.

The smoothing circuit 16 smoothes a voltage including ripples corresponding to the AC voltage obtained across the capacitor 14 and outputs the smoothed voltage to a load.

Further, in the present invention, leakage inductors and capacitors 13 and 14 formed between the primary and secondary sides of the transformer 11
A series resonant circuit is constructed.

The switching current is generated by the resonant current of this series resonant circuit, and the switching current waveform is sinusoidal.

Further, the switching current waveform rises and falls without sudden changes during the period when the switching voltage waveform is at a low level.

Therefore, switching losses and switching noise are reduced.

[Example] Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 2 is a diagram showing an embodiment of the present invention.

In the figure, the input terminal to which a DC voltage is applied is an inductor (inductance value = L+) 21 connected in series,
Connected to the primary winding of transformer 11 and FET 22. The secondary winding of the transformer 11 is connected to a capacitor (capacitance=C,) 13 and a capacitor (capacitance=C2) 14 which are connected in series. A diode 15 is connected in parallel to both ends of the capacitor 14 in a reverse direction. An inductor (inductance value=L,) 23 and a capacitor (capacitance=Cff) 24 are further connected in series to both ends of the capacitor 14. Both ends of the capacitor 24 are connected to an output terminal. Note that the gate of the FET 22 is connected to a frequency control section 25 that generates a predetermined switching control signal.

The characteristic configuration of the present invention is that in the circuit of this embodiment, the secondary winding of the transformer 11 and the circuit disposed at the subsequent stage are coupled via the capacitor 13, and the inductor 21,
The leakage inductor (inductance value=L) 26 formed between the primary and secondary sides of the transformer 11 and the capacitors 13 and 14 constitute a series resonant circuit.

Note that the FET 22 and the frequency control section 25 are connected to the disconnection means 1.
2, and the inductor 23 and capacitor 24 correspond to the smoothing circuit 16.

The operation of the circuit of this embodiment will be explained below.

In the circuit of this embodiment, the AC voltage output from the secondary side of the transformer 11 is applied to the circuit after the capacitor 14 via the capacitor 13 while the FET 22 is in the on state. Furthermore, the charge accumulated in the capacitor 13 is transferred to the FET
22 changes from on state to off state, transformer 1
The reverse voltage induced in the secondary winding of diode 15
discharge through. The capacitor 13 repeats this operation and transmits the AC voltage output from the transformer 11 to the subsequent stage in response to the switching operation of the FET 22. A voltage including ripples is obtained across the capacitor 140 depending on the transmitted AC voltage. This voltage is smoothed by the inductor 23 and the capacitor 24, and the ripple voltage accompanying the discharge of the capacitor 13 via the diode 15 is reduced and output to the load.

Furthermore, in the circuit of this embodiment, a switching current is generated by the resonant current of the series resonant circuit described above, and as shown in the third section, the switching current waveform 105 becomes a sine wave while the FET 22 is in the on state ( ■). Further, the notching current waveform IDS rises and falls without sudden changes during the period when the switching voltage waveform VOS is at a low level (■, ■). In addition, in FIG. 3, L+ = 4.3
u H, C+ =0.41u F, C2=0.23
5 u FXC3 = 220 u F and the winding ratio of the transformer 22 is -10:3.

In this way, according to this embodiment, a current resonant converter with less switching noise and snitching loss can be configured.

In the circuit of this embodiment, the value of the inductance of the transformer 11 is set to a sufficiently large value in order to ensure the discharging operation of the capacitor 13.

Further, the capacitance C1 of the capacitor 24 is the capacitance C1 of the capacitor 1
In order to reduce the ripple voltage output with the discharging operation of capacitors 13 and 14, the capacitances C+ and C of capacitors 13 and 14 are
It is set to a value that is sufficiently larger than 2. Furthermore, if the leakage inductor 26 of the transformer 11 has a value that satisfies a predetermined resonance condition, the inductor 21 is unnecessary.

[Effects of the Invention] As described above, according to the present invention, the AC voltage obtained on the secondary side of the transformer is transmitted to the subsequent stage by capacitor coupling, and a series resonant circuit including this capacitor is formed, thereby achieving switching. A current resonant converter that can reduce noise and switching loss can be realized.

[Brief explanation of drawings]

Figure 1 is a diagram showing the principle configuration of the present invention, Figure 2 is a diagram showing an embodiment of the present invention, Figure 3 is a diagram showing actually measured operating waveforms of this embodiment, and Figure 4 is a diagram of a conventional current resonant converter. FIG. 5 is a diagram showing an example of the configuration. FIG. 5 is a diagram showing operating waveforms of a conventional forward converter. In the figure, 1.41 is a transformer, 2 is an intermittent means, 3.14.24.45 is a capacitor, 5.43.46 is a diode, 6 is a smoothing circuit, 1.23.44 is an inductor, and 2 is an FET. 5 is a frequency control section, 6 is a leakage inductor, 2 is a switching element, 7 is a DC power supply, and 8 is a load. Principle configuration diagram of the present invention No. 11121: Soil disconnection means 1 A diagram showing an embodiment of the present invention Figure 2 A diagram showing actually measured operation waveforms of this embodiment Figure 2 A diagram showing an example of the configuration of a conventional forward converter

Claims (1)

[Claims] (1) A transformer (11) with one of its primary windings connected to a DC power source; and an intermittent device that intermittents the voltage applied from the DC power source through the primary winding of the transformer (11) and converts it into an AC voltage. means (12); a capacitor (13) connected in series with the secondary winding of the transformer (11) and transmitting the obtained AC voltage to a subsequent stage; 11) a leakage inductor formed between the primary side and the secondary side and a capacitor (14) forming a series resonant circuit with the capacitor (13); (13) a diode (15) that absorbs the charge accumulated in the capacitor (14); and a smoothing circuit (16) that smooths the voltage including ripples corresponding to the AC voltage obtained across the capacitor (14) and outputs the smoothed voltage to the load. A current resonant converter characterized by comprising: