JPH03169260A - Resonance type converter - Google Patents

Abstract

PURPOSE:To facilitate the reduction of size, the increase of a frequency and the improvement of an efficiency by applying a rectified voltage to the primary winding of a transformer via a second capacitor when a first switching element is turned on and via a first capacitor when a second switching element is turned on. CONSTITUTION:The rectified output voltage of a full-wave rectifying circuit 1 is applied to the primary winding of a transformer 7 via a second capacitor 3 and a reactor 6 when a first switching element 4 is turned on and via a first capacitor 2 and the reactor 6 when a second switching element 5 is turned on. Therefore, the first and second capacitors 2 and 3, respectively, act for cutting a DC. Thus, a charging current with a large peak value does not flow and a power-factor can be sharply improved. Further, the increase of a switching frequency is facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a resonant converter for obtaining a stabilized DC voltage from an AC power supply.

In a converter that applies a stabilized DC voltage from an AC power supply to a DC load, it rectifies the AC voltage of the AC power supply,
The rectified output voltage is applied to the primary winding of the transformer via a switching element such as a transistor, and the induced voltage in the secondary winding of the transformer is rectified and smoothed by a rectifying and smoothing circuit to obtain an output DC voltage. The switching element is controlled so that the output DC voltage becomes a set value, and various structures have already been proposed. Improvements in efficiency and power factor are desired in such converters.

[Conventional Handling Technique] For example, a conventional converter has a structure not shown in FIG.
3 is a capacitor, 34 is a transformer, 35 is a transistor as a switching element, 36 is a rectifier and smoothing circuit, 3
7 is a control circuit.

A 1 transistor 35 is connected to the negative winding of the 1 lance 34, and a rectifying and smoothing circuit 36 is connected to the secondary winding.

This rectifying and smoothing circuit 36 is shown as being composed of diodes 1, 38, 39, a reactor 40, and a capacitor 4I. Also, the AC voltage of the AC power supply 31 is passed through the aftereffect rectifier circuit 32.
The voltage that has been rectified and charged to the capacitor 33 is applied to the primary winding of the lance 34 via the transistor 35, and the voltage induced in the secondary winding of this transformer 34 is rectified and charged to the capacitor 33. The voltage is rectified and smoothed by the smoothing circuit 36 to become an output DC voltage. This output DC voltage is compared with a set voltage in the control circuit 37, and the on-period of the 1-run transistor 35 is controlled in accordance with the error, so that the output DC voltage is stabilized.

FIG. 7 is an explanatory diagram of voltage and current, where (a) shows the waveforms of the full-wave rectified output voltage 42 and the terminal voltage 43 of the capacitor 33, and (b) shows the charging current 44 of the capacitor 33 and the DC output current 45. and The sine wave AC voltage is rectified by the full wave rectifier circuit 32 and becomes a large pulsating voltage.
The capacitor 33 provides a rectified output voltage with a waveform shown at 43. In that case, the capacitor 33 has 1/1/2 of the AC voltage.
2 laps! t. in lJIL. The charging current 44 flows only during one relatively short period (conduction angle), and becomes zero during the remaining period L2.

In that case, the average value of the charging current 44 is the DC output current 45
Therefore, the peak value of this charging current 44 becomes larger as the conduction angle t1 becomes smaller.

(Problems to be Solved by the Invention) As mentioned above, when the conventional capacitor impsoto type rectifier power supply is used, the charging current flowing through the capacitor 33 is as shown in FIG. 7(b). , for a relatively short period L
Since only 1 flows, the power factor as seen from the AC power supply 31 side becomes very poor. The power factor cosθ of a distorted wave with a waveform different from a sine waveform is cosθ - (power) ÷ (apparent electric power j) - (vo to +v, +I COSθ, +V212
cosθ2! -V. l3cosθ3+...)÷(,
/-V',;"+V';"TV"-;2'-+f
-2-1 - - 1x1o +I+ ++z +13
...It can be expressed as 1. In addition, Vo. lo is the DC voltage 7 current, ■1, TI. V2. 12. V3.
+3 ” ” = fundamental wave, 2nd harmonic, 3rd harmonic, ... voltage current, θ1. θ2, θ3... indicate the phase angle between the voltage and current of each harmonic.

Therefore, compared to the case where a sine wave current flows, when a current with a distorted waveform as shown in FIG.
θ becomes smaller. In the case of a conventional capacitor-impact type rectified power supply, the power factor cos θ is about 45 to 60%.

Furthermore, in order to reduce the peak value of the charging current of the capacitor 33 mentioned above, it is conceivable to use a choke impunto type rectifier power supply in which a choke coil is connected between the full-wave rectifier circuit 32 and the capacitor 33. However, in the case of the Choke Impso 1~ type, the rectified output voltage is the average value of the pulsating current voltage, so it is approximately 0.9% of the effective value of the human voltage.
In addition, when the output current is small, there is a drawback that the rectified output voltage rises rapidly. Furthermore, in order to improve this drawback, it is necessary to considerably increase the inductance of the choke coil, and in this case, a large choke coil is used, which has the disadvantage of increasing the size.

Therefore, in order to achieve miniaturization, condenser Impno 1 type rectified power supplies are more commonly used than choke Impun 1 type rectified power supplies.

In addition, the transistor 35 causes switching loss due to the time it takes to completely turn on or off.
It is possible to reduce the size of the transformer 34 and the rectifying and smoothing circuit 36 by setting the switching frequency to a high frequency of about IMHz or higher, but this will increase the switching loss almost in proportion to the increase in the switching frequency, and the temperature will rise due to the loss. For these reasons, it is difficult to achieve a desired high frequency.

Therefore, a resonant converter has been proposed that uses resonance characteristics to switch at the timing when the current or voltage becomes zero. In such a resonant converter,
In order to stabilize the output DC voltage, variable frequency control method 2 is used.

However, in this frequency variable control method, the frequency change range from no load to maximum load is limited to several tens of kilometres.
Since there is a necessary current that is Il - several Mllz, and the circuit constants corresponding to the lowest frequency are determined, there is a drawback that miniaturization is difficult.

SUMMARY OF THE INVENTION An object of the present invention is to provide a resonant converter that can be easily miniaturized and operated at a high frequency, and can have a high power factor.

[Means to solve the problem]

The resonant converter of the present invention will be described with reference to FIG. 1. The resonant converter includes a full-wave rectifier circuit 1 that rectifies an alternating current voltage of an alternating current power source such as a commercial power source, and a rectified output voltage of the full-wave rectifier circuit 1 that is applied. The first and second capacitors 2 and 3 are connected in series, and the first capacitors are connected in series. A switching element 45 consisting of a second I transistor or the like, a connection point between the first and second capacitors 2.3 connected in series, and a connection point between the first and second switching elements 4.5 connected in series. A transformer 7 with a primary winding connected thereto via a reactor 6, a capacitor 8 for forming a resonant circuit with the reactor 6 in parallel with the primary winding of this transformer 7, and a transformer 7. rectifying and smoothing circuit 9 connected to the secondary winding of the first . Second
a control circuit 1 for stabilizing the output DC voltage of the rectifying and smoothing circuit 9 by alternately controlling the switching elements 4 and 5;
0.

[Function] When the first switching element 4 is on, the rectified output voltage of the full-wave rectifier circuit 1 is applied to the primary winding of the transformer 7 via the second capacitor 3 and the reactor 6, and is applied to the primary winding of the transformer 7 through the second capacitor 3 and the reactor 6. When the switching element 5 is on, the second capacitor 2
The current is applied to the second winding of the transformer 7 via the reactor 1 and the reactor 6. Therefore, the first and second condensers JJ゜2.
3 acts as a DC cassette I, and a capacitor impno 1 type rectifier ti. It will have a different effect than the condenser in this case.

Also, due to the resonant circuit mainly consisting of the reactor 1 and the capacitor 8, a resonant current flows through the first and second switching elements 45, and switching cannot be performed at the point where the current or current IE is zero. It becomes possible.

Therefore, the switching loss can be made negligible.

In addition, the control circuit 10 operates the 12th switching element 4 to stabilize the output DC voltage of the rectifying and smoothing circuit 9.
5, performs switching control at a frequency higher than the resonant frequency, lowers the switching frequency as the output DC current increases, and shifts to 3J, which is approximately the resonant frequency at the rated load. Perform switching with zero current or zero voltage, and perform switching tt.
4 You can eliminate losses.

q [Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a circuit diagram of the main part of the embodiment of the present invention. As mentioned above, the AC voltage of the AC lightning source 11 is rectified by the full-wave rectifier circuit 1, and the rectified output voltage is transferred to the first circuit connected in series. , the second capacitor 2.3, and the first and second switching elements 4.5 connected in series.
．． 3 connection point, and the 1st connection point. Second switching element 4.5
Connect the primary winding of I/lance 7 to the connection point of reactor 1 and 6 via reactor 1 and 6, and connect capacitor 8 in parallel to the primary winding to prevent resonance with reactor 1 and 6. The control circuit 10 monitors the output DC voltage of the rectifying and smoothing circuit 9 which constitutes the circuit and is connected to the secondary winding of the transformer 7, and controls the first and second switching elements so that the voltage reaches the set voltage. 4
, 5.

In addition, the secondary winding of lance 7 is shown in a configuration with a senku-kunoppu, and correspondingly, the rectifier l0 is smooth and the same path! A case of N,i, diode 12, 13 and capacitor 14 is shown. Also Suinoching Soryo 4,5
1 uses a quasi-field effect transistor and has parasitic diodes 15, 16 and parasitic capacitance 1718. This parasitic capacitance can also be a four-digit capacitor.

FIG. 2 is an explanatory diagram of resonance characteristics, where fo is the resonance frequency of the resonance circuit including the reactor 6 and capacitor 8.
When the load is below the rated load, the switching frequency that controls turning on and off of the switching elements 4 and 5 is set to the resonance frequency f. The higher the rI is, for example, and the closer the load is to the fixed hiiragi load, the closer the switching frequency is to the resonant frequency r0. That is, the switching frequency is equal to the resonance frequency r. Therefore, the circuit constant is the resonant frequency f. Therefore, it is possible to make the circuit components smaller.

Figure 3 shows an example of MOS F switching elements 4 and 5.
It is an explanatory diagram of ET (MOS field effect transistor), where 21 is a source electrode, 22 is a train] 1 electrode, 23 is a gate 1-'11 pole, and 24 is a gate I-gate.
25 indicates a parasitic diode. The source electrode 21 is connected to the contact 1 area N' of the 10th example, and the train electrode 22 is connected to the lower contact area N''6. used.

By applying the K1 voltage to the G1 electrode 23, an inversion layer is generated in the P region, and the path of the source electrode 21 → N' region → P region → N- region → N' region → train electrode 22 is formed. A current flows through the capacitor, and the on/off state of this current can be controlled by gate I and voltage. Furthermore, a parasitic diode 25 shown by a dotted line is formed between the 1) region and the N- region. This parasitic diode 25 is 15. in FIG.
It is indicated by the symbol 16. Also, a parasitic capacitance is formed between the source electrode 21 and the train electrode 22.

A power MOSFET is constructed by combining several thousand or tens of thousands of such vertical FET basic cells in a 1-12 configuration.

The control circuit 10 compares the output 12 of the DC voltage from the rectifying and smoothing circuit 9 to see if it is the set value, and the error with respect to the set value is determined by the first and second switching elements 4.5.
The switching frequency of is controlled.

When the first switching element 4 turns on, the rectified output voltage of the full-wave rectifier circuit 1 changes between the capacitor 3 and the rectifier 6.
When the second switching element 5 is turned on, the voltage is applied to the primary winding 6 of the I lance 7 through the capacitor 2 and the reactor 6, and the primary An alternating voltage is applied to the winding C
This will happen. As a result, a voltage is induced in the secondary winding of the lance 7, which is rectified and smoothed by the rectifier and smoothing circuit 9, and becomes an output DC voltage, which is supplied to the load 6 (not shown). .

Part I. The second capacitors 2 and 3 do not smooth the rectified output of the full-wave rectifier circuit I, but act as a direct current blocker. Ichikawa Zurkara, Capacitor Inbuno I.
As with molds, it is no longer possible for large lithoplast currents to flow. Therefore, it is only possible to improve the power factor by 13%. Furthermore, by performing switching at the resonance frequency or a frequency close to it, switching losses in the switching elements 4 and 5 can be reduced to a negligible level, making it easy to increase the frequency.

FIG. 4 is an explanatory diagram of the operation of the embodiment of the invention, in which (a) shows the voltage between the source and the drain of the first switching element 4, and (b) shows the voltage between the source and the drain of the second switching element 5. In the on state, the voltage between the source, I and the rain is O. Also (C). (d) is the first and second
(e) shows the resonant current due to the resonant circuit including the beam AC 1-6 and the capacitor 8;

By setting the switching frequency higher than the resonant frequency, when the switching elements 4 and 5 are engaged, the current flowing through the switching element 4.5 becomes a delayed current. This delayed current flows through the parasitic diodes of switching elements 4 and 5.
15.16, the current flows in the negative direction as shown in (d). That is, when the first switching element 4 is turned on as shown in (a), , as shown in (C), after a delayed current flows in the opposite direction via the parasitic diode l.15,
A part of the resonant spiritual stream flows in the Q direction around 1.

FIG. 5 is an explanatory diagram of voltage and lightning current in an embodiment of the present invention,
(a) shows switching elements 4 and 5 when the load current is low.
The voltage v1 (solid line) and current II (dotted line) are shown. or(
b) shows the voltage V2 (solid line) and current 2 (dotted line) of the switching element 4.5 when the load current is large. That is, when the load current is small, the switching frequency is high, and when the load current is large, the switching frequency is low, and the current I2
Swinging can be performed at the point where becomes zero. Therefore, when the load current increases, the switching loss can be reduced to a negligible level.

(C) is the rectified output voltage ■3, (d
) indicates the current I3, and if the switching element 4.5 is turned on and off at the cycle of the rectified output voltage 3, the current I3 shown in (d) will flow. In other words, a large current to charge the 210V does not flow through the full-wave rectifier circuit 1, but rather flows over a period of approximately half a cycle. Thereby,(
The alternating current I4 shown in (f) flows in response to the alternating current voltage ■4 shown in e). That is, the current 4 has a distorted waveform, but since the compliance angle becomes large, the peak value of the current 4 may be low. As a result, the fundamental wave of the alternating current I4 increases to some extent, and the power factor can be improved, for example, to 90% or more.

The present invention is not limited to the above-described embodiments, but can be modified in various ways.

(Effects of the Invention) As explained above, the present invention provides a connection point between the first and second capacitors 2.3 and the first and second switching elements 4.
, 5, the primary winding of lance 7 is connected via reactor 6, and a capacitor 8 is connected in parallel to the primary winding to connect reactor 6. and a capacitor 8, and the first
, the second capacitors 2 and 3 act to cause a resonant current to flow, and do not smooth out the full-wave rectification flow like the impunto type capacitors, so they do not smooth out the full-wave rectification flow, so the charging charge with a large peak value is No current will flow, thereby significantly improving the power factor.

In addition, the larger the 1't charge current is, the closer the switching frequency is to the resonant frequency of the resonant circuit, and the switching can be performed at the point where the voltage or current is zero, so the switching loss can be reduced to a negligible level. Can be done.

Therefore, it is possible to easily increase the switching frequency to a high frequency.

[Brief explanation of the drawing]

'IS + eyes. 1. Route diagram of main parts of length embodiment of the present invention, 2nd
1 is an explanatory diagram of resonance characteristics, Fig. 3 is an explanatory diagram of MOS FET, Fig. 4 is an explanatory diagram of operation of the embodiment of the present invention, Fig. 5 is an explanatory diagram of voltage and current of the embodiment of the present invention, FIG. 6 is a circuit diagram of the main part of the conventional example, and FIG. 7 is an explanatory diagram of the heavy pressure and heavy flow of the conventional example. ■ is a full-wave rectifier circuit, 2.3 is the first and second capacitor,
4.5 is the first and second switching element, 6 is the reactor
・7 is a transformer, 8 is a capacitor, 17 9 is a rectifying and smoothing circuit, 10 is a control circuit, and 1 1 is an AC power supply.

Claims (1)

[Claims] A full-wave rectifier circuit (1) that rectifies an alternating current voltage, a first circuit connected in series that applies a rectified output voltage of the full-wave rectifier circuit (1),
the second capacitor (2, 3) and the first and second capacitors connected in series;
A connection point between the switching elements (4, 5), the first and second capacitors (2, 3) connected in series, and a connection between the first and second switching elements (4, 5) connected in series. A transformer (7) with a primary winding connected to the point via a reactor (6), and a transformer (7) with a primary winding connected to the reactor (
6) and a capacitor (8) to form a resonant circuit.
, a rectifying and smoothing circuit (9) connected to the secondary winding of the transformer (7), and the first and second switching elements (4, 5) connected in series.
) for stabilizing the output DC voltage of the rectifying and smoothing circuit (9).