JP2004274877A - Boosting chopper circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a boosting chopper circuit which enables soft switching action with little switching loss, even when a reactor current is continuous, and also reduces the loss greatly by shortening the reverse recovery time of a diode connected in series with load. <P>SOLUTION: A first reactor L1, a first diode D1, and load R are connected in series to an input DC power source Ei, and a smoothing capacitor C1 is connected to the load R. A parallel circuit (having a second capacitor C2 connected between the emitter of a first switch Q11 and the cathode of a second diode D2), consisting of the series circuit composed of a second reactor L2, a first switch Q11, and a third diode D3 and the series circuit composed of a second diode D2 and a second switch Q12, is connected in parallel with the series circuit composed of the input DC power source Ei and the first reactor L1. Zero-current switching and zero-voltage switching are enabled, by turning on or turning off the first switch Q11 and the second switch Q12 at the same time under the condition of the current flowing continuously to the first reactor L1. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

TECHNICAL FIELD OF THE INVENTION
[0001]
The present invention relates to a boost chopper circuit, and more particularly to a boost chopper circuit that improves switching characteristics and reduces loss.
[0002]
[Prior art]
Conventionally, as a booster circuit that obtains a boosted DC voltage by boosting an input DC, a DC voltage is input, a current flows through the reactor, and a switching element connected in parallel to the reactor is opened and closed to flow through the reactor. A step-up chopper circuit configured to charge a capacitor provided on the load side with the stored electromagnetic energy and obtain a step-up voltage on the load side by repeating this operation is generally used.
[0003]
FIG. 2 shows a typical example of such a boost chopper circuit. In FIG. 3, a reactor L1, a diode D1, and a load R are connected in series to a DC power supply Ei. A switch (transistor) Q1 is connected in parallel to a series circuit of a DC power supply Ei and a reactor L1, and a capacitor C1 is connected to the load R in parallel.
[0004]
When the switch Q1 turns on operation, the current _{I Q1} flows through the reactor L1, the energy of ^{_{L1 · (I Q1) 2/}} 2 is accumulated. Then, when the switch Q1 causes the turn-off operation, energy stored in the reactor L1 is charged in the capacitor C1, the conversion as the energy of the energy ^{_{L1 · (V C1) 2/}} 2, is accumulated. The charging voltage is increased by the energy stored in the capacitor C1, and the boosted DC voltage is supplied to the load R.
[0005]
The boost chopper circuit having such a configuration has a problem that when the current continuously flows through the reactor even when the switch Q1 is turned on / off, the operation of the switch Q1 becomes a hard switching operation, and a switching loss occurs.
[0006]
A boost chopper circuit shown in FIG. 3 has been proposed as another conventional boost chopper circuit for solving this problem. In this boost chopper circuit, a reactor L1, a diode D1, and a load R are connected in series to a DC power supply Ei as an input, and a series circuit of a switch (transistor) Q11 and a diode D3 instead of the switch Q1 of FIG. A configuration is adopted in which a diode D2 and a series circuit of a switch (transistor) Q12 are connected in parallel, and a capacitor C2 is connected between the emitter of the switch Q11 and the cathode of the diode D2. 2, a capacitor C1 is connected to the load R in parallel.
[0007]
In the step-up chopper circuit of FIG. 3, the switches Q11 and Q12 are configured to turn on / off at the same time. In contrast to the operation of the switches Q11 and Q12, if the current flowing through the reactor is discontinuous, if the turn-on operation of the switches Q11 and Q12 is performed when the current flowing through the reactor is zero, zero current switching is performed. Thereafter, when the switches Q11 and Q12 are simultaneously turned off, current flows through the diode D2, the capacitor C2, and the diode D3, and the capacitor C2 is charged and charged. At this time, since the switches Q11 and Q12 are turned off with the diodes D2 and D3 conducting, the switching operation is zero voltage switching.
[0008]
[Problems to be solved by the invention]
As described above, according to the boost chopper circuit as shown in FIG. 3, a zero current switching operation and a zero voltage switching operation are obtained, so-called soft switching operation becomes possible, and switching loss is small.
[0009]
On the other hand, the current flowing through the reactor is preferably in a continuous state, since the peak value of the switch current is small, and in the current situation where semiconductor switches are widely used, durability is high.
[0010]
However, the boost chopper circuit shown in FIG. 3 has a problem that when the reactor current is continuous, the operation of switches Q11 and Q12 is hard switching.
[0011]
There is also a problem in the reverse recovery time of the diode D1. That is, there is a problem that a large loss occurs due to an overshoot current caused by the reverse recovery time of the reverse recovery characteristic of the diode D1.
[0012]
Therefore, an object of the present invention is to provide a boost chopper circuit that enables a sost switching operation with small switching loss even when the reactor current is continuous.
[0013]
Another object of the present invention is to provide a boost chopper circuit in which the reverse recovery time of a diode connected in series to a load is shortened and the loss is greatly reduced.
[0014]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the boost chopper circuit according to the present invention employs the following characteristic configuration.
[0015]
A first reactor, a first diode, and a load are connected in series to the input DC power supply;
A smoothing capacitor is connected in parallel to the load,
A second reactor, a parallel circuit of a first switch and a second diode, a parallel circuit of a third diode and a second switch, in parallel with the series circuit of the input DC power supply and the first reactor. Are connected, and a second capacitor is connected between an emitter of the first switch and a cathode of the second diode;
In a state where the current is continuously flowing through the first reactor,
The boost chopper circuit according to (1), wherein the first switch and the second switch are simultaneously turned on and turned off to perform zero current switching and zero voltage switching.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of a boost chopper circuit according to the present invention will be described with reference to the accompanying drawings.
[0017]
FIG. 1 is a boost chopper circuit diagram according to one embodiment of the present invention.
In the boost chopper circuit according to the present embodiment, a reactor L1, a diode D1, and a load R are connected in series to an input DC power supply Ei, and a smoothing capacitor C1 is connected to the load R in parallel. Also, a reactor L2 and a switching circuit including switches Q11 and Q12 and diodes D2 and D3 as shown in FIG. 2 are connected in parallel to a series circuit of the input DC power supply Ei and the reactor L1. In this switching circuit, a series circuit of a switch (transistor) Q11 and a diode D3 and a series circuit of a diode D3 and a switch (transistor) Q12 are connected in parallel, and are connected between the emitter of the switch Q11 and the cathode of the diode D2. It has a capacitor C2.
[0018]
In FIG. 1, when the switches Q11 and Q12 are simultaneously turned on while a current is flowing through the reactor L1, the capacitor C2 is charged by the load voltage −Eo applied to the load R, and the reactor L2 and the switch Q11 , The capacitor C2 and the switch Q12 begin to flow current. At this time, −2Eo is applied to reactor L2, and capacitor 2 starts discharging with a change determined by the time constant of reactor L2 and capacitor C2. Further, the current flowing into the switch due to the reverse recovery current of the diode D1 is also limited. As a result, the turn-on operation is a zero-current switching operation and is a soft switching.
[0019]
The turn-off operation operates in the same manner as in FIG. 3, and is a soft switching by a zero voltage switching operation. That is, during the turn-off operation, the differential value (instantaneous change value) of the voltage applied to the switch can be reduced by the capacitor C2, and the switches Q11 and Q12 are turned off with the diodes D2 and D3 conducting. Thus, the switching operation becomes zero voltage switching.
[0020]
When a simulation was performed to confirm the effect of reducing the switching loss of the boost chopper circuit shown in FIG. 1, it was confirmed that the switching loss was reduced by about 40% as compared with the boost chopper circuit shown in FIG.
[0021]
The preferred embodiment of the boost chopper circuit according to the present invention has been described above. However, this is merely an example, and it goes without saying that various modifications can be made in accordance with a specific application.
[0022]
【The invention's effect】
As described above, according to the boost chopper circuit of the present invention, even if the current flowing through the series reactor is in a continuous state, it is possible to theoretically reduce the switching loss to zero and effectively reduce the loss. Further, the loss due to the overshoot current due to the reverse recovery time of the reverse recovery characteristic of the diode connected in series to the load can be reduced. By thus greatly reducing the switching loss, the operating frequency of the circuit can be increased, the circuit components can be reduced in size, and the device as a final product can be reduced in size, weight, and efficiency. Such remarkable effects can be obtained.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of an embodiment of a boost chopper circuit according to the present invention.
FIG. 2 is a typical circuit of a conventional boost chopper circuit.
FIG. 3 is a boost chopper circuit which has solved the problems of the conventional boost chopper circuit shown in FIG.
[Explanation of symbols]
Ei Input power supply L1, L2 Reactor Q11, Q12 Switch D1, D2, D3 Diode

Claims (1)

A first reactor, a first diode, and a load are connected in series to the input DC power supply;
A smoothing capacitor is connected in parallel to the load,
A second reactor, a parallel circuit of a first switch and a second diode, a parallel circuit of a third diode and a second switch, in parallel with the series circuit of the input DC power supply and the first reactor. Are connected, and a second capacitor is connected between the emitter of the first switch and the cathode of the second diode.
In a state where the current is continuously flowing through the first reactor,
The boost chopper circuit according to claim 1, wherein the first switch and the second switch are simultaneously turned on and off to perform zero current switching and zero voltage switching.

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