JP2000156971A - Semiconductor power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize miniaturization, weight reduction and cost reduction by making high-frequency chopper operation which enabling semiconductor switching element. SOLUTION: A step-down chopper 20, constituted of a semiconductor switching element 201 of a monopolar type MOSFET or the like, a winding 221 and a diode 212, and a step-up chopper 21 constituted of a semiconductor switching element 211, a winding 222 and a diode 202 are connected in specified polarities between an input side voltage smoothing capacitor 23a and an output side voltage-smoothing capacitor 23b. An iron core is used in common by the windings 221 and 222, or an output is taken out from the center tap 22s of the windings. As a result, current smoothing reactors 22, 22a and further a power converter as a whole are miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor power converter comprising a buck-boost chopper suitable for use in, for example, a power supply system of an electric vehicle.

[0002]

2. Description of the Related Art FIG. 3 shows a circuit configuration of a known step-down chopper. In FIG. 3, 1 is a semiconductor switch element, 2 is a diode, 3 is a current smoothing reactor, 4a is a voltage smoothing capacitor on the input side, and 4b is a voltage smoothing capacitor on the output side. 100 is a DC power supply, and 110 is a load. In FIG. 3, a monopolar MOSFET is used as the semiconductor switch element 1. Since the operation of this step-down chopper is well known, a detailed description is omitted, but by changing the ON / OFF ratio of the semiconductor switch element 1, the output side (capacitor 4b side) supplied to the load 110 is changed.
Are variable.

FIG. 4 shows a circuit configuration of a known boost chopper. In FIG. 4, reference numeral 5 denotes a semiconductor switch element;
Is a diode, 7 is a current smoothing reactor, 8a is a voltage smoothing capacitor on the input side, and 8b is a voltage smoothing capacitor on the output side. In FIG. 4, a monopolar MOSFET is used for the semiconductor switch element 5. As described above, 100 is a DC power supply and 110 is a load. Since the operation of this step-up chopper is well known, detailed description is omitted, but by changing the on / off ratio of the semiconductor switch element 5, the voltage on the output side (the capacitor 8b side) supplied to the load 110 can be varied. And

[0004]

A step-up / step-down chopper shown in FIG. 5 has been proposed as a circuit configuration in which the choppers of FIGS. 3 and 4 are integrated. In FIG. 5, 10a and 10b are semiconductor switching elements, 11a and 11b are diodes connected in parallel to the semiconductor switching elements 10a and 10b, 12
Is a current smoothing reactor, 13a and 13b are input-side and output-side voltage smoothing capacitors, 100 is a DC power supply as described above, and 110 is a load.

Since the chopping frequency can be increased in order to reduce the size of the chopper, current high-frequency power devices include, as shown in FIG. 5 and FIGS.
A MOSFET having a higher frequency than that of the IGBT is used. As shown in FIG. 5, the MOSFET can be considered as semiconductor switch elements 10a and 10b in which parasitic diodes 14a and 14b are connected in anti-parallel.

In the prior art shown in FIG. 5, the MOSFET itself can be designed as a high-frequency element, but the characteristics of the parasitic diodes 14a and 14b are determined by how the MOSFET is designed. In addition, at present, the frequency characteristics of these parasitic diodes 14a and 14b are
Is about 1/10.

As shown in FIG. 5, even if high frequency diodes 11a and 11b having the same frequency characteristics as MOSFETs are connected in parallel, the frequency characteristics of the diode section are governed by the frequency characteristics of parasitic diodes 14a and 14b. This is because when a current flows through the parallel diodes 11a and 11b, the current also flows through the parasitic diodes 14a and 14b.
Even when the high frequency diodes 11a and 11b connected in parallel end reverse recovery quickly when the diode unit is turned off, the reverse recovery characteristics of the parasitic diodes 14a and 14b are slow.
Is determined by the slow reverse recovery characteristic. For example, the reverse recovery characteristics of the diodes 11b and 14b when the semiconductor switch element 10a is turned on are determined by the reverse recovery characteristics of the parasitic diode 14b.

For this reason, in a circuit as shown in FIG. 5 using MOSFETs, the switching frequency (chopping frequency) must be lowered in accordance with the frequency characteristics of the parasitic diodes 14a and 14b. In the circuit of FIG. 5, the MOSF is used to reduce the size of the current smoothing reactor 12.
Although it is necessary to increase the switching frequency of the ET, the high-frequency characteristics of the MOSFET cannot be sufficiently exhibited due to the effects of the parasitic diodes 14a and 14b as described above, and there is a limit in increasing the frequency. For this reason,
At present, the current smoothing reactor 12 has been increased in size and price.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a semiconductor power converter which eliminates the limitation of the switching frequency caused by the parasitic diode of the semiconductor switching element, and makes it possible to reduce the size of the current smoothing reactor and reduce the manufacturing cost. It is.

[0010]

SUMMARY OF THE INVENTION The present invention relates to a MOSFET.
If the circuit configuration does not allow the current to flow through the parasitic diode of the semiconductor switching device, the operating frequency can be increased to the performance limit of the semiconductor switching device, thereby reducing the size of the current smoothing reactor, which is essential for this type of chopper. And the step-up chopper and the step-down chopper do not operate at the same time.

That is, according to the present invention, a DC-DC converter in which both ends of an input side voltage smoothing capacitor are connected to a positive electrode and a negative electrode of a DC power supply, and both ends of an output side voltage smoothing capacitor are connected to a load. A first terminal of an input-side voltage smoothing capacitor connected to a positive electrode of the DC power supply, and a first end of an output-side voltage smoothing capacitor connected to one end of the load. 2 terminal, and the other end of the input-side voltage smoothing capacitor and the other end of the output-side voltage smoothing capacitor are commonly connected to each other, and a third terminal is provided between the first terminal and the second terminal. A first semiconductor switch element and a first winding of a current smoothing reactor are connected in series, and a first terminal is provided between a connection point between the first semiconductor switch element and the first winding and a third terminal. Die A second diode and a second winding of the current smoothing reactor are connected in series between a first terminal and a second terminal; A second semiconductor switch element is connected between the connection point between the diode and the second winding and the third terminal to form a boost chopper, and the flow polarity of the first semiconductor switch element is changed. , The polarity of the second semiconductor switch element to flow from the first terminal in the direction of the first winding, and the polarity of the flow of the second semiconductor switch element to the direction of the third terminal. The flow polarity of the first diode is a polarity that allows the current to flow from the third terminal in the direction of the first winding, and the flow polarity of the second diode is the direction that the current flows from the second winding in the direction of the first terminal. The current smoothing reactor and the first winding and the second winding of the current smoothing reactor. It is to share the core.

According to a second aspect of the present invention, both ends of an input side voltage smoothing capacitor are connected to a positive electrode and a negative electrode of a DC power supply,
A semiconductor power converter as a DC-DC converter having both ends of an output-side voltage smoothing capacitor connected to a load, wherein one end of an input-side voltage smoothing capacitor connected to a positive electrode of the DC power supply is connected to a first terminal. One end of an output-side voltage smoothing capacitor connected to one end of the load is used as a second terminal connected to the intermediate tap of the current smoothing reactor, and the other end of the input-side voltage smoothing capacitor and the other end of the output-side voltage smoothing capacitor are connected to each other. In a semiconductor power converter commonly connected to form a third terminal, a first semiconductor switch element and a first winding of the current smoothing reactor are connected in series between a first terminal and a second terminal. And a first diode is connected between a connection point between the first semiconductor switch element and the first winding and the third terminal to form a step-down chopper, and the first terminal is connected to the second terminal. A second diode and a second winding of the current smoothing reactor are connected in series between the second diode and the terminal, and a third diode is connected between a connection point between the second diode and the second winding and the third terminal. A step-up chopper is configured by connecting the second semiconductor switch element. The polarity of the semiconductor switch element
The polarity is such that the current flows from the second winding toward the third terminal,
The flow polarity of the first diode is a polarity that allows the current to flow from the third terminal in the direction of the first winding, and the flow polarity of the second diode is the direction that the current flows in the direction of the first terminal from the second winding. It is the polarity to be passed.

According to a third aspect of the present invention, in the semiconductor power converter according to the first aspect, the positive polarity of the first winding of the current smoothing reactor is equal to the second polarity from the connection point with the first semiconductor switch. And the positive polarity of the second winding is the direction from the second terminal to the connection point with the second semiconductor switch. As described in claims 4 and 5, it is desirable to use a monopolar MOSFET as the first and second semiconductor switch elements.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First, FIG. 1 is a circuit diagram showing a first embodiment of the present invention. This semiconductor power converter includes a DC-DC converter connected between an input-side voltage smoothing capacitor 23a and an output-side voltage smoothing capacitor 23b. It consists of a DC converter. Note that the whole including the smoothing capacitors 23a and 23b may be interpreted as a DC-DC converter. 1
00 is a DC power supply as described above, and 110 is a load.

The DC-DC converter has a first terminal (one end of an input-side smoothing capacitor 23a connected to the positive electrode of the DC power supply 100), a second terminal (one end of an output-side smoothing capacitor 23b), and a third terminal. (The other ends of the smoothing capacitors 23a and 23b commonly connected to the negative electrode of the DC power supply 100) are provided with a step-down chopper 20 and a step-up chopper 21.

The step-down chopper 20 is a monopolar type MO.
First semiconductor switch element 201 composed of SFET and first winding (step-down winding) 22 of current smoothing reactor 22
1 is connected in series between the first terminal and the second terminal, and the first diode 212 is connected between the connection point between the semiconductor switch element 201 and the winding 221 and the third terminal. It is configured. Here, the semiconductor switch element 20
1, the connection polarity of the winding 221 and the diode 212 is as illustrated.

On the other hand, the step-up chopper 21 connects the second diode 202 and the second winding (step-up winding) 222 of the current smoothing reactor 22 in series between the first terminal and the second terminal. And a monopolar MOSFE between the connection point between the diode 202 and the winding 222 and the third terminal.
It is configured by connecting a second semiconductor switch element 211 made of T. Here, the semiconductor switch element 211,
The connection polarity of the winding 222 and the diode 202 is as illustrated. The core of the current smoothing reactor 22 is
The first winding 221 and the second winding 222 are shared.

In the above configuration, the first semiconductor switch element 201, diode 212, and winding 221 correspond to the semiconductor switch element 1, diode 2, and current smoothing reactor 3 of FIG. 202 and the winding 222 correspond to the semiconductor switch element 5, the diode 6, and the current smoothing reactor 7 in FIG.

The operation will be described below.
During the operation of the semiconductor switching element 211, as in FIG.
Is turned off, and the semiconductor switch element 201 is switched. When the boost chopper 21 operates, the semiconductor switch element 201 is turned off and the semiconductor switch element 211 is switched, as in FIG. In either case, the voltage on the output side (the capacitor 23b side) supplied to the load 110 is variable by changing the on / off ratio of the semiconductor switch element 201 or 211.

In the case of the step-down chopper operation, a switching voltage is generated in the second winding (step-up side winding) 222 of the current smoothing reactor 22 by switching of the semiconductor switch element 201, but the semiconductor switch element 211 is turned off. There is no effect on the circuit. Also, in the case of the step-up chopper operation, similarly to the case of the step-down chopper, a switching voltage is generated in the first winding (step-down side winding) 221 of the current smoothing reactor 22 by switching of the semiconductor switch element 211. Switch element 2
Since 01 is off, there is no effect on the circuit.

According to this embodiment, a diode is not connected in parallel with the semiconductor switch element as in the above-described step-up / step-down chopper of FIG. 4, the current does not flow through the parasitic diodes of the semiconductor switch elements 201 and 211, and the slow reverse recovery characteristics of these parasitic diodes do not affect the semiconductor switch elements 201 and 211.
The switching frequency can be increased to the performance limit of 11. For this reason, the current smoothing reactor 22 can be reduced in size, and the windings 221 and 222 share the iron core, so that the size, weight, and cost can be further reduced.

Next, FIG. 2 shows a second embodiment of the present invention, and the same components as those in FIG. 1 are denoted by the same reference numerals. 1 in that a current smoothing reactor 22a having a winding with an intermediate tap 22s is used instead of the current smoothing reactor 22 in FIG. The intermediate tap 22 s is connected to a second terminal of the DC-DC converter, that is, the output-side voltage smoothing capacitor 2.
3b is connected to one end. Current smoothing reactor 22
a includes a first winding 221a and a second winding 222a, the first winding 221a being a step-down winding (corresponding to the winding 221 in FIG. 1) in the step-down chopper 20a, and the second winding 221a. The line 222a functions as a boost winding (corresponding to the winding 222 in FIG. 1) in the boost chopper 21a.

In the present embodiment, the step-down chopper 20a,
The operation of the step-up chopper 21a is the same as that of the embodiment of FIG. 1, and the description thereof is omitted. However, also in this embodiment, the switching frequency of the semiconductor switch elements 201 and 211 is increased to the limit, and the intermediate tap of the current smoothing reactor 22a The use of 22s makes it possible to reduce the size and weight and reduce the cost.

[0024]

As described above, according to the present invention, without being affected by the parasitic diode of the semiconductor switch element,
The operating frequency of the semiconductor switch that performs a switching operation as a step-down chopper or a step-up chopper can be increased to its limit. As a result, the current smoothing reactor is made smaller, and its iron core is shared to further reduce the size and weight,
Cost reduction can be achieved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

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

FIG. 3 is a circuit diagram showing a step-down chopper as a conventional technique.

FIG. 4 is a circuit diagram showing a conventional boost chopper.

FIG. 5 is a circuit diagram showing a step-up / step-down chopper as a conventional technique.

[Explanation of symbols]

 Reference Signs List 20 step-down chopper 21 step-up chopper 22, 22a current smoothing reactor 22s intermediate tap 23a, 23b voltage smoothing capacitor 100 DC power supply 110 load 201, 211 semiconductor switch element 202, 212 diode 221, 222, 221a, 222a winding

Claims (5)

[Claims] 1. A semiconductor power converter as a DC-DC converter in which both ends of an input side voltage smoothing capacitor are connected to a positive electrode and a negative electrode of a DC power supply, and both ends of an output side voltage smoothing capacitor are connected to a load. The input-side voltage smoothing capacitor connected to the positive terminal of the DC power supply as a first terminal; the output-side voltage smoothing capacitor connected to one end of the load as a second terminal; In a semiconductor power converter in which the other ends of a smoothing capacitor and an output-side voltage smoothing capacitor are commonly connected to form a third terminal, a first semiconductor switch element and a current are provided between a first terminal and a second terminal. Step-down chopper in which a first winding of a smoothing reactor is connected in series, and a first diode is connected between a connection point between the first semiconductor switch element and the first winding and a third terminal. To As well as it formed, and a second winding of the second diode the current smoothing reactor connected in series between a first terminal and a second terminal,
A step-up chopper is configured by connecting a second semiconductor switch element between a connection point between the second diode and the second winding and the third terminal, and a current flowing through the first semiconductor switch element The polarity is a polarity that allows the current to flow from the first terminal in the direction of the first winding, and the polarity of the current flowing through the second semiconductor switch element is a polarity that allows the current to flow from the second winding to the direction of the third terminal. , The flow polarity of the first diode is set to the polarity that allows the current to flow from the third terminal in the direction of the first winding, and the flow polarity of the second diode is set to the direction that flows from the second winding to the first terminal. And a first core and a second winding of the current smoothing reactor share a single iron core. 2. A semiconductor power converter as a DC-DC converter in which both ends of an input side voltage smoothing capacitor are connected to a positive electrode and a negative electrode of a DC power supply, and both ends of an output side voltage smoothing capacitor are connected to a load. One end of an input-side voltage smoothing capacitor connected to the positive electrode of the DC power supply is a first terminal, and one end of an output-side voltage smoothing capacitor connected to one end of the load is connected to an intermediate tap of a current smoothing reactor. A second terminal, and the other end of the input-side voltage smoothing capacitor and the other end of the output-side voltage smoothing capacitor are commonly connected to form a third terminal. A first semiconductor switch element and a first winding of the current smoothing reactor are connected in series, and a connection point between the first semiconductor switch element and the first winding is connected to a third terminal. A first diode is connected therebetween to form a step-down chopper, and a second diode and a second winding of the current smoothing reactor are connected in series between a first terminal and a second terminal. And
A step-up chopper is configured by connecting a second semiconductor switch element between a connection point between the second diode and the second winding and the third terminal, and a current flowing through the first semiconductor switch element The polarity is a polarity that allows the current to flow from the first terminal in the direction of the first winding, and the polarity of the current flowing through the second semiconductor switch element is a polarity that allows the current to flow from the second winding to the direction of the third terminal. , The conduction polarity of the first diode is set to the polarity that allows the current to flow from the third terminal in the direction of the first winding, and the conduction polarity of the second diode is set to the direction that the current flows from the second winding to the first terminal. A semiconductor power converter characterized in that it has a polarity to allow current to flow. 3. The semiconductor power converter according to claim 1, wherein the first winding of the current smoothing reactor has a positive polarity directed from a connection point with the first semiconductor switch toward a second terminal. 2. The semiconductor power converter according to claim 1, wherein the positive polarity of the second winding is directed from the second terminal to a connection point with the second semiconductor switch. 4. The semiconductor power converter according to claim 1, wherein the first and second semiconductor switch elements are monopolar semiconductor switch elements. 5. The semiconductor power converter according to claim 4, wherein the monopolar semiconductor switch element is a MOSFET.