JPH03128673A - Dc-dc converter - Google Patents

Abstract

PURPOSE:To reduce the stress of a transistor, and to prevent noises by installing an inductance element in series between the secondary side winding of a drive transformer and the control electrode of a MOS transistor for switching. CONSTITUTION:MOS transistors 4, 5 for switching are supplied with the pulse- shaped ACs of a DC-AC conversion section 1 by a drive transformer 2, and load is supplied with the power of a DC power 8 through a transformer 9 and a rectifier circuit 3. Inductance elements 23, 24 are inserted among the secondary windings 21, 22 of the drive transformer 2 and the gates of the transistors 4, 5. When the transistors 4, 5 are turned ON simultaneously, the rise time delay of voltage among the gates and sources of these transistors is lengthened, and the output capacitance of transistors 6, 7 at the time of OFF is charged during that time. Accordingly, spiky current peak values at the time of the rise of the drain and source currents of the transistors 4, 5 at the time of OFF are reduced.

Description

Detailed Description of the Invention Technical Field The present invention relates to a DC-DC converter, and in particular to a DC-DC converter that converts a DC voltage into an AC voltage by alternately controlling on and off at least one pair of switching MOS transistors using a pulsed AC signal from a drive transformer. This invention relates to a DC-DC converter that converts direct current into direct current.

Prior Art An example of a circuit of this type of DC-DC converter is shown in FIG. In the figure, a circuit 1 is a DC-AC converter that converts a first DC voltage source 11 into a pulsed AC voltage by on/off control of transistors 12.13. transformer 2
This pulsed AC voltage is applied to the next stage switching MO
S) Drive transformer for supplying transistor 4.5.

Each control electrode of the transistors 4 and 5 for switching is connected to the beginning of each winding of the secondary windings 21 and 22 of the drive transformer 2, and each source electrode is connected to the end of each winding of the secondary windings 21 and 22. are connected to each other.

Both MOS transistors 4.5 and the primary winding of the transformer 9 are connected in series between the second DC voltage source 8.

In order to apply a similar pulsed AC voltage to each gate electrode of the other pair of switching MOs 5) and 7, the DC-AC converter circuit 1 and the drive transformer 2
A drive circuit with exactly the same configuration is provided, but
It is omitted in FIG. 2 for the sake of simplicity.

This pair of MOS transistors 6.7 is also inserted in series with the secondary winding of the transformer 9 between the second DC voltage source 8.

These switching MO3) transistors 4 to 7 convert the second DC voltage source into an AC voltage, and the converted AC voltage is supplied to the rectifier circuit 3 via the transformer 9 to finally obtain the desired voltage. DC voltage can be obtained.

In this configuration, the pulsed voltage converted into alternating current by the DC-AC conversion circuit 1 is transmitted to the secondary windings 21 and 22 of the transformer 2, respectively, and is applied to each control electrode of the corresponding transistor 4.5.

A pulsed voltage is similarly supplied to each control electrode of the transistor 6.7 from a drive circuit (not shown). in this case,
When transistors 4 and 5 are on, transistor 6.7 is off, and conversely, transistor 4.7 is off.
When transistor 5 is off, transistor 6.7 is controlled to be on.

Therefore, the secondary winding of the transformer 9 is connected to the second DC voltage source 8.
Currents in different directions alternately flow from the voltage source 8, and the second DC voltage source 8 is thus converted into an AC voltage. This AC voltage is rectified and smoothed by the rectifier circuit 3 and output as a desired DC voltage.

In such a conventional DC-DC converter, a switching pulse signal is applied between the gate and source of a switching MOS transistor. If an attempt is made to reduce the delay times at the rise and fall of the drain-source voltage by shortening the delay times at the rise and fall of the switching signal, when the switching transistor 4.5 is turned on, The output capacitance (source,
This results in an increase in the peak value of the current for charging the parasitic capacitance between the drains.

Therefore, the peak value of the spike-like current flowing between the drain and source of the on-transistor 4.5 increases, and the MOS
As the stress applied to transistor 4.5 increases, the noise also increases.

Similarly, when MOS transistor 6.7 is on, the peak value of the current that charges the output capacitance (parasitic capacitance) of transistors 4 and 5 when off increases, causing the same problem as described above.

OBJECT OF THE INVENTION The present invention was made to solve the problems of the conventional devices, and its purpose is to provide a DC-MOS transistor that makes it possible to reduce the stress of switching MO3) transistors and prevent noise. The purpose of the present invention is to provide a DC converter.

Structure of the Invention According to the present invention, at least a pair of MOS transistors are controlled to be turned on and off alternately by a pulsed AC voltage obtained by converting a DC voltage, and the pulsed AC voltage is applied to a control electrode of the MOS transistor. and a DC voltage source that is converted into an AC voltage by the on/off operation of the pair of MOS transistors, and is configured to convert the converted AC voltage into a DC voltage using a rectifier circuit. There is obtained a DC-DC converter characterized in that an inductance element is provided in series between the secondary winding of the drive transformer and the control electrode of the MO3 transistor.

Example Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of an embodiment of the present invention, and parts equivalent to those in FIG. 2 are designated by the same symbols. In Figure 1,
To describe only the parts that are different from FIG. 2, inductance elements 23 and 24 are inserted in series between the beginnings of each of the secondary windings 21 and 22 of the drive transformer 2 and the control ml of the corresponding transistors 4 and 5, respectively. The point is that there is.

It is assumed that an inductance element is similarly provided in series between each control electrode of the other Mo3) transistors 7 and the winding start of the secondary winding of the drive transformer.

The other circuit configurations and operations are the same as those of the circuit shown in FIG. 2, and their explanations will be omitted.

By doing this, when transistors 4.5 are turned on at the same time, the rise delay time of the voltage between the gate and source of these transistors becomes longer due to the inductance 23.24, and the output capacitance of transistor 6.7 when turned off is charged during that time. Therefore, it is possible to reduce the spike-like current peak value at the rise of the drain and source current of the transistor 4.5 when it is on.

Even when the transistors 6.7 are on, the same effect can be obtained by the action of the inductance element.

The inserted inductance elements 23 and 24 may be discrete elements, but in order to reduce the mounting space, leakage inductances generated with equal polarization in the drive transformer 2 can also be actively used. To actively generate this leakage inductance,
For example, it is conceivable to make the winding of the drive transformer 2 larger or to design the transformer to be loosely coupled.

Effects of the Invention As described above, according to the present invention, by inserting an inductance element in series with the gate electrode of a switching MOS transistor, the rise delay time of the drive pulse voltage applied to the gate of the switching MOS transistor can be increased. Therefore, it is possible to reduce stress applied to the switching MO3) transistor and reduce noise.

In particular, if the leakage inductance of the drive transformer is actively used as the inductance element, there is no need to increase the mounting space for the circuit.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of an embodiment of the present invention, Figure 2 is a conventional DC
- It is a figure which shows the circuit example of a DC converter. Explanation of symbols of main parts 2... Drive transformer 3... Rectifier circuits 4 to 7... MoS transistor for switching 8... DC voltage source 21.22 ...Secondary winding

Claims (2)

[Claims] (1) At least one pair of MOs that are alternately controlled on and off by a pulsed AC voltage obtained by converting a DC voltage
S transistor, a drive transformer that supplies the pulsed AC voltage to the control electrode of the MOS transistor, and a DC voltage source that is converted into an AC voltage by the on/off operation of the pair of MOS transistors; A DC-DC converter configured to convert an alternating current voltage into a direct current voltage using a rectifier circuit, wherein an inductance element is provided in series between the secondary winding of the drive transformer and the control electrode of the MOS transistor. A DC-DC converter characterized by: (2) The DC-DC converter according to claim 1, wherein the inductance element is comprised of a leakage inductance of the drive transformer.