JP2716221B2 - DC-DC converter - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC-DC converter, and in particular, converts at least a pair of switching MOS transistors on and off alternately with a pulsed AC signal from a drive transformer to convert a DC voltage into an AC voltage, and then rectify the converted voltage. The present invention relates to a DC-DC converter configured to convert to DC.

2. Description of the Related Art FIG. 2 shows a circuit example of this type of DC-DC converter.
In the figure, a circuit 1 is a DC-AC converter for converting a first DC voltage source 11 into a pulsed AC voltage by controlling on / off of transistors 12 and 13. The transformer 2 is a drive transformer for supplying this pulsed AC voltage to the next-stage switching MOS transistors 4 and 5.

The control electrodes of the switching MOS transistors 4 and 5 are respectively connected to the beginnings of the secondary windings 21 and 22 of the drive transformer 2, and the source electrodes are connected to the secondary windings 21 and 22.
At the end of each volume.

These two MOS transistors 4 and 5 and the primary winding of the transformer 9 are connected in series between the second DC voltage sources 8.

In order to apply the same pulsed AC voltage to the gate electrodes of the other pair of switching MOS transistors 6 and 7, a drive circuit having the same configuration as the DC-AC conversion circuit 1 and the drive transformer 2 is provided. Provided, but the second
In the figure, it is omitted for simplification.

The pair of MOS transistors 6 and 7 are also connected to the second DC voltage source 8.
, And are inserted in series with the secondary winding of the transformer 9.

The switching DC transistors 4 to 7 convert the second DC voltage source into an AC voltage, and supply the converted AC voltage to the rectifier circuit 3 via the transformer 9 to finally obtain the desired DC voltage. A voltage can be obtained.

In such a configuration, the pulse-like voltage converted by the DC-AC conversion circuit 1 is supplied to the secondary winding 21 of the transformer 2 and
The signals are transmitted to the respective control electrodes 22 and input to the respective control electrodes of the corresponding transistors 4 and 5.

A pulse voltage is similarly supplied to each control electrode of the transistors 6 and 7 from a drive circuit (not shown). in this case,
When the transistors 4 and 5 are on, the transistors 6 and 7 are off. Conversely, when the transistors 4 and 5 are off, the transistors 6 and 7 are controlled to be on.

Therefore, a current having a different direction flows alternately from the second DC voltage source 8 to the secondary winding of the transformer 9, and the second DC voltage source 8 is 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 the source of a switching MOS transistor. By shortening each delay time at the time of the rising and falling of this switching signal, and trying to shorten each delay time at the time of the rising and falling of the voltage between the drain and the source, when the switching transistors 4 and 5 are turned on, The peak value of the current for charging the output capacitance (parasitic capacitance between the source and the drain) of the switching transistors 6 and 7 when the other transistor is off increases.

Therefore, the peak value of the spike-like current flowing between the drain-in and the source of the on-transistors 4 and 5 increases,
As the stress applied to the transistors 4 and 5 increases, noise also increases.

Similarly, when the MOS transistors 6 and 7 are on, the peak value of the current for charging the output capacitance (parasitic capacitance) of the transistors 4 and 5 when the MOS transistors 6 and 7 are off increases, and the same problem as described above occurs.

Object of the Invention Therefore, the present invention has been made to solve the problems of the conventional one, and the purpose is to
An object of the present invention is to provide a DC-DC converter capable of reducing stress of a switching MOS transistor and preventing noise.

The DC-DC converter of the present invention has a first MOS transistor having a control electrode and a source / drain path, and has a control electrode and a source / drain path. A second MSO transistor connected in series with the source / drain path of the first transistor, a first terminal for supplying a first pulse voltage to the control electrode of the first MOS transistor, and a second terminal. A second pulse voltage for supplying a second pulse voltage to the control electrode of the MOS transistor;
And a drive transformer for generating the first and second pulse voltages for alternately turning on and off the first and second MOS transistors; and a drive transformer for generating the first and second pulse voltages.
A DC voltage source that is converted to AC by an ON / OFF operation of a MOS transistor; a rectifier circuit that rectifies an AC voltage generated by the first and second MOS transistors; a first terminal of the drive transformer; 1 MOS
A first transistor provided between the control electrodes of the transistor;
A first inductance element for reducing a peak value of a current for charging an output capacitance of the second MOS transistor via a source / drain path of the MOS transistor; a second terminal of the drive transformer; Provided between the control electrodes of the MOS transistor
A second inductance element for reducing a peak value of a current for charging an output capacitance of the first MOS transistor via a source / drain path of the MOS transistor.

Embodiments 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 the same parts as those in FIG. 2 are denoted by the same reference numerals. In FIG. 1, only the parts different from those in FIG. 2 will be described. Inductance elements 2 are provided between the beginnings of the secondary windings 21 and 22 of the drive transformer 2 and the control electrodes of the corresponding transistors 4 and 5, respectively.
3, 24 are inserted in series.

Similarly, it is assumed that an inductance element is provided in series between each control electrode of the other MOS transistors 6 and 7 and the start of the secondary winding of the drive transformer.

Other circuit configurations and operations are the same as those of the circuit of FIG. 2, and the description is omitted.

By doing so, when the transistors 4 and 5 are turned on at the same time, the rise delay time of the voltage between the gate and the source of these transistors is lengthened by the inductances 23 and 24, and the output capacitance of the transistors 6 and 7 when off is charged during that time. The drains of the transistors 4 and 5 at the time of ON,
The spike-like current peak value at the time of rising of the source current can be reduced.

Similarly, when the transistors 6 and 7 are turned on, the same effect can be obtained by the action of the inductance element.

Although the inserted inductance elements 23 and 24 may be discrete, a leakage inductance equivalently generated in the drive transformer 2 can be positively used to reduce the mounting space. In order to positively generate the leakage inductance, for example, it is conceivable to increase the size of the winding of the drive transformer 2 or to design the degree of coupling of the transformer in a loosely coupled state.

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

In particular, if the leakage inductance of the drive transformer is positively used as the inductance element, it is not necessary to increase the circuit mounting space.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG.
FIG. 3 is a diagram illustrating a circuit example of a DC converter. Description of reference numerals of main parts 2 ... Drive transformer 3 ... Rectifier circuit 4-7 ... Switching MOS transistor 8 ... DC voltage source 21,22 ... Secondary winding 23,24 ... Inductance element

Claims (2)

(57) [Claims] A first MOS transistor having a control electrode and a source / drain path; a first MOS transistor having a control electrode and a source / drain path;
A second MSO transistor having a drain path connected in series with the source / drain path of the first transistor; and a first terminal for supplying a first pulse voltage to the control electrode of the first MOS transistor. And a second terminal for supplying a second pulse voltage to the control electrode of the second MOS transistor, wherein the first and second MOS transistors alternately turn on and off the first and second MOS transistors. A drive transformer that generates a pulse voltage of the following, a DC voltage source that is converted into an AC by an on / off operation of the first and second MOS transistors, and a rectified AC voltage generated by the first and second MOS transistors Rectifier circuit, the first terminal of the drive transformer, and the first MO
A first inductance element provided between the control electrodes of the S transistor and configured to reduce a peak value of a current for charging an output capacitance of the second MOS transistor via a source / drain path of the first MOS transistor; And the second terminal of the drive transformer and the second MO.
A second inductance element that is provided between the control electrodes of the S transistor and reduces a peak value of a current that charges an output capacitance of the first MOS transistor via a source / drain path of the second MOS transistor; And a DC-DC converter. 2. The DC-DC converter according to claim 1, wherein said inductance element comprises a leakage inductance of said drive transformer.