JPH0365054A - Dc-dc converter - Google Patents

Abstract

PURPOSE:To reduce the inductance of the smoothing coil of a filter to a half or less and facilitate the size reduction by a method wherein a DC-DC converter is composed of a first DC-DC converter and a second DC-DC con. verter CONSTITUTION:The voltage of an input DC source 1 is transmitted to the secondary side of voltage converting transformers 2 and 11 by switching devices 5 and 10 through the voltage converting transformers 2 and 11 snd converted into a pulse wave by rectifiers 4 and 12. The ON-period of the switching device 3 is equal to the ON-period of the switching device 10 and the frequency of the pulse wave is twice the operating frequency of the switching devices 3 and 10 and the duty of the pulse wave is also twice the duty of the switching devices 3 and 10. The pulse wave is rectified and converted into a DC voltage by a flywheel rectifier 5, a smoothing coil 6 and a smoothing capacitor 7. With this constitution, the inductance of the smoothing coil can be reduced to a half or less. Further, as the duties of the switching devices 5 and 10 are spread only to 50%, the energy of the voltage converting transformers 2 and 11 can be sufficiently discharged within the OFF-period.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a D
C-DC: This relates to two inverters.

[Conventional technology]

Conventionally, as shown in FIG. 3, this type of DC-DC converter has been configured to turn on and off a switching element 3 connected in series to the primary side of an input DC power supply 1 and a voltage conversion transformer 2. A pulse wave is sent to the secondary side via a rectifier 2, and the pulse wave is rectified and smoothed by a rectifier 4, 5, a smoothing coil 6, and a smoothing capacitor 7 to obtain a DC voltage to a load 8 and control this DC voltage. The circuit configuration is such that the output is stabilized by monitoring by the circuit 9 and changing the on-duty of the switching element 30.

[Problem to be solved by the invention]

In the conventional DC-DC converter described above, it is necessary to release the energy stored in the voltage conversion transformer 2 during the off period when the switching element 3 is turned on, and when the on-duty is increased, the energy is released in a short period of time. Therefore, if the surge voltage of the switching element 3 is large, the on-duty can only be reduced to about 60%, and if the on-duty is reduced, the smoothing coil 6 and capacitor 7 must be made larger. Ta.

[Means to solve the problem]

The DC-DC converter of the present invention includes a first DC-DC converter including a first switching element, a first voltage conversion transformer, and a first rectifier, and a second switching element and a second voltage conversion transformer. and a second DC-DC converter, which are connected in parallel via a filter including a rectifier, a smoothing coil, and a smoothing capacitor. A control circuit for controlling the on-duty of the second switch element is connected.

[Effect]

In the present invention, the inductance of the smoothing coil is 1/
2 or less.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a circuit diagram of a DC-DC converter according to an embodiment of the present invention. In the figure, switch elements 3, 10
are the input DC power supply 1 and the voltage conversion transformers 2 and 11, respectively.
The signal is sent to the secondary side via the rectifiers 4 and 12 and converted into a pulse wave. The on periods of the switching elements 3 and 10 are equal, the pulse wave is twice the operating frequency of the switching elements 3 and 10, and the duty is also twice. Flywheel rectifier5. The pulse wave is rectified by the smoothing coil 6 and the smoothing capacitor 7, and becomes a DC voltage.

The output voltage vo is determined by changing the on-duty of the switching elements 3 and 10 in the control circuit 9, and the duty ratio δ is as follows, where n is the turns ratio of the voltage conversion transformer 2,110, and Min is the input voltage. . Housing, rectifier 4, 1
The duty ratio δ' of the pulse wave after 2 is δ=2δ ・−−−−−−−−−−−−−−−−−−−
−−−−−−−−・(2) Even if δ′=1,
δ = 0.5 and the on-duty of 3,190 each switch element is 0.5'! By widening it, the duty in front of the smoothing coil 6 can be increased by 100% of the housing.

The inductance L of the smoothing coil 6 is such that the minimum load current is I
o (癲), and the ON width of switch elements 3 and 10 is TON.
If one period is T, then it reaches. In the case of a single switch circuit, the present circuit can reduce the inductance value to 1/2 or less compared to the conventional circuit. In addition, switch elements 3 and 1
Since the duty of 0 only extends to 50%,
The energy of the voltage conversion transformers 2 and 11 can be sufficiently released during the off period.

2 (tortoise) to (,) show the operating waveforms of the voltages applied to each part of FIG. 1.

〔Effect of the invention〕

As explained above, the DC-DC converter according to the present invention is configured with the first DC-DC converter and the second DC-DC converter, thereby reducing the inductance of the smoothing coil of the filter to 1/2 or less. Therefore, miniaturization is possible. Furthermore, since the duty ratio can be changed within the range of 0-100%, extremely excellent effects such as being suitable for a wide range of input power sources can be obtained.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a DC-DC converter according to an embodiment of the present invention, FIG. 2 is a diagram showing operating waveforms of FIG. 1, and FIG. 3 is a circuit diagram of a conventional DC-DC converter. 1-・am input DC power supply, 2.11-・・transformer,
3.10...Switch element, 4,12...Rectifier, 5...7 Lie wheel rectifier, 6m...Smoothing coil, 7...Smoothing capacitor, 8...Load ,
9...Control circuit.

Claims (1)

[Claims] DC voltage is output as a pulse wave to the secondary side via a voltage conversion transformer by turning on and off a switching element, and this pulse wave is rectified and smoothed by a filter to obtain a DC voltage.
- In the DC converter, the first switch element and the first
A first D consisting of a voltage conversion transformer and a first rectifier.
A second DC-DC converter including a C-DC converter, a second switch element, a second voltage conversion transformer, and a second rectifier.
A DC converter is connected in parallel through a filter consisting of a rectifier, a smoothing coil, and a smoothing capacitor, and the first switch element and the second switch element are connected between the filter output terminal and the first switch element and the second switch element. A DC-DC converter, characterized in that a control circuit for controlling on-duty of the second switch element is connected thereto.