JP2819077B2 - Series resonant DC-DC converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to determination of a failure in a series resonant DC-DC converter.

[0002]

2. Description of the Related Art A DC power supply voltage is directly connected to, for example, different voltage values.
Current voltage or a DC voltage of a different polarity.
Power supply device used in so-called DC-DC converter
Operating at high frequencies to reduce the size and weight of the
For example, a series resonance type converter as shown in FIG.
Converters have recently attracted attention and are widely used. this
The converter is, for example, (a) in the operation waveform diagram shown in FIG.
(B) As shown in the figure, the first and second switch elements S₁, S_Two
Are turned on and off alternately, so that the second inductor
L_TwoAnd capacitor C₁And a second series resonance circuit
Inductor L _TwoAnd capacitor C_TwoTwo series consisting of
In the resonance circuit, the primary winding n of the output transformer T₁And the first
Inductor L₁To apply a high frequency AC voltage
And the second inductor L_TwoThe poles are alternately arranged as shown in FIG.
Resonant current i of different gender_L2Flow. And the current i_L2Out of
Capacitor C₁, C_TwoThe discharge current of FIG.
First and second feedback diodes D₁, D_TwoBy ba
By bypassing, the primary winding n of the output transformer T₁
The current i shown in FIG._T, So that the secondary winding
Line n_TwoThe rectification circuit Rec and the smoothing capacity
DC voltage V₀Output
The output current I is applied to the load connected to the output terminal Out.₀To
Supply.

Incidentally, a series resonant DC-D as described above
When a C converter is used as a power supply for a communication device that requires high reliability, the DC-DC converter is provided with an overvoltage prevention function and an overcurrent prevention function like other types of DC-DC converters. In addition to performing protection, a function of detecting a shortage of output voltage due to, for example, a failure of the DC-DC converter, for example, when the output voltage is equal to or less than a predetermined value even after a certain period of time (generally about 1 second) has elapsed after startup. , Such as transmitting an alarm signal or switching to a standby DC-DC converter.
However, as shown in FIG.
In the large-capacity power supply device constituted by the converters DC ₁ ,..., DC _N , each output circuit of each series resonant DC-DC converter is connected in parallel. Therefore, for example, even if one DC-DC converter fails and the output voltage is not transmitted, the output voltage of the power supply system is maintained by another healthy converter. For this reason, it is extremely difficult to determine the presence or absence of a failure in each converter only by monitoring the output voltage as in the conventional device. Therefore, the series resonance type DC-
As a countermeasure for DC converter,
As shown in the figure, a current i _T flowing through the output transformer T is detected by a current detector, for example, a current transformer CT, and the fact that the detected current has become zero is determined by a failure determination circuit F, and is sent to an alarm signal terminal GS. Means for transmitting an alarm signal to notify that a failure has occurred is employed.

[0004]

According to the above means, even when a plurality of converters are connected in parallel, a failure of each converter can be detected. However, even with this means, it is difficult to detect a failure in the series resonance type DC-DC converter with noise countermeasures. That operating frequency of the series resonant DC-DC converter is greatly affected output current I ₀ as is well known, the operating frequency due to the output current I ₀ becomes smaller reaches up to an audible frequency range is lower. This has the undesirable consequence of generating audible sound from the converter and being a source of noise. Therefore, conventionally, the following measures have been taken. That feedback diode D ₁ as shown in FIG. 2, D ₂ and the third in parallel, a fourth switching element S _3,
Connect the S _4, FIG. 4 (a) (c) a predetermined time the third switching element S ₃ from the first on the switching element S ₁ as t
Only later on, are turned off simultaneously with the off S _1, a fourth switch element S ₄ as shown in FIG. 4 (b) (d), delayed by the second switching element S ₂ for a predetermined time than the ON t ON, S
Turn off simultaneously with off of ₂ . And the switching element S ₁
Of the time on, the capacitor C ₁ by making the bypass circuit of the current i _l2 flowing to inductor L ₂ as shown in FIG. 4 (g), the addition switch element capacitor C ₂ at the time of the on S _2
4g, a bypass circuit for the current i _L2 flowing through the inductor L ₂ is made as shown in FIG. As a result, the current i _T flowing through the primary winding n ₁ of the output transformer T is reduced as shown in FIG. 4F so that the operating frequency does not decrease even when the output current I ₀ approaches zero amperes. Has been done. However, in this case, even if the converter is operating, if the output current I ₀ is zero amperes, the primary winding current i _T of the output transformer T stops flowing, and the output of the current transformer CT also stops. For this reason, even if there is no failure, the failure determination circuit F causes an undesirable situation of generating an alarm signal. In order to prevent this, for example, it is conceivable to stop the operation of the failure determination circuit only when the output current I ₀ becomes zero. However, in this case, a detection circuit of the output current I ₀ is required separately, This results in an increase in cost.

[0005]

The object of the present invention is to provide a bypass circuit for the resonance circuit current as described above to prevent a decrease in operating frequency even in a series resonance type DC-DC converter in a parallel operation state. The purpose is to present means for detecting occurrence.

[0006]

The above object of the present invention is achieved by detecting a current flowing through a second inductor forming a series resonance circuit with a capacitor. That is, the current flowing through the second inductor forming the resonance circuit flows even when the output current becomes zero as long as the converter operates, due to the bypass circuit formed by the switching elements S ₃ and S ₄ . Therefore, by detecting the current of the second inductor, it is possible to reliably determine whether there is a failure. Next, examples of the present invention will be described.

[0007]

FIG. 1 is a circuit diagram showing one embodiment of the present invention. V _i is a DC power source in FIG, S _1, S _2, S _3, S ₄ are first, second, third, fourth switching element, T is the output transformer, Rec rectifying circuit, C is a smoothing capacitor , L ₁ is a first inductor, D _1, D ₂ are first, a second feedback diodes. C ₁ and C ₂ are capacitors, L ₂ is the second
, F is a failure determination circuit, and CC is a converter control circuit, and their configurations are the same as those of the conventional circuit shown in FIG. The second inductor L ₂ and series to form a resonant circuit with the capacitor C _1, C ₂ in the present invention, by connecting a current detector for example the current transformer CT,
As long as the converter as described above is operating, by detecting the current flowing through the inductor L ₂ not to substantially change depending on the magnitude of the output current I _0, it is obtained so as to operate the fault discriminating circuit. Although the present invention has been described above, the present invention is applied to a series resonance type DC-DC converter in which a primary winding current of an output transformer T different from the circuit system of FIG. The same effect can be obtained.

[0008]

As is clear from the above description, according to the present invention, a failure of a series resonance type DC-DC converter with noise suppression can be reliably detected even in a parallel operation state, so that a highly reliable power supply is provided. The construction of the device is possible.
Since the failure can be reliably detected only by changing the connection position of the current detector, a power supply device having the same capacity can be configured without increasing the cost. It is extremely useful in the construction of a power supply system for a communication device requiring high reliability.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of one embodiment of the present invention.

FIG. 2 is an explanatory diagram of a conventional series resonance type DC-DC converter.

FIG. 3 is an operation waveform diagram of a conventional series resonance type DC-DC converter.

FIG. 4 shows a conventional series resonance type DC-DC with noise suppression.
FIG. 4 is an operation waveform diagram of the converter.

[Explanation of symbols]

v _i DC power source S _1, S _2, S _3, S ₄ first, second, third, fourth switching element T output transformer L ₁ first inductor Rec rectifier circuit C smoothing capacitor L ₂ second Inductors C ₁ , C ₂ Resonant capacitors D ₁ , D ₂ First and second feedback diodes Out Output terminal GS Alarm signal terminal DC ₁ , DC _N Series resonance type DC-DC converter CT Current transformer

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yutaka Kouda, 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Seiichi Muroyama 1-16-1 Uchisaiwaicho, Chiyoda-ku, Tokyo Japan Inside Telegraph and Telephone Corporation (72) Inventor Kimihiro Takahashi 1-6-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (56) References JP-A-1-243850 (JP, A) JP-A-1- 234051 (JP, A) JP-A-1-274661 (JP, A) JP-A-1-270768 (JP, A) JP-A-3-103070 (JP, A) JP-A-51-97970 (JP, A) JP-A-3-103071 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H02M 3/00-3/44

Claims (1)

(57) [Claims] 1. A series circuit of first and second switch elements connected to a DC power supply, a series circuit of two resonance capacitors, a series circuit of first and second feedback diodes, and the first and second feedback diodes. An output transformer having a primary winding connected between a connection point of the second switch element and a connection point of the first and second feedback diodes, a series circuit of a first resonance inductor, A second resonance inductor connected between a connection point of the two feedback diodes and a connection point of the two resonance capacitors, and third and fourth switch elements connected in parallel to the first and second feedback diodes; A rectifier circuit connected to a secondary winding of the output transformer, a smoothing capacitor, and a converter control circuit for controlling on / off of the first, second, third, and fourth switch elements. Resonant DC-D
In the C converter, a series resonance type DC-DC converter is provided with a detector of a current flowing through the second resonance inductor, and performing a failure determination based on the presence or absence of the current.