JP2720000B2 - DC-DC converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention has an inverter circuit on the input side and a saturable reactor on the output side.
The present invention relates to a DC-DC converter including a feedback circuit for keeping an output voltage constant and performing resetting by effectively using energy of a saturable reactor.

[0002]

2. Description of the Related Art FIG. 7 shows a circuit of a conventional DC-DC converter 1 having an inverter circuit on the input side, using a saturable reactor on the output side, and having a feedback circuit for keeping the output voltage constant. It is a block diagram. DC-D
The circuit of the C converter 51 includes an input unit, a saturable reactor unit, an output unit, and a feedback unit. The input unit includes a DC power supply 52, an inverter circuit 53 for converting the output of the DC power supply 52 into an AC voltage, and a transformer 54 for transforming the output of the inverter circuit 53. The saturable reactor section includes rectifier diodes 55 and 56 for rectifying the output of the transformer 54 and saturable reactors 59 and 56 for transforming the outputs of the rectifier diodes 55 and 56.
60. The output unit is a feedback diode 6 for smoothing the outputs of the saturable reactors 59 and 60.
1, a smoothing reactor 62 and a smoothing capacitor 63. The feedback section includes a voltage detection circuit 64 that detects the voltage of the smoothing capacitor 63 and a control circuit 65 that performs feedback control of the inverter circuit 53 based on the detection amount of the voltage detection circuit 64. In addition, the saturable reactor 59.6
0 control windings 75 and 77 have reset power supplies 78 and 79, respectively.
And control switch circuits 57 and 58 such as thyristors.

Next, the operation of FIG. 7 will be described. The output voltage of the DC power supply 52 is converted by the inverter circuit 53 into an AC voltage having a certain duty. The AC voltage converted and output by the inverter circuit 53 is transformed through the transformer 54 and input to the saturable reactor. Control windings 75 and 77 of saturable reactors 59 and 60
Are the control switch circuits 57 from the reset power supplies 78 and 79.
A voltage is applied via 58; The control circuit winding 7
Induced electromotive force is generated in the load windings 74 and 76 by the voltage applied to 5.77. This electromotive force becomes a reset voltage (reset amount) for reducing the energy stored in the saturable reactors 59 and 60.

Now, the input voltage of the rectifier diode 55 changes from the forward voltage to the reverse voltage, and the saturable reactor 59
In the next half cycle after the reset voltage is applied, the input voltage of the rectifier diode 55 changes to the forward voltage, and the voltage is transformed to the load winding 74 of the saturable reactor 59 via the transformer 54. However, the output of the saturable reactor 59 is not output due to the unsaturated state. When the unsaturated time elapses, the saturable reactor 59 changes from an unsaturated state to a saturated state. Reactor output comes out only after this saturation state. That is, the output of the saturable reactor 59 is blocked when it is in an unsaturated state, and is output after changing to a saturated state.

In the next half cycle, the input voltage of the rectifier diode 55 changes from the forward voltage to the reverse voltage, and the saturable reactor 59 is released from the saturated state. Saturable reactor 60 operates in a similar manner. The voltage output from the saturable reactors 59 and 60 in the saturated state is smoothed at the output section and applied to the load 66. Further, the smoothing capacitor 63 is detected by the voltage detection circuit 64.
, And the control circuit 65 performs feedback control of the inverter circuit 53 based on the detection amount of the voltage detection circuit 64 to make the voltage applied to the load 66 constant.

[0006]

However, the reset of the saturable reactors 59 and 60 is performed by the reset power supply 78.
This is performed by providing a tertiary winding to the transformer 54 or applying a voltage induced in the tertiary winding to flow a current through the saturable reactors 59 and 60. For this reason,
It is necessary to provide a separate reset power supply and a control switch circuit for controlling the reset amount and a control circuit for controlling the switch circuit, or to provide a tertiary winding. Further, the saturable reactors 59 and 60 use a core material having a good square characteristic for the iron core, control the reset amount to be constant, and use expensive saturable reactors.

SUMMARY OF THE INVENTION An object of the present invention is to provide a DC-DC converter which is applied when the input voltage fluctuates little and uses an inexpensive saturable reactor to reliably perform a reset amount.

[0008]

DISCLOSURE OF THE INVENTION DC-DC of the present invention
The converter is characterized in that a series circuit of a control winding of a saturable reactor and a rectifying diode is directly connected to an output.
Further, a series circuit of a control winding of the saturable reactor and a rectifying diode is directly connected to an input of the inverter circuit. Further, a series circuit of a control winding of the saturable reactor and a rectifying diode is directly connected to another voltage source. Further, a core having non-square characteristics is used for an iron core of the saturable reactor.

[0009]

In the DC-DC converter of the present invention,
When the saturable reactor shifts from the unsaturated state to the saturated state and the DC power is supplied to the load, the energy of the saturable reactor stored in the saturable reactor induces a voltage in the unsaturated control winding of the saturable reactor. The induced voltage is regenerated to the load or DC power supply to reset the saturable reactor.

[0010]

FIG. 1 is a circuit diagram of a DC-DC converter 1 according to a first embodiment of the present invention. FIG. 2 shows the DC-DC converter 1 according to the embodiment.
6 is a time chart at the time of the operation of FIG. The circuit of the DC-DC converter 1 includes an input unit, a saturable reactor unit, an output unit,
It consists of a feedback section. The input unit includes a DC power supply 2, an inverter circuit 3 for converting an output of the DC power supply 2 into an AC voltage, and a transformer 4 for transforming an output of the inverter circuit 3. The saturable reactor section includes a rectifier diode 5 for rectifying the output of the transformer 4.
6, a saturable reactor 7.8 for transforming the output of the rectifier diode 5.6, a rectifier for rectifying the control windings 25 and 27 of the saturable reactor 7.8 and the voltages of the control windings 25 and 27. It is composed of diodes 17 and 18. The output section is constituted by a smoothing circuit composed of a feedback diode 9 for smoothing the outputs of the saturable reactors 7 and 8, a smoothing reactor 10, and a smoothing capacitor 11. The feedback unit includes the smoothing capacitor 11
And a control circuit 16 for controlling the inverter circuit 3 based on the detection amount of the voltage detection circuit 15.

Next, the operation will be described with reference to FIGS. The output voltage of the DC power supply 2 is converted by the inverter circuit 3 into an AC voltage having a certain duty. The AC voltage converted and output by the inverter circuit 3 is input to the transformed saturable reactor unit via the transformer 4. When the input voltage of the rectifier diode 5 changes from the forward voltage to the reverse voltage and the saturable reactor 8 becomes saturated, the current flowing through the load winding 24 of the saturable reactor 7 is cut off, and the saturable reactor 7 is controlled. A voltage is induced in the winding 25. The induced voltage charges the smoothing capacitor 11 via the diode 17 and resets the saturable reactor 7.

After the reset, in the next half cycle, the input voltage of the rectifier diode 5 changes to the forward voltage, and the transformed voltage is applied to the load winding 24 of the saturable reactor 7 via the transformer 4. You. After the elapse of the unsaturated time, the saturable reactor 7 changes from an unsaturated state to a saturated state. When the saturable reactor 7 is in the unsaturated state, the output of the saturable reactor 7 is blocked, and is output after changing to the saturated state.

Thereafter, when the input voltage of the rectifier diode 5 changes from the forward voltage to the reverse voltage, the saturable reactor 7 is released from the saturated state. The saturable reactor 8 operates in the same manner as described above. The voltage output from the saturable reactors 7 and 8 in the saturated state is smoothed at the output unit and applied to the load 12.

Next, the DC-DC converter will be quantitatively described with a focus on the saturable reactor 7. Now, when a forward voltage is applied to the rectifying diode 5, the secondary voltage of the transformer 4, that is, the voltage of the saturable reactor 7 when it is unsaturated is V
1. The unsaturated time is defined as T1, and when a reverse voltage is applied to the rectifying diode 5, the voltage induced in the load winding 24 when the energy of the saturable reactor 7 is reset is V2. Let T2 be the input of the output unit, that is, the period of the voltage applied to the feedback diode 9;
The output period of the transformer 4 when the voltage applied to the rectifier diode 5 is the forward direction is T4, and the half cycle is T5.
The average value voltage VO of the output of the DC-DC converter is VO =
V1 × T3 / T5. On the other hand, the energy stored in the saturable reactor 7 is V1 × T1, the reset amount is V2 × T2, and V1 × T1 = V2 × T2 holds. Also, since T2 and T3 are equal, T1 becomes T1 = T
It is represented by 3 × V2 / V1. Here saturable reactor 7
Is reset via the diode 17 from the control winding 25, and if the winding ratio between the load winding 24 and the control winding 25 is N = (load winding / control winding), V2 = N ×
VO. From this, T1 = N × T3 × T3 / T5. Here, since T3 is proportional to V1, the unsaturated time T1 is inversely proportional to the square of the secondary voltage of the transformer 5.

Thus, when the secondary voltage of the transformer 4 is substantially constant, the unsaturated time can be kept substantially constant without being affected by the iron core material of the saturable reactor 7. That is, even if the iron core has a non-square characteristic as shown in FIG. 3, the unsaturated time of the saturable reactor can be kept constant, and the reset can be reliably performed.

(Second Embodiment) In FIG. 1 of the above embodiment, the outputs of the control windings 25 and 27 of the saturable reactors 7 and 8 are connected in parallel with the smoothing capacitor 11, and the saturable reactors 7 and 8 are connected. In FIG. 4, a series circuit of the control windings 25 and 27 and the rectifier diodes 17 and 18 of the saturable reactors 7.8
Connect to the input of the inverter 3 and saturable reactors 7.8
Is regenerated to the DC power supply 1. The operation of this DC-DC converter is the same as that of FIG.

Third Embodiment Further, in the DC-DC converter of FIG. 5 using a half bridge for the inverter 3, the control windings 25 and 27 of the saturable reactors 7.8 and the rectifier diodes 17 and 18 are connected in series. The circuits are connected to half-bridge DC power supplies 31 and 32, respectively, and the energy accompanying reset of the saturable reactors 7 and 8 is supplied to the DC power supply 3 and 3.
Regenerated to 1.32. The operation of the DC-DC converter is performed in the same manner as in the first embodiment shown in FIG.

(Fourth Embodiment) In FIG. 6, the energy accompanying the reset of the saturable reactors 7, 8 is regenerated to the other voltage sources 36, 37.

[0019]

As described above, according to the present invention, the energy of the saturable reactor can be regenerated by the load or the input DC power supply and reset. Thus, a DC-DC converter with high efficiency and stable operation can be obtained. In addition, a non-square core can be used for the saturable reactor, so that a large-capacity reactor can be used at low cost.

[Brief description of the drawings]

FIG. 1 is a diagram showing a circuit configuration of a DC-DC converter according to a first embodiment of the present invention.

FIG. 2 is a time chart at the time of operation of the DC-DC converter of FIG. 1 of the present invention.

FIG. 3 shows a characteristic diagram of an iron core of a saturable reactor used for the DC-DC converter of the present invention.

FIG. 4 is a diagram showing a circuit configuration of a DC-DC converter according to a second embodiment of the present invention.

FIG. 5 is a diagram showing a circuit configuration of a DC-DC converter according to a third embodiment of the present invention.

FIG. 6 is a diagram showing a circuit configuration of a DC-DC converter according to a fourth embodiment of the present invention.

FIG. 7 is a diagram showing a circuit configuration of a conventional DC-DC converter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 DC-DC converter main body 2 ・ 31 ・ 32 DC power supply 3 Inverter circuit 4 Transformer 5 ・ 6 ・ 17 ・ 18 Rectifying diode 7.8 Saturable reactor 24 ・ 26 Load winding of saturable reactor 25 ・ 27 Saturable reactor Control winding 9 feedback diode 10 DC reactor 11 smoothing capacitor 12 load 15 voltage detection circuit 16 control circuit

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-288775 (JP, A) JP-A-57-75571 (JP, A) JP-A-62-37066 (JP, A) 26812 (JP, U) Actually open 60-114587 (JP, U)

Claims (4)

(57) [Claims] 1. A DC-DC converter having an inverter circuit on an input side, a saturable reactor on an output side thereof, and a feedback circuit for making an output voltage constant, wherein a control winding of the saturable reactor is provided. A DC-DC converter, wherein a series circuit of a line and a rectifying diode is directly connected to an output. 2. A DC-DC converter having an inverter circuit on the input side, a saturable reactor on the output side, and a feedback circuit for keeping the output voltage constant. A DC-DC converter, wherein a series circuit of a line and a rectifying diode is directly connected to an input of the inverter circuit. 3. A DC-DC converter having an inverter circuit on the input side, a saturable reactor on the output side, and a feedback circuit for keeping the output voltage constant. A DC-DC converter, wherein a series circuit of a line and a rectifying diode is directly connected to another voltage source. 4. The DC-DC converter according to claim 1, wherein the core of the saturable reactor is a core having non-square characteristics.