JP3332318B2 - DC-DC converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has an inverter circuit on the input side, uses a saturable reactor on the output side, has a feedback circuit for keeping the output voltage constant, and reduces the energy of the saturable reactor. The present invention relates to a DC-DC converter that is used effectively to perform reset.

[0002]

2. Description of the Related Art FIG. 5 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 1 includes an input unit, a saturable reactor unit, an output unit, and a feedback unit. 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 includes rectifier diodes 65 and 66 for rectifying the output of the transformer 4 and the rectifier diodes 65 and 66.
Are constituted by the saturable reactors 67 and 68 which change the output of the saturable reactor. The output unit is the saturable reactor 67,
The smoothing circuit includes a feedback diode 9, a smoothing reactor 10, and a smoothing capacitor 11 for smoothing the output 68. The feedback section includes a voltage detection circuit 15 that detects the voltage of the smoothing capacitor 11 and a control circuit 16 that performs feedback control of the inverter circuit 3 based on the detection amount of the voltage detection circuit 15. Also, the control windings 7 of the saturable reactors 67 and 68
Rectifier diodes 71 and 72 for rectifying the voltages of the control windings 75 and 78 are connected to 5, 78, and the outputs of the rectifier diodes 71 and 72 are connected to the smoothing capacitor 11.

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 transformed through the transformer 4 and input to the saturable reactor unit. When the input voltage of the rectifier diode 65 changes from the forward voltage to the reverse voltage and the saturable reactor 68 becomes saturated, the current flowing through the load winding 74 of the saturable reactor 67 is cut off and the saturable reactor 67 is controlled. A voltage is induced in the winding 75. This induced voltage causes the diode 71
, The smoothing capacitor 11 is charged, and the saturable reactor 67 is reset.

In the next half cycle after the reset, the input voltage of the rectifier diode 65 changes to a forward voltage, and the transformed voltage is applied to the load winding 74 of the saturable reactor 67 via the transformer 4. You. After the elapse of the unsaturated time, the saturable reactor 67 changes from an unsaturated state to a saturated state. When the saturable reactor 67 is in the unsaturated state, the output of the saturable reactor 67 is blocked, and is output after changing to the saturated state.

After that, when the input voltage of the rectifier diode 65 changes from the forward voltage to the reverse voltage, the saturable reactor 67 is released from the saturated state. The saturable reactor 68 operates in the same manner as described above. Saturable reactor 67,
The voltage output from 68 in the saturated state is smoothed at the output section and applied to the load 12.

Next, the DC-DC converter will be quantitatively described with a focus on the saturable reactor 67. When a forward voltage is applied to the rectifier diode 65, the secondary voltage of the transformer 4, that is, the voltage when the saturable reactor 67 is unsaturated is V1, the unsaturated time is T1, and the rectifier diode 6
When a reverse voltage is applied to the saturable reactor 6
Let V2 be the voltage induced in the load winding 74 when the energy of No. 7 is reset, and let T2 be the output time. Further, the input period of the output unit, that is, the period of the voltage applied to the feedback diode 9 is T3, and the output period of the transformer 4 when the voltage direction applied to the rectifying diode 65 is the forward direction is T3.
4. The half cycle is defined as T5. Then, the average 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 67 is V1 × T1, the reset amount is V2 × T2, and V1 × T1 = V2 × T2 holds. Also, T2
Since T1 and T3 are equal, T1 is represented by T1 = T3 × V2 / V1. Here, since the saturable reactor 67 is reset from the control winding 75 via the diode 71,
Assuming that the winding ratio between the load winding 74 and the control winding 75 is N = (load winding / control winding), V2 = N × VO. From this, Equation 1 is established.

[0007]

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 4.

Thus, when the secondary voltage of the transformer 4 is substantially constant, the unsaturated time T1 can be kept substantially constant without being affected by the iron core material of the saturable reactor 67. Even with an iron core having non-square characteristics, the unsaturated time of the saturable reactor can be kept constant and reset can be reliably performed. As a result, DC with high efficiency and stable operation
-A DC converter can be obtained.

The time obtained by adding the unsaturated period T1 of the saturable reactor 67 to the period T3 applied to the feedback diode 9 is substantially equal to a half cycle (ie, T3 + T1).
≒ T5). When the ratio of the unsaturated time T1 of the saturable reactor 67 to the half cycle T5 is D (= T1 / T5), T3 = (1−D) × T5. The winding ratio N between the control winding 74 and the control winding 75 is given by Expression 2.

[0011]

N = D / (1-D) 2

The voltage V applied to the rectifier diode 71 during the unsaturated time T1 of the saturable reactor 67
71 becomes Equation 3.

[0013]

V71 = V0 + V1 / N

Now, as circuit conditions, V1 = 200 V, V1
Assuming that 0 = 150V and D = 0.1, N = 0.
12, the voltage applied to the rectifier diode 71 is as high as 1816 V from Equation 3.

[0015]

The rectifier diodes 71 and 72 are required to be high-speed diodes having reverse circuit characteristics. For high voltage diodes, it takes time to eliminate residual carriers when a reverse voltage is applied, and there are few high-speed diodes on the market, and it is necessary to take measures such as manufacturing a special diode for DC-DC converters. DC-DC converters have become expensive.

[0016]

In order to solve the above-mentioned problems, in a DC-DC converter according to the present invention, when a saturable reactor shifts from an unsaturated state to a saturated state to supply DC to a load. When the saturable reactor is unsaturated, the stored energy of the saturable reactor is divided into a plurality of control windings to induce a voltage, and the induced voltage is added to the saturable reactor to regenerate to a load or a DC power supply. Is to be reset.

According to a first aspect of the present invention, there is provided 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 series circuit of a control winding of a saturation reactor and a rectifying diode, and a plurality of reset circuits including a voltage dividing capacitor provided at an output of the series circuit were provided, and the reset circuits were connected in series and directly connected to an output. It is characterized by the following.

According to a second aspect of the present invention, there is provided 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 series circuit of a control winding of a saturation reactor and a rectifying diode, and a plurality of reset circuits each including a voltage dividing capacitor provided at an output of the series circuit are provided. The reset circuits are connected in series and input to the inverter circuit. It is characterized by being directly connected to.

According to a third aspect of the present invention, there is provided 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 series circuit of a control winding of a saturating reactor and a rectifying diode, and a plurality of reset circuits including a voltage dividing capacitor provided at an output of the series circuit are provided, and the reset circuits are connected in series to another voltage source. It is characterized by being directly connected.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 1 is a circuit configuration diagram of a DC-DC converter 1 according to a first embodiment of the present invention. The circuit of the DC-DC converter 1 includes an input unit, a saturable reactor unit, an output unit, and a feedback unit. The input unit includes a DC power supply 2, an inverter circuit 3 for converting the output of the DC power supply 2 into an AC voltage, and a transformer 4 for transforming the output of the inverter circuit 3. The saturable reactor section includes rectifier diodes 5 and 6 for rectifying the output of the transformer 4, saturable reactors 7 and 8 for transforming the output of the rectifier diodes 5 and 6, and control windings 25 and 26 of the saturable reactors 7 and 8. 27, 28 and 30, 31, 32,
33 and control windings 25, 26, 27, 28 and 30, 31,
Rectifier diodes 34, 3 for rectifying the voltages of 32, 33
5, 36, 37 and 38, 39, 40, 41 form a series circuit, and smooth the output rectified by this series circuit,
Voltage dividing capacitors 42, 43, 44, 45 and 4 for dividing the voltage
6, 47, 48 and 49 constitute a reset circuit.
This reset circuit is connected in series and directly connected to the output load 12. The output section includes a feedback diode 9 for smoothing the outputs of the saturable reactors 7 and 8, a smoothing reactor 1
0, a smoothing circuit including a smoothing capacitor 11. The feedback section includes a voltage detection circuit 15 for detecting the voltage of 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. In FIG. 1, the windings of the transformer 4 and the saturable reactors 7, 8 are provided.
The mark indicates the beginning of the winding.

Next, the operation of FIG. 1 will be described. The output voltage of the DC power supply 2 is converted by the inverter circuit 3 into an AC voltage having a certain duty. Inverter circuit 3
The AC voltage converted and output by the above 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 windings 25, 26, 27, 28. This induced voltage causes the diodes 34, 3
5, 36, 37, the voltage dividing capacitors 42, 43,
44 and 45 are charged. The voltage across the voltage dividing capacitors 42, 43, 44, 45 connected in series is boosted, charging the smoothing capacitor 11 and resetting 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 by 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. FIG. 5 showing the prior art
Similarly, when a forward voltage is applied to the rectifier diode 5, the secondary voltage of the transformer 4, that is, the voltage when the saturable reactor 7 is unsaturated is V1, the unsaturated time is T1, and the rectifier diode 5 When a reverse voltage is applied to the input of the saturable reactor 7, the voltage induced in the load winding 24 when the energy of the saturable reactor 7 is reset is V2, and the output time is T2. The period of the applied voltage is T3, 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. When the average voltage of the output of the DC-DC converter is VO, VO = V1
× T3 / T5. On the other hand, the energy stored in the saturable reactor 7 is V1 × T1, and this energy is supplied from the control windings 25, 26, 27, and 28, and the reset amount of each control winding is V2 × T2 / 4. Becomes (If the control winding is an n-winding, it becomes V2 × T2 / n). Here, the load winding 24 and the control windings 25, 26, 2
Assuming that the winding ratio of 7, 28 is N '= (load winding / control winding), V2 = 4.times.N'.times.VO.

[0025]

T1 = 4 × 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 V1 of the transformer, and when the secondary voltage of the transformer 4 is almost constant, the unsaturated time T1 is almost unaffected by the core material of the saturable reactor 7. It can be kept constant and reset can be performed reliably.

On the other hand, the time obtained by adding the unsaturated time T1 of the saturable reactor 7 to the period T3 applied to the feedback diode 9 is substantially equal to a half cycle (that is, T3 + T1 ≒ T).
5). When the ratio between the unsaturated time T1 of the saturable reactor 7 and the half cycle T5 is D (= T1 / T5), the winding ratio N 'between the load winding and the control winding is represented by n-winding of the control winding. If
Equation 5 holds.

[0028]

N ′ = n × D / (1−D) 2

The unsaturated time T of the saturable reactor 7 is
The voltage Vd applied to the rectifier diode in the feedback of 1 satisfies Equation 6 when the control winding is an n-winding.

[0030]

Vd = VO / n + V1 / N '

Therefore, in the case of FIG. 1 having four control windings,
Circuit conditions are the same as before, V1 = 200V, VO = 1
Assuming that 50 V and D = 0.1, N ′ = 0.4 from Equation 5
8, Vd = 417 V is applied to each of the rectifier diodes 34, 35, 36, and 37 from Expression 6.

As the rectifier diodes 34, 35, 36, 37 and 38, 39, 40, 41, general high-speed diodes available on the market can be used, and a DC-DC converter can be manufactured at low cost.

(Second Embodiment) In FIG. 1 of the above embodiment, control windings 25 to 2 of saturable reactors 7 and 8 are shown.
The output currents of the saturable reactors 8 and 30 to 33 are connected in series, and then connected in parallel with the smoothing capacitor 11 to supply the energy of the saturable reactors 7 and 8 to the load 12, but in FIG. Control windings 25, 26 and 30, 31 of saturating reactors 7, 8 and rectifier diodes 34, 35
, And the series circuit of 38 and 39 are connected to the input of the inverter 3 to regenerate energy accompanying the reset of the saturable reactors 7 and 8 to the DC power supply 1. In FIG. 2, two reset circuits are provided for each of the saturable reactors with respect to the four circuits shown in FIG. The operation of this DC-DC converter is the same as that of FIG.

(Third Embodiment) Further, an inverter 3
In the DC-DC converter of FIG. 3 using a half bridge for the saturable reactors 7, 8, the control windings 25, 26
, 30 and 31 and rectifier diodes 34, 35 and 38,
The series circuit with the DC power supply 39 is connected to the DC power supplies 51 and 52 of the half bridge, respectively, and regenerates energy accompanying the reset of the saturable reactors 7 and 8 to the DC power supplies 51 and 52. The operation of the DC-DC converter is performed in the same manner as in the first embodiment shown in FIG. In FIG. 3, two reset circuits are provided for each saturable reactor, similarly to FIG.

(Fourth Embodiment) Further, in FIG. 4, the energy accompanying the reset of the saturable reactors 7, 8 is regenerated to the other voltage sources 56, 57.

[0036]

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. Further, a commercially available high-speed diode having a relatively low reverse voltage of a rectifier diode connected in series to the control winding of the saturable reactor can be used. Thereby, an inexpensive DC-DC converter can be obtained.

[Brief description of the drawings]

FIG. 1 shows a DC-DC according to a first embodiment of the present invention.
FIG. 3 is a circuit configuration diagram of a converter.

FIG. 2 shows a DC-DC according to a second embodiment of the present invention.
FIG. 3 is a circuit configuration diagram of a converter.

FIG. 3 shows a DC-DC according to a third embodiment of the present invention;
FIG. 3 is a circuit configuration diagram of a converter.

FIG. 4 shows a DC-DC according to a fourth embodiment of the present invention.
FIG. 3 is a circuit configuration diagram of a converter.

FIG. 5 is a circuit configuration diagram of a conventional DC-DC converter.

FIG. 6 is a time chart at the time of operation of the DC-DC converter of FIG. 5;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 DC-DC converter main body 2, 51, 52 DC power supply 3 Inverter circuit 4 Transformer 5, 6, 34, 35, 36, 37, 38, 39, 40,
41 Diode for rectification 7,8 Saturable reactor 9 Feedback diode 10 Smooth reactor 11 Smoothing capacitor 12 Load 15 Voltage detection circuit 16 Control circuit 24,29 Load winding of saturable reactor 25,26,27,28,30,31 , 32,33 Control winding of saturable reactor 42,43,44,45,46,47,48,49 Voltage dividing capacitor

────────────────────────────────────────────────── ─── Continuing from the front page Examiner Yasuhide Nishimura (56) References JP-A-6-165487 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02M 3/28 H02M 3 / 335

Claims (3)

(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 series circuit of a line and a rectifying diode, and a plurality of reset circuits including a voltage dividing capacitor provided at an output of the series circuit are provided, and the reset circuits are connected in series and directly connected to an output. DC-DC converter. 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 series circuit of a line and a rectifying diode, and a plurality of reset circuits each including a voltage dividing capacitor provided at an output of the series circuit are provided, and the reset circuits are connected in series and directly connected to an input of the inverter circuit. Characteristic DC-DC converter. 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 plurality of reset circuits including a series circuit of a line and a rectifying diode and a voltage dividing capacitor provided at an output of the series circuit are provided, and the reset circuits are connected in series and directly connected to another voltage source. DC-DC converter.