JPH0313825B2 - - Google Patents

Description

[Detailed Description of the Invention] <Technical Field> The present invention outputs a low voltage from a DC power supply.
Regarding DC/DC converters.

<Prior Art> Conventionally, as a method of lowering the voltage of a DC power supply in order to supply a low voltage from the DC power supply to a load, a method using a voltage drop caused by a resistance has been adopted.
If a transistor is used as the resistor in this case,
Since the resistance value is variable, it is possible to supply a constant voltage output to the load by controlling this resistance value, but in principle the power supply current and load current are equal, so the disadvantage is that it is very inefficient. be.

There are other ways to lower the voltage of the DC power supply to a predetermined voltage, such as using an inverter and transformer or using a chopper, but these methods that use magnetic action reduce the weight of the magnetic core. If the coil is large, the weight of the entire converter becomes excessive, and the efficiency of a small coil is generally low, making it difficult to manufacture a compact converter with low loss.

<Object of the Invention> The present invention has been made in view of the above-mentioned problems, and consists of a charging/discharging circuit made up of a capacitor and a diode, and by incorporating this charging/discharging circuit, a system with low loss can be achieved. The purpose is to convert DC voltage, increase conversion efficiency, and simplify the overall circuit of the DC/DC converter.

<Structure of the Invention> In order to achieve the above object, the present invention (specific invention) provides a plurality of stages of capacitors, diodes for connecting these capacitors in series with input/output terminals for charging and discharging, configuring a charging/discharging circuit including diodes for coupling these capacitors in parallel to the input/output terminal;
Furthermore, using the above charge/discharge circuit, the charge/discharge circuit, switch means on the input side and output side for alternately charging and discharging the charge/discharge circuit, and a reactor with a tap for smoothing the output of the output side switch means are provided. , and a diode that sends charging current to the load through the tapped reactor.
This is a converter.

In addition, the invention to be combined with the specific invention is, in order to achieve the above object, to provide a multi-stage capacitor,
A charging/discharging circuit is configured with diodes for connecting these capacitors in series with each other with respect to an input terminal for charging, and diodes for connecting these capacitors in parallel with each other with respect to an output terminal for discharging. , further using the above charge/discharge circuit,
The charging/discharging circuit, switching means on the input and output sides for alternately charging and discharging the charging/discharging circuit, a reactor with a tap for smoothing the output of the switching means on the output side, and a reactor with a tap for supplying the charging current through the reactor with the tap. This is a DC/DC converter that includes a diode that feeds into the load.

<Example> Hereinafter, the present invention will be described in detail based on an example shown in the drawings.

(A) Example of charging/discharging circuit used in the first embodiment of the DC/DC converter Figure 1 shows the first embodiment of the DC/DC converter of the present invention.
~ This is a circuit diagram showing the configuration of a charging/discharging circuit used in the third embodiment, and this charging circuit A has multiple stages of capacitors C1, C2, C3 and charging input terminals 1, 2. capacitor C1,
Diodes D12 and D22 for connecting C2 and C3 in series, and diodes D11 and D2 for connecting the capacitors C1, C2 and C3 in parallel with each other to output terminals 1 and 2 during discharge.
1, D13, and D23. In this embodiment, the plural stages of capacitors C1, C2, and C3 are three stages, and all have approximately the same capacitance. Therefore, the positive terminal (positive electrode +) of the first stage capacitor C1 serves as the positive input terminal for charging and the positive output terminal for charging (hereinafter referred to as input/output positive terminal 1), and the third stage capacitor C1, which is the final stage, The negative terminal (negative electrode -) of C3 serves as both a charging input negative terminal and a charging output negative terminal (hereinafter referred to as input/output negative terminal 2).

Diodes D12 and D22 for connecting these capacitors C1, C2, and C3 in series with both the positive and negative input and output terminals 1 and 2 are connected between the negative terminal of the previous stage capacitor and the positive terminal of the next stage capacitor. Each is connected in the forward direction. That is, the diode D12 is connected to the first stage capacitor C1.
and the positive terminal of the second stage capacitor C2, and the diode D22 is connected between the negative terminal of the second stage capacitor C2 and the positive terminal of the third stage capacitor C3.

Further, diodes D11, D21, for connecting the capacitors C1, C2, C3 in parallel to both the input/output positive and negative terminals 1, 2,
D13 and D23 are respectively connected between the positive terminal of the previous stage capacitor and the positive terminal of the next stage capacitor, and between the negative terminal of the previous stage capacitor and the negative terminal of the next stage capacitor. That is, the diode D11 is connected to the first stage capacitor C1.
The diode D21 is connected between the positive terminal of the capacitor C2 in FIG. 2 and the positive terminal of the third stage capacitor C3, and the diode D13
is connected between the negative terminal of the first stage capacitor C1 and the negative terminal of the second stage capacitor C2, and the diode D23 is connected between the negative terminal of the second stage capacitor C2 and the negative terminal of the third stage capacitor C3. has been done.

In the above configuration, when charging, the DC power supply 3 is connected to both the input and output positive and negative terminals 1 and 2, and the charging current is transferred from the positive terminal of the first stage capacitor C1 to the third stage capacitor C1.
It flows into the negative terminal of stage capacitor C3. At this time, the diodes D12 and D22 connected in series between the capacitors C1 and C3 are in the forward direction with respect to the charging current, and the other diodes D11, D21, D
13 and D23 are all in the opposite direction to the charging current, and the capacitors C1 to C3 are charged in series. The capacitor current flowing through each capacitor C1 to C3 is equal to the power supply current I, and the voltage appearing between input and output terminals 1 and 2 is
This is three times the voltage between the terminals of C3.

Discharge occurs when a load 4 is placed between the input/output positive and negative terminals 1 and 2.
This is done by connecting. The discharge current Ic ₁ of the first stage capacitor C1 is connected to the diode D13,
The discharge current Ic ₂ of the second stage capacitor C2 flows through the diodes D11 and D23,
Further, the discharge current Ic ₃ of the third stage capacitor C3 flows through the diodes D11 and D21. At this time, the diodes D12 and D22 connected in series between the capacitors C1 to C3 have a direction opposite to the discharge current. In this way, capacitor C1~
C3 are discharged in parallel, the load current is the sum of the discharge currents of the respective capacitors C1 to C3, and the load voltage is approximately equal to the charging voltage of each of the capacitors C1 to C3.

In the above circuit, the positive terminal of the third stage capacitor C3, which is the final stage capacitor, and the first
By applying a DC power supply voltage between the negative terminal of each stage capacitor C1, each capacitor C1
~C3 can also be charged in parallel.

Figure 2 shows DC/DC using the above charge/discharge circuit A.
This is a circuit diagram of a converter, and this circuit is the basis of the DC/DC converter of the first embodiment of the present invention, which will be described later. Prior to the first embodiment, the operation of the circuit of FIG. 2 will be explained. . In addition, in this FIG. 2, the circuit configuration inside the charging/discharging circuit A is omitted. The input/output positive terminal 1 of the charging/discharging circuit A is connected to the positive terminal of the DC 3 via the input switching element S1, and the input/output positive terminal 1 is connected to the positive terminal of the load 4 via the output switching element S2 and the reactor 5. connected to the terminal. The input/output negative terminal 2 of the charging/discharging circuit A is connected to the input side of the reactor 5 via a diode D4, and is also connected to the negative terminal of the load 4 and the negative terminal of the DC power source 3 via a diode D5.

In the above configuration, if the input switching element S1 is now on and the output switching element S2 is off, each capacitor C of the charging/discharging circuit A
1 to C3 are charged in series by the DC power supply 3, and at the same time, the charging current is supplied to the load 4 through the diode D4 and the reactor 5.
Next, when the input switching element S1 is off and the output switching element S2 is on, the power supply current does not flow and the discharge current of the charging/discharging circuit A flows to the load 4.
is supplied to

If the time ratio between the charging period and the discharging period of the charging/discharging circuit A due to the on/off operation of both input/output switching elements S1 and S2 is set to 1:3, and both periods are repeated at a very short cycle, the charging/discharging circuit The charging and discharging amounts of each capacitor C1 to C3 in A are equal to each other, the capacitor voltage is a constant value of approximately one-fourth (E _S /4) of the DC power supply voltage E _S , and the load voltage is also equal to the DC power supply voltage E _S almost a quarter of
become. The period during which the power supply current flows is one third of the discharge period, and both switching elements S1,
1/4 of one period in which S2 repeats on/off
Therefore, use the voltage drop due to resistance
Compared to DC/DC conversion methods, it consumes less power and is more efficient.

Furthermore, since the discharge voltage of the charging/discharging circuit A is a quarter of the power supply voltage _Es , that is, the reciprocal of the number of stages of the capacitor, the output voltage can be changed by increasing or decreasing the number of stages of the capacitor of the charging/discharging circuit A. can be made to be an integer fraction of the power supply voltage E _s .

Furthermore, by interposing the reactor 5 before the load 4, the output current is smoothed.
In this case, since the voltage applied to the reactor 5 is only the pulsating component of the capacitor voltage, there is no need for a reactor with a large inductance as in the conventional chopper method, and a small reactor with an inductance several tenths of that is sufficient. , the entire converter can be made compact despite the use of a reactor.

In addition, input/output flow switching elements S1, S
By setting a short-circuit mode in which both switching elements S1 and S2 are turned on at the same time, and an open mode in which both switching elements S1 and S2 are turned off, and by changing the proportion of time occupied by these modes in one cycle,
Output voltage can be changed.

Fig. 4 is a circuit diagram of the first embodiment of the DC/DC converter. In this embodiment, two sets of charge/discharge circuits A shown in Fig. 1 are used, the power supply circuit part and the output circuit part are common, and this Two sets of charging/discharging circuits A
1 and A2 are connected in parallel to a DC power supply 3 and a load 4. Each charging/discharging circuit A1,
Input switching elements S11, S21 and output switching elements S12, S22 are connected to the input/output positive terminals 1, 1 of A2, respectively, and a diode D1 is connected to the input/output negative terminals 2, 2, respectively.
4, D15, D24, and D25 are connected. 6 is a smoothing capacitor connected to the output side of the tapped reactor 51.

Therefore, the input switching element S11 of one charging/discharging circuit A1 and the input switching element S11 of one charging/discharging circuit A1
a set of two output switching elements S22 and one output switching element S1 of the charging/discharging circuit A1;
2 and the set of input switching elements S21 of the other charging/discharging circuit A2 are alternately opened and closed to alternately charge and discharge the two sets of charging/discharging circuits A1 and A2.

In this circuit of Fig. 4, each capacitor C
If the capacitance of 1 to C3 is C, the charging/discharging current is Ic, and the voltage at point P on the input side of reactor 51 is Vp, the capacitors in the charging/discharging circuit connected to point P are connected in series, so Ic = (C/ 3) dVp/dt...(1), and if the Q point voltage of the tap is Vq, then Q
Since the capacitors in the charge/discharge circuit connected to the point are connected for parallel discharge, 3Ic=3C(dVq/dt)...(2), and from equations (1) and (2) above, dVp/dt=3(dVq/dt). dt)...There is the relationship (3), and the voltage pulsation at point P is three times that at point Q. Therefore, if the voltage ripple at point P of the reactor is made three times that at point Q, the current of each capacitor when the capacitors are connected in series is equal to the current of each capacitor when they are connected in parallel, and half It can be seen that the current flows continuously during the period, and the amounts of charge and discharge are equal to each other. Therefore, reactor 51
If you set the tap to the 3:1 position, the above (3)
The relationship shown in the equation holds true, and the power supply current becomes constant.

Furthermore, in the embodiment of FIG. 4, when the tap is fully set on the input side of the reactor 51, that is, on the P point side, and the circuit is equivalent to the circuit shown in FIG. 3, the operation is as follows.

In this case, on the input side of the reactor 5, a diode D14 (or D15) of one charging/discharging circuit A1 and a diode D25 (or D24) of the other charging/discharging circuit A2 are connected in common in the forward direction. pair of diodes D1
4. Out of D25 (or D15, D24), the diode that receives a higher voltage becomes conductive, and the diode that receives a lower voltage becomes non-conductive. Due to the action of these diodes, both charging and discharging circuits A
1 and A2, a current flows through the circuit that applies a high voltage to the input side of the reactor 5. Therefore, the amounts of charge and discharge automatically become equal to each other.

In addition, instead of switching the charging/discharging of each of the charging/discharging circuits A1 and A2 at the same time, for example, assuming that one charging/discharging circuit A1 is in a charging state and the other charging/discharging circuit A2 is in a discharging state, charging/discharging is performed. When switching, first charge one charging/discharging circuit A1, then switch to discharging, and after that, the other charging/discharging circuit A2
to switch from discharging to charging. That is, from the on state of switching elements S11 and S22, switching element S11 off, S12
The switching elements S12 and S21 are sequentially switched on, S22 off, and S21 on.
The switch is turned on. By doing this, even during charging/discharging switching, the charging/discharging circuit A1,
Either A2 is always charging or discharging, and the diodes D14, D24, and
Due to the action of D15 and D25, no current flows through the charge/discharge circuit A1 or A2 during charge/discharge switching, and the switching elements S11 to S22 can switch from on to off or from off to on without current. can. In this way, by slightly shifting the charging/discharging timing of both charge/discharge circuits A1, A2, switching elements S11, S12, S21, S2
2 switching losses are significantly reduced.

(B) Example of a charging/discharging circuit used in a second embodiment of the DC/DC converter FIG. Ao is multiple stages (three stages in this example)
The capacitors C1 to C3 are connected between the negative terminal of the previous stage capacitor and the positive terminal of the next stage capacitor, and these capacitors C1 to C3 are connected in series to both positive and negative input terminals 11 and 21 for charging. It is the same as the charging/discharging circuit A shown in Fig. 1 in that it includes diodes D12 and D22 (the same parts as in Fig. 1 are indicated by the same symbols).
However, both positive and negative output terminals 12 and 22 for discharging are provided separately from the positive and negative input terminals 11 and 21 for charging,
Each of the capacitors C1 to C3 is used as a diode to connect the capacitors C1 to C3 in parallel to both the positive and negative output terminals 12 and 22.
Diodes D16, D26, D36 connected between the positive terminals of the capacitors C1 to C3 and the output positive terminal 12, and diodes D17, D27, D connected between the negative terminals of each capacitor C1 to C3 and the output negative terminal 22.
The circuit configuration is different from the charging/discharging circuit A in FIG. That is, the input positive terminal 14 is the positive terminal of the first stage capacitor C1, and the input negative terminal 21 is the negative terminal of the third stage capacitor C3. A diode D16 is provided on the side of this output positive terminal 12.
is connected between the positive terminal of the first stage capacitor C1 and the output positive terminal 12, the diode D26 is connected between the positive terminal of the second stage capacitor C2 and the output positive terminal 12, and the diode D36 is connected between the third stage capacitor C3.
and the output positive terminal 12, and on the output negative terminal 22 side, the diode D17 is connected between the negative terminal of the first stage capacitor C1 and the output negative terminal 22, and the diode D27 is connected between the second stage capacitor C1 and the output negative terminal 12. A diode D37 connects the third stage capacitor C between the negative terminal of the capacitor C2 and the output negative terminal 22.
3 and the output negative terminal 22, respectively.

In the above configuration, charging is performed by connecting the DC power supply 3 between the input positive and negative terminals 11 and 21, and the charging current is supplied to the first stage capacitor C.
1 to the negative terminal of the third stage capacitor C3. At this time, the diodes D12 and D22 are in the forward direction with respect to the charging current, and the other diodes D26, D36, D17, and D27 are in the opposite direction with respect to the charging current, and the capacitors C1 to C
3 are charged in series.

Discharge is performed by connecting the load 4 between the output positive and negative terminals 12 and 22. The discharge current Ic ₁ of the first stage capacitor C1 is the diode D16, D
17, the discharge current of the second stage capacitor C2
Ic ₂ connects diodes D26, D27 and the third
The discharge current Ic ₃ of the stage capacitor C3 flows through the diodes D36 and D37. Other diode D1
2, D22 is in the opposite direction to this discharge current. In this way, capacitors C1-C3 are discharged in parallel.

In the charging/discharging circuit A shown in FIG. 1, diodes D11, D21, D21,
D13 and D23 are interposed in series, and the number of intervening diodes increases as the number of capacitor stages increases. Therefore, as the number of capacitor stages increases, the voltage drop due to the diodes increases. In contrast, the charging/discharging circuit shown in Figure 5
In Ao, two diodes are interposed between each capacitor C1 to C3 and the output terminals 12, 22, and the number of intervening diodes does not change even if the number of stages of capacitors increases. Therefore, if there are many stages of capacitors, the charging/discharging circuit Ao in Figure 5
is more advantageous because the voltage drop due to the diode is smaller.

Figure 6 shows the DC/discharge circuit using the above charge/discharge circuit Ao.
This is a circuit diagram of a DC converter, and this circuit is
This is the basis of the DC/DC converter of the second embodiment of the present invention, which will be described later, and the operation of the circuit shown in FIG. 6 will be explained prior to the second embodiment.
In addition, in this FIG. 6, the circuit configuration inside the charging/discharging circuit Ao is omitted. An input switching element S3 is connected to the input positive terminal 11 of the charging/discharging circuit Ao.
The positive terminal of the DC power supply 3 is connected to the positive terminal of the DC power supply 3 via the diode D8 and the reactor 5, and the input negative terminal 21 is connected to the positive terminal of the load 4 via the diode D8 and the reactor 5.
The output positive terminal 12 of the charging/discharging circuit Ao is connected to the input side of the reactor 5 via the output switching element S4, and the output negative terminal 22 is directly connected to the negative terminal of the load 4 and the negative terminal of the DC power source 3.

In this DC/DC converter as well, the
Similar to the DC/DC converter, the period during which the power supply current flows is the ON/OFF period of switching elements S3 and S4.
Since the length is a fraction of one OFF period, the conversion efficiency is higher than a method using a voltage drop caused by a resistor.

Figure 8 is a circuit diagram of the second embodiment of DC/DC,
In this embodiment, the charging/discharging circuit Ao shown in FIG.
Using two sets of charging/discharging circuits Ao1, Ao
2 is connected in parallel to the DC power supply 3 and the load 4. Input switching elements S13 and S23 are connected to the input positive terminals 11 and 11 of each charging and discharging circuit Ao1 and Ao2, respectively, and input switching elements S13 and S23 are connected to each input negative terminal 21 and 21, respectively, and a reactor 51 with a tap.
There are diodes D18 and D28 between them, respectively.
is connected. Each charge/discharge circuit Ao1, Ao2
The positive output terminals 12 and 12 of the output terminals 12 and 12 are connected to the tap of the reactor 51 via output switching elements S14 and S24, respectively, and the negative output terminals 2
2 and 22 are directly connected to the negative terminal of the DC power supply 3 and the negative terminal of the load 4, respectively.

This embodiment has the advantage that the power supply current can be made constant, similar to the first embodiment of the DC/DC converter shown in FIG.

Furthermore, in the embodiment of FIG. 8, if the tap is fully set on the input side of the reactor 51 and the circuit is equivalent to the circuit shown in FIG.
Similar to the DC/DC converter shown in the figure, this converter has the advantage of stable operation because the amount of charge and discharge is equal to each other, and the advantage of reducing loss due to switching.

<Effects of the Invention> As described above, the present invention configures a DC/DC converter using a charging/discharging circuit consisting of a capacitor and a diode, and significantly simplifies the overall circuit configuration of the DC/DC converter. This eliminates the need for a large reactor attached to this charging/discharging circuit, and from this point of view as well, the entire DC/DC converter can be made smaller.

Moreover, in the DC/DC converter of the present invention, charging/discharging of the charging/discharging circuit is switched by turning on/off the switch means, and the period during which the power supply current flows is a fraction of one cycle of the on/off period of the switch means. Since the length decreases according to the ratio of output voltage/power supply current, it has the advantage of lower power consumption and extremely high conversion efficiency compared to conventional ones that utilize a voltage drop due to a resistor.

Furthermore, it is also possible to keep the power supply current constant by setting the reactor tap.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a charging/discharging circuit used in the first embodiment of the present invention, and Fig. 2 is a circuit diagram used in the first embodiment.
Basic circuit diagram of DC/DC converter, Figure 3 is the first
A circuit diagram for explaining the operation of the embodiment, FIG. 4 is a circuit diagram of the first embodiment of the present invention, and FIG. 5 is a circuit diagram of the second embodiment of the present invention.
6 is a basic circuit diagram of a DC/DC converter used in the second embodiment. FIG. 7 is a circuit diagram for explaining the operation of the second embodiment. The figure is a circuit diagram of a second embodiment of the present invention. A, Ao...charge/discharge circuit, 1, 2... input/output terminal, 11, 21... input terminal. 12, 22... Output terminal, C1, C2, C3... Capacitor, D1
1, D21, D12, D22, D13, D23...
...Diode, S1, S2...Switching element (switching means), D4, D5...Diode, 3
...DC power supply, 4...load, 5...reactor.

Claims (1)

[Claims] 1 A plurality of capacitors connected in the forward direction between the negative terminal of the capacitor in the previous stage and the positive terminal of the capacitor in the next stage, and used as input/output terminals for charging and discharging during series charging. On the other hand, there is a series coupling diode that couples these capacitors in series with each other, and a positive terminal of the previous stage capacitor and a positive terminal of the next stage capacitor so as to connect the capacitors in parallel to the input/output terminal during parallel discharge. and a parallel coupling diode connected between the negative terminal of the previous stage capacitor and the negative terminal of the next stage capacitor, respectively; In addition to switching the charging/discharging operation of the charging/discharging circuit, the capacitor group in the charging/discharging circuit is charged in series with a DC power supply via the series coupling diode during series charging, and via the parallel coupling diode during parallel discharging. at least two sets of the charging/discharging circuits, and the switching means is configured such that when one charging/discharging circuit is in a charging operation, the other charging/discharging circuit is in a discharging operation. At the same time, the switching means performs a switching operation so as to supply the sum of the charging current of the one charging/discharging circuit and the discharging current of the other charging/discharging circuit to the load as a load current, and the switching means switches the charging/discharging circuit. switching means on the input side and output side for alternately charging and discharging;
The switching means includes a tapped reactor for smoothing the output of the output side switching means, and a diode for sending the charging current flowing into the charging/discharging circuit to the load through the reactor, and this switching means is configured to smooth the output from the other charging/discharging circuit. The DC/DC converter operates to inject a discharge current into the tap of the reactor and supply the sum of the charging current from the one charging/discharging circuit and the discharging current from the tap to the load. DC converter. 2 Multiple stages of capacitors are connected in the forward direction between the negative terminal of the capacitor in the previous stage and the positive terminal of the capacitor in the next stage, and these capacitors are connected in series with each other with respect to the charging input terminal during series charging. between the positive terminal of each capacitor and the output positive terminal, and between the negative terminal of each capacitor and the output negative terminal so that the capacitors are connected in parallel to each other with respect to the output terminal for discharge during parallel discharge. a charging/discharging circuit comprising a parallel coupling diode connected between each terminal; and a charging/discharging circuit that switches the charging/discharging operation of the charging/discharging circuit between series discharging and parallel charging; switching means for charging the capacitor group in series with a DC power supply via the series coupling diode during series charging, and discharging the capacitor group in parallel via the parallel coupling diode during parallel discharge; The switching means is configured such that when one charging/discharging circuit is in a charging operation, the other charging/discharging circuit is in a discharging operation, and the switching means is arranged such that when one charging/discharging circuit is in a charging operation, the other charging/discharging circuit is in a discharging operation, and the charging current of the one charging/discharging circuit is changed from the charging current of the other charging/discharging circuit. The switching means is configured to perform a switching operation so as to supply the sum of the discharge current and the discharge current to the load as a load current, and the switching means includes input side and output side switch means for alternately charging and discharging the charging/discharging circuit;
The switching means includes a tapped reactor for smoothing the output of the output side switching means, and a diode for sending the charging current flowing into the charging/discharging circuit to the load through the reactor, and this switching means is configured to smooth the output from the other charging/discharging circuit. The DC/DC converter operates to inject a discharge current into the tap of the reactor and supply the sum of the charging current from the one charging/discharging circuit and the discharging current from the tap to the load. DC converter.