JPS62221867A - Dc-dc converter - Google Patents

Abstract

PURPOSE:To obtain inversion output voltage lower than input voltage, by connecting a plurality of first condensers storing the energy of an input power source and the energy of a coil, in series when switching elements are OFF. CONSTITUTION:A DC-DC converter is composed of a coil 2, switching elements (hereinafter, TR) 31-32, first condensers 41-42, charging diodes 51-52, discharging diodes 61-62, and a second condenser 7, and current is fed to a load resistor 8. Into the coil 2, energy is stored by the first ON-working of the TR 31-32, and after that, on OFF-working, the total energy of this energy and the energy of an input power source 1 is stored in the first condensers 41-42 via the charging diodes 51-52. After that, when the TR 31-32 are turned ON second, then the energy of the first condensers 41, 42 is respectively shifted to the second condenser 7 via the discharging diodes 61-62. As a result, the output voltage Vo of the second condenser 7 is obtained with polarity opposite to that of input voltage E as the polarity shown in figure.

Description

[Detailed Description of the Invention] [Summary] This is a DC-DC converter that attempts to obtain an inverted output voltage with a small ripple current flowing through an input power source (and which is lower than the input voltage) with a simple circuit.

[Industrial application field]

The present invention relates to an inverting step-down DC-DC converter that inverts an input voltage and obtains a lower output voltage.

[Conventional technology]

A conventional inverted output type DC-DC converter had a configuration shown in FIG. In Figure 4, reference numeral 1' is the input power supply, 2' is the coil, 3' is the transistor, 4' is the first capacitor, 5' is the charging diode, 6' is the discharging diode, and 7' is the second capacitor. , 8' is a load resistance.

This configuration results in a closed loop l when transistor 3' is first turned on. N1 is formed and energy is stored in coil 2'.

Next, when the transistor 3' is turned off, the sum of the energy stored in the coil 2' and the energy of the input power supply 1' becomes a closed loop β. By flowing through the FF, energy is stored in the first capacitor 4'.

Furthermore, when transistor 3' is turned on again, the loop l is closed. H2I and l. N2□ is formed, and the energy of the power source 1' is stored in the coil 2' along the closed loop 1°N1, and a closed loop i. First capacitor 4 along N7
' is transferred to the second capacitor 7'.

By repeating this operation, the output voltage V has a polarity opposite to that of the input power supply 1'. appears across the load resistance B'.

[Problem that the invention seeks to solve]

The device shown in FIG. 4 described above has an excellent feature in that the ripple current flowing into the input power source 1' is small.

Further, the output voltage V0 is expressed by the following equation.

In equation (2), D is the ratio of the on time of the transistor 3' to the operating period of the duty ratio transistor 3'.

E is the voltage of the input power supply 1'.

However, as is clear from equation (2), since there is a relationship D<1, the absolute value 1 vol of Vo is necessarily larger than E.

Therefore, the conventional inverted output type converter has a problem in that it is not possible to obtain an inverted output voltage lower than the input voltage.

[Means for solving problems]

It is an object of the present invention to solve the above problems and to obtain an inverted output/voltage with less ripple current and lower than the input voltage.
- To provide a DC converter.

As shown in FIG. 1, the means for this purpose is to connect two first capacitors in series, as indicated by reference numerals 4I and 42, which store the energy of the power supply 1 and the coil 2 when the switching element is turned off. Accordingly, two switching elements 31 and 32, two charging diodes 51 and 52, and two discharging diodes 61 and 62 are provided.

[For production]

As described above, according to the present invention, a plurality of first capacitors that store the energy of the input power source and the energy of the coil when the switching element is off are generally connected in series.

Therefore, for example, if the two switching elements 31 and 32 are configured to be synchronized, when they are off, energy is stored in the first capacitors 4 and 42 due to the closed loop r-OFF shown by the broken line, and when they are turned on for the second time, energy is stored in the first capacitors 4・L
2. Three closed loops 1 and 3 are formed, and the energy of the power source 1 is stored in the coil 2, and the energy of the capacitor 41 is stored by L2, and the energy of the capacitor 42 is stored by L3.
energy can be transferred to the second capacitor 7, respectively. Therefore, if the capacitances of the first capacitors 41 and 42 are made equal, they will share the voltage E of the input power supply 1, and the voltage appearing across the output capacitor 7 will be half of the conventional voltage. , an inverted output voltage V that is lower than the input voltage E. Now you can get .

An inverted output voltage v0 is obtained, where n is the number of capacitors connected in series, and its absolute value is lower than that of the input terminal E.

〔Example〕

Hereinafter, the present invention will be explained by way of example with reference to the accompanying drawings. FIG. 2 is a diagram showing a first example of the present invention.

In FIG. 2, reference numeral 1 indicates an input power source, 2 indicates a coil, and 3
1 and 32 are switching elements, 41 and 42 are first capacitors, 51 and 52 are charging diodes, 61 and 62 are discharge diodes, 7 is a second capacitor, and 8 is a load resistor.

The switching elements 31 and 32 are composed of bipolar transistors TR and TRz, respectively, but may be composed of other MOSFETs or the like.

Transistors TRI and TRI are synchronized with each other, and a synchronization clock CK is input to their bases.

The input power source 1 is a DC voltage source of voltage E.

Coil 2 is an element in which energy is stored when TRI and TR2 are turned on for the first time.

The first capacitors 41 and 42 are connected in series and have approximately the same capacitance.

Next, the operation of the first embodiment shown in FIG. 2 having the above configuration will be explained.

The energy that turns on the transistors TR and TR2 for the first time is stored in the coil 2.

Next, TRI! :TR, is turned off, a closed coupe nOFF shown by a broken line is formed.

Since the voltage polarity of the coil 2 is as shown in the figure, the sum of the energy of the input power source 1 and the energy stored in the coil 2 is transferred to the first capacitor 41 via the charging diodes 51 and 52. It is stored in 42. At this time, the voltage polarities of both capacitors 41 and 42 are as shown in the figure.

Therefore, the next time TRI and TR2 turn on for the second time, the closed loop l. Along N2+, the energy of input source 1 is stored in coil 2 and the closed loop R0N214 and J
! ON! ff, the energy of the first capacitor 41 is transferred to the first capacitor 4 via the discharging diode 61.
The energy of 2 is transferred to the second capacitor 7 via the discharge diode 62, respectively.

Therefore, the voltage polarity of the second capacitor 7 is as shown in the figure, and the output voltage V has the opposite polarity to the input voltage E. As mentioned above, if the capacitances of the first capacitors 41 and 42 are made to be the same, the capacitors 41 and 42 will each divide the input voltage E by about 2.

Therefore, E and V. The relationship can be expressed by the following equation.

As is clear from equation 0, as explained in the prior art,
E is the input voltage, D is the duty ratio, and D<1.

This results in an output voltage that is lower in absolute value than the input voltage. can be obtained.

FIG. 3 is a diagram showing a second embodiment of the present invention.

The difference from Fig. 2 is that one directly connected first capacitor (reference numeral 43) has been added, and accordingly, one switching element 33, one charging diode 53, and one discharging diode 63 have also been added. be.

With this configuration, the switch notching elements 3 are synchronized with each other.
When 1, 32, 33 are turned on for the first time, closed loop #
When ON+ is off, closed loop l1OFF, and when turned on the second time, closed loop l' 0NII + 10822
+1ON□,.

j' ON! 4 are formed and the energy changes.

According to this second embodiment, V. According to equation 0, the relationship between and E is the inverted output voltage V. is even lower than that of the first embodiment.

〔Effect of the invention〕

As described above, according to the present invention, a plurality of first capacitors that store the energy of the input power source and the energy of the coil when the switching element is off are generally connected in series.

Therefore, for example, if two switching elements 31 and 32 are configured to be synchronized, a closed loop L shown by a broken line occurs when these elements are off. Energy is stored in the first capacitors 41 and 42 by the FF, and when turned on for the second time, L+'
Three closed loops of Lx and L3 are formed, and I stores the energy of the power supply l in the coil 2, L2 stores the energy of the capacitor 41, and L3 stores the energy of the capacitor 4.
2 can be transferred to the second capacitor 7, respectively. For this reason, the first capacitors 41 and 42
If the capacitance stars of are made to be the same, they will share the voltage E of the input type RI, and the voltage appearing across the output capacitor 70 will be about half of the conventional voltage, so the inverted output voltage will be lower than the input voltage E. ■. Now you can get .

The inverted output voltage V. is obtained, and its absolute value is the input voltage E
becomes lower.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle of the present invention, FIG. 2 is a diagram showing a first embodiment of the present invention, FIG. 3 is a diagram showing a second embodiment of the present invention, and FIG.
The figure is an explanatory diagram of the prior art. l...human power supply, 2...coil, 31, 3
2... Switching element, 41, 42... First capacitor, 51, 52... Charging diode, 61, 62...
...Discharge diode, 7...Second capacitor, 8...Load resistance.

Claims (1)

[Claims] When the switching element is turned on for the first time, the energy of the input power source is stored in the coil, and when the switching element is turned off, the energy of the sum of the energy stored in the coil and the input power source energy is stored in the coil for the first time.
In the DC-DC converter, the energy is stored in a capacitor, and when the switching element is turned on for the second time, the energy stored in the first capacitor is transferred to the second capacitor to obtain an output voltage with the opposite polarity to the input voltage. A plurality of first capacitors are connected in series, and a plurality of switching elements synchronized with each other are provided corresponding to the number of first capacitors, and the energy stored in each first capacitor is transferred to the second capacitor. A DC-DC converter characterized in that the DC-DC converter is configured to transfer.