JPH09163722A - Non-insulating-type dc-dc converter with overload protective function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of parts, and make a DC-DC converter small and low cost. SOLUTION: By synchronizing with on and off operation of switching circuits Q1 and L1 connected between an input terminal and an output terminal, a first charging circuit C2 is charged with a first voltage having polarity opposite to the polarity of the input DC voltage. By synchronizing with on and off operation of the switching circuit Q1, a second charging circuit C2 is charged with a second voltage having the same polarity as the input DC voltage and equal to the sum of the input DC voltage and the first voltage. The on and off time of the switching circuit Q1 is adjusted through a control circuit CONT on the basis of a pulse with a pulse width corresponding to a third voltage in proportion to the output DC voltage. When the third voltage becomes below a given level, the switching circuit Q1 is held in a stopped state by the control circuit CONT.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC-DC converter which outputs a constant voltage by stepping up or stepping down an input power supply voltage, and particularly, without providing a transformer or an output cutoff switching element. The present invention relates to a DC-DC converter in which an input voltage does not flow out to an output side during a latch operation in an overload state such as an output short-circuit and stops safely.

[0002]

2. Description of the Related Art In a non-insulated DC-DC converter, it is necessary to prevent the power supply voltage from being applied to the load by electrically interrupting the input and output terminals during overload. FIG. 6 is a circuit diagram showing an example of the configuration of a step-up DC-DC converter having an overload protection function, which stops the operation of the switching transistor when the output voltage under overload continues to decrease for a certain time or longer. Uses a timer latch method. That is, the DC-DC converter of FIG. 6 has a DC-DC converter for stopping the operation of the switching transistor Q10 when the output voltage under overload continues to decrease for a certain period of time.
A second switching transistor Q11 whose bias is set to be turned on only when the DC converter is performing a boosting operation is provided between the input terminal T _IN and the output terminal T _O1, and the second switching transistor Q11 is used. It is designed to shut off between the input and output terminals when overloaded.

The operation of the DC-DC converter shown in FIG. 6 will be described. When the DC-DC converter is operating normally, the first switching transistor Q10
When is on, energy is stored in the coil L10 by the input DC voltage E applied between the input terminal T _IN and the ground potential. When the first switching transistor Q10 is turned off, the energy stored in the coil L10 charges the capacitor C11 via the diode D11 and also turns on the second switching transistor Q10.
It is supplied to the capacitor C12 and the load via 11.
The voltage between the output terminal T _O1 and the ground potential at this time is divided by the series resistors R14 and R15 and added to the port V _DET of the control circuit CONT1. Depending on this voltage, the control circuit CON
T1 adjusts the width of the square wave pulse output from the port OUT, operates the switching transistor Q10 by the square wave pulse having the adjusted pulse width, and keeps the output voltage constant.

On the other hand, if an overload occurs between the output terminal T _O1 and the ground potential due to a short circuit or the like, and this overload state continues longer than the time set by the capacitor C _SCP , the control circuit CONT1 outputs the signal from the port OUT. The output of the square wave pulse is stopped and latched in this state. This turns off the first switching transistor Q10,
Overcurrent is prevented from flowing. Further, since the DC-DC converter does not perform the normal boosting operation, the second switching transistor Q11 is also turned off and the input terminal T _IN and the output terminal T _O1 are electrically separated from each other, and the input DC voltage E Are prevented from being applied to the load.

With respect to FIG. 6, C10 is a capacitor for smoothing the input voltage, C11 is a capacitor for smoothing the output voltage, and the resistors R12 and R13 and the Zener diode ZD form a bias circuit for the second switching transistor Q11. ing.

Japanese Patent Laid-Open No. 6-233522 discloses that
In order to operate the second switching transistor Q11 of FIG. 6 in a phase opposite to that of the first switching transistor Q10, a secondary winding is provided in the coil L10, and the output voltage of the secondary winding causes the second switching transistor Q11 to operate.
An example of turning on and off is described.

[0007] Regardless of whether the input DC voltage E is high or low, in the case of a specification that it is necessary to output a constant voltage within the input DC voltage range, a step-up type DC-DC converter and a step-down type There is a need for a step-up / down type DC-DC converter that is combined with a step-down unit composed of a DC-DC converter. FIG. 7 shows an example of such a step-up / down type DC-DC converter. In FIG. 7, the input DC voltage E
Is a value in the range from a small value E ₁ to a large value E ₂ , the output voltage of the step-up unit is V _UP and the output voltage of the step-down unit is V _UP .
_{When DWN} , E ₁ <V _DWN <E ₂ and E ₂ <V _UP .

The operation of outputting the output voltage V _UP in the boosting portion of the step-up / down type DC-DC converter shown in FIG.
Since it is the same as the step-up DC-DC converter of No. 2, the overlapping description will be omitted. In the step-down unit of the DC-DC converter shown in FIG. 7, the switching transistor Q11 is turned on and off by the output from the port OUT of the control circuit CONT2. Switching transistor Q11
Is on (that is, the port OU of the control circuit CONT2
When the output of T is low), the output voltage V _UP of the booster is applied to the capacitor C12 via the coil L11. At this time, energy is simultaneously accumulated in the coil L11. Next, when the output of the port OUT of the control circuit CONT2 becomes high and the switching transistor Q11 is turned off, the energy accumulated in the coil L11 becomes a discharge current in the same direction as when the switching transistor Q11 is on, and the energy is stored in the coil L11 → Capacitor C1
2 → diode D11 → coil L11 flows in a loop,
Further charge the capacitor C12. A load is connected to the capacitor C12, and energy corresponding to the amount of outflow to the load is supplied from the coil L11 so that the capacitor C1
2 so that the output voltage V _{DWN of} V2 is maintained constant, the ON time width of the switching transistor Q11 is controlled by the control circuit CO.
Controlled by NT2.

[0009]

By the way, in the DC-DC converter shown in FIG. 6, since all the load current passes through the second switching transistor Q11 for shutting off, the switching transistor Q11 depends on the maximum value of the load current. It is necessary to set the base bias current of the
Since it is wastefully consumed by 13 and the Zener diode ZD, the efficiency of the entire DC-DC converter is reduced.
This is remarkable as the average value of the load current is smaller and the output voltage is higher. Furthermore, when a short circuit occurs between the output terminal T _O1 and the ground potential, the switching transistor Q is momentarily
Since a large voltage is applied between the collector and the emitter of 11, it is necessary to select a transistor having a large safe operation area as the switching transistor Q11.

On the other hand, the step-up type DC-DC converter performs only the step-up operation, and the step-down type DC-DC converter performs only the step-down operation. As described above, it is necessary to combine the switching circuit of the step-up part and the switching circuit of the step-down part, and the number of parts is approximately doubled. There is a switching power supply that uses a transformer to realize a step-up / down circuit with one switching unit. However, the transformer is not suitable for downsizing, thinning, and cost reduction because of its high volume, high component height, and high cost. is there.

The present invention has been proposed in view of the above problems, and a first object of the present invention is to reduce the number of parts,
To provide a non-insulated DC-DC converter which is small in size, low in cost, low in manufacturing cost, capable of step-up / down operation, and capable of surely disconnecting between an input terminal and an output terminal at the time of overload. Is. A second object of the present invention is to
In addition to the above-mentioned first object, it is to provide a DC-DC converter capable of generating a plurality of different output voltages.

[0012]

In order to achieve the above-mentioned first object, the present invention is a non-insulated DC-DC converter for converting an input DC voltage into an output DC voltage, wherein an input terminal and an output are provided. A switching element provided in series between the terminal, a charging circuit that is charged by the input DC voltage in conjunction with the switching operation of the switching element, and a charging circuit that causes the switching element to perform a switching operation. A control circuit that generates the output DC voltage, stops the switching operation of the switching element at the time of overload, holds the switching element in an open state, and disconnects between the input terminal and the output terminal. Non-insulated DC-characterized by comprising
A DC converter is provided.

More specifically, the first object of the present invention is a non-isolated DC-D that converts an input DC voltage into an output DC voltage.
A C converter, which has an input terminal to which the input DC voltage is applied, a switching circuit whose input side is connected to the input terminal, and an ON / OFF operation of the switching circuit which is connected to the output side of the switching circuit. A first charging circuit that is synchronously charged with a first voltage having a polarity opposite to that of the input DC voltage, and is connected to an output side of the first charging circuit, and is synchronized with ON / OFF operation of the switching circuit. From the second charging circuit, the second charging circuit having a magnitude corresponding to the sum of the input DC voltage and the first voltage and charged to a second voltage having the same polarity as the DC voltage. An output terminal that receives the second voltage and outputs it as the output DC voltage and a third voltage that is proportional to the output DC voltage, and receives a pulse having a pulse width corresponding to the third voltage by the switching circuit. To adjust the ON period and the OFF period of the switching circuit according to the pulse width, and to supply the pulse to the switching circuit when the third voltage becomes smaller than a predetermined magnitude. And a control circuit for stopping the switching circuit and holding the switching circuit in the off state, and a non-insulated DC-DC converter.

In one embodiment of the present invention, such a DC-DC converter has an input terminal to which the input DC voltage is applied, an output terminal from which the output DC voltage can be taken out, and an input to the input terminal. A switching element to which an electrode is connected, a coil connected between an output electrode of the switching element and a reference potential, and charged and discharged in synchronism with ON and OFF operations of the switching element, and the output electrode of the switching element A first capacitor charged by the coil while the switching element is off, and a capacitor connected between the output terminal and the reference potential. And the sum of the input DC voltage and the voltage across the first capacitor while the switching element is on. A second capacitor charged by a voltage and a voltage proportional to the DC output voltage are received, and a pulse having a pulse width corresponding to the voltage is supplied to the control electrode of the switching element to perform the switching according to the pulse width. While adjusting the ON period and the OFF period of the element, when the voltage becomes smaller than a predetermined magnitude, stop the supply of the pulse to the switching element,
And a control circuit that holds the switching element off, and performs a step-up operation and a step-down operation to generate a predetermined output DC voltage regardless of the magnitude of the input DC voltage with respect to the output DC voltage.

In order to achieve the above-mentioned second object, the non-insulated DC-DC converter according to the present invention generates an output voltage having a magnitude and polarity determined by the input DC voltage and the output DC voltage. The circuit further comprises:

[0016]

The first charging circuit is charged with the first voltage having the opposite polarity to the input DC voltage in synchronization with the ON / OFF operation of the switching circuit whose input side is connected to the input terminal. Then, in synchronization with the on / off operation of the switching circuit,
The second charging circuit is charged to a second voltage having a magnitude corresponding to the sum of the input DC voltage and the first voltage and having the same polarity as the DC voltage. This second voltage is taken out as an output DC voltage from the output terminal. Specifically, in FIG. 1, the switching transistor Q provided on the input power supply line
The switching circuit composed of 1 and the coil L1 provides an inverted rectified output via the diode D1 to the capacitor C2 connected to the connection midpoint between the switching transistor Q1 and the coil L1. Furthermore, the input voltage E by the diode D2 and the rectified voltage stored in the capacitor C2 are
It is inverted and added to the capacitor C3. As a result, an output DC voltage having the same polarity as the input voltage E is obtained.

The control circuit adjusts the ON period and the OFF period of the switching circuit according to the pulse width corresponding to the third voltage proportional to the output DC voltage to keep the DC output voltage constant, and The operation of the switching circuit is stopped when the voltage becomes lower than a predetermined value.

With such a configuration, the output DC voltage and the input DC voltage always have the same polarity, and the voltage conversion operation is performed without being restricted by the high level and the low level of the output DC voltage and the input DC voltage. It is possible to Further, since the switching circuit is inserted in series between the input terminal and the output terminal, when the control circuit latches the switching circuit in the operation stop state, the output terminal is cut off from the input terminal.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of the non-insulated DC-DC converter according to the present invention will be described below with reference to FIGS. FIG. 1 shows a non-insulated DC-DC according to the present invention.
It is a circuit diagram which shows the structure of the DC-DC converter of the timer latch system which is 1st embodiment of a converter. An input voltage E is applied between the input terminal T _IN and the ground potential, and a smoothing capacitor C1 for smoothing the input DC voltage E is connected between the input terminal T _IN and the ground potential. The emitter of the switching transistor Q1 is connected to the input terminal T _IN , one end of the switching coil L1 is connected to the collector of the switching transistor Q1, and the other end is grounded. The switching transistor Q1 is connected to resistors R1 and R2 for applying a bias voltage to its base, and one end of the resistor R2 is connected to the port OUT of the control circuit CONT.

One end of an output smoothing capacitor C2 is connected to the connection point between the switching coil L1 and the switching transistor Q1, and the other end of the capacitor C2 is connected to the cathode of the switching diode D1.
The anode of the diode D1 is grounded. Diode D
The cathode of 1 is connected to the anode of another switching diode D2, and the cathode of the diode D2 is connected to the output terminal T _O1 while being grounded via the output smoothing capacitor C3.

Resistors R3 and R4 for detecting the output voltage are connected in series between the output terminal T _O1 and the ground potential, and the voltage across the resistor R4 is connected to the port V _DET of the control circuit CONT. In the control circuit CONT, a capacitor C _SCP for setting a predetermined period is provided at the port SCP and the port GND.
And the port V _CC of the control circuit CONT is connected to the DC input terminal T _IN .

Next, the operation of the DC-DC converter shown in FIG. 1 will be described. The control circuit CONT outputs a square wave pulse having a predetermined ON period and OFF period from the port OUT and applies it to the base of the switching transistor Q1. In response to this, the switching transistor Q1 performs a switching operation. When the switching transistor Q1 is on, the current i ₁ flows in the switching coil L1 in the direction shown, and energy is stored in the coil L1. On the other hand, when the switching transistor Q1 is off, the energy stored in the coil L1 is
Since the current i ₂ is discharged in the loop of the diode D1, the capacitor C2 and the coil L1 and flows in the direction shown in the figure, the capacitor C2 is charged to the polarity shown in the figure. Then, when the switching transistor Q1 is turned on, the coil L1 is turned on again.
Energy is stored in the input DC voltage E, and the input DC voltage E is connected in series with the charging voltage of the capacitor C2. Therefore,
Since a voltage obtained by adding the input DC voltage E and the charging voltage of the capacitor C2 is applied to the capacitor C3 via the diode D2, a current i ₃ is applied to the capacitor C3 in the direction shown in the drawing.
Flows and the capacitor C3 is charged to the voltage of the polarity shown in the figure. Thereafter, similarly, the switching transistor Q1 is repeatedly turned on and off to continue to accumulate the charge in the capacitor C3, and generate the output voltage V ₁ between the output terminal T _O1 and the ground potential.

As described above, in the DC-DC converter shown in FIG. 1, the switching circuit is constituted by the switching transistor Q1 and the coil L1 provided on the power supply line connecting the input terminal T _IN and the output terminal T _O1. To be done. When the switching circuit is off, the energy stored in the coil L1 causes a reverse polarity (that is,
When the diode D1 conducts, the rectified voltage is charged to the capacitor C2 (the positive side of which is the ground side). Further, since the sum voltage of the input voltage E and the voltage accumulated in the capacitor C2 is inverted and applied to the capacitor C3, the capacitor C3 is charged with the voltage having the same polarity as the input direct DC voltage E. The voltage charged in the capacitor C3, and thus the output voltage V ₁ having the same polarity as the input DC voltage
Is given to the load.

It should be noted that the output voltage V ₁ depends on the length of the ON period of the switching transistor Q1.
That is, a pulse-like voltage having a magnitude obtained according to the on-duty ratio (ratio of the on-period to one cycle of the square-wave pulse) of the square-wave pulse applied to the switching transistor Q1 and the voltage across the capacitor C2. That is, it is the voltage obtained by rectifying the pulse voltage obtained by the sum. Therefore, the DC-DC converter of FIG. 1 can eventually perform the boosting operation when the input DC voltage is lower than the output DC voltage, and can perform the step-down operation in the opposite case.

The output voltage V ₁ appearing between the output terminal T _O1 and the ground potential is divided by the resistors R3 and R4, and the resistor R3
The voltage across 4 is applied to the port V _DET of the control circuit CONT. The control circuit CONT monitors the voltage applied to the port V _DET and keeps the output DC voltage V ₁ constant.
Depending on load fluctuations and input DC voltage fluctuations, the port OU
The pulse width of the square wave pulse output from T is determined, and the on / off period of the switching transistor Q1 is adjusted according to this pulse width. As a result, the input DC voltage E
Is lower than the output DC voltage V ₁ , a step-up operation is performed, and when the input DC voltage E is higher than the output DC voltage V ₁ , a step-down operation is performed to keep the output voltage V constant.

Further, the control circuit CONT has a port V _DET.
The voltage across resistor R4 applied to capacitor C _SCP
When it is detected that the voltage has continuously decreased for a certain period of time or more set by, the output of the square wave pulse from the port OUT is stopped and the state is maintained. As a result, the switching transistor Q1 is held in the off state, the input terminal T _IN and the output terminal T _O1 are electrically cut off, and no output voltage is generated at the output terminal T _O1 .

FIG. 2 shows a non-insulated DC-DC according to the present invention.
It is a circuit diagram which shows the structure of the timer latch system DC-DC converter which is 2nd embodiment of a converter. Comparing this with the DC-DC converter of the first embodiment of FIG. 1, a second output terminal T _O2 is provided so that a second load can be connected. That is, the diode D3 is connected to the second output terminal T _O2 . The capacitor C4 is connected between the anode and the cathode of the diode D3 connected to the midpoint of the connection between the coil L1 and the capacitor C2, and between the second output terminal T _O2 and the ground potential.
Are different in the point that they are connected.

In the second embodiment, the capacitor C2 is charged via the diode D1 by the energy stored in the coil L1 while the switching transistor Q1 is off, and at the same time, the capacitor C4 is input via the diode D3. It is charged to a voltage having a polarity opposite to that of the DC voltage E. Therefore, the DC-DC converter shown in FIG. 2 performs the same operation as described in the first embodiment shown in FIG. ₁ to generate the output voltage V ₁ between the output terminal T _O1 and the ground potential, and further , Between the second output terminal T _O2 and the ground potential, a second output voltage V2 having a polarity opposite to the input DC voltage E and having a desired magnitude determined by the input DC voltage E and the output voltage V1. Can be generated.

FIG. 3 shows a non-insulated DC-DC according to the present invention.
It is a circuit diagram which shows the structure of the DC-DC converter which is 3rd embodiment of a converter, DC of 2nd embodiment of FIG.
Compared with a -DC converter, a difference is that a series circuit of a resistor R3 and a resistor R4 is connected between the second output terminal T _O2 and the ground potential.

Also in this third embodiment, the capacitor C2 is charged through the diode D1 by the energy accumulated in the coil L1 while the switching transistor Q1 is off, and at the same time, the capacitor C4 is input through the diode D3. It is charged to a voltage having the opposite polarity to the voltage E. Therefore, the DC-DC converter shown in FIG. 3 performs the same operation as described in the second embodiment shown in FIG. 2 and outputs the output voltage V _O between the output terminal T _O1 and the ground potential.
₁ is generated, and further, between the second output terminal T _O2 and the ground potential, the polarity of the input DC voltage E is opposite to that of the input DC voltage E and the desired output voltage V1. A second output voltage V ₂ can be generated.

By further expanding the second embodiment shown in FIG.
The other output terminal T _{0 1} for outputting an output voltage V _1, it is possible to install additional output terminal for outputting a desired magnitude of the voltage which is determined by the input DC voltage E and the output voltage V _1. FIG. 4 is a fourth embodiment of the non-insulated DC-DC converter according to the present invention, which is a DC-D in which the above-mentioned output terminal is added.
FIG. 3 is a circuit diagram showing an example of a C converter, showing a third output voltage V ₃ and a fourth output voltage V ₁ in addition to the first output voltage V ₁ and the second output voltage V ₂ described in the second embodiment of FIG. In order to take out the output voltage V ₄ of the above, capacitors C5 to C8 and diodes D4 to D7 are additionally connected to the second embodiment as shown in the figure.

Explaining the DC-DC converter of FIG. 4, the energy stored in the coil L1 while the switching transistor Q1 is on is turned off, and then the switching transistor Q1 is turned off. The coil L1 → diode D1 → capacitor C2 → coil It is discharged in the loop of L1 to charge the capacitor C2. At the same time, the energy of the coil L1 is discharged in the loop of the coil L1 → capacitor C4 → diode D3 → coil L1 to charge the capacitor C4 to the polarity shown, and at the same time, the coil L1 → capacitor C4 → capacitor C5 → diode D5 → capacitor C6 → It is discharged in the loop of the coil L1 to charge the capacitor C5 to the polarity shown in the drawing, and the coil L1 → capacitor C4 → capacitor C5 → capacitor C7 → diode D
7 → Capacitor C8 → Capacitor C6 → Discharge in the loop of coil L1 to charge capacitor C7 to the polarity shown. As a result, when the switching transistor Q1 is repeatedly turned on and off as already described in the third embodiment, the output voltages V ₁ and V _{2 having} the polarities as described above are generated.
In addition, the third output voltage V ₃ is taken out to the third output terminal T _O3 and the fourth output voltage V ₄ is taken out to the fourth output terminal T _O4 .

FIG. 5 shows a non-insulated DC according to the present invention.
Is a fifth embodiment of the -DC converter, a circuit diagram showing another example of a DC-DC converter with additional output terminal of the first output voltages V ₁ as described for the second embodiment of FIG. 2 In addition to the above, the capacitors C9 to C13 and the diodes D8 to D1 are added to the second embodiment so that the second output voltage V ₂ and the third output voltage V ₃ can be taken out.
2 is additionally connected as shown.

In the DC-DC converter of FIG. 5, the coil L1 is turned on while the switching transistor Q1 is on.
The energy stored in is discharged through the loop of coil L1 → diode D1 → capacitor C2 → coil L1 while the switching transistor Q1 is off, and charges the capacitor C2 to the polarity shown. Further, the above-mentioned energy is coil L1 → diode D8 → capacitor C
10 → Discharge through the loop of coil L1 and at the same time coil L1 → capacitor C9 → diode D10 →
The capacitor C11 is discharged through the loop of the capacitor C10 and the coil L1 to charge the capacitor C9 to the polarity shown in the figure, and the coil L1 → the capacitor C9 → the capacitor C12 → the diode D12 → the capacitor C13 → the capacitor C11 → the capacitor C10 → the coil L1. Discharged through the loop to charge capacitor C12 to the polarity shown. Therefore, the switching transistor Q1
Are repeatedly turned on and off, the first output terminal T ₀₁ outputs the first output voltage V ₁ , the second output terminal T _O2 outputs the second output voltage V ₂ , and the third output terminal T 2. The third output voltage V ₃ is taken out from _{O 3} , respectively.

[0035]

As will be understood from the detailed description of the configuration and operation of some embodiments of the present invention given above with reference to the drawings, the present invention provides switching in series between an input terminal and an output terminal. By arranging a circuit or switching element to perform both the switching function for voltage conversion and the overload protection function, it is possible to reduce the number of parts, downsize, and reduce the cost compared to the past. In addition, it is possible to reliably prevent the input DC voltage from flowing out to the load during the overload protection operation.

Further, by arranging the switching circuit or the switching element in series between the input terminal and the output terminal, it is possible to take out the output DC voltage depending on the difference in the ON period of the switching circuit or the switching element. Therefore, both the step-up operation and the step-down operation for the input DC voltage are possible.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a timer latch type DC-DC converter which is a first embodiment of a non-insulated DC-DC converter according to the present invention.

FIG. 2 is a circuit diagram showing a configuration of a timer latch type DC-DC converter which is a second embodiment of a non-insulated DC-DC converter according to the present invention.

FIG. 3 is a circuit diagram showing a configuration of a timer latch type DC-DC converter which is a third embodiment of a non-insulated DC-DC converter according to the present invention.

FIG. 4 is a circuit diagram showing a configuration of a timer latch type DC-DC converter which is a fourth embodiment of a non-insulated DC-DC converter according to the present invention.

FIG. 5 is a circuit diagram showing a configuration of a timer latch type DC-DC converter which is a fifth embodiment of a non-insulated DC-DC converter according to the present invention.

FIG. 6 is a conventional step-up DC-D having an overload protection function.
It is a circuit diagram which shows the structure of an example of a C converter.

FIG. 7: Conventional buck-boost DC- with overload protection function
It is a circuit diagram which shows the structure of an example of a DC converter.

[Explanation of symbols]

Q1 switching transistor, L1: switching coil, C1: input voltage smoothing capacitor, C
2, C3: output voltage smoothing capacitor, T _IN : input terminal, T _{O1 to} T _O4 : output terminal, E: input DC voltage,
V ₁ ~V _4: output DC voltage

Claims (4)

[Claims] 1. A non-insulating DC-DC converter for converting an input DC voltage to an output DC voltage, wherein a switching element is provided in series between an input terminal and an output terminal, and a switching operation of the switching element. And a charging circuit that is charged by the input DC voltage in conjunction with, and causes the switching element to perform a switching operation to generate the output DC voltage from the charging circuit, and stop the switching operation of the switching element when overloaded. To hold the switching element in the open state,
And a control circuit for disconnecting the input terminal and the output terminal from each other.
converter. 2. A non-insulated DC-DC converter for converting an input DC voltage to an output DC voltage, comprising: an input terminal to which the input DC voltage is applied; and a switching circuit having an input side connected to the input terminal. A first charging circuit that is connected to the output side of the switching circuit and that is charged with a first voltage having a polarity opposite to that of the input DC voltage in synchronism with ON and OFF operations of the switching circuit; It is connected to the output side of the charging circuit and has a magnitude corresponding to the sum of the input DC voltage and the first voltage in synchronization with the ON / OFF operation of the switching circuit and has the same polarity as the input DC voltage. A second charging circuit that is charged to a second voltage, an output terminal that receives the second voltage from the second charging circuit and outputs the second voltage as the output DC voltage, and a third proportional to the output DC voltage. A voltage is received and a pulse having a pulse width corresponding to the third voltage is supplied to the switching circuit to adjust the ON period and the OFF period of the switching circuit according to the pulse width, and the third voltage A control circuit that stops the supply of the pulse to the switching circuit and keeps the switching circuit off when is smaller than a predetermined magnitude. converter. 3. A non-insulated DC-DC converter for converting an input DC voltage to an output DC voltage, wherein an input terminal to which the input DC voltage is applied and an output terminal from which the output DC voltage can be taken out. A switching element having an input electrode connected to the input terminal; a coil connected between an output electrode of the switching element and a reference potential and charged and discharged in synchronism with ON and OFF operations of the switching element; A capacitor connected between the output electrode of the switching element and a reference potential, the first capacitor being charged by the coil during a period in which the switching element is off, and the output terminal and the reference potential A capacitor connected between the input DC voltage and both ends of the first capacitor while the switching element is on. A second capacitor that is charged by a voltage that is the sum of the voltage and a voltage that is proportional to the output DC voltage, and supplies a pulse having a pulse width corresponding to the voltage to the control electrode of the switching element. The ON period and the OFF period of the switching element are adjusted according to the width, and when the voltage becomes smaller than a predetermined value, the supply of the pulse to the switching element is stopped and the switching element is turned off. And a control circuit for holding the control circuit for holding the input DC voltage, and performing a step-up operation and a step-down operation so as to generate a predetermined output DC voltage regardless of the magnitude of the input DC voltage with respect to the output DC voltage. 4. The non-insulated DC-DC converter according to claim 1, further comprising: an output voltage having a magnitude and polarity determined by the input DC voltage and the output DC voltage. A non-insulated DC-DC converter, further comprising a circuit for generating the voltage.