JP3391329B2 - Non-insulated DC-DC converter - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-insulated DC-DC converter used in an electric vehicle or the like, and more particularly to a non-insulated DC-DC converter used when charging a low voltage battery with electric power from a high voltage battery.

[0002]

2. Description of the Related Art A first example of a conventional non-insulated DC-DC converter is shown in FIG. The non-insulated DC-DC converter shown in FIG. 7 has input terminals 1b, 1d and output terminals 7a, 7
b. A backflow prevention diode 12, a MOSFET 2 and a choke coil 4 are connected in series between the input terminal 1b and the output terminal 7a.

In addition, one end of the diode 3 is a MOSFET
2 is connected between the connection point of the choke coil 4 and one end of the capacitor 5 is connected between the connection point of the choke coil 4 and the output terminal 7a, and the other ends of the diode 3 and the capacitor 5 are the high voltage battery 1 and the low voltage battery. 7 is connected to the negative electrode side (input terminal 1d and output terminal 7b side). The battery terminal 1a of the high voltage battery 1 is connected to the input terminal 1b via the input cable 1c.

The diode 3 is a diode for circulating the current of the choke coil 4 when the MOSFET 2 is switched off. To the control circuit 6, the negative side of the high voltage battery 1 (the input terminal 1d side), the gate of the MOSFET 2 and the other end of the capacitor 5 are connected. The output terminal 7a is connected to the low voltage battery 7.

In such a configuration, the control circuit 6 drives the MO
By applying a pulse voltage to the gate of SFET2,
The on / off operation of the MOSFET 2 is controlled so that the low voltage battery 7 is charged with the electric power from the high voltage battery 1.

Further, the control circuit 6 fails and the capacitor 5
Becomes an overvoltage, the MOSFET 2 is turned off and the output of the overvoltage is prevented. Further, the backflow prevention diode 12 prevents the reverse current from flowing from the low voltage battery side to the high voltage battery side.

[0007]

By the way, in the above-mentioned conventional non-insulated DC-DC converter, the MOSFET is used.
When 2 is short-circuited due to overvoltage or the like, the power conversion function of the DC-DC converter does not function, and the high-voltage battery voltage appears between the low-voltage output terminals 7a and 7b. Furthermore, an overcurrent from the high voltage battery 1 flows into the non-insulated DC-DC converter via the input cable 1c, the input cable 1c is damaged by heat, and the internal elements of the non-insulated DC-DC converter are damaged. There is a problem of doing. Further, when an electronic device is connected to the non-insulated DC-DC converter, there is a problem that an internal element of the electronic device is damaged.

When the polarities of the low voltage battery 7 are reversed and connected to the output terminals 7a and 7b, the low voltage battery 7
There is also a problem that a short-circuit current flows through the diode 3 due to the reverse flow from the diode 3, and the diode 3 and the like are damaged.

The present invention has been made in order to solve the above-mentioned problems, and by preventing damage to the internal elements due to overvoltage or reverse current, it is possible to appropriately supply electric power and increase the cost. Non-insulated D that can be suppressed
An object is to provide a C-DC converter.

[0010]

To achieve the above object, a non-insulated DC-DC converter according to the present invention includes a first MOSFET and a reactor between a positive end of a high voltage battery and a positive end of a low voltage battery. And the second MOSF
A series circuit with ET is connected so that the first MOSFET is located on the high voltage battery side, one end of the capacitor is between the connection point of the reactor and the second MOSFET, and the other end is the high voltage battery. Connect the diode between the negative terminals of the low voltage battery and the
The terminal of the first MOSFET and the reactor is
Between the connection points, and at the anode end the high voltage battery and the low voltage
Connect it so that it is located between the connection points of the negative electrodes of the battery.
Next, in a non-insulated DC-DC converter for charging a low-voltage battery with electric power from a high-voltage battery, which includes a control circuit for performing pulse control on the first MOSFET, the voltage of the capacitor and the low-voltage battery
The voltage is detected and the polarity of the low voltage battery is opposite.
That the second MOSFET is turned off at this time.
Then, the short circuit current due to the reverse polarity connection of the low voltage battery
A first control circuit for blocking is provided (first invention).

In the first invention, the second M
The high-voltage battery side of the OSFET is controlled by the first control circuit and is controlled by the second MOSFET.
A third MOSFET connected in the reverse direction with respect to T is provided, and the first control circuit is used to charge the capacitor.
Voltage and voltage of the low voltage battery to detect the voltage
If the voltage on the low voltage battery side is higher than
May be detected, and at this time, the first control circuit may turn off the third MOSFET (second invention).

In the first invention, the first MOS is provided.
A high-voltage battery side of the FET is provided with a fourth MOSFET which is controlled by the second control circuit and is connected in the reverse direction to the first MOSFET.
The second control circuit detects the input voltage and reverses the input voltage.
It may be possible to detect that the polarity is changed, and at this time, the second control circuit may turn off the fourth MOSFET (third invention).

Further, in the second invention, the first control circuit is connected between the high-voltage battery side of the first MOSFET and the second MOSFET, and the second MOSFET is connected.
A first driving power source for driving the OSFET, and the first M
The high-voltage battery side of the OSFET and the third MOSFE
A second drive power source connected to the T and driving the third MOSFET, and a low voltage battery side of the second MOSFET are connected in parallel to the low voltage battery to detect the connection state of the low voltage battery. In addition, when the connection of the low-voltage battery is normal, the first detection circuit for driving the first and second drive power supplies and the capacitor are connected in parallel to detect an overvoltage at one end of the capacitor. And a second detection circuit that stops driving the first drive power supply when the overvoltage is detected (fourth invention).

In the first to fourth inventions, the fifth MOSFET turned on / off by the switch circuit is
The first control circuit is connected in series with the capacitor, and the first control circuit is connected between the high-voltage battery side of the first MOSFET and the second MOSFET.
A first drive power supply for driving the MOSFET of the
And a third detection circuit connected in parallel to the high voltage battery on the high voltage battery side of the MOSFET, the third detection circuit, when detecting an input overvoltage, the fifth MOSFET via the switch circuit. May be turned off, the driving of the first drive power supply may be stopped, and the first MOSFET may be turned off via the control circuit (fifth invention).

In the fifth invention, the first MOS is provided.
A first resistor is connected in parallel between the input and output of the FET, the low voltage battery side of the first MOSFET and the high voltage battery side of the capacitor are connected in parallel to the capacitor, and the anode side is the first side. And the second MOS
The second diode is connected to the side of the series connection point of the FET .
Said resistors are connected in parallel, and said first MOSFE
The maximum allowable voltage on the high voltage battery side of T is the first M
It may be determined by the OSFET and the diode and the first and second resistors . (Sixth invention)

Further, in a fourth aspect of the invention, the first drive power source is configured such that a fourth detection circuit causes the second MOSFET to operate.
When the drivable voltage is detected, the second driving power source is instantaneously driven, and the second driving power source is driven by the fifth detection circuit.
When the drivable voltage of the MOSFET is detected, it may be driven instantaneously (seventh invention).

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. In the drawings described below, the same parts as those in FIG. 7 are designated by the same reference numerals.

(First Embodiment) FIG. 1 is a circuit diagram showing a first embodiment of a non-insulated DC-DC converter of the present invention.

The non-insulated DC-DC converter shown in FIG. 1 has input terminals 1b and 1d and output terminals 7a and 7b. A first MOSFET 2, a choke coil 4 and a second MOSF are provided between the input terminal 1b and the output terminal 7a.
ET8 is connected in series.

In addition, one end of the diode 3 is a MOSFET
2 and the choke coil 4 are connected, one end of the capacitor 5 is connected between the choke coil 4 and the output terminal 7a, and the other end of the diode 3 and the capacitor 5 is the input terminal 1d and the output terminal. It is connected between 7b.

One end of the capacitor 5 and the output terminal 7a are connected to the first control circuit 9. The first control circuit 9 controls the second MOSFET 8. Input terminal 1b
A battery terminal 1a of the high-voltage battery 1 is connected to the battery via an input cable 1c.

The negative side of the high voltage battery 1 (the side of the input terminal 1d), the gate of the first MOSFET 2 and one end of the capacitor 5 are connected to the control circuit 6. Output terminal 7
The a and 7b are connected to the positive electrode and the negative electrode of the low voltage battery 7. Next, a non-isolated DC-DC having such a configuration
The operation of the converter will be described.

First, when the voltage applied to the input terminals 1b and 1d is normal, the control circuit 6 causes the first MOSFET 2 to
By applying a pulse voltage to the gate of the
The on / off operation of the SFET 2 is controlled, and the low voltage battery 7 is charged with the electric power from the high voltage battery 1. At this time, the second MOSFET 8 is turned on by the first control circuit 9.

Here, when the first MOSFET 2 is damaged by overvoltage or the like and is in a short-circuit state, the capacitor 5 becomes overvoltage, the first control circuit 9 detects the overvoltage of the capacitor 5, and the second MOSFET 8 is turned off. To do. As a result, the high voltage battery voltage is not directly applied to the low voltage side output terminal. Furthermore, the inflow of overcurrent from the high voltage battery 1 via the input cable 1c is prevented.

When the polarities of the low voltage battery 7 side connected to the output terminals 7a and 7b are reversed, the first control circuit 9 detects the capacitor voltage value and the polarity, and
The MOSFET 8 is turned off. As a result, the short circuit current flowing through the diode 3 is blocked by the reverse current from the low voltage battery 7.

As described above, in the first embodiment, the first
In the case where the MOSFET 2 has a short circuit failure due to an overvoltage or the like and the capacitor 5 has an overvoltage, the first control circuit 9 turns off the second MOSFET 8. Therefore, the high voltage battery voltage is directly applied between the low voltage side output terminals. It is not applied, and further, it is possible to prevent the input cable 1c from being damaged by heat and the internal element of the non-insulated DC-DC converter from being damaged. Also, non-insulated DC-D
Even when an electronic device is connected to the C converter, it is possible to prevent damage to internal elements of the electronic device.

(Second Embodiment) FIG. 2 is a circuit diagram showing a second embodiment of the non-insulated DC-DC converter of the present invention. In the second embodiment, the third MOSFET 10 is connected in series to the input terminal 1b side of the second MOSFET 8. Third MOS
The FET 10 is connected in the reverse direction to the second MOSFET 8.

The second MOSFET 8 and the third M
The OSFET 10 is controlled by the first control circuit 9. The first control circuit 9 detects the voltage of the capacitor 5 and the voltage of the low voltage battery 7.

In such a configuration, the input terminals 1b, 1d
When the voltage applied to the first MOSFET 2 is normal, a pulse voltage is applied from the control circuit 6 to the gate of the first MOSFET 2 to control the on / off operation of the first MOSFET 2 and the power from the high voltage battery 1 is supplied. The low voltage battery 7 is charged. At this time, the second MOSFET 8 and the third MOSFET 8
MOSFET 10 is turned on by the first control circuit 9.

When the input cable 1c is connected to the 0V side as shown by the dotted line in the figure or the connection of the input cable 1c is disconnected, the voltage of the battery 1 side, which should be originally high voltage, that is, the voltage of the capacitor 5 is lower than the low voltage battery voltage. Since it becomes lower, the voltage of the capacitor 5 is detected by the first control circuit 9, and the third MO is detected by the first control circuit 9.
The SFET 10 is turned off.

As a result, the problem caused by the voltage of the battery 1 side, that is, the capacitor 5 becoming lower than the low voltage battery voltage due to the grounding or disconnection of the input cable is eliminated. Further, the operation of the second MOSFET 8 is the same as that of the first embodiment, and therefore the description thereof is omitted here.

(Third Embodiment) FIG. 3 is a circuit diagram showing a third embodiment of the non-insulated DC-DC converter of the present invention.

In the third embodiment, the first MOSFE
The fourth MOSFET 20 is connected in series to the input terminal 1b side of T2. The fourth MOSFET 20 is connected in the opposite direction to the first MOSFET 2.

The fourth MOSFET 20 is controlled by the second control circuit 11A. The second control circuit 11A detects the voltage of the input terminal 1b, and thus detects the source-side voltage of the fourth MOSFET 20.

With such a configuration, when the voltage applied to the input terminal 1b is normal, the control circuit 6 causes the first MOS
By applying the pulse voltage to the gate of the FET 2, the on / off operation of the first MOSFET 2 is controlled, and the low voltage battery 7 is charged with the electric power from the high voltage battery 1. At this time, the second MOSFET 8 and the fourth MOS
The FET 20 is turned on by the first control circuit 9 and the second control circuit 11A, respectively.

When the polarities of the high voltage battery 1 connected to the input terminals 1b and 1d are reversed, the input terminal 1
Since the voltages of b and 1d are below the specified value or have opposite polarities,
The second control circuit 11A detects the input voltage and turns off the fourth MOSFET 20. As a result, the short-circuit current flowing through the diode 3 is blocked.

The operation of the second MOSFET is the same as that of the first embodiment described above, and the detailed description thereof is omitted here. In each of the above-described embodiments, the case where the first to fourth MOSFETs 2, 8, 10 and 20 have N-channels has been described, but the present invention is not limited to this, and P-channel MOSFETs can be used.

(Fourth Embodiment) FIG. 4 is a circuit diagram showing a fourth embodiment when the configuration of the non-insulated DC-DC converter shown in FIG. 2 is changed.

In the fourth embodiment, the non-isolated DC shown in FIG.
-A drive power supply 11 as a first drive power supply, a drive power supply 12 as a second drive power supply, a detection circuit 13 as a first detection circuit, and a detection circuit 14 as a second detection circuit are added to the DC converter. is doing.

The drive power source 11 is a drive source of the second MOSFET 8 and is provided between the input terminal 1b side of the first MOSFET 2 and the gate of the second MOSFET 8. The drive power supply 11 also includes a diode 11-1, a zener diode 11-2, a resistor 11-3, and a capacitor 11-4.

The drive power source 12 is the third MOSFET 10
Drive source of the first MOSFET 2 input terminal 1b
It is provided between the side and the gate of the fourth MOSFET 10. In addition, the drive power source 12 is a diode 12-
1, a Zener diode 12-2, a resistor 12-3, and a capacitor 12-4.

The detection circuit 13 detects the output voltage to the low voltage battery 7, and is connected in parallel with the low voltage battery on the output terminals 7a and 7b side of the second MOSFET 8. Further, the detection circuit 13 includes a photo coupler 13-
1, 13-2 and a resistor 13-3.

The detection circuit 14 detects the output overvoltage and is connected in parallel to the capacitor 5. Also,
The detection circuit 14 includes a photo coupler 14-1, a resistor 14-
2, the Zener diode 14-3 is provided.

In such a configuration, the charging voltage of the capacitor 11-4 of the driving power supply 11 is limited only when the high voltage battery 1 and the low voltage battery 7 are properly connected to the input terminals 1b and 1d and the output terminals 7a and 7b, respectively. Turns on the second MOSFET 8. At this time, the third M
The OSFET 10 is a capacitor 12-4 of the driving power supply 12.
It is turned on by the charging voltage of.

When the charging voltage of the capacitor 5 becomes an overvoltage, the detection circuit 14 short-circuits the capacitor 11-4 and turns off the second MOSFET 8. When the low voltage battery 7 is reversely connected to the output terminals 7a and 7b, the second
Supply of gate power to the MOSFET 8 and the third MOSFET 10 is stopped, and both MOSFETs are turned off.

Input terminals 1b and 1d and output terminals 7a and 7
When the high-voltage battery 1 and the low-voltage battery 7 are reversely connected to b, the zener diode 11-2 of the driving power supply 11 prevents the capacitor 11-4 from being charged. Further, the zener diode 12- of the drive power source 12-
2, the charging of the capacitor 12-4 is also blocked.
As a result, the second MOSFET 8 and the third MOSFET
Both 10 and 10 are turned off.

As described above, in the fourth embodiment, the second
Drive voltages of the MOSFET 8 and the third MOSFET 10 of the capacitors 11-4 and 12- of the drive power supplies 11 and 12.
Since it is obtained by the charging voltage of No. 4, the power consumption can be significantly reduced as compared with the conventional drive circuit including a transformer.

Further, unlike the conventional case, the transistor and the IC for operating the oscillator and the drive circuit, which are required for the control circuit, are unnecessary, so that the increase in the number of parts can be suppressed and the cost can be reduced. It is possible to reduce the size.

(Fifth Embodiment) FIG. 5 is a circuit diagram showing a fifth embodiment when the configuration of the non-insulated DC-DC converter in FIG. 2 is changed.

In the fifth embodiment, non-isolated DC-DC is used.
On the input side of the converter, a detection circuit 9a as a third detection circuit for detecting the input voltage is connected between the input terminals 1b and 1d. The detection circuit 9a includes a Zener diode 9-
1, a resistor 9-2, and photocouplers 9-3 to 9-5. The detection output of the photocoupler 9-5 is the control circuit 6b.
To be given to.

The control circuit 6b is adapted to input the detection signal of the detection circuit 9a to the control circuit 6 shown in FIGS. A second MOS is provided between the input terminal 1b and the output terminal 7a of the non-insulated DC-DC converter.
A drive power supply 6a for driving the FET 8 is connected. The driving power supply 6a includes a diode 6-1, a resistor 6-
2 and a capacitor 6-3. Capacitor 6-3
Is short-circuited by the photocoupler 9-3 of the detection circuit 9a when an overvoltage occurs at the input terminals 1b and 1d, and the second M
OSFET8 is turned off.

A first resistor 2a is provided between the source and drain of the first MOSFET 2, and a second resistor 3a is provided at both ends of the diode 3 and the first resistor 2a is provided. And the second resistor 3a, the input terminal 1
It constitutes a voltage divider between the voltages b and 1d.

Choke coil 4 and second MOSFET 8
A switch circuit 5a is provided between the input terminal 1d and the output terminal 7b. The switch circuit 5a is
Capacitor 5-1, resistor 5-2, fifth MOSFET 3
It has 0.

When an overvoltage (input overvoltage) occurs between the input terminals 1b and 1d, the photocoupler 9-4 of the detection circuit 9a.
Thus, the fifth MOSFET 30 is turned off by short-circuiting the gate and source of the MOSFET 30. Further, when the input overvoltage is detected by the detection circuit 9a,
The capacitor 6-3 is short-circuited by the photocoupler 9-3, and the second MOSFET 8 is also turned off. Further, the control circuit 6b also turns off the first MOSFET 2 by the detection signal of the photocoupler 9-5.

Next, MOSFETs 2, 8, 10 and 3
The operation after 0 is turned off will be described. MOSFET
When 2, 8, and 30 are turned off, choke coil 4
Since the current continues to flow through the diode, this current is diode 3 → choke coil 4 → capacitor 5-1 and MOSFE.
It flows on the route of T30. The current of the choke coil 4 is Δ
It becomes zero at the time of t = (L / V0) I0. Here, L is the value of the choke coil 4, V0 is the sum of the voltage of the capacitor 5-1 and the voltage of the MOSFET 30, and I0 is the current flowing through the choke coil 4. Since the MOSFET 30 has already been turned off, the voltage of the MOSFET 30 becomes the avalanche voltage.

When the current of the choke coil 4 becomes zero, the input terminal 1b. The circuit connected to 1d is the first MO
Only SFET2 and diode 3 are provided. This allows
The sharing of the input voltage of the first MOSFET 2 and the diode 3 is the sharing of the voltage determined by the voltage dividers 2a and 3a.
As a result, the maximum allowable input voltage is
While it is determined by the breakdown voltage of T2, in the fifth embodiment, it is the sum of the breakdown voltage of MOSFET 2 and the breakdown voltage of diode 3.

As described above, in the fifth embodiment, when the input overvoltage is detected by the detection circuit 9a, the second M
OSFET8, fifth MOSFET30, first MOS
Since the FET2 is turned off at the same time, the maximum allowable voltage of the input is conventionally determined by the breakdown voltage of the MOSFET2, whereas the breakdown voltage of the MOSFET2 and the diode 3
Withstand voltage of

In a specific example, the first MOSFET 2 and the diode 3 are 100 V withstand voltage elements, and non-insulated DC is used.
-If the DC converter is operating within 100V, the maximum allowable voltage is 200V. As a result, the first MO
Since it is not necessary to adopt a high withstand voltage SFET 2, it is possible not only to prevent a decrease in efficiency but also to suppress an increase in cost.

(Sixth Embodiment) FIG. 6 is a circuit diagram showing a sixth embodiment when the configuration of the non-insulated DC-DC converter shown in FIG. 4 is changed.

In the sixth embodiment, the non-isolated DC shown in FIG. 4 is used.
-Detection circuit 15, 1 for detecting voltage in DC converter
6 is added.

The detection circuit 15 as the fourth detection circuit is
It detects the drivable voltage of the second MOSFET 8, and includes a Zener diode 15-1 and a photocoupler 15.
-2 is provided. Detection circuit 1 as fifth detection circuit
Reference numeral 6 detects a drivable voltage of the third MOSFET 10, and includes a Zener diode 16-1 and a photocoupler 16-2.

In such a configuration, when the Zener diode 15-1 of the detection circuit 15 reaches the driveable voltage of the second MOSFET 8 or more, it is directly connected to the detection circuit 13 by the photocoupler 15-2.

When the Zener diode 16-1 of the detection circuit 16 reaches the driveable voltage of the third MOSFET 10 or higher, the photocoupler 16-2 causes the detection circuit 1 to be detected.
Directly connected to 3. As a result, the photocouplers 13-1 and 13-2 of the detection circuit 13 cause the second MOSFET to operate.
8. The third MOSFET 10 is instantly turned on.

As described above, in the sixth embodiment, the Zener diode 15-1 of the detection circuit 15 or the detection circuit 1 is used.
6 Zener diode 16-1 is the second MOSFET
8 or the voltage that can be driven by the third MOSFET 10 or higher is reached, the second MOSFET 8 and the third MOSFET
Since T10 is turned on instantly, the second MO
The loss of the SFET 8 and the third MOSFET 10 can be reduced, and a low-cost element can be used.

[0065]

EFFECTS OF THE INVENTION Non-isolated DC-D constructed as described above.
The C converter turns off the second MOSFET provided on the output side of the first MOSFET by the first control circuit when an overvoltage occurs, and when the current on the output side flows backward, The first control circuit turns off the second or third MOSFET having the same polarity as the reverse current, and when the current on the input side flows backward, the second control circuit turns off the third MOSFET. By doing so, it is possible to prevent damage to internal elements due to overvoltage or reverse current.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a non-insulated DC-DC converter of the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of a non-insulated DC-DC converter of the present invention.

FIG. 3 is a circuit diagram showing a third embodiment of a non-insulated DC-DC converter of the present invention.

FIG. 4 is a circuit diagram showing a fourth embodiment when the configuration of the non-insulated DC-DC converter shown in FIG. 2 is changed.

5 is a circuit diagram showing a fifth embodiment in which the configuration of the non-insulated DC-DC converter shown in FIG. 2 is changed.

FIG. 6 is a circuit diagram showing a sixth embodiment when the configuration of the non-insulated DC-DC converter shown in FIG. 4 is changed.

FIG. 7 is a circuit diagram showing an example of a conventional non-insulated DC-DC converter.

FIG. 8 is a diagram for explaining MOSFET characteristics.

[Explanation of symbols]

1 High-voltage battery 1a Battery terminal 1b, 1d Input terminal 1c Input cable 2 1st MOSFET 2a, 3a Voltage divider 3 Diode 4 Choke coil 5 Capacitor 5-1, 6-3, 11-4, 12-4 Capacitor 5- 2, 6-2, 9-2, 11-3, 12-3, 13-
3, 14-2 resistor 5a switch circuit 6, 6b control circuit 6-1, 11-1, 12-1 diode 6a, 11, 12 drive power supply 7 low-voltage battery 7a, 7b output terminal 8 second MOSFET 9 first Control circuits 9-1, 11-2, 12-2, 14-3, 15-1, 1
6-1 Zener diodes 9-3 to 9-5, 13-1, 13-2, 14-1, 15
-2, 16-2 Photocouplers 9a, 13, 14, 15, 16 Detection circuit 10 Third MOSFET 11A Second control circuit 20 Fourth MOSFET 30 Fifth MOSFET

Claims (7)

(57) [Claims] 1. A first MOSFET, a reactor and a second MOSFET between a positive electrode end of a high voltage battery and a positive electrode end of a low voltage battery.
And a series circuit connected to the first MOSFET so that the first MOSFET is located on the high voltage battery side, and one end of a capacitor is connected to the reactor and the second MOS.
The diode is connected between the connection point with the FET and the other end is connected between the connection points between the negative terminals of the high-voltage battery and the low-voltage battery, and the diode is connected with the first MOSFET at the cathode end.
Between the connection point with the reactor and the anode end
Connection point between the negative terminals of the pressure battery and the low voltage battery
In a non-isolated DC-DC converter for connecting electric power from a high-voltage battery to a low-voltage battery, the control circuit including a control circuit connected in between and performing pulse control for the first MOSFET, and the voltage of the capacitor and the voltage of the capacitor. The voltage of the low voltage battery
It is detected that the polarity of the low voltage battery is reversed.
At this time, turn off the second MOSFET,
Prevents short circuit current due to reverse polarity connection of low voltage battery
The first of the non-isolated DC-DC converter comprising a control circuit for so. 2. A high-voltage battery side of the second MOSFET is provided with a third MOSFET which is controlled by the first control circuit and which is connected in an opposite direction to the second MOSFET. , The voltage of the capacitor by the first control circuit and the
The voltage of the low voltage battery is detected and one of the capacitors is detected.
Detects that the voltage on the low voltage battery side is higher than the end
However, at this time, the non-isolated DC-DC converter according to claim 1, wherein the third MOSFET is turned off by the first control circuit. 3. The high-voltage battery side of the first MOSFET is controlled by a second control circuit, and
A fourth MOSFET reversely connected to the first MOSFET is provided, and the second control circuit detects the input voltage and reverses the input voltage.
The non-isolated DC-DC converter according to claim 1, wherein the second control circuit turns off the fourth MOSFET at the time of detecting that the polarity is changed . 4. The first control circuit comprises the first MOS
A first drive power source connected between the high voltage battery side of the FET and the second MOSFET to drive the second MOSFET; a high voltage battery side of the first MOSFET and the third
Connected to the MOSFET of the third MOSF
A second drive power source for driving the ET and a low-voltage battery side of the second MOSFET are connected in parallel to the low-voltage battery to detect a connection state of the low-voltage battery and to normally connect the low-voltage battery. In this case, a first detection circuit that drives the first and second drive power supplies is connected in parallel to the capacitor, and an overvoltage at one end of the capacitor is detected, and when the overvoltage is detected, the first detection circuit The 2nd detection circuit which stops drive of a drive power supply is provided, The non-insulation DC-DC converter of Claim 2 characterized by the above-mentioned. 5. A fifth MOSFET, which is turned on / off by a switch circuit, is connected in series to the capacitor, and the first control circuit includes a high voltage battery side of the first MOSFET and the second MOSFET. A first drive power source connected between the first MOSFET and the second MOSFET, and a third detection circuit connected in parallel to the high voltage battery on the high voltage battery side of the first MOSFET, The third detection circuit, when detecting an input overvoltage, turns off the fifth MOSFET via the switch circuit and stops driving of the first drive power supply,
The non-insulated DC-DC converter according to claim 1, further comprising turning off the first MOSFET via the control circuit. 6. A first circuit is provided between the input and output of the first MOSFET .
One resistor is connected in parallel, the low voltage battery side of the first MOSFET and the high voltage battery side of the capacitor are connected in parallel to the capacitor, and the anode side of the first and second MO
The is connected to a diode in series connection point side of the SFET
2 resistors are connected in parallel, and the maximum allowable voltage on the high-voltage battery side of the first MOSFET is the same as that of the first MOSFET and the diode.
The non-isolated DC-DC converter according to claim 5, wherein the non-isolated DC-DC converter is determined by the first and second resistors . 7. The first drive power supply is instantaneously driven when a driveable voltage of the second MOSFET is detected by a fourth detection circuit, and the second drive power supply is a fifth drive power supply. The non-insulated DC-DC converter according to claim 4, wherein when the drivable voltage of the third MOSFET is detected by the detection circuit, it is driven instantaneously.