JP2012023803A - Dc-dc converter for driving motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DC-DC converter that can be used in a situation that an input-side power supply voltage and an output-side voltage are drastically changed by a load, and that can output an electric power exceeding an electric power supplied from a power supply without using a high-capacity power supply or a high-capacity secondary battery when the load is large.SOLUTION: A DC-DC converter includes: a capacitor that charges an output from a rectification circuit for rectifying an output of an AC power supply; a secondary battery connected in parallel to the capacitor; and a main choke coil and a main switch connected in series between the capacitor and the secondary battery.

Description

  The present invention relates to a DC-DC converter, and more particularly to power supply to a motor drive circuit.

2. Description of the Related Art Conventionally, a DC-DC converter that converts a direct current high voltage power source to a lower voltage direct current constant voltage power source is known. In such a DC-DC converter, a DC power supply having a large current capacity and a high voltage is used, and a predetermined DC constant is set by ignoring power loss by a PWM system that controls the ON interval of the switch element according to the load current. Make a voltage.

  On the other hand, a DC constant voltage DC-DC converter using a choke coil is already known. In this case, the choke coil is a high-frequency cutoff filter, and is used to store energy in the coil at the convex part of the rectangular wave created by switching, and to supply current at the concave part to flatten the output. .

For example, driving an electric vehicle motor that requires a large amount of electric power requires a large amount of electric power during acceleration. In order to cope with such a situation, an electric double layer capacitor, so-called super capacitor, is connected in parallel with the secondary battery and charged with the same voltage that is about 1.4 times the rated voltage of the secondary battery. It has been shown that the electric charge stored in the capacitor can be used for supplying a large amount of electric power during acceleration by utilizing the characteristics superior to those of the secondary battery.

In particular, as for electric vehicles, the capacity on the power supply side is limited and the load fluctuation is large. Therefore, in the existing DC-DC converter, the power supply voltage on the input side and the voltage of the secondary battery output to the motor are greatly increased. In such a situation where there is a fluctuation, there is a problem in that the PWM method cannot be handled by the condition that the capacity of the power source is sufficient, the voltage is constant, and the load fluctuation is small.

Driving a secondary battery and a motor connected thereto can be realized by using a large-capacity power source and a secondary battery. However, for example, in a limited weight and cost system such as a small electric vehicle having a weight of 250 kg or less, there is a problem that a solution by using a large capacity power source and a large amount of a secondary battery is not preferable in terms of cost and weight. It was.

  For example, when accelerating an electric vehicle, the acceleration is proportional to the output torque of the driving motor. The motor torque is proportional to the instantaneous power supplied to the motor. In order to supply sufficient instantaneous power from the in-vehicle secondary battery, a sufficient electrode area is required to reduce the internal resistance of the battery, and as a result, the secondary battery capacity increases. Increasing the secondary battery capacity has a problem in that the battery weight increases, leading to an increase in the size of the vehicle body structure that supports the secondary battery capacity, which causes a fundamental increase in cost.

  An electric vehicle has a heavy load during acceleration, and it must supply power to the motor that exceeds the power supplied from the power source such as a generator. Conventionally, by increasing the capacity of the secondary battery that stores the generator output, In response, the weight increased. An invention of a DC-DC converter that supplies such a large power load during acceleration that addresses such a situation is desired.

  That is, it is a DC-DC converter that can be used in a situation where the voltage of the power supply on the input side and the voltage on the output side fluctuate greatly depending on the load, and does not use a large capacity power supply or a large capacity secondary battery. In addition, there is a demand for a DC-DC converter that can output power exceeding the power supplied from the power source when the load is large.

  In order to solve the above-described problem, a DC-DC converter according to an embodiment of the present invention includes a capacitor that stores an output from a rectifier circuit that rectifies an output of an AC power supply, and a secondary connected in parallel with the capacitor. And a main choke coil and a main switch connected in series between the capacitor and the secondary battery.

In order to solve the above-described problem, a method for controlling a DC-DC converter according to an embodiment of the present invention includes a rectifier circuit connected to a power source and rectifying an output from the power source, and an output from the rectifier circuit. A capacitor for storing electricity, a secondary battery connected in parallel with the capacitor, a sub-choke coil and a sub-switch connected in series between the rectifier circuit and the capacitor, and between the capacitor and the secondary battery A control method of a DC-DC converter including a sub-choke coil and a sub-switch connected in series,
Controlling the sub-semiconductor switch based on a potential difference between the output voltage of the rectifier circuit and a terminal voltage of the capacitor and a current flowing in the semiconductor switch;
And changing the driving frequency of the main semiconductor switch circuit to control the impedance of the main choke coil as a function of the terminal voltage of the capacitor and the potential difference of the secondary battery.

It is the schematic of the motor drive small vehicle which uses the engine generator in which this invention is mounted as a power supply. It is a figure of the electric power control relationship of the capacitor | condenser at the time of driving | running | working of the motor drive small vehicle according to this invention, and a secondary battery. It is a figure which shows embodiment of the DC-DC converter according to this invention. It is a flowchart which shows the subswitch control method at the time of steady operation using the DC-DC converter according to this invention. It is a flowchart which shows the main switch control method at the time of steady operation using the DC-DC converter according to this invention. It is a flowchart which shows the main switch control method at the time of the charge which used the household outlet using the DC-DC converter according to this invention as a power supply. It is a figure which shows embodiment of the DC-DC converter according to this invention.

(General description of the invention)
A DC-DC converter according to an embodiment of the present invention includes a capacitor that stores an output from a rectifier circuit that rectifies an output of an AC power supply, a secondary battery connected in parallel with the capacitor, the capacitor, and the secondary battery. Between the main choke coil and the main switch connected in series.

  In the DC-DC converter having such a configuration, in order to prevent an overcurrent of the rectifier circuit, the auxiliary choke coil connected in series between the rectifier circuit and the capacitor and the charge of the capacitor charged with a high voltage are accelerated. A main choke coil connected in series between the capacitor and the secondary battery for use as an instantaneous power source is placed in order to provide high power to the motor without applying an overvoltage to the secondary battery and the motor. It can be controlled to change the impedance of the choke coil and drop the voltage without power loss.

  The main choke coil has a diode connected in parallel to the coil with the secondary battery side as the anode in order to prevent overvoltage from being applied to the secondary battery, capacitor or switch due to the counter electromotive force generated in the coil when the current is interrupted. May be.

  In the DC-DC converter having such a configuration, the charging current is positive in all phases, but a direct current level shift can be realized by using an impedance change proportional to the frequency of the current fluctuation of the choke coil. .

The DC-DC converter having such a configuration controls the power accumulated in the capacitor by leveling the output fluctuation of the DC-DC converter due to a large load fluctuation using a large-capacity capacitor such as an electric double layer type. Thus, output control is possible, and the maximum power that can be supplied by the power supply can be used effectively.

The DC-DC converter according to another embodiment of the present invention is characterized in that the power source is an engine generator having a significantly smaller output than the maximum power consumption of the motor.

  Further, if such a DC-DC converter is applied to an electric vehicle, the maximum power that can be supplied by the power source can be used effectively, so that the secondary battery capacity does not have to be large. Thereby, the manufacturing cost of the electric vehicle can be suppressed.

  A DC-DC converter according to another embodiment of the present invention is connected to an AC power supply, and rectifies a rectifier circuit that rectifies an output from the power supply, a capacitor that stores an output from the rectifier circuit, and is connected in parallel to the capacitor. A secondary battery, a secondary choke coil and a secondary switch connected in series between the rectifier circuit and the capacitor, a primary choke coil and a primary switch connected in series between the capacitor and the secondary battery, , Including.

  In the DC-DC converter having such a configuration, in order to prevent an overcurrent of the rectifier circuit, the sub choke coil and the sub switch connected in series between the rectifier circuit and the capacitor, and the charge of the capacitor charged with a high voltage are used. A main choke coil and a main switch connected in series between the capacitor and the secondary battery for use as an instantaneous power source during acceleration are arranged, and the motor is powered with high power without applying an overvoltage to the secondary battery and the motor. Therefore, the impedance of the choke coil can be changed independently to reduce the voltage without power loss.

The DC-DC converter having such a configuration performs leveling using a capacitor even if the amount of change in the output power of the motor is large compared to the limited amount of power output from the generator. By charging the capacitor with electric power from the power source and using the stored electric power to output a large amount of power for a short time, the electric power that can be supplied by the generator can be used effectively.

  In the DC-DC converter according to the present embodiment, a power control system that equalizes driving power fluctuations associated with changes in the driving mode of acceleration, constant speed operation, and stop of an automobile within the capacity of the on-vehicle generator is constructed. By significantly reducing the battery capacity, it is possible to achieve a reduction in price and weight.

In order to solve the above-described problem, a method for controlling a DC-DC converter according to an embodiment of the present invention includes a rectifier circuit connected to a power source and rectifying an output from the power source, and an output from the rectifier circuit. A capacitor for storing electricity, a secondary battery connected in parallel with the capacitor, a sub-choke coil and a sub-switch connected in series between the rectifier circuit and the capacitor, and between the capacitor and the secondary battery A control method of a DC-DC converter including a sub-choke coil and a sub-switch connected in series,
Controlling the sub-semiconductor switch based on a potential difference between the output voltage of the rectifier circuit and a terminal voltage of the capacitor and a current flowing in the semiconductor switch;
And changing the driving frequency of the main semiconductor switch circuit to control the impedance of the main choke coil as a function of the terminal voltage of the capacitor and the potential difference of the secondary battery.

Here, the power source may be an engine generator, the DC-DC converter may be connected to a motor, and the motor may provide power for the electric vehicle.

  Examples of the engine generator include a generator that generates a power of a rated 900 W class. Examples of the motor include a rated power of 600 W and a maximum power of 4 KW.

  In the case of this embodiment, the output voltage of the generator may be set to 2 to 5 times the rated voltage of the secondary battery to charge the capacitor.

  The electric charge stored in the capacitor and represented by the product of the voltage difference between the capacitor and the secondary battery and the capacitor capacity may be supplied as instantaneous power for acceleration of the electric vehicle.

  The capacitor is preferably selected to have a capacity sufficient to supply power for 5 to 10 seconds for maximum acceleration.

The secondary battery is preferably limited to a capacity sufficient to supply electric power required for gradual acceleration for 10 minutes after rapid acceleration for the purpose of weight reduction.

If the capacity of the generator is slightly higher than the amount required for constant speed operation of 40-60 Km / H, it is not necessary to use a large output generator like a conventional hybrid vehicle, and it is small and lightweight. Can contribute.

  In addition, when the generator output is small and the motor is used at the maximum power, the capacitance and the power stored in the secondary battery are used up in about 10 minutes, so that it is possible to prevent a continuous high output operation state that damages the motor.

  In addition, since the drive circuit using the DC-DC converter according to the present invention is a lossless power supply system using a high voltage capacitor, the capacity of the secondary battery such as lithium ion, which increases the price and weight of the electric vehicle. Can be reduced to about 1/10, and sufficient electric power can be supplied to the motor for traveling in a pattern in which normal acceleration, constant speed traveling, and stopping are combined.

  Furthermore, according to the present invention, a secondary battery such as lithium ion can be substituted with, for example, a lead secondary battery used in a conventional small electric vehicle, and a cost advantage can be obtained.

  Further, since the loading amount of the secondary battery is reduced, the vehicle body structure can be reduced in size. As a result, the weight of the vehicle body decreases in proportion to the third power of the reduction against the strength that decreases in proportion to the square of the reduction amount of the structural material to be used, so that the vehicle body weight can be significantly reduced.

  By significantly reducing the weight of both the battery and the vehicle body structure, the rolling resistance during vehicle body travel is reduced, and the amount of power required for travel is reduced in proportion to the weight reduction, thereby improving energy utilization efficiency.

  Energy use efficiency can be improved because the generator engine is used for a long time under the optimum fuel efficiency condition of the rated output.

Capacitors are responsible for large voltage fluctuations due to fluctuations in the running load, and capacitors are less susceptible to deterioration due to voltage fluctuations than secondary batteries. Even if the secondary battery is downsized, the use under a large voltage fluctuation condition is reduced, and the life of the secondary battery can be extended.

The voltage difference between the capacitor and the secondary battery is set large in order to increase the amount of charge to be supplied by increasing the use efficiency of the capacitor. In order to make the maximum voltage at the time of operation of the capacitor 2 to 5 times the rated voltage of the secondary battery, in the conventional PWM method, a voltage that significantly exceeds the withstand voltage is applied to the secondary battery every pulse and the secondary battery is deteriorated. . In this method, the overvoltage is absorbed by the choke coil and the overvoltage is not applied to the secondary battery, and sufficient instantaneous power can be supplied to the motor by the electric charge due to the voltage difference with the capacitor.

According to another embodiment of the present invention, a method for controlling a DC-DC converter includes a capacitor and a secondary battery using generated power during frequent stopping in urban areas or surplus generated power during low-speed operation in mountainous areas. It is characterized by charging.

(Description of illustrated embodiment)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In a plurality of embodiments, similar elements or elements performing similar functions are given the same reference numerals, and redundant descriptions are omitted.

(First embodiment)
FIG. 1 is a schematic diagram of a motor-driven small automobile that uses an engine generator on which the present invention is mounted as a power source. The motor-driven small automobile shown in FIG. 1 includes, for example, an engine generator driven by gasoline fuel, a motor, and a secondary battery.

FIG. 2 is a diagram of the power control relationship between the capacitor and the secondary battery during travel of the motor-driven small automobile according to the present invention, and shows the power supply amount during travel. In FIG. 2, from the left, when stopped, the capacitor and secondary battery are fully charged and the generator output is the lowest. During rapid acceleration, the capacitor supplies most of the instantaneous power, and during slow acceleration, the generated power exceeds the power required for acceleration, so the capacitor is charged first. Reduce power generation after charging capacitor and secondary battery at constant speed cruise speed. Even in the second acceleration, the capacitor power is used first, and the secondary battery consumes less power. At low speed operation, the generator output is further reduced.

  FIG. 3 shows a DC-DC converter circuit used in a small automobile with a motor drive weight of 250 kg or less shown in FIG.

  The DC-DC converter according to the present embodiment includes a rectifier circuit 120. The sub choke coil 140, the sub semiconductor switch 160, the capacitor 180, the main choke coil 180, the main semiconductor switch 220, the secondary battery 240, and the control circuit 1000 for the sub semiconductor switch 160 and the main semiconductor switch 220 are included. Unlike the voltage drop due to the resistance, the voltage drop due to the increase in impedance of the choke coil has no power loss. A terminal of the secondary battery 240 is connected to, for example, a power circuit 260 that drives the motor 500. In order to prevent an overvoltage from being applied to the switch or the secondary battery due to a reverse voltage generated in the choke coil when the switch is opened, the anode of the diode 210 is arranged in parallel with the choke coil with the secondary battery side.

The negative output of the rectifier circuit 120, the negative electrode of the large-capacity capacitor 180, the secondary battery 240, and the negative electrode of the motor 500 are directly connected to form an earth bus.

  The sub semiconductor switch 160 is connected to the terminal A of the rectifier circuit 120 via the sub choke coil 140, and the output of the switch 160 is connected to one end of the large-capacitance capacitor 180. The large-capacity capacitor 180 is, for example, a combination of 38 electric double layer capacitors with a withstand voltage of 3.8 V and 500 Farads connected in series in the same direction, and the combined capacitance is 13.2 Farads.

  The sub-semiconductor switch 160 uses a thyristor, an npn-type power transistor, or an IGBT. The anode of the thyristor, the power transistor, or the collector of the IGBT is connected to the sub-choke coil 140, and the cathode of the thyristor, the power transistor, or the emitter of the IGBT. Is connected to the terminal of the capacitor 180, and the gate of the thyristor and IGBT or the base of the power transistor is connected to the output terminal of the microcomputer 1010 for control.

The control method of the sub semiconductor switch 160 compares the voltage V _A of the output terminal of the rectifier circuit 120 with the terminal voltage V _C of the capacitor 180, and turns on the switch when V _A > V _C. By turning off the switch when V _A ≦ V _C and the charging current is zero, the switch is turned off without generating back electromotive force in the choke coil 140, and energy loss is eliminated.

  The sub semiconductor switch circuit 160 is controlled by a digital system using a microcomputer 1010.

  Terminal voltages A and C of the rectifier circuit 120 are connected to AD converter input terminals of the microcomputer, respectively. In the current detection circuit, a conductor is wound several times around the wiring from the capacitor to the secondary battery, both ends of the conductor are connected to the positive and negative input terminals of the OP amplifier circuit, and a resistance element is connected between the negative input terminal and the output terminal To form a negative feedback circuit and detect the current value. This output voltage is input to the AD converter terminal of the microcomputer 1010.

As an initial state, the output to the semiconductor switch 160 is set to zero, which is the same as the terminal voltage V _C of the capacitor 180. The voltage between AC is compared, and when V _A > V _C , the output terminal from the microcomputer 1010 to the semiconductor switch 160 is set to a positive voltage with respect to V _C and the semiconductor switch is turned on. This state is maintained while the current value is positive, and the output terminal is turned off when the current value becomes zero. As a result, the initial state is restored, and the AC voltages are compared again.

  The terminal of the capacitor 180 is connected to the main semiconductor switch 220 via the main choke coil 200.

  The main semiconductor switch circuit 220 is controlled by a digital system using the microcomputer 1020.

The main semiconductor switch 220 uses an npn type power transistor, GTO, or IGBT, and connects the GTO anode, power transistor, or IGBT collector to the main choke coil 200, and the GTO cathode, power transistor, or IGBT emitter. Is connected to the positive terminal of the secondary battery 240, and the gates of the GTO and IGBT or the base of the power transistor are connected to the output terminal of the microcomputer 1020 for control.

The main choke coil 200 turns the current on and off with the main semiconductor switch 220 to limit the excessive charging current from flowing into the secondary battery 240 and prevent the overvoltage from being applied to the motor control circuit 260.

Microcomputer 1020 controls the main semiconductor switch 220 receives the amount of power P _M of the motor control circuit 260 is needed from an accelerator signal 1030, the amount of current by dividing the amount of power in the voltage value of the terminal of the secondary battery 240 I Define _M.

The voltage difference between the terminal of the capacitor 180 and the terminal of the secondary battery 240 is borne by the voltage drop of the main choke coil 200, and the voltage at the B end of the secondary battery 240 becomes 1.4 times the rated voltage. Thus, the on / off frequency of the semiconductor switch circuit 220 is determined.

  The DC-DC converter according to the present embodiment includes the sub switch 160 and the main switch 220, but both of these switches or any one of the switches may be omitted.

(Second embodiment)
FIG. 7 shows a DC-DC converter circuit used in a small vehicle having a motor drive weight of 250 kg or less shown in FIG.

  The control circuit of the sub switch 160 is a digital system using a microcomputer 1010. The control circuit of the circuit main switch circuit 220 is a digital system using a microcomputer 1020.

  Terminals A, C, and B are connected to input terminals of AD converters of microcomputers 1010 and 1020. The accelerator signal of the electric vehicle is connected to the input terminal of the AD converter. In the current detection circuit, a conductor is wound several times around the wiring from the capacitor to the secondary battery, both ends of the conductor are connected to the positive and negative input terminals of the OP amplifier circuit, and a resistance element is connected between the negative input terminal and the output terminal To form a negative feedback circuit and detect the current value. This output voltage is input to the AD converter terminal of each microcomputer.

  The sub semiconductor switch circuit 160 sets the sampling frequency of the microcomputer 1010 to 0.05 ms or more, and connects the voltage between the output terminal of the rectifier 120 and the terminal of the capacitor 180 and between the output terminal of the rectifier 120 and the terminal of the capacitor 180. The wiring current is monitored to determine the switching timing.

The control circuit of the main semiconductor switch 220 captures the motor drive power of the microcomputer 1020 and each terminal voltage information every 10 ms and performs the calculation time until the frequency is determined within 1 ms. The control conditions are updated for each wave, and the control frequency of the main semiconductor switch 220 is determined.

  The AC output of the generator 400 is connected to the double-wave rectifier circuit 120, and the large-capacity capacitor 180 such as an electric double layer type is charged with the DC pulsating power through the sub semiconductor switch circuit 160. The rectifier circuit 120, the capacitor 180, the secondary battery 240, and the negative terminal of the motor 500 are directly connected to form a so-called negative ground.

The output of the engine-driven generator with an output voltage of 100 V and an output power of 900 W is connected to a double-wave rectifier circuit 120 configured with a diode having a breakdown voltage of 566 V or more and a maximum current of 1000 A or more. The output of the rectifier circuit 120 is taken out from the anode terminal of the rectifier circuit 120 through the sub-choke coil 140 of 1 to 10 millihenries. In the case of 50 Hz alternating current, the impedance of the choke coil 140 is 0.312 to 3.12Ω. Thus, even when the terminal voltage of the large-capacitance capacitor 180 serving as the load of the rectifier circuit 120 is zero, the instantaneous maximum current flowing through the rectifier circuit 120 is 452A to 45.2A. The effective current is 320A to 32.0A. In this case, if it is 10 millihenry, an overcurrent of the rectifier circuit can be prevented.

  When the voltage at the terminal of the capacitor 180 is 141 V, the voltage difference 93 V up to the rated voltage 48 V at the terminal of the secondary battery 240 and the amount of charge accumulated in the capacitor 180 with a capacity of 13.2 Farad are 1228 coulombs. Only 48V and 83A power can be supplied to a motor with a maximum power of 4KW for 14.8 seconds. If the electric power of the generator of 900 W is added to this, the maximum acceleration for 19 seconds becomes possible, and with this capacitor and the generator, the small electric vehicle can run as if it is a normal vehicle with an engine. The secondary battery 240 can be positioned as an emergency power source for a continuous steep uphill.

  The terminal voltage of the capacitor, which has been reduced to 48V due to power consumption due to rapid acceleration, is charged again to 141V by surplus power generated in the generator when the vehicle stops or operates at low speed.

The difference between the terminal voltage V _C of the capacitor 180 and the terminal voltage V _B of the secondary battery 240 is V _BC , and the supply power P _M to the motor is divided by V _B to be the supply current I _M. If the value of the choke coil is L Henry, the frequency of the semiconductor switch circuit 1020 is
f = V _BC / (2π · I _M · L)
It becomes. Since the DC power supply is switched on and off with a switch, the effective value is ½. Therefore, in order to supply twice the current, the frequency f is ½.

If the motor is operating at the rated power or higher, V _B is set to 1.4 times the rated voltage of the secondary battery, the voltage effect of the main choke coil is reduced, the charge is stored in the secondary battery in advance, and large power is consumed. Prepare for.

In order to prevent overcharging of the secondary battery 180, it is assumed that the secondary battery is fully charged if V _B is 1.4 times or more of the rated voltage while the motor is operating at the rated voltage or less. _{P M} at this time switch 220 If 10W or less is not turned on.

When the power consumed by the motor is close to the maximum power of the motor and the amount of charge stored in the capacitor decreases and V _C decreases to near V _B , the control of the main semiconductor switch 220 does not decrease the frequency, It is possible to shift to a so-called PWM control system that extends the time width during which the semiconductor switch is on, and to use the current maintaining function of the choke coil to smoothly supply power to the motor.

  In order to charge the secondary battery 240 during parking without using the engine generator, a terminal for charging with a so-called household outlet from an external AC 100V power source is provided at the output of the generator.

If the household electrical outlet to charge the capacitor 180 and the secondary battery 240 sets the accelerator signal P _M value as the rated output power of the engine generator, performs fast charging to the rechargeable battery. When V _B exceeds 1.4 times the rated voltage of the secondary battery, it reduces the supply current value of P _M 1/2. Repeat this, I _A terminates charging as off the main switch when it is less than 5% of the rated output current.

  The order of disposing the main and sub choke coils and semiconductor switches of the present invention is the same regardless of which element is first.

(Function and effect)
With the invention of the lossless power supply system using high voltage capacitors, secondary batteries such as lithium-ion, which cause the price and weight of electric vehicles to increase, can be reduced to less than one-tenth the price of conventional small electric vehicles. A secondary battery can be substituted.

  The increase in weight required for a large-capacity capacitor is negligible, and the increase in cost due to the use of the capacitor is very small compared to the reduction in battery cost.

  Since the load capacity of the secondary battery is reduced, the vehicle body strength can be reduced and the size can be reduced. As a result, the weight of the vehicle body decreases in proportion to the cube of the reduction, whereas the strength decreases in proportion to the square of the reduction amount of the structural material to be used. Therefore, the weight can be significantly reduced.

  The significant weight reduction of both the battery and the vehicle body structure reduces the rolling resistance when the vehicle travels, reduces the amount of power required for travel in proportion to the weight reduction, and improves the energy utilization efficiency.

As the vehicle body becomes smaller, the front projection area decreases and the air resistance decreases, so that the running resistance decreases in proportion to the square of the speed.

  Energy use efficiency is improved because the engine generator is used for a long time under the optimal fuel efficiency condition with a constant load.

  When used in environments such as cities and mountainous areas due to reductions in secondary battery volume, generator downsizing and efficient operation, and reduction in body weight, energy consumption is reduced and environmental costs including materials are usually It is reduced from electric cars and parallel hybrid cars.

  The electric power generated by the on-board engine generator is charged to the capacitor and leveled over time, and the electric power stored in the capacitor is controlled to enable optimal control of the motor. The maximum power that the machine can supply can be used effectively.

  Capacitors are responsible for large voltage fluctuations due to fluctuations in the running load, and capacitors are less susceptible to deterioration due to voltage fluctuations than secondary batteries. Even if the secondary battery is reduced in size, use under a large voltage fluctuation condition is reduced, and the life of the secondary battery is extended.

  Whereas a conventional small electric vehicle requires charging after being used for about 4 hours, the use of a small engine generator eliminates the need for charging.

  The weight reduction eliminates the need for expensive materials and advanced manufacturing techniques for the body of an electric vehicle, and enables automobiles to be manufactured using low-tech and low-cost town factory technology.

Claims (5)

A capacitor that stores the output from the rectifier circuit that rectifies the output of the AC power supply;
A secondary battery connected in parallel with the capacitor;
A main choke coil and a main switch connected in series between the capacitor and the secondary battery;
A DC-DC converter.   The DC-DC converter according to claim 1, wherein the AC power source is an engine generator.   The DC-DC converter according to claim 1 or 2, which is mounted on an electric vehicle. A rectifier circuit connected to the power source and rectifying the output from the power source;
A capacitor for storing the output from the rectifier circuit;
A secondary battery connected in parallel with the capacitor;
A sub-choke coil and a sub-switch connected in series between the rectifier circuit and the capacitor;
A sub-choke coil and a sub-switch connected in series between the capacitor and the secondary battery;
A method for controlling a DC-DC converter including:
Controlling the sub-semiconductor switch based on a potential difference between the output voltage of the rectifier circuit and a terminal voltage of the capacitor and a current flowing in the semiconductor switch;
Controlling the impedance of the main choke coil by changing the drive frequency of the main semiconductor switch circuit as a function of the terminal voltage of the capacitor and the potential difference of the secondary battery;
Including methods.   5. The method of controlling a DC-DC converter according to claim 4, wherein the power source is an engine generator, and the output from the secondary battery drives a motor.

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