JP2009261051A - Discharging circuit for loading on vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharging circuit which can reduce the heat loss at operation of a step-up circuit and also can quickly discharge an output capacitor after finish of operation of a step-up circuit. <P>SOLUTION: This discharging circuit 10 for loading on vehicle, which discharges a charge accumulated in the output capacitor 18 of a step-up circuit 12 for loading on vehicle, is equipped with a resonance circuit, which comprises a capacitor 32 for resonance, an inductor 30 for resonance, and a conductor plate 34 and the resonance frequency of which changes by the change of the ground electrostatic capacitance of the conductor plate 34, a low-discharge resistor 24, through which the charge accumulated in the output capacitor 18 is discharged, and a transistor 22, which is controlled, according to the change of the resonance frequency of the resonance circuit, and leads the discharge current of the output capacitor 18 to the low-discharge resistor 24 when it is ON. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vehicle-mounted discharge circuit that discharges charges stored in an output capacitor of a vehicle-mounted boost converter circuit.

  Motor-driven vehicles such as electric vehicles and hybrid vehicles are widely used. A motor of a motor-driven vehicle is rotated by electric power supplied from a battery and drives wheels. The acceleration / deceleration control of the motor-driven vehicle is performed by adjusting the electric power supplied to the motor according to the operation of the accelerator, the brake, and the like. For this reason, a motor-driven vehicle is equipped with a boost converter circuit that adjusts the electric power supplied from the battery to the motor.

  The boost converter circuit includes an inductor for boosting the battery voltage. The boost converter circuit controls the current flowing from the battery to the inductor to generate an induced electromotive force in the inductor, and charges the output capacitor with a voltage obtained by adding the induced electromotive force to the battery voltage. Then, the voltage between the terminals of the output capacitor is output as a boosted voltage. The boosted voltage can be adjusted by changing the switching timing of the current flowing through the inductor.

  The motor is connected to the output terminal of the boost converter circuit via a circuit that drives the motor. According to such a configuration, the electric power supplied from the battery to the motor can be adjusted by adjusting the boost voltage of the boost converter circuit.

Japanese Patent Laid-Open No. 2007-60789 JP-A-5-252755

  The boost converter circuit is provided with a discharge resistor for discharging the accumulated charge of the output capacitor after stopping its operation. Thus, after the vehicle is stopped and the operation of the boost converter circuit is stopped, the voltage across the terminals of the output capacitor can be reduced. With such a configuration, a worker or a tool handled by an operator contacts the output capacitor during a rescue operation or a vehicle inspection operation in the event of a collision accident, and a secondary failure is caused by the output voltage of the output capacitor. It can be avoided.

  In such a boost converter circuit, as the resistance value of the discharge resistor is smaller, the voltage across the terminals of the output capacitor after the operation of the boost converter circuit is stopped can be quickly reduced. However, if the resistance value of the discharge resistor is reduced, there arises a problem that heat loss increases when the boost converter circuit is operated.

  The present invention has been made for such a problem. That is, an object of the present invention is to provide a discharge circuit that can reduce heat loss during operation of the boost converter circuit and can quickly discharge the output capacitor after the operation of the boost converter circuit is completed.

  The present invention relates to a vehicle-mounted discharge circuit that discharges electric charge stored in an output capacitor of a vehicle-mounted boost converter circuit, and includes a resonance capacitor, a resonance inductor, and a conductor plate. A resonance circuit whose resonance frequency changes due to a change in capacitance to the ground, a discharge resistor for discharging the accumulated charge of the output capacitor, and a control according to a change in the resonance frequency of the resonance circuit. And a switching element that guides a discharge current of the output capacitor to the discharge resistor.

  In the on-vehicle discharge circuit according to the present invention, it is preferable that the conductor plate is attached to a housing that houses the on-vehicle boost converter circuit.

  According to the present invention, it is possible to reduce heat loss during the operation of the boost converter circuit and to quickly discharge the output capacitor after the operation of the boost converter circuit is completed.

  FIG. 1 shows a configuration of a boost converter circuit output unit and a discharge circuit according to the first embodiment of the present invention. Discharge circuit 10 is provided between positive output conductor 14 and negative output conductor 16 of boost converter circuit 12. The discharge circuit 10 discharges the accumulated charge of the output capacitor 18 to the low discharge resistor 24 in accordance with the change in capacitance with respect to the ground conductor of the conductor plate 34 attached to the casing of the boost converter circuit 12. . Here, the ground conductor is a conductor that can be considered to have a ground potential, such as a vehicle body.

  Boost converter circuit 12 includes an output capacitor 18 connected between positive output conductor 14 and negative output conductor 16, and a high discharge resistor 20 connected in parallel to output capacitor 18. When the boost converter circuit 12 is operating, an output voltage is applied to the output capacitor 18. A current based on the voltage across the output capacitor 18 flows through the high discharge resistor 20. The resistance value of the high discharge resistor 20 is determined so that the power consumed as Joule heat is sufficiently smaller than the power for driving the vehicle. After the vehicle stops and the operation of boost converter circuit 12 stops, the accumulated charge in output capacitor 18 is discharged to a high discharge resistance.

  The discharge circuit 10 will be described. The discharge circuit 10 is a circuit that performs discharge control by switching control of the transistor 22. Here, a PNP transistor is used as the transistor 22. The emitter terminal E of the transistor 22 is connected to the positive output conductor 14. The collector terminal C of the transistor 22 is connected to one end of the low discharge resistor 24. The other end of the low discharge resistor 24 is connected to the negative output conductor 16. As a result, the output voltage of the boost converter circuit 12 is applied between the emitter terminal E and the collector terminal C of the transistor 22 via the low discharge resistor 24. Since this applied voltage has the emitter terminal E side as a positive electrode, the current flowing through the collector terminal C and the low discharge resistor 24 can be adjusted by changing the current flowing through the base terminal B.

  One output terminal of the AC voltage source 26 is connected to the positive electrode output conductor 14. The other output terminal of the AC voltage source 26 is connected to one end of the sensitivity adjustment resistor 28. The other end of the sensitivity adjustment resistor 28 is connected to one end of the resonance inductor 30 and one end of the resonance capacitor 32. The other end of the resonance inductor 30 and the other end of the resonance capacitor 32 are connected to the base terminal B of the transistor 22. A conductor plate 34 is connected to a connection line between the resonance capacitor 32 and the base terminal B. The conductor plate 34 is attached to the casing of the boost converter circuit 12.

  The conductor plate 34, the resonance inductor 30 and the resonance capacitor 32 constitute a parallel resonance circuit. The inductance value of the resonance inductor 30 and the capacitance of the resonance capacitor 32 are parallel when the conductor plate 34 is not in contact with a human body or a conductive material worn by the human body (hereinafter referred to as a human body or the like). The resonance frequency is determined so as to match the output voltage frequency of the AC voltage source 26.

  One output terminal of the AC voltage source 26 leads to the emitter terminal E via the positive output conductor 14, and the other output terminal of the AC voltage source 26 via the base terminal B, the parallel resonance circuit and the sensitivity adjustment resistor 28. To form an alternating current loop for the alternating voltage source 26.

  In a state where a human body or the like is not in contact with the conductor plate 34, the resonance frequency of the parallel resonance circuit matches the output voltage frequency of the AC voltage source 26. Therefore, the absolute value of the impedance of the parallel resonance circuit is increased, and the current flowing through the AC current loop is very small. As a result, the current flowing through the base terminal B becomes very small and the current flowing through the collector terminal C and the low discharge resistor 24 is cut off.

  On the other hand, when a human body contacts the conductor plate 34, the capacitance of the conductor plate 34 with respect to the ground conductor changes. The resonance inductor 30 and the resonance capacitor 32 have a certain capacitance with respect to the ground conductor. Therefore, the resonance frequency of the parallel resonance circuit deviates from the output voltage frequency of the AC voltage source 26 by changing the capacitance of the conductor plate 34 with respect to the ground conductor. As a result, the absolute impedance value of the parallel resonant circuit becomes smaller than that at the time of resonance, and a current flows through the alternating current loop.

  Since no DC bias voltage is applied between the base terminal B and the emitter terminal E of the transistor 22, the half-wave rectification of the current flowing in the AC current loop flows in the direction from the emitter terminal E to the base terminal B. It becomes current. Therefore, between the emitter terminal E and the collector terminal C of the transistor 22 is turned on during a half cycle of the current from the emitter terminal E to the base terminal B. In response to the half-wave rectified current flowing in the direction from the emitter terminal E to the base terminal B, the discharge current of the output capacitor 18 flows through the collector terminal C and the low discharge resistor 24. Thereby, the electric charge accumulated in the output capacitor 18 can be discharged.

  When the vehicle stops due to an accident or the like, a person who performs a rescue operation may open the engine compartment. Further, after the vehicle stops and the operation of the boost converter circuit 12 stops, a person who checks the vehicle may open the engine compartment. According to the discharge circuit 10 according to the present embodiment, when a rescue worker, an inspection worker, or the like touches the conductor plate 34 attached to the casing of the boost converter circuit 12 during work, the ground of the conductor plate 34 By changing the capacity, the discharge current of the output capacitor 18 can flow through the low discharge resistor 24. Thereby, the voltage across the terminals of the output capacitor 18 can be quickly reduced. Therefore, during a rescue operation or a vehicle inspection operation in the event of a collision accident, a worker or a tool handled by the operator contacts the output capacitor 18 and a secondary failure is caused by a voltage due to a charge remaining in the output capacitor 18. Can be avoided.

  Furthermore, in the discharge circuit 10 according to the embodiment of the present invention, the body of the boost converter circuit 12 is not touched by a human body or the like, and the body of the human body etc. is not in contact with the conductor plate 34. The current flowing through terminal C is interrupted. Thereby, the heat loss due to the low discharge resistor 24 when the boost converter circuit 12 is operated can be eliminated.

  Note that the relationship between the amount of change in ground capacitance of the conductor plate 34 and the magnitude of the discharge current can be adjusted by changing the output voltage level of the AC voltage source 26, the resistance value of the sensitivity adjustment resistor 28, and the like. It can be said that the relationship between the amount of change in the ground capacity of the conductor plate 34 and the magnitude of the discharge current indicates the sensitivity indicating the ease of the discharge operation. Therefore, the output voltage level of the AC voltage source 26, the resistance value of the sensitivity adjustment resistor 28, and the like are preferably determined in consideration of sensitivity characteristics based on experiments and the like. The resistance value of the low discharge resistor 24 may be determined based on the target time from the start to the end of discharge, the allowable amount of heat generated in the low discharge resistor 24, and the like.

  Next, a discharge circuit according to a second embodiment of the present invention will be described with reference to FIG. The discharge circuit 36 according to the present embodiment is obtained by replacing the parallel resonance circuit of the discharge circuit 10 according to the first embodiment with a series resonance circuit. The same components as those of the discharge circuit 10 of FIG. 1 are denoted by the same reference numerals and description thereof is omitted.

  One output terminal of the AC voltage source 26 is connected to the positive electrode output conductor 14. The other output terminal of the AC voltage source 26 is connected to one end of the sensitivity adjustment resistor 28. The other end of the sensitivity adjustment resistor 28 is connected to the base terminal B. Further, one end of the resonance inductor 38 is connected to the positive output conductor 14. The other end of the resonance inductor 38 is connected to one end of the resonance capacitor 40. The other end of the resonance capacitor 40 is connected to the base terminal B. A conductor plate 34 is connected to a connection line between the resonance capacitor 40 and the base terminal B.

  The conductor plate 34, the resonance inductor 38, and the resonance capacitor 40 constitute a series resonance circuit. The inductance value of the resonance inductor 38 and the capacitance of the resonance capacitor 40 are determined so that the series resonance frequency in a state where no human body is in contact with the conductor plate 34 matches the output voltage frequency of the AC voltage source 26. .

  A loop from one output terminal of the AC voltage source 26 to the emitter terminal E via the positive electrode output lead 14 and further to the other output terminal of the AC voltage source 26 via the base terminal B and the sensitivity adjustment resistor 28. Forms a transistor alternating current loop 42 for the alternating voltage source 26. Further, one output terminal of the AC voltage source 26 reaches one end of the resonance inductor 38 via the positive electrode output lead 14, and AC is further passed through the resonance inductor 38, the resonance capacitor 40, and the sensitivity adjustment resistor 28. The loop reaching the other output terminal of the voltage source 26 forms a resonant circuit alternating current loop 44 for the alternating voltage source 26.

  When the human body or the like is not in contact with the conductor plate 34, the resonance frequency of the series resonance circuit matches the output voltage frequency of the AC voltage source 26. Therefore, the absolute value of the impedance of the series resonance circuit becomes small, and most of the current flowing out from the AC voltage source 26 flows through the resonance circuit AC current loop 44. As a result, the current flowing through the transistor alternating current loop 42 becomes very small. Therefore, the current flowing through the base terminal B becomes very small, and the current flowing through the collector terminal C and the low discharge resistor 24 is cut off.

  On the other hand, when a human body contacts the conductor plate 34, the capacitance of the conductor plate 34 with respect to the ground conductor changes. The resonant inductor 38 and the resonant capacitor 40 have a certain capacitance with respect to the ground conductor. Therefore, the resonance frequency of the series resonance circuit deviates from the AC output voltage frequency of the AC voltage source 26 by changing the capacitance of the conductor plate 34 with respect to the ground conductor. As a result, the impedance absolute value of the series resonant circuit becomes larger than that at the time of resonance, and current flows not only through the resonant circuit alternating current loop 44 but also through the transistor alternating current loop 42.

  Since no DC bias voltage is applied between the base terminal B and the emitter terminal E of the transistor 22, the current flowing through the transistor AC current loop 42 is a half flowing in the direction from the emitter terminal E toward the base terminal B. Wave rectified current. The discharge current of the output capacitor 18 flows through the collector terminal C and the low discharge resistor 24 in accordance with the half-wave rectified current. Thereby, the electric charge accumulated in the output capacitor 18 can be discharged. Therefore, the same effects as those of the discharge circuit 10 according to the first embodiment can be obtained for the discharge circuit 36 according to the second embodiment.

  Next, a discharge circuit according to a third embodiment of the present invention will be described with reference to FIG. The discharge circuit 46 according to the present embodiment is obtained by inserting a rectifying and smoothing circuit 48 between the parallel resonant circuit and the base terminal B in the discharge circuit 10 according to the first embodiment. The rectifying / smoothing circuit 48 of FIG. 3 is connected to the positive output conductor 14, but depending on the configuration of the rectifying / smoothing circuit 48, it may not be connected to the positive output conductor 14. The same components as those of the discharge circuit 10 of FIG. 1 are denoted by the same reference numerals and description thereof is omitted.

  As described above, when a human body or the like comes into contact with the conductor plate 34, the resonance frequency of the parallel resonance circuit deviates from the output voltage frequency of the AC voltage source 26. Thereby, the impedance absolute value of the parallel resonant circuit becomes smaller than that at the time of resonance. In the discharge circuit 10 according to the first embodiment, the current flowing through the base terminal B at this time is a half-wave rectified current. Therefore, the current flowing through the low discharge resistor 24 is also a half-wave rectified current. In the discharge circuit 46 according to the present embodiment, a rectifying / smoothing circuit 48 is provided between the parallel resonant circuit and the base terminal B. The rectifying / smoothing circuit 48 is a circuit for detecting a voltage on the parallel resonant circuit side and outputting a smoothed DC voltage to the base terminal B. The rectifying / smoothing circuit 48 can be constituted by a rectifying element such as a diode, a smoothing capacitor, or the like. A DC voltage source, a transistor, or the like may be used depending on the required performance.

  According to such a configuration, the AC component of the current flowing through the base terminal B when a human body or the like contacts the conductor plate 34 can be reduced. As a result, the AC component of the discharge current flowing through the low discharge resistor 24 can be reduced and the average value of the discharge current can be increased, so that the output capacitor 18 can be discharged more quickly.

  Here, the embodiment in which the rectifying and smoothing circuit 48 is used in the discharge circuit 10 according to the first embodiment has been described. Similarly, the rectifying / smoothing circuit 48 can also be used in the discharge circuit 36 according to the second embodiment. In this case, a rectifying and smoothing circuit 48 may be inserted between the connection point of the resonance capacitor 40 and the sensitivity adjustment resistor 28 in FIG.

  In the above description, the case where a PNP transistor is used as the transistor 22 has been described. The transistor 22 may be an NPN type. In this case, the circuit is configured such that the collector terminal C side is a positive electrode and a voltage is applied between the collector terminal C and the emitter terminal E. Moreover, what was necessary is just to connect the place which connected the end of AC voltage source 26 to the positive electrode output conducting wire 14 in the above to the negative electrode output conducting wire 16.

It is a figure which shows the structure of the step-up converter circuit output part and discharge circuit which concern on 1st Embodiment. It is a figure which shows the structure of the step-up converter circuit output part and discharge circuit which concern on 2nd Embodiment. It is a figure which shows the structure of the step-up converter circuit output part and discharge circuit which concern on 3rd Embodiment.

Explanation of symbols

  10, 36, 46 Discharge circuit, 12 Boost converter circuit, 14 Positive output conductor, 16 Negative output conductor, 18 Output capacitor, 20 High discharge resistor, 22 Transistor, 24 Low discharge resistor, 26 AC voltage source, 28 Sensitivity adjustment Resistor, 30, 38 Resonant inductor, 32, 40 Resonant capacitor, 34 Conductor plate, 42 Transistor alternating current loop, 44 Resonant circuit alternating current loop, 48 Rectifier smoothing circuit.

Claims (2)

A vehicle-mounted discharge circuit that discharges electric charge stored in an output capacitor of a vehicle-mounted boost converter circuit,
A resonance circuit including a resonance capacitor, a resonance inductor, and a conductor plate, wherein a resonance frequency is changed by a change in a ground capacitance of the conductor plate;
A discharge resistor for discharging the accumulated charge of the output capacitor;
A switching element that is controlled according to a change in a resonance frequency of the resonance circuit and guides a discharge current of the output capacitor to the discharge resistor when turned on;
A vehicle-mounted discharge circuit comprising: A discharge circuit for mounting on a vehicle according to claim 1,
The conductor plate is
A discharge circuit for mounting on a vehicle, wherein the discharge circuit for mounting on a vehicle is attached to a casing that houses the boost converter circuit for mounting on a vehicle.

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