JP2016123200A - Driving device and power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a driving device and a power conversion device that can achieve a switching speed matched with a driving state.SOLUTION: A driving device for driving a switching element has a detector for directly or indirectly detecting at least one of conduction current, applied voltage and temperature of the switching element as a driving state of the switching element, a driving part for outputting a driving signal to a control terminal of the switching element, and a controller for controlling the driving part to change the switching speed of the switching element according to the detected driving state. The controller for pre-holding setting information in which each of plural sections obtained by sectioning the variation range of the driving state is associated with a control parameter for defining the highest switching speed out of switching speeds satisfying a predetermined driving condition in the section, extracting the control parameter corresponding to the section containing the detected driving state from the setting information, and controlling the driving part based on the extracted control parameter.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a drive device that drives a switching element that includes a control terminal, and a power conversion device that includes the drive device.

  A driving device that drives a switching element for high output having a large gate capacitance is known (see Patent Document 1). In such a drive device, it is desired to reduce the switching loss in the switching element.

Japanese Patent No. 3271525

  However, further improvement is desired in the technique described in Patent Document 1.

In order to solve the above problem, a drive device according to one embodiment of the present disclosure includes:
A driving device for driving a switching element including a control terminal, a first conduction terminal, and a second conduction terminal,
A detection unit that detects at least one of a conduction current, an applied voltage, and a temperature of the switching element directly or indirectly as a driving state of the switching element;
A drive unit that outputs a drive signal to the control terminal of the switching element;
A controller that controls the drive unit to change a switching speed of the switching element according to the detected drive state;
With
The control unit includes a plurality of sections in which the driving state variation ranges are divided, and a control parameter that defines a highest switching speed among the switching speeds satisfying a predetermined driving condition in each of the plurality of sections. Corresponding setting information is stored in advance, the control parameter corresponding to the section including the detected drive state is extracted from the setting information, and the drive unit is controlled based on the extracted control parameter Is.

  According to the present disclosure, further improvements can be realized.

It is a figure which shows roughly the motor drive system containing the switching element provided with a control terminal. It is a figure which shows schematically the drive device of 1st Embodiment. It is a graph which shows the experimental result performed in order to obtain | require optimal control parameters according to a drive state. It is a graph which shows each switching characteristic when changing charging time. It is a figure which shows roughly an example of the table which the control part of the drive device of 1st Embodiment hold | maintains. It is a timing chart which shows roughly the simulation result of the drive device at the time of turning on a switching element by the proposal technique. It is a timing chart which shows roughly the simulation result of the drive device at the time of turning on a switching element by the method of a comparative example. It is a graph which shows the experimental result performed in order to obtain | require optimal control parameters according to a drive state in 2nd Embodiment. It is a graph which shows each switching characteristic when changing discharge time. It is a figure which shows roughly an example of the table which the control part of the drive device of 2nd Embodiment hold | maintains. It is a timing chart which shows roughly the simulation result of the drive device at the time of turning on a switching element by the proposal technique of a 2nd embodiment. It is a timing chart which shows roughly the simulation result of the drive device at the time of turning on a switching element by the method of a comparative example. It is a graph which shows the experimental result performed in order to obtain | require optimal control parameters according to a drive state in 3rd Embodiment. It is a graph which shows each switching characteristic when changing precharge time. It is a figure which shows roughly an example of the table which the control part of the drive device of 3rd Embodiment hold | maintains. It is a timing chart which shows roughly the simulation result of the drive device at the time of turning on a switching element by the proposal technique of a 3rd embodiment. It is a timing chart which shows roughly the simulation result of the drive device at the time of turning on a switching element by the method of a comparative example. It is a figure which shows schematically the drive device of 4th Embodiment. It is a graph which shows the experimental result performed in order to obtain | require optimal control parameters according to a drive state in 4th Embodiment. It is a graph which shows each switching characteristic when resistance value is changed. It is a figure which shows roughly an example of the table which the control part of the drive device of 4th Embodiment hold | maintains. It is a timing chart which shows roughly the simulation result of the drive device at the time of turning on a switching element by the proposal technique of a 4th embodiment. It is a timing chart which shows roughly the simulation result of the drive device at the time of turning on a switching element by the method of a comparative example. It is a figure which shows schematically the drive device of 5th Embodiment. It is a graph which shows the experimental result performed in order to obtain | require optimal control parameters according to a drive state in 5th Embodiment. It is a graph which shows each switching characteristic when changing charging time. It is a figure which shows roughly an example of the table which the control part of the drive device of 5th Embodiment hold | maintains. It is a timing chart which shows roughly the simulation result of the drive device at the time of turning on a switching element by the proposal technique. It is a timing chart which shows roughly the simulation result of the drive device at the time of turning on a switching element by the method of a comparative example. It is a graph which shows the experimental result performed in order to obtain | require optimal control parameters according to a drive state in 6th Embodiment. It is a figure which shows roughly an example of the table which the control part of the drive device of 6th Embodiment hold | maintains. It is a timing chart which shows roughly the simulation result of the drive device at the time of turning on a switching element by the proposal technique of a 6th embodiment. It is a timing chart which shows roughly the simulation result of the drive device at the time of turning on a switching element by the method of a comparative example. It is a figure which shows schematically the drive device of 7th Embodiment. It is a graph which shows the experimental result performed in order to obtain | require optimal control parameters according to a drive state in 7th Embodiment. 35 schematically shows waveforms of an input current, a gate-source voltage of the switching element, a drain-source voltage of the switching element, and a drain-source voltage of the switching element in the DC-DC converter when the experiment of FIG. 35 is performed. FIG. It is a graph which shows the experimental result performed in order to obtain | require optimal control parameters according to a drive state in 8th Embodiment. In the ninth embodiment, the waveforms of the gate-source voltage of the switching element, the drain-source voltage of the switching element, and the drain-source voltage of the switching element when the switching element is turned on and off are shown. It is a timing chart shown roughly. It is a figure explaining the ideal trapezoid wave used for spreading | diffusion. It is a figure which shows schematically the waveform of the fast Fourier transform of the ideal trapezoid wave superimposed.

(Background to this disclosure)
First, an aspect of one aspect according to the present disclosure will be described.

  2. Description of the Related Art A driving device that controls a switching element of a DC-DC converter is known. In the DC-DC converter, it is desired to reduce the switching loss of the switching element. The switching loss of the switching element is reduced by increasing the response speed of the voltage between the drain and the source.

  However, when the response speed is increased, ringing may occur due to a resonance loop including a parasitic inductance and a parasitic capacitance on the DC-DC converter, and an excessive voltage may be applied to the switching element. For this reason, it is necessary to employ a switching element having a high withstand voltage as the switching element, resulting in an increase in the cost of the circuit. In addition, excessive radiation noise is generated with ringing, which may adversely affect other electrical devices.

  The voltage level of the control signal input to the gate of the switching element is about 5V, for example, whereas the voltage level handled by the DC-DC converter is very high, 200V to 300V. For this reason, in order to successfully propagate the control signal to the DC-DC converter, it is necessary to electrically insulate the reference potentials of the low voltage circuit and the high voltage circuit. Therefore, an isolator composed of a photocoupler or the like is generally provided before the gate of the switching element or before the gate of each switch constituting the driving device. Here, a reference called an in-phase rejection voltage is provided for the isolator. In order to satisfy this criterion, the response speed (that is, the voltage change rate) of the switching element needs to be equal to or less than the voltage change rate determined by the common-mode rejection voltage, and there is a limit to increasing the response speed.

  Therefore, the highest switching speed among the switching speeds in which the switching loss of the switching element is set to a certain value or less, the response speed of the switching element is set to the voltage change rate specified by the isolator, and the ringing voltage is set to a certain value or less By setting, the driving of the switching element can be optimized.

  However, the switching loss, response speed, and ringing voltage vary depending on the driving state of the driven switching element such as the current input / output to / from the switching element, the voltage, the conduction current flowing through the switching element, and the device temperature. Therefore, when actually designing the DC-DC converter, the switching speed is set so that the worst driving state can be satisfied. Therefore, when the driving state is not worst, for example, when the input voltage or the output voltage is low, the set switching speed may not be an optimal value. In this case, the switching element cannot be driven efficiently.

  On the other hand, in the said patent document 1, it is not fully examined about such a subject. Based on the above considerations, the present inventor has come up with the following aspects of the present disclosure.

One aspect of the present disclosure is:
A driving device for driving a switching element including a control terminal, a first conduction terminal, and a second conduction terminal,
A detection unit that detects at least one of a conduction current, an applied voltage, and a temperature of the switching element directly or indirectly as a driving state of the switching element;
A drive unit that outputs a drive signal to the control terminal of the switching element;
A controller that controls the drive unit to change a switching speed of the switching element according to the detected drive state;
With
The control unit includes a plurality of sections in which the driving state variation ranges are divided, and a control parameter that defines a highest switching speed among the switching speeds satisfying a predetermined driving condition in each of the plurality of sections. Corresponding setting information is stored in advance, the control parameter corresponding to the section including the detected drive state is extracted from the setting information, and the drive unit is controlled based on the extracted control parameter Is.

  According to this aspect, the switching element can be driven at the highest switching speed according to the driving state. As a result, the switching loss can be reduced as compared with the case where the switching speed is fixed. In addition, the drive unit can be controlled with a simple control configuration using the setting information.

In the above embodiment,
The control unit may execute a process of extracting the control parameter corresponding to the classification including the detected drive state from the setting information for each cycle of turning on and off the switching element.

  According to this aspect, the switching element can be driven at the highest switching speed in accordance with the drive state for each cycle of switching element on / off.

In the above embodiment,
The control unit may control the drive unit using the control parameter that is dispersed in a predetermined range so that an average value matches the extracted control parameter.

  According to this aspect, since the control parameter varied in a predetermined range so that the average value matches the extracted control parameter, the switching speed is varied. Therefore, the voltage change rate at the time of switching in the switching element is diffused. For this reason, the minimum value and the maximum value of the high-frequency component in switching are dispersed and averaged. As a result, radiation noise generated by switching of the switching element can be reduced.

In the above embodiment,
The drive unit is
A first potential line for applying a first potential;
A second potential line connected to the first conduction terminal of the switching element and providing a second potential smaller than the first potential;
A coil having a first terminal and a second terminal, wherein the second terminal is connected to the control terminal of the switching element;
A charging switch connected between the first potential line and the first terminal of the coil, and for turning on and off the energization between the first potential line and the coil;
A clamp switch connected between the first potential line and the control terminal of the switching element, and for turning on and off energization between the first potential line and the control terminal of the switching element;
A charging diode having an anode connected to the second potential line and a cathode connected to the first terminal of the coil;
Including
The control parameter is a charging time which is an on time of the charging switch,
In the setting information, the plurality of sections are associated with the charging time that defines the highest switching speed among the switching speeds that satisfy the driving condition in each of the plurality of sections.
The control unit may extract the charging time corresponding to the section including the detected driving state from the setting information, and set the extracted charging time as an on time of the charging switch.

  In this aspect, when the charging switch is turned on, a current is supplied from the first potential line to the control terminal of the switching element via the coil, and energy is accumulated in the coil. When the charging switch is turned off after the charging time has elapsed, the charging diode, the coil, the control terminal of the switching element, the first conduction terminal of the switching element, and the loop of the second potential line depend on the energy accumulated in the coil. Current is supplied to the control terminal of the switching element. The longer the charging time, that is, the on-time of the charging switch, the more energy is stored in the coil. Therefore, the switching speed of the switching element can be increased as the on-time of the charging switch becomes longer. As a result, according to this aspect, the switching speed of the switching element can be suitably changed according to the drive state.

In the above embodiment,
The drive unit is
A first potential line for applying a first potential;
A second potential line connected to the first conduction terminal of the switching element and providing a second potential smaller than the first potential;
A coil having a first terminal and a second terminal, wherein the second terminal is connected to the control terminal of the switching element;
A charging switch connected between the first potential line and the first terminal of the coil, and for turning on and off the energization between the first potential line and the coil;
A clamp switch connected between the first potential line and the control terminal of the switching element, and for turning on and off energization between the first potential line and the control terminal of the switching element;
A charging diode having an anode connected to the second potential line and a cathode connected to the first terminal of the coil;
Including
The control parameter is a discharge time which is a time from the turn-off of the charging switch to the turn-on of the clamp switch,
In the setting information, the plurality of sections are associated with the discharge time that defines the highest switching speed among the switching speeds that satisfy the driving condition in each of the plurality of sections.
The control unit may extract the discharge time corresponding to the section including the detected drive state from the setting information, and drive the charging switch and the clamp switch with the extracted discharge time. .

  In this aspect, when the clamp switch is turned on after the discharge time from the turn-off of the charging switch, the energization between the first potential line and the control terminal of the switching element is turned on, and the control terminal of the switching element is the first. Clamped to potential.

  Therefore, the shorter the discharge time, the shorter the time until the control terminal of the switching element is clamped to the first potential. For this reason, the shorter the discharge time, the higher the switching speed of the switching element. As a result, according to this aspect, the switching speed of the switching element can be suitably changed according to the drive state.

In the above embodiment,
The drive unit is
A first potential line for applying a first potential;
A second potential line connected to the first conduction terminal of the switching element and providing a second potential smaller than the first potential;
A coil having a first terminal and a second terminal, wherein the second terminal is connected to the control terminal of the switching element;
A charging switch connected between the first potential line and the first terminal of the coil, and for turning on and off the energization between the first potential line and the coil;
A first clamp switch connected between the first potential line and the control terminal of the switching element, and for turning on and off the energization between the first potential line and the control terminal of the switching element;
A second clamp switch connected between the second potential line and the control terminal of the switching element, and for turning on and off energization between the second potential line and the control terminal of the switching element;
A charging diode having an anode connected to the second potential line and a cathode connected to the first terminal of the coil;
Including
The control parameter is a precharge time that is a time for turning on both the charging switch and the second clamp switch,
In the setting information, the plurality of sections are associated with the precharge time that defines the highest switching speed among the switching speeds that satisfy the driving condition in each of the plurality of sections.
The control unit extracts the precharge time corresponding to the section including the detected driving state from the setting information, and the charging switch and the second clamp switch during the extracted precharge time. Both of the charging switch and the second clamp switch may be turned off when the extracted precharge time elapses.

  In this aspect, in a state where the second clamp switch is turned on, energization between the second potential line and the control terminal of the switching element is turned on. For this reason, the control terminal of the switching element is clamped at the second potential. In a state in which the charging switch is turned on, energization between the first potential line and the coil is turned on, and energy is accumulated in the coil. When both the second clamp switch and the charging switch are turned on, the control terminal of the switching element is clamped at the second potential, so even if the charging switch is turned on, No current is supplied from the first potential line to the control terminal of the switching element.

  When the precharge time has elapsed, both the charging switch and the second clamp switch are turned off. When the second clamp switch is turned off, the energization between the second potential line and the control terminal of the switching element is turned off. For this reason, the control terminal of the switching element is not clamped to the second potential. On the other hand, when the charging switch is turned off, the current due to the energy accumulated in the coil is switched in the charging diode, the coil, the control terminal of the switching element, the first conduction terminal of the switching element, and the loop of the second potential line. It is supplied to the control terminal of the element.

  Therefore, the longer the precharge time, the greater the energy stored in the coil. For this reason, the switching speed of the switching element can be increased as the precharge time becomes longer. As a result, according to this aspect, the switching speed of the switching element can be suitably changed according to the drive state.

In the above embodiment,
The drive unit is
A first potential line for applying a first potential;
A second potential line connected to the first conduction terminal of the switching element and providing a second potential smaller than the first potential;
A coil having a first terminal and a second terminal, wherein the second terminal is connected to the control terminal of the switching element;
A charging switch connected between the first potential line and the first terminal of the coil, and for turning on and off the energization between the first potential line and the coil;
A clamp switch connected between the first potential line and the control terminal of the switching element, and for turning on and off energization between the first potential line and the control terminal of the switching element;
A charging diode having an anode connected to the second potential line and a cathode connected to the first terminal of the coil;
Including
The control parameters include a charging time that is an on time of the charging switch, and a discharging time that is a time from the turning off of the charging switch to the turning on of the clamp switch,
In the setting information, the plurality of sections are associated with the charging time and the discharging time that define the highest switching speed among the switching speeds that satisfy the driving condition in each of the plurality of sections. ,
The control unit extracts the charging time and the discharging time corresponding to the classification including the detected driving state from the setting information, and sets the extracted charging time as an ON time of the charging switch. In addition, the clamp switch may be turned on when the extracted discharge time has elapsed from the turn-off of the charging switch.

  In this aspect, when the charging switch is turned on, a current is supplied from the first potential line to the control terminal of the switching element via the coil, and energy is accumulated in the coil. When the charging switch is turned off after the charging time has elapsed, the charging diode, the coil, the control terminal of the switching element, the first conduction terminal of the switching element, and the loop of the second potential line depend on the energy accumulated in the coil. Current is supplied to the control terminal of the switching element. The longer the charging time, that is, the on-time of the charging switch, the more energy is stored in the coil. Therefore, the switching speed of the switching element can be increased as the on-time of the charging switch becomes longer.

  In addition, when the charging switch is turned on after the on time of the charging switch has elapsed, the clamp switch is turned on after the discharging time from the turning off of the charging switch. Then, energization between the first potential line and the control terminal of the switching element is turned on, and the control terminal of the switching element is clamped at the first potential. Therefore, the shorter the discharge time, the shorter the time until the control terminal of the switching element is clamped to the first potential. For this reason, the shorter the discharge time, the higher the switching speed of the switching element.

  As a result, according to this aspect, by controlling the charging time and the discharging time, the switching speed of the switching element can be changed more finely according to the driving state.

In the above embodiment,
The drive unit is
A first potential line for applying a first potential;
A second potential line connected to the first conduction terminal of the switching element and providing a second potential smaller than the first potential;
A coil having a first terminal and a second terminal, wherein the second terminal is connected to the control terminal of the switching element;
A charging switch connected between the first potential line and the first terminal of the coil, and for turning on and off the energization between the first potential line and the coil;
A first clamp switch connected between the first potential line and the control terminal of the switching element, and for turning on and off the energization between the first potential line and the control terminal of the switching element;
A second clamp switch connected between the second potential line and the control terminal of the switching element, and for turning on and off energization between the second potential line and the control terminal of the switching element;
A charging diode having an anode connected to the second potential line and a cathode connected to the first terminal of the coil;
Including
The control parameter includes a precharge time that is a time for turning on both the charging switch and the second clamp switch, and a discharge that is a time from turning off the charging switch to turning on the first clamp switch. Including time,
In the setting information, the plurality of sections are associated with the precharge time and the discharge time that define the highest switching speed among the switching speeds that satisfy the driving condition in each of the plurality of sections. And
The control unit extracts the precharge time and the discharge time corresponding to the section including the detected drive state from the setting information, and the charging switch and the charge during the extracted precharge time When both of the second clamp switches are turned on and the extracted precharge time has elapsed, both the charging switch and the second clamp switch are turned off, and the extracted from the turn-off of the charging switch. When the discharge time elapses, the first clamp switch may be turned on.

  In this aspect, in a state where the second clamp switch is turned on, energization between the second potential line and the control terminal of the switching element is turned on. For this reason, the control terminal of the switching element is clamped at the second potential. In a state in which the charging switch is turned on, energization between the first potential line and the coil is turned on, and energy is accumulated in the coil. When both the second clamp switch and the charging switch are turned on, the control terminal of the switching element is clamped at the second potential, so even if the charging switch is turned on, No current is supplied from the first potential line to the control terminal of the switching element.

  When the precharge time has elapsed, both the charging switch and the second clamp switch are turned off. When the second clamp switch is turned off, the energization between the second potential line and the control terminal of the switching element is turned off. For this reason, the control terminal of the switching element is not clamped to the second potential. On the other hand, when the charging switch is turned off, the current due to the energy accumulated in the coil is switched in the charging diode, the coil, the control terminal of the switching element, the first conduction terminal of the switching element, and the loop of the second potential line. It is supplied to the control terminal of the element.

  Therefore, the longer the precharge time, the greater the energy stored in the coil. For this reason, the switching speed of the switching element can be increased as the precharge time becomes longer.

  In addition, when the precharge time has elapsed and the charging switch is turned off, the clamp switch is turned on after the discharging time from the turn-off of the charging switch. Then, energization between the first potential line and the control terminal of the switching element is turned on, and the control terminal of the switching element is clamped at the first potential. Therefore, the shorter the discharge time, the shorter the time until the control terminal of the switching element is clamped to the first potential. For this reason, the shorter the discharge time, the higher the switching speed of the switching element.

  As a result, according to this aspect, by controlling the precharge time and the discharge time, the switching speed of the switching element can be changed more finely according to the driving state.

In the above embodiment,
The drive unit is
A first potential line for applying a first potential;
A second potential line connected to the first conduction terminal of the switching element and providing a second potential smaller than the first potential;
A clamp switch connected between the first potential line and the control terminal of the switching element, and for turning on and off energization between the first potential line and the control terminal of the switching element;
A first resistance element connected in series with the clamp switch between the first potential line and the control terminal of the switching element;
A second resistance element having a first terminal and a second terminal, wherein the second terminal is connected to the control terminal of the switching element, and has a resistance value higher or lower than the first resistance element;
A charging switch connected between the first potential line and the first terminal of the second resistance element, and for turning on and off the energization between the first potential line and the second resistance element;
Including
The control parameter is a charging time which is an on time of the charging switch,
In the setting information, the plurality of sections are associated with the charging time that defines the highest switching speed among the switching speeds that satisfy the driving condition in each of the plurality of sections.
The control unit extracts the charging time corresponding to the category including the detected driving state from the setting information, and when the extracted charging time elapses after the charging switch is turned on, the charging And the clamp switch may be turned on.

  In this aspect, when the charging switch is turned on, a current is supplied from the first potential line to the control terminal of the switching element via the second resistance element. When the charging time elapses after the charging switch is turned on, the charging switch is turned off and the clamp switch is turned on. When the clamp switch is turned on, a current is supplied from the first potential line to the control terminal of the switching element via the first resistance element.

  Therefore, when the resistance value of the second resistance element is lower than the resistance value of the first resistance element, the switching speed of the switching element can be increased as the on-time of the charging switch becomes longer. On the other hand, when the resistance value of the first resistance element is lower than the resistance value of the second resistance element, current supply starts via the first resistance element having a lower resistance value as the on-time of the charging switch becomes shorter. The switching speed of the switching element can be increased.

  As a result, according to this aspect, the switching speed of the switching element can be suitably changed according to the drive state.

Other aspects of the disclosure include
A driving device for driving a switching element including a control terminal,
A drive unit that outputs a drive signal to the control terminal of the switching element;
A controller that controls the drive unit to change a switching speed of the switching element according to a driving state of the switching element;
With
The control unit varies control parameters that define the switching speed, and controls the drive unit using the varied control parameters.

  In this aspect, since the control parameter that defines the switching speed is varied and the varied control parameter is used, the switching speed is varied. Therefore, the voltage change rate at the time of switching in the switching element is diffused. For this reason, the minimum value and the maximum value of the high-frequency component in switching are dispersed and averaged. As a result, according to this aspect, radiation noise generated by switching of the switching element can be reduced.

Still other aspects of the disclosure include
A driving device for driving a switching element including a control terminal, a first conduction terminal, and a second conduction terminal,
A detection unit that detects at least one of a conduction current, an applied voltage, and a temperature of the switching element directly or indirectly as a driving state of the switching element;
A drive unit that outputs a drive signal to the control terminal of the switching element;
A controller that controls the drive unit to change a switching speed of the switching element according to the detected drive state;
With
The drive unit is
A first potential line for applying a first potential;
A second potential line connected to the first conduction terminal of the switching element and providing a second potential smaller than the first potential;
A first clamp switch connected between the first potential line and the control terminal of the switching element, and for turning on and off the energization between the first potential line and the control terminal of the switching element;
A first resistance element connected in series with the first clamp switch between the first potential line and the control terminal of the switching element;
The first clamp line is connected in parallel with the first clamp line between the first potential line and the control terminal of the switching element to turn on and off the energization between the first potential line and the control terminal of the switching element. A second clamp switch;
A second resistance element connected in series with the second clamp switch between the first potential line and the control terminal of the switching element, and having a resistance value different from that of the first resistance element;
Including
The control unit is associated with the first section in which the variation range of the driving state is partitioned and the first clamp switch, and the first section in which the variation range of the driving state is partitioned. The first clamp switch or the second clamp corresponding to the section including the detected drive state, which holds setting information in which the different second section and the second clamp switch are associated in advance. A switch is extracted from the setting information, and the extracted first clamp switch or the second clamp switch is used.

  In this aspect, when the first clamp switch is turned on, a current is supplied from the first potential line to the control terminal of the switching element via the first resistance element. When the second clamp switch is turned on, a current is supplied from the first potential line to the control terminal of the switching element via the second resistance element. Since the first resistive element and the second resistive element have different resistance values, the current value supplied to the control terminal of the switching element when the first clamp switch is used and when the second clamp switch is used. Is different. Therefore, according to this aspect, the switching element can be driven at a switching speed corresponding to the driving state. As a result, the switching loss can be reduced as compared with the case where the switching speed is fixed. In addition, the drive unit can be controlled with a simple control configuration using the setting information.

  Still another aspect of the present disclosure is a power conversion apparatus that converts input power and outputs the power, and includes the switching element and the driving apparatus according to any one of the above aspects that drives the switching element. It is.

  These comprehensive or specific modes may be realized as a power conversion device, a motor drive system, a vehicle, a power storage system, a control circuit, a control method, or any combination thereof.

(Embodiment)
Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same reference numerals are used for the same components.

  First, the motor drive system 10 to which the drive device 50 according to the embodiment of the present disclosure is applied will be described.

  FIG. 1 is a diagram schematically showing a motor drive system 10 including a switching element having a control terminal. The motor drive system 10 includes an input power supply E11, a DC-DC converter 20, an inverter 30, and a motor 40.

  The DC-DC converter 20 includes a reactor L11, an input smoothing capacitor C11, a low-side switching element Q11, a high-side switching element Q12, an output smoothing capacitor C12, isolators 91 and 92, and a driving device 50.

  First, the boosting operation will be described. When the drive device 50 performs on / off control of the low-side switching element Q11, the energy of the input power supply E11 moves to the smoothing capacitor C12 via the reactor L11. The voltage of the smoothing capacitor C12 is boosted with respect to the voltage of the input power supply E11. The boosted voltage is converted into an AC voltage by the inverter 30 and the motor 40 is driven by the AC voltage.

  Next, the step-down operation will be described. The AC power generated by the motor 40 is converted into DC power by the inverter 30, and the DC power is stored in the smoothing capacitor C12. When the driving device 50 performs on / off control of the high-side switching element Q12, the energy stored in the smoothing capacitor C12 moves to the input power source E11 via the reactor L11. The voltage of the input power supply E11 is stepped down with respect to the voltage of the smoothing capacitor C12.

  The drive device 50 includes drive units 60 and 60, a detection unit 70, and a control unit 80. One drive unit 60 supplies a drive signal to the gate of the switching element Q11 via the isolator 91. The other drive unit 60 supplies a drive signal to the gate of the switching element Q12 via the isolator 92. The switching elements Q11 and Q12 are turned on and off by, for example, PWM control. Each of the isolators 91 and 92 includes, for example, a photocoupler. Isolators 91 and 92 electrically insulate between drive unit 60 and switching elements Q11 and Q12 while passing control signals from drive unit 60 to switching elements Q11 and Q12, respectively.

  The detection unit 70 detects the driving state of the switching elements Q11 and Q12. The detection unit 70 includes a current sensor 71, a voltage sensor 72, a current sensor 73, a voltage sensor 74, a current sensor 75, and temperature sensors 76 and 77.

  The current sensor 71 detects an input current Iin input from the input power supply E11 to the switching elements Q11 and Q12. The current sensor 71 is provided between the reactor L11 and the connection point K1 between the smoothing capacitor C11 and the line connecting the positive electrode of the input power source E11 and the reactor L11, for example. The voltage sensor 72 detects the input voltage Vin input to the switching elements Q11 and Q12 from the input power supply E11. The voltage sensor 72 is connected in parallel with, for example, the smoothing capacitor C11.

  Current sensor 73 detects drain current Ids (an example of a conduction current) that flows between the source and drain of switching element Q11. The current sensor 73 is provided, for example, between the connection point K2 between the positive connection line W12 and the smoothing capacitor C12, and the drain of the switching element Q12. The current sensor 73 may detect an average value, a peak value, or an effective value of the drain current Ids. Alternatively, the control unit 80 may calculate an average value, a peak value, or an effective value of the drain current Ids detected by the current sensor 73 and use it for controlling the driving unit 60.

  The voltage sensor 74 detects the output voltage Vout output from the DC-DC converter 20. The voltage sensor 74 is provided in parallel with the smoothing capacitor C12, for example. The current sensor 75 detects the output current Iout output from the DC-DC converter 20. The current sensor 75 is provided between the connection point K2 and the inverter 30, for example.

  Temperature sensors 76 and 77 detect junction temperature Tj of switching elements Q11 and Q12, respectively. The temperature sensors 76 and 77 are disposed in close contact with the switching elements Q11 and Q12, for example.

  The control unit 80 acquires the drive state detected by the detection unit 70 from the detection unit 70. Control unit 80 controls drive unit 60 according to the acquired drive state to change the switching speed of switching elements Q11 and Q12. The control of the drive unit 60 by the control unit 80 will be described in detail later.

  As the switching elements Q11 and Q12, for example, a voltage control type switching element such as a metal oxide semiconductor field effect transistor (MOSFET) or an insulated gate bipolar transistor (IGBT) is used.

  Switching elements Q11 and Q12 include a control terminal, a first conduction terminal, and a second conduction terminal. For example, when the switching elements Q11 and Q12 are MOSFETs, the control terminal is a gate, one of the first conduction terminal and the second conduction terminal is a source, and the other is a drain. For example, when the switching elements Q11 and Q12 are IGBTs, the control terminal is a gate, one of the first conduction terminal and the second conduction terminal is a collector, and the other is an emitter.

  One of the first conduction terminal and the second conduction terminal serves as a reference terminal serving as a reference for the voltage of the control terminal. The voltage-controlled switching element has a capacitance formed equivalently between the control terminal and the reference terminal.

  In the following description, the switching elements Q11 and Q12 are MOSFETs, the control terminal is a gate, the first conduction terminal is a source, the second conduction terminal is a drain, the source is a reference terminal, An example having a capacitor Ciss in between will be described. However, as described above, IGBTs can also be used as the switching elements Q11 and Q12.

  In driving device 50 for driving switching elements Q11 and Q12 shown in FIG. 1, it is desired to reduce the switching loss in switching elements Q11 and Q12. As shown in FIG. 1, parasitic inductances Lp1 and Lp2 are generated in the negative connection line W11 and the positive connection line W12 between the DC-DC converter 20 and the inverter 30, respectively. Further, parasitic capacitances Cp1 and Cp2 are generated between the drain and source of the switching elements Q11 and Q12, respectively.

  The switching loss can be reduced by increasing the switching speed of the switching elements Q11 and Q12 and increasing the response speed of the voltage between the drain and source of the switching elements Q11 and Q12 (that is, increasing the voltage change rate).

  However, when the switching speed of the switching elements Q11 and Q12 is increased, the following problem occurs. For example, consider the case where the switching element Q11 is turned on. In this case, the switching element Q11 is on and the switching element Q12 is off. Therefore, a resonance loop of the switching element Q11, the parasitic inductance Lp1, the inverter 30, the parasitic inductance Lp2, and the parasitic capacitance Cp2 is formed.

  As a result, the ringing voltage Vds (H) .H is applied across the parasitic capacitance Cp2 of the switching element Q12 that is turned off. max (the peak value of the drain-source voltage Vds (H)) occurs. Ringing voltage Vds (H). When max is increased, it is necessary to increase the breakdown voltage of the switching elements Q11 and Q12, leading to an increase in size and cost of the switching elements Q11 and Q12.

  The DC-DC converter 20 of the present disclosure includes isolators 91 and 92. Therefore, the voltage change rate between the drain and source of the switching elements Q11 and Q12 needs to be equal to or less than the voltage change rate specified by the common mode rejection voltage of the isolators 91 and 92.

  Therefore, the switching speed satisfying the driving condition that the ringing voltage is lower than the predetermined value and the driving condition that the voltage change rate between the drain and the source is lower than the voltage change rate specified by the common mode rejection voltage of the isolators 91 and 92 are satisfied. Among them, the switching loss can be reduced by setting the switching speed that minimizes the switching loss (that is, the highest switching speed).

  However, the ringing voltage, the drain-source voltage change rate, and the switching loss vary depending on driving states such as currents and voltages input to and output from the switching elements Q11 and Q12.

  Therefore, in the driving device 50 according to the present disclosure, in each of a plurality of sections in which the driving state variation range (that is, the range from the maximum value to the minimum value) is divided, the driving conditions of the ringing voltage and the switching elements Q11 and Q12 Of the switching speeds that satisfy the voltage change rate driving condition, a switching speed that minimizes the switching loss is obtained in advance. A desired switching speed is obtained by changing a control parameter for controlling the drive unit 60. Therefore, in the driving device 50 of the present disclosure, specifically, in each of the plurality of sections, among the control parameters satisfying the driving condition of the ringing voltage and the driving condition of the voltage change rate of the switching elements Q11 and Q12, switching is performed. A control parameter that minimizes the loss is obtained in advance. Then, a table (described later) in which a plurality of sections are associated with control parameters that minimize the switching loss is created in advance.

  The control unit 80 holds the created table in advance. The control unit 80 extracts control parameters corresponding to the sections including the drive state acquired from the detection unit 70 from the held table. The control unit 80 controls the driving unit 60 according to the extracted control parameter for each pulse. Hereinafter, specific control of the drive unit 60 by the control unit 80 will be described for each embodiment of the drive device 50.

(First embodiment)
FIG. 2 is a diagram schematically illustrating the driving device 50 according to the first embodiment. In FIG. 2, in order to simplify the description, the illustration of the isolators 91 and 92 is omitted, and the second potential line W2 of the driving unit 60 is connected to the source of the switching element Q11. However, in the actual DC-DC converter 20, as shown in FIG. 1, the driving unit 60 of the driving device 50 and the switching element Q <b> 11 are connected via an isolator 91, and switching with the driving unit 60 of the driving device 50 is performed. The element Q12 is connected via an isolator 92.

  Since the drive unit 60 that supplies the drive signal to the switching element Q12 has the same configuration as the drive unit 60 that supplies the drive signal to the switching element Q11, detailed illustration is omitted. The drive unit 60 and the control unit 80 may be mounted on the same substrate or may be mounted on separate substrates. This is the same in the following embodiments.

  The drive unit 60 includes a power source E1, a resonance circuit unit 61, and a clamp unit 62. The resonance circuit unit 61 includes a coil L1 and a recovery unit. The collection unit includes a switch SW1 (an example of a charging switch), a switch SW2, a diode D1, and a diode D2 (an example of a charging diode). The clamp unit 62 includes a switch SW3 (an example of a clamp switch, an example of a first clamp switch), a switch SW4 (an example of a second clamp switch), a diode D3, a diode D4, a resistor R1, and a resistor R2.

  A first potential line W1 is connected to the positive electrode of the power source E1. The first potential line W1 applies the first potential Vcc. The second potential line W2 is connected to the negative electrode of the power source E1. The second potential line W2 provides the second potential Vss. The first potential Vcc is higher than the second potential Vss.

  An input terminal Lt1 (an example of a first terminal) of the coil L1 of the resonance circuit unit 61 is connected to the first potential line W1 via the switch SW1. The input terminal Lt1 of the coil L1 is connected to the second potential line W2 via the switch SW2.

  The output side terminal Lt2 (an example of the second terminal) of the coil L1 is connected to the gate of the switching element Q11. The source of the switching element Q11 is connected to the negative electrode of the power source E1 by the second potential line W2. Therefore, the second potential Vss and the source potential of the switching element Q11 are common.

  In general, a MOSFET such as the switching element Q11 has a capacitance formed equivalently between a control terminal (gate) and a reference terminal (source). For this reason, the coil L1 and the gate-source capacitance Ciss of the switching element Q11 constitute an LC series resonance circuit by the connection as shown in FIG.

  In the present disclosure, the first potential line W1 may be a current path having the first potential Vcc, and may not be a wiring. Similarly, the second potential line W2 may be a current path having the second potential Vss, and may not be a wiring. For example, the current path that is not a wiring may be a current path formed by connecting the terminals of the circuit elements.

  The power supply E1 applies the first potential Vcc or the second potential Vss to the gate of the switching element Q11. For example, the power supply E1 fixes the gate potential of the switching element Q11 to the same potential as the first potential Vcc when the switching element Q11 is in the on state. Further, the power source E1 fixes the gate potential of the switching element Q11 to the same potential as the second potential Vss when the switching element Q11 is in the OFF state. In other words, the power source E1 applies a fixed voltage between the gate and the source of the switching element Q11 in a stable state after the switching of the switching element Q11 is completed.

  In the example shown in FIG. 2, the second potential Vss and the source of the switching element Q11 are at the same potential. Therefore, when the gate potential of the switching element Q11 is fixed at the first potential Vcc, the gate voltage (Vgs11) with the source of the switching element Q11 as a reference is equal to Vcc−Vss, that is, the voltage of the power supply E1. When the gate potential of the switching element Q11 is fixed to the second potential Vss, the gate voltage (Vgs11) based on the source of the switching element Q11 is 0V.

  Note that in this disclosure, “A and B are the same potential” and “A potential reaches B potential” means that, for example, between the potential of A and the potential of B This includes the case where a small potential difference derived from the on-resistance and the parasitic resistance of the electric circuit element occurs. The power source E1 may be disposed outside the driving device 50.

  In the present disclosure, “A and B are connected” means not only when A and B are directly connected but also when A and B are connected via another circuit element C. Is also included.

  The switch SW1 is provided between the first potential line W1 and the input side terminal Lt1 of the coil L1. The switch SW2 is provided between the second potential line W2 and the input side terminal Lt1 of the coil L1. In the example of FIG. 2, the switch SW1 is a P-channel MOSFET, and the switch SW2 is an N-channel MOSFET. A parasitic diode having a forward direction from the drain to the source is formed in the P-channel MOSFET. A parasitic diode having a forward direction from the source to the drain is formed in the N-channel MOSFET. Note that the switches SW1 and SW2 may be other switching elements such as bipolar transistors and relays, for example.

  The diode D1 is provided in the reverse direction between the first potential line W1 and the input side terminal Lt1 of the coil L1. The reverse direction is a direction in which current flows from the first potential Vcc side toward the second potential Vss side, with the cathode connected to the higher potential side and the anode connected to the lower potential side. . That is, the diode D1 is connected with a reverse bias between the first potential Vcc and the input side terminal Lt1 of the coil L1.

  The diode D2 is provided in the reverse direction between the second potential line W2 and the input side terminal Lt1 of the coil L1. That is, the diode D2 is connected with a reverse bias between the second potential Vss and the input side terminal Lt1 of the coil L1. The cathode of the diode D1 is connected to the first potential line W1. The anode of the diode D2 is connected to the second potential line W2. The diode D1 and the diode D2 may be, for example, a Schottky barrier diode.

  A series circuit of the switch SW3 and the resistor R1 is provided between the first potential line W1 and the output side terminal Lt2 of the coil L1. A series circuit of the switch SW4 and the resistor R2 is provided between the second potential line W2 and the output side terminal Lt2 of the coil L1. In the example of FIG. 2, the switch SW3 is a P-channel MOSFET, and the switch SW4 is an N-channel MOSFET.

  The diode D3 is provided in the reverse direction between the first potential line W1 and the output side terminal Lt2 of the coil L1. That is, the diode D3 is connected with a reverse bias between the first potential Vcc and the output side terminal Lt2 of the coil L1. The diode D4 is provided in the reverse direction between the second potential line W2 and the output side terminal Lt2 of the coil L1. That is, the diode D4 is connected with the reverse bias between the second potential Vss and the output side terminal Lt2 of the coil L1. The diode D3 and the diode D4 may be, for example, a Schottky barrier diode.

  The drive unit 60 includes a bridge circuit including a coil L1, four switches SW1 to SW4, and four diodes D1 to D4. The switch SW3 and the diode D3 are connected in parallel. When the switch SW3 is in the ON state, when the gate potential of the switching element Q11 becomes higher than the first potential Vcc, current is drawn from the gate of the switching element Q11 through the diode D3. When the gate potential of the switching element Q11 becomes lower than the first potential Vcc, a current is supplied to the gate of the switching element Q11 via the switch SW3. Thus, when the switch SW3 is in the ON state, the gate potential of the switching element Q11 is clamped to the first potential Vcc.

  The switch SW4 and the diode D4 are connected in parallel. When the gate potential of the switching element Q11 becomes higher than the second potential Vss when the switch SW4 is in an on state, current is drawn from the gate of the switching element Q11 via the switch SW4. When the gate potential of the switching element Q11 becomes lower than the second potential Vss, a current is supplied to the gate of the switching element Q11 via the diode D4. Thus, when the switch SW4 is in the ON state, the gate potential of the switching element Q11 is clamped to the second potential Vss.

  The control unit 80 controls the switch SW1, the switch SW2, the switch SW3, and the switch SW4. Specifically, the control unit 80 inputs a pulse signal to the control terminals (gates in FIG. 2) of the switches SW1 to SW4, and turns on and off the switches SW1 to SW4. As a result, the gate-source voltage Vgs11 rises, and a gate current Ig11 is generated and supplied to the gate of the switching element Q11.

  When turning on the switching element Q11, first, the control unit 80 turns on the switch SW1. As a result, the capacitor Ciss between the gate (control terminal) and the source (reference terminal) of the switching element Q11 starts to be charged by the current supplied from the first potential line W1 that applies the first potential Vcc, and the coil L1 is charged. Energy is stored. Thereafter, the control unit 80 turns off the switch SW1. Then, a closed loop is formed by the coil L1, the capacitance Ciss of the switching element Q11, and the diode D2. Then, the energy accumulated in the coil L1 is discharged, and the capacitor Ciss of the switching element Q11 is further charged. Thereafter, the control unit 80 turns on the switch SW3. As a result, the gate potential of the switching element Q11 is clamped to the first potential Vcc.

  On the other hand, when the switching element Q11 is turned off, the control unit 80 first turns on the switch SW2. As a result, the capacitance Ciss of the switching element Q11 starts to be discharged, and the discharged energy is accumulated in the coil L1. Thereafter, the control unit 80 turns off the switch SW2. Then, the energy remaining in the coil C1 and the capacitance Ciss of the switching element Q11 is regenerated to the power source E1 via the diode D1. Then, the control unit 80 turns on the switch SW4. As a result, the gate potential of the switching element Q11 is clamped to the second potential Vss.

  Next, the control of the drive unit 60 by the control unit 80 according to the drive state detected by the detection unit 70 will be described.

  FIG. 3 is a graph showing a result of an experiment performed for obtaining an optimal control parameter according to the driving state. In the example of FIG. 3, an input current Iin (hereinafter referred to as “current ID”) detected by the current sensor 71 (FIG. 1) is adopted as the driving state.

  FIG. 3 shows experimental results when the DC-DC converter 20 shown in FIG. 1 and the driving apparatus 50 of the first embodiment shown in FIG. 2 are used. In FIG. 3, an on time (hereinafter referred to as “charging time”) from when the switch SW <b> 1 is turned on to when it is turned off is employed as a control parameter for controlling the drive unit 60. In the drive unit 60 of FIG. 2, the switching speed of the switching element Q11 increases as the charging time of the switch SW1 increases.

  In FIG. 3, the graph in the left column shows the experimental results when the charging time is set to 65 ns, 70 ns, 75 ns, 80 ns, and 85 ns.

  Further, the graph in the right column in FIG. 3 shows experimental results when the charging time is set to 65 ns and when the charging time is set to an optimum value. In the graph in the right column of FIG. 3, for each current ID, the experimental result of the optimum value is plotted with a triangular mark, and the experimental result of 65 ns is plotted with a diamond mark. Here, the optimum value is a charging time during which the peak value (Vds (H) .max: ringing voltage) of the drain-source voltage Vds (H) of the switching element Q12 can be set to 330 V or less, and the switching loss A charging time that can minimize Eon is employed.

  In FIG. 3, section (a) is a graph showing the relationship between the ringing voltage (Vds (H) .max) and current ID according to the charging time, the vertical axis shows the ringing voltage, and the horizontal axis shows the current. ID is shown.

  Section (b) is a graph showing the relationship between the switching loss (Eon) and the current ID according to the charging time, the vertical axis shows the loss, and the horizontal axis shows the current ID.

  Section (c) is a graph showing the relationship between the voltage change rate (dV (L) / dt) of the drain-source voltage V (L) of the switching element Q11 and the current ID according to the charging time, The vertical axis represents the voltage change rate, and the horizontal axis represents the current ID.

  Section (d) is a graph showing the relationship between the voltage ID (dV (H) / dt) of the voltage V (H) between the drain and source of the switching element Q12 and the current ID according to the charging time. The vertical axis represents the voltage change rate, and the horizontal axis represents the current ID.

  As shown in the left column of section (a), it can be seen that the ringing voltage (Vds (H) .max) increases as the charging time increases. Therefore, in the graph in the left column of section (a), in each current ID, the experimental results of 65 ns, 70 ns, 75 ns, 80 ns, and 85 ns are plotted with rhombus marks in order from the lowest voltage side.

  Here, a condition that the ringing voltage (Vds (H) .max) is set to 330 V or less is imposed, and the maximum charging time that can reduce the ringing voltage to 330 V or less is 65 ns in all current IDs. Therefore, in a method that employs a configuration that does not change the charging time according to the driving state (hereinafter, referred to as “method of comparative example”), 65 ns is set as the charging time. This makes it impossible to set an optimal charging time according to the current ID. For example, when the current ID is 20 A, the charging time is set to 65 ns in the method of the comparative example even though the ringing voltage (Vds (H) .max) is 330 V or less even if the charging time is set to 80 ns. Therefore, the optimum value is not set.

  As shown in the left column of section (b), it can be seen that the switching loss increases as the charging time decreases. Therefore, in the graph in the left column of section (b), the experimental results of 85 ns, 80 ns, 75 ns, 70 ns, and 65 ns are plotted with rhombus marks in order from the lowest switching loss in each current ID.

  Therefore, in the method of the first embodiment (hereinafter referred to as “proposed method”), as shown in the right column of section (a), the ringing voltage (Vds (H) .max) is obtained at each current ID. Is set to the charging time that can minimize the switching loss Eon (that is, the maximum charging time as can be seen from the section (b)).

  Specifically, when the current ID is 5 [A], the charging time is set to 65 ns, when the current ID is 10 [A], the charging time is set to 70 ns, and when the current ID is 15 [A]. The charging time is set to 75 ns, and when the current ID is 20 [A], the charging time is set to 80 ns. As a result, the charging time is optimized.

  In the right column of section (b), the switching loss for each current ID when the optimum value of the charging time set in section (a) is adopted is plotted with a triangular mark. In this case, the switching loss of the proposed method is lower than that of the comparative example in all current IDs, and the switching loss is reduced by 18% when the current ID is 20A.

  As shown in the left column of section (c), the voltage change rate (dV (L) / dt) increases as the charging time increases, as does the ringing voltage (Vds (H) .max). I understand. Therefore, in the graph in the left column of section (c), in each current ID, the voltage change rate (dV (L) / dt) has a diamond shape of the experimental results of 65 ns, 70 ns, 75 ns, 80 ns, and 85 ns in order from the lowest. It is plotted with the mark.

  In the right column of section (c), the voltage change rate (dV (L) / dt) for each current ID when the optimum value of the charging time set in section (a) is adopted is plotted with a triangle mark. Yes. In this case, the voltage change rate (dV (L) / dt) is higher in the proposed method than in the comparative example for all current IDs.

  As shown in the left column of section (d), the voltage change rate (dV (H) / dt) increases as the charging time increases, as does the ringing voltage (Vds (H) .max). I understand. Therefore, in the graph in the left column of section (d), the voltage change rate (dV (H) / dt) for each current ID has a diamond shape of the experimental results of 65 ns, 70 ns, 75 ns, 80 ns, and 85 ns in order from the lowest. It is plotted with the mark.

  In the right column of section (d), the voltage change rate (dV (H) / dt) for each current ID when the optimum value of the charging time set in section (a) is adopted is plotted with a triangle mark. Yes. In this case, the voltage change rate (dV (H) / dt) is higher in the proposed method than in the comparative example for all current IDs.

  The charging time of the proposed method shown in the right column of the section (c) and the charging time of the proposed method shown in the right column of the section (d) are both of the voltage change rate defined by the isolators 91 and 92. The condition is satisfied.

  FIG. 4 is a graph showing each switching characteristic when the charging time is changed when the current ID is 10 [A]. In FIG. 4, section (a) is a graph showing the relationship between the ringing voltage (Vds (H) .max) and charging time, and section (b) shows the voltage change rate (dV (L) / dt) and charging. It is the graph which showed the relationship with time, the section (c) is the graph which showed the relationship between switching loss (Eon) and charging time, and the section (d) is a voltage change rate (dV (H) / dt). It is the graph which showed the relationship between charging time.

  As shown in sections (a), (b), (d), the ringing voltage (Vds (H) .max), the voltage change rate (dV (L) / dt), and the voltage change rate (dV (H) / While dt) increases with increasing charging time, switching loss (Eon) decreases with increasing charging time, as shown in section (c). This is because the ringing voltage (Vds (H) .max), voltage change rate (dV (L) / dt), and voltage change rate (dV (H) / dt) increase the switching speed of the switching elements Q11 and Q12. This is because the switching loss (Eon) has a characteristic that increases as the switching speed increases, but decreases as the switching speed increases.

  In the driving device 50 according to the first embodiment, the ringing voltage (Vds (H) .max) is set to 330 V or less for each current ID as indicated by the triangular mark in the section (a) of FIG. Of the charging times that satisfy the conditions, a charging time (that is, the maximum charging time) at which the switching loss Eon is minimized is obtained in advance, and a table (an example of setting information) is created. The control unit 80 holds the created table in advance.

  FIG. 5 is a diagram schematically illustrating an example of the table 81 held by the control unit 80 of the driving device 50 according to the first embodiment.

  From the experimental results of FIG. 3 and FIG. 4, in the table 81 (an example of the charging table) of the first embodiment, the charging time TA is 65 ns in the range where the current ID is 0 <ID ≦ 5 [A] (an example of the classification). In the range where the current ID is 5 <ID ≦ 10 [A] (an example of classification), the charging time TA is set to 70 ns, and the range where the current ID is 10 <ID ≦ 15 [A] (an example of classification) ), The charging time TA is set to 75 ns, and the charging time TA is set to 80 ns in the range where the current ID is 15 <ID ≦ 20 [A] (an example of classification).

  The control unit 80 acquires the current ID detected by the current sensor 71 (FIG. 1) of the detection unit 70. The control unit 80 extracts the charging time TA corresponding to the acquired current ID from the held table 81. The control unit 80 controls the driving unit 60 so that the ON time of the switch SW1 matches the extracted charging time TA.

  Next, using FIGS. 6 and 7, when the current ID is 20 [A], the waveform of the proposed method of the first embodiment is compared with the waveform of the method of the comparative example.

  FIG. 6 is a timing chart schematically showing a simulation result of the driving device 50 when the switching element Q11 is turned on by the proposed method. FIG. 7 is a timing chart schematically showing a simulation result of the driving device 50 when the switching element Q11 is turned on by the method of the comparative example.

  6 and 7, section (a) is a timing chart of the DC-DC converter 20, where the vertical axis indicates voltage, current, and power, and the horizontal axis indicates time. Section (b) is a timing chart of the driving device 50, where the vertical axis indicates voltage and current, and the horizontal axis indicates time.

  As described with reference to FIG. 3, when the current ID is 20 [A], in the proposed method of FIG. 6, the charging time TA is set to 80 [ns], and in the method of the comparative example of FIG. The charging time TA is set to 65 [ns].

  In FIG. 6, the switch SW1 is turned on during the charging time TA from time tm1 to time tm2. As a result, the gate current Ig11 is supplied from the first potential line W1 to the gate of the switching element Q11, the gate-source voltage Vgs11 of the switching element Q11 gradually increases, and the capacitor Ciss is charged. Further, energy is accumulated in the coil L1.

  When the switch SW1 is turned off at time tm2, the energy stored in the coil L1 is discharged, and further, the gate current Ig11 is supplied to the gate of the switching element Q11, and the gate-source voltage Vgs11 of the switching element Q11. Increases and the capacitor Ciss is charged. As a result, the drain-source current Ids11 of the switching element Q11 begins to increase, and the drain-source voltage Vds (L) of the switching element Q11 begins to decrease.

  At time tm3, the voltage Vgs11 exceeds the threshold value. As a result, the drain-source voltage Vds (L) of the switching element Q11 starts to rapidly decrease, and the drain-source voltage Vds (H) of the switching element Q12 starts to increase.

  At time tm4, the voltage Vds (L) completely falls, the voltage Vds (H) completely rises, and the current Ids11 completely rises.

  The waveform of the voltage Vds (H) after the time tm4 should be essentially flat, but as shown in the section (a), the waveform of the voltage Vds (H) has a swell. The undulation of this waveform is ringing, and the ringing voltage Vds (H). max is defined by the peak value of the voltage Vds (H).

  Eon11 indicates a switching loss of the switching element Q11, starts to increase slightly before time tm3, reaches a peak at time tm3, and falls at time tm4.

  At time tm5, the switch SW3 is turned on. As a result, the voltage Vgs of the switching element Q11 is clamped at the first potential Vcc.

  The outline of the control in the timing chart of FIG. 7 is the same as FIG. 6, but in FIG. 7, the charging time TA is set to 65 [ns], which is shorter than 80 [ns] in FIG.

  For this reason, in FIG. 6, the switching speed is higher than in FIG. Therefore, in FIG. 6, the width of the waveform of the switching loss Eon11 is narrower than that in FIG. 7, and the switching loss Eon11 is smaller than that in FIG.

  In FIG. 6, the ringing voltage Vds (H). Although max is slightly higher, the upper limit of 330 [V] is satisfied.

  In FIG. 6, the voltage change rates of the voltages Vds (H) and Vds (L) are higher as the switching speed is increased than in FIG. 7, but the voltage change rates defined by the isolators 91 and 92 are increased. The condition is satisfied.

(Second Embodiment)
The configuration of the drive device 50 of the second embodiment is the same as the drive device 50 of the first embodiment shown in FIG. Hereinafter, the second embodiment will be described focusing on the differences from the first embodiment.

  The control of the drive unit 60 by the control unit 80 according to the second embodiment in accordance with the drive state detected by the detection unit 70 will be described with reference to FIG.

  FIG. 8 is a graph showing a result of an experiment performed for obtaining an optimal control parameter according to the driving state in the second embodiment. In the example of FIG. 8, the input current Iin (hereinafter referred to as “current ID”) detected by the current sensor 71 (FIG. 1) is employed as the driving state, as in the first embodiment.

  FIG. 8 shows an experimental result when the DC-DC converter 20 shown in FIG. 1 and the driving device 50 shown in FIG. 2 are used. In FIG. 8, the time from when the switch SW1 is turned off to when the switch SW3 is turned on is adopted as a control parameter for controlling the drive unit 60. As described with reference to FIG. 2, the energy accumulated in the coil L1 is discharged during the time from when the switch SW1 is turned off to when the switch SW3 is turned on. Therefore, the time from when the switch SW1 is turned off to when the switch SW3 is turned on is hereinafter referred to as “discharge time”. In the drive unit 60 of FIG. 2, the switching speed of the switching element Q11 increases as the discharge time decreases.

  The graph in the left column in FIG. 8 shows the experimental results when the discharge time is set to 50 ns, 55 ns, 60 ns, 65 ns, and 70 ns.

  Moreover, the graph of the right column in FIG. 8 has shown the experimental result when the discharge time is set to 65 ns and when the discharge time is set to the optimum value. In the graph in the right column of FIG. 8, for each current ID, the experimental result of the optimum value is plotted with a triangular mark, and the experimental result of 65 ns is plotted with a diamond mark. Here, the optimum value is the discharge time during which the peak value (Vds (H) .max: ringing voltage) of the drain-source voltage Vds (H) of the switching element Q12 can be 346V or less, and the switching loss A discharge time that can minimize Eon is employed.

  In FIG. 8, section (a) is a graph showing the relationship between the ringing voltage (Vds (H) .max) and current ID according to the discharge time, the vertical axis shows the ringing voltage, and the horizontal axis shows the current. ID is shown.

  Section (b) is a graph showing the relationship between the switching loss (Eon) and the current ID according to the discharge time, the vertical axis shows the loss, and the horizontal axis shows the current ID.

  Section (c) is a graph showing the relationship between the voltage change rate (dV (L) / dt) of the drain-source voltage V (L) of the switching element Q11 and the current ID according to the discharge time, The vertical axis represents the voltage change rate, and the horizontal axis represents the current ID.

  Section (d) is a graph showing the relationship between the voltage change rate (dV (H) / dt) of the voltage V (H) between the drain and source of the switching element Q12 and the current ID according to the discharge time. The vertical axis represents the voltage change rate, and the horizontal axis represents the current ID.

  As shown in the left column of section (a), it can be seen that the ringing voltage (Vds (H) .max) increases as the discharge time decreases. Therefore, in the graph in the left column of section (a), the experimental results of 70 ns, 65 ns, 60 ns, 55 ns, and 50 ns are plotted with rhombus marks in order from the lowest voltage side in each current ID.

  Here, the condition that the ringing voltage (Vds (H) .max) is set to 346 V or less is imposed, and the minimum discharge time for which the ringing voltage can be set to 346 V or less is 65 ns in all current IDs. Therefore, in a method that employs a configuration that does not change the discharge time according to the driving state (hereinafter, referred to as “method of comparative example”), 65 ns is set as the discharge time. In this case, an optimal discharge time cannot be set according to the current ID. For example, when the current ID is 20 A, even if the discharge time is set to 50 ns, the discharge time is set to 65 ns in the method of the comparative example even though the ringing voltage (Vds (H) .max) is 346 V or less. Therefore, the optimum value is not set.

  As shown in the left column of section (b), it can be seen that the switching loss increases as the discharge time increases. Therefore, in the graph in the left column of section (b), the experimental results of 50 ns, 55 ns, 60 ns, 65 ns, and 70 ns are plotted with rhombus marks in order from the lowest switching loss in each current ID.

  Therefore, in the method of the second embodiment (hereinafter referred to as “proposed method”), as shown in the right column of section (a), the ringing voltage (Vds (H) .max) is obtained at each current ID. Is set to the discharge time that can minimize the switching loss Eon (that is, the minimum discharge time as can be seen from the section (b)).

  Specifically, when the current ID is 2.5 [A], the discharge time is set to 60 ns, when the current ID is 10 [A], the discharge time is set to 65 ns, and the current ID is 15 [A]. Is set to 55 ns, and when the current ID is 20 [A], the discharge time is set to 50 ns. This optimizes the discharge time.

  In the right column of section (b), the switching loss for each current ID when the optimum value of the discharge time set in section (a) is adopted is plotted with a triangular mark. In this case, when the current ID is 10A, the switching loss is the same between the proposed method and the comparative example. When the current ID is other than 10A, the proposed method has a lower switching loss than the comparative example, and the switching is performed when the current ID is 20A. The loss was reduced by 26%.

  As shown in the left column of section (c), the voltage change rate (dV (L) / dt) increases as the discharge time decreases, as does the ringing voltage (Vds (H) .max). I understand. Therefore, in the graph in the left column of section (c), in each current ID, the voltage change rate (dV (L) / dt) has a diamond shape of experimental results of 70 ns, 65 ns, 60 ns, 55 ns, and 50 ns in order from the lowest. It is plotted with the mark.

  In the right column of section (c), the voltage change rate (dV (L) / dt) for each current ID when the optimum value of the discharge time set in section (a) is adopted is plotted with a triangle mark. Yes. In this case, the voltage change rate (dV (L) / dt) is higher in the proposed method than in the comparative example when the current ID is 15 A or more, and is almost the same when the current ID is 10 A or less.

  As shown in the left column of section (d), the voltage change rate (dV (H) / dt) increases as the discharge time decreases, as does the ringing voltage (Vds (H) .max). I understand. Therefore, in the graph in the left column of section (d), the experimental results of 70 ns, 65 ns, 60 ns, 55 ns, and 50 ns of the voltage change rate (dV (H) / dt) are diamond-shaped in order from the lower side for each current ID. It is plotted with the mark.

  In the right column of section (d), the voltage change rate (dV (H) / dt) for each current ID when the optimum value of the discharge time set in section (a) is adopted is plotted with a triangular mark. Yes. In this case, the voltage change rate (dV (H) / dt) is higher in the proposed method than in the comparative example when the current ID is 15 A or more, and is almost the same when the current ID is 10 A or less.

  The discharge time of the proposed method shown in the right column of the section (c) and the discharge time of the proposed method shown in the right column of the section (d) are both of the voltage change rate defined by the isolators 91 and 92. The condition is satisfied.

  FIG. 9 is a graph showing each switching characteristic when the discharge time is changed when the current ID is 10 [A]. In FIG. 9, section (a) is a graph showing the relationship between the ringing voltage (Vds (H) .max) and the discharge time, and section (b) shows the voltage change rate (dV (L) / dt) and the discharge. It is the graph which showed the relationship with time, the section (c) is the graph which showed the relationship between switching loss (Eon) and discharge time, and the section (d) is a voltage change rate (dV (H) / dt). It is the graph which showed the relationship between discharge time.

  As shown in sections (a), (b), (d), the ringing voltage (Vds (H) .max), the voltage change rate (dV (L) / dt), and the voltage change rate (dV (H) / While dt) increases as the discharge time decreases, the switching loss (Eon) decreases as the discharge time decreases as shown in section (c). This is because the ringing voltage (Vds (H) .max), voltage change rate (dV (L) / dt), and voltage change rate (dV (H) / dt) increase the switching speed of the switching elements Q11 and Q12. This is because the switching loss (Eon) has a characteristic that increases as the switching speed increases, but decreases as the switching speed increases.

  In the driving device 50 according to the second embodiment, the ringing voltage (Vds (H) .max) is set to 346 V or less for each current ID as indicated by the triangular mark in the section (a) of FIG. Of the discharge times that satisfy the conditions, a discharge time (that is, the minimum discharge time) at which the switching loss Eon is minimized is obtained in advance, and a table (an example of setting information) is created. The control unit 80 holds the created table in advance.

  FIG. 10 is a diagram schematically illustrating an example of the table 82 held by the control unit 80 of the driving device 50 according to the second embodiment.

  From the experimental results of FIGS. 8 and 9, in the table 82 (an example of the discharge table) of the second embodiment, the discharge time TB is within the range where the current ID is 0 <ID ≦ 2.5 [A] (an example of the section). Is set to 60 ns, and the current ID is in the range of 2.5 <ID ≦ 10 [A] (an example of classification), the discharge time TB is set to 65 ns, and the current ID is in the range of 10 <ID ≦ 15 [A]. In (an example of classification), the discharge time TB is set to 55 ns, and in a range where the current ID is 15 <ID ≦ 20 [A] (an example of the classification), the discharge time TB is set to 50 ns.

  The control unit 80 acquires the current ID detected by the current sensor 71 (FIG. 1) of the detection unit 70. The control unit 80 extracts the discharge time TB corresponding to the acquired current ID from the held table 82. The control unit 80 controls the driving unit 60 so that the discharge time from the turn-off of the switch SW1 to the turn-on of the switch SW3 coincides with the extracted discharge time TB.

  Next, using FIGS. 11 and 12, when the current ID is 20 [A], the waveform of the proposed method of the second embodiment is compared with the waveform of the method of the comparative example.

  FIG. 11 is a timing chart schematically showing a simulation result of the driving device 50 when the switching element Q11 is turned on by the proposed method of the second embodiment. FIG. 12 is a timing chart schematically showing a simulation result of the driving device 50 when the switching element Q11 is turned on by the method of the comparative example.

  11 and 12, section (a) is a timing chart of the DC-DC converter 20, the vertical axis indicates voltage, current, and power, and the horizontal axis indicates time. Section (b) is a timing chart of the driving device 50, where the vertical axis indicates voltage and current, and the horizontal axis indicates time.

  As described with reference to FIG. 8, when the current ID is 20 [A], in the proposed method of FIG. 11, the discharge time TB is set to 50 [ns], and in the method of the comparative example of FIG. The discharge time TB is set to 65 [ns].

  In FIG. 11, when the switch SW1 is turned on at time tn1, the gate current Ig11 is supplied to the gate of the switching element Q11, the gate-source voltage Vgs11 of the switching element Q11 gradually increases, and the capacitor Ciss is charged. The Further, energy is accumulated in the coil L1. When the switch SW1 is turned off at time tn2, the energy accumulated in the coil L1 is discharged. Further, the gate current Ig11 is supplied to the gate of the switching element Q11, and the gate-source voltage Vgs11 of the switching element Q11 is changed. The capacity Ciss is charged. At time tn3, the drain-source current Ids11 of the switching element Q11 starts to increase, and the drain-source voltage Vds (L) of the switching element Q11 starts to decrease.

  At time tn4, the switch SW3 is turned on, and the discharge time TB ends. As a result, the voltage Vgs of the switching element Q11 is clamped at the first potential Vcc. At time tn5 after time tn4, the voltage Vgs11 exceeds the threshold value. As a result, the drain-source voltage Vds (L) of the switching element Q11 starts to rapidly decrease, and the drain-source voltage Vds (H) of the switching element Q12 starts to increase.

  At time tn6, the voltage Vds (L) completely falls, the voltage Vds (H) completely rises, and the current Ids11 completely rises.

  The waveform of voltage Vds (H) after time tn6 should be essentially flat, but as shown in section (a), ringing (swell) occurs in the waveform of voltage Vds (H). ing.

  Eon11 indicates a switching loss of the switching element Q11, starts to increase slightly before time tn3, reaches a peak slightly after time tn5, and falls at time tn6.

  The outline of the control in the timing chart of FIG. 12 is the same as FIG. 11, but in FIG. 12, the discharge time TB is set to 65 [ns], which is longer than 50 [ns] in FIG.

  For this reason, in FIG. 11, the switching speed is higher than in FIG. Therefore, in FIG. 11, the width of the waveform of the switching loss Eon11 is narrower than that of FIG. 12, and the switching loss Eon11 is reduced as compared with FIG.

  In FIG. 11, the ringing voltage Vds (H). Although max is slightly higher, the upper limit value of 346 [V] is satisfied.

  In FIG. 11, the voltage change rate of the voltages Vds (H) and Vds (L) is higher than that of FIG. 12 as the switching speed is increased, but the voltage change rate defined by the isolators 91 and 92 is increased. The condition is satisfied.

(Third embodiment)
The configuration of the drive device 50 of the third embodiment is the same as that of the drive device 50 of the first embodiment shown in FIG. Hereinafter, the third embodiment will be described focusing on differences from the first embodiment.

  The control of the drive unit 60 by the control unit 80 according to the third embodiment in accordance with the drive state detected by the detection unit 70 will be described with reference to FIG.

  FIG. 13 is a graph showing a result of an experiment performed for obtaining an optimal control parameter according to the driving state in the third embodiment. In the example of FIG. 13, the input current Iin (hereinafter referred to as “current ID”) detected by the current sensor 71 (FIG. 1) is employed as the driving state, as in the first embodiment.

  FIG. 13 shows the experimental results when the DC-DC converter 20 shown in FIG. 1 and the driving device 50 shown in FIG. 2 are used. In FIG. 13, the time during which both the switches SW1 and SW4 are turned on is employed as a control parameter for controlling the drive unit 60. As described with reference to FIG. 2, while the switch SW4 is on, the gate of the switching element Q11 is clamped at the second potential Vss. For this reason, even if the switch SW1 is turned on, no gate current is supplied to the gate of the switching element Q11. However, when the switch SW1 is turned on, energy is accumulated in the coil L1. Therefore, the time during which both switches SW1 and SW4 are turned on is hereinafter referred to as “precharge time”. In the drive unit 60 of FIG. 2, as the precharge time becomes longer, the energy stored in the coil L1 increases, so that the switching speed of the switching element Q11 increases.

  The graph in the left column in FIG. 13 shows the experimental results when the precharge time is set to 50 ns, 60 ns, 70 ns, 75 ns, 80 ns, and 90 ns, respectively.

  Further, the graph in the right column in FIG. 13 shows experimental results when the precharge time is set to 60 ns and when the precharge time is set to an optimum value. In the graph in the right column of FIG. 13, for each current ID, the experimental result of the optimum value is plotted with a triangular mark, and the experimental result of 60 ns is plotted with a diamond mark. Here, the optimum value is a precharge time during which the peak value (Vds (H) .max: ringing voltage) of the drain-source voltage Vds (H) of the switching element Q12 can be reduced to 333 V or less. A precharge time that can minimize the loss Eon is employed.

  In FIG. 13, section (a) is a graph showing the relationship between the ringing voltage (Vds (H) .max) and the current ID according to the precharge time, the vertical axis shows the ringing voltage, and the horizontal axis shows Current ID is shown.

  Section (b) is a graph showing the relationship between the switching loss (Eon) and the current ID according to the precharge time, the vertical axis shows the loss, and the horizontal axis shows the current ID.

  Section (c) is a graph showing the relationship between the voltage ID (dV (L) / dt) of the voltage V (L) between the drain and source of the switching element Q11 and the current ID according to the precharge time. The vertical axis indicates the voltage change rate, and the horizontal axis indicates the current ID.

  Section (d) is a graph showing the relationship between the voltage ID (dV (H) / dt) of the voltage V (H) between the drain and source of the switching element Q12 and the current ID according to the precharge time. The vertical axis indicates the voltage change rate, and the horizontal axis indicates the current ID.

  As shown in the left column of section (a), it can be seen that the ringing voltage (Vds (H) .max) increases as the precharge time increases. Therefore, in the graph in the left column of section (a), in each current ID, the experimental results of 50 ns, 60 ns, 70 ns, 75 ns, 80 ns, and 90 ns are plotted with rhombus marks in order from the lowest voltage.

  Here, the condition that the ringing voltage (Vds (H) .max) is set to 333 V or less is imposed, and the maximum precharge time for which the ringing voltage can be set to 333 V or less is 60 ns in all current IDs. Therefore, in a method that employs a configuration that does not change the precharge time according to the driving state (hereinafter referred to as “method of comparative example”), 60 ns is set as the precharge time. This makes it impossible to set an optimal precharge time according to the current ID. For example, when the current ID is 20 A, even if the precharge time is set to 75 ns, the ring charge voltage (Vds (H) .max) is 333 V or less, but the precharge time is set to 60 ns in the method of the comparative example. Because it is set, the optimum value is not set.

  As shown in the left column of section (b), it can be seen that the switching loss increases as the precharge time decreases. Therefore, in the graph in the left column of section (b), the experimental results of 90 ns, 80 ns, 75 ns, 70 ns, 60 ns, and 50 ns are plotted with rhombus marks in order from the lowest switching loss in each current ID.

  Therefore, in the method of the third embodiment (hereinafter referred to as “proposed method”), as shown in the right column of section (a), the ringing voltage (Vds (H) .max) is obtained at each current ID. Among the precharge times that can be reduced to 333 V or less, the precharge time that can minimize the switching loss Eon (that is, the maximum precharge time as can be seen from section (b)) is set.

  Specifically, when the current ID is 2.5 [A], the precharge time is set to 60 ns, when the current ID is 10 [A], the precharge time is set to 70 ns, and the current ID is 15, In the case of 20 [A], the precharge time is set to 75 ns. Thereby, the precharge time is optimized.

  In the right column of section (b), the switching loss for each current ID when the optimum value of the precharge time set in section (a) is adopted is plotted with triangular marks. In this case, when the current ID is 2.5 A, the proposed method and the comparative example have the same switching loss. In other current IDs, the proposed method has a lower switching loss than the comparative example, and the current ID is 20 A. Switching loss was reduced by 23%.

  As shown in the left column of section (c), the voltage change rate (dV (L) / dt) increases as the precharge time increases, as does the ringing voltage (Vds (H) .max). I understand that. Therefore, in the graph in the left column of section (c), in each current ID, the voltage change rate (dV (L) / dt) is an experimental result of 50 ns, 60 ns, 70 ns, 75 ns, 80 ns, and 90 ns in order from the lowest. Are plotted with diamond marks.

  In the right column of section (c), the voltage change rate (dV (L) / dt) for each current ID when the optimum value of the precharge time set in section (a) is adopted is plotted with a triangular mark. ing. In this case, the voltage change rate (dV (L) / dt) is higher in the proposed method than in the comparative example when the current ID is 10 A or more, and is the same when the current ID is 2.5 A.

  As shown in the left column of section (d), the rate of voltage change (dV (H) / dt) increases as the precharge time increases, as does the ringing voltage (Vds (H) .max). I understand that. Therefore, in the graph in the left column of section (d), in each current ID, the voltage change rate (dV (H) / dt) is an experimental result of 50 ns, 60 ns, 70 ns, 75 ns, 80 ns, and 90 ns in order from the lowest. Are plotted with diamond marks.

  In the right column of section (d), the voltage change rate (dV (H) / dt) for each current ID when the optimum value of the precharge time set in section (a) is adopted is plotted with a triangle mark. ing. In this case, the voltage change rate (dV (H) / dt) is higher in the proposed method than in the comparative example when the current ID is 10 A or more, and is the same when the current ID is 2.5 A.

  Note that the precharge time of the proposed method shown in the right column of section (c) and the precharge time of the proposed method shown in the right column of section (d) are both voltage changes defined by the isolators 91 and 92. The rate condition is satisfied.

  FIG. 14 is a graph showing each switching characteristic when the precharge time is changed when the current ID is 10 [A]. In FIG. 14, section (a) is a graph showing the relationship between the ringing voltage (Vds (H) .max) and the precharge time, and section (b) shows the voltage change rate (dV (L) / dt) and It is the graph which showed the relationship with precharge time, Section (c) is the graph which showed the relationship between switching loss (Eon) and precharge time, Section (d) is voltage change rate (dV (H)) / Dt) is a graph showing the relationship between the precharge time.

  As shown in sections (a), (b), (d), the ringing voltage (Vds (H) .max), the voltage change rate (dV (L) / dt), and the voltage change rate (dV (H) / While dt) increases with increasing precharge time, switching loss (Eon) decreases with increasing precharge time, as shown in section (c). This is because the ringing voltage (Vds (H) .max), voltage change rate (dV (L) / dt), and voltage change rate (dV (H) / dt) increase the switching speed of the switching elements Q11 and Q12. This is because the switching loss (Eon) has a characteristic that increases as the switching speed increases, but decreases as the switching speed increases.

  In the driving device 50 according to the third embodiment, the ringing voltage (Vds (H) .max) is set to 333 V or less for each current ID as indicated by the triangular mark in the section (a) of FIG. Of the precharge times that satisfy the conditions, a precharge time (that is, the maximum precharge time) that minimizes the switching loss Eon is obtained in advance, and a table (an example of setting information) is created. The control unit 80 holds the created table in advance.

  FIG. 15 is a diagram schematically illustrating an example of a table 83 held by the control unit 80 of the driving device 50 according to the third embodiment.

  From the experimental results of FIGS. 13 and 14, in the table 83 (an example of the precharge table) of the third embodiment, in the range where the current ID is 0 <ID ≦ 2.5 [A] (an example of the division), the precharge is performed. When the time TC is set to 60 ns and the current ID is in the range of 2.5 <ID ≦ 10 [A] (an example of a section), the precharge time TC is set to 70 ns and the current ID is 10 <ID ≦ 20 [A ] (An example of division), the precharge time TC is set to 75 ns.

  The control unit 80 acquires the current ID detected by the current sensor 71 (FIG. 1) of the detection unit 70. The control unit 80 extracts the precharge time TC corresponding to the acquired current ID from the held table 83. The control unit 80 controls the drive unit 60 so that the precharge time during which both the switches SW1 and SW4 are turned on coincides with the extracted precharge time TC.

  Next, using FIGS. 16 and 17, when the current ID is 20 [A], the waveform of the proposed method of the third embodiment is compared with the waveform of the method of the comparative example.

  FIG. 16 is a timing chart schematically showing a simulation result of the drive device 50 when the switching element Q11 is turned on by the proposed method of the third embodiment. FIG. 17 is a timing chart schematically showing a simulation result of the drive device 50 when the switching element Q11 is turned on by the method of the comparative example.

  16 and 17, a section (a) is a timing chart of the DC-DC converter 20, where the vertical axis indicates voltage, current, and power, and the horizontal axis indicates time. Section (b) is a timing chart of the driving device 50, where the vertical axis indicates voltage and current, and the horizontal axis indicates time.

  As described with reference to FIG. 13, when the current ID is 20 [A], the precharge time TC is set to 75 [ns] in the proposed method of FIG. 16, and the method of the comparative example of FIG. In this case, the precharge time TC is set to 60 [ns].

  In FIG. 16, the switch SW1 is turned on at time tp1. Prior to time tp1, the switch SW4 has been turned on, and the gate of the switching element Q11 is clamped at the second potential Vss. For this reason, the gate current Ig11 is not supplied to the gate of the switching element Q11, and energy is accumulated in the coil L1.

  At time tp2, the switches SW1 and SW4 are turned off. Then, the energy accumulated in the coil L1 is discharged, the gate current Ig11 is supplied to the gate of the switching element Q11, the gate-source voltage Vgs11 of the switching element Q11 gradually increases, and the capacitor Ciss is charged. .

  At time tp3, the drain-source current Ids11 of the switching element Q11 starts to increase, and the drain-source voltage Vds (L) of the switching element Q11 starts to decrease.

  At time tp4, the voltage Vgs11 exceeds the threshold value. As a result, the drain-source voltage Vds (L) of the switching element Q11 starts to rapidly decrease, and the drain-source voltage Vds (H) of the switching element Q12 starts to increase.

  At time tp5, the voltage Vds (L) completely falls, the voltage Vds (H) completely rises, and the current Ids11 completely rises.

  The waveform of the voltage Vds (H) after time tp5 should be essentially flat, but as shown in section (a), ringing (swell) occurs in the waveform of the voltage Vds (H). ing.

  Eon11 indicates a switching loss of the switching element Q11, starts to increase at about time tp3, reaches a peak at about time tp4, and falls at time tp5.

  The outline of the control in the timing chart of FIG. 17 is the same as that in FIG. 16, but in FIG. 17, the precharge time TC is set to 60 [ns], which is shorter than 75 [ns] in FIG.

  For this reason, in FIG. 16, the switching speed is higher than in FIG. Therefore, in FIG. 16, the width of the waveform of the switching loss Eon11 is narrower than that in FIG. 17, and the switching loss Eon11 is smaller than that in FIG.

  In FIG. 16, the ringing voltage Vds (H). Although max is slightly higher, the upper limit value of 333 [V] is satisfied.

  In FIG. 16, the voltage change rates of the voltages Vds (H) and Vds (L) are higher as the switching speed is increased than in FIG. 17, but the voltage change rates defined by the isolators 91 and 92 are increased. The condition is satisfied.

(Fourth embodiment)
FIG. 18 is a diagram schematically illustrating a driving device 50 according to the fourth embodiment. In FIG. 18, in order to simplify the description, the isolators 91 and 92 are not shown, and the second potential line W2 of the driving unit 60 is connected to the source of the switching element Q11. However, in the actual driving device 50, as shown in FIG. 1, the driving unit 60 and the switching element Q11 are connected via an isolator 91, and the driving unit 60 and the switching element Q12 are connected via an isolator 92. It is connected. Hereinafter, the fourth embodiment will be described focusing on the differences from the first embodiment.

  The drive unit 60 includes a power supply E1, a switch SW3a, a switch SW3b, a switch SW3c, a switch SW4, a diode D3, a diode D4, a resistor R1a, a resistor R1b, a resistor R1c, and a resistor R2.

  Between the first potential line W1 and the gate of the switching element Q11, a series circuit of the switch SW3a and the resistor R1a, a series circuit of the switch SW3b and the resistor R1b, and a series circuit of the switch SW3c and the resistor R1c are parallel to each other. Provided. The resistance values of the resistors R1a, R1b, and R1c will be described later.

  A series circuit of the switch SW4 and the resistor R2 is provided between the second potential line W2 and the gate of the switching element Q11. In the example of FIG. 18, the switches SW3a, 3b, and 3c are P-channel MOSFETs, and the switch SW4 is an N-channel MOSFET.

  The diode D3 is provided in the reverse direction between the first potential line W1 and the gate of the switching element Q11. That is, the diode D3 is connected with a reverse bias between the first potential Vcc and the gate of the switching element Q11. The diode D4 is provided in the reverse direction between the second potential line W2 and the gate of the switching element Q11. That is, the diode D4 is connected with a reverse bias between the second potential Vss and the gate of the switching element Q11. The diode D3 and the diode D4 may be, for example, a Schottky barrier diode.

  Next, control of the drive unit 60 by the control unit 80 according to the fourth embodiment in accordance with the drive state detected by the detection unit 70 will be described with reference to FIG.

  FIG. 19 is a graph showing a result of an experiment performed for obtaining an optimal control parameter according to the driving state in the fourth embodiment. In the example of FIG. 19, the input current Iin (hereinafter referred to as “current ID”) detected by the current sensor 71 (FIG. 1) is employed as the driving state, as in the first embodiment.

  FIG. 19 shows experimental results when the DC-DC converter 20 shown in FIG. 1 and the driving device 50 shown in FIG. 18 are used. In FIG. 19, as a control parameter for controlling the drive unit 60, the resistance of the resistor (resistor R1a, resistor R1b, or resistor R1c in FIG. 18) connected between the first potential line W1 and the gate of the switching element Q11. The value Rg is adopted. In the drive unit 60 of FIG. 18, the switching speed of the switching element Q11 increases as the resistance value Rg decreases.

  The graph in the left column in FIG. 19 shows the experimental results when the resistance value Rg is set to 1.2Ω, 1.6Ω, 2.2Ω, 2.5Ω, 3Ω, and 3.5Ω.

  Further, the graph in the right column in FIG. 19 shows experimental results when the resistance value Rg is set to 3.5Ω and when the resistance value Rg is set to an optimum value. In the graph in the right column of FIG. 19, for each current ID, the experimental result of the optimum value is plotted with a triangular mark, and the experimental result of 3.5Ω is plotted with a diamond mark. Here, the optimum value is a resistance value Rg that can reduce the peak value (Vds (H) .max: ringing voltage) of the drain-source voltage Vds (H) of the switching element Q12 to 340V or less. A resistance value Rg that can minimize the loss Eon is employed.

  In FIG. 19, section (a) is a graph showing the relationship between the ringing voltage (Vds (H) .max) and the current ID according to the resistance value Rg, the vertical axis shows the ringing voltage, and the horizontal axis shows Current ID is shown.

  Section (b) is a graph showing the relationship between the switching loss (Eon) and the current ID according to the resistance value Rg, the vertical axis shows the loss, and the horizontal axis shows the current ID.

  Section (c) is a graph showing a relationship between the voltage change rate (dV (L) / dt) of the drain-source voltage V (L) of the switching element Q11 and the current ID according to the resistance value Rg. The vertical axis indicates the voltage change rate, and the horizontal axis indicates the current ID.

  Section (d) is a graph showing the relationship between the voltage change rate (dV (H) / dt) of the drain-source voltage V (H) of the switching element Q12 and the current ID according to the resistance value Rg. The vertical axis indicates the voltage change rate, and the horizontal axis indicates the current ID.

  As shown in the left column of section (a), it can be seen that the ringing voltage (Vds (H) .max) increases as the resistance value Rg decreases. Therefore, in the graph in the left column of section (a), the experimental results of 3.5Ω, 3Ω, 2.5Ω, 2.2Ω, 1.6Ω, and 1.2Ω are shown in order from the lowest voltage for each current ID. Plotted with diamond marks.

  Here, the condition that the ringing voltage (Vds (H) .max) is set to 340 V or less is imposed, and the minimum resistance value Rg that can reduce the ringing voltage to 340 V or less is 3.5Ω in all current IDs. . Therefore, in a method that employs a configuration that does not change the resistance value Rg according to the driving state (hereinafter referred to as “method of comparative example”), 3.5Ω is set as the resistance value Rg. In this case, the optimum resistance value Rg cannot be set according to the current ID. For example, when the current ID is 20 A, even if the resistance value Rg is set to 2.2Ω, the resistance value Rg is less than 340 V even if the ringing voltage (Vds (H) .max) is 340 V or less. Since it is set to 3.5Ω, the optimum value is not set.

  As shown in the left column of section (b), it can be seen that the switching loss increases as the resistance value Rg increases. Therefore, in the graph in the left column of section (b), in each current ID, the experimental results of 1.2Ω, 1.6Ω, 2.2Ω, 2.5Ω, 3Ω, and 3.5Ω in order from the lowest switching loss. Are plotted with diamond marks.

  Therefore, in the method of the fourth embodiment (hereinafter referred to as “proposed method”), as shown in the right column of section (a), the ringing voltage (Vds (H) .max) is obtained at each current ID. Is set to a resistance value Rg that can minimize the switching loss Eon (that is, the minimum resistance value Rg as can be seen from the section (b)).

  Specifically, when the current ID is 2.5 and 5 [A], the resistance value Rg is set to 3.5Ω, and when the current ID is 10 [A], the resistance value Rg is set to 3Ω. When the ID is 15 [A], the resistance value Rg is set to 2.5Ω, and when the current ID is 20 [A], the resistance value Rg is set to 2.2Ω. Thereby, the resistance value Rg is optimized.

  In the right column of section (b), the switching loss for each current ID when the optimum resistance value Rg set in section (a) is adopted is plotted with triangular marks. In this case, when the current ID is 2.5 A and 5 A, the proposed method and the comparative example have the same switching loss. In other current IDs, the proposed method has a lower switching loss than the comparative example, and the current ID is At 20A, the switching loss was reduced by 26%.

  As shown in the left column of section (c), the voltage change rate (dV (L) / dt) increases as the resistance value Rg decreases, as does the ringing voltage (Vds (H) .max). I understand that. Therefore, in the graph in the left column of section (c), in each current ID, the voltage change rate (dV (L) / dt) is 3.5Ω, 3Ω, 2.5Ω, 2.2Ω, The experimental results of 1.6Ω and 1.2Ω are plotted with diamond marks.

  In the right column of the section (c), the voltage change rate (dV (L) / dt) with respect to each current ID when the optimum value of the resistance value Rg set in the section (a) is adopted is plotted with a triangular mark. ing. In this case, when the current ID is 10 A or more, the proposed method has a higher voltage change rate (dV (L) / dt) than the comparative example, and is the same when the current ID is 2.5 A and 5 A. Yes.

  As shown in the left column of section (d), the voltage change rate (dV (H) / dt) increases as the resistance value Rg decreases, as does the ringing voltage (Vds (H) .max). I understand that. Therefore, in the graph in the left column of section (d), in each current ID, the voltage change rate (dV (H) / dt) is 3.5Ω, 3Ω, 2.5Ω, 2.2Ω, The experimental results of 1.6Ω and 1.2Ω are plotted with diamond marks.

  In the right column of section (d), the voltage change rate (dV (H) / dt) with respect to each current ID when the optimum value of the resistance value Rg set in section (a) is adopted is plotted with a triangle mark. ing. In this case, the voltage change rate (dV (H) / dt) is higher in the proposed method than in the comparative example when the current ID is 10 A or more, and is the same when the current ID is 2.5 A and 5 A. Yes.

  The resistance value Rg of the proposed method shown in the right column of section (c) and the resistance value Rg of the proposed method shown in the right column of section (d) are both voltage changes defined by the isolators 91 and 92. The rate condition is satisfied.

  FIG. 20 is a graph showing each switching characteristic when the resistance value Rg is changed when the current ID is 10 [A]. In FIG. 20, section (a) is a graph showing the relationship between the ringing voltage (Vds (H) .max) and the resistance value Rg, and section (b) shows the voltage change rate (dV (L) / dt) and It is the graph which showed the relationship with resistance value Rg, the section (c) is the graph which showed the relationship between switching loss (Eon) and resistance value Rg, and the section (d) is voltage change rate (dV (H) / Dt) is a graph showing the relationship between the resistance value Rg.

  As shown in sections (a), (b), (d), the ringing voltage (Vds (H) .max), the voltage change rate (dV (L) / dt), and the voltage change rate (dV (H) / Although dt) increases as the resistance value Rg decreases, the switching loss (Eon) decreases as the resistance value Rg decreases, as shown in section (c). This is because the ringing voltage (Vds (H) .max), voltage change rate (dV (L) / dt), and voltage change rate (dV (H) / dt) increase the switching speed of the switching elements Q11 and Q12. This is because the switching loss (Eon) has a characteristic that increases as the switching speed increases, but decreases as the switching speed increases.

  In the driving device 50 of the fourth embodiment, as indicated by the triangular mark in the section (a) of FIG. 19, the ringing voltage (Vds (H) .max) is set to 340 V or less for each current ID. Of the resistance values Rg that satisfy the conditions, a resistance value Rg that minimizes the switching loss Eon (that is, the minimum resistance value Rg) is obtained in advance, and a table is created. The control unit 80 holds the created table in advance.

  FIG. 21 is a diagram schematically illustrating an example of the table 84 held by the control unit 80 of the driving device 50 according to the fourth embodiment.

  In the proposed method based on the experimental results of FIGS. 19 and 20, the resistance value Rg is set to 3.5Ω when the current ID is 2.5 and 5 [A], and the resistance value is set when the current ID is 10 [A]. When Rg was set to 3Ω, the resistance value Rg was set to 2.5Ω when the current ID was 15 [A], and the resistance value Rg was set to 2.2Ω when the current ID was 20 [A]. .

  On the other hand, the drive device 50 of the fourth embodiment includes three types of resistors R1a, R1b, and R1c, as shown in FIG. Accordingly, from the experimental results of FIGS. 19 and 20, a resistor having a resistance value of 2.2Ω is employed as the resistor R1a, a resistor having a resistance value of 3Ω is employed as the resistor R1b, and a resistance value of 3 is employed as the resistor R1c. .5Ω resistance is adopted.

  In the table 84 of the fourth embodiment, as shown in FIG. 21, when the current ID is 0 <ID ≦ 5 [A], the switch to be used is a switch corresponding to the resistor R1c having a resistance value of 3.5Ω. When the current ID is set to SW3c and the current ID is 5 <ID ≦ 15 [A], the switch to be used is set to the switch SW3b corresponding to the resistor R1b having a resistance value of 3Ω, and the current ID is 15 <ID ≦ 20 [A]. Then, the switch to be used is set to the switch SW3a corresponding to the resistor R1a having a resistance value of 2.2Ω.

  That is, in the experimental results of FIG. 19, as shown in section (a), the resistance value Rg was set to 2.5Ω when the current ID was 15 [A]. Therefore, even when the current ID is 15 [A], the resistor R1b having a resistance value of 3Ω is used.

  The control unit 80 acquires the current ID detected by the current sensor 71 (FIG. 1) of the detection unit 70. The control unit 80 extracts the switch corresponding to the acquired current ID from the held table 84. The control unit 80 controls the drive unit 60 to use the extracted switch.

  Next, using FIGS. 22 and 23, when the current ID is 20 [A], the waveform of the proposed method of the fourth embodiment is compared with the waveform of the method of the comparative example.

  FIG. 22 is a timing chart schematically showing a simulation result of the driving device 50 when the switching element Q11 is turned on by the proposed method of the fourth embodiment. FIG. 23 is a timing chart schematically showing a simulation result of the driving device 50 when the switching element Q11 is turned on by the method of the comparative example.

  22 and 23, section (a) is a timing chart of the DC-DC converter 20, the vertical axis indicates voltage, current, and power, and the horizontal axis indicates time. Section (b) is a timing chart of the driving device 50, where the vertical axis indicates voltage and current, and the horizontal axis indicates time.

  As described with reference to FIG. 19, when the current ID is 20 [A], the resistance value Rg is set to 2.2 [Ω] in the proposed method of FIG. In the method, the resistance value Rg is set to 3.5 [Ω]. That is, in FIG. 22, the switch SW3a (FIG. 18) is used. In FIG. 23, one type of switch SW3 to which a resistor having a resistance value of 3.5Ω is connected is used.

  In FIG. 22, the switch SW3a is turned on at time tq1. Then, the gate current Ig11 is supplied to the gate of the switching element Q11, the gate-source voltage Vgs11 of the switching element Q11 gradually increases, and the capacitor Ciss is charged. On the other hand, the switches SW3b and SW3c are kept off.

  At time tq2, the drain-source current Ids11 of the switching element Q11 starts to increase, and the drain-source voltage Vds (L) of the switching element Q11 starts to decrease.

  At time tq3, the voltage Vgs11 exceeds the threshold value. As a result, the drain-source voltage Vds (L) of the switching element Q11 starts to rapidly decrease, and the drain-source voltage Vds (H) of the switching element Q12 starts to increase.

  At time tq4, the voltage Vds (L) completely falls, the voltage Vds (H) completely rises, and the current Ids11 completely rises.

  The waveform of the voltage Vds (H) after time tq4 should be essentially flat, but as shown in the section (a), ringing (swell) occurs in the waveform of the voltage Vds (H). ing.

  Eon11 indicates the switching loss of the switching element Q11, starts increasing at about time tq2, reaches a peak at about time tq3, and falls at time tq4.

  The outline of the control in the timing chart of FIG. 23 is the same as FIG. 22, but in FIG. 23, the resistance value Rg is set to 3.5 [Ω], which is higher than 2.2 [Ω] in FIG.

  For this reason, in FIG. 22, the switching speed is higher than in FIG. Therefore, in FIG. 22, the width of the waveform of the switching loss Eon11 is narrower than that in FIG. 23, and the switching loss Eon11 is smaller than that in FIG.

  In FIG. 22, the ringing voltage Vds (H). Although max is slightly higher, the upper limit value of 340 [V] is satisfied.

  In FIG. 22, the voltage change rates of the voltages Vds (H) and Vds (L) are higher than those of FIG. 23 as the switching speed increases, but the voltage change rates defined by the isolators 91 and 92 are increased. The condition is satisfied.

  18 includes three series circuits, that is, a series circuit of a switch SW3a and a resistor 3a, a series circuit of a switch SW3b and a resistor 3b, and a series circuit of a switch SW3c and a resistor 3c. However, the fourth embodiment is not limited to this. The fourth embodiment of the present disclosure may include two series circuits or four or more series circuits. As the number of series circuits increases, the types of resistance values can be increased, so that the switching speed can be changed more finely.

(Fifth embodiment)
FIG. 24 is a diagram schematically illustrating a drive device 50 according to the fifth embodiment. In FIG. 24, the illustration of the isolators 91 and 92 is omitted to simplify the description, and the second potential line W2 of the driving unit 60 is connected to the source of the switching element Q11. However, in the actual driving device 50, as shown in FIG. 1, the driving unit 60 and the switching element Q11 are connected via an isolator 91, and the driving unit 60 and the switching element Q12 are connected via an isolator 92. It is connected. Hereinafter, the fifth embodiment will be described focusing on differences from the first embodiment.

  The drive unit 60 includes a power source E1, a start unit 63, and a clamp unit 62. The start unit 63 includes a switch SW1, a switch SW2, and a resistor R3. The input side terminal Rt31 of the resistor R3 is configured to be connectable to the first potential line W1 via the switch SW1. The input side terminal Rt31 of the resistor R3 is configured to be connectable to the second potential line W2 via the switch SW2. The output side terminal Rt32 of the resistor R3 is connected to the gate of the switching element Q11.

  The resistance value of the resistor R3 is determined to be higher than the resistance value of the resistor R1. In other words, the resistance value of the resistor R1 is determined to be lower than the resistance value of the resistor R3.

  Next, control of the drive unit 60 by the control unit 80 according to the fifth embodiment in accordance with the drive state detected by the detection unit 70 will be described with reference to FIG.

  FIG. 25 is a graph showing a result of an experiment performed for obtaining an optimal control parameter in accordance with the driving state in the fifth embodiment. In the example of FIG. 25, the input current Iin (hereinafter referred to as “current ID”) detected by the current sensor 71 (FIG. 1) is adopted as the driving state, as in the first embodiment.

  FIG. 25 shows an experimental result when the DC-DC converter 20 shown in FIG. 1 and the driving device 50 shown in FIG. 24 are used. In FIG. 25, an on-time (hereinafter referred to as “charging time”) from when the switch SW1 is turned on to when it is turned off is adopted as a control parameter for controlling the drive unit 60. In the drive unit 60 of FIG. 24, as described above, the resistance value of the resistor R3 is determined to be higher than the resistance value of the resistor R1. Therefore, the shorter the charging time of the switch SW1 (that is, the faster the switch SW3 is turned on), the higher the switching speed of the switching element Q11.

  In FIG. 25, the graph in the left column shows the experimental results when the charging time is set to 20 ns, 30 ns, 40 ns, and 45 ns.

  Further, the graph in the right column in FIG. 25 shows experimental results when the charging time is set to 45 ns and when the charging time is set to an optimum value. In the graph in the right column of FIG. 25, the experimental result of the optimum value is plotted with a triangular mark and the experimental result of 45 ns is plotted with a diamond mark for each current ID. Here, the optimum value is the charging time during which the peak value (Vds (H) .max: ringing voltage) of the drain-source voltage Vds (H) of the switching element Q12 can be reduced to 340V or less, and the switching loss A charging time that can minimize Eon is employed.

  In FIG. 25, section (a) is a graph showing the relationship between the ringing voltage (Vds (H) .max) and the current ID according to the charging time, the vertical axis shows the ringing voltage, and the horizontal axis shows the current. ID is shown.

  Section (b) is a graph showing the relationship between the switching loss (Eon) and the current ID according to the charging time, the vertical axis shows the loss, and the horizontal axis shows the current ID.

  Section (c) is a graph showing the relationship between the voltage change rate (dV (L) / dt) of the drain-source voltage V (L) of the switching element Q11 and the current ID according to the charging time, The vertical axis represents the voltage change rate, and the horizontal axis represents the current ID.

  Section (d) is a graph showing the relationship between the voltage ID (dV (H) / dt) of the voltage V (H) between the drain and source of the switching element Q12 and the current ID according to the charging time. The vertical axis represents the voltage change rate, and the horizontal axis represents the current ID.

  As shown in the left column of section (a), it can be seen that the ringing voltage (Vds (H) .max) increases as the charging time decreases, and then decreases after peaking. Therefore, in the graph in the left column of section (a), for example, when the current ID is 10 A, the experimental results of 45 ns, 40 ns, 20 ns, and 30 ns are plotted with rhombus marks in order from the lowest voltage, for example, the current ID is 15 A. , The experimental results of 45 ns, 20 ns, 40 ns, and 30 ns are plotted with rhombus marks in order from the lowest voltage side.

  Here, the condition that the ringing voltage (Vds (H) .max) is set to 340 V or less is imposed, and the minimum charging time for which the ringing voltage can be set to 340 V or less is 45 ns in all current IDs. Therefore, in a method that employs a configuration that does not change the charging time according to the driving state (hereinafter referred to as “method of comparative example”), 45 ns is set as the charging time. This makes it impossible to set an optimal charging time according to the current ID. For example, when the current ID is 20 A, the charging time is set to 45 ns in the method of the comparative example even though the ringing voltage (Vds (H) .max) is 340 V or less even if the charging time is set to 20 ns. Therefore, the optimum value is not set.

  As shown in the left column of section (b), it can be seen that the switching loss increases as the charging time increases. Therefore, in the graph in the left column of section (b), the experimental results of 20 ns, 30 ns, 40 ns, and 45 ns are plotted with rhombus marks in order from the lowest switching loss in each current ID.

  Therefore, in the method of the fifth embodiment (hereinafter referred to as “proposed method”), as shown in the right column of section (a), the ringing voltage (Vds (H) .max) is obtained at each current ID. Is set to a charging time that can minimize the switching loss Eon (that is, the minimum charging time as can be seen from the section (b)).

  Specifically, when the current ID is 2.5 [A], the charging time is set to 40 ns, and when the current ID is 10 [A] and 15 [A], the charging time is set to 45 ns. Is 20 [A], the charging time is set to 20 ns. As a result, the charging time is optimized.

  In the right column of section (b), the switching loss for each current ID when the optimum value of the charging time set in section (a) is adopted is plotted with a triangular mark. In this case, when the current ID is 10A and 15A, the switching loss is the same between the proposed method and the comparative example, and when the current ID is 2.5A and 20A, the proposed method has a lower switching loss than the comparative example. When the ID was 20A, the switching loss was reduced by 38%.

  As shown in the left column of section (c), the voltage change rate (dV (L) / dt) increases as the charging time decreases, like the ringing voltage (Vds (H) .max). After attaching, it can be seen that it has decreased. Therefore, in the graph in the left column of section (c), for example, when the current ID is 10A, the voltage change rate (dV (L) / dt) is a diamond shape in the order of 45 ns, 40 ns, 20 ns, and 30 ns in order from the lowest. For example, when the current ID is 15A, the voltage change rate (dV (L) / dt) is plotted with diamond-shaped marks in the order of 45 ns, 20 ns, 40 ns, and 30 ns in order from the lowest side. .

  In the right column of section (c), the voltage change rate (dV (L) / dt) for each current ID when the optimum value of the charging time set in section (a) is adopted is plotted with a triangle mark. Yes. In this case, the voltage change rate (dV (L) / dt) is the same between the proposed method and the comparative example when the current ID is 10A and 15A, and the proposed method is compared when the current ID is 2.5A and 20A. The voltage change rate (dV (L) / dt) is higher than the example.

  As shown in the left column of section (d), it can be seen that the voltage change rate (dV (H) / dt) increases as the charging time decreases. Therefore, in the graph in the left column of section (d), in each current ID, the voltage change rate (dV (H) / dt) is a diamond mark with the experimental results of 45 ns, 40 ns, 30 ns, and 20 ns in order from the lowest. It is plotted with.

  In the right column of section (d), the voltage change rate (dV (H) / dt) for each current ID when the optimum value of the charging time set in section (a) is adopted is plotted with a triangle mark. Yes. In this case, the voltage change rate (dV (H) / dt) is the same between the proposed method and the comparative example when the current ID is 10A and 15A, and the proposed method is compared when the current ID is 2.5A and 20A. The voltage change rate (dV (H) / dt) is higher than in the example.

  The charging time of the proposed method shown in the right column of the section (c) and the charging time of the proposed method shown in the right column of the section (d) are both of the voltage change rate defined by the isolators 91 and 92. The condition is satisfied.

  FIG. 26 is a graph showing each switching characteristic when the charging time is changed when the current ID is 10 [A]. In FIG. 26, section (a) is a graph showing the relationship between ringing voltage (Vds (H) .max) and charging time, and section (b) shows voltage change rate (dV (L) / dt) and charging. It is the graph which showed the relationship with time, the section (c) is the graph which showed the relationship between switching loss (Eon) and charging time, and the section (d) is a voltage change rate (dV (H) / dt). It is the graph which showed the relationship between charging time.

  As shown in sections (a) and (b), the ringing voltage (Vds (H) .max) and the voltage change rate (dV (L) / dt) increase as the charging time decreases, giving a peak value. After that, it has decreased.

  Also, as shown in section (d), the voltage change rate (dV (H) / dt) increases as the charging time decreases, but as shown in section (c), the switching loss (Eon) is charged. It decreases as time decreases. This is because the voltage change rate (dV (H) / dt) increases as the switching speed of the switching elements Q11 and Q12 increases, but the switching loss (Eon) decreases as the switching speed increases. This is because it has characteristics.

  In the driving device 50 of the fifth embodiment, as indicated by the triangular mark in the section (a) of FIG. 25, the ringing voltage (Vds (H) .max) is set to 340 V or less for each current ID. Of the charging times that satisfy the conditions, a charging time that minimizes the switching loss Eon (that is, the minimum charging time) is obtained in advance, and a table is created. The control unit 80 holds the created table in advance.

  FIG. 27 is a diagram schematically illustrating an example of a table 85 held by the control unit 80 of the driving device 50 according to the fifth embodiment.

  From the experimental results of FIGS. 25 and 26, in the table 85 of the fifth embodiment, when the current ID is 0 <ID ≦ 2.5 [A], the charging time TD is set to 40 ns, and the current ID is 2.5 <. When ID ≦ 15 [A], the charging time TD is set to 45 ns, and when the current ID is 15 <ID ≦ 20 [A], the charging time TD is set to 20 ns.

  The control unit 80 acquires the current ID detected by the current sensor 71 (FIG. 1) of the detection unit 70. The control unit 80 extracts the charging time TD corresponding to the acquired current ID from the held table 85. The control unit 80 controls the drive unit 60 so that the on time of the switch SW1 coincides with the extracted charging time TD.

  Next, using FIGS. 28 and 29, when the current ID is 20 [A], the waveform of the proposed method of the fifth embodiment is compared with the waveform of the method of the comparative example.

  FIG. 28 is a timing chart schematically showing a simulation result of the drive device 50 when the switching element Q11 is turned on by the proposed method. FIG. 29 is a timing chart schematically showing a simulation result of the driving device 50 when the switching element Q11 is turned on by the method of the comparative example.

  28 and 29, a section (a) is a timing chart of the DC-DC converter 20, the vertical axis indicates voltage, current, and power, and the horizontal axis indicates time. Section (b) is a timing chart of the driving device 50, where the vertical axis indicates voltage and current, and the horizontal axis indicates time.

  As described with reference to FIG. 25, when the current ID is 20 [A], in the proposed method of FIG. 28, the charging time TD is set to 20 [ns], and in the method of the comparative example of FIG. The charging time TD is set to 45 [ns].

  In FIG. 28, the switch SW1 is turned on at time tr1. As a result, the gate current Ig11 is supplied from the first potential line W1 to the gate of the switching element Q11, the gate-source voltage Vgs11 of the switching element Q11 gradually increases, and the capacitor Ciss is charged.

  At time tr2, the switch SW1 is turned off and the switch SW3 is turned on. As a result, the voltage Vgs of the switching element Q11 is clamped at the first potential Vcc. Further, the drain-source current Ids11 of the switching element Q11 begins to increase, and the drain-source voltage Vds (L) of the switching element Q11 begins to decrease.

  At time tr3, the voltage Vgs11 exceeds the threshold value. As a result, the drain-source voltage Vds (L) of the switching element Q11 starts to rapidly decrease, and the drain-source voltage Vds (H) of the switching element Q12 starts to increase.

  At time tr4, the voltage Vds (L) completely falls, the voltage Vds (H) completely rises, and the current Ids11 completely rises.

  The waveform of the voltage Vds (H) after time tr4 should be essentially flat, but as shown in section (a), ringing (swell) occurs in the waveform of the voltage Vds (H). ing.

  Eon11 indicates a switching loss of the switching element Q11, starts to increase slightly after the time tr2, reaches a peak slightly after the time tr3, and falls at the time tr4.

  The outline of the control in the timing chart of FIG. 29 is the same as FIG. 28, but in FIG. 29, the charging time TD is set to 45 [ns], which is longer than 20 [ns] in FIG.

  For this reason, in FIG. 28, the switching speed is higher than in FIG. Therefore, in FIG. 28, the width of the waveform of the switching loss Eon11 is narrower than that in FIG. 29, and the switching loss Eon11 is smaller than that in FIG.

  In FIG. 28, as the switching speed increases, the ringing voltage Vds (H). Although max is slightly higher, the upper limit of 340 [V] is satisfied.

  In FIG. 28, the voltage change rates of the voltages Vds (H) and Vds (L) are higher than those of FIG. 29 as the switching speed increases, but the voltage change rates defined by the isolators 91 and 92 are high. The condition is satisfied.

  In the fifth embodiment, as described above, the resistance value of the resistor R3 is determined to be higher than the resistance value of the resistor R1. However, the fifth embodiment is not limited to this, and the resistance value of the resistor R3 may be determined to be lower than the resistance value of the resistor R1. In this case, the switching speed of the switching element Q11 increases as the on time (charge time) from when the switch SW1 is turned on to when it is turned off is longer. Even in this case, control can be performed in the same manner as in the fifth embodiment.

(Sixth embodiment)
The configuration of the driving device 50 of the sixth embodiment is the same as that of the driving device 50 of the first embodiment shown in FIG. Hereinafter, the sixth embodiment will be described focusing on differences from the first embodiment.

  The control of the drive unit 60 by the control unit 80 according to the sixth embodiment in accordance with the drive state detected by the detection unit 70 will be described with reference to FIG.

  FIG. 30 is a graph showing a result of an experiment performed for obtaining an optimal control parameter according to the driving state in the sixth embodiment. In the example of FIG. 30, unlike the first embodiment, an output voltage Vout (hereinafter referred to as “voltage Vdc”) detected by the voltage sensor 74 (FIG. 1) is adopted as the driving state.

  The DC-DC converter 20 shown in FIG. 1 can be applied to, for example, a power conditioner or a charger in which the input power supply E11 is a solar cell. In this case, the voltage Vdc varies. Therefore, in the sixth embodiment, it is assumed that the DC-DC converter 20 shown in FIG. 1 is applied to a system in which the voltage Vdc varies in the range of 320V to 420V.

  FIG. 30 shows an experimental result when the DC-DC converter 20 shown in FIG. 1 and the driving device 50 shown in FIG. 2 are used. In FIG. 30, as a control parameter for controlling the drive unit 60, as in the third embodiment, the time during which both the switches SW1 and SW4 are turned on (hereinafter referred to as “precharge time”). Is adopted. In the drive unit 60 of FIG. 2, as described above, the switching speed of the switching element Q11 increases as the precharge time increases.

  The graph in the left column in FIG. 30 shows experimental results when the precharge time is set to 80 ns, 90 ns, 100 ns, 110 ns, and 120 ns.

  Further, the graph in the right column in FIG. 30 shows experimental results when the precharge time is set to 90 ns and when the precharge time is set to an optimum value. In the graph in the right column of FIG. 30, the optimum experimental results are plotted with triangular marks and the experimental results of 90 ns are plotted with rhombus marks at each voltage Vdc. Here, the optimum value is a precharge time during which the peak value (Vds (H) .max: ringing voltage) of the drain-source voltage Vds (H) of the switching element Q12 can be reduced to 440V or less, and switching is performed. A precharge time that can minimize the loss Eon is employed.

  In FIG. 30, section (a) is a graph showing the relationship between the ringing voltage (Vds (H) .max) and the voltage Vdc according to the precharge time, the vertical axis shows the ringing voltage, and the horizontal axis shows The voltage Vdc is shown.

  The section (b) is a graph showing the relationship between the switching loss (Eon) and the voltage Vdc according to the precharge time, the vertical axis shows the loss, and the horizontal axis shows the voltage Vdc.

  Section (c) is a graph showing the relationship between the voltage change rate (dV (L) / dt) of the drain-source voltage V (L) of the switching element Q11 and the voltage Vdc according to the precharge time. The vertical axis indicates the voltage change rate, and the horizontal axis indicates the voltage Vdc.

  Section (d) is a graph showing the relationship between the voltage change rate (dV (H) / dt) of the drain-source voltage V (H) of the switching element Q12 and the voltage Vdc according to the precharge time. The vertical axis indicates the voltage change rate, and the horizontal axis indicates the voltage Vdc.

  As shown in the left column of section (a), it can be seen that the ringing voltage (Vds (H) .max) increases as the precharge time increases. For this reason, in the graph in the left column of section (a), the experimental results of 80 ns, 90 ns, 100 ns, 110 ns, and 120 ns are plotted with rhombus marks in order from the lower voltage side for each voltage Vdc.

  Here, the condition that the ringing voltage (Vds (H) .max) is set to 440 V or less is imposed, and the maximum precharge time during which the ringing voltage can be set to 440 V or less is 90 ns at all voltages Vdc. Therefore, in a method employing a configuration in which the precharge time is not changed according to the driving state (hereinafter referred to as “method of comparative example”), 90 ns is set as the precharge time. This makes it impossible to set an optimal precharge time according to the voltage Vdc. For example, when the voltage Vdc is 370 V, even if the precharge time is set to 120 ns, the ring charge voltage (Vds (H) .max) is 440 V or less, but in the method of the comparative example, the precharge time is 90 ns. Because it is set, the optimum value is not set.

  As shown in the left column of section (b), it can be seen that the switching loss increases as the precharge time decreases. Therefore, in the graph in the left column of section (b), the experimental results of 120 ns, 110 ns, 100 ns, 90 ns, and 80 ns are plotted with rhombus marks in order from the side with the lowest switching loss at each voltage Vdc.

  Therefore, in the method of the sixth embodiment (hereinafter referred to as “proposed method”), as shown in the right column of section (a), the ringing voltage (Vds (H) .max) is obtained at each voltage Vdc. Is set to a precharge time that can minimize the switching loss Eon (that is, the maximum precharge time as can be seen from the section (b)).

  Specifically, when the voltage Vdc is 320 [V] and 370 [V], the precharge time is set to 120 ns, and when the voltage Vdc is 420 [V], the precharge time is set to 90 ns. Thereby, the precharge time is optimized.

  In the right column of section (b), the switching loss with respect to each voltage Vdc when the optimum value of the precharge time set in section (a) is adopted is plotted with a triangle mark. In this case, when the voltage Vdc is 420 V, the proposed method and the comparative example have the same switching loss. At other voltages Vdc, the proposed method has a lower switching loss than the comparative example, and the switching is performed when the voltage Vdc is 370 V. The loss was reduced by 26%.

  As shown in the left column of section (c), it can be seen that the voltage change rate (dV (L) / dt) does not show much correlation with the precharge time. In the graph in the left column of section (c), for each voltage Vdc, the voltage change rate (dV (L) / dt) is plotted with rhombus marks indicating that the experimental result is that 120 ns is the lowest and 100 ns is the highest. .

  In the right column of section (c), the voltage change rate (dV (L) / dt) with respect to each voltage Vdc when the optimum value of the precharge time set in section (a) is adopted is plotted with a triangle mark. ing. In this case, when the voltage Vdc is other than 420V, the proposed method has a higher voltage change rate (dV (L) / dt) than the comparative example, and is the same when the voltage Vdc is 420V.

  As shown in the left column of section (d), the rate of voltage change (dV (H) / dt) increases as the precharge time increases, as does the ringing voltage (Vds (H) .max). I understand that. Therefore, in the graph in the left column of section (d), the experimental results of 80 ns, 90 ns, 100 ns, 110 ns, and 120 ns of the voltage change rate (dV (H) / dt) are diamond-shaped in order from the lower side at each voltage Vdc. It is plotted with the mark.

  In the right column of section (d), the voltage change rate (dV (H) / dt) with respect to each voltage Vdc when the optimum value of the precharge time set in section (a) is adopted is plotted with a triangular mark. ing. In this case, when the voltage Vdc is other than 420V, the proposed method has a higher voltage change rate (dV (H) / dt) than the comparative example, and is the same when the voltage Vdc is 420V.

  Note that the precharge time of the proposed method shown in the right column of section (c) and the precharge time of the proposed method shown in the right column of section (d) are both voltage changes defined by the isolators 91 and 92. The rate condition is satisfied.

  In the driving device 50 of the sixth embodiment, as indicated by the triangular mark in the section (a) of FIG. 30, the ringing voltage (Vds (H) .max) is set to 440 V or less for each voltage Vdc. Of the precharge times that satisfy the conditions, a precharge time (that is, the maximum precharge time) that minimizes the switching loss Eon is obtained in advance, and a table (an example of setting information) is created. The control unit 80 holds the created table in advance.

  FIG. 31 is a diagram schematically illustrating an example of a table 86 held by the control unit 80 of the driving device 50 according to the sixth embodiment.

  From the experimental results of FIG. 30, in the table 86 of the sixth embodiment, the precharge time TE is set to 120 ns and the voltage Vdc is 370 when the voltage Vdc is in the range of 320 ≦ Vdc ≦ 370 [V] (an example of a section). In the range of <Vdc ≦ 420 [V] (an example of division), the precharge time TE is set to 90 ns.

  The control unit 80 acquires the voltage Vdc detected by the voltage sensor 74 (FIG. 1) of the detection unit 70. The controller 80 extracts the precharge time TE corresponding to the acquired voltage Vdc from the held table 86. The control unit 80 controls the drive unit 60 so that the time during which both the switches SW1 and SW4 are turned on coincides with the extracted precharge time TE.

  Next, using FIGS. 32 and 33, when the voltage Vdc is 370 [V], the waveform of the proposed method of the sixth embodiment is compared with the waveform of the method of the comparative example.

  FIG. 32 is a timing chart schematically showing a simulation result of the driving device 50 when the switching element Q11 is turned on by the proposed method of the sixth embodiment. FIG. 33 is a timing chart schematically showing a simulation result of the driving device 50 when the switching element Q11 is turned on by the method of the comparative example.

  32 and 33, a section (a) is a timing chart of the DC-DC converter 20, the vertical axis indicates voltage, current, and power, and the horizontal axis indicates time. Section (b) is a timing chart of the driving device 50, where the vertical axis indicates voltage and current, and the horizontal axis indicates time.

  As described with reference to FIG. 30, when the voltage Vdc is 370 [V], the precharge time TE is set to 120 [ns] in the proposed method of FIG. 32, and the method of the comparative example of FIG. In this case, the precharge time TE is set to 90 [ns].

  In FIG. 32, the switch SW1 is turned on at time ts1. Note that the switch SW4 has been turned on before time ts1, and the gate of the switching element Q11 is clamped at the second potential Vss. For this reason, the gate current Ig11 is not supplied to the gate of the switching element Q11, and energy is accumulated in the coil L1.

  At time ts2, the switches SW1 and SW4 are turned off. Then, the energy accumulated in the coil L1 is discharged, the gate current Ig11 is supplied to the gate of the switching element Q11, the gate-source voltage Vgs11 of the switching element Q11 gradually increases, and the capacitor Ciss is charged. .

  At time ts3, the drain-source current Ids11 of the switching element Q11 begins to increase, and the drain-source voltage Vds (L) of the switching element Q11 begins to decrease.

  At time ts4, the voltage Vgs11 exceeds the threshold value. As a result, the drain-source voltage Vds (L) of the switching element Q11 starts to rapidly decrease, and the drain-source voltage Vds (H) of the switching element Q12 starts to increase.

  At time ts5, the voltage Vds (L) completely falls, the voltage Vds (H) completely rises, and the current Ids11 completely rises.

  The waveform of the voltage Vds (H) after time ts5 should be essentially flat, but as shown in section (a), ringing (swell) occurs in the waveform of the voltage Vds (H). ing.

  Eon11 indicates a switching loss of the switching element Q11, starts to increase at about time ts3, reaches a peak at about time ts4, and falls at time ts5.

  The outline of the control in the timing chart of FIG. 33 is the same as FIG. 32, but in FIG. 33, the precharge time TE is set to 90 [ns], which is shorter than 120 [ns] in FIG.

  For this reason, in FIG. 32, the switching speed is higher than in FIG. Therefore, in FIG. 32, the width of the waveform of the switching loss Eon11 is narrower than that in FIG. 33, and the switching loss Eon11 is smaller than that in FIG.

  In FIG. 32, as the switching speed increases, the ringing voltage Vds (H). Although max is slightly higher, the upper limit value of 440 [V] is satisfied.

  In FIG. 32, with the increase in switching speed, the voltage change rates of the voltages Vds (H) and Vds (L) are higher than those in FIG. 33, but the voltage change rates defined by the isolators 91 and 92 are increased. The condition is satisfied.

  In the sixth embodiment, the precharge time is adopted as a control parameter for controlling the drive unit 60 as in the third embodiment. Alternatively, in the sixth embodiment, a charging time similar to that of the first embodiment or a discharging time similar to that of the second embodiment may be employed as the control parameter.

(Seventh embodiment)
In the first, third, and fourth embodiments, as shown in the left column of the section (a) of FIGS. 3, 13, and 19, for example, the ringing voltage Vds (H). max decreases as the current ID increases. However, when the reverse recovery time Trr of the parasitic diode of the switching element Q12 is poor or when the parasitic inductances Lp1, Lp2 (FIG. 1) are large, the ringing voltage Vds (H). max may increase as the current ID increases. Such a case is examined in the seventh embodiment.

  FIG. 34 is a diagram schematically illustrating a drive device 50 according to the seventh embodiment. In FIG. 34, the illustration of the isolators 91 and 92 is omitted to simplify the description, and the second potential line W2 of the driving unit 60 is connected to the source of the switching element Q11. However, in the actual driving device 50, as shown in FIG. 1, the driving unit 60 and the switching element Q11 are connected via an isolator 91, and the driving unit 60 and the switching element Q12 are connected via an isolator 92. It is connected. Hereinafter, the seventh embodiment will be described focusing on the differences from the first embodiment.

  The drive unit 60 includes a power source E1 and a clamp unit 62. That is, in the driving device 50 of the seventh embodiment, the switching element Q11 is turned on by turning on the switch SW3, turning off the switch SW4, and clamping the gate of the switching element Q11 to the first potential Vcc. Further, the switch SW3 is turned off, the switch SW4 is turned on, and the switching element Q11 is turned off by clamping the gate of the switching element Q11 to the second potential Vss.

  Next, the control of the drive unit 60 by the control unit 80 according to the seventh embodiment according to the drive state detected by the detection unit 70 will be described with reference to FIG.

  FIG. 35 is a graph showing a result of an experiment performed for obtaining an optimal control parameter according to the driving state in the seventh embodiment. In the example of FIG. 35, unlike the first embodiment, the drain current Ids detected by the current sensor 73 (FIG. 1) is adopted as the driving state.

  FIG. 35 shows the experimental results when the DC-DC converter 20 shown in FIG. 1 and the drive device 50 shown in FIG. 34 are used. In FIG. 35, switching is performed at three speeds by switching the resistance value of the resistor R1 of the driving device 50 of FIG. 34 to three kinds. That is, in FIG. 35, the data of the low speed switching LS when the resistance value of the resistor R1 is increased, the data of the high speed switching HS when the resistance value of the resistor R1 is lowered, and the resistance value of the resistor R1 are set to an intermediate value. The data of the medium speed switching MS is plotted. FIG. 35 plots data of optimum switching AT in which the switching speed is changed to the optimum value according to the drain current Ids by the control of the seventh embodiment.

  In FIG. 35, section (a) shows the relationship between the voltage change rate (dV (L) / dt) of the drain-source voltage Vds (L) of the switching element Q11 and the drain current Ids according to the switching speed. It is a graph, the vertical axis shows the voltage change rate, and the horizontal axis shows the drain current Ids.

  Section (b) is a graph showing the relationship between the voltage change rate (dV (H) / dt) of the drain-source voltage Vds (H) of the switching element Q12 and the drain current Ids according to the switching speed, The vertical axis represents the voltage change rate, and the horizontal axis represents the drain current Ids.

  Section (c) is a graph showing the relationship between the ringing voltage (Vds (H) .max) and the drain current Ids according to the switching speed, the vertical axis shows the ringing voltage, and the horizontal axis shows the drain current Ids. Show.

  As shown in section (a) of FIG. 35, the voltage change rate (dV (L) / dt) is limited to 50 [V / ns] or less by the common mode rejection voltage of the isolators 91 and 92. As shown in section (b) of FIG. 35, the voltage change rate (dV (H) / dt) is limited to 50 [V / ns] or less by the common mode rejection voltage of the isolators 91 and 92. As shown in section (c) of FIG. 35, the ringing voltage (Vds (H) .max) is limited to 420 [V] or less.

  In the section (c) of FIG. 35, in order to satisfy the condition that the ringing voltage (Vds (H) .max) is 420 [V] or less in the range of all drain currents Ids when the switching speed is fixed. Needs to employ low-speed switching LS.

  On the other hand, in the optimum switching AT by the control of the seventh embodiment, the high-speed switching HS is adopted when the drain current Ids is 4 [A] or less, and the medium-speed switching MS when the drain current Ids is 6 [A]. And the low-speed switching LS is employed when the drain current Ids is 7.2 [A]. In a range A2 where 4 <Ids <6 [A], a switching speed is employed so that (Vds (H) .max) <420 [V] is maintained.

  As a result, as shown in sections (a) and (b) of FIG. 35, the voltage change rate (dV (L) / dt) and the voltage change rate (dV (H) / dt) are also 50 [V / ns. The following restrictions are met: For example, as shown in section (a), in the optimum switching AT, the high-speed switching HS is employed in the range A1 where the drain current Ids is from a low current value to a medium current value. As a result, the voltage change rate dV (L) / dt is increased and the switching loss is reduced.

  FIG. 36 shows the input current Iin, the gate-source voltage Vgs11 of the switching element Q11, the drain-source voltage Vds (L) of the switching element Q11, and the switching element when the experiment of FIG. 35 is performed. It is a figure which shows roughly each waveform of the drain-source voltage Vds (H) of Q12.

  In FIG. 36, section (a) shows each waveform when the drain current Ids is 7.2 [A] and the low-speed switching LS, and section (b) shows the low-speed switching LS when the drain current Ids is 4 [A]. The section (c) shows each waveform when the drain current Ids is 4 [A] and the high-speed switching HS is performed.

  As described with reference to section (c) of FIG. 35, when the drain current Ids is 7.2 [A], the ringing voltage (Vds (H) .max) satisfies the condition that it is 420 [V] or less. Therefore, the low speed switching LS is employed in the optimum switching AT. In this case, the ringing voltage (Vds (H) .max) is a relatively large value as shown in section (a) of FIG.

  As described with reference to section (c) of FIG. 35, when the switching speed is fixed, in order to satisfy the condition that the ringing voltage (Vds (H) .max) is 420 [V] or less, Low speed switching LS is employed. When the low-speed switching LS is employed when the drain current Ids is 4 [A], the ringing voltage (Vds (H) .max) is a relatively small value as shown in the section (b) of FIG. become.

  As described with reference to section (c) of FIG. 35, in the optimum switching AT by the control of the seventh embodiment, when the drain current Ids is 4 [A], the high-speed switching HS is employed. In this case, the ringing voltage (Vds (H) .max) is a relatively large value similar to that of the section (a) as shown in the section (c) of FIG.

  Thus, in the control of the seventh embodiment, when the drain current Ids is 4 [A], the high-speed switching HS is employed. As a result, the switching loss is reduced while satisfying the upper limit of the ringing voltage (Vds (H) .max).

  In the seventh embodiment, an experiment is performed using the drive device 50 illustrated in FIG. 34, but the drive device 50 of the present disclosure is not limited to this. Alternatively, by using the drive device 50 shown in FIG. 2 to create a table and control the switching speed as in the first to third embodiments and the sixth embodiment, the seventh embodiment is achieved. You may make it implement | achieve control of embodiment. Further alternatively, the control of the seventh embodiment may be realized by controlling the switching speed using the drive device 50 shown in FIG. 18 as in the fourth embodiment. Further alternatively, the control of the seventh embodiment may be realized by controlling the switching speed using the driving device 50 shown in FIG. 24 as in the fifth embodiment.

(Eighth embodiment)
In the seventh embodiment, as shown in FIG. 35, for example, when the drain current Ids is 7.2 [A], the low speed switching LS is employed. However, depending on the state of the parasitic inductances Lp1 and Lp2 or the parasitic capacitances Cp1 and Cp2 (FIG. 1) of the DC-DC converter 20, the radiation noise may be excessive in the range where the drain current Ids is large even if the low speed switching LS is adopted. Sometimes it becomes.

  For example, due to a large voltage change rate (dV (H) / dt) of the drain-source voltage Vds (H) of the switching element Q12, the swell (high frequency) after the peak value (that is, the ringing voltage) is reached. When the amplitude of the component) is large, the generated radiation noise often increases. In the eighth embodiment, such a case is examined.

  The configuration of the drive device 50 of the eighth embodiment is the same as that of the drive device 50 of the seventh embodiment shown in FIG. The control of the drive unit 60 by the control unit 80 according to the eighth embodiment according to the drive state detected by the detection unit 70 will be described with reference to FIG.

  FIG. 37 is a graph showing a result of an experiment performed for obtaining an optimal control parameter according to the driving state in the eighth embodiment. In the example of FIG. 37, the drain current Ids detected by the current sensor 73 (FIG. 1) is employed as the driving state, as in the seventh embodiment.

  FIG. 37 shows experimental results when the DC-DC converter 20 shown in FIG. 1 and the driving device 50 shown in FIG. 34 are used. In FIG. 37, switching is performed at three speeds by switching the resistance value of the resistor R1 of the driving device 50 in FIG. 34 to three kinds. That is, in FIG. 37, the data of the low speed switching LS when the resistance value of the resistor R1 is increased, the data of the high speed switching HS when the resistance value of the resistor R1 is lowered, and the resistance value of the resistor R1 are set to intermediate values. The data of the medium speed switching MS is plotted. FIG. 37 plots data of low radiation noise switching LN in which the switching speed is further changed according to the drain current Ids by the control of the eighth embodiment in order to reduce the radiation noise.

  In FIG. 37, section (a) is a graph showing the relationship between the ringing voltage (Vds (H) .max) and the drain current Ids according to the switching speed, the vertical axis shows the ringing voltage, and the horizontal axis shows The drain current Ids is shown.

  Section (b) is a graph showing the relationship between the voltage change rate (dV (H) / dt) of the drain-source voltage Vds (H) of the switching element Q12 and the drain current Ids according to the switching speed, The vertical axis represents the voltage change rate, and the horizontal axis represents the drain current Ids.

  Section (c) is a graph showing the relationship between the minimum value (Vds (L) .min) of the drain-source voltage Vds (L) of the switching element Q11 and the drain current Ids according to the switching speed. The axis indicates the minimum voltage value, and the horizontal axis indicates the drain current Ids.

  Section (d) is a graph showing the relationship between the voltage change rate (dV (L) / dt) of the drain-source voltage Vds (L) of the switching element Q11 and the drain current Ids according to the switching speed, The vertical axis represents the voltage change rate, and the horizontal axis represents the drain current Ids.

  As shown in section (a), in the low radiation noise switching LN by the control of the eighth embodiment, in the large current region where the drain current Ids is 6 to 7.2 [A], the switching speed is set to the low speed switching LS. It is further reduced. As a result, the ringing voltage (Vds (H) .max) in the large current region is further reduced.

  As a result, as indicated by the arrow P1 in the section (b), the voltage change rate (dV (H) / dt) of the drain-source voltage of the switching element Q12 in the large current region is reduced.

  Further, in the large current region, by further reducing the switching speed from the low speed switching LS, as shown in the section (c), the minimum value (Vds (Lds) of the drain-source voltage Vds (L) of the switching element Q11. ) .Min) absolute value is reduced.

  As a result, as indicated by the arrow P2 in the section (d), the voltage change rate (dV (L) / dt) of the drain-source voltage of the switching element Q11 in the large current region is reduced.

  Generally, when the voltage change rates (dV (H) / dt) and (dV (L) / dt) are higher than a predetermined level in a large current region, the level of generated radiation noise exceeds an allowable level. On the other hand, in the eighth embodiment, in the large current region, the switching speed is further lowered than the low speed switching LS, and the voltage change rates (dV (H) / dt) and (dV (L) / dt) are reduced. Has been. Therefore, according to the eighth embodiment, it is possible to prevent the level of generated radiation noise from exceeding the allowable level.

  In the eighth embodiment, an experiment is performed using the drive device 50 illustrated in FIG. 34, but the drive device 50 of the present disclosure is not limited to this. Alternatively, by using the drive device 50 shown in FIG. 2 to create a table and control the switching speed as in the first to third embodiments and the sixth embodiment, the eighth embodiment is achieved. You may make it implement | achieve control of embodiment.

(Ninth embodiment)
In the eighth embodiment, as described with reference to FIG. 37, the radiation noise is reduced by adopting a switching speed lower than the low speed switching LS in the large current region. In the ninth embodiment, radiation noise is reduced by a method different from that of the eighth embodiment.

  The configuration of the drive device 50 of the ninth embodiment is the same as that of the drive device 50 of the first embodiment shown in FIG. In the ninth embodiment, similarly to the first embodiment, the control unit 80 uses the table 81 to set the charging time (the ON time of the switch SW1) according to the driving state detected by the detection unit 70. Control. Hereinafter, the control of the drive unit 60 by the control unit 80 of the ninth embodiment will be described focusing on differences from the first embodiment.

  FIG. 38 shows the gate-source voltage Vgs (L) of the switching element Q11 and the drain-source voltage Vds (of the switching element Q11 when the switching elements Q11, Q12 are turned on and off in the ninth embodiment. L) is a timing chart schematically showing waveforms of a drain-source voltage Vds (H) of the switching element Q12.

  In the ninth embodiment, the control unit 80 varies the charging time by a predetermined minute value for each pulse. In this case, the control unit 80 controls the charging time so that the average value of the varying charging times matches the charging time extracted from the table 81. Thus, in the ninth embodiment, the voltage change rates dV (L) / dt and dV (H) / dt of the drain-source voltages of the switching elements Q11 and Q12 are diffused by a minute value for each pulse. .

  In FIG. 38, the switching element Q11 is turned on at times tk1, tk2, and tk3. At time tk2, the control unit 80 controls the drive unit 60 with the charging time CT extracted from the table 81. For example, if the current ID is 20 [A], the drive unit 60 is controlled with the charging time set to 80 [ns] as shown in FIG.

  At time tk1 one pulse before time tk2, control unit 80 controls drive unit 60 with charging time (C−ΔC) T shorter than charging time CT extracted from table 81. For example, if the current ID is 20 [A], the drive unit 60 is controlled by setting the charging time to 75 [ns], which is 5 [ns] shorter than 80 [ns].

  As is apparent from a comparison between the timing chart of the charging time CT at time tk2 and the timing chart of the charging time (C−ΔC) T at time tk1, the charging time (C−ΔC) T is larger than the charging time CT. The drain-source voltages Vds (L) and Vds (H) change gradually. That is, the voltage change rates dV (L) / dt and dV (H) / dt are smaller in the charging time (C−ΔC) T than in the charging time CT.

  At time tk3 after one pulse of time tk2, the control unit 80 controls the drive unit 60 with a charging time (C + ΔC) T longer than the charging time CT extracted from the table 81. For example, if the current ID is 20 [A], the drive unit 60 is controlled by setting the charging time to 85 [ns], which is 5 [ns] longer than 80 [ns].

  As is apparent from a comparison between the timing chart of the charging time CT at time tk2 and the timing chart of the charging time (C + ΔC) T at time tk3, the drain-source is higher in the charging time (C + ΔC) T than in the charging time CT. The inter-voltages Vds (L) and Vds (H) change sharply. That is, the voltage change rates dV (L) / dt and dV (H) / dt are larger in the charging time (C + ΔC) T than in the charging time CT.

  Similarly, after time tk3, control unit 80 varies the charging time. In this case, as described above, the control unit 80 varies the charging time so that the average value of the varying charging time matches the charging time CT extracted from the table 81.

  As described above, when the switching speed is varied by varying the charging time, it is necessary to satisfy the upper limit of the ringing voltage at the maximum switching speed within the range of variation. For example, when the charging time is 85 [ns], if the upper limit of the ringing voltage is exceeded, the charging time stored in the table 81 needs to be set to 75 [ns], for example.

  In FIG. 38, the charging time is varied in three types of CT, (C + ΔC) T, and (C−ΔC) T, but the present disclosure is not limited to this. For example, the charging time may vary in five types: CT, (C + ΔC) T, (C−ΔC) T, (C + 2 × ΔC) T, and (C−2 × ΔC) T. In short, it is only necessary that the average value of the varied charging times matches the charging time stored in the table 81.

  Next, the effect of diffusing the voltage change rates dV (L) / dt and dV (H) / dt by minute values will be described with reference to FIGS.

  FIG. 39 is a diagram for explaining an ideal trapezoidal wave used for diffusion. In FIG. 39, section (a) shows the rising waveform of the ideal trapezoidal wave, and section (b) shows the falling waveform of the ideal trapezoidal wave. In sections (a) and (b), the vertical axis represents voltage and the horizontal axis represents time. Section (c) shows the rise time Tr and reciprocal 1 / Tr of nine types of ideal trapezoidal waves with a voltage change rate dV / dt of 8-16. The rise time of the ideal trapezoidal wave AVG at the bottom of section (c) is 28 [ns], which is the average value of the rise times of the nine ideal trapezoidal waves above it.

  FIG. 40 is a diagram schematically showing the waveform of the superposed ideal trapezoidal wave in the fast Fourier transform (FFT). In FIG. 40, the vertical axis represents the effective voltage value, and the horizontal axis represents the frequency.

  A waveform WV1 shown in FIG. 40 is an FFT of nine types of ideal trapezoidal waves having a voltage change rate dV / dt of 8 to 16 shown in section (c) of FIG. 39 diffused. A waveform WV2 is an FFT of an ideal trapezoidal wave AVG shown in the lowermost stage of the section (c) of FIG. 39, whose rise time Tr is 28 [ns] of the average value of the rise times Tr of nine types of ideal trapezoidal waves. .

  The ideal trapezoidal wave theoretically has a minimum value at n / Tr [MHz] and a maximum value at 1.5 × n / Tr [MHz]. When the ideal trapezoidal wave is diffused, the minimum value and the maximum value are dispersed and averaged. For this reason, when a diffused ideal trapezoidal wave is used, as shown in FIG. 40, the effect of reducing the effective voltage value of the waveform WV1 compared to the waveform WV2 is a maximum value of 1.5 × n / Tr [MHz]. In the largest. The effective voltage value of the harmonic component of the voltage waveform output from the switching element has a positive correlation with the radiation noise intensity. For this reason, if a diffused ideal trapezoidal wave is used, the radiation noise intensity can be reduced.

  As described above, in the ninth embodiment, the charging time varies and the voltage change rates (dV (H) / dt) and (dV (L) / dt) are diffused. Thus, according to the ninth embodiment, the level of generated radiation noise can be prevented from exceeding an allowable level.

  In the ninth embodiment, for example, all charging times stored in the table 81 may be varied. Alternatively, among the charging times stored in the table 81, only the charging time at a location where the level of radiation noise exceeds the allowable level may be varied.

  In the ninth embodiment, the drive unit 60 is controlled by the method of the first embodiment using the drive device 50 shown in FIG. 2, but the drive device 50 of the present disclosure is not limited to this. Alternatively, by using the driving device 50 shown in FIG. 2 to create a table and control the switching speed as in the second embodiment, the third embodiment, and the sixth embodiment, the ninth embodiment can be realized. You may make it implement | achieve control of embodiment.

(Other)
(1) In the first to fifth and ninth embodiments, the input current Iin detected by the current sensor 71 (FIG. 1) is adopted as the driving state detected by the detection unit 70, and the sixth embodiment The output voltage Vout detected by the voltage sensor 74 (FIG. 1) is employed, and the drain current Ids detected by the current sensor 73 (FIG. 1) is employed in the seventh and eighth embodiments. However, the driving device 50 of the present disclosure is not limited to these.

  As the drive state detected by the detector 70, for example, the input voltage Vin detected by the voltage sensor 72 (FIG. 1) may be adopted, or the output current Iout detected by the current sensor 75 (FIG. 1). May be employed, and the junction temperature Tj detected by the temperature sensor 76 or the temperature sensor 77 (FIG. 1) may be employed.

  Furthermore, as a driving state detected by the detection unit 70, any one of the input current Iin, the drain current Ids, and the output current Iout and any one of the input voltage Vin and the output voltage Vout Combinations may be employed. In this case, a table in which control parameters such as charging time are associated with current values and voltage values may be created.

  (2) Although it is preferable that the detection unit 70 directly detects the current and voltage when the switching elements Q11 and Q12 are switched, the present invention is not limited to this. The detection unit 70 includes, for example, input / output currents and input / output voltages of the entire DC-DC converter 20 (current Iin, output current Iout, input voltage Vin, output voltage Vout flowing from the input power supply E11 in the example of FIG. 1), From the control command value of the DC-DC converter 20 (for example, the on-duty ratio, on-period, off-period, switching frequency of the switching element Q11) or circuit constant (for example, the inductance value of the reactor 71, the capacity of the smoothing capacitor C12), etc. It may be calculated. That is, the detection unit 70 may indirectly detect current and voltage when the switching elements Q11 and Q12 are switched.

  (3) In each of the above embodiments, the switching element Q12 is configured by an N-channel MOSFET, but the present disclosure is not limited to this. For example, a diode may be employed as the switching element Q12.

  (4) In each of the above embodiments, the case where the switching element Q11 is turned on has been described. However, the same control can be performed when the switching element Q11 is turned off.

  (5) In the fourth embodiment, the type of switching speed that can be changed depends on the number of series circuits of switches and resistors. In contrast, in the first to third, fifth, and sixth embodiments, the types of switching speed that can be changed can be increased by increasing the number of types of setting time by increasing the number of driving states. . Therefore, according to the first to third, fifth, and sixth embodiments, the switching speed is finely controlled without increasing the number of switches and the number of signal lines as compared with the fourth embodiment. Can do.

  (6) In the above embodiment, a plurality of embodiments having the same circuit configuration of the drive unit 60 may be combined. For example, by combining the first embodiment and the second embodiment, when 0 <ID ≦ 5, the charging time is 65 ns and the discharging time is 60 ns. When 5 <ID ≦ 10, the charging time is 70 ns and the discharging time is 65 ns. The charging time may be set to 75 ns and the discharging time 55 ns when 10 <ID ≦ 15, and the charging time may be set to 80 ns and the discharging time 50 ns when 15 <ID ≦ 20.

  Further, for example, the second embodiment and the third embodiment are combined to set the discharge time 60 ns and the precharge time 60 ns when 0 <ID ≦ 2.5, and the discharge when 2.5 <ID ≦ 10. Set to 65 ns time and 70 ns precharge time, set to 55 ns discharge time and 75 ns precharge time if 10 <ID ≦ 15, set to 50 ns discharge time and 75 ns precharge time if 15 <ID ≦ 20 May be.

  By combining the embodiments as described above, the switching speed can be controlled in various ways.

  The present disclosure is useful for the technical field of power devices such as DC-DC converters.

50 drive device 60 drive unit 70 detection unit 71, 73, 75 current sensor 72, 74 voltage sensor 80 control unit 81, 82, 83 table D2 diode Ids drain current Iin input current Iout output current L1 coil Lt1 input side terminal Lt2 output side Terminal Q11, Q12 Switching element SW1, SW3, SW4 Switch Vin Input voltage Vout Output voltage

Claims (12)

A driving device for driving a switching element including a control terminal, a first conduction terminal, and a second conduction terminal,
A detection unit that detects at least one of a conduction current, an applied voltage, and a temperature of the switching element directly or indirectly as a driving state of the switching element;
A drive unit that outputs a drive signal to the control terminal of the switching element;
A controller that controls the drive unit to change a switching speed of the switching element according to the detected drive state;
With
The control unit includes a plurality of sections in which the driving state variation ranges are divided, and a control parameter that defines a highest switching speed among the switching speeds satisfying a predetermined driving condition in each of the plurality of sections. Corresponding setting information is stored in advance, the control parameter corresponding to the section including the detected drive state is extracted from the setting information, and the drive unit is controlled based on the extracted control parameter ,
Drive device. The control unit executes a process of extracting the control parameter corresponding to the section including the detected drive state from the setting information for each cycle of ON / OFF of the switching element.
The drive device according to claim 1. The control unit controls the driving unit using the control parameter that is dispersed in a predetermined range so that an average value matches the extracted control parameter.
The drive device according to claim 1 or 2. The drive unit is
A first potential line for applying a first potential;
A second potential line connected to the first conduction terminal of the switching element and providing a second potential smaller than the first potential;
A coil having a first terminal and a second terminal, wherein the second terminal is connected to the control terminal of the switching element;
A charging switch connected between the first potential line and the first terminal of the coil, and for turning on and off the energization between the first potential line and the coil;
A clamp switch connected between the first potential line and the control terminal of the switching element, and for turning on and off energization between the first potential line and the control terminal of the switching element;
A charging diode having an anode connected to the second potential line and a cathode connected to the first terminal of the coil;
Including
The control parameter is a charging time which is an on time of the charging switch,
In the setting information, the plurality of sections are associated with the charging time that defines the highest switching speed among the switching speeds that satisfy the driving condition in each of the plurality of sections.
The control unit extracts the charging time corresponding to the classification including the detected driving state from the setting information, and sets the extracted charging time to an on time of the charging switch.
The drive device according to claim 1. The drive unit is
A first potential line for applying a first potential;
A second potential line connected to the first conduction terminal of the switching element and providing a second potential smaller than the first potential;
A coil having a first terminal and a second terminal, wherein the second terminal is connected to the control terminal of the switching element;
A charging switch connected between the first potential line and the first terminal of the coil, and for turning on and off the energization between the first potential line and the coil;
A clamp switch connected between the first potential line and the control terminal of the switching element, and for turning on and off energization between the first potential line and the control terminal of the switching element;
A charging diode having an anode connected to the second potential line and a cathode connected to the first terminal of the coil;
Including
The control parameter is a discharge time which is a time from the turn-off of the charging switch to the turn-on of the clamp switch,
In the setting information, the plurality of sections are associated with the discharge time that defines the highest switching speed among the switching speeds that satisfy the driving condition in each of the plurality of sections.
The control unit extracts the discharge time corresponding to the section including the detected drive state from the setting information, and drives the charging switch and the clamp switch with the extracted discharge time.
The drive device according to claim 1. The drive unit is
A first potential line for applying a first potential;
A second potential line connected to the first conduction terminal of the switching element and providing a second potential smaller than the first potential;
A coil having a first terminal and a second terminal, wherein the second terminal is connected to the control terminal of the switching element;
A charging switch connected between the first potential line and the first terminal of the coil, and for turning on and off the energization between the first potential line and the coil;
A first clamp switch connected between the first potential line and the control terminal of the switching element, and for turning on and off the energization between the first potential line and the control terminal of the switching element;
A second clamp switch connected between the second potential line and the control terminal of the switching element, and for turning on and off energization between the second potential line and the control terminal of the switching element;
A charging diode having an anode connected to the second potential line and a cathode connected to the first terminal of the coil;
Including
The control parameter is a precharge time that is a time for turning on both the charging switch and the second clamp switch,
In the setting information, the plurality of sections are associated with the precharge time that defines the highest switching speed among the switching speeds that satisfy the driving condition in each of the plurality of sections.
The control unit extracts the precharge time corresponding to the section including the detected driving state from the setting information, and the charging switch and the second clamp switch during the extracted precharge time. Both are turned on, and when the extracted precharge time has elapsed, both the charging switch and the second clamp switch are turned off.
The drive device according to claim 1. The drive unit is
A first potential line for applying a first potential;
A second potential line connected to the first conduction terminal of the switching element and providing a second potential smaller than the first potential;
A coil having a first terminal and a second terminal, wherein the second terminal is connected to the control terminal of the switching element;
A charging switch connected between the first potential line and the first terminal of the coil, and for turning on and off the energization between the first potential line and the coil;
A clamp switch connected between the first potential line and the control terminal of the switching element, and for turning on and off energization between the first potential line and the control terminal of the switching element;
A charging diode having an anode connected to the second potential line and a cathode connected to the first terminal of the coil;
Including
The control parameters include a charging time that is an on time of the charging switch, and a discharging time that is a time from the turning off of the charging switch to the turning on of the clamp switch,
In the setting information, the plurality of sections are associated with the charging time and the discharging time that define the highest switching speed among the switching speeds that satisfy the driving condition in each of the plurality of sections. ,
The control unit extracts the charging time and the discharging time corresponding to the classification including the detected driving state from the setting information, and sets the extracted charging time as an ON time of the charging switch. And, when the extracted discharge time has elapsed from the turn-off of the charging switch, the clamp switch is turned on.
The drive device according to claim 1. The drive unit is
A first potential line for applying a first potential;
A second potential line connected to the first conduction terminal of the switching element and providing a second potential smaller than the first potential;
A coil having a first terminal and a second terminal, wherein the second terminal is connected to the control terminal of the switching element;
A charging switch connected between the first potential line and the first terminal of the coil, and for turning on and off the energization between the first potential line and the coil;
A first clamp switch connected between the first potential line and the control terminal of the switching element, and for turning on and off the energization between the first potential line and the control terminal of the switching element;
A second clamp switch connected between the second potential line and the control terminal of the switching element, and for turning on and off energization between the second potential line and the control terminal of the switching element;
A charging diode having an anode connected to the second potential line and a cathode connected to the first terminal of the coil;
Including
The control parameter includes a precharge time that is a time for turning on both the charging switch and the second clamp switch, and a discharge that is a time from turning off the charging switch to turning on the first clamp switch. Including time,
In the setting information, the plurality of sections are associated with the precharge time and the discharge time that define the highest switching speed among the switching speeds that satisfy the driving condition in each of the plurality of sections. And
The control unit extracts the precharge time and the discharge time corresponding to the section including the detected drive state from the setting information, and the charging switch and the charge during the extracted precharge time When both of the second clamp switches are turned on and the extracted precharge time has elapsed, both the charging switch and the second clamp switch are turned off, and the extracted from the turn-off of the charging switch. When the discharge time has elapsed, the first clamp switch is turned on.
The drive device according to claim 1. The drive unit is
A first potential line for applying a first potential;
A second potential line connected to the first conduction terminal of the switching element and providing a second potential smaller than the first potential;
A clamp switch connected between the first potential line and the control terminal of the switching element, and for turning on and off energization between the first potential line and the control terminal of the switching element;
A first resistance element connected in series with the clamp switch between the first potential line and the control terminal of the switching element;
A second resistance element having a first terminal and a second terminal, wherein the second terminal is connected to the control terminal of the switching element, and has a resistance value higher or lower than the first resistance element;
A charging switch connected between the first potential line and the first terminal of the second resistance element, and for turning on and off the energization between the first potential line and the second resistance element;
Including
The control parameter is a charging time which is an on time of the charging switch,
In the setting information, the plurality of sections are associated with the charging time that defines the highest switching speed among the switching speeds that satisfy the driving condition in each of the plurality of sections.
The control unit extracts the charging time corresponding to the category including the detected driving state from the setting information, and when the extracted charging time elapses after the charging switch is turned on, the charging Turning off the switch for turning on and turning on the clamp switch,
The drive device according to claim 1. A driving device for driving a switching element including a control terminal,
A drive unit that outputs a drive signal to the control terminal of the switching element;
A controller that controls the drive unit to change a switching speed of the switching element according to a driving state of the switching element;
With
The control unit varies the control parameter that defines the switching speed, and controls the drive unit using the varied control parameter.
Drive device. A driving device for driving a switching element including a control terminal, a first conduction terminal, and a second conduction terminal,
A detection unit that detects at least one of a conduction current, an applied voltage, and a temperature of the switching element directly or indirectly as a driving state of the switching element;
A drive unit that outputs a drive signal to the control terminal of the switching element;
A controller that controls the drive unit to change a switching speed of the switching element according to the detected drive state;
With
The drive unit is
A first potential line for applying a first potential;
A second potential line connected to the first conduction terminal of the switching element and providing a second potential smaller than the first potential;
A first clamp switch connected between the first potential line and the control terminal of the switching element, and for turning on and off the energization between the first potential line and the control terminal of the switching element;
A first resistance element connected in series with the first clamp switch between the first potential line and the control terminal of the switching element;
The first clamp line is connected in parallel with the first clamp line between the first potential line and the control terminal of the switching element to turn on and off the energization between the first potential line and the control terminal of the switching element. A second clamp switch;
A second resistance element connected in series with the second clamp switch between the first potential line and the control terminal of the switching element, and having a resistance value different from that of the first resistance element;
Including
The control unit is associated with the first section in which the fluctuation range of the driving state is divided and the first clamp switch, and the first section in which the fluctuation range of the driving state is divided. The first clamp switch or the second clamp corresponding to the section including the detected drive state, which holds setting information in which the different second section and the second clamp switch are associated in advance. A switch is extracted from the setting information, and the extracted first clamp switch or the second clamp switch is used.
Drive device. A power conversion device that converts input power and outputs the power,
The switching element;
The driving device according to any one of claims 1 to 11, which drives the switching element.
Power conversion device.