Switch element driving device

Abstract

A switching element driving device is provided, which reduces switching losses while suppressing noise with an inexpensive configuration. The switching element driving device includes: a current sensor configured to measure a load current flowing through a load; a voltage sensor configured to measure an input voltage input from a power supply; and a control unit configured to output a command value of a gate drive voltage to a gate drive voltage supply unit that is configured to supply the gate drive voltage for driving a switching element provided between the power supply and the load, wherein the control unit is further configured to determine the command value of the gate drive voltage based on the load current and the input voltage.

Description

Technical Field

[0001] The present invention relates to a switching element driving device. Background Art

[0002] A voltage-driven switching element needs to increase the switching speed to reduce switching losses; however, due to sudden changes in the gate current, an increase in the switching speed generates noise. Therefore, for example, in Patent Document 1, the gate resistance value is changed based on the drain voltage during conduction / turn-off to change the gate voltage, thereby reducing switching losses while suppressing noise.

[0003] Citation List

[0004] Patent Document

[0005] Patent Document 1: JP2013-5474A Summary of the Invention

[0006] Technical Problem

[0007] However, in the technique disclosed in Patent Document 1, the gate resistance value is changed by switching hardware, which results in an increase in cost.

[0008] In view of this, an object of the present invention is to provide a switching element driving device that can reduce switching losses while suppressing noise with an inexpensive configuration.

[0009] Solution to the Problem

[0010] To achieve the above object, in a first aspect, the present invention provides a switching element driving device including: a current sensor configured to measure a load current flowing through a load; a voltage sensor configured to measure an input voltage input from a power supply; and a control unit configured to output a command value of a gate drive voltage to a gate drive voltage supply unit, the gate drive voltage supply unit being configured to supply the gate drive voltage for driving a switching element provided between the power supply and the load, wherein the control unit is further configured to determine the command value of the gate drive voltage based on the load current and the input voltage.

[0011] The control unit may be configured to determine the command value of the gate drive voltage such that the gate drive voltage increases as the load current increases.

[0012] The control unit may be configured to determine the command value of the gate drive voltage such that the gate drive voltage increases as the input voltage increases.

[0013] The command value of the gate drive voltage can be the sum of the product of a first coefficient and the load current and the product of a second coefficient and the input voltage.

[0014] The first coefficient can be a function of the load current and / or the input voltage.

[0015] The second coefficient can be a function of the load current and / or the input voltage.

[0016] Advantages of the Invention

[0017] According to the present invention, a switching element driving device can be provided, which can reduce switching losses while suppressing noise with an inexpensive configuration. Description of the Drawings

[0018] Figure 1 A switching element driving device according to an embodiment of the present invention is shown;

[0019] Figure 2 is a graph showing the relationship between the first coefficient A and the load current Iout and the input voltage Vin; and

[0020] Figure 3 is a graph showing the relationship between the second coefficient B and the load current Iout and the input voltage Vin.

[0021] List of Reference Numerals

[0022] 100 Switching element driving device

[0023] 110 Current sensor

[0024] 120 Voltage sensor

[0025] 130 Gate drive voltage supply unit

[0026] 140 Gate drive unit

[0027] 150 Control unit Detailed Description of the Invention

[0028] Figure 1 A switching element driving device 100 according to an embodiment of the present invention is shown. The switching element driving device 100 is configured to control the driving of a switching element S, which is a voltage-driven switching element controlled by voltage and is, for example, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). Although the switching element S is Figure 1 the switching element of the buck chopper circuit SDC in

[0029] The switching element driving device 100 includes a current sensor 110, a voltage sensor 120, a gate driving voltage supply unit 130, a gate driving unit 140, and a control unit 150.

[0030] The current sensor 110 measures the current flowing through the load L (load current Iout), and supplies power from the power supply E to the load L.

[0031] The voltage sensor 120 measures the voltage input from the power supply E (input voltage Vin).

[0032] The gate driving voltage supply unit 130 supplies a voltage (gate driving voltage) to the gate driving unit 140 for driving the gate. In this embodiment, the magnitude of the gate driving voltage is variable, and the gate driving voltage supply unit 130 receives a command value of the gate driving voltage, and supplies the gate driving voltage based on the command value to the gate driving unit 140.

[0033] The gate driving unit 140 drives the switching element S provided between the power supply E and the load L. Based on the timing of the gate signal, the gate driving unit 140 supplies the gate driving voltage supplied from the gate driving voltage supply unit 130 to the gate of the switching element to drive the switching element S. For example, a gate resistor RG is connected between the gate driving unit 140 and the switching element S, and the current output from the gate driving unit 140 flows from the gate driving unit 140 through the gate resistor RG to the gate of the switching element S. The gate signal can be output by the control unit 150, or can be output by another device independent of the control unit 150.

[0034] Based on the load current measured by the current sensor 110 and the input voltage measured by the voltage sensor 120, the control unit 150 determines the command value of the gate driving voltage, and outputs the command value to the gate driving voltage supply unit 130.

[0035] Therefore, in this embodiment, the switching element S is driven by a gate driving voltage based on the input voltage and the load current, that is, a gate driving voltage based on the power consumption of the load L.

[0036] In this embodiment, for example, for a light load, the gate driving voltage can be reduced, and the time required for charging the gate capacitance can be extended. As a result, a sudden change in the drain-source voltage of the switching element S can be suppressed, and thus noise can be reduced. On the other hand, for a heavy load, the gate driving voltage can be increased, and the time required for charging the gate capacitance can be shortened. As a result, the mirror time period of the switching element S can be shortened, and thus switching loss can be reduced.

[0037] In addition, in this embodiment, the control unit 150 can be constituted by software. Therefore, in this embodiment, no additional circuits and components are required, and thus, it is possible to reduce switching losses while suppressing noise at a low cost.

[0038] For example, the control unit 150 can be configured to determine a command value such that the gate drive voltage increases as the load current increases. When the input voltage Vin is constant, the power consumption of the load L increases as the load current Iout increases. Therefore, with the configuration described above, the gate drive voltage can be reduced for a light load and increased for a heavy load.

[0039] In addition, the control unit 150 can be configured to determine a command value for the gate drive voltage such that the gate drive voltage increases as the input voltage Vin increases. When the load current Iout is constant, the power consumption of the load L increases as the input voltage Vin increases. Therefore, with the configuration described above, the gate drive voltage can be reduced for a light load and increased for a heavy load.

[0040] The control unit 150 can include a table that separately describes the command values of the gate drive voltage for the input voltage Vin and the load current Iout, or the control unit 150 can be configured to calculate the command value of the gate drive voltage based on the input voltage Vin and the load current Iout.

[0041] For example, the command value of the gate drive voltage can be the sum of the product of the first coefficient A and the load current Iout and the product of the second coefficient B and the input voltage Vin (AIout + BVin). At this time, the first coefficient A and the second coefficient B are set based on, for example, the electrical characteristics of the switching element, the gate resistance value, the input / output specifications of the switching power supply circuit, and the like.

[0042] In this way, in this embodiment, simply rewriting the first coefficient A and the second coefficient B by software enables correction according to the electrical characteristics of the switching element, the gate resistance value, the input / output specifications of the switching power supply circuit, and the like.

[0043] In addition, the first coefficient A and the second coefficient B can be functions of the load current Iout such that the first coefficient A and the second coefficient B can increase as the load current Iout increases. In addition, the first coefficient A and the second coefficient B can be functions of the input voltage Vin such that the first coefficient A and the second coefficient B can increase as the input voltage Vin increases.

[0044] At this time, for example, the first coefficient A can increase as the input voltage Vin increases and increase as the load current Iout increases, as Figure 2As shown. In addition, the second coefficient B can increase as the input voltage Vin increases and increase as the load current Iout increases, as Figure 3 shown therein.

[0045] The present invention has been described above with reference to preferred embodiments of the present invention. Although the present invention has been described herein with specific examples, various modifications and changes can be made thereto without departing from the spirit and scope of the present invention described in the claims.

Claims

1. A switching element driving device, comprising: a current sensor configured to measure a load current flowing through a load; a voltage sensor configured to measure an input voltage input from a power supply; and a control unit configured to output a command value of a gate drive voltage to a gate drive voltage supply unit, the gate drive voltage supply unit being configured to supply the gate drive voltage for driving a switching element of a step-down chopper circuit provided between the power supply and the load, wherein, the control unit is further configured to determine the command value of the gate drive voltage based on a relationship between the load current, the input voltage, and a charging time of a gate capacitance, and determine the command value of the gate drive voltage such that the gate drive voltage increases as the load current increases.

2. The switching element driving device according to claim 1, wherein, The control unit is configured to determine the command value of the gate drive voltage such that the gate drive voltage increases as the input voltage increases.

3. The switching element driving device according to claim 1 or 2, wherein, The command value of the gate drive voltage is a sum of a product of a first coefficient and the load current and a product of a second coefficient and the input voltage.

4. The switching element driving device according to claim 3, wherein, At least one of the first coefficient or the second coefficient is a function of the load current and / or the input voltage.

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