Upper arm driving circuit

Abstract

To provide an upper arm driving circuit and a control method thereof capable of increasing a gate voltage of an upper arm switching element regardless of a potential of an output terminal, thereby enabling high efficiency of a power conversion device.SOLUTION: An upper arm driving circuit includes a charge storage circuit 11 including a capacitor 16 and a reverse current preventing element 17, a charge charging / discharging control circuit 12 including a switching element 14 and a resistor 15, and a reverse current preventing element 13, one end of the capacitor 16 is connected to an output terminal VOUT of a power conversion device through the reverse current preventing element 17 and is connected to a gate of the upper arm output element 2 through the reverse current preventing element 13, and the other end of the capacitor 16 is connected to a reference potential of the power conversion device through the switching element 14 and is connected to the output terminal VOUT of the power conversion device through the resistor 15.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an upper arm driver circuit of a power conversion device. [Background technology]

[0002] 2. Description of the Related Art With the rise in awareness of environmental conservation worldwide, the demand for energy conservation has increased, and power conversion devices are being widely adopted in various fields.

[0003] For power conversion devices installed in the drive systems of railway vehicles, air conditioners, etc., important issues include not only high performance and high efficiency, but also miniaturization, weight reduction, and high reliability.

[0004] As background technology for power conversion devices, there is technology such as Patent Document 1, which discloses, in relation to “an upper arm drive circuit and a control method thereof that can achieve both size and weight reduction and high reliability in a power conversion device having a bridge circuit composed of upper and lower arms”, the following: “An upper arm drive circuit for driving and controlling an upper arm switching element of a power conversion device, comprising: a capacitor connected between a gate of the upper arm switching element and an output terminal of the power conversion device; a reverse current prevention circuit connected between a power supply of the power conversion device and the capacitor, for causing a current to flow from a first terminal connected to the power supply side to a second terminal connected to the capacitor side and preventing a reverse flow of current from the second terminal side to the first terminal side; and a capacitor charging switching element connected in series with the first terminal side or the second terminal side of the reverse current prevention circuit between the power supply and the capacitor, and turned on in synchronization with a command signal for turning on the upper arm switching element.” [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2022-24572 Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, in power conversion devices, important issues include not only high performance and high efficiency, but also size, weight reduction, and high reliability.

[0007] According to the above-mentioned Patent Document 1, "in a power conversion device having a bridge circuit formed of upper and lower arms, it is possible to hold the gate voltage of an upper arm switching element without using a latch circuit."

[0008] However, in the upper arm drive circuit disclosed in Patent Document 1, the gate of the upper arm switching element cannot be turned on when the potential of the output terminal is approximately equal to the power supply potential. For example, since the gate cannot be turned on when the upper arm switching element is in freewheeling operation, there is a disadvantage that synchronous rectification operation for reducing losses cannot be performed.

[0009] An object of the present invention is to provide an upper arm drive circuit and a control method thereof, which can increase the gate voltage of the upper arm switching element regardless of the potential of the output terminal of the power conversion device in a power conversion device having a bridge circuit composed of upper and lower arms, thereby increasing the efficiency of the power conversion device. [Means for solving the problem]

[0010] An upper arm drive circuit for driving and controlling an upper arm output element of a power conversion device according to one embodiment of the present invention comprises a turn-off circuit connected between a reference potential of the power conversion device and a gate of the upper arm output element and for turning off the gate of the upper arm output element, a turn-on circuit connected between a main power supply of the power conversion device and the gate of the upper arm output element and for turning on the gate of the upper arm output element, a charge storage circuit having a first capacitor and a first reverse current prevention element, a charge charging / discharging control circuit having a first switching element and a first resistor, and a second reverse current prevention element, wherein one terminal of the first capacitor is connected to an output terminal of the power conversion device via the first reverse current prevention element and to the gate of the upper arm output element via the second reverse current prevention element, and the other terminal of the first capacitor is connected to the reference potential of the power conversion device via the first switching element and to the output terminal of the power conversion device via the first resistor. Effect of the Invention

[0011] According to the present invention, in a power conversion device having a bridge circuit composed of upper and lower arms, it is possible to realize an upper arm drive circuit and a control method thereof that can increase the gate voltage of the upper arm switching element regardless of the potential of the output terminal of the power conversion device, thereby enabling the efficiency of the power conversion device to be increased. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram showing a specific example of a conventional upper arm driver circuit. [Diagram 2] 11 is a timing chart showing the operation of a conventional upper arm driver circuit. [Diagram 3] 2 is a diagram showing a specific example of an upper arm driver circuit according to the first embodiment of the present invention; FIG. [Figure 4] 4 is a timing chart showing an operation of the upper arm driver circuit according to the first embodiment of the present invention. [Diagram 5] FIG. 11 is a diagram showing a specific example of an upper arm driver circuit according to a second embodiment of the present invention. [Figure 6]FIG. 11 is a diagram showing a specific example of an upper arm driver circuit according to a third embodiment of the present invention. [Figure 7] FIG. 11 is a diagram showing a specific example of an upper arm driver circuit according to a fourth embodiment of the present invention. [Figure 8] FIG. 11 is a diagram showing a specific example of an upper arm driver circuit according to a fifth embodiment of the present invention. [Figure 9] 13 is a timing chart showing the operation of the upper arm driver circuit according to the fifth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same components are designated by the same reference numerals, and detailed description of overlapping parts will be omitted. EXAMPLES

[0014] First, the problems with the above-mentioned conventional upper arm driver circuit will be described in detail with reference to FIG. 1 and FIG.

[0015] FIG. 1 is a diagram showing a schematic configuration of an upper arm driver circuit of a conventional power conversion device, and FIG. 2 is a timing chart showing the operation thereof.

[0016] In the following explanation, an example of a half-bridge circuit having only one leg with upper and lower arms made up of power MOSFETs as output elements will be used; however, the subject matter of the present invention is not limited to this, and the present invention can also be applied to a power conversion device of a three-phase full-bridge circuit configured by connecting another leg of the half-bridge circuit to form a full-bridge configuration and connecting each of the three-phase AC output terminals (U phase, V phase, W phase) to the neutral points of each leg.

[0017] Although the description will be given using a configuration in which a power MOSFET is used as the output element, the output element may also be configured with a switching element such as an IGBT and a free wheel diode connected in inverse parallel thereto.

[0018] In FIG. 1, switching element 2 is an upper arm output element of the power conversion device, and switching element 3 is a lower arm output element of the power conversion device.

[0019] As shown in FIG. 1, in a conventional power conversion device, a load (coil) 4 is connected to an output terminal VOUT, and a main power supply 1 of the power conversion device is connected to a drain terminal of a switching element 2.

[0020] In addition, the upper arm drive circuit has a switching element 7, a backflow prevention element (diode) 8, and a gate delay circuit (resistor) 10 connected in series between the main power supply 1 of the power conversion device and the gate of the switching element 2, a voltage limiting element (Zener diode) 18 and a capacitor 9 connected in parallel between the gate of the switching element 2 and the output terminal VOUT of the power conversion device via the gate delay circuit (resistor) 10, and a switching element 6 connected between the gate of the switching element 2 and the reference potential (ground) of the power conversion device via the gate delay circuit (resistor) 10.

[0021] As shown in FIG. 2, in the upper arm driver circuit of a conventional power conversion device, switching element 6 is turned on in advance, and when main power supply 1 is turned on, the drain voltage of switching element 2 rises to the power supply potential VS of main power supply 1.

[0022] Next, by turning off switching element 6 and turning on switching element 7 by an upper arm on command signal, a current I7 flows from main power supply 1 through switching element 7 and backflow prevention element (diode) 8, and capacitor 9 is charged.

[0023] The voltage rise of the capacitor 9 is limited by a voltage limiting element (Zener diode) 18 to a predetermined value or less.

[0024] Furthermore, charges are injected into the gate of the switching element 2 via the gate delay circuit (resistor) 10, causing the gate voltage VGE of the switching element 2 to increase.

[0025] When the gate voltage VGE of the switching element 2 becomes equal to or higher than a threshold value (Vth), a current starts to flow through the switching element 2.

[0026] Furthermore, when the gate voltage VGE of the switching element 2 rises to a certain value corresponding to the load current, the potential of the output terminal VOUT rises. During the period in which the potential of the output terminal VOUT is rising, the gate voltage VGE hardly rises due to the influence of the feedback capacitance of the switching element 2. This period is called the plateau period, and the gate voltage VGE during this period is called the plateau voltage VP.

[0027] When the potential of the output terminal VOUT rises to approximately the same level as the power supply potential VS of the main power supply 1, the current I7 stops flowing. However, the charge stored in the capacitor 9 continues to charge the gate of the switching element 2 via the gate delay circuit (resistor) 10 until the potential V9 across both terminals of the capacitor 9 becomes equal to the gate voltage VGE of the switching element 2, and the gate voltage VGE can be made sufficiently large, thereby reducing the conduction loss of the switching element 2.

[0028] Next, by turning off switching element 7 and turning on switching element 6 by an upper arm off command signal, the gate of switching element 2 is discharged, switching element 2 is turned off, and the potential of the output terminal VOUT drops to the reference potential (ground).

[0029] As described above, in the upper arm drive circuit of a conventional power conversion device, after the switching element 2 is turned on and the potential at the output terminal VOUT rises, the gate of the switching element 2 is charged only by the charge stored in the capacitor 9, so that the plateau voltage VP at the time of turn-on affects the steady-state gate voltage VGE when the element is on.

[0030] In addition, since it is known that the plateau voltage VP changes depending on the load current and environmental temperature, conventional upper arm drive circuits have the disadvantage that the gate voltage VGE when on changes depending on the usage conditions.

[0031] Furthermore, as described above, current I7 flows only when output terminal VOUT is lower than power supply potential VS of the main power supply 1. Therefore, when the potential of output terminal VOUT rises due to switching of the lower arm, for example when the upper arm transitions from the off state to reflux operation, even if an on command is input to the upper arm drive circuit for synchronous rectification, the output terminal VOUT is already at approximately the same potential as the power supply potential VS of the main power supply 1, so current I7 does not flow and the upper arm cannot be turned on to perform synchronous rectification operation. This is a disadvantage.

[0032] The configuration of an upper arm driver circuit and a control method thereof according to the first embodiment of the present invention will be described with reference to FIGS.

[0033] FIG. 3 is a diagram showing a schematic configuration of an upper arm driver circuit of the power conversion device according to the first embodiment of the present invention, and FIG. 4 is a timing chart showing the operation thereof.

[0034] A main power supply 1 of the power conversion device is connected to the drain terminal of a switching element 2 of the upper arm output element, and the switching element 2 and a switching element 3 of the lower arm output element are connected at an output terminal VOUT, and a load (coil) 4 is connected to the output terminal VOUT.

[0035] In the upper arm drive circuit, a turn-on circuit 5 consisting of a switching element 7 and a reverse current prevention element (diode) 8 is connected between the main power supply 1 and the gate of the switching element 2, a switching element 6 of a turn-off circuit is connected between the gate of the switching element 2 and the reference potential (ground) of the power conversion device, a charge storage circuit 11 consisting of a reverse current prevention element (diode) 17 and a capacitor 16 is connected to the gate of the switching element 2 via a reverse current prevention element (diode) 13, a charge charging and discharging control circuit 12 consisting of a switching element 14 and a resistor 15 is connected between the output terminal VOUT and the reference potential (ground), and one end of the capacitor 16 is connected to the junction of the switching element 14 and the resistor 15.

[0036] As shown in FIG. 4, in the upper arm driver circuit of the power conversion device according to the first embodiment of the present invention, the switching element 6 is turned on in advance, and the main power supply 1 is turned on so that the drain voltage of the switching element 2 rises to the power supply potential VS of the main power supply 1.

[0037] Next, by turning off switching element 6 and turning on switching element 7 by an upper arm on command signal, a current I7 flows from the main power supply 1 through switching element 7 and backflow prevention element (diode) 8, and charge is injected into the gate of switching element 2, thereby increasing the gate voltage VGE of switching element 2.

[0038] When the gate voltage VGE of the switching element 2 becomes equal to or higher than a threshold value (Vth), a current starts to flow through the switching element 2.

[0039] Furthermore, when the gate voltage VGE of the switching element 2 rises to a predetermined value corresponding to the load current, the potential of the output terminal VOUT rises. During the period in which the potential of the output terminal VOUT is rising, the gate voltage VGE hardly rises due to the influence of the feedback capacitance of the switching element 2.

[0040] By turning on the switching element 14 during this plateau period, charge is accumulated in the capacitor 16 via the backflow prevention element (diode) 17 from the output terminal VOUT.

[0041] When the potential of the output terminal VOUT rises to approximately the same as the power supply potential VS of the main power supply 1, the current I7 stops flowing, but when the switching element 14 is turned off at this point, the drain potential of the switching element 14 rises to the same potential as the potential of the output terminal VOUT.

[0042] Then, the potential of the junction 23 between the capacitor 16 and the reverse current prevention element (diode) 17 becomes VOUT+V16 due to the voltage V16 applied across both terminals of the capacitor 16, which is higher than the potential (VOUT+VGE) of the gate of the switching element 2, so that the charge stored in the capacitor 16 is injected into the gate of the switching element 2 via the reverse current prevention element (diode) 13, and the gate potential VGE rises until VGE and V16 become equal. As a result, the gate potential VGE can be made sufficiently large, and the conduction loss of the switching element 2 can be reduced.

[0043] If it is desired to further increase the gate potential VGE to reduce the conduction loss of the switching element 2, the switching element 14 may be turned on (storage of charge in the capacitor 16) and off (injection of charge into the gate of the switching element 2) multiple times.

[0044] Next, by turning off switching element 7 and turning on switching element 6 by an upper arm off command signal, the charge accumulated in the gate of switching element 2 and capacitor 16 is discharged, switching element 2 enters the off state, and the potential of the output terminal VOUT drops to the reference potential (ground).

[0045] According to the upper arm driver circuit and its control method of the first embodiment of the present invention described above, even after the potential of the output terminal VOUT has risen to the power supply potential VS of the main power supply 1 by turning on, the gate voltage VGE of the upper arm switching element 2 can be increased arbitrarily by the charge storage circuit 11 and the charge charging / discharging control circuit 12. This reduces the conduction loss and enables highly efficient control of the power conversion device.

[0046] In FIG. 1, the switching element 7 is connected to the main power supply 1 side via the reverse current prevention element (diode) 8, but the order of these two may be reversed. EXAMPLES

[0047] Second Embodiment Next, the configuration of an upper arm driver circuit according to a second embodiment of the present invention will be described with reference to FIG.

[0048] The differences from FIG. 3 are that a voltage limiting element (Zener diode) 18 and a capacitor 9 are connected between the gate and source (output terminal VOUT) of the switching element 2, a gate delay circuit (resistor) 10 is connected between the reverse current prevention element (diode) 8 and the gate of the switching element 2, and a voltage limiting element (Zener diode) 19 is connected in parallel to the capacitor 16.

[0049] Incidentally, there is no problem if the voltage limiting element (Zener diode) 19 is connected in parallel to the resistor 15.

[0050] In addition, in FIG. 5, the backflow prevention element (diode) 13 is connected to the gate of the switching element 2 via the gate delay circuit (resistor) 10, but there is no problem if the backflow prevention element (diode) 13 is directly connected to the gate of the switching element 2.

[0051] In the configuration of the second embodiment of the present invention shown in FIG. 5, a voltage limiting element (Zener diode) 18 and a capacitor 9 prevent momentary overvoltage from being applied to the gate of the switching element 2, and a gate delay circuit (resistor) 10 limits the gate current, thereby making it possible to appropriately control the switching speed of the switching element 2.

[0052] In addition, the charge stored in the capacitor 9 can further increase the gate voltage VGE of the switching element 2 after the switching element 2 is turned on.

[0053] Furthermore, since the voltage applied to the capacitor 16 can be precisely limited by the voltage limiting element (Zener diode) 19, the gate voltage rise of the switching element 2 by the charge / discharge control circuit 12 can be more precisely controlled. EXAMPLES

[0054] Third Embodiment Next, the configuration of an upper arm driver circuit according to a third embodiment of the present invention will be described with reference to FIG.

[0055] The difference from FIG. 5 is that the resistor 15 is replaced with a switching element 20.

[0056] The switching element 20 is controlled so that when the switching element 14 is on, the switching element 20 is off, and when the switching element 14 is off, the switching element 20 is on.

[0057] By using switching element 20, power consumption can be reduced during the period when switching element 14 is on (the period when charge is stored in capacitor 16) compared to when resistor 15 is used, and the switching speed can be improved when switching element 14 is switched from on to off. EXAMPLES

[0058] Fourth Embodiment Next, the configuration of an upper arm driver circuit according to a fourth embodiment of the present invention will be described with reference to FIG.

[0059] The difference from FIG. 5 is that a switching element 21 is provided in parallel with the capacitor 16.

[0060] In the configurations of the upper arm drive circuit up to the third embodiment, when the switching element 2 is turned off, the charge stored in the capacitance between the gate and source of the switching element 2 as well as the charge stored in the capacitor 16 are discharged via the switching element 6. Therefore, when the switching element 2 is turned off, the turn-off speed of the switching element 2 is reduced by the amount of the capacitor 16.

[0061] According to the configuration of the upper arm drive circuit of Example 4, the turn-off speed of switching element 2 can be increased by turning on switching element 21 prior to turning off switching element 2 and discharging the charge stored in capacitor 16.

[0062] Also, if switching element 14 is turned on while switching element 2 is being turned off, it is possible to accelerate the turn-off speed of switching element 2 halfway through. EXAMPLES

[0063] Next, the configuration of an upper arm driver circuit according to a fifth embodiment of the present invention will be described with reference to FIGS.

[0064] FIG. 8 is a diagram showing a schematic configuration of an upper arm driver circuit of a power converter according to a fifth embodiment of the present invention, and FIG. 9 is a timing chart showing the operation thereof.

[0065] The difference from FIG. 5 is that a switching element 22 is provided between the gate of the switching element 2 and a backflow prevention element (diode) 13.

[0066] In the upper arm driver circuit of the fifth embodiment, the current flowing from the capacitor 16 to the gate of the switching element 2 is controlled by the switching element 22.

[0067] By turning on the switching element 22 after the turn-on plateau period, the charge stored in the capacitor 16 can be injected into the gate of the switching element 2. At this time, the rate of increase in the gate voltage VGE of the switching element 2 can be adjusted by repeating the on and off of the switching element 22 in small time steps.

[0068] Furthermore, when switching element 2 is turned off, if switching element 22 is turned off, the charge stored in capacitor 16 does not flow into the gate of switching element 2, thereby improving the turn-off speed of switching element 2.

[0069] In addition, in order to reduce noise and surge voltage during turn-off, the turn-off speed of switching element 2 can be adjusted by temporarily turning on switching element 22 and injecting the charge stored in capacitor 16 into the gate of switching element 2. [Explanation of symbols]

[0070] 1…Main power supply 2...Upper arm output element (switching element) 3...Lower arm output element (switching element) 4...Load (coil) 5…Turn-on circuit 6...Turn-off circuit (switching element) 7...Switching element 8...Reverse current prevention element (diode) 9…Capacitor 10...Gate delay circuit (resistor) 11...Charge storage circuit 12...Charge and discharge control circuit 13...Reverse current prevention element (diode) 14...Switching element 15…Resistance 16…Capacitor 17...Reverse current prevention element (diode) 18...Voltage limiting element (Zener diode) 19...Voltage limiting element (Zener diode) 20...Switching element 21...Switching element 22...Switching element 23...Contact point between capacitor 16 and reverse current prevention element (diode) 17

Claims

1. In an upper arm drive circuit that drives and controls an upper arm output element of a power conversion device, a turn-off circuit connected between a reference potential of the power conversion device and a gate of the upper arm output element, for turning off the gate of the upper arm output element; a turn-on circuit connected between a main power supply of the power conversion device and a gate of the upper arm output element, for turning on the gate of the upper arm output element; a charge storage circuit including a first capacitor and a first backflow prevention element; a charge / discharge control circuit including a first switching element and a first resistor; a second backflow prevention element; one terminal of the first capacitor is connected to an output terminal of the power conversion device via the first reverse current prevention element and is connected to a gate of the upper arm output element via the second reverse current prevention element; an upper arm drive circuit, characterized in that the other terminal of the first capacitor is connected to a reference potential of the power conversion device via the first switching element and to an output terminal of the power conversion device via the first resistor.

2. 2. The upper arm drive circuit according to claim 1, characterized in that the first reverse current prevention element prevents a reverse flow of current from the one terminal of the first capacitor to the output terminal of the power conversion device, and the second reverse current prevention element prevents a reverse flow of current from the gate of the upper arm output element to the one terminal of the first capacitor.

3. 3. The upper arm drive circuit according to claim 2, characterized in that, when turned on by the turn-on circuit, charge is accumulated from the output terminal of the power conversion device to the one terminal of the first capacitor by turning on the first switching element, and charge is injected from the one terminal of the first capacitor to the gate of the upper arm output element by turning off the first switching element.

4. In an upper arm drive circuit that drives and controls an upper arm output element of a power conversion device, a turn-off circuit connected between a reference potential of the power conversion device and a gate of the upper arm output element, for turning off the gate of the upper arm output element; a turn-on circuit connected between a main power supply of the power conversion device and a gate of the upper arm output element, for turning on the gate of the upper arm output element; a charge storage circuit including a first capacitor and a first backflow prevention element; a charge / discharge control circuit including a first switching element and a second switching element; a second backflow prevention element; one terminal of the first capacitor is connected to an output terminal of the power conversion device via the first reverse current prevention element and is connected to a gate of the upper arm output element via the second reverse current prevention element; an upper arm drive circuit, characterized in that the other terminal of the first capacitor is connected to a reference potential of the power conversion device via the first switching element and is connected to an output terminal of the power conversion device via the second switching element.

5. 5. The upper arm drive circuit according to claim 4, characterized in that the first reverse current prevention element prevents a reverse flow of current from the one terminal of the first capacitor to the output terminal of the power conversion device, and the second reverse current prevention element prevents a reverse flow of current from the gate of the upper arm output element to the one terminal of the first capacitor.

6. 6. The upper arm drive circuit according to claim 5, characterized in that, when turned on by the turn-on circuit, charge is stored from the output terminal of the power conversion device to the one terminal of the first capacitor by turning on the first switching element and turning off the second switching element, and charge is injected from the one terminal of the first capacitor to the gate of the upper arm output element by turning off the first switching element and turning on the second switching element.

7. The upper arm drive circuit according to any one of claims 1 to 6, characterized in that, when turned on by the turn-on circuit, accumulation of charge in the one terminal of the first capacitor and injection of charge into the gate of the upper arm output element are repeated multiple times.

8. 7. The upper arm driver circuit according to claim 1, further comprising a first voltage limiting element connected in parallel to the first capacitor.

9. a third switching element connected in parallel to the first capacitor; 7. The upper arm drive circuit according to claim 1, wherein, when the turn-off circuit turns off the first capacitor, the third switching element is turned on to discharge the charge stored in the first capacitor.

10. 7. The upper arm driver circuit according to claim 1, further comprising a fourth switching element provided between the one terminal of the first capacitor and the gate of the upper arm output element.

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