HV switch unit

Abstract

The present invention relates to an HV switch unit (HVU) comprising an HV switch (HVS) having a plurality of semiconductor switches (S1, S2, Si, Sn) connected in series, and a method for balancing voltage distributions on the switches (S1, S2, Si, Sn) connected in series in the HV switch (HVS), wherein each switch (S1, S2, Si, Sn) is associated with a snubber device (10, 10', 12, 12', 14, 14'), and the method The method includes the steps of: a. determining a first quantity associated with the snubber devices (10, 10', 12, 12', 14, 14') of the first switch (S1); b. determining a second quantity associated with the snubber devices (12, 12', 14, 14') of the second switches (S2, Si, ... Sn); c. comparing the first quantity with the second quantity; and d. adjusting the drive signal (6) of at least the first switch (S1) based on the first quantity based on the comparison.

Description

[Technical Field]

[0001] Background of the Invention The present invention relates to a method for balancing voltage distribution on switches connected in series in a high voltage (HV) switch, each switch having an associated snubber device. The present invention also relates to an HV switch unit. [Background technology]

[0002] An HV switch is a switch that consists of multiple semiconductor switches connected in series and can switch voltages of 500V or more, especially 1kV or more. A series connection of semiconductor switches is sometimes called a switch stack. All semiconductor switches connected in series and acting as a single switch must be turned on and / or off simultaneously to balance the voltage distribution along the switch stack. Small timing discrepancies related to variations in signal propagation delays can cause large voltage imbalances, leading to overvoltage or voltage-related stress that can destroy one or more semiconductor switches and ultimately the HV switch.

[0003] Also, unequal voltage distribution across the switches can occur due to different voltages to ground on the body of the semiconductor switches and different capacitances to ground between the switches. Unequal voltage distribution leads to unequal power loss distribution, which can cause cooling problems.

[0004] The importance of the problem increases with the length of the switch stack, ie, the number of semiconductor switches, the switching frequency and the switching speed. Summary of the Invention [Problem to be solved by the invention]

[0005] Problem to be solved by the invention The object of the present invention is to provide a method and an HV switch that overcomes the above drawbacks. [Means for solving the problem]

[0006] overview According to a first aspect, the present invention relates to a method as claimed in claim 1. A method for balancing voltage distributions on switches connected in series in an HV switch, each switch having an associated snubber device, comprising: a. determining a first quantity related to a snubber device of a first switch, in particular a first voltage across a first snubber energy storage component associated with the first switch; b. determining a second quantity related to the snubber device of the second switch, specifically a second voltage across a second snubber energy storage component associated with the second switch; c. comparing the first amount and the second amount, in particular the first voltage and the second voltage; d. adjusting a drive signal of at least a first switch based on the first amount based on the comparison; A method is disclosed that includes:

[0007] The drive signal of the first switch may be self-regulated. Self-regulated regulation may include regulating the drive signal based on the amount of the HV switch unit without using a controller. Therefore, this term means that the regulated drive signal is not generated by a controller or drive signal generator.

[0008] The snubber device can be used to determine, for example, a voltage as the first quantity, based on which a control signal for controlling the first switch can be adjusted, and thus the switch-on and / or switch-off times, i.e., the switching-on and / or switching-off instants can be adjusted.

[0009] The drive signal can come from a digital controller such as a microcontroller, a programmable logic device such as an FPGA, or other digital logic circuit. "Adjusting the drive signal" can be performed by a separate electronic circuit, the drive signal conditioner. In this way, the drive signal itself can be held constant, i.e., without individual adjustment. In this way, adjustment can be performed very quickly and without interfering with logic circuits or programs, which can be disadvantageously slow. In this way, the drive signal can be the same for all switches connected in series, and adjustment of the switching of one or more, particularly all individual switches, can be performed by the drive signal conditioner. Therefore, only one drive signal needs to be generated, and the controller does not need to generate and / or adjust drive signals for multiple switches. The controller is not burdened with generating multiple drive signals.

[0010] A uniform voltage distribution among multiple semiconductor switches connected in series to form an HV switch can be achieved by varying the switching time of each individual switch, thereby achieving a voltage distribution along the switch stack in each off-state of the HV switch such that individual switch stack components are not subjected to overvoltages or excessive voltage-related stresses.

[0011] This method of shifting the control signals of the semiconductor switches can affect the voltage distribution along the series-connected semiconductor switches and can be applied to hard-switching devices (where a voltage is present before switching on and / or a current is present before switching off).

[0012] The first and second quantities may be determined for adjacent switches. In this method, a snubber device, in particular a resistor-capacitor (RC) snubber or a resistor-capacitor-diode (RCD) snubber, may be provided for each semiconductor switch. Instead of a diode, a separate rectifying component may be used. The sum of the voltages of the snubber energy storage components, in particular capacitors, of two consecutive snubber devices may be divided by a voltage divider, for example comprising a resistor. In particular, the voltage may be divided in half. The resistor may be part of the snubber device. By comparing the intermediate voltage of the snubber device capacitors with the voltage from the voltage divider, the control signal may be shifted in time to reach a state in which the snubber capacitors of consecutive switches have equal voltages. This method can be applied to individually shift the drive signals of any number of series-connected semiconductor switches. This method may adjust the switching time of each semiconductor in a self-regulating manner to reach an equal voltage distribution of all series-connected switches.

[0013] Adjusting the drive signal may include delaying or advancing the drive signal, which may include pulse width modulating the drive signal to obtain the adjusted drive signal.

[0014] A drive signal may be provided, and one of the switches may be driven by the drive signal, while the other switches may be driven by an adjusted drive signal formed by adjusting the drive signal. Thus, an equal voltage distribution along all the switches may be achieved. The adjusted drive signals of the other switches may be different for each switch and adjusted individually. At the same time, only one drive signal may be generated. This makes it easy to maintain logical drive signal generation.

[0015] The voltage across the snubber energy storage component associated with a first switch may be determined as a first quantity, and the voltage across the snubber energy storage component associated with a second switch may be determined as a second quantity, and thus the quantity associated with different snubber devices of different switches may be used to adjust the drive signal of one of the switches.

[0016] The drive signal for the at least one switch may be adjusted based on an amount related to a voltage limiter provided in the snubber device of the at least one switch. For example, a current in the voltage limiter connected across a capacitor of the snubber device may be determined. Alternatively, a voltage driving the voltage limiter may be determined, and the drive signal adjusted before the voltage limiter draws current. The use of a voltage limiter may reduce power dissipation in the snubber device when the voltage is below a limit value, allowing safe operation in burst mode.

[0017] If the voltage on a particular switch needs to be reduced, the switch-on time may be advanced slightly and the switch-off time may be delayed slightly relative to the switching of adjacent switches.

[0018] The idea of ​​the present invention is to introduce small offsets in the switch-on and / or switch-off times of the individual switches in the switch stack that constitutes the HV switch, based on signals available at the local potential level of each switch, in order to compensate for propagation delays and minimize voltage imbalances between the switches.

[0019] The control signal used to determine the timing delay may be obtained by comparing the voltage across the snubber capacitor of a particular switch with the voltage on an adjacent switch, by detecting the current in a voltage limiter connected across the snubber capacitor of that particular switch, or by measuring the voltage driving the voltage limiter and reacting to that value before the voltage limiter draws current.

[0020] If the voltage on a particular switch needs to be reduced, the switch-on time may be advanced slightly and / or the switch-off time may be delayed slightly relative to the switching of adjacent switches.

[0021] According to a further aspect, the present invention relates to an HV switch unit as claimed in claim 9. Such an HV switch unit comprises: a. an HV switch comprising a plurality of semiconductor switches connected in series; b. a snubber device comprising at least one snubber energy storage component connected in parallel with each semiconductor switch; c. at least one drive signal conditioner for conditioning a drive signal for the at least one switch; d. a feedback device for providing a quantity related to the snubber device of the at least one switch to a drive signal conditioner; Equipped with.

[0022] The drive signal conditioner is e. determining a first quantity associated with the snubber device of the first switch, specifically a first voltage across a first snubber energy storage component associated with the first switch; f. determining a second quantity associated with the snubber device of the second switch, specifically a second voltage across a second snubber energy storage component associated with the second switch; g. comparing the first amount to the second amount, particularly the first voltage to the second voltage; h. adjusting the drive signal of at least the first switch based on the first amount based on the comparison. It is structured as follows.

[0023] By adjusting the drive signals, a uniform voltage distribution can be achieved. Thus, individual switches can be protected from overvoltage or voltage stress. Thus, fast HV switches capable of switching high voltages can be achieved. Known solutions address voltage imbalances related to driver variations, not the variations themselves. According to the present invention, the variations are compensated to achieve a proper voltage distribution. The compensation works locally at the driver potential. No extra isolation of additional signals is required.

[0024] As a result, the HV switch unit is configured to turn the switches on and / or off simultaneously, which means that the switches are on and / or off simultaneously, i.e. the outputs of the switches change their state simultaneously.

[0025] The snubber energy storage components of the snubber devices of two adjacent switches may be connected in series at a junction, which may be connected to a comparison component. Thus, a quantity related to two different semiconductor switches and / or their associated snubber devices may be used to adjust the drive signal of one of the switches. The comparison component may be configured to determine which of its input signals or quantities is higher and how higher it is. This is in contrast to a simple comparator, which may only determine which of its input signals or quantities is higher.

[0026] The resistors of the snubber devices of the two adjacent switches may be connected in series at a second node, which may be connected to a comparison component, so that the two voltages are compared and the drive signal is adjusted based on the comparison.

[0027] The comparison component may be incorporated into the drive signal conditioner, so that the HV switch unit of the present invention can be implemented with fewer components.

[0028] At least one of the snubber devices may be provided with a voltage limiter, and a quantity related to the voltage limiter may be provided to a drive signal conditioner for a switch associated with the at least one snubber device. The use of the voltage limiter may reduce power dissipation in the snubber device when the voltage is below a limit value, allowing safe operation in burst mode.

[0029] All or all but one switch may be associated with a drive signal conditioner, and the same drive signal may be provided to one switch and the drive signal conditioners associated with the other switches. The drive signal of one switch may be considered a reference, and the signals used to drive the other switches of the HV switch may be adjusted relative to that drive signal to ensure equal voltage distribution and simultaneous switching of the semiconductor switches.

[0030] A resistor may be connected between the first connection point and the comparison component.

[0031] Further advantages of the present invention are apparent from the description and the drawings. Likewise, the features mentioned above and those to be described below can be used in accordance with the present invention, each individually or in any combination. The illustrated and described embodiments are not to be understood as an exhaustive description of the present invention, but rather have an exemplary nature for the explanation of the present invention. [Brief explanation of the drawings]

[0032] [Figure 1] FIG. 1 is a diagram showing a first embodiment of an HV switch unit with comparative components. [Figure 2] FIG. 10 illustrates a second embodiment of an HV switch unit without an independent comparison component. [Figure 3] FIG. 10 shows a third embodiment of an HV switch unit comprising a snubber device and more than two switches connected in series. [Figure 4]FIG. 10 shows a fourth embodiment of an HV switch unit with a voltage limiter. DETAILED DESCRIPTION OF THE INVENTION

[0033] Detailed Description of the Drawings An HV switch unit HVU, a. An HV switch HVS including a plurality of semiconductor switches S1, S2, Si, and Sn connected in series; b. snubber devices 10, 10', 12, 12', 14, 14' each including at least one snubber energy storage component C1, C1', C2, Ci, Ci', Cn, Cn' connected in parallel with each semiconductor switch S1, S2, Si, Sn; c. at least one drive signal conditioner 8 configured to condition a drive signal of at least one switch S1, S2, Si, Sn; d. a feedback device for providing a quantity related to the snubber device 10, 10', 12, 12', 14, 14' of at least one switch S1, S2, Si, Sn to the drive signal conditioner 8; An HV switch unit comprising:

[0034] All of the above mentioned properties may also be properties of such an HV switch unit HVU.

[0035] Furthermore, there is provided a method for balancing voltage distributions on series-connected switches S1, S2, Si, Sn in an HV switch HVS, wherein each switch S1, S2, Si, Sn has associated thereto a snubber device 10, 10', 12, 12', 14, 14', a. determining a first quantity associated with the snubber device 10, 10' of the first switch S1; b. adjusting the drive signal 6 of the first switch S1 based on a first amount; A method is disclosed that includes:

[0036] All of the above mentioned properties may also be properties of such a method.

[0037] The method further comprises: c. determining a second quantity associated with the snubber device 12, 12', 14, 14' of the second switch S1, S2, Si, Sn; d. comparing the first amount to the second amount; e. adjusting a drive signal of at least a first switch S1 based on the comparison; and It may include:

[0038] FIG. 1 shows an HV switch unit HVU comprising an HV switch HVS comprising two semiconductor switches S1 and S2 connected in series. A first snubber device 10 is associated with the first switch S1, and a second snubber device 12 is associated with the second switch S2. Both snubber devices 10 and 12 comprise snubber energy storage components embodied as capacitors C1 and C2 and resistors R1 and R2, and rectifier components D1 and D2 embodied as diodes. The resistors R1 and R2 form a voltage divider. A junction point CP1 of the snubber energy storage components C1 and C2 is connected to a comparison component 7, and a junction point CP2 of the resistors R1 and R2 is also connected to the comparison component 7.

[0039] Resistors R1 and R2 are not connected directly in parallel with the energy storage components C1 and C2 of the respective snubber devices 10 and 12, but are connected in parallel in a string, i.e., the series connection of the snubber energy storage components C1 and C2 is connected in parallel with the series connection of resistors R1 and R2. This connection results in two voltages available for further processing: the sum of the voltages on the snubber energy storage components C1 and C2 divided by the resistors R1 and R2 at node CP2, and a voltage that is the difference between the charging voltages of the energy storage components C1 and C2 at node CP1. The difference between these two voltages is determined by a comparison component 7 and supplied to a drive signal conditioner 8, which is supplied with a drive signal 3. The drive signal conditioner 8 functions as a pulse shifter and controls the switching time of switch S1, as indicated by the Δt arrow.

[0040] When the HV is switched on or off for a long time (such as during burst mode or after power off), an optional resistor Rdif may be connected to the comparison component between CP1 and CP2 to equalize the voltages on the energy storage components C1 and C2.

[0041] To avoid unequal voltage distribution between switches S1 and S2, the phase of the switching times of switch S1 can be varied. Switch S2 is controlled directly (without a phase-shift circuit) using drive signal 3, i.e., an unregulated drive signal. Switch S1 is controlled by drive signal conditioner 8 (indicated by arrow 6), which is controlled by signal 9 generated by comparison component 7, embodied as an error amplifier. Comparison component 7 subtracts half the voltage on both semiconductor switches S1 and S2, i.e., the voltage at node CP2, from the voltage on energy storage component C2 (at node CP1) of second snubber device 12 associated with second switch S2.

[0042] If the voltage at node CP1 is higher than the voltage at node CP2, it means that the voltage on the second switch S2 is too high and it is necessary to slow down the switching-on moment of switch S1 and / or speed up the switching-off time of switch S1.

[0043] If the voltage at node CP1 is lower than the voltage at node CP2, it means that the voltage on the lower switch S2 is too low and it is necessary to speed up the switching-on moment of switch S1 and / or slow down the switching-off time of switch S1.

[0044] The node CP1 is connected to the low potential of the switch S1, which may be the emitter of an IGBT or the source of a MOS-FET transistor.

[0045] The drive signal conditioner 8 may be embodied as or comprise a digital signal processor (DSP).

[0046] The comparison element 7, the connections to the nodes CP1 and CP2 and the drive signal conditioner 8 can be considered to be a feedback device.

[0047] The embodiment shown in Figure 2 corresponds largely to the embodiment of Figure 1, but does not have a separate comparison component. The comparison component is implemented within the drive signal conditioner 8. The voltage at CP2 is directly compared by the drive signal conditioner 8 with the voltage at node CP1, which is the low potential of switch S1, i.e., the ground potential of the drive signal conditioner 8.

[0048] 3 shows an HV switch unit HVU having more than two, in this case n, switches S1, Si, Sn connected in series, with n-1 switches S1, Si controlled by drive signal conditioner 8 and one switch Sn driven directly by drive signal 3. Drive signal 3 is also supplied to drive signal conditioner 8 and causes each switch S1, Si to speed up or slow down based on an amount determined from snubber devices 10, 12, 14, 10', 12', 14' so that the voltage across terminals 1 and 2 is equally distributed among switches S1, Si, Sn.

[0049] When there are more than two semiconductor switches connected in series, it is useful to connect two snubber devices 10, 10', 12, 12', 14, 14' to each switch S1, Si, Sn, so that the capacitance of each snubber energy storage component C1, C1', Ci, Ci', Cn, Cn' can be twice as low or the resistance of each resistor R1, R1', Ri, Ri', Rn, Rn' can be twice as high as if a single snubber device were associated with each switch S1, Si, Sn.

[0050] The snubber resistor associated with a particular switch is connected to the snubber resistor of the adjacent switch, in this case R1 is connected to Ri and Ri' is connected to Rn'. If there are no adjacent snubber resistors, the resistor is connected to its own capacitor, R1' is connected to C1' and Rn is connected to Cn.

[0051] Switch Sn is directly controlled by drive signal 3, while the signals of switches S1 and Si are shifted in time by drive signal conditioner 8 by comparing the voltages on CP1 and CP2 and the voltages on CPi and CPi'.

[0052] 4, resistors R1 and R2 are not connected in series. Rather, voltage limiters V1 and V2 are provided. As soon as the voltage on C1 or C2 (which is a first quantity associated with snubber device 10 and 12, respectively) exceeds the threshold voltage of the associated voltage limiter V1 and V2, a positive voltage appears on the associated resistor R1 and R2, thus affecting the comparison result of comparator component 7 and leading to adjustment of the drive signal by drive signal conditioner 8.

Claims

1. A method for balancing voltage distributions on a plurality of switches (S1, S2, Si, Sn) connected in series in an HV switch (HVS), wherein snubber devices (10, 10', 12, 12', 14, 14') are associated one-to-one with each of the switches (S1, S2, Si, Sn), comprising: determining a first quantity output from the snubber device (10, 10') associated with a first switch (S1) of the plurality of switches (S1, S2, Si, Sn), the first quantity being a first voltage across a first snubber energy storage component (C1) of the snubber device (10, 10') associated with the first switch (S1); b) determining a second quantity output from the snubber device (12, 12', 14, 14') associated with a second switch (S2, Si, ... Sn) of the plurality of switches (S1, S2, Si, ... Sn), the second quantity being a second voltage across a second snubber energy storage component (C2, Ci, ... Cn) of the snubber device (12, 12', 14, 14') associated with the second switch (S2, Si, ... Sn); c. comparing the first voltage with the second voltage; d. forming a second drive signal (6) by adjusting the first drive signal (3) based on the comparison and driving at least said first switch (S1) with said second drive signal (6); Including, an n-th switch (Sn) (n is a natural number equal to or greater than 2) among the plurality of switches (S1, S2, Si, Sn) is driven by the first drive signal (3), and other switches (S1, S2, Si) among the plurality of switches (S1, S2, Si, Sn) are driven by the second drive signal (6); The second drive signal (6) for driving the other switches (S1, S2, Si) of the plurality of switches (S1, S2, Si, Sn) is formed differently and individually adjusted for each of the other switches (S1, S2, Si), and only one second drive signal (6) is formed at a time.

2. 2. The method of claim 1, wherein the second drive signal (6) for driving at least the first switch (S1) is formed by adjusting the first drive signal (3) in a self-regulating manner.

3. 3. The method of claim 1, wherein the first amount and the second amount are determined for adjacent switches (S1, Si, S2, Sn) of the plurality of switches (S1, S2, Si, Sn).

4. 4. The method according to any one of claims 1 to 3, wherein adjusting the first drive signal (3) comprises delaying or advancing the first drive signal (3).

5. 5. The method according to any one of claims 1 to 4, wherein adjusting the first drive signal (3) comprises pulse width modulation of the first drive signal (3).

6. 6. The method according to claim 1, further comprising adjusting the second drive signal (6) for driving the other switches (S1, S2, Si) of the plurality of switches (S1, S2, Si, Sn) based on an amount determined by a voltage limiter (V1, V2) provided in the snubber device (10, 12) associated with the other switches (S1, S2, Si).

7. An HV switch unit (HVU), comprising: a. An HV switch (HVS) including a plurality of semiconductor switches (S1, S2, Si, Sn) connected in series; b. snubber devices (10, 10', 12, 12', 14, 14') each including at least one snubber energy storage component (C1, C1', C2, Ci, Ci', Cn, Cn') connected in parallel to each of the semiconductor switches (S1, S2, Si, Sn); c. at least one drive signal conditioner (8) for adjusting the first drive signal (3) to form a second drive signal (6) for driving at least one semiconductor switch (S1, S2, Si, Sn) of the plurality of semiconductor switches (S1, S2, Si, Sn); d) a feedback device for supplying the amount of output from the snubber device (10, 10', 12, 12', 14, 14') associated with the at least one semiconductor switch (S1, S2, Si, Sn) to the drive signal conditioner (8); Equipped with The drive signal conditioner (8) e. determining a first quantity output from the snubber device (10, 10') associated with a first semiconductor switch (S1) of the plurality of semiconductor switches (S1, S2, Si, Sn), the first quantity being a first voltage across a first snubber energy storage component (C1) of the snubber device (10, 10') associated with the first semiconductor switch (S1); f) determining a second quantity output from the snubber device (12, 12', 14, 14') associated with a second semiconductor switch (S2, Si, ... Sn) of the plurality of semiconductor switches (S1, S2, Si, ... Sn), the second quantity being a second voltage across a second snubber energy storage component (C2, Ci, ... Cn) of the snubber device (12, 12', 14, 14') associated with the second semiconductor switch (S2, Si, ... Sn); g. comparing the first voltage with the second voltage; h) forming the second drive signal (6) by adjusting the first drive signal (3) based on the comparison, and outputting the second drive signal (6) for driving at least the first semiconductor switch (S1); It is structured as follows: The semiconductor switches (S1, S2, Si, Sn) other than an n-th semiconductor switch (Sn) (n is a natural number of 2 or more) among the plurality of semiconductor switches (S1, S2, Si, Sn) are selectively connected to the drive signal adjuster (8), and the same first drive signal (3) is supplied to the n-th semiconductor switch (Sn) and the drive signal adjuster (8); The drive signal conditioner (8) The second drive signal (6) for driving the other semiconductor switches (S1, S2, Si) among the plurality of semiconductor switches (S1, S2, Si, Sn) is formed by adjusting it differently and individually for each of the other semiconductor switches (S1, S2, Si), and only one second drive signal (6) is formed at a time. The HV switch unit (HVU) is configured as follows.

8. 8. The HV switch unit (HVU) according to claim 7, wherein the snubber energy storage components (C1, C1', C2, Ci, Ci', Cn, Cn') of the snubber devices (10, 10', 12, 12', 14, 14') of two adjacent semiconductor switches (S1, S2, Si, Sn) of the plurality of semiconductor switches (S1, S2, Si, Sn) are connected in series at a first connection point (CP1), and the first connection point (CP1) is connected to a first input terminal (-) of a comparison component (7).

9. 9. The HV switch unit (HVU) according to claim 8, wherein resistors (R1, R2, R1', Ri, Ri', Rn') of the snubber devices (10, 10', 12, 12', 14, 14') of the two adjacent semiconductor switches (S1, S2, Si, Sn) of the plurality of semiconductor switches (S1, S2, Si, Sn) are connected in series at a second connection point (CP2), and the second connection point (CP2) is connected to a second input terminal (+) of the comparison component (7).

10. 10. The HV switch unit (HVU) according to claim 8 or 9, wherein the comparison component (7) is integrated into the drive signal conditioner (8).

11. 11. The HV switch unit (HVU) according to claim 7, wherein the snubber device (10) associated with the first semiconductor switch (S1) of the plurality of semiconductor switches (S1, S2, Si, Sn) is provided with a voltage limiter (V1), an amount determined by the voltage limiter (V1) is supplied to the drive signal conditioner (8) selectively connected to the first semiconductor switch (S1), and the drive signal conditioner (8) further adjusts the second drive signal (6) for driving the first semiconductor switch (S1) based on the amount determined by the voltage limiter (V1).

12. 10. The HV switch unit (HVU) according to claim 9, wherein a resistor (Rdif) is connected between the first connection point (CP1) and the second connection point (CP2).

Images