CIRCUIT ARRANGEMENT FOR SWITCHING SWITCH ELEMENTS

Abstract

The invention relates to a circuit arrangement (100), comprising a control circuit (104) and a switch element (101) for switching between a first and a second switching state of the switch element (101). The control circuit (104) is designed to provide a variable pre-control voltage dependent on the switching state of the switch element. The pre-control voltage is a voltage that is switched as the control voltage at the switch element (101) during one of the two switching states. The control circuit (104) is also designed to vary the pre-control voltage during each of the switching states.

Claims

1. A circuit arrangement (100) comprising: an actuation circuit (104) and a switching element (101), wherein the circuit arrangement (100) is configured to switch over between a first and a second switching state of the switching element (101); wherein the actuation circuit (104) is configured to provide a variable pre-actuation voltage that is dependent on the switching state of the switching element (101), wherein the pre-actuation voltage is a voltage that is applied to the control connection of the switching element (101) as the actuation voltage during one of the two switching states, and wherein the actuation circuit (104) is also configured to vary the pre-actuation voltage during a switching state without the switching state changing.

2. The circuit arrangement (100) as claimed in claim 1, wherein the first switching state is a state in which the switching element (101) is turned on and the second switching state is a state in which the switching element (101) is turned off; wherein the pre-actuation voltage is a turn-off actuation voltage V_off, and wherein the actuation circuit (104) is further configured to change the turn-off actuation voltage V_off during the first switching state of the switching element (101), and to change the turn-off actuation voltage V_off during the second switching state of the switching element (101).

3. The circuit arrangement (100) as claimed in claim 1, wherein the actuation circuit (104) is further configured to reduce the pre-actuation voltage from a first value to a second value during the first switching state of the switching element (101), and to increase the pre-actuation voltage from the second value to the first value during the second switching state of the switching element (101), wherein, when the pre-actuation voltage is a turn-off actuation voltage for turning off the switching element (101), the first value of the turn-off actuation voltage V_offa and the second value of the turn-off actuation voltage V_offb are in a range between V_th and V_min, V_th is higher than or equal to V_offa, and V_offa is higher than V_offb, wherein V_th is the switching threshold value of the switching element (101) and V_min is the minimum permissible actuation voltage of the switching element; and wherein, when the pre-actuation voltage is a turn-on actuation voltage for turning on the switching element (101), the first value of the turn-on actuation voltage V_ona and the second value of the turn-on actuation voltage V_onb are in a range between V_max and V_th, V_max is higher than or equal to V_ona, V_ona is higher than V_onb, and wherein V_max is a maximum permissible actuation voltage of the switching element.

4. The circuit arrangement as claimed in claim 3, wherein the actuation circuit (104) has a switch (102) configured to switch the turn-off actuation voltage over from the first value to the second value, and/or has a switch (106) that is configured to switch the turn-on actuation voltage over from the second value to the first value.

5. The circuit arrangement (100) as claimed in claim 1, wherein the switching element (101) is a power transistor.

6. The use of the circuit arrangement (100) as claimed in claim 1 for reducing switching losses of a switching element (101).

7. A method for actuating a switching element (101) during operation, wherein the switching element has two switching states, wherein the different switching states are set by actuating the switching element with an actuation voltage, the method comprising the steps of: providing (401) a first pre-actuation voltage and a second pre-actuation voltage; applying (402) the second pre-actuation voltage to a control connection of the switching element as the actuation voltage so as to switch the switching element (101) to a first switching state; reducing (403) the first pre-actuation voltage of the switching element (101) while the switching element (101) is in the first switching state; applying (404) the first pre-actuation voltage to the control connection of the switching element as the actuation voltage so as to switch the switching element (101) to a second switching state; increasing (405) the first pre-actuation voltage while the switching element (101) is in the second switching state; and applying (406) the second pre-actuation voltage to the control connection of the switching element as the actuation voltage.

8. The method as claimed in claim 7, wherein the step of reducing (403) the first pre-actuation voltage of the switching element (101) while the switching element (101) is in the first switching state additionally includes reducing the second pre-actuation voltage of the switching element (101); and wherein the step of increasing (405) the first pre-actuation voltage while the switching element (101) is in the second switching state also includes increasing the second pre-actuation voltage.

9. An inverter (501) comprising a circuit arrangement (100) for switching a switching element (101), wherein the circuit arrangement includes an actuation circuit (104) and a switching element (101), wherein the circuit arrangement (100) is configured to switch over between a first and a second switching state of the switching element (101); wherein the actuation circuit (104) is configured to provide a variable pre-actuation voltage that is dependent on the switching state of the switching element (101), wherein the pre-actuation voltage is a voltage that is applied to the control connection of the switching element (101) as the actuation voltage during one of the two switching states, and wherein the actuation circuit (104) is also configured to vary the pre-actuation voltage during a switching state without the switching state changing.

10. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 shows a basic circuit arrangement for actuating a switching element according to one exemplary embodiment,

[0026] FIG. 2 shows a diagram of the actuation voltage in the switching and actuation phases according to one exemplary embodiment,

[0027] FIGS. 2a, 2b, 2c, 2d show switch positions for the actuation voltage in the switching and actuation phases according to one exemplary embodiment,

[0028] FIG. 3 shows a diagram of the actuation voltage in the switching and actuation phases according to a further exemplary embodiment,

[0029] FIGS. 3a, 3b, 3c, 3d show switch positions for the actuation voltage in the switching and actuation phases according to a further exemplary embodiment,

[0030] FIG. 4 shows a flow chart of a method according to one exemplary embodiment,

[0031] FIG. 5 shows a vehicle comprising an inverter according to one exemplary embodiment.

DETAILED DETAILED

[0032] FIG. 1 shows a basic circuit arrangement 100 for actuating a switching element 101, comprising an actuation circuit 104. The controllable switching element 101 shown in FIG. 1 can, for example, be a field-effect transistor (FET) or a variant thereof, an IGBT or another transistor or high-power transistor type. FIG. 1 serves merely to illustrate the method of operation of the circuit arrangement 100 and in particular of the arrangement 104. In a real circuit, the battery voltage V_Batt would not be connected to ground, but rather to a load via a protective circuit, for example.

[0033] FIG. 1 shows a simple principle from which it can be seen that three voltage levels can be switched with the two switches 103 and 102. Switch 103 is used to switch the states of the switching element (V_on, V_off), whereas switch 102 conditions or selects the turn-off actuation voltage (V_offa, V_offb) and therefore allows a variable turn-off actuation voltage. The same arrangement could be used to condition the turn-on actuation voltage (V_ona, V_onb), for example, with switch 102 and to set the switching state of the switching element 101 between V_on and a constant voltage V_off with switch 102.

[0034] By way of example, FIG. 2 shows a profile of an actuation voltage V_T or gate-emitter voltage applied to the control connection at the switch 103 and the profile of the turn-off voltage V_off at the switch 102. FIGS. 2a to 2d show the switch positions, which correspond to the phases of the voltage profile in FIG. 2, of the switch arrangements. To allow easier association of the switch arrangements of FIGS. 2a to 2d with the phases of the voltage profile in FIG. 2, the voltage transitions are depicted in an idealized manner as voltage jumps in the middle of a state phase. In this example, V_on is 15 V, V_offa is 0 V and V_offb is −8 V. As already mentioned, the voltages can also assume other values.

[0035] Starting with the on phase in FIG. 2 and the switch arrangement according to FIG. 2a, in the case of an upward switch position of the switch 103, switch 102 is also initially switched upward, with the result that V_offa=0 volts is initially tapped off at the switch 102. This switch position of the switch 102 is the switch position from the previous phase. The present on phase is now divided into two half phases. In the second half phase, switch 102 is switched downward, with the result that V_offb=−8 V could be tapped off or is present at the switch output. As soon as the switch 103 is switched over to reach the off phase, this voltage V_offb is present at the control connection of the switching element 101 as the actuation voltage V_T. Therefore, in the on phase, the turn-off control voltage, that is to say the voltage used to turn off the transistor 101, is set or conditioned such that the switching element 101 is reliably turned off when switching over switch 103. According to FIG. 2c, the two switches 102, 103 are then set downward.

[0036] The off phase is now also divided into two half phases, however. In the second half phase, switch 102 is set upward in FIG. 2d, with the result that the turn-off actuation voltage V_offa=0 volts is present at the control connection of the switching element 101. This has the effect that, when switching over to the on phase, i.e. corresponding to the on phase in FIG. 2a that is initiated when the positive voltage is switched by the switch 103, the switching losses are reduced compared to a voltage jump from −8 V to +15 V at the gate input.

[0037] The switches 102 and 103 can preferably be implemented electronically and be actuated by a microcontroller, for example. The pre-control can be implemented by current sources or switchable potentials, for example.

[0038] The diagram in FIG. 3 and the switching arrangements 3a to 3d with the corresponding switch positions show an example in which the actuation voltage is set in a variable manner both for V_on and for V_off. The circuit arrangement now has a switch 104 in the positive branch that can switch over between V_ona=+15 V and V_onb=+8 V. The switching of the voltages V_offa and V_offb with the resulting voltage V_off in FIG. 3 occurs in the same way as in FIGS. 2a to 2d. In the on phase, the off phase is now prepared by switching from V_ona to V_onb, with the result that the actuation voltage V_T at the control connection is now switched from 8 V to −8 V instead of from +15 V to −8 V. In the off phase, the actuation voltage V_T is again switched to 15 V, with the result that there can be a reliable and rapid transition to the on state. It should be noted once again that the specified voltage values are only exemplary.

[0039] FIG. 4 shows a flow chart of a method according to one embodiment for actuating a switching element 101 during operation in which the switching element has an on and an off phase. In a first step 401, a turn-off control voltage of 0 V is provided. In the next step 402, the switching element 101 is switched to an on phase with an active positive actuation voltage. The voltage at the control connection, e.g. the gate voltage, therefore only jumps from 0 V to the positive voltage for switching over the switching element 101 that can, for example, be 15 volts. In step 403, the provided turn-off control voltage of the switching element is reduced during the on phase of the switching element. In this phase, the turn-off control voltage is not present at the control connection. The reduction serves for the setting or conditioning, i.e. the preparation of the next switching phase of the switching element 101. In step 404, the provided, reduced turn-off control voltage is applied to the control connection as the active actuation voltage in order to switch the switching element 101 to an off state. Since the voltage is clearly in the negative range, e.g. −8 V or −15 V, the switching element is turned off in an optimum way. In the next step 405, preparation for the next on phase of the switching element 101 is carried out by virtue of the provided turn-off control voltage that is still present at the control connection at this time as the active actuation voltage being raised to 0 V. In step 406, a positive voltage is then applied to the control connection as the active actuation voltage, with the result that the switching element 101 switches over to the on phase with fewer losses.

[0040] Step 403 can additionally include reducing the second pre-actuation voltage of the switching element 101, and step 405 can also include increasing the second pre-actuation voltage. The two pre-actuation voltages can be changed within one step at different times within the state phase, that is to say during a switching state.

[0041] FIG. 5 shows a vehicle 500 comprising an inverter 501 according to one embodiment, which inverter can have a circuit arrangement as described above for actuating a switching element 101.

[0042] The losses when switching to the on state are thus reduced by way of conditioning the turn-off actuation voltage during the off phase of the switching element 101 but, on the other hand, it is ensured that the switching element 101 is switched to a safe off state by way of conditioning the turn-off actuation voltage during the on phase.