Devices for operating semiconductor power switches in the high voltage range

Abstract

The invention provides a device for controlling a plurality of semiconductor power switches (S12, S21) by means of a drive voltage for the clocked operation of a plurality of loads (Last1, Last2) in a high voltage range, wherein the drive voltages (Uh1, Uh2) of the semiconductor power switches can be provided by a transformer. According to the invention, it is provided that the drive voltages (Uh1, Uh2) for the semiconductor power switches are derived from the voltage of the only secondary winding of the transformer, and an electronic voltage level converter circuit is provided in order to obtain the drive voltages (Uh1, Uh2) of the required magnitude from the secondary winding of the transformer.

Description

Technical Field

[0001] The invention relates to a device for simultaneously actuating a plurality of semiconductor power switches in the high voltage range under pulsed loads. Background Art

[0002] With the help of Figure 1 and 2 The control of a semiconductor power switch using a conventional device of the type mentioned in the introduction is explained.

[0003] like Figure 1 As shown in , in order to actuate two semiconductor power switches (MOSFET, IGBT, bipolar transistor), the 15 V voltage required for actuation at the control input (gate, base) always has a defined potential difference with the reference level when the switch is switched on. If this is not the case, the switch cannot be switched on. In the worst case, this can even lead to damage to the semiconductor power switch. The reference level is Figure 1 In the high voltage application shown, for example, 0V ( Figure 1 Circuit variant on the left) or 500V ( Figure 1 In the circuit variant on the right in the figure, the reference level can even jump from 0 V to 500 V when the power switch is turned off or on (high-side problem).

[0004] For Figure 2 In the application in the high voltage range shown by way of example, the drive voltages UL1, Uh are generated by means of a transformer with multiple output voltages. 1 and Uh 2 , these output voltages provide driving voltages at different reference levels in a current-isolated manner. Specifically, the first load Last1 and the second load Last2 are connected in a clocked manner to a zero potential HV- and a positive potential HV+ of, for example, 500 volts via a pair of electronic power switches S1, S12 and S2, S21, respectively. The driving voltage UL1 for operating the switch S1 is supplied from the first secondary winding of the transformer (at Figure 2 The drive voltage Uh used to control the switch S12 is 1 From the second secondary winding of the transformer (at Figure 2 The driving voltage Uh used to control the switch S21 is 2 From the third secondary winding of the transformer ( Figure 2 When the switches S1, S12 and S2 / S21 are closed, the high voltage is applied to the corresponding loads Last1 and Last2, and is separated from the loads when the switches are opened.

[0005] Due to the compact winding structure, electromagnetic interference caused by the clocking of the power semiconductors is transferred to the primary side of the transformer. Therefore, in automotive applications, interference generated in the HV part of the device is transferred to the low-voltage side. In addition, the generated interference can lead to voltage peaks on the other secondary windings of the transformer. These interferences must be reduced relatively expensively with the help of EMC filter components. Another disadvantage of this method is the use of transformers with multiple secondary windings. Due to the required dielectric strength and the use of high-quality and therefore relatively expensive insulating materials, these secondary windings are expensive and expensive. Summary of the invention

[0006] The object of the present invention is to provide a device which can be optimized with regard to EMC and can be produced cost-effectively.

[0007] The invention therefore provides a device for actuating a plurality of semiconductor power switches by means of a drive voltage for clocked operation of a plurality of loads in the high voltage range. The drive voltage is provided by a transformer, wherein the drive voltage for the semiconductor power switches is derived from a single secondary winding of the transformer. A voltage level converter circuit is provided, which extracts a drive voltage having a required voltage level from the voltage generated in the secondary winding of the transformer.

[0008] Preferably, only one transformer with only one secondary winding is required. The operating voltages for any number of PWM-controlled loads are preferably each generated by a simple electronic voltage level converter circuit.

[0009] Compared to devices according to the prior art having a plurality of secondary windings, the device according to the invention is more compact and has less EMC interference.

[0010] The outlay on transformer and EMC filter components is reduced and leads to significant cost savings.

[0011] Electronic voltage level converter circuits are based on the scheme of a charge pump. The term "charge pump" includes a variety of different circuits that increase the value of a voltage or invert the polarity of a DC voltage.

[0012] Charge pumps are used as voltage converters when high output currents are not required or suitable magnetics, such as coils, cannot be used.

[0013] The charge pump sets the voltage of the capacitor to different values ​​by a time sequence between the charging and cascading of the capacitors. This is achieved by periodic switching of the switches.

[0014] These processes are similar to reciprocating piston pumps. The charging of the capacitor corresponds to the filling of the cylinder, and the cascade corresponds to the power increase of the cylinder. The diode preferably acts as an electronic switch, which is switched into the blocking range or the conducting range by the potential difference and charges the capacitor or increases its voltage. Charge pumps can generate very high DC voltages in a multiple cascade. Such a circuit is called a high voltage cascade.

[0015] Advantageously, the clock pulse of the corresponding load is used for the clock pulse of the corresponding charge pump, in particular the PWM pulse of the corresponding load is used for the clock pulse of the charge pump, thereby greatly simplifying the circuit design thereof.

[0016] Preferably, the clocking of the device is realized by a switch, which is connected to the secondary winding of the transformer, charges the charge pump in the closed state, and applies the drive voltage generated in the charge pump to the corresponding semiconductor power switch in the open state. The charge pump clocking is preferably realized by the power switch Sn of the PWM switch. Thus, for example, in the closed state of S1, the capacitor C1 is charged to the voltage UL1 through D1-R1. In the open state, C1 discharges to C12 through D12. The diode D1 is cut off, and the charged capacitor is set to the reference level of the power switch S12. Through Uh1=UL1=15V, the driver is supplied with the necessary voltage by S12. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention is explained in detail below with the aid of the accompanying drawings; in the accompanying drawings:

[0018] Figure 1 The actuation of a semiconductor power switch (MOSFET, IGBT, bipolar transistor) according to the prior art is generally shown.

[0019] Figure 2 Shows Figure 1 actuation by means of the use of a transformer in the high voltage range for galvanic separation of a corresponding drive voltage for the power switch, wherein the drive voltage for the power switch is galvanically separated by means of a secondary winding of the transformer, and

[0020] Figure 3 An embodiment of a device according to the invention for actuating a circuit breaker by means of a transformer having a single secondary winding, from which different operating voltages for the circuit breaker are derived, is shown. DETAILED DESCRIPTION

[0021] Figure 1 and Figure 2 The prior art is described in the introduction.

[0022] Figure 3 An embodiment of the device according to the invention is shown. Figure 2 The device shown in FIG. 1 is different in that the drive voltage UL1 is provided to the electronic load switches S1, S2 by using a transformer with a single secondary winding, and in more detail, the drive voltage UL1 is provided to the two electronic load switches S1 and S2 by using the lower secondary winding of the transformer with three zero potential HV-levels.

[0023] Drive voltage Uh for controlling electronic load switches S12 and S21 1 and Uh 2 The other secondary windings of the transformer are not used to provide Figure 3 Instead, the power is derived from the single secondary voltage of the transformer with the help of a charge pump.

[0024] Used to provide driving voltage Uh 1 The charge pump comprises a capacitor C1 which is connected to the load Last1 on one side connected to the switch S1 and, on the other hand, is connected to a diode D1 at the potential UL1 via a series resistor R1. The drive voltage Uh generated by the charge pump from the voltage UL1 1 Via a diode D12 , it is applied to an electronic switch S12 , which is bridged on the input side by a capacitor C12 .

[0025] Used to provide driving voltage Uh 2 The charge pump comprises a capacitor C2 which is connected to the load Last2 on one side connected to the switch S2 and, on the other hand, is connected to a diode D2 at the potential UL1 via a series resistor R2. The drive voltage Uh generated by the charge pump from the voltage UL1 2 Via a diode D12 , it is applied to an electronic switch S12 , which is bridged on the input side by a capacitor C21 .

[0026] When the switch S1 is closed, the capacitors C1 and C2 are charged to the drive voltage potential UL via the series resistors R1 and R2 and the blocking diodes D1 and D2.

[0027] If the switches S1 and S2 are open, the capacitors C12 and C21 are charged with the charge of the capacitors C1 and C2. This provides the potential Uh required for the activation of the switches S12 and S21. 1 (Uh 2 ) = UL. This process is repeated periodically with the clock pulses of switches S1 and S2.

[0028] The device according to the invention has been explained with the aid of an embodiment having two semiconductor power switches. However, the invention is not restricted thereto. Rather, more than two such switches are conceivable for the device for actuating semiconductor power switches.

Claims

1. A device for simultaneously actuating a plurality of high-side semiconductor power switches (S12, S21) and low-side semiconductor power switches (S1, S2) in the high voltage range under pulse load (Last1, Last2), wherein: The drive voltage (Uh1, Uh2) of the high-side semiconductor power switch (S12, S21) can be provided by a transformer, characterized in that the drive voltage (Uh1, Uh2) for the high-side semiconductor power switch is derived from the voltage (UL1, UL2) of the only secondary winding of the transformer, wherein an electronic voltage level converter circuit is provided to obtain the drive voltage (Uh1, Uh2) in a required size from the secondary winding of the transformer, wherein the electronic voltage level converter circuit comprises a charge pump (C1, R1, D1; C2, R2, D2), wherein the clock beat of the corresponding load (Last1, Last2) is used for the clock beat of the corresponding charge pump, wherein the clock beat of the device is divided into The control circuit is implemented by a corresponding low-side semiconductor power switch among the low-side semiconductor power switches (S1, S2), and the corresponding low-side semiconductor power switch is connected to the secondary winding of the transformer, wherein the corresponding low-side semiconductor power switch (S1, S2) is configured to charge the charge pump in a closed state, and to apply the drive voltage (Uh1, Uh2) generated in the charge pump to the corresponding high-side semiconductor power switch (S12, S21) in an open state, wherein the plurality of high-side semiconductor power switches are bridged by a second capacitor on the input side, and the drive voltage obtained by the charge pump with a required size is applied from the charge pump to the second capacitor bridging the plurality of high-side semiconductor power switches on the input side.

2. The device according to claim 1, wherein: A respective charge pump (C1, R1, D1; C2, R2, D2) for providing a drive voltage (Uh1, Uh2) comprises a first capacitor (C1, C2), one end of which is connected to one side of a load (Last1, Last2), and the other end of which is connected to a first diode (D1, D2) via a series resistor (R1, R2).

3. The device according to claim 2, wherein: The low-side semiconductor power switches (S1, S2) and the corresponding loads (Last1, Last2) and high-side semiconductor power switches (S12, S21) are sequentially connected in series between the low-voltage side potential and the high-voltage side potential of the high voltage.

4. The device according to claim 3, wherein: One end of the first capacitor (C1, C2) is connected to one side of the load (Last1, Last2) connected to the low-side semiconductor power switch (S1, S2).

5. The device according to claim 4, wherein: A drive voltage (Uh1, Uh2) generated from the voltage (UL1, UL2) by the charge pump is applied to the high-side semiconductor power switch (S12, S21) via a corresponding second diode (D12, D21), and the high-side semiconductor power switch is bridged by a corresponding second capacitor (C12, C21) on the input side.

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