WO2020228944A1

WO2020228944A1 - Integrated circuit comprising a power semiconductor switch

Info

Publication number: WO2020228944A1
Application number: PCT/EP2019/062341
Authority: WO
Inventors: Christopher Fromme; Marvin TANNHÄUSER; Lennart Baruschka; Fabian Döbler; Dominic Malane
Original assignee: Siemens Aktiengesellschaft
Priority date: 2019-05-14
Filing date: 2019-05-14
Publication date: 2020-11-19

Abstract

The invention relates to an integrated circuit (100, 200) comprising a power semiconductor switch (110, 120) and a device (120, 220) for determining the voltage drop over the power semiconductor switch, as well as a control circuit which switches on the power semiconductor if the voltage drop over the power semiconductor switch falls below a voltage threshold (141, 241). The invention also relates to a system comprising an integrated circuit of this type.

Description

description

Integrated circuit with power semiconductor switch

The present invention relates to an integrated circuit with a power semiconductor switch and an electronic cal circuit with such an integrated circuit.

It is known to use in electronic circuits such as e.g. In order to use power semiconductors as active switching elements, such as MOSFETs, IG-BTs or GaN-HEMTs, as active switching elements. In order to obtain the desired current and / or voltage curves, these are switched on and off at high to very high frequencies (from a few kilohertz to several megahertz). The ratio of the switch-on duration to the period duration determines the effective value of the current or voltage.

With every switching process, undesired energy losses arise, which are often dominant and which must be minimized. So-called resonant or quasi-resonant approaches are pursued for this purpose: the switch should switch on as precisely as possible when the voltage drop across the switch reaches zero. Switching on too early results in switching losses; switching on too late results in losses due to the voltage drop in the reverse direction. Switching timing accuracies of a few nanoseconds are required, particularly with fast-switching technologies such as GaN or SiC.

From the publication DE 10 2017 212 462 A1 and based on the application PCT / EP2018 / 054788 by the same applicant, circuits and in particular a so-called dual peak current control for reducing switching losses are known.

The power semiconductors are often controlled by external driver circuits which, in particular for determining the optimal switching times, provide information about need the current operating status of the circuit. The current value of the voltage drop across the power semiconductor switch and / or the current flowing through the power semiconductor switch is of particular interest.

As is known from the prior art or at least suggested by it, these parameters have so far been recorded by means of additional discrete circuits. The current flowing through a power semiconductor can be measured, for example, by means of measuring shunts with amplifier circuits or current transformers. There are disadvantages, difficulties such as Interference coupling on the measurement or control lines. Furthermore, measurements have to be carried out in some cases galvanically separated, which means additional effort and considerable additional latencies.

Alternatively, the course of current and / or voltage for a typical application can be measured with expensive laboratory equipment and stored in the memory of the driver circuit in the form of characteristic curves. The measurement in real operation is then completely dispensed with. The disadvantage of this is that for operating states and component tolerances that deviate from the laboratory conditions, the control of the power semiconductor is not carried out with the optimal parameters, which leads to a poorer efficiency of the overall system.

Control accuracies in the nanosecond range are required for low-loss switching, particularly at high switching frequencies.

It is therefore an object of the present invention to indicate an improved circuit with a power semiconductor that achieves this control accuracy.

This object is achieved by an integrated circuit with a power semiconductor switch and a device for determining the voltage drop across the power semiconductor switch and a control circuit which the Power semiconductor switches on when the voltage drop across the power semiconductor switch falls below a voltage threshold.

The voltage threshold value can be set to a fixed value. In a preferred embodiment, the voltage threshold is 0 volts. In this exemplary embodiment, the polarity of the voltage drop across the power semiconductor switch is evaluated and the power semiconductor is switched on when the voltage drop across the power semiconductor switch has become negative.

In alternative exemplary embodiments, the voltage threshold value can be specified via an input of the integrated circuit.

In addition, the integrated circuit can have a timer which outputs a signal after a certain time (which can be fixedly predetermined or can be predetermined via an input of the integrated circuit), with a switch-on of the power semiconductor in response to the signal output by the timer regardless of the There is a voltage drop across the power semiconductor.

Furthermore, the integrated circuit can be equipped with an input via which an activation signal can be entered which is evaluated by the control circuit, the control circuit only turning on the power semiconductor switch if, in addition to the aforementioned conditions for turning on the power semiconductor switch (e.g. The voltage drop across the power semiconductor switch falls below the voltage threshold or the timer signal output) the activation signal signals the "active" state. It should be noted that, depending on the circuit technology used, the "active" state can be entered by a specific voltage value (which can also be zero) or a specific logic signal "0" or "1" or a specific signal sequence. The evaluation and recognition The "active" state is then activated by the control circuit integrated together with the power semiconductor.

In an exemplary embodiment of the present invention, a circuit can additionally be used which provides a value which represents a property of the current flowing through the power semiconductor switch. The control circuit switches off the power semiconductor switch when the current flowing through the power semiconductor switch exceeds a current threshold value.

The current threshold value can be fixed or entered via an input of the integrated circuit.

All elements of the integrated circuit according to the invention are preferably implemented on a uniform die. Alternatively, the power semiconductor switch is implemented on a first die and the other elements on a further die and connected in a uniform housing to form the integrated circuit.

The integration of the power semiconductor switch and at least the control evaluating the voltage drop across the power semiconductor controller according to the present invention offers several advantages over the external wiring of a power semiconductor circuit module that can be realized with conventional technology. On the one hand, parasitic elements, especially parasitic capacitances and inductances, are reduced to a minimum. The effects of the control system integrated in accordance with the invention are, due to the short signal lines, particularly at high operating frequencies, considerably less than with external wiring. The robustness of the circuit against disturbances that are inevitably caused by switching, increases significantly; the signal transit times within the circuit are minimal. In particular for novel power semiconductor switches based on GaN or SiC, which enable very high switching speeds and frequencies, a sufficiently fast control of the power semiconductor switch is made possible by the present invention.

Furthermore, considerable cost savings result from the integration of the control circuit and the power semiconductor switch in a uniform integrated circuit compared to the external wiring of a power semiconductor circuit module that can be implemented using conventional technology. This applies to all exemplary embodiments of the present invention and in particular to the exemplary embodiment in which all elements are implemented on a uniform die.

Finally, there is a significantly reduced space requirement due to the integration in a uniform integrated circuit, which results in further cost and other advantages (e.g. lower space requirement of the electronic components, more compact design of the overall system).

A second aspect of the present invention relates to an integrated circuit with a power semiconductor switch and a circuit for providing a value representing a property of the current flowing through the power semiconductor switch, as well as a control circuit that switches off the power semiconductor switch when the current flowing through the power semiconductor switch exceeds a current threshold value.

In both aspects of the present invention, the integrated circuit in embodiments with an output for outputting the current switching state of the power half be equipped with a conductor switch, for example to enable synchronization with a higher-level controller.

The invention also relates to a system with an integrated circuit according to the present invention. In such a system, the present invention offers an enormous simplification with a simultaneous increase in performance. Half bridges, for example, can be optimally controlled with just one control signal, and the time-consuming calculation of timings can be dispensed with, as can time-consuming measuring circuits to be integrated into the system. In particular with more complex topologies, e.g. Multilevel topologies, which consist of several half bridges, can be used with much simpler DSPs or microcontrollers because both the number of PWM modules and the required computing power are drastically reduced.

In the following, embodiments of the present invention are explained in more detail with reference to two drawings in schematic presen- tation.

Fig. 1 shows a first embodiment of the present invention. An integrated circuit 100 comprises a power semiconductor switch 110 and a device 120 for determining the voltage drop across the power semiconductor switch. A circuit 140 provides a value representing a property of the voltage drop across the power semiconductor switch. In the example of FIG. 1, the value representing the property of the voltage drop across the power semiconductor switch is determined by comparison with a voltage threshold value Vthr. Vthr can be stored in digital form in a memory 141 or input into circuit 140 as an analog value. Vthr can be a fixed voltage threshold. The circuit 140 can be a comparator circuit which compares the voltage value output by the device 120 with the threshold value Vthr compares and provides the comparison result as a binary value. In a preferred embodiment, Vthr =

0 volts is selected and the value re output by circuit 140 in this case represents the polarity of the voltage drop across the power semiconductor switch, for example in digital form, whereby circuit 140 can be designed so that an output value "1" means that the voltage drop is negative across the power semiconductor switch.

The output of the circuit 140 is supplied to a control circuit which controls the power semiconductor switch. In the simplest case (not shown) the output signal of the circuit 140 is supplied directly to a driver circuit 130 which turns on the power semiconductor switch when the output of the circuit 140 assumes a certain value or is within a certain value range.

In a digital embodiment, for example, an output valued “1” of the circuit 140 would cause a corresponding power semiconductor switch-on voltage to be provided by the driver circuit 130 and the power semiconductor switch 110 would be switched on. A digital input valued "0" at the input of the driver circuit, however, would cause the shutdown of the power semiconductor switch-on voltage at the output of the driver circuit 130 and the power semiconductor switch would be switched off.

In a first extension of the simplest case, the control circuit is extended by a timer 150 which, after a certain time has elapsed, outputs a signal which causes the power semiconductor switch to be switched on regardless of the evaluation of the voltage drop across the power semiconductor switch. With this circuit it can be ensured that the power semiconductor switch is also switched on if the voltage does not reach the voltage threshold value, for example due to an unfavorable operating point. The timer can be designed so that the signal for switching on the power semiconductor switch is only output for a certain time and then deactivated again. is activated and this is repeated periodically. The dead time of the timer, ie the time that elapses after the timer is activated before the timer outputs the signal that causes the power semiconductor switch to be switched on regardless of the evaluation of the voltage drop across the power semiconductor switch, can be preset or via a Input of the integrated circuit (not shown) can be entered.

In a preferred embodiment, an activation or control signal is made available at an input 101 of the integrated circuit, which activates the control circuit of the integrated circuit. The control circuit ensures that the power semiconductor switch is only switched on when the activation signal signals "active". In a practical application of this preferred exemplary embodiment, a positive control signal is passed to the integrated circuit by a controller (not shown) which is superordinate to the integrated circuit. A power semiconductor switch according to prior art would turn on in response to this positive control signal immediately, regardless of the state aktuel len - the observance of the optimal switching _Z eitpunkts would not be ensured. In the preferred embodiment, the power semiconductor switch is only switched on if, in addition to the activation signal at input 101, the condition "voltage below the threshold" is met or the timer 150 started by the activation signal signals the expiry of a certain period of time. In this way, the optimum switching _Z can eitpunkt always ge nau be taken. Due to the integration in the integrated circuit itself, very low latencies and high interference immunity can be achieved. In addition, the integrated driver 130 can be optimally matched to the respective power semiconductor switch.

In terms of circuitry, this preferred Ausführungsbei can be implemented game by the activation signal and the The signal supplied by the comparator circuit 140 can be linked by means of a logic AND circuit 160. The result of this AND operation is linked to the output of the timer circuit 150 by means of a logic OR circuit 161, so that either the presence of an activation signal = 1 AND a comparison result = 1 of the comparison of the voltage drop across the power semiconductor switch with Vthr OR the The presence of the signal = 1 from the timer 150 turns on the power semiconductor switch after the defined time span has elapsed. The timer is started by the activation signal = 1 and causes the power semiconductor switch to switch on after a defined period of time. This is done due to the OR link regardless of whether the voltage drop across the power semiconductor switch falls below Vthr or not.

To prevent the power semiconductor switch from being switched off if the switch-on process inevitably changes the voltage drop across the power semiconductor switch and the output signal of the comparator circuit 140 changes accordingly to "0", a "hold" circuit can be provided. which has the effect that a "1" is still supplied after Vthr is undershot, even if the undershooting of Vthr ends immediately after switching on. This “hold” circuit can be integrated into the comparator circuit 140, for example. In the example of FIG. 1, the "Hold" circuit is realized in the form of a flip-flop 162, which receives the output of the comparator circuit 140 at the set input and a "1" received once at the set input as "1" on Outputs the Q output until a "1" has been applied to the reset input. The activation or control signal negated via a NOT circuit 163, which is input via input 101, is input to the reset input of flip-flop 162. In this way it is achieved that the flip-flop 162 is reset on the one hand (and remains) and accordingly the Q output of the flip-flop 162 outputs a "0" as long as the activation signal is not applied or inactive ("0") on the other hand, the flip-flop 162 on the input on the set Input waits as long as the activation signal is active ("1").

Fig. 2 shows a second embodiment of the present invention. Compared to the embodiment shown in FIG. 1, the one shown in FIG. 2 has some additional components that are used to detect and evaluate the current flow through the power semiconductor switch and, in particular, for peak current regulation. These components are explained in more detail below. All other components correspond to those shown in FIG. 1, and their description will not be repeated here. The concordance lxx A 2xx applies, for example power semiconductor switch 110 bears the reference numeral 210 in FIG. 2 and the description for FIG. 1 also applies to FIG. 2, unless otherwise stated below.

The embodiment shown in Fig. 2 expands the integrated circuit of Fig. 1 by a circuit 245 for providing a property of the current flowing through the power semiconductor switch 210 representing the value, the control circuit then switching off the power semiconductor switch 210 when the through the Power semiconductor switch exceeds a current threshold value.

According to the second aspect of the present invention, an integrated circuit according to the invention has the circuit 245 and a control circuit for switching off the power semiconductor switch in response to a current threshold value being exceeded, but not the means for switching on the power semiconductor explained in connection with FIG. 1 when a voltage threshold is reached. In the interest of a compact illustration, the isolated illustration of the second aspect of the present invention is dispensed with here, since the explanations relating to the second aspect of the invention essentially correspond to the explanations relating to the FIGS Fig. 2 compared to Fig. 1, elements 204, 225, 245, 270 to be added coincide.

In order to switch off the power semiconductor switch 210 when the current flowing through the power semiconductor switch exceeds a current threshold value, the current flowing through the power semiconductor switch is measured by a current measuring device 225, for example by means of a measuring circuit (not shown in detail), which has a low but evaluable Voltage drop across a low raw measuring resistor in the current path switched by the power semiconductor switch 210 between the pins 201 and 202 of the integrated circuit 200.

This measured current is fed to a comparator circuit 245 as an analog or digital value. The comparator circuit 245 is also supplied with a current threshold value, also if in analog or digital form. In the preferred exemplary embodiment, the current threshold value is provided by a higher-level controller via an input 204 of the integrated circuit, but it can also be stored directly as a fixed value in the integrated circuit (not shown). The result of the comparison of the measured value for the current through the power semiconductor switch 210 with the current threshold value is used to switch off the power semiconductor switch when the current threshold value is exceeded. In this way, a peak current control (more specifically, a peak power off) implemented the / dt especially with large current changes di, the example orkommen, in exploiting the potential of new technologies such as GaN or SiC _V, enables a robust and precise control of the flow.

In the embodiment of FIG. 2, the result of comparing the measured value for the current through the power semiconductor switch 210 with the current threshold value is preferably supplied as a digital value "0" or "1" to the reset input of a second flip-flop 270 in such a way that a "1" is output and thus resets the flip-flop 270 and there generates an output of "0" at the Q output when the current through the power semiconductor switch exceeds the current threshold value (= peak current). At the set input of flip-flop 270, the activation signal fed in via input 201 is switched on so that a "1" is present at the Q output of the flip-flop and only when the activation signal is active ("1") and at the same time the current through the power semiconductor switch is below the current threshold.

The output of the flip-flop is linked to the output of the logic OR circuit 261 by means of a logic AND circuit 271, so that the following functional dependencies are implemented as a result:

- Basic status: activation signal = 0, power half

circuit switch off

- Switch on the power semiconductor switch: Activation signal = 1, voltage drop across the power semiconductor switch <voltage threshold OR time in timer 250 has expired (AND current through the power semiconductor switch <current threshold)

- Power semiconductor switched on: Activation signal = 1, voltage drop across the power semiconductor switch insignificant, current through the power semiconductor switch <current threshold value

- Switch off the power semiconductor switch: Activation signal = 0 OR current through the power semiconductor switch> current threshold

In further exemplary embodiments, the (digital) circuit breaker control command fed to the driver circuit 130, 230 can be output at an output 205 (not shown in the exemplary embodiment in FIG. 1, but also easily implemented there) of the integrated circuit for a higher-level controller or for Function monitoring purposes are provided. Of course, it is possible to implement the functions described in this description, partly abstractly and partly using specific circuit technology, also using other circuit technology.

It is particularly advantageous to implement all of the circuit elements including the power semiconductor switches on a common die. Where this is not (yet) completely possible due to the semiconductor technology used, several dies can be used, which are combined in a common housing to form an integrated circuit. For example, the power semiconductor switches (with or without measuring circuits 220, 225) can be implemented on one die and the remaining circuit elements on a further die and combined in a common housing to form an integrated circuit. Even the implementation on several dies still offers considerable advantages compared to the external wiring of the power semiconductor switch.

The above description is only of the preferred exemplary embodiments of the invention and is not intended to serve as a definition of the limits and scope of the invention. All equivalent changes and modifications are within the scope of the appended claims.

Claims

1. Integrated circuit (100, 200) with a power semiconductor switch (110, 210) and a device (120, 220) for determining the voltage drop across the power semiconductor switch and a control circuit which switches on the power semiconductor when the voltage drop across the power semiconductor switch is a Voltage threshold value (141, 241) falls below.

2. Integrated circuit according to claim 1, wherein the voltage threshold value (141, 241) is set to a fixed value.

3. Integrated circuit according to claim 2, wherein the voltage threshold value (141, 241) is 0 volts.

4. Integrated circuit according to claim 1, in which the voltage threshold value can be predetermined via an input of the integrated circuit.

5. Integrated circuit according to one of the preceding claims, the control circuit of which has a timer (150, 250) which outputs a signal after a certain time has elapsed and means for switching on the power semiconductor in response to the signal output by the timer regardless of the voltage drop across the Power semiconductors.

6. Integrated circuit according to one of the preceding claims, the control circuit of which evaluates an activation signal that can be input via an input (101, 201) of the integrated circuit and only switches the power semiconductor switch on when the activation signal also signals the "active" state.

7. Integrated circuit according to one of the preceding claims, which additionally has a circuit (245) for the provision of a property of the power half Conductor switch having flowing current representative value and the control circuit switches off the power semiconductor switch when the current flowing through the power semiconductor switch exceeds a current threshold value.

8. Integrated circuit according to claim 7, in which the current threshold value can be input via an input (204) of the integrated circuit.

9. Integrated circuit according to one of the preceding claims with an output (205) for outputting the current switching state of the power semiconductor switch.

10. Integrated circuit (200) with a power semiconductor switch (210) and a circuit (245) for providing a value representing a property of the current flowing through the power semiconductor switch, as well as a control circuit that turns off the power semiconductor switch when the through the Power semiconductor switch current flowing exceeds a current threshold value.

11. Integrated circuit according to claim 10, wherein the current threshold value can be input via an input (204) of the integrated circuit.

12. Integrated circuit according to one of claims 10 or 11 with an output (205) for outputting the current Schaltzu status of the power semiconductor switch.

13. Integrated circuit according to one of the preceding claims, in which all elements are implemented on a uniform die.

14. Integrated circuit according to one of claims 1 to 12, in which the power semiconductor switch is implemented on a first die and the other elements on a further die and connected in a unitary housing to form the integrated circuit.

15. System with an integrated circuit according to one of the preceding claims.