Method and control device for controlling a commutation process of a load current between switching modules
First Claim
1. A method for controlling a commutation process of a load current from a first switching module to a second switching module, wherein the first switching module comprises a first MOSFET and a first inverse diode, and the second switching module comprises a second MOSFET and a second inverse diode, the first MOSFET and the second MOSFET being controlled by a gate-source voltage, the method comprising:
- connecting a first gate-driver unit directly to a gate and a source terminal of the first MOSFET and connecting a second gate-driver unit directly to a gate and source terminal of the second MOSFET;
applying a first control voltage to the first switching module to switch it off for a first time period, wherein the level of the first control voltage is below a predetermined threshold voltage, above which the first MOSFET becomes minimally conductive, and wherein the first time period is selected so that the first inverse diode carries the load current;
applying a second control voltage to the first switching module for a second time period to influence the switch-off behavior of the first inverse diode, wherein the second control voltage has an intermediate level between the level of the first control voltage and the level of the predetermined threshold voltage,applying a third control voltage to the second switching module for switching it on, wherein the level of the third control voltage is above the predetermined threshold voltage, above which the second MOSFET is minimally conductive, in order to cause a commutation of the load current from the first inverse diode to the second MOSFET, wherein a period in which the third control voltage is applied to until the second MOSFET becomes fully conductive is within the second time period;
applying, after an expiration of the second time period, a fourth control voltage with a level below the intermediate level of the second control voltage to the first MOSFET to block it or hold it in the blocking status; and
operating, via a control device, the first switching module and the second switching module in a complementary manner such that when one of the first switching module or the second switching module is conductive, the other of the first switching module or the second switching module is blocked at a same time.
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Abstract
A method and a device for controlling a commutation process of a load current between two switching modules are disclosed that each have a MOSFET that can be controlled by a gate-source voltage, and an intrinsic-body inverse diode. To reduce oscillations in the down-commutation of the inverse diodes caused by parasitic circuit parameters, after switching off one of the switching modules, the gate-source control voltage applied to this switching module is temporarily switched off until being increased again the vicinity of the threshold voltage for switching on the MOSFET, before and while the other switching module is switched on, in order to commutate the current from the inverse diode of the one switching module to the MOSFET of the other switching module.
18 Citations
20 Claims
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1. A method for controlling a commutation process of a load current from a first switching module to a second switching module, wherein the first switching module comprises a first MOSFET and a first inverse diode, and the second switching module comprises a second MOSFET and a second inverse diode, the first MOSFET and the second MOSFET being controlled by a gate-source voltage, the method comprising:
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connecting a first gate-driver unit directly to a gate and a source terminal of the first MOSFET and connecting a second gate-driver unit directly to a gate and source terminal of the second MOSFET; applying a first control voltage to the first switching module to switch it off for a first time period, wherein the level of the first control voltage is below a predetermined threshold voltage, above which the first MOSFET becomes minimally conductive, and wherein the first time period is selected so that the first inverse diode carries the load current; applying a second control voltage to the first switching module for a second time period to influence the switch-off behavior of the first inverse diode, wherein the second control voltage has an intermediate level between the level of the first control voltage and the level of the predetermined threshold voltage, applying a third control voltage to the second switching module for switching it on, wherein the level of the third control voltage is above the predetermined threshold voltage, above which the second MOSFET is minimally conductive, in order to cause a commutation of the load current from the first inverse diode to the second MOSFET, wherein a period in which the third control voltage is applied to until the second MOSFET becomes fully conductive is within the second time period; applying, after an expiration of the second time period, a fourth control voltage with a level below the intermediate level of the second control voltage to the first MOSFET to block it or hold it in the blocking status; and operating, via a control device, the first switching module and the second switching module in a complementary manner such that when one of the first switching module or the second switching module is conductive, the other of the first switching module or the second switching module is blocked at a same time. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification