Method and device for regulating a dead time in switching power supply units
A method for adapting a dead time between the beginning of ab opening process of a first switching element and the beginning of a closing process of a second, serially connected switching element in a switching regulator of a switching power supply unit. The method includes the following steps: a measurement voltage across the second switching element is measured, and the dead time is varied such that the deviation of the measured measurement voltage from a target value of the measurement voltage is minimized or limited. The first and second switching elements are actuated using the thus ascertained dead time. There is also described a device for carrying out such a method. The device includes a measuring unit, a processing unit, and a control unit.
1. A method of adjusting a dead time between a start of opening a first switching element and a start of closing a second switching element that is connected in series with the first switching element in a switching power supply unit, the method comprising:
measuring a measuring voltage across the second switching element, wherein the step of measuring the voltage includes measuring a first overvoltage value of the measuring voltage and a second overvoltage value of the measuring voltage;
comparing the second overvoltage value of the measuring voltage with the first overvoltage value of the measuring voltage and in response to the comparison, varying the dead time to thereby minimize or limit a measured measuring voltage control deviation relative to a measuring voltage target value; and
controlling the first and second switching elements with the dead time thus determined.
2. The method according to claim 1 , wherein the step of varying the dead time includes:
in a first step, initializing the dead time, initializing the first overvoltage value of the measuring voltage, with an overvoltage start value greater than or equal to a maximum measurable overvoltage, and initializing a corrective direction for dead time adjustment;
in a second step, measuring the second overvoltage value of the measuring voltage within a measuring time window within the dead time;
in a third step, reversing the corrective direction, if the second overvoltage value is greater than the first overvoltage value;
in a fourth step, adjusting the dead time, in the corrective direction, by the dead time adjustment; and
in a fifth step, overwriting the first overvoltage value by the second overvoltage value; and
repeating a sequence of the second step to the fifth step at least once.
3. The method according to claim 2 , which comprises determining the dead time adjustment by a multiplication of a difference between the first overvoltage value and the second overvoltage value with a dead time adjustment increment.
4. The method according to claim 2 , which comprises forming the dead time adjustment as a product of:
an amplification factor of at least 1;
a difference between the second overvoltage value and the target value of the measuring voltage raised to a higher power by an index of at least one; and
a dead time adjustment increment.
5. The method according to claim 4 , wherein the amplification factor is selected within a range from 1 to 12, and the index is selected within a range from 1 to 5.
6. The method according to claim 1 , wherein the step of varying the dead time includes:
in a first step, initializing the dead time, initializing the first overvoltaqe value of the measuring voltage, with an overvoltaqe start value greater than or equal to a maximum measurable overvoltaqe, and initializing a corrective direction for dead time adjustment; and
in a second step, measuring the second overvoltage value as a maximum value of the measuring voltage over a complete switching cycle, and, upon determining that the second overvoltage value is smaller than or equal to an overvoltaqe limiting value, overwriting the first overvoltage value by the second overvoltaqe value; and repeating the second step at least once.
7. The method according to claim 6 , which comprises determining the overvoltage limiting value from the target value for the measuring voltage by a multiplication thereof with a tolerance factor of at least 1.
8. The method according to claim 6 , which comprises:
executing a modified fourth step if the second overvoltage value is smaller than or equal to the overvoltage limiting value and if, in a previous cycle of the method, the second overvoltage value was greater than the overvoltage limiting value; and
in the modified fourth step, adjusting the dead time in the corrective direction by a dead time adjustment increment which is multiplied by a predefined step number of at least 1.
9. The method according to claim 8 , which comprises selecting the predefined step number within a range of 12 to 21.
10. A device for adjustment of the dead time by the method according to claim 1 , the device comprising:
a measuring unit for said measuring of the measuring voltage on the switching power supply unit, the measuring voltage including a first overvoltage value of the measuring voltage and a second overvoltage value of the measuring voltage;
a processing unit to be connected to said measuring unit, said processing unit being configured for calculating a dead time value, said processing unit also configured for comparing the second overvoltage value of the measuring voltage with the first overvoltage value of the measuring voltage and in response to the comparison, varying the dead time to thereby minimize or limit a measured measuring voltage control deviation relative to a measuring voltage target value; and
a control unit to be connected to said processing unit, said control unit being configured for controlling the first and second switching elements in the switching controller of the switching power supply unit.
11. The device according to claim 10 , wherein the first and second switching elements are metal oxide semiconductor field effect transistors, and said control unit is configured for controlling said metal oxide semiconductor field effect transistors.
12. In a switching controller of a switching power supply unit having a first switching element and a second switching element connected in series with the first switching element, a device of adjusting a dead time between a start of opening the first switching element and a start of closing the second switching element, the device comprising:
a measuring unit for measuring a measuring voltage across the second switching element, the measuring voltage including a first overvoltage value of the measuring voltage and a second overvoltage value of the measuring voltage;
a processing unit connected to said measuring unit, said processing unit being configured for calculating a dead time value, said processing unit also configured for comparing the second overvoltage value of the measuring voltage with the first overvoltage value of the measuring voltage and in response to the comparison, varying the dead time to minimize or limit a measured measuring voltage control deviation relative to a measuring voltage target value; and
a control unit connected to said processing unit, said control unit being configured for controlling the first and second switching elements in the switching controller of the switching power supply unit with the dead time thus determined.
13. The device according to claim 12 , wherein the first and second switching elements are metal oxide semiconductor field effect transistors, and said control unit is configured for controlling said metal oxide semiconductor field effect transistors.