Method for the PWM actuation of HV components

Abstract

A method for the PWM actuation of more than one HV component for converting the power required by the HV components, in which each HV component is actuated by means of an individual PWM control circuit, and to a device for carrying out the method, wherein individual PWM control circuits are provided for the PWM actuation of 2 . . . n HV components, and wherein means are provided for asymmetrically splitting the phase shifts of the individual PWM actuation provided by the PWM circuitry.

Claims

1. A method for the pulse width modulation (PWM) actuation of more than one high voltage (HV) component for converting the power required by the HV components, in which each HV component is actuated by means of an individual PWM control circuit, in which the individual PWM control circuits are actuated in a phase-shifted manner with respect to one another, and in which the phase shifts are split asymmetrically.

2. A method according to claim 1, in which an odd number of HV components is used.

3. A method according to claim 2, in which the HV components include at least one or more of the following elements: a heating core, a PTC heating core, a ceramic heating core or a resistance heating core.

4. A method according to claim 1, in which the HV components include at least one or more of the following elements: a heating core, a PTC heating core, a ceramic heating core or a resistance heating core.

5. A device for carrying out the method according to claim 1, wherein individual PWM control circuits are provided for the PWM actuation of at least two HV components, and wherein means are provided for asymmetrically splitting the phase shifts of the individual PWM actuation provided by the individual PWM control circuits.

6. A device according to claim 5, wherein the individual PWM control circuits for the PWM actuation of the at least two HV components comprise means for the asymmetric PWM actuation of the following elements: a common oscillator unit for providing a uniform base signal (fPWM base) for all the individual PWM control circuits, and at least two duty cycle units corresponding to the at least two HV components, respectively, and wherein the means for the asymmetric PWM actuation comprise the following elements: at least two phase-shifter units corresponding to the at least two HV components.

7. A device according to claim 6, wherein at least two load switches are provided for the individual PWM actuation of the corresponding at least two HV components.

8. A device according to claim 5, wherein at least two load switches, are provided for the individual PWM actuation of the corresponding at least two HV components.

9. A device according to claim 8, wherein the at least two load switches are IGBTs.

Description

(1) The disclosure will be explained in more detail below with reference to the drawings, in which:

(2) FIG. 1 is a block diagram of an embodiment of the device according to the disclosure for the PWM actuation of HV components.

(3) FIG. 2 is a graph showing a PWM actuation of eight HV components having a symmetrical phase shift.

(4) FIG. 3 is a graph showing a PWM actuation of seven HV components having an asymmetrical phase shift.

(5) FIG. 1 shows, in the form of a block diagram, an embodiment of the device according to the disclosure for the PWM actuation of HV components, in this case in the form of load resistors. The device comprises a PWM control circuit block 10, an oscillator unit 11 and HV components in the form of heating cores 12 to 14.

(6) The PWM control circuit block 10 comprises 0 . . . n duty cycle units 15 to 17, and 0 . . . n phase-shifter units 18 to 20 downstream thereof. The same base signal (f.sub.PWM base) is applied to both the duty cycle units and the phase-shifter units, said base signal being provided by the oscillator unit 11.

(7) At the output of the phase-shifter unit 18, a PWM signal 0 is provided. At the output of the phase-shifter unit 19, a PWM signal 1 is provided, and at the output of the phase-shifter unit 20, a PWM signal n is provided. Relative to one another, these PWM signals have deviations from the symmetrical phase shift, which are generated by the phase-shifter units and are 0.5° to 10°, in particular 1° to 6°, in terms of magnitude.

(8) Each PWM signal is used to actuate the load resistors individually in order to convert the power required by the HV components. Specifically, the load resistor in the load path 12 is actuated by the PWM signal 0, the load resistor in the load path 13 is actuated by the PWM signal 1, and the load resistor in the load path 14 is actuated by the PWM signal n. Each load resistor is fed its individual PWM signal via an individual load switch, in this case via an IGBT. Thus, the load resistor 22 is fed its PWM signal 0 via the IGBT 21. In the same way, the load resistor in the load path 12 is fed its PWM signal 1 via an IGBT, not shown, while the load resistor in the load path 13 is fed its PWM signal n via an IGBT, not shown.

(9) In the graphs in FIG. 2 and FIG. 3, the curve over time of the PWM signals for actuating eight or seven load resistors, respectively, or for converting the power required by the load resistors is plotted on the x-axis, and their amplitude is plotted on the y-axis.

(10) In FIG. 2, the phase shift is split symmetrically while in FIG. 3 the phase shift is split asymmetrically in accordance with the proposal according to the disclosure for the PWM actuation of HV components for converting the power required by the HV component. In addition, it can be seen in FIGS. 2 and 3 that an even number of HV components or load resistors is used in FIG. 2 and an odd number thereof is used in FIG. 3.

(11) Due to the measure of asymmetrically splitting the phase shifts, as reflected in FIG. 3, line-related and field-related disturbances in the range of the system frequency f.sub.system can be reduced or distributed over a larger frequency band or duty factor range. Due to the odd number of load resistors also visible in FIG. 2, the overshoots can be remedied by eliminating the common dividers of f.sub.switch and f.sub.system.