Method for controlling an electrical load by means of pulse width modulation

• US 10,673,542 B2
• Filed: 08/16/2019
• Issued: 06/02/2020
• Est. Priority Date: 02/24/2017
• Status: Active Grant

• Current Assignee: Leopold Kostal GmbH & Company KG
• Original Assignee: Leopold Kostal GmbH & Company KG
• Inventors: Hees, Norbert, Bendicks, Andreas, Wiegand, Marc, Frei, Stephan
• Primary Examiner(s): Vuong, Quochien B
• Application Number:
  US16/543,113
• Publication Number:
  US 20190372683A1
• Time in Patent Office: 291 Days
• CPC Class Codes: H02M 1/08 Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
• CPC Class Codes: H02P 27/085 wherein the PWM mode is adapted on the running conditions of the motor, e.g. the switching frequency
• CPC Class Codes: H04B 15/02 Reducing interference from electric apparatus by means located at or near the interfering apparatus

Abstract

A method for controlling an electrical load by means of pulse width modulation, (PWM) includes specifying a setpoint switching frequency f_setpoint and a setpoint duty ratio d_setpoint and determining the carrier frequency f_ch of a radio transmitter. The actual switching frequency f_sw of the PWM is adapted to the carrier frequency f_ch of the radio transmitter in such a way that a multiple k*f_sw of the actual switching frequency f_sw is equal to the carrier frequency f_ch with an integer factor k. The actual switching frequency f_sw is set to the value closest to the setpoint switching frequency f_setpoint for which the amplitude of the harmonics k*f_sw in the harmonic spectrum of the actual switching frequency f_sw is smaller than the amplitudes of their closest lower (k−1)*f_sw and upper (k+1)*f_sw adjacent harmonics.

Claims

1. A method for controlling an electrical load by means of pulse width modulation (PWM), the method comprising:

specifying a setpoint switching frequency f_setpoint and a setpoint duty ratio d_setpoint of a PWM signal;

determining a carrier frequency f_ch of a radio transmitter;

adapting an actual switching frequency f_sw of the PWM signal to the carrier frequency f_ch of the radio transmitter such that a multiple k*f_sw of the actual switching frequency f_sw is equal to the carrier frequency f_ch with an integer factor k; and

setting the actual switching frequency f_sw to the value closest to the setpoint switching frequency f_setpoint for which the amplitude of a harmonic k*f_sw in a harmonic spectrum of the actual switching frequency f_sw is smaller than the amplitudes of its lower (k−

1)*f_sw and upper (k+1)*f_sw adjacent harmonics.

2. The method of claim 1 further comprising:

setting a duty ratio d of the PWM signal at a ratio m/n that is close to the setpoint duty ratio d_setpoint, where m and n are natural numbers; and

setting the actual switching frequency f_sw to a value for which the frequency k*f_sw assumes the value closest to the setpoint switching frequency f_setpoint for which k/m is a natural number.

3. The method of claim 2 wherein:

n is less than or equal to 10.

4. The method of claim 3 further comprising:

setting the duty ratio d at the smaller ratio m/n that is closest to the setpoint duty ratio d_setpoint for a time T₁, and setting the duty ratio d at the larger ratio m/n that is closest to the setpoint duty ratio d_setpoint for a time T₂, wherein the times T₁ and T₂ are selected such that the duty ratio d on a time average is equal to the setpoint duty ratio d_setpoint.

5. The method of claim 3 further comprising:

setting the duty ratio d at the smaller ratio m/n that is closest to the setpoint duty ratio d_setpoint for a time T₁, and setting the duty ratio d at the larger ratio m/n that is closest to the setpoint duty ratio d_setpoint for a time T₂, wherein the times T₁ and T₂ are selected such that the duty ratio d on a time average is equal to the setpoint duty ratio d_setpoint.

6. The method of claim 2 wherein:

n is less than or equal to 5.

7. The method of claim 1 wherein:

the radio transmitter is an amplitude-modulated radio transmitter.

8. The method of claim 1 wherein:

the radio transmitter is a frequency-modulated radio transmitter.