Wideband rf power supply and control method

Patent metadata

Field	Value
Publication number	US-2024048041-A1
Application number	US-202118276940-A
Country	US
Kind code	A1
Filing date	Dec 17, 2021
Priority date	Feb 22, 2021
Publication date	Feb 8, 2024
Grant date	—

Abstract

A carrier wave generation unit comprising a wideband RF power supply divides a whole modulation wave variable frequency range into a plurality of modulation wave frequency sections associated with the number of PWM pulses N based on upper and lower limit frequencies of a carrier wave. In each modulation wave frequency section, an integer number of PWM pulses N associated to each modulation wave frequency section and the modulation wave frequency fs are used to vary a carrier wave frequency fc based on the relationship of fc=N·fs, thereby synchronizing the frequency between a carrier wave C and a modulation wave S to satisfy periodicity.

First claim

1 . A wideband RF power supply that outputs a sine wave over a wide band in an RF band, comprising:
a DC power source; a single-phase PWM inverter that converts a direct current supplied by the DC power source into an alternate current; an inverter controller that performs PWM control on the single-phase PWM inverter; and a low-pass filter that removes a harmonic component from an inverter output of the single-phase PWM inverter, wherein the inverter controller comprises a PWM control unit and a carrier wave generation unit,
wherein the carrier wave generation unit has:
a carrier wave variable frequency range in which a frequency is limited by an upper limit frequency and a lower limit frequency; and
a modulation wave variable frequency range that is divided into a plurality of modulation wave frequency sections associated with a number of PWM pulses N,
in each modulation wave frequency section, a modulation wave frequency fs and a number of PWM pulses N associated with the modulation wave frequency section being used to output a carrier wave at a carrier wave frequency fc which is defined based on a relationship of fc=N·fs, and

wherein the PWM control unit outputs a PWM pulse to be used to perform the PWM control on the inverter controller by comparing a modulation wave at the modulation wave frequency fs with the carrier wave, so as to output a sine wave at a frequency corresponding to a variable frequency of the modulation wave.

2 . The wideband RF power supply according to claim 1 , wherein the carrier wave generation unit comprises:
a carrier wave upper and lower limit frequency setting unit that sets an upper limit frequency and a lower limit frequency of the carrier wave; a modulation wave frequency section setting unit that divides a whole modulation wave variable frequency range into sections to set a plurality of modulation wave frequency sections, each of which is associated with each number of PWM pulses N; a carrier wave frequency computation unit that changes a number of PWM pulses N for the modulation wave frequency fs into a number of PWM pulses N associated with a modulation wave frequency section that includes the concerned modulation wave frequency fs in each modulation wave frequency section, so as to compute a carrier wave frequency fc by using the changed number of PWM pulses N and the modulation wave frequency fs based on the relationship of fc=N·fs; and a carrier wave output unit that outputs a carrier wave having the carrier wave frequency fc computed by the carrier wave frequency computation unit.

3 . The wideband RF power supply according to claim 2 , wherein the carrier wave upper and lower limit frequency setting unit uses a number of PWM pulses N=N min in a modulation wave frequency section on a high frequency side that includes a maximum modulation wave frequency fs −max in the modulation wave variable frequency range to set a carrier wave upper limit frequency fc −upper =N min ·fs −max and a carrier wave lower limit frequency fc −upper =fc −upper ·N min /(N min +2), and
the modulation wave frequency section setting unit sets, in the plurality of modulation wave frequency sections, a maximum frequency fs −max =fc −upper /N min and a minimum frequency fc −lower /N min of a modulation wave frequency in a modulation wave frequency section N min on a high frequency side that includes the maximum frequency of the modulation wave, and
in a relationship of N>Nunn in a modulation wave frequency section on a low frequency side,
(a) when the carrier wave frequency is shifted to the lower limit frequency fc −lower , sets a maximum frequency fc −lower /(N−2) and a minimum frequency fc −lower /N of the modulation wave frequency, and
(b) when the carrier wave frequency is shifted to the upper limit frequency fc −upper , sets a maximum frequency fc −upper /N and a minimum frequency fc −upper /(N+2) of the modulation wave frequency.

4 . The wideband RF power supply according to claim 1 , wherein the carrier wave generation unit comprises:
a characteristic data storage unit that stores the plurality of modulation wave frequency sections obtained by dividing the modulation wave variable frequency range into sections and setting each section by associating with the number of PWM pulses N; a reading unit that reads a modulation wave frequency section that includes the modulation wave frequency fs and the corresponding number of PWM pulses input in the characteristic data storage unit; carrier wave frequency computation unit that changes the number of PWM pulses N for the modulation wave frequency fs in each modulation wave frequency section into the number of PWM pulses N that is associated with a modulation wave frequency section including the concerned modulation wave frequency fs, and computes the carrier wave frequency fc by using the number of PWM pulses N thus changed and the modulation wave frequency fs based on the relationship of fc=N·fs; and a carrier wave output unit that outputs a carrier wave having the carrier wave frequency fc computed by the carrier wave frequency computation unit.

5 . The wideband RF power supply according to claim 1 , wherein the number of PWM pulses N is an even number,
the number of PWM pulses N associated with a modulation frequency section on a highest frequency side that includes the maximum frequency of the modulation wave is the minimum number of PWM pulses Nina, having the smallest even number, and the numbers of PWM pulses N associated with the modulation wave frequency section on the low frequency side are the values obtained by adding 2 to the number of PWM pulses N in order from the high frequency side to the low frequency side.

6 . The wideband RF power supply according to claim 5 , wherein the minimum number of PWM pulses Nina, is 4.

7 . The wideband RF power supply according to claim 1 , wherein the carrier wave has a waveform of an odd function or an even function.

8 . The wideband RF power supply according to claim 1 , wherein a cutoff frequency of the low-pass filter is either of the following values which is smaller:
a product (n −min ·fs −min (N min )) of the minimum modulation wave frequency fs −min (N min ) and a lowest harmonic order n −min resulting from the minimum number of PWM pulses N min associated with the modulation wave frequency section in the modulation wave frequency section on the high frequency side including the maximum modulation wave frequency fs −max in the modulation wave variable frequency range; or a product (n −min ·fs −min ) of the most minimum modulation wave frequency fs −min and the lowest harmonic order n −min resulting from the minimum number of PWM pulses associated with the modulation wave frequency section in the modulation wave frequency section on the low frequency side including the minimum modulation wave frequency fs −min in the modulation wave variable frequency range.

9 . The wideband RF power supply according to claim 8 , wherein in the modulation wave frequency section on the high frequency side including the maximum modulation wave frequency fs −max in the modulation wave variable frequency range, the most minimum modulation wave frequency fs −min (N min ) is obtained by multiplying the maximum modulation wave frequency fs −max by a value ((N min /(N min +2)).

10 . A control method for a wideband RF power supply that compares a modulation wave with a carrier wave in a PWM inverter to variably output a sine wave output frequency in an RF band,
wherein generation of the carrier wave comprises: (a) a carrier wave upper and lower limit frequency setting step for setting an upper limit frequency and a lower limit frequency of the carrier wave; (b) a modulation wave

Assignees

• Kyosan Electric Mfg

Inventors

• Yuzurihara Itsuo
• Yoneyama Tomohiro
• Kobayashi Shohei
• Hosoyamada Yu

Classifications

• H02M1/12

  Arrangements for reducing harmonics from AC input or output · CPC title

• H02M7/5387

  in a bridge configuration · CPC title

• H02M1/0054 Primary

  Transistor switching losses (periodically suspending operation of switching converter in low power mode H02M1/0035) · CPC title

• H02M7/5395 Primary

  by pulse-width modulation · CPC title

• H02M7/537

  using semiconductor devices only, e.g. single switched pulse inverters · CPC title