High switching frequency direct AC to AC converter

Patent metadata

Field	Value
Publication number	US-11095229-B1
Application number	US-202017030698-A
Country	US
Kind code	B1
Filing date	Sep 24, 2020
Priority date	Sep 24, 2020
Publication date	Aug 17, 2021
Grant date	Aug 17, 2021

Abstract

A direct AC to AC converter includes a modulation stage, a transformer and a de-modulation stage. The modulation stage is configured to convert an AC input voltage with a first frequency into a bipolar PWM voltage with a second frequency, wherein the second frequency is higher than the first frequency. The transformer has a primary winding and secondary winding, wherein the primary winding is coupled to the modulation stage to receive the bipolar PWM voltage. The de-modulation stage is coupled to the secondary winding of the transformer and configured to convert the voltage across the secondary winding of the transformer into an AC output voltage with the first frequency.

First claim

What is claimed is:

1. A direct AC to AC converter comprising:
a modulation stage configured to convert an AC input voltage with a first frequency into a bipolar PWM voltage with a second frequency, wherein the second frequency is higher than the first frequency;
a transformer having a primary winding and secondary winding, wherein the primary winding is coupled to the modulation stage to receive the bipolar PWM voltage; and
a de-modulation stage coupled to the secondary winding of the transformer and configured to convert a voltage across the secondary winding of the transformer into an AC output voltage with the first frequency,

wherein the modulation stage comprises:
a first transistor having a first terminal, a second terminal and a control terminal;
a second transistor having a first terminal, a second terminal and a control terminal, wherein the first terminal of the second transistor is coupled to the first terminal of the first transistor, the second terminal of the second transistor is configured to be coupled to a first terminal of an AC power source providing the AC input voltage;
a third transistor having a first terminal, a second terminal and a control terminal, wherein the second terminal of the third transistor is configured to be coupled to a second terminal of the AC power source;
a fourth transistor having a first terminal, a second terminal and a control terminal, wherein the first terminal of the fourth transistor is coupled to the first terminal of the third transistor, the second terminal of the fourth transistor and the second terminal of the first transistor are coupled together and coupled to a first terminal of the primary winding of the transformer,
a diode bridge having a first input terminal, a second input terminal, a first output terminal and a second output terminal, wherein the first input terminal is configured to be coupled to the first terminal of the AC power source, the second input terminal is configured to be coupled to the second terminal of the AC power source, the first output terminal is configured to provide a power supply voltage, the second output terminal is coupled to a reference ground;
a power supply capacitor coupled between the first output terminal of the diode bridge and the reference ground;
a first driving circuit having a first supply terminal, a second supply terminal, an input terminal and an output terminal, wherein the second supply terminal is coupled to the second terminal of the first transistor, the input terminal is configured to receive a first control signal, the output terminal is coupled to the control terminal of the first transistor;
a first bootstrap capacitor coupled between the first and second supply terminals of the first driving circuit;
a second driving circuit having a first supply terminal, a second supply terminal, an input terminal and an output terminal, wherein the second supply terminal is coupled to the second terminal of the second transistor, the input terminal is configured to receive a second control signal, the output terminal is coupled to the control terminal of the second transistor;
a second bootstrap capacitor coupled between the first and second supply terminals of the second driving circuit;
a third driving circuit having a first supply terminal, a second supply terminal, an input terminal and an output terminal, wherein the second supply terminal is coupled to the second terminal of the third transistor, the input terminal is configured to receive a third control signal, the output terminal is coupled to the control terminal of the third transistor;
a third bootstrap capacitor coupled between the first and second supply terminals of the third driving circuit;
a fourth driving circuit having a first supply terminal, a second supply terminal, an input terminal and an output terminal, wherein the first supply terminal is coupled to the first supply terminal of the first driving circuit, the second supply terminal is coupled to the second terminal of the fourth transistor, the input terminal is configured to receive a fourth control signal, the output terminal is coupled to the control terminal of the fourth transistor
a first low dropout regulator having an input terminal and an output terminal, wherein the input terminal of the first low dropout regulator is coupled to the first output terminal of the diode bridge to receive the power supply voltage, the output terminal of the first low dropout regulator is coupled to the first supply terminal of the first driving circuit;
a second low dropout regulator having an input terminal and an output terminal, wherein the input terminal of the second low dropout regulator is coupled to the first output terminal of the diode bridge to receive the power supply voltage, the output terminal of the second low dropout regulator is coupled to the first supply terminal of the second driving circuit; and
a third low dropout regulator having an input terminal and an output terminal, wherein the input terminal of the third low dropout regulator is coupled to the first output terminal of the diode bridge to receive the power supply voltage, the output terminal of the third low dropout regulator is coupled to the first supply terminal of the third driving circuit.

2. The direct AC to AC converter of claim 1 , wherein the modulation stage further comprises:
a first capacitor having a first terminal and a second terminal, wherein the first terminal is coupled to the second terminal of the second transistor; and
a second capacitor having a first terminal and a second terminal, wherein the first terminal of the second capacitor and the second terminal of the first capacitor are coupled together and coupled to a second terminal of the primary winding of the transformer, the second terminal of the second capacitor is coupled to the second terminal of the third transistor.

3. The direct AC to AC converter of claim 1 , wherein:
when the AC input voltage is in a first half cycle, the second and fourth transistors are maintained on, the first and third transistors are switched at the second frequency; and
when the AC input voltage is in a second half cycle, the first and third transistors are maintained on, the second and fourth transistors are switched at the second frequency.

4. The direct AC to AC converter of claim 1 , wherein the de-modulation stage comprises:
a fifth transistor having a first terminal, a second terminal and a control terminal;
a sixth transistor having a first terminal, a second terminal and a control terminal, wherein the first terminal of the sixth transistor is coupled to the first terminal of the fifth transistor, the second terminal of the sixth transistor is configured to be coupled to a first terminal of a load for providing the AC output voltage;
a seventh transistor having a first terminal, a second terminal and a control terminal, wherein the second terminal of the seventh transistor is configured to be coupled to a second terminal of the load; and
an eighth transistor having a first terminal, a second terminal and a control terminal, wherein the first terminal of the eighth transistor is coupled to the first terminal of the seventh transistor, the second terminal of the eighth transistor and the second terminal of the fifth transistor are coupled together and coupled to a first terminal of the secondary winding of the transformer.

5. The direct AC to AC converter of claim 4 , wherein the de-modulation stage further comprises:
a third capacitor having a first terminal and a second terminal, wherein the first terminal is coupled to the second terminal of the sixth transistor; and
a fourth capacitor having a first terminal and a second terminal, wherein the first terminal of the fourth capacitor and the second terminal of the third capa

Assignees

• Monolithic Power Systems Inc

Inventors

• Hsing Michael
• Yang Eric
• Jiang Jian
• Han Di

Classifications

• H02M5/297

  for conversion of frequency · CPC title

• H02M5/293

  using semiconductor devices only · CPC title

• H02M5/16

  for conversion of frequency · CPC title

• H02M5/12 Primary

  for conversion of voltage or current amplitude only · CPC title

• H02M5/225 Primary

  comprising two stages of AC-AC conversion, e.g. having a high frequency intermediate link · CPC title