# US 12,184,187 B2 · Active reduced voltage switching using a supplemental switch

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- Number: US 12,184,187 B2
- Document ID: US12184187B2
- Status: Granted
- Kind: B2
- Application number: 18/052,964
- Filed: 2022-11-07
- Published: 2024-01-25
- Granted: 2024-12-31
- Earliest claimed: 2022-07-21
- Assignees: Power Integrations, Inc.
- Applicants: Power Integrations, Inc.
- Inventors: David Michael Hugh Matthews
- Web page: https://patentgrep.com/patent/US12184187B2

## CPC

- H02M 3/33523: {with galvanic isolation between input and output of both the power stage and the feedback loop}
- H02M 3/33592: {having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer}
- H02M 1/0009: {Devices or circuits for detecting current in a converter}
- H02M 1/0019: {the disturbance parameters being load current fluctuations}
- H02M 1/0022: {the disturbance parameters being input voltage fluctuations}
- H02M 1/0058: {by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero (using an auxiliary actively switched resonant commutation circuit connected to an intermediate DC voltage or between two push-pull branches of an inverter bridge H02M7/4811; in resonant inverters H02M7/4815; in inverters operating from a resonant DC source H02M7/4826)}
- H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P)

## Abstract

A controller includes a primary controller and a secondary controller to control switching of a power switch and a supplemental switch, respectively, coupled to an energy transfer element, e.g. an energy transfer element of a power converter. A ZV drive circuit are coupled to generate a ZVS signal that enables a ZV switch to store energy in the energy transfer element. The energy stored in the energy transfer element is coupled to reduce a switch voltage across the power switch prior to a next ON section of the primary drive signal. The secondary drive signal is generated in response to the drive signal and the ZVS signal.

## Claims

### Claim 1

A controller for a power converter, the power converter having an energy transfer element and a primary side capacitance, the controller comprising:
a secondary controller comprising;
a forward voltage detector circuit coupled to produce a zero voltage switch (ZVS) enable signal when the power converter is in a discontinuous conduction mode,
a ZVS drive circuit coupled to receive the ZVS enable signal and in response to the ZVS enable signal produce a ZVS drive signal, and
a supplemental switch coupled to a secondary winding of the energy transfer element to receive the ZVS drive signal, and in response to the ZVS drive signal store energy through a current in the energy transfer element, wherein the current enables discharge of the primary side capacitance; and
a primary controller coupled to a primary winding of the energy transfer element, wherein following the discharge of the primary side capacitance the primary controller produces a primary drive signal to store energy in the energy transfer element.

### Claim 2 (depends on 1)

The controller as in claim 1, the primary controller further comprising a primary switch, coupled to the primary winding and to a primary reference ground, an internal capacitance of the primary switch comprising at least a portion of the primary side capacitance, the primary switch coupled to switch in response to the primary drive signal.

### Claim 3 (depends on 2)

The controller of claim 2 wherein the energy stored through current in the energy transfer element is substantially equal to energy stored in the primary side capacitance.

### Claim 4 (depends on 3)

The controller of claim 3, the forward voltage detector circuit comprising:
a forward voltage detector coupled to produce the ZVS enable signal in response to an output parameter of the power converter, wherein
when the ZVS enable signal is asserted, energy is stored in the energy transfer element,
when the ZVS enable signal is deasserted, the energy stored in the energy transfer element is released as current in the primary winding, and
the primary controller receives the ZVS enable signal and is coupled to produce the primary drive signal in response to the ZVS enable signal being deasserted.

### Claim 5 (depends on 4)

The controller of claim 4, further comprising a delay circuit, wherein the delay circuit is coupled to receive the ZVS enable signal and assert a delayed ZVS enable signal, and the primary controller is coupled to produce the primary drive signal in response to the delayed ZVS enable signal being deasserted.

### Claim 6 (depends on 5)

The controller of claim 5, wherein the delay circuit is included in one of the primary controller and the secondary controller.

### Claim 7 (depends on 1)

The controller of claim 1 wherein the ZVS drive circuit is coupled to produce a secondary drive signal in response to an input voltage of the power converter.

### Claim 8 (depends on 1)

The controller of claim 1 wherein the ZVS drive circuit is coupled to produce a secondary drive signal in response to an output current or output voltage of the power converter.

### Claim 9 (depends on 1)

The controller of claim 1 wherein the ZVS drive circuit is coupled to produce a secondary drive signal in response to an input voltage of the power converter and an output current or output voltage of the power converter.

### Claim 10 (depends on 1)

The controller of claim 1 wherein the primary controller is coupled to receive the delayed ZVS enable signal from the forward voltage detector circuit through a communication link, and wherein the primary controller is coupled to generate the primary drive signal in response to the ZVS enable signal.

### Claim 11 (depends on 1)

The controller of claim 1 wherein the ZVS drive circuit comprises a monostable multivibrator circuit.

### Claim 12 (depends on 1)

The controller of claim 1, the secondary controller further comprising a delay circuit coupled to receive the ZVS enable signal and to delay the ZVS enable signal.

### Claim 13 (depends on 12)

The controller of claim 12, wherein the delay circuit is coupled to delay the primary drive signal from enabling the power switch until the primary side capacitance has been discharged.

### Claim 14 (depends on 12)

The controller of claim 12, wherein a delay time of the delay circuit is proportional to at least one of an output current of the power converter, an output voltage of the power converter, and an input voltage of the power converter.

### Claim 15 (depends on 12)

The controller of claim 12, wherein the delay circuit is coupled to increase the delay time in response to an increase in the input voltage of the power converter.

### Claim 16 (depends on 12)

The controller of claim 12, wherein the delay circuit is coupled to increase the delay time in response to a decrease in the output current of the power converter.

### Claim 17 (depends on 1)

The controller of claim 1 wherein the primary controller and the secondary controller are included in a monolithic integrated circuit.

### Claim 18 (depends on 1)

The controller of claim 1 wherein the primary controller and the secondary controller are included in a single integrated circuit package.