# US 2019/0356231 A1 · Quasi-resonant flyback converter controller

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- Number: US 2019/0356231 A1
- Document ID: US20190356231A1
- Status: Published application
- Kind: A1
- Application number: 16/530,900
- Filed: 2019-08-02
- Published: 2019-11-21
- Earliest claimed: 2018-02-12
- Assignees: Silanna Asia Pte Ltd
- Applicants: Silanna Asia Pte Ltd
- Inventors: Aleksandar Radic
- Web page: https://patentgrep.com/patent/US20190356231A1

## CPC

- H02M 3/33523: {with galvanic isolation between input and output of both the power stage and the feedback loop}
- H02M 3/33576: {having at least one active switching element at the secondary side of an isolation transformer}
- H02M 3/33507: {with automatic control of the output voltage or current, e.g. flyback converters (H02M3/33561, H02M3/33569 take precedence)}
- H02M 1/0009: {Devices or circuits for detecting current in a converter}
- H02M 1/0016: {Control circuits providing compensation of output voltage deviations using feedforward of disturbance parameters}
- 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 1/08: Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
- H02M 1/36: Means for starting or stopping converters
- H02M 7/12: using discharge tubes with control electrode or semiconductor devices with control electrode
- H03M 1/12: Analogue/digital converters ({H03M1/001 – } H03M1/10 take precedence)
- Y02B 70/10: Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
- 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)
- H03M: CODING; DECODING; CODE CONVERSION IN GENERAL (using fluidic means F15C4/00; optical analogue/digital converters G02F7/00; coding, decoding or code conversion, specially adapted for particular applications, see the relevant subclasses, e.g. G01D, G01R, G06F, G06T, G09G, G10L, G11B, G11C, H04B, H04L, H04M, H04N; ciphering or deciphering for cryptography or other purposes involving the need for secrecy G09C)
- Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS

## Abstract

A flyback converter includes a primary-side circuit to receive an input voltage, a secondary-side circuit to generate an output voltage, a transformer coupling the primary-side circuit to the secondary-side circuit, a main switch coupled to a primary winding of the transformer, and a converter controller having a primary-side controller in signal communication with the main switch to control an on time and an off time of the main switch and to detect one or more valleys of a resonant waveform developed at the main switch during the off time of the main switch. The primary-side controller is configured to operate in a valley reduction mode of operation upon determining that the output voltage is less than a reference voltage minus a predetermined threshold value. The valley reduction mode of operation includes decrementing, for each switching cycle of the main switch, a number of valleys occurring during that switching cycle.

## Claims

### Claim 1

A flyback converter comprising:
a primary-side circuit configured to receive an input voltage;
a secondary-side circuit configured to generate an output voltage using the input voltage;
a transformer coupling the primary-side circuit to the secondary-side circuit;
a main switch coupled to a primary winding of the transformer and configured to control a current through the primary winding; and
a converter controller comprising:
a primary-side controller in signal communication with the main switch, the primary-side controller being configured to control an on time and an off time of the main switch and to detect one or more valleys of a resonant waveform developed at a node of the main switch during the off time of the main switch;
wherein:
the primary-side controller is configured to operate in a valley reduction mode of operation upon determining that the output voltage is less than a reference voltage of the flyback converter minus a predetermined threshold value; and
the valley reduction mode of operation comprises decrementing, by the primary-side controller, for each switching cycle of the main switch, a number of valleys occurring during that switching cycle of the main switch.

### Claim 2 (depends on 1)

The flyback converter of claim 1, wherein:
the primary-side controller is configured to stop the valley reduction mode of operation upon determining that the output voltage is not less than the reference voltage of the flyback converter minus the predetermined threshold value.

### Claim 3 (depends on 1)

The flyback converter of claim 1, wherein:
during the valley reduction mode of operation, the primary-side controller decrements the number of valleys by one or more for each of the switching cycles of the main switch.

### Claim 4 (depends on 3)

The flyback converter of claim 3, wherein:
during the valley reduction mode of operation, the primary-side controller decrements the number of valleys occurring during each of the switching cycles of the main switch by adjusting the off time of the main switch for each of the switching cycles.

### Claim 5 (depends on 1)

The flyback converter of claim 1, wherein:
the primary-side controller is configured to receive an auxiliary voltage from an auxiliary-winding circuit coupled to the transformer; and
the primary-side controller is configured to detect the number of valleys of the resonant waveform using the auxiliary voltage.

### Claim 6 (depends on 1)

The flyback converter of claim 1, further comprising:
a secondary-side controller, in signal communication with the secondary-side circuit; and
a digital link in signal communication with the primary-side controller and the secondary-side controller;
wherein:
the secondary-side controller is configured to receive the output voltage from the secondary-side circuit and the reference voltage, convert the output voltage into a digital output voltage signal and the reference voltage into a digital reference voltage signal, and transmit the digital output voltage signal and the digital reference voltage signal to the digital link;
the digital link is configured to transmit the digital output voltage signal and the digital reference voltage signal to the primary-side controller; and
the primary-side controller is configured to receive the digital output voltage signal and the digital reference voltage signal and determine if the output voltage is less than the reference voltage minus the predetermined threshold value.

### Claim 7 (depends on 6)

The flyback converter of claim 6, the secondary-side controller comprising:
an analog-to-digital converter (“ADC”) configured to receive the output voltage from the secondary-side circuit and the reference voltage, wherein the ADC is configured to convert the output voltage into the digital output voltage signal and the reference voltage into the digital reference voltage signal; and
an encoder in signal communication with the ADC, wherein the encoder is configured to receive and encode the digital output voltage signal and the digital reference voltage signal into a combined encoded data stream having digital representations of the output voltage and the reference voltage.

### Claim 8 (depends on 7)

The flyback converter of claim 7, wherein the encoder is a finite-state machine.

### Claim 9 (depends on 7)

The flyback converter of claim 7, the primary-side controller comprising:
a decoder configured to receive and decode the combined encoded data stream into a received digital output voltage signal and received digital reference voltage signal; and
a controller in signal communication with the decoder, wherein the controller is configured to receive the received digital output voltage signal and the received digital reference voltage signal and to control the on time and the off time of the main switch based on the received digital output voltage signal and the received digital reference voltage signal.

### Claim 10 (depends on 6)

The flyback converter of claim 6, wherein the digital link is a unidirectional high-speed digital link.

### Claim 11

A method comprising:
receiving, at a primary-side circuit of a flyback converter, an input voltage;
generating, at a secondary-side circuit of the flyback converter, an output voltage using the input voltage, a transformer coupling the primary-side circuit to the secondary-side circuit;
controlling, using a main switch coupled to a primary winding of the transformer, a current through the primary winding;
controlling, by a primary-side controller of the flyback converter, an on time and an off time of the main switch;
detecting, by the primary-side controller, one or more valleys of a resonant waveform developed at a node of the main switch during the off time of the main switch;
determining, by the primary-side controller, that the output voltage is less than a reference voltage of the flyback converter minus a predetermined threshold value;
beginning, by the primary-side controller, a valley reduction mode of operation based on the determination; and
reducing, by the primary-side controller during the valley reduction mode of operation, a number of valleys occurring at the node of the main switch during one or more switching cycles of a plurality of switching cycles of the main switch.

### Claim 12 (depends on 11)

The method of claim 11, further comprising:
stopping, by the primary-side controller, the valley reduction mode of operation upon determining that the output voltage is not less than the reference voltage of the flyback converter minus the predetermined threshold value.

### Claim 13 (depends on 11)

The method of claim 11, further comprising:
decrementing, by the primary-side controller during the valley reduction mode of operation, the number of valleys occurring during each switching cycle of the plurality of switching cycles of the main switch.

### Claim 14 (depends on 13)

The method of claim 13, further comprising:
adjusting, by the primary-side controller during the valley reduction mode of operation, the off time of the main switch by an amount of time corresponding to an integer number of valleys to decrement the number of valleys occurring during each switching cycle of the plurality of switching cycles of the main switch.

### Claim 15 (depends on 11)

The method of claim 11, further comprising:
receiving, by the primary-side controller, an auxiliary voltage from an auxiliary-winding circuit coupled to the transformer; and
detecting, by the primary-side controller, the number of valleys of the resonant waveform using the auxiliary voltage.

### Claim 16 (depends on 11)

The method of claim 11, wherein:
the flyback converter further comprises a secondary-side controller, in signal communication with the secondary-side circuit;
the flyback converter further comprises a digital link in signal communication with the primary-side controller and the secondary-side controller; and
the method further comprises:
receiving, by the secondary-side controller, the output voltage from the secondary-side circuit and the reference voltage;
converting, by the secondary-side controller, the output voltage into a digital output voltage signal and the reference voltage into a digital reference voltage signal;
transmitting, by the secondary-side controller, the digital output voltage signal and the digital reference voltage signal to the digital link;
transmitting, by the digital link, the digital output voltage signal and the digital reference voltage signal to the primary-side controller; and
receiving, by the primary-side controller, the digital output voltage signal and the digital reference voltage signal, the digital output voltage signal and the digital reference voltage signal being used to determine, by the primary-side controller, that the output voltage is less than the reference voltage of the flyback converter minus the predetermined threshold value.

### Claim 17 (depends on 16)

The method of claim 16, wherein:
the secondary-side controller further comprises an analog-to-digital converter (“ADC”) and an encoder in signal communication with the ADC; and
the method further comprises:
receiving, by the ADC, the output voltage from the secondary-side circuit and the reference voltage;
converting, by the ADC, the output voltage into the digital output voltage signal and the reference voltage into the digital reference voltage signal;
receiving, by the encoder, the digital output voltage signal and the digital reference voltage signal; and
encoding, by the encoder, the digital output voltage signal and the digital reference voltage signal into a combined encoded data stream having digital representations of the output voltage and the reference voltage.

### Claim 18 (depends on 17)

The method of claim 17, wherein the encoder is a finite-state machine.

### Claim 19 (depends on 17)

The method of claim 17, wherein:
the primary-side controller further comprises a decoder and a controller in signal communication with the decoder; and
the method further comprises:
receiving, by the decoder, the combined encoded data stream;
decoding, by the decoder, the combined encoded data stream into a received digital output voltage signal and received digital reference voltage signal;
receiving, by the controller, the received digital output voltage signal and the received digital reference voltage signal; and
controlling, by the controller, the on time and the off time of the main switch based on the received digital output voltage signal and the received digital reference voltage signal.

### Claim 20 (depends on 16)

The method of claim 16, wherein the digital link is a unidirectional high-speed digital link.