# US 2017/0288555 A1 · Method for driving a resonant converter, and corresponding device and computer program product

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- Number: US 2017/0288555 A1
- Document ID: US20170288555A1
- Status: Published application
- Kind: A1
- Application number: 15/631,795
- Filed: 2017-06-23
- Published: 2017-10-05
- Earliest claimed: 2015-10-01
- Assignees: STMicroelectronics S.r.l.
- Applicants: STMicroelectronics S.r.l.
- Inventors: Lorenzo Trevisan; Massimiliano Picca; Roberto Cardu; Cristian Porta
- Web page: https://patentgrep.com/patent/US20170288555A1

## CPC

- H02M 3/33573: {Full-bridge at primary side of an isolation transformer}
- H02M 1/08: Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
- H02M 3/01: {Resonant DC/DC converters}
- H02M 3/33507: {with automatic control of the output voltage or current, e.g. flyback converters (H02M3/33561, H02M3/33569 take precedence)}
- H02M 3/33523: {with galvanic isolation between input and output of both the power stage and the feedback loop}
- H02M 3/3376: {with automatic control of output voltage or current}
- 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 1/38: Means for preventing simultaneous conduction of switches
- 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)
- Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS

## Abstract

A resonant converter includes a primary switching circuit including a primary winding and upper and lower switching half-bridge circuits alternately activated during switching cycles of the resonant converter responsive to switching control signals. The switching half-bridge circuits each include a phase node to drive the primary winding. A resonance inductor is coupled to the primary winding. A secondary resonant circuit has a secondary winding magnetically coupled to the primary winding and a resonance capacitor electrically coupled to the secondary winding. A driving circuit generates the switching control signals and senses if a voltage on the phase node of one of the upper and lower switching half-bridge circuits is a negative voltage. The driving circuit adjusts the switching control signals for the switching half-bridge circuit to be activated next switching cycle by a shift time reduced each switching cycle until the negative voltage is less than a negligible under-voltage value.

## Claims

### Claim 1

A resonant converter, comprising:
a primary switching circuit including a primary winding and including upper and lower switching half-bridge circuits configured to be alternately activated during switching cycles of the resonant converter in response to switching control signals, the upper and lower switching half-bridge circuits each including a phase node coupled to drive the primary winding, and the primary switching circuit including a resonance inductor coupled to the primary winding;
a secondary resonant circuit having a secondary winding magnetically coupled to the primary winding and a resonance capacitor electrically coupled to the secondary winding; and
a driving circuit coupled to the primary switching circuit, the driving circuit configured to generate the switching control signals and to sense if a voltage on the phase node of one of the upper and lower switching half-bridge circuits is a negative voltage, and further configured to adjust the switching control signals for the upper or lower switching half-bridge circuit that is to be activated in a next switching cycle by a shift time that is reduced each switching cycle until the negative voltage is less than a negligible under-voltage value.

### Claim 2 (depends on 1)

The resonant converter of claim 1, wherein the driving circuit is further configured, in switching cycles subsequent to a switching cycle where the driving circuit senses no negative voltage on the phase node of one of the upper and lower switching half-bridge circuits, to delay the switching control signals by a small amount until the driving circuit senses the voltage on the phase node of one of the upper and lower switching half-bridge circuits is a negative voltage.

### Claim 3 (depends on 1)

The resonant converter of claim 1, wherein the shift time is initially longer than a maximum resonance period of a resonance network formed by the resonance inductor and the resonance capacitor.

### Claim 4 (depends on 1)

The resonant converter of claim 1, wherein each of the upper and lower switching half-bridge circuits comprises a high-side switch and a low-side switch with the phase node being defined at an interconnection of the high-side and low-side switches, each of the high-side and low-side switches being a transistor.

### Claim 5 (depends on 4)

The resonant converter of claim 4, wherein each of the transistors comprises a power MOSFET.

### Claim 6 (depends on 5)

The resonant converter of claim 5, wherein the driving circuit is further configured to control each of the upper and lower switching half-bridge circuits to delay a dead time between turning off the high-side MOSFET and turning on the low-side MOSFET and between turning off the low-side MOSFET and turning on the high-side MOSFET.

### Claim 7 (depends on 6)

The resonant converter of claim 6, wherein each MOSFET has a parasitic capacitance and wherein the dead time less than one-fourth of a minimum secondary resonance period defined by a minimum value of a parasitic capacitance between a source and drain of each MOSFET and a minimum value of the resonance inductor.

### Claim 8 (depends on 7)

The resonant converter of claim 7, wherein the shift time is much greater a maximum main resonance period of a resonant network formed by the resonance inductor and the resonance capacitor.

### Claim 9 (depends on 1)

The resonant converter of claim 1, wherein the secondary winding of the secondary resonant circuit includes first and second ends and wherein the resonant converter further comprises a secondary rectification stage including a first rectification switch coupled between the first end of the secondary winding and a reference node and a second rectification switch coupled between the second end of the secondary wind and the reference node, each of the first and second rectification switches configured to receive a control signal from the driving circuit.

### Claim 10

A resonant converter, comprising:
a primary switching circuit including,
a primary winding;
a resonance inductor coupled in series with the primary winding; and
a primary full-bridge switching circuit including an upper switching half-bridge circuit and a lower switching half-bridge circuit coupled to the resonance inductor coupled in series with the primary winding, the primary full-bridge switching circuit in operation driving the primary winding coupled in series with the resonance inductor in response to switching control signals;
a secondary resonant circuit having a secondary winding magnetically coupled to the primary winding and a resonance capacitor electrically coupled to the secondary winding;
a secondary rectification stage coupled to the secondary winding of the secondary resonant circuit that in operation rectifies a signal across the secondary winding in response to switching control signals; and
a driving circuit that in operation detects whether a phase signal, which is provided by one of the upper and lower switching half-bridge circuits in response to a first control signal applied to the one of the upper and lower switching half-bridge circuits, exceeds a first threshold value, and the driving circuit in operation, in response to the phase signal exceeding the first threshold value, controlling a time shift between the first control signal and a second control signal applied to the other one of the upper and lower switching half-bridge circuits, and the driving circuit in operation adjusting the time shift each switching cycle of the first and second control signals until the phase signal does not exceed a second threshold value.

### Claim 11 (depends on 10)

The resonant converter of claim 10, wherein the secondary resonant circuit comprises the resonance capacitor coupled in parallel with the secondary winding.

### Claim 12 (depends on 10)

The resonant converter of claim 10, wherein each of the switching half-bridge circuits comprises a high-side transistor and a low-side transistor coupled in series between a supply voltage node that in operation receives a supply voltage and a reference node that in operation receives a reference voltage.

### Claim 13 (depends on 12)

The resonant converter of claim 12, wherein each of the high-side and low-side transistors comprises a MOS transistor.

### Claim 14 (depends on 13)

The resonant converter of claim 13, wherein the first threshold value has a value that causes switching of the MOS transistors of the switching half-bridge circuits not to occur under zero-voltage and zero-current switching conditions, and wherein the second threshold value has a value that causes switching of the MOS transistors of the switch half-bridge circuits to occur under zero-voltage switching and quasi zero-current switching conditions.

### Claim 15 (depends on 10)

The resonant converter of claim 10, wherein in the driving circuit is further configured, once the phase signal does not exceed the first threshold value, to reduce the time shift until the phase signal does not exceed the second threshold value, the first threshold value having a greater magnitude than the second threshold value.

### Claim 16 (depends on 10)

The resonant converter of claim 10, wherein the shift time is initially set to a value that is longer than a time of maximum resonance of a main resonance network formed by the resonance inductor and the resonance capacitor.

### Claim 17

A method, comprising:
receiving phase signals on phase nodes of an upper switching half-bridge circuit and a lower switching half-bridge circuit of a resonant converter, each of the upper switching half-bridge circuit and lower half-bridge circuit including a high-side switch and a low side switch;
driving a primary winding and a resonance inductive element with the phase signals;
detecting an under voltage or an over voltage in the phase signals;
providing a time shift between a first control signal applied to the high-side and low-side switches of one of the upper and lower switching half-bridge circuits and a second control signal applied to the high-side and low-side switches of the other one of the upper and lower switching half-bridge circuits; and
reducing a value of the time shift starting from an initial nominal value by an incremental value each cycle of the first and second control signals until the under voltage or over voltage in the phase signal is approximately zero.

### Claim 18 (depends on 17)

The method of claim 17 further comprising:
providing for each of the upper and lower switching half-bridge circuits a dead time between a switching off of the high-side switch and a switching on of the low-side switch; and
providing for each of the upper and lower switching half-bridge circuits the dead time between a switching off of the low-side switch and a switching on of the high-side switch.

### Claim 19 (depends on 18)

The method of claim 18, wherein detecting the under voltage or the over voltage in the phase signals occurs during the dead time, the under voltage or over voltage arising from a secondary resonance that occurs due to parasitic capacitances of the switches and a resonant inductive component of the resonant converter.

### Claim 20 (depends on 19)

The method of claim 19, wherein detecting the under voltage or the over voltage in the phase signal comprises detecting an under voltage of a falling edge of the phase signal on the phase node of the upper switching half-bridge circuit that results during the dead time associated with the first control signal applied to the upper switching half-bridge circuit.