August 17, 2019 by Sam Holland
The STEVAL-DPSLLCK1, by STMicroelectronics, is a 3-kilowatt isolated full bridge logical link control (LLC) DC-DC resonant converter that turns 375V–425V to 48V, and a maximum current of 62.5A.
This digitally controlled kit consists of a control board, a power board and an adapter board. The control board is based on the STM32F334R8 microcontroller (MCU) and is joined to the power board by a standard 64-pin DIN 41612 connector.
Besides sensing and conditioning circuits, the power board includes gate drivers, an auxiliary power supply, a high-frequency transformer, a resonant tank, and power switches.
The STEVAL-DPS334C1 control board includes an STM32F334 MCU that manages adaptive synchronous rectification (SR) metal-oxide-semiconductor field-effect transistors (MOSFET) and controls the LLC converter.
An SR technique, facilitated by the synchronous-rectifier STP310N10F7 MOSFETs, is used to turn on the channel of low voltage MOSFETs to reduce conduction losses.
This MCU is from the STM32F3x4 product line and it addresses digital power conversion applications, such as welding, lighting, inverters for solar systems, wireless chargers, and digital switch mode power supplies (D-SMPS).
The STM32F334R8 MCU features new temperature and voltage compensated hi-res timers and ultrafast comparators for better regulation and increased safety.
It runs preloaded software, and it communicates status information via the System Management Bus (SMBus), controlled area network (CAN), universal synchronous/asynchronous receiver/transmitter (USART), and opto-coupled serial communication.
The MCU incorporates a high-performance Arm Cortex-M4 32-bit reduced instruction set computer (RISC) core with a floating-point unit (FPU), which belongs to the latest generation of Arm processors for embedded systems.
The Arm Cortex-M4 processor has a reduced pin count and low-power consumption to enable it to meet the needs of MCU implementation, thereby delivering remarkable computational performance and an advanced response to interrupts.
Both in full bridge configuration, the primary side of the board is based on ST’s MDmesh DM2 Power MOSFETs, while the secondary side is based on STripFET F7 LV MOSFETs.
The STW70N60DM2 (used for this kit) offers very low recovery charge and time combined with low drain-source on-resistance, aka RDS(on).
Beyond being Zener-protected, the STW70N60DM2 diode features low on-resistance and has super low gate charge and input capacitance.
This fast recovery diode MOSFET belongs to the ST’s STPOWER family and will perform well, even after exposure to large voltage transients, namely thanks to its high dv/dt ruggedness.
The STMicroelectronics STEVAL-DPSLLCK1 Evaluation Kit DC-DC Converter. Image courtesy of STMicroelectronics.
The STripFET F7 Power MOSFET (STP310N10F7) uses the seventh generation design rules of STMicroelectronics’ STripFET technology.
For that reason, it exhibits the lowest RDS(on) of all packages. To reduce conduction losses, synchronous rectification (SR) with STP310N10F7 is used on the secondary side.
The aux power supply circuit of this kit is based on the VIPER27HD high-performance controller chip, which regulates voltages to the gate driver integrated circuits, the control board (which receives 5 V through its D-SMPS connector) and the signal conditioning circuits.
Viper 27 is an offline converter with pulse width modulation (PWM) operation, frequency jittering for low EMI, two levels of over-current protection, hysteretic thermal protection, and an 800 V avalanche rugged power section.
This device has on-board soft start, safe auto-restart (after a fault condition), and overvoltage protection.
The STEVAL-DPSADP01 adapter board has a JTAG (named after the Joint Test Action Group who codified it) connector to facilitate programming and debugging communication.
The board also has embedded transceivers for the RS-232 and CAN protocols. This adapter provides several communication interface options for the MCU.
Some of the kit’s protection mechanisms include over-temperature protection, under-voltage or overvoltage protection, and short-circuit protection.
The kit is built with a modular approach that enables hardware and firmware modularity and portability to steer the design of digital switch mode power supply solutions. Typically, this kit would be used in telecommunication applications; for example, it could be used in AC-DC power supply units that are used in servers and telecom infrastructures.
All in all, the STEVAL-DPSLLCK1 converter, given its output synchronous rectification feature and a high performing STM32 microcontroller, will help users to develop highly efficient digital SMPS solutions—especially if they wish to meet the requirements set by bodies like Energy Star, 80 Plus, and Erp Lot 6.
