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UM2948
User manual
Getting started with the STEVAL-SCR002V1 SCR based inrush current limiter
board with non-isolated gate driver
Introduction
Improvement of power density and reliability is a major trend for power supply manufacturers. Moving from passives and
mechanical parts to silicon devices considerably contributes to this progress.
During the startup of an AC-DC power converter, the high current due to the charge of the DC bulk capacitor can rise up to 10
times the nominal steady state current of the system. This inrush current induces a voltage drop on the AC mains that might
affect the operation of other equipment connected to the same power network.
The inrush triggers or damages the serial devices, such as the circuit breaker, the wire fuse, the capacitor, or the bridge rectifier.
To preserve the safety of the electrical installation and the reliability of the power converter, it is necessary to limit this inrush
current.
The
STEVAL-SCR002V1
evaluation board introduces a simple and innovative AC-DC front-end circuit. The bridge rectifier
consists of diodes and silicon-controlled rectifiers (SCRs) that are implemented in the bridge low side.
An uninsulated power supply and a few SMD discrete components make the design very compact. The board can be easily
implemented on existing PFC or fly-back converters for plug-and-play tests. The solution, based on the high temperature
TN1605H-6T
SCRs, totally replaces front-end electro-mechanical relays, bypassing the inrush current-limiting resistor.
Figure 1.
STEVAL-SCR002V1 evaluation board
UM2948 - Rev 1 - July 2022
www.st.com
For further information contact your local STMicroelectronics sales office.
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Summary of Contents for ST STEVAL-SCR002V1
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Page 1: Figure 1. Steval-Scr002V1 Evaluation Board
UM2948 User manual Getting started with the STEVAL-SCR002V1 SCR based inrush current limiter board with non-isolated gate driver Introduction Improvement of power density and reliability is a major trend for power supply manufacturers. Moving from passives and mechanical parts to silicon devices considerably contributes to this progress. -
Page 2: Getting Started
Getting started Safety precautions Danger: Use the STEVAL-SCR002V1 board only after applying a fire-resistant cover. The cover is not included in the board package. There is danger of serious personal injury, property damage or death due to electrical shock and burn hazards if the kit or components are improperly used or installed incorrectly. -
Page 3: Features
• Low EMI noise (EN55014 and EN55022) solution Circuit and purpose STEVAL-SCR002V1 purpose is to bypass the NTC via the SCRs. The SCR driver consists of a triac and two diodes. At system startup, inrush current is limited by the NTC (see Section 3.1... -
Page 4: Connection And Startup
UM2948 Connection and startup Connection and startup The figures below show the circuit diagram and the physical position of the components on the board. Figure 2. STEVAL-SCR002V1: circuit simplified schematic Figure 3. STEVAL-SCR002V1 components STEVAL-SCR002V1 pinout: • EN: enable pin. The NTC is bypassed as long as the enable pin is supplied with a positive voltage (from 3.3 to 15 V) •... -
Page 5: Figure 4. Connection Example Of The Steval-Scr002V1 To A Boost Converter (Pfc) - Relay Replacement
UM2948 Connection and startup Figure 4. Connection example of the STEVAL-SCR002V1 to a boost converter (PFC) - relay replacement UM2948 - Rev 1 page 5/28... -
Page 6: Operation
IEC61000-4-11 (voltage dips, short interruptions, and immunity tests for voltage variations). Figure 6. Schematic of the STEVAL-SCR002V1 connected to PFC Startup At system power-up, the EN signal is disabled and no gate current is applied to the Q1 gate terminal. Then, the triac remains off and no current can flow through the SCR gates. -
Page 7: Steady State
UM2948 Steady state Figure 7. Startup phase - PFC bulk capacitor precharge (EN = 0 V) During the positive half sine wave, the current flows through D3, boost inductor and diode, NTC, and D6. During the negative half sine wave, the current flows through D4, boost inductor and diode, NTC, and D5. With EN = 0 V, inrush current is limited by the NTC. -
Page 8: Figure 9. Example Of Scr Leakage Current (Tj = 125°C)
UM2948 SCR gate driver with automatic switching operation Figure 9. Example of SCR leakage current (Tj = 125°C) The evaluation board solution is low side bypass topology: the TN1605H-6T SCR gate driver is implemented with Z0110MN STTH110A connected in series to the SCR gates. This solution allows controlling only the SCR positively biased without sensing the polarity of the AC line signal. -
Page 9: Performance
1500 W PSU. The PSU is rated at 93% efficiency with 80% load power, with the schematic modified as shown in the figure below. Figure 11. STEVAL-SCR002V1 performance test configuration The original configuration, which uses a mechanical relay, has been replaced by connecting the STEVAL- SCR002V1 low side SCR bypass solution. -
Page 10: Conducted Emi Noise
We achieved the same IEC61000-4-4 withstanding level with the original configuration using a relay and an NTC. The low side bypass SCR solution has no impact on the burst immunity system performance. Table 1. IEC61000-4-4 test results for the STEVAL-SCR002V1 Original Coupling... -
Page 11: Surge Robustness
UM2948 Surge robustness Surge robustness We performed the lightning surge robustness according to the IEC61000-4-5 test. We tested four configurations: positive and negative surges with 90° and 0° phase angles as shown below. Figure 15. IEC61000-4-5 surge test configuration The EN pin is supplied with 5 V DC, the low side SCRs bypass the NTC, and the PFC output capacitor is already charged through the NTC. -
Page 12: Figure 17. Waveforms Resulting From The 2 Kv Iec61000-4-5 Test (B Configuration)
UM2948 Surge robustness Figure 17. Waveforms resulting from the 2 kV IEC61000-4-5 test (B configuration) The figure below shows how the positively biased SCR handles the surge current, during the surge test at 0° phase angle. Figure 18. Waveforms resulting from the 2 kV IEC61000-4-5 test (C and D configurations) During the IEC 61000-4-5 lightning surge test, the triac, diodes, and SCR measured values are within the specified values. -
Page 13: Thermal Management
Thermal management Thermal management For a safe and reliable operation, it is important to keep the junction temperature of the SCR below its maximum junction temperature. The STEVAL-SCR002V1 uses two high temperature TN1605H-6T SCRs that can operate at up to 150°C. -
Page 14: Temperature Measurements
UM2948 Temperature measurements Figure 20. Junction temperature calculation Temperature measurements We measured the SCR and bridge diode case temperatures applying the following conditions: • = 60°C • Load power = 1000 W 1000 • = 230 V /50 Hz Ip = 2 ⋅ = 6.15A→Pd = 1.84W At P = 1000 W, the maximum case temperatures measured are 125°C and 130°C on the SCR and the bridge diode. -
Page 15: Board Possible Modifications
• Igt at 0°C = 1.4 x Igt at 25°C = 35 mA (refer to Z0110MN datasheet on www.st.com); • EN supply is between 3.3 and 15 V; • Rated power for SMD 1206 package is 0.75 W. -
Page 16: Pwm Driver Control
UM2948 PWM driver control PWM driver control STEVAL-SCR002V1 enable pin connected to the Z0110MN gate can be controlled through a DC or PWM signal. PWM driver control signal allows significantly reducing the driver power consumption with a 12 V power supply. -
Page 17: Bom Reduction
UM2948 BOM reduction BOM reduction As explained in Section 3.1 Startup, low side bridge diodes are useful only during the PFC output capacitor precharge startup phase. Therefore, you can remove one low side diode to reduce the bill of materials. However, this modification results in doubling the PFC output capacitor precharge duration, as shown in the figure below. -
Page 18: Topology Sum-Up
UM2948 Topology sum-up Topology sum-up The low side topology and its dedicated non-insulated driver allow to easily replace electromechanics and/or passive elements while dealing with the inrush current into a complete solid state solution. This results in the following advantages for the designers: •... -
Page 19: Board Layout
UM2948 Board layout Board layout Figure 25. STEVAL-SCR002V1 top side layout Figure 26. STEVAL-SCR002V1 bottom side layout UM2948 - Rev 1 page 19/28... -
Page 20: Schematic Diagrams
UM2948 Schematic diagrams Schematic diagrams Figure 27. STEVAL- SRC002V1 circuit schematic A T-filter (R1-C1-R2) is placed on top of the Z0110MN gate to maximize the EFT immunity of the low side ICL driver. Refer to AN5649 for further information. UM2948 - Rev 1 page 20/28... -
Page 21: Bill Of Materials
UM2948 Bill of materials Bill of materials Item Q.ty Ref. Part/value Description Manufacturer Order code 10 A, 1000 V, GBJ bridge rectifier GBJ1010 10 nF, 25 V, ±10%, X7R, Capacitor SMD, 0805 STTH110A, D1, D2 1000 V, 1 A ultra-fast diode STTH110A NTC1 22 R... -
Page 22: Board Versions
UM2948 Board versions Board versions Table 7. STEVAL-SCR002V1 versions PCB version Schematic diagrams Bill of materials STEVAL$SCR002V1A STEVAL$SCR002V1A schematic diagrams STEVAL$SCR002V1A bill of materials 1. This code identifies the STEVAL-SRC002V1 evaluation board first version. It is printed on the board PCB. -
Page 23: Regulatory Compliance Information
UM2948 Regulatory compliance information Regulatory compliance information Notice for US Federal Communication Commission (FCC) For evaluation only; not FCC approved for resale FCC NOTICE - This kit is designed to allow: (1) Product developers to evaluate electronic components, circuitry, or software associated with the kit to determine whether to incorporate such items in a finished product and (2) Software developers to write software applications for use with the end product. -
Page 24: Revision History
UM2948 Revision history Table 8. Document revision history Date Revision Changes 04-Jul-2022 Initial release. UM2948 - Rev 1 page 24/28... -
Page 25: Table Of Contents
UM2948 Contents Contents Getting started ..............2 Safety precautions . -
Page 26: List Of Tables
IEC61000-4-4 test results for the STEVAL-SCR002V1 ........ -
Page 27: List Of Figures
Schematic of the STEVAL-SCR002V1 connected to PFC........ - Page 28 ST’s terms and conditions of sale in place at the time of order acknowledgment. Purchasers are solely responsible for the choice, selection, and use of ST products and ST assumes no liability for application assistance or the design of purchasers’...
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