Electrical Circuit Design Principles

Step-by-Step Guide for Inverter Module Design and systems engineering for Traction Motor in EVs   System Engineering Design Step 1: Define System Requirements • Vehicle-Level Requirements: ◦ Voltage Range ◦ Power level (e.g., 50 kW to 250 kW) ◦ Cooling method (air or liquid) ◦ Safety and protection (ISO 26262, ASIL levels) Functional Requirements: ◦ Motor control (Field-Oriented Control - FOC) ◦ Torque/speed response time ◦ Regenerative braking ◦ Fault detection (short circuit, overvoltage, overheating) Non-Functional Requirements: ◦ Size, weight, cost ◦ Efficiency target (>95%) ◦ EMI/EMC compliance Step 2: Functional Architecture Definition • Define subsystem blocks: ◦ Power stage (IGBT or SiC MOSFETs) ◦ Gate driver circuit ◦ Current and voltage sensing ◦ Control board (MCU, DSP, FPGA) ◦ HV & LV power interfaces ◦ Communication (CAN, LIN) Step 3: Safety & Standards Compliance • ISO 26262 – Functional safety • ISO 21434 – Cybersecurity (if connected to VCU) • IEC 61851 / ISO 15118 – Charging interface coordination • Automotive EMI/EMC: CISPR 25, ISO 11452 • Thermal runaway mitigation and insulation standards (IEC 60664, 61140) Step 4: Control System Development • Motor control algorithms: ◦ Field-Oriented Control (FOC) ◦ Space Vector PWM (SVPWM) ◦ Torque and speed loops Sensor fusion: ◦ Resolver / Hall sensor integration ◦ Current sensors for vector control • Software-in-the-loop (SIL), HIL testing Hardware Design Phase Step 5: Power Circuit Design • Topology: 3-phase inverter (6-switch) using IGBTs or SiC MOSFETs • DC Link Capacitor Design: ◦ Rated for ripple current ◦ Film/ceramic or electrolytic • Snubber circuit: For voltage spike suppression • Current Sensors: Shunt, Hall-effect, or Rogowski coil Step 6: Gate Driver Circuit Design • Fast switching, isolated gate drivers • Fault protection (UVLO, overcurrent, desaturation detection) • Dead-time control and soft switching Step 7: Control Board (PCB) Design • Processor: Automotive-grade MCU/DSP (e.g., TI C2000, NXP S32K, Infineon Aurix) • Interfaces: ◦ CAN, SPI, UART, PWM ◦ Resolver/Hall interface • Power Supply: DC-DC converters (LV to 3.3V/5V rails) Step 8: Thermal Management Design • Heatsinks and/or liquid-cooled baseplate • Thermistors or RTDs for junction temperature monitoring • Thermal simulation (ANSYS, Simcenter) Step 9: EMI/EMC Filtering • Input/output filters (LC filters, CM chokes) • Shielding and grounding strategy • Layout optimization: minimize loop areas, use ground planes Step 10: Mechanical Integration • Connector types (HVIL, LV, signal) • Enclosure design (IP67/69 rated) • Vibration resistance (ISO 16750) • Mounting and serviceability Step 11: Prototype & Testing • Validation stages: ◦ Bench test (no load) ◦ Dyno test with PMSM motor ◦ Vehicle integration testing • Test cases: ◦ Full load, partial load ◦ High/low temperature ◦ Fault injection and safe state fallback Step 12: Documentation & Release

Today I spent time studying the interlock logic of a 420kV GIS circuit breaker, where: CRP (Control & Relay Panel) is supplied by Siemens LCC (Local Control Cubicle) is supplied by NHVS In high-voltage systems, a circuit breaker (CB) cannot be allowed to open or close freely. Every operation must pass through a strict interlock logic to ensure safety, reliability, and protection of equipment & personnel. CB Close Interlock Before the breaker can close, the following conditions must be satisfied: Disconnector condition – DS1 & DS2 must be in the same position (both open or both closed). This prevents CB from closing when line isolators are mismatched. Selector switch – Must be in correct position (Normal / Remote). This ensures only one command source is active. Health checks – CB oil pressure healthy SF6 gas pressure healthy Motor not running overtime CB not overloaded No pole discrepancy No Lockout are operated Trip circuit supervision Healthy If any of these are abnormal, the breaker will not close. CB Open Interlock Breaker opening also requires specific conditions, mainly for safe operation: CB oil pressure must be healthy (to ensure mechanism works properly). Spring charging condition must be OK. Interlock logic confirms breaker can only open when protection panel gives order and auxiliary conditions are satisfied. This prevents a situation where the breaker is stuck due to mechanical/electrical constraints. Logic Design The interlock circuit combines AND / OR gate principles using auxiliary contacts, relays (K3, K12, K22, K23, etc.), and signals from the protection panel. AND gates → all conditions must be true (healthy) before breaker can operate. OR gates → allows alternative paths (e.g., local or remote operation). This design ensures the CB operation is always fail-safe – meaning if there’s any doubt, the breaker won’t operate. Mostafa Al-Hossain Sub Assistant Engineer Reverie Power & Automation Engineering Ltd. 13-09-25

Signal Integrity Simplified: The One Concept That Unlocks High-Speed Design "It takes years to master high-speed PCB design." If you've heard this, you're not alone. This belief keeps countless engineers from pursuing advanced PCB design skills. But what if understanding ONE core concept could dramatically accelerate your path to high-speed design competence? The Transmission Line Revelation Early in my career, I avoided high-speed design. It seemed impossibly complex - filled with arcane formulas, specialized tools, and terminology I didn't understand. It was where the 'real' electrical engineers did 'black magic'. Then I had a breakthrough that changed everything: ALL signal integrity issues at their core relate to transmission line theory. Once I deeply understood how signals propagate along PCB traces as transmission lines, suddenly: - Impedance control made intuitive sense - Reflection problems became predictable - Cross-talk had clear solutions - EMI sources became obvious This single concept - viewing PCB traces as transmission lines rather than simple connections - unlocked an entire field that previously seemed impenetrable. From Concept to Competence in Weeks, Not Years Here's the step-by-step path I took to rapidly build signal integrity expertise: Master transmission line fundamentals (2 weeks) Learn to calculate and control impedance (1 week) Understand reflection mechanics and termination (1 week) Apply principles to real designs (4 weeks) Within just 8 weeks of focused learning, I was confidently handling 1Gbps+ designs that previously would have intimidated me. The Practical Application That Proves It Works Recently, one of my mentees (just 6 months into his hardware career) was tasked with designing a board with LPDDR4 memory - typically considered an advanced challenge. Rather than memorizing DDR4 design rules, he focused on understanding the transmission line characteristics of the signals. The result? His first DDR4 design passed simulation and validation on the first attempt - something his manager couldn't believe. When asked how long he'd been doing high-speed design, expecting to hear "years," his answer was simply: "About 6 weeks of focused study on the right things." Accelerate Your Own Mastery If you want to rapidly develop signal integrity expertise: Start with transmission line fundamentals - not just tools or checklists Use simple test boards to validate your understanding Focus on WHY rules exist, not just memorizing them Simplify complex problems by relating them back to basic principles You can develop professional-level signal integrity skills in MONTHS, not years - but only if you focus on the fundamental concepts that everything else builds upon. Question for hardware engineers: What's one "advanced" PCB design concept you've been avoiding because it seems too complex? #SignalIntegrity #PCBDesign #HighSpeedDesign #HardwareEngineering

High-current DC/DC regulators are often plagued by EMI issues due to high dv/dt and di/dt switching transients during MOSFET commutation. These transients lead to both conducted and radiated EMI, which can severely affect system performance, especially in industries such as automotive and communications, where EMI compliance is crucial. To address this, optimizing the PCB layout is one of the most effective ways to reduce EMI at no extra cost. By carefully designing the power stage layout, engineers can minimize the parasitic inductance of the switching loop, thus reducing voltage overshoot, ringing, and overall EMI emissions. For instance, placing input capacitors close to the MOSFETs, and using a vertically oriented power loop in a multilayer PCB structure can significantly reduce the parasitic loop area. This optimization results in improved EMI performance, lowering the overshoot by up to 4V compared to conventional designs. In this white paper from Texas Instruments, we dive deeper into how specific layout changes can help mitigate EMI for high-current regulators. By leveraging best practices, such as minimizing switching loop area and using high-frequency decoupling capacitors, engineers can enhance system stability and comply with stringent EMI standards more easily.

Why the risetime (RT) of a digital signal is so important for #EMC and #signalintegrity? Rise (and fall) time are key parameters that contribute to the high-frequency spectral content of the waveform. The levels of the emissions in the regulatory frequency range are therefore strongly dependent on the risetimes and falltimes of these pulses. Here we have an analytical formula showing that the spectrum of a clock signal decays 20dB/decade until f=1/πRT, and 40dB/decade after. Simulation in #ansys #hfss #circuits show a very good agreement for this approach where a 1MHz clock signal with 20ns risetime was used. We also have measurements showing a good correlation for a 1MHz clock signal with 12.5ns risetime. The animation shows from a simulation perspective how the waveform in time domain and the spectrum changes as we change the rise/fall times from 5ns to 100ns. Note that even for a 1MHz clock signal, the spectrum content changes by several dBs at higher frequencies (+100Mhz)! Reference from measurements and analytical formula is "Introduction to Electromagnetic Compatibility" from Clayton Paul, which I'm sure most of you are very familiar with.

PVT variations- 1) Process (P) • Process variation = run-to-run, die-to-die and within-die (local) variations in device geometry, doping, oxide thickness • Geometrical variations (L, W): up to ~±2–10% depending on node and feature (patterning, OPC). • Threshold voltage (Vth) / drive current (Ion): variability can be up to ~±5–10% Effect - • Delay spread, timing failures, SRAM stability (Vmin), increased leakage (for some corners), lower yield. • Within-die mismatch affects analog matching, SRAM bitcell failure, and critical paths. Mitigation- 1. Statistical timing + variation-aware sign-off (Monte-Carlo, SSTA) — design to statistical yield 2. Adaptive Body Bias (ABB) / Static Body Bias (SBB) — shift Vth per-die or per-block to recover speed or cut leakage. 3. Design margins & conservative corners — guardbanding 4. Sizing & redundancy — upsizing transistors on critical paths; spare rows/columns and ECC for memories. 5. Layout techniques for matching — common-centroid, interdigitation, dummy fingers 6. Process control & calibration — on-chip sensors (ring oscillators, corner detectors) + post-silicon calibration (voltage trim). 7. Variation-tolerant circuit styles — error detection/recovery , differential signaling 2) Voltage (V) • (I/O, analog) ±5%; core rails ~±1–3% . Transient droops during switching can be (tens of mV). • Transient droop (IR drop + decoupling limits) can cause VDD reductions of several % to >10% Effect- • Delay is sensitive to VDD near Vth: small % change in VDD → larger % change in delay. • Lower VDD increases delay and higher VDD increases leakage and stress. Mitigation- 1. Robust power-grid & decoupling 2. Fast local regulators / LDOs / point-of-load converters 3. Dynamic Voltage and Frequency Scaling (DVFS) with margining 4. OCV (on-chip variation) and timing monitors (Razor, canaries) that trigger corrective action (voltage bump or clock slow-down). 5. Power aware synthesis / floorplanning 3) Temperature (T) • Chips operation-consumer ~−40°C to +85°C; industrial/automotive up to +125°C or more. On-chip hotspot delta from ambient can be 20–60°C • parameters (mobility, leakage, bandgap) depend on T — mobility decreases with increasing T (leakage/subthreshold current increases with T. Mobility and resistivity changes are of a few % to tens of % Effect - • higher T → slower carrier mobility → longer delay, but there are cases of temperature inversion (delay decreases with temperature in some corners near threshold because Vth shifts dominate). Leakage increases strongly with T (exponential). • Large ΔT across chip causes frequency variations and potential hot-spot induced failures. Mitigation- 1. Thermal management — heat sinks, active cooling, airflow, PCB thermal vias. 2. On-chip temperature sensors & dynamic thermal management (DTM) — throttle frequency, migrate workload, DVFS 3. Place sensitive circuits away from hot blocks 4. Worst-case sign-off + silicon monitoring

For identifying short circuits on prototype PCBs during bring-up I usually follow two quick approaches:   The first approach uses a thermal camera to identify any hotspots on components that could be caused by footprint errors, overvoltage faults, reverse polarity and so on. Fault finding in this way can be done on individual voltage rails (depending on the power tree) or system level, but usually requires a significant amount of current to identify potential problems.   For some designs, injecting a large current may not be the preferred method or may not give a reliable result if there is a very low resistance short circuit present. For sensitive boards I like to inject a small current into the short-circuited rail and measure the voltage drop between the injection point and several test points or components across the board on the same net. I'm using high resolution 6.5 or 7.5 digit multimeters, so only a small test current is needed to measure a voltage drop large enough to pinpoint the location of the fault. This is a rather quick way to find static problems on a single rail. In the visualization shown, I've plotted the voltage measured at each coordinate in the same net and created a 2D surface that is warped according to the measured voltage value. This type of visualization is not necessary for debugging, I just wanted to give a visual representation of what is going on at the PCB level.   I use 'homemade' test leads, using ICT test probes that can be replaced when they're worn or when I need very fine probes for small components. #electronics #hardware #hardwaredesign

🕵️ Analog Designers = Circuit Detectives! Ever designed a circuit that looked perfect in simulation but fell apart in real life? Welcome to the world of circuit mysteries! Great analog designers aren’t just engineers—they’re detectives. Every design is a crime scene, every measurement a clue, and every bug a hidden suspect. Let’s step into the mind of a circuit detective and solve some classic cases! 🔍 🔎 Case #1: The Missing Gain – Who’s Lying? Your amplifier simulated at 40 dB, but when you measure it, you barely get 30 dB. What happened? Possible suspects: • Parasitic Capacitance – A sneaky criminal that forms between layout traces and silicon, rolling off your high-frequency gain. • Bias Shift – If your current source isn’t stable, your transistor’s gm changes, making gain disappear like a thief in the night. • Layout Coupling – Stray signals are whispering secrets across your chip, messing up your expected response. 🔹 Detective’s Trick: Compare your measured frequency response to your simulated one. Is the gain loss at high frequencies? Parasitics are to blame. Is it at all frequencies? Check your biasing. 🔎 Case #2: The Noise That Came From Nowhere 👻 Your circuit was silent in simulation, but the lab bench tells a different story—hiss, hum, and jitter! Where’s the noise coming from? Possible suspects: • Thermal Noise – Resistors are always talking; at high values, they start shouting! • Flicker Noise – Low-frequency noise lurking in MOSFETs, worse if your bias current is too low. • Power Supply Ripple – Noise hitching a ride on your supply, sneaking into sensitive nodes. 🔹 Detective’s Trick: Zoom into the noise spectrum. If it’s mostly low-frequency, flicker noise is the villain. If it’s broadband, thermal noise is involved. If you see spikes? Power supply issues! 🔎 Case #3: The Phantom Current – Where Did It Go? Your circuit is drawing more current than expected, but nothing looks wrong. Where’s the current disappearing? Possible suspects: • Leakage Paths – A slow, silent killer, especially in deep submicron nodes. • Unwanted Short Circuits – Did you accidentally connect an ESD diode to ground? • Biasing Gone Rogue – Current mirrors don’t always behave—check if all transistors are in saturation. 🔹 Detective’s Trick: Use a thermal camera or a simple IR sensor—hot spots often reveal where current is leaking away. 🔎 Case #4: The Perfect Simulation & Broken Silicon Everything was flawless in SPICE, but the fabricated chip is behaving like a completely different design. Why? Possible suspects: • Stray Capacitance – The PCB traces and bond wires have their own hidden capacitances, shifting your poles and zeros. • IR Drop – Your “5V” supply isn’t really 5V when large currents flow through PCB traces or silicon routing. • Mismatch – Even “identical” transistors aren’t truly identical, causing offsets and gain errors.

𝗣𝗮𝗿𝗮𝘀𝗶𝘁𝗶𝗰 𝗰𝗮𝗽𝗮𝗰𝗶𝘁𝗮𝗻𝗰𝗲 𝗶𝘀 𝘁𝗵𝗲 𝗿𝗼𝗼𝘁 𝗼𝗳 𝗮𝗹𝗹 𝗲𝘃𝗶𝗹. 😈 In analog design, in RF, in digital, in high-speed circuits, at low noise-just everywhere. Too much input, output, or feedback parasitic capacitance in your design, and your circuit is doomed, with poor performance, oscillations, or high noise. I always try to estimate the parasitic capacitance of pads on the PCB, so I can include it in simulations or find ways to minimize it. I use the parallel plate formula to calculate the parasitic capacitance of short traces and pads on the PCB, together with the substrate dielectric constant and thickness. But the parallel plate capacitance formula, used by many online calculators and CAD tools, and the one we learned about in high school, is not accurate enough. It’s mainly correct for infinite plates. Once the plates are finite and spaced too far apart, fringing fields become dominant, and the actual capacitance is much larger. Much larger. And in high-speed design, even 0.1 pF of not accounted for capacitance can be a disaster. Avi Cohen just released a great article showing how to add a correction factor to this formula, depending on the size of the plates (or pads on the PCB) and the distance between them (i.e., stackup thickness).  He used an RLC extractor from CST (the 3D EM simulator) to calculate the exact capacitance and compare it to the simple formula. He showed that large errors, sometimes dozens of percent, can happen. The online calculators and tools will fool you! 😐 You must add these correction factors if you want a good estimation of the parasitic capacitance on your board.

Post #178BD0HBE Which Circuit is Safe? Understanding Electrical Safety"- 1️⃣ Safety First – Choose the Right Circuit!- The image compares two circuits (A and B) to determine which is safe. Circuit A has the neutral wire connected to the switch, while Circuit B has the phase (live) wire controlled by the switch. Circuit B is the safe option. 2️⃣ Operating Principle:- In Circuit B, the switch interrupts the phase (live) wire, ensuring the circuit is de-energized when the switch is off. This prevents any live current from reaching the load (bulb) or exposed parts, reducing the risk of electric shock. In contrast, Circuit A keeps the phase wire live even when the switch is off, posing a shock hazard if the neutral connection fails or is tampered with. This principle is fundamental to safe electrical design, ensuring the circuit is fully isolated during maintenance or accidental contact. 3️⃣ Application:- Circuit B is widely used in residential, commercial, and industrial lighting systems, including homes, offices, schools, and hospitals. It is a standard practice in electrical installations per safety codes like the National Electrical Code (NEC) and International Electrotechnical Commission (IEC) standards. This wiring method is also applied in appliance control circuits and outdoor lighting, where safety is paramount. Its versatility makes it essential for ensuring user safety across diverse environments. 4️⃣ Importance in Electrical Distribution Systems:- Using Circuit B enhances safety by minimizing electrical hazards, protecting users from accidental shocks, and preventing short circuits or fires. It ensures compliance with safety regulations, reduces maintenance risks for electricians, and supports reliable power distribution. Properly wired circuits like B are critical for the stability and efficiency of electrical grids, safeguarding both infrastructure and human life. Additionally, it aids in energy efficiency by preventing unnecessary power flow and supports long-term system reliability, making it a cornerstone of modern electrical engineering. #ElectricalSafety #CircuitDesign #ElectricalEngineering #SafetyFirst #PowerDistribution #EngineeringTips #ElectricalInstallation #TechForGood #LearnEngineering #SafetyStandards