{ "node": { "id": "term:pulse-width-modulation", "type": "Term", "label": "Pulse-width modulation", "properties": { "id": "pulse-width-modulation", "name": "Pulse-width modulation", "abbr": "PWM", "section": "topic-data", "definition": "Controlling average power by switching fully on and off at a fixed frequency and varying the fraction of each period spent on, the duty ratio. It drives fans, pumps and contactor coils, sets the output of DC/DC converters and inverters, and signals available current on the 1 kHz control pilot of an AC charger.", "formula": "V_avg = D·V_supply", "related": [ "mosfet", "buck-boost-converter", "control-pilot", "coil-economiser", "inverter" ], "example": { "title": "Convert duty cycle to an ideal average", "text": "An ideal switch applying 12 V for 25% of each period produces a 3 V time average at the switching node. The instantaneous signal remains a 0/12 V waveform; a real converter also depends on topology and filtering." }, "url": "https://lemonergy.com/learn/glossary/pulse-width-modulation/", "mentions": [ "charger", "contactor" ] } }, "edges": [ { "id": "edge:5239", "source": "term:pulse-width-modulation", "target": "topic:topic-data", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:5240", "source": "term:pulse-width-modulation", "target": "term:mosfet", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:5241", "source": "term:pulse-width-modulation", "target": "term:buck-boost-converter", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:5242", "source": "term:pulse-width-modulation", "target": "term:control-pilot", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:5243", "source": "term:pulse-width-modulation", "target": "term:coil-economiser", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:5244", "source": "term:pulse-width-modulation", "target": "term:inverter", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:mentions/pulse-width-modulation/charger", "source": "term:pulse-width-modulation", "target": "term:charger", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:mentions/pulse-width-modulation/contactor", "source": "term:pulse-width-modulation", "target": "term:contactor", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:5247", "source": "term:pulse-width-modulation", "target": "visual:pwm", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } } ], "neighbors": [ { "id": "topic:topic-data", "type": "Topic", "label": "Data, communication and electronics", "properties": { "id": "topic-data", "name": "Data, communication and electronics", "lede": "The control units, chips, protocols and file formats through which a battery is measured, controlled and logged.", "context": "Separate quantities from encoding and transport.", "example": "2500 in a log might mean 25.00 °C, 2.5 V or raw counts. Units and scale must accompany the value.", "lesson_url": "https://lemonergy.com/learn/fundamentals/battery-basics/", "lesson_label": "Open battery basics" } }, { "id": "term:mosfet", "type": "Term", "label": "MOSFET", "properties": { "id": "mosfet", "name": "MOSFET", "aka": [ "metal–oxide–semiconductor field-effect transistor", "power MOSFET" ], "section": "topic-data", "definition": "A transistor switched by the voltage on its gate, with an on-resistance of milliohms or less in power parts. Low-voltage packs use back-to-back pairs as charge and discharge switches, since each conducts backwards through its body diode; BMS chips use small ones for balancing, and silicon-carbide MOSFETs switch 800 V inverters.", "related": [ "protection-circuit", "pulse-width-modulation", "cell-balancing", "inverter", "buck-boost-converter" ], "url": "https://lemonergy.com/learn/glossary/mosfet/", "mentions": [ "bms" ] } }, { "id": "term:buck-boost-converter", "type": "Term", "label": "Buck and boost converters", "properties": { "id": "buck-boost-converter", "name": "Buck and boost converters", "aka": [ "buck converter", "boost converter", "step-down converter", "step-up converter", "bidirectional DC/DC converter" ], "section": "topic-data", "definition": "Switch-mode circuits that step a DC voltage down (buck) or up (boost) using a fast switch, an inductor and a capacitor, often above 95% efficient. With transistors in place of diodes the same circuit runs both ways, charging a battery from a bus or discharging into it, as in stationary storage and on-board boosters that let 800 V cars use 400 V chargers.", "related": [ "dc-dc-converter", "pulse-width-modulation", "mosfet", "active-balancing", "split-pack" ], "url": "https://lemonergy.com/learn/glossary/buck-boost-converter/", "mentions": [ "stationary-storage", "capacitor" ] } }, { "id": "term:control-pilot", "type": "Term", "label": "Control pilot", "properties": { "id": "control-pilot", "name": "Control pilot", "abbr": "CP", "aka": [ "proximity pilot", "PP" ], "section": "topic-infrastructure", "definition": "The signal wire in an AC or CCS charging connector: the charger puts a ±12 V square wave on it whose duty cycle tells the vehicle the maximum current, and the vehicle answers by switching resistors. The proximity pilot beside it tells the vehicle a plug is inserted.", "related": [ "sae-j1772", "plc-green-phy", "ccu", "onboard-charger" ], "url": "https://lemonergy.com/learn/glossary/control-pilot/", "mentions": [ "charger" ] } }, { "id": "term:coil-economiser", "type": "Term", "label": "Contactor coil economiser", "properties": { "id": "coil-economiser", "name": "Contactor coil economiser", "aka": [ "coil economizer", "economiser", "PWM coil drive" ], "section": "topic-hvsafety", "definition": "A circuit that drives a contactor coil hard to close it, then cuts the power to the much lower level needed to hold it shut, often by pulse-width modulation. A typical 500 A contactor holds on under 2 W at 12 V; the saving matters for heat and for the low-voltage supply when several contactors stay closed for hours.", "related": [ "contactor", "pulse-width-modulation", "auxiliary-battery", "battery-disconnect-unit" ], "url": "https://lemonergy.com/learn/glossary/coil-economiser/", "mentions": [] } }, { "id": "term:inverter", "type": "Term", "label": "Inverter", "properties": { "id": "inverter", "name": "Inverter", "aka": [ "power conversion system", "PCS" ], "section": "topic-pack", "definition": "The power electronics that turn the battery’s DC into AC for a motor or the grid, and back again for charging. In stationary storage it is called the power conversion system and its rating in kW or MW sets the system’s power independently of the battery’s energy.", "related": [ "pre-charge", "dc-dc-converter", "stationary-storage", "energy-management-system", "direct-current", "iec-62477-1" ], "url": "https://lemonergy.com/learn/glossary/inverter/", "mentions": [] } }, { "id": "term:charger", "type": "Term", "label": "Charger", "properties": { "id": "charger", "name": "Charger", "section": "topic-charging", "definition": "The power electronics that convert mains or DC supply into the controlled current and voltage a battery needs. For lithium-ion it runs the CC-CV profile within the limits the BMS communicates, and stops rather than floats when the cell is full.", "related": [ "cc-cv-charging", "bms", "onboard-charger", "dc-fast-charging" ], "url": "https://lemonergy.com/learn/glossary/charger/", "mentions": [] } }, { "id": "term:contactor", "type": "Term", "label": "Contactor", "properties": { "id": "contactor", "name": "Contactor", "section": "topic-hvsafety", "definition": "A heavy-duty electrically operated switch that connects the pack to the vehicle or inverter and opens it on fault or shutdown. Packs use at least two, one per pole, plus a pre-charge path to avoid welding them on the first connection.", "related": [ "pre-charge", "battery-disconnect-unit", "pyrofuse", "bms" ], "url": "https://lemonergy.com/learn/glossary/contactor/", "mentions": [ "inverter" ] } }, { "id": "visual:pwm", "type": "Visual", "label": "Duty cycle controls average voltage", "properties": { "title": "Duty cycle controls average voltage", "summary": "An ideal pulse train alternates between zero and the supply voltage.", "readout": "50% of 12 V gives a 6 V time average.", "formula": "V_average = D V_supply", "note": "Unfiltered ideal waveform; actual output depends on the converter circuit and control.", "software": { "status": "reference", "label": "Reference concept", "body": "This shows V_avg = duty × V_supply for a pulse train. A real converter also requires topology, filtering, switching losses and control.", "href": "../chapter-1/" }, "html": "
Ideal 12 V pulse train
Ideal 12 V pulse trainTime (switching periods) versus Voltage (V). Switched voltage; Time average. Interpretation follows the graphs.003.517210.53144Time (switching periods)Voltage (V)
Switched voltageTime average (dashed)
" } } ] }