USB Power Delivery Standard Power Range (SPR) covers contracts up to 100W, while Extended Power Range (EPR) adds higher fixed voltage levels and can reach 240W. Crossing that boundary is a system change, not a charger-label change: the source, USB-C cable, sink, connectors, power conversion and negotiation must all support the intended EPR operation.
SPR and EPR describe power ranges
The USB-IF USB Power Delivery overview states that USB PD can provide up to 240W and identifies new 28V, 36V and 48V fixed levels associated with 140W, 180W and 240W. Before EPR, the commonly cited upper SPR case was 20V at 5A, or 100W.
| Range | Fixed-voltage scope | Upper power context | System implication |
|---|---|---|---|
| SPR | Includes 5V, 9V, 15V and 20V fixed supply levels. | Up to 100W in the 20V, 5A case. | Source, cable and sink still negotiate a supported contract; lower-power cables and devices can limit the result. |
| EPR | Adds 28V, 36V and 48V fixed supply levels and an EPR operating mode. | Up to 140W, 180W and 240W at the corresponding 5A fixed levels. | Requires an EPR-capable source, EPR-rated cable, EPR-capable sink and an accepted EPR contract. |
These are capability ceilings, not a promise that every EPR port offers every voltage or that every device will request the maximum. A 140W laptop, 180W tool system and 240W battery product can implement different subsets and thermal policies.
Four gates must open before power rises above 100W
- The source must advertise EPR capability. Its PD controller and power stage must support the offered voltage and current.
- The cable must be suitable for EPR. Cable identity is part of deciding whether the path can enter the intended higher-voltage range.
- The sink must support and request EPR. A device that needs only SPR will not become an EPR load because a higher-wattage charger is attached.
- The contract and power path must remain valid. Connectors, thermal design, firmware and protection behavior still have to operate within the exact product design.
TI’s technical comparison of SPR and EPR describes EPR fixed levels at 28V, 36V and 48V up to 5A and distinguishes the EPR mode from ordinary SPR operation. Use those figures as protocol context, not as a claim about a particular ChargeKeku product.
An EPR cable is necessary but not sufficient
An EPR-rated cable communicates relevant capability, but it cannot make an SPR source or sink negotiate EPR. It also does not prove data rate, display support, connector durability or performance in an installed routing. The existing 240W USB-C cable guide owns cable marking and selection details.
For an end-to-end requirement, identify the cable length, rated current and EPR marking, then verify the cable identity with appropriate equipment. Measure the finished assembly under the intended load and inspect both connectors. Do not treat an e-marker reading as a substitute for loaded electrical and thermal validation.
EPR changes voltage-management and design margin
Above the SPR range, the product must safely manage higher bus voltages. Component ratings, creepage and clearance, connector behavior, power-stage topology, transient response, firmware state handling and protection strategy all become part of the product design. The USB-C connector shape remains familiar, but the electrical design behind it is not interchangeable with a low-power port.
EPR also supports Adjustable Voltage Supply (AVS) behavior in the relevant specification framework. AVS and PPS are not interchangeable labels. PPS is already part of the broader PD ecosystem and is covered by a separate task; EPR identifies the extended power range and its operating requirements. A product brief should state which fixed and adjustable modes the exact source and sink actually support.
Select a chain from the sink backward
| Question | Evidence to request | Failure if assumed |
|---|---|---|
| What does the sink request? | Exact supported PD/EPR profiles, firmware and behavior across battery and temperature states. | An oversized source may stay at an SPR or lower contract. |
| What does the source offer? | Port-specific fixed/adjustable profiles, simultaneous-port policy and sustained test record. | Marketing total wattage may not be available on the target port. |
| What cable completes the path? | EPR/current identity, length, finished-cable record and connector evidence. | The connection may not enter or sustain the intended range. |
| How is the result verified? | Negotiated contract, device-side behavior, loaded voltage/current and temperature method. | One displayed wattage can hide negotiation, throttling or measurement differences. |
A controlled EPR validation plan
- Record the exact source port, cable, sink, firmware, battery state and ambient condition.
- Confirm source and sink documentation names the intended EPR profiles; do not infer capability from USB-C alone.
- Verify cable identity and physical condition with equipment rated for the expected range.
- Observe the negotiated PD contract using an appropriately rated analyzer; avoid improvised exposed conductors.
- Apply the real sink workload and allow the system to reach a stable thermal state under defined stop criteria.
- Record power behavior at start-up, sustained load, battery-state transitions and reconnects.
- Repeat across samples and after changes to the cable, port controller, firmware, enclosure or power stage.
Common SPR-versus-EPR mistakes
- Calling every USB PD 3.x port an EPR port.
- Assuming a 240W cable makes a 100W charger deliver more power.
- Reading charger total wattage as per-port wattage.
- Using “EPR,” “AVS” and “PPS” as synonyms.
- Publishing a maximum without stating the exact voltage, current and supported device.
- Testing higher-voltage power paths with unrated adapters, meters or exposed breakout wiring.
Specify the complete EPR path
Start with the sink’s required profiles, then define the source port, cable identity, length, environment and acceptance method. Review the USB-C to USB-C charging cable category only after those requirements are clear. A category route does not prove that every cable is EPR-rated, supports the same data functions or will deliver the maximum with every device.