Over the previous couple of years, the USB Sort-C® with Energy Supply (PD) commonplace has been adopted in all kinds of electronics. This adoption has been pushed by advantages similar to a unified port (decreasing e-waste), the comfort of a reversible connector, and high-power functionality.
As Desk 1 exhibits, the most recent launch of USB PD 3.1 extends the ability functionality of USB as much as 240 W, greater than doubling the 100 W of obtainable energy from the earlier USB PD 3.0 specification. This enables a variety of recent purposes to now be powered from USB. With a purpose to cut back e-waste, the European Union and India have began passing laws mandating USB Sort-C for private electronics in 2025, and it’s anticipated that this pattern will doubtless lengthen to different purposes similar to energy instruments, good audio system, vacuum cleaners, e-bike chargers and networking. These traits and rules are forcing producers to hunt out easy and cheap methods to transform the ability connectors on their merchandise from a barrel jack to a USB-C connector.
Desk 1 USB energy requirements the place the most recent USB PD 3.1 launch extends the ability functionality of USB as much as 240 W. Supply: Texas Devices
On this Energy Tip, we’ll talk about system energy concerns and exhibit how one can shortly and simply implement a USB-C connector and energy administration circuitry that negotiates the suitable USB PD contract for the ability necessities your design.
USB PD energy flows
It’s also value noting that there are three forms of energy circulate within the USB PD ecosystem: gadgets that may solely sink energy, gadgets that may solely supply energy, or gadgets that permit bi-directional energy circulate (dual-role energy.) On this article, we’ll deal with sink-only purposes.
Earlier than a sink system using USB PD can settle for energy from a USB PD energy supply, some hand-shaking and negotiation should happen between the system being powered and the ability supply. It is because the voltage on the USB PD energy bus may be variable from 5 V to 48 V, relying on the ability functionality of the ability supply. Clearly, you wouldn’t wish to apply 48 V to a sink system that’s solely designed to function from a 15 V enter supply. In a USB PD sink utility, a devoted system known as a port controller is required to carry out this energy contract negotiation and supply protections like over-current and over-voltage. Beforehand, including a USB PD port controller configured with the right performance required in-depth information of the USB certification and a considerable amount of firmware growth effort. To simplify the ability structure and cut back design complexity, a preprogrammed USB PD controller permits the designer to configure the utmost and minimal voltage and present sink functionality by way of a easy resistor-divider setting, as proven in Desk 2. This removes the necessity for exterior electrically erasable programmable read-only reminiscence (EEPROM), an MCU, or any sort of firmware growth.
Desk 2 The ADCIN pin of a preprogrammed USB PD controller that permits designers to configure the max and min voltage in addition to the present sink functionality by way of a easy resistor divider setting. Supply: Texas Devices
Negotiating energy contracts and matching system energy necessities
Earlier than changing your product to USB PD, you will need to perceive the restrictions and necessities of the USB PD ecosystem. On the supply aspect of the cable, a USB PD energy supply will probably be offering energy to your system, however the individual utilizing your product may join completely any USB PD adapter or different energy supply. You must contemplate what energy contract is required to supply full energy to your system. As well as, contemplate how your system will behave if inadequate energy is out there from that adapter.
The obtainable present by way of the USB Sort-C cable is restricted to three A for voltages under 20 V, and 5 A for voltages 20 V and above. Moreover, USB PD energy sources are solely required to generate the minimal voltage needed to supply rated energy on the most allowed cable present. For instance, a forty five W adapter will usually present a most output voltage of 15 V, since 45 W divided by 3 A is 15 V.
What in case your system is designed to run from a 15 V supply, however wants 50 W of energy? On this case, it is advisable to configure your port controller to just accept a better voltage contract (e.g., 20 V) to make sure you have sufficient energy to run your system, and it is advisable to guarantee your system is designed to deal with this barely increased enter voltage. This may increasingly require you to make slight modifications to your product past simply including the USB Sort-C connector and port controller. Moreover, usually you continue to need your product to be purposeful when linked to a USB PD supply with inadequate energy capability, however maybe function at diminished efficiency stage.
Design instance
Think about, a product that should cost a 4S-7S battery at 27 W that was beforehand powered by way of a 15 V barrel jack. On this instance, a buck-or-boost converter was used, because the battery voltage might be increased or decrease than the 15 V enter, relying on the state of cost. Changing this design to a USB PD enter solely requires a easy stand-alone USB PD controller just like the TPS25730 and buck-boost battery charger. Determine 1 exhibits the system structure. You may see that only some elements have been required to transform the barrel jack to a USB PD port. The straightforward resistors linked to the ADCIN1 by way of ADCIN4 pins set the ability profile with out the necessity for any firmware growth. On this case, the product should nonetheless cost from a 5 V energy supply regardless that obtainable energy is diminished, so the TPS25730 is configured for a 20 V most voltage and 5 V minimal voltage, with the working present set to three A.
Determine 1 The 27W USB PD sink-only charger reference design block diagram. Supply: Texas Devices
Enter voltage dynamic energy administration
Moreover supporting a USB PD supply enter, the design must also assist legacy USB enter sources, similar to 5 V and a couple of A. To keep away from collapse of the enter voltage when the enter energy is restricted, the BQ25756E offers an enter voltage dynamic power-management characteristic within the BQ25756E which is able to cut back the cost present if the enter voltage drops to a price set by the parameter Vin_dpm. The Vin_dpm must be set barely decrease than the enter voltage minus the voltage drop by way of the cable and energy path in order that it could actually maximize the battery cost present whereas not overloading the enter supply, or creating an instability on the enter bus.
Determine 2 exhibits experimental outcomes charging from a 5 V, 2 A supply with a 1 meter USB cable (0.25 Ω resistance). Whenever you set Vin_dpm to 4.75 V, you may see that the enter cost present is restricted and unstable (left aspect of Determine 2). When correctly configured, with the Vin_dpm set to 4.35 V to account for the resistive drop, the enter voltage is secure and the cost present is elevated by 50%, which is able to considerably shorten charging occasions.
Determine 2 Enter dynamic energy administration when charging from a 5 V, 2 A supply with a 1 m USB cable. Supply: Texas Devices
Implementing USB PD
With a simplified USB PD controller and battery charger structure, you don’t must have in-depth information of USB PD. Not solely are you able to eradicate the necessity for an additional MCU and EEPROM (and exert no firmware effort), however you should use only a easy resistor divider to configure your voltage and present sink functionality and shortly convert your barrel jack to a USB Sort-C enter. For full particulars of the instance design highlighted right here, try the 27W USB Energy Supply Sink-Solely Charger Reference Design for 4- to 7-Cell Batteries.
Writer bios
Max Wang has been a programs engineer for the Energy Design Providers staff at Texas Devices, the place he’s accountable for energy resolution and reference designs for industrial and private electronics purposes. He just lately created a collection of high-efficiency compact AC/DC and DC/DC USB Sort-C® PD charger options. Earlier than becoming a member of TI, he labored at Delta, Energy Integrations, and Infineon. He has a grasp’s diploma in electrical engineering from Zhejiang College in Hangzhou, China.
Brian King is a programs supervisor and senior member technical employees at Texas Devices. He has over 28 years of expertise in energy provide design, specializing in remoted AC-DC and DC-DC purposes. Brian has labored immediately with clients to assist over 1300 enterprise alternatives and has designed over 750 distinctive energy provides utilizing a broad vary of TI energy provide controllers with a deal with maximizing effectivity and minimizing resolution measurement and value. He has printed over 45 articles associated to energy provide design, and since 2016 is the lead organizer and content material curator for the Texas Devices Energy Provide Design Seminar (PSDS) collection, which offers coaching to 1000’s of energy engineers worldwide frequently. Brian acquired an MSEE and a BSEE from the College of Arkansas.
Relate Content material
- Energy Suggestions #129: Driving excessive voltage silicon FETs in 1000-V flybacks
- Energy Suggestions #128: Designing a excessive voltage DC-link capacitor energetic precharge circuit
- Energy Suggestions #75: USB Energy Supply for automotive programs
- USB: Deciphering the signaling, connector, and energy supply variations
- USB Energy Supply: incompatibility-derived foibles and failures
googletag.cmd.push(perform() { googletag.show(‘div-gpt-ad-native’); });
–>
The put up Energy Suggestions #130: Migrating from a barrel jack to USB Sort-C PD appeared first on EDN.
