Over the previous few years, the USB Sort-C® with Energy Supply (PD) normal 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 reveals, the newest launch of USB PD 3.1 extends the ability functionality of USB as much as 240 W, greater than doubling the 100 W of accessible energy from the earlier USB PD 3.0 specification. This permits 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 possible prolong to different purposes similar to energy instruments, good audio system, vacuum cleaners, e-bike chargers and networking. These tendencies 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 newest 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 focus on 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 is usually price noting that there are three kinds of energy stream within the USB PD ecosystem: gadgets that may solely sink energy, gadgets that may solely supply energy, or gadgets that enable bi-directional energy stream (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 improvement 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 kind of firmware improvement.
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 constraints and necessities of the USB PD ecosystem. On the supply facet of the cable, a USB PD energy supply shall be offering energy to your system, however the particular person utilizing your product may join completely any USB PD adapter or different energy supply. You must take into account what energy contract is required to offer full energy to your system. As well as, take into account how your system will behave if inadequate energy is out there from that adapter.
The accessible present by way of the USB Sort-C cable is restricted to three A for voltages beneath 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 offer 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’s essential to configure your port controller to just accept the next voltage contract (e.g., 20 V) to make sure you have sufficient energy to run your system, and it’s essential to guarantee your system is designed to deal with this barely increased enter voltage. This will 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 related to a USB PD supply with inadequate energy capability, however maybe function at decreased efficiency stage.
Design instance
Contemplate, 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 may very well 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 reveals the system structure. You’ll be able to see that just a few elements had been required to transform the barrel jack to a USB PD port. The straightforward resistors related to the ADCIN1 by way of ADCIN4 pins set the ability profile with out the necessity for any firmware improvement. On this case, the product should nonetheless cost from a 5 V energy supply although accessible energy is decreased, 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 also needs to 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 gives an enter voltage dynamic power-management function within the BQ25756E which can cut back the cost present if the enter voltage drops to a price set by the parameter Vin_dpm. The Vin_dpm ought to be set barely decrease than the enter voltage minus the voltage drop by way of the cable and energy path in order that it might probably maximize the battery cost present whereas not overloading the enter supply, or creating an instability on the enter bus.
Determine 2 reveals experimental outcomes charging from a 5 V, 2 A supply with a 1 meter USB cable (0.25 Ω resistance). Once you set Vin_dpm to 4.75 V, you may see that the enter cost present is restricted and unstable (left facet 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 can 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 have to 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 utilize 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 techniques engineer for the Energy Design Companies crew at Texas Devices, the place he’s liable 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 techniques supervisor and senior member technical workers 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 instantly with prospects 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 dimension and value. He has revealed 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 gives coaching to 1000’s of energy engineers worldwide regularly. Brian acquired an MSEE and a BSEE from the College of Arkansas.
Relate Content material
- Energy Ideas #129: Driving excessive voltage silicon FETs in 1000-V flybacks
- Energy Ideas #128: Designing a excessive voltage DC-link capacitor energetic precharge circuit
- Energy Ideas #75: USB Energy Supply for automotive techniques
- USB: Deciphering the signaling, connector, and energy supply variations
- USB Energy Supply: incompatibility-derived foibles and failures
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The submit Energy Ideas #130: Migrating from a barrel jack to USB Sort-C PD appeared first on EDN.
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