50 lines
2.4 KiB
Markdown
50 lines
2.4 KiB
Markdown
The PD blocker removes Power Delivery (PD) capabilities from USB-C connections and provides over-voltage protection.
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<img src="picture/v2_front.webp" title="front" height="250"/>
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<img src="picture/v2_back.webp" title="back" height="250"/>
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purpose
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=======
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Some USB-C devices do not require the Power Delivery features available on USB-C, mainly higher voltage and current.
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The device could not even be rated for higher voltages.
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But chargers might be stuck at higher voltage, or mischievous eMarked cables (with PD-capable chips built in) could raise the voltage, permanently damaging it.
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The PD blocker protects your [expensive] USB-C device from such damages.
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usage
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=====
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Insert the PD blocker in line, between the power source (e.g. charger or host computer), cable, and your device.
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It can be inserted between any two of these components, and will work the same.
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Plug and receptacle can be either side, and it is reversible along the axis of the connectors (like normal USB-C connectors).
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The PD blocker will prevent any Power Delivery communication, such as raising the voltage.
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And when over-voltage is detected (Vbus > 5.5V), power is cut and an OVP LED indicating the culprit side lights up.
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Connect the PD blocker before the target device for the protection to take effect before it can reach it.
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All other features of USB-C are preserved (e.g. USB2, USB3, USB4, SBU, orientation detection)
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Some alternate modes requiring PD communication will not work anymore though.
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mode of operation
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=================
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To prevent PD communication, capacitors are placed on the CC lines.
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They smooth out the 300 Kbps BMC signal used for PD communication.
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It still allows the identification of Rp, Rd, and Ra used for orientation and role detection.
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Additionally there is an over-voltage protection circuit.
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VBUS (on either side) is compared to a reference voltage.
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When VBUS is below 5.5V, p-channel MOSFETs are switched on, and allow VBUS going from one side to the other.
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When VBUS is above 5.5V, the p-channel MOSFETs are switched off, and prevent VBUS interconnection, cutting the power.
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warning
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=======
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The PD blocker can block up to 36V.
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PD rev 2.0 specifies voltages up to 20V.
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PD rev 3.0 specifies voltages up to 48V, but I haven't seen any power source using this new capability yet.
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The PD blocker can take a seconds (at 5.6V) until the over-voltage protection take effect.
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Connect the PD blocker before the target device for the protection to take effect before it can reach it.
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