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Possible Faults and Protection Flow in PAG1 - KBA231878

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Possible Faults and Protection Flow in PAG1 - KBA231878

Author: SananyaM_56           Version: **

The faults in PAG1 are divided into source-side faults, load-side faults, and internal faults.

Source-Side faults

Load-Side faults

Internal faults

Overcurrent

Overcurrent

Over temperature

Undervoltage

Short circuit

Overvoltage

Undervoltage

Overvoltage

For more details about the test cases and relevant procedures for these protection schemes, see the 18W PAG1S+PAG1P Design files. Also see the PAG1P Primary Side Start up Controller datasheet and PAG1S - CYPAS111 USB-PD Power Adapter Secondary Side Controller datasheet.

For all protection schemes, the following general flow of protection applies:

Fault event > Immediate protective action > Post-fault behaviour

The following changes must be made in the EZ-PD Configuration Utility tool. See the test report of the 18W PAG1P+PAG1S design file for relevant waveforms.

  1. Threshold: The set voltage/current level in percentage for protective action. It specifies the excess voltage margin (in percentage of the rated voltage) that is allowed before the overvoltage protection mechanism kicks in.
  2. Retry Count: The number of times the N-Type NFET Gate Driver (NGDO) attempts to supply power after the fault condition.
  3. Debounce period: The minimum time (in µs) for which the fault has to persist. Transient events that last for short durations can be ignored by the firmware. This parameter specifies the debounce period (in us) that should be applied before a fault is detected.

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Figure 1. OCP feature in EZ-PD Configuration utility

See the following for PAG1 load-side protection of events. See the PAG1S - CYPAS111 USB-PD Power Adapter Secondary Side Controller datasheet for details.

Protection Feature

Fault Event

Immediate Protective Action

Post-Fault Behavior

Overcurrent Protection

Current increases beyond the set OCP threshold.

For example, 3x1.2 = 3.6 A

NGDO turns off in approximately 10 µs

Retry the set “Retry Count” times.

Turn off NGDO if fault persists.

For example, Retry Count = 2

Overvoltage Protection

Voltage exceeds the set OVP threshold.

For example, 5x1.2 = 6 V

NGDO turns off in approximately 10 µs

Retry the set “Retry Count” times.

Turn off NGDO if fault persists.

For example, Retry Count = 2

Undervoltage Protection

Output voltage falls below the set UVP threshold.

For example: 5x 0.7 = 3.5 V

NGDO turns off in approximately 10 µs

Retry the set “Retry Count” times.

Turn off NGDO if fault persists.

For example, Retry Count = 2

Short-Circuit Protection

Output current exceeds the threshold value of 6 A.

NGDO turns off in approximately 10 µs

Retry the set “Retry Count” times.

Turn off NGDO if fault persists.

For example, Retry Count = 2

Over-temperature Protection

Temperature at the sense point exceeds the cut-off value.

NGDO turns off in approximately 10 µs

Wait for the temperature to fall below the Restart value.

Turn on NGDO.

When any of these fault conditions occur, detach and the reattach the USB type-C cable to reestablish the contract. To always retry, make the Retry Count as 255.

The following table lists the PAG1 source-side fault conditions and their detection pins:

Fault Condition

Detection Pin

Input Undervoltage

VDDD700

Input Overvoltage

VDDD700

Overcurrent

CS

Secondary Over Voltage

OVP_AUX

Figure 2. Flyback converter circuit with Cypress’s primary side controller PAG1P

See the following table for PAG1 source-side protection flow of events. See the PAG1P Primary Side Start up Controller datasheet for details.

Protection Feature

Fault Event

Immediate Protective Action

Post-Fault Behavior

Undervoltage Protection

VDD falls below 90 V.

(debounce = 30 ms)

Gate pulses are turned off.

Auto-restart if VDD700>100 V.

PAG1P will wait TAR seconds before a soft start. This sequence is repeated three times.

Overvoltage Protection

VDD rises above 448 V.

Gate pulses are turned off.

Auto-restart if VDD<445 V.

PAG1P will wait TAR seconds before a soft start. This sequence is repeated thrice.

Overcurrent Protection

When the CS pin voltage exceeds V_CSTH1 = 0.5 V.

Limits the primary current by turning OFF the primary FET.

Output voltage falls. Delivers limited power because of limited duty (for closed loop) and auto restarts (for open loop)

Secondary Overvoltage Protection

OVP_AUX pin voltage exceeds 1.2 V. (blanking time=2 us)

Gate pulses are turned off.

Auto-restart if OVP_AUX < 1.2 V

  • OVP_AUX functionality is applicable only if the system is in open loop. For example: Soft start.
  • The undervoltage fault handling flow mentioned here is for Non-x-cap mode.
  • The overvoltage fault handling flow is the same for both with x-cap and without x-cap conditions
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