Patent Application
20160204711
1. Field of the Invention
This invention relates to Alternating Current (AC) and Direct Current (DC) Power Adapters, also referred to as power supplies, car and/or wall adapters. More particularly, the invention relates to a short circuit detection retry limiter operable to inhibit conventional Power Adapter retry circuitry from causing additional damage after detection of a short circuit in power conductors and/or electrical hardware connected to the Power Adapter.
2. Description of Related Art
Power Adapters are used to provide DC electrical power for a wide range of power consuming devices, such as cellular telephones and other power consuming devices for ongoing operation of such devices and/or for re-charging batteries of these devices. Many power consuming devices have standardized power requirements, such as the 5 Volt Direct Current (VDC) power available from a Universal Serial Bus (USB) interface, enabling a single Power Adapter to be utilized to power and/or charge different devices and/or multiple devices simultaneously.
Each power consuming device may be connected to the Power Adapter via an adapter cable that may or may not have been provided by the supplier of the Power Adapter. The quality and/or condition of such adapter cables and their connectors may vary widely, as does user treatment of the adapter cables. Normal use and/or user abuse may result in unintended interconnections within the adapter cable and/or its connectors resulting in intermittent short circuits between the power conductors. Such short circuits may develop, for example, in an adapter cable as the adapter cable is repeatedly bent/flexed/stretched and internal strands of the conductors break and/or the cable insulation is compromised.
As some detectable “short circuits” are passing occurrences, for example from interconnect and/or disconnect action, instead of permanently disabling itself upon detection of a short circuit a Power Adapter may be configured to shut off for a short period and then supply a short circuit recovery test pulse to test if the short condition is still present. If the short circuit is no longer present, power delivery to the connected power consuming devices is once again energized. If a short circuit indication is again detected, the Power Adapter will wait another time interval before initiating another test current pulse.
Therefore, an object of the invention is to provide Power Adapter solutions that overcome deficiencies in the prior art.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, where like reference numbers in the drawing figures refer to the same feature or element and may not be described in detail for every drawing figure in which they appear and, together with a general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the invention.
The initial contact between frayed conductor strands of an adapter cable is typically low resistance, whereupon the Power Adapter detects a short circuit and folds back or reduces the average current delivered to the fault as designed. However, the inventor's have recognized that, over time, a transient short circuit resulting from cable fray or the like may evolve into a more substantive resistive short which the Power Adapter may no longer detect as being a short circuit. This is especially true for higher current model Power Adapters where normal load resistances do not differ greatly from the resistance level selected to be indicative of a short circuit. Once an adapter cable or connector short circuit has transitioned into a resistive short circuit, then the Power Adapter's available power can be delivered to the fault and the fault region begins to heat, melt and/or char the cable, the connector and/or the surrounding area, potentially resulting in significant damage.
Because the short circuit recovery test current pulses of conventional Power Adapters will continue indefinitely, this may enable a short circuit, such as frayed conductors of an attached adapter cable, to further develop into a resistive short that is no longer detectable by the Power Adapter, leading to further resistive short heat generation, melting and charring, even if the Power Adapter has “short circuit detection protection”.
To prevent these forms of failure, the inventors have developed a Power Adapter with an automatic retry limiter. That is, circuitry of the Power Adapter that monitors for current test pulses indicating the presence of a short circuit. Should a number of current test pulses be detected which exceeds a threshold number of test pulses, the Power Adapter is shut down until reset. Thus, the scenario of an intermittent short evolving into a hazardous resistive fault may be greatly reduced, thereby improving the safety of the Power Adapter.
As shown in
The voltage regulator 15 of the power supply portion 2 further includes current monitoring circuitry wherein if an out of range current level is detected, the voltage regulator 15 disables output voltage power delivery and shifts to a repeating test current pulse mode wherein a test pulse is generated according to a preset interval (such as one second) to determine if the short circuit is still present. If monitoring of the test pulse indicates the short circuit is no longer present, normal operation (power delivery to the connected power consuming devices) is resumed. If not, a further time interval is initiated and another current pulse generated.
The Power Adapter has over-current-event detection circuitry, such as a pulse detector 30, coupled to the voltage regulator 15, monitoring the voltage regulator 15 for current pulses. To prevent false pulse counts, the pulse detector 30 may be configured to recognize only pulses of a specific magnitude and/or duration. If a conforming current pulse is detected, a digital counter 35 coupled to the pulse detector 30 is incremented. To avoid accumulation of unrelated short circuit event re-try pulse counts, the digital counter 35 may be configured to reset to zero counts if no pulses are detected during a preset period of time.
If the digital counter 35 reaches a preset maximum pulse value a disable signal is activated by the digital counter 35 which engages a disable latch 40, for example a silicon-controlled rectifier (SCR) enabled by a pulse delivered to the gate of the SCR. Once enabled, a voltage delivered through the SCR disables the voltage regulator 15 of the power supply portion 2. Because the SCR stays engaged until current flowing through it is discontinued, once the SCR is enabled by the digital counter 35 reaching the maximum pulse value it will stay latched on, maintaining the disable signal for the voltage regulator 15, and thereby disabling the power supply portion 2 (and thus the AC Adapter) until AC power 20 is removed. A further reset delay circuit, such as a capacitor network 45 may be applied to set an off period before the current through the engaged SCR reaches a minimum value, enabling disconnection of the disable latch 40 only after a preset minimum interval of power removal (disconnection of the AC Adapter from AC power 20 and reconnection).
An exemplary DC Power Adapter for use, for example, with the 12 VDC power typically available in automobiles is shown in
In a method of operation, as shown for example in
The method of operation similarly applies to the DC Power Adapter embodiment of
One skilled in the art will appreciate that the automatic retry limiter prevents endless short circuit test pulse generation by the voltage regulator, without inhibiting automatic recovery by the Power Adapter from momentary short circuits. It will also automatically limit power to a short circuit in the connected device such as a cellular handset or portable music device. The automatic counter reset also prevents accumulation of fault counts so as to not incorrectly attribute them to a normally functioning adapter cable or connected device.
Where in the foregoing description reference has been made to materials, ratios, integers or components having known equivalents then such equivalents are herein incorporated as if individually set forth.
While the present invention has been illustrated by the description of the embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative apparatus, methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departure from the spirit or scope of applicant's general inventive concept. Further, it is to be appreciated that improvements and/or modifications may be made thereto without departing from the scope or spirit of the present invention as defined by the following claims.
| Number | Date | Country | |
|---|---|---|---|
| 62102233 | Jan 2015 | US |
