Field

The invention relates to an accessory. Background

Various accessories such as battery chargers are very widespread due to popularity of various portable apparatuses such as mobile phones. The interplay between the accessory and the connected device requires further sophistication. One specific problem: how to detect whether the accessory is connected to or disconnected from the connected device? Brief description

The present invention seeks to provide an improved accessory. According to an aspect of the present invention, there is provided an accessory as specified in claim 1 .

The invention may provide the advantage that the accessory detects it is connected to or disconnected from the connected device.

List of drawings

Example embodiments of the present invention are described below, by way of example only, with reference to the accompanying drawings, in which

Figures 1 , 2 and 3 illustrate example embodiments of an accessory and a connected device; and

Figures 4 and 5 illustrate further example embodiments of the accessory and the connected device.

Description of embodiments

The following embodiments are only examples. Although the specification may refer to "an" embodiment in several locations, this does not necessarily mean that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments. Furthermore, words "comprising" and "including" should be understood as not limiting the described embodiments to consist of only those features that have been mentioned and such embodiments may contain also features/structures that have not been specifically mentioned.

Figure 1 illustrates example embodiments of an accessory 100 and a connected device 160.

The accessory 100 comprises a connector 120 coupleable with a counterpart connector 140 of the connected device 160, and an electronic circuit 1 10.

The electronic circuit 1 10 is configured to control the accessory 100 such that a voltage from an ID pin 130 of the connector 120 is measured, and if the voltage is zero, the electronic circuit 1 10 determines that the counterpart connector 140 is disconnected 1 18 as it does not feed a detection voltage into the connector 120, or else the electronic circuit 1 10 determines that the counterpart connector 140 is connected 1 16 as it continues to feed the detection voltage into the connector 120.

In an example embodiment, the electronic circuit 1 10 is configured to control the accessory 100 such that if the accessory 100 acts as a host, the ID pin 130 of the connector 120 is connected 1 12 to the ground, or else if the accessory 100 acts as a device, the ID pin 130 of the connector 120 is disconnected 1 14 from the ground.

This feature utilizes the fact that an electronic circuit 150 of the connected device 160 detects from the ID pin 130 of the counterpart connector 140 whether the accessory 100 acts as a host (in which case the accessory 100 connects 1 12 the ID pin 130 of the connector 120 to the ground), or as a device (in which case the accessory 100 disconnects 1 14 the ID pin 130 of the connector 120 from the ground), and, in order to be able to perform the detection, the electronic circuit 150 of the connected device 160 first feeds 152 detection voltage into the ID pin 130, whereupon, the electronic circuit 150 of the connected device performs the detection 154. If the current flows, the ID pin 130 is connected to the ground, or if there is high impedance, the ID pin 130 is disconnected from the ground. In essence, the novel feature utilizes the detection voltage applied to the ID pin 130 to detect whether the accessory 100 is connected to or disconnected from the connected device 160.

In an example embodiment, the accessory 100 operates according to the USB OTG (Universal Serial Bus On-The-Go) -standard. The USB OTG allows a USB device (a mobile phone, for example) to act as a host, which allows another USB device (a USB flash drive, for example) to be coupled with it.

There are many types of accessories 100 that may be connected to a host device 160, a charger 100 connected via a USB interface to a cellular phone 160 for example.

In an example embodiment, the connector 120 is a Universal Serial Bus USB connector, and the counterpart connector 140 is a USB counterpart connector.

As shown in Figure 4, the USB 1 .x/2.0 mini/micro connector has five contacts specified: VBUS 210, D- 308, D+ 310, ID 130, and GND 326.

An example embodiment uses the operation of the ID pin 130. The operation is specified so, that it determines if the device is plugged to "host" or "device":

ID pin 130 connected to ground: host; or

ID pin 130 not connected to the ground (high impedance): device. In order to detect the state of the ID pin 130, the connected device 160 applies some voltage to the ID pin 130, and then determines with ID comparators 400 if a current flows or not to detect if the ID pin 130 is connected to the ground.

As shown in Figure 4, the accessory 100 may comprise an ID impedance selection switch 406, which connects the ID pin 130 to the ground, or disconnects the ID pin 130 from the ground. The connected device 160 may comprise a pull-up resistor 402 to ensure that a signal in the ID pin 130 will be a valid logic level if high-impedance is introduced (if the ID pin 130 is disconnected from the ground by the ID impedance selection switch 406). In the example embodiments, this detection voltage is used to detect the presence of a host by an OTG device detection comparator 404 in the accessory 100. In addition this information may be used to detect when the host is removed, as the detection voltage then drops to zero.

In an example embodiment, the accessory 100 implements a zero power charger, which is initially powered only after the host (a cellular phone for example) is connected. After the initial connection and power up, there is no way to detect if the phone battery is full and not drawing current, or if the host was removed. The example embodiments, allow the detection of the host removal, which may then initiate the shutdown of the charger to a zero power state.

Figure 5 illustrates an example embodiment of operation of the zero power charger 100: voltage levels of the ID pin 130 and the VBUS pin 210 are shown as experienced by the accessory 100 and the connected device 160:

500) In an initial state, the device 160 is not connected to the charger 100.

502) The device 160 is connected to the charger 100.

504) The device detects that the ID pin 130 is grounded by the charger 100 and sets the VBUS 210 on.

506) The charger 100 sets the ID pin 130 impedance to a floating state and due to that the ID pin 130 goes to an up state by the ID pull-up.

508) The charger's 100 AC/DC power converter supplies 5 Volts to the VBUS pin 210.

510) The device 160 switches own VBUS pin 210 supply voltage down, and the charging will be started.

512) The charger 100 is removed from the device 160.

514) After a few seconds delay, the charger 100 is switched off.

In an example embodiment of Figure 2, the accessory 100 is a battery charger and the accessory 100 further comprises an electrical input connector 202 coupleable with mains electricity 200 (operating at 100-240VAC and 50-60Hz, for example), an AC/DC power converter 206 transforming a mains electricity power from the electrical input connector 202 to a lower voltage power for the connector 120, and an on/off-switch 204 between the electrical input connector 202 and the AC/DC power converter 206.

The connector 120 feeds power to a battery 220 of the connected device 160 via a charging circuit 222 if the on/off switch 204 is controlled on by the electronic circuit 1 10 such that the AC/DC power converter 206 is connected to the mains electricity 200, and if the electronic circuit 1 10 deternnines that the counterpart connector 140 is connected as it continues to feed the detection voltage into the connector 120.

In an example embodiment, the electronic circuit 1 10 is further configured to control the accessory 100 such that the accessory 100 first acts as a device and the ID pin 130 of the connector 120 is disconnected 1 14 from the ground, whereupon, if the electronic circuit 1 10 determines that the counterpart connector 140 is connected as it feeds 152 the detection voltage into the connector 120, the accessory 100 is controlled to act as a host and the ID pin 130 of the connector 120 is connected 1 12 to the ground, and the electronic circuit 1 10 controls the on/off-switch 204 on so that the the connector 120 starts to feed the power to the connected device 160 to be charged.

In an example embodiment, the electronic circuit 1 10 is configured to control the accessory 100 such that if the electrical input connector 202 remains connected to the mains electricity 200, but the electronic circuit 1 10 determines that the counterpart connector 140 is disconnected 1 18 as it does not anymore feed the detection voltage into the connector 120, the on/off- switch 204 is controlled off such that the AC/DC power converter 206 is disconnected from the mains electricity 200, whereby the accessory 100 stops to consume the mains electricity power.

Figure 3 illustrates a further example embodiment with hardware design details for a zero power USB charger 100. Naturally, this example embodiment illustrates just one implementation, as the required functionality may be implemented by other other hardware designs as well, such as with a microprocessor, for example. In an example embodiment, the operation of the charger 100 may be based on using both the host and device modes of USB OTG specification. The fact that in host mode the connected device 160 is required to feed voltage to the USB connector 120 is utilized to wake up the charger 100. After this wakeup normal charging will commence.

In an example embodiment, initially, the charger 100 is disconnected from the mains 200 with a relay 314. As a phone 160 or another USB OTG compatible device is connected, the charger 100 appears to be of USB OTG device type. This will cause the phone 160 to feed a voltage to the USB VBUS line 210, and a short pulse send by a power on pulse circuit 320 closes the relay 314 with relay control FETs 316, which starts the charger 100. The charger 100 will then change itself to a host type charger, which will cause the device 160 to detect it and a normal charging will start.

The advantage of this method is that it requires zero power when a device 160 is not connected.

In an initial state, AC supply connectors of the relay 314 are open, and no power is fed to the circuitry. The USB ID pin 130 is grounded by second connectors of the relay 314 which makes the charger 100 to indicate itself as a USB OTG type of a device.

In an example embodiment, the charger 100 is powered up by connecting a USB OTG compatible device 160 to the charger 100. The connected device 160 will recognize the charger 100 as a USB OTG type of device and will then supply 5V to the USB VBUS line 210. This will generate a pulse of about 500ms to a relay coil to set it to a power on state. A latch type of relay may be used to avoid a state change, for example in an AC power failure situation. The charger 100 is now indicated as a USB device and the connected device 160 will switch the USB VBUS 210 off and wait until the charger 100 will switch the VBUS 210 on. In an example embodiment, if an AC power is present, this will happen immediately, but if not, the charger 100 will be on a power on state until the AC power will be present the next time and the charger 100 will wake up then immediately. This kind of latch type of operation makes the functionality very easy to use and the device 160 will not recognize any AC power failures and will start again after the AC power will appear again.

In an example embodiment, the charger 100 may also wake up by a power on switch 312 if a device 160 without the USB OTG support is used. The power switch 312 needs also to be pressed, if a battery 220 of the connected device 160 is empty.

In an example embodiment, the charger 100 will power off when a charging current drops under 20mA, which is measured by a current amplifier 306 and a sense resistor 304, and there is no voltage in the USB ID pin 130. In an example embodiment, there is a delay circuit 318, which stops the charging with the relay control FETs after the delay, In an example embodiment, the delay of the delay circuit 318 is about seven seconds. The delay circuit 318 also avoids an unwanted power off switching. If the USB ID pin 130 has voltage, the output of a comparator 324 goes near zero, whereby a reference of a comparator 322 changes and it keeps the charging on, even if the charging current drops to zero,

In an example embodiment, the AC/DC power part 300 may be based of Tl's UCC28710D reference design with a custom transformer from Wurth. In an example embodiment, the connector 120 may provide a maximum 5V/2A output power.

It will be obvious to a person skilled in the art that, as technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the example embodiments described above but may vary within the scope of the claims.