Startup circuit and high speed cable using the same
A High Definition Multimedia Interface (HDMI) cable carries high speed encoded data, which are transmitted differentially over data channels, along with a clock. A Mobile High-Definition Link (MHL) cable carries high speed data which are multiplexed to achieve smaller connectors with fewer pins. A MHL-to-HDMI cable is proposed, which includes an embedded MHL to HDMI adapter device for demultiplexing the received MHL-formatted signal and outputting an HDMI-formatted signal. The embedded circuit is powered by a combination of power sources, the power being harvested from the high-speed HDMI signals themselves, including a startup circuit harvesting power from a low speed HDMI signal when power from the high-speed HDMI signals is not available.
1. A startup circuit for supplying a power signal of a predetermined voltage to an electronic device, the startup circuit comprising:
a power harvesting driver for obtaining an electrical power of a lower voltage, lower than the predetermined voltage, from at least one differential signal line coupled to the electronic device and powered by the electronic device; and
a voltage raiser circuit for receiving the lower voltage and outputting the power signal of the predetermined voltage.
2. The startup circuit of claim 1 , further comprising:
a presence detector indicating an availability of the electrical power of the lower voltage; and
a first switch device for switching the electrical power of the lower voltage to the voltage raiser circuit provided the presence detector indicates the electrical power of the lower voltage is available.
3. The startup circuit of claim 2 , further comprising a bootstrapping circuit for generating a startup voltage by obtaining power from at least one auxiliary control line coupled to the electronic device and supplying the obtained start-up voltage to the voltage raiser circuit provided the presence detector indicates the electrical power of the lower voltage is not available.
4. The startup circuit of claim 3 , wherein the bootstrapping circuit comprises:
a storage capacitor for storing the startup voltage;
a second switch for Switching the startup voltage from the storage capacitor to the voltage raiser circuit; and
a third switch for charging the storage capacitor from the at least one of the auxiliary control line.
5. The startup circuit of claim 4 , wherein the bootstrapping circuit comprises a startup control logic circuit for operating the second and third switches according to a predefined sequence.
6. The startup circuit of claim 5 , wherein the control logic circuit comprises an oscillator and a counter for generating the predefined sequence.
7. The startup circuit of claim 6 , wherein the bootstrapping circuit comprises a first resistor for use in charging the storage capacitor, and a second resistor for supplying the startup voltage to the startup control logic circuit.
8. The startup circuit of claim 1 , the startup circuit being embedded in a cable.
9. The startup circuit as described in claim 1 , the electronic device being a High Definition Multimedia Interface (HDMI) sink device.
10. The startup circuit as described in claim 1 , the predetermined voltage being nominally about 5V.
11. The startup circuit as described in claim 9 , wherein the at least one differential signal line is a high speed Transition Minimized Differential Signaling (TMDS) channel, and the at least one auxiliary signal line is a Consumer Electronics Control (CEC) line.
12. A method for providing a power signal of a predetermined voltage to an input of a HDMI sink device from an electronic device generating HDMI signals from another input of the HDMI sink device, the method comprising:
(a) connecting the electronic device to the input and the another input of the HDMI sink device;
(b) obtaining an electrical power of a lower voltage, lower than the predetermined voltage, from at least one of the HDMI signals on the another input; and
(c) increasing the lower voltage to the predetermined voltage in a voltage raiser circuit; and
(d) supplying the predetermined voltage to the input of the HDMI sink device.
13. The method of claim 12 , further comprising:
indicating an availability of the electrical power of the lower voltage; and
switching the electrical power of the lower voltage to the voltage raiser circuit provided the electrical power of the lower voltage is available.
14. The method of claim 12 , further comprising generating a startup voltage by obtaining power from at least one auxiliary control lines coupled between the HDMI sink device and the electronic device, and supplying the obtained startup voltage to the voltage raiser circuit provided the electrical power of the lower voltage is not available.
15. The method of claim 14 , wherein the generating the startup voltage comprises:
charging a storage capacitor to the startup voltage from the at least one auxiliary control lines; and
switching the startup voltage from the storage capacitor to the voltage raiser circuit.
16. The method of claim 15 , wherein the charging the storage capacitor comprises charging the storage capacitor until a predefined level of charge is reached, and switching power stored in the capacitor to the voltage raiser circuit.
17. The method of claim 16 , wherein the charging and the switching is performed according to a predefined sequence; and repeating the predefined sequence until the electrical power of the lower voltage is available.
18. The method of claim 12 , wherein the predetermined voltage is nominally about 5V.
19. The method of claim 12 , wherein the at least one of the HDMI signals is a high speed Transition Minimized Differential Signaling (TMDS) channel, and the at least one auxiliary signal line is a Consumer Electronics Control (CEC) line.
20. A method for providing a power signal of a predetermined voltage to an electronic device coupled to a start circuit through at least one differential signal line and at least one auxiliary control signal line, the method comprising:
(a) obtaining an electrical power of a lower voltage, lower than the predetermined voltage, from the at least one differential signal line through a power harvesting driver;
(b) increasing the lower voltage to the predetermined voltage in a voltage raiser circuit; and
(c) supplying the predetermined voltage from the voltage raiser circuit to the electronic device.
21. The method of claim 20 further comprising:
indicating an availability of the electrical power of the lower voltage;
switching the electrical power of the lower voltage to the voltage raiser circuit provided the electrical power of the lower voltage is available;
generating a startup voltage by obtaining power from the at least one auxiliary control line; and
supplying the obtained startup voltage to the voltage raiser circuit provided the electrical power of the lower voltage is not available.