Systems, methods, and media for providing power to an HDMI source

Systems, methods, and media for providing power to an HDMI source are provided. In accordance with some implementations, methods for providing power to an HDMI source are provided, the methods comprising: providing an AC signal to an HPD line of an HDMI port; determining that an L-C circuit is present on the HPD line when applying the AC signal; and in response to determining that an L-C circuit is present on the HPD line, connecting a power source to an HDMI 5V line of the HDMI port. In some implementations, the AC signal is a 231 kHz waveform. In some implementations, the AC signal is generated using a clock output. In some implementations, the methods further comprise integrating the clock output to provide the AC signal. In some implementations, the methods further comprise switching the frequency of the AC signal.

BACKGROUND

With recent advances in video and graphics rendering and communications has come source media devices (hereinafter, each an “HDMI source”) that are capable of plugging into an HDMI port of a sink media device (hereinafter, an “HDMI sink”) such as a television or monitor.

Currently, simple HDMI sources use external power supplies to provide power to those sources because the HDMI specification does not provide for an HDMI sink (such as a television) to provide power to the HDMI source through its HDMI connector. Avoiding using an external power supply may be desirable for a variety of reasons, such as cost and ease of use.

SUMMARY

Systems, methods, and media for providing power to an HDMI source are provided. In accordance with some implementations, methods for providing power to an HDMI source are provided, the methods comprising: providing an AC signal to an HPD line of an HDMI port; determining that an L-C circuit is present on the HPD line when applying the AC signal; and in response to determining that an L-C circuit is present on the HPD line, connecting a power source to an HDMI 5V line of the HDMI port. In some implementations, the AC signal is a 231 kHz waveform. In some implementations, the AC signal is generated using a clock output. In some implementations, the methods further comprise integrating the clock output to provide the AC signal. In some implementations, the methods further comprise switching the frequency of the AC signal. In implementations, determining that an L-C circuit is present on the HPD line comprises determining whether the AC signal is resonating in the L-C circuit. In some implementations, the methods further comprise: detecting a value of an HPD line of an HDMI sink; and providing the value to an HPD line of an HDMI source. In some implementation, the methods further comprise: determining that an L-C circuit is not present on the HPD line when applying the AC signal; and in response to determining that an L-C circuit is not present on the HPD line, disconnecting a power source from an HDMI 5V line of the HDMI port.

In accordance with some implementations, circuits for providing power to an HDMI source are provided, the circuits comprising: a microcontroller configured to: provide an AC signal to an HPD line of an HDMI port; determine that an L-C circuit is present on the HPD line when applying the AC signal; and in response to determining that an L-C circuit is present on the HPD line, connect a power source to an HDMI 5V line of the HDMI port. In some implementations, the AC signal is a 231 kHz waveform. In some implementations, the AC signal is generating using a clock output of the microcontroller. In some implementations, the circuits further comprise an integrator coupled to the clock output which integrates to the clock output to provide the AC signal. In some implementations, the microcontroller also switches the frequency of the AC signal. In some implementations, determining that an L-C circuit is present on the HPD line comprises determining whether the AC signal is resonating in the L-C circuit. In some implementations, the microcontroller also: detects a value of an HPD line of an HDMI sink; and provides the value to an HPD line of an HDMI source. In some implementations, the microcontroller also: determines that an L-C circuit is not present on the HPD line when applying the AC signal; and in response to determining that an L-C circuit is not present on the HPD line, disconnects a power source from an HDMI 5V line of the HDMI port.

DETAILED DESCRIPTION

In accordance with some implementations, mechanisms are provided for detecting if an HDMI source is connected to an HDMI port and, if yes, providing power through the HDMI port (e.g., using pin18of the port's HDMI connector, which is normally used by a TV to detect the presence of an HDMI source).

An example 100 of a mechanism in accordance with some implementations is shown inFIG. 1. As illustrated, mechanism100can be implemented as a detection module102that is present between an HDMI sink104and an HDMI source106. In some implementations, the detection module uses a presence line110(e.g., an “HPD” line) of a port108to detect the presence of the HDMI source by applying a low voltage stimulus (e.g., which may be harmless to an unpowered source) to determine if a resonant L-C circuit112of the HDMI source can be detected. When the resonant L-C circuit of the HDMI source has been detected, the detection module may then apply a supply voltage (e.g., a 5V supply voltage via a “permanent 5V” line114) to a supply voltage line116(e.g., an “HDMI 5V” line). The sink in turn may set presence line110(e.g., the “HPD” line) active high and the detection module may then propagate the active high signal to the source.

Although detection module102ofFIG. 1is illustrated as being located between a port of HDMI source106and HDMI sink104, the detection module can be integrated with or can be part of HDMI sink104in some implementations so that the port of the HDMI sink is port108in some implementations.

The detection module may then continuously or periodically probe presence line110(e.g., the “HPD” line) to detect the removal of the HDMI source, in which case the detection module may disconnect the supply voltage (e.g., from the “permanent 5V” line) from supply voltage line116(e.g., the “HDMI 5V” line).

FIG. 2shows an example of an analog front end of a detection circuit that is part of an HDMI sink in area202and an example of a resonant L-C circuit to be detected in area204, in accordance with some implementations.

The voltage sources V1and V2inFIG. 2represent general purpose outputs (GPOs) of a microcontroller (or other suitable device(s)) and the active low signal OEMDET# can be used to inform the microcontroller (or other suitable device(s)) when the L-C circuit has been detected.

The voltage source VCC represents a 3.3V power supply (or any other suitable power supply) of the analog front end (which can also be used to power a microcontroller (or other suitable device(s)) (not shown) if desired).

The HDMI sink detects the HDMI source by detecting the presence of a resonant L1-C3circuit in the HDMI source. The resonant frequency can be determined by L1and the equivalent capacitance (Ceq) of C1, C2, and C3in series (e.g., as shown in the example ofFIG. 2, L1can be 100 μH, Ceq can be 4.76 nF, and the resonant frequency can be 231 kHz, in some implementations). In this example, when the HDMI source is not connected, the waveform on the HPD line can be triangular at 231 kHz with a peak-peak value of 340 mV centered around 0V. This signal can be generated by driving the integrator circuit R1-C1with a 0V-3.3V 231 kHz square wave from the GPO V1.

When the HDMI source is connected, the circuit in the example ofFIG. 2resonates at 231 kHz and the amplitude of the waveform on HPD line is a sine wave with a peak-peak amplitude of:

898⁢⁢mV=3.3⁢⁢V·H⁢⁢1·G·ReqG2·R⁢⁢1+Req,wherein⁢:G=1+C⁢⁢1/C⁢⁢2=2;Q=ω·L⁢⁢1RS=2·π·231⁢⁢kHz·100⁢⁢µH⁢20⁢⁢Ω=7.25Rp=Rs·(1+Q2)=1072⁢⁢ΩReq=R⁢⁢8//R2//R5//Rp=480⁢⁢Ω;⁢andH⁢⁢1=4/π=1.27,
which is the 1st harmonic of a unity square wave.

It is assumed in the above calculations that (i) the serial resistance RSof the inductor is 2052, which takes into account the DC resistance, the core loss at 231 kHz and skin effect, and (ii) C3>>(C1·C2)/(C1+C2).

As shown, this signal is AC coupled by C4to the 350 mV DC bias of Q1and turns on Q1during the positive phase of the waveform (350 mV+898 mV/2=799 mV). The R7-C5circuit on the collector of Q1filters the active low signal OEMDET# which instructs the microcontroller (or other suitable device) to apply HDMI 5V to the HDMI source (e.g., as shown inFIG. 1).

Because the detection signal is AC coupled to Q1, detection can be performed when the HPD line is high or low (as driven by V2at 0 or 3.3V, for example); thus, the detection can be performed periodically to detect the removal of the HDMI source as well.

Although not shown inFIG. 2, any suitable circuit for connecting and disconnecting a supply voltage (e.g., a 5V voltage) from the HDMI sink to the HDMI source under the control of the microcontroller (or other suitable device) can be provided in some implementations. For example, a switch controlled by the microcontroller can be used to connect and disconnect the supply voltage from the HDMI sink to the HDMI source.

Another example 300 of a circuit for implementing some implementations of mechanisms disclosed herein is illustrated inFIG. 3. As shown, circuit300includes many of the same components as shown inFIG. 2. For example, the transistor, resistors, and capacitors shown in area202ofFIG. 2are also shown inFIG. 3. The voltage sources V1and V2ofFIG. 2are shown inFIG. 3by two GPOs of microcontroller308(which can be any suitable device (e.g., a hardware processor for controlling the operation of the mechanisms described herein) such as an MSP430G2001IPW14 microcontroller available from Texas Instruments of Dallas, Tex.). The voltage source VCC ofFIG. 2is shown inFIG. 3by a 3.3V regulator310(which can be any suitable device for providing power, such as a TLV70033 regulator available from Texas Instruments of Dallas, Tex.). Regulator310can receive power at its input from a permanent 5V source302(e.g., a USB port of a TV) or the HDMI 5V line between the source HDMI receptacle304and the sink HDMI receptacle306, via diodes D1(which can be any suitable diodes). A switch which provides power between the permanent 5V line and the HDMI 5V line (described above in connection withFIG. 1) can be provided by controllable switch510(which can be any suitable device for controlling a connection between a source of power and the HDMI 5V line, such as a TPS2051 switch available from Texas Instruments of Dallas, Tex.).

In accordance with some implementations, instructions that can be executed in a microcontroller (or other suitable device) in conjunction with the circuits ofFIGS. 2 and 3are illustrated inFIGS. 4A, 4B, and 4C.

As shown, the instructions at lines01-06define a state variable as having one of three possible states (“idle,” “normal source,” and “power-over-HDMI source”) and set the state's initial value.

The instructions at lines08-16turn ON or OFF a GPO that controls a switch that connects the permanent 5V line to the HDMI 5V line.

The instructions at lines18-24set the value on the HPD line at the source connector as either a 0 or a 1.

The instructions at lines26-28determine a state of the HPD line at the sink connector.

The instructions at lines30-33return whether 5V is at the output of the switch (i.e., at the HDMI 5V line between the sink and the source).

The instructions at lines34-36check the signal of the collector of transistor Q1to determine whether an L-C circuit is detected.

The instructions at lines38-51apply a clock signal at different frequencies (e.g., 231 kHz, 231 kHz+3%, 231 kHz−3%, 231 kHz+6%, 231 kHz−6%, . . . , 231 kHz+15%, 231 kHz−15%, and/or any other suitable frequencies) to the HPD line to determine whether the L-C circuit can be detected. As shown in these instructions, the clock signal can be provided at different frequencies to account for tolerances in the characteristics of the inductor and the capacitor making up the L-C circuit.

The instructions at lines52-80form the main procedure of the instructions and execute an infinite loop that perform three different groups of steps based on whether the process is in one of the three difference states.

As shown, if the state is the idle state, the process:a. turns off the 5V switch;b. sets the HPD line at the source to match the HPD line at the sink;c. if 5V is on the HDMI 5V line, sets the state to the normal source state;d. if 5V is not on the HDMI 5V line and the HPD line is connected to an L-C circuit, sets the state to a power-over-HDMI source state; ande. if 5V is not on the HDMI 5V line and the HPD line is not connected to an L-C circuit, delays the process by one second and leaves the state in the idle state.

If the state is in the normal source state, the process:a. turns off the 5V switch;b. sets the HPD line at the source to match the HPD line at the sink; andc. if the HDMI 5V line is not at 5V, sets the state to the idle state.

If the state is in the power-over-HDMI source state, the process:a. turns on the 5V switch;b. sets the HPD line at the source to match the HPD line at the sink;c. if the HPD line is not connected to an L-C circuit, sets the state to an idle state; andd. if the HPD line is connected to an L-C circuit, delays the process by one second and leaves the state in the power-over-HDMI source state.

The provision of the examples described herein (as well as clauses phrased as “such as,” “e.g.,” “including,” and the like) should not be interpreted as limiting the claimed subject matter to the specific examples; rather, the examples are intended to illustrate only some of many possible aspects.

Although the disclosed subject matter has been described and illustrated in the foregoing illustrative implementations, it is understood that the present disclosure has been made only by way of example, and that numerous changes in the details of implementation of the disclosed subject matter can be made without departing from the spirit and scope of the disclosed subject matter, which is limited only by the claims that follow. Features of the disclosed implementations can be combined and rearranged in various ways.