CN204291210U - Interface circuit - Google Patents

Abstract

The utility model discloses an interface circuit, which comprises an HDMI terminal compatible with MHL, a main chip and a charging control chip; the equipment insertion signal end of the HDMI terminal is connected with the equipment insertion detection end of the main chip; and the equipment insertion signal end of the HDMI terminal is also connected with the control end of the charging control chip. Through the equipment of main chip inserts the detection terminal with the control end of charging control chip shares the equipment of HDMI terminal and inserts the signal end, has simplified the circuit, has reduced the occupation to the port of main chip, is convenient for PCB typesetting wiring. Meanwhile, the protection resistor connected in series on the port of the main chip is saved, and the cost of the product is reduced.

Description

an interface circuit

technical field

The utility model relates to the field of electronic technology, in particular to an interface circuit.

Background technique

With the gradual popularization and promotion of digital TV and portable audio-visual equipment, users have an increasing demand for presenting digital high-definition content of portable audio-visual equipment on high-definition TV anytime, anywhere. MHL (Mobile High-Definition Link, mobile terminal high-definition audio-visual standard Interface) technology came into being, MHL only uses a signal cable to present the high-definition audio and video content of MHL equipment on high-definition TV through the standard HDMI (High Definition Multimedia Interface, high-definition multimedia interface) input interface.

Generally, in order to ensure continuous operation of the MHL device, the receiving end provides power to the MHL device for charging. A typical application scheme is shown in Figure 1. The device insertion signal end of the MHL-compatible HDMI terminal is connected to the device insertion detection end of the main chip, and the charging control signal end of the main chip is connected to the control of the charging control chip. end connection. When an MHL device is inserted into an MHL-compatible HDMI terminal, the device insertion signal end of the HDMI terminal changes from low level to high level to generate a device insertion signal MHL_IN_SENSE, and the main chip outputs a high level charge control after receiving the device insertion signal MHL_IN_SENSE The signal Charge_EN is sent to the control terminal of the charging control chip, and the charging control chip outputs the charging voltage to charge the MHL device.

The MHL charging scheme provided by the prior art needs to use two I/O (Input/Output, input and output) ports of the main chip, while occupying the port resources of the main chip, a PCB (Printed Circuit Board, printed circuit board) is also added. The difficulty of typesetting and routing.

Contents of the invention

The technical problem to be solved by the utility model is to provide an interface circuit, simplify the MHL charging circuit, reduce the occupation of the main chip port, and facilitate PCB layout and wiring.

An interface circuit provided by an embodiment of the utility model includes an MHL-compatible HDMI terminal, a main chip and a charging control chip;

The device insertion signal end of the HDMI terminal is connected to the device insertion detection end of the main chip;

The device insertion signal end of the HDMI terminal is also connected to the control end of the charging control chip.

Preferably, the interface circuit further includes a filter circuit;

The device insertion signal end of the HDMI terminal is connected to the device insertion detection end of the main chip, specifically: the device insertion signal end of the HDMI terminal is connected to the device insertion detection end of the main chip through the filter circuit;

The device insertion signal end of the HDMI terminal is also connected to the control end of the charging control chip, specifically: the device insertion signal end of the HDMI terminal is connected to the control end of the charging control chip through the filter circuit.

Preferably, the filter circuit includes a first resistor R1 and a first capacitor C1;

The first end of the first resistor R1 is connected to the device insertion signal end of the HDMI terminal, the second end of the first resistor R1 is connected to the device insertion detection end of the main chip, and the first resistor R1 The second terminal is also connected to the control terminal of the charging control chip;

A first end of the first capacitor C1 is connected to a device insertion signal end of the HDMI terminal, and a second end of the first capacitor C1 is grounded.

Preferably, the interface circuit further includes a second resistor R2;

A first end of the second resistor R2 is connected to the device insertion signal end of the HDMI terminal, and a second end of the second resistor R2 is grounded.

Preferably, the interface circuit further includes a third resistor R3;

The first terminal of the third resistor R3 is connected to the second terminal of the first resistor R1, and the second terminal of the third resistor R3 is connected to the control terminal of the charging control chip.

Preferably, the output terminal of the charging control chip is connected to the charging power output terminal of the HDMI terminal.

Preferably, the interface circuit further includes a second capacitor C2;

The first terminal of the second capacitor C2 is connected to the output terminal of the charging control chip, and the second terminal of the second capacitor C2 is grounded.

The interface circuit provided by the embodiment of the utility model reduces the occupation of the ports of the main chip and simplifies the charging circuit by inserting the equipment of the HDMI terminal into the signal terminal and simultaneously connecting the equipment of the main chip into the detection terminal and the control terminal of the charging control chip , to facilitate PCB layout and wiring. At the same time, the protection resistor connected in series to the port of the main chip is saved, thereby reducing the cost of the product.

Description of drawings

FIG. 1 is a schematic diagram of charging an MHL device through MHL provided by the prior art;

Fig. 2 is a structural schematic diagram of an embodiment of the interface circuit provided by the utility model;

FIG. 3 is a circuit diagram of the interface circuit of the embodiment shown in FIG. 2 .

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention.

Referring to FIG. 2 , it is a schematic structural diagram of an embodiment of the interface circuit provided by the present invention.

The interface circuit includes an MHL compatible HDMI terminal, a main chip 102 and a charging control chip 103 .

The device insertion signal end of the HDMI terminal 101 is connected to the device insertion detection end of the main chip 102 .

The device insertion signal end of the HDMI terminal 101 is also connected to the control end of the charging control chip 103 .

Wherein, the main chip 102 and the charging control chip 103 are IC (Integrated Circuit, integrated circuit) chips.

The device insertion signal end of the HDMI terminal 101 is a low level when there is no MHL device inserted, and the device insertion signal end of the HDMI terminal 101 is a high level when an MHL device is inserted (that is, in FIG. 2 ). MHL_IN_SENSE signal).

Both the equipment insertion detection terminal of the main chip 102 and the control terminal of the charging control chip 103 are connected to the equipment insertion signal terminal of the HDMI terminal 101, and share the level signal of the equipment insertion signal terminal. The main chip 102 detects the insertion of the device by detecting the level of the device insertion detection terminal. The charging control chip 103 turns on/off the output of the charging voltage according to the level of the control terminal. Only one I/O port of the main chip 102 can be used to realize the insertion detection and charging control of the MHL device.

Referring to FIG. 3 , it is a circuit diagram of the interface circuit of the embodiment shown in FIG. 2 .

In a specific implementation, in order to avoid the influence of noise, the interface circuit preferably further includes a filter circuit.

The device insertion signal end of the HDMI terminal 101 is respectively connected to the device insertion detection end of the main IC 102 (ie, the main chip) and the charging control end of the charging control IC 103 (ie, the charging control chip) through the filter circuit.

The filter circuit preferably includes a first resistor R1 and a first capacitor C1.

The first end of the first resistor R1 is connected to the device insertion signal end of the HDMI terminal, the second end of the first resistor R1 is connected to the device insertion detection end of the main chip, and the first resistor R1 The second terminal of the charging control chip is also connected to the control terminal.

A first end of the first capacitor C1 is connected to a device insertion signal end of the HDMI terminal, and a second end of the first capacitor C1 is grounded.

At the same time, the first resistor R1 is also used as a protection resistor of the line, and plays a role of protecting the chip.

Further, in order to ensure the stability of the line voltage between the HDMI terminal 101 and the main IC 102 and the charging control IC 103, the interface circuit further includes a second resistor R2.

A first end of the second resistor R2 is connected to the device insertion signal end of the HDMI terminal 101 , and a second end of the second resistor R2 is grounded.

When no MHL device is plugged in, the device insertion signal end of the HDMI terminal 101 can be stably in a low level state through the second resistor R2, effectively preventing malfunctioning of the circuit. When an MHL device is plugged in, the second resistor R2 forms a voltage divider with other resistors in the circuit to stabilize the line voltage and protect the chip.

The interface circuit preferably further includes a third resistor R3.

The first terminal of the third resistor R3 is connected to the second terminal of the first resistor R1 , and the second terminal of the third resistor R3 is connected to the control terminal of the charging control IC 103 .

The third resistor R3 is used to limit the current input to the control terminal of the charge control IC 103 to protect the charge control IC 103 .

The output end of the charging control IC 103 is connected to the charging power output end (ie, pin 18 ) of the HDMI terminal 101 .

The interface circuit preferably further includes a second capacitor C2.

A first end of the second capacitor C2 is connected to the output end of the charging control IC 103 , and a second end of the second capacitor C2 is grounded.

The charging voltage output from the output terminal of the charging control IC 103 is filtered by the second capacitor C2 to stabilize the output of the charging voltage.

As shown in FIG. 3 , the MHL-compatible pin 2 is the device insertion signal end of the HDMI terminal 101 in this embodiment, and the pin 18 is the charging power output end of the HDMI terminal 101 in this embodiment. Those skilled in the art can select different pins as the device insertion signal end and the charging power output end of the HDMI terminal 101 according to actual needs. This embodiment is only an example of the utility model, and the selection of specific pins should not be regarded as a limitation of the utility model.

When the MHL device is plugged in, the pin 2 of the HDMI terminal 101 changes from a low level to a high level, that is, the control terminal of the charging control IC103 is at a high level, and the output terminal of the charging control IC103 outputs the charging voltage. Pin 18 is output to charge MHL devices.

When the MHL device is pulled out, the pin 2 of the HDMI terminal 101 changes from high level to low level, that is, the control terminal of the charging control IC 103 is low level, and the charging control IC 103 turns off the output of the charging voltage.

The interface circuit provided by the embodiment of the present invention transmits the device insertion signal to the main chip 102 at the same time by connecting the equipment insertion detection terminal of the main chip 102 and the control terminal of the charging control chip 103 by connecting the equipment insertion signal end of the HDMI terminal 101 The device insertion detection terminal and the control terminal of the charging control chip 103 reduce the occupation of the ports of the main chip 102, simplify the charging circuit of the MHL, and facilitate layout and wiring of the PCB. At the same time, the protection resistor connected in series to the port of the main chip 102 is saved, thereby reducing the cost of the product.

The above is a preferred embodiment of the present utility model, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present utility model, some improvements and modifications can also be made, these improvements and modifications It is also regarded as the protection scope of the present utility model.

Claims (7)

1. an interface circuit, is characterized in that, comprises the HDMI terminal of compatible MHL, master chip and charge controlling chip;

The equipment insertion signal end of described HDMI terminal inserts test side with the equipment of described master chip and is connected;

The equipment of described HDMI terminal inserts signal end and is also connected with the control end of described charge controlling chip.

2. interface circuit as claimed in claim 1, it is characterized in that, described interface circuit also comprises filter circuit;

The equipment insertion signal end of described HDMI terminal inserts test side with the equipment of described master chip and is connected, and is specially: the equipment insertion signal end of described HDMI terminal inserts test side by described filter circuit with the equipment of described master chip and is connected;

The equipment of described HDMI terminal inserts signal end and is also connected with the control end of described charge controlling chip, is specially: the equipment of described HDMI terminal is inserted signal end and is connected with the control end of described charge controlling chip by described filter circuit.

3. interface circuit as claimed in claim 2, it is characterized in that, described filter circuit comprises the first resistance R1 and the first electric capacity C1;

The first end of described first resistance R1 inserts signal end with the equipment of described HDMI terminal and is connected, described second end of the first resistance R1 and the equipment of described master chip insert test side, and second end of described first resistance R1 is also connected with the control end of described charge controlling chip;

The first end of described first electric capacity C1 inserts signal end with the equipment of described HDMI terminal and is connected, the second end ground connection of described first electric capacity C1.

4. interface circuit as claimed in claim 3, it is characterized in that, described interface circuit also comprises the second resistance R2;

The first end of described second resistance R2 inserts signal end with the equipment of described HDMI terminal and is connected, the second end ground connection of described second resistance R2.

5. interface circuit as claimed in claim 4, it is characterized in that, described interface circuit also comprises the 3rd resistance R3;

The first end of described 3rd resistance R3 is connected with second end of described first resistance R1, and second end of described 3rd resistance R3 is connected with the control end of described charge controlling chip.

6. interface circuit as claimed in claim 5, is characterized in that, the output of described charge controlling chip is connected to the charge power supply output connection of described HDMI terminal.

7. interface circuit as claimed in claim 6, it is characterized in that, described interface circuit also comprises the second electric capacity C2;

The first end of described second electric capacity C2 is connected with the output of described charge controlling chip, the second end ground connection of described second electric capacity C2.