Power input circuit of vehicle-mounted display screen

Abstract

The utility model relates to a power supply circuit of a vehicle-mounted display screen, in particular to a power supply input circuit of the vehicle-mounted display screen, which comprises a voltage detection circuit, the input end of the voltage detection circuit is electrically connected with a switching circuit, and the output end of the voltage detection circuit is electrically connected with a starting circuit; when a power supply of the vehicle-mounted display screen is switched from normal power supply to short circuit, the voltage detection circuit is switched on by the switching circuit and is connected to the common mode inductance filter circuit, voltage detection is carried out on the output end of the common mode inductance filter circuit, and the voltage detection circuit outputs and drives the starting circuit to be started. The input end of the starting circuit obtains the voltage which is not fully dropped at the output end of the pi-type filter circuit, the output end of the starting circuit outputs high voltage and large current to the grid electrode of the MOS tube to rapidly change the grid-source electrode voltage Vgs, and the MOS tube is closed. Electric energy stored in the pi-type filter circuit can be prevented from being released and consumed to a power supply short-circuit point, and a screen cannot be quickly turned black, so that the testing requirements of a vehicle enterprise are met.

Description

Technical Field

[0001] The utility model relates to a vehicle-mounted display screen power supply circuit, in particular to a vehicle-mounted display screen power supply input circuit. Background Art

[0002] Due to the demand for intelligent car cockpits, the demand for large-size car displays is growing rapidly. Because large-size displays consume a lot of power, traditional diode anti-reverse designs use MOS tubes as anti-reverse connection components in the power input circuit of large-size car displays because diode devices have high power consumption under large currents.

[0003] However, with the advancement of technology of domestic automakers and suppliers, automakers have gradually increased their requirements for the electrical performance of automotive parts, and need to perform short-term interruption tests on large-size in-vehicle displays. The traditional in-vehicle display power input circuit cannot meet the test requirements. Figure 1 As shown in FIG. 1 , the traditional vehicle display screen power input circuit is mainly output to the vehicle display screen through the rectifier circuit DZ1, the common mode inductor filter circuit F1, the MOS tube Q1, the voltage divider circuit, and the π-type filter circuit. The triode Q2 is also added to the voltage divider circuit, which is in a closed state when the vehicle display screen is dormant, and is used to control the dormant current of the vehicle display screen. However, when the power IN+ and IN- of the circuit are instantly short-circuited from the normal state, the voltage of the source D and the drain S of the MOS tube Q1 drops instantly. In theory, the voltage of the gate G of the MOS tube Q1 will also drop synchronously. When the gate-source voltage Vgs is less than the turn-on voltage of the MOS tube Q1, the MOS tube Q1 should be turned off. Therefore, in theory, the MOS tube Q1 can be turned off when the drain S voltage drops to the set voltage by adjusting the resistor R2 and R3 voltage divider. However, in actual applications, due to the manufacturing process of the MOS tube Q1, there is a large gate capacitance between the gate G and the source D and the drain S. Therefore, when the drain S voltage drops instantly at a speed of microseconds, the gate G voltage will drop at almost the same slope as the drain S and source D voltages due to the gate capacitance between GS and GD. The electric energy of the capacitance between GS takes several milliseconds to be completely consumed by the voltage divider resistor R3, so that the gate-source voltage Vgs is reduced to the voltage at which the MOS tube Q1 is turned off. Therefore, due to the traditional vehicle display power input circuit and the gate capacitance characteristics of the MOS tube, when the power supply changes from normal power supply to short circuit, the MOS tube cannot be quickly turned off, resulting in the energy storage device of the π-type filter circuit of the MOS tube being quickly released and consumed by the power short-circuit point through the MOS tube. The energy storage device fails to achieve the energy storage effect expected during the design, which leads to the vehicle display screen being quickly powered off and a black screen when a short-term interruption test is performed, and therefore cannot meet the test requirements of the car companies. Utility Model Content

[0004] The utility model aims to provide a power input circuit for a vehicle display screen which will not quickly lose power and turn into a black screen when a short-term interruption test is performed, so as to meet the testing requirements of automobile companies.

[0005] The power input circuit of the vehicle-mounted display screen described in the utility model includes a voltage detection circuit, the input end of the voltage detection circuit is electrically connected to a switch circuit, and the output end is electrically connected to a start-up circuit; when the power supply of the vehicle-mounted display screen changes from normal power supply to short circuit, the voltage detection circuit is turned on by the switch circuit to connect to the common-mode inductor filter circuit, the output end of the common-mode inductor filter circuit is subjected to voltage detection, and the start-up circuit is driven to start by the output of the voltage detection circuit, the voltage at the output end of the π-type filter circuit that has not fully dropped is obtained from the input end of the start-up circuit, and a high voltage and a large current are output to the gate of the MOS tube through the output end of the start-up circuit to quickly change the gate-source voltage Vgs and turn off the MOS tube.

[0006] The power input circuit of the vehicle display screen described in the utility model, after the power input circuit of the vehicle display screen is connected to the power supply, when the vehicle display screen is subjected to a short-time interruption test, the power supply changes from normal power supply to short circuit, the switch circuit connects the voltage detection circuit with the output end of the common-mode inductor filter circuit, the voltage detection circuit detects the voltage change at the output end of the common-mode inductor filter circuit, outputs a driving signal to drive the start-up circuit to start, the voltage at the output end of the π-type filter circuit that has not yet fully dropped is obtained from the input end of the start-up circuit, and a high voltage and a large current are output to the gate of the MOS tube through the output end of the start-up circuit to quickly change the gate-source voltage Vgs, and turn off the MOS tube, thereby preventing the electric energy stored in the π-type filter circuit from being released and consumed to the power short-circuit point, and the screen will not quickly turn black, so as to meet the testing requirements of the automobile enterprise, so that in the actual application of the whole vehicle, the components of the vehicle display screen can maintain normal operation during a longer power short-circuit time, and when a transient electrical fault occurs in the whole vehicle, there is a greater probability that the normal vehicle speed display and other functions can be maintained, thereby improving the safety of the user's vehicle use.

[0007] As a preferred solution of the utility model, a Schmitt trigger circuit is provided between the voltage detection circuit and the start-up circuit, the input end of the Schmitt trigger circuit is electrically connected to the output end of the voltage detection circuit, and the output end of the Schmitt trigger circuit is electrically connected to the start-up end of the start-up circuit.

[0008] As a preferred solution of the utility model, the switching circuit includes two switching transistors, wherein the base of an NPN-type switching transistor inputs a start signal through a first bias resistor, the emitter is grounded, and the collector is electrically connected to the base of another PNP-type switching transistor through a second bias resistor; the collector of the other PNP-type switching transistor is connected to the input end of the voltage detection circuit, the emitter is connected to the cathode of the diode, and the anode of the diode is connected to the output end of the common-mode inductor filter circuit.

[0009] As a preferred solution of the utility model, the voltage detection circuit includes a comparator, the non-inverting input terminal of the comparator is connected between a first non-inverting voltage-dividing resistor and a second non-inverting voltage-dividing resistor, the first non-inverting voltage-dividing resistor and the second non-inverting voltage-dividing resistor are connected in series, one end of the first non-inverting voltage-dividing resistor is connected to the supply voltage input of the comparator, and one end of the second non-inverting voltage-dividing resistor is grounded; the inverting input terminal of the comparator is connected between the first inverting voltage-dividing resistor and the second inverting voltage-dividing resistor, the first inverting voltage-dividing resistor and the second inverting voltage-dividing resistor are connected in series, one end of the first inverting voltage-dividing resistor is electrically connected to the collector of the PNP type switching transistor, and one end of the second inverting voltage-dividing resistor is grounded; the output terminal of the comparator is electrically connected to the input terminal of the Schmitt trigger circuit.

[0010] As a preferred solution of the utility model, the voltage detection circuit also includes a feedback resistor and a pull-up resistor at the output end of the comparator, one end of the feedback resistor is connected to the output end of the comparator, and the other end is connected to the non-inverting input end of the comparator; one end of the pull-up resistor at the output end of the comparator is electrically connected to the power supply voltage of the comparator, and the other end is electrically connected to the output end of the comparator.

[0011] As a preferred solution of the utility model, the voltage detection circuit also includes a common-phase filter capacitor, an inverting filter capacitor and a comparator output filter capacitor, one end of the common-phase filter capacitor is electrically connected to the common-phase input terminal of the comparator, and the other end is grounded; one end of the inverting filter capacitor is electrically connected to the inverting input terminal of the comparator, and the other end is grounded; one end of the comparator output filter capacitor is electrically connected to the output terminal of the comparator, and the other end is grounded.

[0012] As a preferred solution of the utility model, the Schmitt trigger circuit includes a Schmitt trigger, the input end of the Schmitt trigger is electrically connected to the output end of the comparator, and the output end is electrically connected to the start-up end of the start-up circuit.

[0013] As a preferred solution of the utility model, the starting circuit includes two driving transistors, wherein the base of an NPN-type driving transistor is electrically connected to the output end of the Schmitt trigger, the emitter is grounded, and the collector is electrically connected to the base of another PNP-type driving transistor through a third bias resistor; the emitter of the other PNP-type driving transistor is electrically connected to the output end of the π-type filter circuit, and the collector is electrically connected to the gate of the MOS tube through a current limiting resistor. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The circuit diagram of the power input circuit of the traditional vehicle display screen;

[0015] Figure 2 This is the schematic diagram of the power input circuit of the vehicle-mounted display screen of the utility model;

[0016] Figure 3 The utility model is a circuit diagram of the power input circuit of the vehicle-mounted display screen. DETAILED DESCRIPTION

[0017] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0018] The power input circuit of a vehicle-mounted display screen is as follows: Figure 2 As shown, it includes a voltage detection circuit, the input end of the voltage detection circuit is electrically connected to a switch circuit, and the output end is electrically connected to a start-up circuit; when the power supply of the vehicle display screen changes from normal power supply to short circuit, the voltage detection circuit is turned on by the switch circuit and connected to the common-mode inductor filter circuit, and the output end of the common-mode inductor filter circuit is voltage-detected, and the start-up circuit is turned on by the output of the voltage detection circuit, and the voltage that has not fully dropped at the output end of the π-type filter circuit is obtained from the input end of the start-up circuit, and a high voltage and a large current are output to the gate of the MOS tube Q1 through the output end of the start-up circuit to quickly change the gate-source voltage Vgs, and turn off the MOS tube Q1.

[0019] After the power input circuit of the vehicle display screen is connected to the power supply, when the vehicle display screen is tested for a short interruption, the power supply changes from normal power supply to short circuit, and the switch circuit connects the voltage detection circuit with the output end of the common-mode inductor filter circuit. The voltage detection circuit detects the voltage change at the output end of the common-mode inductor filter circuit, and outputs a drive signal to drive the start-up circuit to start. The voltage at the output end of the π-type filter circuit that has not yet fully dropped is obtained from the input end of the start-up circuit, and a high voltage and a large current are output to the gate of the MOS tube through the output end of the start-up circuit to quickly change the gate-source voltage Vgs, turn off the MOS tube, and prevent the electric energy stored in the π-type filter circuit from being released and consumed to the power short-circuit point, and the screen will not quickly turn black to meet the testing requirements of the car companies, so that in the actual application of the whole vehicle, the components of the vehicle display screen can maintain normal operation for a longer power short-circuit time, and when a transient electrical fault occurs in the whole vehicle, there is a greater probability that the normal vehicle speed display and other functions can be maintained, thereby improving the safety of users' use of the vehicle.

[0020] like Figure 3As shown, the switching circuit includes two switching transistors, wherein the base of an NPN type switching transistor Q31 is input with a start signal through a first bias resistor R5, the emitter is grounded, and the collector is electrically connected to the base of another PNP type switching transistor Q32 through a second bias resistor R4; the collector of the other PNP type switching transistor Q32 is connected to the input end of the voltage detection circuit, the emitter is connected to the cathode of the diode D1, and the anode of the diode D1 is connected to the output end of the common mode inductor filter circuit.

[0021] The base of the NPN switching transistor Q31 inputs a start signal through the first bias resistor R5, the NPN switching transistor Q31 starts working, and drives the PNP switching transistor Q32 to start working through the second bias resistor R4, the emitter and collector of the PNP switching transistor Q32 are connected, and the voltage detection circuit is connected to the output end of the common mode inductor filter circuit F1 through the diode D1. The diode D1 plays a role in protecting the comparator when the power supply is reversely connected.

[0022] The voltage detection circuit includes a comparator U1, a non-inverting input terminal of the comparator U1 is connected between a first non-inverting voltage-dividing resistor R7 and a second non-inverting voltage-dividing resistor R8, the first non-inverting voltage-dividing resistor R7 and the second non-inverting voltage-dividing resistor R8 are connected in series, one end of the first non-inverting voltage-dividing resistor R7 is connected to a supply voltage input to the comparator U1, and one end of the second non-inverting voltage-dividing resistor R8 is grounded; an inverting input terminal of the comparator U1 is connected between a first inverting voltage-dividing resistor R9 and a second inverting voltage-dividing resistor R10, the first inverting voltage-dividing resistor R9 and the second inverting voltage-dividing resistor R10 are connected in series, one end of the first inverting voltage-dividing resistor R9 is electrically connected to a collector of a PNP type switching transistor Q32, and one end of the second inverting voltage-dividing resistor R10 is grounded; an output terminal of the comparator U1 is electrically connected to an input terminal of a Schmitt trigger circuit.

[0023] The comparator U1 outputs a start signal by comparing the voltage between the first in-phase voltage-dividing resistor R7 and the second in-phase voltage-dividing resistor R8 connected to the in-phase input terminal with the voltage detected at the output terminal of the common-mode inductor filter circuit between the first inverting voltage-dividing resistor R9 and the second inverting voltage-dividing resistor R10 connected to the inverting input terminal. The voltage detection circuit also includes a feedback resistor R6, one end of which is connected to the output terminal of the comparator U1, and the other end is connected to the in-phase input terminal of the comparator U1. The voltage at the output terminal of the comparator U1 is fed back to the voltage at the in-phase input terminal of the comparator U1 through the feedback resistor R6, and the output of the comparator U1 is dynamically adjusted, so that the output of the comparator U1 is smoother and more stable. The output terminal of the voltage detection circuit is also provided with a pull-up resistor R11, one end of which is electrically connected to the power supply voltage of the comparator U1, and the other end is electrically connected to the output terminal of the comparator U1.

[0024] The voltage detection circuit also includes a common-phase filter capacitor C5, an inverting filter capacitor C6 and a comparator output filter capacitor C7, wherein one end of the common-phase filter capacitor C5 is electrically connected to the common-phase input terminal of the comparator U1, and the other end is grounded; one end of the inverting filter capacitor C6 is electrically connected to the inverting input terminal of the comparator U1, and the other end is grounded; one end of the comparator output filter capacitor C7 is electrically connected to the output terminal of the comparator, and the other end is grounded. The common-phase filter capacitor C5, the inverting filter capacitor C6 and the comparator output filter capacitor C7 can filter out clutter and reduce interference.

[0025] A Schmitt trigger circuit is provided between the voltage detection circuit and the start-up circuit. The Schmitt trigger circuit includes a Schmitt trigger U2. The input end of the Schmitt trigger U2 is electrically connected to the output end of the comparator U1, and the output end is electrically connected to the start-up end of the start-up circuit.

[0026] The startup circuit includes two driving transistors, wherein the base of an NPN-type driving transistor Q41 is electrically connected to the output end of the Schmitt trigger U2, the emitter is grounded, and the collector is electrically connected to the base of another PNP-type driving transistor Q42 through a third bias resistor R12; the emitter of the other PNP-type driving transistor Q42 is electrically connected to the output end of the π-type filter circuit, and the collector is electrically connected to the gate of the MOS tube Q1 through a current limiting resistor R13.

[0027] The operating voltage of the vehicle display screen is generally 8.5-18.5V. When the external input voltage is within the rated range, the comparator U1 outputs a low-level signal, the Schmitt trigger U2 outputs a low-level signal, and the NPN-type driving transistor Q41 and the PNP-type driving transistor Q42 are both in the off state. When the vehicle display screen is tested for a short-term interruption, the power supply changes from normal power supply to short circuit. The input voltage of the vehicle display screen drops from 11V to nearly 0V within 20us, and the current flow on the power line reverses. The electric energy stored in the capacitors C3, C4 and the inductor L1 in the π-type filter circuit begins to be rapidly released and consumed to the power short-circuit point. In the process of the voltage dropping from 11V to nearly 0V, when the voltage is lower than 7V, the output of the comparator U1 changes from a low-level signal to a high-level signal, and the Schmitt trigger U2 simultaneously outputs a high-level signal, driving the NPN-type driving transistor Q41 and the PNP-type driving transistor Q42 from the off state to the on state. This process is less than 10us. Since the circuit of the utility model can quickly detect and respond to voltage drops, after the NPN-type driving transistor Q41 and the PNP-type driving transistor Q42 are turned on, the circuit can obtain the voltage that has not fully dropped from the filter energy storage circuit composed of the inductor L1 and capacitors C3 and C4 of the subsequent stage, and transmit it to the gate G of the MOS tube Q1 through the current limiting resistor R13, and use high voltage and large current to quickly change the gate-source voltage Vgs of the gate, so that Vgs quickly changes from -11~-4V to 0~0.7V, and the MOS tube Q1 is turned off. Finally, when the power input end of the vehicle display screen is short-circuited, the anti-reverse MOS tube Q1 is quickly turned off, thereby preventing the electric energy stored in the subsequent energy storage circuit from being released and consumed to the power short-circuit point, so that the vehicle display screen can maintain normal operation for a longer time when a momentary short-circuit occurs. It is measured that the time from the short-circuit application to the complete shutdown of the anti-reverse MOS tube Q1 is less than 15us.

[0028] The above embodiments are only used to illustrate the detailed scheme of the utility model. The utility model is not limited to the above detailed scheme, that is, it does not mean that the utility model must rely on the above detailed scheme to be implemented. Those skilled in the art should understand that any improvement to the utility model, equivalent replacement of various raw materials of the utility model product, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the utility model.

Claims

1. A power input circuit for a vehicle-mounted display screen, characterized in that: The invention comprises a voltage detection circuit, wherein the input end of the voltage detection circuit is electrically connected to a switch circuit, and the output end is electrically connected to a start-up circuit; when the power supply of the vehicle display screen changes from normal power supply to short circuit, the voltage detection circuit is connected to the common-mode inductor filter circuit by the switch circuit, and the voltage of the output end of the common-mode inductor filter circuit is detected, and the start-up circuit is driven to start by the output of the voltage detection circuit, and the voltage at the output end of the π-type filter circuit that has not fully dropped is obtained from the input end of the start-up circuit, and a high voltage and a large current are output to the gate of the MOS tube (Q1) through the output end of the start-up circuit to quickly change the gate-source voltage Vgs and turn off the MOS tube (Q1).

2. The power input circuit of the vehicle-mounted display screen according to claim 1, characterized in that: A Schmitt trigger circuit is provided between the voltage detection circuit and the start-up circuit, wherein the input end of the Schmitt trigger circuit is electrically connected to the output end of the voltage detection circuit, and the output end of the Schmitt trigger circuit is electrically connected to the start-up end of the start-up circuit.

3. The power input circuit of the vehicle-mounted display screen according to claim 2, characterized in that: The switch circuit comprises two switch transistors, wherein the base of an NPN switch transistor (Q31) is input with a start signal through a first bias resistor (R5), the emitter is grounded, and the collector is electrically connected to the base of another PNP switch transistor (Q32) through a second bias resistor (R4); the collector of the other PNP switch transistor (Q32) is connected to the input end of a voltage detection circuit, the emitter is connected to the cathode of a diode (D1), and the anode of the diode (D1) is connected to the output end of a common-mode inductor filter circuit.

4. The power input circuit of the vehicle-mounted display screen according to claim 3, characterized in that: The voltage detection circuit comprises a comparator (U1), wherein a non-inverting input end of the comparator (U1) is connected between a first non-inverting voltage-dividing resistor (R7) and a second non-inverting voltage-dividing resistor (R8), the first non-inverting voltage-dividing resistor (R7) and the second non-inverting voltage-dividing resistor (R8) are connected in series, one end of the first non-inverting voltage-dividing resistor (R7) is connected to a supply voltage inputted by the comparator (U1), and one end of the second non-inverting voltage-dividing resistor (R8) is grounded; an inverting input end of the comparator (U1) is connected between a first inverting voltage-dividing resistor (R9) and a second inverting voltage-dividing resistor (R10), the first inverting voltage-dividing resistor (R9) and the second inverting voltage-dividing resistor (R10) are connected in series, one end of the first inverting voltage-dividing resistor (R9) is electrically connected to a collector of a PNP type switching transistor (Q32), and one end of the second inverting voltage-dividing resistor (R10) is grounded; and an output end of the comparator (U1) is electrically connected to an input end of a Schmitt trigger circuit.

5. The power input circuit of the vehicle-mounted display screen according to claim 4, characterized in that: The voltage detection circuit also includes a feedback resistor (R6) and a pull-up resistor (R11) at the output end of the comparator, wherein one end of the feedback resistor (R6) is connected to the output end of the comparator (U1), and the other end is connected to the non-inverting input end of the comparator (U1); one end of the pull-up resistor (R11) at the output end of the comparator is electrically connected to the power supply voltage of the comparator (U1), and the other end is electrically connected to the output end of the comparator (U1).

6. The power input circuit of the vehicle-mounted display screen according to claim 5, characterized in that: The voltage detection circuit also includes a common-phase filter capacitor (C5), an inverting filter capacitor (C6) and a comparator output filter capacitor (C7); one end of the common-phase filter capacitor (C5) is electrically connected to the common-phase input terminal of the comparator (U1), and the other end is grounded; one end of the inverting filter capacitor (C6) is electrically connected to the inverting input terminal of the comparator (U1), and the other end is grounded; one end of the comparator output filter capacitor (C7) is electrically connected to the output terminal of the comparator (U1), and the other end is grounded.

7. The power input circuit of the vehicle-mounted display screen according to claim 6, characterized in that: The Schmitt trigger circuit comprises a Schmitt trigger (U2), wherein the input end of the Schmitt trigger (U2) is electrically connected to the output end of the comparator (U1), and the output end is electrically connected to the start-up end of the start-up circuit.

8. The power input circuit of the vehicle-mounted display screen according to claim 7, characterized in that: The start-up circuit comprises two driving transistors, wherein the base of an NPN-type driving transistor (Q41) is electrically connected to the output end of a Schmitt trigger (U2), the emitter is grounded, and the collector is electrically connected to the base of another PNP-type driving transistor (Q42) through a third bias resistor (R12); the emitter of the other PNP-type driving transistor (Q42) is electrically connected to the output end of a π-type filter circuit, and the collector is electrically connected to the gate of a MOS tube (Q1) through a current limiting resistor (R13).

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