Power supply device for a conference terminal and conference terminal device

Abstract

The application relates to a power supply device for a conference terminal and a conference terminal device, which comprises a first power supply branch and a second power supply branch connected in parallel, the first power supply branch is connected to a power adapter as a power supply source through a first power supply input end, the second power supply branch is connected to a POE-PD as a power supply source through a second power supply input end, and the power supply device further comprises a first MOS switch tube, the first MOS switch tube is connected in series in the first power supply branch; a second MOS switch tube, the second MOS switch tube is connected in series in the second power supply branch; and a power supply switching module, the power supply switching module is used for controlling the conduction and the cut-off of the first MOS switch tube and the second MOS switch tube according to the connected power supply source, and controlling the second MOS switch tube to always be in the cut-off state when the power adapter is connected to the power supply. The problems of large power consumption and large load end voltage drop of the existing power supply device are solved.

Description

TECHNICAL FIELD

[0001] The application relates to a power supply device for a conference terminal and a conference terminal device, and belongs to the field of power supply devices. BACKGROUND

[0002] The conference terminal product uses two power supply modes of a power adapter and a POE_PD, and can be powered by the power adapter alone or the POE_PD alone, and when both are plugged in, the power adapter is used preferentially.

[0003] As shown in the prior art, the processing mode for preferentially using the power adapter for power supply is realized by adding a power diode to the power supply path of the power adapter and the POE_PD. Figure 1 However, since the power diode has a forward conduction voltage drop, it has its own dissipation power consumption, thereby causing temperature rise and power utilization rate reduction, which is particularly obvious under a high-power load. Since the power adapter is a standard purchased part and the output voltage amplitude cannot be adjusted, in order to realize preferential use of the power adapter for power supply when both are plugged in, only the POE_PD output voltage can be reduced to realize preferential conduction of the diode on the power adapter path. However, this further increases the current value of the POE_PD power supply, resulting in greater dissipation power consumption of the diode on the POE_PD power supply path when the POE_PD is used alone. Moreover, when a larger capacitive load is powered, the starting current is too large, resulting in a power diode with a higher rated current.

[0004] SUMMARY

[0005] The application provides a power supply device for a conference terminal and a conference terminal device, which can solve the problems of large power loss caused by the power diode on the power supply path and load end voltage caused by power switching in the prior art power supply device for the conference terminal product.

[0006] The application provides the following technical solutions:

[0007] The first aspect of the embodiment of the application provides a power supply device for a conference terminal, which comprises:

[0008] The first power supply branch and the second power supply branch are connected in parallel, the first power supply branch is connected to a power adapter through a first power supply input end as a power supply, and the second power supply branch is connected to a POE_PD through a second power supply input end as a power supply;

[0009] The first MOS switch tube is connected in series in the first power supply branch and is used for controlling the on-off of the first power supply branch;

[0010] ​A second MOS switch tube is connected in series in the second power supply branch, and is used for controlling on-off of the second power supply branch.

[0011] A power supply switching module is used for controlling on-off of the first MOS switch tube and the second MOS switch tube according to the accessed power supply, and controlling the second MOS switch tube to be always in an off state when the power adapter accesses power supply.

[0012] The technical scheme of the present application uses a MOS switch tube to replace a power diode, because the MOS tube has a small conduction voltage drop, reduces power consumption, and reduces voltage drop of a load end during power supply switching.

[0013] Further, according to the power supply device in the first aspect of the present application, the power supply switching module comprises:

[0014] A first drive circuit, an input end of the first drive circuit is connected to the first power supply input end, a control signal output end of the first drive circuit is connected to a control end of the first MOS switch tube, and the first drive circuit is used for controlling on-off of the first MOS switch tube according to a power supply signal of the first power supply input end;

[0015] A second drive circuit, an input end of the second drive circuit is connected to the second power supply input end, a control signal output end of the second drive circuit is connected to a control end of the second MOS switch tube, and the second drive circuit is used for controlling on-off of the second MOS switch tube according to a power supply signal of the second power supply input end;

[0016] A switching exclusion circuit, an input end of the switching exclusion circuit is connected to the first power supply input end, a control output end of the switching exclusion circuit is connected to the second drive circuit, and the switching exclusion circuit is used for disconnecting the second drive circuit from the second MOS switch tube when the power adapter accesses power supply, so that the second MOS switch tube is always in an off state.

[0017] The technical scheme of the present application can disconnect the second drive circuit when the power adapter accesses power supply, so that the second drive circuit loses control over the second MOS switch circuit, and the second MOS switch circuit is turned off. Only when the power adapter supplies power, can the power adapter supply be used preferentially when the power adapter accesses.

[0018] Further, according to the power supply device in the first aspect of the present application, the switching exclusion circuit comprises a fourth MOS switch tube (U4) and a switching control branch, the fourth MOS switch tube (U4) is connected in series in a control loop of the second drive circuit.

[0019] The control input end of the switch control branch is connected with the first power input end, the control output end of the first switch control branch is connected with the control end of the fourth MOS switch tube (U4), and the fourth MOS switch tube (U4) is controlled to be turned on or turned off.

[0020] The switching and mutual exclusion circuit of the application sets the fourth MOS switch tube and connects the fourth MOS switch tube in the control loop of the second driving circuit, so that the fourth MOS switch tube is immediately turned off when the power adapter is connected, the second driving circuit is turned off, the power supply path of the POE-PD is turned off, and the power adapter is ensured to have priority in power supply.

[0021] Further, the power supply device according to the first aspect of the application, the first driving circuit comprises two mutually exclusive first switch branches and second switch branches;

[0022] The input end of the first switch branch is connected with the first power input end, the output end of the first switch branch is connected with the control end of the second switch branch, and the output end of the first switch branch is connected with the ground through the resistor (R8);

[0023] The input end of the second switch branch is connected with the source of the first MOS switch tube, and the output end of the second switch branch is connected with the ground through the series resistor (R9);

[0024] The gate of the first MOS switch tube is connected with the output end of the second switch branch through the series resistor (R10).

[0025] The technical scheme of the application sets the mutually exclusive first switch branch and second switch branch, ensures that the first switch branch is maintained to be turned on and the second switch circuit is maintained to be turned off when the power adapter is connected, so that the gate voltage of the first MOS switch tube can be quickly pulled down and then turned on, and the power adapter power supply channel is ensured to be turned on.

[0026] Further, the power supply device according to the first aspect of the application, the second driving circuit comprises mutually exclusive third switch branches and fourth switch branches;

[0027] The input end of the third switch branch is connected with the second power input end through the fourth MOS switch tube (U4), the output end of the third switch branch is connected with the control end of the fourth switch branch, and the output end of the third switch branch is connected with the ground through the resistor (R11);

[0028] The input end of the fourth switch branch is connected with the source of the second MOS switch tube, and the output end of the fourth switch branch is connected with the ground through the series resistor (R12);

[0029] The gate of the second MOS switch tube is connected with the output end of the second switch branch through the series resistor (R13).

[0030] The third switch branch and the fourth switch branch are set to be mutually exclusive conduction, so that when the POE-PD is connected, the fourth switch circuit is maintained in the off state, and the gate voltage of the fourth MOS switch tube can be pulled down in time to quickly conduct.

[0031] Further, according to the power supply device in the first aspect of the present application, the switch control branch includes mutually exclusive conduction of the first NPN transistor (Q1) and the second NPN transistor (Q2), and resistors (R5, R6);

[0032] The base of the first NPN transistor (Q1) is connected to the first power supply input end, the collector of the first NPN transistor (Q1) is connected to the base of the second NPN transistor (Q2) and then connected to the second power supply input end, the emitter of the first NPN transistor (Q1) is connected to the emitter of the second NPN transistor (Q2) and then grounded, the collector of the second NPN transistor (Q2) is connected to the second power supply input end through the resistor (R5), and the collector of the second NPN transistor (Q2) is connected to the gate of the fourth MOS switch tube (U4) through the resistor (R6).

[0033] The first NPN transistor (Q1) and the second NPN transistor (Q2) are set to be mutually exclusive conduction, so that in the case of connecting the power adapter, the gate potential of U4 is pulled up by R5, U4 is completely cut off, and the power adapter is ensured to be preferentially powered.

[0034] Further, according to the power supply device in the first aspect of the present application, the first switch branch includes a first PNP transistor, the emitter of the first PNP transistor is connected to the first power supply input end, the collector of the first PNP transistor is connected to the ground through a series resistor (R8), and the collector and the base of the first PNP transistor are connected.

[0035] The second switch branch includes a diode (D4) and a second PNP transistor, the anode of the diode (D4) is connected to the source of the first MOS switch tube, the cathode of the diode (D4) is connected to the emitter of the second PNP transistor, and the base of the second PNP transistor is connected to the collector of the first PNP transistor.

[0036] The diode D4 is set to ensure that the emitter of Q3B is always in reverse bias during the conduction of the first MOS switch tube, Q3B is completely turned off, and the gate voltage of U1 can be as low as possible, so that the first MOS switch tube is always maintained in the conduction state during the connection of the power adapter.

[0037] Further, according to the power supply device in the first aspect of the present application, the third switch branch comprises a third PNP triode and a resistor (R11), the emitter of the third PNP triode is connected to the second power input terminal, the collector of the third PNP triode is connected to the ground through the resistor (R11), and the collector of the third PNP triode is connected to the base of the third PNP triode.

[0038] The fourth switch branch comprises a diode (D5) and a fourth PNP triode, the anode of the diode (D5) is connected to the source of the second MOS switch tube, the cathode of the diode (D5) is connected to the emitter of the fourth PNP triode, and the base of the second PNP triode is connected to the collector of the first PNP triode.

[0039] The present application sets the diode D5 to ensure that the emitter of Q3D is always reverse-biased during the conduction of the second MOS switch tube, so that Q3D is completely turned off, and the gate voltage of U2 can be as low as possible, ensuring that the second MOS switch tube is always in the on state during the connection of the POE_PD power supply.

[0040] Further, according to the power supply device in the first aspect of the present application, the power supply device further comprises a soft-start circuit, the soft-start circuit comprises a third MOS switch tube and a soft-start control circuit, the third MOS switch tube is connected in series in the power supply output terminal and the power supply path of the load, and the soft-start control circuit is used to delay the conduction of the third MOS switch tube.

[0041] The present application prevents the impact current through the soft-start.

[0042] The second aspect of the present application provides a conference terminal device comprising the power supply device in the first aspect of the present application.

[0043] The present application has the advantages that the MOS switch tube is used to replace the power diode in the original power supply path, and the MOS switch tube has extremely low voltage drop when it is in the fully on state, which can reduce the power dissipation loss compared with the high voltage drop of the original power diode.

[0044] The present application selects the power adapter to supply power preferentially, and the MOS switch tube on the two power supply branches is switched to achieve this, and the MOS switch tube has almost no voltage drop when it is on, which improves the power supply efficiency, reduces the energy consumption, and realizes that the voltage drop of the load end power supply is within 5% when the path between the power adapter and the POE_PD is switched.

[0045] The above description is only a summary of the technical scheme of the present application, in order to more clearly understand the technical means of the present application, and the content of the specification can be implemented, the following will be described in detail with the preferred embodiments of the present application and the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 is a structural schematic diagram of an existing power supply device;

[0047] Figure 2 is a structural schematic diagram of a power supply device provided by an embodiment of the present application;

[0048] Figure 3 is a circuit schematic diagram of a power supply device provided by an embodiment of the present application. DETAILED DESCRIPTION

[0049] The specific embodiments of the present application are described in further detail below in conjunction with the accompanying drawings and embodiments. The following embodiments are used to illustrate the present application, but are not used to limit the scope of the present application.

[0050] Figure 2 is a power supply device for a conference terminal provided by an embodiment of the present application, as shown in Figure 2 The power supply device includes two power supply branches, i.e., a first power supply branch and a second power supply branch, which are connected in parallel. The first power supply branch uses a power adapter as a power supply, and the second power supply branch uses a POE-PD as a power supply.

[0051] The first power supply branch includes a first power supply input end for connecting a power adapter as a power supply, and the second power supply branch includes a second power supply input end for connecting a POE-PD as a power supply. Both the first power supply branch and the second power supply branch are connected to a load (a conference terminal product) through a power supply output end to realize dual power supply for the load.

[0052] Both the POE-PD and the power adapter can supply power to the load independently. When the POE-PD and the power adapter are connected at the same time, the power adapter is used preferentially.

[0053] Further, as shown in Figure 1 The power supply device further includes a first MOS switch tube and a second MOS switch tube. The first MOS switch tube is connected in series in the first power supply branch, and the second MOS switch tube is connected in series in the second power supply branch. When the first MOS switch tube works in a cut-off state, the first power supply branch is disconnected; and when the second MOS switch tube works in a cut-off state, the second power supply branch is disconnected.

[0054] The embodiment realizes power supply switching of the power adapter and the POE-PD by switching the on-off of the first MOS switch tube and the second switch tube.

[0055] Further, the power supply device further comprises a power supply switching module, which is configured to switch the working states of the first MOS switch tube and the second MOS switch tube, and specifically:

[0056] In the case of only POE-PD access to power supply, the power supply switching module controls the second MOS switch tube to be in the on state, and as soon as the power adapter is detected to access, the first MOS switch tube is controlled to be on, and the second MOS switch tube is controlled to be off.

[0057] In the case of only the power adapter access to power supply, the first MOS switch tube is controlled to be in the on state all the time, and the second MOS switch tube is controlled to be in the off state all the time, so as to ensure that in the case of the power adapter access, whether the POE-PD accesses to power supply or not, the power adapter is always used for power supply.

[0058] In the case of the power adapter and the POE-PD simultaneously access to power supply, the first MOS switch tube is immediately controlled to be on, and the second MOS switch tube is controlled to be off.

[0059] Optionally, as Figure 2 , the power supply switching module comprises a first drive circuit, a second drive circuit and a switching exclusion circuit.

[0060] Specifically, the control signal output end of the first drive circuit is connected to the control end of the first MOS switch tube, and is configured to control the off and on of the first MOS switch tube. Meanwhile, the power supply end of the first drive circuit is connected to the first power supply input end, and when the power adapter is connected, the first drive circuit is connected, and when the power adapter is disconnected, the first drive circuit is disconnected.

[0061] The control signal output end of the second drive circuit is connected to the control end of the second MOS switch tube, and is configured to control the off and on of the second MOS switch tube. Meanwhile, the power supply end of the second drive circuit is connected to the second power supply input end, and when the POE-PD is connected, the second drive circuit is connected, and when the POE-PD is disconnected, the second drive circuit is disconnected.

[0062] The power supply end of the switching exclusion circuit is connected to the first power supply input end, and when the power adapter is connected to the power supply, the switching exclusion circuit is connected, and when the power adapter is disconnected, the switching exclusion circuit is disconnected, and loses the control of the second drive circuit. The control signal output end of the switching exclusion circuit is connected to the second drive circuit, and is configured to control the on and off of the second drive circuit.

[0063] Based on the circuit structure of the above power supply switching module, the switching control of the first power supply branch and the second power supply branch is completed by the first drive circuit, the second drive circuit and the switching exclusion circuit. Specifically:

[0064] When only the power adapter is connected to the power supply, the first driving circuit automatically sets the first MOS switch tube in the fully on state, and the power supply signal output by the power adapter is transmitted to the power output terminal through the first MOS switch tube.

[0065] At this time, whether the POE_PD is connected or not, the switching exclusion circuit sets the second driving circuit in the invalid state, and the control of the second driving circuit to the second MOS switch tube is disconnected, so that the second MOS switch tube is always in the off state regardless of whether the POE_PD is connected or not.

[0066] When only the POE_PD is connected to the power supply, the first driving circuit is automatically invalid due to the absence of the power adapter, and the control of the first driving circuit to the first MOS switch tube is disconnected, so that the first MOS switch tube works in the off state.

[0067] At this time, the switching exclusion circuit is also in the invalid state due to the absence of the power adapter, so that the control of the second driving circuit is invalid, and the second driving circuit is in the active state, which automatically sets the second MOS switch tube in the fully on state, and the power supply signal output by the POE_PD is transmitted to the power output terminal through the second MOS switch tube.

[0068] At this time, if the power adapter is connected, the switching exclusion circuit sets the second driving circuit in the invalid state after obtaining the power supply signal of the power adapter, and the second MOS switch tube changes from the fully on state to the off state. At the same time, due to the connection of the power adapter, the first driving circuit is also connected again, outputs the control signal, sets the first MOS switch tube in the fully on state, and switches the power supply from the POE_PD to the power adapter.

[0069] When the power adapter and the POE_PD are connected to the power supply at the same time, the switching exclusion circuit responds the fastest and immediately sets the second driving circuit in the invalid state, so that the second MOS switch tube is in the off state. At the same time, the first driving circuit sets the first MOS switch tube in the fully on state, and the power supply signal output by the power adapter is transmitted to the power output terminal through the first MOS switch tube.

[0070] The MOS switch tube is used to replace the power diode in the original power supply path in the embodiment of the application. The MOS switch tube has extremely low voltage drop when it is in the fully on state, and can reduce the power dissipation loss compared with the high voltage drop of the original power diode. In addition, when the power adapter is selected to supply power preferentially, the MOS switch tubes on the two power supply branches are switched to realize this, and the MOS switch tube has almost no voltage drop when it is on, which improves the power supply efficiency, reduces the energy consumption, and realizes that the voltage drop of the load end power supply is within 5% when the path between the power adapter and the POE_PD is switched.

[0071] Optionally, the power supply device further comprises a soft start circuit, which is arranged at the power output end of the first power supply branch and the second power supply branch, and is used for realizing soft start of the load power supply path.

[0072] Specifically, the soft start circuit comprises a third MOS switch tube and a soft start control module, the soft start control module comprises a soft start control unit, the third MOS switch tube is connected in series between the power output end and the load, and the soft start control unit has a delay start mechanism inside, which is used for delaying the conduction of the third MOS switch tube after power-on, so that the power supply switching module has completed switching work before the power supply path of the load is started.

[0073] Further, the soft start circuit further comprises an external control unit, which is used for on-off control of the soft start circuit.

[0074] By arranging the soft start circuit, the power supply path of the load can be delayed to start, so that the excessive conduction impact current caused by the capacitive load when the capacitive load is powered can be avoided.

[0075] Figure 3 The circuit principle diagram of the power supply device is shown in FIG. 1, wherein the first MOS switch tube of the power supply device is a P-channel MOS tube U1, and the second MOS switch tube is a P-channel MOS tube U2. Figure 3 Figure 3 The U1 and U2 are P-channel MOS tubes of NXP PMK35EP, wherein the U1 is responsible for on-off of the first power supply branch of the power supply adapter, and the U2 is responsible for on-off of the second power supply branch of the POE-PD.

[0076] It should be noted that in other embodiments, appropriate P-MOS types can be selected according to the actual input voltage and rated working current. The P-channel MOS tubes shown below are used to describe the embodiments of the present application. Figure 3

[0077] Optionally, referring to FIG. 2, the first driving circuit comprises mutually exclusive PNP transistors Q3A and Q3B, resistors R8-R10, a capacitor C1 and a diode D4. Figure 3

[0078] ​​​Specifically, the emitter of the PNP triode Q3A is connected to the first power input, the collector of the PNP triode Q3A is connected to the ground through the resistor R8, the base of the PNP triode Q3A is connected to the collector, the collector of the PNP triode Q3A is connected to the base of the PNP triode Q3B, the emitter of the PNP triode Q3B is connected to the source of the P-channel MOS U1 through the reverse-connected diode D4, and the collector of the PNP triode Q3B is connected to the ground through the resistor R9. The drain of the P-channel MOS U1 is connected to the first power input, the source of the P-channel MOS U1 is connected to the power output, the gate of the P-channel MOS U1 is connected to the collector of the PNP triode Q3B through the resistor R10, and the capacitor C1 is connected between the gate and the source of the P-channel MOS U1, and the capacitor C1 is used for filtering.

[0079] In the embodiment, the PNP triode Q3A and the PNP triode Q3B are array PNP tubes with consistent parameters.

[0080] When the power adapter is connected to the power supply, the emitter of the Q3A obtains a high potential and is immediately turned on, and the Q3B is in the off state. The resistor R9 pulls down the gate voltage of the U1, and then the U1 is completely turned on (V1gs = -12V), so that the first power supply branch is powered on and the load is powered by the power adapter.

[0081] The diode D4 ensures that the emitter of the Q3B is reverse-biased during the conduction of the U1, and the Q3B is completely turned off, so that the gate voltage of the U1 is as low as possible. In addition, the gate voltage of the U1 should be as close to the source voltage as possible when the Q3B is turned on. Therefore, the forward conduction voltage drop of the diode D4 should be as small as possible. In this embodiment, the diode D4 is a Schottky diode or a germanium tube.

[0082] Optionally, referring to Figure 3 The second driving circuit includes the mutually exclusive PNP triode Q3C and the PNP triode Q3D, the resistors R11-R13, the capacitor C2, and the diode D5.

[0083] Specifically, the emitter of the PNP triode Q3C is connected to the second power input terminal through the fourth MOS switch tube U4 of P channel, the collector of the PNP triode Q3C is grounded through the resistor R11, the base of the PNP triode Q3C is connected to the collector, and the collector of the PNP triode Q3C is connected to the base of the PNP triode Q3D, the emitter of the PNP triode Q3D is connected to the source of the P channel MOS tube U2 through the reverse connected diode D5, and the collector of the PNP triode Q3D is grounded through the resistor R12. The drain of the P channel MOS tube U2 is connected to the second power input terminal, the source of the P channel MOS tube U2 is connected to the power output terminal, the gate of the P channel MOS tube U2 is connected to the collector of the PNP triode Q3D through the resistor R13, and the gate and the source of the P channel MOS tube U2 are further connected to the capacitor C2, which is used for filtering.

[0084] In order to prevent the power reverse interference caused by the existence of the diode in U1 and U2 when the power adapter and the POE_PD are connected for power supply at the same time, the drain of U1 and U2 is connected to the external power supply. The PNP triode Q3C and the PNP triode Q3D in the embodiment are both array PNP tubes, and have the same parameters.

[0085] When the POE-PD is connected for power supply, the emitter of Q3C obtains a high potential in the case that U4 is turned on, and will be immediately turned on, while Q3D is in the cut-off state, and the resistor R12 pulls down the gate voltage of U2. Subsequently, U2 is completely turned on (V2gs = -12V), so that the second power supply branch is electrified, and the power adapter supplies power to the load.

[0086] The function of D5 is to ensure that the emitter of Q3D is reverse biased during the conduction of U2, and Q3D is completely turned off, so that the gate voltage of U2 can be as low as possible. In addition, the gate voltage of U2 should be as close to the source voltage as possible when Q3D is turned on, so the forward conduction voltage drop of diode D5 should be as small as possible. In this regard, the D5 in the embodiment is selected to be a Schottky diode or a germanium tube.

[0087] Optionally, referring to Figure 2 , the switching exclusive circuit includes the mutually exclusive NPN triode Q1 and NPN triode Q2, the P channel MOS tube U4, the resistors R1-R7, and the capacitor C3.

[0088] Specifically, the base of the NPN triode Q1 is connected to the first power input terminal through the resistor R1, the collector of the NPN triode Q1 is connected to the base of the NPN triode Q2, and then connected to the second power input terminal through the resistor R4, the emitter of the NPN triode Q1 is connected to the emitter of the NPN triode Q2, and then grounded, and the collector of the NPN triode Q2 is connected to the second power input terminal through the resistor R5.

[0089] The gate of U4 is connected to the collector of Q2 through resistor R6, the source of U4 is connected to the second power input, the drain of U4 is connected to the ground through resistor R7, and meanwhile, the drain of U4 is connected to the emitter of PNP transistor Q3C, and the gate and the source of U4 are further connected with capacitor C3 for filtering.

[0090] When the power adapter is connected to the first power input for power supply, the base of Q1 is turned on due to the positive bias voltage, and when Q1 is turned on, the base voltage of Q2 is 0, and Q2 is turned off; at this time, the gate potential of U4 is pulled high by resistor R5, and U4 is turned off; after U4 is turned off, the emitter potential of Q3C is pulled low by resistor R7, and Q3C is turned off; after Q3C is turned off, the base potential of Q3D is pulled low by resistor R11, and Q3D is turned on; after Q3D is turned on, the gate potential of U2 is pulled high, and U2 is in the off state, and the second power supply branch is disconnected; at this time, whether the POE_PD is connected or not, the power adapter is selected for power supply.

[0091] Optionally, referring to Figure 3 , the slow start circuit comprises NPN transistor Q4, resistors R16-R21, capacitors C5-C7, and diodes D1-D3.

[0092] Specifically, the third P-channel MOS tube U3 is connected in series in the power supply loop from the power supply output to the load, resistors R17 and capacitor C5 are connected in parallel and then connected in series with R16 to form an RC charging circuit. C5 is connected to the power supply output through the forward connected diode D1; the positive terminal of capacitor C6 is connected to the source of U3, the negative terminal of C6 is connected to the gate of U3 through the forward connected diode D3, and the negative terminal of C6 is connected to the collector of Q4 through the series resistor R19; the positive terminal of capacitor C7 is connected to the drain of U3, the negative terminal of C7 is connected to the gate of U3 through the series resistor R21, the gate of U3 is connected to the ground through resistor R20, the source of U3 is connected to the collector of Q4 through the series resistors R18 and R19, the emitter of Q4 is connected to the ground, and the base of Q4 is connected to capacitor C5.

[0093] When initially powered on, the base voltage of Q4 is 0, Q4 is in the off state, the voltage across capacitor C6 is 0, the gate-source voltage Vgs of U3 is 0, and U3 is in the off state. The voltage at the power supply output charges capacitor C5 through the RC charging circuit, and after a period of RC charging delay, Q4 is turned on, and the voltage at the power supply output charges capacitor C6 through resistor R19 to delay the opening of U3. When Vgs reaches the opening voltage of U3, U3 is turned on.

[0094] Once U3 reaches the Miller plateau, capacitor C7, resistors R21 and R20 slow down the full conduction of U3 to avoid excessive inrush current from subsequent capacitive loads. D3 ensures that U3 is not affected by external interference during the Miller phase. When power is off, Q4 turns off, and C6 discharges through resistor R18, turning off U3. This embodiment controls the degree of conduction of U4 by controlling the rise slope of the gate-source voltage of U3, thus solving the problem of excessive starting current caused by large capacitive loads.

[0095] Diode D2 is the input for external control of the power-on and power-off of the soft-start circuit. When the input signal is high, the soft-start circuit is powered on; when the input signal is low, the soft-start circuit is powered off.

[0096] Since the soft-start channel is handled by an NXP PMK35EP (P-MOS) U3, the source of U3 is connected to the power supply output terminal to prevent the body diode of U3 (P-MOS) from conducting to supply power to the load before soft start.

[0097] based on Figure 3 The circuit schematic shown below illustrates the specific working process of this embodiment of the application:

[0098] When only the second power supply input is connected to POE_PD for power supply, and the power adapter is not connected, Q1 is off and Q2 is on. At this time, the gate potential of U4 is pulled low by resistor R6, and U4 is fully turned on. With U4 on, the emitter potential of Q3C is equal to the VCC voltage of 12V, and the emitter of Q3C receives a forward bias voltage and turns on. At this time, Q3D is off, the gate voltage of U2 is pulled low by resistor R12, and U2 is fully turned on (V2gs = -12V). The second power supply branch is powered on and supplies power to the load through POE-PD.

[0099] When the first power input terminal is connected to the power adapter, the emitter of Q3A receives a high potential and immediately conducts, while Q3B is in the off state. Resistor R9 pulls down the gate of U1, and U1 is fully turned on (V1gs = -12V). The first power supply branch is energized, supplying power to the load through the power adapter. At this time, with the power adapter supplying power, the base of Q1 receives a positive bias voltage and conducts. With Q1 conducting, the base voltage of Q2 is 0, and Q2 is off. The gate potential of U4 is pulled up by resistor R5, and U4 is off. After U4 is off, the emitter potential of Q3C is pulled down by resistor R7, and Q3C is off. When Q3C is off, the base potential of Q3D is pulled down by resistor R11, and Q3D conducts. After Q3D conducts, the gate potential of U2 is pulled up, and U2 is in the off state. The second power supply branch is disconnected. At this time, regardless of whether PoE_PD is connected, the power adapter is selected for power supply.

[0100] When the power adapter of the first power supply input and the POE_PD of the second power supply input are connected to supply power at the same time, U2 will be immediately cut off, and only the power adapter supplies power.

[0101] When the power adapter is disconnected, Q3A is immediately cut off, and Q3B is turned on. After Q3B is turned on, the gate potential of U1 is pulled up, and U1 is in the cut-off state, and the first power supply branch is disconnected. At the same time, when the power adapter is disconnected, Q1 is cut off, and Q2 is turned on. At this time, the gate potential of U4 is pulled down by the resistor R6, and U4 is fully turned on. As described above, the second power supply branch is powered on, and the POE_PD starts to supply power.

[0102] In summary, the power supply device of the embodiment of the application replaces the power diode with the P-channel MOS tube, and sets the power supply switching module to switch the power supply, thereby reducing the power consumption, improving the power supply efficiency, and realizing that the voltage drop of the load end power supply is within 5% when the path between the power adapter and the POE_PD is switched.

[0103] The embodiment of the application also provides a conference terminal device comprising the power supply device of the above embodiment, which will not be described here.

[0104] The technical features of the above embodiments can be combined in any way. To make the description concise, all possible combinations of the technical features in the above embodiments are not described, but as long as the combination of the technical features does not exist, it should be considered as the scope of the description.

[0105] The above embodiments only express several implementation manners of the application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that for ordinary skilled persons in the art, without departing from the concept of the application, some modifications and improvements can be made, which are all within the protection scope of the application. Therefore, the protection scope of the patent of the application should be subject to the appended claims.

Claims

1. A power supply device for a conference terminal, comprising a first power supply branch and a second power supply branch connected in parallel, the first power supply branch being connected to a power adapter as a power supply source through a first power supply input terminal, and the second power supply branch being connected to a POE-PD as a power supply source through a second power supply input terminal, characterized in that, The power supply device further comprises: a first MOS switch tube connected in series in the first power supply branch for controlling on-off of the first power supply branch; a second MOS switch tube connected in series in the second power supply branch for controlling on-off of the second power supply branch; a source of the first MOS switch tube is connected with a power supply output terminal, and a source of the second MOS switch tube is connected with the power supply output terminal; a power supply switching module for controlling on-off of the first MOS switch tube and the second MOS switch tube according to an accessed power supply, and for controlling the second MOS switch tube to be always in an off state when the power adapter accesses power supply; the power supply switching module comprises a first drive circuit, the first drive circuit comprises two mutually exclusive first and second switch branches, an input terminal of the first switch branch is connected with a first power supply input terminal, an output terminal of the first switch branch is connected with a control terminal of the second switch branch, and the output terminal of the first switch branch is connected with ground through a resistor (R8), the first switch branch comprises a first PNP transistor, an emitter of the first PNP transistor is connected with the first power supply input terminal, a collector of the first PNP transistor is connected with ground through a series resistor (R8), and the collector of the first PNP transistor is connected with a base thereof; an input terminal of the second switch branch is connected with a source of the first MOS switch tube, an output terminal of the second switch branch is connected with ground through a series resistor (R9), and the second switch branch comprises a diode (D4) and a second PNP transistor, an anode of the diode (D4) is connected with the source of the first MOS switch tube, a cathode of the diode (D4) is connected with an emitter of the second PNP transistor, and a base of the second PNP transistor is connected with a collector of the first PNP transistor; the first drive circuit is used for making the second PNP transistor completely off through the diode (D4) when the power adapter accesses power supply, so that the first MOS switch tube is set in a completely on state.

2. The power supply apparatus for a conference terminal according to claim 1, wherein the power supply switching module further comprises: a second drive circuit, an input terminal of the second drive circuit is connected with a second power supply input terminal, a control signal output terminal of the second drive circuit is connected with a control terminal of the second MOS switch tube, and the second drive circuit is used for controlling on-off of the second MOS switch tube according to a power supply signal of the second power supply input terminal; a switching exclusive circuit, an input terminal of the switching exclusive circuit is connected with a first power supply input terminal, a control output terminal of the switching exclusive circuit is connected with the second drive circuit, and the switching exclusive circuit is used for making the second drive circuit disconnect control of the second MOS switch tube when the power adapter accesses power supply, so that the second MOS switch tube is always in an off state.

3. The power supply apparatus for a conference terminal according to claim 2, wherein the switching exclusive circuit comprises a fourth MOS switch tube (U4) and a switch control branch, the fourth MOS switch tube (U4) is connected in series in a control loop of the second drive circuit; The control input end of the switch control branch is connected to the first power input end, and the control output end of the switch control branch is connected to the control end of the fourth MOS switch tube (U4) for controlling the on-off of the fourth MOS switch tube (U4).

4. The power supply apparatus for a conference terminal according to claim 1, wherein The gate of the first MOS switch tube is connected to the output end of the second switch branch through a series resistor (R10).

5. The power supply apparatus for a conference terminal according to claim 2, wherein The second drive circuit comprises a third switch branch and a fourth switch branch which are mutually exclusive and conductive. The input end of the third switch branch is connected to the second power input end through the fourth MOS switch tube (U4), the output end of the third switch branch is connected to the control end of the fourth switch branch, and the output end of the third switch branch is connected to the ground through a resistor (R11). The input end of the fourth switch branch is connected to the source of the second MOS switch tube, and the output end of the fourth switch branch is connected to the ground through a series resistor (R12). The gate of the second MOS switch tube is connected to the output end of the fourth switch branch through a series resistor (R13).

6. The power supply apparatus for a conference terminal according to claim 3, wherein The switch control branch comprises a first NPN transistor (Q1) and a second NPN transistor (Q2) which are mutually exclusive and conductive, and resistors (R5, R6). The base of the first NPN transistor (Q1) is connected to the first power supply input end, the collector of the first NPN transistor (Q1) and the base of the second NPN transistor (Q2) are connected to the second power supply input end, the emitter of the first NPN transistor (Q1) and the emitter of the second NPN transistor (Q2) are connected to the ground, the collector of the second NPN transistor (Q2) is connected to the second power supply input end through a resistor (R5), and the collector of the second NPN transistor (Q2) is connected to the gate of the fourth MOS switch tube (U4) through a resistor (R6).

7. The power supply apparatus for a conference terminal according to claim 5, wherein The third switch branch comprises a third PNP transistor and a resistor (R11), the emitter of the third PNP transistor is connected to the second power supply input end, the collector of the third PNP transistor is connected to the ground through a series resistor (R11), and the collector of the third PNP transistor is connected to the base of the third PNP transistor. The fourth switch branch comprises a diode (D5) and a fourth PNP transistor, the anode of the diode (D5) is connected to the source of the second MOS switch tube, the cathode of the diode (D5) is connected to the emitter of the fourth PNP transistor, and the base of the fourth PNP transistor is connected to the collector of the third PNP transistor.

8. The power supply apparatus for a conference terminal according to claim 1, wherein The power supply device further comprises a soft start circuit, the soft start circuit comprises a third MOS switch tube and a soft start control circuit, the third MOS switch tube is connected in series in the power supply path of the power supply output end and the load, and the soft start control circuit is used for delaying the conduction of the third MOS switch tube.

9. A conference terminal device, characterized by The power supply device comprises the power supply device according to any one of claims 1-8.

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