A reference current generating circuit with a starting circuit

Abstract

The invention discloses a reference current generating circuit with a starting circuit, which is applied to the starting circuit of the reference circuit of the LED display screen driving chip. The reference circuit comprises a reference circuit and a starting circuit which are connected to each other. The reference circuit comprises a PMOS tube 1, a PMOS tube 2, a PMOS tube 3 and an NMOS tube 1. The starting circuit comprises a PMOS tube 4, a PMOS tube 5, an inverter 1, a resistor 4 and a Schmitt trigger. The source electrodes of the PMOS tube 4 and the PMOS tube 5 are connected to the source electrode of the PMOS tube 3 and to a power supply end. The gate electrode of the PMOS tube 4 is connected to the gate electrode of the PMOS tube 3. The drain electrode of the PMOS tube 4 is connected to the input end of the inverter 1 and one end of the resistor 4. The other end of the resistor 4 is connected to a ground end. The output end of the inverter 1 is connected to the input end of the Schmitt trigger. The output end of the Schmitt trigger is connected to the gate electrode of the PMOS tube 5. The drain electrode of the PMOS tube 5 is connected to the gate electrode of the NMOS tube 1. In the starting circuit of the invention, the driving circuit comprises the Schmitt trigger, has no intermediate state, and improves the stability and anti-interference ability of the reference circuit.

Description

Technical Field

[0001] The invention relates to a starting circuit of a reference circuit of a LED display screen driving chip, in particular to a reference current generating circuit with a starting circuit. Background Art

[0002] Figure 1 It is a commonly used startup circuit and reference circuit.

[0003] The reference circuit of the LED display driver chip has multiple stable states. For example, when V1=VX=VY=0, PM1, PM2, PM3, and NM1 are all turned off, and the reference circuit can also be stable, but the required reference current cannot be generated. Therefore, a startup circuit is required to enable the reference circuit to work normally.

[0004] Figure 1 In the figure, PM1, PM2, PM3, and PM4 form a current mirror. When the current flowing through PM1, PM2, and PM3 is very small or zero, the current of PM4 will also be very small or zero. The voltage V0 at the drain end of PM4 will be pulled down very low by R4. V0 controls PM5 to turn on after passing through inverters INV1 and INV2, forming a strong pull-up on the gate voltage V1 of NM1. V1 gradually increases. When V1 is greater than the threshold voltage VTH of NM1, NM1 is turned on and pulls the potential of V2 down, so that PM1, PM2, PM3, and PM4 are turned on, and the reference circuit is started. As V2 decreases, the current flowing through PM1, PM2, PM3, and PM4 gradually increases, causing the voltage V0 to increase. When the current flowing through PM1, PM2, PM3, and PM4 is large to a certain extent, V0 exceeds the flip voltage of inverter INV1, and the gate voltage of PM5 flips from a low level to a high level, PM5 is turned off, the startup circuit is turned off, and the reference circuit works normally.

[0005] Since the inverter has a certain probability of operating in the intermediate state, that is, the input and output voltages of the inverter are both at the intermediate potential between VDD and GND, and PM5 is driven by the inverter, during the startup process, as the V0 voltage increases, the startup circuit has a certain probability of stabilizing in the intermediate state, and PM5 has a weak pull-up on the V1 potential, causing the reference circuit to work abnormally.

[0006] Therefore, how to solve the above-mentioned technical problems becomes an issue to be solved urgently. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a reference current generating circuit with a startup circuit in view of the above-mentioned deficiencies in the prior art, wherein the corresponding PMOS tube driving circuit includes a Schmitt trigger, and the characteristic of the Schmitt trigger is that there are only two stable states. For input signals with two different change directions of negative decreasing and positive increasing, the Schmitt trigger has different threshold voltages. The output will change only when the input voltage changes sufficiently, and the output voltage is VDD or GND. Therefore, during the startup process, the corresponding PMOS tube will only be in a strong pull-up state or a shutdown state, without an intermediate state, thereby improving the stability of the reference circuit.

[0008] In order to solve the above technical problems, a reference current generating circuit with a startup circuit of the present invention comprises a reference circuit and a startup circuit connected to each other, wherein the reference circuit comprises a PMOS tube 1, a PMOS tube 2 and a PMOS tube 3 whose sources are connected together, a power supply voltage is input into the sources of the three PMOS tubes, and the gates of the three PMOS tubes are connected together; the drain of the PMOS tube 1 is respectively connected to one end of the resistor 1 and the resistor 2, the other end of the resistor 1 is connected to the emitter of the zero PNP type triode, the base, the collector of the zero PNP type triode and the other end of the resistor 2 are connected together and connected to the ground end; the drain of the PMOS tube 2 is respectively connected to the emitter of the first PNP type triode and one end of the resistor 3, the base, the collector of the first PNP type triode and the other end of the resistor 3 are connected together and connected to the ground end, the positive input end of the amplifier is connected to the drain of the PMOS tube 2, The negative electrode of the input end of the amplifier is connected to the drain of the PMOS tube 1, the output end of the amplifier is connected to the gate of the NMOS tube 1, the gate and drain of the PMOS tube 3 are connected together and connected to the drain of the NMOS tube 1, and the source of the NMOS tube 1 is connected to the ground end. It is characterized in that: the starting circuit includes a PMOS tube 4, a PMOS tube 5, an inverter 1, a resistor 4 and a Schmitt trigger, the sources of the PMOS tube 4 and the PMOS tube 5 are connected to the source of the PMOS tube 3 and connected to the power supply end, the gate of the PMOS tube 4 is connected to the gate of the PMOS tube 3, the drain of the PMOS tube 4 is connected to the input end of the inverter 1 and one end of the resistor 4, the other end of the resistor 4 is connected to the ground end, the output end of the inverter 1 is connected to the input end of the Schmitt trigger, the output end of the Schmitt trigger is connected to the gate of the PMOS tube 5, and the drain of the PMOS tube 5 is connected to the gate of the NMOS tube 1.

[0009] The positions of the inverter 1 and the Schmitt trigger in the further startup circuit are interchanged.

[0010] After the present invention adopts the above circuit structure, the startup circuit includes a Schmitt trigger SCHMITT TRIGGER. The Schmitt trigger is characterized in that it has only two stable states. For input signals with two different change directions of negative decreasing and positive increasing, the Schmitt trigger has different threshold voltages. Only when the input voltage changes sufficiently, the output will change, and the output voltage is VDD or GND. Therefore, during the startup process, PM5 will only be in a strong pull-up state or a shutdown state, without an intermediate state, which improves the stability of the reference circuit; in addition, the positions of the Schmitt trigger and the inverter in the startup circuit can be interchanged, which improves the flexibility of the circuit structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a commonly used start-up circuit and reference circuit in the prior art;

[0012] Figure 2 The invention relates to a reference current generating circuit with a starting circuit. DETAILED DESCRIPTION

[0013] The present invention will be further described in detail below with reference to the embodiments in the accompanying drawings, but this does not constitute any limitation to the present invention.

[0014] like Figure 2As shown, a reference current generating circuit with a startup circuit of the present invention comprises a reference circuit and a startup circuit connected to each other, wherein the reference circuit comprises a PMOS tube 1, a PMOS tube 2 and a PMOS tube 3 whose sources are connected together, a power supply voltage is input to the sources of the three PMOS tubes, and the gates of the three PMOS tubes are connected together; the drain of the PMOS tube 1 is respectively connected to one end of the resistor 1 and the resistor 2, the other end of the resistor 1 is connected to the emitter of the zero PNP type triode, the base, the collector of the zero PNP type triode and the other end of the resistor 2 are connected together and connected to the ground; the drain of the PMOS tube 2 is respectively connected to the emitter of the first PNP type triode and one end of the resistor 3, the base, the collector of the first PNP type triode and the other end of the resistor 3 are connected together and connected to the ground, the positive input terminal of the amplifier is connected to the drain of the PMOS tube 2, and the amplifier The negative electrode of the input end of the amplifier is connected to the drain of the PMOS tube 1, the output end of the amplifier is connected to the gate of the NMOS tube 1, the gate and drain of the PMOS tube 3 are connected together and connected to the drain of the NMOS tube 1, and the source of the NMOS tube 1 is connected to the ground end. The startup circuit includes a PMOS tube 4, a PMOS tube 5, an inverter 1, a resistor 4 and a Schmitt trigger. The sources of the PMOS tube 4 and the PMOS tube 5 are connected to the source of the PMOS tube 3 and connected to the power supply end, the gate of the PMOS tube 4 is connected to the gate of the PMOS tube 3, the drain of the PMOS tube 4 is connected to the input end of the inverter 1 and one end of the resistor 4, the other end of the resistor 4 is connected to the ground end, the output end of the inverter 1 is connected to the input end of the Schmitt trigger, the output end of the Schmitt trigger is connected to the gate of the PMOS tube 5, and the drain of the PMOS tube 5 is connected to the gate of the NMOS tube 1.

[0015] Another embodiment of the present invention is to Figure 2 The positions of inverter 1 and Schmitt trigger in the startup circuit are swapped.

[0016] In the specific use of the present invention, since the characteristic of the Schmitt trigger is that it has only two stable states, for input signals with two different change directions of negative decreasing and positive increasing, the Schmitt trigger has different threshold voltages. Only when the input voltage changes sufficiently, the output will change, and the output voltage is VDD or GND. Therefore, during the startup process, Figure 2 PM5 will only be in a strong pull-up state or a shutdown state, with no intermediate state, which improves the stability of the reference circuit.

[0017] In summary, the present invention has been made into actual samples for long-term testing as described in the specification and the illustrated contents. From the results of the use test, it can be proved that the present invention can achieve its intended purpose, and its practical value is beyond doubt. The above embodiments are only used to illustrate the present invention, and are not intended to limit the present invention in any form. Any person with ordinary knowledge in the relevant technical field, if it does not depart from the scope of the technical features of the present invention, uses the equivalent embodiments of the technical content disclosed by the present invention to make partial changes or modifications, and does not depart from the technical features of the present invention, all still fall within the scope of the technical features of the present invention.

Claims

1. A reference current generating circuit with a startup circuit, comprising a reference circuit and a startup circuit connected to each other, wherein the reference circuit comprises a PMOS tube 1, a PMOS tube 2 and a PMOS tube 3 whose sources are connected together, a power supply voltage is input to the sources of the three PMOS tubes, and the gates of the three PMOS tubes are connected together; the drain of the PMOS tube 1 is respectively connected to one end of a resistor 1 and a resistor 2, the other end of the resistor 1 is connected to the emitter of a zero PNP type transistor, and the base, the collector of the zero PNP type transistor and the other end of the resistor 2 are connected together to the ground terminal The drain of the PMOS tube 2 is respectively connected to the emitter of the first PNP type transistor and one end of the resistor 3, the base, collector and the other end of the resistor 3 of the first PNP type transistor are connected together and connected to the ground terminal, the positive electrode of the input end of the amplifier is connected to the drain of the PMOS tube 2, the negative electrode of the input end of the amplifier is connected to the drain of the PMOS tube 1, the output end of the amplifier is connected to the gate of the NMOS tube 1, the gate and drain of the PMOS tube 3 are connected together and connected to the drain of the NMOS tube 1, and the source of the NMOS tube 1 is connected to the ground terminal, characterized in that: The startup circuit comprises a PMOS tube 4, a PMOS tube 5, an inverter 1, a resistor 4 and a Schmitt trigger, the sources of the PMOS tube 4 and the PMOS tube 5 are connected to the source of the PMOS tube 3 and to the power supply end, the gate of the PMOS tube 4 is connected to the gate of the PMOS tube 3, the drain of the PMOS tube 4 is connected to the input end of the inverter 1 and one end of the resistor 4, the other end of the resistor 4 is connected to the ground end, the output end of the inverter 1 is connected to the input end of the Schmitt trigger, the output end of the Schmitt trigger is connected to the gate of the PMOS tube 5, and the drain of the PMOS tube 5 is connected to the gate of the NMOS tube 1.

2. The reference current generating circuit with a startup circuit according to claim 1, characterized in that The positions of inverter 1 and Schmitt trigger in the startup circuit are interchanged.

Images