CN111193387A

CN111193387A - Ultralow-loss low-end ideal diode

Info

Publication number: CN111193387A
Application number: CN202010116370.7A
Authority: CN
Inventors: 陈石平; 彭进双
Original assignee: Augur Intelligence Technology Guangzhou Co ltd
Current assignee: Augur Intelligence Technology Guangzhou Co ltd
Priority date: 2020-02-25
Filing date: 2020-02-25
Publication date: 2020-05-22

Abstract

The invention discloses an ultra-low loss low-end ideal diode which comprises a combinational logic control circuit and a first NMOS tube, wherein the combinational logic control circuit comprises a second NMOS tube, a third NMOS tube, a first resistor and a second resistor, the drain electrode of the first NMOS tube is connected with the source electrode and the power supply cathode of the second NMOS tube, the source electrode of the first NMOS tube is electrically connected with the source electrode of the third NMOS tube, the grid electrode of the first NMOS tube is electrically connected with the drain electrode of the third NMOS tube, the grid electrode of the second NMOS tube is connected with the drain electrode of the second NMOS tube and the grid electrode of the third NMOS tube, the drain electrode of the second NMOS tube is connected with the power supply anode through the first resistor, the drain electrode of the third NMOS tube is connected with the power supply anode through the second resistor, and a load is connected between the power supply anode and the source electrode of the first NMOS tube. The invention has the function of preventing backflow, can protect the preceding stage circuit, has very low loss, simple circuit and strong practicability.

Description

Ultralow-loss low-end ideal diode

Technical Field

The invention relates to the technical field of power diodes, in particular to an ultra-low loss low-end ideal diode.

Background

The diode has a one-way conduction characteristic, has a function of preventing backward flow, is applied more and more, and particularly has smaller voltage drop on a power supply connected in series with the Schottky diode, so that the Schottky diode is popular with more and more designers. Since the voltage drop of the schottky diode is still larger than that of the MOS transistor, for some voltage sensitive circuits, the MOS transistor with low impedance characteristic is more likely to be used, and the reliability of the product is improved. At present, a plurality of USB power switches (power distribution switches) are provided with a backflow prevention function, such as an MP62055 chip. Since when an external device is connected to the USB port of the computer, the device must not be able to reverse current flow into the VBus of the computer, which would otherwise burn the computer. At present, the Oring circuit is applied to many occasions, has the effect of ensuring that each single power supply is independent of each other and does not have the backflow phenomenon, is most commonly applied to a current-sharing circuit, and meets different power requirements.

Therefore, an ideal diode with ultra-low loss is needed, which further reduces the voltage drop, has the functions of preventing backflow, protecting the front stage, minimizing the loss and prolonging the working time of the battery.

In addition, the most similar technical implementation schemes of the invention are as follows, but all have certain disadvantages:

diode scheme: the diode is a natural Oring circuit because of its unidirectional conductivity, and the most basic Oring circuit is to add a diode at the output terminal. The diode is connected in series with the power supply, the circuit is simple, and the defect is that the diode has about 0.6V voltage drop, and the voltage drop is proportional to the power loss of the input current. As the current increases, the voltage drop also becomes larger, as power can be reduced by replacing with a schottky diode, but the power loss ratio is larger: taking schottky diode SS54 as an example, the voltage drops corresponding to currents 0.1A, 1A, 10A, and 20A are 0.3V, 0.4V, 0.85V, and 1.4V, respectively, and the losses corresponding to currents are 0.03W, 0.4W, 8.5W, and 28W, respectively, meaning that the larger the current passing, the larger the losses. Schottky diodes have the disadvantage of a voltage drop, which translates into a current loss, which is at least in the milliampere range.

MCU + PMOS pipe scheme: the circuit characteristics need an extra auxiliary voltage, Microcontroller (MCU), use two way AD of MCU to carry out voltage acquisition to the drain electrode (D utmost point) and the source electrode (S utmost point) of PMOS pipe, compare voltage magnitude between them, and then control switching on and cutting off of PMOS pipe, and the operating current loss that has the shortcoming is milliampere level at least, and current loss is very big, and need use extra auxiliary voltage and MCU, and the scheme is with high costs.

NPN pair transistor + NMOS pipe scheme: the circuit is characterized in that an additional auxiliary voltage is needed, two NPN tubes of the same manufacturer in the same batch are used, so that the voltages of two collectors can be basically equal, or two NPN triode pair tubes packaged together are preferably selected to be almost equal, so that the proper switching and backflow prevention functions can be guaranteed, the bias resistance of the triode with the defect is kilo-ohm level, the static working current loss is at least milliampere level, the current loss is large, and the additional auxiliary voltage is needed.

PNP geminate transistor + PMOS transistor scheme: the device of two PNP triodes packaged together is selected, so that two collecting electrodes can be almost equal, proper switching and backflow prevention functions can be guaranteed, the bias resistance of the triodes with the defects is kilo-ohm, the static working current loss is at least milliampere, and the current loss is very large.

Ideal diode scheme: using the chip LTC4413, Linear Technology (Linear Technology) introduced a dual channel ideal diode LTC4413, which was designed specifically for reducing heat, voltage drop and board area and extending battery life. The device is well suited for applications requiring ideal diode or functionality to achieve load sharing or automatic switching between two input sources. LTC4413 has low forward voltages of 80mV and 210mV at 500mA and 2A, respectively, with leakage currents of only 1uA, a significant improvement over discrete diode "OR" solutions. LTC4413 contained two 100mOhm P-channel MOSFETs. The maximum forward current of each MOSFET is limited to a constant 2.6A, and an internal thermal limit circuit can protect the device in the event of a fault. The method has the following defects: the output current is 1A high, the quiescent current is lower than 40 muA, and reverse backward flow current lower than 1 muA flows from the output end OUT to the input end IN; the 9uA open drain STAT pin indicates the conduction state of the selected channel and can be used to drive an external P-channel MOSFET to control a third standby power supply; LTC4413 is expensive.

The PMOS pair transistor + power PMOS transistor scheme: the invention patent (an ultra-low loss ideal diode, application number: CN201810920906.3) uses a double PMOS pair transistor combination control logic circuit to control a power PMOS transistor, has low insertion loss, is suitable for ultra-low power consumption application occasions, and can be used as a high-end (used between a load and a power supply anode) ultra-low power consumption ideal power diode. However, due to the large channel on-resistance, high cost, slow speed, and few alternatives of the PMOS transistor, the NMOS transistor is usually used in low-end applications (between the load and the negative electrode of the power supply).

NMOS transistors use electrons as "majority carriers", which have a higher mobility than the "majority carrier" holes of PMOS transistors. Under the same physical density, the NMOS has higher transconductance and lower on-resistance than the PMOS. The on-resistance of the NMOS is 1/3-1/2 of PMOS with the same size, and the NMOS generally needs less silicon chips for the same on-resistance, so the grid capacitance and threshold voltage of the NMOS are lower than those of the PMOS.

The NMOS transistor has much wider application occasions than the PMOS transistor, and the NMOS transistor which can be realized by the PMOS transistor can also be realized by the PMOS transistor. Almost all switching power supply topologies prefer to use NMOS transistors (rather than PMOS transistors) such as forward, flyback, push-pull, half-bridge, full-bridge, etc. topologies. Under the condition of the same process and size area, the on-resistance of the PMOS tube is larger than that of the NMOS tube, so that the on-loss of the PMOS switch tube is larger than that of the NMOS switch tube. In addition, the NMOS tube has the advantages of multiple applications, multiple requirements, multiple models and low price, and is suitable for the condition (low-end driving) when being connected with the cathode of a power supply.

The ultra-low power high side ideal diode is suitable for the case of connecting the positive pole of the power supply (high side drive) and "sources" current to the load circuit, while the ultra-low power low side ideal diode turns the load on or off the negative pole of the power supply, so it "sinks" current from the load.

Therefore, there is a need for a lower loss, less expensive, and more versatile ideal diode for NMOS transistor-based low-end applications.

Disclosure of Invention

In view of the above-mentioned drawbacks of the prior art, the present invention provides an ultra-low loss low-side ideal diode to overcome the shortcomings of the prior art.

In order to achieve the above object, the present invention provides an ultra-low loss low-side ideal diode, which is characterized in that: including combinational logic control circuit and first NMOS pipe, combinational logic control circuit includes second NMOS pipe, third NMOS pipe, first resistance and second resistance, the source electrode and the power negative pole of second NMOS pipe are connected to the drain electrode of first NMOS pipe, the source electrode of third NMOS pipe is connected to the source electrode electricity of first NMOS pipe, the drain electrode of third NMOS pipe is connected to the grid electricity of first NMOS pipe, the drain electrode of second NMOS pipe and the grid of third NMOS pipe are connected to the grid of second NMOS pipe, the drain electrode of second NMOS pipe is through first resistance connection power supply positive pole, the drain electrode of third NMOS pipe is through second resistance connection power supply positive pole. The LOAD is connected between a power supply anode VCC (LOAD +) and a source electrode (LOAD-) of the first NMOS tube, and when the voltage LOAD-is not less than the voltage GND, the NMOS tube is conducted; otherwise, the NMOS tube is cut off, thereby preventing the GND current from flowing backwards to the load-protecting the load-load circuit. When the positive pole VCC (LOAD +) of the power supply is reversely connected with the negative pole GND of the power supply, the reverse connection prevention protection effect can be achieved.

Preferably, the grid electrode of the first NMOS transistor is electrically connected to the drain electrode of the third NMOS transistor, and the drain electrode of the third NMOS transistor is connected to the positive electrode of the power supply through the second resistor.

Preferably, the grid electrode of the second NMOS tube is connected to the drain electrode of the second NMOS tube and the grid electrode of the third NMOS tube, and the drain electrode of the second NMOS tube is connected to the positive electrode of the power supply through the first resistor.

Preferably, the static loss of the combinational logic control circuit is very low, the current loss is less than microampere level, and if 2 resistors are connected in series with 100M omega resistors, the static current loss can be as low as 100 nA.

Preferably, the circuit has a function of preventing backflow and has a low conduction voltage drop.

Preferably, the second NMOS transistor and the third NMOS transistor are two NMOS transistors of the same type or two NMOS transistors having the same parameters and packaged together.

Preferably, the first NMOS transistor may use NMOS transistors with different on-current magnitudes. Compared with a PMOS tube, the NMOS tube has more advantages: low on-resistance, low on-loss, many types, cheaper price and wide application. For high-power control, the NMOS tube can select the on-resistance between the D pole and the S pole to be several milliohms, the power tube device combination logic control circuit with large passing current consists of double NMOS tubes and resistors, after voltage selection and comparison are conducted between the drain electrode (D pole) and the source electrode (S pole) of the NMOS tube, different levels are output to control the on-off of the NMOS tube, the NMOS tube with the on-resistance between the D pole and the S pole of several milliohms is selected, and the large current (hundreds of amperes) can pass, so that the voltage drop through the NMOS tube is small, the NMOS tube can be approximated to an ideal diode, and the NMOS tube is suitable for being used for the condition (low-end drive) when the power supply is connected with the negative pole.

The invention has the beneficial effects that:

the invention has the function of preventing backflow and can protect the preceding stage circuit; the loss is very low, and the static current loss can be as low as 100 nA; the combined logic control circuit is used, so that the circuit is simple, the application is more, the demands are more, the models are more, the price is low, and the practicability is high.

The conception, the specific structure and the technical effects of the present invention will be further described with reference to the accompanying drawings to fully understand the objects, the features and the effects of the present invention.

Drawings

FIG. 1 is a schematic diagram of a circuit employing discrete NMOS transistors in accordance with the present invention.

Detailed Description

The embodiments of the invention will be described in detail below with reference to the drawings, but the invention can be implemented in many different ways as defined and covered by the claims.

As shown in fig. 1, the combinational logic control circuit is composed of 2 NMOS transistors (V2, V3) of the same type or NMOS pair transistors packaged together with the same parameters, and 2 series resistors (R1, R2), and controls the on and off of the NMOS transistor (V1): when the voltage LOAD-is not less than the voltage GND, the NMOS tube (V1) is conducted; and on the contrary, the NMOS tube (V1) is cut off, so that the GND current is prevented from flowing back to the LOAD-through the NMOS tube (V1), and the LOAD-LOAD circuit is protected. Because the NMOS tube belongs to a voltage device, the current of the NMOS tube is very small when the NMOS tube is switched on and switched off, the NMOS tube is connected with a resistor with a large resistance value in series, the NMOS tube can be ignored, and only very small current (smaller than microampere level) is lost when the NMOS tube is switched on.

Furthermore, the NMOS geminate transistors have the same parameters and are symmetrical double-N-channel MOS transistors, so that parameter consistency can be kept as far as possible when the temperature changes. The circuit adjusts the size of the series resistor of two drain electrodes (D poles) of the NMOS geminate transistors according to different loss requirements, and the loss requirements are met. The static loss of the circuit is very low, the current loss is less than microampere level, if 2 resistors are connected in series with a 100M omega resistor, the static current loss is less than 100nA, the circuit has the function of preventing backflow and has very low forward voltage.

The combination logic control circuit comprises double NMOS tubes (V2, V3) and 2 resistors (R1, R2), wherein the NMOS tube (V1) can use NMOS tubes with different on-state current sizes, and different power requirements are met. The invention has the function of preventing backflow and can protect the preceding stage circuit; the loss is very low, and the static current loss is less than 100 nA; the combined logic control circuit is simple, low in cost and high in practicability, is particularly suitable for application of the NB-IoT ultra-low loss ideal diode circuit, and is very simple and low in cost. Wherein,

and an NMOS tube with proper on-resistance between the D pole and the S pole is selected according to different loss requirements, so that the loss requirements are met. For high-power control, an NMOS can select the on-resistance between a D pole and an S pole to be several milliohms, a power tube device combination logic control circuit with large passing current consists of double NMOS tubes and resistors, after voltage selection and comparison are conducted between a drain electrode (D pole) and a source electrode (S pole) of the NMOS tubes, different levels are output to control the on-off of the NMOS tubes, and the NMOS tubes belong to voltage devices, so that the current of the NMOS tubes is very small when the NMOS tubes are switched on and switched off and can be ignored, and only very small current (smaller than microampere level) is lost when the NMOS tubes are switched on. The NMOS tube with the on-resistance between the D pole and the S pole of several milliohms can pass a large current (hundreds of amperes), so that the voltage drop of the NMOS tube is small, and the NMOS tube can be approximated to an ideal diode.

The PCB is designed according to the schematic diagram for testing, the model number of the NMOS tubes (V1, V2 and V3) is 2N7002, and the PCB is tested after assembly.

The NMOS transistors (V2, V3) adopt two independent 2N7002 transistors, the test circuit is as shown in fig. 1, the turn-on typical value vgs (th) of the 2N7002 transistor is 1.6V (1V to 2.5V), and the test results are as shown in table 1: when VCC is powered by 5.0V (both series resistors are 10 MOmega), the static loss current IL is 0.7 muA, V2 and V3 are both in the variable resistor area, V1 is conducted, and 0.1A current can pass after the VCC is connected with a load; after GND is connected with the positive pole of a 5.0V power supply (equivalent to reverse connection, VCC is connected with the negative pole of the power supply), the reverse static loss current IB is 0.4 muA (no backward current flows into LOAD-, and the LOAD-voltage is 0V). The two series resistors are respectively welded to be 100M omega, 1M omega and 100k omega, and the test results are shown in Table 1. In addition, the model numbers of all 3 NMOS transistors are changed to AO3420, and the test results are shown in Table 1. The combinational logic control circuit can effectively control the NMOS (V1) tube to be switched on and off, and can pass through a plurality of amperes of current after being connected with a load, namely, the NMOS tube can pass through a large current and has a backflow prevention function, so that the application range is greatly expanded.

TABLE 1 two different types of NMOS transistors

The invention has the beneficial effects that: compared with the traditional power diode or triode control current loss milliampere level, the static current loss is smaller by more than two orders of magnitude; compared with an ideal diode (LTC4413), the static loss current is reduced by more than one order of magnitude, and the reverse flow current is not stored. The circuit greatly reduces the static loss of equipment, prolongs the working time of a battery, has high equipment maintenance cost and low loss, is suitable for the application of the NB-IoT ultralow-loss low-end ideal diode circuit, and has the advantages of simplicity and low cost.

The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.

Claims

1. An ultra-low loss low-side ideal diode, comprising: the power supply circuit comprises a combinational logic control circuit and a first NMOS tube, wherein the combinational logic control circuit comprises a second NMOS tube, a third NMOS tube, a first resistor and a second resistor, the drain electrode of the first NMOS tube is connected with the source electrode of the second NMOS tube and the negative electrode of a power supply, the source electrode of the first NMOS tube is electrically connected with the source electrode of the third NMOS tube, the grid electrode of the first NMOS tube is electrically connected with the drain electrode of the third NMOS tube, the grid electrode of the second NMOS tube is connected with the drain electrode of the second NMOS tube and the grid electrode of the third NMOS tube, the drain electrode of the second NMOS tube is connected with the positive electrode of the power supply through the first resistor, and the drain electrode of the third NMOS tube is connected with the positive electrode of the power supply through the second resistor; the load is connected between the positive electrode VCC of the power supply and the source electrode of the first NMOS tube, and when the voltage load-is not less than the voltage GND, the NMOS tube is conducted; otherwise, the NMOS tube is cut off, the GND current is prevented from flowing backwards to the load-, and the load-load circuit is protected; when the positive pole VCC of the power supply is reversely connected with the negative pole GND of the power supply, the reverse connection prevention protection effect is achieved.

2. An ultra-low loss low side ideal diode as defined in claim 1, wherein: and a load is connected between the power supply anode VCC and the source electrode of the first NMOS tube.

3. An ultra-low loss low side ideal diode as defined in claim 1, wherein: the first NMOS tube uses NMOS tubes with different on-state currents.

4. An ultra-low loss low side ideal diode as defined in claim 1, wherein: the second NMOS tube and the third NMOS tube are two NMOS tubes with the same type or two NMOS tubes which have the same parameters and are packaged together.

5. An ultra-low loss low side ideal diode as defined in claim 1, wherein: the static current loss of the combinational logic control circuit is less than microampere level.

6. An ultra-low loss low side ideal diode as defined in claim 1, wherein: the resistance values of the first resistor and the second resistor are adjustable so as to meet the requirement of low power consumption.