A high-side ideal diode based on a bandgap reference

Abstract

The utility model discloses a kind of high-end ideal diode based on band gap reference, including high-end load switch MOS tube, voltage comparator and band gap reference voltage module, the high-end load switch MOS tube, voltage comparator and band gap reference voltage module composition integral circuit, the MOS tube is PMOS tube or NMOS tube.This circuit has the function of preventing backflow, can protect front-stage circuit;With lower loss, small static current loss;Use high-end load switch and voltage comparator, circuit is simple, cost is very low, and practicality is strong;Voltage comparator is used to compare the voltage of the voltage divider of MOS tube output end and reference voltage, band gap reference voltage source has higher precision, strong anti-interference ability, and there is no backflow current;Reduce the static loss of equipment, prolong the working time of battery, equipment maintenance cost is low, loss reduces greatly, suitable for thing networking NB-IoT ultra-low loss ideal diode circuit application, circuit is very simple and has very low cost advantage.

Description

Technical Field

[0001] This utility model relates to the field of diode technology, specifically to a high-end ideal diode based on a bandgap reference. Background Technology

[0002] Diodes, due to their unidirectional conduction characteristics and reverse current prevention capabilities, are increasingly used, especially Schottky diodes connected in series, which offer the advantage of lower voltage drop in power supplies and are gaining popularity among designers. However, since the voltage drop of a Schottky diode is still greater than that of a MOSFET, for some voltage-sensitive circuits, MOSFETs with low impedance characteristics are preferred to improve product reliability. Many USB power switches (distribution switches) now incorporate reverse current prevention, such as the MP62055 chip. This is because when an external device is connected to a computer's USB port, the device must not allow current to flow back into the computer's VBus, otherwise it will damage the computer. Currently, orifice circuits are used in many applications to ensure that each individual power supply is independent and prevents reverse current flow. They are most commonly used in current sharing circuits to meet different power requirements.

[0003] Therefore, an ideal diode is needed, an ideal diode with ultra-low loss, to further reduce voltage drop and have reverse current protection and front-end protection functions, so as to minimize losses.

[0004] Existing MOSFET control schemes use a Zener diode as a reference voltage. The input voltage is compared with the voltages across the source and drain of the MOSFET using a voltage comparator to determine the gate voltage and thus control the PMOS transistor's conduction and cutoff. However, a voltage regulation value below 6V indicates Zener breakdown. Zener breakdown has a negative temperature coefficient; as temperature increases, the depletion layer shrinks, and valence electrons in the atoms rise to higher energies. A relatively small electric field can excite these electrons, causing Zener breakdown. Due to its negative temperature coefficient, the voltage stability of Zener breakdown is poor, typically ±(5~10)%. Using a Zener diode as the reference voltage leads to low accuracy in the voltage comparator, easily causing misjudgments.

[0005] Since almost no semiconductor components in the real physical world have temperature-independent parameters, and Zener diodes are no exception, as long as some devices with positive and negative temperature coefficients can be found, and their errors can be canceled out by appropriate combinations, temperature-independent quantities can be obtained, and these parameters are independent of the power supply. Common methods for solving temperature drift are as follows:

[0006] 1. Replace BJT transistors with FETs: FETs primarily involve majority carriers in conduction, while BJTs involve both majority and minority carriers. Minority carrier concentration is significantly affected by factors such as temperature and radiation. Since majority carrier concentration is less affected by external temperature, light, and radiation, FETs are more suitable for environments with significant variations. This is why MOSFETs are generally considered more stable. Therefore, FETs offer better temperature stability and radiation resistance than BJTs, making them the preferred choice for applications with highly variable environments.

[0007] 2. Differential amplifier circuit: Its parameter symmetry has a mutual compensation effect, which can suppress temperature drift, stabilize the static operating point and suppress common-mode signals.

[0008] 3. Matched Pair Transistors, or simply Pair Transistors, are two transistors of the same type (NPN, PNP, NMOS, or PMOS) with extremely similar parameters, fabricated on the same substrate and packaged in a single chip. The temperatures of the two transistors affect each other, and ambient temperature has the same effect on both transistors. The noise figures, characteristic curves, and amplification factors of the two transistors are required to be as identical as possible, with consistency achieved within 10%, or even 1%. In this case, by constructing a circuit using specific wiring methods, the noise of the transistors themselves, temperature-induced zero-point drift, and the influence of common-mode signals on differential-mode signals can be largely canceled out.

[0009] 4. In applications with high power requirements, two Zener diodes with opposite temperature coefficients can be connected in series for compensation. Due to mutual compensation, the temperature coefficient is greatly reduced, reaching as low as 0.0005% / ℃.

[0010] A bandgap voltage reference (simply called a bandgap) is a circuit that utilizes the bandgap characteristic of the band structure of semiconductor materials to realize a voltage reference source. Its principle is to use two current generators with different temperature coefficients, making the voltage difference in their outputs inversely proportional to the temperature, thus achieving a temperature-stable voltage reference. A classic bandgap reference uses the sum of a voltage with a positive temperature coefficient and a voltage with a negative temperature coefficient; their temperature coefficients cancel each other out, achieving a temperature-independent voltage reference of approximately 2.50V. Because its reference voltage is close to the bandgap voltage of silicon, it is also called a bandgap reference.

[0011] A bandgap voltage reference source typically consists of a current source, an amplifier, and a differential voltage amplifier. It is a commonly used voltage reference source, characterized by high stability and good temperature stability, and is widely used in analog circuits, power management, and other fields. Based on this idea, the bandgap voltage reference source offers high accuracy. To replace the Zener diode, a high-end ideal diode based on the bandgap reference is designed to meet the needs of more advanced applications. Therefore, we propose a high-end ideal diode based on the bandgap reference to address the aforementioned issues. Utility Model Content

[0012] The purpose of this invention is to provide a high-end ideal diode based on a bandgap reference to solve the problems mentioned in the background art.

[0013] To achieve the above objectives, this utility model provides the following technical solution: a high-side ideal diode based on a bandgap reference, comprising a high-side load switching MOSFET, a voltage comparator, and a bandgap reference voltage module, wherein the high-side load switching MOSFET, the voltage comparator, and the bandgap reference voltage module constitute an integrated circuit, and the MOSFET is a PMOS transistor or an NMOS transistor.

[0014] Preferably, the voltage comparator determines whether the high-side load switch MOSFET is turned on or off by comparing the voltage divider at the output of the MOSFET with the reference voltage.

[0015] Preferably, the voltage comparator is a Schmitt trigger.

[0016] Compared with the prior art, the beneficial effects of this utility model are: this circuit has the function of preventing backflow, which can protect the front-end circuit; it has low loss and low static current loss; it uses a high-end load switch and a voltage comparator, the circuit is simple, the cost is very low, and it is highly practical; the voltage comparator compares the voltage divider at the output of the MOSFET with the reference voltage, the bandgap reference voltage source has higher accuracy, strong anti-interference ability, and no backflow current; it reduces the static loss of the device, extends the battery working time, reduces the device maintenance cost, and greatly reduces losses. It is suitable for IoT NB-IoT ultra-low loss ideal diode circuit applications, the circuit is very simple and has a very low cost advantage. Attached Figure Description

[0017] Figure 1 This is a block diagram of the bandgap reference high-side ideal diode with a PMOS transistor as the main component of the present invention.

[0018] Figure 2 This is a block diagram of the bandgap reference high-side ideal diode with an NMOS transistor as the main component of this utility model.

[0019] Figure 3 This utility model Figure 1 Forward conduction simulation;

[0020] Figure 4 This utility model Figure 1 Reverse cutoff simulation;

[0021] Figure 5 This utility model Figure 2 Forward conduction simulation;

[0022] Figure 6 This utility model Figure 2 Reverse cutoff simulation. Detailed Implementation

[0023] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model. Example

[0024] Reference Figure 1 This is the first embodiment of the present invention. This embodiment provides a high-side ideal diode based on a bandgap reference, including a high-side load switching MOSFET, a voltage comparator, and a bandgap reference voltage module. The main body of the high-side load switching MOSFET is a PMOS transistor V1, and the gate of the PMOS transistor V1 is connected to the output terminal of the voltage comparator. The non-inverting terminal of the voltage comparator is connected to one end of R1 and R2, and the inverting terminal is connected to one end of R3 and the reference voltage U2. The output terminal of the voltage comparator is an open-drain output and requires an external pull-up resistor R4. The reference voltage module generates a voltage VN = 2.494V.

[0025] When forward biased, meaning the input voltage VCC is greater than the output voltage Vout, this is equivalent to the voltage VP at the non-inverting input of the voltage comparator being less than the voltage VN at the inverting input: VP = Vout × R2 / (R1 + R2) < VN = 2.494V. The output of voltage comparator U1 is low (approximately 0V), and VCC conducts to Vout through the body diode of the PMOS transistor. Vout = VCC - 0.7V. GS =0V-Vout=-Vout<V TP V TP When the input voltage VCC is less than the output voltage Vout, it is equivalent to the voltage VP at the non-inverting input of the voltage comparator being greater than the voltage VN at the inverting input. The voltage comparator outputs a high level, Vout, and the PMOS transistor V1 is turned off to prevent the Vout current from flowing back into VCC and to protect the VCC power supply front-end circuit.

[0026] The voltage comparator compares the voltage drop across the output of the MOSFET with the reference voltage to determine whether the high-side load switch MOSFET is on or off. This prevents the output power from flowing back into the input power, protects the input power supply's pre-amplifier circuit, and provides higher anti-interference capability.

[0027] The voltage comparator is a Schmitt trigger, exhibiting priority hysteresis loop propagation characteristics. The threshold voltage of this type of voltage comparator changes rapidly with changes in the output voltage, enhancing its anti-interference capability. Hysteresis voltage comparators possess hysteresis characteristics, i.e., inertia, thus providing a certain degree of anti-interference capability; however, the stronger the anti-interference capability, the lower the sensitivity. A hysteresis voltage comparator circuit has two threshold voltages: VT1, which causes a jump in the output voltage Vout as the input voltage VCC gradually increases; and VT2, which causes a jump in the output voltage Vout as the input voltage VCC gradually decreases. VT1 ≠ VT2, and the circuit exhibits hysteresis characteristics. Similar to a single-threshold voltage comparator, when the input voltage changes in one direction, the output voltage Vout jumps only once.

[0028] PMOS transistor V1 can be used with different on-current values. For high-power power supply control, the on-resistance R between the drain and source of the PMOS transistor can be selected. DS(ON) A power transistor device with a voltage rating of several milliohms and a large current carrying capacity has a small voltage drop when carrying a large current, meaning it has a very low forward voltage and can be approximated as an ideal diode. Example

[0029] This embodiment is based on the circuit of Embodiment 1. Figure 1 Based on this, replace the PMOS transistor V1 with an NMOS transistor and add a bias voltage source VBIAS (a charge pump power supply or other high-voltage DC power supply can be used) to ensure that VBIAS > VCC + V TN V TN The turn-on threshold voltage of the NMOS transistor, such as Figure 2 As shown, the reference voltage module VP = 2.494V.

[0030] When forward biased, meaning the input voltage VCC is greater than the output voltage Vout, it's equivalent to the voltage VP at the non-inverting input of the voltage comparator being greater than the voltage VN at the inverting input: the output of the voltage comparator is high, VBIAS > VCC + V TN When the input voltage VCC is less than the output voltage Vout, it is equivalent to the voltage VP at the non-inverting input of the voltage comparator being less than the voltage VN at the inverting input: the voltage comparator outputs a low level, the NMOS transistor V1 is turned off, preventing the Vout current from flowing back into VCC and protecting the VCC power supply pre-amplifier circuit.

[0031] Simulation test:

[0032] according to Figure 1 , Figure 2 The circuit schematic was simulated and tested using National Instruments' Multisim simulation software (version V14.0). The voltage comparator selected was the LM293P (with dual operational amplifiers), with an open-drain (OD) output, requiring an external pull-up resistor. The PMOS transistor selected was from ON Semiconductor, model NVTFS5124PLTAG, with a minimum turn-on threshold voltage of V. TP(MIN) =-1.5V, maximum value V TP(MAX) =-2.5V, typical value V not given. TP The conduction current can reach -6A, and the conduction impedance R DS(ON) =0.26Ω(V GS =-10V), R DS(ON) =0.38Ω (V GS =-4.5V). The NMOS transistor used is from NXP, model BSP030, with a minimum turn-on threshold voltage of V. TN(MIN) =1V, maximum value V TN(MAX) =2.8V, typical value V not given. TN The conduction current reaches 10A, and the conduction impedance R DS(ON) =30mΩ (V) GS =10V), R DS(ON) =50mΩ (V) GS =4.5V).

[0033] The bandgap reference voltage source device used is the TI TL431IPK, a three-terminal adjustable shunt regulator that meets specified thermal stability over applicable automotive, commercial, and military temperature ranges. The output voltage can be set to any value between Vref (approximately 2.5V, simulated 2.494V) and 36V using two external resistors. Its typical output impedance is 0.2Ω. The active output circuitry of this type of device exhibits very pronounced conduction characteristics, making it ideal for replacing Zener diodes in many applications, such as onboard regulators, adjustable power supplies, and switching power supplies. The TL431 series devices have the same functionality and electrical characteristics but are available in different DBV, DBZ, and PK package pinouts.

[0034] The TL431 is available in three grades: B, A, and Standard, with initial tolerances of 0.5%, 1%, and 2% respectively at 25°C, offering high accuracy. Furthermore, low output temperature drift ensures excellent stability across the entire temperature range. The load resistance is RL = 10Ω, and specific simulation tests are as follows.

[0035] Example 1 Simulation

[0036] Simulation of a high-side ideal diode with a bandgap reference, consisting of PMOS transistors.

[0037] DC power supply forward conduction simulation test: VCC=12V (switch J1 closed, switch J2 open), meaning the input voltage VCC is greater than the output voltage Vout. This is equivalent to the voltage VP at the non-inverting input of the voltage comparator being less than the voltage VN at the inverting input: VP=Vout×R2 / (R1+R2)=11.7V×10kΩ / (10kΩ+38kΩ)=2.44V<VN=2.494V. The output of the voltage comparator is low (72.5mV, test point PR2). When PMOS transistor V1 is forward conducting, the output voltage Vout=11.7V (11.697V measured with a digital multimeter in voltage mode). The forward voltage drop of PMOS transistor V1 is 12V-11.7V=0.3V, which is lower than the forward voltage drop of the diode Vout. F The power supply output current at the positive terminal is 1.17A, corresponding to the on-resistance R. DS(ON) =0.3V / 1.17A=0.256Ω, which is not much different from the datasheet data. Specific simulation results are as follows: Figure 3 As shown.

[0038] DC power supply reverse cutoff simulation test: The input voltage VCC is less than the output voltage Vout. After switch J1 is closed, switch J2 also closes, meaning Vout = VCC2 = 12.1V > VCC = 12V. VP = Vout × R2 / (R1 + R2) = 12.1V × 10kΩ / (10kΩ + 38kΩ) = 2.52V > VN = 2.494V. The voltage comparator output is high (12.1V, test point PR2), PMOS transistor V1 is cut off, and the reverse current is 0A (test point PR4, negligible). It can be considered that no reverse current occurs. The specific simulation is as follows: Figure 4 As shown.

[0039] Example 2 Simulation

[0040] Simulation of a high-side ideal diode with a bandgap reference, consisting of NMOS transistors.

[0041] Circuit in Example 1 Figure 1 Based on this, replace the PMOS transistor V1 with an NMOS transistor and add a bias voltage source VBIAS. For ease of simulation, use a high-voltage DC power supply for VBIAS, ensuring that VBIAS = 15V > VCC + V. TN V TN This is the turn-on threshold voltage for the NMOS transistor.

[0042] DC power supply forward conduction simulation test: VCC=12V (switch J1 closed), when forward conducting, the output voltage Vout of NMOS transistor V1 is 11.9V (11.894V measured by a digital multimeter in voltage mode), VP=2.494V>VN=Vout×R2 / (R1+R2)=2.48V, the voltage comparator U1A outputs a high level (15.0V, test point PR2), NMOS transistor V1 conducts, and the forward voltage drop is 12V-11.9V=0.1V, which is lower than the forward voltage drop V of the diode. F It is also lower than Figure 1 The PMOS transistor V1 has a forward voltage drop, and the positive output current of the power supply is 1.19A, corresponding to a forward impedance R. DS(ON) =0.1V / 1.19A=0.084Ω, which is not much different from the datasheet data; the specific simulation is as follows. Figure 5 As shown, the forward conduction simulation voltage drop is very small, the loss is less than that in Example 1, the on-resistance of the NMOS transistor is lower than that of the PMOS transistor, and the NMOS transistor has excellent conduction characteristics.

[0043] DC power supply reverse cutoff simulation test: After switch J1 is closed, switch J2 is also closed. Conversely, when the input voltage VCC is less than the output voltage Vout, i.e., Vout = VCC2 = 12.1V > VCC = 12V, it is equivalent to the voltage VP at the non-inverting terminal of the voltage comparator being greater than the voltage VN at the inverting terminal: VP = 2.494V > VN = Vout × R2 / (R1 + R2) = 2.48V. The voltage comparator output is low (90.9mV, test point PR2), the NMOS transistor V1 is cut off, and the reverse current is -178nA (test point PR4), which can be ignored. The specific simulation is as follows. Figure 6 As shown, the reverse cutoff simulation loss is the same as in Example 1.

[0044] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-side ideal diode based on a bandgap reference, comprising a high-side load switching MOSFET, a voltage comparator, and a bandgap reference voltage module, characterized in that: The high-side load switch MOSFET, voltage comparator, and bandgap reference voltage module form an integrated circuit. The MOSFET is either a PMOS or an NMOS transistor. The gate of the high-side load switch MOSFET is connected to the output terminal of the voltage comparator. The non-inverting terminal of the voltage comparator is connected to one end of resistors R1 and R2, and the inverting terminal of the voltage comparator is connected to one end of resistor R3 and the reference voltage U.

2. The high-side ideal diode based on a bandgap reference according to claim 1, characterized in that: The voltage comparator determines whether the high-side load switch MOSFET is on or off by comparing the voltage divider at the output of the MOSFET with the reference voltage.

3. The high-side ideal diode based on a bandgap reference according to claim 1, characterized in that: The voltage comparator is a Schmitt trigger.

Images