High-voltage LDO foldback overcurrent protection feedforward circuit and overcurrent protection method based thereon

Abstract

The present invention discloses a high-voltage LDO foldback overcurrent protection feedforward circuit and an overcurrent protection method based thereon. The high-voltage LDO foldback overcurrent protection feedforward circuit comprises: an LDO loop and an overcurrent protection loop; the LDO loop is used to generate an output voltage and provide a detection current and a feedback voltage based on an input reference voltage of a first operational amplifier; the overcurrent protection loop is used to introduce a detection current to increase the positive terminal voltage of a second operational amplifier, and when it is detected that the positive terminal voltage is higher than the feedback voltage, the overcurrent protection is triggered to open a switching current mirror, and the switching current mirror controls the output terminal voltage of the first operational amplifier so that the output terminal current of the first operational amplifier is accurately copied to the output terminal of the LDO loop.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor design, and more specifically, relates to a high-voltage LDO (Low Dropout Regulator, low voltage difference linear regulator) foldback overcurrent protection feedforward circuit. Background Art

[0002] There are generally two types of existing overcurrent protection technologies:

[0003] refer to Figure 1 The logic shuts down the power tube mode, and the overcurrent protection loop works in the comparator mode. The current limit threshold is set by the comparator. When the limit threshold is reached, the power device is turned off. Under abnormal load, the power supply may frequently trigger the switch overcurrent protection. For high-power systems, there will be frequent current shocks, causing chip stress damage or EMI interference to the system.

[0004] against Figure 1 The following problems exist in the logic shutdown action: if the overcurrent signal is latched and not restored after shutdown, the system generally needs to be restarted to resume normal operation. If the overcurrent signal is not latched, the load abnormality will repeatedly trigger the release of overcurrent protection, causing large fluctuations in the output current and voltage, causing impact and EMI interference to the system application.

[0005] refer to Figure 2 In the constant current output limiting mode, the overcurrent protection loop works in the operational amplifier mode. The operational amplifier current limiting threshold is reached. When the limit threshold is reached, the gate of the power device reaches charge balance. At this time, the power device outputs a constant current. The power supply may be in the overcurrent protection state for a long time. For high-power systems, there will be a long-term overload situation, which will cause thermal damage to the chip and shorten its life.

[0006] against Figure 2 In this application mode, the constant current limiting method requires the overcurrent protection loop to operate in the operational amplifier area, and a certain frequency compensation is required to prevent the loop from self-excitation. The current limiting protection action of this application method reacts relatively slowly. In the event of a sudden short circuit, the transient current is large and lasts for a long time. The current limiting value is a fixed value. The abnormal load causes the system to continuously output high power, causing thermal damage to the chip and reducing its life. Summary of the Invention

[0007] The purpose of the present invention is to address the problems existing in the prior art and provide a high-voltage LDO foldback overcurrent protection feedforward circuit and an overcurrent protection method based thereon, so as to solve at least one of the above technical problems.

[0008] According to one aspect of the present invention, there is provided a high-voltage LDO foldback overcurrent protection feed-forward circuit, comprising: an LDO loop and an overcurrent protection loop;

[0009] The LDO loop is used to generate an output voltage and provide a detection current and a feedback voltage according to the input reference voltage of the first operational amplifier;

[0010] The overcurrent protection loop is used to introduce a detection current to increase the positive terminal voltage of the second operational amplifier. When it is detected that the positive terminal voltage is higher than the feedback voltage, the overcurrent protection is triggered to open the switching current mirror. The switching current mirror controls the output terminal voltage of the first operational amplifier so that the output terminal current of the first operational amplifier is accurately copied to the output terminal of the LDO loop.

[0011] As a further technical solution, the overcurrent protection loop also includes a clamping module, the input end of the clamping module is respectively connected to the mirror power tube and the detection current, and the output end is respectively connected to the positive end of the second operational amplifier and the input end of the feedforward and loop compensation unit.

[0012] As a further technical solution, the feedforward and loop compensation unit is used to convert the detection current into a voltage signal and perform frequency compensation and signal feedforward on the overcurrent protection loop.

[0013] As a further technical solution, the mirror power tube is mirrored with the output power tube at the output end of the LDO loop, and is used to mirror the output current of the output power tube to the overcurrent protection loop as a detection current.

[0014] As a further technical solution, the overcurrent protection loop also includes a switching current mirror; the input end of the switching current mirror is connected to the output end of the second operational amplifier, and the output end is connected to the gate end of the NMOS tube, and the NMOS tube and the output power tube are mirror images.

[0015] According to one aspect of the present invention, there is provided an overcurrent protection method based on the high-voltage LDO foldback overcurrent protection feedforward circuit, comprising:

[0016] When the constant resistance mode is abnormal, the output current causes the positive terminal voltage of the second operational amplifier to rise to the feedback voltage, triggering the overcurrent protection. The output of the second operational amplifier increases, turning on the switch current mirror to pull down the current, and the output current decreases. If the resistive load remains unchanged at this time, the output voltage begins to decrease, the feedback voltage decreases, and this process repeats gradually until the current value is limited to a low value.

[0017] According to one aspect of the present invention, there is provided an overcurrent protection method for the high-voltage LDO foldback overcurrent protection feedforward circuit, comprising:

[0018] When the constant voltage mode is abnormal, the output port is mistakenly connected to a strong voltage source lower than the LDO output voltage, and the output current increases. At this time, the feedback voltage decreases, which is equivalent to a decrease in the current limit value. The output current of the first operational amplifier and the pull-down current of the switch current mirror reach a balance, and the output current is lower than the current limit setting value.

[0019] According to one aspect of the present invention, there is provided an overcurrent protection method based on the high-voltage LDO foldback overcurrent protection feedforward circuit, comprising:

[0020] During a momentary short circuit, the detection current and the positive terminal voltage of the second operational amplifier increase rapidly, the switching current mirror is turned on by the feedforward circuit, and the output voltage of the first operational amplifier is quickly pulled down. The gate terminal voltage of the LDO power tube increases, and the output current drops to a low value.

[0021] According to one aspect of the present invention, a low dropout linear regulator (LDO) is provided, comprising the high-voltage LDO foldback overcurrent protection feed-forward circuit.

[0022] According to one aspect of the present invention, an integrated circuit chip is provided, comprising the low dropout linear regulator LDO.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention uses a current mirror to mirror the output current of the LDO power tube to the current detection loop. The detection current flows into the feedforward and loop compensation circuit, causing Vsense to increase until it exceeds the VFB voltage to trigger the overcurrent protection loop. After the current limit is triggered, the overcurrent protection loop returns the current limit value to a low value, reducing the risk of long-term abnormal load continuous heat.

[0025] Under abnormal CV (constant voltage) and CR (constant resistance) loads, the output voltage and current change stably and smoothly without causing voltage and current stress shock or EMI interference.

[0026] The present invention has a rapid current limiting action during instantaneous short circuit, thereby reducing the risk of damage.

[0027] The present invention can automatically restore system output after the load is restored. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural diagram of the prior art.

[0029] Figure 2 It is a structural diagram of the second prior art.

[0030] Figure 3 This is a schematic diagram of the circuit structure provided by an embodiment of the present invention.

[0031] Figure 4 Schematic diagram of output voltage and current simulation waveforms provided by an embodiment of the present invention.

[0032] Figure 5 A schematic diagram of the instantaneous short-circuit voltage and current simulation waveform provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solution of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0034] An embodiment of the present invention provides a high-voltage LDO foldback overcurrent protection feedforward circuit, comprising: an LDO loop and an overcurrent protection loop; the LDO loop is configured to generate an output voltage and provide a detection current and a feedback voltage based on an input reference voltage of a first operational amplifier; the overcurrent protection loop is configured to introduce a detection current to increase the positive terminal voltage of a second operational amplifier, and when the positive terminal voltage is detected to be higher than the feedback voltage, trigger the overcurrent protection to open a switching current mirror, which controls the output terminal voltage of the first operational amplifier so that the output terminal current of the first operational amplifier is accurately replicated to the output terminal of the LDO loop.

[0035] like Figure 3 As shown, the positive terminal of the first operational amplifier (i.e., operational amplifier A in the figure) is connected to the reference voltage, and the output is connected to the gate terminal of the NMOS transistor NM1. The drain terminal of the NMOS transistor NM1 is respectively connected to the drain terminal and gate terminal of the PMOS transistor PM1 and the gate terminal of the PMOS transistor PM_Power. The drain terminal of the PMOS transistor PM_Power is connected in series with R1 and R2 to form a feedback resistor. The feedback resistor divider is connected to the negative terminal of the operational amplifier A, which forms a basic LDO loop, i.e., an LDO loop.

[0036] Furthermore, the source end of the NMOS transistor NM1 is grounded, and the source ends of the PMOS transistor PM1 and the PMOS transistor PM_Power are connected to the power supply VBAT respectively.

[0037] Figure 3 In the figure, the negative terminal of the second operational amplifier (i.e., operational amplifier B) is connected to the VFB feedback, and the output terminal is connected to the input terminal of the switching current mirror. The output of the switching current mirror is connected to the gate terminal of the NMOS tube NM1. The gate terminal of the mirror tube PM_Sense and the gate terminal of PM_Power are connected to form a current mirror. The drain terminal of the mirror tube PM_Sense and Vout are connected to the input of the clamping module (i.e., the clamping module). The output of the clamping module is connected to the feedforward and loop compensation module and the input of operational amplifier B. The feedforward and loop compensation module is connected across the input and output of operational amplifier B, forming an overcurrent protection loop as a whole.

[0038] Furthermore, a source end of the mirror transistor PM_Sense is connected to the power supply VBAT.

[0039] It should be noted that the clamping module acts on the drain of the mirror transistor PM_Sense, causing its voltage to follow Vout, and bears the voltage difference from the drain of PM_Sense to Vsense, so that the current is accurately replicated and the detection current flows in and out of the module.

[0040] The feedforward and loop compensation unit converts the detected current into a voltage signal and performs frequency compensation and signal feedforward for the OCP (overcurrent protection) control loop. It should be noted that the feedforward and loop compensation unit can be implemented using established technologies in the art, and the present invention does not limit its specific structure.

[0041] When the overcurrent protection is triggered, the NM1 gate voltage is controlled by the switch current mirror. When fully turned on, the NM1 current is accurately copied by the switch current mirror, so that the PM_Power tube output current is accurately limited.

[0042] The high-voltage LDO foldback overcurrent protection feedforward circuit provided in an embodiment of the present invention uses a current mirror PM_Sense to mirror the output current of the LDO power tube PM_Power to a current detection loop. The detected current flows into the feedforward and compensation circuit, causing Vsense to increase until it exceeds the VFB voltage, triggering the overcurrent protection loop.

[0043] Based on the same inventive concept as the above embodiment, an embodiment of the present invention further provides an overcurrent protection method based on the high-voltage LDO foldback overcurrent protection feedforward circuit, comprising:

[0044] In an abnormal CR mode, when the output current causes Vsense to rise to VFB, the current limiting loop is triggered. The output of op amp B increases, turning on the switch current mirror module to pull down the current. This causes the NM1 gate voltage to decrease, the PM_Power gate voltage to increase, and the output current to decrease. If the resistive load remains unchanged at this time, the output voltage begins to decrease, and the VFB voltage decreases. This cycle gradually repeats, until the current is limited to a low value.

[0045] Based on the same inventive concept as the above embodiment, an embodiment of the present invention further provides an overcurrent protection method for the high-voltage LDO foldback overcurrent protection feedforward circuit, comprising:

[0046] When the CV mode is abnormal, the output port is mistakenly connected to a strong voltage source lower than the LDO output voltage, and the output current increases. At this time, VFB decreases, which is equivalent to a decrease in the current limit value. The output current of op amp A and the pull-down current of the switch current mirror reach a balance, and the output current is lower than the current limit setting value.

[0047] Based on the same inventive concept as the above embodiment, an embodiment of the present invention further provides an overcurrent protection method based on the high-voltage LDO foldback overcurrent protection feedforward circuit, comprising:

[0048] During a short circuit, Isense and Vsense increase rapidly, the switch current mirror is turned on by the feedforward circuit, and the output voltage of op amp A is quickly pulled down. The PM_Power gate voltage increases, and the output current drops to a low value. The instantaneous short circuit waveform can be referred to Figure 5 . Figure 5 In the case of a short circuit, the output current increases instantly, the overcurrent protection circuit responds quickly, and the duration of the transient high current is very short.

[0049] Furthermore, in the embodiment of the present invention, for abnormal recovery, when the abnormal load is reduced to the current limit trigger value, the output voltage begins to increase, and VFB increases until it returns to normal output voltage and current. The trigger and recovery waveforms can be referred to Figure 4 .

[0050] Figure 4 In the example, the waveform in box A shows the load increasing until the overcurrent protection is triggered, with the current and voltage slowly decreasing to a constant value. The waveform in box B shows the output load decreasing until the overcurrent protection is restored, with the current and voltage slowly increasing to normal output. It's important to note that regardless of the CR or CV load abnormality, the circuit achieves limiting balance, and the output transitions smoothly throughout the entire process, without repeated on-off switching.

[0051] Based on the same inventive concept as the aforementioned embodiment, the present invention further provides a low-dropout linear regulator (LDO) including the aforementioned high-voltage LDO foldback overcurrent protection feedforward circuit. When the low-dropout linear regulator provided by the embodiment of the present invention is used, the overcurrent protection performance can be significantly improved.

[0052] According to one aspect of the present invention, an integrated circuit chip is provided. The integrated circuit chip includes the aforementioned low-dropout linear regulator with a high-voltage LDO foldback overcurrent protection feedforward circuit. The integrated circuit chip is used as a key component of a power module in an integrated circuit system to provide a stable power supply voltage for the system. The specific structure of the low-dropout linear regulator with a high-voltage LDO foldback overcurrent protection feedforward circuit in the integrated circuit chip is not further described herein.

[0053] In summary, the key technical features of the present invention are that they solve the existing technical problems using a simple structure, and the overcurrent protection function performance is greatly improved:

[0054] ① Achieve gradual foldback adjustment of output current and voltage during overcurrent protection, and adjust the transition smoothly.

[0055] ② Add the Clamping module to replicate the detection current with high precision and accurate trigger point.

[0056] ③ Add feedforward and loop compensation structure to make the loop respond quickly during transient short circuit.

[0057] ④ Use a switching current mirror to accurately control the final output current after foldback.

[0058] ⑤After the abnormality is recovered, the output can be restored automatically.

[0059] It should be noted that the above embodiments are only examples, and the technical solutions of the various embodiments can be combined and are all within the protection scope of the present invention.

[0060] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or to implicitly indicate the quantity of the technical features indicated. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features.

[0061] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A high-voltage LDO foldback overcurrent protection feedforward circuit, characterized in that: include: LDO loop and overcurrent protection loop; The LDO loop is configured to generate an output voltage and provide a detection current and a feedback voltage based on an input reference voltage of the first operational amplifier; the output of the first operational amplifier is connected to the gate terminal of an NMOS transistor, the gate terminal of the NMOS transistor is connected to the source terminal, and the drain terminal of the NMOS transistor is respectively connected to the drain terminal and gate terminal of the first PMOS transistor, the gate terminal of the mirror power transistor, and the gate terminal of the output power transistor; the drain terminal of the output power transistor is connected in series with a feedback resistor to the negative terminal of the first operational amplifier, thereby forming an LDO loop; The negative terminal of the second operational amplifier is connected to the feedback voltage, and the output terminal is connected to the input terminal of the switching current mirror. The output of the switching current mirror is connected to the gate terminal of the NMOS tube. The gate terminal of the mirror power tube is connected to the gate terminal of the output power tube to form a current mirror. The drain terminal and the output voltage of the mirror power tube are connected to the input of the clamping module. The output of the clamping module is connected to the feedforward and loop compensation unit and the positive terminal of the second operational amplifier. The feedforward and loop compensation unit is connected across the input and output of the second operational amplifier to form an overcurrent protection loop. The overcurrent protection loop is used to introduce a detection current to increase the positive terminal voltage of the second operational amplifier. When it is detected that the positive terminal voltage is higher than the feedback voltage, the overcurrent protection is triggered to open the switching current mirror. The switching current mirror controls the output terminal voltage of the first operational amplifier so that the output terminal current of the first operational amplifier is accurately copied to the output terminal of the LDO loop.

2. A high-voltage LDO foldback overcurrent protection feedforward circuit according to claim 1, characterized in that: The mirror power tube is mirrored with the output power tube at the output end of the LDO loop, and is used to mirror the output current of the output power tube to the overcurrent protection loop as a detection current.

3. An overcurrent protection method based on the high-voltage LDO foldback overcurrent protection feedforward circuit according to any one of claims 1-2, characterized in that: include: When the constant resistance mode is abnormal, the output current causes the positive terminal voltage of the second operational amplifier to rise to the feedback voltage, triggering the overcurrent protection. The output of the second operational amplifier increases, turning on the switch current mirror to pull down the current, and the output current decreases; If the resistance load remains unchanged at this time, the output voltage begins to decrease, the feedback voltage decreases, and this process repeats gradually until the current value is limited to a low value.

4. An overcurrent protection method based on the high-voltage LDO foldback overcurrent protection feedforward circuit according to any one of claims 1-2, characterized in that: include: When the constant voltage mode is abnormal, the output port is mistakenly connected to a strong voltage source lower than the LDO output voltage, and the output current increases. At this time, the feedback voltage decreases, which is equivalent to a decrease in the current limit value. The output current of the first operational amplifier and the pull-down current of the switch current mirror reach a balance, and the output current is lower than the current limit setting value.

5. An overcurrent protection method based on the high-voltage LDO foldback overcurrent protection feedforward circuit according to any one of claims 1-2, characterized in that: include: During a momentary short circuit, the detection current and the positive terminal voltage of the second operational amplifier increase rapidly, the switching current mirror is turned on by the feedforward circuit, and the output voltage of the first operational amplifier is quickly pulled down. The gate terminal voltage of the LDO power tube increases, and the output current drops to a low value.

6. A low dropout linear regulator LDO, characterized in that: The invention comprises the high-voltage LDO foldback overcurrent protection feedforward circuit according to any one of claims 1 to 2.

7. An integrated circuit chip, characterized in that: The invention comprises the low-dropout linear regulator LDO as claimed in claim 6.

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