High-voltage LDO turn-back type overcurrent protection feed-forward circuit and overcurrent protection method based on same

Abstract

The invention discloses a high-voltage LDO turn-back type overcurrent protection feed-forward circuit and an overcurrent protection method based on the high-voltage LDO turn-back type overcurrent protection feed-forward circuit. The high-voltage LDO turn-back type overcurrent protection feed-forward circuit comprises an LDO loop and an overcurrent protection loop. The LDO loop is used for generating an output voltage according to an input reference voltage of the first operational amplifier and providing a detection current and a feedback voltage; the over-current protection loop is used for introducing detection current, so that the positive end voltage of the second operational amplifier is increased, when it is detected that the positive end voltage is higher than feedback voltage, over-current protection is triggered to open the switch current mirror, and the switch current mirror controls the output end voltage of the first operational amplifier; and the current of the output end of the first operational amplifier is accurately copied to the output end 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 usually two types of existing overcurrent protection technologies: 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.

[0003] against Figure 1 The logic shutdown action has the following problems: if the latched overcurrent signal is 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 the output current and voltage to fluctuate significantly, causing impact and EMI interference to the system application.

[0004] refer to Figure 2 In constant current output limiting mode, the overcurrent protection loop works in operational amplifier mode. Through the operational amplifier current limiting threshold, the gate of the power device reaches charge balance when the limiting threshold is reached. At this time, the power device outputs a constant current, and the power supply may be in an 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 reduce its life.

[0005] against Figure 2 The constant current limiting method requires the overcurrent protection loop to work 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. When a short circuit occurs, 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

[0006] The purpose of the present invention is to provide a high-voltage LDO foldback overcurrent protection feedforward circuit and an overcurrent protection method based thereon in view of the problems existing in the prior art, so as to solve at least one of the above-mentioned technical problems.

[0007] According to one aspect of the present invention, there is provided a high-voltage LDO foldback overcurrent protection feedforward circuit, comprising: 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 according to an input reference voltage of the first operational amplifier; 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 switch current mirror. The switch 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.

[0008] 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.

[0009] 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.

[0010] 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.

[0011] 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.

[0012] 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: When the constant resistance mode is abnormal, the output current causes the positive terminal voltage of the second operational amplifier to increase 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.

[0013] 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: 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.

[0014] 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: During a momentary short circuit, the detection current and the positive terminal voltage of the second operational amplifier increase rapidly, the switch 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.

[0015] According to one aspect of the present invention, a low dropout linear regulator LDO is provided, comprising the high voltage LDO foldback overcurrent protection feedforward circuit.

[0016] According to one aspect of the present invention, an integrated circuit chip is provided, comprising the low dropout linear regulator LDO.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention uses a current mirror to mirror the output current of the LDO power tube to the current detection loop, and the detection current flows into the feedforward and loop compensation circuit, so that Vsense increases until it is higher than the VFB voltage to trigger the overcurrent protection loop. After the current limiting is triggered, the current limiting value is returned to a low value through the overcurrent protection loop, thereby reducing the risk of long-term abnormal load continuous heat.

[0018] Under abnormal loads of CV (constant voltage) and CR (constant resistance), the output voltage and current of the present invention change stably and smoothly without causing voltage and current stress shock or EMI interference.

[0019] The present invention has rapid current limiting action during instantaneous short circuit, thereby reducing the risk of damage.

[0020] The present invention can automatically restore the system output after the load is restored. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of the prior art one.

[0022] Figure 2 It is a structural schematic diagram of the prior art 2.

[0023] Figure 3 A schematic diagram of a circuit structure provided for an embodiment of the present invention.

[0024] Figure 4 A schematic diagram of output voltage and current simulation waveforms provided by an embodiment of the present invention.

[0025] 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

[0026] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] 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 used to generate an output voltage and provide a detection current and a feedback voltage according to 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 switch current mirror, and the switch 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.

[0028] 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, the output is connected to the gate terminal of the NMOS tube NM1, the drain terminal of the NMOS tube NM1 is respectively connected to the drain terminal and gate terminal of the PMOS tube PM1 and the gate terminal of the PMOS tube PM_Power, the drain terminal of the PMOS tube PM_Power is connected in series with R1 and R2 to form a feedback resistor, and the feedback resistor is connected to the negative terminal of the operational amplifier A by voltage division, which constitutes a basic LDO loop, i.e., an LDO loop.

[0029] Furthermore, the source end of the NMOS transistor NM1 is grounded. The source ends of the PMOS transistor PM1 and the PMOS transistor PM_Power are respectively connected to the power supply VBAT.

[0030] Figure 3 In the figure, the negative terminal of the second operational amplifier (i.e., operational amplifier B in the figure) is connected to the VFB feedback, the output terminal is connected to the input terminal of the switch current mirror, the output of the switch current mirror is connected to the gate terminal of the NMOS tube NM1, the gate terminal of the mirror tube PM_Sense is connected to the gate terminal of PM_Power 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 the operational amplifier B, the feedforward and loop compensation module is connected across the input and output of the operational amplifier B, and the whole constitutes an overcurrent protection loop.

[0031] Furthermore, a source end of the mirror transistor PM_Sense is connected to the power supply VBAT.

[0032] It should be noted that the clamping module acts on the drain end of the mirror tube PM_Sense, making its voltage follow Vout, bearing the voltage difference from the drain end of PM_Sense to Vsense, making the current replication accurate, and detecting the current flowing in and out of the module.

[0033] The function of the feedforward and loop compensation unit is to convert the detected current into a voltage signal and perform frequency compensation and signal feedforward on the OCP (overcurrent protection) control loop. It should be noted that the feedforward and loop compensation unit can be implemented using mature technologies in the field, and the present invention does not limit its specific structure.

[0034] 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.

[0035] The high-voltage LDO foldback overcurrent protection feedforward circuit provided in the embodiment of the present invention mirrors the output current of the LDO power tube PM_Power to the current detection loop through the current mirror PM_Sense, and the detection current flows into the feedforward and compensation circuit, so that Vsense increases until it is higher than the VFB voltage to trigger the overcurrent protection loop.

[0036] Based on the same inventive concept as the above embodiment, the embodiment of the present invention further provides an overcurrent protection method based on the high-voltage LDO foldback overcurrent protection feedforward circuit, comprising: When the CR mode is abnormal, when the output current raises Vsense to the VFB voltage to trigger the current limiting loop, the output of op amp B increases, the switch current mirror module is turned on to pull down the current, so that the gate voltage of NM1 decreases, the gate voltage of PM_Power increases, and the output current decreases. If the resistance load remains unchanged at this time, the output voltage begins to decrease, the VFB voltage decreases, and this process repeats gradually, and the current value is limited to a low value.

[0037] Based on the same inventive concept as the above embodiment, the embodiment of the present invention further provides an overcurrent protection method of the high-voltage LDO foldback overcurrent protection feedforward circuit, comprising: 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 are balanced, and the output current is lower than the current limit setting value.

[0038] Based on the same inventive concept as the above embodiment, the embodiment of the present invention further provides an overcurrent protection method based on the high-voltage LDO foldback overcurrent protection feedforward circuit, comprising: 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 gate voltage of PM_Power increases, and the output current drops to a low value. The waveform of the short circuit can be referred to Figure 5 . Figure 5 In the circuit, the output current increases instantly after a short circuit, the overcurrent protection circuit responds quickly, and the transient high current lasts for a very short time.

[0039] Furthermore, in the embodiment of the present invention, for abnormal recovery, when the abnormal load is reduced to within the current limiting trigger value, the output voltage begins to increase, and VFB increases until it returns to the normal output voltage and current. The trigger and recovery waveforms can be referred to Figure 4 .

[0040] Figure 4 In the figure, the waveform in box A is when the load increases to trigger the overcurrent protection, and the current and voltage slowly decrease to a constant value. The waveform in box B is when the output load decreases to restore the overcurrent protection, and the current and voltage slowly increase to normal output. It should be noted that regardless of the CR or CV load abnormality, the circuit will reach a limit balance, and the output will transition smoothly throughout the process without repeated switching.

[0041] Based on the same inventive concept as the above embodiment, the present invention also provides a low voltage dropout linear regulator LDO, including the high voltage LDO foldback overcurrent protection feedforward circuit. When the low voltage dropout linear regulator provided by the embodiment of the present invention is applied, the overcurrent protection function performance can be greatly improved.

[0042] According to one aspect of the present invention, an integrated circuit chip is provided, the integrated circuit chip comprising the above-mentioned low voltage dropout linear regulator with a high voltage LDO foldback overcurrent protection feedforward circuit, which is used as an important 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 voltage dropout linear regulator with a high voltage LDO foldback overcurrent protection feedforward circuit in the integrated circuit chip will not be described in detail here.

[0043] In summary, the key technical features of the present invention are that a simple structure is used to solve the problems of the prior art, and the performance of the overcurrent protection function is greatly improved: ① Realize asymptotic foldback adjustment of output current and voltage during over-current protection, and adjust the transition smoothly.

[0044] ② Add the Clamping module to replicate the detection current with high precision and accurate trigger point.

[0045] ③ Add feedforward and loop compensation structure to make the loop respond quickly during transient short circuit.

[0046] ④ Use a switching current mirror to accurately control the final output current after foldback.

[0047] ⑤After the abnormality is recovered, the output can be restored automatically.

[0048] It should be noted that the above-mentioned multiple embodiments are only examples, and the technical solutions of various embodiments can be combined, all of which are within the protection scope of the present invention.

[0049] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0050] Although 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 the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present 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 used to generate an output voltage and provide a detection current and a feedback voltage according to an input reference voltage of the first operational amplifier; 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 switch current mirror. The switch 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. According to claim 1, a high-voltage LDO foldback overcurrent protection feedforward circuit is characterized in that: The overcurrent protection loop also includes a clamping module, the input end of which is respectively connected to the mirror power tube and the detection current, and the output end of which is respectively connected to the positive end of the second operational amplifier and the input end of the feedforward and loop compensation unit.

3. According to claim 2, a high-voltage LDO foldback overcurrent protection feedforward circuit is characterized in that: 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.

4. According to claim 2, a high-voltage LDO foldback overcurrent protection feedforward circuit is 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.

5. The high-voltage LDO foldback overcurrent protection feedforward circuit according to claim 1, characterized in that: 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.

6. An overcurrent protection method based on the high-voltage LDO foldback overcurrent protection feedforward circuit according to any one of claims 1 to 5, 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 increase to the feedback voltage, triggering the overcurrent protection, the output of the second operational amplifier increases, the switch current mirror is turned on 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.

7. An overcurrent protection method based on the high-voltage LDO foldback overcurrent protection feedforward circuit according to any one of claims 1 to 5, 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.

8. An overcurrent protection method based on the high-voltage LDO foldback overcurrent protection feedforward circuit according to any one of claims 1 to 5, 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 switch 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.

9. A low dropout linear regulator LDO, characterized in that: The invention comprises the high voltage LDO foldback overcurrent protection feedforward circuit as described in any one of claims 1 to 5.

10. An integrated circuit chip, characterized in that: The invention comprises the low dropout linear regulator LDO as claimed in claim 9.

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