Over-current protection method and multi-channel power supply circuit

Abstract

The invention provides an overcurrent protection method and a multi-channel power supply circuit, and the multi-channel power supply circuit comprises a boost circuit which boosts an input voltage and then supplies power to a load; the overcurrent protection method comprises the steps that when current flowing through the bypass power tube is larger than a first threshold value, the bypass power tube is controlled to be switched off rapidly, first current is controlled to flow to the output end, and when the output duration of the first current reaches preset output duration or the first current is larger than a second threshold value, the bypass power tube is switched off rapidly; and controlling the first current to be gradually reduced to zero within the first time. When the multi-channel power supply circuit has an overcurrent fault in a straight-through mode, the bypass power tube is controlled to be quickly turned off, and the first current is controlled to compensate the output voltage so as to prevent the output end voltage from being quickly pulled down to negative voltage due to an overlarge current change rate. And meanwhile, the current change rate of the inductive load / equivalent inductor is reduced by controlling the first current to be slowly reduced to zero, so that the output voltage is prevented from being pulled down to a negative value.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of switching power supply, and particularly relates to a method for over-current protection and a multi-channel power supply circuit. BACKGROUND

[0002] Power Management Integrated Circuit (PMIC), which is mainly characterized by high integration, encapsulates traditional multi-output power supply in a chip, making multi-power supply application scenarios more efficient and smaller in size. PMIC is an indispensable key component in today's electronic devices, which provides power supply for various devices with its outstanding performance and multifunctionality, from mobile phones and smartwatches to cars and industrial equipment.

[0003] As shown in the prior art multi-channel power supply circuit for electronic product power supply, when the battery Vin has low power, the multi-channel power supply circuit works in boost mode, and the boost circuit works to convert Vin to Vout for power supply to the subsequent load. When the battery Vin has sufficient power, the multi-channel power supply circuit works in bypass mode, the boost circuit does not work, the bypass power tube Q3 is turned on, and the battery Vin directly supplies power to the subsequent load. When the multi-channel power supply circuit works in bypass mode and an over-current fault occurs, the controller will pull down the gate of the bypass power tube Q3 to ground to turn off the bypass power tube Q3, thereby performing over-current protection. Figure 1 However, in actual use, as shown in the prior art multi-channel power supply circuit for electronic product power supply, it is found through research that when the connection line between the output end and the load is too long (equivalent inductance Lr is introduced) or the load contains an inductive load, after the bypass power tube Q3 is turned off for over-current protection, the output end voltage Vout will be pulled down to negative voltage because the current flowing through the equivalent inductance Lr and / or the inductive load cannot be suddenly changed. When Vout is pulled down to negative voltage, V GND -Vout is greater than the threshold voltage Vth of the bypass power tube Q3 (N-type power tube), thereby causing the bypass power tube Q3 to be mistakenly turned on. At this time, the voltage difference between Vin and Vout is large, which will cause the bypass power tube Q3 to be damaged instantaneously.

[0004] Figure 2 In view of the technical problem that the bypass power tube is turned off for over-current protection in the above multi-channel power supply circuit, the inductive load / equivalent inductance pulls down the output to negative voltage, causing the bypass power tube to be mistakenly turned on and damaged, the prior art has not provided an effective solution. SUMMARY

[0005] The application belongs to the field of switching power supply, and particularly relates to a method for over-current protection and a multi-channel power supply circuit.

[0006] ​In order to solve the technical problem that when the multi-channel power supply circuit turns off the bypass power tube for over-current protection, the inductive load / equivalent inductance pulls down the output to negative voltage, causing the bypass power tube to be misdirected on and damaged, the present application provides an over-current protection method and a multi-channel power supply circuit, the multi-channel power supply circuit comprising: a boost circuit for boosting the input voltage and supplying power to the load; a bypass power tube for directly supplying power to the load when turned on, and the over-current protection method comprising:

[0007] When the current flowing through the bypass power tube is greater than a first threshold value, the bypass power tube is quickly turned off, and a first current is controlled to flow to the output end,

[0008] When the output duration of the first current reaches a preset output duration or the first current is greater than a second threshold value, the first current is gradually reduced to zero within a first time.

[0009] Preferably, the boost circuit comprises a freewheeling tube, and the first current is generated by controlling the conduction of the freewheeling tube.

[0010] Further, when the first current is greater than the second threshold value, the freewheeling tube is turned off, and the turn-off duration of the freewheeling tube is the first time.

[0011] Further, the freewheeling tube is a P-type power tube, and the gate of the freewheeling tube is connected to the input voltage to control the slow turn-off of the freewheeling tube.

[0012] Further, the bypass power tube is an N-type power tube, and the gate of the bypass power tube is connected to the ground to control the quick turn-off of the bypass power tube.

[0013] Further, the absolute value of the difference between the first threshold value and the second threshold value is less than a preset threshold value.

[0014] Further, the bypass power tube is turned off while the freewheeling tube is turned on.

[0015] Further, the output end of the multi-channel power supply circuit comprises an equivalent inductance and / or an inductive load.

[0016] A multi-channel power supply circuit suitable for the over-current protection method described above, the multi-channel power supply circuit comprising: a boost circuit for boosting the input voltage and supplying power to the load; a bypass power tube for directly supplying power to the load when turned on.

[0017] An over-current protection method for an LDO circuit, the LDO circuit comprising a first power tube connected between an input end and an output end,

[0018] when the current flowing through the first power tube is greater than a first threshold value, controlling the first power tube to be turned off quickly at a first speed and controlling the first current to flow to an output terminal,

[0019] when the output duration of the first current reaches a preset output duration or the first current is greater than a second threshold value, controlling the first current to gradually decrease to zero within a first time.

[0020] Preferably, a second power tube is connected between the input terminal and the output terminal, and the first current is generated by controlling the second power tube to be turned on,

[0021] when the first current is greater than the second threshold value or the on duration of the second power tube reaches the preset output duration, controlling the second power tube to be turned off, and the off duration of the second power tube is the first time.

[0022] Preferably, the second power tube is a P-type power tube, and the gate of the second power tube is connected to an input voltage to control the second power tube to be turned off slowly.

[0023] Further, the first power tube is an N-type power tube, and the gate of the first power tube is connected to ground to control the first power tube to be turned off quickly.

[0024] In this scheme, when the multi-channel power supply circuit has an overcurrent fault in the pass-through mode, the bypass power tube is controlled to be turned off quickly, and the first current is controlled to flow to the output terminal to avoid the current change rate of the inductive load / equivalent inductance being too large to quickly pull down the output terminal voltage to negative voltage. At the same time, when the first current is used to compensate for the pulled-down output voltage, the first current is also controlled to decrease to zero slowly to reduce the current change rate of the inductive load / equivalent inductance, thereby preventing the output voltage from being pulled down to a negative value. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 for a multi-channel power supply circuit;

[0026] Figure 2 for a signal waveform diagram when the multi-channel power supply circuit in the prior art performs overcurrent protection;

[0027] Figure 3 for a signal waveform diagram when the multi-channel power supply circuit uses this scheme to perform overcurrent protection;

[0028] Figure 4 for the overcurrent protection method proposed in this scheme applied to an LDO circuit. DETAILED DESCRIPTION

[0029] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in various forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0030] like Figure 2 As shown, when the multi-channel power supply circuit operates in pass-through mode, the bypass power transistor Q3 is turned on (Q3 is an N-type power transistor), and Vin directly supplies power to the downstream load. In pass-through mode, if an overcurrent fault occurs at time t1, the gate of the bypass power transistor Q3 is grounded at time t1, causing Q3 to turn off quickly, and the bypass current Ipass drops to zero. Since the output of the multi-channel power supply circuit is connected to an inductive load, Vout will be pulled down to a negative voltage after time t1, and at time t2, due to V GND -Vout is greater than the threshold voltage of the bypass power transistor Q3, so the bypass power transistor Q3 is mis-turned on at time t2. Furthermore, the difference between Vin and Vout is large at this time, resulting in a large bypass current Ipass, which causes the bypass power transistor Q3 to fail instantaneously.

[0031] To address the aforementioned problems, existing technologies propose a solution—adjusting the turn-off speed of the bypass power transistor Q3 for overcurrent protection. However, in practice, it has been found that adjusting the turn-off speed of Q3 to a suitable level is difficult. If the turn-off speed is too fast, the di / dt of the inductive load will be very large, resulting in a severe negative voltage Vout; if the turn-off speed is too slow, the bypass current Ipass will be too large during turn-off, potentially damaging the bypass power transistor Q3. Therefore, while the proposed solution is theoretically feasible, it is extremely difficult to implement in practice, and thus cannot effectively solve the aforementioned problems.

[0032] To address the aforementioned technical problems, this invention proposes an overcurrent protection method for a multi-channel power supply circuit, wherein the multi-channel power supply circuit is as follows: Figure 1 As shown, it includes a boost circuit and a bypass power transistor. The boost circuit is connected to the input and output terminals. In boost mode, the boost circuit boosts the input voltage to the output voltage to power the subsequent load. The bypass power transistor is directly connected to the input and output terminals. In shoot-through mode, the bypass power transistor is turned on, and the input voltage directly powers the subsequent load. Furthermore, the overcurrent protection method includes the following steps:

[0033] In direct-on mode, if the current flowing through the bypass power transistor exceeds the first threshold, the bypass power transistor is controlled to turn off rapidly at a first speed, and the first current is controlled to flow to the output terminal. This is to prevent the inductive load / equivalent inductance di / dt from becoming too large when the bypass power transistor is turned off rapidly, thus avoiding the output voltage from being pulled down to a negative voltage.

[0034] When the output duration of the first current reaches the preset output duration or the first current is greater than the second threshold, the first current is controlled to gradually decrease to zero within the first time period, so as to reduce the current change rate of the inductive load / equivalent inductance and avoid the output voltage from dropping to a negative value.

[0035] As described above, when an overcurrent fault occurs in the multi-channel power supply circuit in shoot-through mode, the bypass power transistor is quickly turned off, and the first current is controlled to flow to the output terminal to prevent the current change rate of the inductive load / equivalent inductor from being too large and rapidly pulling the output voltage down to a negative voltage. Simultaneously, while using the first current to compensate for the pulled-down output voltage, the first current is also controlled to slowly decrease to zero to reduce the current change rate of the inductive load / equivalent inductor, thereby preventing the output voltage from falling to a negative value. Therefore, this solution solves the problem of the bypass power transistor being mis-conducted and burned out when the inductive load / equivalent inductor pulls the output voltage down to a negative voltage during overcurrent protection, and also achieves overcurrent protection for the multi-channel power supply circuit.

[0036] In one embodiment, preferably, to simplify the circuit and control and reduce costs, the freewheeling diode in the boost circuit is controlled to conduct to generate a first current, which is simultaneously turned on while the bypass power transistor is rapidly turned off. Simultaneously, during the freewheeling diode's conduction period, if the first current exceeds a second threshold, the freewheeling diode is controlled to turn off slowly, significantly reducing the current change rate (di / dt) of the inductive load / equivalent inductance, thereby preventing the output voltage from dropping to a negative voltage. The first and second thresholds are two thresholds with similar values. Obviously, the bypass power transistor is an N-type power transistor (with a switchable body diode direction), and controlling the gate of the bypass power transistor to ground allows for rapid turn-off at the first speed.

[0037] Furthermore, the freewheeling diode is a P-type power transistor (with a switchable body diode orientation). This allows for easy control of the freewheeling diode's slow turn-off, and prevents it from being mistakenly turned back on due to a drop in output voltage after turn-off. Specifically, the slow turn-off of the freewheeling diode can be achieved by directly controlling the input voltage connected to its gate. As the output voltage decreases, the gate-source voltage of the freewheeling diode gradually increases, causing it to gradually turn off. When the gate-source voltage exceeds the threshold voltage, the freewheeling diode is completely turned off, thus achieving a slow turn-off.

[0038] It should be noted that the "first time" is not a fixed value, but only represents a period of time. This indicates that the freewheeling diode needs to be turned off for a sustained period, rather than being turned off rapidly (approximately zero). In actual control, the turn-off time of the freewheeling diode varies under different control methods, and different turn-off times under different control methods all fall within the range defined by the "first time." For example, in this application, the slow turn-off of the freewheeling diode is achieved by controlling the gate connection input voltage (connected to the input terminal via a resistor). The time difference between the gate connection input voltage and the complete turn-off of the freewheeling diode is the "first time." Similarly, the "first speed" in "the bypass power transistor is turned off rapidly at a first speed" is not a fixed speed threshold. It only indicates that the bypass power transistor is turned off rapidly, with the turn-off time close to zero, meaning the turn-off time of the bypass power transistor is less than the "first time," rather than requiring the bypass power transistor to turn off at a specific speed threshold.

[0039] In another embodiment, theoretically, a first current could be provided by briefly turning on a bypass power transistor, and then slowly turning it off when the on-time of the bypass power transistor reaches a preset output duration. Alternatively, theoretically, a first current could be provided by an additional current source, and then slowly reduced to zero when the output duration of the first current reaches a preset output duration. However, in practice, it has been found that the on-time of the bypass power transistor is difficult to control to a reasonable duration, because the overcurrent typically reaches more than 10 amperes, and the bypass power transistor is very likely to be burned out during this operation (the bypass power transistor is turned off when the temperature is high and a negative voltage occurs). Similarly, in practice, it has also been found that when providing the first current through a current source, it is necessary to detect current information, transmit current information, and then control the current source to output the first current. During this process, the output voltage has already been pulled down to a negative voltage, and the bypass power transistor may be mistakenly turned on and burned out. Therefore, under the current level of technology, the feasibility of either briefly turning on a bypass power transistor to provide the first current or using an additional current source to provide the first current is low. However, with technological advancements, both of these approaches have the potential to become feasible. Improved manufacturing processes can increase the current limit of the power transistor, and optimized sampling techniques can significantly shorten sampling and data transmission times. However, given the current technological level, this approach prioritizes using the freewheeling transistor to generate the initial current, as this method is easier to implement.

[0040] Specifically, such as Figure 1 and Figure 3As shown, from time 0 to t0, the multi-channel power supply circuit operates in pass-through mode. At this time, the bypass power transistor Q3 is turned on, while the main power transistor Q1 and the freewheeling transistor Q2 are turned off. The input voltage Vin directly supplies power to the load. If an overcurrent fault occurs at time t0, the gate of the bypass power transistor Q3 is grounded to quickly turn it off, and the freewheeling transistor Q2 is turned on simultaneously. At this time, the bypass current Ipass decreases to 0, and the inductor current IL gradually increases. At time t1, the inductor current increases to the second threshold, so the gate of the freewheeling transistor Q2 is connected to the input voltage Vin. As the output voltage decreases, the gate-source voltage of the freewheeling transistor Q2 gradually increases, and the freewheeling transistor Q2 gradually turns off until it is completely turned off at time t2. During the turn-off process of the freewheeling transistor Q2, the di / dt of the inductive load / equivalent inductance is small, preventing the output voltage from being pulled down to a negative voltage.

[0041] This invention also proposes a multi-channel power supply circuit suitable for the overcurrent protection method described above. The multi-channel power supply circuit includes a boost circuit and a bypass power transistor. The boost circuit is connected to the input terminal and the output terminal. In boost mode, the boost circuit boosts the input voltage and converts it into an output voltage to power the subsequent load. The bypass power transistor is directly connected to the input terminal and the output terminal. In direct mode, the bypass power transistor is turned on, and the input voltage directly powers the subsequent load.

[0042] In addition, when an LDO circuit uses an N-type power transistor and its output is connected to an equivalent inductive / inductive load, if the N-type power transistor is turned off during an overcurrent fault, the output voltage will be pulled down to a negative voltage, causing the N-type power transistor to mis-conduct and burn out. Based on the same inventive concept, the overcurrent protection method for the above-mentioned multi-channel power supply circuit is also applicable to the overcurrent protection of LDO circuits. Therefore, this invention also proposes an overcurrent protection method for an LDO circuit, wherein the LDO circuit includes a first power transistor connected to the input and output terminals, and the overcurrent protection method includes:

[0043] When the current flowing through the first power transistor exceeds a first threshold, the first power transistor is controlled to turn off rapidly at a first speed, and the first current is controlled to flow to the output terminal.

[0044] And when the output duration of the first current reaches the preset output duration or the first current is greater than the second threshold, the first current is controlled to gradually decrease to zero within the first time period.

[0045] Preferably, a second power transistor is connected between the input and output terminals. The second power transistor is controlled to conduct to generate a first current, and when the first current is greater than a second threshold or when the output duration of the first current is a preset output duration, the second power transistor is controlled to turn off for a first time. The first threshold and the second threshold are not significantly different.

[0046] The second power transistor is a P-type power transistor, and its gate is connected to the input voltage to control its slow turn-off. The first power transistor is an N-type power transistor, and its gate is grounded to control its fast turn-off.

[0047] Specifically, such as Figure 4 As shown, when the LDO circuit is working, the first power transistor Q1 is turned on and the second power transistor Q2 is turned off. At this time, the input voltage Vin is stepped down to supply power to the load. If an overcurrent fault occurs during the operation of the LDO circuit, the gate of the first power transistor Q1 is grounded to quickly turn off the first power transistor Q1 and simultaneously turn on the second power transistor Q2. When the current flowing through the second power transistor Q2 increases to the second threshold (or the conduction time of the second power transistor Q2 reaches the preset output duration), the gate of the second power transistor Q2 is connected to the input voltage Vin. As the output voltage decreases, the gate-source voltage of the second power transistor Q2 gradually increases, and the freewheeling transistor Q2 gradually turns off until it is completely turned off. During the turn-off process of the second power transistor Q2, the di / dt of the inductive load / equivalent inductance is small, which avoids the output voltage being pulled down to a negative voltage and the first power transistor Q1 being mistakenly turned on and damaged.

[0048] It should be noted that the specific implementations and corresponding illustrations provided are merely one way of describing the implementation method of the present invention, and are not intended to limit the specific structure of the implementation scheme of the present invention. Various changes or modifications can be made to these implementation schemes without departing from the principles and essence of the present invention, but all such changes and modifications fall within the protection scope of the present invention.

[0049] Although the embodiments are described and illustrated separately above, some common technologies are involved. Those skilled in the art can replace and integrate them between the embodiments. If there is any content not explicitly described in one embodiment, then another embodiment that is described can be referred to.

[0050] The embodiments described above do not constitute a limitation on the scope of protection of this technical solution. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the above embodiments should be included within the scope of protection of this technical solution.

Claims

1. An overcurrent protection method for a multi-channel power supply circuit, characterized in that, The multi-channel power supply circuit includes: a boost circuit to boost the input voltage and then supply power to the load; and a bypass power transistor, which, when turned on, directly supplies power to the load with the input voltage. The overcurrent protection method includes: When the current flowing through the bypass power transistor exceeds a first threshold, the bypass power transistor is quickly turned off, and the first current is directed to the output terminal. When the output duration of the first current reaches a preset output duration or the first current is greater than a second threshold, the first current is controlled to gradually decrease to zero within a first time period.

2. The overcurrent protection method as described in claim 1, characterized in that, The boost circuit includes a freewheeling diode, and the first current is generated by controlling the freewheeling diode to be turned on.

3. The overcurrent protection method as described in claim 2, characterized in that, When the first current is greater than the second threshold, the freewheeling diode is controlled to be turned off, and the turn-off time of the freewheeling diode is the first time.

4. The overcurrent protection method as described in claim 3, characterized in that, The freewheeling diode is a P-type power diode, and the gate of the freewheeling diode is connected to the input voltage to control the freewheeling diode to turn off slowly.

5. The overcurrent protection method as described in claim 1, characterized in that, The bypass power transistor is an N-type power transistor, and the gate of the bypass power transistor is grounded to control the rapid turn-off of the bypass power transistor.

6. The overcurrent protection method as described in claim 3, characterized in that, The absolute value of the difference between the first threshold and the second threshold is less than the preset threshold.

7. The overcurrent protection method as described in claim 2, characterized in that, The bypass power transistor is turned off while the freewheeling transistor is turned on.

8. The overcurrent protection method as described in claim 1, characterized in that, The output of the multi-channel power supply circuit includes an equivalent inductance and / or an inductive load.

9. A multi-channel power supply circuit applicable to the overcurrent protection method according to any one of claims 1-8, characterized in that, The multi-channel power supply circuit includes: a boost circuit, which boosts the input voltage to supply power to the load; and a bypass power transistor, which, when turned on, directly supplies power to the load from the input voltage.

10. An overcurrent protection method for an LDO circuit, the LDO circuit including a first power transistor connected to an input terminal and an output terminal, characterized in that, When the current flowing through the first power transistor exceeds a first threshold, the first power transistor is quickly turned off, and the first current is directed to the output terminal. When the output duration of the first current reaches a preset output duration or the first current is greater than a second threshold, the first current is controlled to gradually decrease to zero within a first time period.

11. The overcurrent protection method as described in claim 10, characterized in that, A second power transistor is connected between the input terminal and the output terminal. The first current is generated by controlling the second power transistor to conduct. When the first current is greater than the second threshold or the conduction time of the second power transistor reaches the preset output time, the second power transistor is controlled to turn off, and the turn-off time of the second power transistor is the first time.

12. The overcurrent protection method as described in claim 11, characterized in that, The second power transistor is a P-type power transistor, and the gate of the second power transistor is connected to the input voltage to control the second power transistor to turn off slowly.

13. The overcurrent protection method as described in claim 10, characterized in that, The first power transistor is an N-type power transistor, and the gate of the first power transistor is grounded to control the first power transistor to turn off quickly.

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