Switching power supply overcurrent protection detection device

Abstract

This application discloses an overcurrent protection detection device for a switching power supply, relating to the technical field of emergency protection circuit devices, including a switching transistor M. A Output circuit, power supply stage and protection circuit, the switching transistor M A Drain input chip power supply voltage V IN The switching transistor M A The power supply stage is connected to the switching node SW in the output circuit, and the power supply stage controls the switching transistor M. A and the power transistor M in the output circuit B The gate voltage is sampled by the protection circuit connected to the output circuit switching node SW, and the output terminal of the protection circuit is connected to the power supply stage, providing a fast and accurate overcurrent protection detection device for switching power supplies.

Description

Technical Field

[0001] This application relates to the field of emergency protection circuit devices, specifically to an overcurrent protection detection device for a switching power supply. Background Technology

[0002] Switching power supplies are used in electronic equipment. They utilize modern power electronics technology to control the on and off time ratio of switching transistors to maintain a stable output voltage. Switching power supplies are generally composed of pulse width modulation (PWM) control ICs and MOSFETs. In order to ensure that the power supply operates safely and reliably in harsh environments and under sudden failure conditions, and to protect the safety of the switching power supply itself and the load, protection circuits are usually set up for switching power supplies based on their principles and characteristics, such as overvoltage, undervoltage, overheat, and overcurrent protection circuits.

[0003] Like other electronic devices, short circuits are the most serious fault in switching power supplies. When a fault occurs in the power grid or a short circuit occurs in the grid-side load, the current becomes too large. If the circuit current is detected to be too large, it may not be able to cut off the current in the circuit quickly enough, which will damage the switching power supply and cause unnecessary economic losses to the equipment. At this time, a power supply overcurrent protection detection device with fast response speed and high accuracy is needed to monitor and protect the switching power supply. Therefore, it is necessary to provide a switching power supply overcurrent protection detection device to solve the problems mentioned in the background art. Summary of the Invention

[0004] To achieve the above objectives, this application provides the following technical solution: a switching power supply overcurrent protection detection device, including a switching transistor M. A Output circuit, power supply stage and protection circuit, the switching transistor M A Drain input chip power supply voltage V IN The switching transistor M A The source is connected to the switching node SW in the output circuit, and the power stage control switch M A and the power transistor M in the output circuit B The gate voltage is sampled by the protection circuit connected to the output circuit switching node SW, and the output terminal of the protection circuit is connected to the power supply stage.

[0005] The protection circuit includes a PTAT circuit, an output current mirror, a current mirror group, a sampling circuit, and a comparison circuit. The PTAT circuit outputs a current I. PTAT The output current mirror is then connected to a current mirror group, which includes M. C -M H The M C -M H The sources are all connected to the internal stable voltage VDD, where M G and M HThe branch circuit is connected to the output terminal of the output current mirror, and the M C and M D The branch circuit formed is connected to the sampling circuit, and the M E and M F The branch circuit is connected to the comparison circuit.

[0006] Furthermore, as a preferred embodiment, the power supply stage provides a switching transistor M. A and power transistor M B The gate voltage, the power supply stage is a power switch M A and power transistor M B Provide two opposite signals to control the power switch M A and power transistor M B The switch.

[0007] Furthermore, preferably, the output circuit further includes an inductor L, a capacitor C, and a load resistor RL, and the switching node SW is located at the switching transistor M. A Source and power transistor M B Between the switching node SW, inductor L, and load resistor RL, the capacitor C is connected in parallel with the load resistor R. L Above, and the power transistor M B The source is grounded.

[0008] Furthermore, as a preferred embodiment, the switching transistor M A and power transistor M B All use N-type MOSFETs.

[0009] Furthermore, preferably, the sampling circuit includes sampling resistors R connected in series. S and M S Wherein M S The gate is connected to the internal stable voltage VDD, and the M S The source is connected to the switch node SW.

[0010] Furthermore, preferably, the comparison circuit includes M I Series R A The grounding constitutes branch 1 and M J Series R B Branch 2 is formed by grounding.

[0011] Furthermore, as a preferred embodiment, the M I The gate is connected to the sampling circuit, and the M J Gate connection M P and PGND, the M P The gate is connected to the internal stable voltage VDD.

[0012] Furthermore, as a preferred embodiment, the current I PTATThe output is achieved through an output current mirror, which includes M. K and M L .

[0013] Furthermore, preferably, the PTAT circuit includes M M -M Q Transistor Q A Transistor Q B and resistance R C One branch route is M M Series M N Transistor Q A The grounding configuration is as follows, and another branch is M. O Series M P Resistance R C and transistor Q B Grounding configuration.

[0014] Furthermore, as a preferred embodiment, the M M and M O A current mirror is constructed to make the current flowing through the two branches equal, and the driving voltage is also the same, generating a self-biased circuit, namely M. Q Same as M M The gate is common, and the M M M O and M Q The source is connected to the internal stable voltage VDD, M Q The drain outputs the current I PTAT .

[0015] Compared with the prior art, this application provides a switching power supply overcurrent protection detection device, which has the following advantages:

[0016] In this application, the switching transistor M... A On, power transistor M B At cutoff, the voltage at node SW is close to the chip power supply voltage V. IN ; in the switching transistor M A Cut-off, power transistor M B When conducting, M I and M J The threshold voltage is V A and V B Current I PTAT For flow through R A and R B The sum of the currents generates a corresponding comparison voltage V. NB and V PB Load current I LOAD Flow through sampling resistor R S The generated sampling voltage is connected to M. I Gate control M I The conduction generates a comparison voltage VNB The M P Connect PGND to control M J The conduction generates a comparison voltage V PB Compare voltage V NB and V PB The load current I is input to the comparator. LOAD Excessively large V NB >V PB The comparator outputs an OCPOUT signal to cut off the current path and achieve protection. The entire process utilizes I... PTAT The temperature characteristics are compensated for by the temperature drift of the resistor, so that the protection threshold remains stable at different temperatures, improving the control accuracy of the protection circuit and disconnecting the circuit in time during overcurrent. Attached Figure Description

[0017] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0018] Figure 1 A schematic diagram of the overall circuit structure of a switching power supply overcurrent protection and detection device;

[0019] Figure 2 A schematic diagram of the protection circuit structure of a switching power supply overcurrent protection detection device;

[0020] Figure 3 A schematic diagram of the PATA circuit structure of a switching power supply overcurrent protection and detection device;

[0021] Figure 4 This is a schematic diagram of the overall working process of a switching power supply overcurrent protection and detection device.

[0022] In the diagram: 1. Chip power supply voltage V IN 2. Switching transistor M A 3. Output circuit; 4. Power supply stage; 5. Protection circuit; 51. PTAT circuit; 52. Output current mirror; 53. Current mirror group; 54. Sampling circuit; 55. Comparison circuit; 56. Comparator. Detailed Implementation

[0023] Please see Figures 1-4 In this embodiment of the application, a switching power supply overcurrent protection detection device includes a switching transistor M. A 2. Output circuit; 3. Power supply stage; 4. Protection circuit; 5. The switching transistor M A 2. Drain input chip power supply voltage V IN 1. The switching transistor M A The source of power supply stage 4 is connected to the switching node SW in the output circuit 3, and the power supply stage 4 controls the switching transistor M. A2 and the power transistor M in the output circuit 3 B The gate voltage is sampled by the protection circuit 5 connected to the switching node SW of the output circuit 3, and the output terminal of the protection circuit 5 is connected to the power supply stage 4.

[0024] The protection circuit 5 includes a PTAT circuit 51, an output current mirror 52, a current mirror group 53, a sampling circuit 54, and a comparison circuit 55. The PTAT circuit 51 outputs a current I. PTAT The output current mirror 52 is then connected to the current mirror group 53, which includes M. C -M H The M C -M H The sources are all connected to the internal stable voltage VDD, where M G and M H The branch circuit is connected to the output terminal of the output current mirror 52, and the M C and M D The branch circuit formed is connected to the sampling circuit 54, and the M E and M F The branch circuit is connected to the comparison circuit 55.

[0025] It needs to be explained that in the switching transistor M A 2. On, power transistor M B At cutoff, the voltage at node SW is close to the chip power supply voltage V. IN 1; In the switching transistor M A 2. Cut-off, power transistor M B When the circuit is turned on, if the load current is too large, the voltage at node SW will be lower than zero, triggering overcurrent protection. The protection circuit 5 will quickly output a shutdown signal OCPOUT to protect the circuit from overcurrent damage. The protection circuit 5 will return to normal and allow the system to work normally until the current drops to the rated value.

[0026] In a preferred embodiment, the power supply stage 4 provides a switching transistor M. A 2 and power transistor M B The gate voltage, the power supply stage 4 is the power switch M A 2 and power transistor M B Provide two opposite signals to control the power switch M A 2 and power transistor M B The switch.

[0027] It needs to be explained that, according to the switching transistor M A 2 and power transistor M B The switching power supply operates in two phases: the energy storage phase and the freewheeling phase, depending on whether it is turned on or off.

[0028] In this embodiment, as Figure 1The output circuit 3 further includes an inductor L, a capacitor C, and a load resistor RL, and the switching node SW is located at the switching transistor M. A 2 source transistors and power transistor M B Between the switching node SW, inductor L, and load resistor RL, the capacitor C is connected in parallel with the load resistor R. L Above, and the power transistor M B The source is grounded.

[0029] It needs to be explained that during the energy storage stage: the control signal causes the switching transistor M... A 2 is on, power transistor M B Cut-off, DC source and switching transistor M A 2. Inductor L, capacitor C, and load resistor R L A path is formed, and current flows from power stage 4 through switching transistor M. A 2 and SW flow to inductor L. At this time, inductor L stores energy, and capacitor C flows to load resistor R. L Power supply. Due to the characteristics of inductance, the current will gradually increase.

[0030] Freewheeling stage: The control signal causes the switching transistor M to... A 2. Cut-off, power transistor M B Turn on, power transistor M B Inductor L, capacitor C, and load resistor A circuit is formed, and capacitor C continues to supply power to the load RL. Simultaneously, due to the back electromotive force of inductor L, the output voltage V... OUT The current in inductor L gradually decreases, remaining relatively stable.

[0031] The inductor L and capacitor C store and release energy, and at the same time, the inductor L and capacitor C form an LC filter circuit to produce a smooth output voltage.

[0032] In a preferred embodiment, the switching transistor M A 2 and power transistor M B All use N-type MOSFETs.

[0033] It needs to be explained that the current mirror group 53 is connected via M C -M H The constructed precision current mirror network will V RS Converted into a comparable voltage signal.

[0034] In a preferred embodiment, the sampling circuit 54 includes sampling resistors R connected in series. S and M S Wherein M S The gate is connected to the internal stable voltage VDD, and the M S The source is connected to the switch node SW.

[0035] In a preferred embodiment, the comparison circuit 55 includes M I Series R A The grounding constitutes branch 1 and M J Series R B Branch 2 is formed by grounding.

[0036] In a preferred embodiment, the M I The gate is connected to the sampling circuit 54, the M J Gate connection M P and PGND, the M P The gate is connected to the internal stable voltage VDD.

[0037] It needs to be explained that M I and M J The threshold voltage is V A and V B Current I PTAT For flow through R A and R B The sum of the currents generates a corresponding comparison voltage V. NB and V PB Load current I LOAD Flow through sampling resistor R S The generated sampling voltage is connected to M. I Gate control M I The conduction generates a comparison voltage V NB The M P Connect PGND to control M J The conduction generates a comparison voltage V PB Compare voltage V NB and V PB The load current I is input to the comparator 56. LOAD V is too large NB >V PB The comparator 56 outputs an OCPOUT signal to cut off the current path and achieve protection.

[0038] In a preferred embodiment, the current I PTAT The output is transmitted through an output current mirror 52, which includes M. K and M L .

[0039] It should be explained that the output current mirror 52 outputs a proportionally scaled current, forcing the two currents to be equal.

[0040] In a preferred embodiment, the PTAT circuit 51 includes M M -M Q Transistor Q A Transistor Q Band resistance R C One branch route is M M Series M N Transistor Q A The grounding configuration is as follows, and another branch is M. O Series M P Resistance R C and transistor Q B Grounding configuration.

[0041] In a preferred embodiment, the M M and M O A current mirror is constructed to make the current flowing through the two branches equal, and the driving voltage is also the same, generating a self-biased circuit, namely M. Q Same as M M The gate is common, and the M M M O and M Q The source is connected to the internal stable voltage VDD, M Q The drain outputs the current I PTAT .

[0042] It needs to be explained that, using I PTAT The temperature characteristics are compensated for resistor temperature drift, so that the protection threshold remains stable at different temperatures.

[0043] In practical implementation, in the switching transistor M A 2. On, power transistor M B At cutoff, the voltage at node SW is close to the chip power supply voltage V. IN 1; In the switching transistor M A 2. Cut-off, power transistor M B When conducting, M I and M J The threshold voltage is V A and V B Current I PTAT For flow through R A and R B The sum of the currents generates a corresponding comparison voltage V. NB and V PB Load current I LOAD Flow through sampling resistor R S The generated sampling voltage is connected to M. I Gate control M I The conduction generates a comparison voltage V NB The M P Connect PGND to control M J The conduction generates a comparison voltage V PB Compare voltage V NB and V PB The load current I is input to the comparator 56. LOAD V is too largeNB >V PB The comparator 56 outputs an OCPOUT signal to cut off the current path and achieve protection. The entire process utilizes I... PTAT The temperature characteristics are compensated for the temperature drift of the resistor, so that the protection threshold remains stable at different temperatures, improving the control accuracy of the protection circuit 5 and disconnecting the circuit in time during overcurrent.

[0044] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in this application, based on the technical solution and application concept of this application, should be included within the scope of protection of this application.

Claims

1. A switching power supply overcurrent protection detection device, characterized in that: Including switching transistor M A (2), output circuit (3), power supply stage (4) and protection circuit (5), wherein the switching transistor M A (2) Drain input chip power supply voltage V IN (1) The switching transistor M A (2) The source is connected to the switching node SW in the output circuit (3), and the power supply stage (4) controls the switching transistor M. A (2) and the power transistor M in the output circuit (3) B The gate voltage is sampled by the protection circuit (5) connected to the switch node SW of the output circuit (3), and the output terminal of the protection circuit (5) is connected to the power supply stage (4). The protection circuit (5) includes a PTAT circuit (51), an output current mirror (52), a current mirror group (53), a sampling circuit (54), and a comparison circuit (55). The PTAT circuit (51) outputs a current I. PTAT The output current mirror (52) is then connected to the current mirror group (53), which includes M. C -M H The M C -M H The sources are all connected to the internal stable voltage VDD, where M G and M H The branch circuit is connected to the output terminal of the output current mirror (52), and the M C and M D The branch circuit is connected to the sampling circuit (54), and the M E and M F The branch circuit is connected to the comparison circuit (55).

2. The switching power supply overcurrent protection detection device according to claim 1, characterized in that: The power stage (4) provides the switching transistor M A (2) and power transistor M B The gate voltage of the power supply stage (4) is the power switch M. A (2) and power transistor M B Provide two opposite signals to control the power switch M A (2) and power transistor M B The switch.

3. The switching power supply overcurrent protection detection device according to claim 1, characterized in that: The output circuit (3) also includes an inductor L, a capacitor C, and a load resistor RL. The switching node SW is located at the switching transistor M. A (2) Source and power transistor M B Between the switching node SW, inductor L, and load resistor RL, the capacitor C is connected in parallel with the load resistor R. L Above, and the power transistor M B The source is grounded.

4. The switching power supply overcurrent protection detection device according to claim 3, characterized in that: The switching transistor M A (2) and power transistor M B All use N-type MOSFETs.

5. The switching power supply overcurrent protection detection device according to claim 1, characterized in that: The sampling circuit (54) includes sampling resistors R connected in series. S and M S Wherein M S The gate is connected to the internal stable voltage VDD, and the M S The source is connected to the switch node SW.

6. The switching power supply overcurrent protection detection device according to claim 5, characterized in that: The comparison circuit (55) includes M I Series R A The grounding constitutes branch 1 and M J Series R B Branch 2 is formed by grounding.

7. The switching power supply overcurrent protection detection device according to claim 6, characterized in that: The M I The gate is connected to the sampling circuit (54), the M J Gate connection M P and PGND, the M P The gate is connected to the internal stable voltage VDD.

8. The switching power supply overcurrent protection detection device according to claim 7, characterized in that: The current I PTAT The output is provided through an output current mirror (52), which includes M. K and M L .

9. The switching power supply overcurrent protection detection device according to claim 8, characterized in that: The PTAT circuit (51) includes M M -M Q Transistor Q A Transistor Q B and resistance R C One branch route is M M Series M N Transistor Q A The grounding configuration is as follows, and another branch is M. O Series M P Resistance R C and transistor Q B Grounding configuration.

10. The switching power supply overcurrent protection detection device according to claim 9, characterized in that: The M M and M O A current mirror is constructed to make the current flowing through the two branches equal, and the driving voltage is also the same, generating a self-biased circuit, namely M. Q Same as M M The gate is common, and the M M M O and M Q The source is connected to the internal stable voltage VDD, M Q The drain outputs the current I PTAT .

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