A switching power supply with an output anti-inrush high voltage ideal low-loss circuit

Abstract

The utility model discloses a switch power supply with output prevent high voltage ideal low loss type circuit has, including input, transformer, rectifier diode, filter capacitance, prevent high voltage controller MX5050L and external N channel MOSFET, the secondary output of transformer is rectified after rectifier diode, gets the stable DC output through filter capacitance filtering, prevent high voltage controller MX5050L and external N channel MOSFET cooperate and use, when the load end produces high voltage and fills in the fault, MX5050L closes MOSFET rapidly, and the reverse current is blocked from the output load and flows back to the input. The utility model discloses that ideal diode controller MX5050L is used with external MOSFET, has realized quick reverse recovery and reverse current blocking, has effectively prevented the influence of load end high voltage and fills in the fault to the normal work of power supply, and moreover has reduced the power consumption and pressure drop, under the input micro short circuit condition, MX5050L can close MOSFET rapidly, prevents the reverse current and flows back to the short circuit power supply, ensures uninterrupted operation.

Description

Technical Field

[0001] This utility model belongs to the field of switching power supply technology, and in particular relates to a switching power supply with an ideal low-loss circuit that prevents high voltage output. Background Technology

[0002] With the widespread application of switching power supplies, all electronic products and industrial equipment require them to provide stable DC power. Especially in industrial equipment, the load characteristics of switching power supplies are constantly changing, resulting in varying currents. This significantly impacts the stability of the power supply's output, potentially causing drastic changes in output characteristics, triggering protection mechanisms, and halting output, leading to malfunctions in industrial equipment. Particularly in industrial equipment with motor or inductive loads, the high voltage back electromotive force generated at the power supply's output during startup or stalling has the greatest impact on normal operation. The output voltage may suddenly drop, or even damage the power supply, resulting in no output.

[0003] Traditional high-voltage protection circuits use a Schottky diode connected in series between the power supply output and the load as a protection design (e.g., Figure 1 (As shown) Schottky diodes are widely used in power system design to provide protection under various input power failure conditions and prevent high voltage from entering the power supply output. Power system designs using power Schottky diodes provide protection under transient conditions. Industrial systems traditionally use Schottky diodes to provide reverse polarity protection to prevent incorrect field power wiring and to provide immunity to lightning and industrial surges. However, the forward voltage drop of Schottky diodes can cause significant power losses under high current, thus requiring more heat sinks and larger PCB space for thermal management. Forward conduction losses and associated thermal management reduce efficiency and increase system cost and space.

[0004] In existing technologies, P-channel MOSFETs are also used to replace Schottky diodes to provide reverse protection, i.e., as... Figure 2 As shown. To reduce the forward voltage drop of the diode, the P-channel MOSFET is replaced with a Schottky diode, and the body diode is oriented in the same direction as the Schottky diode. During normal operation, the MOSFET's body diode is forward biased and conducts for a very short time until the gate voltage is pulled below the source, at which point the MOSFET turns on. This solves the problem of reverse leakage current in Schottky diodes, preventing higher power losses during reverse conduction due to the sharp increase in reverse leakage current with increasing junction temperature. However, since the P-channel MOSFET does not block reverse current, it does not rectify line interference, which is a drawback, making it less than ideal. Utility Model Content

[0005] This utility model addresses the problems in the prior art by proposing the following technical solution: A switching power supply with an ideal low-loss circuit for output high voltage sink protection includes an input terminal, a transformer, a rectifier diode, a filter capacitor, an MX5050L high voltage sink protection controller, and an external N-channel MOSFET. The secondary output of the transformer is rectified by the rectifier diode and then filtered by the filter capacitor to obtain a stable DC output. The MX5050L high voltage sink protection controller works in conjunction with the external N-channel MOSFET. When a high voltage sink fault occurs at the load terminal, the MX5050L quickly turns off the MOSFET, blocking the reverse current from flowing back from the output load to the input terminal.

[0006] As a preferred embodiment of the above technical solution, the anti-drain high voltage controller MX5050L detects the source-to-drain voltage of the MOSFET. When the voltage exceeds a set threshold, it charges the MOSFET gate through the charge pump gate drive to turn on the MOSFET. When the current is reversed, it quickly discharges the MOSFET and turns off the base diode.

[0007] As a preferred embodiment of the above technical solution, the continuous drain current of the external N-channel MOSFET is more than twice the rated value, the reverse breakdown voltage from drain to source is greater than 40V, the threshold turn-on voltage from gate to source is about 4.5V, and the turn-on resistance between drain and source is 50 milliohms.

[0008] As a preferred embodiment of the above technical solution, the switching power supply further includes an inductor, which is connected in series with a filter capacitor to further smooth the DC output.

[0009] As a preferred embodiment of the above technical solution, the switching power supply is of the HF150W-LSW series and has a specification of 26V6A.

[0010] The beneficial effects of this utility model are as follows: This practical switching power supply uses an ideal diode controller MX5050L in conjunction with an external MOSFET to achieve rapid reverse recovery and reverse current blocking, effectively preventing the impact of high voltage sinking faults on the normal operation of the power supply. It not only reduces power consumption and voltage drop, and improves the output efficiency and stability of the power supply, but also allows the MX5050L to quickly turn off the MOSFET under micro-short circuit conditions, preventing reverse current from flowing back to the short-circuited power supply and ensuring uninterrupted operation. Attached Figure Description

[0011] Figure 1 The diagram shown is a Schottky diode circuit diagram; Figure 2 The diagram shown is a reverse protection circuit diagram for a P-channel MOSFET. Figure 3 The diagram shown is a pinout and pin information diagram of the diode controller MX5050L in a switching power supply with an output anti-sinking high-voltage ideal low-loss circuit according to an embodiment. Figure 4 The diagram shown is a circuit block diagram of the diode controller MX5050L in a switching power supply with an ideal low-loss circuit for output anti-sinking high voltage. Figure 5 The diagram shown is a circuit diagram of a switching power supply with an ideal low-loss circuit for output anti-sinking high voltage. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Example

[0013] like Figures 3-5 As shown, a switching power supply with an ideal low-loss circuit for output high voltage protection includes an input terminal, a transformer, a rectifier diode, a filter capacitor, an MX5050L high voltage protection controller, and an external N-channel MOSFET. Its circuit components and connection methods are as follows: Input Terminal: Receives external AC power input; Transformer T1: Converts the input AC voltage to the required low-voltage AC voltage; Rectifier Diodes D4 and D7: Rectify the AC voltage output from the transformer secondary winding into DC voltage; Filter Capacitors C13, C14, C27, C28, and C29: Filter the rectified DC voltage to obtain a smooth DC output; Resistors R16, R17, R19, and R20: Used for current limiting, voltage division, and detection functions in the circuit; Inductor L2: Connected in series with the filter capacitors to further smooth the DC output and reduce ripple; High Voltage Protection Controller MX5050L: Detects and controls the conduction and cutoff of the external N-channel MOSFET to achieve high voltage protection; External N-channel MOSFET Q3: Used as the main switching element in conjunction with the MX5050L to achieve low-loss protection; The specific connection method is as follows: One end of the secondary winding of transformer T1 is connected to the anode of diode D4, and the anode of diode D7 is also connected to one end of the secondary winding of transformer T1. One end of resistor R19 is connected to the anode of D4, and one end of capacitor C13 is connected to the other end of resistor R19. The other end of capacitor C13 is connected to the cathode of D4. The cathodes of D7 and D4 are connected together and then connected to the positive terminal of capacitor C14. The other end of the secondary winding of transformer T1 is connected to output -V, and the negative terminal of C14 is also connected to output -V. Capacitors C27 and C28 are connected in parallel across C14. The two ends of resistors R16 and R17 are also connected in parallel across C14. One end of inductor L2 is connected to the positive terminal of C28, and the other end of L2 is connected to the positive terminal of C29. The negative terminal of C29 is connected to output -V. The positive terminal of C29 is connected to pin 4 of the high-voltage protection controller MX5050L U1, the input detection terminal. The source of MOSFET Q3 is connected to pin 4 of U1. The gate of Q3 is connected to pin 5 of U1 through resistor R17 (to drive the MOSFET to turn on and off). Pin 6 of U1 is connected to the drain of Q3. The drain of Q3 is connected to +V (output positive terminal). Resistor R20 is connected between pin 6 and pin 5 (VS) as auxiliary power supply for U1. Capacitor C13 is connected between pin 5 (VS) and -V. Pin 2 is connected to -V. Pin 3 is OFF and left floating.

[0014] The MX5050L operates as follows: When power is initially supplied, load current flows from the source through the MOSFET body diode to the drain. Once the body diode voltage exceeds 20mV, the MX5050L begins charging the MOSFET gate through a charge pump current source. During forward operation, the MOSFET gate is charged until the MOSFET turns on, and the GATE-IN pin, connected to a Zener diode, clamps a 14V voltage within the MX5050L. The MX5050L is designed to regulate the MOSFET gate-IN input voltage. If the MOSFET current drops below a certain level, and the MOSFET voltage falls below the 20mV voltage regulation point, the GATE pin voltage will be reduced until the voltage across the MOSFET is controlled within the 20mV region. If the MOSFET source-drain voltage exceeds 20mV, the gate-source voltage will increase and eventually reach 14V, with the GATE-IN pin Zener clamped internally within the MX5050L.

[0015] If the MOSFET current reverses, it's due to a high-voltage sink fault at the load side, causing the voltage between the MX5050L's IN and OUT pins to drop below -10mV. The MX5050L quickly discharges the MOSFET through a GATE-IN gate. This reverse current originates from the load. The MX5050L responds to the voltage reversal condition within 50 nanoseconds. The actual time required to turn off the MOSFET depends on the charge held by the gate capacitance; a MOSFET with an effective gate capacitance of 47nF can turn off within 260 nanoseconds. The MX5050L's VS pin is the primary power supply pin for all internal circuitry, and also serves as the auxiliary power port for bias and internal gate drive. For typical MX5050L applications, the VS pin can also be directly connected to the OUT pin.

[0016]

[0017] When choosing a MOSFET, the disadvantage of using a Schottky diode is its forward voltage drop, which reduces the usable voltage. As the load current increases, the associated power loss also increases. Replacing it with an N-channel MOSFET eliminates the need for a diode heatsink or large heatsink in the PCB layout, saving copper area. Important MOSFET electrical parameters are: maximum continuous drain current ID, maximum source current (i.e., body diode) IS, maximum drain-source voltage VDS, gate-to-source threshold voltage VGS, and drain-source turn-on resistance RON. With a power supply output of 26V 6A, a MOSFET with a continuous drain current ID more than twice the rated value, a drain-to-source reverse breakdown voltage of 40V, a gate-to-source threshold voltage VGS of 5V, and a drain-source turn-on resistance RON of 50 milliohms is selected. The power loss of a MOSFET is significantly lower than that of a Schottky diode.

[0018] For continuous operation with a micro-short circuit, the MX5050L addresses the need for many power systems to withstand brief interruptions in the power supply line or micro-short circuits at the input, ensuring uninterrupted operation. When a micro-short circuit occurs at the input, the LM74700-Q1 reacts quickly to turn off the MOSFET, preventing reverse current from flowing back to the short-circuited power source. During the input short circuit, the output remains on because the output holding capacitor isolates it from the input short circuit and provides load current until the input recovers from the micro-short circuit. (This means that the power supply's malfunction protection mode will not occur, allowing continuous power supply to the load and ensuring device stability.) An ideal reverse polarity protection circuit, when used in conjunction with an external N-channel MOSFET, provides low-loss protection against reverse input power supply connection and blocks reverse current from flowing back from the output load to the input. This is the ideal solution for reverse polarity protection. This is the ideal diode circuit solution.

[0019] In an ideal circuit design, an external N-channel MOSFET is driven to simulate an ideal diode with ultra-low forward voltage drop and negligible reverse current. The ideal diode controller possesses important characteristics such as low quiescent current, ultra-low shutdown current, regulated forward voltage, and fast reverse current response, enabling it to simulate an ideal diode in various applications. The power MOSFET, once connected, ensures that the body diode blocks reverse current when the MOSFET is turned off. Because the MOSFET conducts during forward conduction, the forward voltage drop and power dissipation are significantly reduced. The ideal diode controller detects the reverse current through the MOSFET and turns it off, thus allowing the body diode to block the reverse current.

[0020] The MX5050L ideal diode controller, used in conjunction with an external MOSFET, functions as an ideal diode rectifier when connected in series with a power supply. This controller allows the MOSFET to replace the reverse-biased diode in the main circuit, thereby reducing power consumption and voltage drop. The MX5050L controller provides charge pump gate drive for the external N-channel MOSFET and fast-response comparator, turning off the MOSFET when the current reverses.

[0021] The above embodiments are only used to illustrate the technical solution of this utility model, and are not intended to limit it.

Claims

1. A switching power supply with an ideal low-loss circuit for output anti-sinking high voltage, characterized in that, The system includes an input terminal, a transformer, rectifier diodes, filter capacitors, an anti-high voltage sinking controller MX5050L, and an external N-channel MOSFET. The secondary output of the transformer is rectified by the rectifier diodes and then filtered by the filter capacitors to obtain a stable DC output. The anti-high voltage sinking controller MX5050L works in conjunction with the external N-channel MOSFET. When a high voltage sinking fault occurs at the load end, the MX5050L quickly turns off the MOSFET, blocking the reverse current from flowing back from the output load to the input terminal.

2. A switching power supply with an ideal low-loss circuit for output anti-sinking high voltage as described in claim 1, characterized in that, The external N-channel MOSFET has a continuous drain current more than twice the rated current, a drain-to-source reverse breakdown voltage greater than 40V, a gate-to-source threshold turn-on voltage of 5V, and a turn-on resistance of 50 milliohms between the drain and source.

3. A switching power supply with an ideal low-loss circuit for output anti-sinking high voltage as described in claim 1, characterized in that, The switching power supply also includes an inductor, which is connected in series with a filter capacitor to further smooth the DC output.

4. A switching power supply with an ideal low-loss circuit for output anti-sinking high voltage as described in claim 1, characterized in that, The switching power supply is model HF150W-LSW series, with a specification of 26V 6A.

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