High-side switch short circuit detection circuit, protection circuit and switching power supply using same

Abstract

The invention discloses a high-side switch short circuit detection circuit, a protection circuit and a switching power supply applying the same, the high-side switch short circuit detection circuit comprises an operational amplifier, the positive input end of the operational amplifier is connected with NMOS source voltage, the reverse input end of the operational amplifier is connected with one end of a second resistor, and the output end of the operational amplifier is connected with a PMOS grid; the PMOS is connected between the operational amplifier and the comparator and used for converting the voltage difference between the drain electrode and the source electrode of the NMOS into voltage relative to the ground; and the positive end of the comparator is connected with the converted voltage relative to the ground, the negative end of the comparator is connected with the short-circuit threshold voltage, and a voltage comparison result is output. The method is flexible in application, simple and effective, and design resources and cost are reduced while detection accuracy and reliability are guaranteed.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor design, and in particular relates to a high-side switch short-circuit detection circuit, a protection circuit, and a switching power supply using the same. Background Art

[0002] MOS switches are essential components in switching power supplies. NMOS transistors (NMOS) are commonly used as switching devices due to their advantages, including simple control, low on-resistance, and fast switching speed. With technological advancements and increasing performance requirements, NMOS transistors are increasingly used in switching power supply high-side switches or other high-side driver circuits to drive external devices. Due to the increasing complexity of modern electronic systems, improper operation can cause the high-side NMOS drain to short to ground, potentially damaging the NMOS switch. Therefore, high-side NMOS switches often require short-circuit detection circuitry to prevent device damage.

[0003] Existing high-side switch short-circuit detection circuits generally require generating related reference circuits in the high-voltage domain, which requires a large number of high-voltage components, resulting in excessive area and increased design complexity. In addition, existing detection circuits usually need to detect current, but due to the high complexity of current and current sampling accuracy issues, they cannot meet the needs of high-demand applications. Summary of the Invention

[0004] To solve at least one of the above technical problems, the present invention provides a high-side switch short-circuit detection circuit, which is flexible in application, simple and effective, and reduces design resources and costs while ensuring detection accuracy and reliability.

[0005] According to one aspect of the present invention, a high-side switch short-circuit detection circuit is provided, comprising: an operational amplifier, wherein the positive input terminal thereof is connected to the source voltage of the NMOS, the negative input terminal thereof is connected to one end of the second resistor, and the output terminal thereof is connected to the gate of the PMOS; The PMOS is connected between the operational amplifier and the comparator and is used to convert the voltage difference between the drain and source of the NMOS into a voltage relative to the ground; The comparator has its positive terminal connected to the converted relative ground voltage, its negative terminal connected to the short-circuit threshold voltage, and outputs a voltage comparison result.

[0006] Preferably, the drain and source of the PMOS are connected to one end of a first resistor and a second resistor respectively, the other end of the first resistor is grounded, and the other end of the second resistor is connected to the drain of the NMOS.

[0007] Preferably, the positive input terminal of the operational amplifier is further connected to the anode of a first voltage stabilizing diode, and the cathode of the first voltage stabilizing diode is connected to the drain of the NMOS.

[0008] Preferably, the positive terminal of the comparator is further connected to the cathode of a second voltage stabilizing diode, and the anode of the second voltage stabilizing diode is grounded.

[0009] Preferably, the short-circuit threshold voltage is generated by an internal reference voltage.

[0010] Preferably, the short-circuit threshold voltage is set by external software.

[0011] Preferably, when the input signal of the NMOS gate is at a high level, if the voltage difference between the drain and the source of the NMOS is greater than the short-circuit threshold voltage, the high-side switch NMOS is turned off.

[0012] According to one aspect of the present invention, a high-side switch short-circuit protection circuit is provided, comprising the short-circuit detection circuit, wherein the output end of the short-circuit detection circuit is connected to a drive circuit, and the drive circuit is further connected to an input signal of the high-side switch NMOS gate. When the input signal is at a high level, if the voltage difference between the NMOS drain and source is greater than the short-circuit threshold voltage, the high-side switch NMOS tube is turned off.

[0013] Preferably, the output end of the driving circuit is connected to the NMOS gate.

[0014] According to one aspect of the present invention, a switching power supply is provided, which is equipped with the high-side switch short-circuit detection circuit or the high-side switch short-circuit protection circuit.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention proposes a high-side switch short-circuit detection circuit. After voltage conversion is performed through the operational amplifier virtual short principle and PMOS, voltage comparison is performed, and then the presence of a short circuit is determined based on the voltage comparison result. The circuit is simple to implement, does not require external discrete components, and reduces system costs.

[0016] The present invention can generate a short-circuit threshold voltage through an internal reference voltage, and can also set the short-circuit threshold voltage through external software according to application requirements. It does not require current detection and has a flexible application range.

[0017] In summary, the present invention does not require the generation of relevant reference circuits in the high-voltage domain, nor does it require current detection, and can reduce design resources and costs while ensuring detection accuracy and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, a brief introduction will be given below to the drawings used in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 A schematic diagram of a high-side switch short-circuit detection circuit provided by an embodiment of the present invention.

[0020] Figure 2 A schematic diagram of a high-side switch short-circuit protection circuit provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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 making creative work are within the scope of protection of the present invention. In addition, the technical features in the various embodiments or single embodiments provided by the present invention are arbitrarily combined with each other to form a new technical solution. This combination is not restricted by the sequence of steps and / or structural composition mode, but must be based on the ability of ordinary technicians in this field to implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that this combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0022] In response to the current situation where existing high-side switch short-circuit detection circuits need to generate related reference circuits in the high-voltage domain, which increases the design complexity, or require current detection, making it difficult to meet high-demand applications, the present invention proposes a flexible, simple and effective high-side switch short-circuit detection circuit, which reduces design resources and costs while ensuring detection accuracy and reliability.

[0023] The present invention provides a high-side switch short-circuit detection circuit, which includes an operational amplifier, a PMOS and a comparator. After voltage conversion is performed with the PMOS based on the operational amplifier virtual short principle, voltage comparison is performed, and then it is determined whether the high-side switch NMOS is short-circuited based on the voltage comparison result.

[0024] Specifically, the operational amplifier has a positive input connected to the NMOS source voltage, a negative input connected to one end of the second resistor, and an output connected to the PMOS gate. The positive input of the operational amplifier is also connected to the anode of a first zener diode, and the cathode of the first zener diode is connected to the NMOS drain.

[0025] The PMOS is connected between the operational amplifier and the comparator and is configured to convert a voltage difference between the drain and source of the NMOS into a voltage relative to ground. The drain and source of the PMOS are respectively connected to one end of a first resistor and a second resistor, the other end of the first resistor is grounded, and the other end of the second resistor is connected to the drain of the NMOS.

[0026] The comparator has a positive terminal connected to the converted voltage relative to ground and a negative terminal connected to the short-circuit threshold voltage, and outputs a voltage comparison result. The positive terminal of the comparator is also connected to the cathode of a second voltage stabilizing diode, and the anode of the second voltage stabilizing diode is grounded.

[0027] In this invention, when the gate signal input signal VPWM of the high-side switch NMOS is high, if the voltage difference between the drain VBAT and the source SW of the NMOS is greater than a specified reference voltage VDSTH (i.e., the short-circuit threshold voltage), the high-side switch is shorted to ground. VDSTH is the set high-side switch short-circuit threshold voltage. The voltage difference between the VBAT voltage and the SW voltage is converted into a current and ultimately into a low-voltage domain voltage. The resulting low-voltage domain voltage is compared with VDSTH to determine whether the high-side switch NMOS is relatively shorted to ground.

[0028] See also Figure 1 The figure shows a specific short-circuit detection circuit. The SW voltage is connected to the positive input of the op amp (OP), and the negative input is connected to one end of R2. Using the op amp's virtual short principle, the SW voltage relative to VBAT is converted into a current (VBAT - SW) / R2. This current flows through the PMOS transistor (PMOS) into one end of R1, with the other end of R1 connected to ground. Ultimately, the voltage difference between VBAT and SW is converted to a voltage relative to ground, VDS. VDS is connected to the positive terminal of the comparator, COMP, and the short-circuit threshold voltage, VDSTH, is connected to the negative terminal of the comparator. The positive and negative voltages of the comparator are compared. When VPWM is high, the comparator output voltage, VS, is valid. A high VS indicates that the high-side switch, NMOS, is short-circuited to ground, ultimately shutting down the high-side switch, protecting the switch.

[0029] In practical applications, Figure 1 As shown in the figure, two Zener diodes are used to clamp the voltage to prevent excessive voltage difference. AVDD in the figure represents the internally generated low-voltage power supply.

[0030] Preferably, the short-circuit threshold voltage VDSTH can be generated by the internal reference voltage of the switching power supply, or can be set by external software according to application needs to meet user customization requirements.

[0031] Based on the same inventive concept, an embodiment of the present invention also provides a high-side switch short-circuit protection circuit, including the short-circuit detection circuit, the output end of the short-circuit detection circuit is connected to the drive circuit, and the drive circuit is also connected to the input signal of the high-side switch NMOS gate. When the input signal is at a high level, if the voltage difference between the NMOS drain and source is greater than the short-circuit threshold voltage, the high-side switch NMOS tube is turned off.

[0032] See also Figure 2The figure shows a complete high-side switch NMOS short-circuit protection circuit. VDSTH can be generated by an internal reference voltage or set by external software according to application requirements. When the high-side switch NMOS gate signal input signal VPWM is high, if the voltage difference between the drain VBAT and the source SW of the NMOS is greater than the specified reference voltage VDSTH, it indicates that the high-side switch is short-circuited to ground, and then the high-side switch tube is turned off.

[0033] Figure 2 In the embodiment, the driving circuit can be realized by cascading inverters.

[0034] Based on the same inventive concept, an embodiment of the present invention further provides a switching power supply, which is equipped with the high-side switch short-circuit detection circuit or the high-side switch short-circuit protection circuit.

[0035] Unless otherwise specified, the above technologies are all known technologies.

[0036] The terms "including" and "having" and any variations thereof in the description and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions, for example, a process, method, system, product or apparatus that includes a series of steps or units is not necessarily limited to the steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products or apparatuses.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A high-side switch short-circuit detection circuit, characterized in that: include: an operational amplifier, wherein the positive input terminal thereof is connected to the source voltage of the NMOS, the negative input terminal thereof is connected to one end of the second resistor, and the output terminal thereof is connected to the gate of the PMOS; The PMOS is connected between the operational amplifier and the comparator and is used to convert the voltage difference between the drain and source of the NMOS into a voltage relative to the ground; The comparator has its positive terminal connected to the converted relative ground voltage, its negative terminal connected to the short-circuit threshold voltage, and outputs a voltage comparison result.

2. A high-side switch short-circuit detection circuit according to claim 1, characterized in that: The drain and source of the PMOS are connected to one end of a first resistor and a second resistor respectively. The other end of the first resistor is grounded, and the other end of the second resistor is connected to the drain of the NMOS.

3. The high-side switch short-circuit detection circuit according to claim 1, wherein: The positive input terminal of the operational amplifier is also connected to the anode of a first voltage stabilizing diode, and the cathode of the first voltage stabilizing diode is connected to the drain of the NMOS.

4. The high-side switch short-circuit detection circuit according to claim 1, wherein: The positive terminal of the comparator is also connected to the cathode of a second voltage stabilizing diode, and the anode of the second voltage stabilizing diode is grounded.

5. The high-side switch short-circuit detection circuit according to claim 1, wherein: The short-circuit threshold voltage is generated by an internal reference voltage.

6. A high-side switch short-circuit detection circuit according to claim 1, characterized in that: The short-circuit threshold voltage is set by external software.

7. A high-side switch short-circuit detection circuit according to claim 1, characterized in that: When the input signal of the NMOS gate is at a high level, if the voltage difference between the drain and the source of the NMOS is greater than the short-circuit threshold voltage, the high-side switch NMOS is turned off.

8. A high-side switch short-circuit protection circuit, characterized in that: It includes the short-circuit detection circuit according to any one of claims 1 to 7, wherein the output end of the short-circuit detection circuit is connected to a drive circuit, and the drive circuit is also connected to an input signal of the high-side switch NMOS gate. When the input signal is at a high level, if the voltage difference between the NMOS drain and the source is greater than the short-circuit threshold voltage, the high-side switch NMOS tube is turned off.

9. A high-side switch short-circuit protection circuit according to claim 8, characterized in that: The output end of the driving circuit is connected to the NMOS gate.

10. A switching power supply, characterized in that: Equipped with the high-side switch short-circuit detection circuit described in any one of claims 1-7, or the high-side switch short-circuit protection circuit described in any one of claims 8-9 3.

Images