Current detection circuit based on Oring switching tube

Abstract

The utility model relates to the technical field of overcurrent protection, in particular to a current detection circuit based on an Oring switch tube, which comprises an Oring circuit and an operational amplifier U1, and the Oring circuit comprises an MOS (metal oxide semiconductor) tube Q1; the source electrode of the Q1 is connected with a positive end pin PINVOUT +, the drain electrode of the Q1 is connected with an output voltage positive end VOUT +, the grid electrode of the Q1 is connected with a control pin ORINGG, the positive input end of the operational amplifier U1 is connected between the drain electrode of the Q1 and the output voltage positive end VOUT +, the reverse input end of the operational amplifier U1 is connected between the source electrode of the Q1 and the positive end pin PINVOUT +, and the output end of the operational amplifier U1 is connected to a current output end IOUT. Compared with the common secondary side current detection circuit and Oring circuit design, the current detection circuit provided by the utility model uses fewer devices, and saves the design space and cost of a power supply module.

Description

Technical Field

[0001] The utility model relates to the technical field of overcurrent protection, and in particular to a current detection circuit based on an Oring switch tube. Background Art

[0002] With the rapid development of power electronics technology, high-frequency switching power supplies have been widely used in fields such as computers, communications, industrial processing, and aerospace. To ensure safe operation, power module design requires numerous protection circuits, including input overvoltage and undervoltage protection, output overvoltage and undervoltage protection, short-circuit and overcurrent protection, and module overtemperature protection. The module determines whether to trigger the corresponding protection by monitoring input, output, and temperature information.

[0003] Common short-circuit and overcurrent protection designs include primary-side overcurrent protection and secondary-side overcurrent protection. Primary-side overcurrent protection often uses a current transformer and a small resistor to detect input current and determine if the module is short-circuited or overcurrent-prone. Secondary-side overcurrent protection primarily detects output current and determines if the module is short-circuited or overcurrent-prone. When either overcurrent protection circuit is triggered, it shuts off the module output and attempts to restart it after a certain interval. If the short circuit or overcurrent persists, the protection is activated again and the process repeats. An oscilloscope can be used to detect the output waveform during this state. This protection mode is called "hiccup" protection.

[0004] Due to the special working conditions of current-sense resistors, commonly used small chip resistors cannot meet their power requirements. Large, low-resistance copper resistors are usually used as current-sense resistors. In power module design, large copper resistors will affect the size of the power module and reduce the power density of the power module. However, the pursuit of small size and high power density in switching power supplies requires better solutions as replacements. Utility Model Content

[0005] The utility model improves the secondary-side current detection circuit and combines it with the Oring circuit to provide a current detection circuit based on the Oring switch tube. Compared with the commonly used secondary-side current detection circuit and Oring circuit design, the utility model uses fewer components, saving the design space and cost of the power module.

[0006] The embodiment of the utility model is implemented by the following technical solutions: a current detection circuit based on an Oring switch tube, composed of an Oring circuit and an operational amplifier U1, wherein the Oring circuit includes a MOS tube Q1;

[0007] The source of the MOS tube Q1 is connected to the positive end pin PIN_VOUT+, the drain of the MOS tube Q1 is connected to the output voltage positive end VOUT+, the gate of the MOS tube Q1 is connected to the control pin ORING_G, the positive input end of the operational amplifier U1 is connected between the drain of the MOS tube Q1 and the output voltage positive end VOUT+, the negative input end of the operational amplifier U1 is connected between the source of the MOS tube Q1 and the positive end pin PIN_VOUT+, and the output end of the operational amplifier U1 is connected to the current output end IOUT.

[0008] According to a preferred embodiment, further comprising a voltage dividing resistor R1, a voltage dividing resistor R4 and an auxiliary source;

[0009] The voltage dividing resistor R1 is connected in series between the drain of the MOS tube Q1 and the positive input end of the operational amplifier U1, the voltage dividing resistor R4 is connected in series between the voltage dividing resistor R1 and the positive power input end of the operational amplifier U1, and the auxiliary source is connected between the voltage dividing resistor R4 and the positive power input end of the operational amplifier U1.

[0010] According to a preferred embodiment, further comprising an input resistor R2 and an input resistor R3;

[0011] The input resistor R2 is connected in series between the voltage dividing resistor R1 and the positive input end of the operational amplifier U1, and the input resistor R3 is connected in series between the source of the MOS tube Q1 and the negative input end of the operational amplifier U1.

[0012] According to a preferred embodiment, further comprising a feedback resistor R5;

[0013] The first end of the feedback resistor R5 is connected to the output end of the operational amplifier U1, and the second end of the feedback resistor R5 is connected between the input resistor R3 and the negative input end of the operational amplifier U1.

[0014] According to a preferred embodiment, further comprising a capacitor C1 and a capacitor C2;

[0015] The first end of the capacitor C1 is connected between the input resistor R2 and the positive input end of the operational amplifier U1, the first end of the capacitor C2 is connected to the positive power input end of the operational amplifier U1, and the second ends of the capacitor C1 and the capacitor C2 are connected to the negative power input end of the operational amplifier U1.

[0016] According to a preferred embodiment, the negative end of the operational amplifier U1 is connected to the output voltage positive end VOUT+.

[0017] According to a preferred embodiment, the positive end of the operational amplifier U1 is supplied with a 5V voltage.

[0018] The technical scheme of the current detection circuit based on the Oring switch tube has at least the following advantages and beneficial effects: (1) compared with the commonly used secondary side current detection circuit and Oring circuit design, the current detection circuit based on the Oring switch tube has fewer devices, saves the power module design space and cost; (2) when the power module outputs the reverse current, due to the internal impedance of the MOS tube, there is a voltage difference between the output voltage and the external voltage, the voltage difference value is equal to the voltage drop of the MOS tube, when the reverse current is larger, the tube voltage drop is larger, therefore, the output voltage of the current detection circuit can be used to judge and trigger the anti-inversion protection. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 A principle diagram of the current detection circuit based on the Oring switch tube is provided for the embodiment 1 of the utility model.

[0020] Figure 2 An equivalent circuit diagram of the current detection circuit when the current is 0 is provided for the embodiment 1 of the utility model.

[0021] Figure 3 An equivalent circuit diagram of the current detection circuit when the current is positive is provided for the embodiment 1 of the utility model.

[0022] Figure 4 An equivalent circuit diagram of the current detection circuit when the current is reverse is provided for the embodiment 1 of the utility model.

[0023] Figure 5 A normal output voltage range schematic diagram of the operational amplifier is provided for the embodiment 1 of the utility model. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the embodiments of the utility model clearer, the technical scheme in the embodiments of the utility model will be described clearly and completely in combination with the drawings in the embodiments of the utility model, obviously, the described embodiments are part of the embodiments of the utility model, rather than all the embodiments. The components of the embodiments of the utility model described and shown in the drawings here can be arranged and designed in various different configurations.

[0025] Embodiment 1

[0026] Figure 1 A principle diagram of the current detection circuit based on the Oring switch tube is provided for the utility model. Referring to the principle diagram of the current detection circuit based on the Oring switch tube shown in the drawing, the current detection circuit based on the Oring switch tube is obtained by combining the anti-reverse circuit Oring and the secondary side current detection circuit, and is specifically composed of the Oring circuit and the operational amplifier U1. Figure 1

[0027] ​Regarding the Oring circuit, it should be noted that when the external voltage at the output end of the power module is normal, the switch tube in the Oring circuit is turned on, the power module outputs normally, and the switch tube conduction causes minimal loss to the power module. When the external voltage at the output end of the power module is too high, the switch tube in the Oring circuit is turned off. At this time, the switch tube exhibits the properties of a diode, and the external high voltage cannot enter the power module through the reverse diode, thus protecting the internal circuit of the power module from damage.

[0028] Specifically in this embodiment, the ORing circuit includes a MOS transistor Q1. Based on the internal resistance of the MOS transistor Q1 when it is turned on, this embodiment treats the MOS transistor Q1 as a resistor, and then determines the output current of the power module by detecting the voltages at the front and rear ends of the MOS transistor Q1.

[0029] Specifically, the source of the MOS transistor Q1 is connected to the positive terminal pin PIN_VOUT+, the drain of the MOS transistor Q1 is connected to the output voltage positive terminal VOUT+, the gate of the MOS transistor Q1 is connected to the control pin ORING_G, the positive input terminal of the operational amplifier U1 is connected between the drain of the MOS transistor Q1 and the output voltage positive terminal VOUT+, and the reverse input terminal of the operational amplifier U1 is connected between the source of the MOS transistor Q1 and the positive terminal pin PIN_VOUT+.

[0030] The current flowing through the MOS transistor Q1 forms a voltage difference at both ends of the MOS transistor Q1. The voltage at the front and rear ends of the MOS transistor Q1 is then detected and input into the operational amplifier U1 for output. The output end of the operational amplifier U1 is connected to the current output end IOUT. The output current of the power module can be determined based on the output voltage of the operational amplifier U1. Furthermore, when the output voltage of the operational amplifier U1 exceeds the set maximum current value, the power module triggers overcurrent protection.

[0031] In addition, when the power module outputs reverse current, due to the internal impedance of the MOS tube, there is a voltage difference between the output voltage and the external voltage. The voltage difference is equal to the voltage drop of the MOS tube. When the reverse current is larger, the tube voltage drop is larger. Therefore, it can also support judgment through the output voltage of the current detection circuit op amp to trigger the anti-backflow protection.

[0032] Furthermore, in this embodiment, the current detection circuit also includes a voltage divider resistor R1, a voltage divider resistor R4 and an auxiliary source. The positive terminal of the operational amplifier U1 is powered by the 5V voltage output by the auxiliary source, and the negative terminal of the operational amplifier U1 is connected to the output voltage positive terminal VOUT+.

[0033] Voltage-dividing resistors R1 and R4 are used to divide the 5V voltage supplied by the positive terminal of operational amplifier U1 and input it to the positive input of operational amplifier U1, so that the operational amplifier has an output voltage in the zero-current state. Specifically, in this embodiment, the voltage-dividing resistor R1 is connected in series between the drain of MOS transistor Q1 and the positive input of operational amplifier U1, the voltage-dividing resistor R4 is connected in series between the voltage-dividing resistor R1 and the positive power input of operational amplifier U1, and the auxiliary source is connected between the voltage-dividing resistor R4 and the positive power input of operational amplifier U1.

[0034] Furthermore, in this embodiment, the current detection circuit further includes an input resistor R2 and an input resistor R3. Specifically, the input resistor R2 is connected in series between the voltage divider resistor R1 and the positive input terminal of the operational amplifier U1, and the input resistor R3 is connected in series between the source of the MOS transistor Q1 and the negative input terminal of the operational amplifier U1.

[0035] Furthermore, in this embodiment, the current detection circuit further includes a feedback resistor R5; a first end of the feedback resistor R5 is connected to the output terminal of the operational amplifier U1, and a second end of the feedback resistor R5 is connected between the input resistor R3 and the inverting input terminal of the operational amplifier U1. It should be noted that the output magnification of the operational amplifier U1 can be adjusted by adjusting the resistance values ​​of the input resistor R2, the input resistor R3, and the feedback resistor R5.

[0036] Furthermore, in this embodiment, the current detection circuit also includes a capacitor C1 and a capacitor C2, which are used to stabilize the key voltage value; the first end of the capacitor C1 is connected between the input resistor R2 and the positive input terminal of the operational amplifier U1, and the first end of the capacitor C2 is connected to the positive power input terminal of the operational amplifier U1; the negative power supply of the operational amplifier U1 is connected to the positive output of the power module. Specifically in this embodiment, the second ends of the capacitor C1 and the capacitor C2 are connected to the negative power input terminal of the operational amplifier U1.

[0037] As can be seen from the above, the current detection circuit based on the Oring switch tube provided by the present invention uses fewer components than the commonly used secondary-side current detection circuit and Oring circuit design, saving power module design space and cost.

[0038] Now let's analyze the function of the current detection circuit provided above. The following three working states are explained in turn:

[0039] State 1: Output 0 current, that is, when the power module is in no-load state:

[0040] When the power module is no-load and outputs zero current, the output voltage of the power module is equal to the external voltage. The positive input of U1 is the 5V voltage divided by R1 and R4, and the negative input is 0V. The output of the output end is the difference between the two inputs of U1 amplified by R5 / R3 times. At this time, the equivalent circuit diagram of the current detection circuit is as follows: Figure 2 shown.

[0041] Affected by the voltage at the positive input terminal of U1, the output voltage at the output terminal of U1 is not 0V, and the amplitude of each resistor in the current detection circuit is not adjusted. Therefore, the output voltage at this time is recorded as Vo1, Vo1 = 5V*R1 / (R1+R4)*R5 / R3.

[0042] State 2, outputting forward current, that is, when the power module is outputting normally:

[0043] When the power module outputs forward current normally, due to the internal resistance of Q1, there is a voltage difference between the output voltage and the external voltage, and the voltage difference is equal to the voltage drop V of Q1. mos At this time, the equivalent circuit diagram of the current detection circuit is as follows Figure 3 shown.

[0044] Consider Q1 as a resistor. The positive input of U1 is the 5V voltage divided by R1 and R4, and the negative input is -V mos At this time, the output voltage is recorded as Vo2, Vo2=[5V*R1 / (R1+R4)-(-V mos )]*R5 / R3.

[0045] Q1's tube voltage drop V mos Affected by the current, when the output current is larger, the tube voltage drop V mos The larger the value, the greater the maximum output current can be set according to the output requirements when designing the actual power module. At this time, the maximum tube voltage drop V mos,max , and the maximum output voltage Vo of U1 can be obtained from this 2,max When the output current of the power module exceeds the maximum output current, that is, the output voltage of U1 exceeds Vo 2,max When the control chip determines that the module output is overcurrent, the power module triggers the overcurrent protection and shuts down the output.

[0046] State 3, output reverse current, that is, when the power module outputs reverse current:

[0047] When the power module outputs reverse current, due to the internal resistance of Q1, there is a voltage difference between the output voltage and the external voltage, and the voltage difference is equal to the voltage drop V of Q1. mos At this time, the equivalent circuit diagram of the current detection circuit is as follows Figure 4 shown.

[0048] Consider Q1 as a resistor. The positive input of U1 is the 5V voltage divided by R1 and R4, and the negative input is V mosAt this time, the output voltage is recorded as Vo3 = [5V*R1 / (R1+R4)-V mos ]*R5 / R3.

[0049] Q1's tube voltage drop V mos Affected by the current, when the reverse current is larger, the tube voltage drop V mos The larger the value, the greater the reverse current. When designing the actual power module, the maximum reverse current can be set according to the needs. At this time, the maximum reverse tube voltage drop can be obtained, and the minimum output voltage Vo of U1 can be obtained from this. 3,min When the reverse current of the power module exceeds the maximum reverse current, the output voltage of U1 is less than Vo 3,min When the control chip determines that the module output is backflowing, the power module triggers protection to shut down Q1 and output.

[0050] According to the above analysis, the output range of U1 can be drawn as follows Figure 5 As shown. Figure 5 It can be seen that U1 output is Vo 3,min To Vo 2,max When the U1 output is greater than Vo, the power module works normally. 2,max When the overcurrent protection is triggered, the power module output is turned off. When the output of U1 is less than Vo 3,min When , the power module triggers the anti-backflow protection, turning off Q1 and the power module output.

[0051] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A current detection circuit based on an Oring switch tube, characterized in that: It is composed of an Oring circuit and an operational amplifier U1, wherein the Oring circuit includes a MOS tube Q1; The source of the MOS transistor Q1 is connected to the positive terminal pin PIN_VOUT+, the drain of the MOS transistor Q1 is connected to the output voltage positive terminal VOUT+, the gate of the MOS transistor Q1 is connected to the control pin ORING_G, the positive input terminal of the operational amplifier U1 is connected between the drain of the MOS transistor Q1 and the output voltage positive terminal VOUT+, the reverse input terminal of the operational amplifier U1 is connected between the source of the MOS transistor Q1 and the positive terminal pin PIN_VOUT+, and the output terminal of the operational amplifier U1 is connected to the current output terminal IOUT.

2. The current detection circuit based on the Oring switch tube according to claim 1, characterized in that: It also includes a voltage divider resistor R1, a voltage divider resistor R4 and an auxiliary source; The voltage-dividing resistor R1 is connected in series between the drain of the MOS tube Q1 and the positive input terminal of the operational amplifier U1. The voltage-dividing resistor R4 is connected in series between the voltage-dividing resistor R1 and the positive power input terminal of the operational amplifier U1. The auxiliary source is connected between the voltage-dividing resistor R4 and the positive power input terminal of the operational amplifier U1.

3. The current detection circuit based on the Oring switch tube according to claim 2, characterized in that: Also includes input resistor R2 and input resistor R3; The input resistor R2 is connected in series between the voltage divider resistor R1 and the positive input terminal of the operational amplifier U1 , and the input resistor R3 is connected in series between the source of the MOS transistor Q1 and the negative input terminal of the operational amplifier U1 .

4. The current detection circuit based on the Oring switch tube according to claim 3, characterized in that: Also includes feedback resistor R5; A first end of the feedback resistor R5 is connected to the output end of the operational amplifier U1 , and a second end of the feedback resistor R5 is connected between the input resistor R3 and the inverting input end of the operational amplifier U1 .

5. The current detection circuit based on the Oring switch tube according to claim 3, characterized in that: Also included are capacitor C1 and capacitor C2; The first end of the capacitor C1 is connected between the input resistor R2 and the positive input terminal of the operational amplifier U1, the first end of the capacitor C2 is connected to the positive power input terminal of the operational amplifier U1, and the second ends of the capacitor C1 and the capacitor C2 are connected to the negative power input terminal of the operational amplifier U1.

6. The current detection circuit based on an Oring switch tube according to any one of claims 2 to 5, characterized in that: The negative power supply terminal of the operational amplifier U1 is connected to the output voltage positive terminal VOUT+.

7. The current detection circuit based on the Oring switch tube according to claim 6, characterized in that: The positive terminal of the operational amplifier U1 is powered by a 5V voltage.

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