Overcurrent detection protection circuit, overcurrent monitoring method, power supply and industrial sewing machine

Abstract

The invention provides an over-current detection protection circuit, an over-current monitoring method, a power supply and an industrial sewing machine, and the circuit comprises a current sampling unit which is connected with the output end of a power supply and is configured to collect an output current signal of the output end; the operational amplifier processing unit is connected with the current sampling unit and is configured to amplify and filter the output current signal; the hysteresis comparison unit is connected with the operational amplifier processing unit and is configured to adjust overcurrent protection response time and / or overcurrent protection recovery time; and the overcurrent signal generation unit is connected with the hysteresis comparison unit and is configured to generate an overcurrent signal according to an overcurrent output current signal, so that a power supply stops working based on the overcurrent signal, and overcurrent protection is completed. The invention provides an overcurrent detection and protection scheme in which overcurrent protection response time and recovery time can be flexibly and conveniently adjusted.

Description

Technical Field

[0001] The present application belongs to the technical field of power supply design, and relates to an overcurrent detection circuit, and in particular to an overcurrent detection protection circuit, an overcurrent monitoring method, a power supply and an industrial sewing machine. Background Art

[0002] In the prior art, switching power supplies are used to power various industrial equipment. Taking industrial sewing machines as an example, the low-voltage stepper motors and electromagnets on the industrial sewing machines need to be powered by a flyback power supply or a forward power supply. The stepper motor and electromagnet loads may be damaged and short-circuited, or the output plug is inserted incorrectly, which will cause the power output to be in a short-circuit or overloaded state.

[0003] The power supply protection method currently used in the industry is passive short-circuit protection, so the power supply will not be protected under certain output overload conditions; or under output short-circuit conditions, because the transformer is a non-standard part, the incoming material consistency is not high, and there are deviations in the inductance, leakage inductance and coupling between coils, some transformers will not be able to successfully perform passive short-circuit protection, causing damage to the power supply circuit or even explosion, bringing serious safety problems. Therefore, the existing power supply protection scheme cannot actively detect the power supply output current. If an overload or short circuit occurs, an overcurrent signal is output to the control chip, and the control chip stops running the switching power supply to achieve the purpose of overcurrent protection. Summary of the invention

[0004] The present application provides an overcurrent detection protection circuit, an overcurrent monitoring method, a power supply and an industrial sewing machine, which are used to solve the problem of how to flexibly perform overcurrent detection and protection while actively detecting the output current of the power supply.

[0005] In a first aspect, the present application provides an overcurrent detection protection circuit, which includes: a current sampling unit, connected to the output end of a power supply, and configured to collect an output current signal from the output end; an operational amplifier processing unit, connected to the current sampling unit, and configured to amplify and filter the output current signal; a hysteresis comparison unit, connected to the operational amplifier processing unit, and configured to adjust an overcurrent protection response time and / or an overcurrent protection recovery time; an overcurrent signal generating unit, connected to the hysteresis comparison unit, and configured to generate an overcurrent signal according to the overcurrent output current signal, so as to stop the power supply from working based on the overcurrent signal and complete overcurrent protection.

[0006] In an implementation of the first aspect, the current sampling unit includes a current sampling resistor; one end of the current sampling resistor is connected to the output end of the transformer of the power supply, and the other end is connected to the operational amplifier processing unit; the transformer outputs a supply voltage at the positive end of the energy storage capacitor after diode rectification.

[0007] In an implementation of the first aspect, the hysteresis comparison unit includes: a first RC charge-discharge circuit and a first hysteresis comparator; the first RC charge-discharge circuit includes a first diode, a third resistor, a seventh resistor and a second capacitor; the output end of the operational amplifier processing unit is respectively connected to the anode of the first diode and one end of the seventh resistor, the cathode of the first diode is connected to one end of the third resistor, the other end of the third resistor and the other end of the seventh resistor are both connected to one end of the second capacitor, and the other end of the second capacitor is grounded; one end of the second capacitor is also connected to the negative phase input end of the first hysteresis comparator.

[0008] In an implementation of the first aspect, the values ​​of the third resistor and the second capacitor are configured to adjust the overcurrent protection response time; the values ​​of the seventh resistor and the second capacitor are configured to adjust the overcurrent protection recovery time.

[0009] In an implementation of the first aspect, the hysteresis comparison unit includes: a second RC charge and discharge circuit and a second hysteresis comparator; one end of the second hysteresis comparator is connected to the operational amplifier processing unit, and the other end is connected to one end of the second RC charge and discharge circuit, and the other end of the second RC charge and discharge circuit is connected to the overcurrent signal generating unit.

[0010] In an implementation of the first aspect, the overcurrent signal generating unit includes an optocoupler; the hysteresis comparison unit is connected to the light-emitting side of the optocoupler, and in response to the output current signal overcurrent, the light-emitting side of the optocoupler emits light, and the overcurrent signal is generated after the photosensitive side of the optocoupler is turned on.

[0011] In an implementation of the first aspect, the circuit also includes: a PWM (Pulse Width Modulation) chip; the PWM chip is connected to the output end of the overcurrent signal generating unit, and is configured to receive the overcurrent signal and stop outputting the PWM wave so that the power supply stops working and completes overcurrent protection.

[0012] In a second aspect, the present application provides a power supply overcurrent monitoring method, which is applied to the circuit, and the method includes: adjusting the resistance and capacitance values ​​in the RC charge and discharge circuit in the hysteresis comparison unit to determine the overcurrent protection response time and / or the overcurrent protection recovery time; collecting the output current signal at the output end; amplifying and filtering the output current signal; in response to the output current signal overcurrent, generating an overcurrent signal according to the overcurrent output current signal, so as to stop the power supply based on the overcurrent signal to complete the overcurrent protection.

[0013] In a third aspect, the present application provides a power supply, comprising: the circuit described above.

[0014] In a fourth aspect, the present application provides an industrial sewing machine, which is powered by the power supply.

[0015] As described above, the overcurrent detection protection circuit, overcurrent monitoring method, power supply and industrial sewing machine described in the present application have the following beneficial effects:

[0016] The overcurrent protection response time of this application is fast, which can reach 50us level. The protection response time of the existing technology is more than 30ms. The shorter the time of this application, the less stress the circuit and components will have, which greatly improves the safety, reliability and life of the electric control.

[0017] The hiccup time or overcurrent protection recovery time of this application is long, which can reach more than 1s. The hiccup time of the prior art can only reach 500ms. The longer the time of this application, the less stress the circuit and components will have, which greatly improves the safety, reliability and life of the electric control.

[0018] The overcurrent protection response time and hiccup time of the present application are adjustable and do not affect the startup time of the electronic control. In the prior art, increasing the hiccup time will slow down the startup of the electronic control, and increasing the overcurrent protection response time will affect other performance of the power supply. However, the two time adjustments of the present application do not affect other performance at all, greatly improving the performance of the electronic control.

[0019] The overcurrent of the present application is precisely adjustable. The sampling resistor, amplifier gain, and hysteresis comparison parameters can be adjusted to adjust the overcurrent. The existing technology cannot adjust the overcurrent, and generally can only protect the output short circuit. It will not protect under the output overload condition. The power supply continues to work, which will damage the circuit and eventually explode the board.

[0020] The application of this application is wide. In addition to being applied to flyback power supplies or forward power supplies, other switching power supplies such as BUCK and BOOST can also use the circuit structure solution of this application for overcurrent protection.

[0021] The entire overcurrent detection includes a current sampling unit, an operational amplifier processing unit, a hysteresis comparison unit and an overcurrent signal generating unit. The overall circuit structure is simple and the cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Shown is a schematic diagram of the structural connection of the overcurrent detection protection circuit described in an embodiment of the present application.

[0023] Figure 2 Shown is a circuit schematic diagram of the overcurrent detection protection circuit described in an embodiment of the present application.

[0024] Figure 3 Shown is a first circuit schematic diagram of a forward transformer of the overcurrent detection protection circuit described in an embodiment of the present application.

[0025] Figure 4Shown is a second circuit schematic diagram of a forward transformer of the overcurrent detection protection circuit described in an embodiment of the present application.

[0026] Figure 5 Shown is an overcurrent protection response waveform diagram of the overcurrent detection protection circuit described in an embodiment of the present application.

[0027] Figure 6 Shown is an overcurrent protection recovery waveform diagram of the overcurrent detection protection circuit described in an embodiment of the present application.

[0028] Figure 7 Shown is a principle flow chart of the power supply overcurrent monitoring method described in an embodiment of the present application.

[0029] Figure 8 Shown is a schematic diagram of the structure of the power supply described in an embodiment of the present application.

[0030] Fig. 9 Shown is a schematic diagram of the structure of the industrial sewing machine described in an embodiment of the present application.

[0031] Component number description

[0032] 1 Overcurrent detection protection circuit

[0033] 11 Current sampling unit

[0034] 12 Operational Amplifier Processing Unit

[0035] 13. Hysteresis comparison unit

[0036] 14 Overcurrent signal generation unit

[0037] Steps S71 to S74 DETAILED DESCRIPTION

[0038] The following describes the embodiments of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. The present application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0039] It should be noted that the illustrations provided in the following embodiments are only used to illustrate the basic concept of the present application in a schematic manner, and therefore the illustrations only show components related to the present application rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0040] The technical solutions in the embodiments of the present application will be described in detail below in conjunction with the drawings in the embodiments of the present application.

[0041] See also Figure 1 , which is a schematic diagram showing the structural connection of the overcurrent detection protection circuit described in the embodiment of the present application. Figure 1 As shown, this embodiment provides an overcurrent detection protection circuit 1, which specifically includes: a current sampling unit 11, an operational amplifier processing unit 12, a hysteresis comparison unit 13 and an overcurrent signal generating unit 14.

[0042] The current sampling unit 11 is connected to the output end of the power supply and is configured to collect the output current signal of the output end.

[0043] The operational amplifier processing unit 12 is connected to the current sampling unit 11 and is configured to amplify and filter the output current signal.

[0044] The hysteresis comparison unit 13 is connected to the operational amplifier processing unit 12 and is configured to adjust the overcurrent protection response time and / or the overcurrent protection recovery time.

[0045] The overcurrent signal generating unit 14 is connected to the hysteresis comparing unit 13 and is configured to generate an overcurrent signal according to the overcurrent output current signal, so as to stop the power supply from working based on the overcurrent signal and complete the overcurrent protection.

[0046] In one embodiment, the current sampling unit includes a current sampling resistor.

[0047] One end of the current sampling resistor is connected to the output end of the transformer of the power supply, and the other end is connected to the operational amplifier processing unit; the transformer outputs the supply voltage at the positive terminal of the energy storage capacitor after diode rectification.

[0048] See also Figure 2 , which is a circuit schematic diagram of the overcurrent detection protection circuit described in the embodiment of the present application. Figure 2 As shown, the current sampling unit 11 includes a current sampling resistor R4. One end of the current sampling resistor R4 is connected to the output end of the transformer T1 of the power supply, and the other end is connected to the operational amplifier processing unit 12; the transformer T1 outputs the supply voltage at the positive end of the energy storage capacitor 2 after rectification by the diode 1. In practical applications, T1 can be a flyback transformer, which outputs a 100V supply voltage through rectification by the diode 1.

[0049] In one embodiment, the hysteresis comparison unit includes: a first RC charge-discharge circuit and a first hysteresis comparator.

[0050] The first RC charging and discharging circuit includes a first diode, a third resistor, a seventh resistor and a second capacitor.

[0051] The output end of the operational amplifier processing unit is respectively connected to the anode of the first diode and one end of the seventh resistor, the cathode of the first diode is connected to one end of the third resistor, the other end of the third resistor and the other end of the seventh resistor are both connected to one end of the second capacitor, and the other end of the second capacitor is grounded.

[0052] One end of the second capacitor is also connected to the negative phase input end of the first hysteresis comparator.

[0053] like Figure 2 As shown, the hysteresis comparison unit 13 includes: a first RC charge-discharge circuit and a first hysteresis comparator U1B. The first RC charge-discharge circuit includes a first diode D1, a third resistor R3, a seventh resistor R7 and a second capacitor C2. The output end of the operational amplifier processing unit 12 is respectively connected to the anode of the first diode D1 and one end of the seventh resistor R7, the cathode of the first diode D1 is connected to one end of the third resistor R3, the other end of the third resistor R3 and the other end of the seventh resistor R7 are both connected to one end of the second capacitor C2, and the other end of the second capacitor C2 is grounded. One end of the second capacitor C2 is also connected to the negative phase input end (pin 6) of the first hysteresis comparator U1B.

[0054] In one embodiment, the values ​​of the third resistor and the second capacitor are configured to adjust the overcurrent protection response time; the values ​​of the seventh resistor and the second capacitor are configured to adjust the overcurrent protection recovery time.

[0055] like Figure 2 As shown, the values ​​of the third resistor R3 and the second capacitor C2 are configured to adjust the overcurrent protection response time; the values ​​of the seventh resistor R7 and the second capacitor C2 are configured to adjust the overcurrent protection recovery time.

[0056] In one embodiment, the overcurrent signal generating unit includes an optical coupler.

[0057] The hysteresis comparison unit is connected to the light-emitting side of the optocoupler. In response to the output current signal overcurrent, the light-emitting side of the optocoupler emits light, and the light-sensitive side of the optocoupler is turned on to generate the overcurrent signal.

[0058] like Figure 2 As shown, the overcurrent signal generating unit 14 includes an optocoupler U2. The hysteresis comparison unit 13 is connected to the light-emitting side of the optocoupler U2. In response to the output current signal overcurrent, the light-emitting side of the optocoupler U2 emits light, and the light-sensitive side of the optocoupler U2 is turned on to generate the overcurrent signal OC.

[0059] Combination Figure 2The overall structure of the overcurrent detection protection circuit is described in detail as follows:

[0060] The current sampling resistor R4 amplifies the current sampling signal through the operational amplifier processing unit 12. The operational amplifier processing unit 12 includes a chip U1A, a capacitor C1, a capacitor C3, a resistor R5, a resistor R8, and a resistor R9. Pin 3 of the chip U1A is connected to one end of R5, and the other end of R5 is connected to the ground. Pin 2 of the chip U1A is connected to one end of the resistor R8, one end of the resistor R9, and one end of the capacitor C3. The other end of the resistor R8 is connected to the other end of the current sampling resistor R4. Pin 1 of the chip U1A is connected to the other end of the resistor R9 and the other end of the capacitor C3. Pin 8 of the chip U1A is connected to a 5V power supply and one end of the capacitor C1. The other end of the capacitor C1 is connected to the power ground. Pin 4 of the chip U1A is connected to the power ground.

[0061] The operational amplifier processing unit 12 amplifies the filtered signal and sends it to the first RC charging and discharging circuit, including a third resistor R3, a seventh resistor R7, a second capacitor C2, and a first diode D1. The left end of the seventh resistor R7 is connected to pin 1 of the chip U1A and the anode of the first diode D1, and the other end is connected to one end of the second capacitor C2 and one end of the third resistor R3. The other end of the resistor R3 is connected to the cathode of the diode D1.

[0062] The voltage after the first RC charge and discharge circuit is connected to the first hysteresis comparator circuit, which includes a chip U1B and resistors R1 / R2 / R6. Pin 5 of chip U1B is connected to one end of R1 / R2 / R6, the other end of resistor R1 is connected to pin 7 of U1B, the other end of resistor R2 is connected to ground, and the other end of resistor R6 is connected to the power supply.

[0063] The output voltage of the first hysteresis comparator circuit is transmitted to the overcurrent signal generating unit 14 and is detected and converted by the optical coupler U2 to generate an overcurrent signal OC.

[0064] Combination Figure 2 The circuit shown in the figure, the working principle of the overcurrent detection protection circuit is described in detail as follows:

[0065] When the output current of the power supply is too large, the overcurrent forms a voltage drop through the current sampling resistor R4, and there is a negative voltage at the left end of R8. The operational amplifier processing unit 12 inverts and amplifies the negative voltage signal, and outputs a high level at pin 1 of the chip U1A. This high level charges the second capacitor C2 through the first diode D1 and the third resistor R3. When the voltage at pin 6 of the chip U1B is greater than the voltage at pin 5 of the chip U1B, pin 7 of the chip U1B outputs a low level, and then the voltage at pin 1 of the optocoupler U2 is higher than the voltage at pin 2. The internal diode of the optocoupler is forward-conducted, and the voltage at pin 4 of the optocoupler U2 becomes a low level. The overcurrent signal OC becomes a low level. The low level signal indicates that the output current of the power supply is too large, which is fed back to the PWM chip. The PWM chip stops outputting PWM waves, the power supply stops working, the output current is reduced to zero, and the overcurrent protection response is completed.

[0066] After the power supply is protected and the output current decreases, the voltage drop on the current sampling resistor R4 becomes lower, the negative voltage on the left end of the resistor R8 decreases, the high level of the output pin 1 of the chip U1A after reverse amplification decreases, and the voltage on the second capacitor C2 is discharged through the seventh resistor R7. When the voltage of pin 6 of the chip U1B is lower than the voltage of pin 5, pin 7 of the chip U1B outputs a high level, the internal diode of the optocoupler U2 is cut off, and pins 4 and 3 of the optocoupler U2 are disconnected. The OC signal is pulled high by the PWM chip, the chip re-sends the PWM wave, and the power supply starts working again. This process time is called the hiccup time.

[0067] The overcurrent protection response time can be set by modifying the values ​​of the third resistor R3 and the second capacitor C2, and the hiccup time or overcurrent protection recovery time can be set by modifying the values ​​of the resistor R7 and the capacitor C2, so as to meet the actual working requirements of different products. Generally, the resistance of the third resistor R3 is relatively small, and the resistance of the seventh resistor R7 is relatively large. The overcurrent protection response time is generally set to less than 10ms, and can even reach less than 100us. The protection recovery time is generally set to more than 300ms to achieve the purpose of protecting the circuit when overcurrent occurs.

[0068] The first hysteresis comparator circuit makes the comparison level of pin 5 of chip U1B jump from high level to low level state, which is higher than that of pin 7 of chip U1B, and makes the comparison level of pin 5 of chip U1B jump from low level to high level state, which is lower than that of pin 5. In this way, a level difference is left to achieve the purpose of setting the power protection recovery time.

[0069] The compared signal is given to the overcurrent signal generating unit 14, which includes an optocoupler U2, resistors R10 / R12 / R11, and a capacitor C4. Pin 1 of the optocoupler U2 is connected to one end of R10 / R12, and the other end of R12 is connected to pin 2 of U2. The other end of the resistor R10 is connected to the power supply 5V, pin 3 of the optocoupler U2 is connected to the primary ground PGND, pin 4 of the optocoupler U2 is connected to one end of the resistor R11, and the other end of R11 is connected to one end of the capacitor C4 and the output OC signal, and the other end of the capacitor C4 is connected to the primary ground PGND.

[0070] Combination Figure 2 The circuit shown, the adjustment principle of the overcurrent protection response time and / or overcurrent protection recovery time (or hiccup time) of the overcurrent detection protection circuit is described in detail as follows:

[0071] When the output is unloaded and has no current, the output pin 1 of the op amp U1A is low level, that is, the input pin 6 of the comparator U1B is low level. At this time, the output of pin 7 is 5V, and the voltage of pin 5 is set at 3V by the designed resistance value of resistors R2 / R1 / R6; when the output becomes an overcurrent state, the output of pin 1 of the op amp U1A is greater than 3V, and the capacitor C2 is charged through D1 / R3. When the voltage is greater than 3V, the output level of pin 7 of the comparator flips from 5V to 0V, triggering the overcurrent protection. This charging time is the overcurrent response time, which is approximately one RC time. Assuming that R3 is set to 100Ω and C2 is set to 10uf, the overcurrent response time is approximately 1ms.

[0072] After the power supply circuit stops working, the output current drops to zero, and the output voltage of op amp U1A is zero. At this time, the voltage on capacitor C2 is 3V, which will be discharged through resistor R7, and the voltage on C2 will slowly drop. At this time, the output voltage of pin 7 of comparator U1B is 0V, and the voltage of pin 5 will be less than the previous 3V. Through resistance calculation, it is set at 2V, so when the voltage of capacitor C2 drops below 2V, the output voltage of the comparator changes from 0V to 5V, and the overcurrent protection is restored. This discharge time is the short-circuit recovery time. Assuming that resistor R7 is set to 300K, the recovery time is about 1s.

[0073] Therefore, by adjusting the value of R3 / R7 / C2, the protection response time and recovery time can be flexibly adjusted: by fixing the value of C2, adjusting R3 or R7 alone can adjust the two times within a certain range. If you want to adjust the two times in a larger range, you can adjust the value of C2; adjusting the value of the hysteresis comparator R1 / R2 / R6 can adjust the range of the hysteresis voltage, that is, the 2V and 3V mentioned above, and then flexibly adjusting the two voltages can adjust the RC charge and discharge voltage target value, thereby achieving the purpose of adjusting the protection response time and recovery time.

[0074] According to the above principles, it can be understood that the protection response time is 1ms and the recovery time is 1s, which is 1000 times different. The protection response time is crucial for power supply overcurrent protection. The faster the time, the better. The circuit and power components are subjected to great stress during short circuit. The longer the time, the greater the probability of damage to the circuit and power components; the longer the recovery time, the better, and the longer the components are, the less likely they are to be damaged. During the hiccup process of the power supply, during the protection response time, the power supply is still working, and the circuit and components are rapidly heating up. During the recovery time, the circuit stops working, and the circuit and components are slowly dissipating heat. When the heat generated in each cycle is greater than the heat dissipation, the temperature of the component is in a rising state. When it is greater than the maximum temperature that the device can withstand, the device is damaged; when the temperature of the component rises to a certain value below the maximum temperature, the heat generated is equal to the heat dissipation, and the component is not damaged. The above explains why the two times are flexible and adjustable and have a wide adjustment range.

[0075] In one embodiment, the circuit further includes: a PWM chip.

[0076] The PWM chip is connected to the output end of the overcurrent signal generating unit, and is configured to receive the overcurrent signal and stop outputting the PWM wave so that the power supply stops working and completes overcurrent protection.

[0077] See also Figure 3 , which is a schematic diagram of the first circuit of the forward transformer of the overcurrent detection protection circuit described in the embodiment of the present application. Figure 3 As shown, Figure 3 The overcurrent signal is COMP, and the circuit 1 further includes: a PWM chip U3. The PWM chip U3 is connected to the output end of the overcurrent signal generating unit 14, and is configured to receive the overcurrent signal COMP, stop outputting the PWM wave, so that the power supply stops working, and completes the overcurrent protection. In actual applications, the PWM chip U3 is combined with Q1, Q2, D2, and D3 to realize the forward transformer circuit structure.

[0078] like Figure 3As shown, the current sampling unit 11 includes a current sampling resistor R4. One end of the current sampling resistor R4 is connected to the output end of the transformer T1 of the power supply, and the other end is connected to the operational amplifier processing unit 12; the transformer T1 outputs the supply voltage at the positive end of the energy storage capacitor 2 after rectification by the diode 1. In practical applications, T1 can be a flyback transformer, which outputs a 100V voltage through diode rectification. The hysteresis comparison unit 13 includes: a first RC charge-discharge circuit and a first hysteresis comparator U1B. The first RC charge-discharge circuit includes a first diode D1, a third resistor R3, a seventh resistor R7 and a second capacitor C2. The output end of the operational amplifier processing unit 12 is respectively connected to the anode of the first diode D1 and one end of the seventh resistor R7, the cathode of the first diode D1 is connected to one end of the third resistor R3, the other end of the third resistor R3 and the other end of the seventh resistor R7 are both connected to one end of the second capacitor C2, and the other end of the second capacitor C2 is grounded. One end of the second capacitor C2 is also connected to the negative input end (pin 6) of the first hysteresis comparator U1B. The values ​​of the third resistor R3 and the second capacitor C2 are configured to adjust the overcurrent protection response time; the values ​​of the seventh resistor R7 and the second capacitor C2 are configured to adjust the overcurrent protection recovery time. The overcurrent signal generating unit 14 includes an optocoupler U2. The hysteresis comparison unit 13 is connected to the light-emitting side of the optocoupler U2. In response to the output current signal overcurrent, the light-emitting side of the optocoupler U2 emits light, and the light-sensitive side of the optocoupler U2 is turned on to generate the overcurrent signal OC.

[0079] In another embodiment, the hysteresis comparison unit includes: a second RC charge-discharge circuit and a second hysteresis comparator.

[0080] One end of the second hysteresis comparator is connected to the operational amplifier processing unit, and the other end is connected to one end of the second RC charge-discharge circuit, and the other end of the second RC charge-discharge circuit is connected to the overcurrent signal generating unit.

[0081] See also Figure 4 , which is a schematic diagram of the second circuit of the forward transformer of the overcurrent detection protection circuit described in the embodiment of the present application. Figure 4 As shown, the hysteresis comparison unit 13 includes: a second RC charge-discharge circuit (R3, R14, R15, Q3, R10 and C2) and a second hysteresis comparator U1B. One end of the second hysteresis comparator U1B is connected to the operational amplifier processing unit 12, and the other end is connected to one end of the second RC charge-discharge circuit (one end of R3), and the other end of the second RC charge-discharge circuit (the non-common end of R10 and C2) is connected to the overcurrent signal generating unit 14.

[0082] like Figure 4As shown, this embodiment still uses the principle of charging and discharging the capacitor to set the protection response time and recovery time. Figure 2 , Figure 3 In comparison, the RC charging and discharging circuit is placed after the hysteresis comparator. When overcurrent occurs, pin 7 of comparator U1B outputs a low level, transistor Q3 is turned on, and capacitor C2 is charged. When the voltage on C2 becomes high, optocoupler U2 is turned on, and power supply PWM chip U3 stops outputting PWM wave, and the power supply stops working. After overcurrent protection, capacitor C2 is slowly discharged through R10. When the capacitor voltage drops below 0.7V, optocoupler U2 is cut off, and the power supply resumes working. The protection response time and recovery time are set by adjusting the value of R15 / R10 / C2.

[0083] Combination Figure 2 , Figure 3 and Figure 4 It can be seen from the comparison that the present application achieves the purpose of adjusting the overcurrent protection response time and the recovery working time by setting different circuits for capacitor charging and discharging.

[0084] Furthermore, in different practical applications, the present application can modify the models of the operational amplifier chip U1 and the optical coupler U2 to achieve the purpose of current detection and signal processing.

[0085] See also Figure 5 , which shows the overcurrent protection response waveform of the overcurrent detection protection circuit described in the embodiment of the present application. Figure 5 As shown, the overcurrent signal waveform of the actual test is shown. It can be seen that the overcurrent protection response delay is ms, specifically △t=4.371ms.

[0086] See also Figure 6 , which shows the overcurrent protection recovery waveform of the overcurrent detection protection circuit described in the embodiment of the present application. Figure 6 As shown, the overcurrent signal waveform of the actual test is shown, and it can be seen that the overcurrent protection recovery time is 1s, specifically △t=1.077s.

[0087] Therefore, the present application connects a sampling resistor in series in the power supply output circuit to detect the output overload current or short-circuit current. The op amp circuit amplifies and filters the current signal. The hysteresis comparison circuit prevents false triggering and adjusts the hiccup time. When the output is overloaded or short-circuited, the secondary overcurrent signal is transmitted back to the primary PWM chip through the optocoupler. After the chip detects the overcurrent signal, it stops sending the PWM wave, so that the power supply stops working and achieves the purpose of overcurrent protection.

[0088] See also Figure 7 , which is a principle flow chart of the power supply overcurrent monitoring method described in the embodiment of the present application. Figure 7As shown, this embodiment provides a power supply overcurrent monitoring method, which is applied to the overcurrent detection protection circuit, and the overcurrent detection protection circuit includes: a current sampling unit, connected to the output end of the power supply, configured to collect the output current signal of the output end; an operational amplifier processing unit, connected to the current sampling unit, configured to amplify and filter the output current signal; a hysteresis comparison unit, connected to the operational amplifier processing unit, configured to adjust the overcurrent protection response time and / or overcurrent protection recovery time; an overcurrent signal generation unit, connected to the hysteresis comparison unit, configured to generate an overcurrent signal according to the overcurrent output current signal, so as to stop the power supply from working based on the overcurrent signal and complete the overcurrent protection. The method specifically includes the following steps:

[0089] S71, adjusting the resistance and capacitance values ​​in the RC charging and discharging circuit in the hysteresis comparison unit to determine the overcurrent protection response time and / or overcurrent protection recovery time.

[0090] S72, collecting the output current signal of the output end.

[0091] S73, amplifying and filtering the output current signal.

[0092] S74, in response to the output current signal being overcurrent, generating an overcurrent signal according to the overcurrent output current signal, so as to stop the power supply from working based on the overcurrent signal, thereby completing overcurrent protection.

[0093] Therefore, this embodiment can actively detect the output current of the power supply, amplify and filter the current signal, and then make a comparison and judgment. After judging that it is overcurrent, the power supply controls the PWM chip to turn off the output.

[0094] The protection scope of the power supply overcurrent monitoring method described in the embodiment of the present application is not limited to the execution order of the steps listed in the present embodiment. All solutions implemented by adding, reducing or replacing steps in the prior art based on the principles of the present application are included in the protection scope of the present application.

[0095] The overcurrent detection protection circuit described in the embodiment of the present application can implement the power supply overcurrent monitoring method described in the present application, but the implementation device of the power supply overcurrent monitoring method described in the present application includes but is not limited to the structure of the overcurrent detection protection circuit listed in the present embodiment. All structural deformations and replacements of the prior art made according to the principles of the present application are included in the protection scope of the present application.

[0096] In the several embodiments provided in the present application, it should be understood that the disclosed circuit device or method can be implemented in other ways. For example, the circuit device embodiments described above are only schematic. For example, the division of modules / units is only a logical function division. There may be other division methods in actual implementation, such as multiple modules or units can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or modules or units, which can be electrical, mechanical or other forms.

[0097] The modules / units described as separate components may or may not be physically separated, and the components displayed as modules / units may or may not be physical modules, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules / units may be selected according to actual needs to achieve the purpose of the embodiments of the present application. For example, the functional modules / units in the various embodiments of the present application may be integrated into one processing module, or each module / unit may exist physically separately, or two or more modules / units may be integrated into one module / unit.

[0098] Those of ordinary skill in the art should further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0099] See also Figure 8 , which is a schematic diagram of the structure of the power supply described in the embodiment of the present application. Figure 8 As shown, this embodiment provides a power supply, and the power supply includes: the overcurrent detection protection circuit.

[0100] The overcurrent detection protection circuit includes: a current sampling unit, connected to the output end of the power supply, configured to collect the output current signal of the output end; an operational amplifier processing unit, connected to the current sampling unit, configured to amplify and filter the output current signal; a hysteresis comparison unit, connected to the operational amplifier processing unit, configured to adjust the overcurrent protection response time and / or the overcurrent protection recovery time; an overcurrent signal generating unit, connected to the hysteresis comparison unit, configured to generate an overcurrent signal according to the overcurrent output current signal, so as to stop the power supply from working based on the overcurrent signal and complete the overcurrent protection.

[0101] Therefore, the power supply with the overcurrent detection protection circuit provided in this embodiment has the following characteristics:

[0102] (1) The overcurrent protection response time of the power supply is fast, which can reach 50us level. The protection response time of the existing technology is more than 30ms. The shorter the time, the less stress on the circuit and components, which greatly improves the safety, reliability and life of the electric control.

[0103] (2) The hiccup time of the power supply, or the overcurrent protection recovery time, is long and can reach more than 1s. The hiccup time of the existing technology can only reach 500ms. The longer the time, the less stress on the circuit and components, which greatly improves the safety, reliability and life of the electronic control.

[0104] (3) The overcurrent protection response time and hiccup time in the power supply are adjustable. And it does not affect the startup time of the electronic control. In the prior art, increasing the hiccup time will slow down the startup of the electronic control, and increasing the overcurrent protection response time will affect other performance of the power supply. However, the two time adjustments of the present application do not affect other performance at all, greatly improving the performance of the electronic control.

[0105] (4) The overcurrent in the power supply is precisely adjustable. The sampling resistor, op amp gain, and hysteresis comparison parameters can be adjusted to adjust the overcurrent. The existing technology cannot adjust the overcurrent and can generally only protect the output from short circuits. It will not protect under overload conditions. The power supply will continue to work, which will damage the circuit and eventually explode the board.

[0106] (5) The application of power supply types is wide. In addition to being applied to flyback power supplies or forward power supplies, other switching power supplies such as BUCK and BOOST can also be applied to overcurrent protection by this application.

[0107] (6) In the power supply, the entire overcurrent detection includes a current sampling unit, an operational amplifier processing unit, a hysteresis comparison unit and an overcurrent signal generating unit. The overall circuit structure is simple and the cost is low.

[0108] See also Fig. 9 , which is a schematic diagram of the structure of the industrial sewing machine described in the embodiment of the present application. Fig. 9As shown, this embodiment provides an industrial sewing machine, which is powered by the power supply. The power supply includes: the overcurrent detection protection circuit. The overcurrent detection protection circuit includes: a current sampling unit connected to the output end of the power supply, configured to collect the output current signal of the output end; an operational amplifier processing unit connected to the current sampling unit, configured to amplify and filter the output current signal; a hysteresis comparison unit connected to the operational amplifier processing unit, configured to adjust the overcurrent protection response time and / or overcurrent protection recovery time; an overcurrent signal generation unit, connected to the hysteresis comparison unit, configured to generate an overcurrent signal according to the overcurrent output current signal, so as to stop the power supply from working based on the overcurrent signal and complete the overcurrent protection.

[0109] like Fig. 9 As shown, in actual applications, the low-voltage stepper motor and electromagnet on the industrial sewing machine need to be powered by a flyback power supply or a forward power supply. The stepper motor and electromagnet load may be damaged and short-circuited, or the output plug may be inserted incorrectly, resulting in the power output being in a short-circuit or overloaded state. The flyback power supply or forward power supply with the overcurrent detection protection circuit in the present application is used to power the low-voltage stepper motor and electromagnet on the industrial sewing machine, thereby actively detecting the power output current. If the power supply is overloaded or short-circuited, an overcurrent signal is output to the control chip, and the control chip stops running the switching power supply to achieve the protection purpose.

[0110] Therefore, the present application is provided with an RC charging and discharging circuit and a unidirectional charging and discharging circuit. The capacitor is charged through a diode and a small resistance resistor, and the capacitor is discharged through a large resistance resistor, and combined with a hysteresis comparator circuit, the RC charging and discharging circuit is delayed, and different circuits are set for capacitor charging and discharging. Specifically, when overcurrent occurs, the capacitor is charged through a diode and a small resistor, and the charging time is the overcurrent protection response time; when the protection is restored, the diode is reversely cut off, and the capacitor is discharged through a large resistor, and the discharge time is the protection recovery time; the protection time and recovery time are adjustable. The hysteresis comparator sets different judgment voltages, leaving a voltage difference, so that the circuit has an overcurrent protection recovery time. The present application realizes active current detection and current signal processing to protect overcurrent.

[0111] The descriptions of the processes or structures corresponding to the above-mentioned figures have different emphases. For parts that are not described in detail in a certain process or structure, please refer to the relevant descriptions of other processes or structures.

[0112] The above embodiments are merely illustrative of the principles and effects of the present application and are not intended to limit the present application. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed in the present application shall still be covered by the claims of the present application.

Claims

1. An overcurrent detection protection circuit, characterized in that: The circuit comprises: A current sampling unit is connected to the output terminal of the power supply and is configured to collect an output current signal of the output terminal; an operational amplifier processing unit, connected to the current sampling unit, and configured to amplify and filter the output current signal; A hysteresis comparison unit, connected to the operational amplifier processing unit, configured to adjust an overcurrent protection response time and / or an overcurrent protection recovery time; The overcurrent signal generating unit is connected to the hysteresis comparing unit and is configured to generate an overcurrent signal according to the overcurrent output current signal, so as to stop the power supply from working based on the overcurrent signal and complete the overcurrent protection.

2. The circuit according to claim 1, characterized in that The current sampling unit includes a current sampling resistor; One end of the current sampling resistor is connected to the output end of the transformer of the power supply, and the other end is connected to the operational amplifier processing unit; the transformer outputs the supply voltage at the positive terminal of the energy storage capacitor after diode rectification.

3. The circuit according to claim 1, characterized in that The hysteresis comparison unit includes: a first RC charge-discharge circuit and a first hysteresis comparator; The first RC charging and discharging circuit includes a first diode, a third resistor, a seventh resistor and a second capacitor; The output end of the operational amplifier processing unit is respectively connected to the anode of the first diode and one end of the seventh resistor, the cathode of the first diode is connected to one end of the third resistor, the other end of the third resistor and the other end of the seventh resistor are both connected to one end of the second capacitor, and the other end of the second capacitor is grounded; One end of the second capacitor is also connected to the negative phase input end of the first hysteresis comparator.

4. The circuit according to claim 3, characterized in that: The values ​​of the third resistor and the second capacitor are configured to adjust the overcurrent protection response time; the values ​​of the seventh resistor and the second capacitor are configured to adjust the overcurrent protection recovery time.

5. The circuit according to claim 1, characterized in that The hysteresis comparison unit includes: a second RC charge-discharge circuit and a second hysteresis comparator; One end of the second hysteresis comparator is connected to the operational amplifier processing unit, and the other end is connected to one end of the second RC charge-discharge circuit, and the other end of the second RC charge-discharge circuit is connected to the overcurrent signal generating unit.

6. The circuit according to claim 1, characterized in that The overcurrent signal generating unit includes an optical coupler; The hysteresis comparison unit is connected to the light-emitting side of the optocoupler. In response to the output current signal overcurrent, the light-emitting side of the optocoupler emits light, and the light-sensitive side of the optocoupler is turned on to generate the overcurrent signal.

7. The circuit according to claim 1, characterized in that The circuit also includes: a PWM chip; The PWM chip is connected to the output end of the overcurrent signal generating unit, and is configured to receive the overcurrent signal and stop outputting the PWM wave so that the power supply stops working and completes overcurrent protection.

8. A power supply overcurrent monitoring method, characterized in that: Applied to the circuit according to any one of claims 1 to 7, the method comprising: Adjust the resistance and capacitance values ​​in the RC charging and discharging circuit in the hysteresis comparison unit to determine the overcurrent protection response time and / or overcurrent protection recovery time; Collecting output current signal of output terminal; amplifying and filtering the output current signal; In response to the output current signal being overcurrent, an overcurrent signal is generated according to the overcurrent output current signal, so as to stop the power supply from working based on the overcurrent signal, thereby completing overcurrent protection.

9. A power supply, characterized in that: The power supply comprises: the circuit according to any one of claims 1 to 7.

10. An industrial sewing machine, characterized in that: The industrial sewing machine is powered by the power supply described in claim 9.

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