Undervoltage protection circuit

Abstract

The utility model discloses an under-voltage protection circuit, which comprises an isolation transformer, an under-voltage regulation circuit, an enabling end control circuit, an auxiliary power supply circuit and a comparator power supply circuit, and the synonym end of the isolation transformer is connected with the input end of the auxiliary power supply circuit; the output end of the auxiliary power supply circuit is connected with the input end of the comparator power supply circuit; the output end of the comparator power supply circuit is connected with the input end of the under-voltage regulation circuit; the output end of the under-voltage adjusting circuit is connected with the second input end of the enabling end control circuit, the first input end of the enabling end control circuit is connected with the power input end, and the second output end of the enabling end control circuit is connected with the enabling control end pin. According to the utility model, high-voltage signals can be compared through the comparator, and the circuit works normally when undervoltage does not occur; when under-voltage occurs, the output of the chip is controlled by connecting the output of the enabling end control circuit to the enabling end of the IC, the whole circuit is protected under the abnormal condition of the input voltage of the power supply, so that the circuit is prevented from being damaged, and the stability is high.

Description

Technical Field

[0001] The utility model relates to the technical field of switching power supplies, in particular to an undervoltage protection circuit. Background Art

[0002] Compared to linear power supplies, switching power supplies boast smaller size, higher efficiency, and higher power. They are widely used in automotive, photovoltaic, industrial control, medical, and handheld devices. With the continuous advancement of technology, switching power supplies are moving towards higher frequencies, higher power, and smaller sizes. However, insufficient power supply voltage or transient waveforms can sometimes cause damage or malfunction. Undervoltage protection circuits can effectively prevent circuit damage or malfunction caused by insufficient power supply voltage or transient waveforms. Undervoltage protection circuits are commonly used in various electrical devices, such as power transformers, capacitors, and voltage regulators, to ensure safe and reliable operation despite abnormal power supply voltages.

[0003] Undervoltage protection circuits use undervoltage protection devices (such as electronic fuses, ultra-low voltage triggers, etc.) as control elements. By detecting whether the input power supply voltage is lower than the set threshold, it controls the conduction of the switching element, putting the circuit in or out of working state. Specifically, there are two main ways to implement undervoltage protection circuits: one is to directly add an undervoltage protection device to the circuit. When the input power supply voltage is lower than the set value, the protection device will disconnect the circuit at the output end, thereby playing a role in protecting the circuit; the other is to control the switching state of the circuit by controlling the conduction of external devices (such as relays, transistors, etc.) to achieve undervoltage protection. Regardless of which method is used to implement the undervoltage protection circuit, its core is the undervoltage protection device, which can quickly disconnect the circuit at the output end when the circuit power supply voltage is lower than the preset value, thereby preventing circuit damage or abnormal operation.

[0004] In summary, existing circuits suffer from poor stability and high power consumption when the power input voltage is abnormal. When selecting an undervoltage protection device, factors such as its cutoff speed, voltage withstand capability, and repeatability must be considered to ensure that the circuit is protected quickly and reliably under abnormal conditions. Therefore, to ensure that the circuit is protected quickly and reliably under abnormal conditions, the power supply system must have this function, and research into a new undervoltage protection circuit is urgently needed. Summary of the Invention

[0005] In view of this, the present invention aims to provide an undervoltage protection circuit to solve the problems of poor stability and high power consumption in the existing circuit when the power input voltage is abnormal.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0007] An undervoltage protection circuit includes an isolation transformer TIB, an undervoltage regulation circuit, an enable end control circuit, an auxiliary power supply circuit, and a comparator power supply circuit, wherein the opposite-signal terminal of the isolation transformer TIB is connected to the input end of the auxiliary power supply circuit; the output end of the auxiliary power supply circuit is connected to the input end of the comparator power supply circuit; the output end of the comparator power supply circuit is connected to the input end of the undervoltage regulation circuit; the output end of the undervoltage regulation circuit is connected to the second input end of the enable end control circuit, the first input end of the enable end control circuit is connected to the power input end Vin+, and the second output end of the enable end control circuit is connected to the enable control end pin UVLO.

[0008] Furthermore, the enable end control circuit includes a resistor R1, a resistor R2, a resistor R3, a resistor R4 and a capacitor C1; wherein, one end of the resistor R1 is connected to the power input terminal Vin+ as the first input end of the enable end control circuit, and the other end of the resistor R1 is commonly connected to one end of the resistor R2, one end of the capacitor C1, one end of the resistor R3, and one end of the resistor R4, and this connection point is connected to the output end of the undervoltage regulation circuit as the second input end of the enable end control circuit; the other end of the capacitor C1, the other end of the resistor R3, and the other end of the resistor R4 are commonly grounded; the other end of the resistor R2 is connected to the enable control end pin UVLO of the chip IC as the output end of the enable end control circuit.

[0009] Furthermore, the auxiliary power supply circuit includes a diode D5, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C5 and a resistor R5; wherein, the opposite-name end of the isolation transformer T1B is connected to the anode of the diode D5, and the cathode of the diode D5 is commonly connected to one end of the capacitor C5, one end of the capacitor C4, one end of the capacitor C3, one end of the capacitor C2, and one end of the resistor R5, and this connection point is connected to the input end of the comparator power supply circuit as the output end of the auxiliary power supply circuit; the other end of the isolation transformer T1B is commonly grounded with the other end of the capacitor C5, the other end of the capacitor C4, the other end of the capacitor C3, the other end of the capacitor C2, and the other end of the resistor R5.

[0010] Furthermore, the comparator power supply circuit includes a resistor R6 and a diode D4, one end of the resistor R6 is connected to the output end of the auxiliary power supply circuit as the input end of the comparator power supply circuit; the other end of the resistor R6 is connected to the cathode of the diode D4, and the connection point is connected to the input end of the undervoltage regulation circuit as the output end of the comparator power supply circuit.

[0011] Furthermore, the undervoltage regulation circuit includes a resistor R7, a resistor R8, a resistor R9, a resistor R10, a resistor R11, a diode D1, a diode D2, a diode D3, a capacitor C6, a capacitor C7 and a comparator, wherein one end of the capacitor C6 is commonly connected to pin 5 of the comparator, pin 6 of the comparator, and one end of the resistor R11, and the connection point is connected to the output end of the comparator power supply circuit as the input end of the undervoltage regulation circuit; the cathode of the diode D1 is commonly connected to one end of the resistor R10, one end of the capacitor C7, and pin 3 of the comparator, and the connection point is connected to the negative end of the power supply; the resistor The other end of R10, the other end of capacitor C7, pin 2 of the comparator, and the other end of capacitor C6 are connected together; the anode of diode D1 is connected to one end of resistor R9, the other end of resistor R9 is connected to the anode of diode D3, and this connection point is connected to the second input end of the enable end control circuit as the output end of the undervoltage regulation circuit; the cathode of diode D3 is connected to the cathode of diode D3 and pin 4 of the comparator; the other end of resistor R11 is connected to one end of resistor R7, one end of resistor R8, the anode of diode D2, and pin 2 of the comparator; the other end of resistor R7 and the other end of resistor R8 are grounded together.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0013] The undervoltage protection function is realized by the comparator in the undervoltage regulation circuit, and the AC pulse signal is filtered through the output signal transmitted by the rectification filter, which solves the oscillation problem of the AC pulse signal during signal transmission through the transformer, can achieve the purpose of voltage stabilization, and can increase the operating frequency of the output starting voltage, reducing the loss of the entire circuit.

[0014] In summary, in the present invention, the auxiliary winding of the isolation transformer is connected to the auxiliary power supply circuit, the output of the auxiliary power supply circuit is connected to the comparator power supply circuit, the high-voltage input of the circuit is connected to the input of the undervoltage regulation circuit, and then connected to the enable end control circuit through the output of the undervoltage regulation circuit, and finally connected to the enable end of the IC through the output of the enable end control circuit to control the output of the chip, thereby protecting the entire circuit. The present invention can compare the high-voltage voltage signal through the comparator. When there is no undervoltage, the circuit works normally; when there is undervoltage, the output of the enable end control circuit is connected to the enable end of the IC to control the output of the chip, protecting the entire circuit in the event of abnormal power input voltage, thereby preventing damage and having strong stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the undervoltage protection circuit of the utility model;

[0016] Figure 2 Schematic diagram of an enabling terminal control circuit in an embodiment;

[0017] Figure 3is a schematic diagram of an auxiliary power supply circuit in an embodiment;

[0018] Figure 4 is a schematic diagram of a comparator power supply circuit in an embodiment;

[0019] Figure 5 Schematic diagram of the undervoltage regulation circuit in the embodiment.

[0020] The present invention is further explained below with reference to the accompanying drawings and specific embodiments. DETAILED DESCRIPTION

[0021] like Figure 1 As shown, the undervoltage protection circuit provided by the present invention includes an isolation transformer TIB, an undervoltage regulation circuit 1, an enable end control circuit 2, an auxiliary power supply circuit 3 and a comparator power supply circuit 4, wherein the opposite-signal end of the isolation transformer TIB is connected to the input end of the auxiliary power supply circuit 3, the output end of the auxiliary power supply circuit 3 is connected to the input end of the comparator power supply circuit 4, the output end of the comparator power supply circuit 4 is connected to the input end of the undervoltage regulation circuit 1, the output end of the undervoltage regulation circuit 1 is connected to the second input end of the enable end control circuit 2, the first input end of the enable end control circuit 2 is connected to the power input end Vin+, and the second output end of the enable end control circuit 2 is connected to the enable control end pin UVLO.

[0022] In the above technical solution, the functions of each part are as follows:

[0023] The isolation transformer TIB is used to transmit the primary DC signal from the primary to the power supply circuit 3 on the auxiliary side in an isolated form;

[0024] The auxiliary power supply circuit 3 is used to convert the primary DC signal of the isolation transformer TIB to the auxiliary side to provide a stable DC power supply for the comparator power supply circuit 4;

[0025] The comparator power supply circuit 4 is used to transmit the output signal of the auxiliary power supply to the comparator in the undervoltage regulation circuit 1 through voltage stabilization.

[0026] The undervoltage regulation circuit 1 is used to perform undervoltage protection on the signal output by the comparator power supply circuit 4 and input it to the enable control circuit 2;

[0027] The enable control circuit 2 is used to receive the input of the power input terminal Vin+ and pull the main circuit voltage and current into the enable terminal control circuit 2, so as to achieve the function of controlling the chip IC (IC is the object controlled by the present invention).

[0028] Example 1

[0029] The undervoltage regulation circuit provided in this embodiment includes an isolation transformer T1B, an undervoltage regulation circuit 1, an enable terminal control circuit 2, an auxiliary power supply circuit 3, and a comparator power supply circuit 4. Wherein:

[0030] like Figure 2 As shown, the enable end control circuit 2 includes a resistor R1, a resistor R2, a resistor R3, a resistor R4 and a capacitor C1; wherein, one end of the resistor R1 is connected to the power input terminal Vin+ as the first input end of the enable end control circuit 2, and the other end of the resistor R1 is commonly connected to one end of the resistor R2, one end of the capacitor C1, one end of the resistor R3, and one end of the resistor R4. The connection point (A1) is connected to the output end of the undervoltage regulation circuit 1 as the second input end of the enable end control circuit 2; the other end of the capacitor C1, the other end of the resistor R3, and the other end of the resistor R4 are commonly grounded; the other end of the resistor R2 is connected to the enable control end pin UVLO of the chip IC as the output end of the enable end control circuit 2.

[0031] like Figure 3 As shown, the auxiliary power supply circuit 3 includes a diode D5, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C5 and a resistor R5; wherein, the opposite-polarity end of the isolation transformer T1B is connected to the anode of the diode D5, and the cathode of the diode D5 is commonly connected to one end of the capacitor C5, one end of the capacitor C4, one end of the capacitor C3, one end of the capacitor C2, and one end of the resistor R5. The connection point (P+12V) serves as the output end of the auxiliary power supply circuit 3 and is connected to the input end of the comparator power supply circuit 4; the other end of the isolation transformer T1B and the other end of the capacitor C5, the other end of the capacitor C4, the other end of the capacitor C3, the other end of the capacitor C2, and the other end of the resistor R5 are commonly grounded.

[0032] like Figure 4 As shown, comparator power supply circuit 4 includes resistor R6 and diode D4. One end of resistor R6 serves as the input of comparator power supply circuit 4 and is connected to the output of auxiliary power supply circuit 3. The other end of resistor R6 is connected to the cathode of diode D4. This connection point (+5V) serves as the output of comparator power supply circuit 4 and is connected to the input of undervoltage regulation circuit 1. In this solution, resistor R6 is connected to the cathode of Zener diode D4, so that its regulated output is a fixed voltage that powers the comparator in undervoltage regulation circuit 1 and provides a reference voltage.

[0033] like Figure 5As shown, the undervoltage regulation circuit 1 includes a resistor R7, a resistor R8, a resistor R9, a resistor R10, a resistor R11, a diode D1, a diode D2, a diode D3, a capacitor C6, a capacitor C7 and a comparator, wherein one end of the capacitor C6 is commonly connected to the 5th pin of the comparator, the 6th pin of the comparator, and one end of the resistor R11, and the connection point is connected to the output end (+5V) of the comparator power supply circuit 4 as the input end of the undervoltage regulation circuit 1; the cathode of the diode D1 is commonly connected to one end of the resistor R10, one end of the capacitor C7, and the 3rd pin of the comparator, and the connection point is connected to the negative terminal (A3) of the power supply; The other end of resistor R10, the other end of capacitor C7, pin 2 of the comparator, and the other end of capacitor C6 are connected together; the anode of diode D1 is connected to one end of resistor R9, the other end of resistor R9 is connected to the anode of diode D3, and this connection point is connected to the second input terminal (A1) of the enable end control circuit 2 as the output end of the undervoltage regulation circuit 1; the cathode of diode D3 is connected to the cathode of diode D3 and pin 4 of the comparator; the other end of resistor R11 is connected to one end of resistor R7, one end of resistor R8, the anode of diode D2, and pin 2 of the comparator; the other end of resistor R7 and the other end of resistor R8 are grounded together.

[0034] In the above technical solution, resistors R1, R3 and R4 act as a voltage divider circuit, and then C1 is filtered and connected to the enable control terminal UVLO input terminal of the IC; the opposite-name terminal of the isolation transformer T1B is connected to the diode D5; and then capacitors C2, C3, C4, C5 and resistor R5 (C2, C3, C4, C5 and R5 are connected in parallel) are connected to form an auxiliary power supply circuit 3 and a rectifier and filter circuit.

[0035] At the beginning, after the input signal of the isolation transformer TIB is rectified, the energy storage filter capacitor C (including C2, C3, C4, and C5) begins to charge and store energy. The voltage needs to be built up slowly, so the power supply voltage, that is, the waveform of the auxiliary power supply circuit 3, has a slow climbing process at the beginning. When the energy storage filter capacitor C (C2, C3, C4, and C5) is fully charged, the voltage of the rectifier energy storage filter circuit reaches stability.

[0036] In this embodiment, the resistor R6 is 1K, the diode D4 is BZT52C5V1-TP (MCC), the voltage is pulled down by the resistor R6, the voltage is stabilized to 5.1V by the diode D4, and then input to the power input terminal of the comparator; the control chip IC is LM5022MM, the power input Vin+ is 9-36V, and the UVLO protection point is 1.25V, so the resistor R1 is 5.6K, the resistors R3 and R4 are 2K, the capacitor C1 is 47nf / 50V, and the resistor R2 is 75R.

[0037] The above are only preferred embodiments of the present invention. It should be pointed out that the above preferred embodiments should not be regarded as limitations of the present invention. For ordinary technicians in this technical field, several improvements can be made without departing from the scope of the present invention. Improvements to the undervoltage regulation circuit and transformer structure should also be regarded as within the scope of protection of the present invention.

Claims

1. An undervoltage protection circuit, characterized in that: The invention comprises an isolation transformer TIB, an undervoltage regulation circuit (1), an enable end control circuit (2), an auxiliary power supply circuit (3) and a comparator power supply circuit (4), wherein the opposite-signal end of the isolation transformer TIB is connected to the input end of the auxiliary power supply circuit (3); the output end of the auxiliary power supply circuit (3) is connected to the input end of the comparator power supply circuit (4); the output end of the comparator power supply circuit (4) is connected to the input end of the undervoltage regulation circuit (1); the output end of the undervoltage regulation circuit (1) is connected to the second input end of the enable end control circuit (2); the first input end of the enable end control circuit (2) is connected to the power supply input end Vin+; and the second output end of the enable end control circuit (2) is connected to the enable control end pin UVLO.

2. The undervoltage protection circuit according to claim 1, wherein: The enabling end control circuit (2) comprises a resistor R1, a resistor R2, a resistor R3, a resistor R4 and a capacitor C1; wherein one end of the resistor R1 is connected to the power input terminal Vin+ as the first input end of the enabling end control circuit (2); the other end of the resistor R1 is commonly connected to one end of the resistor R2, one end of the capacitor C1, one end of the resistor R3 and one end of the resistor R4; the connection point is connected to the output end of the undervoltage regulation circuit (1) as the second input end of the enabling end control circuit (2); the other end of the capacitor C1 is commonly grounded together with the other end of the resistor R3 and the other end of the resistor R4; the other end of the resistor R2 is connected to the enabling control end pin UVLO of the chip IC as the output end of the enabling end control circuit (2).

3. The undervoltage protection circuit according to claim 1, wherein: The auxiliary power supply circuit (3) comprises a diode D5, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C5 and a resistor R5; wherein, the opposite-name end of the isolation transformer T1B is connected to the anode of the diode D5, and the cathode of the diode D5 is commonly connected to one end of the capacitor C5, one end of the capacitor C4, one end of the capacitor C3, one end of the capacitor C2 and one end of the resistor R5; the connection point is connected to the input end of the comparator power supply circuit (4) as the output end of the auxiliary power supply circuit (3); the other end of the isolation transformer T1B is commonly grounded with the other end of the capacitor C5, the other end of the capacitor C4, the other end of the capacitor C3, the other end of the capacitor C2 and the other end of the resistor R5.

4. The undervoltage protection circuit according to claim 1, wherein: The comparator power supply circuit (4) includes a resistor R6 and a diode D4. One end of the resistor R6 serves as the input end of the comparator power supply circuit (4) and is connected to the output end of the auxiliary power supply circuit (3). The other end of the resistor R6 is connected to the cathode of the diode D4. This connection point serves as the output end of the comparator power supply circuit (4) and is connected to the input end of the undervoltage regulation circuit (1).

5. The undervoltage protection circuit according to claim 1, wherein: The undervoltage regulation circuit (1) comprises a resistor R7, a resistor R8, a resistor R9, a resistor R10, a resistor R11, a diode D1, a diode D2, a diode D3, a capacitor C6, a capacitor C7 and a comparator, wherein one end of the capacitor C6 is commonly connected to the 5th pin of the comparator, the 6th pin of the comparator and one end of the resistor R11, and the connection point is connected to the output end of the comparator power supply circuit (4) as the input end of the undervoltage regulation circuit (1); the cathode of the diode D1 is commonly connected to one end of the resistor R10, one end of the capacitor C7 and the 3rd pin of the comparator, and the connection point is connected to the negative end of the power supply; the resistor R The other end of 10, the other end of capacitor C7, pin 2 of the comparator, and the other end of capacitor C6 are connected together; the anode of diode D1 is connected to one end of resistor R9, the other end of resistor R9 is connected to the anode of diode D3, and the connection point is connected to the second input end of the enable end control circuit (2) as the output end of the undervoltage regulation circuit (1); the cathode of diode D3 is connected to the cathode of diode D3 and pin 4 of the comparator; the other end of resistor R11 is connected to one end of resistor R7, one end of resistor R8, the anode of diode D2 and pin 2 of the comparator; the other end of resistor R7 and the other end of resistor R8 are grounded together.

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