A pulse signal generating circuit and switching power supply

Abstract

The present invention discloses a pulse signal generating circuit and a switching power supply. The generating circuit includes a signal acquisition circuit, a control circuit and a level flipping circuit; the signal acquisition circuit is used to acquire a state signal of the switching power supply and input it into the control circuit; the control circuit is used to output a first control signal when the state signal is in a normal working state to control the switching power supply to maintain normal working, and output a second control signal when the state signal is in an abnormal working state to control the switching power supply to enter an intermittent working state; the level flipping circuit is used to control the control circuit to continuously output the first control signal when the state signal is in a normal working state, and to control the control circuit to cyclically output the second control signal within a pause time and continuously output the first control signal within a working time T2 when the state signal is in an abnormal working state; thus, when the switching power supply enters an abnormal working condition, the switching power supply controls itself to enter an intermittent working state according to the generated pulse signal.

Description

Technical Field

[0001] The present invention relates to a pulse signal generation technology, and in particular to a scenario where a switching power supply requires an adjustable pulse control signal. Background Art

[0002] The over-temperature, overload and other protection functions of the switching power supply are its important performance indicators. These protection functions can take timely protective measures when the switching power supply enters an abnormal working state. The protection modes include hiccups, lockout, intermittent operation and other forms. The intermittent working protection mode can customize the working time and rest time of the switching power supply when the switching power supply is in abnormal working conditions such as over-temperature and overload, and cycle before the abnormal working condition is relieved. This protection mode can not only prevent the switching power supply from being damaged due to long-term operation in an abnormal state, but also can intermittently supply power to the back-end equipment to avoid the back-end system from being out of control or losing data when there is no power supply for a long time. The intermittent working protection mode can flexibly control the startup and shutdown time of the switching power supply, and can also control the switching power supply to have a relatively reasonable intermittent output under abnormal working conditions. The existing intermittent working function is mainly realized by a timing circuit. The timing circuit does not have advantages in terms of device composition, complexity, cost, etc. The existing technology has the following main features:

[0003] Currently, commonly used timing control circuits widely adopt digital control circuit solutions based on microprocessor timers. On the one hand, this solution requires an external digital controller, which makes the device costly and the peripheral circuits more complex, resulting in a waste of space and cost. On the other hand, the digital controller solution is more suitable for short-time, high-precision delay control circuits, but does not meet the requirements of longer timing in switching power supply overload protection.

[0004] There are also time-delay protection circuits built with analog components, but these are complex and costly. Control ICs with built-in overcurrent protection often experience hiccups or fail to self-recover after an overload, making it impossible to achieve controlled intermittent operation of the switching power supply. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a pulse signal generating circuit and a switching power supply to achieve intermittent protection of the switching power supply under abnormal conditions such as overheating and overload.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] In a first aspect, a pulse signal generating circuit is provided, applied to a switching power supply, comprising: a signal acquisition circuit, a control circuit, and a level flipping circuit; the signal acquisition circuit having a first input terminal for connecting to an external power supply, a second input terminal for receiving a status signal of the switching power supply, wherein the status signal includes an abnormal working state signal and a normal working state signal, and an output terminal connected to the first input terminal of the control circuit; the control circuit having a second input terminal connected to the output terminal of the level flipping circuit, the output terminal of the control circuit being connected to the input terminal of the level flipping circuit, and the output terminal of the control circuit being further connected to the control terminal of the switching power supply;

[0008] The signal acquisition circuit is used to collect the status signal of the switching power supply and input it into the control circuit;

[0009] The control circuit is configured to output a first control signal when the status signal indicates a normal working state to control the switching power supply to maintain normal working state, and output a second control signal when the status signal indicates an abnormal working state to control the switching power supply to enter an intermittent working state;

[0010] The level flipping circuit is used to control the control circuit to continuously output the first control signal when the status signal is in a normal working state, and to control the control circuit to continuously output the second control signal within a preset pause time T1 when the status signal is in an abnormal working state, and after the pause time T1 ends, control the control circuit to continuously output the first control signal within a preset working time T2, and after the working time T2 ends, control the control circuit to continuously output the second control signal again within the pause time T1.

[0011] Furthermore, the level-flipping circuit includes: a resistor R4, a resistor R5, a diode D1, and a capacitor C1; one end of the resistor R4 serves as an input end of the level-flipping circuit, and the other end is connected to the anode of the diode D1; the cathode of the diode D1 is connected to one end of the capacitor C1 and one end of the resistor R5, and serves as an output end of the level-flipping circuit; the other end of the capacitor C1 and the other end of the resistor R5 are grounded.

[0012] Furthermore, the resistor R4 is an adjustable resistor.

[0013] Furthermore, the resistor R5 is an adjustable resistor.

[0014] Furthermore, the signal acquisition circuit includes a resistor R1 and a resistor R2, one end of the resistor R1 serves as the first input end of the signal acquisition circuit, and the other end is connected to one end of the resistor R2 and serves as the output end of the signal acquisition circuit; the other end of the resistor R2 serves as the second input end of the signal acquisition circuit.

[0015] Furthermore, the control circuit includes an operational amplifier U1A and a resistor R3, one end of the resistor R3 is connected to the non-inverting input terminal of the operational amplifier U1A and serves as the first input terminal of the control circuit, the inverting input terminal of the operational amplifier U1A serves as the second input terminal of the control circuit, and the other end of the resistor R3 is connected to the output terminal of the operational amplifier U1A and serves as the output terminal of the control circuit.

[0016] In a second aspect, a pulse signal generating circuit is provided, which is applied to a switching power supply, and includes a signal acquisition circuit, a control circuit and a level flipping circuit; the signal acquisition circuit includes a resistor R1 and a resistor R2; the control circuit includes an operational amplifier U1A and a resistor R3; the level flipping circuit includes: a resistor R4, a resistor R5, a diode D1, and a capacitor C1; one end of the resistor R1 is used to connect to an external power supply, and the other end of the resistor R1 is connected to one end of the resistor R2, one end of the resistor R3, and the non-inverting input end of the operational amplifier U1A; the other end of the resistor R2 is used to access the status signal of the switching power supply, wherein the status signal includes an abnormal working status signal and a normal working status signal; the other end of the resistor R3 is connected to the output end of the operational amplifier U1A and one end of the resistor R4, and is used to connect to the control end of the switching power supply; the other end of the resistor R4 is connected to the anode of the diode D1; the cathode of the diode D1 is connected to one end of the capacitor C1, one end of the resistor R5, and the inverting input end of the operational amplifier U1A; the other end of the capacitor C1 and the other end of the resistor R5 are grounded.

[0017] In a third aspect, a switching power supply is provided, comprising a switching tube TR1, an optocoupler OC1, a main circuit and the pulse signal generating circuit as described above, wherein the control end of the switching tube TR1 is connected to the main circuit, the first end of the switching tube TR1 is connected to the signal acquisition circuit as the switching power supply status signal output end of the switching power supply, and the second end of the switching tube TR1 is grounded; the anode of the light-emitting diode of the optocoupler OC1 is used to connect to an external power supply, the cathode is connected to the control circuit, the collector of the transistor of the optocoupler OC1 is connected to the protection control pin Control pin of the main circuit, and the emitter collector of the transistor of the optocoupler OC1 is grounded; when the main circuit operates abnormally, an abnormal operating status signal is output to control the switching tube TR1 to be turned on, and when the main circuit operates normally, a normal operating status signal is output to control the switching tube TR1 to be turned off.

[0018] The working principle of the present invention will be analyzed in conjunction with specific embodiments. Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The pulse signal generating circuit of the present invention, when entering abnormal working conditions such as overload, overtemperature, overhumidity, etc., enables the switching power supply to control itself to enter an intermittent working state according to the generated pulse signal.

[0020] 2. The pulse signal generating circuit of the present invention can sample the output current of the switching power supply, which can be used to control the overload protection function of the switching power supply. It can also sample the operating temperature of the switching power supply, which can be used to control the over-temperature protection function of the switching power supply. It can also sample the operating humidity of the switching power supply, which can be used to control the over-humidity protection function of the switching power supply, thereby realizing multiplexing functions of the circuit.

[0021] 3. The pulse signal generating circuit of the present invention can adjust the operating time and rest time of the switching power supply during intermittent operation by adjusting the resistance values ​​of resistors R4 and R5, and has the function of independently adjusting the pulse width and pulse time interval;

[0022] 4. The pulse signal generating circuit of the present invention does not use a digital control chip, which reduces the complexity of the circuit and the development cost of the switching power supply, and has advantages in terms of space and cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of an application principle of a pulse signal generating circuit according to an embodiment of the present invention in a switching power supply;

[0024] Figure 2 This is another application principle diagram of the pulse signal generating circuit according to an embodiment of the present invention in a switching power supply. DETAILED DESCRIPTION

[0025] To make the technical solution of the present invention clearer, the following is a clear and complete description of the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only partial embodiments of the present invention, and those skilled in the art can make other modifications, replacements, or changes to the present invention without inventive effort, which still fall within the scope of protection of the present invention.

[0026] like Figure 1 As shown, Figure 1 The figure shows a schematic diagram of the application of the pulse signal generating circuit of this embodiment in a switching power supply. In this embodiment, a pulse signal generating circuit is provided, which is applied to the switching power supply and includes: a signal acquisition circuit, a control circuit, and a level flipping circuit. The first input terminal of the signal acquisition circuit is used to connect to an external power supply, and the second input terminal is used to receive a status signal of the switching power supply, wherein the status signal includes an abnormal working state signal and a normal working state signal. The output terminal of the signal acquisition circuit is connected to the first input terminal of the control circuit; the second input terminal of the control circuit is connected to the output terminal of the level flipping circuit, and the output terminal of the control circuit is connected to the input terminal of the level flipping circuit. The output terminal of the control circuit is also used to connect to the control terminal of the switching power supply.

[0027] The signal acquisition circuit is used to collect the status signal of the switching power supply and input it into the control circuit;

[0028] The control circuit is configured to output a first control signal when the status signal indicates a normal working state to control the switching power supply to maintain normal working state, and output a second control signal when the status signal indicates an abnormal working state to control the switching power supply to enter an intermittent working state;

[0029] The level flipping circuit is used to control the control circuit to continuously output the first control signal when the status signal is in a normal working state, and to control the control circuit to continuously output the second control signal within a preset pause time T1 when the status signal is in an abnormal working state, and after the pause time T1 ends, control the control circuit to continuously output the first control signal within a preset working time T2, and after the working time T2 ends, control the control circuit to continuously output the second control signal again within the pause time T1.

[0030] Specifically, the switching power supply includes a switching tube TR1, an optocoupler OC1, and a main circuit. The control end of the switching tube TR1 is connected to the main circuit, the first end of the switching tube TR1 is connected to the signal acquisition circuit as the switching power supply status signal output end of the switching power supply, and the second end of the switching tube TR1 is grounded; the anode of the light-emitting diode of the optocoupler OC1 is used to connect to an external power supply, and the cathode is connected to the control circuit. The collector of the transistor of the optocoupler OC1 is connected to the protection control pin of the main circuit, and the emitter collector of the transistor of the optocoupler OC1 is grounded; when the main circuit operates abnormally, an abnormal operating status signal is output to control the switching tube TR1 to be turned on. When the main circuit operates normally, a normal operating status signal is output to control the switching tube TR1 to be turned off.

[0031] Specifically, the switch tube TR1 is a MOS tube (hereinafter referred to as MOS tube TR1 ), the control end of the MOS tube TR1 is a gate, the first end is a drain, and the second end is a source.

[0032] As a specific embodiment of the level flipping circuit, the level flipping circuit includes: a resistor R4, a resistor R5, a diode D1, and a capacitor C1; one end of the resistor R4 serves as an input end of the level flipping circuit, and the other end is connected to the anode of the diode D1; the cathode of the diode D1 is connected to one end of the capacitor C1 and one end of the resistor R5, and serves as the output end of the level flipping circuit; the other end of the capacitor C1 and the other end of the resistor R5 are grounded.

[0033] like Figure 2As shown, to facilitate adjustment of the pulse width and pulse time interval, resistors R4 and R5 are adjustable resistors. Users can easily change the resistance values ​​of resistors R4 and R5 by adjusting the adjustable resistor knobs. When the switching power supply enters an abnormal state but the external environment is not as harsh as before, adjusting the knobs of adjustable resistors R4 or R5 to change the resistance value can easily change the rest time T1 and working time T2 in the intermittent working state, effectively protecting the switching power supply.

[0034] As a specific embodiment of the signal acquisition circuit, the signal acquisition circuit includes a resistor R1 and a resistor R2, one end of the resistor R1 serves as the first input end of the signal acquisition circuit, and the other end is connected to one end of the resistor R2 and serves as the output end of the signal acquisition circuit; the other end of the resistor R2 serves as the second input end of the signal acquisition circuit.

[0035] As a specific embodiment of the control circuit, the control circuit includes an operational amplifier U1A and a resistor R3, one end of the resistor R3 is connected to the non-inverting input terminal of the operational amplifier U1A as the first input terminal of the control circuit, the inverting input terminal of the operational amplifier U1A serves as the second input terminal of the control circuit, and the other end of the resistor R3 is connected to the output terminal of the operational amplifier U1A as the output terminal of the control circuit.

[0036] The application scheme of the pulse signal generating circuit of this embodiment in a switching power supply is as follows: the signal G1 input by the MOS tube TR1 is the overtemperature signal of the switching power supply, which can also be an overload signal or an overhumidity signal. The control signal output by the pulse signal generating circuit is connected to the cathode of the light-emitting diode of the switching power supply isolation feedback optocoupler OC1, and the collector of the switching power supply isolation feedback optocoupler OC1 is connected to the overtemperature protection control pin of the switching power supply.

[0037] The working principle of this embodiment is analyzed as follows:

[0038] Signal G1, connected to the gate of MOS transistor TR1, is the switching power supply's overtemperature (or overload or overhumidity) signal. For example, when the temperature of the switching power supply's internal components exceeds specifications, signal G1 outputs a high level; otherwise, it outputs a low level. The Control pin is the switching power supply's protection control pin. When the Control pin is low, the switching power supply shuts down and enters a protection state; otherwise, the switching power supply does not enter a protection state.

[0039] When the switching power supply is working normally, the signal G1 is at a low level, the MOS tube TR1 cannot be turned on, the external power supply VCC is connected to the non-inverting input terminal of the operational amplifier U1A through the resistor R1, and the initial level of the inverting input terminal of the operational amplifier U1A is 0. At this time, the operational amplifier U1A outputs a high level to charge the capacitor C1 through the resistor R4, and the voltage of the inverting input terminal of the operational amplifier U1A rises. Due to the conduction voltage drop of the diode D1, the voltage of the non-inverting input terminal of the operational amplifier U1A is always greater than the voltage of the inverting input terminal. The output terminal of the operational amplifier U1A maintains a high level, and the voltage drop of the light-emitting diode of the optocoupler OC1 is less than the conduction voltage. The light-emitting diode side of the optocoupler OC1 is cut off and no current flows through it. Then the transistor side of the optocoupler OC1 is also in the cut-off state, and the protection control pin Control pin is high, and the switching power supply does not enter the protection state.

[0040] When the switching power supply enters an abnormal working state, such as over-temperature, overload, over-humidity, etc., the signal G1 changes from low level to high level, the MOS tube TR1 is turned on, and the voltage division result of the resistors R1, R2 and R3 is used as the input of the op amp U1A non-inverting input terminal. At the moment when the MOS tube TR1 is turned on, the voltage at the op amp U1A non-inverting input terminal is At this time, the voltage U2 at the inverting input of op amp U1A is ≈ VCC, and U1 is less than U2 (the same-inverting end is less than the reverse end). Then the output of op amp U1A changes from a high level to a low level, and the voltage of the light-emitting diode of the optocoupler OC1 is greater than the conduction voltage drop. Current flows through the light-emitting diode side of the optocoupler OC1, and the transistor side of the optocoupler OC1 is turned on, pulling the protection control pin low. The switching power supply is turned off and enters the dormant state (also called the protection state). After the output of op amp U1A changes to a low level, the voltage at the non-inverting input of op amp U1A will change to At the same time, capacitor C1 continues to discharge through resistor R5, and the voltage at the inverting input of op amp U1A decreases accordingly. After the pause time T1 (that is, the duration of the control circuit outputting the second control signal), the voltage at the inverting input of op amp U1A drops to less than the voltage U3 at the non-inverting input of op amp U1A. The output of op amp U1A changes from a low level to a high level, and the voltage drop of the light-emitting diode of optocoupler OC1 is less than the conduction voltage. The light-emitting diode side of optocoupler OC1 is cut off and no current flows through it. Then the transistor side of optocoupler OC1 becomes cut off again, and the protection control pin Controlpin returns to a high level. The switching power supply is released from the protection state and enters the working state. The voltage at the non-inverting input of the operational amplifier U1A becomes U1 again. At the same time, the operational amplifier U1A charges the capacitor C1 through the resistor R4, and the voltage at the inverting input of the operational amplifier U1A rises accordingly. After the working time T2, when the voltage at the inverting input of the operational amplifier U1A rises to a level greater than the voltage U1 at the non-inverting input of the operational amplifier U1A, the output of the operational amplifier U1A changes from a high level to a low level again, and the switching power supply is turned off again to enter the protection state, and the cycle continues.

[0041] It should be noted that the rest time T1, which is the time it takes for the voltage at the inverting input of op amp U1A to begin to drop below the voltage at its non-inverting input U3, represents the protection time of the switching power supply during intermittent operation. This rest time T1 can be adjusted by setting the resistance value of resistor R5 and the capacitance value of capacitor C1. The operating time T2, which is the time it takes for the voltage at the inverting input of op amp U1A to begin to rise above the voltage at its non-inverting input U1, represents the operating time of the switching power supply during intermittent operation. This operating time T2 can be adjusted by setting the resistance value of resistor R4 and the capacitance value of capacitor C1. The severity of the environment in which the switching power supply enters an abnormal state varies. For more severe environments, the rest time T1 and operating time T2 can be adjusted by setting the resistance values ​​of resistors R4 and R5 and the capacitance value of capacitor C1. Shortening the operating time T2 and lengthening the rest time T1 can ensure that the switching power supply receives effective protection appropriate to the severity of the environment.

[0042] The above is only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention is described in detail based on the embodiments, ordinary technicians in the field can modify or replace the specific implementation methods of the present invention. Any modifications or replacements that do not depart from the spirit and scope of the present invention are within the scope of protection of the claims of the present invention.

Claims

1. A pulse signal generating circuit, applied to a switching power supply, characterized in that: include: Signal acquisition circuit, control circuit and level flip circuit; The first input terminal of the signal acquisition circuit is used to connect to an external power supply, the second input terminal is used to receive a status signal of the switching power supply, wherein the status signal includes an abnormal working state signal and a normal working state signal, and the output terminal is connected to the first input terminal of the control circuit; the second input terminal of the control circuit is connected to the output terminal of the level flipping circuit, the output terminal of the control circuit is connected to the input terminal of the level flipping circuit, and the output terminal of the control circuit is further used to connect to the control terminal of the switching power supply; The signal acquisition circuit is used to collect the status signal of the switching power supply and input it into the control circuit; The control circuit is configured to output a first control signal when the status signal indicates a normal working state to control the switching power supply to maintain normal working state, and output a second control signal when the status signal indicates an abnormal working state to control the switching power supply to enter an intermittent working state; The level flipping circuit is used to control the control circuit to continuously output the first control signal when the status signal is in a normal working state, and to control the control circuit to continuously output the second control signal within a preset pause time T1 when the status signal is in an abnormal working state, and after the pause time T1 ends, control the control circuit to continuously output the first control signal within a preset working time T2, and after the working time T2 ends, control the control circuit to continuously output the second control signal again within the pause time T1.

2. A pulse signal generating circuit according to claim 1, characterized in that: The level-flipping circuit includes: a resistor R4, a resistor R5, a diode D1, and a capacitor C1; one end of the resistor R4 serves as the input end of the level-flipping circuit, and the other end is connected to the anode of the diode D1; the cathode of the diode D1 is connected to one end of the capacitor C1 and one end of the resistor R5, and serves as the output end of the level-flipping circuit; the other end of the capacitor C1 and the other end of the resistor R5 are grounded.

3. A pulse signal generating circuit according to claim 2, characterized in that: The resistor R4 is an adjustable resistor.

4. A pulse signal generating circuit according to claim 2, characterized in that: The resistor R5 is an adjustable resistor.

5. A pulse signal generating circuit according to any one of claims 1 to 4, characterized in that: The signal acquisition circuit includes a resistor R1 and a resistor R2. One end of the resistor R1 serves as the first input end of the signal acquisition circuit, and the other end is connected to one end of the resistor R2 and serves as the output end of the signal acquisition circuit; the other end of the resistor R2 serves as the second input end of the signal acquisition circuit.

6. A pulse signal generating circuit according to any one of claims 1 to 4, characterized in that: The control circuit includes an operational amplifier U1A and a resistor R3. One end of the resistor R3 is connected to the non-inverting input end of the operational amplifier U1A and serves as the first input end of the control circuit. The inverting input end of the operational amplifier U1A serves as the second input end of the control circuit. The other end of the resistor R3 is connected to the output end of the operational amplifier U1A and serves as the output end of the control circuit.

7. A pulse signal generating circuit, applied to a switching power supply, characterized in that: Including signal acquisition circuit, control circuit and level flip circuit; The signal acquisition circuit includes resistors R1 and R2; the control circuit includes an operational amplifier U1A and a resistor R3; the level flipping circuit includes: resistors R4, R5, diode D1, and capacitor C1; one end of resistor R1 is used to connect to an external power supply, and the other end of resistor R1 is connected to one end of resistor R2, one end of resistor R3, and the non-inverting input end of operational amplifier U1A; the other end of resistor R2 is used to access the status signal of the switching power supply, wherein the status signal includes an abnormal working status signal and a normal working status signal; the other end of resistor R3 is connected to the output end of operational amplifier U1A and one end of resistor R4, and is used to connect to the control end of the switching power supply; the other end of resistor R4 is connected to the anode of diode D1; the cathode of diode D1 is connected to one end of capacitor C1, one end of resistor R5, and the inverting input end of operational amplifier U1A; the other end of capacitor C1 and the other end of resistor R5 are grounded.

8. A switching power supply, characterized in that: It includes a switching tube TR1, an optocoupler OC1, a main circuit and a pulse signal generating circuit as described in any one of claims 1 to 7, the control end of the switching tube TR1 is connected to the main circuit, the first end of the switching tube TR1 is connected to the signal acquisition circuit as the switching power supply status signal output end of the switching power supply, and the second end of the switching tube TR1 is grounded; the anode of the light-emitting diode of the optocoupler OC1 is used to connect to the external power supply, and the cathode is connected to the control circuit, the collector of the triode of the optocoupler OC1 is connected to the protection control pin Controlpin of the main circuit, and the emitter collector of the triode of the optocoupler OC1 is grounded; when the main circuit works abnormally, the abnormal working status signal is output to control the switching tube TR1 to be turned on, and when the main circuit works normally, the normal working status signal is output to control the switching tube TR1 to be turned off.

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