Switching power supply circuit

Abstract

The utility model provides a switching power supply circuit, comprising a thermistor module which comprises a negative temperature coefficient thermistor and has a first end connected to a power supply input end; the input end of the rectifier module is connected with the second end of the thermistor module, and the output end is connected to the power supply output end; the relay is configured to control a current path between the first end and the second end of the thermistor module to be conducted when being electrified; the cut-off switch is configured to switch on an electrifying loop of the relay when the cut-off switch is switched on; the first switch driving module is configured to drive the cut-off switch to be switched on when the voltage of the output end of the rectification module is higher than a first threshold value; and the overvoltage protection module is configured to form a cut-off loop to cut off an output path from the rectifier module to the power supply output end when the voltage of the output end of the rectifier module is higher than a second threshold value. The switching power supply circuit has an automatic soft start function and an automatic overvoltage protection function, and is simple in circuit structure and low in implementation cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of switching power supply, in particular to a switching power supply circuit. BACKGROUND

[0002] In order to reduce the output voltage ripple, the AC / DC power switching power supply is generally connected with a large-capacity filter capacitor at the output end. The circuit using rectification and capacitor filtering has an inherent defect, that is, a very large instantaneous impact current will be formed at the moment of connecting the input power supply because the initial voltage on the capacitor is zero. Such a large current often leads to input fusing and causes fatal damage to the subsequent circuit. In the prior art, there is a circuit structure using a thermistor to realize soft start. However, after the soft start of the circuit is completed, the thermistor needs to be disconnected from the power supply circuit under the control of an additional microcontroller during normal operation. Therefore, many circuit components need to be used, the circuit structure is complex, and the implementation cost is high.

[0003] The existing switching power supply also has the problem of unstable voltage during use. During use, when the input voltage is too high, the switching power supply is very easy to burn out, which seriously affects the service life and working reliability of the switching power supply. In the existing overvoltage detection and protection scheme, a comparator circuit and a voltage stabilizing circuit are generally used, or an external microcontroller and a comparator are used to judge whether it is overvoltage after analog-to-digital conversion. The existing scheme needs many components and has a complex circuit loop and high cost. Practical new type content

[0004] In view of the problems in the prior art, the purpose of the present application is to provide a switching power supply circuit with a soft start function, which automatically disconnects the thermistor from the power supply circuit during normal operation, and has an automatic overvoltage protection function, and the circuit structure is simple and the implementation cost is low.

[0005] The embodiment of the present application provides a switching power supply circuit, which comprises:

[0006] The thermistor module comprises at least one negative temperature coefficient thermistor, and the first end of the thermistor module is connected to the power supply input end;

[0007] The rectifier module is connected to the second end of the thermistor module, and the output end of the rectifier module is connected to the power supply output end;

[0008] The relay is configured to control the conduction of the current path between the first end and the second end of the thermistor module when energized;

[0009] The cut-off switch is configured to make the energization loop of the relay conductive when conductive;

[0010] The first switch driving module is configured to drive the cut-off switch to be turned on when the output voltage of the rectifier module is higher than a first threshold value.

[0011] The overvoltage protection module is configured to form a cut-off loop to cut off the output path of the rectifier module to the power output end when the output voltage of the rectifier module is higher than a second threshold value.

[0012] In some embodiments, the first switch driving module comprises:

[0013] The first voltage stabilizing diode has a first end connected to the positive output end of the rectifier module, and is configured to be turned on when the voltage input at the first end is higher than the first threshold value.

[0014] The first capacitor has a first end connected to the second end of the first voltage stabilizing diode and the control end of the cut-off switch, respectively, and a second end connected to the negative output end of the rectifier module.

[0015] In some embodiments, the overvoltage protection module comprises:

[0016] The cut-off switch is configured to form a cut-off loop to cut off the output path of the rectifier module to the power output end when turned on.

[0017] The second switch driving module is configured to drive the cut-off switch to be turned on when the output voltage of the rectifier module is higher than the second threshold value, and the second threshold value is greater than the first threshold value.

[0018] In some embodiments, the second switch driving module comprises:

[0019] The at least one second voltage stabilizing diode has a first end connected to the positive output end of the rectifier module, and is configured to be turned on when the voltage input at the first end is higher than the second threshold value.

[0020] The second capacitor has a first end connected to the second end of the second voltage stabilizing diode and the control end of the cut-off switch, respectively, and a second end connected to the negative output end of the rectifier module.

[0021] In some embodiments, the cut-off switch is further connected to the control end of the cut-off switch, and is configured to drive the cut-off switch to be turned off when turned on.

[0022] In some embodiments, a first feedback module is further included, and the first feedback module is configured to output a first level signal or a second level signal based on the on-off state of the cut-off switch.

[0023] In some embodiments, the first feedback module comprises:

[0024] The first optoelectronic coupler is connected between the cut-off switch and the positive output end of the rectifier module.

[0025] The first optoelectronic diode is configured to output a first level signal or a second level signal according to a light signal of the first optoelectronic coupler.

[0026] In some embodiments, a second feedback module is further included, and the second feedback module is configured to output the first level signal or the second level signal based on a conduction state of the cut-off switch.

[0027] In some embodiments, the second feedback module includes:

[0028] The second optoelectronic coupler is connected between the cut-off switch and a control terminal of the relay.

[0029] The second optoelectronic diode is configured to output a first level signal or a second level signal according to a light signal of the second optoelectronic coupler.

[0030] In some embodiments, the relay is an electromagnetic relay, and the cut-off switch is configured to make a NO terminal of the electromagnetic relay conductive when the cut-off switch is turned on, and to make an NC terminal of the electromagnetic relay conductive when the cut-off switch is turned off.

[0031] The switch power supply circuit provided by the present application has the following advantages:

[0032] The switch power supply circuit provided by the present application has the following advantages: BRIEF DESCRIPTION OF DRAWINGS

[0033] Other features, objects, and advantages of the present application will become more apparent from the following detailed description of non-limiting embodiments thereof, read in conjunction with the accompanying drawings.

[0034] Figure 1 FIG. 1 is a structural block diagram of a switch power supply circuit according to an embodiment of the present application.

[0035] Figure 2 is a structural block diagram of a switching power supply circuit with feedback function according to an embodiment of the present application;

[0036] Figure 3 is a circuit diagram of a switching power supply circuit according to an embodiment of the present application. DETAILED DESCRIPTION

[0037] Example implementations will now be described more fully with reference to the accompanying drawings. Example implementations can be implemented in any

[0038] To solve the technical problems in the prior art, the present application provides a switching power supply circuit for converting alternating current into direct current to power subsequent loads. Figure 1 is a structural block diagram of a switching power supply circuit according to an embodiment of the present application. As shown in Figure 1 The switching power supply circuit includes a power input end and a power output end (BUS+, BUS-). The power input end inputs alternating current, and the power output end outputs direct current to power loads. The switching power supply circuit includes: a thermistor module including at least one negative temperature coefficient thermistor (NTC thermistor), a first end of the thermistor module being connected to the power input end; a rectifier module, an input end of the rectifier module being connected to a second end of the thermistor module, an output end of the rectifier module being connected to the power output end, the rectifier module being configured to convert alternating current into direct current; a relay configured to control a conduction of a current path between the first end and the second end of the thermistor module when powered on; a cut-off switch configured to make a conduction circuit of the relay conductive when turned on; and a first switch driving module configured to drive the cut-off switch to conduct when the output end voltage of the rectifier module is higher than a first threshold value.

[0039] Therefore, the application serially connects a thermistor module at the power input end, and the thermistor module includes at least one negative temperature coefficient thermistor. When the device with the switching power supply circuit starts, because the current is large, the resistance value of the thermistor module is large, which is beneficial to reduce the current input to the rectifier module from the power input end, thereby effectively limiting the inrush current and realizing the soft start function. When the circuit normally works, after the output voltage of the rectifier module is stable and reaches the first threshold value, the first switch driving module drives the cutoff switch to conduct, so that the relay conducts the current path between the two ends of the thermistor module, and the thermistor module is separated from the power input end, thereby realizing automatic cutting of the thermistor from the power supply circuit when the circuit normally works, without affecting the normal operation of the circuit, without the need for external microcontroller control, simple circuit structure, low implementation cost, small switching power supply size, and beneficial to prolong the service life of the switching power supply.

[0040] In order to solve the problem that the switching power supply circuit is easily damaged by high voltage during use, in this embodiment, the switching power supply circuit also has an overvoltage protection function. As shown in Figure 1 , the switching power supply circuit also includes an overvoltage protection module configured to form a cutoff loop to cut off the output path of the rectifier module to the power output end when the output end voltage of the rectifier module is higher than a second threshold value. By providing the overvoltage protection module, overvoltage protection is automatically provided to the subsequent load.

[0041] The overvoltage protection module includes: a cutoff switch configured to form a cutoff loop to cut off the output path of the rectifier module to the power output end when conducting; and a second switch driving module configured to drive the cutoff switch to conduct when the output end voltage of the rectifier module is higher than the second threshold value, the second threshold value being greater than the first threshold value. When the switching power supply circuit works, if the input voltage of the power input end is greater than the maximum specified input voltage, the output voltage of the rectifier module is higher than the second threshold value, and the cutoff switch conducts, thereby forming a cutoff loop to cut off the output path of the rectifier module to the power output end, to protect the subsequent load circuit. The overvoltage protection module can realize protection of the load circuit when the input voltage is too large, and can automatically realize the overvoltage protection function without the need for a microcontroller to judge, which is beneficial to simplify the circuit structure, reduce the cost and the size of the switching power supply, realize abnormal high voltage protection, and prolong the service life of the switching power supply.

[0042] As shown in Figure 2 , in this embodiment, the switching power supply circuit also includes a first feedback module configured to output a first level signal or a second level signal based on the conduction state of the cutoff switch. The switching power supply circuit also includes a second feedback module configured to output a first level signal or a second level signal based on the conduction state of the cutoff switch. Through the output of the first feedback module and the second feedback module, the working state of the current switching power supply circuit can be indicated.

[0043] Figure 3 is a circuit diagram of a switching power supply circuit according to an embodiment of the present application. The switching power supply circuit will be described below in conjunction with Figure 3 The circuit structure of the switching power supply circuit will be further described. It should be understood that the circuit structure shown is only an example and is not intended to limit the scope of protection of the present application. Figure 3 The circuit structure shown is only an example and is not intended to limit the scope of protection of the present application.

[0044] As shown in Figure 3 The switching power supply circuit includes a power input terminal J1, a relay k1, a thermistor module, a cut-off switch Q1, a rectifier module CR1, cut-off switches Q2 and Q3, a first switch driving module, a second switch driving module, a first feedback module, a second feedback module, a capacitor C3, and power output terminals V+ and V-. The two ends of the capacitor C3 are respectively connected to the positive and negative output terminals of the rectifier module CR1, and the two ends of the capacitor C3 are respectively connected to the positive and negative terminals V+ and V- of the power output terminals. As shown in Figure 3 The thermistor module includes two NTC thermistors R1 and R2 connected in series. The number of thermistors is only an example, and in other embodiments, the thermistor module can also include one, three or more thermistors. The relay is an electromagnetic relay with a coil, a normally open NO terminal and a normally closed NC terminal. The rectifier module CR1 is a full-wave rectifier bridge. The cut-off switch Q1, the cut-off switches Q2 and Q3 can each be a MOS tube (Metal-Oxide-Semiconductor Field-Effect Transistor). The switching power supply circuit further includes a resistor R9 and a voltage stabilizing diode Z4. The resistor R9 and the resistor R5 form a voltage dividing circuit for providing a configuration voltage to the cut-off switch Q1. The voltage stabilizing diode Z4 serves as a protection diode to prevent damage to the resistor R9 when the voltage in the circuit is too high.

[0045] The first switch driving module includes a first voltage stabilizing diode Z1 and a first capacitor C1. The first switch driving module further includes a resistor R5 and a resistor R6 connected in series between the first voltage stabilizing diode Z1 and the first end of the first capacitor C1. The first end of the first voltage stabilizing diode Z1 is connected to the positive output terminal of the rectifier module CR1, and the first voltage stabilizing diode Z1 is configured to be turned on when the voltage input at the first end is higher than a first threshold value, i.e. when the output voltage of the positive output terminal of the rectifier module CR1 is higher than the first threshold value. The first end of the first capacitor C1 is connected to the second end of the first voltage stabilizing diode Z1 through the resistor R6 and the resistor R5, and the first end of the first capacitor C1 is also connected to the control terminal of the cut-off switch Q1. The second end of the first capacitor C1 is connected to the negative output terminal of the rectifier module CR1.

[0046] The second switch driving module comprises at least one second Zener diode and a second capacitor C2. In this embodiment, two second Zener diodes Z2 and Z3 are provided in series, which are denoted as Zener diode Z2 and Zener diode Z3 respectively below. The number of second Zener diodes is only an example, and in other embodiments, the number of second Zener diodes can be one, three or more. The second switch driving module further comprises a resistor R7 connected in series between the second capacitor C2 and the off switch Q3, a resistor R4 connected in series between the Zener diode Z3 and the second capacitor C2, and a resistor R5 connected in series between the second capacitor C2 and the off switch Q2. The first end of the Zener diode Z2 is connected to the positive output end of the rectifier module CR1, the second end of the Zener diode Z2 is connected to the first end of the Zener diode Z3, the second end of the Zener diode Z3 is connected to the first end of the second capacitor C2 through the resistor R4. The first end of the second capacitor C2 is also connected to the control ends of the off switches Q2 and Q3 through the resistor R5, and the second end of the second capacitor C2 is connected to the negative output end of the rectifier module CR1.

[0047] The Zener diode Z2 and the Zener diode Z3 are configured to be turned on when the voltage input at the first end is higher than a second threshold value, i.e. the output voltage at the positive output end of the rectifier module CR1 is higher than the second threshold value, and the second threshold value is a value higher than the first threshold value. When the off switches Q2 and Q3 are turned on, two off circuits are formed at the output end of the rectifier: (1) the rectifier CR1, the Zener diodes Z2 and Z3, the resistor R4, the resistor R5 and the off switch Q2; (2) the rectifier CR1, the Zener diodes Z2 and Z3, the resistor R4, the resistor R7 and the off switch Q7. The output current of the rectifier CR1 is shunted through the two off circuits. The off switches Q2 and Q3 are also connected to the control end of the cut-off switch Q1, and the off switches Q2 and Q3 are configured to drive the cut-off switch Q1 to be turned off when turned on.

[0048] In this embodiment, the first feedback module comprises a first optocoupler CPT1A and a first photodiode D1. The first optocoupler CPT1A is connected between the cutoff switch Q2 and the forward output end of the rectifier module CR1. One end of the first photodiode D1 is connected to the VCC power supply through a resistor R8, and the first photodiode D1 is configured to output a first level signal or a second level signal according to the optical signal of the first optocoupler CPT1A. The second feedback module comprises a second optocoupler CPT1B and a second photodiode D2. The second optocoupler CPT1B is connected between the cutoff switch Q1 and the control end of the relay k1. One end of the second photodiode D2 is connected to the VCC power supply through a resistor R10, and is configured to output a first level signal or a second level signal according to the optical signal of the second optocoupler CPT1B. In this embodiment, the first level signal is a low level signal, and the second level signal is a high level signal.

[0049] The working principle of the switch power supply circuit of this embodiment will be described in detail below. Figure 3 The working principle of the switch power supply circuit of this embodiment will be described in detail below.

[0050] When the device starts, at the moment of accessing the input AC power supply, the current is large, the NO end of the relay k1 remains in the open state, the NTC thermistors R1 and R2 are connected to the input power supply end J1, and the resistance values of the NTC thermistors R1 and R2 are large, which is beneficial to reduce the current input to the rectifier module CR1, thereby limiting the inrush current and realizing the automatic soft start function. As the device runs, after the voltage of the input power supply stabilizes, the resistance values of the NTC thermistors R1 and R2 gradually decrease, the output voltage of the rectifier module CR1 gradually increases to a first threshold value, the first zener diode Z1 is turned on, and the output current of the rectifier module CR1 charges the first capacitor C1 through the resistors R5 and R6. After the first capacitor C1 is fully charged, the cutoff switch Q1 is turned on, so that the coil power supply loop of the relay k1 is turned on, and the normally open NO end of the relay is turned on, thereby separating the two NTC thermistors R1 and R2 from the power supply input end J1, so as not to affect the normal operation of the switch power supply circuit. At this time, a low level signal is output through the second feedback module for use by the main controller of the later stage of the switch power supply circuit.

[0051] In the working of the switching power supply circuit, when the input voltage of the power supply input terminal J1 is greater than the maximum voltage of the specified input, the output voltage of the rectifier module CR1 increases to a second threshold value, at which time the second voltage stabilizing diodes Z2 and Z3 are turned on, the output current of the rectifier module CR1 charges the second capacitor C2 through the resistor R4, and after the second capacitor C2 is fully charged, the switches Q2 and Q3 are turned on, the high voltage is immediately cut off, the subsequent circuit is protected, and at the same time the switch Q1 is cut off, the power supply loop of the coil of the relay k1 loses power, the normally closed NC terminal of the relay k1 is turned on, and through the second feedback module, a high level is output, indicating that the current corresponds to a high voltage signal. Through the first feedback module, a high level signal is output, indicating that the current overvoltage condition occurs.

[0052] In summary, the switching power supply circuit of the present application has the following advantages:

[0053] The present application has a thermistor module connected in series at the power supply input terminal, which includes at least one negative temperature coefficient thermistor. When the device with the switching power supply circuit is started, due to the large current, the resistance value of the thermistor module is large, which is beneficial to reduce the current input to the rectifier module from the power supply input terminal, thereby effectively limiting the inrush current and realizing the soft start function. When the circuit is working normally, after the output voltage of the rectifier module stabilizes and reaches a first threshold value, the first switch driving module drives the cut-off switch to conduct, so that the relay conducts the current path between the two terminals of the thermistor module, and the thermistor module is separated from the power supply input terminal, thereby realizing the automatic cut-off of the thermistor from the power supply circuit when the circuit is working normally, without affecting the normal operation of the circuit. The switching power supply circuit of the present application also has an automatic overvoltage protection function, which forms a cut-off loop when the output voltage of the rectifier module is higher than a second threshold value to cut off the output path from the rectifier module to the power supply output terminal, thereby protecting the subsequent load. The switching power supply circuit does not need an external microcontroller for control, the circuit structure is simple, the implementation cost is low, the switching power supply is small in size, and it is beneficial to prolong the service life of the switching power supply.

[0054] The above is a further detailed description of the present application in combination with a specific preferred embodiment, which cannot be considered as limiting the specific implementation of the present application to these descriptions. For ordinary skilled persons in the technical field to which the present application belongs, without departing from the concept of the present application, a number of simple deductions or substitutions can be made, which should be considered as falling within the protection scope of the present application.

Claims

1. A switching power supply circuit, characterized by comprising: The application relates to a temperature sensor module, comprising: a thermistor module comprising at least one negative temperature coefficient thermistor, a first end of the thermistor module being connected to a power input end; a rectifier module, an input end of the rectifier module being connected to a second end of the thermistor module, and an output end of the rectifier module being connected to a power output end; a relay configured to control a conduction of a current path between the first end and the second end of the thermistor module when energized; a cut-off switch configured to make a conduction circuit of the relay conductive when turned on; a first switch driving module configured to drive the cut-off switch to conduct when a voltage at the output end of the rectifier module is higher than a first threshold value; an overvoltage protection module configured to form a cut-off circuit to cut off an output path of the rectifier module to the power output end when a voltage at the output end of the rectifier module is higher than a second threshold value.

2. The switching power supply circuit according to claim 1, characterized by The first switch driving module comprises: a first voltage stabilizing diode, a first end of the first voltage stabilizing diode being connected to a positive output end of the rectifier module, the first voltage stabilizing diode being configured to conduct when a voltage input at the first end is higher than the first threshold value; a first capacitor, a first end of the first capacitor being connected to a second end of the first voltage stabilizing diode and a control end of the cut-off switch respectively, and a second end of the first capacitor being connected to a negative output end of the rectifier module.

3. The switching power supply circuit according to claim 1, characterized by The overvoltage protection module comprises: a cut-off switch configured to form a cut-off circuit to cut off an output path of the rectifier module to the power output end when turned on; a second switch driving module configured to drive the cut-off switch to conduct when a voltage at the output end of the rectifier module is higher than a second threshold value, the second threshold value being greater than the first threshold value.

4. The switching power supply circuit according to claim 3, characterized in that, The second switch driving module comprises: at least one second voltage stabilizing diode, a first end of the second voltage stabilizing diode being connected to a positive output end of the rectifier module, the second voltage stabilizing diode being configured to conduct when a voltage input at the first end is higher than the second threshold value; a second capacitor, a first end of the second capacitor being connected to a second end of the second voltage stabilizing diode and a control end of the cut-off switch respectively, and a second end of the second capacitor being connected to a negative output end of the rectifier module.

5. The switching power supply circuit according to claim 3, wherein The cut-off switch is further connected to the control end of the cut-off switch, and the cut-off switch is configured to drive the cut-off switch to turn off when turned on.

6. The switching power supply circuit according to claim 3, wherein The application further comprises a first feedback module configured to output a first level signal or a second level signal based on a conduction state of the cut-off switch.

7. The switching power supply circuit according to claim 6, characterized in that The first feedback module comprises: a first optoelectronic coupler connected between the cut-off switch and the positive output end of the rectifier module; a first optoelectronic diode configured to output the first level signal or the second level signal according to a light signal of the first optoelectronic coupler.

8. The switching power supply circuit according to claim 1, characterized by The application further comprises a second feedback module configured to output a first level signal or a second level signal based on a conduction state of the cut-off switch.

9. The switching power supply circuit according to claim 8, characterized in that, The second feedback module comprises: a second optoelectronic coupler connected between the cut-off switch and a control end of the relay; a second optoelectronic diode configured to output the first level signal or the second level signal according to a light signal of the second optoelectronic coupler.

10. The switching power supply circuit according to claim 1, characterized by The relay is an electromagnetic relay, and the NO end of the electromagnetic relay is conducted when the cut-off switch is turned on, and the NC end of the electromagnetic relay is conducted when the cut-off switch is turned off.

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