Power supply circuit, circuit board and electronic equipment

Abstract

The utility model relates to the technical field of power supplies, and discloses a power supply circuit, a circuit board and electronic equipment. The power supply circuit comprises a power supply generation circuit, a constant voltage feedback circuit, a constant current feedback circuit and an isolation feedback circuit, the power supply generation circuit can generate output voltage and output current, the constant voltage feedback circuit comprises a voltage division circuit and an adjustable parallel voltage stabilizer, the voltage division circuit can output divided voltage after dividing the output voltage, and the adjustable parallel voltage stabilizer is connected with the isolation feedback circuit. The adjustable shunt regulator can output a constant-voltage feedback signal according to the divided voltage, the constant-current feedback circuit can output a constant-current feedback signal according to the output current, and the isolation feedback circuit can output an isolation feedback signal according to the constant-voltage feedback signal or the constant-current feedback signal. Therefore, the power supply generation circuit adjusts the magnitude of the output voltage and / or the output current according to the isolation feedback signal. Therefore, the adjustable shunt voltage stabilizer is used as a core device of the feedback loop, the voltage stabilization value can be flexibly adjusted, the circuit structure can be simplified, and the circuit cost can be reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of power supply, in particular to a power supply circuit, a circuit board and an electronic device. Background Art

[0002] When the inverter is started, it is usually necessary to soft-start the bus, that is, to slowly increase the bus voltage in stages to the preset value, and then start the inversion. Bus soft-start can avoid current shock, ensure the reliability and stability of the inverter startup, and protect the internal circuits and equipment of the inverter.

[0003] Bus soft-start generally uses an auxiliary source as the soft-start source. During the bus soft-start process, the auxiliary source is usually required to output a constant current. The constant current is used to slowly charge the bus capacitor to avoid generating a large surge current. When the bus voltage reaches the preset value, the bus soft-start ends. At this time, the auxiliary source needs to output a constant voltage. Therefore, the auxiliary source usually supports constant current and constant voltage output.

[0004] In order to ensure that the auxiliary source achieves constant current and constant voltage output, a feedback loop needs to be constructed, the purpose of which is to continuously adjust the output voltage or current according to the real-time output voltage or current feedback so that the output voltage or current remains constant. In traditional technology, the feedback loop usually uses a large number of operational amplifiers to achieve a more stable and reliable feedback effect. However, this feedback loop is not only complex in structure, but also has a relatively high circuit cost. Utility Model Content

[0005] An object of the embodiments of the present utility model is to provide a power supply circuit, a circuit board and an electronic device, which can solve the technical problems of the complex feedback loop structure of the auxiliary source and the high circuit cost.

[0006] In a first aspect, an embodiment of the utility model provides a power supply circuit, comprising:

[0007] A power generation circuit, used for generating an output voltage and an output current;

[0008] A constant voltage feedback circuit, comprising a voltage divider circuit and an adjustable shunt regulator, wherein the voltage divider circuit is electrically connected to the power generation circuit and the adjustable shunt regulator, respectively, and is used to divide the output voltage and then output a divided voltage, and the adjustable shunt regulator is used to output a constant voltage feedback signal according to the divided voltage;

[0009] A constant current feedback circuit, electrically connected to the power generation circuit and the adjustable shunt regulator, respectively, for outputting a constant current feedback signal according to the output current;

[0010] An isolated feedback circuit is electrically connected to the power generation circuit, the adjustable parallel regulator and the constant current feedback circuit, respectively, and is used to output an isolated feedback signal according to the constant voltage feedback signal or the constant current feedback signal, so that the power generation circuit adjusts the output voltage and / or output current according to the isolated feedback signal.

[0011] In a second aspect, an embodiment of the utility model provides a circuit board, comprising the power supply circuit as described above.

[0012] In a third aspect, an embodiment of the utility model provides an electronic device, comprising the circuit board as described above.

[0013] In the power supply circuit provided by the embodiment of the utility model, it includes a power supply generating circuit, a constant voltage feedback circuit, a constant current feedback circuit and an isolated feedback circuit. The power supply generating circuit can generate an output voltage and an output current. The constant voltage feedback circuit includes a voltage divider circuit and an adjustable parallel regulator. The voltage divider circuit can divide the output voltage and then output the divided voltage. The adjustable parallel regulator can output a constant voltage feedback signal according to the divided voltage. The constant current feedback circuit can output a constant current feedback signal according to the output current. The isolated feedback circuit can output an isolated feedback signal according to the constant voltage feedback signal or the constant current feedback signal, so that the power supply generating circuit adjusts the output voltage and / or the output current according to the isolated feedback signal. Therefore, the present embodiment uses an adjustable parallel regulator as the core component of the feedback loop. On the one hand, the voltage regulation value of the adjustable parallel regulator can be adjusted to any value, which is conducive to improving the flexibility of the voltage regulation value adjustment, thereby facilitating the circuit design. On the other hand, it can simplify the circuit structure and reduce the circuit cost on the basis of ensuring that the feedback loop achieves a stable and reliable feedback effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] One or more embodiments are illustrated only as examples in the corresponding drawings, and these examples do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings represent similar elements, and unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0015] Figure 1 It is a structural schematic diagram of a power supply circuit provided by an embodiment of the utility model;

[0016] Figure 2 This is a schematic diagram of a power supply circuit structure provided by another embodiment of the utility model;

[0017] Figure 3 It is a circuit structure diagram of a power supply circuit provided by an embodiment of the utility model;

[0018] Figure 4 It is a principle schematic diagram of a PI control circuit provided by an embodiment of the utility model. DETAILED DESCRIPTION

[0019] In order to facilitate the understanding of the present application, the present application is described in more detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that when an element is described as "connected" to another element, it can be directly connected to the other element, or there can be one or more intermediate elements therebetween. In addition, the terms "first", "second", etc. are used only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0020] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as those commonly understood by those skilled in the art in the technical field of the present invention. The terms used in this specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used in this specification includes any and all combinations of one or more of the related listed items.

[0021] The present utility model provides a power supply circuit. Figure 1 The power supply circuit 100 includes a power supply generating circuit 10 , a constant voltage feedback circuit 20 , a constant current feedback circuit 30 and an isolation feedback circuit 40 .

[0022] The power generation circuit 10 can receive an input power supply, wherein the input power supply can be a DC power supply or an AC power supply, and the power generation circuit 10 can generate an output voltage or an output current according to the input power supply. In this embodiment, the power generation circuit 10 can adopt any suitable type of power topology such as a flyback topology.

[0023] The constant voltage feedback circuit 20 includes a voltage divider circuit 21 and an adjustable shunt regulator 22 .

[0024] The voltage divider circuits 21 are electrically connected to the power generation circuits 10 , respectively, and can divide the output voltage and then output the divided voltage.

[0025] The adjustable shunt regulator 22 is electrically connected to the voltage divider circuit 21 and can output a constant voltage feedback signal according to the divided voltage, wherein the constant voltage feedback signal is a feedback signal for adjusting the output voltage to a constant voltage.

[0026] The constant current feedback circuit 30 is electrically connected to the power generation circuit 10 and the adjustable parallel regulator 22 respectively, and can output a constant current feedback signal according to the output current, wherein the constant current feedback signal is a feedback signal for adjusting the output current to a constant current.

[0027] The isolated feedback circuit 40 is electrically connected to the power generation circuit 10, the adjustable parallel regulator 22 and the constant current feedback circuit 30, respectively, and can output an isolated feedback signal according to the constant voltage feedback signal or the constant current feedback signal, so that the power generation circuit 10 adjusts the output voltage and / or output current according to the isolated feedback signal, for example, adjusting the output voltage to a constant voltage value and / or adjusting the output current to a constant current value.

[0028] Therefore, this embodiment uses an adjustable shunt regulator as the core component of the feedback loop. On the one hand, the voltage regulation value of the adjustable shunt regulator can be adjusted to any value, which is conducive to improving the flexibility of voltage regulation value adjustment, thereby facilitating circuit design. On the other hand, it can simplify the circuit structure and reduce the circuit cost while ensuring that the feedback loop achieves a stable and reliable feedback effect.

[0029] In some embodiments, see Figure 2 The power generation circuit 10 includes a starting circuit 11, a controller 12, a switch circuit 13, a current sampling circuit 14, a transformer 15, a power supply circuit 16 and a rectifier and filter circuit 17.

[0030] The startup circuit 11 can receive an input voltage. When the power supply circuit 100 is powered on, the startup circuit 11 can supply power to the controller 12 according to the input voltage, so that the controller 12 can be powered on and work.

[0031] The controller 12 is electrically connected to the start-up circuit 11. When the controller 12 is powered on and works, it can output a PWM (Pulse Width Modulation) signal.

[0032] The switch circuit 13 is electrically connected to the controller 12 and can be in an on state or an off state according to a PWM signal.

[0033] In some embodiments, see Figure 3 The switch circuit 13 includes a first MOS tube M1, a fifth resistor R5 and a third diode D3.

[0034] One end of the fifth resistor R5 is electrically connected to the controller 12 and the cathode of the third diode D3 respectively, the other end of the fifth resistor R5 is electrically connected to the anode of the third diode D3 and the gate of the first MOS transistor M1 respectively, the drain of the first MOS transistor M1 is electrically connected to the transformer 15, and the source of the first MOS transistor M1 is electrically connected to the current sampling circuit 14.

[0035] In this embodiment, when the PWM signal is at a high level, the first MOS tube M1 is in a conducting state, and when the PWM signal is at a low level, the first MOS tube M1 is in a shut-off state. The fifth resistor R5 can limit the gate current flowing from the controller 12 to the first MOS tube M1, and the third diode D3 can accelerate the discharge speed of the first MOS tube M1, thereby increasing the shut-off speed of the first MOS tube M1.

[0036] The current sampling circuit 14 is electrically connected to the controller 12 and the switch circuit 13 respectively, and can sample the current flowing through the switch circuit 13 .

[0037] See also Figure 3 , the current sampling circuit 14 includes a sixth resistor R6.

[0038] One end of the sixth resistor R6 is electrically connected to the source of the first MOS transistor Q1 , and the other end of the sixth resistor R6 is grounded.

[0039] The larger the current flowing through the sixth resistor R6, the larger the voltage drop of the sixth resistor R6. The controller 12 can adjust the duty cycle of the output PWM signal according to the voltage drop of the sixth resistor R6 to achieve current loop control. If the current flowing through the sixth resistor R6 is too large, the controller 12 can directly control the first MOS tube Q1 to be in the off state to avoid damage to the device.

[0040] The transformer 15 is electrically connected to the switch circuit 13 , and can receive an input voltage and utilize the input voltage to perform energy coupling to generate alternating current.

[0041] See also Figure 3 The transformer 15 includes a first primary winding Lp, a second primary winding La and a first secondary winding Ls.

[0042] The opposite end of the first primary winding Lp can receive the input voltage V in The same-name end of the first primary winding Lp is electrically connected to the drain of the first MOS tube Q1, the same-name end of the second primary winding La is electrically connected to the power supply circuit 16, the opposite-name end of the second primary winding La is grounded, and the first secondary winding Ls is electrically connected to the rectifier and filter circuit 17.

[0043] When the first MOS tube Q1 is in the on state, the first primary winding Lp stores energy. When the first MOS tube Q1 is in the off state, the first primary winding Lp transfers the stored energy to the first secondary winding Ls. At this time, the first secondary winding Ls generates alternating current by coupling the energy of the first primary winding Lp. At the same time, the second primary winding La also couples the energy of the first secondary winding Ls to generate alternating current.

[0044] The power supply circuit 16 is electrically connected to the controller 12 and the second primary winding La respectively, and can output a power supply voltage VCC according to the alternating current generated by the second primary winding La. The power supply voltage VCC can replace the start-up circuit 11 to supply power to the controller 12 .

[0045] See also Figure 3 , the power supply circuit 16 includes a fourth diode D4 and a third capacitor C3.

[0046] The anode of the fourth diode D4 is electrically connected to the same-name end of the second primary winding La, the cathode of the fourth diode D4 is electrically connected to the controller 12 and one end of the third capacitor C3 respectively, and the other end of the third capacitor C3 is grounded.

[0047] The fourth diode D4 can rectify the AC power generated by the second primary winding La into DC power to power the controller 12, and the third capacitor C3 can filter the DC power to ensure that the DC power used to power the controller 12 is sufficiently smooth and stable.

[0048] The rectifying and filtering circuit 17 is electrically connected to the first secondary winding Ls, and can rectify and filter the alternating current generated by the first secondary winding Ls to generate an output voltage and an output current.

[0049] See also Figure 3 The rectifying and filtering circuit 17 includes a fifth diode D5 and a fourth capacitor C4.

[0050] The anode of the fifth diode D5 is electrically connected to the same-name end of the first secondary winding Ls, the cathode of the fifth diode D5 is electrically connected to one end of the fourth capacitor C4, the constant voltage feedback circuit 20 and the constant current feedback circuit 30, and the other end of the fourth capacitor C4 and the opposite-name end of the first secondary winding Ls are grounded.

[0051] The fifth diode D5 can rectify the AC power generated by the first secondary winding Ls into DC power to supply power to the load RL, and the fourth capacitor C4 can filter the DC power to ensure that the DC power used to supply power to the load RL is sufficiently smooth and stable. It can be understood that the DC power mentioned here refers to the output voltage and the output current.

[0052] In order to further elaborate on the design process of the power generation circuit 10, Figure 3 The design process of the power generation circuit 10 is described.

[0053] First, the magnetic core of the transformer 15 is determined.

[0054] The core of the transformer 15 can be determined by the AP (Area Product) method, that is, the area product method, where the core area product is expressed by the following formula:

[0055] AP=A w *A e

[0056] Wherein, AP is the core area product of transformer 15, A w A is the window area of ​​the core that can be wound with wire, e is the effective cross-sectional area of ​​the core.

[0057] The core area product and the magnetic core have a preset mapping relationship, and different core area products may correspond to different magnetic cores. Therefore, after determining the core area product of the transformer 15, the corresponding magnetic core may be determined according to the preset mapping relationship.

[0058] Next, the turns ratio of the first primary winding Lp to the first secondary winding Ls is determined according to the magnetic core of the transformer 15 .

[0059] The magnetic core and the transformer size have a preset mapping relationship, and different core area products can correspond to different magnetic cores. Therefore, after determining the magnetic core of the transformer 15, the size of the transformer 15 can be determined according to the preset mapping relationship. The turns ratio of the first primary winding Lp to the first secondary winding Ls can be determined by the size of the transformer 15, wherein the turns ratio of the first primary winding Lp to the first secondary winding Ls is expressed by the following formula:

[0060]

[0061] Wherein, N is the turns ratio of the first primary winding Lp to the first secondary winding Ls, L is the inductance ratio of the first primary winding Lp to the first secondary winding Ls, I e is the magnetic flux length, A e is the cross-sectional area of ​​the magnetic core wound by the first primary winding Lp and the first secondary winding Ls, μ e is the magnetic permeability.

[0062] Next, the maximum duty cycle of the PWM signal output by the controller 12 is determined according to the turns ratio of the first primary winding Lp to the first secondary winding Ls.

[0063] The maximum duty cycle of the PWM signal is expressed as follows:

[0064]

[0065] Among them, D max is the maximum duty cycle of the PWM signal, V bmax is the maximum output voltage of transformer 15, V in is the input voltage of the transformer 15, and N is the turns ratio of the first primary winding Lp to the first secondary winding Ls.

[0066] Next, the inductance of the first primary winding Lp is determined according to the maximum duty cycle of the PWM signal.

[0067] The inductance of the first primary winding Lp is expressed by the following formula:

[0068]

[0069] Where, Lp is the inductance of the first primary winding Lp, V in_min is the input voltage of transformer 15 under the worst working condition, D max is the maximum duty cycle of the PWM signal, P in is the input power of the transformer 15, f is the operating frequency of the transformer 15, and K is the current ripple waveform factor.

[0070] Next, the inductance of the first secondary winding Ls is determined according to the inductance of the first primary winding Lp and the turns ratio between the first primary winding Lp and the first secondary winding Ls.

[0071] The inductance of the first secondary winding Ls is expressed by the following formula:

[0072] L s =N 2 *L p

[0073] Among them, L s is the inductance of the first secondary winding Ls, N is the turns ratio of the first primary winding Lp to the first secondary winding Ls, L p is the inductance of the first primary winding Lp.

[0074] Finally, the inductance of the second primary winding La is determined according to the inductance of the first primary winding Lp.

[0075] The inductance of the second primary winding La is expressed by the following formula:

[0076]

[0077] Among them, L a is the inductance of the second primary winding La, VCC is the power supply voltage of the controller 12, V in is the input voltage of transformer 15, L p is the inductance of the first primary winding Lp.

[0078] See also Figure 3 The voltage divider circuit 21 includes a seventh resistor R7 and an eighth resistor R8.

[0079] One end of the seventh resistor R7 is electrically connected to the power generation circuit 10 , the other end of the seventh resistor R7 is electrically connected to one end of the eighth resistor R8 and the adjustable parallel regulator 22 , and the other end of the eighth resistor R8 is grounded.

[0080] The seventh resistor R7 and the eighth resistor R8 can divide the output voltage generated by the power generation circuit 10 and output the divided voltage. The divided voltage can be expressed as Vs=Vo*R8 / (R7+R8), where Vo is the output voltage. It can be seen that the divided voltage Vs is proportional to the voltage Vo. Therefore, by adjusting the resistance values ​​of the seventh resistor R7 and the eighth resistor R8, the proportional relationship between the divided voltage Vs and the output voltage Vo can be adjusted.

[0081] Please continue reading Figure 2 The adjustable shunt regulator 22 is a three-port device, and the three ports of the adjustable shunt regulator 22 are respectively an anode 22a, a cathode 22b and a reference terminal 22c.

[0082] An anode 22 a of the adjustable parallel regulator 22 is grounded, a cathode 22 b of the adjustable parallel regulator 22 is electrically connected to the isolated feedback circuit 40 , and a reference end 22 c of the adjustable parallel regulator 22 is electrically connected to the voltage divider circuit 21 .

[0083] The adjustable shunt regulator 22 can be set to any suitable regulated voltage value, and the adjustable shunt regulator 22 can output a constant voltage feedback signal according to the regulated voltage value and the divided voltage.

[0084] In some embodiments, the model of the adjustable shunt regulator 22 is TL431. TL431 is an adjustable shunt regulator with three terminals. Due to its excellent performance and low price, it can be widely used in single-chip microcomputer precision switching power supplies or precision linear regulated power supplies.

[0085] The equivalent circuit diagram of TL431 can be found in Figure 3 ,like Figure 3 As shown, the equivalent circuit diagram of TL431 includes an operational amplifier U1, a second transistor Q2 and a sixth diode D6.

[0086] The inverting input terminal of the operational amplifier U1 can receive the reference voltage Vref, the non-inverting input terminal of the operational amplifier U1 is the reference terminal 22c of the adjustable parallel regulator 22, the output terminal of the operational amplifier U1 is electrically connected to the base of the second transistor Q2, the collector of the second transistor Q2 is electrically connected to the cathode of the sixth diode D6, the connection point between the collector of the second transistor Q2 and the cathode of the sixth diode D6 is the cathode 22b of the adjustable parallel regulator 22, the emitter of the second transistor Q2 and the anode of the sixth diode D6 are grounded, and the connection point between the emitter of the second transistor Q2 and the anode of the sixth diode D6 is the anode 22a of the adjustable parallel regulator 22.

[0087] It can be understood that by setting the reference voltage Vref, the voltage regulation value of the adjustable parallel regulator 22 can be set, which is beneficial to improving the flexibility of adjusting the voltage regulation value of the adjustable parallel regulator 22.

[0088] When the divided voltage is greater than the reference voltage VREF, the output terminal of the operational amplifier U1 outputs a high level, so the second transistor Q2 is in a conducting state. At this time, the collector voltage of the second transistor Q2 is a low level, that is, the constant voltage feedback signal output by the adjustable parallel regulator 22 is a low level.

[0089] When the divided voltage is less than the reference voltage VREF, the output terminal of the operational amplifier U1 outputs a high level, so the second transistor Q2 is in a cut-off state. At this time, the collector voltage of the second transistor Q2 is a high level, and the constant voltage feedback signal output by the adjustable parallel regulator 22 is a high level.

[0090] In some embodiments, please refer to Figure 2 The constant voltage feedback circuit 20 also includes a compensation circuit 23 .

[0091] The compensation circuit 23 is electrically connected to the voltage divider circuit 21 , the adjustable shunt regulator 22 and the isolation feedback circuit 40 respectively, and can form a negative feedback loop of the adjustable shunt regulator 22 .

[0092] In some embodiments, see Figure 3 , the compensation circuit 23 includes a ninth resistor R9 and a fourth capacitor C4.

[0093] One end of the ninth resistor R9 is electrically connected to the cathode 22b of the adjustable parallel regulator 22, the other end of the ninth resistor R9 is electrically connected to one end of the fourth capacitor C4, and the other end of the fourth capacitor C4 is electrically connected to the voltage divider circuit 21 and the reference end 22c of the adjustable parallel regulator 22 respectively.

[0094] like Figure 3 As shown, the output end of the operational amplifier U1 in the adjustable parallel regulator 22 is electrically connected to the base of the second transistor Q2, and the output of the collector of the second transistor Q2 is fed back to the non-inverting input end of the operational amplifier U1 through the fourth capacitor C4 and the ninth resistor R9. Therefore, the ninth resistor R9 and the fourth capacitor C4 can constitute a negative feedback loop of the adjustable parallel regulator 22.

[0095] Since the ninth resistor R9 and the fourth capacitor C4 can form a negative feedback loop of the adjustable parallel regulator 22, the present embodiment can form a PI (Proportiona l-Integra l) control circuit through the ninth resistor R9, the fourth capacitor C4 and the adjustable parallel regulator 22. The PI control circuit is a closed-loop control circuit that can achieve error adjustment. The difference voltage between the divided voltage Vs of the output voltage Vo and the reference voltage Vref is input into the PI control circuit. At this time, the PI control circuit can perform a PI operation on the difference voltage, and output the voltage after the PI operation at the collector of the second transistor Q2, and use the voltage as a constant voltage feedback signal, which is conducive to suppressing oscillation when the output voltage Vo changes drastically, thereby improving the stability and reliability of the constant voltage feedback.

[0096] Combine the following Figure 3 and Figure 4 , the principle of PI operation of PI control circuit is explained in more detail. It can be understood that Figure 4 The operational amplifier U2 in the Figure 3 The adjustable parallel regulator 22 shown is equivalent to that obtained, wherein the inverting input terminal of the operational amplifier U2 is the non-inverting input terminal of the operational amplifier U1, the non-inverting input terminal of the operational amplifier U2 is the inverting input terminal of the operational amplifier U1, and the output terminal of the operational amplifier U2 is the collector of the second transistor Q2.

[0097] like Figure 4 As shown, the ninth resistor R9 and the fourth capacitor C4 connected in series between the inverting input terminal of the operational amplifier U2 and the output terminal of the operational amplifier U2 form a negative feedback loop of the operational amplifier U2, so the ninth resistor R9, the fourth capacitor C4 and the operational amplifier U2 can form a PI control circuit. According to the principle of virtual short and virtual disconnection of the operational amplifier, the following relationship can be obtained:

[0098]

[0099] Among them, i f is the current flowing into the ninth resistor R9, i1 is the current flowing through the seventh resistor R7, V o is the output voltage generated by the power generation circuit 10, and R9 is the resistance value of the ninth resistor.

[0100] The voltage across the fourth capacitor C4 is expressed by the following formula:

[0101]

[0102] Among them, U C is the voltage across the fourth capacitor C4, and C4 is the capacitance of the fourth capacitor C4.

[0103] Then, the output voltage of operational amplifier U2 is expressed as follows:

[0104]

[0105] Among them, U 431 is the output voltage of the operational amplifier U2, and R7 is the resistance value of the seventh resistor.

[0106] It can be seen from the above formula that the AC component of the output voltage of the operational amplifier U2 is the result of the PI operation of the output voltage Vo generated by the power generation circuit 10. Therefore, using the output voltage of the operational amplifier U2 as a constant voltage feedback signal is beneficial to suppress oscillation when the output voltage Vo changes drastically, thereby improving the stability and reliability of the constant voltage feedback.

[0107] In some embodiments, please refer to Figure 2 The constant current feedback circuit 30 includes a current detection circuit 31 and a first switch circuit 32 .

[0108] The current detection circuit 31 is electrically connected to the power generation circuit 10 and can output a first control signal according to the output current.

[0109] The first control signal includes a first level type signal and a second level type signal, the first level type signal and the second level type signal are different level type signals, for example, the first level type signal is a high level signal, the second level type signal is a low level signal, or the first level type signal is a low level signal, the second level type signal is a high level signal.

[0110] The first switch circuit 32 is electrically connected to the current detection circuit 31 and the isolation feedback circuit 40 respectively, and can output a constant current feedback signal according to the first control signal.

[0111] In some embodiments, please refer to Figure 3 The first switch circuit 32 includes a tenth resistor R10, an eleventh resistor R11, a twelfth resistor R12, a thirteenth resistor R13, a fourteenth resistor R14, a third transistor Q3, a fourth transistor Q4 and a second MOS transistor M2.

[0112] One end of the tenth resistor R10 is electrically connected to the current detection circuit 31, the other end of the tenth resistor R10 is electrically connected to the base of the third triode Q3, the collector of the third triode Q3 is electrically connected to one end of the eleventh resistor R11, the other end of the eleventh resistor R11 is electrically connected to the base of the fourth triode Q4, the emitter of the fourth triode Q4 is electrically connected to the power generation circuit 10, the collector of the fourth triode Q4 is electrically connected to one end of the twelfth resistor R12, the other end of the twelfth resistor R12 is respectively electrically connected to one end of the thirteenth resistor R13 and the gate of the second MOS tube M2, the drain of the second MOS tube M2 is electrically connected to one end of the fourteenth resistor R14, the other end of the fourteenth resistor R14 is electrically connected to the isolation feedback circuit 40, and the emitter of the third triode Q3, the other end of the thirteenth resistor R13 and the source of the second MOS tube M2 are grounded.

[0113] When the first control signal is a high level signal, the third transistor Q3 is turned on, the fourth transistor Q4 is also turned on, and the output voltage Vo is applied to the gate of the second MOS transistor M2 through the fourth transistor Q4 and the twelfth resistor R12, so the second MOS transistor M2 is also turned on, and the drain voltage of the second MOS transistor M2 is pulled to the ground, and the constant current feedback signal is a low level at this time.

[0114] When the first control signal is a low level signal, the third transistor Q3 is turned off, and the fourth transistor Q4 is also turned off, so that the second MOS tube M2 is turned off, and at this time the constant current feedback signal is a high level.

[0115] The power supply circuit 100 should be able to switch between a constant voltage mode and a constant current mode to ensure that the power supply generating circuit 10 generates a constant output voltage or a constant output current. The power supply circuit 100 also includes a control circuit to control the mode switching, wherein the constant voltage mode means that the power supply generating circuit 10 generates a constant output voltage, but the output current is not necessarily constant, and the constant current mode means that the power supply generating circuit 10 generates a constant output current, but the output voltage is not necessarily constant.

[0116] In some embodiments, please refer to Figure 2 , the constant current feedback circuit 30 also includes a control circuit 33.

[0117] The control circuit 33 is electrically connected to the first switch circuit 32 , and can control the first switch circuit 32 to output a constant current feedback signal in response to an input second control signal.

[0118] In some embodiments, see Figure 3 , the control circuit 33 includes a first resistor R1 and a first transistor Q1.

[0119] One end of the first resistor R1 can receive the input second control signal, the other end of the first resistor R1 is electrically connected to the base of the first transistor Q1, the collector of the first transistor Q1 is electrically connected to the first switch circuit 32, and the emitter of the first transistor Q1 is grounded.

[0120] like Figure 2 As shown, when the second control signal is a high level signal, the first transistor Q1 pulls down the base voltage of the third transistor Q3. At this time, no matter how the output current changes, that is, no matter whether the first control signal is a high level signal or a low level signal, the third transistor Q3 is cut off, so that the second MOS tube M2 will be turned off, which is equivalent to the constant current feedback not working. The isolated feedback circuit 40 only outputs the corresponding isolated feedback signal to the power generation circuit 10 according to the constant voltage feedback signal, so that the power generation circuit 10 generates a constant output voltage according to the isolated feedback signal. At this time, the power circuit 100 will work in the constant voltage mode.

[0121] When the second control signal is a low level signal, the first transistor Q1 is cut off. At this time, the current detection circuit 31 normally outputs the first control signal according to the output current, and the first switch circuit 32 also normally outputs the constant current feedback signal according to the first control signal. At this time, the isolation feedback circuit 40 mainly outputs the corresponding isolation feedback signal to the power generation circuit 10 based on the constant current feedback signal, so that the power generation circuit 10 generates a constant output current according to the isolation feedback signal. At this time, the power supply circuit 100 will operate in the constant current mode.

[0122] In some embodiments, see Figure 2 The isolated feedback circuit 40 includes a signal isolation circuit 41 and a photoelectric isolation circuit 42 .

[0123] The signal isolation circuit 41 is electrically connected to the adjustable shunt regulator 22 and the constant current feedback circuit 30 respectively. The signal isolation circuit 41 includes a node 40a, and the voltage of the node 40a can be controlled according to the constant voltage feedback signal and the constant current feedback signal.

[0124] In some embodiments, see Figure 3 , the signal isolation circuit 41 includes a first diode D1 and a second diode D2.

[0125] The anode of the first diode D1 is electrically connected to the photoelectric isolation circuit 42 and the anode of the second diode D2 at the node 40 a , the cathode of the first diode D1 is electrically connected to the adjustable shunt regulator 22 , and the cathode of the second diode D2 is electrically connected to the constant current feedback circuit 30 .

[0126] When the cathode of the first diode D1 is a high level signal and the cathode of the second diode D2 is a low level signal, the voltage at the node 40 a is a low level signal.

[0127] When the cathode of the first diode D1 is a low level signal and the cathode of the second diode D2 is a high level signal, the voltage at the node 40 a is a low level signal.

[0128] When the cathode of the first diode D1 and the cathode of the second diode D2 are both high level signals, the voltage of the node 40 a is a high level signal.

[0129] When the cathode of the first diode D1 and the cathode of the second diode D2 are both low level signals, the voltage of the node 40 a is a low level signal.

[0130] It can be understood that the first diode D1 and the second diode D2 can avoid mutual influence between the constant voltage feedback signal output by the adjustable parallel regulator 22 and the constant current feedback signal output by the constant current feedback circuit 30. For example, when the power supply circuit 100 is in the constant current mode, it can avoid the constant voltage feedback signal output by the adjustable parallel regulator 22 affecting the constant current feedback, thereby ensuring that the power supply generating circuit 10 generates a constant output current.

[0131] The photoelectric isolation circuit 42 is electrically connected to the power generation circuit 10 and is electrically connected to the signal isolation circuit 41 at a node 40 a , and can output an isolated feedback signal according to the voltage of the node 40 a .

[0132] In some embodiments, see Figure 3 The photoelectric isolation circuit 42 includes an optical coupler U3, a second resistor R2, a third resistor R3, a fourth resistor R4 and a second capacitor C2.

[0133] The optocoupler U3 includes a light emitting diode VD1 and a phototransistor VT1, the anode of the light emitting diode VD1 is electrically connected to one end of the second resistor R2 and one end of the third resistor R3, respectively, the other end of the second resistor R2 is electrically connected to the power generation circuit 10, the other end of the third resistor R3 is electrically connected to the cathode of the light emitting diode VD1 and the signal isolation circuit 41 at the node 40a, the collector of the phototransistor VT1 is electrically connected to one end of the fourth resistor R4 and one end of the second capacitor C2, respectively, the other end of the fourth resistor R4 is electrically connected to the controller 12, and the other end of the second capacitor C2 and the emitter of the phototransistor VT1 are grounded.

[0134] When the voltage of the node 40a is a low level signal, the light emitting diode VD1 has current flowing through it and can emit light, and the phototransistor VT1 receives the light emitted by the light emitting diode VD1 and is in a conducting state. At this time, the controller 12 reduces the duty cycle of the output PWM signal.

[0135] When the voltage at the node 40a is a high level signal, the light emitting diode VD1 and the phototransistor VT1 are both turned off, and the controller 12 increases the duty cycle of the output PWM signal.

[0136] In order to further explain the working principle of the power supply circuit 100 provided by the embodiment of the utility model, Figure 4 To elaborate.

[0137] When the power supply circuit 100 is required to be in constant current mode, the input second control signal is a low level signal, and the first transistor Q1 is turned off. If the output current is less than the preset current, the first control signal output by the current detection circuit 31 is a low level signal, so the third transistor Q3, the fourth transistor Q4 and the second MOS transistor M2 are all turned off, and the second diode D2 is also reversely turned off. At this time, the voltage of the node 40a is a high level signal, and the light-emitting diode VD1 and the phototransistor VT1 are both turned off, so the controller 12 increases the duty cycle of the output PWM signal, so that the conduction time of the first MOS transistor M1 becomes longer, and the energy stored in the first primary winding Lp becomes more, then the first secondary winding Ls couples the energy of the first primary winding Lp to generate an alternating The current increases, so that the output current also increases; if the output current is greater than the preset current, the first control signal output by the current detection circuit 31 is a high-level signal, so the third transistor Q3, the fourth transistor Q4 and the second MOS tube M2 are all turned on, the second diode D2 is also forward-conducted, the light-emitting diode VD1 has current flowing through it and can emit light, the phototransistor VT1 receives the light emitted by the light-emitting diode VD1 and is in a conducting state, at this time the controller 12 reduces the duty cycle of the output PWM signal, so that the conduction time of the first MOS tube M1 becomes shorter, the energy stored in the first primary winding Lp becomes less, and the alternating current generated by the first secondary winding Ls coupling the energy of the first primary winding Lp becomes smaller, so that the output current also becomes smaller. Therefore, after this constant current feedback, the output current can be kept constant.

[0138] When the power supply circuit 100 is required to be in constant voltage mode, the input second control signal is a high level signal. At this time, the first transistor Q1 is turned on, and the base voltage of the third transistor Q3 is pulled down. Then, no matter whether the output current is greater than the preset current or less than the preset current, that is, no matter whether the first control signal output by the current detection circuit 31 is a high level signal or a low level signal, the third transistor Q3, the fourth transistor Q4 and the second MOS tube M2 are all cut off, and the second diode D2 is also reversely cut off, so the voltage of the node 40a will be mainly controlled by the constant voltage feedback signal output by the adjustable parallel regulator 22, and the feedback regulation of the output voltage is realized by the constant voltage feedback signal.

[0139] In the constant voltage mode, if the output voltage is less than the preset voltage, the constant voltage feedback signal output by the adjustable parallel regulator 22 is a high level signal, that is, the voltage at the node 40a is a high level signal, so the light-emitting diode VD1 and the phototransistor VT1 are both turned off. At this time, the controller 12 increases the duty cycle of the output PWM signal, so that the conduction time of the first MOS tube M1 becomes longer, and the energy stored in the first primary winding Lp becomes more, so that the alternating current generated by the first secondary winding Ls coupling the energy of the first primary winding Lp becomes larger, thereby increasing the output voltage; if the output voltage is greater than the preset voltage , the constant voltage feedback signal output by the adjustable parallel regulator 22 is a low level signal, that is, the voltage of the node 40a is a low level signal, the light emitting diode VD1 has current flowing through it and can emit light, the phototransistor VT1 receives the light emitted by the light emitting diode VD1 and is in a conducting state, at this time, the controller 12 reduces the duty cycle of the output PWM signal, so that the conduction time of the first MOS tube M1 becomes shorter, the energy stored in the first primary winding Lp becomes less, and the alternating current generated by the first secondary winding Ls coupling the energy of the first primary winding Lp becomes smaller, so that the output voltage also becomes smaller. Therefore, through this constant voltage feedback, the output voltage can be kept constant.

[0140] As another embodiment of the present invention, the present invention provides a circuit board, which includes the power supply circuit as described above, wherein the circuit board can be an independent circuit board or a circuit board formed by splicing multiple circuit boards.

[0141] As another embodiment of the present invention, the embodiment of the present invention further provides an electronic device, which includes the circuit board as described above.

[0142] Finally, it should be noted that the utility model can be implemented in many different forms and is not limited to the embodiments described in this specification. These embodiments are not intended to be additional limitations on the content of the utility model. The purpose of providing these implementation methods is to make the understanding of the disclosure of the utility model more thorough and comprehensive. In addition, under the idea of ​​the utility model, the above-mentioned technical features continue to be combined with each other, and there are many other changes in different aspects of the utility model as described above, which are all considered to be within the scope of the utility model specification; further, for ordinary technicians in this field, they can be improved or transformed according to the above description, and all these improvements and transformations should belong to the scope of protection of the claims attached to the utility model.

Claims

1. A power supply circuit, characterized in that: include: A power generation circuit, used for generating an output voltage and an output current; A constant voltage feedback circuit, comprising a voltage divider circuit and an adjustable shunt regulator, wherein the voltage divider circuit is electrically connected to the power generation circuit and the adjustable shunt regulator, respectively, and is used to divide the output voltage and then output a divided voltage, and the adjustable shunt regulator is used to output a constant voltage feedback signal according to the divided voltage; A constant current feedback circuit, electrically connected to the power generation circuit and the adjustable shunt regulator, respectively, for outputting a constant current feedback signal according to the output current; An isolated feedback circuit is electrically connected to the power generation circuit, the adjustable parallel regulator and the constant current feedback circuit, respectively, and is used to output an isolated feedback signal according to the constant voltage feedback signal or the constant current feedback signal, so that the power generation circuit adjusts the output voltage and / or output current according to the isolated feedback signal.

2. The power supply circuit according to claim 1, characterized in that: The constant voltage feedback circuit also includes a compensation circuit; The compensation circuit is electrically connected to the voltage divider circuit, the adjustable shunt regulator and the isolation feedback circuit respectively, and is used to form a negative feedback loop of the adjustable shunt regulator.

3. The power supply circuit according to claim 1, characterized in that: The constant current feedback circuit comprises: a current detection circuit, electrically connected to the power generation circuit, and configured to output a first control signal according to the output current; The first switch circuit is electrically connected to the current detection circuit and the isolation feedback circuit respectively, and is used for outputting a constant current feedback signal according to the first control signal.

4. The power supply circuit according to claim 3, characterized in that: The constant current feedback circuit also includes a control circuit; The control circuit is electrically connected to the first switch circuit, and is used to control the first switch circuit to output the constant current feedback signal in response to an input second control signal.

5. The power supply circuit according to claim 4, characterized in that: The control circuit includes a first transistor and a first resistor; One end of the first resistor is used to receive the second control signal, the other end of the first resistor is electrically connected to the base of the first transistor, the collector of the first transistor is electrically connected to the first switch circuit, and the emitter of the first transistor is grounded.

6. The power supply circuit according to claim 1, characterized in that: The isolated feedback circuit comprises: A signal isolation circuit, electrically connected to the adjustable shunt regulator and the constant current feedback circuit, respectively, the signal isolation circuit comprising a node, for controlling the voltage of the node according to the constant voltage feedback signal and the constant current feedback signal; The photoelectric isolation circuit is electrically connected to the power generation circuit and to the signal isolation circuit at the node, and is used to output an isolated feedback signal according to the voltage of the node.

7. The power supply circuit according to claim 6, characterized in that: The signal isolation circuit includes a first diode and a second diode; The anode of the first diode is electrically connected to the photoelectric isolation circuit and the anode of the second diode at the node, respectively, the cathode of the first diode is electrically connected to the adjustable parallel regulator, and the cathode of the second diode is electrically connected to the constant current feedback circuit.

8. The power supply circuit according to claim 6, characterized in that: The photoelectric isolation circuit includes an optical coupler, a second resistor, a third resistor, a fourth resistor and a second capacitor; The optocoupler includes a light emitting diode and a phototransistor, the anode of the light emitting diode is electrically connected to one end of the second resistor and one end of the third resistor respectively, the other end of the second resistor is electrically connected to the power generation circuit, the other end of the third resistor is electrically connected to the cathode of the light emitting diode and the signal isolation circuit at the node respectively, the collector of the phototransistor is electrically connected to one end of the fourth resistor and one end of the second capacitor respectively, the other end of the fourth resistor is electrically connected to the power generation circuit, and the other end of the second capacitor and the emitter of the phototransistor are grounded.

9. A circuit board, characterized in that: Comprising the power supply circuit according to any one of claims 1 to 8.

10. An electronic device, characterized in that: Comprising the circuit board as claimed in claim 9.

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