Flyback power supply and electric equipment

Abstract

The invention provides a flyback power supply and electric equipment. The flyback power supply comprises a transformer which is provided with a primary side and a secondary side connected with a rectifier tube, and the output end of the secondary side is used for providing output voltage; the first controllable switch is connected with the primary side and is used for controlling the on or off of the primary side; the closed-loop control circuit is connected with the output end of the secondary side and the first controllable switch and used for sending a control signal to the first controllable switch according to the output voltage, the control signal comprises the on time and the off time of the primary side, and the control signal is used for controlling the output voltage to be maintained at the preset voltage after the flyback power supply completes the starting stage; and the starting suppression circuit is connected with the closed-loop control circuit and is used for generating a suppression signal in the starting stage of the flyback power supply, and the suppression signal is used for reducing the conduction time in the control signal. According to the flyback power supply, the cost and the size of the flyback power supply can be reduced.

Description

Technical Field

[0001] The present application relates to the technical field of electronic circuits, and in particular to a flyback power supply and an electrical device. Background Art

[0002] A flyback power supply is a switching power supply topology that uses a transformer to provide an output voltage with a preset voltage value. Due to its high safety and strong stability, it is widely used in the charging field.

[0003] After the flyback power supply is powered on, it has a startup phase and a stabilization phase. After the flyback power supply completes the startup phase, it reaches the stabilization phase, at which time the output end of the flyback power supply can stably provide a preset voltage. In the startup phase of the flyback power supply, the output voltage fails to reach the preset voltage. When the primary side of the flyback power supply transformer is turned off and the secondary side is turned on, the current drop value of the secondary side during the on-time is small. Therefore, when the secondary side is turned off and the primary side is turned on, there is still a large current in the secondary side.

[0004] This will result in a large reverse withstand voltage spike in the rectifier tube when the secondary side is turned off and a large current in the primary side during the re-conduction process of the primary side. Therefore, the primary side switch needs to bear a large drain-source stress (DS) when the primary side is turned off again.

[0005] In order to reduce the damage of reverse withstand voltage spike and drain-source stress to power devices, in the related art, when designing a flyback power supply, a rectifier tube with greater withstand voltage capability and a primary-side switch are usually selected. Power devices with greater withstand voltage capability are larger in size and more expensive, which results in a larger size and higher overall cost of the flyback power supply. Summary of the invention

[0006] The present application provides a flyback power supply and an electrical device. Various aspects involved in the present application are introduced below.

[0007] In a first aspect, a flyback power supply is provided, comprising: a transformer having a primary side and a secondary side connected to a rectifier tube, the output end of the secondary side being used to provide an output voltage; a first controllable switch connected to the primary side and used to control the on or off of the primary side; a closed-loop control circuit connected to the output end of the secondary side and the first controllable switch, respectively, and used to send a control signal to the first controllable switch according to the output voltage, the control signal comprising the on time and off time of the primary side, and the control signal being used to control the output voltage to maintain a preset voltage after the flyback power supply completes the startup phase; a startup inhibition circuit connected to the closed-loop control circuit, and used to generate an inhibition signal during the startup phase of the flyback power supply, the inhibition signal being used to reduce the on time in the control signal.

[0008] Optionally, the closed-loop control circuit includes: a first resistor voltage divider circuit, connected to the output end of the secondary side, the first resistor voltage divider circuit having a first voltage divider point, and the first voltage divider point is used to divide the output voltage; an output feedback circuit, connected to the first voltage divider point, and used to output a feedback signal according to the voltage of the first voltage divider point; a pulse width modulation controller, having a control end, a detection end and a compensation end, the detection end is connected to the primary side to collect the current signal of the primary side when the primary side is turned on, the compensation end is connected to the output feedback circuit to receive the feedback signal, and the control end is connected to the gate of the first controllable switch to send a control signal to the first controllable switch, and the control signal is determined according to the feedback signal and / or the current signal.

[0009] Optionally, the startup inhibition circuit is connected to the detection end, and the startup inhibition circuit is also used to send the inhibition signal to the detection end, and the inhibition signal is used to increase the current signal to reduce the conduction time in the control signal.

[0010] Optionally, the output feedback circuit includes: a parallel voltage regulator integrated circuit, including a reference terminal, an anode terminal and a cathode terminal, the reference terminal is connected to the first voltage dividing point, the anode terminal is grounded, and the cathode terminal is used to output a feedback current according to the voltage of the first voltage dividing point; an optocoupler, including an input terminal and an output terminal, the input terminal is connected to the parallel voltage regulator integrated circuit, the output terminal is connected to the compensation terminal, and the optocoupler is used to convert the feedback current into the feedback signal.

[0011] Optionally, the startup inhibition circuit is connected to the reference terminal and the cathode terminal respectively, and the inhibition signal is used to increase the feedback current to change the feedback signal, and the changed feedback signal is used to reduce the conduction time in the control signal.

[0012] Optionally, the startup inhibition circuit includes: a second controllable switch, connected to the cathode end and the reference end respectively, and the second controllable switch is used to control the conduction or disconnection of the circuit from the cathode end to the reference end; a signal providing circuit, including a capacitor and a resistor connected in series, the connection point of the capacitor and the resistor is connected to the gate of the second controllable switch, the capacitor is connected to the output end of the secondary side, and the resistor is grounded, and the signal providing circuit is used to send an inhibition signal to the second controllable switch during the startup phase of the flyback power supply, and the inhibition signal is used to control the second controllable switch to be in the on state to increase the feedback current.

[0013] Optionally, the startup inhibition circuit includes: a third controllable switch, connected to the reference voltage supply terminal and the detection terminal respectively, and the third controllable switch is used to control the circuit from the reference voltage supply terminal to the detection terminal to be turned on or off; a comparison circuit, having a positive input terminal, a negative input terminal and an output terminal, the positive input terminal is connected to the reference voltage supply terminal, the negative input terminal is connected to the output terminal of the secondary side, and the output terminal is connected to the gate of the third controllable switch, and the comparison circuit is used to send an inhibition signal to the third controllable switch during the startup phase of the flyback power supply, and the inhibition signal is used to control the third controllable switch to be in a conductive state to increase the current signal.

[0014] Optionally, the negative input terminal is connected to the output terminal of the secondary side through the second voltage dividing point of the second resistor voltage divider circuit, and the other end of the second resistor voltage divider circuit is grounded; the positive input terminal is connected to the reference voltage supply terminal through the third voltage dividing point of the third resistor voltage divider circuit, and the other end of the third resistor voltage divider circuit is grounded.

[0015] Optionally, the first controllable switch is grounded via a sampling resistor, and the detection end is connected to a connection point between the first controllable switch and the sampling resistor.

[0016] In a second aspect, an electrical device is provided, comprising the flyback power supply as described in the first aspect.

[0017] The flyback power supply provided in the embodiment of the present application includes a startup inhibition circuit connected to a closed-loop control circuit, and the startup inhibition circuit is used to generate an inhibition signal in the startup phase of the flyback power supply, and the inhibition signal is used to reduce the on-time in the control signal. This can lengthen the off-time in the control signal, allowing the secondary side to have more time to reduce the current therein when the primary side is turned off, thereby increasing the current drop value during the on-time of the secondary side, and even allowing the current to drop to 0 during the on-time of the secondary side, thereby eliminating the need for the power devices (first controllable switch and rectifier tube) in the flyback power supply to have a large withstand voltage, which helps to reduce the cost and size of the flyback power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of the structure of a flyback power supply provided in one embodiment of the present application.

[0019] Figure 2 A schematic diagram of the structure of a flyback power supply provided in another embodiment of the present application.

[0020] Figure 3 A schematic diagram of the relationship between the conduction time of Q1 and the voltage signal at the compensation terminal provided in an embodiment of the present application.

[0021] Figure 4A schematic diagram of the structure of a flyback power supply provided in yet another embodiment of the present application.

[0022] Figure 5 A schematic diagram of the structure of a flyback power supply provided in yet another embodiment of the present application.

[0023] Figure 6 A schematic diagram of the structure of a flyback power supply provided in yet another embodiment of the present application. DETAILED DESCRIPTION

[0024] In order to facilitate understanding of the present application, the present application is described in more detail below based on exemplary embodiments and in conjunction with the accompanying drawings. The same or similar reference numerals are used in the accompanying drawings to represent the same or similar modules. It should be understood that the accompanying drawings are only exemplary and the scope of protection of the present application is not limited thereto.

[0025] In order to enable those skilled in the art to better understand the present application, Figure 1 The working principle of a flyback power supply provided in an embodiment of the present application is introduced.

[0026] The flyback power supply 10 is a power supply device. Figure 1 The flyback power supply 10 may include a transformer SPS, a first controllable switch Q1 and a closed-loop control circuit 110 .

[0027] Transformer SPS is an electrical device that works on the principle of electromagnetic induction and is mainly used to change the voltage. Figure 1 As shown, the transformer SPS includes a primary side and a secondary side. The primary side can also be called the primary side, and the primary side includes a primary winding (or primary winding) and an input capacitor C1. The input end of the primary winding is connected to the input power supply DC, and the input voltage provided by the input power supply DC to the primary winding through the input end is Vin. The secondary side can also be called the secondary side, and the secondary side includes a secondary winding (or secondary winding), a rectifier tube D1, an output capacitor C2 and a load RL. The secondary side has an output end, and the output end is used to provide an output voltage Vout.

[0028] The first controllable switch Q1 is connected to the primary side and is used to control the on or off of the primary side. For example, when the gate input of the first controllable switch Q1 is high level, the power supply DC is supplied, the primary side is in the on state, and the current I1 (or called the primary side current I1 or the primary current I1) passes through the primary winding. At this time, the secondary side is in the off state, that is, no current passes through the secondary winding; when the gate input of the first controllable switch Q1 is low level, the power supply DC is powered off, the primary side is in the off state, and the current on the primary winding drops rapidly. At this time, due to the electromagnetic induction principle and the setting of the rectifier tube, the secondary side can be turned on, that is, the current I2 (or called the secondary side current I2 or the secondary current I2) passes through the secondary winding; when the gate input of the first controllable switch Q1 is switched from low level to high level again, the primary side is in the on state and the secondary side is in the off state. It can be seen that the on-time of the primary side (ie, the on-time of the first controllable switch Q1) is the same as the off-time of the secondary side, and the off-time of the primary side (ie, the off-time of the first controllable switch Q1) is the same as the on-time of the secondary side.

[0029] The working process of the flyback power supply includes the startup phase and the stabilization phase. The startup phase is the phase from the primary side being powered on to the output voltage provided by the output end of the secondary side reaching the preset voltage for the first time; the stabilization phase is the phase when the output voltage provided by the output end of the secondary side is stabilized at the preset voltage. In other words, the stabilization phase is the working phase of the flyback power supply after completing the startup phase.

[0030] The closed-loop control circuit 110 can also be called a voltage adjustment circuit. The closed-loop control circuit 110 is connected to the output terminal of the secondary side and the gate of the first controllable switch Q1 respectively. The closed-loop control circuit 110 can set the value of the preset voltage, or in other words, the closed-loop control circuit 110 can set the output voltage in the stable phase to a different preset voltage as required. At the same time, the closed-loop control circuit 110 can also be used to monitor the output voltage and send a control signal to the first controllable switch Q1 according to the output voltage. The control signal is used to control the output voltage in the stable phase to maintain the preset voltage. In addition, the control signal is also used to increase the output voltage to the preset voltage as soon as possible during the startup phase. The control signal includes the on-time T of the primary side. on and the off time T off .

[0031] However, during the startup phase of the flyback power supply, when the primary side of the flyback power supply's transformer SPS is turned off and the secondary side is turned on, the current drop value of the secondary side during the on-time (the change in current from on to off) is small.

[0032] This is because: on the one hand, the output voltage provided by the flyback power supply during the startup phase cannot reach the preset voltage value, and the current drop value of the secondary side during the conduction time is proportional to the output voltage, so the output voltage is small and the current drop value is also small; on the other hand, in order to increase the output voltage to the preset voltage as quickly as possible during the startup phase, the T on Will cause T off will be shorter, which will also result in a smaller current drop value on the secondary side during the conduction time.

[0033] In order to facilitate understanding of the above principle, the current drop value of the secondary side is small during the conduction time in the startup phase of the flyback power supply. Figure 2 This is explained.

[0034] like Figure 2 As shown, the closed-loop control circuit 110 may include a first resistor voltage divider circuit 111 , an output feedback circuit 112 , and a pulse width modulation controller 113 .

[0035] The first resistor voltage divider circuit 111 is connected to the output terminal of the secondary side and the ground respectively, that is, the output terminal of the secondary side is grounded through the first resistor voltage divider circuit 111. The first resistor voltage divider circuit 111 includes a resistor R1 and a resistor R2, and the connection point between the resistor R1 and the resistor R2 is a first voltage dividing point of the first resistor voltage divider circuit 111, and the first voltage dividing point is used to divide the output voltage.

[0036] Based on this, the voltage V fen and output voltage V out The calculation formula is as follows.

[0037]

[0038] In some embodiments, the selection of resistors R1 and R2 can be used to determine the value of the preset voltage. For example, from formula (1), when the voltage V fen When the preset output voltage is a constant value, the preset output voltage (ie, the preset voltage) is only related to R1 and R2. That is, when R1 and R2 are selected differently, the preset voltage value set by the flyback power supply is different, that is, the output voltage value in the stable stage is different.

[0039] The output feedback circuit 112 is connected to the first voltage dividing point and is used to output a feedback signal according to the voltage of the first voltage dividing point. The feedback signal is used to characterize the difference between the output voltage and the preset voltage. For example, the feedback signal can be a voltage signal. The greater the difference between the output voltage and the preset voltage, the greater the value of the voltage signal. In this case, the T in the control signal needs to be on The larger the voltage is, the longer the conduction time of the first controllable switch Q1 is. In other words, when the output voltage is less than the preset voltage, the value of the voltage signal (hereinafter referred to as Vcomp ) is larger, accordingly, V GATE The longer the high level time is, the longer the conduction time of Q1 is, that is, T on The larger the V out During the establishment process, V out The set value has not been reached yet, T on The maximum value that can be achieved will be reached until Q1 is turned off because the PWM controller 113 itself only allows a 50% duty cycle or the detection terminal of the PWM controller 113 detects 1V.

[0040] The pulse width modulation (PWM) controller 113 is used to send a control signal to the first controllable switch Q1. Figure 2 As shown, the PWM controller 113 has a control terminal ( Figure 2 Pin 7 in the detection terminal ( Figure 2 Pin 3) and the compensation terminal ( Figure 2 Pin 1 in the circuit). The detection terminal is connected to the primary side to collect the current signal of the primary side when the primary side is turned on. The compensation terminal is connected to the output feedback circuit 112 to receive the feedback signal. The control terminal is connected to the gate of the first controllable switch Q1 to send a control signal to the first controllable switch Q1. The control signal is determined based on the feedback signal and / or the current signal to maintain the output voltage at a preset voltage in the stable stage, and to increase the output voltage to a preset voltage as quickly as possible in the startup stage while ensuring the safety of each device in the closed-loop control circuit 110. The control signal is a pulse width modulation signal including T on and T off .

[0041] In some embodiments, the detection terminal can be connected to the sampling resistor R6 to collect the current signal of the primary side when the primary side is turned on. Figure 2 As shown, the first controllable switch Q1 is grounded through the sampling resistor R6, and the detection end is connected to the connection point between the first controllable switch Q1 and the sampling resistor R6.

[0042] The embodiment of the present application does not specifically limit the type of the PWM controller 113, as long as the PWM controller can generate a control signal according to the above current signal and feedback signal. For example, the PWM controller is but not limited to any of the following: UC2844 chip, UCC28C59 chip or SCM1710A. Preferably, as Figure 2 As shown, the PWM controller is a UC2844 chip, and the control end, the detection end, and the compensation end are marked as VGATE, ISENSE, and COMP, respectively.

[0043] The embodiment of the present application does not specifically limit the output feedback circuit 112. As an example, Figure 2 As shown, the output feedback circuit 112 may include a shunt regulator integrated circuit 114 and an optical coupler O1.

[0044] The shunt voltage regulator integrated circuit 114 can be understood as a device that provides a stable voltage reference, and the shunt voltage regulator integrated circuit 114 includes a reference terminal, an anode terminal and a cathode terminal. The reference terminal is connected to the first voltage dividing point, the anode terminal is grounded, and the cathode terminal is used to output a feedback current according to the voltage of the first voltage dividing point.

[0045] Specifically, in the stable stage of the flyback power supply, due to the characteristics of the shunt regulator integrated circuit 114 itself, the voltage of the pin of the reference end will be stabilized at a fixed value, wherein the fixed value is the reference voltage provided inside the shunt regulator integrated circuit 114 .

[0046] For example, Figure 2 As shown, the shunt regulator integrated circuit 114 is TL431, the reference end can be marked as PIN3 pin, the cathode end can be marked as PIN1 pin, and the PIN3 pin is fixed at about 2.5V in the stable stage. The voltage V TL431_PIN3 That is, the voltage V at the first voltage dividing point fen It can be seen that the output voltage of the secondary side is related to the voltage V TL431_PIN3 The relationship is as follows.

[0047]

[0048] The cathode terminal can output a feedback current I3 according to the difference between the voltage at the first voltage division point and the reference voltage inside the shunt regulator integrated circuit 114 .

[0049] The embodiment of the present application does not specifically limit the type of the shunt regulator integrated circuit 114. For example, the shunt regulator integrated circuit 114 can be, but is not limited to, any of the following integrated circuits: TL431, TLV431, LM431, TLVH431, NCP431, AP431, etc.

[0050] The optocoupler O1 is also called a photoelectric coupler or a photoelectric isolator. It is an electronic device that converts an electrical signal into an optical signal and then converts the optical signal into an electrical signal. The optocoupler O1 includes an input end and an output end. The input end is connected to the cathode end of the parallel voltage regulator integrated circuit 114, and the output end of the optocoupler O1 is connected to the compensation end of the pulse width modulation controller 113. The optocoupler O1 is used to convert the feedback current I3 into a feedback signal and send the feedback signal to the compensation end of the pulse width modulation controller 113. Optionally, as Figure 2As shown, the input end of the optical coupler O1 is connected to the cathode end of the parallel regulator integrated circuit 114 through the resistors R3, R1, R4 and the capacitor C3.

[0051] As mentioned above, the larger the voltage signal representing the feedback signal, the more T in the control signal needs to be on The larger the value, the longer the conduction time of the first controllable switch Q1 is. The principle is as follows.

[0052] Among them, in the startup stage, due to the characteristics of TL431 itself, when Vout is less than the set value, the voltage V of PIN3 pin of TL431 is reduced by the voltage divider of R1 and R2. TL431_PIN3 is less than 2.5V, so the PIN1 pin voltage V TL431_PIN1 The larger the voltage is, the higher the PIN1 pin voltage V TL431_PIN1 The relationship with the feedback current I3 is as follows.

[0053]

[0054] According to formula (3), the larger the voltage VTL431_PIN1 of the PIN1 pin is, the smaller the output feedback current I3 is. The smaller the feedback current I3 is, the less the optocoupler O1 will be turned on, which will cause the output voltage (i.e. feedback signal) V comp The value of is larger.

[0055] When Q1 is turned on, the current on the sampling resistor R6 increases with time in a diagonal manner, and the slope remains unchanged. When the voltage V on R6 isense Arrival V comp Q1 is turned off only when V comp The larger it is, the longer the Q1 conduction time will be.

[0056] To facilitate understanding of V comp 、V isense And the relationship between Q1 conduction time, the following is combined Figure 3 a- Figure 3 b explains this. Figure 3 a, V comp1 Small value, V isense1 The value can reach V faster comp1 Value, V GATE1 The high level time is short, that is, the conduction time of Q1 is short. Figure 3 V in Figure b comp2 The value is relatively large, V isense2 It takes a long time to reach V comp2 Value, V GATE2 The high level time is long, that is, the Q1 conduction time is long.

[0057] The following describes the changes in the primary-side current I1 during the on-time of the primary side and the changes in the secondary-side current I2 during the on-time of the secondary side. Since I1 and I2 are continuously changing, I is used in the following text. p represents the primary side current, where I p_s is the current at the initial moment of primary conduction, I p_e is the current at the end of the primary side conduction; I s Represents the secondary side current, where I s_s is the current at the initial moment of conduction on the secondary side, I s_e is the current at the end of secondary conduction.

[0058] For the primary side current I p When Q1 is turned on, the initial value of the primary current is I p_s is the secondary side current I s_e The specific calculation formula for the current converted according to the turns ratio is as follows.

[0059]

[0060] Where N is the ratio of the number of turns on the primary side of the transformer SPSsps to the number of turns on the secondary side. As Q1 turns on, the primary side current changes by Δi P Calculate according to the following formula.

[0061]

[0062] Among them, T on is the conduction time of Q1. When Q1 is about to turn off, the primary side current I p_e Calculate according to the following formula.

[0063]

[0064] For the secondary side current I s , when Q1 is just turned off, the secondary side current I s_s The calculation formula is as follows.

[0065] I s_s =I p_e *N 2 (7)

[0066] As the secondary side is turned on, the secondary side current decreases according to the following formula.

[0067]

[0068] Among them, T off is the conduction time of the secondary side, that is, the off time of the primary side. Before the primary side is turned on again, the secondary side current I s_e The calculation of is as follows.

[0069]

[0070] From formula (9), we can know that at T off and L s When the current drop value of the secondary side is fixed (i.e. the change in the secondary current) Δi s and output voltage V out In the start-up phase of the flyback power supply, since the output voltage has not yet reached the set value, that is, V out When it is very small, Δi s Also very small.

[0071] Therefore, when Q1 is turned on again in the next switching cycle, i s It has not decreased much, and is still a large value, that is, I s_e This value is relatively large. That is, when the secondary side is turned off and the primary side is turned on, the current in the secondary side is not zero. This will lead to two major problems: 1. Due to I s_e 1. When Q1 is turned on again, due to I s_e Larger, according to formula (4), I p_s Larger, according to formula (6) leads to I p_e It is larger, that is, the primary side current is larger before Q1 is turned off, because the voltage stress when Q1 is turned off is positively correlated with the current flowing through Q1 when it is turned off, resulting in a larger DS stress when Q1 is turned off.

[0072] In order to reduce the damage of reverse withstand voltage spike and drain-source stress to power devices, in the related art, when designing a flyback power supply, a rectifier tube with greater withstand voltage capability and a primary-side switch are usually selected. Power devices with greater withstand voltage capability are larger in size and more expensive, which results in a larger size and higher overall cost of the flyback power supply.

[0073] The embodiment of the present application provides a flyback power supply, which includes a startup inhibition circuit connected to a closed-loop control circuit, and the startup inhibition circuit can be used to generate an inhibition signal in the startup phase of the flyback power supply, and the inhibition signal is used to reduce the on-time in the control signal. This can lengthen the off-time in the control signal, allowing the secondary side to have more time to reduce the current therein when the primary side is turned off, thereby increasing the current drop value during the on-time of the secondary side, and even allowing the current to drop to 0 during the on-time of the secondary side, thereby eliminating the need for the power devices (the first controllable switch Q1 and the rectifier tube) in the flyback power supply to have a large withstand voltage, which helps to reduce the cost and size of the flyback power supply.

[0074] Combine the following Figure 4-Figure 6 The flyback power supply provided in the embodiment of the present application is described in detail.

[0075] like Figure 4 As shown, the flyback power supply 40 may include a transformer SPS and a first controllable switch Q1, a closed-loop control circuit 410, and a startup suppression circuit 420. The transformer SPS, the first controllable switch Q1, and the closed-loop control circuit 410 are consistent with the transformer SPS, the first controllable switch Q1, and the closed-loop control circuit 110 described above, and are not described in detail here.

[0076] The startup inhibition circuit 420 is connected to the closed-loop control circuit 410. The startup inhibition circuit 420 is used to generate an inhibition signal during the startup phase of the flyback power supply. The inhibition signal is used to reduce the on-time T in the control signal output by the closed-loop control circuit 410. on In other words, the inhibit signal is used to increase the off time in the control signal during the startup phase.

[0077] The suppression signal in the embodiment of the present application can reduce the T on , which means T off According to formula (6), I p_e decreases, that is, when Q1 is turned off, the primary current I1 decreases, so the turn-off stress of Q1 is reduced. In addition, according to formula (7), I s_s Reduce, according to formula (8) Δi s Increase, according to formula (9), I s_e The secondary current I2 is reduced, that is, when D1 is turned off, the secondary current I2 is reduced, so the D1 turn-off stress is reduced. In this way, when designing a flyback power supply, it is not necessary for the power devices (the first controllable switch Q1 and the rectifier tube) in the flyback power supply to have a large withstand voltage, which helps to reduce the cost and size of the flyback power supply.

[0078] The embodiment of the present application does not specifically limit the form of the inhibition signal.

[0079] For example, Figure 5 As shown, when the startup inhibition circuit 420 is connected to the reference terminal (i.e., PIN3 pin) and the cathode terminal (i.e., PIN1 pin) of the parallel voltage regulator integrated circuit 414 in the closed-loop control circuit 410, the inhibition signal generated by the startup inhibition circuit 420 during the startup phase of the flyback power supply 40 is to automatically reduce the value of the voltage signal representing the feedback signal (V comp For example, the suppression signal is a signal that can increase the feedback current I3 output by the PIN1 pin. The suppression signal can change the feedback signal V by increasing the feedback current. comp The changed feedback signal V comp ',Vcomp 'V comp Small, so V GATE The high level time becomes shorter, that is, the changed signal V comp 'Used to reduce the on-time in the control signal.

[0080] For example, Figure 6 As shown, when the startup inhibition circuit 420 is connected to the detection end of the PWM controller 413 in the closed-loop control circuit 410, the startup inhibition circuit 420 is used to generate an inhibition signal and send the inhibition signal to the detection end during the startup phase of the flyback power supply 40. The inhibition signal can be a signal that automatically increases the value of the current signal on the primary side when the primary side is turned on during the startup phase. In other words, the inhibition signal can add a current value (I4 in the following text) to the detection end during the startup phase. Based on this, the value of the current on the primary side detected by the detection end is additionally increased by the current value attached by the inhibition signal, and the time for the detection end to detect 1V will be shortened. Since Q1 will be closed when 1V is detected, it is equivalent to reducing the conduction time in the control signal.

[0081] The present embodiment of the present application does not specifically limit the structure of the startup inhibition circuit 420 that can generate the feedback current I3 that increases the output of the PIN1 pin. Figure 5 As shown, the startup inhibition circuit 420 includes: a second controllable switch Q2 and a signal providing circuit 421 .

[0082] The input terminal and the output terminal of the second controllable switch Q2 are respectively connected to the cathode terminal and the reference terminal of the parallel voltage regulator integrated circuit 414. The second controllable switch Q2 is used to control the conduction or disconnection of the circuit from the cathode terminal to the reference terminal.

[0083] The signal providing circuit 421 includes a capacitor C7 and a resistor R7 connected in series, a connection point Vd of the capacitor C7 and the resistor R7 is connected to the gate of the second controllable switch Q2, the other end of the capacitor C7 is connected to the output end Vout of the secondary side, and the other end of the resistor R7 is grounded. Due to the working characteristics of the capacitor C7, when Vout is continuously changing (i.e., in the startup phase), a current will flow through C7, so that a non-zero voltage will be present at the connection point Vd (the voltage is an inhibition signal), based on which the gate of the second controllable switch Q2 is at a high level (i.e., the second controllable switch Q2 is turned on); when Vout is a stable value (i.e., in the stable phase), no current will flow through C7, so that the voltage at the connection point Vd is 0, based on which the gate of the second controllable switch Q2 is at a low level (i.e., the second controllable switch Q2 is turned off).

[0084] The above setting realizes generating an inhibition signal during the startup phase of the flyback power supply 40. The inhibition signal is used to control the second controllable switch Q2 to be in the on state. After the second controllable switch Q2 is turned on, the voltage of the PIN1 pin of the parallel voltage regulator integrated circuit 414 can be lowered. Based on this, the feedback current I3 is increased.

[0085] The present embodiment of the present application does not specifically limit the structure of the startup inhibition circuit 420 that can generate an inhibition signal that automatically increases the value of the current signal on the primary side. Figure 6 As shown, the startup inhibition circuit 420 includes: a third controllable switch Q3 and a comparison circuit AMP1.

[0086] The input terminal and the output terminal of the third controllable switch Q3 are respectively connected to the reference voltage supply terminal and the detection terminal of the PWM controller 413 . The third controllable switch Q3 is used to control the on or off of the circuit from the reference voltage supply terminal to the detection terminal.

[0087] The comparison circuit AMP1 or comparator AMP1 has a positive input terminal, a negative input terminal and an output terminal. The positive input terminal is connected to the reference voltage supply terminal, and the reference voltage supply terminal is connected to a stable voltage value. For example, the reference voltage supply terminal can be connected to the reference voltage terminal VREF of the PWM controller 413, and the reference voltage terminal VREF can provide a stable voltage value, and the voltage value is a preset voltage. For example, the preset voltage is 5V. The negative input terminal is connected to the output terminal of the secondary side, and the output terminal is connected to the gate of the third controllable switch Q3. The comparison circuit AMP1 can be based on the output voltage V OUT The comparison result is made with the voltage of the reference voltage terminal VREF, and the comparison result is sent to the third controllable switch Q3 as an inhibition signal.

[0088] Specifically, during the startup phase, due to the output voltage V OUT It has not been established yet, that is, V OUT The preset voltage is not reached. At this time, the voltage at the negative input terminal of the comparison circuit AMP1 is less than the voltage at the positive input terminal. The output terminal of the comparison circuit AMP1 sends a high level (the high level is an inhibition signal) to the gate of the third controllable switch Q3, so that the third controllable switch Q3 is turned on. The conduction of the third controllable switch Q3 causes the current to flow through the third controllable switch Q3 to the detection terminal ISENSE of the PWM controller 413 and the sampling resistor R6. Assume that this current is I4. At this time, it is equivalent to that during the conduction time of the first controllable switch Q1, the current signal detected by ISENSE increases. That is to say, the change in the current on the sampling resistor R6 increases by I4 on the basis of formula (5). Compared with not increasing I4, the voltage on R6 also increases. Therefore, V ISENSE The time to rise to 1V is shortened, and V ISENSEWhen the voltage reaches 1V, the first controllable switch Q1 will be turned off. Therefore, the feedback signal is equivalent to reducing the on-time in the control signal.

[0089] In some embodiments, Figure 6 As shown, the negative input terminal of the comparison circuit AMP1 is connected to the output terminal of the secondary side through the second voltage dividing point of the second resistor voltage dividing circuit. The second resistor voltage dividing circuit includes R7 and R10 connected in series, wherein R7 is respectively connected to the negative input terminal and the output terminal of the secondary side, and the other end of R10 is grounded. The positive input terminal of the comparison circuit AMP1 is connected to the reference voltage supply terminal through the third voltage dividing point of the third resistor voltage dividing circuit. The third resistor voltage dividing circuit includes R8 and R9 connected in series, wherein R8 is respectively connected to the positive input terminal of the comparison circuit AMP1 and the reference voltage supply terminal, and the other end of R9 is grounded.

[0090] The second resistor voltage divider circuit and the third resistor voltage divider circuit are provided to protect the comparison circuit AMP1 and reduce the influence of external noise and interference.

[0091] In some embodiments, in order to regulate and control I4, a resistor R11 may be further connected between the third controllable switch Q3 and the detection terminal ISENSE of the PWM controller 413 .

[0092] The embodiment of the present application does not specifically limit the type of the first controllable switch Q1, the second controllable switch Q2 or the third controllable switch Q3. For example, the first controllable switch Q1, the second controllable switch Q2 or the third controllable switch Q3 can be any one of the following switches: a metal oxide semiconductor field effect transistor (MOSFET), an insulated gate bipolar transistor (IGBT), a gate turn-off thyristor (GTO), etc. Preferably, as Figure 5-Figure 6 As shown, the first controllable switch Q1, the second controllable switch Q2 or the third controllable switch Q3 is a MOSFET.

[0093] The embodiment of the present application also provides an electric device, which includes the relay circuit described above. The embodiment of the present application does not specifically limit the electric device. As an example, the electric device can be any of various types of computer system devices that are mobile or portable and perform wireless communication. For example, the electric device can be a mobile phone or a smart phone (for example, it can be a phone based on iPhone TM, or a phone based on Android TM), a portable game device (for example, Nintendo DS TM, Play Station Portable TM, Gameboy Advance TM, iPhone TM), a laptop, a personal digital assistant (personal digital assistant, PDA), a portable Internet device, a music player and a data storage device, other handheld devices and such as watches, in-ear headphones, pendants, headphones, etc. Alternatively, the electric device can also be other wearable devices, for example, such as electronic glasses, electronic clothes, electronic bracelets, electronic necklaces, electronic tattoos, electric devices, smart watches or head-mounted displays (head mount display, HMD). For another example, the electrical equipment may also be vehicle-mounted electrical equipment, such as a vehicle computer, a driving recorder, a vehicle central control system, or a vehicle-mounted positioning device.

[0094] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0095] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0096] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0097] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0098] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the process or function described in the embodiment of the present application is generated in whole or in part. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions may be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium, for example, the computer instructions may be transmitted from a website site, computer, server or data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (digital subscriber line, DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) mode to another website site, computer, server or data center. The computer-readable storage medium may be any available medium that can be read by a computer or a data storage device such as a server or data center that includes one or more available media integrated. The available medium may be a magnetic medium (eg, a floppy disk, a hard disk, a magnetic tape), an optical medium (eg, a digital video disc (DVD)), or a semiconductor medium (eg, a solid state disk (SSD)).

[0099] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A flyback power supply, characterized in that: include: A transformer having a primary side and a secondary side connected to a rectifier tube, wherein an output end of the secondary side is used to provide an output voltage; A first controllable switch, connected to the primary side, for controlling the on or off of the primary side; a closed-loop control circuit, connected to the output terminal of the secondary side and the first controllable switch, respectively, for sending a control signal to the first controllable switch according to the output voltage, the control signal including the on-time and off-time of the primary side, and the control signal for controlling the output voltage to maintain a preset voltage after the flyback power supply completes the startup phase; A startup inhibition circuit is connected to the closed-loop control circuit and is used to generate an inhibition signal during the startup phase of the flyback power supply, wherein the inhibition signal is used to reduce the on-time in the control signal.

2. The flyback power supply according to claim 1, characterized in that: The closed-loop control circuit comprises: A first resistor voltage divider circuit is connected to the output terminal of the secondary side, the first resistor voltage divider circuit has a first voltage dividing point, and the first voltage dividing point is used to divide the output voltage; an output feedback circuit, connected to the first voltage dividing point, and configured to output a feedback signal according to the voltage of the first voltage dividing point; A pulse width modulation controller comprises a control end, a detection end and a compensation end, wherein the detection end is connected to the primary side to collect the current signal of the primary side when the primary side is turned on, the compensation end is connected to the output feedback circuit to receive the feedback signal, and the control end is connected to the gate of the first controllable switch to send a control signal to the first controllable switch, and the control signal is determined according to the feedback signal and / or the current signal.

3. The flyback power supply according to claim 2, characterized in that: The startup inhibition circuit is connected to the detection end, and is also used to send the inhibition signal to the detection end, and the inhibition signal is used to increase the current signal to reduce the conduction time in the control signal.

4. The flyback power supply according to claim 2, characterized in that: The output feedback circuit comprises: A parallel voltage stabilization integrated circuit, comprising a reference terminal, an anode terminal and a cathode terminal, wherein the reference terminal is connected to the first voltage dividing point, the anode terminal is grounded, and the cathode terminal is used to output a feedback current according to the voltage of the first voltage dividing point; The optical coupler comprises an input end and an output end, wherein the input end is connected to the parallel voltage regulator integrated circuit, and the output end is connected to the compensation end. The optical coupler is used to convert the feedback current into the feedback signal.

5. The flyback power supply according to claim 4, characterized in that: The startup inhibition circuit is connected to the reference terminal and the cathode terminal respectively, and the inhibition signal is used to increase the feedback current to change the feedback signal, and the changed feedback signal is used to reduce the conduction time in the control signal.

6. The flyback power supply according to claim 5, characterized in that: The startup inhibition circuit comprises: A second controllable switch, connected to the cathode end and the reference end respectively, and the second controllable switch is used to control the conduction or disconnection of the circuit from the cathode end to the reference end; A signal providing circuit comprises a capacitor and a resistor connected in series, wherein a connection point of the capacitor and the resistor is connected to a gate of the second controllable switch, the capacitor is connected to an output terminal of the secondary side, and the resistor is grounded. The signal providing circuit is used to send an inhibition signal to the second controllable switch during a startup phase of the flyback power supply, wherein the inhibition signal is used to control the second controllable switch to be in an on state to increase the feedback current.

7. The flyback power supply according to claim 3, characterized in that: The startup inhibition circuit comprises: A third controllable switch, connected to the reference voltage supply terminal and the detection terminal respectively, and the third controllable switch is used to control the conduction or disconnection of the circuit from the reference voltage supply terminal to the detection terminal; A comparison circuit having a positive input terminal, a negative input terminal and an output terminal, wherein the positive input terminal is connected to the reference voltage supply terminal, the negative input terminal is connected to the output terminal of the secondary side, and the output terminal is connected to the gate of the third controllable switch. The comparison circuit is used to send an inhibition signal to the third controllable switch during the startup phase of the flyback power supply, and the inhibition signal is used to control the third controllable switch to be in a conducting state to increase the current signal.

8. The flyback power supply according to claim 7, characterized in that: The negative input terminal is connected to the output terminal of the secondary side through the second voltage dividing point of the second resistor voltage dividing circuit, and the other end of the second resistor voltage dividing circuit is grounded. The positive input terminal is connected to the reference voltage supply terminal through the third voltage dividing point of the third resistor voltage dividing circuit, and the other end of the third resistor voltage dividing circuit is grounded.

9. The flyback power supply according to claim 2, characterized in that: The first controllable switch is grounded via a sampling resistor, and the detection end is connected to a connection point between the first controllable switch and the sampling resistor.

10. An electrical device, characterized in that: The invention comprises a flyback power supply as claimed in any one of claims 1 to 9.

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