A load impedance adaptive flyback power supply circuit and a method for implementing the same

Abstract

The application provides a load impedance adaptive flyback power supply circuit and an implementation method thereof, and the circuit comprises a filter circuit, a flyback power conversion circuit, an RCC auxiliary source power supply circuit, an output voltage and current acquisition and control circuit, a PWM pulse width modulation circuit and an isolation driving circuit; the application can be used for the working condition of a large range of load impedance variation, impedance adaptive adjustment, automatic switching of constant voltage and constant current double output modes, and limiting power output in the adjacent impedance state through a primary side current overcurrent protection circuit, so as to meet the voltage and current output requirements of the power supply in the full load range. Through the use of the circuit of the application, the bus current impact caused by the load variation can be reduced, the reliability and safety of the circuit are improved, the application can be applied to the isolation DC-DC power conversion with a large range of load impedance variation and different load states, and has better applicability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of flyback power supply circuit, and particularly relates to a load impedance adaptive flyback power supply circuit and an implementation method thereof. BACKGROUND

[0002] At present, the commonly used flyback power supply is generally in a single constant voltage output mode. When the load impedance of the flyback power supply becomes smaller, the output current increases, and the output power increases with the increase of the output current due to the constant output voltage. For the flyback power supply without primary side overcurrent protection function, when the output power exceeds the maximum output capacity of the power supply, the power supply may be burned out due to over power. For the flyback power supply with primary side overcurrent protection function, when the output power is too large to cause the primary side current of the converter to exceed the overcurrent protection threshold, the output drive duty cycle of the PWM controller of the power supply decreases, and the output voltage of the power supply decreases. At this time, the output voltage and current fluctuate with the load impedance, and the output of the power supply is not controlled. Therefore, as described above, the current flyback power supply is not suitable for the working condition with large load impedance variation range, cannot adjust the output mode according to the actual load variation, and cannot meet the use requirements of wide load range and dual output mode. SUMMARY

[0003] The present application provides a load impedance adaptive flyback power supply circuit and an implementation method thereof, and aims to solve the problem that the current flyback power supply is not suitable for the working condition with large load impedance variation range, cannot adjust the output mode according to the actual load variation, and cannot meet the use requirements of wide load range and dual output mode.

[0004] To achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0005] The present application provides a load impedance adaptive flyback power supply circuit, which comprises a filter circuit, a flyback power conversion circuit, an RCC auxiliary source power supply circuit, an output voltage and current acquisition and control circuit, a PWM pulse width modulation circuit and an isolation drive circuit. Wherein:

[0006] The input bus is filtered by the filter circuit to supply power to the flyback power conversion circuit and the RCC auxiliary source power supply circuit. The flyback power conversion circuit provides voltage and current for the power supply load after isolation conversion, and sends the output voltage and current acquisition signal to the output voltage and current acquisition and control circuit, and sends the primary side current acquisition signal IS to the PWM pulse width modulation circuit.

[0007] The RCC auxiliary source power supply circuit is used to provide voltage and current for the output voltage and current acquisition and control circuit and the PWM pulse width modulation circuit through isolation conversion.

[0008] The output voltage and current acquisition and control circuit is used to form a voltage and current loop feedback signal FFK based on the power supply output voltage and current acquisition signal.

[0009] The PWM pulse width modulation circuit is configured to perform power slow start, primary side over-current protection, current slope compensation and PWM pulse width adjustment based on the primary side current collection signal IS and the voltage current loop feedback signal FFK, and output a PWM drive signal to the isolation drive circuit.

[0010] The isolation drive circuit is configured to output a MOS tube drive signal based on the PWM drive signal, realize primary and secondary side ground isolation, and control the turn-on and turn-off of the primary side power MOS tube in the flyback power conversion circuit.

[0011] In some embodiments, the filter circuit includes a common mode filter circuit and a differential mode filter circuit, which are configured to eliminate common mode and differential mode interference between the bus and the internal circuit of the power supply.

[0012] In some embodiments, the flyback power conversion circuit is the main power conversion circuit of a flyback power supply, and is configured to complete the isolation conversion through a flyback DC-DC converter.

[0013] Further, the flyback power conversion circuit: collects the primary side current through a current transformer, and sends a primary side current collection signal IS to the PWM pulse width modulation circuit; receives an output drive signal from the isolation drive circuit, and realizes switch control and duty cycle adjustment of the primary side power MOS tube.

[0014] In some embodiments, the PWM pulse width modulation circuit includes a single-ended drive controller and its peripheral circuit, which receives the primary side current collection signal IS and the voltage current loop feedback signal FFK, and outputs the PWM drive signal.

[0015] In some embodiments, the RCC auxiliary source power supply circuit includes a high-frequency self-excited magnetic isolation RCC circuit, which realizes magnetic isolation and stable voltage output through self-excited drive.

[0016] In some embodiments, the output voltage and current collection and control circuit includes an output voltage collection circuit, an output voltage PID negative feedback control circuit, an output current collection circuit, an output current PID negative feedback control circuit, and a feedback signal comparison circuit.

[0017] Further, the output voltage and current collection and control circuit differentially amplifies the received power output voltage and current collection signal, compares the processed signal with the threshold voltage of the PID negative feedback control circuit, forms a voltage current loop feedback signal FFK, and sends it to the PWM pulse width modulation circuit.

[0018] In some embodiments, the isolation drive circuit converts the PWM drive signal into a MOS tube drive signal and sends it to the primary power MOS tube in the flyback power conversion circuit to control the MOS tube switch; by adjusting the output side drive resistance in the isolation drive circuit, the rising edge and falling edge waveforms of the MOS tube drive signal are adjusted, and the turn-on and turn-off speed of the MOS tube is adjusted.

[0019] The application further provides an implementation method of the load impedance adaptive flyback power supply circuit, comprising the following steps:

[0020] S1, filtering the input bus to obtain a filtered input signal; performing power conversion on the filtered input signal to provide voltage and current for the power supply load, and collecting a primary side current collection signal IS;

[0021] S2, the RCC auxiliary source power supply circuit provides voltage and current for the output voltage and current collection and control circuit and the PWM pulse width modulation circuit; the output voltage and current collection and control circuit performs differential amplification processing on the output voltage and current collection signal, and forms a voltage and current loop feedback signal FFK after loop operation;

[0022] S3, the PWM pulse width modulation circuit realizes power supply slow start, primary side overcurrent protection, current slope compensation and PWM pulse width adjustment based on the primary side current collection signal IS and the voltage and current loop feedback signal FFK, and generates a PWM drive signal;

[0023] S4, the isolation drive circuit outputs a MOS tube drive signal based on the PWM drive signal, realizes primary and secondary ground isolation, controls the turn-on and turn-off of the primary power MOS tube in the flyback power conversion circuit, and enables the flyback power supply to output voltage and current in the full load range.

[0024] Compared with the prior art, the load impedance adaptive flyback power supply circuit and the implementation method thereof have the following beneficial effects:

[0025] The application discloses a load impedance adaptive flyback power supply circuit, which comprises a filter circuit, a flyback power conversion circuit, an RCC auxiliary source power supply circuit, an output voltage and current collection and control circuit, a PWM pulse width modulation circuit and an isolation driving circuit.

[0026] The application realizes constant voltage and constant current dual-mode output automatic switching through a single topology, integrates a voltage source and a current source, reduces the number of used components, improves power supply power density and reliability, controls the production cost of the power supply, and has high economic value. BRIEF DESCRIPTION OF DRAWINGS

[0027] The accompanying drawings for describing the application are used to provide further understanding of the application, form a part of the application, and are used to explain the application and do not constitute improper limitation of the application.

[0028] Figure 1 The accompanying drawings for describing the application are used to provide further understanding of the application, form a part of the application, and are used to explain the application and do not constitute improper limitation of the application.

[0029] Figure 2 A principle schematic diagram of a filter circuit in the load impedance adaptive flyback power supply circuit and the implementation method thereof;

[0030] Figure 3 A principle schematic diagram of a flyback power conversion circuit in the load impedance adaptive flyback power supply circuit and the implementation method thereof;

[0031] Figure 4 A principle schematic diagram of an RCC auxiliary source power supply circuit in the load impedance adaptive flyback power supply circuit and the implementation method thereof;

[0032] Figure 5 A principle schematic diagram of an output voltage and current collection and control circuit in the load impedance adaptive flyback power supply circuit and the implementation method thereof;

[0033] Figure 6 A principle schematic diagram of a PWM pulse width modulation circuit in the load impedance adaptive flyback power supply circuit and the implementation method thereof;

[0034] Figure 7 A principle schematic diagram of an isolation driving circuit in the load impedance adaptive flyback power supply circuit and the implementation method thereof. DETAILED DESCRIPTION

[0035] In order to make the objects, technical solutions, and advantages of the embodiments of the present application clearer, the following will be combined with the accompanying drawings for the embodiments of the present application to make a clear and complete description of the technical solutions in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. The components of the embodiments of the present application described and shown in the accompanying drawings can be arranged and designed in various different configurations.

[0036] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative labor are within the scope of protection of the present application.

[0037] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

[0038] In the description of the embodiments of the present application, it should be noted that if the terms "upper", "lower", "horizontal", "inner" and the like indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, or the orientation or position relationship when the product of the present application is usually placed, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second" and the like are only used for differentiation and cannot be understood as indicating or implying relative importance.

[0039] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly inclined. For example, "horizontal" only means that its direction is relatively more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined.

[0040] In the description of the embodiments of the present application, it should be noted that unless otherwise explicitly specified and limited, if the terms "arrangement", "installation", "connection", "connection" appear, they should be understood in a broad sense, for example, they can be fixedly connected, or can be detachably connected, or integrally connected; can be mechanically connected, or can be electrically connected; can be directly connected, or can be indirectly connected through an intermediate medium; can be the communication between the two elements inside. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0041] As shown in Figure 1 The present application provides a load impedance adaptive flyback power supply circuit, which comprises a filter circuit, a flyback power conversion circuit, an RCC auxiliary source power supply circuit, an output voltage and current acquisition and control circuit, a PWM pulse width modulation circuit and an isolation driving circuit; wherein:

[0042] The input bus is filtered by the filter circuit to supply power to the flyback power conversion circuit and the RCC auxiliary source power supply circuit; the flyback power conversion circuit provides voltage and current for the power supply load after isolation conversion, and sends the output voltage and current acquisition signal to the output voltage and current acquisition and control circuit, and sends the primary side current acquisition signal IS to the PWM pulse width modulation circuit;

[0043] The RCC auxiliary source power supply circuit is used to provide voltage and current for the output voltage and current acquisition and control circuit and the PWM pulse width modulation circuit through isolation conversion;

[0044] The output voltage and current acquisition and control circuit is used to form a voltage and current loop feedback signal FFK based on the power supply output voltage and current acquisition signal;

[0045] The PWM pulse width modulation circuit is used for power slow start, primary side over-current protection, current slope compensation and PWM pulse width adjustment based on the primary side current collection signal IS and the voltage current loop feedback signal FFK, and outputs a PWM drive signal to the isolation drive circuit;

[0046] The isolation drive circuit is used for outputting a MOS tube drive signal based on the PWM drive signal, realizing primary and secondary side ground isolation, and controlling the turn-on and turn-off of the primary side power MOS tube in the flyback power conversion circuit.

[0047] The present application realizes adaptive adjustment of the flyback power output to the load impedance by collecting the power output voltage and current signals in real time and feeding back to the PWM pulse width modulation circuit for dynamic adjustment, and ensures stable output of the flyback power under different load conditions. The flyback power conversion circuit converts the voltage and current through isolation to provide the power load, improving the conversion efficiency. The RCC auxiliary source power supply circuit realizes magnetic isolation and stable output, reducing energy loss. The present application can realize stable output of voltage and current in the full load range by comprehensively applying output voltage and current collection, PID negative feedback control, PWM pulse width modulation and isolation drive, and has good applicability.

[0048] The functions of each circuit in the present application are further described as follows:

[0049] The filter circuit is composed of a common mode filter circuit and a differential mode filter circuit. The common mode and differential mode interference between the bus and the internal circuit of the power supply is eliminated through the common mode filter circuit and the differential mode filter circuit, so that the power supply has good electromagnetic compatibility characteristics;

[0050] The flyback power conversion circuit is the main power conversion circuit of the flyback power supply. The input bus is powered after being filtered by the filter circuit, and the isolation conversion is completed through the flyback DC-DC converter to provide the voltage and current required for the power load. The circuit collects the primary side current through the current transformer and sends the primary side current collection signal IS to the PWM pulse width modulation circuit to realize the primary side over-current protection function and limit the maximum output power of the power supply. The primary side power MOS tube of the circuit receives the output drive signal from the isolation drive circuit to realize switching control and duty cycle adjustment. The output side of the circuit collects the output voltage and output current signals and sends the output voltage and current collection signals to the output voltage and current collection and control circuit;

[0051] The RCC auxiliary source power supply circuit adopts a high-frequency self-excited magnetic isolation RCC circuit, which has high power density and small size. The input bus is powered after being filtered by the filter circuit, and the isolation conversion provides the voltage and current required for the output voltage and current collection and control circuit and the PWM pulse width modulation circuit to work;

[0052] Output voltage current acquisition and control circuit: the circuit receives output voltage current acquisition signals from the flyback power conversion circuit, respectively completes signal acquisition and processing through differential amplification circuit, compares the processed signals with threshold voltage of PID negative feedback control circuit, forms voltage loop feedback signals and current loop feedback signals, compares the two feedback signals, and takes the lower voltage as the signal of COMP end (output end of internal error amplifier) of PWM controller in PWM pulse width modulation circuit;

[0053] PWM pulse width modulation circuit: the circuit is based on single-ended drive controller (in actual working conditions, the single-ended drive controller can be selected but is not limited to UC1843), receives primary side current acquisition signal IS from the flyback power conversion circuit and feedback signal FFK from the output voltage current acquisition and control circuit, and realizes power slow start power-on, primary side overcurrent protection, current slope compensation, PWM pulse width regulation and other functions through its peripheral circuit, and sends the output PWM drive signal to the isolation drive circuit;

[0054] Isolation drive circuit: the circuit receives the PWM drive signal from the PWM pulse width modulation circuit, realizes primary and secondary ground isolation through a drive transformer, and sends the output drive signal to the primary power MOS tube in the flyback power conversion circuit to control the MOS tube switch.

[0055] The circuit structure and working mechanism of the load impedance adaptive flyback power supply circuit and the implementation method thereof will be analyzed below in combination with the drawings.

[0056] As shown in Figure 2 The filter circuit is composed of common mode filter circuit and differential mode filter circuit. The common mode filter circuit is composed of common mode filter inductor L1 and capacitors C1-C6, wherein the 1 pin of the common mode filter inductor L1 is connected to the bus positive line Vin+, the 2 pin of the common mode filter inductor L1 is connected to one end of the differential mode filter inductor L2, the 3 pin of the common mode filter inductor L1 is connected to the bus return line VinGnd, the 4 pin of the common mode filter inductor L1 is connected to the power supply return line VinGnd2 of the later stage power circuit, the 1 pin and the 3 pin of the common mode filter inductor L1 are homonymous, and the 2 pin and the 4 pin of the common mode filter inductor L1 are homonymous. One end of the filter capacitor C1 is connected to the 1 pin of the common mode filter inductor L1; the other end is connected to the filter capacitors C2 and C3, the other end of the filter capacitor C2 is connected to the 3 pin of the common mode filter inductor L1, and the other end of the filter capacitor C3 is connected to the shell ground. One end of the filter capacitor C5 is connected to the 2 pin of the common mode filter inductor L1, and the other end is connected to the filter capacitors C4 and C6, the other end of the filter capacitor C6 is connected to the 4 pin of the common mode filter inductor L1, and the other end of the filter capacitor C4 is connected to the shell ground.

[0057] The differential mode filter circuit is composed of a differential mode filter inductor L2 and capacitors C7 and C8. One end of the differential mode filter inductor L2 is connected to the pin 2 of the common mode filter inductor L1, and the other end is connected to the positive line Vin2+ of the power supply of the subsequent power circuit. One end of the filter capacitor C7 is connected to the pin 2 of the common mode filter inductor L1, and the other end is connected to the return line VinGnd2 of the power supply of the subsequent power circuit. One end of the filter capacitor C8 is connected to the positive line Vin2+ of the power supply of the subsequent power circuit, and the other end is connected to the return line VinGnd2 of the power supply of the subsequent power circuit.

[0058] The common mode filter circuit and the differential mode filter circuit are used to eliminate the common mode and differential mode interference between the bus and the internal circuit of the power supply, so that the power supply has good electromagnetic compatibility characteristics. The values of the filter inductors and capacitors are determined according to the actual working conditions.

[0059] As shown in Figure 3 The flyback power conversion circuit is composed of a primary current collection circuit, an RCD voltage spike absorption circuit, a flyback power transformer T1, a power MOS tube Q1 and a gate-source parallel resistor R4, an output rectifier diode V1, an output filter capacitor C9, an output current sampling resistor R2 and a parallel filter capacitor C13, and an output voltage sampling filter capacitor C11.

[0060] The primary current collection circuit is composed of a current transformer L3, a magnetic reset resistor R3, a filter capacitor C12, and a signal output diode V3. The pin 1 of the current transformer L3 is connected to the positive line Vin2+ of the power supply, the pin 2 of the current transformer L3 is connected to the pin 1 of the flyback power transformer T1, the anode of the signal output diode V3 is connected to the pin 3 of the current transformer L3, and the cathode of the signal output diode V3 is connected to the CS end (current detection end) of the PWM controller in the PWM pulse width modulation circuit. The magnetic reset resistor R3 is connected in parallel with the filter capacitor C12, one end of which is connected to the pin 3 of the current transformer L3, and the other end of which is connected to the pin 4 of the current transformer L3. The anode of the signal output diode V3 is connected to the pin 3 of the current transformer L3, and the cathode of the signal output diode V3 is connected to the CS end (current detection end) of the PWM controller in the PWM pulse width modulation circuit.

[0061] The primary current collection circuit collects the primary current through the current transformer L3 and sends the primary current collection signal IS to the PWM pulse width modulation circuit, thereby realizing primary overcurrent protection. The magnetic reset resistor R3 functions to reset the current transformer when the primary current is zero, thereby avoiding the magnetic saturation of the current transformer.

[0062] The RCD voltage spike absorption circuit in the flyback power conversion circuit is composed of an absorption resistor R1, an absorption capacitor C10 and a diode V2. The absorption resistor R1 is connected in parallel with the absorption capacitor C10, one end of which is connected to pin 1 of the flyback power transformer T1, and the other end of which is connected to the cathode of the diode V2. The anode of the diode V2 is connected to pin 2 of the flyback power transformer T1. The RCD voltage spike absorption circuit functions to absorb the drain-source voltage spike of the power MOS tube Q1 when the power MOS tube Q1 is turned off, so as to avoid excessive voltage stress of the power MOS tube when it is turned off.

[0063] The drain of the power MOS tube Q1 in the flyback power conversion circuit is connected to pin 2 of the flyback power transformer T1, the source is connected to the power circuit supply return line VinGnd2, and the gate is connected to the output Vgs+ of the isolation drive circuit. The gate-source parallel resistor R4 has one end connected to the gate of the MOS tube Q1 and the other end connected to the source of the MOS tube Q1. Pin 3 of the flyback power transformer T1 is connected to the anode of the output rectifier diode V1, and pin 4 is connected to one end of the output filter capacitor C9, which has the same name as the other end of pin 4 and the same name as pin 2 and pin 3. The cathode of the output rectifier diode V1 is connected to the other end of the output filter capacitor C9, i.e. the output supply positive terminal Vout+ of the power supply. The output current sampling resistor R2 and its parallel filter capacitor C13 are connected in parallel, one end of which is connected to pin 4 of the flyback power transformer T1, and the other end of which is connected to the output supply ground VoutGnd of the power supply. The output voltage sampling filter capacitor C11 has one end connected to the output supply positive terminal Vout+ of the power supply and the other end connected to the output supply ground VoutGnd of the power supply.

[0064] The power MOS tube Q1 in the flyback power conversion circuit receives the output drive signal of the isolation drive circuit, realizes switching control and duty cycle adjustment, and realizes primary and secondary magnetic isolation through the flyback transformer T1. The basic working principle is as follows: when the power MOS tube Q1 is turned on, the flyback transformer T1 stores energy, the output rectifier diode V1 is cut off, and the output filter capacitor C9 supplies power to the load of the subsequent power supply; when the power MOS tube Q1 is turned off, the flyback transformer T1 supplies power to the secondary side, the output rectifier diode V1 is turned on, and the output filter capacitor C9 is charged, while the load of the subsequent power supply is supplied with power.

[0065] As shown in Figure 4 The RCC auxiliary source power supply circuit adopts a high-frequency self-excited magnetic isolation RCC circuit, which is composed of a flyback transformer T2, an NPN triode Q2, diodes V4-V8, a voltage stabilizing diode V9, capacitors C14-C17, a starting resistor R5 and a resistor R6.

[0066] The one end of the starting resistor R5 is connected with the positive line Vin2+ of the power supply circuit, i.e. the 1 pin of the flyback transformer T2, and the other end is connected with the base of the triode Q2. The collector of the triode Q2 is connected with the 2 pin of the flyback transformer T2, and the emitter of the triode Q2 is connected with the return line VinGnd2 of the power supply circuit. The cathode of the diode V7 is connected with the base of the triode Q2, and the anode of the diode V7 is connected with the emitter of the triode Q2. The cathode of the voltage stabilizing diode V9 is connected with the base of the triode Q2, and the anode of the voltage stabilizing diode V9 is connected with the anode of the diode V5. The one end of the resistor R6 is connected with the base of the triode Q2, and the other end is connected with the cathode of the diode V6. The capacitor C15 is connected with the diode V6 in parallel, and the anode of the diode V6 is connected with the cathode of the diode V5, i.e. the 3 pin of the flyback transformer T2. The one end of the capacitor C16 is connected with the anode of the diode V5, and the other end is connected with the 4 pin of the flyback transformer T2, i.e. the return line VinGnd2 of the power supply circuit. The anode of the diode V4 is connected with the 5 pin of the flyback transformer T2, and the cathode of the diode V4 is connected with the positive end Vcc+ of the auxiliary power supply. The one end of the capacitor C14 is connected with the positive end Vcc+ of the auxiliary power supply, and the other end is connected with the 6 pin of the flyback transformer T2, i.e. the return line CGnd of the auxiliary power supply. The anode of the diode V8 is connected with the 7 pin of the flyback transformer T2, and the cathode of the diode V8 is connected with the return line CGnd of the auxiliary power supply. The one end of the capacitor C17 is connected with the return line CGnd of the auxiliary power supply, and the other end is connected with the 8 pin of the flyback transformer T2, i.e. the negative end Vcc- of the auxiliary power supply. The 1 pin, 3 pin, 6 pin and 8 pin of the flyback transformer T2 are the same end, and the 2 pin, 4 pin, 5 pin and 7 pin of the flyback transformer T2 are the same end.

[0067] The RCC auxiliary power supply circuit realizes the magnetic isolation and stable output by the self-excitation driving. The voltage stabilizing diode V9 controls the triode Q2 to be turned on by the current shunt with the base of the triode Q2. The capacitor C16 is a voltage storage capacitor. When the triode Q2 is turned on, the voltage stabilizing diode V9 is reversely broken down, and the voltage of the capacitor C16 is about the reverse breakdown voltage of the voltage stabilizing diode V9. When the triode Q2 is turned off, the voltage of the auxiliary winding Nb of the flyback transformer T2 is reversed, the diode V5 is turned on, and the capacitor C16 provides a charging circuit. The voltage of the auxiliary winding Nb is about the voltage of the capacitor C16, i.e. the reverse breakdown voltage of the voltage stabilizing diode V9. At this time, the output voltage of the RCC auxiliary power supply circuit is proportional to the voltage of the auxiliary winding Nb, and the RCC auxiliary power supply circuit realizes the output voltage stabilization control by the cooperation of the capacitor C16 and the voltage stabilizing diode V9. Since the voltage stabilization function of the circuit is realized by the breakdown of the voltage stabilizing diode, the high-precision voltage stabilizing diode can be used to improve the output voltage accuracy. The current shunt control of the voltage stabilizing diode and the base of the switching triode realizes the feedback control function of the power output. The circuit can adapt to a wide input voltage range. The secondary side of the RCC auxiliary power supply circuit adopts half-wave rectification to supply power for the output voltage and current collection and control circuit and the PWM pulse width modulation circuit.

[0068] As Figure 5As shown, the output voltage current acquisition and control circuit is composed of an output voltage acquisition circuit, an output voltage PID negative feedback control circuit, an output current acquisition circuit, an output current PID negative feedback control circuit, and a feedback signal comparison circuit, wherein:

[0069] The output voltage acquisition circuit is composed of differential adjusting resistors R7-R10, filter capacitors C18 and C19, an operational amplifier N1, power supply current limiting protection resistors R11 and R12, power supply filter capacitors C20 and C21, and an operational amplifier gain resistor R13. One end of the differential adjusting resistor R8 is connected to the positive end Vout+ of the output voltage acquisition signal, and the other end is connected to the non-inverting terminal of the operational amplifier N1. The differential adjusting resistor R9 and the filter capacitor C18 are connected in parallel, one end of which is connected to the non-inverting terminal of the operational amplifier N1, and the other end is connected to the auxiliary source supply return line CGnd. One end of the differential adjusting resistor R7 is connected to the negative end VoutGnd of the output voltage acquisition signal, and the other end is connected to the inverting terminal of the operational amplifier N1. The differential adjusting resistor R10 and the filter capacitor C19 are connected in parallel, one end of which is connected to the inverting terminal of the operational amplifier N1, and the other end is connected to the auxiliary source supply return line CGnd. One end of the power supply current limiting protection resistor R11 is connected to the negative end Vcc- of the auxiliary source supply, and the other end is connected to the negative power supply terminal of the operational amplifier N1. One end of the power supply filter capacitor C20 is connected to the negative power supply terminal of the operational amplifier N1, and the other end is connected to the auxiliary source supply return line CGnd. One end of the power supply current limiting protection resistor R12 is connected to the positive end Vcc+ of the auxiliary source supply, and the other end is connected to the positive power supply terminal of the operational amplifier N1. One end of the power supply filter capacitor C21 is connected to the positive power supply terminal of the operational amplifier N1, and the other end is connected to the auxiliary source supply return line CGnd. The operational amplifier gain resistor R13 is connected to the gain setting terminal of the operational amplifier N1. The reference terminal of the operational amplifier N1 is connected to the auxiliary source supply return line CGnd.

[0070] The output voltage acquisition circuit converts the power supply output voltage acquisition signal into the input signal of the subsequent output voltage PID negative feedback control circuit through the differential adjusting resistors R7-R10 and the operational amplifier gain resistor R13, and simultaneously realizes high resistance isolation between the power supply output power ground VoutGnd and the internal control ground CGnd, avoiding the influence of the power supply load side ground line disturbance on the power supply steady-state operation during the power supply operation.

[0071] The output voltage PID negative feedback control circuit is composed of double operational amplifier N2 (operational amplifier A part), resistors R21-R27 and capacitors C22-C27. Among them, the resistor R21 and the capacitor C22 are connected in series and then connected in parallel with the resistor R22, forming a resistance-capacitance network, one end of which is connected to the output end of the operational amplifier N1 in the output voltage acquisition circuit, and the other end is connected to the inverting terminal of the operational amplifier N2A. The resistor R25 and the capacitor C25 are connected in series and then connected in parallel with the capacitor C24, forming a resistance-capacitance network, one end of which is connected to the inverting terminal of the operational amplifier N2A, and the other end is connected to the output terminal of the operational amplifier N2A. One end of the resistor R23 is connected to the Vref end (reference voltage end) of the PWM controller in the PWM pulse width modulation circuit, and the other end is connected to the non-inverting terminal of the operational amplifier N2A. The resistor R24 and the capacitor C23 are connected in parallel, one end of which is connected to the non-inverting terminal of the operational amplifier N2A, and the other end is connected to the auxiliary source power return line CGnd. The power supply current limiting protection resistor R26 is connected to the negative end Vcc- of the auxiliary source power supply at one end, and the other end is connected to the negative power supply end of the operational amplifier N2. The power supply filtering capacitor C26 is connected to the negative power supply end of the operational amplifier N2 at one end, and the other end is connected to the auxiliary source power return line CGnd. The power supply current limiting protection resistor R27 is connected to the positive end Vcc+ of the auxiliary source power supply at one end, and the other end is connected to the positive power supply end of the operational amplifier N2. The power supply filtering capacitor C27 is connected to the positive power supply end of the operational amplifier N2 at one end, and the other end is connected to the auxiliary source power return line CGnd.

[0072] The output voltage PID negative feedback control circuit receives the voltage signal converted from the output voltage acquisition circuit, compares it with the threshold voltage at the non-inverting terminal of the operational amplifier, performs negative feedback PID loop operation, and finally forms the output voltage feedback signal. The resistors R23 and R24 are threshold voltage dividing resistors, which can set appropriate threshold voltages by selecting different proportional resistance values.

[0073] The output current acquisition circuit is composed of differential adjusting resistors R14-R17, filter capacitors C33 and C35, an operational amplifier N3, power supply current limiting protection resistors R18 and R19, power supply filter capacitors C32 and C34, and an operational amplifier gain resistor R20.

[0074] The output current acquisition circuit converts the power supply output current acquisition signal into an input signal of the output current PID negative feedback control circuit in the rear stage through the differential adjusting resistors R14-R17 and the operational amplifier gain resistor R20, and simultaneously realizes high resistance isolation of the power supply output power ground VoutGnd and the internal control ground CGnd, so as to avoid the influence of the ground line disturbance of the power supply load side on the power supply steady state operation in the power supply working process.

[0075] The output current PID negative feedback control circuit of the present application is composed of a double operational amplifier N2 (operational amplifier B part), resistors R28-R32 and capacitors C28-C31. The resistor R29 and the capacitor C30 are connected in series and then connected in parallel with the resistor R30, forming a resistance-capacitance network, one end of which is connected to the output end of the operational amplifier N3 in the output current acquisition circuit, and the other end is connected to the inverting terminal of the operational amplifier N2B. The resistor R28 and the capacitor C29 are connected in series and then connected in parallel with the capacitor C28, forming a resistance-capacitance network, one end of which is connected to the inverting terminal of the operational amplifier N2B, and the other end is connected to the output end of the operational amplifier N2B. The resistor R31 is connected to the Vref end of the PWM controller in the PWM pulse width modulation circuit at one end, and connected to the non-inverting terminal of the operational amplifier N2B at the other end. The resistor R32 and the capacitor C31 are connected in parallel, one end of which is connected to the non-inverting terminal of the operational amplifier N2B, and the other end is connected to the auxiliary source supply loop CGnd.

[0076] The output current PID negative feedback control circuit receives the voltage signal converted from the output current acquisition circuit, compares it with the threshold voltage of the inverting input terminal of the operational amplifier, carries out negative feedback PID loop operation, and finally forms the output current feedback signal. Resistors R31 and R32 are threshold voltage dividing resistors, and the appropriate threshold voltage is set by selecting different proportional resistors.

[0077] The feedback signal comparison circuit is composed of resistors R33 and R34 and diodes V10-V13. One end of resistor R33 is connected to the output terminal of operational amplifier N2A, the other end is connected to the cathodes of diodes V10 and V11, the anode of diode V10 is connected to auxiliary source supply loop CGnd, and the anode of diode V11 is connected to the COMP terminal of the PWM controller in the PWM pulse width modulation circuit. One end of resistor R34 is connected to the output terminal of operational amplifier N2B, the other end is connected to the cathodes of diodes V12 and V13, the anode of diode V13 is connected to auxiliary source supply loop CGnd, and the anode of diode V12 is connected to the COMP terminal of the PWM controller in the PWM pulse width modulation circuit.

[0078] The feedback signal comparison circuit receives the output voltage feedback signal from the output voltage PID negative feedback control circuit and the output current feedback signal from the output current PID negative feedback control circuit, compares the two, outputs the lower voltage value, and sends the finally formed feedback signal to the COMP terminal of the PWM controller in the PWM pulse width modulation circuit to realize closed-loop regulation. Diodes V10 and V13 are negative voltage clamping diodes, which prevent the finally formed feedback signal from being negative voltage and affecting the normal operation of the PWM pulse width modulation circuit.

[0079] The overall working mechanism of the output voltage and current acquisition and control circuit is as follows: when the power supply output is high voltage and small current, the output current acquisition circuit outputs low voltage, the output voltage of the output current PID negative feedback control circuit is higher than that of the output voltage PID negative feedback control circuit, and the power supply works in the voltage loop to realize constant voltage stable output. When the output current of the power supply increases to the set constant current output threshold, the output voltage of the output current PID negative feedback control circuit is lower than that of the output voltage PID negative feedback control circuit, and the power supply works in the current loop to realize constant current stable output. Thus, the power supply realizes adaptive adjustment of constant voltage and constant current dual output modes according to the load impedance.

[0080] Furthermore, in the output voltage and current acquisition and control circuit of the application, as a preferred embodiment, a one-stage operational amplifier reverse following circuit can be added in the rear stage of the output voltage acquisition circuit, the circuit output signal is the telemetry signal of the power output voltage, thereby realizing the power output voltage telemetry function; a one-stage operational amplifier reverse following circuit can be added in the rear stage of the output current acquisition circuit, the circuit output signal is the telemetry signal of the power output current, thereby realizing the power output current telemetry function; the Vref level in the output voltage PID negative feedback control circuit can be replaced by an external injection level, thereby realizing the power output voltage remote control function; the Vref level in the output current PID negative feedback control circuit can be replaced by an external injection level, thereby realizing the power output current remote control function.

[0081] As shown in Figure 6 The PWM pulse width modulation circuit is composed of PNP transistor Q3, diode V14, resistors R35-R41, capacitors C36-C41 and PWM controller U1.

[0082] Wherein, one end of the resistor R35 is connected to the cathode of the diode V14, and the other end is connected to the Vref end of the PWM controller U1; the anode of the diode V14 is connected to the base of the triode Q3; one end of the resistor R37 is connected to the Vref end of the PWM controller U1, and the other end is connected to the anode of the diode V14; one end of the capacitor C36 is connected to the base of the triode Q3, and the other end is connected to the collector of the triode Q3, that is, the auxiliary source power return line CGnd; one end of the resistor R38 is connected to the Vref end of the PWM controller U1, and the other end is connected to the emitter of the triode Q3, that is, the COMP end of the PWM controller U1; one end of the resistor R39 is connected to the FB end (the inverting input end of the internal error amplifier) of the PWM controller U1, and the other end is connected to the auxiliary source power return line CGnd; the capacitor C37 and the resistor R40 are connected in parallel, one end of which is connected to the CS end of the PWM controller U1, and the other end is connected to the auxiliary source power return line CGnd; one end of the capacitor C38 is connected to the CS end of the PWM controller U1, and the other end is connected to the RtCt end (the internal fixed-frequency oscillator setting end) of the PWM controller U1; one end of the capacitor C39 is connected to the RtCt end of the PWM controller U1, and the other end is connected to the auxiliary source power return line CGnd; one end of the resistor R41 is connected to the RtCt end of the PWM controller U1, and the other end is connected to the Vref end of the PWM controller U1; one end of the capacitor C41 is connected to the Vref end of the PWM controller U1, and the other end is connected to the auxiliary source power return line CGnd; one end of the capacitor C40 is connected to the Vcc end (the power supply end) of the PWM controller U1, and the other end is connected to the auxiliary source power return line CGnd; one end of the resistor R36 is connected to the auxiliary source power positive end Vcc+, and the other end is connected to the Vcc end of the PWM controller U1; the COMP end of the PWM controller U1 receives the feedback signal FFK from the output voltage and current acquisition and control circuit, and the OUT end (the driving output end) of the PWM controller U1 transmits the PWM driving signal PWM-out to the rear-stage isolation driving circuit.

[0083] The PWM pulse width modulation circuit is based on a single-ended driving controller Figure 6 The PWM controller U1 is UC1843, and in actual working conditions, the single-ended driving controller can be selected but is not limited to UC1843, receives the primary side current acquisition signal IS from the flyback power conversion circuit and the feedback signal FFK from the output voltage and current acquisition and control circuit, and through its peripheral circuit, realizes the functions of power supply slow start power-on, primary side overcurrent protection, current slope compensation, PWM pulse width regulation, etc., and sends the output PWM driving signal to the isolation driving circuit. By adjusting the parameters of the peripheral circuit, the power supply slow start power-on time, the working frequency, and the appropriate primary side overcurrent protection threshold can be adjusted.

[0084] As Figure 7As shown, the isolation driving circuit is composed of diodes V15-V18, resistors R42-R45, capacitors C42 and C43, and driving transformer T3.

[0085] In the isolation driving circuit of the application, the capacitor C42 is connected in parallel with the diode V15, the cathode of the diode V15 is connected to the OUT terminal of the PWM controller U1 in the PWM pulse width modulation circuit, and the anode of the diode V15 is connected to one end of the resistor R42; the other end of the resistor R42 is connected to the 1 pin of the driving transformer T3; the 2 pin of the driving transformer T3 is connected to the GND terminal (power supply ground terminal) of the PWM controller U1 in the PWM pulse width modulation circuit, that is, the auxiliary source power supply return line CGnd; the capacitor C43 is connected in parallel with the resistor R43, one end of which is connected to the 3 pin of the driving transformer T3, and the other end is connected to the cathode of the diode V16; the anode of the diode V16 is connected to the 4 pin of the driving transformer T3, that is, the output driving ground VinGnd2 (power circuit power supply return line VinGnd2); the 1 pin and the 3 pin of the driving transformer T3 are the same name terminals, and the 2 pin and the 4 pin are the same name terminals; the diode V17 is connected in parallel with the resistor R44, the cathode of the diode V17 is connected to the cathode of the diode V16, and the anode of the diode V17 is connected to the anode of the diode V18; the diode V18 is connected in parallel with the resistor R45, and the cathode of the diode V18 is the output Vgs+ terminal of the isolation driving circuit, which is connected to the gate of the power MOS tube Q1 in the flyback power conversion circuit.

[0086] In the isolation driving circuit of the application, the capacitor C42 is a primary side direct current blocking capacitor, which can avoid the existence of direct current component in the primary side current of the driving transformer, thereby preventing the transformer from being saturated. The capacitor C43 and the diode V16 can solve the problem that the output driving voltage amplitude of the circuit changes with the duty cycle in the case of single-ended driving on the input side of the circuit. The resistor R42, the diode V15 and the resistor R43 can solve the remaining driving problem of the circuit after the input power is turned off, so that the capacitors C42 and C43 are quickly discharged and the driving transformer T3 is quickly magnetically reset after the input power is turned off. When the output is high, the diode V18 is turned on, and the resistor R44 is an output driving rising edge adjustment resistor; when the output is low, the diode V17 is turned on, and the resistor R45 is an output driving falling edge adjustment resistor. By adjusting the resistance values of the resistors R44 and R45, the rising edge and falling edge waveforms of the output driving signal of the circuit can be adjusted, so that the turn-on and turn-off speed of the MOS tube is adjusted, and the problems such as oscillation and voltage spike caused by the distributed parameters in the power circuit are solved.

[0087] In summary, the load impedance adaptive flyback power supply circuit and the implementation method thereof can improve the stability of the system, enhance the anti-interference ability of the system, realize load impedance adaptive output regulation, and optimize the power supply efficiency. In addition, the application can improve the control precision and flexibility, simplify the circuit system, and improve the maintenance convenience.

[0088] Finally, it needs to be explained that the above is only the preferred embodiment of the present application, and does not limit the present application in any form; anyone skilled in the art can easily implement the present application according to the description and the above; however, anyone skilled in the art can make some changes, modifications and equivalent changes within the scope of the technical solutions of the present application without departing from the scope of the present application, and the equivalent embodiments of the present application are disclosed; at the same time, any equivalent changes, modifications and evolution of the above embodiments according to the essence of the present application are still within the protection scope of the technical solutions of the present application.

Claims

1. A load impedance adaptive flyback power supply circuit, characterized in that, The circuit includes a filter circuit, a flyback power converter circuit, an RCC auxiliary power supply circuit, an output voltage and current acquisition and control circuit, a PWM pulse width modulation circuit, and an isolation drive circuit; wherein: After being filtered by the filter circuit, the input bus supplies power to the flyback power converter circuit and the RCC auxiliary power supply circuit. After completing the isolation conversion, the flyback power converter circuit provides voltage and current to the power load and sends its output voltage and current acquisition signal to the output voltage and current acquisition and control circuit, and sends the primary current acquisition signal IS to the PWM pulse width modulation circuit. The RCC auxiliary power supply circuit is used to: provide voltage and current to the output voltage and current acquisition and control circuit and the PWM pulse width modulation circuit through isolation transformation; The output voltage and current acquisition and control circuit is used to: generate a voltage and current loop feedback signal FFK based on the power supply output voltage and current acquisition signal; The PWM pulse width modulation circuit is used for: power supply soft start, primary side overcurrent protection, current slope compensation and PWM pulse width adjustment based on the primary side current acquisition signal IS and voltage and current loop feedback signal FFK, and outputs PWM drive signal to the isolation drive circuit. The isolation drive circuit is used to: output MOS transistor drive signals based on PWM drive signals to achieve primary and secondary side ground isolation, and control the turn-on and turn-off of the primary side power MOS transistor in the flyback power converter circuit.

2. The load impedance adaptive flyback power supply circuit according to claim 1, characterized in that, The filtering circuit includes a common-mode filtering circuit and a differential-mode filtering circuit, which are used to eliminate common-mode and differential-mode interference between the bus and the internal circuit of the power supply.

3. The load impedance adaptive flyback power supply circuit according to claim 1, characterized in that, The flyback power conversion circuit is the main power conversion circuit of the flyback power supply, and the flyback power conversion circuit is used to complete the isolation conversion through the flyback DC-DC converter.

4. The load impedance adaptive flyback power supply circuit according to claim 3, characterized in that, The flyback power converter circuit: acquires the primary current through a current transformer and sends the primary current acquisition signal IS to the PWM pulse width modulation circuit; receives the output drive signal from the isolation drive circuit to realize the switching control and duty cycle adjustment of the primary power MOSFET.

5. The load impedance adaptive flyback power supply circuit according to claim 1, characterized in that, The PWM pulse width modulation circuit includes a single-ended drive controller and its peripheral circuits, which receives the primary current acquisition signal IS and the voltage and current loop feedback signal FFK, and outputs the PWM drive signal.

6. The load impedance adaptive flyback power supply circuit according to claim 1, characterized in that, The RCC auxiliary power supply circuit includes a high-frequency self-excited magnetically isolated RCC circuit, which achieves magnetically isolated regulated output through self-excited driving.

7. The load impedance adaptive flyback power supply circuit according to claim 1, characterized in that, The output voltage and current acquisition and control circuit includes an output voltage acquisition circuit, an output voltage PID negative feedback control circuit, an output current acquisition circuit, an output current PID negative feedback control circuit, and a feedback signal comparison circuit.

8. The load impedance adaptive flyback power supply circuit according to claim 7, characterized in that, The output voltage and current acquisition and control circuit performs differential amplification processing on the received power output voltage and current acquisition signals, and compares the processed signal with the threshold voltage of the PID negative feedback control circuit to form a voltage and current loop feedback signal FFK, which is then sent to the PWM pulse width modulation circuit.

9. The load impedance adaptive flyback power supply circuit according to claim 1, characterized in that, The isolation drive circuit isolates and transforms the PWM drive signal into a MOSFET drive signal, and sends it to the primary-side power MOSFET in the flyback power converter circuit to control the switching of the MOSFET. By adjusting the output-side drive resistor in the isolation drive circuit, the rising and falling edge waveforms of the MOSFET drive signal are adjusted, thereby adjusting the turn-on and turn-off speed of the MOSFET.

10. The method for implementing the load impedance adaptive flyback power supply circuit according to any one of claims 1-9, characterized in that, Includes the following steps: S1. Filter the input bus to obtain the filtered input signal; perform power conversion on the filtered input signal to provide voltage and current to the power supply load, and acquire the primary current acquisition signal IS. S2 and RCC auxiliary power supply circuits provide voltage and current to the output voltage and current acquisition and control circuit and the PWM pulse width modulation circuit; the output voltage and current acquisition and control circuit performs differential amplification on the output voltage and current acquisition signal, and forms the voltage and current loop feedback signal FFK after loop operation; S3, the PWM pulse width modulation circuit is based on the primary side current acquisition signal IS and the voltage and current loop feedback signal FFK to realize power supply soft start, primary side overcurrent protection, current slope compensation and PWM pulse width adjustment, and generate PWM drive signal; S4. The isolation drive circuit outputs a MOSFET drive signal based on the PWM drive signal to achieve primary and secondary side ground isolation, and controls the turn-on and turn-off of the primary side power MOSFET in the flyback power conversion circuit, so that the flyback power supply can output voltage and current across the entire load range.

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