A voltage stabilizing control circuit applied to a multi-output flyback topology

Abstract

The application discloses a kind of applied to the steady voltage control circuit of multiple output flyback topology, it is related to the auxiliary power supply power supply field of multiple output, including transformer, primary side drive switch circuit, feedback control loop and several groups of secondary side output loop and load simulation circuit, by introducing a load simulation circuit consisting of diode, capacitor and resistance in key secondary output loop, and feedback sampling point is moved to the capacitor, by fine design, the time constant of load simulation circuit is matched with the load time constant of each output loop, so that the load change of non-steady voltage road is dynamically " mapped " to feedback end, this design can intelligently guide controller to adjust duty cycle, ensure that each output voltage can be maintained above rated value under all load conditions, fundamentally avoid system downtime, the circuit with extremely low cost significantly improves the reliability and load adaptability of power supply.

Description

Technical Field

[0001] This invention relates to the field of auxiliary power supply for multi-output circuits, specifically a voltage regulation control circuit applied to a multi-output flyback topology. Background Technology

[0002] Generally, for a multi-flyback topology, each output corresponds to a transformer winding. Since the transformer is not ideal, there is leakage inductance between each group of coils. The presence of this leakage inductance makes the cross-regulation between each path very poor, especially when the regulated circuit is at zero load and the unregulated circuit is at full load. At this time, the voltage of the unregulated circuit will drop below the error voltage, which will cause the entire system to malfunction or even restart. Summary of the Invention

[0003] The purpose of this invention is to provide a voltage regulation control circuit for a multi-output flyback topology to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a voltage regulation control circuit applied to a multi-output flyback topology, comprising a transformer T1, a primary-side drive switch circuit, a feedback control loop and several sets of secondary-side output loops, and further comprising a load simulation circuit, wherein the input terminal of the load simulation circuit is coupled to one of the sets of secondary-side output loops, the output terminal is connected to the ground reference corresponding to the secondary-side output loop, and the voltage sampling point of the feedback control loop is connected to the load simulation circuit;

[0005] The load simulation circuit is configured to generate a simulated load signal based on the voltage change of the secondary output circuit, and apply the signal to the voltage sampling point of the feedback control circuit, so that the feedback control circuit adjusts the duty cycle of the primary drive switch circuit according to the load condition of the secondary output circuit, thereby maintaining the voltage of all secondary output circuits within a set range.

[0006] Preferably, the load simulation circuit includes a diode Ds, a polarized capacitor Cs, and a resistor Rs. The anode of the diode Ds is coupled to the secondary output circuit. The polarized capacitor Cs and the resistor Rs are connected in parallel, with one end connected to the cathode of the diode Ds and the other end connected to the ground reference corresponding to the secondary output circuit. The voltage sampling point of the feedback control circuit is connected to the cathode of the diode Ds.

[0007] Preferably, the feedback control loop includes an optocoupler, a voltage divider sampling unit, and a voltage regulator unit. The voltage divider sampling unit includes resistors R2 and R3 connected in series. The cathode of the diode Ds is connected between resistors R2 and R3. The other end of resistor R2 is connected to the anode of the optocoupler. One end of the voltage regulator unit is connected to the cathode of the optocoupler, and the other end is grounded.

[0008] Preferably, the voltage regulator unit includes a voltage regulator integrated component IC2 and a resistor R4. One end of the resistor R4 is connected to the resistor R3, and the other end is connected to the anode of the voltage regulator integrated component IC2. The cathode of the voltage regulator integrated component IC2 is connected to the cathode of the optocoupler.

[0009] Preferably, the secondary output circuit includes a diode Dn, an inductor Ln, a polarized capacitor Cn, and a load RLn. The polarized capacitor Cn and the load RLn are connected in parallel. The cathode of the diode Dn is connected to the polarized capacitor Cn, and the anode is connected to the inductor Ln. The other end of the inductor Ln is connected to the polarized capacitor Cn. The anode of the diode Ds is connected between the inductor Ln and the diode Dn.

[0010] Preferably, the primary-side drive switch circuit includes a MOSFET Q1, a drive diode, a resistor R1, and a non-polarized capacitor C3. The non-polarized capacitor C3 is connected in parallel with the resistor R1 and then connected to the cathode of the drive diode. The anode of the drive diode is connected to the MOSFET Q1.

[0011] Preferably, the time constant of the polarized capacitor Cs and the resistor Rs is on the same order of magnitude as the time constant of any of the secondary output circuits under rated load.

[0012] Preferably, the ratio of the time constant of the polarized capacitor Cs and the resistor Rs to the time constant of the secondary output circuit is between 0.2 and 5.

[0013] Preferably, the resistance value of the resistor Rs is set such that its power consumption at the rated output voltage is less than 100 milliwatts.

[0014] In summary, the beneficial effects of this invention are:

[0015] This invention cleverly enables the power supply control system to sense load changes in unregulated output circuits by introducing a load simulation circuit composed of diodes, capacitors, and resistors, and using its voltage as a feedback signal. The core of this invention lies in designing a time constant that matches the time constant of each output circuit, thereby dynamically simulating the load characteristics of heavily loaded branches. This guides the controller to promptly increase energy supply when auxiliary circuits are heavily loaded, fundamentally solving the problem of poor cross-regulation caused by transformer leakage inductance. At extremely low cost, it ensures that all output branches maintain a stable voltage no lower than the rated value under drastic load changes, effectively preventing system downtime or restarts, and significantly improving the reliability, load adaptability, and cost-effectiveness of the power supply. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of a voltage regulation control circuit applied to a multi-output flyback topology according to the present invention.

[0018] Figure 2 This is a schematic diagram of a voltage regulation control circuit applied to a multi-output flyback topology according to the present invention.

[0019] Figure 3 This is a prior art circuit diagram of a voltage regulation control circuit applied to a multi-output flyback topology according to an embodiment of the present invention. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. These drawings are simplified schematic diagrams, which are only used to illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention.

[0021] To facilitate understanding of the present invention, a more complete description of the invention will be given below with reference to the accompanying drawings, which illustrate several embodiments of the invention. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of the invention will be more thorough and complete.

[0022] All features disclosed in this specification, or all steps in all disclosed methods or processes, may be combined in any way, except for mutually exclusive features and / or steps.

[0023] Any feature disclosed in this specification (including any appended claims, abstract, and drawings) may be replaced by other equivalent or similar features for a similar purpose, unless specifically stated otherwise. That is, unless specifically stated otherwise, each feature is merely one example of a series of equivalent or similar features.

[0024] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, a direct connection, or an indirect connection through an intermediate medium; they can refer to the internal communication of at least two elements or the interaction relationship of at least two elements, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0025] Before introducing this embodiment, let's first explain the existing multi-flyback topology, referring to... Figure 2 The conventional design suffers from a problem where RL1, RL2, and RL3 are variable loads in the circuit. Since these three loads originate from the control circuit, their magnitude can change from zero load to maximum load. Typically, an LDO or buck circuit is used for voltage regulation at the front end. However, LDOs or buck circuits usually cannot boost the voltage. Assuming load RL1 is in a dormant state, with a load close to zero, while one or more of RL2...RLn are at maximum load, due to the transformer being a non-ideal transformer, such as... Figure 3 This leakage inductance (L1, L2, ..., Ln) causes the corresponding output voltage to be lower than the rated value. Once the voltage is lower than the rated value, it will cause the system to shut down or restart. The conventional way to solve this problem is to reduce the leakage inductance of the transformer (L1, L2, ..., Ln). However, due to the physical characteristics, this leakage inductance cannot be infinitely close to 0. Moreover, it is very costly to change this phenomenon. An improved voltage regulator circuit will solve this problem.

[0026] Please see Figure 1The present invention provides an embodiment of a voltage regulation control circuit applied to a multi-output flyback topology, comprising a transformer T1, a primary-side drive switch circuit, a feedback control loop, several sets of secondary-side output loops, and a load simulation circuit. By introducing the load simulation circuit, the feedback control loop is tricked into "sensing" the load status of the secondary-side output loops. The voltage change of the secondary-side output loops generates a simulated load signal, which is applied to the voltage sampling point of the feedback control loop. This causes the feedback control loop to adjust the duty cycle of the primary-side drive switch circuit according to the load status of the secondary-side output loops, thereby maintaining the voltage of all secondary-side output loops within a set range.

[0027] Specifically, the load simulation circuit includes a diode Ds, a polarized capacitor Cs, and a resistor Rs. The anode of the diode Ds is coupled to the secondary-side output circuit, which is typically the output circuit with the most drastic load changes or the most critical output circuit. In this embodiment, it is connected to the primary-side output circuit. The polarized capacitor Cs and the resistor Rs are connected in parallel, with one end connected to the cathode of the diode Ds and the other end connected to the ground reference corresponding to the secondary-side output circuit. The voltage sampling point of the feedback control circuit is connected to the cathode of the diode Ds.

[0028] The feedback control loop includes an optocoupler, resistors R2 and R3, a voltage regulator IC2, and resistor R4. The voltage regulator IC2 can be a TL431. Resistors R2 and R3 are connected in series. The cathode of the diode Ds is connected between resistors R2 and R3. The other end of resistor R2 is connected to the anode of the optocoupler. One end of resistor R4 is connected to resistor R3, and the other end is connected to the anode of the voltage regulator IC2. The cathode of the voltage regulator IC2 is connected to the cathode of the optocoupler, and the anode is grounded. The other side of the optocoupler is connected to the offline controller, which moves the voltage sampling point to the positive terminal of capacitor Cs.

[0029] The secondary output circuit includes a diode Dn, an inductor Ln, a polarized capacitor Cn, and a load RLn. The polarized capacitor Cn and the load RLn are connected in parallel. The cathode of the diode Dn is connected to the polarized capacitor Cn, and the anode is connected to the inductor Ln. The other end of the inductor Ln is connected to the polarized capacitor Cn. The anode of the diode Ds is connected between the inductor Ln and the polarized capacitor Cn.

[0030] The primary-side drive switch circuit includes a MOSFET Q1, a drive diode, a resistor R1, and a non-polarized capacitor C3. The non-polarized capacitor C3 is connected in parallel with the resistor R1 and then connected to the cathode of the drive diode. The anode of the drive diode is connected to the MOSFET Q1, and the MOSFET Q1 is connected to an offline controller.

[0031] After introducing Ds, Cs, and Rs, and connecting the power supply R2 and sampling R3 of the voltage regulation feedback circuit to the positive terminal of Cs, while ensuring that the time constants of Cs and Rs are comparable to those of other circuits under rated load, we take values ​​of 0.2 to 5 times. This ensures that the voltages V1, V2, ..., Vn will not fall below the design value under any dynamic or static load. This allows an LDO or buck circuit to provide a stable voltage to the subsequent system. Since the time constant formed by the filter capacitor and load of each circuit is generally on the order of magnitude, C1*RL1≈C2*RL2≈…≈Cn*RLn. Because Rs is a dummy load, to avoid increasing power consumption, its resistance value is usually relatively large, typically designed to be within 100mW. We also use a smaller capacitor Cs to ensure that Cs*Rs approaches C1*RL1, which meets the design requirements.

[0032] The specific workflow is as follows:

[0033] 1. When the load on the secondary output circuit increases

[0034] The output voltage of the secondary side output circuit tends to decrease. Since the anode of Ds is connected to the output terminal of Vn, its anode voltage also decreases. If the voltage V_Cs at the positive terminal of Cs is higher than (Vn - V_Ds) at this time, Ds will be reverse biased and cut off. Cs can only discharge slowly through the large resistor Rs, and V_Cs will decrease slowly.

[0035] When the feedback circuit samples a decrease in V_Cs, it interprets it as "the voltage of the main feedback circuit V1 is decreasing," and thus increases the duty cycle to inject more energy into the transformer.

[0036] This increased energy is supplied to all secondary circuits simultaneously. The heavily loaded secondary output circuit receives the much-needed energy, and its voltage is maintained. The lightly loaded secondary output circuit, due to excess energy, will have a slightly higher voltage. However, since the sampling point is not on the lightly loaded secondary output circuit, this rise will not be "seen" and corrected by the feedback circuit. The system successfully avoids voltage collapse in the Vn circuit.

[0037] 2. When the load on the secondary output circuit is reduced

[0038] The output voltage of the secondary side output circuit tends to rise, and the anode voltage of Ds increases. When it is higher than (V_Cs + V_Ds), Ds turns on, and the secondary side output circuit charges the capacitor Cs, causing the voltage of V_Cs to rise. The feedback control circuit samples the rise of V_Cs and interprets it as "the voltage of the main feedback circuit V1 is too high". Therefore, it reduces the duty cycle and reduces the total energy transfer.

[0039] This action prevents the secondary-side output circuit voltage from spikering under light load, and also prevents the secondary-side output circuit voltage from becoming too high due to excessive energy under light load.

[0040] A specific example is as follows:

[0041] Design V1: 12V, 24W; V2: 12V, 12W; V3: 24V, 30W;

[0042] C1 uses 1000uF, C2 uses 470uF, and C3 uses 270uF.

[0043] The equivalent RL1 = 6Ω, RL2 = 12Ω, and RL3 = 19.2Ω were calculated.

[0044] C1*RL1=1000uF *6Ω=6000u,

[0045] C2*RL2=470uF *12Ω=5640u,

[0046] C3*RL3=270uF*19.2Ω=5184u.

[0047] To control no-load power consumption and reduce system losses, Rs is set to 3kΩ, with a loss of 48mW. The time constant is approximately equal to that of other loops, calculated at 5500µF. Therefore, Cs = 1.8µF. Alternatively, Cs = 2.2µF can be chosen.

[0048] Recalculating Rs*Cs = 2.2uF * 3kΩ = 6600u, this is approximately 1.18 times the average value.

[0049] In summary, this invention cleverly enables the power supply control system to sense load changes in the unregulated output circuit by introducing a load simulation circuit composed of diodes, capacitors, and resistors, and using its voltage as a feedback signal. The core of this invention lies in designing a time constant that matches the time constant of each output circuit, thereby dynamically simulating the load characteristics of heavily loaded branches. This guides the controller to promptly increase energy supply when the auxiliary circuit is heavily loaded, fundamentally solving the problem of poor cross-regulation caused by transformer leakage inductance. At extremely low cost, it ensures that all output branches maintain a stable voltage no lower than the rated value under drastic load changes, effectively preventing system downtime or restarts, and significantly improving the reliability, load adaptability, and cost-effectiveness of the power supply.

[0050] The above description is merely a specific embodiment of the invention, but the scope of protection of the invention is not limited thereto. Any variations or substitutions conceived without inventive effort should be included within the scope of protection of the invention. Therefore, the scope of protection of the invention should be determined by the scope defined in the claims.

Claims

1. A voltage regulator control circuit applied to a multi-output flyback topology, comprising a transformer (T1), a primary-side drive switching circuit, a feedback control loop, and several sets of secondary-side output loops, characterized in that: It also includes a load simulation circuit, the input of which is coupled to one of the secondary-side output circuits, the output of which is connected to the ground reference corresponding to the secondary-side output circuit, and the voltage sampling point of the feedback control circuit is connected to the load simulation circuit. The load simulation circuit is configured to generate a simulated load signal based on the voltage change of the secondary output circuit, and apply the signal to the voltage sampling point of the feedback control circuit, so that the feedback control circuit adjusts the duty cycle of the primary drive switch circuit according to the load condition of the secondary output circuit, thereby maintaining the voltage of all secondary output circuits within a set range. The load simulation circuit includes a diode (Ds), a polarized capacitor (Cs), and a resistor (Rs). The anode of the diode (Ds) is coupled to the secondary output circuit. One end of the polarized capacitor (Cs) and the resistor (Rs) are connected in parallel to the cathode of the diode (Ds), and the other end is connected to the ground reference corresponding to the secondary output circuit. The voltage sampling point of the feedback control circuit is connected to the cathode of the diode (Ds). The time constant of the polarized capacitor (Cs) and the resistor (Rs) is on the same order of magnitude as the time constant of any secondary output circuit under rated load.

2. The voltage regulation control circuit applied to a multi-output flyback topology according to claim 1, characterized in that: The feedback control loop includes an optocoupler, a voltage divider sampling unit, and a voltage regulator unit. The voltage divider sampling unit includes a resistor (R2) and a resistor (R3) connected in series. The cathode of the diode (Ds) is connected between the resistor (R2) and the resistor (R3). The other end of the resistor (R2) is connected to the anode of the optocoupler. One end of the voltage regulator unit is connected to the cathode of the optocoupler, and the other end is grounded.

3. The voltage regulation control circuit applied to a multi-output flyback topology according to claim 2, characterized in that: The voltage regulator unit includes a voltage regulator integrated component (IC2) and a resistor (R4). One end of the resistor (R4) is connected to the resistor (R3), and the other end is connected to the anode of the voltage regulator integrated component (IC2). The cathode of the voltage regulator integrated component (IC2) is connected to the cathode of the optocoupler.

4. A voltage regulation control circuit for a multi-output flyback topology according to claim 3, characterized in that: The secondary output circuit includes a diode (Dn), an inductor (Ln), a polarized capacitor (Cn), and a load (RLn). The polarized capacitor (Cn) and the load (RLn) are connected in parallel. The cathode of the diode (Dn) is connected to the anode of the polarized capacitor (Cn). The anode of the diode (Dn) is connected to one end of the inductor (Ln). The other end of the inductor (Ln) is connected to the cathode of the polarized capacitor (Cn). The anode of the diode (Ds) is connected between the inductor (Ln) and the diode (Dn).

5. A voltage regulation control circuit for a multi-output flyback topology according to claim 4, characterized in that: The primary-side drive switching circuit includes a MOSFET (Q1), a drive diode, a resistor (R1), and a non-polarized capacitor (C3). The non-polarized capacitor (C3) is connected in parallel with the resistor (R1) and then connected to the cathode of the drive diode. The anode of the drive diode is connected to the MOSFET (Q1).

6. A voltage regulation control circuit for a multi-output flyback topology according to claim 5, characterized in that: The ratio of the time constant of the polarized capacitor (Cs) and the resistor (Rs) to the time constant of the secondary output circuit is between 0.2 and 5.

7. A voltage regulation control circuit for a multi-output flyback topology according to claim 6, characterized in that: The resistance value of the resistor (Rs) is set such that its power consumption at the rated output voltage is less than 100 milliwatts.

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