Power supply circuit and switching power supply

Abstract

The invention discloses a power supply circuit and a switching power supply, the power supply circuit comprises a controlled voltage source and an auxiliary power output unit, the controlled voltage source is connected in series in an output power loop where a secondary side winding of a main power transformer is located, and the auxiliary power output unit is connected with the controlled voltage source; when the switching power supply works, if the output voltage is in a rated voltage range, the controlled voltage source is controlled to be represented as a low-impedance conductor, so that the voltage at the two ends of the primary side power supply winding is not influenced; when the switching power supply works, if the output is short-circuited or the output voltage is lower than a set value, the controlled voltage source is controlled to be represented as a voltage source, the voltage at the two ends of the secondary side winding of the main power transformer is raised, then the voltage at the two ends of the primary side power supply winding is raised, and secondary side auxiliary power supply voltage is provided through the auxiliary power output unit. The problems that under wide-voltage and high-voltage input, when low voltage or short-circuit constant current is output, the voltage of a primary side power supply circuit and a secondary side power supply circuit of a switching power supply is unstable, and an existing power supply circuit is complex in design are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of power supply, and in particular to a power supply circuit and a switching power supply. Background Art

[0002] At present, the input end of the switching power supply faces many applications with higher voltage (such as three-phase voltage) and wide voltage (such as PV photovoltaic), and the demand for wide voltage output and constant current applications at the output end is also increasing, which places higher and higher requirements on the switching power supply. In the case of wide output voltage or short-circuit constant current, the traditional switching power supply often uses the auxiliary forward winding of the transformer as the power supply circuit, and realizes step-down power supply by designing the transformer turns ratio to provide a suitable operating voltage for active devices such as control ICs.

[0003] like Figure 1 This is the schematic diagram of the traditional transformer auxiliary forward winding power supply circuit. This design method requires the use of multiple windings provided by the transformer to realize the auxiliary source power supply. The transformer winding space utilization rate is low, which affects the miniaturization design of the transformer and increases the complexity of the transformer design. When adding more windings, the winding space, safety distance, and wire selection must also be considered, and the cost will also increase relatively. In addition, because the input voltage is higher and the range is wider, a multi-stage voltage stabilization circuit has to be used for voltage stability and loss sharing, resulting in higher losses and higher costs. Summary of the invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a power supply circuit and a switching power supply, which can at least solve one of the technical problems existing in the prior art to a certain extent.

[0005] As a first aspect of the present invention, the technical solution of the embodiment of the power supply circuit provided is as follows:

[0006] A power supply circuit is applied to a switching power supply, the switching power supply comprising a secondary winding of a main power transformer, a primary power supply winding and a control unit, the secondary winding of the main power transformer and the primary power supply winding are coupled, the control unit is configured to support a constant current output when the output of the switching power supply is short-circuited or a constant voltage output when the output voltage is lower than a set value, wherein:

[0007] The power supply circuit comprises a controlled voltage source and an auxiliary power output unit, the controlled voltage source is connected in series in the output power loop where the secondary winding of the main power transformer is located, and the auxiliary power output unit is connected to the controlled voltage source;

[0008] When the switching power supply is in operation, if the output voltage is within the rated voltage range, the controlled voltage source is controlled to be characterized as a low impedance conductor, so as not to affect the voltage across the primary power supply winding;

[0009] When the switching power supply is working, if the output is short-circuited or the output voltage is lower than the set value, the controlled voltage source is controlled to be characterized as a voltage source, the voltage across the secondary winding of the main power transformer is raised, and then the voltage across the primary power supply winding is raised, and the secondary auxiliary power supply voltage is provided through the auxiliary power output unit.

[0010] Preferably, the controlled voltage source includes an auxiliary transformer and a controlled short-circuit module, the primary winding of the auxiliary transformer is connected in series in the output power circuit of the switching power supply, and the secondary side is connected to the controlled short-circuit module; when the switching power supply is working, if the output voltage is within the rated voltage range, the controlled short-circuit module is controlled to be turned on, so that the secondary winding of the auxiliary transformer is short-circuited by the controlled short-circuit module; when the switching power supply is working, if the output is short-circuited or the output voltage is lower than the set value, the controlled short-circuit module is controlled to be disconnected, so that the secondary winding of the auxiliary transformer generates a voltage source through inductive coupling with its primary winding, and the voltage source provides a secondary auxiliary power supply voltage through the auxiliary power output unit.

[0011] Preferably, the controlled short-circuit module comprises a switch tube, and the switch tube is connected in parallel with the secondary winding of the auxiliary transformer.

[0012] Preferably, the switch tube is a MOS tube.

[0013] As a second aspect of the present invention, the technical solution of the embodiment of the switching power supply provided is as follows:

[0014] A switching power supply, comprising a secondary winding of a main power transformer, a primary power supply winding and a control unit, wherein the secondary winding of the main power transformer and the primary power supply winding are coupled, and the control unit is configured to support a constant current output when the output of the switching power supply is short-circuited or a constant voltage output when the output voltage is lower than a set value, wherein: the switching power supply also includes the power supply circuit described in any one of the first aspects above.

[0015] Preferably, the control unit includes a constant current and constant voltage control IC.

[0016] Preferably, the constant current and constant voltage control IC is SGM2904.

[0017] Preferably, the control unit performs feedback closed-loop control by sampling the output voltage of the switching power supply.

[0018] Preferably, the switch tube is controlled by the control unit so that the switch tube is directly driven on the secondary side of the main power transformer of the switching power supply.

[0019] Preferably, the lowest value of the output voltage allowed by the switching power supply approaches 0V; and / or the ratio of the maximum value to the minimum value of the input voltage allowed by the switching power supply is greater than 4.

[0020] The beneficial effects of the present invention are:

[0021] (1) When the power output unit of the switching power supply is under low voltage or short circuit constant current, the power supply circuit of the embodiment of the present invention controls the controlled voltage source to be characterized as a voltage source, thereby raising the voltage across the secondary winding of the main power transformer, thereby raising the voltage across the primary power supply winding, and providing a secondary auxiliary power supply voltage through the auxiliary power output unit, thereby maintaining the original power supply function of the power supply unit, thereby reducing the number of devices and energy transmission windings;

[0022] (2) The power supply circuit of the embodiment of the present invention solves the problem of increased device loss and overheating due to the excessively wide voltage range of the turns ratio design of the power supply unit in the existing circuit under a wide input voltage range, and the energy of the controlled voltage source can be effectively recovered to achieve high-efficiency conversion;

[0023] (3) The present invention simultaneously solves the current overshoot and undershoot problems caused by short circuit in constant current, improves the dynamic response of the constant current circuit, and solves the EMI problem caused by the winding of the switching device;

[0024] (4) The present invention achieves the goals of high efficiency, low cost and high performance by adding a simple controlled voltage source unit, and there is no need to compromise and optimize the device selection and the number of transformer windings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the schematic diagram of the traditional transformer auxiliary forward winding power supply circuit;

[0026] Figure 2 A specific circuit block diagram of a switching power supply provided by an embodiment of the present invention;

[0027] Figure 3 for Figure 2 A simplified schematic diagram when the energy storage power source is a transformer;

[0028] Figure 4 Based on Figure 3 A specific circuit schematic diagram;

[0029] Figure 5 for Figure 4 The power supply effect diagram of the circuit measurement;

[0030] Figure 6 for Figure 4 The circuit removes the power supply effect diagram of the invented power supply circuit. DETAILED DESCRIPTION

[0031] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0032] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0033] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application are described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, the process, method, system, product or equipment comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or equipment.

[0034] It should be understood that, in the specification, claims and drawings, when a step is described as being connected to another step, the step may be directly connected to the other step, or be connected to the other step through a third step; when an element / unit is described as being "connected" to another element / unit, the element / unit may be "directly connected" to the other element / unit, or be "connected" to the other element / unit through a third element / unit.

[0035] In addition, the drawings of the present disclosure are only schematic diagrams of the present disclosure and are not necessarily drawn to scale. The same symbols in the drawings represent the same or similar parts, and thus repeated descriptions thereof will be omitted. Some of the block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented using software, or implemented in one or more hardware modules or integrated circuits, or implemented in different networks and / or processor devices and / or microcontroller units.

[0036] Figure 2 A specific circuit block diagram of a switching power supply provided in an embodiment of the present invention can provide a stable voltage for the primary and secondary power supply circuits when outputting low voltage or short-circuit constant current under wide voltage and high voltage input.

[0037] It should be noted that the terms "primary side" and "secondary side" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated.

[0038] See also Figure 2 , which includes a power input unit 01, an input sampling unit 02, an energy transmission unit 03, a controlled voltage source unit 04, a power output unit 05, a power supply unit 06, a main control unit 07, an auxiliary power output unit 08, and an output sampling and control unit 09.

[0039] The power input unit 01 is a power (energy) injection end, which can be connected to a wide voltage and high voltage input. The unit is connected to the energy transmission unit 03 through the input sampling unit 02. The input sampling unit 02 can sample the input voltage, input current or input power. The energy transmission unit 03 transmits or stores energy. The size of its energy transmission is controlled by the main control unit 07. The main control unit 07 obtains the control amount of energy through the connection feedback between the input sampling unit 02 and the output sampling and control unit 09 for control. The secondary side of the energy transmission unit 03 is connected to the power output unit 05 through the controlled voltage source unit 04 to form a power circuit. The controlled voltage source 04 is connected in series in the power circuit. When the output of the power output unit 05 is short-circuited or the voltage is lower than the set value, the circuit of the controlled voltage source 04 is characterized as a voltage source connected in series in the power circuit. According to Kirchhoff's voltage law, in the same power circuit, the voltage of the secondary port of the energy transmission unit 03 is effectively increased because of the voltage source.

[0040] The controlled voltage source unit 04 is also connected to the auxiliary power output unit 08 and the output sampling and control unit 09. After receiving the output signal, the output sampling and control unit 09 controls the action of the controlled short-circuit module in the controlled voltage source unit 04 through comparison processing, so that it short-circuits the controlled voltage source 04 (at this time, the voltage source circuit is characterized as a low-impedance conductor) or opens the controlled voltage source 04 (at this time, the voltage source circuit is characterized as a voltage source); when the controlled voltage source 04 circuit is characterized as a voltage source, the secondary side output voltage of the energy transmission unit 03 is output and utilized through the auxiliary power output unit 08.

[0041] The output sampling and control unit 09 forms a closed-loop feedback with the main control unit 07, which can effectively control the output current or voltage at a set value.

[0042] Figure 3 for Figure 2 A simplified schematic diagram when the energy storage power source is a transformer. Figure 4 Based on Figure 3 For a specific circuit diagram, please refer to Figure 4 The control unit includes a constant current and constant voltage control IC. The constant current and constant voltage control IC can be selected by a person skilled in the art as needed, and the present invention does not limit it. Figure 3The constant current and constant voltage control IC in the circuit is SGM2904 from Shengbang Microelectronics. Pin 8 of the chip is VCC2, which is connected to one end of the auxiliary power output unit diodes C4 and D3, and also to one end of the power output unit D4.

[0043] In a specific embodiment, the energy transmission unit includes a main power transformer TX1, a switch device Q1 and other RC devices. The main power transformer TX1 includes a primary winding P1, a secondary winding P2 and a primary power supply winding S1. The lower end of the winding P1, the upper end of the winding P2 and the upper end of the winding S1 are the same end. The lower end of the winding P1 is connected to one end of the switch device Q1, the upper end of the winding P2 is connected to the anode of the diode D2, and the upper end of the winding S1 is connected to the anode of the diode D6. When the switch device Q1 is switched by the main control unit, the winding P1, the winding P2 and the winding S1 together constitute an energy transmission device. When the switch device Q1 changes from the on state to the off state, since the inductor current cannot change suddenly, the lower end of the winding P1 is at a high level, and the upper end of the winding P2 and the upper end of the winding S1 are also at a high level.

[0044] In a specific embodiment, the controlled voltage source includes an auxiliary transformer TX2 and a switch device Q2, wherein the switch device Q2 is a controlled short-circuit module, and the diode D3 and other RC devices constitute an auxiliary power output unit. The auxiliary transformer TX2 includes a primary winding P1' and a secondary winding S1' winding, and the primary winding P1' and the secondary winding S1' have coupling characteristics. One end of the primary winding P1' is connected to one end of the secondary winding S1 of the energy transmission unit, and the other end is connected to one end of the output sampling resistor Rsense, and is connected in series with the power output unit and the secondary winding S1 of the energy transmission unit to form a power loop. One end of the secondary winding S1' of the auxiliary transformer TX2 is connected to one end of the switch device Q2, and the other end is connected to the other end of the switch device Q2 and the anode end of the diode D3 of the auxiliary power output unit. When the switch device Q2 is closed, the winding S1' is short-circuited by the switch device Q2. Due to the winding coupling characteristics, the winding P1' is short-circuited, and the winding P1' is equivalent to a low-impedance conductor in the circuit; when the switch device Q2 is disconnected, the winding S1' is equivalent to an open circuit. Due to the winding coupling characteristics, the winding P1' is released from the short-circuit state, and the winding P1' is equivalent to an inductor L in the circuit.

[0045] In a specific embodiment, the output sampling and control unit 09 includes a resistor Rsense, resistors R11 and R12 for sampling the output voltage, and a driving circuit such as a voltage comparator ZR431, which together with the main control unit form a control closed loop. The voltage on the current sampling resistor Rsense is fed back to the main control unit to control the output current to obtain a constant output current Io; the output voltage Vout is divided and sampled by resistors R11 and R12 to obtain a feedback voltage Vfb, which is transmitted to the control unit to control the output voltage and the short-circuit module.

[0046] In a specific embodiment, the comparison input terminal of the voltage comparator ZR431 is connected to the feedback voltage Vfb of the feedback pin of the constant current and constant voltage control IC, the output terminal of the comparator is connected to one end of the resistor R3 and one end of the resistor R4, the other end of the resistor R4 is connected to the VCC2 pin of the constant current and constant voltage control IC, and the other end of the resistor R3 is connected to the drive pin of the switch device Q2. The feedback voltage Vfb is compared with the reference voltage of the voltage comparator ZR431, and the comparison result is characterized by the high and low output voltage of the voltage comparator ZR431. Relevant technical personnel should know that when the feedback voltage Vfb is lower than the reference voltage of the voltage comparator ZR431, the output voltage of the voltage comparator ZR431 is high level, and when the feedback voltage Vfb is higher than the reference voltage of the voltage comparator ZR431, the output voltage of the voltage comparator ZR431 is low level, so the output voltage of the voltage comparator ZR431 can be controlled by the feedback voltage Vfb, that is, the driving and shutting down of the switch device Q2 can be controlled.

[0047] The resistance value of each resistor is directly represented by its figure mark. In a specific embodiment, the voltage division value is Vfb=Vout×R12 / (R11+R12). By setting the resistance values ​​of resistors R11 and R12, the critical voltage Vout1 required for switching control of the switching device Q2 can be set. When the output voltage Vout of the switching power supply is higher than the critical voltage Vout1, the output voltage of the voltage comparator ZR431 is low, the switching device Q2 is closed, and the secondary winding P1' of the auxiliary transformer TX2 is equivalent to a low-impedance conductor in the circuit. At this time, the voltage VP1 across the winding P1' is basically 0V; when the output voltage Vout of the switching power supply is lower than the critical voltage Vout1, the output voltage of the voltage comparator ZR431 is high, the switching device Q2 is disconnected, and the secondary winding P1' of the auxiliary transformer TX2 is equivalent to an inductor L in the circuit. Since the control current Io of the constant current and constant voltage control unit is constantly controlled, relevant technicians should know that the current change in the power circuit is basically constant, so the voltage VP1=L×ΔI / Δt of the winding P1' is also constant.

[0048] Please go back Figure 3 , the simplified schematic diagram is a two-port network, and the output power circuit is equivalent to the energy transfer unit secondary winding S1 voltage VS1 and the controlled voltage source voltage VP1 in series. According to Kirchhoff's voltage law, VS1 = Vout + VP1. When the output port voltage Vout of the switching power supply is 0 (i.e., the output is short-circuited or low voltage), VS1 is mainly controlled by VP1. When the output port voltage Vout of the switching power supply is a high voltage, VS1 is controlled by Vout. Relevant technical personnel should know that due to the characteristics of the energy transfer unit, the power supply voltage Vcc1 is affected by the size of the VS1 voltage, so the power supply voltage Vcc1 is affected by the voltage source VP1. The higher the VP1 voltage, the higher the Vcc1.

[0049] Furthermore, the higher the VP1 voltage is, the higher the voltage Vcc2 on the auxiliary power output unit C4 is, and the more energy is obtained. According to the above, the voltage of VP1 is controlled by Io controlled by the output sampling and control unit, so the supply voltages Vcc1 and Vcc2 can be effectively provided and stably controlled, and are basically not affected by changes in the input voltage.

[0050] Figure 5 for Figure 4 The power supply effect diagram of the circuit measurement, Figure 6 for Figure 4 The circuit removes the power supply effect diagram of the invented power supply circuit, where EN is the enable signal indicating that the output voltage Vout is short-circuited, Q2 is the enable signal indicating that the auxiliary transformer TX2 winding S1' is short-circuited, and VCC1 is Figure 4 The output supply voltage VCC1 and VCC2 are Figure 4 The output power supply voltage VCC2 can be seen at time t1: Figure 5 The output terminal of the switching power supply is short-circuited, and the output voltage Vout drops, but the supply voltages VCC1 and VCC2 remain basically unchanged; Figure 6 The output terminal of the switching power supply is short-circuited, the output voltage Vout drops, and the supply voltages VCC1 and VCC2 drop accordingly.

[0051] In summary, the present invention solves the problem of unstable voltage of the primary and secondary power supply circuits of the switching power supply and complex design of the existing power supply circuit when outputting low voltage or short-circuit constant current under wide voltage and high voltage input.

[0052] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A power supply circuit, applied to a switching power supply, the switching power supply comprising a secondary winding of a main power transformer, a primary power supply winding and a control unit, the secondary winding of the main power transformer and the primary power supply winding having a coupling relationship, the control unit being configured to support a constant current output when the output of the switching power supply is short-circuited or a constant voltage output when the output voltage is lower than a set value, characterized in that: The power supply circuit comprises a controlled voltage source and an auxiliary power output unit, the controlled voltage source is connected in series in the output power loop where the secondary winding of the main power transformer is located, and the auxiliary power output unit is connected to the controlled voltage source; When the switching power supply is in operation, if the output voltage is within the rated voltage range, the controlled voltage source is controlled to be characterized as a low impedance conductor, so as not to affect the voltage across the primary power supply winding; When the switching power supply is working, if the output is short-circuited or the output voltage is lower than the set value, the controlled voltage source is controlled to be characterized as a voltage source, the voltage across the secondary winding of the main power transformer is raised, and then the voltage across the primary power supply winding is raised, and the secondary auxiliary power supply voltage is provided through the auxiliary power output unit.

2. The power supply circuit according to claim 1, characterized in that: The controlled voltage source includes an auxiliary transformer and a controlled short-circuit module. The primary winding of the auxiliary transformer is connected in series in the output power circuit of the switching power supply, and the secondary side is connected to the controlled short-circuit module. When the switching power supply is working, if the output voltage is within the rated voltage range, the controlled short-circuit module is controlled to be turned on, so that the secondary winding of the auxiliary transformer is short-circuited by the controlled short-circuit module. When the switching power supply is working, if the output is short-circuited or the output voltage is lower than the set value, the controlled short-circuit module is controlled to be disconnected, so that the secondary winding of the auxiliary transformer generates a voltage source through inductive coupling with its primary winding, and the voltage source provides a secondary auxiliary power supply voltage through the auxiliary power output unit.

3. The power supply circuit according to claim 2, characterized in that: The controlled short-circuit module includes a switch tube, and the switch tube is connected in parallel with the secondary winding of the auxiliary transformer.

4. The power supply circuit according to claim 3, characterized in that: The switch tube is a MOS tube.

5. A switching power supply, comprising a secondary winding of a main power transformer, a primary power supply winding and a control unit, wherein the secondary winding of the main power transformer and the primary power supply winding are coupled, and the control unit is configured to support a constant current output when the output of the switching power supply is short-circuited or a constant voltage output when the output voltage is lower than a set value, characterized in that: The switching power supply further comprises the power supply circuit according to any one of claims 1 to 5.

6. The switching power supply according to claim 5, characterized in that: The control unit includes a constant current and constant voltage control IC.

7. The switching power supply according to claim 6, characterized in that: The constant current and constant voltage control IC is SGM2904.

8. The power supply circuit according to claim 5, characterized in that: The control unit performs feedback closed-loop control by sampling the output voltage of the switching power supply.

9. The power supply circuit according to claim 8, characterized in that: The switch tube is controlled by the control unit so that the switch tube is directly driven on the secondary side of the main power transformer of the switching power supply.

10. The switching power supply according to claim 7, characterized in that: The lowest value of the output voltage allowed by the switching power supply approaches 0V; and / or the ratio of the maximum value to the minimum value of the input voltage allowed by the switching power supply is greater than 4.

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