Double-transistor forward switching power supply circuit for meter of internet of things

Abstract

The utility model relates to a two-transistor forward switching power supply circuit used for an Internet of Things meter. The two-transistor forward switching power supply circuit comprises an AC rectification filter circuit, a switching tube driving and transformer circuit, a voltage feedback circuit, a switching power supply chip U2 and a control circuit which are electrically connected. The AC rectification filter circuit comprises a filter module, a rectifier bridge and a conditioning module which are electrically connected; the filter module is connected with the rectifier bridge, and the rectifier bridge is connected with the DC-IN through the conditioning module; the device is reasonable in design, compact in structure and convenient to use.

Description

Technical Field

[0001] The utility model relates to a double-tube forward switching power supply circuit for an Internet of Things meter. Background Art

[0002] With the rapid development and widespread adoption of IoT technology, various smart metering devices, such as smart electricity, water, and gas meters, are placing increasingly stringent power supply requirements. These devices typically require long-term stable, reliable, highly efficient, and compact power supply solutions to accommodate the multi-core modular power supply requirements of multiple chips, including metering, management, clocking, and storage. Furthermore, IoT meters often require a wide input voltage range to accommodate diverse power supply environments, and they place high demands on electromagnetic compatibility and reliability. The dual-switch forward switching power supply is an ideal solution for these requirements. Due to its unique advantages, the dual-switch forward topology is well-suited for these new IoT metering applications.

[0003] After analyzing the power supply requirements of IoT meters, it was found that IoT meters have higher requirements for switching power supply design due to their diversified and efficient communications and the need for scalable functional applications. Analysis shows that most smart meters on the market use linear power supplies and flyback switching power supplies. The efficiency of linear power supplies is between 50% and 70%, while the efficiency of switching power supplies can be as high as over 90%. The efficiency is particularly low under light load or standby mode. When working at full load, it generates a lot of heat and has a large power loss. The volume and weight are usually much larger than switching power supplies. The adaptability to input voltage changes is poor. As power demand increases, the efficiency disadvantage of linear power supplies becomes more prominent, making them unsuitable for IoT meters requiring high-power power supplies. Linear power supplies are difficult to achieve wide-range voltage regulation and multiple outputs. Under light load conditions, the iron loss of the transformer and the turn-on and turn-off losses of the switch tube account for a large proportion of the flyback switching power supply, resulting in low light load efficiency. The switch tube withstands a high voltage spike at the moment of turn-off, requiring additional protection circuits to reduce voltage stress. The power density of the flyback power supply is relatively low in high-power applications.

[0004] In view of the above-mentioned technical problems of different power supply structures, the present application provides a dual-tube forward switching power supply circuit suitable for a new type of Internet of Things meter, which has high power density, high dynamic response, low output ripple, and optional soft switching technology (such as ZVS, ZCS) to adapt to the new type of Internet of Things meter. Utility Model Content

[0005] The technical problem to be solved by the present invention is generally to provide a dual-tube forward switching power supply circuit for an Internet of Things meter, which can meet the power supply demand when the Internet of Things meter is given more technical functional requirements.

[0006] In order to solve the above problems, the technical solution adopted by the present invention is:

[0007] A dual-tube forward switching power supply circuit for an Internet of Things meter, comprising an electrically connected AC rectifier filter circuit, a switch tube drive and transformer circuit, a voltage feedback circuit, a switching power supply chip U2, and a control circuit;

[0008] The AC rectifier filter circuit includes a filter module, a rectifier bridge and a conditioning module that are electrically connected;

[0009] The filter module is connected to the rectifier bridge, and the rectifier bridge is connected to DC-IN through the conditioning module;

[0010] DC-IN is connected to the switching power supply chip U2;

[0011] The switch tube drive and transformer circuit includes an electrically connected drive module and a transformer module;

[0012] The driver module is connected to the DC-IN and the PWM channel and IS channel of the switching power supply chip U2;

[0013] The voltage feedback circuit is connected to the comp channel of the switching power supply chip U2.

[0014] As a further improvement of the above technical solution:

[0015] The filter module includes an electrically connected winding inductor L1 and a safety capacitor C1;

[0016] A varistor R3 is connected in parallel between the neutral line N and the live line L;

[0017] Connect a resistor RX between the live wire L at one end and the filter module;

[0018] The rectifier bridge includes electrically connected rectifier diodes D1, D2, D3 and D4;

[0019] The conditioning module includes filter capacitors E1 and E2 connected in series between DC-IN and the ground terminal;

[0020] Connect the voltage divider resistors R1 and R2 in series at both ends of the filter capacitor E1.

[0021] Voltage divider resistors R5 and R6 are connected in series at both ends of the filter capacitor E2.

[0022] The driving module includes transistors Q1, Q3, Q4 and Q6, MOS upper tube Q2, and MOS lower tube Q5; the voltage conversion circuit includes PT1 transformer and transformer T1;

[0023] Pin 6 of the switching power supply chip U2 outputs a PWM control signal, the PWM control signal is electrically connected to the PT1 transformer, and the PT1 transformer is electrically connected to the MOS upper tube Q2;

[0024] The PWM control signal is electrically connected through the parallel reverse diode D10 and resistor R16 and then split into two paths, one path connected to the bases of the series-connected transistors Q1 and Q3, and the other path connected to the bases of the series-connected transistors Q4 and Q6;

[0025] The collector of transistor Q1 is connected to VCC and the emitter is output through resistor R10;

[0026] The collector of transistor Q3 is connected to the input end of resistor R10 and the emitter is grounded;

[0027] The collector of transistor Q3 is connected to the ground through diode D9 in one path and connected to the primary coil of PT1 transformer in another path through series resistor R11 and capacitor C3;

[0028] The secondary coil pin 3 of the PT1 transformer is connected to the gate of the MOSG upper tube Q2 through the series capacitor C4 and resistor R8;

[0029] Connect a resistor R12 and a reverse-connected diode D5 in parallel between the gate of the MOSG upper tube Q2 and the pin 4 of the secondary coil of the PT1 transformer;

[0030] The collector of transistor Q4 is connected to VCC and the emitter is output through resistor R10;

[0031] The collector of transistor Q6 is connected to the input end of resistor R18 and the emitter is grounded;

[0032] The collector of transistor Q6 is connected to ground through diode D14 and connected to the gate of MOSG lower tube Q5 through resistor R19.

[0033] Connect capacitor C5 between the source and drain of MOSG upper tube Q2, and connect the source to pin 4 of the secondary coil of PT1 transformer; the source is connected to pin 5 of the primary coil of transformer T1, and the drain is connected to DC-IN. The drain passes through parallel resistor R7 and capacitor C2, and then through reverse-connected diode D6 to pin 3 of the primary coil of transformer T1.

[0034] The source of the MOSG upper tube Q2 is connected to ground through the parallel resistor R15 and capacitor C11 and then through the reverse-connected diode D13;

[0035] Connect capacitor C15 between the source and drain of the lower MOSG tube Q5. The source is connected to ground through resistor R33 and to Is. The drain is connected to pin 3 of the primary coil of transformer T1.

[0036] Connect the secondary winding of transformer T1 to terminal PVCC; connect diode D7, resistor R9, and capacitor C6 to pin 6 of transformer T1's secondary winding. One path of diode D7 connects to pin 7 of the secondary winding through resistor R13 and capacitor C9 in series. The other path of diode D7 connects to the output terminal of capacitor C6 through the output filter unit composed of inductor L2 and parallel capacitors C7 and C8 to output VCC-12V. Reverse-connect diode D8 between the input terminal of inductor L2 and pin 7.

[0037] Transformer T1 secondary coil pin 10 outputs VCC-15V;

[0038] Capacitors C2 and C15 are the switch tube drain peak voltage absorption capacitors;

[0039] Diodes D7 and D11 are unidirectional conducting diodes, inductor L2 is an energy storage inductor, diode D8 is a freewheeling diode, and capacitors C7 and C8 are output filter capacitors;

[0040] Resistors R9 and R13 and capacitors C6 and C9 form a peak voltage absorption circuit.

[0041] The voltage feedback circuit includes an optocoupler D15; pin 4 of the optocoupler D15 is connected to the comp signal, and pin 1 is connected to VCC-15V.

[0042] VCC_15V is connected to pin 1 of the three-terminal voltage regulator U1 through the voltage divider resistors R21 and R24. The voltage is divided by the voltage divider resistors R20 and R22 and connected to pin 2 of the optocoupler D15.

[0043] The resistance values ​​of R22 and R20 and the current flowing through the optocoupler 1 and 2 pins jointly determine the operating current flowing through the switching power supply chip U1;

[0044] R23 is connected in series with C17 and in parallel with C16 to absorb the voltage spike from VCC_15V and ensure the voltage divider value connected to U1 is stable;

[0045] The optocoupler pin 4 is connected to the pin 1 of the switching power supply chip U2.

[0046] In the switching power supply chip U2, pin 1 is the voltage feedback pin, pin 2 is the feedback pin and is grounded, pin 3 is the current detection pin connected to the IS channel through resistor R28, pin 3 is grounded through capacitor C20, pin 4 is grounded through capacitor C21 and connected to pin 8 through resistor R29; pin 5 is grounded, pin 6 is connected to the PWM channel, and pin 7 is connected to the control circuit;

[0047] The control circuit includes a resistor R25 with one end connected to DC-IN and the other end connected to pin 7 of the switching power supply chip U2. Pin 7 of the switching power supply chip U2 is also connected to VCC through a resistor R26.

[0048] After passing through diode D16, PVCC is divided into two paths through resistor R27. One path is connected to ground through reverse-connected diode D18, and the other path is connected to the filter module composed of inductor L4 and parallel capacitors C18 and C19, and then connected to resistor R27 and VCC.

[0049] DC-IN provides startup voltage for switching power supply chip U2 through voltage division by R25 and R26; PVCC power supply adopts BUCK topology, inductor L4 is energy storage inductor, diode D18 is freewheeling diode, capacitors C18 and C19 are filter capacitors, and diode D17 is clamping diode.

[0050] Beneficial effects of the present invention: The present invention provides a dual-tube forward switching power supply circuit suitable for a new type of Internet of Things meter, aiming to address the higher power supply requirements required by the Internet of Things meter for improved performance and functionality, and to meet the power requirements of smart Internet of Things meters in an environment with increased functional requirements. The dual-tube forward switching power supply can continuously transfer energy to the transformer when the two switching tubes are turned on, greatly reducing switching losses, thereby improving the overall conversion efficiency of the power supply, and the voltage stress borne by the switching tube is relatively small. It adapts to a wide range of input voltages and can operate stably in environments with unstable power supply or large voltage fluctuations, meeting the requirements of the Internet of Things meter for complex power grid environments. The output voltage is less affected by the load, the load regulation rate is high, and the magnetic reset circuit is simple. The circuit has a high degree of discrete device construction, high parameter flexibility, low maintenance cost, clear working logic, and convenient problem troubleshooting, avoiding the high cost and maintenance cost of highly integrated switching power supply control chips. The present invention has a reasonable design, low cost, durability, safety and reliability, simple operation, time-saving and labor-saving, money-saving, compact structure, and is easy to use. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is an AC rectifier and filter circuit of the utility model.

[0052] Figure 2 This is a switch tube drive and transformer circuit of the utility model.

[0053] Figure 3 This is the voltage feedback circuit of the utility model.

[0054] Figure 4 This is a switching power supply chip control circuit of the utility model.

[0055] Figure 5 This is a block diagram of the utility model. DETAILED DESCRIPTION

[0056] like Figure 1-4A dual-tube forward switching power supply circuit for an Internet of Things meter includes an electrically connected AC rectifier and filter circuit, a switch tube drive and transformer circuit, a voltage feedback circuit, a switching power supply chip U2, and a control circuit;

[0057] The switch tube driver is preferably as follows Figure 2 Totem Pole Drive.

[0058] Control circuit, electrically connected to the switching power supply chip U2;

[0059] The switching power supply chip U2 is also electrically connected to a magnetic reset circuit, a BUCK output circuit, and an auxiliary power supply;

[0060] The AC rectifier filter circuit includes a filter module, a rectifier bridge and a conditioning module that are electrically connected;

[0061] The filter module is connected to the rectifier bridge, and the rectifier bridge is connected to DC-IN through the conditioning module;

[0062] DC-IN is connected to the switching power supply chip U2;

[0063] The switch tube drive and transformer circuit includes an electrically connected drive module and a transformer module;

[0064] The driver module is connected to the DC-IN and the PWM channel and IS channel of the switching power supply chip U2;

[0065] The voltage feedback circuit is connected to the comp channel of the switching power supply chip U2.

[0066] Specific as Figure 1 The figure shows a rectifier and filter circuit of a dual-tube forward switching power supply for a new type of Internet of Things meter of the present invention, including a varistor R3, a wirewound resistor RX, a winding inductor L1, a safety capacitor C1, rectifier diodes D1, D2, D3, D4, filter capacitors E1, E2, and voltage divider resistors R1, R2, R5, and R6; the varistor R3 is connected in parallel between the neutral line and the live line. When a surge high voltage is applied, the varistor quickly breaks down and turns on, and its resistance drops rapidly, causing the resistor to be in a conducting state, providing a discharge path for the surge high voltage to protect the back-end circuit. RX plays a current limiting role in the circuit to prevent excessive current from damaging the back-end circuit. The safety capacitor C1 is used for filtering in the anti-interference circuit, filtering common-mode and differential-mode interference respectively. Rectifier diodes D1, D2, D3, and D4 rectify the AC power into high-voltage DC power, and smooth the high-voltage DC power with ripples through filter capacitors E1 and E2. R1, R2, R5, and R6 are connected in series for voltage division, R1 and R2 are connected in parallel with E1, and R5 and R6 are connected in parallel with E2.

[0067] Figure 2The figure shows the switch tube drive and transformer circuit of the utility model. The 6th pin of the switching power supply chip outputs the PWM control signal, which drives the power MOSFET to turn on or off through the totem pole structure. The upper tube Q2 is driven by the totem pole structure and the PT1 transformer for floating ground. C4, R8, R12, and D5 suppress oscillation and accelerate the shutdown of the MOSFET. The lower tube Q5 is driven directly by the totem pole structure. When the PWM outputs a high-level signal, Q1 and Q4 are turned on, Q3 and Q6 are turned off, and the MOSFET base input is high. At this time, the switch tube is turned on. When the PWM outputs a low-level signal, Q1 and Q4 are turned off, Q3 and Q6 are turned on, and the MOSFET base is pulled to the ground low level. At this time, the switch tube is turned off. C2 and C15 are the switch tube drain peak voltage absorption capacitors. When the switch is on, T1's primary generates an induced electromotive force, coupling energy to the secondary winding through the same-name terminal. When the switch is off, no energy is transferred from T1's primary. A path is formed through D6 and D13, transferring residual magnetic energy to the power input, completing magnetic reset. R7, C2, R15, and C11 form a snubber circuit to reduce MOSFET stress. When the switch is on, the T1 secondary winding obtains the required voltage through a step-down topology. D7 and D11 are unidirectional conducting diodes, L2 and L3 are energy storage inductors, D8 and D12 are freewheeling diodes, C7, C8, C12, and C13 are output filter capacitors, and R9, C6, R13, C9, R14, C10, R17, and C14 form a spike voltage absorption circuit.

[0068] Figure 3 The figure shows the voltage feedback circuit of the present invention. VCC_15V is connected to pin 1 of the TL431 via voltage-divider resistors R21 and R24. R20 and R22 divide the voltage and connect it to one end of the optocoupler. The resistance of R22 determines the current flowing through U1. R23 is connected in series with C17 and in parallel with C16 to absorb voltage spikes from VCC_15V and ensure a stable voltage divider value connected to U1. The other end of the optocoupler is connected to pin 1 of the switching power supply chip U2.

[0069] Figure 4The figure shows the control circuit of the switching power supply chip of the present invention. U2 is the switching power supply chip. Pin 1 is the voltage feedback pin, which is connected to the internal amplifier to control the PWM duty cycle. Pin 2 is the feedback pin, which is grounded. Pin 3 is the current detection pin. Through the voltage divider R33 and R28 and the filter input C20, it is connected to the source end of the power MOSFET and the sampling end of the inductor current. It is used to detect the magnitude of the inductor current flowing through the power MOSFET and, together with the COMP signal, control the system duty cycle. Pin 4 can set the switching frequency by configuring the values ​​of R29 and C21. Pin 5 is the chip ground pin. Pin 6 is the PWM generation pin, which outputs the PWM control signal to turn the MOSFET on and off. Pin 7 is the chip power pin connected to VCC. Pin 8 is the reference voltage output pin, which provides the reference voltage for the oscillation frequency pin. DC-IN provides startup voltage for the power chip through the voltage divider of R25 and R26. After the chip starts, the chip is powered by the PVCC of T1 output terminal. The PVCC power supply adopts the BUCK topology. The diode D16 is single-phase conductive. L4 is the energy storage inductor, D18 is the freewheeling diode, C18 and C19 are filter capacitors, and D17 is the clamping diode to prevent the power chip from being broken down by excessive input voltage.

[0070] This practical information adopts a dual-tube forward switching power supply circuit logic architecture design, providing lower output ripple and better load regulation rate, high power efficiency; it has good EMI performance and generates relatively small electromagnetic interference.

[0071] The present invention is fully described for the purpose of clearer disclosure, and the prior art will not be listed one by one.

[0072] Finally, it should be noted that the above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may be modified or some of the technical features thereof may be replaced with equivalents. It is obvious for those skilled in the art to combine multiple technical solutions of the present invention. However, these modifications or replacements do not deviate from the spirit and scope of the technical solutions of the embodiments of the present invention. Any technical content not fully described in this utility model is generally known technology.

Claims

1. A dual-transistor forward switching power supply circuit for an Internet of Things meter, characterized by: It includes an electrically connected AC rectifier filter circuit, a switch tube drive and transformer circuit, a voltage feedback circuit, a switching power supply chip U2 and a control circuit; The AC rectifier filter circuit includes a filter module, a rectifier bridge and a conditioning module that are electrically connected; The filter module is connected to the rectifier bridge, and the rectifier bridge is connected to DC-IN through the conditioning module; DC-IN is connected to the switching power supply chip U2; The switch tube drive and transformer circuit includes an electrically connected drive module and a transformer module; The driver module is connected to the DC-IN and the PWM channel and IS channel of the switching power supply chip U2; The voltage feedback circuit is connected to the comp channel of the switching power supply chip U2.

2. The dual-transistor forward switching power supply circuit for an Internet of Things meter according to claim 1, characterized in that: The filter module includes an electrically connected winding inductor L1 and a safety capacitor C1; A varistor R3 is connected in parallel between the neutral line N and the live line L; Connect a resistor RX between the live wire L at one end and the filter module; The rectifier bridge includes electrically connected rectifier diodes D1, D2, D3 and D4; The conditioning module includes filter capacitors E1 and E2 connected in series between DC-IN and the ground terminal; Connect the voltage divider resistors R1 and R2 in series at both ends of the filter capacitor E1. Voltage divider resistors R5 and R6 are connected in series at both ends of the filter capacitor E2.

3. The dual-transistor forward switching power supply circuit for an Internet of Things meter according to claim 1, characterized in that: The driving module includes transistors Q1, Q3, Q4 and Q6, MOS upper tube Q2, and MOS lower tube Q5; the voltage conversion circuit includes PT1 transformer and transformer T1; Pin 6 of the switching power supply chip U2 outputs a PWM control signal, the PWM control signal is electrically connected to the PT1 transformer, and the PT1 transformer is electrically connected to the MOS upper tube Q2; The PWM control signal is electrically connected through the parallel reverse diode D10 and resistor R16 and then split into two paths, one path connected to the bases of the series-connected transistors Q1 and Q3, and the other path connected to the bases of the series-connected transistors Q4 and Q6; The collector of transistor Q1 is connected to VCC and the emitter is output through resistor R10; The collector of transistor Q3 is connected to the input end of resistor R10 and the emitter is grounded; The collector of transistor Q3 is connected to the ground through diode D9 in one path and connected to the primary coil of PT1 transformer in another path through series resistor R11 and capacitor C3; The secondary coil pin 3 of the PT1 transformer is connected to the gate of the MOSG upper tube Q2 through the series capacitor C4 and resistor R8; Connect a resistor R12 and a reverse-connected diode D5 in parallel between the gate of the MOSG upper tube Q2 and the pin 4 of the secondary coil of the PT1 transformer; The collector of transistor Q4 is connected to VCC and the emitter is output through resistor R10; The collector of transistor Q6 is connected to the input end of resistor R18 and the emitter is grounded; The collector of transistor Q6 is connected to ground through diode D14 and connected to the gate of MOSG lower tube Q5 through resistor R19. Connect capacitor C5 between the source and drain of MOSG upper tube Q2, and connect the source to pin 4 of the secondary coil of PT1 transformer; the source is connected to pin 5 of the primary coil of transformer T1, and the drain is connected to DC-IN. The drain passes through parallel resistor R7 and capacitor C2, and then through reverse-connected diode D6 to pin 3 of the primary coil of transformer T1. The source of the MOSG upper tube Q2 is connected to ground through the parallel resistor R15 and capacitor C11 and then through the reverse-connected diode D13; Connect capacitor C15 between the source and drain of the lower MOSG tube Q5. The source is connected to ground through resistor R33 and to Is. The drain is connected to pin 3 of the primary coil of transformer T1. Connect the secondary winding of transformer T1 to terminal PVCC; connect diode D7, resistor R9, and capacitor C6 to pin 6 of transformer T1's secondary winding. One path of diode D7 connects to pin 7 of the secondary winding through resistor R13 and capacitor C9 in series. The other path of diode D7 connects to the output terminal of capacitor C6 through the output filter unit composed of inductor L2 and parallel capacitors C7 and C8 to output VCC-12V. Reverse-connect diode D8 between the input terminal of inductor L2 and pin 7. Transformer T1 secondary coil pin 10 outputs VCC-15V; Capacitors C2 and C15 are the switch tube drain peak voltage absorption capacitors; Diodes D7 and D11 are unidirectional conducting diodes, inductor L2 is an energy storage inductor, diode D8 is a freewheeling diode, and capacitors C7 and C8 are output filter capacitors; Resistors R9 and R13 and capacitors C6 and C9 form a peak voltage absorption circuit.

4. The dual-transistor forward switching power supply circuit for an Internet of Things meter according to claim 1, characterized in that: The voltage feedback circuit includes an optocoupler D15; pin 4 of the optocoupler D15 is connected to the comp signal, and pin 1 is connected to VCC-15V. VCC_15V is connected to pin 1 of the three-terminal voltage regulator U1 through the voltage divider resistors R21 and R24. The voltage is divided by the voltage divider resistors R20 and R22 and connected to pin 2 of the optocoupler D15. The resistance values ​​of R22 and R20 and the current flowing through the optocoupler 1 and 2 pins jointly determine the operating current flowing through the switching power supply chip U1; R23 is connected in series with C17 and in parallel with C16 to absorb the voltage spike from VCC_15V and ensure the voltage divider value connected to U1 is stable; The optocoupler pin 4 is connected to the pin 1 of the switching power supply chip U2.

5. The dual-transistor forward switching power supply circuit for an Internet of Things meter according to claim 1, characterized in that: In the switching power supply chip U2, pin 1 is the voltage feedback pin, pin 2 is the feedback pin and is grounded, pin 3 is the current detection pin connected to the IS channel through resistor R28, pin 3 is grounded through capacitor C20, pin 4 is grounded through capacitor C21 and connected to pin 8 through resistor R29; pin 5 is grounded, pin 6 is connected to the PWM channel, and pin 7 is connected to the control circuit; The control circuit includes a resistor R25 with one end connected to DC-IN and the other end connected to pin 7 of the switching power supply chip U2. Pin 7 of the switching power supply chip U2 is also connected to VCC through a resistor R26. After passing through diode D16, PVCC is divided into two paths through resistor R27. One path is connected to ground through reverse-connected diode D18, and the other path is connected to the filter module composed of inductor L4 and parallel capacitors C18 and C19, and then connected to resistor R27 and VCC. DC-IN provides startup voltage for switching power supply chip U2 through voltage division by R25 and R26; PVCC power supply adopts BUCK topology, inductor L4 is energy storage inductor, diode D18 is freewheeling diode, capacitors C18 and C19 are filter capacitors, and diode D17 is clamping diode.

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