Low cost linear power supply with transient overload for electric energy meter and terminal

Abstract

The utility model discloses a kind of low-cost linear power supply of electric energy meter and terminal with transient overload, including AC voltage reduction circuit and DC voltage stabilizing circuit, further include succession transient overload power supply circuit.Transient overload power supply circuit includes AC control circuit, push-pull voltage doubler circuit and energy storage circuit, using the mode of capacitor energy storage to improve driving voltage, meet the requirement with transient overload.The utility model keeps the main body structure unchanged on the basis of traditional low-cost, low-power linear power supply scheme of electric energy meter and terminal equipment, only by increasing transient overload power supply circuit, it can effectively meet the demand of driving relay and other transient high-power load, and the scheme structure is simpler compared with increasing transformer power, replacing for switching power supply etc., with the advantages of low cost, small size etc..

Description

Technical Field

[0001] This utility model belongs to the field of linear power supplies, specifically relating to a low-cost linear power supply with transient heavy load on an energy meter and terminal. Background Technology

[0002] With the rapid development of smart grids, electricity meters and terminals, as core equipment for electricity metering and management, face increasingly stringent requirements for performance and reliability. Traditional electricity meters and terminals typically employ linear power supply schemes to meet the demands for low power consumption and low cost. However, with the increasing prevalence of high-power appliances in homes, electricity meters and terminals need to handle higher current loads during peak electricity consumption periods, posing new challenges to the transient load-bearing capacity of power systems.

[0003] Existing linear power supply solutions have significant shortcomings when facing transient heavy loads (such as the instantaneous high-power load required by relay drive coils when disconnecting load switches). The main reason is that their transformers are designed for low power and cannot provide enough energy to drive high-power relays (such as 9W loads) in a short time, resulting in unreliable relay operation. Increasing the transformer power or increasing the output voltage to meet the transient heavy load requirements would not only increase cost and size but may also exceed the space limitations inside the electricity meter.

[0004] Although switching power supply solutions can solve the problem of transient heavy load, they are also more expensive and have poor electromagnetic compatibility (EMC) performance, with excessive startup transient current, making them unsuitable for applications such as electricity meters and terminals. Utility Model Content

[0005] This invention proposes a low-cost linear power supply with transient heavy load capability for an energy meter and terminal, the purpose of which is to solve the problems of high cost and large size of existing linear power supplies when meeting transient heavy load requirements.

[0006] The technical solution of this utility model is as follows: A low-cost linear power supply with transient heavy load for an energy meter and terminal includes an AC step-down circuit and a DC voltage regulator circuit, as well as a relay drive circuit. The output terminal of the AC step-down circuit is connected to the input terminal of the DC voltage regulator circuit. The low-cost linear power supply with transient heavy load for the energy meter and terminal also includes a transient heavy load power supply circuit. The first AC output terminal AC of the AC step-down circuit is connected to the control terminal of the transient heavy load power supply circuit, and the output terminal VDD of the DC voltage regulator circuit is connected to the power supply terminal of the transient heavy load power supply circuit. The output terminal V_QL of the transient heavy load power supply circuit is used to power the relay drive circuit. The transient heavy-load power supply circuit includes an AC control circuit, a push-pull voltage multiplier circuit, and an energy storage circuit. The AC control circuit includes an NPN transistor V6 connected to the control terminal of the transient heavy-load power supply circuit. The push-pull voltage multiplier circuit includes a capacitor C5, a diode V3, a diode V4, an NPN transistor V5, and a PNP transistor V7. The energy storage circuit includes a capacitor C6. Under the control of the NPN transistor V6, the NPN transistor V5 and the PNP transistor V7 alternately conduct and cut off, thereby charging the capacitor C6 through the power supply terminal of the transient heavy-load power supply circuit and the capacitor C5, so that the output voltage of the energy storage circuit is twice the output voltage VDD of the DC voltage regulator circuit.

[0007] As a further improvement to the energy meter and terminal with transient heavy load low-cost linear power supply: in the AC control circuit, the control terminal of the transient heavy load power supply circuit is connected to the base of NPN transistor V6 through resistor R4, the collector of NPN transistor V6 is connected to the power supply terminal of the transient heavy load power supply circuit through resistor R1, and the emitter is grounded.

[0008] As a further improvement to the energy meter and terminal with transient heavy load low-cost linear power supply: the collector of NPN transistor V6 is also connected to one end of resistor R2, and the other end of resistor R2 is simultaneously connected to the base of NPN transistor V5 and the base of PNP transistor V7. In the push-pull voltage multiplier circuit, the collector of NPN transistor V5 is connected to the power supply terminal of the transient heavy load power supply circuit, and the collector of PNP transistor V7 is grounded; the emitter of NPN transistor V5 is connected to the emitter of PNP transistor V7 and to one end of resistor R6; the other end of resistor R6 is connected to one end of capacitor C5. The power supply terminal of the transient heavy load power supply circuit is connected to the positive terminal of diode V3, the negative terminal of diode V3 is connected to the positive terminal of diode V4 and to the other end of capacitor C5; the negative terminal of diode V4 is the output terminal of the push-pull voltage multiplier circuit.

[0009] As a further improvement to the energy meter and terminal with transient heavy load low-cost linear power supply: in the energy storage circuit, one end of resistor R3 is connected to the output end of the push-pull voltage multiplier circuit as the input end of the energy storage circuit, and the other end of resistor R3 is connected to one end of capacitor C6, and the other end of capacitor C6 is grounded. The other end of resistor R3 is the output terminal of the energy storage circuit and the output terminal V_QL of the transient heavy load power supply circuit.

[0010] As a further improvement to the energy meter and terminal with transient heavy load, the energy storage circuit also includes a discharge resistor R5 connected in parallel with capacitor C6.

[0011] As a further improvement to the energy meter and terminal with transient heavy load low-cost linear power supply: the AC step-down circuit includes protection devices and a linear transformer T1.

[0012] As a further improvement to the energy meter and terminal with transient heavy load low-cost linear power supply: the protection device includes a varistor RV1 connected between the L line and the N line.

[0013] As a further improvement to the energy meter and the low-cost linear power supply with transient heavy load: the protection device includes a thermistor RT1 connected between the terminal corresponding to the N line on the primary side of the linear transformer T1 and the N line.

[0014] As a further improvement to the energy meter and terminal with transient heavy load low-cost linear power supply: the DC voltage regulator circuit includes a full-bridge rectifier circuit and a voltage regulator circuit; The output terminal of the AC step-down circuit is connected to the input terminal of the full-bridge rectifier circuit, the output terminal of the full-bridge rectifier circuit is connected to the input terminal of the voltage regulator circuit, and the output terminal of the voltage regulator circuit is the output terminal VDD of the DC voltage regulator circuit.

[0015] As a further improvement to the energy meter and terminal with transient heavy load low-cost linear power supply: the voltage regulator circuit includes input filter capacitors C1 and C2, output filter capacitors C3 and C4, and linear regulator D1; The positive output terminal of the full-bridge rectifier circuit is connected to the input terminal VIN of the linear regulator D1 and grounded through the parallel input filter capacitors C1 and C2. The negative output terminal of the full-bridge rectifier circuit is grounded. The output terminal of the linear regulator D1 is the output terminal of the voltage regulator circuit and is grounded through the parallel output filter capacitors C3 and C4. The ground terminal GND of the linear regulator D1 is grounded.

[0016] Compared with the prior art, the present invention has the following advantages: 1. This utility model maintains the main structure of the traditional low-cost, low-power linear power supply scheme for electricity meters and terminal equipment, and can effectively meet the needs of instantaneous high-power loads such as driving relays by simply adding a transient heavy-load power supply circuit. Moreover, this scheme is simpler in structure than the scheme of increasing transformer power or replacing it with a switching power supply, and has the advantages of low cost and small size.

[0017] 2. This utility model, through the coordinated control of the AC control circuit and the push-pull voltage multiplier circuit, utilizes the energy of capacitor C5 and the power supply terminal VDD to charge the energy storage capacitor C6 to nearly twice the VDD voltage without increasing the output voltage of the linear transformer T1. This ensures that the system can still provide sufficient transient drive voltage under a wide range of AC input (especially low voltage input), avoiding the problem of insufficient heavy load capacity under low voltage input in traditional solutions.

[0018] 3. Since the push-pull voltage multiplier circuit generates a multiplier voltage on the energy storage capacitor C6, rather than by directly increasing the secondary voltage of the transformer, the output voltage VDD of the linear regulator D1 can be maintained at a low and stable level. This reduces the voltage withstand requirements of the downstream relay driver chip and other circuits, and avoids the additional material costs caused by increasing the main power supply voltage VDD. Attached Figure Description

[0019] Figure 1 This is a schematic diagram showing the connection relationship between the linear power supply of this utility model and the relay, MCU and peripheral parts of the energy meter or terminal; Figure 2 This is a circuit diagram of the AC step-down circuit, DC voltage regulator circuit, and transient heavy-load power supply circuit in this utility model; Figure 3 This is a circuit diagram of the relay drive circuit in this utility model. Detailed Implementation

[0020] The technical solution of this utility model will now be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments.

[0021] like Figure 1 and Figure 2 A low-cost linear power supply for an energy meter and terminal with transient heavy load includes an AC step-down circuit, a DC voltage regulator circuit, a transient heavy load power supply circuit, and a relay drive circuit.

[0022] The output of the AC step-down circuit is connected to the input of the DC voltage regulator circuit. The AC step-down circuit is used to perform voltage conversion, and then the DC voltage regulator circuit provides the main power supply for the system.

[0023] Specifically, the AC step-down circuit includes protection devices and a linear transformer T1. The protection devices are used for overvoltage and overcurrent protection at the front end of the linear transformer, including a varistor RV1 connected between the L line and the N line, and a thermistor RT1 connected between the terminal corresponding to the N line on the primary side of the linear transformer T1 and the N line. Since the power consumption of the electricity meter and terminal equipment is low under normal operating conditions, the linear transformer T1 is typically a low-power transformer.

[0024] The DC voltage regulator circuit includes a full-bridge rectifier circuit and a voltage regulator circuit. The output terminal of the AC step-down circuit is connected to the input terminal of the full-bridge rectifier circuit, which converts AC power to DC power. Its output terminal is connected to the input terminal of the voltage regulator circuit. The voltage regulator circuit includes input filter capacitors C1 and C2, output filter capacitors C3 and C4, and a linear regulator D1. The positive terminal of the full-bridge rectifier circuit's output is connected to the input terminal VIN of the linear regulator D1 and grounded through the parallel input filter capacitors C1 and C2. The negative terminal of the full-bridge rectifier circuit's output is grounded. The output terminal of the linear regulator D1 is the output terminal of the voltage regulator circuit (i.e., the output terminal VDD of the DC voltage regulator circuit) and grounded through the parallel output filter capacitors C3 and C4. The ground terminal GND of the linear regulator D1 is grounded. Low-voltage AC power is converted to DC power V_DC by a full-bridge rectifier chip V1. After passing through input filter capacitors C1 and C2, linear regulator D1, and output filter capacitors C3 and C4, a stable DC power supply VDD is output to power the system's backend MCU and peripherals. To ensure overall power efficiency, the input voltage V_DC of D1 should not be too high.

[0025] Furthermore, the first AC output terminal AC of the AC step-down circuit is connected to the control terminal of the transient heavy-load power supply circuit, while the output terminal VDD of the DC regulated circuit is connected to the power supply terminal of the transient heavy-load power supply circuit. The output terminal V_QL of the transient heavy-load power supply circuit is used to power the relay drive circuit.

[0026] The transient heavy-load power supply circuit includes an AC control circuit, a push-pull voltage multiplier circuit, and an energy storage circuit. This scheme uses capacitor energy storage to increase the driving voltage to meet the requirements of transient heavy load. Therefore, a higher heavy-load power supply voltage is needed, while the main system's power supply voltage VDD is lower. To ensure a stable high voltage for the heavy-load power supply under AC power supply conditions, this scheme uses the AC control circuit to convert the AC signal output from the linear transformer T1 into a control signal, controlling the push-pull voltage multiplier circuit to generate a voltage twice VDD, and storing the energy through the energy storage circuit. Figure 2 The AC control circuit includes an NPN transistor V6 connected to the control terminal of the transient heavy-load power supply circuit. The push-pull voltage multiplier circuit includes a capacitor C5, a diode V3, a diode V4, an NPN transistor V5, and a PNP transistor V7. The energy storage circuit includes a capacitor C6. Under the control of the NPN transistor V6, the NPN transistor V5 and the PNP transistor V7 alternately conduct and cut off, thereby charging capacitor C6 through the power supply terminal of the transient heavy-load power supply circuit and capacitor C5, so that the output voltage of the energy storage circuit is twice the output voltage VDD of the DC voltage regulator circuit.

[0027] Specifically, in the AC control circuit, the control terminal of the transient heavy-load power supply circuit is connected to the base of NPN transistor V6 through resistor R4. The collector of NPN transistor V6 is connected to the power supply terminal of the transient heavy-load power supply circuit through resistor R1, and its emitter is grounded. The collector of NPN transistor V6 is also connected to one end of resistor R2, and the other end of resistor R2 is simultaneously connected to the base of NPN transistor V5 and the base of PNP transistor V7.

[0028] In the push-pull voltage multiplier circuit, the collector of NPN transistor V5 is connected to the power supply terminal of the transient heavy-load power supply circuit, and the collector of PNP transistor V7 is grounded. The emitter of NPN transistor V5 is connected to the emitter of PNP transistor V7 and to one end of resistor R6. The other end of resistor R6 is connected to one end of capacitor C5. The power supply terminal of the transient heavy-load power supply circuit is connected to the anode of diode V3, and the cathode of diode V3 is connected to the anode of diode V4 and to the other end of capacitor C5. The cathode of diode V4 is the output terminal of the push-pull voltage multiplier circuit.

[0029] In the energy storage circuit, one end of resistor R3 serves as the input terminal of the energy storage circuit and is connected to the output terminal of the push-pull voltage multiplier circuit. The other end of resistor R3 is connected to one end of capacitor C6, and the other end of capacitor C6 is grounded. The other end of resistor R3 is the output terminal of the energy storage circuit and also the output terminal V_QL of the transient heavy-load power supply circuit. The energy storage circuit also includes a bleeder resistor R5 connected in parallel with capacitor C6.

[0030] The operation process of the transient heavy-load power supply circuit is as follows: 1. The working process of the AC control circuit: When the first AC output terminal (AC) of the AC step-down circuit is in the positive half-cycle, the voltage drives the NPN transistor V6 to conduct through resistor R4, pulling its collector potential down to near ground level. At this time, the voltage across resistor R2 decreases, causing the NPN transistor V5 to turn off and the PNP transistor V7 to conduct.

[0031] When AC is in the negative half-cycle, NPN transistor V6 is cut off, and VDD pulls up the collector voltage of V6 through resistor R1, which in turn turns on NPN transistor V5 and turns off PNP transistor VV7.

[0032] 2. The charging and discharging process of a push-pull voltage multiplier circuit: When NPN transistor V5 is off and PNP transistor V7 is on (AC positive half-cycle): VDD charges capacitor C5 through diode V3, and at this time the voltage across C5 is close to VDD.

[0033] When NPN transistor V5 is turned on and PNP transistor V7 is turned off (AC negative half-cycle): VDD and C5 are connected in series (the voltage across C5 is close to VDD and the voltage cannot change abruptly), and together they charge the energy storage capacitor C6 through diode V4. Since C5 and VDD are superimposed, C6 can eventually be charged to about twice VDD (e.g., if VDD=12V, then V_QL≈24V).

[0034] Resistor R6 is used to limit the charging and discharging current of C5 to prevent overload from affecting the stability of the front-end power supply.

[0035] 3. Transient power supply and replenishment mechanism of energy storage circuit: The energy storage capacitor C6 (e.g., 3000μF) stores high voltage to provide a large instantaneous current (e.g., 9W / 12V, lasting 50ms) for the relay drive circuit.

[0036] During relay operation, C6 discharges, causing a voltage drop. However, the continuous power replenishment by the push-pull voltage multiplier circuit (charging once every half AC cycle) ensures that the voltage of C6 does not fall below the minimum value required for relay operation (e.g., 12V) within 50ms.

[0037] Additionally, resistor R3 limits the charging current of C6 to prevent overload of the front-end circuit. The bleeder resistor R5 releases any residual charge in C6 after a power outage.

[0038] like Figure 3 The main component of the relay driver circuit is the relay driver chip D3 (common models: 8251S, PN7705, BL5616). The power supply terminal of the relay driver chip D3 is connected to the energy storage circuit V_QL, and its control pins are connected to the I / O ports (RelayOff, RelayOn) of the system MCU. The MCU can control the control pins of the relay driver chip D3 to achieve relay tripping / closing actions. Resistors R7 and R8 are pull-down resistors for the control signals, ensuring that the relay driver chip does not malfunction when the I / O state is uncontrollable during the initial power-on startup of the MCU. Resistor R9 is the relay driver current limiting parameter setting resistor, which can adjust the maximum output current limit of the relay driver chip D3.

[0039] It should be noted that, as will be apparent to those skilled in the art, this utility model is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this utility model. The scope of this utility model is defined by the claims rather than the foregoing description.

Claims

1. A low-cost linear power supply for an energy meter and terminal with transient heavy load, comprising an AC step-down circuit and a DC voltage regulator circuit, and further comprising a relay drive circuit, wherein the output terminal of the AC step-down circuit is connected to the input terminal of the DC voltage regulator circuit, characterized in that: The low-cost linear power supply with transient heavy load for the energy meter and terminal also includes a transient heavy load power supply circuit. The first AC output terminal AC of the AC step-down circuit is connected to the control terminal of the transient heavy load power supply circuit, the output terminal VDD of the DC voltage regulator circuit is connected to the power supply terminal of the transient heavy load power supply circuit, and the output terminal V_QL of the transient heavy load power supply circuit is used to power the relay drive circuit. The transient heavy-load power supply circuit includes an AC control circuit, a push-pull voltage multiplier circuit, and an energy storage circuit. The AC control circuit includes an NPN transistor V6 connected to the control terminal of the transient heavy-load power supply circuit. The push-pull voltage multiplier circuit includes a capacitor C5, a diode V3, a diode V4, an NPN transistor V5, and a PNP transistor V7. The energy storage circuit includes a capacitor C6. Under the control of the NPN transistor V6, the NPN transistor V5 and the PNP transistor V7 alternately conduct and cut off, thereby charging the capacitor C6 through the power supply terminal of the transient heavy-load power supply circuit and the capacitor C5, so that the output voltage of the energy storage circuit is twice the output voltage VDD of the DC voltage regulator circuit.

2. The energy meter and terminal with transient heavy load as described in claim 1, characterized in that: In the AC control circuit, the control terminal of the transient heavy-load power supply circuit is connected to the base of the NPN transistor V6 through resistor R4, and the collector of the NPN transistor V6 is connected to the power supply terminal of the transient heavy-load power supply circuit through resistor R1, while the emitter is grounded.

3. The energy meter and terminal with transient heavy load as described in claim 2, characterized in that: The collector of NPN transistor V6 is also connected to one end of resistor R2, and the other end of resistor R2 is connected to the base of NPN transistor V5 and the base of PNP transistor V7. In the push-pull voltage multiplier circuit, the collector of NPN transistor V5 is connected to the power supply terminal of the transient heavy load power supply circuit, and the collector of PNP transistor V7 is grounded; the emitter of NPN transistor V5 is connected to the emitter of PNP transistor V7 and to one end of resistor R6; the other end of resistor R6 is connected to one end of capacitor C5. The power supply terminal of the transient heavy load power supply circuit is connected to the positive terminal of diode V3, the negative terminal of diode V3 is connected to the positive terminal of diode V4 and to the other end of capacitor C5; the negative terminal of diode V4 is the output terminal of the push-pull voltage multiplier circuit.

4. The energy meter and low-cost linear power supply with transient heavy load as described in any one of claims 1 to 3, characterized in that: In the energy storage circuit, one end of resistor R3 is connected to the output of the push-pull voltage multiplier circuit as the input terminal of the energy storage circuit, and the other end of resistor R3 is connected to one end of capacitor C6, and the other end of capacitor C6 is grounded. The other end of resistor R3 is the output terminal of the energy storage circuit and the output terminal V_QL of the transient heavy load power supply circuit.

5. The energy meter and terminal with transient heavy load as described in claim 4, characterized in that: The energy storage circuit also includes a discharge resistor R5 connected in parallel with capacitor C6.

6. The energy meter and terminal with transient heavy load as described in claim 1, characterized in that: The AC step-down circuit includes protection devices and a linear transformer T1.

7. The energy meter and terminal with transient heavy load as described in claim 6, characterized in that: The protection device includes a varistor RV1 connected between the L line and the N line.

8. The energy meter and terminal with transient heavy load as described in claim 6, characterized in that: The protection device includes a thermistor RT1 connected between the terminal corresponding to the N line on the primary side of the linear transformer T1 and the N line.

9. The energy meter and terminal with transient heavy load as described in claim 1, characterized in that: The DC voltage regulator circuit includes a full-bridge rectifier circuit and a voltage regulator circuit; The output terminal of the AC step-down circuit is connected to the input terminal of the full-bridge rectifier circuit, the output terminal of the full-bridge rectifier circuit is connected to the input terminal of the voltage regulator circuit, and the output terminal of the voltage regulator circuit is the output terminal VDD of the DC voltage regulator circuit.

10. The energy meter and terminal with transient heavy load as described in claim 9, characterized in that: The voltage regulator circuit includes input filter capacitors C1 and C2, output filter capacitors C3 and C4, and a linear regulator D1; The positive output terminal of the full-bridge rectifier circuit is connected to the input terminal VIN of the linear regulator D1 and grounded through the parallel input filter capacitors C1 and C2. The negative output terminal of the full-bridge rectifier circuit is grounded. The output terminal of the linear regulator D1 is the output terminal of the voltage regulator circuit and is grounded through the parallel output filter capacitors C3 and C4. The ground terminal GND of the linear regulator D1 is grounded.

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