Reliable power-on starting device for RC power supply three-phase meter

Abstract

The utility model discloses a device for reliably powering on and starting an RC power supply three-phase meter, relates to the technical field of RC electricity meters, and aims to solve the technical problem that the current RC power supply scheme can cause PFO (Performance Frequency Oscillator) jitter and MCU (Microprogrammed Control Unit) 'reset 'of the electricity meter under the condition that'external power supply voltage' is in a low-voltage condition due to the limitation of load capacity, so that the electricity meter cannot reliably operate. Comprising a power-on detection circuit and a voltage sampling circuit, the power-on detection circuit comprises a triode Q5, a resistor R40, a resistor R49, a resistor R64, a resistor R65 and a capacitor C97, and a collector electrode of the triode is connected with the resistor R49 and the capacitor C97 in parallel. According to the method, the problem of continuous reset caused by insufficient loading capacity is avoided, the electric meter is stably kept in a power failure sleep mode SLEEP, and when the voltage is increased to be sufficient for loading, the electric meter is switched to a power-on full-speed POWERON mode, so that the stability and reliability of a power-on mechanism of the electric meter are ensured.

Description

Technical Field

[0001] The utility model relates to the technical field of RC electric meters, and more specifically, to a device for reliably powering on and starting a three-phase RC power meter. Background Art

[0002] Currently, a common power-on detection method for electric meters is that an embedded MCU monitors whether the electric meter is powered on through a "power-on signal" detection port (denoted as). Refer to Figure 1 :

[0003] Pulled up to VMCU, so the default state is high. The +3.6V network is connected to the rectified and filtered DC power supply. When the three-phase meter is externally powered, the +3.6V network becomes high, and the triode Q5 conducts, becomes low. The embedded MCU judges that is low and regards the current state as powered on. When the three-phase meter is externally powered off, the +3.6V network becomes low, and the triode Q5 cuts off, becomes high. The embedded MCU judges that is high and regards the current state as powered off.

[0004] Among them:

[0005] (a) I_smps, the load-carrying capacity that the switch-mode power supply (SMPS) can provide.

[0006] (b) I_rc, the load-carrying capacity that the resistor-capacitor step-down power supply (RC) can provide.

[0007] (c) I_mcu, the current capacity required to support the operation of the main MCU and the weak-current part of the entire electric meter.

[0008] In this case:

[0009] In the "power-on full speed" POWER_ON mode, the electric meter operates at high speed with all functions and requires 3 milliamperes, denoted as I_ON.

[0010] In the "power-off sleep" SLEEP mode, the electric meter is in a low-power consumption mode and only requires 0.002 milliamperes, denoted as I_SLEEP.

[0011] If I_smps > I_mcu or I_rc > I_mcu, then the driving load-carrying capacity of the power supply is sufficient to support the reliable operation of the entire electric meter system.

[0012] If I_smps < I_mcu or I_rc < I_mcu, then the driving load-carrying capacity of the power supply is not sufficient to support the operation of the entire electric meter system, which will cause the electric meter to jitter and the MCU to "reset", and the electric meter cannot operate reliably.

[0013] For an electricity meter using a switched-mode power supply (SMPS), since the load-carrying capacity I_smps of the power supply is relatively strong, generally, while the power consumption is low, it must also satisfy I_smps > I_mcu. Therefore, by only judging it is possible to easily and reliably distinguish the power-on / power-off state.

[0014] For an electricity meter using a resistor-capacitor step-down power supply (RC), since the load-carrying capacity I_rc of the power supply is weak, the situation becomes delicate. When the "external supply voltage" (referring to VR / VY / VB-input) reaches 48 volts, it starts to change from high to low. However, at this time, I_rc is far from sufficient to support the full-speed operation of the entire electricity meter (I_rc < I_ON). Only when the "external supply voltage" reaches more than 96 volts, is the load-carrying capacity of I_rc sufficient. That is, the range between 48 volts and 96 volts is a "blind area". In this interval, although a "power-on signal" is given, the load-carrying capacity of the RC power supply is insufficient. Therefore, by only judging it is not possible to reliably switch the power-on / power-off mode.

[0015] A typical half-wave rectified RC meter power supply circuit, refer to Figure 2 :

[0016] Now, let's evaluate the "driving load-carrying capacity I_rc of the RC power supply" as follows:

[0017] Capacitive reactance Xc = 1 / (2 * f * C)

[0018] Load current Ic = U / Xc = 2 * f * C * U

[0019] Among them,

[0020] f, 50Hz

[0021] C, depends on the device values of CP1 / CP2 / CP3. For a current 4VA meter, the designed value in this design is 0.22 μF.

[0022] U, depends on the supply voltage of VR / VY / VB-input.

[0023] Considering that only half-wave rectification is provided in this circuit, it is necessary to multiply by 0.5 again.

[0024] Considering that there will be a certain error in the capacitor device itself, so give a 10% discount. Therefore, the actual load-carrying capacity:

[0025] Load current I_rc = Ic = U / Xc = 2 * f * C * U * 0.5 * 0.9

[0026] Based on the above formula, we calculate the meter load capacity I_rc under some voltage conditions, refer to Figure 3 It can be seen that for a 4VA RC meter (CP1 / CP2 / CP3 value is 0.22uF), it can still operate normally when the single-phase power supply is 96V. However, if the external power supply voltage is further reduced to below 96V, it will not be able to operate stably due to insufficient I_rc load. In this case, The main MCU will vibrate unstably. The meter is constantly switching between the "full speed" POWER_ON mode and the "power-off sleep" SLEEP mode. From the outside, it looks like the meter is constantly "resetting". Obviously, this is unacceptable.

[0027] In order to solve this problem of RC power supply, there are two conventional processing methods.

[0028] One is to switch to a switching power supply solution;

[0029] The second is to still use the RC power supply solution, and only increase the capacitance of the RC power supply's voltage drop capacitors CP1 / CP2 / CP3 to increase the I_rc load capacity of the RC power supply. For example, change the capacitor C from 0.22uF to 0.41uF. Of course, the meter's own consumption will also increase from 4VA to 8VA. Based on the above formula, we calculate the meter's load capacity I_rc under some voltage conditions, refer to Figure 4 ;

[0030] However, the above processing method still has some shortcomings. Figure 2 :

[0031] (1) The capacitance value of capacitors CP1 / CP2 / CP3 increases, and the cost increases;

[0032] (2) The power consumption (VA value) of the meter itself also increases. The cost of this power consumption is borne by the mains power grid, which undoubtedly increases the grid cost, reduces grid efficiency, and causes energy waste;

[0033] (3) Some electric meter bidding specifications clearly require a lower VA value. If the capacitance is increased, the requirement cannot be met.

[0034] In view of this, we propose a device for reliable power-on and starting of a three-phase meter with an RC power supply. Utility Model Content

[0035] The purpose of the utility model is to overcome the shortcomings of the prior art, meet the actual needs, and provide a device for reliable power-on startup of a three-phase meter with an RC power supply, so as to solve the problem that the current RC power supply solution, due to the limited load capacity, will cause the meter to start when the "external power supply voltage" is at a low voltage. Technical problems such as jitter and MCU "reset" that cause the electricity meter to operate unreliably.

[0036] To solve the above technical problems, the present utility model provides the following technical solution: A device for reliable power-on startup of an RC power three-phase meter, including a power-on detection circuit and a voltage sampling circuit;

[0037] The power-on detection circuit includes a triode Q5, resistors R40, R49, R64, R65, and a capacitor C97. The collector of the triode is connected in parallel with the resistor R49 and the capacitor C97, and a connection for power-on detection is formed between the resistor R49 and the capacitor C97. One end of the resistor R49 is connected to VMCU, and one end of the capacitor C97 is grounded;

[0038] The voltage sampling circuit includes an AA node connected to the external power supply voltage of the R phase of the electricity meter, a BB node connected to the external power supply voltage of the Y phase of the electricity meter, a CC node connected to the external power supply voltage of the B phase of the electricity meter, and ADC0 node, ADC1 node, and ADC2 node connected to the ADC in the embedded MCU.

[0039] The present utility model uses the voltage sampling circuit to detect the external power supply voltages of the R phase, Y phase, and B phase on the three-phase meter in real time, and combines the ADC0, ADC1, and ADC2 nodes connected to the ADC of the embedded MCU to collect the "external power supply voltage". The collected data is used to calculate the value of VR-Input, and further evaluate the load-carrying capacity current I_rc. If it is predicted that the "external power supply voltage" is not sufficient to generate enough I_rc load-carrying capacity, that is, I_rc < I_ON, then the power-on signal is ignored Let the electricity meter remain in the "power-off sleep" SLEEP mode. If it is predicted that the "external power supply voltage" is sufficient to generate enough I_rc load-carrying capacity, that is, I_rc > I_ON, then it will be officially switched to the "power-on full speed" POWER_ON mode, avoiding unstable jitter caused by insufficient I_rc load-carrying capacity and inability to operate stably, and preventing the main MCU from Continuously switching between the "power-on full speed" POWER_ON mode and the "power-off sleep" SLEEP mode, so as to ensure that the electricity meter will not continuously "reset" due to insufficient load-carrying capacity under low voltage conditions, but will stably remain in the "power-off sleep" SLEEP mode. Only when the voltage continues to rise to a sufficient load-carrying level, the electricity meter will switch to the "power-on full speed" POWER_ON mode, thus ensuring the stable and reliable power-on mechanism of the electricity meter.

[0040] ​​Preferably, the emitter of the triode Q5 is grounded, and the base of the triode Q5 is connected to the resistor R40. The other end of the resistor R40 is connected in parallel to the resistors R64 and R65. One end of the resistor R64 is connected to the +3.6VDC power supply, and one end of the resistor R65 is grounded.

[0041] Preferably, a resistor R1, a resistor R4, a resistor R7, and a resistor R25 are connected in series between the AA node and the ADC0 node. A resistor R10 and a capacitor C4 are connected in parallel between the resistor R7 and the resistor R25. A capacitor C5 is connected between the resistor R25 and the ADC0 node, and one ends of the capacitor C4 and the capacitor C5 are both grounded.

[0042] Preferably, a resistor R2, a resistor R5, a resistor R8, and a resistor R26 are connected in series between the BB node and the ADC1 node. A resistor R11 and a capacitor C6 are connected in parallel between the resistor R8 and the resistor R26. A capacitor C7 is connected between the resistor R26 and the ADC1 node, and one ends of the capacitor C6 and the capacitor C7 are both grounded.

[0043] Preferably, a resistor R3, a resistor R6, a resistor R9, and a resistor R27 are connected in series between the CC node and the ADC2 node. A resistor R12 and a capacitor C8 are connected in parallel between the resistor R9 and the resistor R27. A capacitor C9 is connected between the resistor R27 and the ADC2 node, and one ends of the capacitor C8 and the capacitor C9 are both grounded.

[0044] Compared with the prior art, the beneficial effects of the present utility model are as follows:

[0045] 1. Through the voltage sampling circuit, the present utility model can detect the external power supply voltages of the R phase, Y phase, and B phase on the three-phase meter in real time. By combining the ADC0, ADC1, and ADC2 nodes with the ADC of the embedded MCU, the "external power supply voltage" can be collected. The collected data is used to calculate the value of VR-Input, and further evaluate the load-carrying capacity current I_rc. If it is predicted that the "external power supply voltage" is not sufficient to generate enough I_rc load-carrying capacity, that is, I_rc < I_ON, then the power-on signal is ignored, and the electric meter remains in the "power-off sleep" SLEEP mode. If it is predicted that the "external power supply voltage" is sufficient to generate enough I_rc load-carrying capacity, that is, I_rc > I_ON, it will be officially switched to the "power-on full speed" POWER_ON mode, avoiding unstable jitter caused by insufficient I_rc load-carrying capacity and inability to operate stably, and preventing the main MCU from following the unstable ones. Constantly switching between the "full speed" POWER_ON mode and the "power-off sleep" SLEEP mode ensures that the meter will not be constantly "reset" due to insufficient load capacity under low voltage conditions, but will be stable in the "power-off sleep" SLEEP mode. Only when the voltage continues to rise to a sufficient load will the meter switch to the "full speed" POWER_ON mode, thus ensuring the stability and reliability of the meter's power-on mechanism.

[0046] 2. The utility model also saves costs by designing a voltage sampling circuit, which does not require the addition of additional devices or the replacement of capacitors with larger capacitance. It also reduces the power consumption of the electric meter itself, saves the cost of the power grid, improves the efficiency of the power grid, reduces energy waste, and has a lower VA value, which can meet the requirements of the bidding specifications of the electric meter. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is the power-on detection circuit in the utility model;

[0048] Figure 2 It is a half-wave rectified RC meter power supply circuit;

[0049] Figure 3 This is a schematic diagram of the meter load capacity I_rc under specific voltage conditions of the 4VARC meter under the RC power supply solution;

[0050] Figure 4 This is a schematic diagram of the meter load capacity I_rc under specific voltage conditions of the 8VARC meter under the RC power supply solution;

[0051] Figure 5 It is the voltage sampling circuit in the utility model;

[0052] Figure 6 This is a power-on signal monitoring flow chart in the utility model. DETAILED DESCRIPTION

[0053] like Figure 1 , Figure 5 , Figure 6 As shown, the utility model relates to a device for reliable power-on startup of an RC power three-phase meter, comprising a power-on detection circuit and a voltage sampling circuit;

[0054] In an embodiment of the utility model, the power-on detection circuit includes a transistor Q5, a resistor R40, a resistor R49, a resistor R64, a resistor R65, and a capacitor C97. The collector of the transistor is connected in parallel with the resistor R49 and the capacitor C97, and a connection for power-on detection is formed between the resistor R49 and the capacitor C97. One end of the resistor R49 is connected to VMCU, and one end of the capacitor C97 is grounded. The emitter of the transistor Q5 is grounded, and the base of the transistor Q5 is connected to the resistor R40. The other end of the resistor R40 is connected in parallel with the resistor R64 and the resistor R65. One end of the resistor R64 is connected to a +3.6VDC power supply, and one end of the resistor R65 is grounded.

[0055] In an embodiment of the utility model, the voltage sampling circuit includes an AA node connected to the R-phase external power supply voltage of the meter, a BB node connected to the Y-phase external power supply voltage of the meter, a CC node connected to the B-phase external power supply voltage of the meter, and an ADC0 node, an ADC1 node, and an ADC2 node connected to the ADC in the embedded MCU;

[0056] In an embodiment of the utility model, a resistor R1, a resistor R4, a resistor R7, and a resistor R25 are connected in series between the AA node and the ADC0 node, a resistor R10 and a capacitor C4 are connected in parallel between the resistor R7 and the resistor R25, a capacitor C5 is connected between the resistor R25 and the ADC0 node, and one end of the capacitor C4 and the capacitor C5 are both grounded;

[0057] In an embodiment of the present utility model, a resistor R2, a resistor R5, a resistor R8, and a resistor R26 are connected in series between the BB node and the ADC1 node, a resistor R11 and a capacitor C6 are connected in parallel between the resistor R8 and the resistor R26, a capacitor C7 is connected between the resistor R26 and the ADC1 node, and one end of the capacitor C6 and the capacitor C7 are both grounded;

[0058] In an embodiment of the present utility model, a resistor R3, a resistor R6, a resistor R9, and a resistor R27 are connected in series between the CC node and the ADC2 node. A resistor R12 and a capacitor C8 are connected in parallel between the resistor R9 and the resistor R27. A capacitor C9 is connected between the resistor R27 and the ADC2 node, and one ends of the capacitor C8 and the capacitor C9 are both grounded. Through a voltage sampling circuit, the external power supply voltages of the R phase, Y phase, and B phase on the three-phase meter are detected in real time, and in combination with the ADCs of the embedded MCU connected to the ADC0, ADC1, and ADC2 nodes, the "external power supply voltage" is collected. The collected data is used to calculate the value of VR-Input, and further evaluate the load-carrying capacity current I_rc. If it is predicted that the "external power supply voltage" is not sufficient to generate enough I_rc load-carrying capacity, that is, I_rc < I_ON, then the power-on signal is ignored, and the meter remains in the "power-off sleep" SLEEP mode. If it is predicted that the "external power supply voltage" is sufficient to generate enough I_rc load-carrying capacity, that is, I_rc > I_ON, then it is officially switched to the "power-on full speed" POWER_ON mode, avoiding unstable jitter caused by insufficient I_rc load-carrying capacity and inability to operate stably, and preventing the main MCU from continuously switching between the "power-on full speed" POWER_ON mode and the "power-off sleep" SLEEP mode due to instability, so as to ensure that the meter will not continuously "reset" due to insufficient load-carrying capacity under low voltage conditions, but will stably remain in the "power-off sleep" SLEEP mode. Only when the voltage continues to rise to a sufficient load-carrying level will the meter switch to the "power-on full speed" POWER_ON mode, thus ensuring the stable and reliable power-on mechanism of the meter.

[0059] Working principle: This embodiment provides a device for reliable power-on startup of an RC power three-phase meter. When in use, after the embedded MCU detects a "power-on signal", it enables the ADC sampling to sample the externally applied voltage, and enables the timer TIMER to constrain the acquisition time window. If within a 100-millisecond time window (under 50Hz conditions, 5 waveform cycles), I_rc is continuously detected and calculated and evaluated;

[0060] Then, through the voltage sampling circuit, the external power supply voltages of the R phase, Y phase, and B phase on the three-phase meter are detected, and in combination with the ADCs of the embedded MCU connected to the ADC0, ADC1, and ADC2 nodes, the "external power supply voltage" is collected. The collected data is used to calculate the value of VR-Input, and further evaluate the load-carrying capacity current I_rc;

[0061] If the results of 5 calculations are all Irc > I_ON, then it is officially switched to the "power-on full speed" POWER_ON mode, and the meter operates in the power-on mode at full function and high speed. At this time, the power consumption overhead is I_ON;

[0062] If the result of any one of the five calculations does not satisfy Irc > I_ON, then return to the "power-off sleep" SLEEP mode again. At this time, the power consumption overhead is only I_SLEEP;

[0063] If it is predicted that the "external power supply voltage" is not sufficient to generate sufficient I_rc load capacity, that is, I_rc < I_ON, then the power-on signal is ignored, and the electricity meter remains in the "power-off sleep" SLEEP mode;

[0064] If it is predicted that the "external power supply voltage" is sufficient to generate sufficient I_rc load capacity, that is, I_rc > I_ON, then it is officially switched to the "power-on full speed" POWER_ON mode to avoid unstable jitter caused by insufficient I_rc load capacity and inability to operate stably, and prevent the main MCU from continuously switching between the "power-on full speed" POWER_ON mode and the "power-off sleep" SLEEP mode. Thus, it is ensured that under low voltage conditions, the electricity meter will not continuously "reset" due to insufficient load capacity, but will stably remain in the "power-off sleep" SLEEP mode. Only when the voltage continues to rise to a sufficient load capacity will the electricity meter switch to the "power-on full speed" POWER_ON mode. Thereby, the stability and reliability of the power-on mechanism of the electricity meter are ensured.

[0065] The embodiments disclosed in the present invention are preferred embodiments, but not limited thereto. Those of ordinary skill in the art can easily understand the spirit of the present invention based on the above embodiments and make different extensions and changes. However, as long as they do not depart from the spirit of the present invention, they are within the protection scope of the present invention.​

Claims

1. A device for reliable power-on startup of a RC power three-phase meter, characterized in that: Including power-on detection circuit and voltage sampling circuit; The power-on detection circuit includes a transistor Q5, a resistor R40, a resistor R49, a resistor R64, a resistor R65, and a capacitor C97, wherein the collector of the transistor is connected in parallel with the resistor R49 and the capacitor C97, and a PFO for power-on detection is formed between the resistor R49 and the capacitor C97, one end of the resistor R49 is connected to VMCU, and one end of the capacitor C97 is grounded; The voltage sampling circuit includes an AA node connected to the R phase external power supply voltage of the meter, a BB node connected to the Y phase external power supply voltage of the meter, a CC node connected to the B phase external power supply voltage of the meter, and ADC0 node, ADC1 node, and ADC2 node connected to the ADC in the embedded MCU.

2. The device for reliable power-on startup of a RC power three-phase meter according to claim 1, characterized in that: The emitter of the transistor Q5 is grounded, and the base of the transistor Q5 is connected to the resistor R40. The other end of the resistor R40 is connected in parallel to the resistor R64 and the resistor R65. One end of the resistor R64 is connected to a +3.6VDC power supply, and one end of the resistor R65 is grounded.

3. The device for reliable power-on startup of a RC power three-phase meter according to claim 1, characterized in that: Resistors R1, R4, R7, and R25 are connected in series between the AA node and the ADC0 node, resistors R10 and capacitors C4 are connected in parallel between the resistors R7 and R25, capacitors C5 are connected between the resistors R25 and the ADC0 node, and one ends of the capacitors C4 and C5 are both grounded.

4. The device for reliable power-on startup of a RC power three-phase meter according to claim 1, characterized in that: Resistors R2, R5, R8, and R26 are connected in series between the BB node and the ADC1 node, resistors R11 and capacitor C6 are connected in parallel between the resistor R8 and the resistor R26, capacitor C7 is connected between the resistor R26 and the ADC1 node, and one end of the capacitor C6 and the capacitor C7 are both grounded.

5. The device for reliable power-on startup of a RC power three-phase meter according to claim 1, characterized in that: Resistors R3, R6, R9, and R27 are connected in series between the CC node and the ADC2 node, resistors R12 and capacitors C8 are connected in parallel between the resistors R9 and R27, capacitors C9 are connected between the resistors R27 and the ADC2 node, and one ends of the capacitors C8 and C9 are both grounded.

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