Voltage regulation circuit applied to electric energy meter and electric energy meter

Abstract

The invention relates to a voltage regulation circuit applied to an electric energy meter and the electric energy meter, and belongs to the field of electric energy meters. The voltage regulation circuit comprises a feedback regulation circuit, a DC / DC conversion chip used for outputting a first preset voltage at an output end when a voltage received by an enable end is greater than a first threshold voltage, and a voltage mapping circuit used for mapping a voltage of a power supply end to the output end when the voltage received by the enable end is greater than a second threshold voltage, the current-limiting protection chip is used for cutting off the output end when the current of the current-limiting end exceeds a preset current; the output end of the DC / DC conversion chip is connected with the feedback regulation circuit and the current-limiting protection chip respectively; the output end of the feedback regulation circuit is connected with the feedback end of the DC / DC conversion chip; the output end and the current-limiting end of the current-limiting protection chip are used for connecting a low-voltage element; the feedback adjusting circuit is used for adjusting the first preset voltage according to the working voltage of the low-voltage element. According to the invention, power can be directly supplied to low-voltage elements in the electric energy meter and timely supplied after a fault is removed.

Description

TECHNICAL FIELD

[0001] The application relates to a voltage regulating circuit applied to an electric energy meter and the electric energy meter, and belongs to the field of electric energy meters. BACKGROUND

[0002] The smart electric meter is an electronic instrument for electric energy metering, which can be installed in a power load circuit (such as an alternating current mains) or a resident's house. The internal part of the electric meter comprises a main processor, a metering chip, a memory, electronic circuits and the like electronic elements. The working voltage required by the electronic elements during work is usually low-voltage direct current, which is generally supplied to the low-voltage elements through the power supply circuit in the electric meter. The power supply circuit in the electric meter can convert alternating current high voltage into direct current low voltage, that is, AC / DC conversion.

[0003] At present, there are two schemes for the internal working power supply of the electric meter: (1) a linear power supply scheme; and (2) a switching power supply scheme.

[0004] For the linear power supply scheme: the alternating current voltage coupled and output by the secondary coil of the linear transformer is subjected to full-wave rectification by a rectifier bridge and is subjected to smoothing filtering to become a 16-volt direct current voltage (which varies with the load condition).

[0005] For the switching power supply scheme: the alternating current 220V is converted into a 15-volt direct current or a 12-volt direct current by using a high-frequency switching semiconductor device.

[0006] The working voltage of the low-voltage elements in the electric meter is generally 3.3V or 5V. The voltage output by the linear power supply scheme and the switching power supply scheme is too high and cannot be directly supplied to the low-voltage elements (such as the main chip) of the electric meter. At the same time, the linear power supply scheme and the switching power supply scheme do not have a short-circuit protection function. When there is a short circuit caused by a fault or a too large load at the rear end, the front-end chip will be directly damaged, the power supply circuit will have no voltage output, and the use of the electric meter will be further affected, thereby causing troubles to the user. SUMMARY

[0007] The application aims to provide a voltage regulating circuit applied to an electric energy meter and the electric energy meter, so as to solve the problems that the voltage regulating scheme in the prior art cannot directly supply power to the low-voltage elements in the electric meter and cannot normally supply power after a fault is removed.

[0008] To achieve the above-mentioned purpose, the scheme of the application comprises:

[0009] The application discloses a voltage regulating circuit applied to an electric energy meter.

[0010] The output end of the DC / DC conversion chip is connected with the input end of the feedback regulating circuit, the power supply end of the current limiting protection chip and the enable end of the current limiting protection chip respectively.

[0011] The output end of the feedback regulating circuit is connected with the feedback end of the DC / DC conversion chip.

[0012] The output end and the current limiting end of the current limiting protection chip are used for connecting the same low-voltage element in the electric energy meter.

[0013] The feedback regulating circuit is used for adjusting the size of the first preset voltage according to the working voltage of the low-voltage element.

[0014] Further, the feedback regulating circuit comprises a first feedback regulating resistor and a second feedback regulating resistor.

[0015] One end of the first feedback regulating resistor is connected with the feedback end of the DC / DC conversion chip and one end of the second feedback regulating resistor respectively, the other end of the first feedback regulating resistor is connected with the output end of the DC / DC conversion chip, and the other end of the second feedback regulating resistor is grounded.

[0016] Further, the application further comprises a first voltage stabilizing resistor arranged on a connecting line between the enable end of the DC / DC conversion chip and the power supply line, and used for stabilizing the voltage on the enable end of the DC / DC conversion chip.

[0017] The application further comprises a first filtering capacitor with an anode plate connected with the enable end of the DC / DC conversion chip and a cathode plate grounded, and used for filtering the signal on the power supply line.

[0018] Further, the application further comprises a second filtering capacitor with an anode plate connected with the input end of the feedback regulating circuit and a cathode plate grounded, and used for filtering the adjusted first preset voltage.

[0019] Further, the application further comprises an LC filtering circuit used for reducing the ripple of the signal outputted by the output end of the DC / DC conversion chip.

[0020] The first filter inductor in the LC filter circuit is connected in series on the connecting line between the output end of the DC / DC conversion chip and the input end of the feedback adjustment circuit; one end of the third filter capacitor in the LC filter circuit is connected to the filter end of the DC / DC conversion chip, and the other end is connected to one end of the first filter inductor for connecting the output end of the DC / DC conversion chip.

[0021] Further, the second voltage stabilizing resistor for stabilizing the voltage on the enable end of the current limiting protection chip is arranged on the connecting line between the enable end of the current limiting protection chip and the output end of the DC / DC conversion chip.

[0022] Further, the adjusting resistor for adjusting the preset current size is arranged in series on the connecting line between the current limiting end of the current limiting protection chip and the low-voltage element.

[0023] Further, the fourth filter capacitor for filtering the signal output by the output end of the current limiting protection chip is arranged in series on the connecting line between the adjusting resistor and the low-voltage element; and the fifth capacitor for controlling the rising rate of the voltage output by the output end of the current limiting protection chip is arranged with one end connected to the soft start end of the current limiting protection chip and the other end connected to one end of the adjusting resistor for connecting the low-voltage element.

[0024] Further, the anti-reverse diode for preventing voltage from flowing backward is arranged in series on the connecting line between the output end of the current limiting protection chip and the low-voltage element, and the conduction direction thereof points to the low-voltage element.

[0025] The electric energy meter of the present application comprises the voltage adjustment circuit applied to the electric energy meter as described above.

[0026] The beneficial effects of the present application are: as an opening invention, the present application provides a voltage regulating circuit applied to an electric energy meter and the electric energy meter, comprising a feedback regulating circuit, a DC / DC conversion chip for outputting a first preset voltage at the output end when the voltage received at the enable end is greater than the first threshold voltage thereof, and a current limiting protection chip for mapping the voltage at the power supply end to the output end when the voltage received at the enable end is greater than the second threshold voltage thereof, and cutting off the output end when the current at the current limiting end exceeds the preset current; further comprising; the output end of the DC / DC conversion chip is connected to the input end of the feedback regulating circuit, the power supply end of the current limiting protection chip and the enable end of the current limiting protection chip respectively; the output end of the feedback regulating circuit is connected to the feedback end of the DC / DC conversion chip; the output end and the current limiting end of the current limiting protection chip are used to connect the same low-voltage element in the electric energy meter; the feedback regulating circuit is used to adjust the size of the first preset voltage according to the working voltage of the low-voltage element. The present application, on the one hand, converts the high-voltage power on the power line into low-voltage power for output by using the DC / DC conversion chip, and accurately adjusts the voltage value output by the DC / DC conversion chip through the feedback regulating circuit, so that the low-voltage element can be directly provided with power supply according to the adjusted voltage value; on the other hand, by adding the current limiting protection chip, the power supply channel to the low-voltage element can be quickly cut off when the low-voltage element has a short circuit or a large load fault, so as to protect the DC / DC conversion chip and the feedback regulating circuit at the front end from being damaged, and after the fault is cleared, the power supply channel of the voltage regulating circuit to the low-voltage element is restored, and the low-voltage element is supplied with power in time. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a structural schematic diagram of a voltage regulating circuit applied to an electric energy meter provided by an embodiment of the present application;

[0028] Figure 2 is a structural schematic diagram of a current limiting protection chip in Figure 1 . DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the present application will be further described in detail below with reference to the drawings and embodiments.

[0030] The idea of the present application is to use a voltage conversion chip, a feedback regulating circuit and a current limiting protection chip to complete accurate regulation and protection of the power supply voltage.

[0031] Specifically: including a DC / DC conversion chip for outputting a first preset voltage at the output end when the voltage received at the enable end is greater than its first threshold voltage; including a current limiting protection chip for mapping the voltage of the power supply end to the output end when the voltage received at the enable end is greater than its second threshold voltage, and cutting off the output end when the current at the current limiting end exceeds the preset current; further including a feedback regulation circuit; the output end of the DC / DC conversion chip is connected to the input end of the feedback regulation circuit, the power supply end of the current limiting protection chip and the enable end of the current limiting protection chip respectively; the output end of the feedback regulation circuit is connected to the feedback end of the DC / DC conversion chip; the output end and the current limiting end of the current limiting protection chip are used to connect the same low-voltage element in the electric energy meter; the feedback regulation circuit is used to adjust the size of the first preset voltage according to the working voltage of the low-voltage element.

[0032] An embodiment of a voltage regulation circuit applied to an electric energy meter:

[0033] Figure 1 is a structural schematic diagram of a voltage regulation circuit applied to an electric energy meter provided by an embodiment of the present application, as Figure 1 shown, the voltage regulation circuit comprises a DC / DC conversion chip 10, a current limiting protection chip 20 and a feedback regulation circuit 30.

[0034] Among them, the DC / DC conversion chip 10 comprises 6 pins, pin 1 is a voltage driving pin, pin 2 is a ground end GND, pin 3 is a feedback end FB, pin 4 is an enable end SHDN (high level effective, low level ineffective), pin 5 is a power supply end VIN and pin 6 is an output end SW; the DC / DC conversion chip 10 is used to output a first preset voltage at its output end SW when the voltage received at its enable end SHDN is greater than the first threshold voltage of its enable end SHDN, and the chip is disabled when the voltage received at its enable end SHDN is less than or equal to the first threshold voltage of its enable end SHDN.

[0035] Among them, the first threshold voltage of the enable end SHDN of the DC / DC conversion chip 10 is generally 1.2V, and can also be other voltage values, which is determined by the selected DC / DC conversion chip 10 itself (because different models of DC / DC conversion chips have different internal specifications for the first threshold voltage of their enable end SHDN), and the present application does not make special limitation, and the subsequent example is taken that the first threshold voltage of the enable end SHDN of the DC / DC conversion chip 10 is 1.2V for example.

[0036] Among them, the first preset voltage can be 5V, or 3.3V, or 12V, etc., which is determined according to the working voltage of the load connected at the back end, and the present application does not make special limitation, and the subsequent example is taken that the first preset voltage is 5V for example.

[0037] That is, when the enable end SHDN of the DC / DC conversion chip 10 receives a voltage greater than 1.2V, the DC / DC conversion chip 10 is enabled and starts to work, and the output end of the DC / DC conversion chip 10 outputs a first preset voltage of 5V; when the enable end SHDN of the DC / DC conversion chip 10 receives a voltage less than or equal to 1.2V, the DC / DC conversion chip is closed.

[0038] The DC / DC conversion chip 10 can output the input voltage in the form of pulses by controlling the conduction and non-conduction of the output end SW. The current limiting protection chip 20 includes six pins, the pin 1 is a power supply end VIN, the pin 2 is a ground end GND, the pin 3 is an enable end EN / Fault (high level effective and low level ineffective), the pin 4 is a soft start end SS, the pin 5 is a current limiting end ILIM, and the pin 6 is an output end OUT. The current limiting protection chip 20 is used to map the voltage of the power supply end VIN to the output end OUT when the voltage received by the enable end is greater than the second threshold voltage of the enable end EN / Fault, and the chip as a whole is disabled when the voltage received by the enable end EN / Fault is less than the third threshold voltage of the enable end EN / Fault, and the output end OUT is cut off when the current of the current limiting end ILIM exceeds the preset current.

[0039] Figure 2 The current limiting protection chip 20 is a current limiting protection chip provided by the embodiment of the application. Figure 1 The internal circuit structure of the current limiting protection chip in the current limiting protection chip 20 is shown in FIG. 2. Figure 2 The enable end EN / Fault of the current limiting protection chip 20 is high level effective and low level ineffective, which can control the working state of the current limiting protection chip 20.

[0040] When the voltage applied to the enable end EN / Fault of the current limiting protection chip 20 is higher than the second threshold voltage, the current limiting protection chip 20 is enabled, the internal field effect transistor 201 is turned on, the circuit starts to work normally, and the current can flow from the power supply end VIN to the output end OUT, that is, the voltage of the power supply end is mapped to the output end to supply power to the load.

[0041] When the voltage applied to the enable end EN / Fault of the current limiting protection chip 20 is lower than the third threshold voltage, the current limiting protection chip 20 is disabled, the internal field effect transistor 201 is turned off, the connection between the power supply end VIN and the output end OUT is cut off, and the power supply to the load is stopped. This control mode facilitates flexible opening or closing of the chip according to actual needs, thereby controlling the working state of the entire circuit.

[0042] The second threshold voltage of the enable end EN / Fault of the current limiting protection chip 20 is generally 1.39V, and can also be other voltage values, which is determined by the selected current limiting protection chip 20 itself (because different models of current limiting protection chips have different internal specifications for the second threshold voltage of the EN / Fault), and the present application does not make special limitations, and the subsequent example is taken as an example that the second threshold voltage of the enable end EN / Fault of the current limiting protection chip 20 is 1.39V.

[0043] The third threshold voltage of the enable end EN / Fault of the current limiting protection chip 20 is generally 1.33V, and can also be other voltage values, which is determined by the selected current limiting protection chip 20 itself (because different models of current limiting protection chips have different internal specifications for the third threshold voltage of the EN / Fault), and the present application does not make special limitations, and the subsequent example is taken as an example that the third threshold voltage of the enable end EN / Fault of the current limiting protection chip 20 is 1.33V.

[0044] Although the second threshold voltage and the third threshold voltage of the enable end EN / Fault of the current limiting protection chip 20 are determined by the selected current limiting protection chip 20 itself, in principle, the second threshold voltage of the enable end EN / Fault of the current limiting protection chip 20 is greater than the third threshold voltage.

[0045] That is, when the voltage received by the enable end EN / Fault of the current limiting protection chip 20 is greater than 1.39V, the voltage of the power supply end VIN of the current limiting protection chip 20 is mapped to the output end OUT, and when the voltage received by the enable end EN / Fault of the current limiting protection chip 20 is less than 1.33V, the chip is disabled as a whole.

[0046] It can be understood that for those skilled in the art, it should be known that in order for the DC / DC conversion chip 10 to work normally, the DC / DC conversion chip 10 needs power supply, so the power supply end VIN of the DC / DC conversion chip 10 can be connected with the power line VCC1, and the DC / DC conversion chip 10 also needs to be grounded, so the ground end GND of the DC / DC conversion chip can be grounded. The ground end GND of the current limiting protection chip 20 also needs to be grounded.

[0047] Specifically, the output end SW of the DC / DC conversion chip 10 is connected with the input end of the feedback regulation circuit 30, the power supply end VIN of the current limiting protection chip 20 and the enable end EN / Fault of the current limiting protection chip 20 respectively; the output end of the feedback regulation circuit 30 is connected with the feedback end FB of the DC / DC conversion chip 10; the output end OUT and the limiting end ILIM of the current limiting protection chip 20 are used to connect the same low-voltage element in the electric energy meter.

[0048] As an optional embodiment, the enable end EN / Fault of the current-limiting protection chip 20 can not be connected with the output end SW of the DC / DC conversion chip 10, but connected with other power supply lines.

[0049] The feedback adjusting circuit 30 is configured to adjust the size of the first preset voltage according to the working voltage of the low-voltage element in the electric energy meter connected with the output end OUT and the current-limiting end ILIM of the current-limiting protection chip 20.

[0050] It can be understood that when there are multiple low-voltage elements in the electric energy meter, if the working voltages required by these low-voltage elements are the same, the output end OUT of the current-limiting protection chip 20 can be connected with all the low-voltage elements respectively, and these low-voltage elements also need to be connected with the current-limiting end ILIM of the current-limiting protection chip 20; if the working voltages required by these low-voltage elements are different, the number of voltage adjusting circuits can be determined according to the types of the working voltages required by the low-voltage elements, and the number of voltage adjusting circuits is equal to the number of the types of the working voltages. The output end and the current-limiting end ILIM of the current-limiting protection chip 20 in the same voltage adjusting circuit are connected with the low-voltage elements of the same type, so that the connected low-voltage elements in the electric energy meter can work normally, and the voltage cannot enter the front-end DC / DC conversion chip 10 and the feedback adjusting circuit 20 and cause damage to them, thereby ensuring that the DC / DC conversion chip can continue to provide stable working voltage after the fault is removed.

[0051] The feedback adjusting circuit 30 comprises a first feedback adjusting resistor R1 and a second feedback adjusting resistor R2. One end of the first feedback adjusting resistor R1 is connected with the feedback end FB of the DC / DC conversion chip 10 and one end of the second feedback adjusting resistor R2 respectively; the other end of the first feedback adjusting resistor R1 is connected with the output end SW of the DC / DC conversion chip 10; and the other end of the second feedback adjusting resistor R2 is grounded GND.

[0052] The one end of the first feedback adjusting resistor R1 connected with the feedback end FB of the DC / DC conversion chip 10 is the output end of the feedback adjusting circuit 30, and the one end of the first feedback adjusting resistor R1 connected with the output end SW of the DC / DC conversion chip 10 is the input end of the feedback adjusting circuit 30.

[0053] The feedback adjusting circuit 30 adjusts the size of the first preset voltage according to the working voltage of the low-voltage element in the electric energy meter connected with the output end OUT and the current-limiting end ILIM of the current-limiting protection chip 20. The feedback adjusting circuit 30 comprises a first feedback adjusting resistor R1 and a second feedback adjusting resistor R2. One end of the first feedback adjusting resistor R1 is connected with the feedback end FB of the DC / DC conversion chip 10 and one end of the second feedback adjusting resistor R2 respectively; the other end of the first feedback adjusting resistor R1 is connected with the output end SW of the DC / DC conversion chip 10; and the other end of the second feedback adjusting resistor R2 is grounded GND.

[0054] The voltage V FB of the feedback end FB of the DC / DC conversion chip 10 is related to the first preset voltage V out1 and the relationship between the first feedback adjusting resistor R1 and the second feedback adjusting resistor R2 is as follows formula (1):

[0055]

[0056] The voltage V of the feedback end FB of the DC / DC conversion chip 10 FB is constant, related to the model of the selected DC / DC conversion chip, and is generally 0.8V; and the first preset voltage V out1 is related to the working voltage required by the low-voltage element in the electric energy meter. In this embodiment, the working voltage required by the low-voltage element in the electric energy meter is taken as an example, that is, the first preset voltage V out1 is 5V, V FB =0.8V, and V out1 =5V are substituted into formula (1), then According to the commonly used resistance value of the resistor, the resistance value of the second feedback adjusting resistor R2 can be selected as 3.3KΩ, and the resistance value of the first feedback adjusting resistor R1 is 18KΩ. R2=3.3KΩ, R1=18KΩ, V FB =0.8V are substituted into formula (1) again, then V out1 ≈5.16V can be calculated.

[0057] The resistance values of the selected second feedback adjusting resistor R2 of 3.3KΩ and the first feedback adjusting resistor R1 of 18KΩ, and the calculated V out1 is 5.16V, and the theoretical value is 5V. Because the voltage is calculated by using the voltage dividing resistor, there is an error. The voltage range required by the MCU of the electric energy meter is 1.8-5.5V, so 5.16V is within the allowed voltage working range and can meet the requirements.

[0058] It can be understood that if V out1 is closer to 5V, the resistance value of the second feedback adjusting resistor R2 and the resistance value of the first feedback adjusting resistor R1 can be replaced again so that V out1 is closer to 5V.

[0059] It can be understood that when the voltage output at the output end of the DC / DC conversion chip 10 exceeds or is less than the voltage value within the allowed error range, the resistance value of the second feedback adjusting resistor R2 and the resistance value of the first feedback adjusting resistor R1 can be replaced again to change the voltage output at the output end of the DC / DC conversion chip 10 again, so that the voltage output at the output end of the DC / DC conversion chip 10 is always maintained within the allowed error range of 5V.

[0060] By adjusting the resistance value of the second feedback adjusting resistor R2 and the resistance value of the first feedback adjusting resistor R1, the value of V out1 , that is, the output voltage value of the DC / DC conversion chip 10, V out1The resistance value of the second feedback adjusting resistor R2 and the resistance value of the first feedback adjusting resistor R1 can be precisely adjusted according to the second feedback. The voltage value can be 12V, 5V, 3.3V, etc. When the working voltage required by the low-voltage element in the electric energy meter is 12V or 3.3V, the principle of the first feedback adjusting resistor R1 and the second feedback adjusting resistor R2 adjusting the size of the first preset voltage according to the working voltage of the low-voltage element in the feedback adjusting circuit is similar to the principle of the first feedback adjusting resistor R1 and the second feedback adjusting resistor R2 when the working voltage required by the low-voltage element in the electric energy meter is 5V. Details are not repeated here.

[0061] In order to solve the problems of low efficiency and complicated steps caused by replacing the resistor every time, as an optional embodiment, the first feedback adjusting resistor R1 and the second feedback adjusting resistor R2 can be selected as a sliding resistor. In this way, the resistance value of the first feedback adjusting resistor R1 and the second feedback adjusting resistor R2 can be changed by sliding the sliding resistor.

[0062] In order to stabilize the voltage on the enable end SHDN of the DC / DC conversion chip 10 and make the DC / DC conversion chip 10 work stably, as an optional embodiment, a first voltage stabilizing resistor R w1 .

[0063] The first voltage stabilizing resistor R w1 The voltage flowing into the enable end SHDN can be set to ensure that the voltage on the enable end SHDN is stabilized within a suitable range, so as to stably control the opening and closing of the DC / DC conversion chip 10.

[0064] In order to smooth the input voltage, filter the high-frequency noise and ripple on the power line VCC1, make the voltage input to the input end VIN of the DC / DC conversion chip 10 more stable, and reduce the influence of voltage fluctuation on the work of the DC / DC conversion chip 10, as an optional embodiment, a first filter capacitor C1 is further included.

[0065] Specifically, the anode plate of the first filter capacitor C1 is connected to the enable end SHDN of the DC / DC conversion chip 10, and the cathode plate of the first filter capacitor C1 is grounded GND, which can filter the signal on the power line VCC1.

[0066] The voltage on the power line VCC1 is input to the supply end VIN of the DC / DC conversion chip 10 after being filtered by the first filter capacitor C1. The DC / DC conversion chip 10 can convert the high input voltage on the power line VCC1 into a low voltage output through the action of an internal metal-oxide-semiconductor field-effect transistor (MOSFET).

[0067] To increase the filtering effect of the signal on the power line VCC1, as an optional implementation, a filter capacitor is further included, both of whose anode plates are connected to the power line VCC1, and both of whose cathode plates are connected to the ground GND.

[0068] To reduce the ripple of the signal output from the output end SW of the DC / DC conversion chip 10, as an optional implementation, an LC filter circuit is further included.

[0069] Specifically, the LC filter circuit includes a first filter inductor L1 and a third filter capacitor C3. The first filter inductor L1 is connected in series on the connecting line between the output end SW of the DC / DC conversion chip 10 and the input end of the feedback adjustment circuit 30. One end of the third filter capacitor C3 is connected to the filter end CB of the DC / DC conversion chip 10, and the other end is connected to one end of the output end SW of the DC / DC conversion chip 10 used in connection with the first filter inductor L1.

[0070] When the feedback adjustment circuit 30 includes a first feedback adjustment resistor R1 and a second feedback adjustment resistor R2, the first filter inductor L1 is connected in series on the connecting line between the output end SW of the DC / DC conversion chip 10 and the first feedback adjustment resistor R1.

[0071] The first filter inductor L1 is used to provide a constant output current, while also affecting the power conversion efficiency and output voltage ripple. By adjusting the inductance value of the first filter inductor L1, the output voltage ripple can be reduced.

[0072] By connecting the first filter inductor L1 in series on the connecting line between the output end SW of the DC / DC conversion chip 10 and the input end of the feedback adjustment circuit 30, energy can be stored (current through inductance increases, magnetic field energy increases) when the signal is output from the output end SW of the DC / DC conversion chip 10, and energy can be released (current continues to flow) when the output end SW of the DC / DC conversion chip 10 is turned off. In combination with the third filter capacitor C3, voltage conversion and smooth output current can be achieved, the output current ripple can be reduced, and the voltage value output by the DC / DC conversion chip 10 can have a very good ripple, which can reach 4‰ and 1‰.

[0073] The output terminal SW of the DC / DC conversion chip 10 is a switching node, which is connected with the LC filter circuit and the output load, and plays a core role in voltage conversion, current transmission, control of output voltage and current, and cooperation with protection mechanism, and is crucial for the DC / DC conversion chip 10 to realize stable step-down conversion function.

[0074] The following will specifically introduce how to realize voltage conversion and power output, control of output voltage and current, and cooperation with protection function.

[0075] 1) Realize voltage conversion and power output: the output terminal SW of the DC / DC conversion chip 10 is a switching node, which is connected with the internal N-type MOS tube. When the DC / DC conversion chip 10 works, the internal N-type MOS tube switches, so that the potential of the output terminal SW alternately changes. When the N-type MOS tube connected with the output terminal SW is turned on, the input voltage charges the first filter inductor L1 through the N-type MOS tube, and the electric energy is stored in the first filter inductor L1 in the form of magnetic field energy; when the N-type MOS tube connected with the output terminal SW is turned off and the bottom MOS tube is turned on, the first filter inductor L1 releases energy, and the electric signal is output to the LC filter circuit through the output terminal SW pin, and then flows to the current limiting protection circuit 20 and the feedback regulation circuit 30, so as to realize the function of converting the input voltage into stable output voltage and supplying power for the load.

[0076] Exemplarily, in the typical application circuit of 5V / 600mA step-down regulator, the LC filter circuit composed of the first filter inductor L1 and the third filter capacitor C4 connected with the output terminal SW can convert the input voltage on the power line VCC1 into stable 5V output voltage, and provide 600mA current for the load.

[0077] 2) Control output voltage and current: the DC / DC conversion chip 10 adjusts the output voltage and current by controlling the switching frequency and duty cycle of the output terminal SW. According to the load demand, the internal control logic adjusts the switching state of the output terminal SW, and changes the charging and discharging time of the first filter inductor L1. When the load current increases, the on-time of the output terminal SW is increased (i.e. the duty cycle is increased), so that the first filter inductor L1 stores more energy, thereby providing greater output current; on the contrary, the on-time is reduced to reduce the output current. When the load transient changes, the DC / DC conversion chip 10 can quickly adjust the switching state of the output terminal SW, stabilize the output voltage and current, and ensure the normal work of the load.

[0078] 3) Cooperation to achieve protection function: in the short circuit protection process, the output end SW of the DC / DC conversion chip 10 plays a key role. When the output is short-circuited, the output current rises rapidly, and after the DC / DC conversion chip 10 detects the overcurrent condition, the N-type MOS tube switch connected with the output end SW will be controlled to act. The top power switch will be quickly turned off to prevent overvoltage, and then the bottom power switch will be turned on until the output current decreases to a certain extent, and then the top power switch will be tried to be turned on again, and the cycle will continue until the short circuit fault is eliminated, ensuring the safety of the chip and the circuit.

[0079] In order to reduce the noise on the adjusted first preset voltage, as an optional implementation, it further comprises a second filtering capacitor C2 for filtering the adjusted first preset voltage. The anode plate of the second filtering capacitor C2 is connected to the input end of the feedback regulation circuit 30, and the cathode plate of the second filtering capacitor C2 is grounded GND.

[0080] When the feedback regulation circuit 30 comprises a first feedback regulation resistor R1 and a second feedback regulation resistor R2, the anode plate of the second filtering capacitor C2 is connected to one end of the first feedback regulation resistor R1 for connecting the output end SW of the DC / DC conversion chip 10.

[0081] In order to stabilize the voltage on the enable end EN / Fault of the current limiting protection chip 20 and enable the current limiting protection chip 20 to work stably, as an optional implementation, it further comprises a second voltage stabilizing resistor R W2 .

[0082] The second voltage stabilizing resistor R W2 influences the voltage on the enable end EN / nFAULT of the current limiting protection chip 20, and further determines whether the current limiting protection chip 20 is enabled. A suitable resistance value of the second voltage stabilizing resistor R W2 can ensure that the voltage on the enable end EN / nFAULT is stabilized in a suitable range within the normal input voltage range, so as to ensure that the current limiting protection chip 20 works stably.

[0083] In order to adjust the preset current of the current limiting protection chip 20, so that the voltage regulation circuit has a wider application market, as an optional implementation, it further comprises an adjusting resistor R5 connected in series on the connecting line between the current limiting end ILIM of the current limiting protection chip 20 and the low-voltage element, for adjusting the size of the preset current.

[0084] The following describes how the adjusting resistor R5 adjusts the preset current I LIMIT of the current limiting protection chip 20.

[0085] The first preset voltage outputted by the output terminal SW of the DC / DC conversion chip 10 is inputted to the power supply terminal VIN of the current-limiting protection chip 20 after being adjusted, and is outputted through the output terminal OUT of the current-limiting protection chip 20 after passing through the current-limiting protection chip 20, thereby supplying power for the low-voltage elements in the electric energy meter.

[0086] The fifth pin of the current-limiting protection chip 20 is the current-limiting terminal ILIM, which plays a current-limiting role, and the preset current of the current-limiting protection chip 20 can be adjusted by adjusting the resistance R5, that is, when the preset current I LIM is set, if the power consumption of the circuit (for example, the low-voltage elements in the electric energy meter) connected to the rear-end external interface of the current-limiting protection chip 20 is greater than the preset current I LIM , the current-limiting protection chip 20 cuts off the voltage output of the output terminal OUT, thereby ensuring that the front-end circuit (for example, the DC / DC conversion chip 10 and the feedback adjustment circuit 30) is not affected by the overloading of the external interface circuit; when the power consumption of the rear-end external interface circuit is reduced and is less than the preset current I LIM , the current-limiting protection chip 20 resumes normal work and the output terminal OUT normally outputs voltage.

[0087] When the external interface circuit is not faulty and normally works, the power consumption of the circuit will not exceed the current-limiting value, and the current-limiting protection chip 20 will not trigger the overcurrent protection action.

[0088] The relationship between the adjusting resistance R5 and the preset current I LIMIT is shown in the following formula (2):

[0089] I LIMIT = correlation coefficient × R ILIM (2)

[0090] R ILIM is the current-limiting resistance connected to the current-limiting terminal ILIM, that is, the adjusting resistance R5; the correlation coefficient is generally 10.5×10 -3 , which is a coefficient fitted by comparing the reference voltage generated by the current source in the current-limiting protection chip 20 flowing through the external adjusting resistance R5 with the voltage value converted by the internal conversion module after the actual detected current value.

[0091] Figure 2 is a kind of Figure 1 internal circuit structure diagram of the current-limiting protection chip provided by the embodiment of the application, as Figure 2As shown, the current source 202 is 9.8 μA, and the reference voltage is generated by passing the current source 202 through an external current-limiting resistor (i.e., the regulating resistor R5). The reference voltage is compared with the actual detected voltage. Because there is some deviation between the theoretically designed value and the actual measured value, according to the data statistical fitting of the actual test distribution, the calculated value is more accurate if the coefficient is 10.5 x 10 -3 Therefore, the correlation coefficient is taken as 10.5 x 10 -3 .

[0092] To provide better and more stable voltage for low-voltage components, as an optional implementation, a fourth filter capacitor C4 is further included in series on the connecting line between the regulating resistor R5 and the low-voltage components, for filtering the signal output by the output terminal OUT of the current-limiting protection chip 20.

[0093] To avoid the impact of voltage mutation on the load and ensure that the circuit components enter the working state safely and stably, as an optional implementation, a fifth capacitor C5 is further included, one end of which is connected to the soft start terminal SS of the current-limiting protection chip 20, and the other end is connected to the regulating resistor R5 for connecting one end of the low-voltage components, for controlling the rising rate of the voltage output by the output terminal OUT of the current-limiting protection chip 20.

[0094] The functions realized by the cooperation between the fifth capacitor C5 and the soft start terminal SS will be described in detail below.

[0095] The soft start terminal SS mainly plays a role in controlling the rising rate of the output voltage, suppressing the inrush current, and reducing electromagnetic interference in the circuit, which is of great significance to ensuring the stable start and reliable operation of the circuit.

[0096] Specifically, (1) controlling the rising rate of the output voltage: the soft start terminal SS of the current-limiting protection chip 20 sets the rising rate of the output voltage when the current-limiting protection chip 20 is turned on by connecting a fifth capacitor C5 to ground.

[0097] The fifth capacitor C5 limits the rising rate of the output voltage when the current-limiting protection chip 20 is turned on by the following formula (3):

[0098]

[0099] wherein, I SS represents the charging current, and the typical value is 1 μA; Gain ss represents the gain ratio, and the typical value is 6.2°; C SS represents the capacitance value of the ground capacitor connected to the soft start terminal SS, which is the capacitance value of the fifth capacitor C5 in this embodiment. Therefore, by changing the size of the fifth capacitor C5, the rising slope of the voltage output by the current-limiting protection chip 20 can be adjusted (i.e., the rising rate of the output voltage). ), in some voltage-sensitive circuit, the appropriate rate of rise can avoid the voltage mutation impact on the load, to ensure the safe and stable circuit elements into the working state.

[0100] (2) to suppress the inrush current: in hot plug or circuit start-up process, excessive inrush current may cause damage to the power supply and other elements in the circuit. By connecting a fifth capacitor C5 to the ground of the soft start end SS of the current limiting protection chip 20, the output voltage can be slowly raised, and the size of the inrush current I IN-RUSH is limited.

[0101] The fifth capacitor C5 limits the inrush current I IN-RUSH by the following formula (4):

[0102]

[0103] Where V IN represents the chip input voltage, that is, the voltage of pin 1; C OUT represents the output capacitor, C4; t ss represents the total slope time of the output voltage rising from 0 to V IN , which is determined by C SS and VIN, C SS represents the capacitance value of the ground capacitor connected to the soft start end SS, which is the capacitance value of the fifth capacitor C5 in this embodiment. Reasonably setting the capacitance value of the fifth capacitor C5 can effectively suppress the inrush current and protect the circuit.

[0104] (3) reduce electromagnetic interference: slow output voltage rising process helps to reduce the conducted and radiated interference generated when the circuit starts. Fast voltage change is easy to produce high frequency harmonics, which causes electromagnetic interference to the surrounding circuit. The soft start process controlled by the soft start end SS can smooth the voltage change, reduce the strength of electromagnetic interference, and improve the electromagnetic compatibility of the whole system.

[0105] In order to prevent voltage backflow and damage to the front-end DC / DC conversion chip 10 and the feedback regulation circuit 30, as an optional implementation, it also includes: a reverse prevention diode D1 connected in series on the connecting line between the output end OUT of the current limiting protection chip 20 and the low-voltage element, and the conduction direction points to the low-voltage element, for preventing voltage backflow.

[0106] The voltage output by the current limiting protection chip 20 passes through the reverse prevention diode D1, and then passes through the fifth capacitor C5 and the fourth filter capacitor C4 for filtering, and is output to the circuit for use by the circuit. The reverse prevention diode D1 has the effect of preventing reverse flow. When there is overvoltage and overcurrent in the back end, the reverse prevention diode D1 is reverse blocked, preventing the voltage from affecting the front-end circuit through the circuit.

[0107] The embodiment of the application provides a voltage regulating circuit applied to an electric energy meter.

[0108] An embodiment of an electric energy meter:

[0109] The embodiment of the application provides an electric energy meter.

[0110] The detailed description of the voltage regulating circuit applied to the electric energy meter can be referred to the related description in the foregoing embodiment of the voltage regulating circuit applied to the electric energy meter, and details are not described herein.

[0111] The electric energy meter provided by the embodiment of the application can achieve the same beneficial effects as the foregoing voltage regulating circuit applied to the electric energy meter, and details are not described herein.

Claims

1. A voltage regulation circuit for use in an electricity meter, characterized in that, The device includes a DC / DC converter chip that outputs a first preset voltage when the voltage received at the enable terminal is greater than its first threshold voltage; a current limiting protection chip that maps the voltage at the power supply terminal to the output terminal when the voltage received at the enable terminal is greater than its second threshold voltage, and cuts off the output terminal when the current at the current limiting terminal exceeds a preset current; and a feedback regulation circuit. The output of the DC / DC converter chip is connected to the input of the feedback regulation circuit, the power supply terminal of the current limiting protection chip, and the enable terminal of the current limiting protection chip, respectively. The output of the feedback regulation circuit is connected to the feedback terminal of the DC / DC converter chip; The output and current-limiting terminals of the current-limiting protection chip are used to connect to the same low-voltage component in the energy meter; The feedback adjustment circuit is used to adjust the magnitude of the first preset voltage according to the operating voltage of the low-voltage component.

2. The voltage regulation circuit for an electricity meter according to claim 1, characterized in that, The feedback adjustment circuit includes a first feedback adjustment resistor and a second feedback adjustment resistor; One end of the first feedback adjustment resistor is connected to the feedback terminal of the DC / DC converter chip and one end of the second feedback adjustment resistor, respectively. The other end of the first feedback regulating resistor is connected to the output terminal of the DC / DC conversion chip; The other end of the second feedback regulating resistor is grounded.

3. The voltage regulation circuit applied to an electricity meter according to claim 1, characterized in that, Also includes: A first voltage-regulating resistor is disposed on the connection line between the enable terminal of the DC / DC converter chip and the power supply line to stabilize the voltage at the enable terminal of the DC / DC converter chip. It also includes a first filter capacitor for filtering signals on the power line, with the anode plate connected to the enable terminal of the DC / DC converter chip and the cathode plate grounded.

4. The voltage regulation circuit for an electricity meter according to claim 1, characterized in that, Also includes: The anode plate is connected to the input terminal of the feedback regulation circuit, and the cathode plate is grounded. The second filter capacitor is used to filter the regulated first preset voltage.

5. The voltage regulation circuit applied to an electricity meter according to claim 1, characterized in that, Also includes: An LC filter circuit for reducing the ripple of the signal output from the output terminal of the DC / DC converter chip; The first filter inductor in the LC filter circuit is connected in series on the connection line between the output terminal of the DC / DC converter chip and the input terminal of the feedback adjustment circuit. One end of the third filter capacitor in the LC filter circuit is connected to the filter terminal of the DC / DC converter chip, and the other end is connected to the end of the first filter inductor used to connect to the output terminal of the DC / DC converter chip.

6. The voltage regulation circuit for an electricity meter according to claim 1, characterized in that, Also includes: A second Zener resistor is disposed on the connection line between the enable terminal of the current limiting protection chip and the output terminal of the DC / DC conversion chip to stabilize the voltage at the enable terminal of the current limiting protection chip.

7. The voltage regulation circuit applied to an electricity meter according to claim 1, characterized in that, Also includes: An adjusting resistor, connected in series on the connection line between the current limiting terminal of the current limiting protection chip and the low-voltage component, is used to adjust the preset current.

8. The voltage regulation circuit for an electricity meter according to claim 7, characterized in that, Also includes: A fourth filter capacitor connected in series on the connection line between the regulating resistor and the low-voltage component, used to filter the signal output from the output terminal of the current limiting protection chip. And a fifth capacitor, one end of which is connected to the soft-start terminal of the current limiting protection chip, and the other end of which is connected to the regulating resistor for connecting one end of the low-voltage component, for controlling the rise rate of the voltage output from the output terminal of the current limiting protection chip.

9. The voltage regulation circuit for an electricity meter according to any one of claims 1-8, characterized in that, Also includes: A reverse-current protection diode is connected in series on the connection line between the output terminal of the current limiting protection chip and the low-voltage component, with the conduction direction pointing towards the low-voltage component, to prevent voltage reverse flow.

10. An electricity meter, characterized in that, Includes the voltage regulation circuit applied to an electricity meter as described in any one of claims 1-9.

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