阅读说明：本技术 一种即热式电热水器及其电源电路 (Instant electric water heater and power circuit thereof ) 是由 谭永哲 王圣贤 曹冠忠 于 2020-04-08 设计创作，主要内容包括：本发明公开了一种即热式电热水器及其电源电路,电源电路包括：交流电源,用于连接市电；整流电路,将所述交流电源提供的交流电转换为直流电；变压器,所述变压器包括与所述整流电路连接的初级绕组和至少两个次级绕组,初级绕组与开关电源芯片连接,所述第一次级绕组向所述开关电源芯片提供反馈信号,所述第二次级绕组设有用于检测当前市电电压的检测电路。本发明基于变压器中绕组线圈的输出电压和绕组线圈匝数比近似的原理,在变压器中的第二次级绕组上设置检测电路,根据同相设计,使得该绕组对初级绕组得电压变化有很好的跟随特性,从而可以达到实时检测当前市电电压的目的,节省了光耦,降低电源成本,减小电源的体积。(The invention discloses an instant electric water heater and a power circuit thereof, wherein the power circuit comprises: the alternating current power supply is used for connecting commercial power; the rectifying circuit is used for converting alternating current provided by the alternating current power supply into direct current; the transformer comprises a primary winding and at least two secondary windings, the primary winding is connected with the switching power supply chip, the primary winding provides a feedback signal for the switching power supply chip, and the secondary winding is provided with a detection circuit for detecting the current mains supply voltage. The invention is based on the principle that the output voltage of the winding coil in the transformer is approximate to the turn ratio of the winding coil, the detection circuit is arranged on the second secondary winding in the transformer, and the winding has good following characteristic to the voltage change of the primary winding according to the in-phase design, thereby achieving the purpose of detecting the current mains voltage in real time, saving the optical coupler, reducing the power cost and reducing the volume of the power supply.)

1. A power circuit of an instant electric water heater is characterized in that: the method comprises the following steps:

the alternating current power supply is used for connecting commercial power;

the rectifying circuit is used for converting alternating current provided by the alternating current power supply into direct current;

the transformer comprises a primary winding and at least two secondary windings, the primary winding is connected with the switching power supply chip, the first secondary winding provides feedback signals for the switching power supply chip, and the second secondary winding is provided with a detection circuit for detecting the current mains supply voltage.

2. The power supply circuit of the instant electric water heater according to claim 1, wherein:

a diode D9, a capacitor C41 and a dummy load R71 are arranged in a loop of the detection circuit, wherein the dummy load R71 is connected with the capacitor C41 in parallel;

preferably, the resistance value range of the dummy load is 10-100 kilo-ohms.

3. The power circuit of the tankless electric water heater of claim 2, further comprising:

a voltage division circuit and/or a filter circuit are/is arranged behind the dummy load R71 in parallel;

preferably, the voltage dividing circuit comprises a resistor R79 and a resistor R80, and the resistor R79 and the resistor R80 are connected in series and then connected in parallel with the dummy load R71;

preferably, the filter circuit is a resistance-capacitance filter circuit, the resistance-capacitance filter circuit includes a resistor R81 and an energy storage capacitor E5, and the resistor R81 and the energy storage capacitor E5 are connected in series and then connected in parallel to two ends of the resistor R80.

4. The power supply circuit of the instant electric water heater according to any one of claims 1-3, characterized in that:

the primary winding is connected with a buffer circuit in parallel and used for providing a current loop for the primary winding of the transformer when the primary winding is switched off.

5. The power circuit of the tankless electric water heater of claim 4, further comprising:

the buffer circuit comprises a diode D7, a high-voltage capacitor C26 and a discharge resistor, wherein the diode D7 is connected with the high-voltage capacitor C26 in series, and two ends of the high-voltage capacitor C26 are connected with the discharge resistors in series in parallel.

6. The power supply circuit of the instant electric water heater according to any one of claims 1-3, characterized in that:

an MOSFET is integrated in the switching power supply chip, and provides a switching signal for the primary winding to drive the primary winding, so that energy is transferred to the first secondary winding and the second secondary winding;

preferably, the switching power supply chip is an LNK6774K chip.

7. The power circuit of the tankless electric water heater of claim 6, further comprising:

a feedback pin of the switching power supply chip is connected with the anode of the first secondary winding through a resistor voltage divider, and the cathode of the first secondary winding is grounded with the primary winding and used for sampling feedback voltage;

preferably, the resistor voltage divider comprises a capacitor C30, a resistor R66, a resistor R67, and a resistor R69; the capacitor C30, the resistor R66 and the resistor R67 are connected in parallel and then connected in series with the resistor R69.

8. The power supply circuit of the instant electric water heater according to any one of claims 1-3, characterized in that:

the energy storage circuit comprises an energy storage capacitor E1, is connected with the rectifying circuit, is used for charging the energy storage capacitor E1 and provides energy for the switching power supply chip through the energy storage capacitor E1.

9. The power supply circuit of the instant electric water heater according to claim 1, wherein:

the transformer also comprises a third secondary winding, wherein the third secondary winding is provided with an application circuit and then is filtered into smooth 12V direct current through resistance-capacitance to supply power to a system.

10. An instant electric water heater is characterized in that: power supply circuit comprising an tankless electric water heater according to any of claims 1 to 9.

Technical Field

The invention belongs to the technical field of electric water heaters, and particularly relates to an instant electric water heater and a power circuit thereof.

Background

The instant electric water heater is a common and practical furniture appliance, is a household appliance, and has the main characteristics of simplicity, safety and convenience. The power supply of the instant electric water heater is a linear power supply scheme with low power, and if the power is increased, the problems of heavy weight, large volume and high cost of the linear power supply become more prominent.

For example, chinese patent application No. CN201611012409.0 discloses an application circuit of an instant electric water heater, which comprises a main control circuit, a power supply circuit, a utility power detection circuit, a water pump control circuit, a heating plate control circuit, a temperature sensing circuit, and a display module, wherein in the utility power detection circuit, a resistor R22 and a resistor R26 are connected in series and then connected in parallel with a resistor R24 and a resistor R25 to an input end of an optical coupler, the utility power is rectified and then converted into a voltage value through feedback of the optical coupler, a current utility power voltage value is measured through the voltage value output by the utility power detection circuit, and a relationship between the high voltage value and an output voltage of the optical coupler is calculated according to output conditions of the current circuit under different utility power voltages.

However, the use of the optical coupler as a detection means has the following disadvantages:

1. due to the influence of the service life of the photoelectric element, the transmission ratio may change after a period of time;

2. the requirement on the linearity of the optical coupler is high;

3. because the optical coupler is arranged at a high-voltage and system power supply end, the safety is considered, and a sufficient safety distance is needed, so that the size of the optical coupler is larger.

In view of the above, the present invention is particularly proposed.

Disclosure of Invention

The technical problem to be solved by the invention is to overcome the defects of the prior art and provide a power circuit of an instant electric water heater, which saves cost and reduces volume.

In order to solve the technical problems, the invention adopts the technical scheme that:

a power supply circuit for an electric tankless water heater, comprising:

the alternating current power supply is used for connecting commercial power;

the rectifying circuit is used for converting alternating current provided by the alternating current power supply into direct current;

the transformer comprises a primary winding and at least two secondary windings, the primary winding is connected with the switching power supply chip, the first secondary winding provides feedback signals for the switching power supply chip, and the second secondary winding is provided with a detection circuit for detecting the current mains supply voltage.

Further, in the above-mentioned case,

a diode D9, a capacitor C41 and a dummy load R71 are arranged in a loop of the detection circuit, wherein the dummy load R71 is connected with the capacitor C41 in parallel;

preferably, the resistance value range of the dummy load is 10-100 kilo-ohms.

Further, in the above-mentioned case,

a voltage division circuit and/or a filter circuit are/is arranged behind the dummy load R71 in parallel;

preferably, the voltage dividing circuit comprises a resistor R79 and a resistor R80, and the resistor R79 and the resistor R80 are connected in series and then connected in parallel with the dummy load R71;

preferably, the filter circuit is a resistance-capacitance filter circuit, the resistance-capacitance filter circuit includes a resistor R81 and an energy storage capacitor E5, and the resistor R81 and the energy storage capacitor E5 are connected in series and then connected in parallel to two ends of the resistor R80.

Further, in the above-mentioned case,

the primary winding is connected with a buffer circuit in parallel and used for providing a current loop for the primary winding of the transformer when the primary winding is switched off.

Further, in the above-mentioned case,

the buffer circuit comprises a diode D7, a high-voltage capacitor C26 and a discharge resistor, wherein the diode D7 is connected with the high-voltage capacitor C26 in series, and two ends of the high-voltage capacitor C26 are connected with the discharge resistors in series in parallel.

Further, in the above-mentioned case,

an MOSFET is integrated in the switching power supply chip, and provides a switching signal for the primary winding to drive the primary winding, so that energy is transferred to the first secondary winding and the second secondary winding;

preferably, the switching power supply chip is an LNK6774K chip.

Further, in the above-mentioned case,

a feedback pin of the switching power supply chip is connected with the anode of the first secondary winding through a resistor voltage divider, and the cathode of the first secondary winding is grounded with the primary winding and used for sampling feedback voltage;

preferably, the resistor voltage divider comprises a capacitor C30, a resistor R66, a resistor R67, and a resistor R69; the capacitor C30, the resistor R66 and the resistor R67 are connected in parallel and then connected in series with the resistor R69.

Further, in the above-mentioned case,

the energy storage circuit comprises an energy storage capacitor E1, is connected with the rectifying circuit, is used for charging the energy storage capacitor E1 and provides energy for the switching power supply chip through the energy storage capacitor E1.

Further, in the above-mentioned case,

the transformer also comprises a third secondary winding, wherein the third secondary winding is provided with an application circuit and then is filtered into smooth 12V direct current through resistance-capacitance to supply power to a system.

An electric tankless water heater comprising a power circuit as described above.

After the technical scheme is adopted, compared with the prior art, the invention has the following beneficial effects.

1. The invention is based on the principle that the output voltage of the winding coil in the transformer is approximate to the turn ratio of the winding coil, the detection circuit is arranged on the second secondary winding in the transformer, and the winding has good following and tracking characteristics on the voltage change of the primary winding according to the same-phase design, thereby achieving the purpose of detecting the current mains voltage in real time, not only enabling the water outlet temperature of the instant electric water heater to be more stable, but also saving the optical coupler, reducing the power cost, reducing the volume of the power supply and facilitating the processing production and transportation.

2. According to the invention, the switching power supply chip U1 with the MOSFET integrated inside is adopted, so that a power supply circuit does not need to be additionally provided with an MOS (metal oxide semiconductor field effect transistor), the size of the switching power supply is smaller, the MOSFET inside provides a switching signal for the primary winding of the transformer T1 to drive the primary winding of the transformer, and the energy is transferred to the secondary winding.

3. According to the invention, the primary winding and the secondary winding of the transformer are grounded, so that the feedback voltage of the primary winding can be directly transmitted to the power management chip U1 through the resistor divider, the use of voltage feedback devices is reduced, the size of a power supply is further reduced, the service life problem of a photoelectric element is avoided, and the fault points are reduced.

The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention, are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention without limiting the invention to the right. It is obvious that the drawings in the following description are only some embodiments, and that for a person skilled in the art, other drawings can be derived from them without inventive effort. In the drawings:

FIG. 1 is a schematic diagram of a power supply circuit of the instant electric water heater of the present invention;

FIG. 2 is a schematic diagram of the detection circuit of the present invention.

It should be noted that the drawings and the description are not intended to limit the scope of the inventive concept in any way, but to illustrate it by a person skilled in the art with reference to specific embodiments.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and the following embodiments are used for illustrating the present invention and are not intended to limit the scope of the present invention.

In the description of the present invention, it should be noted that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; may be directly connected or indirectly connected through an intermediate. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

As shown in fig. 1 and fig. 2, the present invention provides a power circuit of an instant electric water heater, comprising:

the alternating current power supply is used for connecting commercial power;

the rectifying circuit is used for converting alternating current provided by the alternating current power supply into direct current;

the transformer comprises primary windings 1 and 3 connected with the rectifying circuit and at least two secondary windings, the primary windings are connected with the switching power supply chip, feedback signals are provided for the switching power supply chip by the primary windings 4 and 5, and a detection circuit used for detecting the current mains voltage is arranged at the secondary windings 6 and 7.

Specifically, as shown in fig. 1, the power circuit of the instant electric water heater of the present invention includes an ac power source, which is connected to the mains supply to supply ac power to the power circuit; the commercial power passes through the power supply protection circuit, the power supply filter circuit and the start protection circuit one by one and then passes through the rectifier circuit, the rectifier circuit comprises a rectifier bridge, alternating current of the commercial power is converted into high-voltage direct current through the rectifier bridge, the high-voltage direct current is reduced into low-voltage direct current through the transformer T1, then the low-voltage direct current is filtered into smooth 12V direct current through the resistance-capacitance filter to supply power to a system, and meanwhile, a second secondary winding of the transformer is provided with a detection circuit for detecting the current commercial power voltage.

In detail, with the continuous improvement of the living standard of people, more and more electronic equipment members are in the house, and the electricity consumption of each household is also continuously increased. Especially, in the peak time of power consumption in summer, the power supply of the commercial power is very tight, so that the power supply voltage in the house of a user often fluctuates, and on one hand, some low voltages have great damage to the electric water heater and can greatly shorten the service life of an electric appliance, and on the other hand, the power of heating water of the electric water heater is unstable, so that the water outlet temperature of the instant electric water heater is unstable, and the use of the user is influenced. In the invention, based on the principle that the output voltage of a winding coil in a transformer and the turn ratio of the winding coil are approximate in a power circuit, the detection circuit is arranged on the ends 6 and 7 of the secondary winding in the transformer T1, and the winding has good following and tracking characteristics on the voltage change of the primary winding according to the same-phase design, thereby achieving the purpose of detecting the current mains voltage in real time, not only ensuring the water outlet temperature of the instant electric water heater to be more stable, but also saving an optical coupler, reducing the power cost, reducing the volume of the power supply and facilitating the processing, production and transportation.

Further, a diode D9, a capacitor C41 and a dummy load R71 are arranged in a loop of the detection circuit, wherein the dummy load R71 is connected with the capacitor C41 in parallel; preferably, the resistance value range of the dummy load is 10-100 kilo-ohms.

A voltage division circuit and a filter circuit are connected behind the dummy load R71 in parallel; preferably, the voltage dividing circuit includes a plurality of voltage dividing resistors; preferably, the filter circuit is a resistance-capacitance filter circuit.

In detail, in order to ensure the power supply following performance, a large-impedance dummy load R71 is used for providing a loop, a small capacitor C41 is used for filtering, then voltage is acquired in a voltage division mode through a resistor R79 and a resistor R80, the voltage enters an energy storage capacitor E5 through a resistor R81, and the voltage change of two ends of the energy storage capacitor E5 can represent the fluctuation condition of the mains voltage. In order to facilitate the system to identify the voltage, the detection winding and the system power supply winding are processed in common.

Furthermore, the power protection circuit comprises a FUSE and a piezoresistor, wherein the FUSE FUSE1 is used for limiting input current, and the piezoresistor RV1 is used for suppressing high-voltage spikes of external input, so that the high-voltage surge is prevented from damaging a rear-stage circuit.

The power supply filter circuit comprises an X capacitor, a discharge resistor and a common mode inductor. The X capacitor CX2 plays a wave filtering role in differential mode interference; the discharge resistors, namely the resistor R90, the resistor R91 and the resistor R93 are connected in series to provide a discharge channel for the filter circuit, and a plurality of resistors are connected in series to form the filter circuit, so that the bearing power is dispersed, the resistor requirement is reduced, the manufacturing cost is reduced, and the service life is prolonged; the common mode inductor L1 is used for attenuating common mode current, filtering common mode electromagnetic interference on the line, and inhibiting the internal circuit, namely the switching power supply, from emitting electromagnetic interference outwards while inhibiting external interference, thereby playing a role in EMI filtering.

The start-up protection circuit uses the thermistor NTC1 with negative temperature coefficient, effectively inhibits surge current formed by surge voltage generated during start-up, and when the circuit enters into steady-state operation, the thermistor NTC1 generates heat due to continuous working current in the circuit, so that the resistance value of the thermistor NTC1 becomes very small, and the influence on the circuit can be ignored.

In some embodiments of the present invention, the power circuit further includes a storage circuit, which includes a storage capacitor E1, and the storage capacitor E1 is charged by the rectifying circuit and provides energy to the subsequent load, i.e., the switching power chip, via the storage capacitor E1.

Furthermore, the primary winding is connected in parallel with a buffer circuit for providing a current loop for the primary winding 1 and 3 ends of the transformer when the transformer is turned off. The buffer circuit comprises a diode D7, a high-voltage capacitor C26, a discharge resistor R1 and a resistor R3 which are connected in series, wherein the diode D7 is connected with the high-voltage capacitor C26 in series, and two ends of the high-voltage capacitor C26 are connected with a plurality of discharge resistors R1 and R3 which are connected in series in parallel.

Furthermore, an MOSFET is integrated in the switching power supply chip, and the MOSFET provides a switching signal for the ends 1 and 3 of the primary winding to drive the primary winding, so that energy is transferred to the ends 4 and 5 of the first secondary winding and then to the ends 6 and 7 of the second secondary winding; preferably, the switching power supply chip is an LNK6774K chip.

In detail, the MOSFET is integrated in the switching power supply chip U1, so that the power circuit does not need to be additionally provided with an MOS transistor, the size of the switching power supply becomes smaller, the internal MOSFET provides a switching signal for the ends 1 and 3 of the primary winding of the transformer T1, drives the primary winding of the transformer, so that energy is transferred to the ends 4 and 5 of the primary winding and then the ends 6 and 7 of the secondary winding, and the turn ratio of each winding coil of the isolation transformer T1 is approximate to the voltage ratio.

Further, in the present invention, a feedback pin of the switching power supply chip is connected to the anode of the first secondary winding through a resistor voltage divider, and the cathode of the first secondary winding is grounded to the primary winding for sampling a feedback voltage. The resistor voltage divider comprises a capacitor C30, a resistor R66, a resistor R67 and a resistor R69; the capacitor C30, the resistor R66 and the resistor R67 are connected in parallel and then are connected in series with the resistor R69.

In detail, the ends 4 and 5 of the first secondary winding are grounded with the ends 1 and 3 of the primary winding, so that the feedback voltage of the ends 4 and 5 of the first secondary winding can be directly transmitted to the power management chip U1 through the resistor divider, the use of an optical coupler is reduced, the size of a power supply is further reduced, the problem of service life of a photoelectric element is solved, and fault points are reduced.

The second secondary winding 6, 7 terminal in the transformer T1 of the present invention is used for detecting the voltage of the current commercial power, and since the output voltage of the winding coil and the winding coil turns ratio are similar, the commercial power voltage can be evaluated by the output voltage of the second secondary winding 6, 7 terminal. And because the design uses the same-phase design, namely the winding directions of the primary winding and the second secondary winding are the same, the winding has good following and tracking characteristics on the voltage change of the primary winding.

Furthermore, the transformer also comprises a third secondary winding 8 and 9 end, wherein the third secondary winding is provided with an application circuit and then is filtered into smooth 12V direct current through resistance-capacitance to supply power to a system.

In detail, after the RC resistors and capacitors at the ends of the third secondary winding 8 and 9 are connected in series, that is, the resistor R73 is connected in parallel with the resistor R74 and then connected in series with the capacitor C20, and is connected in parallel with the rectifier diode D6, which is used for suppressing the influence of the reverse peak voltage and the surge voltage on the diode D6, so as to protect the diode D6 from damage caused by insufficient voltage resistance. Diode D6 acts as a unidirectional conductor to ensure the polarity of the following circuit. The capacitor E3 and the capacitor C34 are energy storage capacitors, store electric energy output by the 8 and 9 ends of the third secondary winding and provide energy for a rear-stage circuit. The resistor R2 is a load resistor at the end of the third secondary winding 8, 9, and provides a loop for the end of the third secondary winding 8, 9, stabilizing the working state of the power supply. The capacitor C1 is an output filter capacitor, and improves the stability of the output voltage.

Furthermore, a Y capacitor is used between the pin 3 of the primary winding of the transformer T1 and the pin 8 of the third secondary winding, so that common-mode interference is reduced, output voltage fluctuation is reduced, and output ripple is improved. Unlike the conventional connection method, in consideration of the problem of leakage current, a capacitor having a small capacitance value is selected by connecting 2 capacitors, i.e., a capacitor CY1 and a capacitor CY2 in series.

The invention also provides an instant electric water heater, which comprises the power circuit of the instant electric water heater. By adopting the power supply circuit to detect the current commercial power voltage in real time, the water outlet temperature of the instant electric water heater is more stable, the optical coupler is also saved, the power supply cost is reduced, the size of the power supply is reduced, and the instant electric water heater is convenient to process, produce and transport.

Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.