A power supply for a small household appliance

Abstract

This utility model relates to the field of power supply technology, specifically to a power supply for small household appliances, including an isolated power supply circuit, an overvoltage protection circuit, an overcurrent protection circuit, a chip peripheral circuit, and a negative feedback circuit. The isolated power supply circuit of this power supply has electrical isolation characteristics and incorporates multiple circuit combinations such as an overvoltage protection circuit, an overcurrent protection circuit, a current-type control chip, and a negative feedback circuit. Among them, the isolated power supply circuit uses a transformer in the power loop and a TL431 and optocoupler in the signal loop. The overvoltage protection circuit uses a proportional voltage divider of the output resistor and then connects to a self-locking protection circuit. The overcurrent protection circuit adds a current sampling resistor below the high-frequency switching device MOSFET. The voltage collected on the current sampling resistor is transmitted to the current-type control chip, which internally shuts down the PWM wave, thereby shutting down the MOSFET, thus protecting the circuit and preventing the risk of electric shock.

Description

Technical Field

[0001] This utility model relates to the field of power supply technology, and in particular to a power supply for small household appliances. Background Technology

[0002] Currently, in some small household appliances, such as air purifiers, LED lighting power supplies, and handheld vacuum cleaners, the control circuits require relatively low DC voltages to drive components such as microcontrollers and sensors. However, the circuit topologies of the power supplies for these appliances are Buck or Boost circuits. Since the inputs of these circuits are typically connected to AC 220V AC mains power...

[0003] However, Buck and Boost circuits lack electrical isolation devices, so when a circuit malfunctions, it can easily cause electric shock hazards, posing no guarantee for human safety or equipment protection, which greatly reduces the safety and lifespan of the circuit in practical applications. Utility Model Content

[0004] The purpose of this utility model is to provide a power supply for small household appliances, aiming to solve the problems of poor safety performance and short lifespan of traditional power supply products for household appliances.

[0005] To achieve the above objectives, in a first aspect, this utility model provides a power supply for small household appliances, including an isolated power supply circuit, an overvoltage protection circuit, an overcurrent protection circuit, a chip peripheral circuit, and a negative feedback circuit; the isolated power supply circuit is connected to the overvoltage protection circuit, the overcurrent protection circuit, the chip peripheral circuit, and the negative feedback circuit, respectively, and the chip peripheral circuit is connected to the overvoltage protection circuit, the overcurrent protection circuit, and the negative feedback circuit, respectively.

[0006] In the isolated power circuit, the isolation device in the power section is made of a high-frequency transformer, and the isolation device in the signal section is made of TL431 and optocoupler.

[0007] The peripheral circuit of the chip is built using a chip-based circuit, which has high integration, small size and can achieve high-efficiency voltage conversion, far exceeding the circuit built with discrete devices.

[0008] The negative feedback circuit is constructed using a TL431 and an optocoupler, wherein the optocoupler is an electrical isolation device for the signal section.

[0009] The overvoltage protection circuit is constructed using a TL431, an optocoupler, and a self-locking circuit.

[0010] Secondly, this utility model also provides a method for protecting the power supply circuit of a small household appliance, which is applied to the power supply of a small household appliance as described in the first aspect above, and includes the following steps;

[0011] The overcurrent protection circuit uses a current sensing resistor to detect the high-frequency transformer section of the isolated power supply circuit and transmits the detected voltage signal to the chip's external circuitry.

[0012] The overvoltage protection circuit uses an output resistor to divide the voltage and then connects it to a self-locking circuit to detect the high-frequency transformer section, and transmits the detected voltage signal to the peripheral circuit of the chip.

[0013] When the voltage signal is overvoltage, the self-locking circuit is activated to protect the isolated power supply circuit, and the output is constant voltage.

[0014] This utility model discloses a power supply for small household appliances. The isolated power supply circuit has electrical isolation characteristics and incorporates multiple circuit combinations, including an overvoltage protection circuit, an overcurrent protection circuit, a current-type control chip, and a negative feedback circuit. The isolated power supply circuit uses a transformer in the power loop and a TL431 and optocoupler in the signal loop. The overvoltage protection circuit employs a proportional voltage divider based on the output resistor before connecting to a self-locking protection circuit to protect the circuit. The overcurrent protection circuit employs a current sampling resistor added below the high-frequency switching device MOSFET. The voltage sampled across this resistor is transmitted to the current-mode control chip. The chip's internal operation shuts down the PWM wave, thereby turning off the MOSFET and protecting the circuit from electric shock. The negative feedback circuit, capable of switching between 0A and 2A, significantly improves the power supply's energy efficiency, safety, and lifespan. This power supply uses the chip's peripheral circuitry as its control section. The chip boasts high integration and a small size, allowing for a more compact and miniaturized circuit design. Furthermore, the simplified peripheral circuitry reduces the probability of failure. The integrated shielding layer and differential signal design enhance its resistance to external electromagnetic interference (EMI). This solution addresses the issues of poor safety performance and short lifespan in traditional household appliance power supplies. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1This is a schematic diagram of a power supply for a small household appliance provided by this utility model.

[0017] Figure 2 This is a schematic diagram of the isolated power supply circuit provided by this utility model.

[0018] Figure 3 This is a schematic diagram of the peripheral circuit of the chip provided by this utility model.

[0019] Figure 4 This is a schematic diagram of the negative feedback circuit provided by this utility model.

[0020] Figure 5 This is a schematic diagram of the overvoltage protection circuit provided by this utility model.

[0021] Figure 6 This is a flowchart of a power supply circuit protection method for small household appliances provided by this utility model.

[0022] In the diagram: 1-Isolation power supply circuit, 2-Overvoltage protection circuit, 3-Overcurrent protection circuit, 4-Chip peripheral circuit, 5-Negative feedback circuit. Detailed Implementation

[0023] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this utility model, and should not be construed as limiting this utility model.

[0024] Please see Figures 1 to 5 In a first aspect, this utility model provides a power supply for a small household appliance, including an isolated power circuit 1, an overvoltage protection circuit 2, an overcurrent protection circuit 3, a chip peripheral circuit 4, and a negative feedback circuit 5; the isolated power circuit 1 is connected to the overvoltage protection circuit 2, the overcurrent protection circuit 3, the chip peripheral circuit 4, and the negative feedback circuit 5 respectively, and the chip peripheral circuit 4 is connected to the overvoltage protection circuit 2, the overcurrent protection circuit 3, and the negative feedback circuit 5 respectively.

[0025] In this embodiment of the invention, the isolated power supply circuit 1 of the power supply has electrical isolation characteristics and incorporates multiple circuit combinations, including the overvoltage protection circuit 2, the overcurrent protection circuit 3, the current-type control chip, and the negative feedback circuit 5. The isolated power supply circuit 1 uses a transformer in the power circuit and a TL431 and optocoupler in the signal circuit. The overvoltage protection circuit 2 uses a proportional voltage divider based on the output resistor before connecting to a self-locking protection circuit to protect the circuit. The overcurrent protection circuit 3 employs a current sampling resistor added below the high-frequency switching device MOSFET. The voltage sampled across the current sampling resistor is transmitted to the current-type control chip. The chip's internal operation shuts down the PWM wave, thereby turning off the MOSFET and protecting the circuit from electric shock. The negative feedback circuit 5 can switch between 0A and 2A, significantly improving the power supply's energy efficiency, safety performance, and lifespan. This power supply uses the chip's peripheral circuit 4 as its control section. The chip has high integration and a small size, allowing for a more compact and miniaturized circuit design. Furthermore, the peripheral circuit 4 is easy to assemble, reducing the probability of failure. The integrated shielding layer and differential signal design within the chip enhance its resistance to external electromagnetic interference (EMI). This solves the problems of poor safety performance and short lifespan in traditional household appliance power supplies.

[0026] Furthermore, the isolation power circuit 1 uses a high-frequency transformer as the isolation device in the power section, and a TL431 and optocoupler are used together to construct the isolation device in the signal section.

[0027] In this embodiment of the utility model, the isolation power circuit 1 uses a high-frequency transformer as the isolation device in the power section, and a TL431 and optocoupler as the isolation device in the signal section. The input is connected to 220V AC mains power, passing through an EMI circuit composed of an X capacitor, a Y capacitor, and a common-mode inductor. Its main function is to reduce interference and propagation caused by high-frequency devices to the power grid. The two resistors after the X capacitor are used to absorb the energy stored in the X capacitor. After passing through the rectifier bridge, the original sinusoidal mains voltage becomes a rippled DC voltage. After passing through the filter capacitor, the voltage becomes a DC voltage with ripple. The DC voltage after the filter capacitor is sent to the high-frequency transformer. When the MOSFET is on, the voltage direction of the primary winding of the transformer is positive at the top and negative at the bottom, and the transformer begins to store energy. The voltage direction of the secondary winding is negative at the top and positive at the bottom, according to the same polarity of the voltage at the same terminal of the transformer. Therefore, the secondary diode does not conduct, and the output load is powered through the output capacitor. When the MOSFET is off, the polarity of the primary winding changes to negative at the top and positive at the bottom. The voltage polarity of the secondary winding is positive at the top and negative at the bottom, according to the same polarity of the voltage at the same terminal, and the secondary diode conducts. The secondary winding provides energy to the output capacitor and the output load.

[0028] The primary winding, through a preset turns ratio, ensures that the voltage on the secondary winding becomes the expected output voltage. An RCD snubber circuit is added to one side of the transformer. Because the transformer is hand-wound, the coupling is less than 100%, resulting in a small portion of inductance not being coupled to the secondary side. This portion of inductance is called leakage inductance. During the primary-side MOSFET's turn-off period, the leakage inductance generates a large reflected voltage, which is not clamped by the secondary side. Therefore, in each cycle of power supply operation, the leakage inductance energy is absorbed by the RCD circuit, significantly reducing the voltage spikes of the MOSFET and decreasing the voltage stress on the MOSFET.

[0029] The transformer used provides electrical isolation between the primary and secondary circuits, cutting off direct connection between the equipment and the mains power supply, and completely isolating the live parts of the equipment from the parts accessible to the human body. Even if a fault occurs in the internal circuit of the equipment, such as a short circuit or component damage, the casing and other accessible parts will not become live, thus preventing electric shock and ensuring personal safety. Since there is no direct electrical connection between the primary and secondary windings, but only magnetic field coupling, common-mode interference signals are difficult to transmit to the secondary circuit through the transformer. This helps improve the electromagnetic compatibility (EMC) of the equipment, enabling it to operate stably in complex electromagnetic environments, reducing interference to other equipment, and also reducing its own susceptibility to external interference. Adding an RCD circuit near the transformer addresses the electromagnetic interference (EMI) generated by voltage spikes and current changes during switching. The RCD circuit absorbs this energy, reducing the rate of voltage and current change, thereby reducing the intensity of EMI and helping to meet EMC standards. This minimizes interference to other electronic equipment and circuits in the vicinity during operation. The EMI to other internal circuits of the appliance and external devices is relatively small, effectively suppressing electromagnetic interference.

[0030] Furthermore, the peripheral circuit 4 of the chip is built using a chip, which has high integration, small size and can achieve high-efficiency voltage conversion, far exceeding the circuit built with discrete devices.

[0031] In this embodiment of the invention, the peripheral circuit 4 of the chip is built using common discrete components. Their function is to output a PWM wave to the driving circuit of the MOSFET. However, since the driving waveform is a signal with a small current, the circuit is susceptible to interference and fluctuations. Therefore, the peripheral circuit 4 uses a chip-based circuit. Chips have high integration, small size, and can achieve high-efficiency voltage conversion (efficiency exceeding 90%), far surpassing circuits built with discrete components. Furthermore, the chip's internal digital control algorithm enables more precise signal processing and feedback control.

[0032] The chip's peripheral circuit 4 has eight pins, including a VCC power supply pin, an output voltage feedback pin, a current detection pin, a MOSFET drive pin, and a MOSFET switching frequency setting pin. The chip's VCC power supply uses an auxiliary winding within the transformer, and a voltage regulator circuit is added to ensure stable VCC power. The MOSFET switching frequency setting pin uses an RC charging circuit; different resistance and capacitance values ​​are set to change the MOSFET's switching frequency.

[0033] Furthermore, the negative feedback circuit 5 is constructed using a TL431 and an optocoupler, wherein the optocoupler is an electrical isolation device for the signal section.

[0034] In this embodiment of the invention, the negative feedback circuit 5 is constructed using a TL431 and an optocoupler. The optocoupler is an electrical isolation device for the signal section. By performing a resistor-based voltage divider on the output voltage Vo, the R terminal of the TL431 fluctuates around 2.5V. When the output voltage decreases, the internal resistance Rka of the TL431 increases, reducing the current flowing through the LED and simultaneously reducing the current of the phototransistor. The output stage of the phototransistor is connected to the COM pin of the aforementioned chip. Through internal chip regulation, the duty cycle of the PWM wave in the next cycle is increased, resulting in increased energy transfer from the transformer in the next cycle. After several cycles of regulation, the output voltage Vo stabilizes.

[0035] Furthermore, the overvoltage protection circuit 2 is constructed by combining a TL431, an optocoupler, and a self-locking circuit.

[0036] In this embodiment of the utility model, the overvoltage protection circuit 2 is constructed by TL431, optocoupler and self-locking circuit. By dividing the output voltage with resistors, after passing through TL431 and optocoupler, when the output voltage reaches the overvoltage point, the current of the phototransistor increases, causing the two transistors to conduct one after the other, forming a self-locking circuit, which in turn triggers the chip to turn off the PWM wave so that the primary transformer no longer stores energy and the secondary output voltage will not continue to rise, thus realizing the protection circuit function.

[0037] Please see Figure 6 Secondly, this utility model also provides a method for protecting the power supply circuit of a small household appliance, applied to the power supply of a small household appliance as described in the first aspect above, including the following steps;

[0038] The S1 overcurrent protection circuit 3 uses a current sensing resistor to detect the high-frequency transformer section of the isolated power supply circuit 1 and transmits the detected voltage signal to the chip peripheral circuit 4.

[0039] S2 overvoltage protection circuit 2 uses the method of output resistor voltage division and then connecting to self-locking circuit to detect the high frequency transformer part, and transmits the detected voltage signal to the chip peripheral circuit 4;

[0040] When the voltage signal is overvoltage, the self-locking circuit is activated to protect the isolated power supply circuit 1, and the output is constant voltage.

[0041] The above-disclosed embodiments are merely preferred embodiments of a power supply for small household appliances according to the present invention, and should not be construed as limiting the scope of the present invention. Those skilled in the art can understand that implementing all or part of the above embodiments and making equivalent changes according to the claims of the present invention still fall within the scope of the present invention.

Claims

1. A power supply for small household appliances, characterized in that... ； It includes isolated power supply circuits, overvoltage protection circuits, overcurrent protection circuits, chip peripheral circuits, and negative feedback circuits; The isolated power supply circuit is connected to the overvoltage protection circuit, the overcurrent protection circuit, the chip peripheral circuit, and the negative feedback circuit, respectively. The chip peripheral circuit is connected to the overvoltage protection circuit, the overcurrent protection circuit, and the negative feedback circuit, respectively.

2. The power supply for small household appliances as described in claim 1, characterized in that... ； The isolation power circuit uses a high-frequency transformer as the isolation device in the power section and a TL431 and optocoupler as the isolation device in the signal section.

3. The power supply for small household appliances as described in claim 1, characterized in that... ； The peripheral circuit of the chip is built using a chip-based circuit. The chip has a high degree of integration, small size, and can achieve high-efficiency voltage conversion, far exceeding the circuit built with discrete devices.

4. The power supply for small household appliances as described in claim 1, characterized in that... ； The negative feedback circuit is constructed using a TL431 and an optocoupler, wherein the optocoupler is an electrical isolation device for the signal section.

5. The power supply for small household appliances as described in claim 1, characterized in that... ； The overvoltage protection circuit is constructed using a TL431, an optocoupler, and a self-locking circuit.

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