Dual-power supply circuit suitable for household ultraviolet phototherapy instrument

Abstract

The invention provides a dual-power-supply power supply circuit suitable for a household ultraviolet phototherapy instrument. The dual-power-supply power supply circuit comprises an ultra-low-power-consumption on-off and slow-start circuit, a power supply automatic switching circuit and a load circuit. The ultra-low power consumption startup and shutdown and slow start circuit comprises a lithium battery voltage VBAT, a capacitor C1, a field effect transistor Q1, a resistor R1, a resistor R2, a triode Q3, a resistor R3, a resistor R4, a Schottky diode D3, a key K1, a Schottky diode D4 and a resistor R5. The load circuit comprises a low dropout regulator (LDO) and a micro control unit (MCU). Therefore, the power consumption of the battery is extremely low during shutdown, the slow start circuit avoids one circuit at the moment of a load, normal startup is ensured, automatic switching of the adapter and the lithium battery is realized, normal startup of the lithium battery in a low-voltage state is ensured, and the safety and reliability of the whole machine are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of switch control of household ultraviolet light therapy devices, and particularly to a dual-power supply circuit applicable to household ultraviolet light therapy devices. Background Art

[0002] In order to facilitate patients to perform adjuvant treatment by ultraviolet irradiation in a home environment under the guidance of doctors for vitiligo, psoriasis, eczema, atopic dermatitis and other skin diseases, in recent years, household ultraviolet light therapy devices have become more and more popular. In order to further facilitate the operation of patients, household ultraviolet light therapy devices often use an internal lithium battery for power supply, charge the battery through an adapter, and also need to consider the power consumption problem of the battery when the device is turned off. Through research, it is found that the household ultraviolet light therapy devices currently powered by lithium batteries and adapters mainly have the following problems: 1. The use of the device depends on whether the battery is charged. The adapter can only charge the battery, and the device can be powered only after the battery is fully charged, which is very inconvenient to use; 2. After the device is turned off, the shutdown current at the battery end can reach the mA level, and the device may not be able to start after being left unused for a period of time (usually 1-2 months); 3. A triode is used as the switch between the battery and the load circuit, and the conduction voltage drop is relatively large. When used in high-power applications, the power consumption and heat generation of the switch are large, and an additional radiator needs to be added, which cannot meet the requirements of the development trend of household ultraviolet products to be more compact and smaller; 4. There is no soft-start circuit. When the battery is in a low-power state and the load-carrying capacity is relatively weak, after the switch is turned on, it may trigger the overcurrent protection of the battery, resulting in the device being unable to start; 5. Lack of safety protection measures. During the use process, once a power abnormality occurs, it may damage the device and even pose a safety hazard to patients. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems in the related art to some extent.

[0004] To this end, the object of the present invention is to provide a dual-power supply circuit applicable to household ultraviolet light therapy devices, with extremely low battery power consumption when turned off, a soft-start circuit to avoid instantaneous short-circuit of the load, ensure normal startup, realize automatic switching between the adapter and the lithium battery, ensure normal startup even in the low-voltage state of the lithium battery, and improve the safety and reliability of the whole machine.

[0005] To achieve the above object, the present invention provides a dual-power supply circuit applicable to a household ultraviolet light therapy device, which includes an ultra-low power consumption switch and soft-start circuit, a power supply automatic switching circuit, and a load circuit; the ultra-low power consumption switch and soft-start circuit includes a lithium battery voltage VBAT, a capacitor C1, a field effect transistor Q1, a resistor R1, a resistor R2, a triode Q3, a resistor R3, a resistor R4, a Schottky diode D3, a button K1, a Schottky diode D4, and a resistor R5. The S pole and G pole of the field effect transistor Q1 are connected through the capacitor C1. The lithium battery voltage VBAT is connected to one ends of the capacitor C1 and the resistor R2. The G pole of the field effect transistor Q1 is connected to the collector of the triode Q3 through the resistor R1. The other end of the resistor R2 is connected to one end of the resistor R1. One end of the resistor R3 is connected to the base of the triode Q3. The base and emitter of the triode Q3 are connected through the resistor R4. One end of the Schottky diode D3 is connected to the collector of the triode Q3. The other end of the Schottky diode D3 is respectively connected to one end of the button K1 and the Schottky diode D4. The other end of the Schottky diode D4 is connected to the resistor R5. The load circuit includes a low dropout linear regulator LDO and a micro control unit MCU. The low dropout linear regulator LDO is connected to the micro control unit MCU. The KEY CHECK pin of the MCU is connected between the Schottky diode D4 and the resistor R5. The POWER ON / OFF pin of the MCU is connected to the other end of the resistor R3.

[0006] In addition, the dual-power supply circuit applicable to a household ultraviolet light therapy device proposed according to the above application may further have the following additional technical features: Specifically, the power supply automatic switching circuit includes an adapter output voltage V_ADAPTER, a Schottky diode D1, a Schottky diode D2, a lithium battery charging management circuit, a field effect transistor Q2, a resistor R6, and a resistor R7 arranged in sequence. The adapter output voltage V_ADAPTER is respectively connected to one ends of the Schottky diode D1, the Schottky diode D2, and the resistor R7. The other end of the Schottky diode D1 is connected to the S pole of the field effect transistor Q2. The other end of the Schottky diode D2 is connected to the lithium battery voltage VBAT through the lithium battery charging management circuit. The D pole of the field effect transistor Q2 is connected to the D pole of the field effect transistor Q1. The G pole of the field effect transistor Q2 is connected to one end of the resistor R6. The other end of the resistor R6 is connected to one end of the resistor R7.

[0007] Specifically, the load circuit further includes a transient voltage suppression diode TVS1 and a positive temperature coefficient self - recovering fuse F1. One end of the transient voltage suppression diode TVS1 is connected to the other end of the Schottky diode D1 and one end of the positive temperature coefficient self - recovering fuse F1, and the other end of the positive temperature coefficient self - recovering fuse F1 is connected to the low dropout linear regulator LDO.

[0008] Specifically, an LDO output voltage VDD is provided between the low dropout linear regulator LDO and the micro - control unit MCU, and the LDO output voltage VDD is connected to the other end of the resistor R5.

[0009] Specifically, the emitter of the triode Q3, the lithium - battery charging management circuit, the low dropout linear regulator LDO, the micro - control unit MCU, the resistor R7, and the other end of the key K1 are all grounded.

[0010] Compared with the prior art, the present invention has the following advantages: 1. After the device is shut down, the lithium - battery and the load circuit including devices such as the MCU and LDO are completely cut off, and the battery power consumption is extremely low, about only 10 μA.

[0011] 2. The soft - start circuit can make the field - effect transistor MOSFET conduct slowly after power - on, so that the capacitors in the load circuit have a slow charging process, avoiding the phenomenon that when the field - effect transistor MOSFET conducts quickly, the capacitors in the load circuit charge too fast, which is equivalent to a momentary short - circuit, causing the lithium - battery to trigger over - current protection and resulting in the inability to power on.

[0012] 3. It realizes two power sources, namely the adapter and the lithium - battery, and automatically switches to supply power to the load circuit by using one of them or both at the same time.

[0013] 4. The semiconductor electronic switch in the battery - powered circuit uses a MOSFET with an extremely low on - resistance to replace the triode, so that the lithium - battery can still work properly to power on even in a low - voltage state.

[0014] 5. It has over - voltage and over - current protection for the load circuit, improving the safety and reliability of the whole machine.

[0015] The additional aspects and advantages of the present invention will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above - mentioned and / or additional aspects and advantages of the present invention will become obvious and easy to understand from the following description of the embodiments in conjunction with the drawings, where: Figure 1 is a circuit diagram of a dual - power - supply circuit applicable to a household ultraviolet light therapy instrument of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] Embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where like or similar reference numerals denote like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention. On the contrary, the embodiments of the present invention include all variations, modifications, and equivalents falling within the spirit and scope of the appended claims.

[0018] The dual - power - supply circuit applicable to a household ultraviolet light therapy device according to an embodiment of the present invention will be described below with reference to the accompanying drawings.

[0019] As Figure 1 shown, a dual - power - supply circuit applicable to a household ultraviolet light therapy device according to an embodiment of the present invention includes an ultra - low - power on - off and soft - start circuit, a power - supply automatic switching circuit, and a load circuit.

[0020] Among them, the ultra - low - power on - off and soft - start circuit includes a lithium - battery voltage VBAT, a capacitor C1, a field - effect transistor Q1, a resistor R1, a resistor R2, a triode Q3, a resistor R3, a resistor R4, a Schottky diode D3, a key K1, a Schottky diode D4, and a resistor R5. The S - pole and G - pole of the field - effect transistor Q1 are connected through the capacitor C1. The lithium - battery voltage VBAT is connected to one ends of the capacitor C1 and the resistor R2. The G - pole of the field - effect transistor Q1 is connected to the collector of the triode Q3 through the resistor R1. The other end of the resistor R2 is connected to one end of the resistor R1. One end of the resistor R3 is connected to the base of the triode Q3. The base and emitter of the triode Q3 are connected through the resistor R4. One end of the Schottky diode D3 is connected to the collector of the triode Q3. The other end of the Schottky diode D3 is respectively connected to one end of the key K1 and the Schottky diode D4. The other end of the Schottky diode D4 is connected to the resistor R5.

[0021] Among them, the load circuit includes a low - dropout linear regulator LDO and a micro - control unit MCU. The low - dropout linear regulator LDO is connected to the micro - control unit MCU. The KEY CHECK pin of the MCU is connected between the Schottky diode D4 and the resistor R5. The POWER ON / OFF pin of the MCU is connected to the other end of the resistor R3. An LDO output voltage VDD is provided between the low - dropout linear regulator LDO and the micro - control unit MCU. The LDO output voltage VDD is connected to the other end of the resistor R5.

[0022] It should be noted that when the button K1 is pressed, the capacitor C1 is charged through the resistor R1 and the Schottky diode D3, and the voltage between the G and S of the field effect transistor Q1 rises slowly. When the voltage value reaches and exceeds the conduction voltage threshold of the G and S of the field effect transistor Q2, the field effect transistor Q1 begins to conduct gradually, thereby realizing soft start and supplying power to the load circuit at the same time; the MCU in the load circuit starts to detect the state of KEY_CHECK after the button is continuously pressed for 2 seconds. When it is judged to be a continuous low level, the micro control unit MCU will control the POWER_ON / OFF to output a high level, so that the triode Q3 conducts. At this time, when the button K1 is released, the field effect transistor Q1 can still maintain the conducting state, thereby realizing power on; in the power-on state, when the button K1 is pressed and the micro control unit MCU in the load circuit detects that the state of KEY_CHECK is a continuous low level, the micro control unit MCU will control the POWER_ON / OFF to output a low level, so that the triode Q3 is turned off. After the triode Q3 is turned off, the field effect transistor Q1 will also be turned off, thereby realizing power off.

[0023] Wherein, the power supply automatic switching circuit includes an adapter output voltage V_ADAPTER, a Schottky diode D1, a Schottky diode D2, a lithium battery charging management circuit, a field effect transistor Q2, a resistor R6 and a resistor R7 arranged in sequence. The adapter output voltage V_ADAPTER is respectively connected to one ends of the Schottky diode D1, the Schottky diode D2 and the resistor R7. The other end of the Schottky diode D1 is connected to the S pole of the field effect transistor Q2. The other end of the Schottky diode D2 is connected to the lithium battery voltage VBAT through the lithium battery charging management circuit. The D pole of the field effect transistor Q2 is connected to the D pole of the field effect transistor Q1. The G pole of the field silencer Q2 is connected to one end of the resistor R6, and the other end of the resistor R6 is connected to one end of the resistor R7.

[0024] It should be noted that the working principle of the adapter and the lithium battery power supply automatic switching circuit is as follows: (1) When both the lithium battery and the adapter are present, the output voltage V_ADAPTER of the adapter is applied to the S pole of the field effect transistor Q2 through the Schottky diode D1 and to the G pole of the field effect transistor Q2 through the resistor R6. At this time, the voltage difference between the G and S of the field effect transistor Q2 is a positive voltage, which does not meet the conduction condition of the P-channel field effect transistor. Therefore, the field effect transistor Q2 is in the off state. Even if the button K1 is pressed to turn on the machine to make Q1 conduct, at this time, the battery voltage VBAT is applied to the D pole of the field effect transistor Q2 through the field effect transistor Q1. Since the battery voltage VBAT is lower than the output voltage V_ADAPTER of the adapter, the battery voltage cannot make the body diode inside the field effect transistor Q2 conduct, and at this time Q2 is already in the off state. At this time, the output voltage V_ADAPTER of the adapter supplies power to the load circuit through the positive temperature coefficient self-recovery fuse F1, and at the same time charges the lithium battery through the Schottky diode D2 and the lithium battery charging management circuit; (2) When the adapter power supply is removed, if the button K1 is pressed to turn on the machine at this time, the battery voltage VBAT will be applied to the D pole of the field effect transistor Q2 through the field effect transistor Q1, and then through the body diode inside the field effect transistor Q2 to the S pole of the field effect transistor Q2. Because the adapter has been removed at this time, the G pole voltage of the field effect transistor Q2 is close to 0V, thus forming a negative voltage difference between the G and S of the field effect transistor Q2, and exceeding the G, S conduction voltage threshold of the field effect transistor Q2, meeting the conduction condition of the P-channel field effect transistor. Therefore, the field effect transistor Q2 is in the on state, and the battery voltage supplies power to the load circuit through the field effect transistor Q1, the field effect transistor Q2, and the positive temperature coefficient self-recovery fuse F1; (3) When the adapter is connected to the device again, as described in (1), the power supply situation automatically switches to the adapter supplying power to the load circuit and charging the lithium battery at the same time.

[0025] The lithium battery supplies power to the load circuit through the loop composed of the field effect transistors Q1 and Q2. Since the field effect transistors Q1 and Q2 are semiconductor electronic switches, there will still be a certain voltage difference after conduction. If triodes are selected, the voltage difference after conduction is generally 0.3V. After passing through 2 triodes, the battery voltage will be reduced by at least 0.6V, which will affect the power supply of the load circuit and even cause the situation of not being able to work. The greater the current of the load circuit, the greater this influence. For the circuit designed this time, P-channel field effect transistors with a conduction resistance of only 0.002Ω are selected for the field effect transistors Q1 and Q2. Considering the power of the household ultraviolet light therapy instrument, even when the current output by the lithium battery reaches 5A, the voltage drop after passing through the field effect transistors Q1 and Q2 is only 0.02V after being added together, and the influence on the load circuit is greatly reduced. Even when the lithium battery is in a low voltage state, it can realize normal startup and operation.

[0026] In an embodiment of the present invention, as Figure 1As shown, the load circuit further includes a transient voltage suppression diode TVS1 and a positive temperature coefficient self - recovering fuse F1. One end of the transient voltage suppression diode TVS1 is connected to the other end of the Schottky diode D1 and one end of the positive temperature coefficient self - recovering fuse F1. The other end of the positive temperature coefficient self - recovering fuse F1 is connected to the low dropout linear regulator LDO.

[0027] The emitter of the triode Q3, the lithium - battery charging management circuit, the low dropout linear regulator LDO, the micro - control unit MCU, the resistor R7, and the other end of the key K1 are all grounded.

[0028] It should be noted that the transient voltage suppression diode TVS1 and the positive temperature coefficient self - recovering fuse F1 form an over - voltage and over - current protection circuit. When the voltage supplying power to the load circuit exceeds a certain value, the transient voltage suppression diode TVS1 will act quickly to reduce the voltage, thereby protecting the load circuit from being damaged due to excessive voltage input. When abnormal conditions such as overload or short - circuit occur in the load circuit, the positive temperature coefficient self - recovering fuse F1 will act to cut off the power supply to the load circuit, thus avoiding phenomena such as overheating and damage to the whole machine caused by long - term short - circuit.

[0029] In the description of this specification, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of these features. In the description of the present invention, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

[0030] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above - mentioned terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0031] Although the embodiments of the present invention have been shown and described above, it can be understood that the above - mentioned embodiments are exemplary and cannot be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and deformations to the above - mentioned embodiments within the scope of the present invention.

Claims

1. A dual-power supply circuit applicable to a household ultraviolet light therapy device, characterized in that, It includes an ultra-low-power on / off and soft-start circuit, a power supply automatic switching circuit, and a load circuit; The ultra-low-power on / off and soft-start circuit includes a lithium battery voltage VBAT, a capacitor C1, a field-effect transistor Q1, a resistor R1, a resistor R2, a triode Q3, a resistor R3, a resistor R4, a Schottky diode D3, a button K1, a Schottky diode D4, and a resistor R5. The S pole and G pole of the field-effect transistor Q1 are connected through the capacitor C1. The lithium battery voltage VBAT is connected to one ends of the capacitor C1 and the resistor R2. The G pole of the field-effect transistor Q1 is connected to the collector of the triode Q3 through the resistor R1. The other end of the resistor R2 is connected to one end of the resistor R1. One end of the resistor R3 is connected to the base of the triode Q3. The base and emitter of the triode Q3 are connected through the resistor R4. One end of the Schottky diode D3 is connected to the collector of the triode Q3. The other end of the Schottky diode D3 is respectively connected to one end of the button K1 and the Schottky diode D4. The other end of the Schottky diode D4 is connected to the resistor R5; The load circuit includes a low-dropout linear regulator LDO and a microcontroller unit MCU. The low-dropout linear regulator LDO is connected to the microcontroller unit MCU. The KEY CHECK pin of the MCU is connected between the Schottky diode D4 and the resistor R5. The POWER ON / OFF pin of the MCU is connected to the other end of the resistor R3.

2. The dual-power supply circuit applicable to a household ultraviolet light therapy device according to claim 1, wherein, The power supply automatic switching circuit includes an adapter output voltage V_ADAPTER, a Schottky diode D1, a Schottky diode D2, a lithium battery charging management circuit, a field-effect transistor Q2, a resistor R6, and a resistor R7 arranged in sequence. The adapter output voltage V_ADAPTER is respectively connected to one ends of the Schottky diode D1, the Schottky diode D2, and the resistor R7. The other end of the Schottky diode D1 is connected to the S pole of the field-effect transistor Q2. The other end of the Schottky diode D2 is connected to the lithium battery voltage VBAT through the lithium battery charging management circuit. The D pole of the field-effect transistor Q2 is connected to the D pole of the field-effect transistor Q1. The G pole of the field-effect transistor Q2 is connected to one end of the resistor R6. The other end of the resistor R6 is connected to one end of the resistor R7.

3. The dual-power supply circuit for a household ultraviolet light therapy device according to claim 2, characterized in that, The load circuit further includes a transient voltage suppression diode TVS1 and a positive temperature coefficient self-resetting fuse F1. One end of the transient voltage suppression diode TVS1 is connected to the other end of the Schottky diode D1 and one end of the positive temperature coefficient self-resetting fuse F1. The other end of the positive temperature coefficient self-resetting fuse F1 is connected to the low-dropout linear regulator LDO.

4. The dual-power supply circuit for a household ultraviolet light therapy device according to claim 1, characterized in that, An LDO output voltage VDD is provided between the low-dropout linear regulator LDO and the microcontroller unit MCU. The LDO output voltage VDD is connected to the other end of the resistor R5.

5. The dual-power supply circuit for a household ultraviolet light therapy device according to claim 2, wherein, The emitter of the triode Q3, the lithium battery charging management circuit, the low-dropout linear regulator LDO, the microcontroller unit MCU, the resistor R7, and the other end of the button K1 are all grounded.

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