Low-power power supply circuit for converting alternating current commercial power into direct current 24V

Abstract

The utility model provides a low-power power supply circuit for converting AC commercial power into DC 24V. The low-power power supply circuit comprises a rectifier bridge BRG1, a depletion type N-channel field effect transistor Q1, a self-recovery fuse F1, a resistor R1, a current-limiting resistor R3, a normally-closed optocoupler relay OP1, a current-limiting resistor R2, a voltage-regulator tube D1, a TVS tube D2, a capacitor C1, an enhanced N-channel field effect transistor Q2, a divider resistor R4, a divider resistor R5, a filter capacitor C2 and a DC-DC sub-circuit. The low-power power supply circuit for converting AC commercial power into DC 24V has the advantages of simple circuit structure and high stability and reliability. A full-wave rectification signal is further intercepted into an oscillation signal by using an optocoupler relay instead of using a transformer to control a switch of a field-effect tube, and 220V alternating current voltage is converted into 24V direct current voltage through voltage stabilization after the amplitude is reduced, so that the voltage can be used for supplying power to micro electric appliances.

Description

Technical Field

[0001] This utility model belongs to the field of power supply technology, and in particular relates to a low-power power supply circuit that converts AC mains power to DC 24V. Background Technology

[0002] In low-power, low-voltage DC power supply applications, one approach is to use a transformer in the circuit design, while the other is to design without a transformer. Miniaturization, low cost, and high reliability are particularly important in micro-electronic devices with limited internal space. Designs using transformers place high demands on the power supply's size and the final product, making miniaturization and low cost difficult to achieve. Currently, there are two existing technical approaches for transformerless designs: one is a "capacitor voltage divider" scheme with capacitors connected in series in the AC path, and the other is a scheme that uses resistors for voltage division directly after rectification. The disadvantages of these two schemes are poor load-carrying capacity, high circuit losses, and significant heat generation, which are detrimental to improving the power supply's lifespan and reliability.

[0003] For example, the existing Chinese invention patent with publication number CN102185500A provides a practical transformerless switching power supply, which belongs to the "transformerless solution". It draws power from the mains input terminal, and after rectification and voltage division, it is used as the control signal for the MOSFET. It belongs to the front-end control technology route, that is, controlling the output from the input. The output stability and reliability are both poor. Utility Model Content

[0004] In view of this, the present invention aims to propose a low-power power supply circuit that converts AC mains power to 24V DC power to solve the problem of poor reliability of existing low-power low-voltage DC power supply circuits.

[0005] To achieve the above objectives, the technical solution of this utility model is implemented as follows:

[0006] A low-power power supply circuit for converting AC mains power to 24V DC includes a rectifier bridge BRG1, a depletion-type N-channel MOSFET Q1, a resettable fuse F1, a resistor R1, a current-limiting resistor R3, a normally closed optocoupler relay OP1, a current-limiting resistor R2, a Zener diode D1, a TVS diode D2, a capacitor C1, an enhancement-type N-channel MOSFET Q2, voltage divider resistors R4 and R5, a filter capacitor C2, and a DC-DC sub-circuit.

[0007] The input terminals 1 and 3 of the rectifier bridge BRG1 receive AC mains power, the positive output terminal 2 is connected to the drain D of the depletion-type N-channel field-effect transistor Q1, and the negative output terminal 4 is grounded.

[0008] The source S of the depletion-type N-channel field-effect transistor Q1 is connected to pin 1 of the normally closed optocoupler relay OP1 through a series self-resetting fuse F1 and a current-limiting resistor R3. One end of the resistor R1 is connected to the gate G of the depletion-type N-channel field-effect transistor Q1, and the other end is grounded.

[0009] The normally closed optocoupler relay OP1 has its pin 3 connected to the gate G of the depletion-type N-channel field-effect transistor Q1 through a current-limiting resistor R2.

[0010] The Zener diode D1 and capacitor C1 are connected in parallel. One end of the Zener diode D1 is connected to the source S of the depletion-type N-channel field-effect transistor Q1, and the other end is connected to the gate G of the depletion-type N-channel field-effect transistor Q1.

[0011] The drain D of the enhancement-mode N-channel MOSFET Q2 is connected to pin 2 of the normally closed optocoupler relay OP1, the source S is grounded, and the gate G is grounded through the voltage divider resistor R5; one end of the voltage divider resistor R4 is connected to the source S of the depletion-mode N-channel MOSFET Q1 through the resettable fuse F1, and the other end is connected to the gate G of the enhancement-mode N-channel MOSFET Q2.

[0012] The anode of the filter capacitor C2 is connected to the source S of the depletion-type N-channel MOSFET Q1 through a resettable fuse F1, and the cathode is grounded.

[0013] One end of the TVS diode D2 is connected to the source S of the depletion-type N-channel field-effect transistor Q1 through a resettable fuse F1, and the other end is grounded.

[0014] The positive input terminal of the DC-DC sub-circuit is connected to the source S of the depletion-type N-channel MOSFET Q1 through a self-resetting fuse F1, and the negative terminal is grounded.

[0015] Furthermore, the DC-DC sub-circuit adopts a linear DC-DC circuit.

[0016] Furthermore, the linear DC-DC circuit includes a voltage regulator REG1 and a filter capacitor C3. Pin 1 of the voltage regulator REG1 is connected to the source S of the depletion-type N-channel MOSFET Q1 through a resettable fuse F1, pin 2 is grounded, and pin 3 is connected to the anode of the filter capacitor C3. The cathode of the filter capacitor C3 is grounded.

[0017] Compared with existing technologies, the AC mains power to DC 24V low-power power supply circuit described in this utility model has the following advantages:

[0018] This invention discloses a low-power AC mains power to 24V DC power supply circuit, which features a simple circuit structure and high stability and reliability. By using an optocoupler relay to control the switching of a field-effect transistor instead of a transformer, the full-wave rectified signal is further truncated into an oscillation signal. After amplitude reduction and voltage regulation, the 220V AC voltage is converted to 24V DC voltage, which can be used to power micro-electronic devices. Furthermore, compared to capacitor and resistor voltage dividers, this power supply circuit has lower losses and higher load capacity. It also widely uses semiconductor devices, making it easy to integrate; most components can be integrated into a single integrated circuit. Attached Figure Description

[0019] The accompanying drawings, which form part of this utility model, are used to provide a further understanding of the utility model. The illustrative embodiments of the utility model and their descriptions are used to explain the utility model and do not constitute an undue limitation of the utility model. In the drawings:

[0020] Figure 1 This is a circuit diagram of a low-power power supply circuit that converts AC mains power to 24V DC, as described in an embodiment of this utility model. Detailed Implementation

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0022] In the description of this utility model, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0023] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0024] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0025] A low-power AC mains power to DC 24V power supply circuit includes a rectifier bridge BRG1, a depletion-type N-channel MOSFET Q1, a resettable fuse F1, a resistor R1, a current-limiting resistor R3, a normally closed optocoupler relay OP1, a current-limiting resistor R2, a Zener diode D1, a TVS diode D2, a capacitor C1, an enhancement-type N-channel MOSFET Q2, voltage divider resistors R4 and R5, a filter capacitor C2, and a DC-DC sub-circuit.

[0026] The input terminals 1 and 3 of the aforementioned rectifier bridge BRG1 receive AC mains power, the positive output terminal 2 is connected to the drain D of the depletion-type N-channel MOSFET Q1, and the negative output terminal 4 is grounded.

[0027] The source S of the aforementioned depletion-type N-channel MOSFET Q1 is connected to pin 1 of a normally closed optocoupler relay OP1 via a series resettable fuse F1 and a current-limiting resistor R3. One end of the resistor R1 is connected to the gate G of the depletion-type N-channel MOSFET Q1, and the other end is grounded.

[0028] The 3rd pin of the normally closed optocoupler relay OP1 is connected to the gate G of the depletion-type N-channel field-effect transistor Q1 through the current-limiting resistor R2.

[0029] The Zener diode D1 and capacitor C1 are connected in parallel. One end of the Zener diode D1 is connected to the source S of the depletion-type N-channel MOSFET Q1, and the other end is connected to the gate G of the depletion-type N-channel MOSFET Q1.

[0030] Specifically, the cathode of Zener diode D1 is connected to the source S of depletion-type N-channel MOSFET Q1, and the anode is connected to the gate G of depletion-type N-channel MOSFET Q1.

[0031] The drain D of the aforementioned enhancement-mode N-channel MOSFET Q2 is connected to pin 2 of the normally closed optocoupler relay OP1, the source S is grounded, and the gate G is grounded through the voltage divider resistor R5; one end of the voltage divider resistor R4 is connected to the source S of the depletion-mode N-channel MOSFET Q1 through the resettable fuse F1, and the other end is connected to the gate G of the enhancement-mode N-channel MOSFET Q2.

[0032] The anode of the aforementioned filter capacitor C2 is connected to the source S of the depletion-type N-channel MOSFET Q1 via a resettable fuse F1, and the cathode is grounded.

[0033] The positive input terminal of the aforementioned DC-DC sub-circuit is connected to the source S of the depletion-type N-channel MOSFET Q1 via a resettable fuse F1, while the negative terminal is grounded.

[0034] Preferably, the circuit further includes a resistor R1, and the gate G of the depletion-type N-channel field-effect transistor Q1 is grounded through the resistor R1. One end of the resistor R1 is connected to the gate G of the depletion-type N-channel field-effect transistor Q1, and the other end is grounded.

[0035] Preferably, the circuit further includes a TVS diode D2, one end of which is connected to the source S of a depletion-type N-channel MOSFET Q1 via a resettable fuse F1, and the other end is grounded.

[0036] Preferably, the DC-DC sub-circuit adopts a linear DC-DC circuit. Specifically, the linear DC-DC circuit includes a voltage regulator REG1 and a filter capacitor C3. Pin 1 of the voltage regulator REG1 is connected to the source S of the depletion-type N-channel MOSFET Q1 through a resettable fuse F1, pin 2 is grounded, and pin 3 is connected to the anode of the filter capacitor C3. The cathode of the filter capacitor C3 is grounded.

[0037] The working principle of this power supply circuit is as follows: First, the mains power is rectified by bridge BRG1 and then connected to the drain (D) of depletion-type N-channel MOSFET Q1. Since the drain (D) and source (S) of Q1 are initially conducting, and pins 3 and 4 of the normally closed optocoupler relay OP1 are also conducting, the rectified voltage signal is transmitted to the anode of filter capacitor C2 through Q1 and resettable fuse F1. At this time, as the anode voltage of filter capacitor C2 gradually increases, after being divided by voltage divider resistors R4 and R5, it reaches the preset operating point voltage, causing the drain (D) and source (S) of enhancement-type N-channel MOSFET Q2 to conduct, thereby grounding pin 2 of the normally closed optocoupler relay OP1.

[0038] Subsequently, the voltage difference between pins 1 and 2 of the normally closed optocoupler relay OP1 energizes the internal LED. The current-limiting resistor R3 limits the current, preventing excessive current from damaging the LED. At this point, the LED illuminates, causing pins 3 and 4 of the OP1 output to disconnect. The source voltage (S) of the depletion-type N-channel MOSFET Q1 charges capacitor C1 through resistor R1 and capacitor C1. When the voltage reaches the Zener breakdown voltage of the Zener diode D1, the voltage difference between the gate voltage (G) and source voltage (S) of the depletion-type N-channel MOSFET Q1 is clamped to the Zener breakdown voltage of D1, simultaneously meeting the turn-off condition of the depletion-type N-channel MOSFET Q1. At this point, the drain voltage (D) and source voltage (S) of the depletion-type N-channel MOSFET Q1 are turned off.

[0039] Finally, after the depletion-mode N-channel MOSFET Q1 is turned off, as the anode voltage of the filter capacitor C2 continuously decreases, the gate voltage G of the enhancement-mode N-channel MOSFET Q2 also continuously decreases after being divided by voltage divider resistors R4 and R5. After the turn-off condition of the enhancement-mode N-channel MOSFET Q2 is met, the drain (D) and source (S) of the enhancement-mode N-channel MOSFET Q2 are turned off, and the internal LED of the normally closed optocoupler relay OP1 is turned off, thereby turning on pins 3 and 4 of the normally closed optocoupler relay OP1 again. The capacitor C1 discharges through the internal circuit of pins 3 and 4 of OP1 and the current-limiting resistor R2. The current-limiting resistor R2 limits the current and protects the internal circuit of the output terminal of the normally closed optocoupler relay OP1.

[0040] When pins 3 and 4 of the normally closed optocoupler relay OP1 are turned on again, the voltage difference between the gate (G) and source (S) of the depletion-type N-channel field-effect transistor (DFET) Q1 decreases, reaching the turn-on condition of the DFET Q1. The drain (D) and source (S) of the DFET Q1 then return to the on state.

[0041] The above describes a complete turn-on-off-turn-on process. This process repeats continuously, forming a feedback control switching circuit. The voltage regulator REG1 and filter capacitor C3 then produce a stable and reliable low-voltage DC output. The voltage regulator REG1 and filter capacitor C3 at the back end of the circuit are common linear DC-DC circuits, and therefore will not be described further here.

[0042] Furthermore, in this circuit, the resettable fuse F1 and TVS diode D2 provide overvoltage protection. The principle is as follows: if the voltage across the filter capacitor C2 is too high during a circuit malfunction or external impact, causing the TVS diode D2 to break down, the current flowing through the resettable fuse F1 increases. This increases the impedance of the resettable fuse F1 until it turns off, disconnecting the circuit and thus protecting the Zener diode REG1 and the connected load. Because this is a non-isolated design, adding protection circuitry effectively improves the reliability and safety of this power supply circuit.

[0043] In this type of power supply circuit, the control signal for the MOSFET comes from the MOSFET's output terminal, which is a feedback control technique—using the output to control the input. Compared to pre-stage control, feedback control makes the output less prone to runaway, resulting in a more stable and reliable circuit, and is a more advanced technique.

[0044] This invention discloses a low-power AC mains power to 24V DC power supply circuit, which features a simple circuit structure and high stability and reliability. By using an optocoupler relay to control the switching of a field-effect transistor instead of a transformer, the full-wave rectified signal is further truncated into an oscillation signal. After amplitude reduction and voltage regulation, the 220V AC voltage is converted to 24V DC voltage, which can be used to power micro-electronic devices. Furthermore, compared to capacitor and resistor voltage dividers, this power supply circuit has lower losses and higher load capacity. It also widely uses semiconductor devices, making it easy to integrate; most components can be integrated into a single integrated circuit.

[0045] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A low-power power supply circuit that converts AC mains power to 24V DC, characterized in that: It includes a rectifier bridge BRG1, a depletion-type N-channel MOSFET Q1, a resettable fuse F1, a resistor R1, a current-limiting resistor R3, a normally closed optocoupler relay OP1, a current-limiting resistor R2, a Zener diode D1, a TVS diode D2, a capacitor C1, an enhancement-type N-channel MOSFET Q2, a voltage divider resistor R4, a voltage divider resistor R5, a filter capacitor C2, and a DC-DC sub-circuit; The input terminals 1 and 3 of the rectifier bridge BRG1 receive AC mains power, the positive output terminal 2 is connected to the drain D of the depletion-type N-channel field-effect transistor Q1, and the negative output terminal 4 is grounded. The source S of the depletion-type N-channel field-effect transistor Q1 is connected to pin 1 of the normally closed optocoupler relay OP1 through a series self-resetting fuse F1 and a current-limiting resistor R3. One end of the resistor R1 is connected to the gate G of the depletion-type N-channel field-effect transistor Q1, and the other end is grounded. The normally closed optocoupler relay OP1 has its pin 3 connected to the gate G of the depletion-type N-channel field-effect transistor Q1 through a current-limiting resistor R2. The Zener diode D1 and capacitor C1 are connected in parallel. One end of the Zener diode D1 is connected to the source S of the depletion-type N-channel field-effect transistor Q1, and the other end is connected to the gate G of the depletion-type N-channel field-effect transistor Q1. The drain D of the enhancement-mode N-channel MOSFET Q2 is connected to pin 2 of the normally closed optocoupler relay OP1, the source S is grounded, and the gate G is grounded through the voltage divider resistor R5; one end of the voltage divider resistor R4 is connected to the source S of the depletion-mode N-channel MOSFET Q1 through the resettable fuse F1, and the other end is connected to the gate G of the enhancement-mode N-channel MOSFET Q2. The anode of the filter capacitor C2 is connected to the source S of the depletion-type N-channel MOSFET Q1 through a resettable fuse F1, and the cathode is grounded. One end of the TVS diode D2 is connected to the source S of the depletion-type N-channel field-effect transistor Q1 through a resettable fuse F1, and the other end is grounded. The positive input terminal of the DC-DC sub-circuit is connected to the source S of the depletion-type N-channel MOSFET Q1 through a self-resetting fuse F1, and the negative terminal is grounded.

2. The low-power power supply circuit for converting AC mains power to 24V DC according to claim 1, characterized in that: The DC-DC sub-circuit adopts a linear DC-DC circuit.

3. The low-power power supply circuit for converting AC mains power to 24V DC according to claim 2, characterized in that: The linear DC-DC circuit includes a voltage regulator REG1 and a filter capacitor C3. Pin 1 of the voltage regulator REG1 is connected to the source S of the depletion-type N-channel MOSFET Q1 through a resettable fuse F1, pin 2 is grounded, pin 3 is connected to the anode of the filter capacitor C3, and the cathode of the filter capacitor C3 is grounded.

Images