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

Abstract

The invention provides a low-power power supply circuit for converting alternating current commercial power into direct current 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 the alternating current mains supply into the direct current 24V has the advantages of being simple in circuit structure and high in 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] The invention belongs to the technical field of power supply, and in particular relates to a low-power power supply circuit for converting AC mains power into DC 24V. Background Art

[0002] In the application of low-power and low-voltage DC power supplies, one solution is to use a transformer in the circuit, and the other solution is to not use a transformer in the circuit. In miniature electrical appliances with a small space inside the casing, it is particularly important to achieve miniaturization, low cost and high reliability. The design using a transformer places high demands on the volume and finished product of the power supply, making it difficult to achieve miniaturization and low cost. There are currently two existing technical routes for designs that do not use a transformer in the circuit: one is the "capacitor voltage division" solution of connecting a capacitor in series on the AC path, and the other is the solution of directly using a resistor to divide the voltage after rectification. The disadvantages of these two solutions are poor load capacity, large circuit loss, and severe heat generation, which are not conducive to improving the service life and reliability of the power supply.

[0003] For example, the existing Chinese invention patent with publication number CN102185500A provides a practical transformerless switching power supply which belongs to the "solution without using a transformer". It draws power from the AC input terminal and uses it as the control signal of the MOS tube after rectification and voltage division. It belongs to the front-stage control technology route, that is, it controls the output from the input, and the output stability and reliability are poor. Summary of the invention

[0004] In view of this, the present invention aims to provide a low-power power supply circuit for converting AC mains into DC 24V, so as to solve the problem of poor reliability of existing low-power low-voltage DC power supply circuits.

[0005] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0006] A low-power power supply circuit for converting AC mains into DC 24V, comprising 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 tube Q2, a voltage divider resistor R4, a voltage divider resistor R5, a filter capacitor C2, and a DC-DC sub-circuit;

[0007] The input terminal 1 and the input terminal 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 the pin 1 of the normally closed optocoupler relay OP1 through a self-recovery fuse F1 and a current-limiting resistor R3 connected in series. 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 pin 3 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;

[0010] The voltage regulator tube D1 and the capacitor C1 are connected in parallel, and one end of the voltage regulator tube D1 is connected to the source S of the depletion type N-channel field effect tube Q1, and the other end of the voltage regulator tube D1 is connected to the gate G of the depletion type N-channel field effect tube Q1;

[0011] The drain D of the enhanced N-channel field effect transistor Q2 is connected to the 2nd pin of the normally closed optocoupler relay OP1, the source S is grounded, and the gate G is grounded through the voltage-dividing resistor R5; one end of the voltage-dividing resistor R4 is connected to the source S of the depletion-type N-channel field effect transistor Q1 through the resettable fuse F1, and the other end is connected to the gate G of the enhanced N-channel field effect transistor Q2;

[0012] The anode of the filter capacitor C2 is connected to the source S of the depletion type N-channel field effect transistor Q1 through the self-recovery fuse F1, and the cathode is grounded;

[0013] One end of the TVS tube D2 is connected to the source S of the depletion-type N-channel field effect tube Q1 through the self-recovery 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 field effect transistor Q1 through a self-recovery fuse F1, and the negative terminal is grounded.

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

[0016] Furthermore, the linear DC-DC circuit includes a voltage regulator REG1 and a filter capacitor C3, wherein pin 1 of the voltage regulator REG1 is connected to the source S of the depletion-type N-channel field effect transistor Q1 through a self-recovery 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.

[0017] Compared with the prior art, the low-power power supply circuit for converting AC mains power into DC 24V described in the present invention has the following advantages:

[0018] The low-power power supply circuit for converting AC mains power into 24V DC described in the present invention has the advantages of simple circuit structure, high stability and reliability. By not using a transformer, but using an optical coupler relay to control the switch of a field effect tube, the full-wave rectified signal is further intercepted as an oscillation signal, and the amplitude is reduced and then subjected to voltage stabilization to realize the conversion of 220V AC voltage into 24V DC voltage, which can be used as power supply for micro-electrical appliances. At the same time, compared with the "capacitor voltage division" and "resistor voltage division" schemes, this power supply circuit has small losses and strong load capacity, and semiconductor devices are widely used in the circuit, which is easy to integrate, and most of the devices in the circuit can be integrated to make an "integrated circuit". BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0020] Figure 1 This is a circuit schematic diagram of a low-power power supply circuit for converting AC mains power into DC 24V according to an embodiment of the present invention. DETAILED DESCRIPTION

[0021] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0022] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0023] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

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

[0025] A low-power power supply circuit for converting AC mains into DC 24V, comprising 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-stabilizing tube D1, a TVS tube D2, a capacitor C1, an enhanced N-channel field effect tube Q2, a voltage-dividing resistor R4, a voltage-dividing resistor R5, a filter capacitor C2, and a DC-DC subcircuit.

[0026] 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.

[0027] The source S of the above-mentioned depletion-type N-channel field effect transistor Q1 is connected to pin 1 of the normally closed optocoupler relay OP1 through a series-connected self-recovery 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.

[0028] The pin 3 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] After the voltage regulator D1 and the capacitor C1 are connected in parallel, one end 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 .

[0030] Specifically, the cathode of the voltage regulator tube D1 is connected to the source S of the depletion type N-channel field effect transistor Q1 , and the anode of the voltage regulator tube D1 is connected to the gate G of the depletion type N-channel field effect transistor Q1 .

[0031] The drain D of the above-mentioned enhanced N-channel field effect transistor Q2 is connected to the 2nd foot of the normally closed optocoupler relay OP1, the source S is grounded, and the gate G is grounded through the voltage-dividing resistor R5; one end of the voltage-dividing resistor R4 is connected to the source S of the depletion-type N-channel field effect transistor Q1 through the resettable fuse F1, and the other end is connected to the gate G of the enhanced N-channel field effect transistor Q2.

[0032] The anode of the filter capacitor C2 is connected to the source S of the depletion type N-channel field effect transistor Q1 through the self-recovery fuse F1, and the cathode is grounded.

[0033] The positive input terminal of the DC-DC sub-circuit is connected to the source S of the depletion-type N-channel field effect transistor Q1 through the self-recovery fuse F1, and the negative terminal is grounded.

[0034] Preferably, the circuit further includes a resistor R1, 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 comprises a TVS tube D2, one end of which is connected to the source S of the depletion-type N-channel field effect tube Q1 through a resettable fuse F1, and the other end of which is grounded.

[0036] Preferably, the DC-DC subcircuit adopts a linear DC-DC circuit. Specifically, the linear DC-DC circuit includes a voltage regulator REG1 and a filter capacitor C3, wherein the pin 1 of the voltage regulator REG1 is connected to the source S of the depletion-type N-channel field effect transistor Q1 through a self-recovery fuse F1, the pin 2 is grounded, the pin 3 is connected to the anode of the filter capacitor C3, and the cathode of the filter capacitor C3 is grounded.

[0037] The working principle of this power supply circuit is as follows: First, the city power is connected to the drain D of the depletion type N-channel field effect tube Q1 after the rectifier bridge BRG1. Since the drain D and source S of the depletion type N-channel field effect tube Q1 are turned on in the initial state, and the output terminals 3 and 4 of the normally closed optocoupler relay OP1 are also turned on, the rectified voltage signal is transmitted to the anode of the filter capacitor C2 through the depletion type N-channel field effect tube Q1 and the self-recovery fuse F1. At this time, as the anode voltage of the filter capacitor C2 gradually rises, after being divided by the voltage-dividing resistors R4 and R5, it reaches the preset action point voltage, so that the drain D and source S of the enhanced N-channel field effect tube Q2 are turned on, so that the 2nd foot of the normally closed optocoupler relay OP1 is grounded.

[0038] Afterwards, the voltage difference between pin 1 and pin 2 of the normally closed optocoupler relay OP1 will energize the internal light-emitting diode of the normally closed optocoupler relay OP1. Among them, the current limiting resistor R3 plays a current limiting role to prevent the internal light-emitting diode of the normally closed optocoupler relay OP1 from being damaged by excessive current. At this time, since the internal light-emitting diode of the normally closed optocoupler relay OP1 emits light, pins 3 and 4 of the output end of the normally closed optocoupler relay OP1 are disconnected, and the source S voltage of the depletion type N-channel field effect transistor Q1 charges the capacitor C1 through the resistor R1 and the capacitor C1. When the Zener breakdown voltage of the voltage regulator D1 is reached, the gate G and source S voltage difference of the depletion type N-channel field effect transistor Q1 is clamped to the Zener breakdown voltage of the voltage regulator D1, and the shutdown condition of the depletion type N-channel field effect transistor Q1 is reached at the same time. At this time, the drain D and source S of the depletion type N-channel field effect transistor Q1 are turned off.

[0039] Finally, after the depletion-type N-channel field effect transistor Q1 is turned off, as the anode voltage of the filter capacitor C2 continues to decrease, after being divided by the voltage-dividing resistors R4 and R5, the gate G voltage of the enhancement-type N-channel field effect transistor Q2 also continues to decrease. When the turn-off condition of the enhancement-type N-channel field effect transistor Q2 is reached, the drain D and source S of the enhancement-type N-channel field effect transistor Q2 are turned off, and the light-emitting diode inside the normally closed optocoupler relay OP1 is turned off, so that pins 3 and 4 of the normally closed optocoupler relay OP1 are turned on again, and the capacitor C1 is discharged through the internal circuits of pins 3 and 4 of OP1 and the current-limiting resistor R2. The current-limiting resistor R2 plays a current-limiting role to protect the internal circuit of the output end 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 Q1 is reduced, reaching the turn-on condition of the depletion-type N-channel field effect transistor Q1, and the drain D and source S of the depletion-type N-channel field effect transistor Q1 return to the turned-on state again.

[0041] The above describes a complete on-off-on process. This process is repeated to form a feedback control switch circuit, which then passes through the voltage regulator REG1 and the filter capacitor C3 to form a stable and reliable low-voltage DC voltage output. Among them, the voltage regulator REG1 and the filter capacitor C3 at the back end of the circuit are common linear DC-DC circuits, so they will not be described here.

[0042] In addition, the resettable fuse F1 and TVS tube D2 in this circuit play an overvoltage protection role for the circuit. The principle is: when the circuit is abnormal or there is an external impact, if the voltage of the filter capacitor C2 is too high, the TVS tube D2 will break down. At this time, the current flowing through the resettable fuse F1 increases, and the impedance of the resettable fuse F1 increases until it is turned off, disconnecting the circuit, thereby protecting the voltage regulator tube REG1 and the subsequent load. This is because this case is a non-isolated solution, so adding a protection circuit can effectively improve the reliability and safety of this power supply circuit.

[0043] The control signal of the MOS tube in this power supply circuit comes from the output end of the MOS tube, which belongs to the feedback control technology route, that is, using the output to control the input. Compared with the pre-stage control, the feedback control is less likely to lose control, the circuit is more stable and reliable, and it is a more advanced technology route.

[0044] The low-power power supply circuit for converting AC mains power to 24V DC described in the present invention has the advantages of simple circuit structure, high stability and reliability. Instead of using a transformer, an optocoupler relay is used to control the switch of a field effect tube, and the full-wave rectified signal is further intercepted as an oscillation signal. After the amplitude is reduced, the voltage is stabilized to realize the conversion of 220V AC voltage to 24V DC voltage, which can be used as power supply for micro-electrical appliances. At the same time, compared with the "capacitor voltage division" and "resistor voltage division" schemes, this power supply circuit has small loss and strong load capacity, and semiconductor devices are widely used in the circuit, which is easy to integrate, and most of the devices in the circuit can be integrated to make an "integrated circuit".

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

Claims

1. A low-power power supply circuit for converting AC mains into DC 24V, characterized in that: Including rectifier bridge BRG1, depletion type N-channel field effect transistor Q1, self-recovery fuse F1, resistor R1, current limiting resistor R3, normally closed optocoupler relay OP1, current limiting resistor R2, voltage regulator tube D1, TVS tube D2, capacitor C1, enhanced N-channel field effect transistor Q2, voltage divider resistor R4, voltage divider resistor R5, filter capacitor C2, and DC-DC sub-circuit; The input terminal 1 and the input terminal 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 the pin 1 of the normally closed optocoupler relay OP1 through a self-recovery fuse F1 and a current-limiting resistor R3 connected in series. 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 pin 3 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; The voltage regulator tube D1 and the capacitor C1 are connected in parallel, and one end of the voltage regulator tube D1 is connected to the source S of the depletion type N-channel field effect tube Q1, and the other end of the voltage regulator tube D1 is connected to the gate G of the depletion type N-channel field effect tube Q1; The drain D of the enhanced N-channel field effect transistor Q2 is connected to the 2nd pin of the normally closed optocoupler relay OP1, the source S is grounded, and the gate G is grounded through the voltage-dividing resistor R5; one end of the voltage-dividing resistor R4 is connected to the source S of the depletion-type N-channel field effect transistor Q1 through the resettable fuse F1, and the other end is connected to the gate G of the enhanced N-channel field effect transistor Q2; The anode of the filter capacitor C2 is connected to the source S of the depletion type N-channel field effect transistor Q1 through the self-recovery fuse F1, and the cathode is grounded; One end of the TVS tube D2 is connected to the source S of the depletion-type N-channel field effect tube Q1 through the self-recovery 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 field effect transistor Q1 through a self-recovery fuse F1, and the negative terminal is grounded.

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

3. A low-power power supply circuit for converting AC mains power into DC 24V according to claim 2, characterized in that: The linear DC-DC circuit includes a voltage regulator REG1 and a filter capacitor C3, wherein pin 1 of the voltage regulator REG1 is connected to the source S of the depletion-type N-channel field effect transistor Q1 through a self-recovery 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.

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