Power supply output control circuit and switching power supply

Abstract

The utility model discloses a power supply output control circuit and a switching power supply, and the power supply output control circuit comprises a transformer, an isolation drive circuit, and a switching circuit. The input end of the transformer is used for being connected with a signal input end, receiving a power input signal and outputting a power output signal; the switching circuit is connected with the first output end and the signal output end of the transformer; and the isolation driving circuit is connected with the second output end of the transformer and the switching circuit and is used for switching on or switching off the switching circuit according to the power output signal, so that the isolation driving circuit takes the power output signal output by the second output end of the transformer as an energy source for driving the switching circuit to be switched on or switched off. Therefore, the design difficulty and cost are reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of power supply, in particular to a power supply output control circuit and a switching power supply. Background Art

[0002] A switching power supply, also known as a switching power supply or a switching converter, is a high-frequency power conversion device. Existing switching power supplies generally set an output switch in the output path to control the output of the switching power supply. However, the existing output switch requires the design of an additional voltage circuit to provide an energy source to drive the output switch to conduct or switch, which increases the design difficulty and cost. Utility Model Content

[0003] The embodiments of the utility model provide a power output control circuit and a switching power supply to solve the problems of difficulty and high cost in designing the existing power output control circuit.

[0004] A power output control circuit comprises a transformer, an isolation drive circuit and a switch circuit;

[0005] The input end of the transformer is used to connect to the signal input end, to receive a power input signal, and to output a power output signal;

[0006] The switch circuit is connected to the first output terminal and the signal output terminal of the transformer;

[0007] The isolation driving circuit is connected to the second output terminal of the transformer and the switch circuit, and is used to turn on or off the switch circuit according to the power supply output signal.

[0008] Further, the switch circuit includes a first NMOS tube;

[0009] The source and drain of the first NMOS transistor are connected between the first output terminal of the transformer and the signal output terminal, and the gate of the first NMOS transistor is connected to the isolation drive circuit.

[0010] Further, the switch circuit includes a first NMOS transistor and a second NMOS transistor;

[0011] The source of the first NMOS tube is connected to the first output end of the transformer, the drain of the first NMOS tube is connected to the drain of the second NMOS tube, the source of the second NMOS tube is connected to the signal output end, and the gate of the first NMOS tube and the gate of the second NMOS tube are connected to the isolation drive circuit.

[0012] Further, the isolation driving circuit includes a photocoupler;

[0013] The first input end of the photoelectric coupler is used to receive a control signal, and the second input end of the photoelectric coupler is used to connect to a negative connection end;

[0014] The first output end of the photoelectric coupler is connected to the second output end of the transformer, and the second output end of the photoelectric coupler is connected to the switch circuit.

[0015] Furthermore, the power output control circuit also includes a voltage stabilizing circuit;

[0016] The voltage stabilizing circuit is connected to the first output end of the transformer, the second output end of the transformer and the isolation driving circuit, and is used to provide a regulated voltage to the isolation driving circuit.

[0017] Further, the voltage stabilizing circuit includes a first transistor, a first diode and a first resistor;

[0018] The first end of the first transistor is connected to the second output end of the transformer, the second end of the first transistor is connected to the isolation drive circuit, the third end of the first transistor is connected to the cathode of the first diode, and the anode of the first diode is connected to the first output end of the transformer;

[0019] A first end of the first resistor is connected to the second output end of the transformer, and a second end of the first resistor is connected to a connection node between the third end of the first transistor and the cathode of the first diode.

[0020] Further, the transformer comprises a primary winding, a first secondary winding and a second secondary winding;

[0021] The first end of the primary winding is used for a power input terminal, and the second end of the primary winding is coupled to the ground;

[0022] The first end of the first secondary winding is connected to the isolation drive circuit, the second end of the first secondary winding is connected to the first end of the second secondary winding, and the second end of the second secondary winding is connected to the signal output end;

[0023] A connection node between the second end of the first secondary winding and the first end of the second secondary winding is connected to the switch circuit.

[0024] Furthermore, the power output control circuit also includes a rectifier and filter circuit;

[0025] The input end of the rectification and filtering circuit is connected to the first output end of the transformer and the second output end of the transformer, and the output end of the rectification and filtering circuit is connected to the isolation drive circuit and the switching circuit, and is used to rectify and filter the power supply output signal.

[0026] Further, the rectification and filtering circuit includes a first rectification diode, a first filtering capacitor, a second rectification diode and a second filtering capacitor;

[0027] The anode of the first rectifier diode is connected to the first end of the first secondary winding, and the cathode of the first rectifier diode is connected to the isolation drive circuit;

[0028] An anode of the second rectifier diode is connected to the second end of the first secondary winding and the first end of the second secondary winding, and a cathode of the second rectifier diode is connected to the switch circuit;

[0029] The first end of the first filter capacitor is connected to the cathode of the first rectifier diode and the isolation drive circuit, and the second end of the first filter capacitor is connected to the cathode of the second rectifier diode and the switch circuit;

[0030] A first end of the second filter capacitor is connected to the cathode of the second rectifier diode and the switch circuit, and a second end of the second filter capacitor is connected to the second end of the second secondary winding and the signal output end.

[0031] A switching power supply comprises the above-mentioned power output control circuit.

[0032] The above-mentioned power output control circuit and switching power supply, the power output control circuit, includes a transformer, an isolation drive circuit and a switching circuit; the input end of the transformer is used to connect the signal input end, for receiving the power input signal, and outputting the power output signal; the switching circuit is connected to the first output end and the signal output end of the transformer; the isolation drive circuit is connected to the second output end of the transformer and the switching circuit, for turning on or off the switching circuit according to the power output signal, so that the isolation drive circuit uses the power output signal output by the second output end of the transformer as an energy source for driving the switching circuit to turn on or off, thereby reducing the design difficulty and cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the utility model, the drawings required for use in the description of the embodiments of the utility model will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0034] Figure 1 This is a circuit diagram of a power output control circuit in one embodiment of the utility model;

[0035] Figure 2It is a circuit diagram of a switching power supply in one embodiment of the utility model.

[0036] In the figure: 1. power supply output control circuit; 11. transformer; 12. isolation drive circuit; 13. switch circuit; 14. voltage stabilizing circuit; 15. rectifier filter circuit; 2. rectifier bridge circuit; 3. power supply control chip. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0038] It should be understood that the utility model can be implemented in different forms and should not be interpreted as being limited to the embodiments proposed herein. On the contrary, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the utility model to those skilled in the art.

[0039] In order to thoroughly understand the present invention, detailed structures and steps will be presented in the following description to illustrate the technical solution proposed by the present invention. The preferred embodiments of the present invention are described in detail below, but in addition to these detailed descriptions, the present invention may also have other implementations.

[0040] This embodiment provides a power output control circuit 1, such as Figure 1 As shown, it includes a transformer 11 (T1), an isolation drive circuit 12 and a switch circuit 13; the input end of the transformer 11 is used to connect the signal input end, for receiving a power input signal, and outputting a power output signal; the switch circuit 13 is connected to the first output end and the signal output end (V+, V-) of the transformer 11; the isolation drive circuit 12 is connected to the second output end E of the transformer 11 and the switch circuit 13, for turning on or off the switch circuit 13 according to the power output signal.

[0041] As an example, the input end of the transformer 11 is used to connect to the signal input end, to receive the power input signal, and to output the power output signal. Specifically, the signal input end is used to receive the rectifier bridge circuit 2 in the switching power supply. The output end of the rectifier bridge circuit 2 is used to connect to the public power grid, and the output end of the rectifier bridge circuit 2 is used to output the power input signal. The rectifier bridge circuit 2 converts the AC signal input from the public power grid into a DC signal, i.e., the power input signal. The transformer 11 performs power conversion on the power input signal and outputs the power output signal.

[0042] As an example, the transformer 11 includes a first output terminal and a second output terminal. The switch circuit 13 is connected to the first output terminal and the signal output terminal of the transformer 11. When the switch circuit 13 is turned on, the signal output terminal outputs the power output signal output by the first output terminal of the transformer 11, and the signal output terminal is used to connect a load device. The load device may be an electrical device or a charging device. The isolation drive circuit 12 is connected to the second output terminal E of the transformer 11 and the switch circuit 13, and is used to turn on or off the switch circuit 13 according to the power output signal. In this example, the isolation drive circuit 12 uses the power output signal output by the second output terminal E of the transformer 11 as an energy source for driving the switch circuit 13 to turn on or off, thereby reducing the design difficulty and cost.

[0043] For example, Figure 1 As shown, the transformer 11 includes a first output terminal, a second output terminal and a third output terminal. Among them, the first output terminal and the third output terminal are main output terminals, and the first output terminal and the second output terminal are auxiliary output terminals. The first output terminal of the transformer 11 is connected to the switch circuit 13, the switch circuit 13 is connected to the V+ terminal of the signal output terminal, the third output terminal of the transformer 11 is connected to the V- terminal of the signal output terminal, and the second output terminal E of the transformer 11 is connected to the isolation drive circuit 12.

[0044] In one embodiment, the switch circuit 13 includes a first NMOS transistor Q1 ; the source and drain of the first NMOS transistor Q1 are connected between the first output terminal and the signal output terminal of the transformer 11 , and the gate of the first NMOS transistor Q1 is connected to the isolation drive circuit 12 .

[0045] As an example, the source of the first NMOS tube Q1 is connected to the first output end of the transformer 11, and the drain of the first NMOS tube Q1 is connected to the signal output end, or the source of the first NMOS tube Q1 is connected to the signal output end, and the drain of the first NMOS tube Q1 is connected to the first output end of the transformer 11, which can be selected according to actual experience.

[0046] In this embodiment, since the P-type MOS tube requires an additional voltage circuit that provides a negative voltage as a driving energy source, and the first NMOS tube Q1 is turned on by a positive voltage, the isolation driving circuit 12 can directly use the power output signal output by the second output terminal E of the transformer 11 to drive the first NMOS tube Q1 to turn on or off. Therefore, compared with using a P-type MOS tube, the design difficulty and cost can be reduced.

[0047] In one embodiment, if Figure 1As shown, the switch circuit 13 includes a first NMOS transistor Q1 and a second NMOS transistor Q2; the source of the first NMOS transistor Q1 is connected to the first output end of the transformer 11, the drain of the first NMOS transistor Q1 is connected to the drain of the second NMOS transistor Q2, the source of the second NMOS transistor Q2 is connected to the signal output end, and the gate of the first NMOS transistor Q1 and the gate of the second NMOS transistor Q2 are connected to the isolation drive circuit 12.

[0048] In this embodiment, two NMOS transistors, namely the first NMOS transistor Q1 and the second NMOS transistor Q2 are used, which can achieve better control over the output of the switching power supply compared to using one NMOS transistor.

[0049] In one embodiment, the isolation driving circuit 12 includes a photocoupler U2; a first input terminal A of the photocoupler U2 is used to receive a control signal, and a second input terminal K of the photocoupler U2 is used to connect to a negative connection terminal; a first output terminal C of the photocoupler U2 is connected to a second output terminal E of the transformer 11, and a second output terminal of the photocoupler U2 is connected to a switching circuit 13.

[0050] As an example, the control signal may be a control signal output by the power control chip 3 in the switching power supply. Exemplarily, the photocoupler U2 includes a light emitting diode and a phototransistor, the anode of the light emitting diode is the first input terminal A of the photocoupler U2, the cathode of the light emitting diode is the second input terminal K of the photocoupler U2, the collector of the phototransistor is the first output terminal C of the photocoupler U2, and the emitter of the phototransistor is the second output terminal of the photocoupler U2. In this embodiment, when the control signal is a high-level signal, the light emitting diode generates a light signal, and the phototransistor receives the light signal and turns on, so that the power output signal output by the second output terminal E of the transformer 11 drives the switch circuit 13 to turn on. When the control signal is a low-level signal, the light emitting diode does not generate a light signal, and the phototransistor cannot receive the light signal and turns on, so that the power output signal output by the second output terminal E of the transformer 11 drives the switch circuit 13 to turn off. In addition, the photocoupler U2 can also isolate the load device and the power control chip 3 to improve the circuit safety.

[0051] As an example, the power control chip 3 is connected to the signal output terminal and the isolation drive circuit 12, and is used to detect the output voltage or output current, and output a control signal to the isolation drive circuit 12 according to the output voltage or output current, thereby controlling the switch circuit 13 to be turned on or off. The power control chip 3 is connected to the first input terminal A of the photocoupler U2 through the resistor R8. Figure 1 As shown, the On / Off terminal is connected to the power control chip 3.

[0052] In one embodiment, the power output control circuit 1 further includes a voltage stabilizing circuit 14 ; the voltage stabilizing circuit 14 is connected to the first output terminal of the transformer 11 , the second output terminal E of the transformer 11 and the isolation drive circuit 12 , and is used to provide a regulated voltage to the isolation drive circuit 12 .

[0053] In this embodiment, a regulated voltage is provided to the isolation drive circuit 12 through the voltage stabilizing circuit 14 to prevent the power output signal output from the second output terminal E of the transformer 11 from breaking down components in the switch circuit 13, such as the first NMOS transistor Q1 and / or the second NMOS transistor Q2, thereby ensuring the safety and reliability of the switch circuit 13.

[0054] In one embodiment, the voltage stabilizing circuit 14 includes a first transistor Q8, a first diode ZD1 and a first resistor R9; a first end of the first transistor Q8 is connected to the second output end E of the transformer 11, a second end of the first transistor Q8 is connected to the isolation driving circuit 12, a third end of the first transistor Q8 is connected to the cathode of the first diode ZD1, and an anode of the first diode ZD1 is connected to the first output end of the transformer 11; a first end of the first resistor R9 is connected to the second output end E of the transformer 11, and a second end of the first resistor R9 is connected to a connection node between the third end of the first transistor Q8 and the cathode of the first diode ZD1.

[0055] As an example, the first transistor Q8 may be a bipolar transistor or a field effect transistor. The first transistor Q8 has a first terminal as a collector or a source, a second terminal as an emitter or a drain, and a third terminal as a collector or a gate.

[0056] In this embodiment, the first end of the first transistor Q8 is connected to the second output end E of the transformer 11, the second end of the first transistor Q8 is connected to the isolation drive circuit 12, the third end of the first transistor Q8 is connected to the cathode of the first diode ZD1, and the anode of the first diode ZD1 is connected to the first output end of the transformer 11; the first end of the first resistor R9 is connected to the second output end E of the transformer 11, and the second end of the first resistor R9 is connected to the connection node between the third end of the first transistor Q8 and the cathode of the first diode ZD1, so as to ensure the stability of the power output signal output to the switch circuit 13. It should be noted that the resistance value of the first resistor R9 can be selected according to actual experience.

[0057] In one embodiment, the transformer 11 includes a primary winding, a first secondary winding and a second secondary winding; the first end of the primary winding is used for a power input terminal, and the second end of the primary winding is coupled to the ground; the first end of the first secondary winding is connected to the isolation drive circuit 12, the second end of the first secondary winding is connected to the first end of the second secondary winding, and the second end of the second secondary winding is connected to the signal output terminal; the connection node between the second end of the first secondary winding and the first end of the second secondary winding is connected to the switching circuit 13.

[0058] In this embodiment, by configuring the coil turns ratio between the primary winding, the first secondary winding, and the second secondary winding, the power output control circuit 1 can provide a driving voltage to the switch circuit 13 while outputting a suitable output voltage, thereby eliminating the need for an additional voltage circuit and reducing the design difficulty and cost. It is understandable that the coil turns ratio between the primary winding, the first secondary winding, and the second secondary winding can be configured according to actual experience, and is not limited here.

[0059] In one embodiment, the power supply output control circuit 1 also includes a rectifier and filter circuit 15; the input end of the rectifier and filter circuit 15 is connected to the first output end of the transformer 11 and the second output end E of the transformer 11, and the output end of the rectifier and filter circuit 15 is connected to the isolation drive circuit 12 and the switch circuit 13, and is used to rectify and filter the power supply output signal.

[0060] The input end of the rectifier and filter circuit 15 is connected to the first output end of the transformer 11 and the second output end E of the transformer 11, and the output end of the rectifier and filter circuit 15 is connected to the isolation drive circuit 12 and the switch circuit 13, and is used to rectify and filter the power supply output signal to ensure that the power supply output signal after filtering can stably drive the switch circuit 13 to turn on.

[0061] In one embodiment, the rectification and filtering circuit 15 includes a first rectification diode D1, a first filtering capacitor C1, a second rectification diode D3 and a second filtering capacitor C2; the anode of the first rectification diode D1 is connected to the first end of the first secondary winding, and the cathode of the first rectification diode D1 is connected to the isolation drive circuit 12; the anode of the second rectification diode D3 is connected to the second end of the first secondary winding and the first end of the second secondary winding, and the cathode of the second rectification diode D3 is connected to the switch circuit 13; the first end of the first filtering capacitor C1 is connected to the cathode of the first rectification diode D1 and the isolation drive circuit 12, and the second end of the first filtering capacitor C1 is connected to the cathode of the second rectification diode D3 and the switch circuit 13; the first end of the second filtering capacitor C2 is connected to the cathode of the second rectification diode D3 and the switch circuit 13, and the second end of the second filtering capacitor C2 is connected to the second end of the second secondary winding and the signal output end.

[0062] The capacitance values ​​of the first filter circuit and the second filter capacitor C2 are selected based on actual experience.

[0063] In this embodiment, the power output signal output from the second output terminal E of the transformer 11 is filtered by the first rectifier diode D1 and the first filter capacitor C1, and the power output signal output from the first output terminal of the transformer 11 is filtered by the second rectifier diode D3 and the second filter capacitor C2, thereby ensuring that the power output control circuit 1 can operate stably.

[0064] This embodiment provides a switching power supply, including the power output control circuit 1 mentioned above.

[0065] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention.

Claims

1. A power output control circuit, characterized in that: Including transformer, isolation drive circuit and switch circuit; The input end of the transformer is used to connect to the signal input end, to receive a power input signal, and to output a power output signal; The switch circuit is connected to the first output terminal and the signal output terminal of the transformer; The isolation driving circuit is connected to the second output terminal of the transformer and the switch circuit, and is used to turn on or off the switch circuit according to the power supply output signal.

2. The power output control circuit according to claim 1, characterized in that: The switch circuit includes a first NMOS tube; The source and drain of the first NMOS transistor are connected between the first output terminal of the transformer and the signal output terminal, and the gate of the first NMOS transistor is connected to the isolation drive circuit.

3. The power output control circuit according to claim 1, characterized in that: The switch circuit includes a first NMOS tube and a second NMOS tube; The source of the first NMOS tube is connected to the first output end of the transformer, the drain of the first NMOS tube is connected to the drain of the second NMOS tube, the source of the second NMOS tube is connected to the signal output end, and the gate of the first NMOS tube and the gate of the second NMOS tube are connected to the isolation drive circuit.

4. The power output control circuit according to claim 1, characterized in that: The isolation driving circuit includes a photocoupler; The first input end of the photoelectric coupler is used to receive a control signal, and the second input end of the photoelectric coupler is used to connect to a negative connection end; The first output end of the photoelectric coupler is connected to the second output end of the transformer, and the second output end of the photoelectric coupler is connected to the switch circuit.

5. The power output control circuit according to claim 1, characterized in that: The power output control circuit also includes a voltage stabilizing circuit; The voltage stabilizing circuit is connected to the first output end of the transformer, the second output end of the transformer and the isolation driving circuit, and is used to provide a regulated voltage to the isolation driving circuit.

6. The power output control circuit according to claim 5, characterized in that: The voltage stabilizing circuit includes a first transistor, a first diode and a first resistor; The first end of the first transistor is connected to the second output end of the transformer, the second end of the first transistor is connected to the isolation drive circuit, the third end of the first transistor is connected to the cathode of the first diode, and the anode of the first diode is connected to the first output end of the transformer; A first end of the first resistor is connected to the second output end of the transformer, and a second end of the first resistor is connected to a connection node between the third end of the first transistor and the cathode of the first diode.

7. The power output control circuit according to claim 1, characterized in that: The transformer comprises a primary winding, a first secondary winding and a second secondary winding; The first end of the primary winding is used for a power input terminal, and the second end of the primary winding is coupled to the ground; The first end of the first secondary winding is connected to the isolation drive circuit, the second end of the first secondary winding is connected to the first end of the second secondary winding, and the second end of the second secondary winding is connected to the signal output end; A connection node between the second end of the first secondary winding and the first end of the second secondary winding is connected to the switch circuit.

8. The power output control circuit according to claim 7, characterized in that: The power output control circuit also includes a rectifier and filter circuit; The input end of the rectification and filtering circuit is connected to the first output end of the transformer and the second output end of the transformer, and the output end of the rectification and filtering circuit is connected to the isolation drive circuit and the switching circuit, and is used to rectify and filter the power supply output signal.

9. The power output control circuit according to claim 8, characterized in that: The rectification and filtering circuit comprises a first rectification diode, a first filtering capacitor, a second rectification diode and a second filtering capacitor; The anode of the first rectifier diode is connected to the first end of the first secondary winding, and the cathode of the first rectifier diode is connected to the isolation drive circuit; An anode of the second rectifier diode is connected to the second end of the first secondary winding and the first end of the second secondary winding, and a cathode of the second rectifier diode is connected to the switch circuit; The first end of the first filter capacitor is connected to the cathode of the first rectifier diode and the isolation drive circuit, and the second end of the first filter capacitor is connected to the cathode of the second rectifier diode and the switch circuit; A first end of the second filter capacitor is connected to the cathode of the second rectifier diode and the switch circuit, and a second end of the second filter capacitor is connected to the second end of the second secondary winding and the signal output end.

10. A switching power supply, characterized in that: Comprising the power output control circuit as claimed in any one of claims 1 to 9.

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