A constant current auxiliary power supply circuit

Abstract

The present invention relates to a constant current auxiliary power supply circuit, comprising a rectifier circuit and a constant current circuit, wherein the rectifier circuit is connected to one end of the auxiliary winding of the transformer, and the constant current circuit is connected to the rectifier circuit; the rectifier circuit is used to rectify the voltage of the auxiliary winding of the transformer, and the constant current circuit is used to control the output of the rectifier circuit so that its output current remains constant. The constant current auxiliary power supply circuit of the present invention is based on the clamping function of the VCC of the controller, and uses a constant current to power the VCC of the controller. The power supply current can be set equal to the required current of the controller according to the requirements of the controller, thereby avoiding additional losses and improving the working efficiency of the entire power supply system; at the same time, the constant current auxiliary power supply circuit of the present invention can reduce the heat generation of the entire circuit due to the small additional losses, thereby improving the reliability of the circuit.

Description

Technical Field

[0001] The invention relates to a constant current auxiliary power supply circuit. Background Art

[0002] In the field of isolated DCDC power supply applications, the controller on the primary side requires an additional power supply circuit to provide power. We call this power supply circuit an auxiliary power supply circuit. The more common auxiliary power supply circuits are:

[0003] (1) Independent buck circuit;

[0004] (2) Auxiliary winding of sampling transformer plus dv / dt rectifier circuit;

[0005] However, an independent buck circuit requires higher cost and larger layout space. Considering the cost and the very limited space of the DCDC power supply, in DCDC power supply applications, the transformer auxiliary winding plus dv / dt rectifier circuit is generally used as the auxiliary power supply circuit of the controller, such as Figure 1 As shown;

[0006] However, since the voltage after the transformer auxiliary winding plus the dv / dt rectifier circuit is not a stable voltage, the rectified voltage needs a voltage regulator circuit. Common linear voltage regulator circuits are as follows: Figure 2 As shown, a linear voltage regulator circuit is set at the output end of the dv / dt rectifier circuit, and the base voltage of the transistor Q2 is clamped by the voltage regulator D4 to obtain a stable voltage Vout to supply power to the VCC of the controller. At this time, the voltage value of Vout is the conduction voltage of the voltage regulator D4 minus the PN junction voltage drop Vbe voltage of the transistor Q2. However, at this time, the voltage difference between the rectified voltage and the VCC of the controller is all applied to the transistor Q2, causing the transistor Q2 to suffer great losses. These losses not only affect the efficiency of the entire power supply system, but also cause problems such as heat and reliability. Summary of the invention

[0007] In order to solve the above technical defects in the prior art, the present invention proposes a constant current auxiliary power supply circuit, which is based on the clamping function of the controller VCC, controls the output current, and uses a constant power supply current to power the VCC of the controller, thereby avoiding additional losses and improving the efficiency of the entire power supply system.

[0008] The present invention provides a constant current auxiliary power supply circuit, comprising a rectifier circuit and a constant current circuit;

[0009] The rectifier circuit is connected to one end of the auxiliary winding of the transformer, and the constant current circuit is connected to the rectifier circuit;

[0010] The rectifier circuit is used to rectify the voltage of the auxiliary winding of the transformer, and the constant current circuit is used to control the output of the rectifier circuit so that its output current remains constant.

[0011] As a preferred implementation, the constant current circuit utilizes the reverse breakdown voltage drop of the voltage regulator tube, the PN junction voltage drop of the transistor and the fixed resistance value of the resistor in the constant current circuit to make the average charging current in the constant current circuit constant.

[0012] As a preferred implementation, the rectifier circuit includes a first resistor R1, a rectifier capacitor C1, a first diode D1, a second diode D2 and a second capacitor C2;

[0013] One end of the first resistor R1 is connected to the auxiliary winding of the transformer, the other end of the first resistor R1 is connected to one end of the rectifier capacitor C1, the other end of the rectifier capacitor C1 is simultaneously connected to the cathode of the first diode D1 and the anode of the second diode D2, and the cathode of the second diode D2 is connected to the VCC of the controller;

[0014] One end of the second capacitor C2 is connected to the cathode of the second diode D2, and the other end of the second capacitor C2 is grounded;

[0015] The anode of the first diode D1 is connected to the constant current circuit.

[0016] As a preferred implementation, the constant current circuit includes a second resistor R2, a third resistor R3, a voltage regulator D3, a third capacitor C3, and a PNP transistor Q1;

[0017] The collector of the PNP transistor Q1 is connected to the anode of the first diode D1, the emitter of the PNP transistor Q1 is connected to the second resistor R2, the other end of the second resistor R2 is grounded, the base of the collector of the PNP transistor Q1 is connected to the anode of the voltage regulator D3, the cathode of the voltage regulator D3 is grounded, and the third resistor R3 is connected between the base and collector of the PNP transistor Q1;

[0018] The anode of the first diode D1 is also connected to the third capacitor C3, and the other end of the third capacitor C3 is grounded.

[0019] As a preferred implementation, when the transformer auxiliary winding voltage is positive, the first diode D1 is not conducting and the Zener diode D3 is conducting. At this time, the base voltage of the PNP transistor Q1 is the negative value of the reverse breakdown voltage drop of the Zener diode D3, and the current on the second resistor R2 is a constant value. The current charges the third capacitor C3 through the PNP transistor Q1.

[0020] As a preferred implementation, when the transformer auxiliary winding voltage is a reverse voltage, the first diode D1 is turned on and the Zener diode D3 is turned on. At this time, the base voltage of the PNP transistor Q1 is the negative value of the reverse breakdown voltage drop of the Zener diode D3, and the current on the second resistor R2 is a constant value. The current charges the rectifier capacitor C1 through the PNP transistor Q1 and the first diode D1.

[0021] As a preferred implementation, when the transformer auxiliary winding voltage is a reverse voltage, the first diode D1 is turned on, and at this time the third capacitor C3 charges the rectifier capacitor C1 through the first diode D1.

[0022] As a preferred implementation, when the transformer auxiliary winding voltage is positive, the rectifier capacitor C1 is turned on, and at this time, the current on the rectifier capacitor C1 supplies power to the controller's VCC through the second diode D2;

[0023] The average current of the controller's VCC power supply provided by the rectifier capacitor C1 is:

[0024]

[0025] Wherein, Vz represents the reverse breakdown voltage drop of the voltage regulator D3, Veb represents the PN junction conduction voltage of the PNP transistor Q1, and R2 represents the resistance value of the second resistor R2.

[0026] Compared with the prior art, the present invention has the following significant advantages and beneficial effects:

[0027] (1) Compared with the conventional auxiliary power supply circuit which adopts the auxiliary winding of the transformer plus the dv / dt rectifier circuit plus the linear voltage regulator circuit, the constant current auxiliary power supply circuit of the present invention is based on the clamping function of the VCC of the controller and adopts a constant current to supply power to the VCC of the controller. The power supply current can be set to be slightly larger than the required current of the controller according to the requirements of the controller, thereby avoiding additional losses and improving the working efficiency of the entire power supply system;

[0028] (2) The constant current auxiliary power supply circuit of the present invention can reduce the heat generation of the entire circuit due to the small additional loss, thereby improving the reliability of the circuit.

[0029] Other features and advantages of the present invention will be described in the following description, and part of them will become obvious from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0031] Figure 1 The diagram is a schematic diagram of an auxiliary power supply circuit using a transformer auxiliary winding plus a dv / dt rectifier circuit as a controller.

[0032] Figure 2 is based on Figure 1 The circuit shown is a schematic diagram of a circuit after a linear voltage regulator circuit is set.

[0033] Figure 3 It is a schematic diagram of a constant current auxiliary power supply circuit according to an embodiment of the present invention.

[0034] Figure 4 and Figure 5 1 is a schematic diagram of the output current of the constant current auxiliary power supply circuit when the VCC load of the controller is different in one embodiment of the present invention. DETAILED DESCRIPTION

[0035] It is easy to understand that according to the technical solution of the present invention, without changing the essential spirit of the present invention, a person skilled in the art can imagine various embodiments of the present invention. Therefore, the following specific embodiments and drawings are only exemplary descriptions of the technical solution of the present invention, and should not be regarded as the whole of the present invention or as a limitation or limitation of the technical solution of the present invention. On the contrary, the purpose of providing these embodiments is to enable those skilled in the art to understand the present invention more thoroughly. The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the innovative concept of the present invention.

[0036] like Figure 3 As shown, the constant current auxiliary power supply circuit of this embodiment includes a rectifier circuit and a constant current circuit;

[0037] The rectifier circuit is connected to one end of the auxiliary winding of the transformer, and the constant current circuit is connected to the rectifier circuit;

[0038] The rectifier circuit is used to rectify the voltage of the auxiliary winding of the transformer, and the constant current circuit is used to control the output of the rectifier circuit so that its output current remains constant.

[0039] The constant current circuit utilizes the reverse breakdown voltage drop of the voltage regulator tube, the PN junction voltage drop of the transistor and the fixed resistance value of the resistor in the constant current circuit to make the average charging current in the constant current circuit constant.

[0040] The rectifier circuit includes a first resistor R1, a rectifier capacitor C1, a first diode D1, a second diode D2 and a second capacitor C2;

[0041] One end of the first resistor R1 is connected to the auxiliary winding of the transformer, the other end of the first resistor R1 is connected to one end of the rectifier capacitor C1, the other end of the rectifier capacitor C1 is simultaneously connected to the cathode of the first diode D1 and the anode of the second diode D2, and the cathode of the second diode D2 is connected to the VCC of the controller;

[0042] One end of the second capacitor C2 is connected to the cathode of the second diode D2, and the other end of the second capacitor C2 is grounded;

[0043] The anode of the first diode D1 is connected to the constant current circuit.

[0044] The constant current circuit includes a second resistor R2, a third resistor R3, a voltage regulator D3, a third capacitor C3, and a PNP transistor Q1;

[0045] The collector of the PNP transistor Q1 is connected to the anode of the first diode D1, the emitter of the PNP transistor Q1 is connected to the second resistor R2, the other end of the second resistor R2 is grounded, the base of the collector of the PNP transistor Q1 is connected to the anode of the voltage regulator D3, the cathode of the voltage regulator D3 is grounded, and the third resistor R3 is connected between the base and collector of the PNP transistor Q1;

[0046] The anode of the first diode D1 is also connected to the third capacitor C3, and the other end of the third capacitor C3 is grounded.

[0047] When the power supply is working normally, an alternating voltage will be generated at both ends of the auxiliary winding of the transformer. When the voltage of the auxiliary winding of the transformer is reverse voltage, that is, the voltage at the ground end of the auxiliary winding of the transformer is higher than that at the other end of the winding, the first diode D1 is turned on, and at the same time, the cathode voltage of the voltage regulator D3 is higher than the anode voltage, and the voltage regulator D3 is turned on (due to the clamping function of the controller at this time, when the winding voltage of the third capacitor C3 is reverse voltage, the voltage at both ends of the third capacitor C3 will not be discharged to 0, and the voltage at the ungrounded end of the third capacitor C3 is still negative and lower than the reverse breakdown voltage drop Vz of the voltage regulator D3, and the voltage regulator D3 is turned on), the reverse breakdown voltage drop of the voltage regulator D3 is Vz, then the voltage applied to the second resistor R2 is Vz-Veb, Veb represents the PN junction conduction voltage of the PNP transistor Q1, and the current passing through the second resistor R2 is:

[0048]

[0049] Since the reverse breakdown voltage drop Vz of the voltage regulator tube D3 and the PN junction conduction voltage Veb of the PNP transistor Q1 are both constant values, the current I flowing through the second resistor R2 is also constant. The constant current charges the rectifier capacitor C1 through the PNP transistor Q1 and the first diode D1.

[0050] When the transformer auxiliary winding voltage is positive, the first diode D1 is not conducting, and the cathode voltage of the voltage regulator D3 is higher than the anode voltage, and the voltage regulator D3 is conducting. At this time, the current passing through the second resistor R2 is also:

[0051]

[0052] The fixed current continuously charges the third capacitor C3 through the PNP transistor Q1, and during the period when the transformer auxiliary winding voltage is positive, the electric energy charged by the fixed current for the third capacitor C3 will be charged to the rectifier capacitor C1 through the first diode D1 when the transformer auxiliary winding voltage is reverse voltage;

[0053] In summary, during the period t when the transformer auxiliary winding voltage is positive 1 Inside, the fixed current I charges the third capacitor C3 through the PNP transistor Q1;

[0054] During the period t when the transformer auxiliary winding voltage is negative 2 The constant current I charges the rectifier capacitor C1 through the PNP transistor Q1 and the first diode D1. 1 During the time period, the electric energy charged by the constant current I through the PNP transistor Q1 for the third capacitor C3 is charged by the first diode D1 for the rectifier capacitor C1;

[0055] At the same time, during the period t when the transformer auxiliary winding voltage is positive 1 Since the voltage on the side of the rectifier capacitor C1 connected to the first capacitor R1 is higher than the other side, the rectifier capacitor C1 is turned on, and the current on the rectifier capacitor C1 supplies power to the controller's VCC through the second diode D2. The current of the power supply is approximately equal to the average current charged to the rectifier capacitor C1 during the entire charging cycle, that is:

[0056] T=t 1 +t 2

[0057]

[0058] Combination Figure 4 and Figure 5 It can be seen that when the VCC load of the controller is different, the constant current auxiliary power supply circuit of this embodiment can make the output power supply current constant. It only needs to control it to be equal to or slightly higher than the current required by the controller to avoid additional losses. The constant current auxiliary power supply circuit of the present invention has a simple structure and high reliability and has certain promotion value.

[0059] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

[0060] It should be understood that in order to simplify the present invention and help those skilled in the art understand the various aspects of the present invention, in the above description of the exemplary embodiments of the present invention, the various features of the present invention are sometimes described in a single embodiment or described with reference to a single figure. However, the present invention should not be interpreted as the features included in the exemplary embodiments are all necessary technical features of the patent claims.

[0061] Those skilled in the art will appreciate that all or part of the processes of the above-mentioned embodiments can be implemented by instructing related hardware through a computer program, and the program can be stored in a computer-readable storage medium, wherein the computer-readable storage medium is a disk, an optical disk, a read-only storage memory, or a random access memory, etc.

[0062] It should be understood that the modules, units, components, etc. included in the device of an embodiment of the present invention can be adaptively changed to be set in a device different from the embodiment. The different modules, units, or components included in the device of the embodiment can be combined into one module, unit, or component, or they can be divided into multiple sub-modules, sub-units, or sub-components.

[0063] The modules, units or components in the embodiments of the present invention may be implemented in hardware, or in software running on one or more processors, or in a combination thereof. It should be understood by those skilled in the art that a microprocessor or a digital signal processor (DSP) may be used in practice to implement the embodiments of the present invention. The present invention may also be implemented as a computer program product or computer-readable medium for executing part or all of the methods described herein.

Claims

1. A constant current auxiliary power supply circuit, It is characterized in that Including a rectifier circuit and a constant current circuit; The rectifier circuit is connected to one end of the auxiliary winding of the transformer, and the constant current circuit is connected to the rectifier circuit; The rectifier circuit is used to rectify the voltage of the auxiliary winding of the transformer, and the constant current circuit is used to control the output of the rectifier circuit so that its output current remains constant; The rectifier circuit comprises a first resistor (R1), a rectifier capacitor (C1), a first diode (D1), a second diode (D2) and a second capacitor (C2); One end of the first resistor (R1) is connected to the auxiliary winding of the transformer, the other end of the first resistor (R1) is connected to one end of the rectifier capacitor (C1), the other end of the rectifier capacitor (C1) is simultaneously connected to the cathode of the first diode (D1) and the anode of the second diode (D2), and the cathode of the second diode (D2) is connected to the VCC of the controller; One end of the second capacitor (C2) is connected to the cathode of the second diode (D2), and the other end of the second capacitor (C2) is grounded; The anode of the first diode (D1) is connected to the constant current circuit; The constant current circuit comprises a second resistor (R2), a third resistor (R3), a voltage regulator tube (D3), a third capacitor (C3), and a PNP transistor (Q1); The collector of the PNP triode (Q1) is connected to the anode of the first diode (D1), the emitter of the PNP triode (Q1) is connected to the second resistor (R2), the other end of the second resistor (R2) is grounded, the base of the collector of the PNP triode (Q1) is connected to the anode of the voltage regulator tube (D3), the cathode of the voltage regulator tube (D3) is grounded, and the third resistor (R3) is connected between the base and the collector of the PNP triode (Q1); The anode of the first diode (D1) is also connected to the third capacitor (C3), and the other end of the third capacitor (C3) is grounded.

2. The constant current auxiliary power supply circuit as claimed in claim 1, It is characterized in that The constant current circuit utilizes the reverse breakdown voltage drop of the voltage regulator tube, the PN junction voltage drop of the triode and the fixed resistance value of the resistor in the constant current circuit to make the average charging current in the constant current circuit constant.

3. The constant current auxiliary power supply circuit as claimed in claim 1, It is characterized in that When the transformer auxiliary winding voltage is positive, the first diode (D1) is not conducting and the voltage regulator (D3) is conducting. At this time, the base voltage of the PNP transistor (Q1) is the negative value of the reverse breakdown voltage drop of the voltage regulator (D3), and the current on the second resistor (R2) is a constant value. The current charges the third capacitor (C3) through the PNP transistor (Q1).

4. The constant current auxiliary power supply circuit as claimed in claim 3, It is characterized in that When the transformer auxiliary winding voltage is a reverse voltage, the first diode (D1) is turned on, and the voltage regulator (D3) is turned on. At this time, the base voltage of the PNP transistor (Q1) is a negative value of the reverse breakdown voltage drop of the voltage regulator (D3), and the current on the second resistor (R2) is a constant value. The current charges the rectifier capacitor (C1) through the PNP transistor (Q1) and the first diode (D1).

5. The constant current auxiliary power supply circuit as claimed in claim 3, It is characterized in that When the transformer auxiliary winding voltage is a reverse voltage, the first diode (D1) is turned on, and at this time the third capacitor (C3) charges the rectifier capacitor (C1) through the first diode (D1).

6. The constant current auxiliary power supply circuit as claimed in claim 3, It is characterized in that When the transformer auxiliary winding voltage is positive, the rectifier capacitor (C1) is turned on. At this time, the current on the rectifier capacitor (C1) supplies power to the controller's VCC through the second diode (D2); The average current of the rectifier capacitor (C1) supplying power to the controller's VCC is: Wherein, Vz represents the reverse breakdown voltage drop of the voltage regulator (D3), Veb represents the PN junction conduction voltage of the PNP transistor (Q1), and R2 represents the resistance value of the second resistor (R2).

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