Self-locking power supply circuit

Abstract

The invention relates to the technical field of power supply circuits, and discloses a self-locking power supply selection circuit, which comprises a first secondary power supply circuit, a second secondary power supply circuit, a power supply selection circuit and a selection holding circuit, and is characterized in that the input end of the first secondary power supply circuit and the input end of the second secondary power supply circuit are connected to a transformer; the output end of the first secondary power supply circuit is connected to the secondary power supply loop through a one-way conductive device, the output end of the second secondary power supply circuit is directly connected to the secondary power supply loop, and the input end of the primary power supply loop is connected to the transformer; the input end of the power supply selection circuit and the input end of the second secondary power supply circuit are connected to the transformer, the output end of the power supply selection circuit is connected to the input end of the selection holding circuit, and the output end of the selection holding circuit is connected with the input end of the second secondary power supply circuit. According to the invention, secondary power supply voltage selection and holding functions are realized, and the functions that secondary power supply is faster than primary power supply during starting and the voltage is lower than that of the primary power supply after steady-state work are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of power supply circuits, and particularly to a self-locking power supply circuit. Background Art

[0002] A switching power supply is a high-frequency power conversion device, which mainly uses power electronic switching devices (such as transistors, MOS transistors, thyristors, etc.). Through a control circuit, the electronic switching devices are periodically "turned on" and "turned off", so that the power electronic switching devices perform pulse modulation on the input voltage, thereby realizing functions such as voltage conversion, adjustable output voltage, and automatic voltage stabilization. At present, the existing DC / DC switching power supply circuit with synchronous rectification and complex control cannot realize the function of high voltage on the secondary power supply loop when powered on and switching to low voltage when entering the steady state, resulting in high steady-state power consumption and reduced overall circuit efficiency. Summary of the Invention

[0003] Based on the above, the present invention provides a self-locking power supply circuit to realize the selection and maintenance of the secondary power supply voltage in the switching power supply circuit, so that the secondary power supply is faster than the primary during startup, the voltage is lower than the primary after steady state, and at the same time, the voltage difference of the secondary power supply linear voltage regulation is reduced, and the voltage regulation power consumption is reduced.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A self-locking power supply circuit includes a first secondary power supply circuit, a second secondary power supply circuit, a power supply selection circuit, and a selection and maintenance circuit;

[0006] The input end of the first secondary power supply circuit and the input end of the second secondary power supply circuit are connected to a transformer. The output end of the first secondary power supply circuit is connected to the secondary power supply loop through a unidirectional conductive device. The output end of the second secondary power supply circuit is directly connected to the secondary power supply loop. The input end of the primary power supply loop is connected to the transformer;

[0007] The input end of the power supply selection circuit and the input end of the second secondary power supply circuit are connected to a transformer. The output end of the power supply selection circuit is connected to the input end of the selection and maintenance circuit;

[0008] The output end of the selection and maintenance circuit is connected to the input end of the second secondary power supply circuit.

[0009] As a preferred scheme of a self-locking power supply circuit, the first secondary power supply circuit includes a first unidirectional conductive device, a second unidirectional conductive device, a first capacitor, a second capacitor, a third capacitor, a second resistor, a first resistor, and a first triode;

[0010] The positive electrode of the first one-way electrical conductor and the positive electrode of the first capacitor are connected to the input terminal of the first secondary power supply circuit. The positive electrode of the second capacitor, the positive electrode of the second resistor, and the positive electrode of the first resistor are connected to the negative electrode of the first one-way electrical conductor device. The negative electrode of the second capacitor, the positive electrode of the second resistor, the positive electrode of the second one-way electrical conductor device, and the negative electrode of the third capacitor are grounded. The negative electrode of the second one-way electrical conductor device and the positive electrode of the third capacitor are connected to the base of the first triode, and the collector of the first triode is connected to the negative electrode of the first one-way electrical conductor device.

[0011] As a preferred solution of a self-locking power supply circuit, the structure of the second secondary power supply circuit is the same as that of the first secondary power supply circuit;

[0012] The second secondary power supply circuit includes a fourth one-way electrical conductor device, a sixth one-way electrical conductor device, a fourth capacitor, a fifth capacitor, a sixth capacitor, a fifth resistor, a seventh resistor, and a second triode;

[0013] The positive electrode of the fourth one-way electrical conductor and the positive electrode of the fourth capacitor are connected to the input terminal of the second secondary power supply circuit. The positive electrode of the fifth capacitor, the positive electrode of the seventh resistor, and the positive electrode of the fifth resistor are connected to the negative electrode of the fourth one-way electrical conductor device. The negative electrode of the fifth capacitor, the negative electrode of the seventh resistor, the positive electrode of the sixth one-way electrical conductor device, and the negative electrode of the sixth capacitor are grounded. The negative electrode of the sixth one-way electrical conductor device and the positive electrode of the sixth capacitor are connected to the base of the second triode, and the collector of the second triode is connected to the negative electrode of the fourth one-way electrical conductor device.

[0014] As a preferred solution of a self-locking power supply circuit, the power supply selection circuit includes a sixth resistor, a ninth resistor, a fifth one-way electrical conductor device, and a first voltage reference device;

[0015] The positive electrode of the sixth resistor is connected to the input terminal of the second secondary power supply circuit. The negative electrode of the sixth resistor is connected to the reference terminal of the first voltage reference device and the positive electrode of the ninth resistor. The anode of the first voltage reference device and the negative electrode of the ninth resistor are grounded. The cathode of the first voltage reference device is connected to the negative electrode of the fifth one-way electrical conductor device.

[0016] As a preferred solution of a self-locking power supply circuit, the selection and holding circuit includes a third resistor, a fourth resistor, an eighth resistor, a seventh capacitor, a third triode, and a fourth triode;

[0017] The positive electrode of the third resistor and the positive electrode of the fourth resistor are connected to the input end of the first secondary power supply circuit. The negative electrode of the third resistor and the collector of the fourth triode are connected to the base of the third triode. The negative electrode of the fourth resistor is connected to the emitter of the third triode. The collector of the third triode is connected to the base of the fourth triode. The emitter of the fourth triode, the negative electrode of the seventh capacitor, and the negative electrode of the eighth resistor are grounded.

[0018] As a preferred solution of a self-locking power supply circuit, the transformer generates three self-power supply voltages, which are 15V, 15V, and 6.8V, and supply power to the first secondary power supply circuit, the second secondary power supply circuit, and the primary power supply circuit respectively.

[0019] As a preferred solution of a self-locking power supply circuit, the first secondary power supply circuit, the second secondary power supply circuit, and the secondary power supply circuit are powered by the transformer.

[0020] During the startup process, the secondary power supply circuit is powered by the second secondary power supply circuit. When reaching the steady state, the secondary power supply circuit is powered by the transformer through the first secondary power supply circuit, and the power supply voltage is 6.8V.

[0021] During the startup process, the primary power supply circuit is powered by the transformer. When reaching the steady state, the primary power supply circuit is powered by the transformer, and the power supply voltage is 15V.

[0022] As a preferred solution of a self-locking power supply circuit, the first unidirectional conductive device, the second unidirectional conductive device, the third unidirectional conductive device, the fourth unidirectional conductive device, the fifth unidirectional conductive device, and the sixth unidirectional conductive device are diodes.

[0023] The beneficial effects of the present invention are:

[0024] In the self-locking power supply circuit provided by the present invention, it includes a first secondary power supply circuit, a second secondary power supply circuit, a power supply selection circuit, and a selection and hold circuit. The input ends of the first secondary power supply circuit and the second secondary power supply circuit are both connected to a transformer. The output end of the first secondary power supply circuit is connected to the secondary power supply loop through a unidirectional conductive device. The output end of the second secondary power supply circuit is directly connected to the secondary power supply loop. The input end of the power supply selection circuit is connected to the input end of the first secondary power supply circuit. The input end of the selection and hold circuit is connected to the output end of the power supply selection circuit. In the present invention, at startup, the secondary power supply and the primary power supply can be started simultaneously, and during the startup process, the secondary voltage is higher than or equal to the primary voltage. After startup is completed, the second secondary power supply circuit with greater turn-off power consumption is turned off, and the first secondary power supply circuit with smaller power consumption is selected to maintain the operation of each secondary circuit and enter the self-locking state. Additionally, during the circuit startup process and when the second secondary power supply circuit is in any overvoltage, undervoltage, or other states, the first secondary power supply circuit stops supplying power, and the second secondary power supply circuit supplies power throughout the steady-state operation process, achieving synchronous power supply for primary and secondary startup, steady-state power supply selection, and self-locking functions. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for describing the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the content of the embodiments of the present invention and these drawings.

[0026] Figure 1 is the circuit block diagram provided by the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the following will further describe the present invention in detail with reference to the drawings. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0028] As Figure 1 shown, the self-locking power supply selection circuit provided by the embodiment of the present invention includes a first secondary power supply circuit N101, a second secondary power supply circuit N201, a power supply selection circuit N301, a selection and hold circuit N401, and a power transformer T1.

[0029] Among them, the input ends of the first secondary power supply circuit N101, the second secondary power supply circuit N201, and the primary power supply loop are connected to the power transformer T1 to obtain the energy transferred by the power transformer T1. The output end of the first secondary power supply circuit N101 is connected to the secondary power supply loop through a unidirectional conduction device, and the output end of the second secondary power supply circuit N201 is directly connected to the secondary power supply loop. Further, the input end of the power supply selection circuit N301 and the input end of the second secondary power supply circuit N201 are connected to the power transformer T1, and the input end of the selection holding circuit N401 is connected to the output end of the power supply selection circuit N301.

[0030] Specifically, the power transformer T1 generates three self-power supply voltages, VccP, VccS1, and VccS2, which are 15V, 15V, and 6.8V respectively. Among them, VccP is used for power supply to the primary power supply loop, VccS1 and VccS2 are used for secondary power supply, VccS2 is the power supply for the second secondary power supply circuit N201, and VccS1 is the power supply for the second secondary power supply circuit N201.

[0031] The structure and connection of the first secondary power supply circuit N101 in the self-locking power supply selection circuit provided by the embodiment of the present invention can be described as follows: including a first unidirectional conduction device D1, a second unidirectional conduction device D2, a first capacitor C1, a second capacitor C2, a third capacitor C3, a second resistor R2, a first resistor R1, and a first triode Q1. In the embodiment of the present invention, the first unidirectional conduction device D1, the second unidirectional conduction device D2, and other unidirectional conduction devices are preferably diodes.

[0032] The positive electrode of the first unidirectional conduction device D1 and the positive electrode of the first capacitor C1 are connected to the input end of the first secondary power supply circuit N101. The positive electrode of the second capacitor C2, the positive electrode of the second resistor R2, and the positive electrode of the first resistor R1 are connected to the negative electrode of the first unidirectional conduction device D1. The negative electrode of the second capacitor C2, the positive electrode of the second resistor R2, the positive electrode of the second unidirectional conduction device D2, and the negative electrode of the third capacitor C3 are grounded. The negative electrode of the second unidirectional conduction device D2 and the positive electrode of the third capacitor C3 are connected to the base of the first triode Q1, and the collector of the first triode Q1 is connected to the negative electrode of the first unidirectional conduction device D1.

[0033] Among them, in the first secondary power supply circuit N101, the first capacitor C1, the first unidirectional conductive device D1, and the second capacitor C2 rectify to generate a 7.5V DC voltage. The first resistor R1, the second unidirectional conductive device D2, and the first triode Q1 form a linear voltage regulator to stabilize the voltage at 6.8V. The second resistor R2 in the circuit is used to discharge the second capacitor C2, and the third capacitor C3 is used to filter the base of the first triode Q1. The second secondary power supply circuit N201 has the same structure and connection as the first secondary power supply circuit N101. In the second secondary power supply circuit N201, the fourth capacitor C4, the fourth unidirectional conductive device D4, and the fifth capacitor C5 rectify to generate an 18V DC voltage. The fifth resistor R5, the sixth unidirectional conductive device D6, and the second triode Q2 form a linear voltage regulator to stabilize the voltage at 6.8V. The seventh resistor R7 in the circuit is used to discharge the fifth capacitor C5, and the sixth capacitor C6 is used to filter the base of Q2.

[0034] During the startup process, both the first secondary power supply circuit N101 and the second secondary power supply circuit N201 generate a voltage of 6.8V. Due to the existence of the third unidirectional conductive device D3, the third unidirectional conductive device D3 bears a 0.5V voltage drop, making the voltage of the second secondary power supply circuit N201 higher than that of the first secondary power supply circuit N101. When the two paths are connected in parallel to supply power to the secondary power supply loop, the path with the higher voltage supplies power, and the path with the lower voltage N101 is reverse-biased and cut off. The second triode Q2 bears an 11.2V voltage drop.

[0035] The secondary power supply loop is powered by the second secondary power supply circuit N201. The primary voltage VccP and the secondary voltage VccS1 supplied by the T1 power transformer are both 15V. During the startup process, the secondary power supply VccS and the primary power supply VccP start simultaneously. The secondary voltage is equal to or higher than the primary voltage. The greater the voltage, the faster the startup. In a DC / DC switching power supply circuit with synchronous rectification and complex control, if the secondary voltage is higher than the primary voltage, the secondary chip starts first, and it can wait for the primary control quality to prevent the situation where when the primary chip starts and gives a signal to the secondary chip, the secondary chip has not started, resulting in a non-monotonic startup process.

[0036] The power supply selection circuit N301 includes the sixth resistor R6, the ninth resistor R9, the fifth unidirectional conductive device D5, and the first voltage reference device N1. Among them, the positive pole of the sixth resistor R6 is connected to the input end of the second secondary power supply circuit N201. The negative pole of the sixth resistor R6 is connected to the reference end of the first voltage reference device N1 and the positive pole of the ninth resistor R9. The anode of the first voltage reference device N1 and the negative pole of the ninth resistor R9 are grounded. The cathode of the first voltage reference device N1 is connected to the negative pole of the fifth unidirectional conductive device D5.

[0037] The first voltage reference device N1 is preferably TL431 with a reference value of 2.495V. By setting reasonable resistances for the sixth resistor R6 and the ninth resistor R9, when the voltage division across the ninth resistor R9 exceeds 2.495V, it proves that the output startup process is completed, and the first voltage reference device N1 conducts. Approximately, the base of the second triode Q2 is approximately grounded through the fifth unidirectional conductive device D5 and the first voltage reference device N1, and the second triode Q2 turns off, that is, the VccS1 voltage with greater power consumption is turned off, and it is selected to be powered by the VccS2 with smaller power consumption. That is, VccS is powered by the first secondary power supply circuit N101 to maintain the operation of each secondary circuit. And the first triode Q1 only bears a voltage drop of 0.7V, which can be almost ignored, thereby reducing the loss of the secondary chip and improving the overall efficiency of the circuit.

[0038] The selection and hold circuit N401 includes: the third resistor R3, the fourth resistor R4, the third triode Q3, the fourth triode Q4, the eighth resistor R8, and the seventh capacitor C7. Among them, the selection and hold circuit N401 is a self-locking circuit. When the first voltage reference device N1 is grounded, the base of the third triode Q3 is pulled low, and the third triode Q3 conducts. The base of the fourth triode Q4 is pulled high through voltage division by the fourth resistor R4 and the eighth resistor R8, and the fourth triode Q4 conducts. At this time, the base of the third triode Q3 is connected to the collector of the fourth triode Q4. Due to the characteristics of the NPN-type triode and the PNP-type triode: the NPN-type triode conducts at high level, and the PNP-type triode conducts at low level, the circuit enters the self-locking state. Without powering off the power supply, Vccsctrl is always at low level, and the base of the triode Q2 is connected to Vccsctrl, so that the second triode Q2 is turned off throughout the process after the circuit starts.

[0039] During the startup process, the waveform diagram of the voltage of the primary power supply circuit and the secondary power supply circuit changing with the startup time. The abscissa is time, and the ordinate is voltage. In the picture, VccS is the secondary voltage waveform, and VccP is the primary voltage waveform. VccS represents one of VccS2 and VccS1, which is the result of the power supply selection circuit. It is VccS1 when power is applied. After the power-on process ends, the second secondary power supply circuit N201 is cut off through the power supply selection circuit. At this time, the power supply is the first secondary power supply circuit N101, that is, VccS2. The circuit realizes that VccS is a higher voltage during the startup process, and the startup is faster. After the startup is completed, VccS drops to a lower voltage, making the loss of the secondary chip lower, realizing a high voltage and a fast rise during the startup process of secondary VccS, and then becoming a low voltage after entering the steady-state working process to reduce the loss.

[0040] When the power is turned on, if VccS1 is in any overvoltage, undervoltage or other states, VccS2 will no longer supply power. The steady-state working process is powered by VccS1 throughout. VccS2 is higher than VccS1, and the higher power supply will cause higher losses in the secondary chip, resulting in a decrease in the overall efficiency of the circuit. At the same time, it will also cause insufficient derating of the power supply for the secondary chip.

[0041] Note that the above is only the preferred embodiment of the present invention and the technical principles applied. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described here. Various obvious changes, re-adjustments and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments. Without departing from the concept of the present invention, more other equivalent embodiments can be included, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A self-locking power supply selection circuit, characterized in that It includes a first secondary power supply circuit, a second secondary power supply circuit, a power supply selection circuit, and a selection and holding circuit; The input end of the first secondary power supply circuit and the input end of the second secondary power supply circuit are connected to a transformer. The output end of the first secondary power supply circuit is connected to the secondary power supply loop through a unidirectional conductive device. The output end of the second secondary power supply circuit is directly connected to the secondary power supply loop. The input end of the primary power supply loop is connected to the transformer; The input end of the power supply selection circuit and the input end of the second secondary power supply circuit are connected to the transformer. The output end of the power supply selection circuit is connected to the input end of the selection and holding circuit; The output end of the selection and holding circuit is connected to the input end of the second secondary power supply circuit.

2. The self-locking power supply selection circuit according to claim 1, characterized in that The first secondary power supply circuit includes a first unidirectional conductive device, a second unidirectional conductive device, a first capacitor, a second capacitor, a third capacitor, a second resistor, a first resistor, and a first triode; The positive electrode of the first unidirectional conductive device and the positive electrode of the first capacitor are connected to the input end of the first secondary power supply circuit. The positive electrode of the second capacitor, the positive electrode of the second resistor, and the positive electrode of the first resistor are connected to the negative electrode of the first unidirectional conductive device. The negative electrode of the second capacitor, the positive electrode of the second resistor, the positive electrode of the second unidirectional conductive device, and the negative electrode of the third capacitor are grounded. The negative electrode of the second unidirectional conductive device and the positive electrode of the third capacitor are connected to the base of the first triode. The collector of the first triode is connected to the negative electrode of the first unidirectional conductive device.

3. The self-locking power supply selection circuit according to claim 1, wherein The structure of the second secondary power supply circuit is the same as that of the first secondary power supply circuit; The second secondary power supply circuit includes a fourth unidirectional conductive device, a sixth unidirectional conductive device, a fourth capacitor, a fifth capacitor, a sixth capacitor, a fifth resistor, a seventh resistor, and a second triode; The positive electrode of the fourth unidirectional conductive device and the positive electrode of the fourth capacitor are connected to the input end of the second secondary power supply circuit. The positive electrode of the fifth capacitor, the positive electrode of the seventh resistor, and the positive electrode of the fifth resistor are connected to the negative electrode of the fourth unidirectional conductive device. The negative electrode of the fifth capacitor, the negative electrode of the seventh resistor, the positive electrode of the sixth unidirectional conductive device, and the negative electrode of the sixth capacitor are grounded. The negative electrode of the sixth unidirectional conductive device and the positive electrode of the sixth capacitor are connected to the base of the second triode. The collector of the second triode is connected to the negative electrode of the fourth unidirectional conductive device.

4. The self-locking power supply selection circuit according to claim 1, characterized in that, The power supply selection circuit includes a sixth resistor, a ninth resistor, a fifth unidirectional conductive device, and a first voltage reference device; The positive electrode of the sixth resistor is connected to the input end of the second secondary power supply circuit. The negative electrode of the sixth resistor is connected to the reference end of the first voltage reference device and the positive electrode of the ninth resistor. The anode of the first voltage reference device and the negative electrode of the ninth resistor are grounded. The cathode of the first voltage reference device is connected to the negative electrode of the fifth unidirectional conductive device.

5. The self-locking power supply selection circuit according to claim 1, wherein The selection and holding circuit includes a third resistor, a fourth resistor, an eighth resistor, a seventh capacitor, a third triode, and a fourth triode; The positive electrode of the third resistor and the positive electrode of the fourth resistor are connected to the input end of the first secondary power supply circuit. The negative electrode of the third resistor and the collector of the fourth triode are connected to the base of the third triode. The negative electrode of the fourth resistor is connected to the emitter of the third triode. The collector of the third triode is connected to the base of the fourth triode. The emitter of the fourth triode, the negative electrode of the seventh capacitor, and the negative electrode of the eighth resistor are grounded.

6. The self-locking power supply selection circuit according to claim 1, wherein The transformer generates three self-powered voltages, which are 15V, 15V, and 6.8V, and supply power to the first secondary power supply circuit, the second secondary power supply circuit, and the primary power supply loop respectively.

7. The self-locking power supply selection circuit according to claim 1, wherein The first secondary power supply circuit, the second secondary power supply circuit, and the secondary power supply loop are powered by the transformer; During the startup process, the secondary power supply loop is powered by the second secondary power supply circuit. When reaching the steady state, the secondary power supply loop is powered by the transformer through the first secondary power supply circuit, and the supply voltage is 6.8V; During the startup process, the primary power supply loop is powered by the transformer. When reaching the steady state, the primary power supply loop is powered by the transformer, and the supply voltage is 15V.

8. The self-locking power supply selection circuit according to claim 1, wherein The first unidirectional conductive device, the second unidirectional conductive device, the third unidirectional conductor, the fourth unidirectional conductive device, the fifth unidirectional conductive device, and the sixth unidirectional conductive device are diodes.

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