Power supply circuit and switch power supply using same

Abstract

The present application discloses a power supply circuit, used for supplying power to a low-voltage circuit at the back end. The power supply circuit comprises a voltage sampling circuit, a current limiting circuit, a control circuit, an energy storage capacitor, and a voltage regulator, wherein the voltage sampling circuit samples a rectified input voltage; the current limiting circuit adjusts, on the basis of the change of the input voltage, a current flowing to the energy storage capacitor; the control circuit enables or disables the current limiting circuit on the basis of the magnitude of the input voltage. By means of the voltage regulator, the power supply circuit is connected to the low-voltage circuit at the back end, so as to reduce the voltage input to the low-voltage circuit at the back end. When the input voltage is smaller than or equal to a set threshold, the control circuit enables the current limiting circuit, and then the input voltage is used to supply power to the low-voltage circuit at the back end and simultaneously charge the energy storage capacitor; and when the input voltage is greater than the set threshold, the control circuit disables the current limiting circuit, and then the energy storage capacitor supplies power to the low-voltage circuit at the back end. By means of the arrangement above, the circuit structure of the power supply circuit is simplified, thereby reducing the size of a switch power supply and improving the power supply efficiency of the circuit.

Description

Power supply circuit and switching power supply using the same Technical Field

[0001] The present application relates to the field of power management technology, and in particular to a power supply circuit and a switching power supply using the same. Background Art

[0002] With the increasing popularity of smart homes, high-voltage electrical devices are placing increasingly stringent requirements on the cost and size of auxiliary power supply circuits. Common power supply methods for the control circuits in existing high-voltage devices include: a front-end switching power supply, followed by an LDO (low-dropout linear regulator) that steps down the voltage to the supply voltage, a switching power supply that steps down the voltage directly to the supply voltage, a resistor-limited current diode that stabilizes the supply voltage, and a valley-powered chip that provides power. These power supply methods fail to achieve high power efficiency while miniaturizing and reducing the cost of the control circuit. Summary of the Invention

[0003] In order to address the deficiencies of the prior art, the present application aims to provide a power supply circuit with a simple structure and high power efficiency, and a switching power supply using the same.

[0004] To achieve the above objectives, this application adopts the following technical solutions:

[0005] On the one hand, the present application provides a power supply circuit for supplying power to a low-voltage circuit at the rear end. The power supply circuit includes a voltage sampling circuit, a current limiting circuit, a control circuit, an energy storage capacitor and a voltage regulator. The voltage sampling circuit samples the rectified input voltage. The current limiting circuit is connected in series between the voltage sampling circuit and the energy storage capacitor, and adjusts the current flowing to the energy storage capacitor according to the change of the input voltage. The input end of the control circuit is connected to the voltage sampling circuit, the output end of the control circuit is connected to the current limiting circuit, and the current limiting circuit is turned on or off according to the size of the input voltage. The voltage regulator is connected to the energy storage capacitor, and the power supply circuit is connected to the low-voltage circuit at the rear end through the voltage regulator to reduce the voltage input to the low-voltage circuit at the rear end; the control circuit turns on the current limiting circuit when the input voltage is less than or equal to the set threshold, and the input voltage supplies power to the low-voltage circuit at the rear end and charges the energy storage capacitor at the same time. The control circuit turns off the current limiting circuit when the input voltage is greater than the set threshold, and the energy storage capacitor supplies power to the low-voltage circuit at the rear end.

[0006] Furthermore, the current limiting circuit includes at least a switching element and an operational amplifier, the switching element is connected in series between the input voltage and the energy storage capacitor, the first input terminal of the operational amplifier receives a current representing the current flowing through the switching element, the second input terminal of the operational amplifier is connected to the voltage sampling circuit, and the output terminal of the operational amplifier is connected to the control terminal of the switching element; the operational amplifier adjusts the current flowing through the switching element according to the input voltage so that the phase of the input voltage and the phase of the current flowing through the switching element remain consistent.

[0007] Furthermore, the switch element is a PMOS tube.

[0008] Furthermore, the control circuit includes a comparator and a reference voltage source, the first input end of the comparator is connected to the voltage sampling circuit, the second input end of the comparator is connected to the reference voltage source, and the output end of the comparator is connected to the control end of the switching element; the comparator controls the switching element to disconnect when the input voltage is greater than the voltage of the reference voltage source.

[0009] Furthermore, the voltage sampling circuit includes at least one regulating resistor, and the second input terminal of the operational amplifier and the first input terminal of the comparator are respectively connected to the common node of two adjacent regulating circuits.

[0010] Furthermore, the adjustment resistor includes a first resistor, a second resistor and a third resistor connected in series, the second input terminal of the operational amplifier is connected to the common node of the first resistor and the second resistor, and the first input terminal of the comparator is connected to the common node of the second resistor and the third resistor; by adjusting the resistance value of the first resistor, the second resistor and / or the third resistor, or adjusting the voltage of the reference voltage source, the conduction interval of the switching element is adjusted.

[0011] Furthermore, the current limiting circuit also includes a voltage divider resistor, which is connected in series between the input voltage and the first input terminal of the operational amplifier; by adjusting the resistance values ​​of the first resistor, the second resistor, the third resistor and / or the voltage divider resistor, the ratio of the input voltage to the current flowing through the switching element is adjusted.

[0012] Furthermore, the power supply circuit is connected to the high-voltage power supply module, and the load is powered by the high-voltage power supply module. The power supply circuit and the high-voltage power supply module are integrated in the same package, and the power supply circuit and the high-voltage power supply module share the input node of the package to obtain the input voltage.

[0013] Furthermore, the package is connected to an external energy storage capacitor through its power supply node, so that the energy storage capacitor is charged when the input voltage is less than or equal to a set threshold.

[0014] On the other hand, the present application also provides a switching power supply, which includes the power supply circuit in the first aspect above.

[0015] Compared with the prior art, the present invention uses a power supply circuit composed of a voltage stabilizer, an energy storage capacitor, a voltage sampling circuit, a current limiting circuit and a control circuit. When the input voltage is lower than a set threshold, the current limiting circuit is controlled to be turned on. The input voltage supplies power to the back-end circuit through the voltage stabilizer, and at the same time the energy storage capacitor starts to charge to achieve valley power extraction, which simplifies the circuit structure of the power supply circuit, thereby reducing the design cost of the circuit. In addition, the circuit has a smaller layout area and has higher power efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG1 is a schematic diagram of a power supply circuit in an embodiment of the present application.

[0017] FIG2 is a circuit topology diagram of a power supply circuit in an embodiment of the present application.

[0018] FIG3 is a timing diagram of input voltage in an embodiment of the present application.

[0019] FIG4 is a schematic diagram of a switching power supply in an embodiment of the present application. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the specific implementation of the present application will be clearly and completely described below in conjunction with the drawings in the implementation of the present application.

[0021] The terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit this application. "First", "second", "third", and "fourth" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first", "second", "third", and "fourth" may explicitly or implicitly include at least one of such features. The singular forms "a", "an", and "the" used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0022] As shown in Figure 1, the present application provides a power supply circuit 100 for supplying power to a low-voltage circuit 200 at the back end. The power supply circuit 100 is generally used in power supply devices in smart homes as an auxiliary power supply circuit for the power supply devices. Since the power supply devices are powered by the mains, the mains is rectified by the AC-DC rectifier circuit to form a pulsating direct current (i.e., the input voltage Vin described later), and the input voltage Vin varies periodically.

[0023] The power supply circuit 100 includes at least a voltage sampling circuit 11, a current limiting circuit 12, a control circuit 13, an energy storage capacitor 14, and a voltage regulator 15. The voltage sampling circuit 11 samples the rectified input voltage Vin. The current limiting circuit 12 is connected in series between the voltage sampling circuit 11 and the energy storage capacitor 14, and adjusts the current flowing to the energy storage capacitor 14 according to the change of the input voltage Vin. The input end of the control circuit 13 is connected to the voltage sampling circuit 11, and the output end of the control circuit 13 is connected to the current limiting circuit 12. The control circuit 13 turns on or off the current limiting circuit 12 according to the magnitude of the input voltage Vin. The voltage regulator 15 is connected to the energy storage capacitor 14. The power supply circuit 100 is connected to the low-voltage circuit 200 at the back end through the voltage regulator 15 to reduce the voltage input to the low-voltage circuit at the back end, and the voltage ripple of the low-voltage voltage input to the back end is reduced through the voltage regulator 15.

[0024] It should be noted that the voltage regulator 15 is a common low dropout linear regulator 15 (LDO), which achieves stable voltage output by controlling the power consumption in the tube, and will not be explained in detail in this application.

[0025] As an implementation method, the control circuit 13 turns on the current limiting circuit 12 when the input voltage Vin is less than or equal to a set threshold. At this time, the input voltage Vin supplies power to the rear low-voltage circuit 200 and the energy storage capacitor 14 is charged.

[0026] Furthermore, the control circuit 13 turns off the current limiting circuit 12 when the input voltage Vin is greater than the set threshold. At this time, the current path between the voltage input node receiving the input voltage Vin and the low-voltage circuit 200 at the rear end is cut off, and the low-voltage circuit 200 at the rear end is powered through the energy storage capacitor 14.

[0027] In an embodiment of the present application, the current limiting circuit 12 can adjust the current flowing to the energy storage capacitor 14 according to the change of the input voltage Vin, so that the phase of the input voltage Vin and the phase of the current flowing to the energy storage capacitor 14 remain basically consistent, thereby improving the power supply circuit 100 and the PF value of the circuit system using the power supply circuit 100.

[0028] Through the above arrangement, the circuit structure formed by the voltage sampling circuit 11, current limiting circuit 12, control circuit 13, energy storage capacitor 14, and voltage regulator 15 is relatively simple, which facilitates circuit integration, reduces circuit layout area, and thus reduces the production cost of the power supply circuit 100 and the circuit system using the power supply circuit 100. In addition, the above solution also has high power efficiency.

[0029] Exemplarily, the input voltage Vin varies periodically. Therefore, within a first period, the input voltage Vin is less than or equal to a set voltage, allowing the input voltage Vin to power the low-voltage circuit 200 at the rear end while simultaneously charging the energy storage capacitor 14. Within a second period, when the input voltage Vin is greater than the set voltage, the control circuit 13 controls the current limiting circuit 12 to disconnect, allowing the low-voltage circuit 200 at the rear end to be powered via the energy storage capacitor 14. The sum of the first and second periods is the variation period of the input voltage Vin. Therefore, through the above configuration, the energy storage capacitor 14 is charged and discharged at equal intervals, preventing damage to the low-voltage circuit 200 at the rear end when the input voltage Vin rises to its peak value.

[0030] As shown in FIG2 , as an implementation, the current limiting circuit 12 includes at least a switching element Q1 and an operational amplifier U1. The switching element Q1 is connected in series between the voltage input node and the energy storage capacitor 14. The first input terminal of the operational amplifier U1 is connected to the first terminal of the switching element Q1 and receives a current representing the current flowing through the switching element Q1. The second input terminal of the operational amplifier U1 is connected to the voltage sampling circuit 11, and the output terminal of the operational amplifier U1 is connected to the control terminal of the switching element Q1.

[0031] Specifically, the operational amplifier U1 adjusts the current flowing through the switching element Q1 according to the input voltage Vin so that the phase of the input voltage Vin and the phase of the current flowing through the switching element Q1 remain consistent, thereby improving the PF value of the power supply circuit 100 and the circuit system using the power supply circuit 100, thereby improving the power supply efficiency.

[0032] Exemplarily, the switching element Q1 is a PMOS transistor, the gate of which is connected to the output terminal of the operational amplifier U1, the source of which receives the input voltage Vin, and the drain of which is connected to the energy storage capacitor 14. The first input terminal of the operational amplifier U1 receives a current representing the current flowing through the PMOS transistor, so that the PMOS transistor operates in the amplification region, thereby adjusting the phase of the current flowing through the PMOS transistor and improving the PF value of the power supply circuit 100.

[0033] In some examples, the current limiting circuit 12 further includes a voltage-dividing resistor R0 connected in series between the voltage input node and the first input terminal of the operational amplifier U1. By adjusting the resistance of the voltage-dividing resistor R0, the ratio of the input voltage Vin to the current flowing through the switching element Q1 is adjusted, thereby adjusting the PF value of the power supply circuit 100 and the circuit system using the power supply circuit 100, thereby improving power supply efficiency.

[0034] As shown in Figure 2, as an implementation method, the control circuit 13 includes a comparator U2 and a reference voltage source U3, the first input end of the comparator U2 is connected to the voltage sampling circuit 11, the second input end of the comparator U2 is connected to the reference voltage source U3, and the output end of the comparator U2 is connected to the control end of the switching element Q1.

[0035] Specifically, the reference voltage source U3 is used to provide a constant voltage. The comparator U2 outputs a control signal when the input voltage Vin is greater than the voltage of the reference voltage source U3. The control terminal of the switch element Q1 receives the control signal and is disconnected in response to the control signal. This prevents damage to the downstream low-voltage circuit 200 when the input voltage Vin reaches a peak.

[0036] In the above scheme, the comparator U2, the reference voltage source U3, and the switch element Q1 form a basic functional unit. This disconnects the power supply circuit 100 from the downstream low-voltage circuit 200 when the input voltage Vin reaches its peak value, and supplies power to the downstream low-voltage circuit 200 through the power supply circuit 100 when the input voltage Vin is at its valley value. This valley power supply method ensures the service life of the downstream low-voltage circuit 200, and the circuit system using this power supply circuit 100 has low voltage ripple and a high power factor.

[0037] As an implementation, the voltage sampling circuit 11 includes at least one regulating resistor, and the second input terminal of the operational amplifier U1 and the first input terminal of the comparator U2 are respectively connected to a common node of two adjacent regulating resistors.

[0038] The conduction interval of the switch element Q1 is adjusted by changing the adjustment resistor, or the ratio of the input voltage Vin to the current flowing through the switch element Q1 is adjusted by changing the adjustment resistor.

[0039] As shown in FIG2 , in an embodiment of the present application, the adjustment resistor includes a first resistor R1 , a second resistor R2 and a third resistor R3 , and the first resistor R1 , the second resistor R2 and the third resistor R3 are connected in series between the input voltage Vin and the zero potential reference point GND.

[0040] Specifically, a first input terminal of the operational amplifier U1 is connected to a common node of the voltage divider resistor R0 and the first end of the switch element Q1 , and a second input terminal of the operational amplifier U1 is connected to a common node of the first resistor R1 and the second resistor R2 .

[0041] By adjusting the resistance values ​​of the first resistor R1, the second resistor R2, the third resistor R3, and / or the voltage divider resistor R0, the ratio of the input voltage Vin to the current flowing through the switch element Q1 is adjusted, thereby improving the PF value and power efficiency of the power supply circuit 100 and the circuit system using the power supply circuit 100.

[0042] Furthermore, the first input terminal of the comparator U2 is connected to the common node of the second resistor R2 and the third resistor R3, the second input terminal of the comparator U2 is connected to the reference voltage source U3, and the reference voltage source U3 is connected in series between the second input terminal of the comparator U2 and the zero potential reference point GND.

[0043] The conduction interval of the switch element Q1 is adjusted by adjusting the resistance of the first resistor R1 , the second resistor R2 and / or the third resistor R3 , or adjusting the voltage of the reference voltage source U3 .

[0044] It should be noted that, depending on the size and power parameters of the back-end low-voltage circuit 200 , it has different rated operating thresholds, and the conduction interval of the switch element Q1 is adjusted to adapt to different back-end low-voltage circuits 200 .

[0045] The present application also provides a voltage-current waveform diagram as shown in Figure 3, which shows the rectified input voltage Vin, the main power current, and the valley current. The main power current is the current flowing through the load, where the load 400 can be a camera, a lamp, a central control panel, a display, etc. The valley current is the current flowing through the switching element Q1 when the input voltage Vin is less than the set threshold, or when the input voltage Vin is at the first time.

[0046] As shown in Figure 4, as an implementation method, the power supply circuit 100 is connected to the high-voltage power supply module 300, and the high-voltage power supply module 300 is used to power the load 400. The power supply circuit 100 and the high-voltage power supply module 300 are integrated in the same package, and the power supply circuit 100 and the high-voltage power supply module 300 share the input node of the package to obtain the input voltage Vin.

[0047] It can be understood that since the structure of the power supply circuit 100 provided in this application is relatively simple, it is possible for the power supply circuit 100 and the high-voltage power supply module 300 to share a common package, thereby reducing the power supply circuit 100 and the circuit system using it to occupy a smaller layout area, thereby reducing production costs.

[0048] In the embodiment of the present application, the above-mentioned package is connected to an external energy storage capacitor 14 through its power supply node, and the energy storage capacitor 14 is charged through the power supply node when the input voltage Vin is less than or equal to a set threshold.

[0049] The above arrangement facilitates replacement of the energy storage capacitor 14 , thereby improving the maintainability of the power supply circuit 100 .

[0050] In an embodiment of the present application, the comparator U2 receives a voltage signal representing the input voltage Vin through the common node of the second resistor R2 and the third resistor R3, and controls the switching element Q1 to close when the voltage of the voltage signal is less than or equal to the voltage of the reference voltage source U3, thereby charging the energy storage capacitor 14 through the input voltage Vin, and at the same time, the input voltage Vin provides the voltage to drive the low-voltage circuit 200 at the back end. The operational amplifier U1 receives a current representing the current flowing through the switching element Q1 and adjusts the current so that the phase of the current flowing through the switching power supply remains substantially consistent with the phase of the input voltage Vin. When the voltage of the voltage signal is greater than the voltage of the reference voltage source U3, the comparator U2 controls the switching element Q1 to be disconnected, and at this time, the voltage to drive the low-voltage voltage at the back end is provided through the energy storage capacitor 14.

[0051] The above solution uses valley power extraction to maintain the voltage required for the operation of the back-end low-voltage circuit 200 and ensures that the circuit system using the power supply circuit 100 has a higher PF value and power efficiency.

[0052] It can be understood that the circuit structure in the above solution is relatively simple and can be integrated with other circuits to reduce costs and circuit board area.

[0053] As shown in FIG4 , the present application further provides a switching power supply 10, which includes the aforementioned power supply circuit 100, a rear-end low-voltage circuit 200, and a high-voltage power supply module 300. The switching power supply 10 supplies power to a load 400 via the high-voltage power supply module 300. The power supply circuit 100 is connected to the rear-end low-voltage circuit 200 to provide a voltage to drive the rear-end low-voltage circuit 200. The rear-end low-voltage circuit 200 controls the load 400 via the high-voltage power supply module 300.

[0054] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all such improvements and changes should fall within the scope of protection of the claims appended to this application.

Claims

1. A power supply circuit for supplying power to a low-voltage circuit at the rear end, characterized in that: include: A voltage sampling circuit, a current limiting circuit, a control circuit, an energy storage capacitor, and a voltage regulator. The voltage sampling circuit samples the rectified input voltage. The current limiting circuit is connected in series between the voltage sampling circuit and the energy storage capacitor and adjusts the current flowing to the energy storage capacitor according to changes in the input voltage. The input end of the control circuit is connected to the voltage sampling circuit. The output end of the control circuit is connected to the current limiting circuit. The current limiting circuit is turned on or off according to the magnitude of the input voltage. The voltage regulator is connected to the energy storage capacitor. The power supply circuit is connected to the low-voltage circuit at the back end through the voltage regulator to reduce the voltage input to the low-voltage circuit at the back end. The control circuit turns on the current limiting circuit when the input voltage is less than or equal to the set threshold, and the input voltage supplies power to the low-voltage circuit at the back end and charges the energy storage capacitor at the same time. The control circuit turns off the current limiting circuit when the input voltage is greater than the set threshold, and the energy storage capacitor supplies power to the low-voltage circuit at the back end.

2. The power supply circuit according to claim 1, wherein: The current limiting circuit at least includes a switch element and an operational amplifier, the switch element is connected in series between the input voltage and the energy storage capacitor, a first input terminal of the operational amplifier receives a current representing the current flowing through the switch element, a second input terminal of the operational amplifier is connected to the voltage sampling circuit, and an output terminal of the operational amplifier is connected to a control terminal of the switch element; The operational amplifier adjusts the current flowing through the switching element according to the input voltage, so that the phase of the input voltage and the phase of the current flowing through the switching element remain consistent.

3. The power supply circuit according to claim 2, wherein: The switch element is a PMOS tube.

4. The power supply circuit according to claim 2, characterized in that: The control circuit includes a comparator and a reference voltage source, wherein a first input terminal of the comparator is connected to the voltage sampling circuit, a second input terminal of the comparator is connected to the reference voltage source, and an output terminal of the comparator is connected to the control terminal of the switch element; The comparator controls the switching element to be turned off when the input voltage is greater than the voltage of the reference voltage source.

5. The power supply circuit according to claim 4, characterized in that: The voltage sampling circuit includes at least one regulating resistor, and the second input terminal of the operational amplifier and the first input terminal of the comparator are respectively connected to a common node of two adjacent regulating circuits.

6. The power supply circuit according to claim 5, characterized in that: The regulating resistor includes a first resistor, a second resistor, and a third resistor connected in series, the second input terminal of the operational amplifier is connected to a common node of the first resistor and the second resistor, and the first input terminal of the comparator is connected to the common node of the second resistor and the third resistor; The conduction interval of the switch element is adjusted by adjusting the resistance of the first resistor, the second resistor and / or the third resistor, or adjusting the voltage of the reference voltage source.

7. The power supply circuit according to claim 6, characterized in that: The current limiting circuit further includes a voltage dividing resistor connected in series between the input voltage and the first input terminal of the operational amplifier; The ratio of the input voltage to the current flowing through the switch element is adjusted by adjusting the resistance values of the first resistor, the second resistor, the third resistor and / or the voltage divider resistor.

8. The power supply circuit according to claim 1, wherein: The power supply circuit is connected to a high-voltage power supply module, and the load is powered by the high-voltage power supply module. The power supply circuit and the high-voltage power supply module are integrated in the same package, and the power supply circuit and the high-voltage power supply module share an input node of the package to obtain the input voltage.

9. The power supply circuit according to claim 8, characterized in that: The package is connected to the external energy storage capacitor through its power supply node, so that the energy storage capacitor is charged when the input voltage is less than or equal to the set threshold.

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

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