Control circuit for reducing no-load loss and switching power supply

Abstract

The utility model discloses a control circuit for reducing no-load loss and a switching power supply. The control circuit comprises an AC input loop, a thermosensitive device, a control device and a driving module; the thermosensitive device is connected in series in the AC input loop; the control device is connected in parallel to two ends of the thermosensitive device; the input end of the driving module is connected with a control signal, the output end of the driving module is electrically connected with the control device, the control signal is related to the size of the load, and the driving module is used for controlling the control device to be switched on or switched off according to the control signal. When the load is small, the control signal input into the driving module is small, so that the driving module controls the control device to be disconnected, and the energy loss on the control device is further reduced when the load is no-load. When the load is large, the control signal input into the driving module is large, so that the driving module controls the control device to be conducted to short-circuit the thermosensitive device, and the energy loss of the thermosensitive device is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of switching power supplies, in particular to a control circuit and a switching power supply for reducing no-load loss. Background Art

[0002] In power supply design, a thermistor device is usually connected in series to the AC input circuit to reduce the inrush current during startup. During operation, the thermistor loss is relatively high. Generally, a relay is connected in parallel across the thermistor. After startup, the relay is energized to bypass the thermistor; adding a relay also increases the no-load loss synchronously. The relay line loss is about 450 mW. Therefore, it will be very difficult to reduce the overall no-load power consumption to less than 500 mW. Summary of the Utility Model

[0003] The utility model provides a control circuit and a switching power supply for reducing no-load loss to reduce no-load loss.

[0004] According to one aspect of the utility model, a control circuit for reducing no-load loss is provided, including: an AC input loop, a thermistor device, a control device, and a driving module;

[0005] The thermistor device is connected in series to the AC input loop;

[0006] The control device is connected in parallel across the thermistor device;

[0007] The input end of the driving module receives a control signal, and the output end of the driving module is electrically connected to the control device.

[0008] The control signal is related to the size of the load, and the driving module is used to control the conduction or cut-off of the control device according to the control signal.

[0009] Optionally, the control device includes a first transistor, and the output end of the driving module is electrically connected to the gate of the first transistor.

[0010] Optionally, the driving module includes a first comparator;

[0011] The first input end of the first comparator receives a reference voltage, the second input end of the first comparator receives the control signal, and the output end of the first comparator is electrically connected to the gate of the first transistor.

[0012] Optionally, the control device includes a relay;

[0013] The relay includes a coil and a contact group;

[0014] The contact group is connected in parallel across the thermistor device;

[0015] The first end of the coil is connected to a fixed power supply, and the second end of the coil is electrically connected to the output end of the driving module.

[0016] Optionally, the driving module includes: a second comparator and a second transistor;

[0017] The first input end of the second comparator is connected to a reference voltage, the second input end of the second comparator is connected to the control signal, and the output end of the second comparator is electrically connected to the gate of the second transistor;

[0018] The first pole of the second transistor is electrically connected to the second end of the coil, and the second end of the second transistor is connected to a ground potential signal.

[0019] Optionally, the driving module further includes a first voltage dividing resistor and a second voltage dividing resistor;

[0020] The first end of the first voltage dividing resistor is electrically connected to the fixed power supply, and the second end of the first voltage dividing resistor is electrically connected to the first end of the second voltage dividing resistor;

[0021] The second end of the second voltage dividing resistor is connected to a ground potential signal, and the first end of the second voltage dividing resistor is used to generate the reference voltage.

[0022] Optionally, the driving module further includes a diode and a current limiting resistor;

[0023] The first end of the diode is connected to the control signal, the second end of the diode is electrically connected to the first end of the current limiting resistor, and the second end of the current limiting resistor is electrically connected to the input end of the driving module.

[0024] Optionally, the control signal is a PWM signal, and the duty cycle and / or frequency of the PWM signal are related to the size of the load.

[0025] Optionally, the driving module further includes a filter capacitor, the first end of the filter capacitor is electrically connected to the input end of the driving module, and the second end of the filter capacitor is connected to a ground potential signal.

[0026] According to another aspect of the present invention, a switching power supply is provided, and the switching power supply includes the control circuit for reducing no-load loss described in any one of the above.

[0027] The driving module in the embodiment of the present invention controls the controller device to conduct or turn off according to the control signal. Specifically, when the load is small, the control signal input to the driving module is small, so that the driving module controls the controller device to disconnect, thereby reducing the energy loss on the controller device during no-load. When the load is large, the control signal input to the driving module is large, so that the driving module controls the controller device to conduct and short-circuit the thermosensitive device, reducing the energy loss of the thermosensitive device.

[0028] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present utility model, nor is it used to limit the scope of the present utility model. Other features of the present utility model will become easily understood through the following description. Description of the Drawings

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model, the following will briefly introduce the drawings required for use in the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0030] Figure 1 A control circuit for reducing no-load loss provided for an embodiment of the present utility model;

[0031] Figure 2 A schematic structural diagram of another control circuit for reducing no-load loss provided for an embodiment of the present utility model. Detailed Embodiments

[0032] In order to enable those skilled in the art to better understand the solution of the present utility model, the following will clearly and completely describe the technical solutions in the embodiments of the present utility model in conjunction with the drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present utility model.

[0033] It should be noted that the terms "first", "second", etc. in the description and claims of the present utility model and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present utility model described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0034] Figure 1 A control circuit for reducing no-load loss provided for an embodiment of the present utility model, referring to Figure 1 and this control circuit includes:

[0035] AC input circuit, thermal device 10, control device, and drive module 30;

[0036] The thermal device 10 is connected in series to the AC input circuit;

[0037] The control device is connected in parallel across the two ends of the thermal device 10;

[0038] The input end of the drive module 30 receives the control signal Gate, and the output end of the drive module 30 is electrically connected to the control device;

[0039] The control signal Gate is related to the magnitude of the load, and the drive module 30 is used to control the conduction or cutoff of the control device according to the control signal.

[0040] The AC input circuit includes a first input terminal ACL, a second input terminal CAN, a rectification module 40, and a first capacitor C1. The first input terminal ACL of the AC input circuit is electrically connected to the first input terminal of the rectification module 40, the second input terminal ACN of the AC input circuit is electrically connected to the second input terminal of the rectification module 40, the first output terminal of the rectification module 30 is electrically connected to the first end of the first capacitor C1, and the second end of the first capacitor C1 is connected to the ground potential signal GND, that is, grounded. The first end of the thermal device 10 is electrically connected to the second output terminal of the rectification module 40, and the second end of the thermal device 10 is electrically connected to the second end of the first capacitor C1. Among them, the thermal device 10 can be a thermistor, and the thermistor is connected in series in the AC input circuit to reduce the starting current and avoid damaging other devices in the circuit due to excessive current at the moment of power-on of the device. The rectification module 40 can be a half-wave rectification circuit, a full-wave rectification circuit, or a bridge rectification circuit. In this embodiment, a bridge rectification circuit is taken as an example. Optionally, a fuse FS is connected between the first input terminal ACL of the AC input circuit and the first input terminal of the rectification module 40.

[0041] The control device can be a switch, which conducts or cuts off under the control of the drive module 30. The control signal Gate can be a voltage signal, and the magnitude of the control signal Gate is positively correlated with the magnitude of the load. If the load is large, the control signal Gate is large; if the load is small, the control signal Gate is small. The control device is used to conduct or cut off according to the magnitude of the control signal Gate. Specifically, when the load is small, the control signal Gate is small, and the drive module 30 responds to the control signal Gate to control the control device to cut off. When the load is large, the control signal Gate is large, and the drive module responds to the control signal Gate to control the control device to conduct.

[0042] In the embodiment of the present utility model, the driving module controls the conduction or cutoff of the control device according to the control signal. Specifically, when the load is small, the control signal input to the driving module is small, so that the driving module controls the control device to turn off, thereby reducing the energy loss on the control device during no-load. When the load is large, the control signal input to the driving module is large, so that the driving module controls the control device to conduct to short-circuit the thermosensitive device, reducing the energy loss on the thermosensitive device.

[0043] Continue to refer to Figure 1 , optionally, the control device includes a first transistor Q1, and the output end of the driving module 30 is electrically connected to the gate of the first transistor Q1.

[0044] The transistor Q1 has the characteristics of high frequency, low noise and high input impedance, so the transistor can be used as a switch. In this embodiment, the first transistor Q1 is exemplarily shown as an NMOS transistor. When the load is small, the control signal Gate is also small, and the driving module 30 generates a low level in response to the control signal Gate and transmits it to the gate of the first transistor Q1 to control the first transistor Q1 to turn off. When the load is large, the control signal is also large, and the driving module 30 generates a high level in response to the control signal and transmits it to the gate of the first transistor Q1 to control the first transistor Q1 to conduct.

[0045] Continue to refer to Figure 1 , optionally, the driving module 30 includes a first comparator M1;

[0046] The first input end of the first comparator M1 is connected to the reference voltage Vref, the second input end of the first comparator M1 is used as the input end of the driving module 30 to connect the control signal Gate, and the output end of the first comparator M1 is electrically connected to the gate of the first transistor Q1.

[0047] The first power supply end of the first comparator M1 is electrically connected to the fixed power supply VCC, and the second power supply end of the first comparator M1 is connected to the ground potential signal GND. When the control signal Gate is greater than the reference voltage Vref, the voltage output by the output end of the first comparator M1 is the voltage of the fixed power supply VCC, and the voltage of the fixed power supply VCC is a high voltage, which is greater than the ground potential signal GND, thereby causing the first transistor Q1 to conduct. When the control signal Gate is less than the reference voltage Vref, the voltage output by the output end of the first comparator M1 is the ground potential signal GND, controlling the first transistor Q1 to turn off.

[0048] Continue to refer to Figure 1 , optionally, the driving module 30 further includes a first voltage dividing resistor R1 and a second voltage dividing resistor R2;

[0049] The first end of the first voltage-dividing resistor R1 is electrically connected to the fixed power supply VCC, and the second end of the first voltage-dividing resistor R1 is electrically connected to the first end of the second voltage-dividing resistor R2;

[0050] The second end of the second voltage-dividing resistor R2 is connected to the ground potential signal GND, and the first end of the second voltage-dividing resistor R2 is used to generate the reference voltage Vref.

[0051] The first voltage-dividing resistor R1 and the second voltage-dividing resistor R2 are connected in series between the fixed power supply VCC and the ground potential signal GND in sequence to form a voltage-dividing circuit. The first end of the second voltage-dividing resistor R1 is electrically connected to the first input terminal of the first comparator M1, and the potential at the first end of the second voltage-dividing resistor R1 is the reference voltage Vref.

[0052] Continue to refer to Figure 1 Optionally, the control signal Gate is a PWM signal, and the frequency or duty cycle of the PWM signal is related to the size of the load.

[0053] The control signal Gate is a PWM signal output from the IC. The frequency of the PWM signal is positively correlated with the size of the load, or the duty cycle of the PWM signal is positively correlated with the size of the load (the ratio of the time of the high level within one pulse period to the duration of one pulse period).

[0054] Continue to refer to Figure 1 Optionally, the driving module 30 further includes a filter capacitor C0. The first end of the filter capacitor C0 is electrically connected to the input terminal of the driving module 30, and the second end of the filter capacitor 30 is connected to the ground potential signal GND. Specifically, the first end of the filter capacitor C0 is electrically connected to the second input terminal of the first comparator M1. The filter capacitor CO is used to convert the PWM signal into a fixed voltage value and input it into the first comparator M1.

[0055] Continue to refer to Figure 1 Optionally, the driving module 30 further includes a diode D1 and a current-limiting resistor R3;

[0056] The first end of the diode D1 is connected to the control signal Gate, the second end of the diode D1 is electrically connected to the first end of the current-limiting resistor R3, and the second end of the current-limiting resistor R3 is electrically connected to the input terminal of the driving module 30, that is, to the second input terminal of the first comparator M1. The input terminal of the driving module 30 is connected to the control signal Gate through the diode D1 and the current-limiting resistor R3. Among them, the first end of the diode D1 can be the anode of the diode, and the second end of the diode D1 can be the cathode of the diode D1. The diode D1 conducts unidirectionally to prevent the voltage of the first comparator M1 from affecting the magnitude of the control signal Gate.

[0057] When the load is small and the duty cycle of the PWM signal is small, the voltage input to the second input terminal of the first comparator M1 is less than the reference voltage Vref. The output terminal of the first comparator M1 outputs a low level, controlling the first transistor Q1 to turn off. Thus, when the load is no-load or light-load, the energy loss is reduced. When the load is large and the duty cycle of the PWM signal is large, the voltage input to the second input terminal of the first comparator M1 is greater than the reference voltage Vref. The output terminal of the first comparator M1 outputs a high level, controlling the first transistor Q1 to turn on. Thus, when the load is heavy-load, the thermal component 10 is short-circuited, reducing the energy loss on the thermal component 10.

[0058] Figure 2 FIG. Figure 2 6 shows a schematic structural diagram of another control circuit for reducing no-load loss provided by an embodiment of the present invention. Optionally, the AC input loop includes a first input terminal ACL, a second input terminal CAN, a rectification module 40, a first capacitor C1, and a fuse FS. The fuse FS and the thermal component 10 are connected in series between the first input terminal ACL of the AC input loop and the first input terminal of the rectification module 40. The second input terminal ACN of the AC input loop is electrically connected to the second input terminal of the rectification module 40. The first output terminal of the rectification module 40 is electrically connected to the first end of the first capacitor C1. The second end of the first capacitor C1 is connected to the ground potential signal GND, that is, grounded. The second output terminal of the rectification module 40 is electrically connected to the second end of the first capacitor C1.

[0059] Optionally, the control device includes a relay. The relay includes a coil L1 and a contact group L2;

[0060] The contact group L2 is connected in parallel across the two ends of the thermal component 10;

[0061] The first end of the coil L1 is connected to the fixed power supply VCC, and the second end of the coil L1 is electrically connected to the output terminal of the drive module 30.

[0062] The drive module 30 includes: a second comparator M2 and a second transistor Q2;

[0063] The first input terminal of the second comparator M2 is connected to the reference voltage Vref, the second input terminal of the second comparator M2 is connected to the control signal Gate, and the output terminal of the second comparator M2 is electrically connected to the gate of the second transistor Q2;

[0064] The first pole of the second transistor Q2 is electrically connected to the second end of the coil L2, and the second end of the second transistor Q2 is connected to the ground potential signal GND.

[0065] The first pole of the second transistor Q2 serves as the output terminal of the driving module 30 and is electrically connected to the second end of the coil L1. The first power supply terminal of the second comparator M2 is electrically connected to the fixed power supply VCC, and the second power supply terminal of the second comparator M2 is connected to the ground potential signal GND. When the control signal Gate is greater than the reference voltage Vref, the voltage output at the output terminal of the second comparator M2 is the voltage of the fixed power supply VCC. The voltage of the fixed power supply VCC is a high voltage, which is greater than the ground potential signal GND, thereby enabling the second transistor Q2 to conduct. After the second transistor Q2 conducts, a path is formed between the fixed power supply VCC, the coil L1, and the ground potential signal GND, and a current flows through the coil L1, thereby causing the contact group L2 to be attracted, short-circuiting the thermal device 10, and reducing the loss of the thermal device 10. When the control signal Gate is less than the reference voltage Vref, the voltage output at the output terminal of the second comparator M2 is the ground potential signal GND, controlling the second transistor Q2 to turn off, thereby causing no current to flow through the coil L1, the contact group L2 to disconnect, and reducing the loss on the relay during no-load operation.

[0066] The reference voltage Vref is generated by a first resistor R1 and a second resistor R2 connected in series between the fixed power supply VCC and the ground potential signal GND in sequence. The first end of the first resistor R1 is electrically connected to the fixed power supply VCC, the second end of the first resistor R1 is electrically connected to the first end of the second resistor R2, the second end of the second resistor R2 is connected to the ground potential signal GND, and the first end of the second resistor R2 is also electrically connected to the first input terminal of the second comparator M2.

[0067] Same Figure 1 Similarly, Figure 2 The control circuit for reducing no-load loss shown in [reference] also includes a diode D1, a current-limiting resistor R3, and a filter capacitor C0. The first end of the diode D1 is connected to the control signal Gate, the second end of the diode D1 is electrically connected to the first end of the current-limiting resistor R3, and the second end of the current-limiting resistor R3 is electrically connected to the second input terminal of the second comparator M2. The first end of the filter capacitor C0 is electrically connected to the input terminal of the driving module 30, that is, the second input terminal of the second comparator M2, and the second end of the filter capacitor C0 is connected to the ground potential signal GND.

[0068] The embodiment of the present invention also provides a switching power supply, including the control circuit for reducing no-load loss in any of the above embodiments, and the beneficial effects of the switching power supply are the same as those of the control circuit for reducing no-load loss, which will not be elaborated here.

[0069] The switching power supply further includes a boost circuit and / or a buck circuit. Both the boost circuit and the buck circuit include a voltage regulating transistor. The voltage output by the boost circuit or the buck circuit is adjusted by regulating the duty cycle or frequency of the signal applied to the voltage regulating transistor. The boost circuit and the buck circuit are both circuits in the prior art and will not be described again here. The output pin of the chip is connected to the gate of the voltage regulating transistor in the boost circuit or the buck circuit to control the conduction and cutoff of the voltage regulating transistor. Moreover, the chip is in the Burst mode when it is no-load or light-load. In the Burst mode, the driving is discontinuous, and the duty cycle of the signal input from the output pin of the chip to the voltage regulating transistor will decrease. Therefore, the signal applied to the gate of the voltage regulating transistor in the boost circuit or the buck circuit can be used as the control signal Gate connected to the control circuit for reducing no-load loss, so that when it is no-load, the signal output from the output pin of the chip is discontinuous and the duty cycle decreases, making the energy of the control signal Gate unable to reach the magnitude of the reference voltage Vref, thereby causing the control device to turn off and reducing the loss on the control device during no-load. When the input power increases and the load increases, the chip exits the Burst mode and enters the Normal mode. In the Normal mode, the driving of the voltage regulating transistor is continuous, the duty cycle is relatively large, and the energy of the control signal Gate exceeds the magnitude of the reference voltage Vref, thereby controlling the conduction of the control device. In other embodiments, the control signal Gate connected to the control circuit for reducing no-load loss can also be the signal applied to the gate of the voltage regulating transistor in the LLC circuit or the PFC circuit. This embodiment does not make specific limitations on this.

[0070] It should be understood that the various forms of the processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in the present utility model can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution of the present utility model can be achieved. No limitations are imposed herein.

[0071] The above specific embodiments do not constitute a limitation on the protection scope of the present utility model. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present utility model shall be included within the protection scope of the present utility model.

Claims

1. A control circuit for reducing no-load loss, characterized in that, Comprising: AC input circuit, thermosensitive device, control device and drive module; The thermosensitive device is serially connected in the AC input circuit; The control device is connected in parallel across the two ends of the thermosensitive device; The input end of the drive module is connected to a control signal, and the output end of the drive module is electrically connected to the control device; The control signal is related to the size of the load, and the drive module is used to control the conduction or cut-off of the control device according to the control signal.

2. The control circuit for reducing no-load loss according to claim 1, wherein The control device includes a first transistor, and the output end of the drive module is electrically connected to the gate of the first transistor.

3. The control circuit for reducing no-load loss according to claim 2, wherein The drive module includes a first comparator; The first input end of the first comparator is connected to a reference voltage, the second input end of the first comparator is connected to the control signal, and the output end of the first comparator is electrically connected to the gate of the first transistor.

4. The control circuit for reducing no-load loss according to claim 1, characterized in that The control device includes a relay; The relay includes a coil and a contact group; The contact group is connected in parallel across the two ends of the thermosensitive device; The first end of the coil is connected to a fixed power supply, and the second end of the coil is electrically connected to the output end of the drive module.

5. The control circuit for reducing no-load loss according to claim 4, wherein The drive module includes: a second comparator and a second transistor; The first input end of the second comparator is connected to a reference voltage, the second input end of the second comparator is connected to the control signal, and the output end of the second comparator is electrically connected to the gate of the second transistor; The first pole of the second transistor is electrically connected to the second end of the coil, and the second end of the second transistor is connected to a ground potential signal.

6. The control circuit for reducing no-load loss according to claim 3 or 5, characterized in that The drive module further includes a first voltage-dividing resistor and a second voltage-dividing resistor; The first end of the first voltage-dividing resistor is electrically connected to a fixed power supply, and the second end of the first voltage-dividing resistor is electrically connected to the first end of the second voltage-dividing resistor; The second end of the second voltage-dividing resistor is connected to a ground potential signal, and the first end of the second voltage-dividing resistor is used to generate the reference voltage.

7. The control circuit for reducing no-load loss according to claim 3 or 5, characterized in that The drive module further includes a diode and a current-limiting resistor; The first end of the diode is connected to the control signal, the second end of the diode is electrically connected to the first end of the current-limiting resistor, and the second end of the current-limiting resistor is electrically connected to the input end of the drive module.

8. The control circuit for reducing no-load loss according to claim 3 or 5, characterized in that, The control signal is a PWM signal, and the duty cycle and / or frequency of the PWM signal are related to the size of the load.

9. The control circuit for reducing no-load loss according to claim 8, characterized in that, The drive module further includes a filter capacitor, the first end of the filter capacitor is electrically connected to the input end of the drive module, and the second end of the filter capacitor is connected to a ground potential signal.

10. A switching power supply, characterized in that, The switching power supply includes the control circuit for reducing no-load loss according to any one of claims 1-9.

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