Anti-backflow circuit and method for battery charging power supply

Abstract

The invention relates to an anti-backflow circuit and method for a battery charging power supply, belongs to the technical field of power supplies, and solves the problems that no-load and light-load efficiency of the power supply can be influenced by forbidding a BURST mode of a primary side control IC, and current backflow can be caused by using a BUCK circuit. According to the circuit, a power input detection circuit detects a power input state signal at a positive voltage node of a primary side of a transformer; the control signal generation device provides a control signal according to the power input state signal; the control circuit comprises a triode of which the base receives the control signal and is used for controlling whether the triode is in a cut-off state according to the control signal; the relay is connected to a collector electrode of the triode and used for controlling whether a coil of the relay is disconnected or not according to the cut-off state or the on state of the triode so as to disconnect or connect the secondary power supply of the transformer and the rechargeable battery, and the relay is powered by a BUCK circuit receiving the secondary power supply of the transformer. The power supply efficiency is improved through an anti-backflow circuit formed by the power supply input detection circuit and the relay.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power supply, in particular to a reverse flow prevention circuit and method for a battery charging power supply. BACKGROUND

[0002] Auxiliary power supply using auxiliary winding: an auxiliary winding is constructed in the secondary of the main transformer, and then a full-wave rectification, full-bridge rectification or half-wave, half-bridge rectification circuit is used, followed by an RC low-pass filter circuit to smooth the voltage, and finally an LDO to generate an accurate supply voltage or reference voltage to power the various ICs in the secondary.

[0003] Reverse flow prevention circuit using MOS tube: a reverse flow prevention circuit is constructed using a comparator and a MOS tube connected in series in the circuit, the positive and negative input terminals of the comparator are respectively connected across the D and S poles of the MOS tube, and the D and S poles of the MOS tube are connected in series at the high side of the power supply output, the comparator detects the direction of the output current, and when the direction of the power supply current changes from output to input, the comparator cuts off the driving voltage of the MOS tube, preventing the battery from reverse charging the power supply.

[0004] When the power supply is in no-load state, to reduce the no-load power consumption, the primary control IC will enter BURST mode and work intermittently, at this time the energy transmitted to the secondary side is reduced, and under this working condition, the auxiliary power supply in the secondary side built with the auxiliary winding often has a low voltage, which causes the ICs in the secondary to malfunction, this is because the voltage feedback in the secondary side comes from the main winding output, and the auxiliary winding is limited by the cross regulation rate and cannot maintain the voltage. The traditional solution is to disable the BURST mode of the primary control IC, and add a resistor as a dummy load to the power supply output to increase the energy transmitted from the primary to the secondary when the power supply is in no-load to light-load state, thereby maintaining the voltage of the auxiliary winding. The disadvantage of this method is that it greatly affects the no-load and light-load efficiency of the power supply, especially for LLC topology power supply, after disabling the BURST mode, to reduce the voltage gain at light load, the switching frequency of the primary half-bridge continuously rises, causing the switching loss to also increase.

[0005] When the power supply input is connected to the mains AC and the power supply output is connected to the battery, the MCU controls the output relay of the power supply to be attracted, and the power supply starts to charge the battery. At this time, the mains AC input of the power supply is cut off, if the auxiliary power supply in the secondary is constructed using an auxiliary winding, since the energy transmission from the primary to the secondary stops, the auxiliary power supply will also power off, and the relay powered by the auxiliary power supply will also naturally turn off, disconnecting the power supply from the battery, so the battery will not reverse charge the power supply; but if the auxiliary power supply in the secondary is constructed using a BUCK circuit, since the BUCK circuit takes power from the output capacitor of the power supply, after the relay is attracted, the output capacitor of the power supply is connected to the battery, even if the energy transmission from the primary stops, the BUCK circuit will not power off, which will cause the output relay to continue to be attracted after the mains AC input is cut off, and the battery will reverse charge the output capacitor of the power supply. SUMMARY

[0006] In view of the above analysis, the embodiments of the present application aim to provide an anti-inrush circuit and method for battery charging power supply to solve the problem that the conventional anti-inrush circuit greatly affects the no-load and light-load efficiency of the power supply and the use of BUCK circuit causes current inrush.

[0007] In one aspect, the embodiments of the present application provide an anti-inrush circuit for battery charging power supply, comprising: a power input detection circuit, configured to detect a power input state signal at a positive voltage node of a primary side of a transformer; a control signal generation device, configured to provide a control signal according to the power input state signal; a control circuit, comprising a triode, a base of which receives the control signal, configured to control whether the triode is in an off state according to the control signal; a relay, connected to a collector of the triode, configured to control whether a coil of the relay is disconnected according to the off state or on state of the triode, thereby disconnecting or connecting the connection between a secondary side power supply of the transformer and a charging battery, wherein the relay is powered by a BUCK circuit receiving the secondary side power supply of the transformer.

[0008] The anti-inrush circuit constructed by the power input detection circuit and the relay is powered by the BUCK circuit, which reduces the complexity of the circuit, reduces the cost, and at the same time avoids the loss problem caused by the on-resistance of the MOS tube in the conventional anti-inrush circuit, further improving the power supply efficiency.

[0009] Based on the further improvement of the above device, the BUCK circuit comprises a first transformer and a second transformer, the first transformer is configured to step down the voltage at the power output capacitor of the secondary side of the transformer to a first direct current power voltage, wherein the first direct current power voltage is used to power the relay; the second transformer is configured to step down the first direct current power voltage to a second direct current power voltage, wherein the second direct current power voltage is used to power the power input detection circuit.

[0010] Based on the further improvement of the above device, the power input detection circuit comprises an optoelectronic coupler, wherein the input end of the optoelectronic coupler is connected to the positive terminal of the rectifier of the primary side of the transformer or the positive terminal of the bus capacitor; the output end of the optoelectronic coupler receives the second direct current power voltage and is connected to the input end of the control signal generation device.

[0011] Based on the further improvement of the above device, the power input detection circuit further comprises a first resistor and a second resistor, and the optoelectronic coupler comprises a light emitting diode as an input side component and a phototriode as an output side component, wherein one end of the first resistor is connected to the positive terminal of the rectifier of the transformer primary side or the positive terminal of the bus capacitor, the other end of the first resistor is connected to the anode of the light emitting diode, and the cathode of the light emitting diode is connected to the ground terminal of the transformer primary side; one end of the second resistor is connected to the second DC power voltage, the other end of the resistor is connected to the collector of the phototriode and the input terminal of the control signal generation device, and the emitter of the phototriode is connected to the ground terminal of the transformer secondary side.

[0012] Based on the further improvement of the above device, the control signal generation device is used to determine that the power input terminal is connected to the transformer primary side when the power input state signal is a raised voltage, and output a high level signal as the control signal according to the raised voltage; and determine that the power input terminal is disconnected from the transformer primary side when the power input state signal is a lowered voltage, and output a low level signal as the control signal according to the lowered voltage.

[0013] Based on the further improvement of the above device, the control circuit is further used to turn on the triode when the control signal is a high level signal, so that the coil of the relay is attracted, and then the switch of the relay is closed to connect the transformer secondary side power supply with the charging battery, thereby charging the charging battery; when the control signal is a low level signal, the triode is turned off, so that the coil of the relay is disconnected, and then the switch of the relay is opened to disconnect the transformer secondary side power supply from the charging battery, thereby preventing the charging battery from being reversely charged to the transformer secondary side power supply.

[0014] Based on the further improvement of the above device, the control circuit further comprises a first bias resistor, a second bias resistor, and a current limiting resistor, wherein one end of the first bias resistor is connected to the ground terminal of the transformer secondary side, the other end of the first bias resistor is connected to the base of the triode and one end of the second bias transistor; the other end of the second bias transistor is connected to the control signal output terminal of the control signal generation device; one end of the current limiting resistor is connected to the collector of the triode, the other end of the current limiting resistor is connected to one end of the relay; and the other end of the relay is connected to the first DC power voltage.

[0015] Based on a further improvement of the above device, the anti-backflow circuit for the battery charging power supply also includes a freewheeling diode connected in parallel with the relay, wherein the anode of the freewheeling diode is connected to one end of the relay, and the cathode of the freewheeling diode is connected to the first DC power supply voltage and the other end of the relay.

[0016] On the other hand, embodiments of the present invention provide a method for preventing backflow in a battery charging power supply, comprising: detecting a power input status signal at a positive voltage node on the primary side of a transformer; providing a control signal to a control circuit based on the power input status signal; controlling whether a transistor in the control circuit is in a cutoff state based on the control signal; and causing a relay to engage or disengage based on the cutoff or conduction state of the transistor, thereby disconnecting or connecting the connection between the secondary power supply of the transformer and the charging battery, wherein the relay is powered by a BUCK circuit that receives the secondary power supply of the transformer.

[0017] A further improvement to the above method, based on the cutoff or conduction state of the transistor, causes the relay to open or close, thereby disconnecting or connecting the transformer secondary power supply and the rechargeable battery, further includes: when the transistor is in the cutoff state, the relay coil is disconnected, and then the relay switch is opened, thereby disconnecting the transformer secondary power supply from the rechargeable battery to prevent the rechargeable battery from reverse charging the transformer secondary power supply; when the transistor is in the conduction state, the relay coil is closed, and then the relay switch is closed, thereby connecting the transformer secondary power supply to the rechargeable battery so that the transformer secondary power supply charges the rechargeable battery.

[0018] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: 1. The backflow prevention circuit constructed using optocouplers and relays reduces circuit complexity and cost, while avoiding the loss problem caused by the on-resistance of MOSFETs in traditional backflow prevention circuits, further improving power efficiency.

[0019] 2. The BUCK circuit, as an auxiliary power supply, greatly improves the overall efficiency of the power supply under no-load and light-load conditions, while also enhancing the reliability of the auxiliary power supply.

[0020] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0021] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts. Figure 1 This is a block diagram of an anti-backflow circuit for a battery charging power supply according to an embodiment of the present invention. Figure 2 This is the output circuit of the transformer secondary power supply according to an embodiment of the present invention; Figure 3 This is an auxiliary power supply circuit for the secondary side of a transformer according to an embodiment of the present invention; Figure 4 This is a power input detection circuit according to an embodiment of the present invention; Figure 5 A BUCK circuit diagram according to an embodiment of the present invention; and Figure 6 This is a flowchart of a method for preventing backflow in a battery charging power supply according to an embodiment of the present invention. Detailed Implementation

[0022] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0023] refer to Figure 1 A specific embodiment of the present invention discloses an anti-backflow circuit for a battery charging power supply, including a power input detection circuit 101, a control signal generation device 102, a control circuit 103, a relay 104, and a freewheeling diode D9.

[0024] The power input detection circuit 101 is used to detect the power input status signal at the positive voltage node VDD on the primary side of the transformer. The power input detection circuit 101 includes an optocoupler, wherein the input terminal of the optocoupler is connected to the positive terminal of the rectifier on the primary side of the transformer or the positive terminal of the bus capacitor; the output terminal of the optocoupler receives a second DC power supply voltage and is connected to the input terminal of the control signal generation device.

[0025] Specifically, refer to Figure 4The power input detection circuit 101 also includes a first resistor R104 and a second resistor R100, and an optocoupler comprising a light-emitting diode PT1A as the input side component and a phototransistor PT1B as the output side component. The light-emitting diode PT1A emits light according to the connected power supply voltage (also known as the node voltage) VDD, and the phototransistor PT1B receives the light emitted from the light-emitting diode PT1A and generates a current based on the received light; the magnitude of this current is positively correlated with the received light. One end of the first resistor R104 is connected to the power supply voltage VDD, which can be the positive terminal of the rectifier on the primary side of the transformer or the positive terminal of the bus capacitor. The other end of the first resistor R104 is connected to the anode of the light-emitting diode PT1A, and the cathode of the light-emitting diode PT1A is connected to the ground terminal GND (also known as the primary voltage reference ground) of the transformer primary side. One end of the second resistor R100 is connected to the second DC power supply voltage (i.e., 5V power supply voltage), and the other end of the resistor is connected to the collector of the phototransistor PT1B and the input terminal CON2 of the control signal generation device (i.e., ...). Figure 4 The AC_DETEC in the transformer, and the emitter of the phototransistor PT1B are connected to the ground terminal PGND (also known as the secondary voltage reference ground) of the transformer secondary side.

[0026] The control signal generation device 102 is used to provide control signals based on the power input status signal. The control signal generation device 102 may include a microcontroller, a field-programmable gate array (FPGA), and a complex programmable logic device (CPLD).

[0027] Specifically, the control signal generation device 102 is used to determine that the power input terminal is connected to the primary side of the transformer when the power input state signal is an increased voltage, and output a high-level signal as a control signal based on the increased voltage; and to determine that the power input terminal is disconnected from the primary side of the transformer when the power input state signal is a decreased voltage, and output a low-level signal as a control signal based on the decreased voltage.

[0028] refer to Figure 2 The control circuit 103 includes a transistor Q7, whose base receives a control signal, i.e., the control signal is received through the terminal CON2 of the microcontroller. The control circuit is used to control whether the transistor Q7 is in the cut-off state according to the control signal and outputs the control signal through the output terminal TR of the microcontroller.

[0029] Specifically, the control circuit 103 is also used to turn on transistor Q7 when the control signal is a high-level signal, causing the coil of the relay to be energized, and then the switch of relay K1 to close to connect the secondary power supply of the transformer to the rechargeable battery, thereby charging the rechargeable battery; when the control signal is a low-level signal, transistor Q7 is turned off, causing the coil of relay K1 to be de-energized, and then the switch of relay K1 to open to disconnect the secondary power supply of the transformer from the rechargeable battery, thereby preventing the rechargeable battery from reversing to charge the secondary power supply of the transformer.

[0030] The control circuit 103 also includes a first bias resistor R53, a second bias resistor R52, and a current-limiting resistor R50. One end of the first bias resistor R53 is connected to the ground terminal PGND of the transformer secondary side, and the other end of the first bias resistor R53 is connected to the base B of transistor Q7 and one end of the second bias transistor R52. The other end of the second bias transistor R52 is connected to the control signal output terminal TR of the control signal generation device. One end of the current-limiting resistor R50 is connected to the collector C of transistor Q7, and the emitter E of transistor Q7 is connected to the ground terminal PGND of the transformer secondary side. The other end of the current-limiting resistor R50 is connected to one end of relay K1; and the other end of relay K1 is connected to the first DC power supply voltage V12.

[0031] The freewheeling diode D9 is connected in parallel with the relay K1. The anode of the freewheeling diode D9 is connected to one end of the relay K1, and the cathode of the freewheeling diode D9 is connected to the first DC power supply voltage 12V and the other end of the relay K1.

[0032] Relay 104, connected to the collector of transistor Q7, controls whether the relay coil is open or closed based on the transistor's cutoff or on state, thereby disconnecting or connecting the power supply between the transformer secondary and the rechargeable battery. The relay is powered by a BUCK circuit receiving the transformer secondary power supply. For example, the power supply could be a lead-acid battery charger, a lithium-ion battery charger, or a two-wheeled electric vehicle charger. The relay is a four-pin device, with two pins for the coil and two pins for the switch. When a low voltage (typically 5V~24V) is applied to the coil, the switch pins close, and the two coil contacts of the relay are connected to a 12V voltage and the collector of the transistor, respectively. PE2 is the grounding network identifier; LF3 is the power output common-mode filter inductor; C26 is the power output filter capacitor.

[0033] refer to Figure 3The BUCK circuit includes a first converter and a second converter. Specifically, the first converter steps down the voltage VOUT at the power output capacitor on the secondary side of the transformer to a first DC power supply voltage of 12V, which powers the relay. The second converter steps down the first DC voltage of 12V to a second DC power supply voltage of 5V, which powers the power input detection circuit 101. EC9 is the BUCK input filter electrolytic capacitor; C31 is the BUCK input filter ceramic capacitor; R58 is the BUCK chip enable pin current limiting resistor; R69 is the BUCK chip loop compensation resistor; C37 and C33 are the BUCK chip loop compensation capacitors; R57 is the BUCK chip current detection resistor; C29 is the bootstrap power supply capacitor, providing drive voltage bias for the internal MOSFET of the BUCK chip; C32 is the output filter capacitor, filtering out high-frequency noise; EC10 is the output electrolytic capacitor, storing energy and smoothing the output voltage. R60 is the base bias resistor for transistor Q8; Q8 is used to increase current output capability; EC8 is an energy storage and filtering capacitor.

[0034] Compared with existing technologies, the reverse current prevention circuit for battery charging power supply provided in this embodiment, constructed using an optocoupler and a relay, reduces circuit complexity and cost. It also avoids the losses caused by the on-resistance of the MOSFET in traditional reverse current prevention circuits, further improving power supply efficiency. Furthermore, the BUCK circuit, acting as an auxiliary power supply, significantly improves the overall efficiency of the power supply under no-load and light-load conditions, while also enhancing the reliability of the auxiliary power supply.

[0035] A specific embodiment of the present invention discloses a method for preventing backflow in a battery charging power supply, comprising: detecting a power input status signal at the positive voltage node of the primary side of a transformer; providing a control signal to a control circuit based on the power input status signal; controlling whether a transistor in the control circuit is in a cutoff state based on the control signal; and causing a relay to engage or disengage based on the cutoff or conduction state of the transistor, thereby disconnecting or connecting the connection between the secondary power supply of the transformer and the charging battery, wherein the relay is powered by a BUCK circuit that receives the secondary power supply of the transformer.

[0036] Specifically, the method of energizing or de-energizing the relay based on the transistor's cutoff or conduction state, thereby disconnecting or connecting the transformer secondary power supply and the rechargeable battery, further includes: when the transistor is in the cutoff state, the relay coil is disconnected, and then the relay switch is opened, thereby disconnecting the transformer secondary power supply from the rechargeable battery to prevent the rechargeable battery from reversing the charging of the transformer secondary power supply; when the transistor is in the conduction state, the relay coil is energized, and then the relay switch is closed, thereby connecting the transformer secondary power supply to the rechargeable battery so that the transformer secondary power supply can charge the rechargeable battery.

[0037] In the following text, refer to Figures 2 to 5 The backflow prevention circuit for a battery charging power supply according to an embodiment of the present invention will be described in detail by way of specific examples.

[0038] Using a BUCK circuit to draw power from the power supply output capacitor and step it down to the required voltage is another way to build an auxiliary power supply. Since the input of the BUCK circuit comes directly from the power supply output, it is not affected by the cross-regulation rate and also avoids the problem of affecting power supply efficiency under light load.

[0039] This technical solution selects a BUCK circuit to construct the auxiliary power supply on the secondary side of the power supply, and adds an AC input detection circuit to avoid the problem of battery current flowing back into the power supply output capacitor after the AC mains input is cut off, so as to meet the national standard requirements for power supply safety.

[0040] like Figure 2 As shown, EC5, EC6, and EC7 are the output capacitors of the power supply, such as electrolytic capacitors, used for energy storage and filtering. Relay K1 controls the connection between the output electrolytic capacitor and the battery. Resistor R50 is used for current limiting. Transistor Q7 controls the activation and deactivation of the relay. Bias resistors R52 and R53 provide DC bias voltage to the base of transistor Q7. TR is a terminal label used to connect to the microcontroller output port. When the microcontroller outputs a high level, transistor Q7 conducts, and the relay activates; when the microcontroller outputs a low level, transistor Q7 is deactivated, and relay K1 deactivates. Freewheeling diode D9 provides a freewheeling path for the current after the relay deactivates.

[0041] When the power input is connected to AC mains and the power outputs V+ and V- are connected to the positive and negative terminals of the battery, the microcontroller outputs a high-level signal to TR. Subsequently, transistor Q7 conducts, relay K1 is energized, and the power supply charges the battery. The 12V and 5V voltages required by the various ICs on the secondary side of the power supply are provided by the BUCK circuit. HF32FV-G / 12-HSTF (K1) is an "ultra-miniature medium-power relay." HF32FV indicates the product series (miniature power relay); G indicates the contact structure code (1 normally open group); 12 indicates the coil voltage (12VDC); and HSTF indicates the package / characteristic code (usually indicating a standard tube-packaged type).

[0042] Figure 2 and Figure 3 These are all circuit modules on the secondary side of the power supply. The primary side of the transformer is the power input section connected to the mains power, and the secondary side is the power output section. The power supply consists of two parts: the primary side and the secondary side. The primary side (i.e., the first-order side) and the secondary side (i.e., the second-order side) are isolated from each other by transformers, optocouplers, and safety capacitors.

[0043] Figure 2 It is the output section of the secondary side of the power supply. Figure 3 It is the auxiliary power supply section on the secondary side of the power supply. The output section and the auxiliary power supply section on the secondary side of the power supply are two independent power supply modules.

[0044] refer to Figure 3 The BUCK circuit control chip U8 is a BUCK circuit control IC with a built-in high-side MOSFET, used to control the MOSFET switch and maintain a stable output voltage. The input voltage of the BUCK circuit is provided by the voltage on the power supply output capacitor (Vout), and the BUCK circuit steps down the Vout voltage to 12V. Inductor L5 is used for energy storage. Freewheeling diode D12 is used to freewheel the inductor during MOSFET turn-off to maintain energy output. Voltage reference chip U6 (i.e., linear regulator) is used to further regulate the 12V output voltage of the BUCK circuit to 5V. The BUCK circuit control chip U8 includes the following pins: VIN is the chip power input pin; FB is the output voltage feedback pin; BST is the bootstrap capacitor pin, providing the drive voltage to the gate of the upper MOSFET; SW is floating ground; IS is the peak current detection pin; EN is the enable pin, active high, for switching power supply operation; COMP is the loop compensation terminal. The series RC network between COMP and ground is used to compensate for the closed-loop control of the system; GND is the chip ground.

[0045] Figure 4For the AC input detection circuit, VDD can be powered from any positive voltage on the primary side (such as the positive output of the rectifier bridge, the positive terminal of the bus capacitor, etc.). PT1A and PT1B are the input and output of the transistor optocoupler, and AC_DETEC is connected to the microcontroller's level detection pin.

[0046] Power is drawn from the primary-side control IC's power supply pin (VDD), where the voltage is lower, which helps reduce power consumption. When the power input is connected to AC mains, the primary-side control IC starts up, generating a voltage on VDD. Current flows through the current-limiting resistor R104 to the input of the optocoupler, increasing the current flowing through the optocoupler's output. This increases the voltage drop across resistor R100, causing the voltage detected by AC_DETEC to decrease. The microcontroller detects this low voltage and determines that the power input is connected to AC mains. When the power input is disconnected from AC mains, the primary side loses power, there is no current at the optocoupler's input, and the optocoupler's output is cut off. The voltage detected by AC_DETEC increases, and the microcontroller detects this high voltage and determines that the power input is cut off. It outputs a low-level signal to TR, turning off transistor Q7. The power output relay disconnects from the battery, preventing the battery from reversing its charge.

[0047] The technical feature of this invention lies in the combination of the following two circuits: A BUCK circuit structure is used to reduce the main output voltage of the power supply to the required auxiliary power supply voltage, thereby mitigating the impact of the auxiliary power supply constructed through the auxiliary winding on the overall light-load and no-load efficiency of the power supply. (Reference) Figure 5 The BUCK circuit structure includes: a switching transistor, a freewheeling diode, an inductor, and an output capacitor.

[0048] refer to Figure 4 The power supply voltage VDD is connected to the power supply pin of the control IC. Its function is to sample the mains input status. Since the mains input and the power supply voltage of the control IC are causally related, the power supply voltage of the control IC can indicate whether the power supply has been connected to the mains input. In fact, any voltage node on the primary side that is causally related to the mains input can be connected to this point to sample the mains input status.

[0049] Resistor R104 is used for current limiting. Optocouplers PT1A and PT1B are a single unit. PT1A is the LED portion of the optocoupler, located on the primary side of the power supply, while PT1B is the phototransistor portion, located on the secondary side. When VDD is high, the LED's light emission increases, the phototransistor's conduction level increases accordingly, and the voltage at AC_DATEC decreases. The microcontroller can thus determine the AC input status of the power supply. The 5V power supply is connected to the 5V auxiliary power supply output to provide voltage bias. Resistor R100 is used to provide voltage divider bias. AC_DATEC is connected to the microcontroller's voltage detection pin to detect the voltage at this point and obtain the AC input status of the power supply.

[0050] An AC input detection circuit is constructed using an optocoupler, and a microcontroller controls the output relay to solve the problem that after the AC input is cut off when using the power supply voltage VDD, the power supply cannot disconnect from the battery, causing the battery to charge the power supply in reverse.

[0051] The beneficial technical effects of this invention are as follows: Comparing the lithium battery charging power supply (rated output current 10A) using this invention with a lithium battery charging power supply of the same specification using an auxiliary winding, under the conditions of 220V / 50Hz input and 54.6V output voltage, the technical solution of this invention reduces the no-load power consumption by 1.6W; with a load of 1A, the technical solution of this invention improves the power supply efficiency by 10.4%; with a load of 2.5A, the technical solution of this invention improves the power supply efficiency by 2.3%; and with a load of 5A, the technical solution of this invention improves the power supply efficiency by 1.2%. It is evident that this invention significantly improves the no-load and light-load efficiency of the power supply.

[0052] Those skilled in the art will understand that all or part of the processes of the methods described in the above embodiments can be implemented by a computer program instructing related hardware, and the program can be stored in a computer-readable storage medium. The computer-readable storage medium may be a disk, optical disk, read-only memory, or random access memory, etc.

[0053] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A backflow prevention circuit for a battery charging power supply, characterized by, The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay.

2. The backflow prevention circuit for a battery charging power supply according to claim 1, characterized by, The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay.

3. The backflow prevention circuit for a battery charging power supply according to claim 2, characterized by, The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay.

4. The backflow prevention circuit for a battery charging power supply according to claim 3, wherein The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay.

5. The backflow prevention circuit for a battery charging power supply according to claim 1, wherein The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay.

6. The backflow prevention circuit for a battery charging power supply according to claim 2, wherein The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The application relates to a power input detection circuit, a control signal generation device, a control circuit and a relay. The When the control signal is a low-level signal, the transistor is cut off, so that the coil of the relay is disconnected, and then the switch of the relay is disconnected to disconnect the transformer secondary side power supply from the charging battery, thereby preventing the charging battery from reverse charging the transformer secondary side power supply.

7. The backflow prevention circuit for a battery charging power supply according to claim 6, wherein The control circuit further comprises a first bias resistor, a second bias resistor, and a current limiting resistor, wherein, One end of the first bias resistor is connected to the ground end of the transformer secondary side, and the other end of the first bias resistor is connected to the base of the transistor and one end of the second bias transistor; The other end of the second bias transistor is connected to the control signal output end of the control signal generation device; One end of the current limiting resistor is connected to the collector of the transistor, and the other end of the current limiting resistor is connected to one end of the relay; and The other end of the relay is connected to the first DC power supply voltage.

8. The backflow prevention circuit for a battery charging power supply according to claim 2, wherein Further comprising a freewheeling diode connected in parallel with the relay, wherein, The anode of the freewheeling diode is connected to one end of the relay, and the cathode of the freewheeling diode is connected to the first DC power supply voltage and the other end of the relay.

9. A backflow prevention method for a battery charging power supply, characterized by, Comprising: detecting a power input state signal at a positive voltage node of a transformer primary side; providing a control signal to a control circuit according to the power input state signal; controlling whether a transistor in the control circuit is in an off state or an on state according to the control signal; according to the off state or the on state of the transistor, causing the relay to be disconnected or attracted, thereby disconnecting or connecting the connection between the transformer secondary side power supply and the charging battery, wherein the relay is powered by a BUCK circuit receiving the transformer secondary side power supply.

10. The method of claim 9, wherein, According to the off state or the on state of the transistor, causing the relay to be disconnected or attracted, thereby disconnecting or connecting the connection between the transformer secondary side power supply and the charging battery further comprises: when the transistor is in the off state, the coil of the relay is disconnected, and then the switch of the relay is disconnected, thereby disconnecting the transformer secondary side power supply from the charging battery to prevent the charging battery from reverse charging the transformer secondary side power supply; when the transistor is in the on state, the coil of the relay is attracted, and then the switch of the relay is closed, thereby connecting the transformer secondary side power supply to the charging battery, so that the transformer secondary side power supply charges the charging battery.

Images