Lossless sampling circuit and control method thereof

Abstract

The invention provides a lossless sampling circuit and a control method thereof, and the circuit comprises a sampling module, one end of which is connected with the voltage output end of a storage battery, and the other end of which is grounded; sampling points are arranged in the sampling module; the source electrode of the switch module is connected with the voltage output end of the storage battery, and the drain electrode is connected with one end of the sampling module; the first end of the driving module is connected with the voltage output end of the storage battery, the second end is grounded, and the third end is connected with the grid of the switch module; the driving control module outputs high-level voltage to the control signal input end of the driving module and inputs low-level voltage to the driving module through the control signal input end; the driving module is used for being disconnected when the low-level voltage is received; when high-level voltage is received, the switch is switched on; when the vehicle-mounted charger is in a working state, the storage battery is used for supplying power to the sampling module and also used for supplying power to the driving module. According to the scheme, the quiescent current of the sampling module is reduced.

Description

Technical Field

[0001] This invention relates to the field of automotive batteries, and more particularly to a non-destructive sampling circuit and a control method for the non-destructive sampling circuit. Background Technology

[0002] In the field of three-in-one on-board chargers, the on-board charger integrates three major functions: OBC (On-Board Charger), DCDC (DC-DC Converter), and PDU (Power Distribution Unit), and requires a battery to power the machine.

[0003] The common vehicle design for a three-in-one on-board charger is the KL15 node, which relies on a vehicle signal to wake up and then uses the battery to provide 12V power. Due to considerations regarding battery standby time, OEMs have strict requirements for the static loss of the battery by the on-board charger in non-operating modes. In recent years, OEM standards have increased from 3mA to 1mA, and many companies are now proposing requirements of less than 0.2mA.

[0004] Therefore, developing a lossless sampling circuit with low quiescent current while ensuring sampling stability and high precision has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] To address the aforementioned technical deficiencies, this invention provides a lossless sampling circuit and its control method. A switching module and a driving module are introduced to control the on / off state of the lossless sampling circuit. The sampling circuit is only activated when the on-board charger is operating, avoiding the static current caused by the sampling module being continuously connected to the circuit. The battery voltage is also used as the driving voltage for the driving module, saving on the hardware cost of an external power supply. Furthermore, the driving circuit does not introduce new static current.

[0006] This invention provides a lossless sampling circuit for use in an on-board charger, comprising: a sampling module, a switching module, a driving module, and a driving control module;

[0007] The sampling module has one end connected to the voltage output terminal of the battery and the other end grounded; the sampling module is equipped with sampling points for sampling the output voltage of the battery.

[0008] The source of the switching module is connected to the voltage output terminal of the battery; the drain of the switching module is connected to one end of the sampling module.

[0009] The drive module has a first terminal connected to the voltage output terminal of the battery, a second terminal grounded, and a third terminal connected to the gate of the switch module.

[0010] The drive control module is configured to output a high voltage to the control signal input terminal of the drive module to wake up the drive module when the on-board charger is in working state; and to input a low voltage to the drive module through the control signal input terminal when the on-board charger is in non-working state.

[0011] The driving module is configured to remain in an off state when receiving the low voltage, while the sampling module remains in an off state; and is configured to:

[0012] When the high voltage is received, the switching module is driven to turn on, so as to turn on the sampling circuit where the sampling module is located, and to sample the output voltage of the battery;

[0013] When the on-board charger is in operation, the battery is used to power the sampling module and also to power the drive module.

[0014] When the on-board charger is not in operation, the battery stops supplying power to the sampling module and the drive module.

[0015] Optionally, the drive module includes: a drive voltage divider unit and a clamping unit;

[0016] The clamping unit is connected between the source and gate of the switching module; it is used to clamp the gate voltage.

[0017] The driving voltage divider unit has one end connected to the voltage output terminal of the battery and the gate of the switching module, and the other end grounded. The control signal input terminal is connected to the driving control module.

[0018] The drive voltage divider unit is used to turn on the circuit when it receives the high flat voltage input from the drive control module, and to provide the gate drive voltage to the switch module after dividing the output voltage of the battery, so as to drive the switch module to turn on; or it is used to turn off when it receives the low flat signal, so as to disconnect the drive circuit.

[0019] Optionally, the driving voltage divider unit includes: a transistor;

[0020] The collector of the transistor is connected to the voltage output terminal of the battery and the gate of the switching module, while the emitter is grounded; the base serves as the control signal input terminal and is connected to the drive control module.

[0021] Optionally, the driving voltage divider unit further includes: a first driving voltage divider resistor and a second driving voltage divider resistor;

[0022] One end of the first driving voltage divider resistor is connected to the voltage output terminal of the battery, and the other end is connected to one end of the second driving voltage divider resistor;

[0023] The other end of the second driving voltage divider resistor is connected to the collector of the transistor; the gate of the switching module is connected to the node between the other end of the first driving voltage divider resistor and one end of the second driving voltage divider resistor.

[0024] The first driving voltage divider resistor, the second driving voltage divider resistor, and the transistor are used to provide the gate driving voltage to the switching module after the battery voltage is divided when the transistor receives the high voltage and turns on, so as to control the switching module to turn on.

[0025] Optionally, the voltage clamping unit includes a Zener diode, the negative and positive terminals of which are respectively connected to the source and gate of the switching module; and the positive terminal of the Zener diode is connected to the other end of the first driving voltage divider resistor and one end of the second driving voltage divider resistor at the same node.

[0026] Optionally, the driving module further includes a first current-limiting resistor and a first resistor;

[0027] One end of the first current-limiting resistor is connected to the drive control module as the control signal input terminal, and the other end is connected to the base of the transistor;

[0028] One end of the first resistor is connected to the base of the transistor, and the other end is grounded.

[0029] Optionally, the sampling module includes: a first sampling voltage divider resistor and a second sampling voltage divider resistor;

[0030] One end of the first sampling voltage divider resistor is connected to one end of the second sampling voltage divider resistor, and the other end of the first sampling voltage divider resistor is connected to the drain of the switching module; the other end of the second sampling voltage divider resistor is grounded; the sampling point is set on the output line between the first sampling voltage divider resistor and the second sampling voltage divider resistor.

[0031] Optionally, the sampling module further includes a capacitor; the capacitor is connected in parallel across the two ends of the second sampling voltage divider resistor.

[0032] Optionally, the lossless sampling circuit further includes a second resistor; the second resistor is connected in parallel between the source and drain of the transistor.

[0033] The present invention also provides a control method for a lossless sampling circuit, applied to a lossless sampling circuit as described in any of the foregoing claims of the present invention, the method comprising:

[0034] When the on-board charger is in operation, the drive control module outputs a high voltage to the control signal input terminal of the drive module; the battery supplies power to the sampling module and also supplies power to the drive module.

[0035] When the driving module receives the high voltage, it drives the switching module to conduct, thereby activating the sampling circuit where the sampling module is located.

[0036] The output voltage of the battery is sampled through the sampling points provided in the sampling module;

[0037] When the on-board charger is not in working state, the drive control module inputs a low voltage to the drive module through the control signal input terminal;

[0038] When the drive module receives the low voltage, it remains disconnected, and the sampling module remains disconnected; the battery stops supplying power to the sampling module and the drive module.

[0039] Compared with existing technologies, the above technical solution has the following advantages:

[0040] 1. Introduce a switching module and a driving module to control the on / off state of the lossless sampling circuit, avoiding the high static current caused by the sampling module being constantly connected to the circuit.

[0041] 2. The voltage of the sampled object (battery) is used as the driving voltage of the driving module, which saves the hardware cost of the external power supply; at the same time, the driving circuit does not introduce new static current.

[0042] 3. It ensures sampling accuracy and sampling stability.

[0043] 4. The sampled voltage object (battery voltage) serves as a voltage source to drive the sampling circuit. The sampled voltage object (battery voltage) is not easily affected by the weak MOS conduction current and will not experience voltage fluctuations or slight switching power supply jitter due to insufficient load-carrying capacity of the object voltage. Compared with the scheme of driving logic with external auxiliary power supply, the scheme of this invention does not have the problem of static loss of auxiliary circuit, or even the power consumption of the whole machine considering the efficiency of flyback power supply. Attached Figure Description

[0044] Figure 1 A schematic diagram of a sampling circuit is shown.

[0045] Figure 2 A schematic diagram of a lossless sampling circuit according to an embodiment of the present invention is shown;

[0046] Figure 3A flowchart of a control method for a lossless sampling circuit according to an embodiment of the present invention is shown;

[0047] Figure label:

[0048] 1-Sampling module;

[0049] 2-Switch module;

[0050] 3-Driver module;

[0051] 31-Drive voltage divider unit;

[0052] 32-Clamping unit;

[0053] R1 - First driving voltage divider resistor

[0054] R2 - Second driving voltage divider resistor;

[0055] R3 - First current-limiting resistor;

[0056] R4 - First resistor;

[0057] R5 - First sampling voltage divider resistor; R6 - Second sampling voltage divider resistor;

[0058] R7 - Second resistor;

[0059] Q1 - MOSFET;

[0060] Q2 - Transistor;

[0061] C1, C11 - Capacitors;

[0062] D1 - Zener diode. Detailed Implementation

[0063] The advantages of the present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments.

[0064] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0065] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0066] In the description of this invention, it should be understood that the terms "inner" and "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0067] In the description of this invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to mechanical or electrical connections, or internal connections between two components. They can be direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0068] In the following description, suffixes such as "module," "part," or "unit" used to denote elements are used only for the convenience of the description of the invention and have no specific meaning in themselves. Therefore, "module" and "part" can be used interchangeably.

[0069] Since the on-board charger needs to sample the battery voltage (output voltage of the DC-DC converter), the typical design uses a resistor divider followed by sampling by the MCU / DSP (Digital Signal Processor) using an ADC (Analog-to-Digital Converter). A specific design is as follows... Figure 1 The signal DC_OUT is the battery voltage, which is generally in the range of 9-16V. After being divided by R235 and R240 (for example, with a resistance ratio of 10:1), and with capacitor C11 connected in parallel across R240, the signal voltage range entering the DSP sampling after being divided by R235 and R240 is reduced to 0.8V–1.45V. However, at this time, the static current is at most 16V / 11K resistance, which will result in a static current of 1.45mA, which may even be difficult to meet the national standard requirements. Under non-operating conditions, the battery is still connected to the DCDC output terminal, causing the sampling resistor of the three-in-one DCDC output voltage of the vehicle charger to always be in a state of voltage difference, which will continuously generate static current.

[0070] To reduce this quiescent current, the conventional approach is to increase the total resistance without changing the ratio of R235 and R240, thereby reducing the current flowing through the sampling resistor and thus the machine's quiescent current. For example, when R235 and R240 are 11K and 1K respectively, the current flowing through R235 and R240 is 1mA, which is the quiescent current. If the two resistors are proportionally increased by 10 times, to 110K and 1K, the quiescent current could theoretically be reduced to 0.1mA. However, actual testing has not achieved this level, with approximately 0.5mA of current still present, possibly due to leakage current from the PCB board, which is difficult to completely eliminate. Even if increasing the resistance can reduce the quiescent current to some extent, this method poses risks to the machine's consistency and stability. Excessively high resistance often leads to reduced voltage sampling immunity, and significantly reduced sampling stability and accuracy, which is undeniable in on-board charging equipment with high accuracy and safety requirements.

[0071] To address the aforementioned issues of low stability and accuracy, the inventors of this invention, through repeated experiments, proposed a method using a switching transistor to determine whether sampling needs to begin based on the current operating state of the on-board three-in-one charger. When the on-board three-in-one charger is in a wake-up state (auxiliary power is working), sampling can be initiated via DSP chip control; when the three-in-one charger is in a sleep state (auxiliary power is off), sampling can be deactivated via DSP chip control.

[0072] Furthermore, considering the operating conditions and sampling requirements of the on-board three-in-one charger, it can be found that the battery voltage is always present during operation. Therefore, it is proposed for the first time to use the battery voltage (the sampled voltage) itself as the control voltage for the entire switching circuit. The sampled voltage serves as both the drive voltage and the power supply voltage for the sampling circuit. When the battery is charged and the three-in-one auxiliary power supply is in the wake-up phase, the battery voltage is introduced into the drive circuit, and the ADC port detects and samples the battery's output voltage. When the battery is charged and the three-in-one auxiliary power supply is in the sleep phase, the DSP chip controls the drive circuit to shut down, the ADC port does not need to detect the battery voltage, and the sampling circuit has no effective loop due to the isolation of the MOS switch, thus no quiescent current is generated.

[0073] The biggest obstacle in the development of this drive voltage source lies in conventional technical biases. In typical MOS drive logic, the drive voltage originates from an isolated power supply. For example, a 14V battery voltage is converted to a stable 12V through a low-power DC-DC topology such as a flyback power supply, and then stepped down to drive the switching MOS. It's easy to understand that typical logic wouldn't use the sampled object as the drive voltage for its own drive circuit. However, conventional external power supply logic has auxiliary circuit static losses, and even the overall power consumption involves considering the efficiency of the flyback power supply.

[0074] Through repeated experiments and demonstrations, the inventors of this invention proposed that the sampled voltage object can be used to drive the sampling circuit, overcoming the technical prejudice that the sampled voltage object cannot be used as a voltage source to drive the sampling circuit. Furthermore, the inventors discovered that, compared to the conventional approach of deriving the driving voltage from an isolated power supply, the sampled voltage object (battery voltage) is less susceptible to the influence of weak MOS conduction current and will not experience voltage fluctuations or slight switching power supply jitter due to insufficient load-carrying capacity. Therefore, it is more suitable for logic that uses the sampled voltage object to drive the sampling circuit. There is also no need for additional auxiliary power supply to the driving circuit, eliminating the static losses of auxiliary circuits and the need to consider the efficiency of the flyback power supply in the overall power consumption. The same control logic can also be used for other voltages with similar characteristics in the same field, such as power battery voltage and PFC post-stage bus voltage, providing various static current optimization schemes for sampling circuits and demonstrating promising application prospects.

[0075] Figure 2 A schematic diagram of a lossless sampling circuit structure conforming to an embodiment of the present invention is shown. (See also...) Figure 2 The lossless sampling circuit includes: a sampling module 1, a switching module, a driving module 3, and a driving control module.

[0076] The sampling module 1 has one end connected to the voltage output terminal of the battery and the other end grounded; the sampling module 1 is provided with sampling points for sampling the output voltage of the battery.

[0077] The source of the switching module is connected to the voltage output terminal of the battery; the drain of the switching module is connected to one end of the sampling module 1. In a specific example, the switching module is a MOSFET Q1.

[0078] The drive module 3 has a first end connected to the voltage output terminal of the battery, a second end grounded, and a third end connected to the gate of the switch module.

[0079] The drive control module is configured to output a high voltage to the control signal input terminal of the drive module 3 to wake up the drive module 3 when the on-board charger is in a working state; and to input a low voltage to the drive module 3 through the control signal input terminal when the on-board charger is in a non-working state. In a specific example, the drive control module is a DSP chip, which controls the drive module 3 by outputting a high or low voltage GPIO drive signal, thereby switching the on or off state of the sampling module 1.

[0080] The driving module 3 is used to keep the battery in an open state when the low voltage is received, while the sampling module 1 remains open; and is used to drive the switching module to turn on when the high voltage is received, so as to turn on the sampling circuit where the sampling module 1 is located and sample the output voltage of the battery.

[0081] When the on-board charger is in operation, the battery powers both the sampling module 1 and the drive module 3. When the on-board charger is not in operation, the battery stops supplying power to both the sampling module 1 and the drive module 3.

[0082] The lossless sampling circuit provided by this invention introduces a switching module for switching. When the three-in-one charger is in a non-operating state, the battery voltage is not sampled under the control of the switching module, thus ensuring no current flow in the sampling module and eliminating losses. If the system is in an operating state according to vehicle control requirements, the sampling module is then connected through the switching module to collect the battery voltage. Compared to solutions that amplify the sampling resistor value, this invention can maintain a lower or even eliminate the static current introduced by directly connecting the sampling module to the circuit without affecting the effectiveness and accuracy of the sampling function.

[0083] Meanwhile, in the solution provided by this invention, the voltage of the sampled object (battery voltage) is used as the voltage source of the sampling module. It also breaks through the conventional R&D thinking inertia and uses the battery voltage as the voltage source of the drive module. There is no need to introduce a new drive voltage source, which saves hardware costs while realizing the power supply and drive of the drive module.

[0084] The further ingenious aspect lies in the fact that while utilizing the battery as the voltage source for the operating voltage, it does not increase the quiescent current in the non-operating state of the system (it is negligible and will not affect the OEM's requirements for quiescent current). Since the drive module also directly uses the battery voltage divider as the drive voltage, the losses in this circuit would typically need to be considered as quiescent current losses. However, the drive module designed in this invention only conducts when the system is in the operating state, along with the sampling module, and does not conduct when the system is in the non-operating state. Therefore, no current flows through the drive circuit in this state, and no quiescent current is introduced. Thus, the total quiescent current in the drive module and sampling module in this solution is almost negligible compared to the OEM's requirements, demonstrating a significant effect on reducing or eliminating the quiescent current in the battery sampling circuit.

[0085] In a further preferred embodiment of the present invention, the driving module 3 includes a driving voltage divider unit 31 and a clamping unit 32. The clamping unit 32 is connected between the source and gate of the switching module; it is used to clamp the gate voltage and protect the switching module. The driving voltage divider unit 31 has a first end connected to the gate, a second end grounded, and a third end connected to the driving signal output terminal of the driving control module. The driving voltage divider unit 31 is used to turn on its driving circuit when it receives a high-level signal input from the driving control module, and to provide a gate driving voltage to the switching module after dividing the output voltage of the battery, so as to drive the switching module to turn on, thereby turning on the sampling circuit of the sampling module 1 to sample the battery voltage; or it is used to turn off its driving circuit when it receives a low-level signal input from the driving control module, and the switching module remains in the off state. At this time, since the driving module 3 is not turned on, no static current is generated, so even if the voltage output terminal of the battery is connected, the driving module 3 is disconnected and no static current is generated when the three-in-one system is in a non-working state.

[0086] In one optional embodiment, the drive voltage divider unit 31 includes a transistor Q2. The collector of the transistor Q2 is connected to the voltage output terminal of the battery and the gate of the switching module, and the emitter is grounded; the base is connected to the drive control module as the control signal input terminal. The transistor Q2 is configured to turn on when receiving the high flat voltage, divide the battery voltage and provide the gate drive voltage of the switching module to turn on the drive circuit; or turn off when receiving the low flat signal to disconnect the drive circuit.

[0087] In an optional embodiment, the driving voltage divider unit 31 further includes: a first driving voltage divider resistor R1 and a second driving voltage divider resistor R2. One end of the first driving voltage divider resistor R1 is connected to the voltage output terminal of the battery, and the other end is connected to one end of the second driving voltage divider resistor R2. The other end of the second driving voltage divider resistor R2 is connected to the collector of the transistor Q2; the gate of the switching module is connected to the node between the other end of the first driving voltage divider resistor R1 and one end of the second driving voltage divider resistor R2. The first driving voltage divider resistor R1, the second driving voltage divider resistor R2, and the transistor Q2 are used to turn on when the transistor Q2 receives the high voltage, divide the battery voltage, and provide the gate driving voltage to the switching module to control the switching module to turn on and sample the battery voltage. In a specific example, the resistance ratio of the first driving voltage divider resistor R1 and the second driving voltage divider resistor R2 is 10:1. The specific resistance ratio depends on the selection of the transistor Q2 (MOS transistor) and the magnitude of the battery voltage. In this embodiment, taking the 12V voltage of the target sampled battery as an example, the voltage is divided by the transistor Q2, the first driving voltage divider resistor R1 and the second driving voltage divider resistor R2 (with a resistance ratio of 10:1 as an example). After the voltage is divided, the gate voltage of the transistor Q2 is reduced from 12V to about 1V, so as to realize the conduction of the transistor Q2.

[0088] Optionally, the voltage clamping unit 32 includes: a Zener diode D1, the negative and positive terminals of which are respectively connected to the source and gate of the switching module; and the positive terminal of the Zener diode D1 is connected to the other end of the first driving voltage divider resistor R1 and one end of the second driving voltage divider resistor R2 at the same node; the Zener diode D1 is used to clamp the voltage and protect the MOSFET Q1.

[0089] In a further embodiment, the drive module 3 further includes a first current-limiting resistor R3 and a first resistor R4. One end of the first current-limiting resistor R3 serves as the control signal input terminal connected to the drive control module, and the other end is connected to the base of the transistor Q2; the first current-limiting resistor R3 acts as a current control device for the transistor Q2, ensuring that the circuit does not exceed the DSP's current-sinking switching capability. One end of the first resistor R4 is connected to the base of the transistor Q2, and the other end is grounded; the first resistor R4 serves as a resistor for conventionally controlling the turn-off of the transistor Q2, optimizing the switching waveform.

[0090] In one embodiment of the present invention, the sampling module 1 includes: a first sampling voltage divider resistor R5 and a second sampling voltage divider resistor R6. One end of the first sampling voltage divider resistor R5 is connected to one end of the second sampling voltage divider resistor R6, and the sampling point is set on the output line between the first sampling voltage divider resistor R5 and the second sampling voltage divider resistor R6. The other end of the first sampling voltage divider resistor R5 is connected to the drain of the switching module; the other end of the second sampling voltage divider resistor R6 is grounded. In a specific example, the resistance ratio of the first sampling voltage divider resistor R5 to the second sampling voltage divider resistor R6 is approximately 10:1 to ensure that the voltage entering the ADC port is within 3.3V and has a certain resolution; resistors commonly used in driving circuits are selected, such as 2KΩ and 10KΩ resistors.

[0091] In a further optional embodiment, the sampling module 1 further includes a capacitor C1; the capacitor C1 is connected in parallel across the two ends of the second sampling voltage divider resistor R6.

[0092] Further optionally, a second resistor R7 is included, which is connected in parallel between the source and drain of the switching module. The second resistor R7 is designed for product compatibility; if the customer has a customized product and does not have quiescent current issues, R250 can be used for direct sampling, and the drive circuit is not mounted during surface mounting.

[0093] The following is combined Figure 2 The specific embodiments shown illustrate the solution of the present invention in detail:

[0094] The VBAD signal input to the gate of Q2 is the GPIO drive signal of the main control chip (DSP chip), which controls whether the sampling circuit is turned on or off. In the sampling circuit, the DCVOUT network number represents the 12V battery voltage. In this invention, a MOS transistor Q1 and a corresponding drive module 3 are added to control the on / off state of the sampling circuit; the drive module 3 consists of resistors R1, R2, R3, R4, Q2, and D1.

[0095] Both the sampling circuit and drive module 3 use the battery voltage as the drive voltage. When the on-board charger (three-in-one) is not in operation, the DSP chip pulls the VBAD signal low, Q2 does not conduct, and therefore Q1 does not conduct either. At this time, there is no voltage across the voltage divider resistors R5 and R6, and the sampling circuit generates almost no quiescent current. Since drive module 3 also directly uses the battery voltage as the drive voltage, the loss in this circuit also needs to be considered as quiescent current loss. However, at this time, the Q-drive transistor Q2 is in the off stage, so no current flows through the drive circuit. Overall, no current flows through the sampling circuit and the Q2 drive circuit, and the overall quiescent current is very low.

[0096] When the machine is in operation, the DSP chip controls VBAD to go high, and the battery voltage is output to drive module 3. After being divided by Q2, R1, and R2, the voltage is supplied to the gate of Q1, driving Q1 to conduct. The sampling circuit is also activated. After being divided by R5, R6, and Q1, the DSP chip samples the effective battery voltage. D79 is used to clamp the voltage and protect the gate of Q1. Both the sampling circuit and drive module 3 use the battery voltage as the drive voltage, eliminating the need for an additional voltage source, saving hardware and costs. This achieves the driving of Q1 without introducing new quiescent current when using the battery voltage as the voltage source. The sum of the quiescent currents of the two circuit modules is almost negligible when the machine is not in operation.

[0097] The present invention also provides a control method for a lossless sampling circuit, which is applied to the lossless sampling circuit described in any of the preceding claims.

[0098] Figure 3 A schematic flowchart illustrating a control method for a lossless sampling circuit according to an embodiment of the present invention is shown. (See also...) Figure 3 The method includes steps S1 to S5:

[0099] S1: When the on-board charger is in operation, the drive control module outputs a high voltage to the control signal input terminal of the drive module; the battery supplies power to the sampling module and also supplies power to the drive module.

[0100] S2: When the driving module receives the high voltage, it drives the switching module to conduct, thereby connecting the sampling circuit where the sampling module is located;

[0101] S3: The output voltage of the battery is sampled through the sampling points provided in the sampling module;

[0102] S4: When the on-board charger is not in working state, the drive control module inputs a low voltage to the drive module through the control signal input terminal;

[0103] S5: When the drive module receives the low voltage, it remains disconnected, and the sampling module remains disconnected; the battery stops supplying power to the sampling module and the drive module.

[0104] This invention provides a control method for a lossless sampling circuit. When the on-board charger is in operation, the switching module is turned on to activate the sampling circuit containing the sampling module, thereby sampling the output voltage of the battery. The battery simultaneously provides operating voltage to both the sampling module and the drive module, eliminating the need for a new drive voltage source. Furthermore, by stopping the battery from supplying power to both the sampling module and the drive module when the on-board charger is not in operation, the method cleverly avoids the issue of static current loss that would typically occur in the drive module, which also directly uses a voltage divider from the battery as its drive voltage.

[0105] In summary, the lossless sampling circuit and its control method provided by this invention introduce a switching module for switching. When the three-in-one charger is in a non-operating state, the battery voltage is not sampled under the control of the switching module. When the three-in-one charger is in an operating state, the battery voltage is sampled under the control of the switching module. The sampling module achieves zero quiescent current and no losses. Furthermore, it breaks through conventional R&D thinking by using the voltage of the sampled object (battery voltage) as the voltage source for both the sampling module and the drive module, eliminating the need for a new drive voltage source, saving hardware costs while providing power to the drive module; and it also avoids introducing new quiescent current. The total quiescent current in the circuit provided by this solution is almost negligible compared to the requirements of OEMs, demonstrating a significant effect in reducing or eliminating the quiescent current of the battery sampling circuit.

[0106] When the battery voltage is used as the sampled object, the sampled object voltage can be directly used as the driving force of the sampling circuit. The same control logic can also be used on other voltages with the same characteristics in the same field, such as the power battery voltage, the PFC downstream bus voltage, etc. It can provide a variety of static current optimization schemes for sampling circuits and has an expandable application prospect.

Claims

1. A lossless sampling circuit applied to an on-board charger, characterized in that, include: Sampling module, switching module, driving module, and driving control module; The sampling module has one end connected to the voltage output terminal of the battery and the other end grounded; the sampling module is equipped with sampling points for sampling the output voltage of the battery. The source of the switching module is connected to the voltage output terminal of the battery; the drain of the switching module is connected to one end of the sampling module. The drive module has a first terminal connected to the voltage output terminal of the battery, a second terminal grounded, and a third terminal connected to the gate of the switch module. The drive control module is used to output a high voltage to the control signal input terminal of the drive module when the on-board charger is in working state, thereby waking up the drive module. And when the on-board charger is not in operation, it can input a low voltage to the drive module through the control signal input terminal; The driving module is configured to remain in an off state when receiving the low voltage, while the sampling module remains in an off state; and is configured to: When the high voltage is received, the switching module is driven to turn on, so as to turn on the sampling circuit where the sampling module is located, and to sample the output voltage of the battery; When the on-board charger is in operation, the battery is used to power the sampling module and also to power the drive module. When the on-board charger is not in operation, the battery stops supplying power to the sampling module and the drive module.

2. The lossless sampling circuit as described in claim 1, characterized in that, The drive module includes: a drive voltage divider unit and a clamping unit; The clamping unit is connected between the source and gate of the switching module; it is used to clamp the gate voltage. The driving voltage divider unit has one end connected to the voltage output terminal of the battery and the gate of the switching module, and the other end grounded. The control signal input terminal is connected to the driving control module. The drive voltage divider unit is used to turn on the circuit when it receives the high flat voltage input from the drive control module, and to provide the gate drive voltage to the switch module after dividing the output voltage of the battery, so as to drive the switch module to turn on; or it is used to turn off when it receives the low flat signal, so as to disconnect the drive circuit.

3. The lossless sampling circuit as described in claim 2, characterized in that, The driving voltage divider unit includes: a transistor; The collector of the transistor is connected to the voltage output terminal of the battery and the gate of the switching module, while the emitter is grounded; the base serves as the control signal input terminal and is connected to the drive control module.

4. The lossless sampling circuit as described in claim 3, characterized in that, The driving voltage divider unit further includes: a first driving voltage divider resistor and a second driving voltage divider resistor; One end of the first driving voltage divider resistor is connected to the voltage output terminal of the battery, and the other end is connected to one end of the second driving voltage divider resistor; The other end of the second driving voltage dividing resistor is connected to the collector of the transistor; and the gate of the switch module is connected to a node between the other end of the first driving voltage dividing resistor and the one end of the second driving voltage dividing resistor. The first driving voltage dividing resistor, the second driving voltage dividing resistor and the transistor are configured to, when the transistor is turned on by receiving the high flat voltage, provide the gate driving voltage to the switch module to control the switch module to be turned on, after the battery voltage is divided.

5. The lossless sampling circuit of claim 4, wherein The voltage clamping unit comprises a Zener diode, the negative electrode and the positive electrode of the Zener diode are respectively connected to the source and the gate of the switch module; and the positive electrode of the Zener diode and the other end of the first driving voltage dividing resistor and the one end of the second driving voltage dividing resistor are connected to the same node.

6. The lossless sampling circuit of claim 5, wherein The driving module further comprises a first current limiting resistor and a first resistor; The one end of the first current limiting resistor is connected to the control signal input end of the driving control module, and the other end is connected to the base of the transistor; The one end of the first resistor is connected to the base of the transistor, and the other end is grounded.

7. The lossless sampling circuit of claim 6, wherein The sampling module comprises a first sampling voltage dividing resistor and a second sampling voltage dividing resistor; The one end of the first sampling voltage dividing resistor is connected to the one end of the second sampling voltage dividing resistor, the other end of the first sampling voltage dividing resistor is connected to the drain of the switch module, the other end of the second sampling voltage dividing resistor is grounded, and the sampling point is arranged on the output line between the first sampling voltage dividing resistor and the second sampling voltage dividing resistor.

8. The lossless sampling circuit of claim 7, wherein The sampling module further comprises a capacitor, and the capacitor is connected in parallel across the second sampling voltage dividing resistor.

9. The lossless sampling circuit of claim 8, wherein The lossless sampling circuit further comprises a second resistor, and the second resistor is connected in parallel between the source and the drain of the transistor.

10. A control method of a lossless sampling circuit, characterized by, The method is applied to the lossless sampling circuit of any one of claims 1-9, and the method comprises: When the vehicle charger is in the working state, the driving control module outputs a high flat voltage to the control signal input end of the driving module; the battery supplies power to the sampling module and the driving module; When the driving module receives the high flat voltage, the driving module drives the switch module to be turned on, so as to turn on the sampling circuit in which the sampling module is arranged; The output voltage of the battery is sampled through the sampling point arranged in the sampling module; When the vehicle charger is in the non-working state, the driving control module inputs a low flat voltage to the driving module through the control signal input end; When the driving module receives the low flat voltage, the driving module remains in the off state, and the sampling module also remains in the off state; the battery stops supplying power to the sampling module and the driving module.

Images