A power supply management circuit for vehicle-mounted RTC

Abstract

The present invention belongs to the technical field of automobile instruments, and specifically relates to a power supply management circuit of a vehicle-mounted RTC. The power supply management circuit of the vehicle-mounted RTC includes not only a battery power supply circuit, but also a system power supply circuit. The system power supply circuit is connected in parallel with the battery power supply circuit, and the parallel point is used to connect the power supply input end of the RTC. A switch tube is also arranged in series on the battery power supply circuit. The switch tube is used to conduct when the voltage at the output end of the vehicle system power supply is less than a set voltage threshold, so as to power the vehicle-mounted RTC through the power supply battery, and disconnect when the voltage at the output end of the vehicle system power supply is greater than the set voltage threshold, so as to power the vehicle-mounted RTC through the vehicle system power supply. That is, by using the power supply battery to power the RTC only when the vehicle system power supply does not output voltage (that is, the vehicle is powered off), the use time of the power supply battery is reduced, that is, the time interval for replacing the power supply battery will be extended, and the number of times the power supply battery is replaced is reduced within the same time, that is, the maintenance cost due to frequent replacement of the power supply battery is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of automobile instruments, and in particular relates to a power supply management circuit of an on-vehicle RTC. Background Art

[0002] With the development and improvement of vehicle-mounted electronic technology, many assembly parts contain clock display functions, such as: instrument assembly, central control audio assembly, commercial bus on-board clock, etc. Therefore, the on-board end needs to use RTC (real-time clock). Based on the requirement of continuous operation of RTC, the RTC needs to be continuously powered. If there is a power interruption, the on-board RTC will be reset, resulting in inaccurate RTC time.

[0003] Different types of vehicles have different power supply methods for on-board RTC. The power supply for RTC clock in passenger cars is provided by the power supply of the whole vehicle. When the vehicle is parked and turned off, the power supply of the whole vehicle is not cut off, and all assembly parts will enter low power consumption mode. In low power consumption mode: the standby working current of a single assembly part is required to be less than 1mA; the sleep current of the whole vehicle is less than 20mA. For passenger car customers, it will not affect customer use within 3 months.

[0004] The electrical design of commercial vehicles is different from that of passenger vehicles. Commercial vehicles are designed with a "main switch" at the main power supply, that is, when the vehicle is turned off, the main switch is disconnected. Therefore, for assemblies with "RTC clock" requirements, in order to keep the internal clock running normally, there is a "battery" inside the assembly to power the "RTC clock module" to maintain the operation of the RTC clock. The characteristics of these "batteries" are "non-rechargeable", and their voltage is generally 3.3V or 3.6V, and as time goes by, the discharge voltage will gradually decrease. After it decreases to a certain level, the power supply battery needs to be replaced. That is, when the power supply battery is used to power the on-board RTC, there will be a need to regularly replace the power supply battery of the on-board RTC due to battery life to ensure the normal power supply of the on-board RTC, so there will be maintenance costs caused by frequent replacement of power supply batteries in the use of commercial vehicles. Summary of the invention

[0005] The object of the present invention is to provide a power supply management circuit for a vehicle-mounted RTC, so as to solve the problem that in the prior art, when a separate power supply battery is set for a commercial vehicle to power the vehicle-mounted RTC, the power supply battery needs to be frequently replaced, resulting in subsequent maintenance costs.

[0006] To solve the above technical problems, the present invention provides a power supply management circuit for a vehicle-mounted RTC, including a battery power supply circuit, the battery power supply circuit including a power supply battery connected in series to the battery power supply circuit, and also including a system power supply circuit; one end of the system power supply circuit is connected in parallel with one end of the battery power supply circuit, and the parallel point is used to connect the power supply input end of the RTC, the other end of the system power supply circuit is used to connect the vehicle system power supply output end, and the other end of the battery power supply circuit is connected to the ground end; a switch tube is also connected in series to the battery power supply circuit, and the switch tube is used to be turned on when the voltage at the vehicle system power supply output end is less than a set voltage threshold, so as to power the vehicle-mounted RTC through the power supply battery, and to be turned off when the voltage at the vehicle system power supply output end is greater than the set voltage threshold, so as to power the vehicle-mounted RTC through the vehicle system power supply.

[0007] Its beneficial effects are as follows: by setting a power supply management circuit including a system power supply circuit and a battery power supply circuit, and setting a switch tube on the battery power supply circuit to disconnect when there is vehicle system power output and turn on when there is no vehicle system power output, that is, by setting the switch tube, when there is vehicle system power output, the vehicle-mounted RTC can be powered by the system power supply, and when there is no vehicle system power output, the vehicle-mounted RTC can be powered by the power supply battery, thereby ensuring a continuous and uninterrupted power supply process for the vehicle-mounted RTC, and only when there is no vehicle system power output, the vehicle-mounted RTC will be powered by the power supply battery, namely, the use time of the power supply battery is reduced, and thus the time interval for replacing the power supply battery will be extended, namely, compared with the prior art method of only using the power supply battery to power the RTC, the number of times the power supply battery is replaced is reduced within the same time, thereby reducing the maintenance cost of replacing the power supply battery.

[0008] Furthermore, the control end of the switch tube is connected to the system power supply circuit.

[0009] By connecting the control end of the switch tube to the system power supply circuit, the on and off of the switch tube can be controlled by the voltage on the system power supply circuit. That is, when there is no voltage on the system power supply circuit, the switch tube is controlled to be turned on, so that when the system power supply does not supply power to the RTC, the RTC is powered by the power supply battery. When there is voltage on the system power supply circuit, the switch tube is controlled to be disconnected, so that when the system power supply supplies power to the RTC, the power supply process of the power supply battery to the RTC is blocked by disconnecting the switch tube.

[0010] Furthermore, a first anti-reverse diode is connected in series on the system power supply circuit, and the conduction direction of the first anti-reverse diode is the same as the power supply direction of the system power supply circuit.

[0011] An anti-reverse diode is set on the system power supply circuit to prevent the power supply battery from discharging into the system and causing vehicle safety problems when the power supply battery supplies power to the RTC, thereby ensuring the safety of the power supply battery supplying power to the RTC.

[0012] Furthermore, a second anti-reverse diode is connected in series in the circuit between the power supply battery and the parallel point, and the conduction direction of the second anti-reverse diode is the same as the power supply direction of the battery power supply circuit.

[0013] An anti-reverse diode is set on the battery power supply circuit, so that the power supply battery can only discharge outward through the battery power supply circuit, blocking the charging of the power supply battery. Because the power supply battery is a non-rechargeable power supply battery, the setting of the anti-reverse diode ensures that the power supply battery is not charged, thereby ensuring the safety of the power supply battery, that is, ensuring the safety of the vehicle.

[0014] Furthermore, the control end of the switch tube is also connected to the ground end via a sampling resistor.

[0015] By connecting a sampling resistor in series between the ground terminal and the control terminal of the switch tube, and sampling the voltage of the sampling resistor, it is possible to determine whether the vehicle system power supply has a voltage output, and then by obtaining the sampling result of the sampling resistor, the switch tube state of the switch tube can be obtained.

[0016] Furthermore, the system power supply circuit also includes a capacitor, and the capacitor string is arranged between the system power supply circuit and the ground terminal.

[0017] By setting a capacitor between the system power supply circuit and the ground terminal, it can play a filtering role when the system is powered on, and in the initial stage of system power disconnection, the capacitor can discharge the electrical energy stored in it, thereby gradually reducing the output voltage of the system power supply circuit to ensure continuous and uninterrupted power supply to the RTC during the mode conversion from the vehicle system power supply to the power supply battery.

[0018] Furthermore, a current limiting resistor is connected in series between the parallel point and the power supply input terminal of the RTC.

[0019] By connecting a loop resistor in series between the parallel point and the power supply input terminal of the RTC, the battery overload and explosion can be prevented when the vehicle-end load is short-circuited. That is, when the RTC circuit is short-circuited, the current output by the power supply battery and the system power supply is limited, thereby improving system safety.

[0020] Furthermore, the switch tube is a MOS tube, the source and drain of the MOS tube are connected in series between the positive electrode of the power supply battery and the parallel point, and the gate of the MOS tube is connected to the system power supply circuit.

[0021] When the switch tube is a MOS tube, and by connecting the on-off end (i.e., source and drain) of the MOS tube in series to the power supply circuit, and connecting the control end (i.e., gate) of the MOS tube to the system power supply circuit, it can be achieved that when there is a voltage output at the output end of the vehicle system power supply and the voltage is greater than the set voltage threshold, the control end and the conduction end of the MOS tube cannot form a conduction voltage drop, so the MOS tube cannot be turned on, and the system power supply supplies power to the RTC at this time; when there is no voltage output at the output end of the vehicle system power supply or the output voltage is less than the set voltage threshold (i.e., when the system power supply cannot supply power to the RTC), the control end and the conduction end of the MOS tube form a conduction voltage drop, so the MOS tube is turned on, and the power supply battery supplies power to the RTC. Based on the above analysis, by setting the switch tube to a MOS tube, and through the above setting, it can be disconnected when the system power supply supplies power to the RTC, and turned on when the system power supply does not supply power to the RTC, so that the power supply supplies power to the RTC, that is, through this setting, there is no need to set a controller for the switch tube, and the on-off process of the switch tube can be realized, and the power supply demand of the RTC can be met. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the power supply management circuit of the vehicle-mounted RTC of the present invention;

[0023] Figure 2 It is the circuit working sequence of the power supply management circuit of the vehicle-mounted RTC of the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0025] Embodiment of the power supply management circuit of the vehicle RTC:

[0026] The present embodiment is aimed at the power supply management of the on-board RTC of a commercial vehicle (hereinafter referred to as the vehicle), and a power supply management circuit for the on-board RTC is designed. In order to ensure the continuous and uninterrupted power supply of the on-board RTC of the vehicle, a battery power supply circuit for powering the RTC by a power supply battery is provided in the circuit of the present embodiment. In order to extend the service life of the power supply battery, a switch tube is provided on the battery power supply circuit in the present embodiment, and a system power supply circuit for powering the on-board RTC by a system power supply is added, so that when the output voltage of the system power supply is greater than the set voltage threshold (that is, when the system power supply is working externally), the switch tube is disconnected, and then the on-board RTC is powered by the system power supply circuit. That is, by adding the system power supply circuit, the use time of the power supply battery is reduced, thereby increasing the service life of the power supply battery, and the time interval for replacing the power supply battery will be extended. That is, compared with the method of only using the power supply battery to power the RTC in the prior art, the number of times the power supply battery is replaced is reduced within the same time, thereby reducing the maintenance cost of replacing the power supply battery.

[0027] The specific power supply management circuit of the vehicle RTC in this embodiment is as follows: Figure 1 As shown:

[0028] The system power supply circuit includes a ground terminal, a system power supply circuit and a battery power supply circuit. The specific system power supply circuit includes a system power supply input terminal, a system power supply output terminal, a first anti-reverse diode D1 arranged in series between the system power supply input terminal and the system power supply output terminal, and a capacitor arranged in series between the system power supply input terminal and the ground terminal. The system power supply input terminal is used to connect the vehicle system power supply output terminal (i.e. Figure 1 VDD3V3), Figure 1 As shown in , the system power of the vehicle is switched by the main switch and then output by the conversion module to 3.3V power. The voltage of the vehicle system power output terminal connected to the system power output terminal of the embodiment is 3.3V. The conduction direction of the first anti-reverse diode D1 is the same as the power supply direction of the system power supply circuit. Based on the setting of the first anti-reverse diode D1, when the power supply battery supplies power to the RTC, it can avoid the power supply battery from discharging to the system to cause vehicle safety problems, thereby ensuring the safety of the power supply battery supplying power to the RTC. Moreover, by connecting a capacitor in series between the system power supply input terminal and the ground terminal, it can play a filtering role when the system is powered, and in the initial stage of the system power supply disconnection, because the capacitor stores electrical energy, it can be discharged to the outside, thereby enabling the output voltage of the system power supply circuit to gradually decrease, to ensure that in the process of switching the mode from the vehicle system power supply to the power supply battery, the RTC is continuously and uninterruptedly powered.

[0029] The specific battery power supply circuit includes a battery power supply output terminal, a power supply battery BAT1 connected in series between the ground terminal and the battery power supply output terminal, a second anti-reverse diode D3 and a switch tube Q1; wherein the battery power supply output terminal is connected to the system power supply output terminal to form a total output terminal (the connection point is Figure 1 The total output terminal is connected to the power supply input terminal of the vehicle RTC through the loop resistor R2 (i.e. Figure 1 VDD33_RTC in the circuit), the switch tube Q1 is a MOS tube, the source and drain of the MOS tube are connected in series between the positive electrode of the power supply battery and the battery power supply output terminal, and a second anti-reverse diode is also connected in series between the source of the MOS tube and the positive electrode of the power supply battery, and the conduction direction of the second anti-reverse diode is the same as the power supply direction of the battery power supply circuit. The gate of the MOS tube is connected to the circuit between the input terminal of the system power supply circuit and the output terminal of the system power supply circuit through the third anti-reverse diode D2, and the gate of the MOS tube is also connected to the ground terminal through the detection resistor R1.

[0030] Through the setting of the MOS tube in this embodiment, when the switch tube is a MOS tube, and by connecting the on-off end (i.e., the source and the drain) of the MOS tube between the power supply battery and the battery power supply output end, and connecting the control end (i.e., the gate) of the MOS tube to the circuit between the system power supply input end and the system power supply output end, it can be achieved that when the vehicle system power supply output end has a voltage output and the voltage is greater than the set voltage threshold, the control end and the conduction end of the MOS tube cannot form a conduction voltage drop, so the MOS tube cannot be turned on, and the system power supply is used to power the RTC at this time; when the vehicle system power supply output end has no voltage output or the output voltage is less than the set voltage threshold (i.e., the system power supply cannot power the RTC), the control end and the conduction end of the MOS tube form a conduction voltage drop, so the MOS tube is turned on, and the power supply battery supplies power to the RTC. Based on the above analysis, by setting the switch tube to a MOS tube, and through the above setting, it can be disconnected when the system power supply supplies power to the RTC, and turned on when the system power supply does not supply power to the RTC, so that the power supply can supply power to the RTC. That is, through this setting, there is no need to set a controller for the switch tube, and the on-off process of the switch tube can be realized and the power supply requirements of the RTC can be met.

[0031] The second anti-reverse diode D3 is set so that discharge can only be done through the power supply battery, blocking the process of charging the power supply battery. Since the power supply battery is a non-rechargeable power supply battery, the setting of the anti-reverse diode ensures that the power supply battery is not charged, thereby ensuring the safety of the power supply battery, that is, ensuring the safety of the vehicle.

[0032] The detection resistor R1 is set between the ground terminal and the gate of the MOS tube (i.e., the control terminal), and the gate of the MOS tube is connected to the system power supply input terminal. Therefore, the voltage across the detection resistor can be used to determine whether the vehicle system power supply has a voltage output, and then by obtaining the voltage of the detection resistor, the switching state of the MOS tube can be obtained.

[0033] like Figure 1 In this embodiment, a loop resistor R2 is also connected in series between the total output terminal and the power supply input terminal of the RTC. The setting of the loop resistor R2 can prevent the battery from overloading and causing explosion when the vehicle-end load is short-circuited, and when the RTC circuit is short-circuited, it limits the current output by the power supply battery and the system power supply, thereby improving system safety.

[0034] Based on the power supply management circuit setting of the vehicle RTC of this embodiment, the following process of the power supply management method of the vehicle RTC can be implemented:

[0035] 1. When the system is working normally (such as Figure 2 The main switch shown is in the open state): power monitoring circuit (i.e. Figure 1After the circuit (the circuit connected to the MOS tube control end in the circuit) samples the system operating voltage, the MOS switch is disconnected and the system power supply supplies power to the "RTC" clock.

[0036] 1) The system power supply VDD3V3 supplies power to the RTC clock power supply VDD33_RTC through the diode D1.

[0037] 2) The system power supply VDD3V3 forms a loop to the ground (GND) through the diode D2 and the resistor R1, so that the voltage at point "B" is close to VDD3V3. At this time, the switch tube Q1 is in the cut-off state.

[0038] 3) When the battery BAT voltage is lower than the system VDD3V3 (3.3V), Figure 1 The voltage at point "C" shown is close to the system VDD3V3 (3.3V) voltage, and the diode D3 is in the cut-off state, so the BAT battery cannot be charged.

[0039] 4) When the battery BAT voltage is higher than the system VDD3V3 (3.3V), Figure 1 The voltage at point "C" shown is close to the voltage of the battery BAT (3.6V), the Q1 tube is cut off, and the freewheeling diode of the Q1 tube is cut off, ensuring that the battery "BAT (3.6V)" cannot supply power to VDD33_RTC.

[0040] 2. When the system is powered off (such as Figure 2 The main switch shown is in the off state): After the voltage monitoring circuit does not sample the system operating voltage, the MOS switch is turned on, and the "RTC" power supply battery supplies power to the "RTC" clock.

[0041] 1) The system power supply VDD3V3 gradually decreases, causing the voltage at the sampling point "B" to gradually decrease. When the voltage at the sampling point "B" is greater than 0.5V, the Q1 tube is turned on and quickly switches to BAT1 to power the RTC clock circuit.

[0042] 2) When the system power supply VDD3V3 drops to 0V, the B voltage is "0V", the transistor Q1 is fully turned on, and the BAT battery supplies power to the RTC clock circuit.

[0043] 3) When the system power supply VDD3V3 drops to 0V, the diode D1 is in the cut-off state, and the BAT1 battery cannot supply power to the system VDD3V3.

[0044] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. The patent protection scope of the present invention shall be based on the claims. All equivalent structural changes made using the contents of the description and drawings of the present invention should also be included in the protection scope of the present invention.

Claims

1. A power supply management circuit for an on-vehicle RTC, comprising a battery power supply circuit, wherein the battery power supply circuit comprises a power supply battery connected in series to the battery power supply circuit, characterized in that: It also includes a system power supply circuit; one end of the system power supply circuit is connected in parallel with one end of the battery power supply circuit, the parallel point is used to connect the power supply input end of the RTC, the other end of the system power supply circuit is used to connect the vehicle system power supply output end, and the other end of the battery power supply circuit is connected to the ground end; a switch tube is also arranged in series on the battery power supply circuit, the control end of the switch tube is connected to the system power supply circuit, and is connected to the ground end through a sampling resistor; the on-off end of the switch tube is connected in series between the power supply battery and the parallel point, and the switch tube is used to be turned on when the voltage at the output end of the vehicle system power supply is less than the set voltage threshold, so as to power the vehicle-mounted RTC through the power supply battery, and to be disconnected when the voltage at the output end of the vehicle system power supply is greater than the set voltage threshold, so as to power the vehicle-mounted RTC through the vehicle system power supply.

2. The power supply management circuit of the vehicle-mounted RTC according to claim 1, characterized in that: A first anti-reverse diode is also connected in series on the system power supply circuit, and the conduction direction of the first anti-reverse diode is the same as the power supply direction of the system power supply circuit.

3. The power supply management circuit of the vehicle-mounted RTC according to claim 1, characterized in that: A second anti-reverse diode is also connected in series on the circuit between the power supply battery and the parallel point, and the conduction direction of the second anti-reverse diode is the same as the power supply direction of the battery power supply circuit.

4. The power supply management circuit of the vehicle-mounted RTC according to claim 1, characterized in that: The system power supply circuit also includes a capacitor, and the capacitor string is arranged between the system power supply circuit and the ground terminal.

5. The power supply management circuit of the vehicle-mounted RTC according to claim 1, characterized in that: A current limiting resistor is also arranged in series between the parallel point and the power supply input terminal of the RTC.

6. The power supply management circuit of the vehicle-mounted RTC according to claim 1, characterized in that: The switch tube is a MOS tube, the source and drain of the MOS tube are connected in series between the positive electrode of the power supply battery and the parallel point, and the gate of the MOS tube is connected to the system power supply circuit.

Images