Reset circuit using KL15 ignition signal for hard reset
By designing a reset circuit that utilizes the KL15 ignition signal, the high cost and reset failure problems caused by the hard reset function relying on external chips in the prior art are solved, and the MCU hard reset function with wide applicability, low cost and reliability is achieved.
Patent Information
- Application Number
- CN202411624345.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-14
- Publication Date
- 2025-03-04
AI Technical Summary
In existing automotive electronic controllers, the hard reset function relies on external reset chips, resulting in high hardware cost, large PCB space, and failure in resetting the hardware watchdog when the MCU software is abnormal.
A reset circuit that uses the KL15 ignition signal to hard reset is designed to realize forced reset of the MCU through discrete components (such as the first resistor, the second resistor, the third resistor, the first capacitor and the transistor), replacing the traditional external reset chip.
The design is widely applicable, has low hardware costs, is easy to implement and has high reliability, and has good scalability. It can help customers reduce costs and improve efficiency, while flexibly adapting to different customers' different needs.
Smart Images
Figure CN119561530A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of automobile electronic controllers, and in particular to a reset circuit utilizing a KL15 ignition signal for hard reset. Background Art
[0002] With the rapid development of automotive electronic technology, electronic control units (ECUs) are increasingly used in automobiles. However, the extensive use of ECU controllers also brings the risk of increased software complexity, especially in modules involving functional safety, which may lead to serious consequences. To deal with such problems, the commonly used solution is to add a "hard reset" function to the MCU in the controller, that is, when the software runs abnormally, the MCU is automatically restarted through a "hard reset", thereby eliminating or reducing the uncontrollable factors caused by software abnormalities.
[0003] Most current "hard reset" solutions rely on external reset chips or watchdog reset chips. Since almost every controller needs to be configured with this reset function, this solution significantly increases the hardware cost. At the same time, if the MCU software runs abnormally, in many cases, the hardware dog feeding signal is still normal, but the program is abnormal. In actual operation, more users will perform KL15 power (key power) operations on the entire vehicle when they encounter problems. In this case, since the chip is already in an abnormal state, the hardware watchdog cannot reset the MCU normally. In the current automotive manufacturing industry, hardware cost control has become an important assessment indicator for car manufacturers and parts suppliers, so this solution is gradually becoming less economical at this stage. In addition, adding external chips also takes up valuable PCB space. With the increase in controller functions and size restrictions, how to achieve reliable functions with the least components has become as important as cost control. Summary of the invention
[0004] In order to overcome the above-mentioned shortcomings, the present invention provides a reset circuit which utilizes the KL15 ignition signal for hard reset.
[0005] The present invention achieves the above-mentioned purpose through the following technical solutions:
[0006] A reset circuit using a KL15 ignition signal for hard reset comprises a first resistor, a second resistor, a third resistor, a first capacitor and a triode, wherein the base of the triode is electrically connected to the first resistor via the second resistor and the first capacitor, one end of the second resistor is connected to the first resistor, the other end of the second resistor is electrically connected to the first capacitor, the emitter of the triode is grounded, and the collector of the triode is externally connected to a DC voltage power supply via the third resistor.
[0007] Preferably, a second capacitor is further included, and the collector of the transistor is grounded via the second capacitor. The second capacitor can stabilize the output voltage value of the collector of the transistor.
[0008] Preferably, the resistance of the second resistor R2 is 20 MΩ.
[0009] Preferably, the transistor is a 2N3904 transistor.
[0010] Preferably, the capacitance value of the first capacitor C1 is 100nF.
[0011] The beneficial effects of the present invention are as follows: in the reset circuit using the KL15 ignition signal hard reset, the traditional external reset chip or external watchdog chip is replaced by a discrete component design, and has the advantages of wide applicability, low hardware cost, easy implementation and high reliability. Its design has good scalability, and can flexibly adapt to the differentiated needs of different customers while helping customers reduce costs and improve efficiency. BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The present invention will now be described by way of example with reference to the accompanying drawings, in which:
[0013] Figure 1 It is a circuit schematic diagram of the present invention;
[0014] Figure 2 It is a circuit simulation diagram of the present invention. DETAILED DESCRIPTION
[0015] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention.
[0016] like Figure 1 and Figure 2 As shown, a reset circuit using a KL15 ignition signal for hard reset includes a first resistor R1, a second resistor R2, a third resistor R3, a first capacitor C1 and a transistor Q1, wherein the base of the transistor Q1 is electrically connected to the first capacitor C1 and the first resistor R1, one end of the second resistor R2 is connected to the first resistor, and the other end is electrically connected to the first capacitor C1, the emitter of the transistor Q1 is grounded, and the collector of the transistor Q1 is externally connected to a DC voltage power supply through the third resistor R3.
[0017] In the vehicle system, the KL15 ignition signal is commonly present in each ECU. The present invention utilizes the ignition signal to realize the forced reset of the MCU, thereby providing a solution without an external reset chip. The present invention has the advantages of wide applicability, low hardware cost, easy implementation and high reliability. Its design has good scalability, and can flexibly adapt to the differentiated needs of different customers while helping customers reduce costs and improve efficiency.
[0018] In this system, KL15: vehicle ignition signal; VDD_MCU: MCU power supply, which is normal power, converts the vehicle battery power into the power supply voltage required by MCU through LDO; RESET_MCU: reset signal transmitted to MCU.
[0019] When KL15 is powered on, the first capacitor C1 will be charged. The charging time of the first capacitor C1 is determined by the circuit characteristics when the input switch KL15 is turned on. In the initial state, C1 is charged through the current limiting resistor R1. According to the basic principle of capacitor charging, the relationship between its charging voltage V(t) and time can be expressed as: V(t) = V KL15 ×(1-e -t / R1C1 ), when the first capacitor C1 is charged to a certain voltage value, so that the current flowing into the base of the transistor Q1 is reduced to a level insufficient to maintain its on state, Q1 will change from the on state to the off state, thereby restoring RESET_MCU to a high level. Figure 1 The circuit shown in the figure calculates the charging time. The first capacitor C1 is 100nF, the first resistor, i.e. the current limiting resistor R1, is 10kΩ, and the input voltage KL15 is generally 12V. When KL15 is turned on, the first capacitor C1 starts to charge through the first resistor R1. The charging time constant τ of the capacitor is calculated as follows:
[0020] τ 充电 =R1*C1=10,000Ω*100*10 -9 F = 0.0001 seconds (1 millisecond). After one time constant (1 millisecond), the voltage on the first capacitor C1 has reached about 63% of the maximum voltage value (12V). Generally speaking, after charging for about 5 time constants, the capacitor is close to being fully charged (reaching about 99% of the final voltage). Therefore, the charging time of the first capacitor C1 is about 5 milliseconds, which is enough to reset the MCU.
[0021] When KL15 is disconnected, the first capacitor C1 is slowly discharged through the second resistor R2. The time constant of the discharge process is τdischarge=R2*C1=20,000,000Ω*100*10-9F=2 seconds. It usually takes 5τdischarge=10 seconds to discharge to close to 0V (about 1% or less). The discharge time of the first capacitor can be adjusted by adjusting the resistance value of the second resistor to ensure that the capacitor has sufficient time to recover to the initial state before the next trigger. This charging and discharging design ensures that the RESET_MCU signal can be triggered quickly after a short charging time.
[0022] The transistor selected in this circuit is the 2N3904 transistor. Common small-signal NPN transistors usually start to conduct at a few microamperes. In order to realize the function of this circuit, it is necessary to select a transistor with a higher base current starting threshold. The minimum base current of the 2N3904 transistor depends on the required collector current (i.e., the operating point) and the DC current gain of the transistor. Generally speaking, the base current needs to be large enough to ensure that the transistor enters the saturation region or the linear operating region. By calculating its starting conduction base current in the linear operating region and the saturation region, it is about 10uA. In this circuit scheme, the base current of the transistor Q1 is about 5uA, which is much smaller than the conduction threshold.
[0023] Specifically, the capacitance value of the first capacitor C1 is 100nF.
[0024] Specifically, the transistor Q1 is a 2N3904 transistor.
[0025] Specifically, the resistance of the second resistor R1 is 20 MΩ.
[0026] The above is based on the present invention as an inspiration. Through the above description, relevant staff can make various changes and modifications without departing from the technical idea of this invention. The technical scope of this invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.
Claims
1. A reset circuit using a KL15 ignition signal hard reset, characterized in that: It includes a first resistor, a second resistor, a third resistor, a first capacitor and a transistor, the base of the transistor is electrically connected to the first resistor through the second resistor and the first capacitor, one end of the second resistor is connected to the first resistor, the other end of the second resistor is electrically connected to the first capacitor, the emitter of the transistor is grounded, and the collector of the transistor is externally connected to a DC voltage power supply through the third resistor.
2. The reset circuit for hard reset using KL15 ignition signal according to claim 1, characterized in that: A second capacitor is also included, and the collector of the transistor is grounded via the second capacitor.
3. The reset circuit for hard reset using KL15 ignition signal according to claim 1, characterized in that: The transistor is an NPN transistor.
4. The reset circuit for hard reset using KL15 ignition signal according to claim 1, characterized in that: The transistor is a 2N3904 transistor.
5. The reset circuit using the KL15 ignition signal hard reset according to claim 1, characterized in that: The capacitance value of the first capacitor and the resistance value of the first resistor can determine the charging time of the first capacitor C1. The charging time is the time when RESET_MCU generates a low level reset. The capacitance value of the first capacitor C1 selected in the present invention is 100nF, and the resistance value of the first resistor R1 selected is 10KΩ.
6. The reset circuit using the KL15 ignition signal hard reset according to claim 1, characterized in that: The capacitance value of the first capacitor and the resistance value of the second resistor can determine the discharge time of the first capacitor C1. The discharge time is sufficient time for the capacitor to recover to its initial state when KL15 is turned off. The capacitance value of the first capacitor C1 selected in the present invention is 100nF, and the resistance value of the second resistor R2 selected is 20MΩ.