CN201589807U - A voltage detection circuit of a reset circuit - Google Patents

Abstract

The utility model provides a voltage detection circuit of a reset circuit, which includes an electronic switch and a voltage stabilizing diode, the cathode of the voltage stabilizing diode is connected to a system power supply, and the anode is connected to the first of the electronic switch through a first resistor. pole and grounded through a second resistor, the second pole of the electronic switch is connected to a standby power supply through a third resistor, the third pole of the electronic switch is connected to one end of a fourth resistor, and the other end of the fourth resistor One end is used as an output end to output a chip reset signal. The voltage detection circuit of the reset circuit provided by the preferred embodiment of the utility model can solve the fault caused by the existing reset circuit when the standby power supply is much slower than the system power supply, the circuit is simple, and the voltage detection circuit can be adjusted according to different situations Potential, high portability, and uses discrete components, good adjustable performance, low cost, high reliability.

Description

A voltage detection circuit of a reset circuit

technical field

The utility model belongs to the technical field of voltage detection circuits, in particular to a voltage detection circuit of a reset circuit.

Background technique

In various household appliances, various reset circuits are often used, including reset circuits using integrated circuit chips, and reset circuits using discrete components. Considering various factors such as cost, the most commonly used ones are Reset circuit using discrete components.

Referring to Fig. 1, it is a common reset circuit in the prior art, wherein, when the power supply +3.3_STB is powered on, since the voltage across the capacitor C1 cannot change abruptly, the voltage sampled by the base B of the triode Q1 through the resistor R2 is low, And the voltage of the emitter E is high, at this time, the emitter E and the collector C are turned on, so that the collector C is high, at this time, the output chip reset signal MCURESET is high level, and the reset of the chip MCU is valid. Subsequently, the power supply +3.3_STB charges the capacitor C1 through the resistor R1. When the base B potential of the triode Q1 is (3.3-0.7-0.6)=2V, the triode Q1 is cut off, the chip restart signal MCURESET signal is low, and the chip MCU Reset removed.

When the power supply +3.3_STB is powered off, the charge of the capacitor C1 is discharged through the diode between pin 1 and pin 3 of the diode device D1. As the potential of +3.3_STB decreases rapidly, the potential of the base B of the transistor Q1 becomes lower. , and the triode Q1 is turned on due to the energy storage capacitor C2, and the chip restart signal MCURESET becomes high until the charge is completely discharged through the resistor R4. The function of the Zener diode D2 is to stabilize the potential of the chip reset signal MCURESET, and prevent the reset pin MCU RESET PIN of the chip from being damaged when the +3.3_STB voltage overshoots. The resistor R3 and capacitor C3 play the role of current limiting and anti-interference.

The advantage of the above reset circuit is that the cost is low, and the purpose of adjusting the parameters of the reset signal can be achieved by adjusting the parameters of each device, and it is flexible to use. However, the power supply used by household appliances usually provides two or more different voltages to meet the different power consumption requirements during startup and standby, so the power-on and power-off sequences of different voltages are often different. , which can cause different kinds of system failures.

For example, in a certain type of TV, the power supply component supplies one 12V voltage and one +3.3_STB voltage to the core board, where the +3.3_STB voltage is used as the power supply voltage of the power management module of the core board of the TV, and is shown in Figure 1 The power supply in the +3.3_STB power supply only consumes about 10 mA in the entire TV core. When the TV is turned on, the +3.3_STB voltage is tens of milliseconds faster than the 12V voltage. Turn off the TV 220V AC When powering on, due to the light current load of +3.3_STB, the power-off is slower than 12V voltage for more than 3 seconds. At this time, there will be problems if the reset circuit shown in Figure 1 is used.

Usually, the 5V voltage or 3.3V voltage used by the peripheral devices in the core is converted by using different voltage conversion devices through the 12V voltage. Therefore, when the 12V is powered down to 0, the above voltages will all become 0. , if the +3.3_STB has not been powered off at this time, the system will not reset, and then supply 12V power to the core, because each device is equivalent to no reset, and the core of the running program and the registers that need to work normally are not If it is initialized to the required value, the movement will not continue to work and will be in a "deadlock" state.

The causes of this failure are usually as follows: 1. The user shuts down the TV quickly within 3 seconds and then starts it again, so that the TV is in a dead state; These two situations often occur in the family, especially in summer. The second phenomenon often occurs. In summer, the grid load is heavy, and sometimes it is automatically protected when it is too large. Turn off the TV directly, and then turn it on again, and you can’t wake it up with the remote control. Only by manually turning off the TV AC and waiting for more than 5 seconds to turn it on again can it return to normal.

Today, people have higher and higher requirements on the reliability of electrical appliances. In order to enhance the reliability of electrical appliances and improve the market competitiveness of electrical appliances, it is necessary to solve the above faults.

Utility model content

The purpose of the utility model is to provide a voltage detection circuit of a reset circuit to increase the reliability of the existing reset circuit and avoid reset failure due to the power-down time difference between the system voltage and the standby voltage.

The technical scheme of the utility model is:

A voltage detection circuit for a reset circuit, comprising an electronic switch and a Zener diode, the cathode of the Zener diode is connected to a system power supply, the anode is connected to the first pole of the electronic switch through a first resistor and passed through a first The two resistors are grounded, the second pole of the electronic switch is connected to a standby power supply through a third resistor, the third pole of the electronic switch is connected to one end of a fourth resistor, and the other end of the fourth resistor is output as an output terminal. A chip reset signal.

Said voltage detection circuit, wherein said electronic switch is a PNP transistor, and its first, second and third poles are base, emitter and collector respectively.

In the voltage detection circuit, the collector of the triode is grounded through a fifth resistor.

In the voltage detection circuit, the other end of the fourth resistor is grounded through a capacitor.

The voltage detection circuit, wherein the voltage detection circuit further includes a Schottky diode, the anode of the Schottky diode is connected to the other end of the fourth resistor, and the cathode is connected to a general-purpose input and output pin of a chip to obtain a control Signal.

In the voltage detection circuit, the control signal is at low level when the standby power supply works alone.

The voltage detection circuit of the reset circuit provided by the preferred embodiment of the utility model can solve the fault caused by the existing reset circuit when the standby power supply is much slower than the system power supply, the circuit is simple, and the voltage detection circuit can be adjusted according to different situations Potential, high portability, and uses discrete components, good adjustable performance, low cost, high reliability.

Description of drawings

Fig. 1 is the circuit diagram of existing a kind of reset circuit;

Fig. 2 is a circuit diagram of a voltage detection circuit of a reset circuit provided by a preferred embodiment of the present invention;

Fig. 3 is a circuit diagram after the voltage detection circuit of the reset circuit provided by the preferred embodiment of the present invention is applied to the existing reset circuit.

Detailed ways

In order to make the purpose, technical solution and advantages of the utility model clearer, the utility model will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the utility model, and are not intended to limit the utility model.

Referring to Fig. 2, a voltage detection circuit of a reset circuit provided by a preferred embodiment of the present invention includes a PNP transistor Q2 and a Zener diode D3, the cathode of the Zener diode D3 is connected to the power supply +12V_ALL, and the anode passes through The resistor R5 is connected to the base B of the triode Q2, the anode of the regulator tube D3 is also grounded through the resistor R6, and the emitter E of the triode Q2 is connected to the power supply +3.3_STB through the resistor R7 as the output voltage source of the voltage detection circuit , the collector C of the triode Q2 is grounded through the resistor R8, and the chip reset signal MCURESET is output through the resistor R9. In order to prevent the interference of the short-term power failure, the output terminal of the chip reset signal MCURESET is grounded through a capacitor C4.

The triode Q2 is used as an output voltage switch of the voltage detection circuit, and as other implementation manners, other electronic switches may also be used for replacement.

In a preferred embodiment of the present utility model, the zener diode D3 is a 5.6V zener tube. Therefore, when the above-mentioned voltage detection circuit is powered down to 5.6+3.3-0.6=8.3V when the power supply +12V_ALL is powered down, the triode Q2 The emitter E and the collector C are turned on. At this time, because the power supply +3.3_STB is powered off slower than the power supply +12V_ALL, the chip reset signal MCURESET is at a high level, and the chip is reset.

The voltage detection circuit provided by the utility model is used as an auxiliary part of the reset circuit, and it is required to stop working when the electrical appliance is in normal operation and enters the standby state. Therefore, it is necessary to add a Schottky diode D4, and the cathode of the Schottky diode D4 is connected to A general-purpose input and output pin MCU GPIO of the chip obtains a control signal SAR1, and the anode is connected to the output terminal of the chip reset signal MCURESET to control the effective time of the reset signal MCURESET. The above chip is powered by +3.3_STB, as long as +3.3_STB is not Power off, it can work normally.

It should be noted that the control signal SAR1 connected to the cathode of the Schottky diode D4 is obtained from a general-purpose input and output pin MCU GPIO of the chip. When the power +12V_ALL is powered on, the control signal SAR1 is high when the chip is operating normally. When the whole machine enters the standby state, the control signal SAR1 is low level.

Referring to Figure 3, it is the reset circuit after adding the above voltage detection circuit. The original reset circuit is described in the background technology. When the power supply +3.3_STB is much slower than the power supply +12V_ALL, the power supply +12V_ALL quickly powers off and then on. Electricity will lead to system disorder, unable to reset and cause failure to start the machine. At this time, the above-mentioned voltage detection circuit can solve this failure.

The working principle of the reset circuit after adding the above voltage detection circuit is as follows: when the power supply +12V_ALL and +3.3_STB are normal, the transistor Q2 is in the cut-off state, and cooperates with the original reset circuit, the chip reset signal MCURESET is low level. When the power supply +12V_ALL is powered down to 5.6+3.3-0.6=8.3V after the AC is turned off under normal working conditions, the emitter E and collector C of the triode Q2 are turned on. If the power supply +3.3_STB is still there, then The control signal SAR1 is high, the collector C of the transistor Q2 outputs a high level, then the chip reset signal MCURESET becomes high, the chip enters the reset state, and then the power supply +12V_ALL is powered on again when the power supply +3.3_STB has not been powered off. Then when the power reaches 8.3V, the transistor Q2 is cut off, the chip reset signal MCURESET becomes low level again, and the reset is released, then the chip restarts and enters the normal state.

When the chip is required to enter the standby state, the control signal SAR1 is at a low level, and at this time the power supply +12V_ALL is at a low level, although the emitter E and the collector C of the triode Q2 are turned on, but since the control signal SAR1 is low, The chip reset signal MCURESET is clamped to the level of 0.3V by the Schottky diode D4, which is a low level for the chip reset, and the chip will not reset. When it becomes low level, due to the above-mentioned clamping effect, it will not enter the reset state and is still in the standby state. When the standby state enters the power-on state, the control signal SAR1 is pulled high to enter the state of the voltage detection circuit operating.

The sensitivity of the voltage detection circuit is reduced by capacitor C4, which can prevent accidental power supply +12V_ALL power-off spikes. The chip can work normally, but the reset problem is caused by the voltage detection circuit.

The above-mentioned voltage detection circuit can solve the fault caused by the existing reset circuit when the standby power supply is much slower than the system power supply. The circuit is simple, and the voltage detection potential can be adjusted according to different situations. It has high portability and uses discrete components, good adjustable performance, low cost and high reliability.

It should be understood that the above description is only a preferred embodiment of the present utility model, and is not intended to limit the protection scope of the present utility model. For those of ordinary skill in the art, any modification, equivalent replacement and Improvements and the like should all be included within the protection scope of the present utility model.

Claims (6)

1. the voltage detecting circuit of a reset circuit, it is characterized in that: described voltage detecting circuit comprises an electronic switch and a voltage stabilizing diode, the negative electrode of described voltage stabilizing diode connects a system power supply, anode connects first utmost point of described electronic switch and passes through one second resistance eutral grounding by one first resistance, second utmost point of described electronic switch connects a standby power by one the 3rd resistance, the 3rd utmost point of described electronic switch connects an end of one the 4th resistance, and the other end of described the 4th resistance is exported a chip reset signal as output terminal.

2. voltage detecting circuit according to claim 1 is characterized in that, described electronic switch is the positive-negative-positive triode, its first, second and the 3rd utmost point be respectively base stage, emitter-base bandgap grading and collector.

3. voltage detecting circuit according to claim 2 is characterized in that, the collector of described triode is also by one the 5th resistance eutral grounding.

4. voltage detecting circuit according to claim 1 is characterized in that, the other end of described the 4th resistance is by a capacity earth.

5. according to the described voltage detecting circuit of arbitrary claim in the claim 1 to 4, it is characterized in that, described voltage detecting circuit also comprises a schottky diode, the anode of described schottky diode connects the other end of the 4th resistance, and the general input and output pin that negative electrode connects a chip obtains a control signal.

6. voltage detecting circuit according to claim 5 is characterized in that, control signal was a low level when described standby power worked independently.

Images