CN221783913U

CN221783913U - A dual power supply switching circuit

Info

Publication number: CN221783913U
Application number: CN202323639511.1U
Authority: CN
Inventors: 梅晨凯
Original assignee: Zhejiang Dusun Electron Co ltd
Current assignee: Zhejiang Dusun Electron Co ltd
Priority date: 2023-12-29
Filing date: 2023-12-29
Publication date: 2024-09-27
Anticipated expiration: 2033-12-29

Abstract

The utility model provides a dual-power supply switching circuit which comprises an ideal diode module, a dual-power supply switching module, a hysteresis comparison module and an overvoltage protection module, wherein the ideal diode module comprises a P-MOSFET (metal-oxide-semiconductor field effect transistor) Q3, a PNP triode Q4 and a PNP triode Q5, the dual-power supply switching module comprises a P-MOSFET Q1 and a capacitor C1, the hysteresis comparison module comprises an NPN triode Q7 and an NPN triode Q6, and the overvoltage protection module comprises a PNP triode Q9 and a voltage stabilizing diode D1. The utility model has the advantages that the ideal diode module can realize the function of unidirectional conduction of the diode, the conduction voltage drop is extremely small and can be ignored generally, and the power loss and the heat are greatly reduced; the hysteresis comparison module can enable the circuit to have different trigger thresholds under the condition that the voltage is increased in the positive direction and decreased in the negative direction, and circuit instability caused by voltage noise or jitter is avoided.

Description

Dual-power switching circuit

Technical Field

The utility model belongs to the technical field of power supply, and particularly relates to a dual-power switching circuit.

Background

When the normal power fails suddenly or fails, the device is automatically switched to the standby power supply through the double-power supply switching, so that the device can still normally operate. Most commonly elevators, fire protection, monitoring, lighting etc.

The diode in the current dual-power switching circuit is a common device, and the diode has the characteristics of forward conduction, reverse conduction and a conduction voltage in the forward conduction, and the conduction voltage is about 0.3V-0.7V according to different materials. When the current is larger, the diode has larger power consumption, so that the heat generation is serious; in addition, in the dual power supply switching circuit, circuit instability is sometimes caused by voltage noise or jitter, so that power loss is caused.

Disclosure of utility model

Based on the above-mentioned problems, it is an object of the present utility model to provide a dual power switching circuit, which has overvoltage protection and hysteresis comparison functions, prevents circuit instability caused by voltage noise or jitter, and greatly reduces power loss and heat.

The technical scheme of the utility model is as follows: a dual power supply switching circuit comprises an ideal diode module, a dual power supply switching module, a hysteresis comparison module and an overvoltage protection module,

The ideal diode module comprises a P-MOSFET Q3, a PNP triode Q4 and a PNP triode Q5, wherein the D end of the P-MOSFET Q3 is connected with an input power supply VCC1, the connection part of the G end of the P-MOSFET Q3 and the C end of the PNP triode Q5 is VCQ5, the S end of the P-MOSFET Q3 is connected with the E end of the PNP triode Q5, the connection part of the B end of the PNP triode Q5 and the B end of the PNP triode Q4 is VBASE, the C end of the PNP triode Q5 is grounded through a resistor R9, the E end of the PNP triode Q4 is connected with an input power supply VCC1, the VBASE is connected with the C end of the PNP triode Q4, the C end of the PNP triode Q4 is grounded through a resistor R8, the S end of the P-MOSFET Q3 is connected with an output end VOUT,

The dual power supply switching module comprises a P-MOSFET Q1 and a capacitor C1, wherein the D end of the P-MOSFET Q1 is connected with a power supply VDD_5V, the G end of the P-MOSFET Q1 is grounded through a resistor R1 and is connected with an input power supply VCC1 through a resistor R2, the S end of the P-MOSFET Q1 is connected with an output end VOUT and is grounded through the capacitor C1 and a resistor R14,

The hysteresis comparison module comprises an NPN triode Q7 and an NPN triode Q6, wherein the end B of the NPN triode Q7 is connected with one end of a resistor R16, the other end of the resistor R16 is respectively connected with an input power VCC through a resistor R6 and grounded through a resistor R10, the end B of the NPN triode Q6 is connected with the end C of the NPN triode Q7, the end C of the NPN triode Q6 and the end C of the NPN triode Q7 are respectively connected with a power VDD_5V through a resistor R5 and a resistor R4, the end E of the NPN triode Q7 and the end E of the NPN triode Q6 are grounded through a resistor R11, the end C of the NPN triode Q6 is also connected with the end G of a P-MOSFET Q8, the end D of the P-MOSFET Q8 is connected with the end G of the P-MOSFET Q2 through a resistor R7, the end S of the P-MOSFET Q2 is connected with the input power VCC through a resistor R3, the end P-MOSFET Q2 is connected with the end Q2 through a resistor R15, the end Q2 is grounded through a resistor R1,

The overvoltage protection module comprises a PNP triode Q9 and a voltage stabilizing diode D1, wherein the E end of the PNP triode Q9 is connected with an input power supply VCC, the B end of the PNP triode Q9 is connected with a resistor R13, the other end of the resistor R13 is connected with the input power supply VCC through a resistor R12 respectively, the other end of the resistor R13 is grounded through the voltage stabilizing diode D1, and the C end of the PNP triode Q9 is connected with the G end of the P-MOSFET Q2.

Further, the P-MOSFET is model CJ2301.

Further, the model numbers of the PNP triodes are MMBT3906.

Further, the model of the NPN triode is MMBT3904.

The utility model has the advantages and positive effects that: by adopting the technical scheme, the ideal diode module can realize the function of unidirectional conduction of the diode, and the conduction voltage drop is extremely small and can be ignored generally, so that the power loss and the heat are greatly reduced; the hysteresis comparison module can enable the circuit to have different trigger thresholds under the condition that the voltage is increased in the positive direction and decreased in the negative direction, and circuit instability caused by voltage noise or jitter is avoided.

Drawings

Fig. 1 is a schematic view of the overall structure of the present utility model.

Fig. 2 is a schematic diagram of an ideal diode module.

Fig. 3 is a schematic diagram of a dual power switching module.

FIG. 4 is a schematic diagram of a hysteresis comparison module.

Fig. 5 is a simulation diagram of a hysteresis-free comparison module.

Fig. 6 is a simulation diagram with a hysteresis comparison module.

Fig. 7 is a schematic diagram of an overvoltage protection module.

Fig. 8 is a simulation diagram of an overvoltage protection module.

Fig. 9 is a circuit diagram of the present utility model.

Fig. 10 is a waveform simulation diagram of the input voltage VCC and the output voltage VOUT during the VCC rising process.

Fig. 11 is a waveform simulation diagram of the input voltage VCC and the output voltage VOUT during the VCC falling process.

Description of the embodiments

As shown in fig. 1, the technical scheme of the utility model is as follows: comprises an ideal diode module, a dual-power switching module, a hysteresis comparison module and an overvoltage protection module,

As shown in fig. 2, the ideal diode module includes a P-MOSFET Q3, a PNP transistor Q4, and a PNP transistor Q5, the D terminal of the P-MOSFET Q3 is connected to the input power VCC1, the connection between the G terminal of the P-MOSFET Q3 and the C terminal of the PNP transistor Q5 is VCQ5, the S terminal of the P-MOSFET Q3 is connected to the E terminal of the PNP transistor Q5, the connection between the B terminal of the PNP transistor Q5 and the B terminal of the PNP transistor Q4 is VBASE, the C terminal of the PNP transistor Q5 is further grounded through a resistor R9, the E terminal of the PNP transistor Q4 is connected to the input power VCC1, the VBASE is connected to the C terminal of the PNP transistor Q4, the C terminal of the PNP transistor Q4 is grounded through a resistor R8, and the S terminal of the P-MOSFET Q3 is connected to the output terminal VOUT.

When VCC1 > VOUT, P-MOSFET Q3 will raise VOUT to VCC1-0.7V through its own body diode (if VOUT itself is greater than VCC1-0.7V, the body diode will not conduct); meanwhile, as VBASE is grounded through R8, namely VBASE=0V, VBE=VBASE-VCC 1 < -0.7V of the PNP triode Q4 accords with the conduction condition, the PNP triode Q4 is conducted and is in a critical saturated state, and VBASE is pulled up to VCC1-0.7V; vbe=0v or > -0.7v of PNP transistor Q5 at this time, in the off state or slightly on state, collector current ICQ5 of Q5 is 0 or small; the grid electrode of the P-MOSFET Q3 is pulled to the ground by a resistor R9 or the voltage is lower, VGS is smaller than the starting voltage-2V, the conduction condition is met, Q3 is conducted, VOUT is directly connected with VCC1, and forward conduction is achieved.

When VCC1 < = VOUT, VBASE is grounded through R8, namely VBASE = 0V, VBE = VBASE-VOUT < -0.7V of PNP triode Q5 accords with the conduction condition, PNP triode Q5 switches on, and VBASE is pulled up to VOUT-0.7V. vbe=vbase-VCC 1=vout-0.7V-VCC 1 > -0.7V of PNP transistor Q4, is not in compliance with the on condition, and Q4 is in the off state. And because the resistors R8 and R9 take values, Q5 is in a saturated conduction state, VGS of Q3 is equal to the saturated conduction voltage VCE of Q5, namely-0.3V, which is larger than the starting voltage-2V, and the resistor does not accord with the conduction condition, and Q3 is in a closing state.

In summary, in this circuit, the P-MOSFET Q3 is turned on only when the voltage VCC1 on the left side is greater than the voltage VOUT on the right side, and the on-resistance Rdson is very small, usually only several tens of mΩ, due to the characteristics of the MOSFET, so that the on-voltage drop is very small in most cases.

As shown in fig. 3, the dual power switching module includes a P-MOSFET Q1 and a capacitor C1, wherein a D end of the P-MOSFET Q1 is connected to a power supply vdd_5v, a G end of the P-MOSFET Q1 is grounded through a resistor R1 and is connected to an input power supply VCC1 through a resistor R2, and an S end of the P-MOSFET Q1 is connected to an output end VOUT and is grounded through the capacitor C1 and a resistor R14.

For convenience, the ideal diode circuit is replaced by a diode symbol, and it is assumed that the forward conduction voltage drop of the diode D3 is close to 0.

When VCC1 < 2.3V, P-MOSFET Q1 will increase VOUT to 5-0.7=4.3V through its own body diode, at this time, VGS=VCC1-VOUT < -2V of Q1 accords with the conduction condition, Q1 switches on, VOUT and VDD_5V are directly connected, VGS further reduces, Q1 keeps on.

When 2.3V < VCC1 < 4.3V, VGS of p-MOSFET Q1 does not meet the on condition, Q1 is turned off and VOUT continues to be generated by vdd_5v through the body diode of Q1, remaining at 5-0.7=4.3V.

When VCC1 > 4.3V, VGS of P-MOSFET Q1 does not meet the on condition, Q1 is off, vout=vcc 1.

It should be noted here that when 2.3V < VCC1 < 4.3V is in this interval, the output voltage VOUT is generated by vdd_5v through the body diode of Q1, and there is a 0.7 drop across the body diode, resulting in the output voltage VOUT dropping, which not only affects the subsequent output voltage, but also generates power consumption and heat on the P-MOSFET Q1, thereby damaging Q1. In the practical application process, the hysteresis comparison module can avoid the interval.

As shown in FIG. 4, the hysteresis comparison module comprises an NPN triode Q7 and an NPN triode Q6, wherein the end B of the NPN triode Q7 is connected with one end of a resistor R16, the other end of the resistor R16 is respectively connected with an input power VCC through the resistor R6 and grounded through a resistor R10, the end B of the NPN triode Q6 is connected with the end C of the NPN triode Q7, the end C of the NPN triode Q6 and the end C of the NPN triode Q7 are respectively connected with a power VDD_5V through a resistor R5 and a resistor R4, the end E of the NPN triode Q7 and the end E of the NPN triode Q6 are both grounded through a resistor R11, the end C of the NPN triode Q6 is also connected with the end G of a P-MOSFET Q8, the end S of the P-MOSFET Q8 is grounded, the end D of the P-MOSFET Q8 is connected with the end G of the P-MOSFET Q2 through the resistor R7, the end S of the P-MOSFET Q2 is connected with the end P-MOSFET Q2 through the resistor R15, and the end Q2 is connected with the end Q2 through the resistor R1.

The hysteresis comparison module can change the inversion threshold of the output voltage Vst by adjusting the resistance values of the resistors R4, R5 and R11, i.e. can cause Vst to invert at different VCCs. The following effects can be achieved by matching an N-MOSFET Q8 and a P-MOSFET Q2: when VCC rises to an on threshold VCCopen, Q2 is turned on, and an output voltage VCC 1=vcc; when VCC falls to the off threshold VCCclose, Q2 is turned off, and the output voltage VCC 1=0v. Typically VCCopen > VCCclose, and both voltage thresholds can be adjusted. VCCopen =6.2v was taken in this example, vcccs=5v. This has two benefits, 1: adding hysteresis, if the VCC voltage has interference or jitter, avoiding frequent switching of the follow-up dual-power switching circuit and causing instability of the circuit; 2: in order to avoid the heat generation of the P-MOSFET Q1 in the interval of 2.3V < VCC1 < 4.3V in the dual power supply switching circuit, the VCC1 is cut off directly when the VCC1 is less than 5V.

Before VCC rises to 6.2V, NPN triode Q7 is cut off due to the existence of divider resistors R6 and R10, the base electrode of NPN triode Q6 is connected to VDD_5V through R4, the emitter electrode is connected to ground through R11, the voltage is in accordance with the conduction condition, Q6 is turned on, the output voltage Vst of the hysteresis comparison module is pulled down to a level close to ground, N-MOSFET Q8 is turned off, P-MOSFET Q2 is turned off, the output voltage VCC1 of Q2 is 0V, and the power supply of the whole circuit is provided by VDD_5V. The base current and collector current of Q6 combine to form an emitter current ICQ6 flowing through R11, creating a voltage V1' across R11.

When VCC rises to 6.2V, the voltage divided by R10 is applied to the base of Q7, at this time, the difference between the base voltage V2 and the emitter voltage V1 'of Q7 reaches 0.7, defined as V2', i.e. VBE of Q7 reaches 0.7V, which meets the on condition, Q1 is turned on, and Q7 enters the saturated on state due to the values of R6, R16, R4 and R11, the collector voltage of Q7, i.e. the base voltage of Q6, is pulled down to v3=v1+0.3, and V1 is the emitter voltage of Q6, which is equal to the difference between the base voltage V3 and the emitter voltage V1 of Q6 at this time, which is only 0.3V, does not meet the on condition, Q6 is turned off, the output voltage Vst of the hysteresis comparison module is pulled up to vdd_5v by R5, n-MOSFET Q8 is turned on, P-MOSFET Q2 is turned on, and output voltage VCC of Q2=vcc of the whole circuit is supplied by VCC. The base current and collector current of Q7 combine to emitter current ICQ7 flowing through R11, creating a voltage V1 "on R11, ICQ7 < ICQ6 due to the values of R6, R16, R4 and R5, such that V1" < V1', note that the difference between V1 "and V1' is the key to the hysteresis comparison module.

During the process of VCC rising to 6.2V and then falling, since the value of the voltage V1 at R11 is V1 ", the base voltage v2=v2″ of Q7 is V1" =v1 "+0.7V, and since V1" < V1', V2 "< V2', VCC can fall to a level less than 6.2V without turning off Q7, V2 < V2" is not caused until VCC falls to the off threshold value 5V, and Q7 is turned off, so that the circuit state is turned over again, vst is pulled down, N-MOSFET Q8 is turned off, P-MOSFET Q2 is turned off, the output voltage VCC1 of Q2 is 0V, and the power supply of the whole circuit is provided by vdd_5v.

In the following, we simulate the working state and output state of the dual power switching module under the condition of the hysteresis comparison module.

As shown in fig. 5, for the hysteresis-free comparison module, the middle waveform input voltage VCC is set to rise from 0V to 10V and then fall to 0V from the leftmost end; the uppermost waveform is the stabilized power supply vdd_5v; the lowest square waveform is the output voltage VOUT, and by the two scales being called out, it can be seen that when VCC rises to about 2.3V, the output voltage VOUT starts to drop and falls to about 4.3V, until VCC rises to about 4.3V, the output voltage VOUT starts to follow the VCC rise, and this state is also present during the VCC drop, conforming to the judgment of voltage drop in this interval of 2.3V < VCC1 < 4.3V when introducing the dual power supply switching module.

As shown in fig. 6, with the hysteresis comparison module, when VCC rises to about 6.2V, VOUT begins to have an output, and the output follows the VCC voltage; when VCC drops to about 5V, the output voltage VOUT is switched from VCC power to vdd_5v power. It can be seen that the hysteresis comparison module provides a larger on threshold VCCopen =6.2v and a smaller off threshold VCCclose =5v, which meets the above criteria and perfectly avoids VOUT voltage drop during VCC rise and drop.

In summary, the hysteresis comparison module can enable the circuit to have different trigger thresholds under the condition that the voltage increases positively and decreases negatively, so as to avoid unstable circuit caused by voltage noise or jitter.

As shown in fig. 7, the overvoltage protection module includes a PNP triode Q9 and a zener diode D1, the E terminal of the PNP triode Q9 is connected to an input power VCC, the B terminal of the PNP triode Q9 is connected to a resistor R13, the other terminal of the resistor R13 is connected to the input power VCC through a resistor R12, and is grounded through the zener diode D1, and the C terminal of the PNP triode Q9 is connected to the G terminal of the P-MOSFET Q2.

The function of the overvoltage protection circuit is to cut off VCC in order to protect the following circuits after the input voltage VCC exceeds a certain value (in this case, about 8.2V). Wherein D1 is a zener diode having a voltage regulation value of 7.5V.

When VCC < 7.5V, almost all the voltage is on zener diode D1, VBE of PNP transistor Q9 is approximately 0, and Q9 is off without conforming to the on condition. The P-MOSFET Q2 is pulled down to a level close to ground by R7, VGS < -2V of Q2 accords with the conduction condition, Q2 is conducted, and the circuit output VCC1=VCC.

When 7.5 < VCC < 8.2V, the zener diode D1 operates normally, the regulated voltage is 7.5V, the remaining voltage is applied to the resistor R12, 0V < VBE < 0.7V of the PNP transistor Q9, the on condition is not met, Q9 is turned off, and in the former case Q2 is turned on, and the circuit output VCC1 = VCC.

When VCC > =8.2v, the zener diode D1 works normally, the regulated voltage is 7.5V, the rest voltage is applied to the resistor R12, the voltage across the resistor R12 exceeds 0.7V, Q9 can be turned on, and Q9 is in a saturated on state due to the resistance selection of the resistors R13 and R7, and the collector voltage vcq9=vcc-0.3V of Q9. At this time, vgs=vcq9-vcc= -0.3V > -2V of the P-MOSFET Q2, the on condition is not met, Q2 is turned off, and the circuit output voltage VCC1 is 0, thereby realizing overvoltage protection.

In this embodiment, the P-MOSFET is of the type CJ2301.

In this embodiment, the model of the PNP transistor is MMBT3906.

In this embodiment, the model of NPN triode is MMBT3904.

In this embodiment, the turn-on condition of the P-MOSFET is VGS < vgsth= -2V, the body diode voltage drop of the P-MOSFET is 0.7V, the turn-on voltage drop VBE of the npn transistor is=0.7v, and it is assumed that the turn-on voltage drop VBE of the PNP transistor is= -0.7v, and the saturation VCE of the PNP transistor is= -0.3V.

As shown in fig. 8, the operating state of the overvoltage protection circuit is simulated. The input voltage is VCC, and the collector voltage of PNP triode is also the gate voltage of P-MOSFET Q2 is VCQ9. It can be seen that when VCC rises to around 8.2V, VCQ9 is pulled high, whereupon Q2 is turned off and the overvoltage protection circuit becomes active and the output voltage VCC1 drops to 0. The situation in the VCC falling process is similar to the rising process.

And (5) performing a simulation on the whole circuit. As shown in fig. 9, a circuit diagram is shown with LTSpice.

As shown in fig. 10, the change condition of the input voltage VCC and the output voltage VOUT is analyzed, and in the process of rising VCC, when VCC reaches before 6.2V, VOUT is always constant at 5V, that is, vdd_5v due to the existence of the hysteresis comparison module; when VCC reaches 6.2V, VOUT begins to follow VCC; when VCC reaches 8.2V, the overvoltage protection circuit is active, VCC is turned off, and VOUT becomes constant VDD_5V.

As shown in fig. 11, when VCC falls to about 8.2V during the falling process, the overvoltage protection circuit releases protection, and VOUT starts to follow VCC; when VCC drops to around 5V, VOUT switches from VCC to constant vdd_5v due to the presence of the hysteresis comparison module. In the whole VCC change process, no drop of the output voltage VOUT occurs, namely the P-MOSFET Q1 does not generate heat.

The foregoing describes one embodiment of the present utility model in detail, but the description is only a preferred embodiment of the present utility model and should not be construed as limiting the scope of the utility model. All equivalent changes and modifications within the scope of the present utility model are intended to be covered by the present utility model.

Claims

1. A dual power switching circuit, characterized in that it includes an ideal diode module, a dual power switching module, a hysteresis comparison module and an overvoltage protection module,

The ideal diode module includes a P-MOSFET tube Q3, a PNP transistor Q4, and a PNP transistor Q5. The D end of the P-MOSFET tube Q3 is connected to the input power supply VCC1, the G end of the P-MOSFET tube Q3 and the C end of the PNP transistor Q5 are connected at VCQ5, the S end of the P-MOSFET tube Q3 is connected to the E end of the PNP transistor Q5, the B end of the PNP transistor Q5 and the B end of the PNP transistor Q4 are connected at VBASE, the C end of the PNP transistor Q5 is also grounded through a resistor R9, the E end of the PNP transistor Q4 is connected to the input power supply VCC1, VBASE is connected to the C end of the PNP transistor Q4, and the C end of the PNP transistor Q4 is grounded through a resistor R8, and the S end of the P-MOSFET tube Q3 is connected to the output end VOUT.

The dual power switching module includes a P-MOSFET tube Q1 and a capacitor C1. The D terminal of the P-MOSFET tube Q1 is connected to the power supply VDD_5V, the G terminal of the P-MOSFET tube Q1 is grounded through a resistor R1, and is connected to the input power supply VCC1 through a resistor R2. The S terminal of the P-MOSFET tube Q1 is connected to the output terminal VOUT, and is grounded through the capacitor C1 and the resistor R14 respectively.

The hysteresis comparison module includes an NPN transistor Q7 and an NPN transistor Q6. The B end of the NPN transistor Q7 is connected to one end of a resistor R16. The other end of the resistor R16 is connected to the input power supply VCC through the resistor R6 and to ground through the resistor R10. The B end of the NPN transistor Q6 is connected to the C end of the NPN transistor Q7. The C end of the NPN transistor Q6 and the C end of the NPN transistor Q7 are connected to the power supply VDD_5V through the resistor R5 and the resistor R4 respectively. The E end of the NPN transistor Q7 and the E end of the NPN transistor Q6 are connected to the power supply VDD_5V through the resistor R11. The C end of the NPN transistor Q6 is also connected to the G end of the P-MOSFET tube Q8, the S end of the P-MOSFET tube Q8 is grounded, the D end of the P-MOSFET tube Q8 is connected to the G end of the P-MOSFET tube Q2 through a resistor R7, the S end of the P-MOSFET tube Q2 is connected to the input power supply VCC, the S end of the P-MOSFET tube Q2 is connected to the G end of the P-MOSFET tube Q2 through a resistor R3, the D end of the P-MOSFET tube Q2 is grounded through a resistor R15, and the D end of the P-MOSFET tube Q2 is the power supply VCC1,

The overvoltage protection module includes a PNP transistor Q9 and a voltage stabilizing diode D1. The E end of the PNP transistor Q9 is connected to the input power supply VCC, the B end of the PNP transistor Q9 is connected to the resistor R13, the other end of the resistor R13 is connected to the input power supply VCC through the resistor R12 and to the ground through the voltage stabilizing diode D1, and the C end of the PNP transistor Q9 is connected to the G end of the P-MOSFET tube Q2.

2. A dual power switching circuit according to claim 1, characterized in that: the model of the P-MOSFET tube is CJ2301.

3. A dual power supply switching circuit according to claim 1, characterized in that: the model of the PNP transistors is MMBT3906.

4. A dual power supply switching circuit according to claim 1, characterized in that: the model of the NPN transistors is MMBT3904.