CN109412255B

CN109412255B - Low-loss high-reliability double-circuit power supply switching circuit

Info

Publication number: CN109412255B
Application number: CN201811227995.XA
Authority: CN
Inventors: 灞卞嘲; 山峰
Original assignee: Ningbo Sanxing Smart Electric Co Ltd
Current assignee: Ningbo Sanxing Smart Electric Co Ltd
Priority date: 2018-10-22
Filing date: 2018-10-22
Publication date: 2021-11-19
Anticipated expiration: 2038-10-22
Also published as: CN109412255A

Abstract

A low-loss high-reliability double-circuit power supply switching circuit comprises an AC-DC conversion unit, a DC-DC conversion unit, a battery assembly and a battery charging and discharging management unit, and is characterized in that: the output end of the DC-DC conversion unit is electrically connected with the anode of the first diode, the drain electrode of the first PMOS tube and the anode of the fourth diode respectively, the output end of the battery charging and discharging management unit is electrically connected with the anode of the battery component and the source electrode of the second PMOS tube respectively, and the cathode of the battery component is grounded. The low-loss high-reliability double-circuit power supply switching circuit can simultaneously give consideration to the power supply utilization efficiency, the maximum utilization of the battery capacity and the switching reliability.

Description

Low-loss high-reliability double-circuit power supply switching circuit

Technical Field

The invention relates to the technical field of double-circuit power supply switching circuits, in particular to a low-loss high-reliability double-circuit power supply switching circuit.

Background

For a system with a backup battery power supply, the power supply part has a two-way power supply switching circuit, and the circuit determines whether the power supply of the system is from the commercial power or the backup battery, for example, a 5V power supply system of a concentrator adopts the functional circuit.

A two-way power supply switching circuit of a conventional 5V power supply system applied to a concentrator is shown in fig. 1, in the figure, D1 ' and D2 ' are schottky diodes, Q1 ' is a PMOS, J1 ' is an NPN triode, and U1 ' is a comparator; the circuit utilizes the unidirectional conduction characteristic of a diode, when U1 'judges that the output voltage V12V of an AC-DC conversion unit is higher than a set voltage VREF, the output is low level, Q1' is cut off, and the power supply of the rear end voltage V5V is from the output V5.3V of the DC-DC conversion unit; when the U1 'judges that V12V is lower than the set voltage VREF, the output is high, Q1' is turned on, and the rear end voltage V5V supplies power from the higher voltage of the output of the DC-DC conversion unit and the output of the battery pack. The circuit is very simple, but because the diode has forward voltage drop, even if a schottky diode with lower forward voltage drop is adopted, the voltage drop of about 0.3V is generally generated under small current (within 0.1A), if the circuit current is larger (say 3A), the voltage drop of more than 0.4V is generally generated on the schottky diode under the room temperature condition, and if a diode mode is adopted on a 5V system to realize double-circuit power supply switching, at least 5% of efficiency is lost, so that the utilization efficiency of the circuit power supply is very low.

Another two-way power supply switching circuit applied to a 5V power supply system of a concentrator is shown in fig. 2, wherein Q2 'and Q3' are PMOS; j2 'and J3' are NPN triodes; u2 'is a comparator with complementary output, and this circuit replaces the diode with the field effect transistor Q2' and Q3 ', and the body resistance of the field effect transistor is small, and can be within 30m Ω, so the output of the DC-DC conversion unit can be reduced to 5.1V, and the voltage after passing through Q2' can be ensured to be about 5V. However, the circuit still has the following defects: 1. the charging voltage of the battery pack must be lower than the output voltage of the DC-DC conversion unit by 5.1V, resulting in that the voltage capacity of the battery pack cannot be maximally utilized; 2. when the power source switching action is generated, Q2 'and Q3' are simultaneously actuated, and there is necessarily a short period of time during which both Q2 'and Q3' are in the on state, so that it occurs that the output of the DC-DC conversion unit is charged to the battery pack through Q2 'and Q3', or the battery pack is charged to the output capacitance of the DC-DC conversion unit through Q2 'and Q3', or even to the output capacitance of the AC-DC conversion unit through the parasitic diode of the fet inside the DC-DC conversion unit.

Therefore, the existing double-power supply switching circuit is difficult to simultaneously consider the problems of power supply utilization efficiency, maximum utilization of battery capacity and switching reliability.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: provided is a low-loss high-reliability two-way power supply switching circuit which can simultaneously achieve both power supply utilization efficiency, maximum utilization of battery capacity, and switching reliability.

The technical solution of the invention is as follows: a low-loss high-reliability double-circuit power supply switching circuit comprises an AC-DC conversion unit, a DC-DC conversion unit, a battery assembly and a battery charging and discharging management unit, and is characterized in that: the battery charging and discharging management system further comprises a comparator with two complementary outputs, a first diode, a second diode, a third diode, a fourth diode, a first PMOS tube, a second PMOS tube, a third PMOS tube, a first NPN triode, a second NPN triode, a third NPN triode, a first resistor, a second resistor, a third resistor, a fourth resistor and a fifth resistor, wherein the AC input end of the AC-DC conversion unit is electrically connected with a mains supply, the DC output end of the AC-DC conversion unit is respectively and electrically connected with the input end of the DC-DC conversion unit, the non-inverting input end of the comparator and the input end of the battery charging and discharging management unit, the output end of the DC-DC conversion unit is respectively and electrically connected with the anode of the first diode, the drain electrode of the first PMOS tube and the anode of the fourth diode, and the output of the battery charging and discharging management unit is respectively and electrically connected with the anode of the battery component, The source electrode of the second PMOS tube is electrically connected, the negative electrode of the battery component is grounded, the drain electrode of the second PMOS tube is respectively and electrically connected with the anode of the second diode, the anode of the third diode and the drain electrode of the third PMOS tube, the cathode of the first PMOS tube, the source electrode of the third diode and the source electrode of the third PMOS tube are all electrically connected together to serve as a rear-end power supply, the grid electrode of the first PMOS tube is electrically connected with the collector electrode of the first NPN type triode through a first resistor, the grid electrode of the first PMOS tube is also electrically connected with the cathode electrode of the second diode, the in-phase output end of the comparator is electrically connected with the base electrode of the first NPN type triode through a second resistor, the emitter electrode of the first NPN type triode is grounded, the reverse-phase output end of the comparator is electrically connected with the base electrode of the second NPN type triode through a fourth resistor, and the reverse-phase output end of the comparator is also electrically connected with the base electrode of the third NPN type triode through a fifth resistor, the collector of the second NPN type triode is electrically connected with the grid of the second PMOS tube, the collector of the third NPN type triode is electrically connected with the grid of the third PMOS tube through a third resistor, the grid of the third PMOS tube is electrically connected with the cathode of the fourth diode, and the emitters of the second NPN type triode and the third NPN type triode are both grounded.

The working principle of the low-loss high-reliability double-power supply switching circuit is as follows:

when the mains supply is normal, the output voltage V12V of the AC-DC conversion unit is higher than the reference voltage VREF of the comparator, the in-phase output end of the comparator outputs high level, the first NPN type triode is conducted, and therefore the grid-source voltage difference of the first PMOS tube is smaller than the conduction threshold voltage (namely V-source voltage difference is V-source voltage difference)_GS<Vgth) is conducted, the second PMOS tube and the third PMOS tube are both cut off, and power is supplied to a rear end voltage V5V by mains supply after passing through the AC-DC conversion unit, the DC-DC conversion unit and the first PMOS tube; when the mains supply is insufficient or power-off, the AC-DC conversion unitThe output voltage V12V of the battery pack is lower than the reference voltage VREF, the in-phase output end of the comparator outputs a low level, the first NPN type triode is cut off, the reverse-phase output end of the comparator outputs a high level, the second NPN type triode and the third NPN type triode are conducted, so that the second PMOS tube and the third PMOS tube are both conducted, and the battery pack supplies power to the rear end voltage V5V after passing through the second PMOS tube and the third PMOS tube; when the mains supply is powered off, the switching process of supplying power by the battery assembly is as follows: the second PMOS transistor is firstly conducted → the drain voltage VQ15 of the second PMOS transistor rises → then (VQ15-0.3V)>(V5V-Vgth), the first PMOS tube is cut off, wherein-Vgth is the conduction threshold voltage of the PMOS tube, the diode is a Schottky diode for example, 0.3V is the forward voltage drop of the Schottky diode → the first PMOS tube and the third PMOS tube are both cut off at the moment, the rear end voltage V5V selects the circuit with higher voltage (the circuit where the battery pack is located) from two power supplies by the two diodes of the first diode and the third diode for power supply → the output voltage V5.1V of the DC-DC conversion unit is reduced, and (V5.1V-0.3V)<(V5V-Vgth), the third PMOS tube is conducted, and the battery assembly supplies power to the rear end voltage V5V after passing through the second PMOS tube and the third PMOS tube to complete the switching of the power supply; when the commercial power is powered up again, V5.1V voltage rises → when (V5.1V-0.3V)>(V5V-Vgth), the third PMOS transistor is turned off → at this time, the first PMOS transistor and the third PMOS transistor are both turned off, the rear end voltage V5V selects the circuit with higher voltage (the circuit where the mains supply is located) from the two power supplies by the two diodes of the first diode and the third diode for power supply → the second PMOS transistor is turned off → VQ15 is dropped, and (VQ15-0.3V)<(V5V-Vgth), the first PMOS tube is conducted, and mains supply supplies power to the rear end voltage V5V through the AC-DC conversion unit, the DC-DC conversion unit and the first PMOS tube to complete the switching of the power supply, and the second PMOS tube and the third PMOS tube are not necessarily cut off in sequence, but do not influence the working process of power supply switching.

After adopting the structure, the invention has the following advantages:

the low-loss high-reliability double-circuit power supply switching circuit adopts the field effect tube as the switching switch of the two power supply circuits, reduces the voltage drop of the circuit and improves the conversion efficiency of the power supply; the two diodes, namely the second diode and the fourth diode, are utilized during switching to ensure that the first PMOS tube and the third PMOS tube of the change-over switch of the two power supply loops are not conducted at the same time, which is similar to the dead zone effect, so that the output of the commercial power and the output of the battery assembly are mutually independent, and only electric energy can be provided to the rear end, and the power supply cannot flow backwards; by utilizing the two diodes, namely the first diode and the third diode, in the short time when the first PMOS tube and the third PMOS tube of the change-over switch of the two power supply loops are both in a cut-off state (dead zone), the power supply with higher voltage is automatically selected to supply power to the rear end, so that the smooth switching of the two power supplies is ensured, and the power supply at the rear end is not powered off; furthermore, the maximum charging voltage of the battery assembly is not affected by other factors of the circuit.

Preferably, the rear end voltage is 5V. The arrangement applies the low-loss high-reliability double-power supply switching circuit to a common 5V power supply system.

Preferably, the output of the AC-DC conversion unit is 12V, and the output of the DC-DC conversion unit is 5.1V. The reasonable voltage setting can make the device type selection easier and the power supply conversion more convenient and reliable.

Preferably, the voltage of the battery assembly is 4.8V. The arrangement can well meet the use requirement.

Preferably, the battery assembly includes a plurality of nickel metal hydride batteries. The nickel-hydrogen battery has high capacity, long service life and better overall performance.

Preferably, the battery assembly comprises 4-section 1.2V nickel-metal hydride batteries. The arrangement can well meet the use requirement.

Preferably, the first diode, the second diode, the third diode and the fourth diode are schottky diodes. The Schottky diode has small voltage drop and low energy consumption, thereby ensuring that the circuit performance is more excellent.

Preferably, the first diode, the second diode, the third diode and the fourth diode are of the type BAT 15-099. The Schottky diode of the model is commonly used, and the performance is stable and excellent.

Preferably, the type of the comparator is MAX912 or MAX 913. The type comparator is commonly used, and the performance is stable and excellent.

Preferably, the first PMOS transistor, the second PMOS transistor and the third PMOS transistor are of the type SI2333 CDS. The PMOS transistor is commonly used and has stable and excellent performance.

Description of the drawings:

fig. 1 is a circuit diagram of a dual power switching circuit of the prior art;

FIG. 2 is a circuit diagram of another prior art dual power switching circuit;

FIG. 3 is a circuit diagram of a low loss, high reliability dual power switching circuit of the present invention;

in the prior art figures: d1 ', D2' -Schottky diode, Q1 ', Q2', Q3 '-PMOS tube, J1', J2 ', J3' -NPN type triode, U1 ', U2' -comparator;

in the figure of the invention: u1-comparator, D1-first diode, D2-second diode, D3-third diode, D4-fourth diode, Q1-first PMOS tube, Q2-second PMOS tube, Q3-third PMOS tube, J1-first NPN type triode, J2-second NPN type triode, J3-third NPN type triode, R1-first resistor, R2-second resistor, R3-third resistor, R4-fourth resistor and R5-fifth resistor.

Detailed Description

The invention is further described with reference to the following embodiments in conjunction with the accompanying drawings.

Example (b):

a low-loss high-reliability two-way power supply switching circuit comprises an AC-DC conversion unit, a DC-DC conversion unit, a battery assembly, a battery charging and discharging management unit, a comparator U1 with two complementary outputs, a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a first PMOS tube Q1, a second PMOS tube Q2, a third PMOS tube Q3, a first NPN type triode J1, a second NPN type triode J2, a third NPN type triode J3, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4 and a fifth resistor R5, wherein the AC input end of the AC-DC conversion unit is electrically connected with a mains supply, the DC output end of the AC-DC conversion unit is respectively electrically connected with the input end of the DC-DC conversion unit, the non-phase input end of the comparator U1 and the input end of the battery charging and discharging management unit, the output end of the DC-DC conversion unit is electrically connected to the anode of a first diode D1, the drain of a first PMOS transistor Q1, and the anode of a fourth diode D4, the output of the battery charge and discharge management unit is electrically connected to the anode of a battery assembly and the source of a second PMOS transistor Q2, the cathode of the battery assembly is grounded, the drain of a second PMOS transistor Q2 is electrically connected to the anode of a second diode D2, the anode of a third diode D3, and the drain of a third PMOS transistor Q3, the cathode of the first diode D1, the source of a first PMOS transistor Q1, the cathode of a third diode D3, and the source of a third PMOS transistor Q3 are electrically connected together as a rear-end power source, the gate of the first PMOS transistor Q1 is electrically connected to the collector of a first NPN-type triode J1 through a first resistor R1, the gate of the first PMOS transistor Q1 is further electrically connected to the cathode of a second diode D6, and the in-phase resistor U1 of the comparator U3527 is electrically connected to the cathode of the first NPN-type triode 2 An emitter of the first NPN transistor J1 is grounded, an inverted output terminal of the comparator U1 is electrically connected to a base of the second NPN transistor J2 through a fourth resistor R4, an inverted output terminal of the comparator U1 is also electrically connected to a base of a third NPN transistor J3 through a fifth resistor R5, a collector of the second NPN transistor J2 is electrically connected to a gate of the second PMOS transistor Q2, a collector of the third NPN transistor J3 is electrically connected to a gate of the third PMOS transistor Q3 through a third resistor R3, a gate of the third PMOS transistor Q3 is electrically connected to a cathode of the fourth diode D4, and emitters of the second NPN transistor J2 and the third NPN transistor J3 are both grounded. In this embodiment, the output of the AC-DC conversion unit is 12V, the output of the DC-DC conversion unit is 5.1V, and the back-end voltage is 5V; the battery component comprises 4 sections of 1.2V nickel-metal hydride batteries; the first diode D1, the second diode D2, the third diode D3 and the fourth diode D4 are Schottky diodes; the model of the first diode D1, the second diode D2, the third diode D3 and the fourth diode D4 is BAT 15-099; the type of the comparator U1 is MAX912 or MAX 913; the model of the first PMOS tube Q1, the second PMOS tube Q2 and the third PMOS tube Q3 is SI2333 CDS.

when the mains supply is normal, the output voltage V12V of the AC-DC conversion unit is higher than the reference voltage VREF of the comparator U1, the in-phase output terminal of the comparator U1 outputs a high level, and the first NPN transistor J1 is turned on, so that the difference between the gate-source voltages of the first PMOS transistor Q1 is smaller than the turn-on threshold voltage (i.e., V voltage V1 is lower than the turn-on threshold voltage)_GS<-Vgth) is turned on, and the second PMOS transistor Q2 and the third PMOS transistor are both turned off, and power is supplied to the back end voltage V5V by the mains supply through the AC-DC conversion unit, the DC-DC conversion unit and the first PMOS transistor Q1; when the mains supply is insufficient or the mains supply is powered off, the output voltage V12V of the AC-DC conversion unit is lower than the reference voltage VREF, the in-phase output end of the comparator U1 outputs a low level, the first NPN type triode J1 is cut off, the reverse phase output end of the comparator U1 outputs a high level, the second NPN type triode J2 and the third NPN type triode J3 are conducted, so that the second PMOS tube Q2 and the third PMOS tube Q3 are both conducted, and the battery component supplies power to the rear end voltage V5V through the second PMOS tube Q2 and the third PMOS tube Q3; when the mains supply is powered off, the switching process of supplying power by the battery assembly is as follows: the second PMOS transistor Q2 is turned on first → the drain voltage VQ15 of the second PMOS transistor Q2 rises → One (VQ15-0.3V)>(V5V-Vgth), the first PMOS transistor Q1 is turned off, where-Vgth is the turn-on threshold voltage of the PMOS transistor, 0.3V is the forward voltage drop of the schottky diode → at this time, the first PMOS transistor Q1 and the third PMOS transistor Q3 are both turned off, the back end voltage V5V is powered by the first schottky diode D1 and the third schottky diode D3 which select the circuit with the higher voltage battery component from the two power supplies → the output voltage V5.1V of the DC-DC conversion unit is reduced, and (V5.1V-0.3V)<(V5V-Vgth), the third PMOS tube Q3 is conducted, and power is supplied to the rear end voltage V5V by the battery component through the second PMOS tube Q2 and the third PMOS tube Q3, so that the switching of a power supply is completed; when the commercial power is powered up again, V5.1V voltage rises → when (V5.1V-0.3V)>(V5V-Vgth), the third PMOS transistor Q3 is cut off → the first PMOS transistor Q1 and the third PMOS transistor Q3 are both cut off at this time, the back end voltage V5V is supplied by the first schottky diode D1 and the third schottky diode D3 which select the circuit of the commercial power with higher voltage from the two power supplies → the second PMOS transistor Q2 is cut off → VQ15 is dropped, and (VQ15-0.3V)<(V5V-Vgth), the first PMOS tube Q1 is conducted, and mains supply supplies power to the rear end voltage V5V through the AC-DC conversion unit, the DC-DC conversion unit and the first PMOS tube Q1 to complete the switching of the power supply, and the switching-off sequence of the second PMOS tube Q2 and the third PMOS tube Q3 is not necessary, but the working process of power supply switching is not influenced.

The low-loss high-reliability double-circuit power supply switching circuit adopts the field effect tube as the switching switch of the two power supply circuits, reduces the voltage drop of the circuit and improves the conversion efficiency of the power supply; when in switching, the two diodes, namely the second Schottky diode D2 and the fourth Schottky diode D4, are utilized to ensure that a first PMOS tube Q1 and a third PMOS tube Q3 of a selector switch of two paths of power supply loops are not conducted at the same time, and the action similar to a dead zone is realized, so that the output of commercial power and the output of a battery assembly are mutually independent, electric energy can be provided only to the rear end, and the power supply cannot flow backwards; by utilizing the two diodes of the first Schottky diode D1 and the third Schottky diode D3, in the short time when the first PMOS tube Q1 and the third PMOS tube Q3 of the change-over switches of the two power supply loops are in a dead zone of a cut-off state, the power supply of the power supply with higher voltage is automatically selected to supply power to the rear end, so that the two power supplies are ensured to be smoothly switched, and the power supply of the rear end is not powered off; furthermore, the maximum charging voltage of the battery assembly is not affected by other factors of the circuit.

Claims

1. A low-loss high-reliability double-circuit power supply switching circuit comprises an AC-DC conversion unit, a DC-DC conversion unit, a battery assembly and a battery charging and discharging management unit, and is characterized in that: the battery charging and discharging management circuit further comprises a comparator (U1) with two complementary outputs, a first diode (D1), a second diode (D2), a third diode (D3), a fourth diode (D4), a first PMOS tube (Q1), a second PMOS tube (Q2), a third PMOS tube (Q3), a first NPN type triode (J1), a second NPN type triode (J2), a third NPN type triode (J3), a first resistor (R1), a second resistor (R2), a third resistor (R3), a fourth resistor (R4) and a fifth resistor (R5), wherein the AC input end of the AC-DC conversion unit is electrically connected with the mains supply, the DC output end of the AC-DC conversion unit is electrically connected with the input end of the DC-DC conversion unit, the non-inverting input end of the comparator (U1) and the input end of the battery charging and discharging management unit, and the output end of the DC-DC conversion unit is electrically connected with the anode (D1) of the first diode, A drain of the first PMOS transistor (Q1), an anode of the fourth diode (D4) are electrically connected, an output of the battery charge and discharge management unit is electrically connected to an anode of the battery assembly, a source of the second PMOS transistor (Q2), a cathode of the second PMOS transistor (Q2) is electrically connected to an anode of the second diode (D2), an anode of the third diode (D3), and a drain of the third PMOS transistor (Q3), a cathode of the first diode (D1), a source of the first PMOS transistor (Q1), a cathode of the third diode (D3), and a source of the third PMOS transistor (Q3) are all electrically connected together as a rear power source, a gate of the first PMOS transistor (Q1) is electrically connected to a collector of the first NPN type triode (J1) through a first resistor (R1), a gate of the first PMOS transistor (Q1) is further electrically connected to a cathode of the second diode (D2), the non-inverting output end of the comparator (U1) is electrically connected with the base electrode of the first NPN type triode (J1) through a second resistor (R2), the emitter of the first NPN type triode (J1) is grounded, the inverting output end of the comparator (U1) is electrically connected with the base of the second NPN type triode (J2) through a fourth resistor (R4), the inverting output end of the comparator (U1) is also electrically connected with the base electrode of a third NPN type triode (J3) through a fifth resistor (R5), the collector of the second NPN type triode (J2) is electrically connected with the grid of a second PMOS tube (Q2), the collector of the third NPN type triode (J3) is electrically connected with the grid electrode of a third PMOS tube (Q3) through a third resistor (R3), the grid electrode of the third PMOS tube (Q3) is electrically connected with the cathode of a fourth diode (D4), the emitters of the second NPN type triode (J2) and the third NPN type triode (J3) are grounded.

2. The two-way power switching circuit of claim 1, wherein: the rear end voltage is 5V.

3. A low-loss high-reliability two-way power switching circuit according to claim 2, wherein: the output of the AC-DC conversion unit is 12V, and the output of the DC-DC conversion unit is 5.1V.

4. A low-loss high-reliability two-way power switching circuit according to claim 2, wherein: the voltage of the battery assembly was 4.8V.

5. The two-way power switching circuit of claim 1, wherein: the battery assembly includes a plurality of nickel-metal hydride batteries.

6. The two-way power switching circuit of claim 4, wherein: the battery assembly comprises 4 1.2V nickel-metal hydride batteries.

7. The two-way power switching circuit of claim 1, wherein: the first diode (D1), second diode (D2), third diode (D3), and fourth diode (D4) are Schottky diodes.

8. The two-way power switching circuit of claim 7, wherein: the model of the first diode (D1), the second diode (D2), the third diode (D3) and the fourth diode (D4) is BAT 15-099.

9. The two-way power switching circuit of claim 1, wherein: the type of the comparator (U1) is MAX912 or MAX 913.

10. The two-way power switching circuit of claim 1, wherein: the first PMOS tube (Q1), the second PMOS tube (Q2) and the third PMOS tube (Q3) are in the SI2333CDS model.