A serial-parallel automatic switching control circuit for a DC power supply

Abstract

The present invention discloses a series-parallel automatic switching control circuit for a DC power supply, which includes the interconnection of multiple N-channel MOS transistors on a photovoltaic module, and a relay K1 is used to switch between series and parallel connections to achieve different voltage outputs on both sides. The present invention has the following advantages and effects: Through switch switching, the automatic switching between series and parallel of the DC power supply is simply realized, facilitating the combined use of power supplies.

Description

Technical Field

[0001] The present invention relates to the technical field of circuits, and particularly relates to a series-parallel automatic switching control circuit for a DC power supply. Background Art

[0002] In some cases, the DC power supply needs to switch between high-voltage output and low-voltage output, that is, it is necessary to achieve the switching between series and parallel connections.

[0003] In the prior art, diodes are mostly used to achieve such switching technology. However, due to the relatively large conduction power loss of the diodes, the operating cost is increased.

[0004] This patent proposes to use MOS transistors to achieve the purpose of series-parallel switching. Summary of the Invention

[0005] The purpose of the present invention is to provide a series-parallel automatic switching control circuit for a DC power supply with low loss, high safety and convenient switching.

[0006] The above technical purpose of the present invention is achieved through the following technical solutions: a series-parallel automatic switching control circuit for a DC power supply, including a plurality of photovoltaic modules. The negative terminals of the photovoltaic modules are each connected to an N-channel MOS transistor A, and the positive terminals are each connected to an N-channel MOS transistor B. A plurality of basic units composed of the photovoltaic modules, MOS transistor A and MOS transistor B are connected in parallel with each other to form a basic circuit. One end of the basic circuit is externally connected to a single or parallel battery pack, and a relay K1 is connected to the single or parallel battery pack. The relay K1 includes a coil K1, a normally open contact K1-1 and a normally closed contact K1-2, and a switch K2 is provided on the relay K1;

[0007] The negative terminals of the photovoltaic modules are each connected to an N-channel MOS transistor C, and it is connected to the source electrode. The drain electrode of the MOS transistor C is connected to the positive electrode of the adjacent photovoltaic module to form a series power supply mode of the photovoltaic modules;

[0008] A DC / DC boost circuit is connected in parallel at both ends of one of the photovoltaic modules. A delay circuit OP2 is connected to the output end of the DC / DC boost circuit. The normally closed contact K1-2 is connected in series at the input end of the DC / DC boost circuit. The output end of the delay circuit OP2 is respectively connected to the gates of the MOS transistors A and B;

[0009] A delay circuit OP1 is connected in parallel at both ends of another photovoltaic module. The output ends of the delay circuit OP1 are both connected to the gate of the MOS transistor C. The normally open contact K1-1 is connected in series at the input end of the delay circuit OP1;

[0010] The drain of MOS transistor C at the negative terminal of the series power supply composed of photovoltaic modules is connected to the negative terminal of a high-voltage series battery pack, and the other end of the series battery pack is connected to the positive terminal of the series power supply composed of photovoltaic modules.

[0011] It is further set that: MOS transistor A includes MOS transistors Q5, Q6, Q7, and Q8, and diodes are provided on the gates of MOS transistors Q6 - Q8.

[0012] It is further set that: A transient diode is connected across the drain and source of MOS transistor C.

[0013] It is further set that: Both delay circuit OP1 and delay circuit OP2 include a comparator and two resistors connected in series between the positive and negative terminals of the photovoltaic modules. The Vn and Vp terminals of the comparator are respectively connected between the two resistors. Capacitors are connected in parallel on the resistors where the Vp terminal is located and close to the photovoltaic module end. The resistor-capacitor parallel circuit is connected to Vp after passing through diode D.

[0014] In summary, the present invention has the following beneficial effects: Through switch switching, the automatic switching between series and parallel of the DC power supply is simply realized, which facilitates the combined use of the power supplies. Brief Description of the Drawings

[0015] Figure 1 It is the circuit diagram of the control circuit. Detailed Description of the Embodiment

[0016] The present invention will be further described in detail below with reference to the drawings.

[0017] A series-parallel automatic switching control circuit for a DC power supply, mainly used for switching between parallel and series of a DC power supply, includes a total of four photovoltaic modules V1, V2, V3, and V4.

[0018] An N-channel MOS transistor is provided at each end of photovoltaic modules V1 - V4. Among them, according to the function, the MOS transistor connected to the negative side is MOS transistor A, and the MOS transistor located on the positive side is MOS transistor B. Specifically, the negative terminal of photovoltaic module V1 is connected to MOS transistor Q8, and the positive terminal is connected to MOS transistor Q1; the negative terminal of photovoltaic module V2 is connected to MOS transistor Q7, and the positive terminal is connected to MOS transistor Q2; the negative terminal of photovoltaic module V3 is connected to MOS transistor Q6, and the positive terminal is connected to MOS transistor Q3; the negative terminal of photovoltaic module V4 is connected to MOS transistor Q5, and the positive terminal is connected to MOS transistor Q4. Among them, Q1 - Q4 belong to MOS transistor B, and Q5 - Q8 are MOS transistor A.

[0019] A basic unit is formed by photovoltaic modules V1 - V4 and corresponding MOS transistors A and MOS transistors B at both ends respectively. The basic units are connected in parallel with each other to form a basic circuit, and a single or parallel battery pack is externally connected to the basic circuit. A relay K1 is connected to the single or parallel battery pack. The relay K1 includes a coil K1, a normally open contact K1-1, and a normally closed contact K1-2, and a switch K2 is provided on the relay K1.

[0020] A MOS transistor Q9, a MOS transistor Q10, a MOS transistor Q11, and a MOS transistor Q12 are respectively connected to the negative electrodes of the photovoltaic modules V1, V2, V3, and V4. The MOS transistors Q9 - Q12 are classified as MOS transistors C. The source of the MOS transistor Q9 is connected to the negative electrode of the photovoltaic module V1, and the drain is connected to the positive electrode of the photovoltaic module V2; the source of the MOS transistor Q10 is connected to the negative electrode of the photovoltaic module V2, and the drain is connected to the positive electrode of the photovoltaic module V3; the source of the MOS transistor Q11 is connected to the negative electrode of the photovoltaic module V3, and the drain is connected to the positive electrode of the photovoltaic module V4; the source of the MOS transistor Q12 is connected to the negative electrode of the photovoltaic module V4, and the negative electrode of a series battery pack is connected to the drain. The other positive electrode of the series battery is connected to the positive electrode of the photovoltaic module V1. After Q9 - Q12 are turned on, four independent photovoltaic power sources can form a series power supply.

[0021] A delay circuit OP1 is connected in parallel across the two ends of the photovoltaic module V1, and the normally open contact K1-1 is connected to the input end of the delay circuit. The gates of the MOS transistors Q9, Q10, Q11, and Q12 are all connected to the output end of the delay circuit OP1.

[0022] A DC / DC boost circuit is connected in parallel across the two ends of the photovoltaic module V4, and the normally closed contact K1-2 is provided at the input end of the DC / DC boost circuit. A delay circuit OP2 is provided at the output end of the DC / DC boost circuit, and the output end of the delay circuit OP2 is respectively connected to the gates of the MOS transistors Q1 - Q8.

[0023] Among them, all the above MOS are N-channel MOS transistors, and transient diodes TVS1 - TVS4 are provided between the drains and sources of the MOS transistors Q9 - Q12. Since Q9 - Q12 cannot be turned on simultaneously, the drain and source of the last turned-on MOS transistor will bear a high voltage, even exceeding its own limit voltage, and the MOS transistor is at risk of being broken down. The use of the TVS transient diode is to protect the MOS transistor from being broken down in this case.

[0024] Diodes D2 - D4 are provided at the gates of MOS transistors Q6 - Q8, which can prevent the parallel MOS transistors from being triggered to conduct when power supplies are in series by supplying power to their gates. Taking diode D2 in the figure as an example: Without D2, when the power supplies are in series, Q11 conducts, and the positive pole of PV4 will supply power to the gate of Q5 through Q11 and R5, triggering Q5 to conduct. After adding D2, the conduction of Q5 can be avoided.

[0025] The delay circuit OP1 and the delay circuit OP2 both include a comparator and two resistors connected in series between the positive and negative poles of the photovoltaic module. The Vn and Vp terminals of the comparator are respectively connected between the two resistors. Capacitors are connected in parallel to the resistors at the end where the Vp terminal of the comparator is located and is closer to the photovoltaic module. The resistor - capacitor parallel circuit is connected to Vp after passing through diode D.

[0026] The purpose of the delay circuits OP1 and OP2 is to prevent the series - parallel circuit from being interconnected and damaging the power supply or load when the MOS transistors are in a semi - conducting and semi - off state.

[0027] Working principle: (1) When the switch K2 is disconnected, the normally - closed contact of the relay K1 - 2 conducts, and the DC / DC boost regulator outputs voltage. After R19 and R20 divide the voltage, it supplies power to the positive phase of Vp of the voltage comparator OP2. Since the circuit composed of OP2 has the characteristics of delayed power supply and rapid power loss, the gates of the Q1 - Q8 MOS transistors will be powered on with a delay, that is, the Q1 - Q8 MOS transistors conduct with a delay. In this way, after the contact of K1 - 2 conducts, the 8 MOS transistors responsible for parallel connection are connected after a period of time, and the power supply enters the parallel state with a delay after the action of the K2 control switch.

[0028] At the same time when the contact of K1 - 2 conducts, the contact of K1 - 1 disconnects. Due to the characteristics of delayed power supply and rapid power loss of the OP1 loop, the gates of the Q9 - Q12 MOS transistors originally responsible for series connection lose power rapidly, and Q9 - Q12 turn off rapidly, and the series loop is quickly disconnected.

[0029] (2) After K2 is connected, the normally - closed contact of K1 - 2 disconnects, and the output of OP2 loses power rapidly, and the Q1 - Q8 MOS transistors turn off rapidly, and the parallel state is released; at the same time, the normally - open contact of K1 - 1 connects, and OP1 outputs voltage after a period of time, and the Q9 - Q12 MOS transistors are connected with a delay, and the power supply enters the series state.

[0030] Among them, the principle of delayed power-on and rapid power-off is illustrated by taking the OP1 circuit as an example. The negative phase Vn of the comparator OP1 is powered by the voltage division of R18 and R17, and the positive phase Vp is powered by the voltage division of R16 and R15. Here, R15 is connected in parallel with the capacitor C1, and after being connected in parallel, it is connected in series with the diode D12. After the comparator power supply is turned on, due to the effect of the capacitor, the voltage division output of R16 and R15 is zero (ignoring the diode voltage drop). After a period of time when the capacitor is fully charged, the voltage division output gradually changes from 0V to the voltage division value of the two resistors R16 and R15. Here, it is designed that the voltage division output of R16 and R15 is higher than the voltage division of R18 and R17. In this way, after a period of time, the positive phase voltage at the input end of OP1 is higher than the negative phase voltage, and the output voltage of the OP1 comparator supplies power to the gate of the MOS transistor. In this way, the MOS transistor conducts after a period of time after the switch K2 operates. If the power supply applied to OP1 is disconnected, the capacitor C1 will quickly discharge through R15, and due to the existence of the diode D12, it prevents the capacitor from discharging to the OP1 operational amplifier. Therefore, the output of OP1 can be quickly reduced to 0V, and the MOS transistor can be quickly turned off.

[0031] This specific embodiment is only an explanation of the present invention, and it is not a limitation of the present invention. After reading this specification, those skilled in the art can make modifications that do not contribute creatively to this embodiment as needed, but as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A series-parallel automatic switching control circuit for a DC power supply, characterized in that: It includes a number of photovoltaic modules. The negative terminals of the photovoltaic modules are all connected to an N-channel MOS transistor A, and the positive terminals are all connected to an N-channel MOS transistor B. A number of basic units composed of the photovoltaic modules, MOS transistor A and MOS transistor B are connected in parallel with each other to form a basic circuit. One end of the basic circuit is externally connected to a low-voltage single battery or a parallel battery pack. A relay K1 is connected to the low-voltage single battery or the parallel battery pack. The relay K1 includes a coil K1, a normally open contact K1-1 and a normally closed contact K1-2. A switch K2 is provided on the coil of the relay K1; the negative terminals of the photovoltaic modules are all connected to an N-channel MOS transistor C, and it is connected to the source electrode. The drain electrode of the MOS transistor C is connected to the positive electrode of the adjacent photovoltaic module to form a series power supply mode of the photovoltaic modules; a DC / DC boost circuit is connected in parallel at both ends of one of the photovoltaic modules. A delay circuit OP2 is connected to the output end of the DC / DC boost circuit. The normally closed contact K1-2 is connected in series at the input end of the DC / DC boost circuit. The output end of the delay circuit OP2 is respectively connected to the gates of the MOS transistors A and B; a delay circuit OP1 is connected in parallel at both ends of another photovoltaic module. The output ends of the delay circuit OP1 are all connected to the gate of the MOS transistor C. The normally open contact K1-1 is connected in series at the input end of the delay circuit OP1; the negative electrode of a high-voltage series battery pack is connected to the drain electrode of the MOS transistor C at the negative terminal of the series power supply composed of the photovoltaic modules. The other end of the series battery pack is connected to the positive terminal of the series power supply composed of the photovoltaic modules; the MOS transistor A includes MOS transistors Q6, Q7 and Q8. Diodes are provided on the gates of the MOS transistors Q6-Q8.

2. The series-parallel automatic switching control circuit of a DC power supply according to claim 1, characterized in that: A transient diode is connected across the drain and source electrodes of the MOS transistor C.

3. The automatic series-parallel switching control circuit of a DC power supply according to claim 1, characterized in that: Both the delay circuit OP1 and the delay circuit OP2 include a comparator and two resistors connected in series between the positive and negative electrodes of the photovoltaic module. The Vn and Vp terminals of the comparator are respectively connected between the two resistors. Capacitors are connected in parallel on the resistors where the Vp terminal of the comparator is located and close to the photovoltaic module end. The resistor-capacitor parallel circuit is connected to the Vp after passing through the diode D.

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