Slow start circuit and power converter

Abstract

The invention discloses a slow start circuit and a power converter. The power converter comprises a controller, a first MOS tube, a second MOS tube, a relay and a capacitor. The first end of the relay is used for being connected with a power input end, and the second end of the relay is connected with the first end of the capacitor. The first MOS tube and the second MOS tube are connected in series and then connected in parallel to the two ends of the relay; and the controller is used for controlling the first MOS tube and the second MOS tube to work in a linear region during slow start, so that the voltage on the capacitor is gradually increased, the arc discharge or adhesion phenomenon during the action of the relay can be avoided, and the safety of the relay is ensured.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to a slow-start circuit and a power converter. Background Art

[0002] In household energy storage, industrial and commercial energy storage, and smart battery backup power products, large-capacity capacitors are installed inside the product for slow start. Figure 1 In order to avoid a large surge current impact, a resistor R is usually used to slowly charge the large-capacity capacitor C, so that the voltage of the capacitor C increases slowly. In conjunction with the relay K, when the slow start ends, the relay K will be closed and the resistor R will be bypassed.

[0003] However, a general relay is a mechanical device. Under high current conditions, controlling the on and off of the relay will cause arcing and sticking of the mechanical contact switch inside the relay, thereby causing failure of the power supply product. Summary of the invention

[0004] In view of this, the present application provides a slow-start circuit and a power converter, which can avoid arcing or sticking when the relay is actuated, thereby ensuring the safety of the relay.

[0005] The present application provides a slow-start circuit, comprising: a controller, a first MOS tube, a second MOS tube, a relay and a capacitor;

[0006] The first end of the relay is used to connect to the power input end, and the second end of the relay is connected to the first end of the capacitor;

[0007] The first MOS tube and the second MOS tube are connected in series and then connected in parallel at two ends of the relay;

[0008] The controller is used to control the first MOS transistor and the second MOS transistor to operate in a linear region during slow start, so that the voltage on the capacitor gradually increases.

[0009] Preferably, the controller is further used to control the relay to be turned on and control the first MOS tube and the second MOS tube to be turned off after the soft start is completed.

[0010] Preferably, the first MOS transistor and the second MOS transistor are connected in series back to back.

[0011] Preferably, it also includes: a driving circuit;

[0012] The controller connects the gate of the first MOS transistor and the gate of the second MOS transistor through the driving circuit;

[0013] The controller is used for intermittently sending a pulse width modulation (PWM) signal to the driving circuit.

[0014] Preferably, it also includes: an optical coupler;

[0015] The controller is connected to the driving circuit via the optical coupler.

[0016] Preferably, the driving circuit comprises a first triode and a second triode;

[0017] The input end of the optical coupler is connected to the controller;

[0018] The first output terminal of the optical coupler is connected to the working voltage, and the base of the first transistor and the base of the second transistor are both connected to the second output terminal of the optical coupler;

[0019] The collector of the first transistor is connected to the working voltage, the emitter of the first transistor is connected to the emitter of the second transistor, the emitter of the first transistor is connected to the second end of the first MOS transistor, the first end of the first MOS transistor is connected to the first end of the relay; the first end of the second MOS transistor is connected to the second end of the first MOS transistor, the second end of the second MOS transistor is connected to the first end of the capacitor, and the second end of the capacitor is grounded;

[0020] The second end of the first MOS tube is connected to a working ground.

[0021] Preferably, it also includes: a third triode;

[0022] The controller is connected to the base of the third transistor, the emitter of the third transistor is grounded, the collector of the third transistor is connected to the second input end of the optocoupler, and the first input end of the optocoupler is connected to the first voltage.

[0023] Preferably, it also includes: a pulse width driver chip, a transformer and a voltage doubler rectifier circuit;

[0024] The controller is connected to the input end of the pulse width driver chip, the power supply end of the pulse width driver chip is connected to the second voltage, the output end of the pulse width driver chip is connected to the primary winding of the transformer, the first end of the secondary winding of the transformer is connected to the first input end of the voltage doubler rectifier circuit, the second end of the secondary winding is connected to the second input end of the voltage doubler rectifier circuit, the first output end of the voltage doubler rectifier circuit outputs the working voltage, and the second output end of the voltage doubler rectifier circuit outputs the working ground.

[0025] Preferably, the controller is further used to control the first MOS tube and the second MOS tube to be turned on and the relay to be turned off when overcurrent or short circuit is confirmed, and control the first MOS tube and the second MOS tube to be turned off after a preset time.

[0026] The present application also provides a power converter, comprising a power conversion circuit and the above-described slow-start circuit;

[0027] The slow-start circuit is connected to the input end of the power conversion circuit.

[0028] The slow-start circuit provided in the present application controls the two MOS tubes to work in the linear region during slow-start, presenting impedance characteristics, limiting the current impact during the slow-start process, making the current of the capacitor rise slowly, and protecting the safety of the capacitor. In addition, the two MOS tubes cooperate with the relay action to avoid arcing and adhesion of the mechanical contact switch inside the relay, thereby causing failure of the power supply product. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of a slow-start circuit in the prior art;

[0030] Figure 2 A schematic diagram of a slow-start circuit provided in an embodiment of the present application;

[0031] Figure 3 A schematic diagram of another slow-start circuit provided in an embodiment of the present application;

[0032] Figure 4 A schematic diagram of another slow-start circuit provided in an embodiment of the present application;

[0033] Figure 5 A schematic diagram of a working power generation circuit in a slow-start circuit provided in an embodiment of the present application;

[0034] Figure 6 A schematic diagram of a power converter provided in an embodiment of the present application. DETAILED DESCRIPTION

[0035] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the embodiments of the present application are further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0036] The embodiments of the present application do not specifically limit the application scenarios of the slow-start circuit, for example, it can be the input end of a power converter, the power converter can be an inverter, or a converter in a communication power supply. The present application also does not specifically limit the application scenarios of the inverter, for example, it can be a household inverter, or an industrial and commercial inverter.

[0037] The implementation method of the slow-start circuit provided in the embodiment of the present application is described below in conjunction with the accompanying drawings.

[0038] See also Figure 2 , which is a schematic diagram of a slow-start circuit provided in an embodiment of the present application.

[0039] The embodiment of the present application provides a slow-start circuit, including: a controller 100, a first MOS transistor Q4, a second MOS transistor Q5, a relay K and a capacitor C.

[0040] The first end of the relay K is used to connect to the power input terminal IN, and the second end of the relay K is connected to the first end of the capacitor C.

[0041] The first MOS transistor Q4 and the second MOS transistor Q5 are connected in series and then connected in parallel at two ends of the relay K.

[0042] The controller 100 is used to control the first MOS transistor Q4 and the second MOS transistor Q5 to operate in a linear region during slow start, so that the voltage on the capacitor C gradually increases.

[0043] It should be understood that slow start means that when the system is just powered on, in order to avoid excessive surge current and damage to the capacitor or subsequent circuit, the capacitor needs to be charged with a slow current increase gradually. The voltage on the capacitor can power the subsequent circuit or load.

[0044] It should be understood that MOS tubes can work in the linear region or the saturation region. When the MOS tube works in the saturation region, it is a pure switch with only two states: on and off. However, when the MOS tube works in the linear region, it can show the characteristics of resistance.

[0045] In a possible implementation, the first MOS transistor Q4 and the second MOS transistor Q5 can be connected back to back, such as Figure 2 As shown, Figure 2 The body diode of the first MOS tube Q4 and the body diode of the second MOS tube Q5 are not shown in the figure. Figure 3 As shown, the body diodes of the two MOS transistors are connected back to back, that is, the anode of the body diode D4 of the first MOS transistor Q4 is connected to the anode of the body diode D5 of the second MOS transistor Q5.

[0046] The controller can control the power supply voltage to be applied between the gate sources of the first MOS transistor Q4 and the second MOS transistor Q5 which are back-to-back, so that the first MOS transistor Q4 and the second MOS transistor Q5 work in the linear region. At this time, the first MOS transistor Q4 and the second MOS transistor Q5 are equivalent to a resistor, which slowly charges the capacitor C. The voltage of the capacitor C is slowly upgraded, thereby avoiding a large surge current during instantaneous startup.

[0047] The controller 100 is also used to control the relay to conduct after the slow start is completed, and control the first MOS transistor Q4 and the second MOS transistor Q5 to be turned off. This application does not specifically limit the implementation method of the controller, for example, it can be a microprocessor or a single-chip microcomputer.

[0048] The end of the slow start can be realized by detecting the voltage across the capacitor C. For example, when the voltage of the capacitor C reaches a certain threshold voltage, the slow start is considered to be ended. The controller immediately drives the relay K to make the relay K in the on state, and then the controller 100 controls the back-to-back first MOS transistor Q4 and the second MOS transistor Q5 to be in the off state, providing a path for the subsequent large current to flow through the relay K, thereby avoiding the need to set a large heat dissipation device for the first MOS transistor Q4 and the second MOS transistor Q5.

[0049] The following introduces a specific implementation method of the controller controlling the first MOS transistor and the second MOS transistor.

[0050] See also Figure 4 , which is a schematic diagram of another slow-start circuit provided in an embodiment of the present application.

[0051] The slow-start circuit provided in the embodiment of the present application further includes: a driving circuit;

[0052] The controller connects the gate of the first MOS transistor and the gate of the second MOS transistor through the driving circuit; the controller is used to intermittently send a pulse width modulation PWM signal to the driving circuit. For example, MOS_DRI in the figure represents the PWM signal output by the controller.

[0053] In order to achieve signal isolation and avoid interference, the buffer circuit provided in the embodiment of the present application further includes: an optical coupler U1;

[0054] The controller is connected to the driving circuit via the optical coupler U1.

[0055] In a possible implementation, the driving circuit includes a first transistor Q2 and a second transistor Q3;

[0056] The input end of the optical coupler U1 is connected to the controller;

[0057] The first output terminal 4 of the optocoupler U1 is connected to the working voltage VDD. Specifically, the first output terminal 4 of the optocoupler U1 is connected to the working voltage VDD through the fifth resistor R5. The base of the first transistor Q2 and the base of the second transistor Q3 are both connected to the second output terminal 3 of the optocoupler U1.

[0058] The collector of the first transistor Q2 is connected to the working voltage VDD, specifically, the collector of the first transistor Q2 is connected to the working voltage VDD through the sixth resistor R6. The emitter of the first transistor Q2 is connected to the emitter of the second transistor Q3, and the emitter of the first transistor Q2 is connected to the second end of the first MOS transistor Q4, specifically, the emitter of the first transistor Q2 is connected to the second end of the first MOS transistor Q4 through the eighth resistor R8 and the ninth resistor R9 connected in series. The first end of the first MOS transistor Q4 is connected to the first end of the relay K; the first end of the second MOS transistor Q5 is connected to the second end of the first MOS transistor Q4, the second end of the second MOS transistor Q5 is connected to the first end of the capacitor, and the second end of the capacitor is grounded.

[0059] The second end of the first MOS transistor Q4 is connected to the working ground VSS. In addition, the second output end 3 of the optical coupler U1 is connected to the working ground VSS through the seventh resistor R7.

[0060] In order to increase the driving capability, the slow-start circuit provided in the embodiment of the present application further includes: a third transistor Q1;

[0061] The controller is connected to the base of the third transistor Q1, the emitter of the third transistor Q1 is grounded, the collector of the third transistor Q1 is connected to the second input terminal 2 of the optocoupler U1, and the first input terminal 1 of the optocoupler U1 is connected to a first voltage, for example, the first voltage is 5V.

[0062] In order to limit the current, the controller is connected to the base of the third transistor Q1 through the first resistor R1, the second resistor R2 is connected between the base and the emitter of the third transistor Q1, and the emitter of the third transistor Q1 is grounded GND.

[0063] At the startup moment, the auxiliary power supply supplies 5V, and the controller is powered normally. The controller sends a control signal MOS_DRI in a high level state, so that the first output terminal 4 and the second output terminal 3 of the optocoupler U1 are in a conductive state. The controller intermittently sends a pulse width modulation signal, so that the optocoupler pull-up power supply VDD-VSS is in a slow rising process.

[0064] The following introduces a working power supply generation circuit in combination with the power supply generation process of VDD and VSS.

[0065] See also Figure 5 , which is a schematic diagram of a working power generation circuit in a slow-start circuit provided in an embodiment of the present application.

[0066] The slow-start circuit provided in the embodiment of the present application further includes: a pulse width driving chip U2, a transformer T1 and a voltage doubler rectifier circuit. The voltage doubler rectifier circuit provided in the embodiment of the present application includes a first diode D1 and a second diode D2.

[0067] The pulse width modulation signal DPWM output by the controller is connected to the input end of the pulse width driving chip U2. Specifically, the pulse width modulation signal DPWM output by the controller is connected to the input end of U2 through the tenth resistor R10.

[0068] The power supply end of the pulse width driver chip U2 is connected to a second voltage, for example, the second voltage is 12V, the output end of the pulse width driver chip U2 is connected to the primary winding of the transformer T1, the first end of the secondary winding of the transformer T1 is connected to the first input end of the voltage doubler rectifier circuit, that is, the first end of the secondary winding is connected to the anode of D1 through the fifth capacitor C5, and the second end of the secondary winding is connected to the second input end of the voltage doubler rectifier circuit, that is, the anode of D2. The first output end of the voltage doubler rectifier circuit outputs the working voltage VDD, and the second output end of the voltage doubler rectifier circuit outputs the working ground VSS. A sixth capacitor C6 is connected between VDD and VSS. The functions of the capacitors described above are mainly for filtering and achieving the purpose of voltage stabilization.

[0069] Specifically, the two output pins of U2 are connected to the first end of C4 through the twelfth resistor R12 and the thirteenth resistor R13 respectively, and the second end of C4 is connected to the first end of the primary winding. The power supply end of U2 is connected to 12V, and the power supply end of U2 is grounded through the second capacitor C2 and the third capacitor C3 connected in parallel.

[0070] The signal input terminal of U2 is grounded via the first capacitor C1.

[0071] The two enable pins of U2 are connected to 12V through the eleventh resistor R11.

[0072] In addition, the slow-start circuit provided in the embodiment of the present application can also realize protection against overcurrent or short circuit. Specifically, the controller is also used to control the first MOS tube and the second MOS tube to be turned on and the relay to be turned off when overcurrent or short circuit is confirmed, and control the first MOS tube and the second MOS tube to be turned off after a preset time.

[0073] Continue to see Figure 4When overcurrent or short circuit occurs, it is necessary to cut off the high current path. At this time, the controller controls MOS_DRI to a high level, so that a large current briefly passes through the first MOS tube Q4 and the second MOS tube Q5 path, and then immediately controls the relay K to be turned off. After a delay of several milliseconds, MOS_DRI is immediately controlled to a low level to turn off the first MOS tube Q4 and the second MOS tube Q5, thereby cutting off the high current path for protection. Since the relay K is cut off in the zero current state, the arcing phenomenon of the relay K is effectively avoided, and the service life of the relay K is extended.

[0074] Based on the slow-start circuit provided in the above embodiments, the embodiments of the present application further provide a power converter, which will be described in detail below in conjunction with the accompanying drawings.

[0075] See also Figure 6 , which is a schematic diagram of a power converter provided in an embodiment of the present application.

[0076] The power converter provided in the embodiment of the present application includes a power conversion circuit 600 and the above-mentioned slow-start circuit 700;

[0077] The slow-start circuit 700 is connected to the input end of the power conversion circuit 600 .

[0078] Since the power converter provided in the embodiment of the present application includes the soft-start circuit introduced above, the safety of the relay can be guaranteed, thereby improving the safety of the entire power converter.

[0079] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0080] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A slow-start circuit, characterized in that: include: A controller, a first MOS tube, a second MOS tube, a relay and a capacitor; The first end of the relay is used to connect to the power input end, and the second end of the relay is connected to the first end of the capacitor; The first MOS tube and the second MOS tube are connected in series and then connected in parallel at two ends of the relay; The controller is used to control the first MOS transistor and the second MOS transistor to operate in a linear region during slow start, so that the voltage on the capacitor gradually increases.

2. The circuit according to claim 1, characterized in that The controller is further used to control the relay to be turned on and control the first MOS tube and the second MOS tube to be turned off after the slow start is completed.

3. The circuit according to claim 1, characterized in that The first MOS transistor and the second MOS transistor are connected in series back to back.

4. The circuit according to any one of claims 1 to 3, characterized in that: Also includes: Driving circuit; The controller connects the gate of the first MOS transistor and the gate of the second MOS transistor through the driving circuit; The controller is used for intermittently sending a pulse width modulation (PWM) signal to the driving circuit.

5. The circuit according to claim 4, characterized in that Also includes: Optocoupler; The controller is connected to the driving circuit via the optical coupler.

6. The circuit according to claim 5, characterized in that The driving circuit comprises a first triode and a second triode; The input end of the optical coupler is connected to the controller; The first output terminal of the optical coupler is connected to the working voltage, and the base of the first transistor and the base of the second transistor are both connected to the second output terminal of the optical coupler; The collector of the first transistor is connected to the working voltage, the emitter of the first transistor is connected to the emitter of the second transistor, the emitter of the first transistor is connected to the second end of the first MOS transistor, the first end of the first MOS transistor is connected to the first end of the relay; the first end of the second MOS transistor is connected to the second end of the first MOS transistor, the second end of the second MOS transistor is connected to the first end of the capacitor, and the second end of the capacitor is grounded; The second end of the first MOS tube is connected to a working ground.

7. The circuit according to claim 6, characterized in that Also includes: The third triode; The controller is connected to the base of the third transistor, the emitter of the third transistor is grounded, the collector of the third transistor is connected to the second input end of the optocoupler, and the first input end of the optocoupler is connected to the first voltage.

8. The circuit according to claim 6, characterized in that Also includes: Pulse width driver chip, transformer and voltage doubler rectifier circuit; The controller is connected to the input end of the pulse width driver chip, the power supply end of the pulse width driver chip is connected to the second voltage, the output end of the pulse width driver chip is connected to the primary winding of the transformer, the first end of the secondary winding of the transformer is connected to the first input end of the voltage doubler rectifier circuit, the second end of the secondary winding is connected to the second input end of the voltage doubler rectifier circuit, the first output end of the voltage doubler rectifier circuit outputs the working voltage, and the second output end of the voltage doubler rectifier circuit outputs the working ground.

9. The circuit according to any one of claims 1 to 3, characterized in that: The controller is further used to control the first MOS tube and the second MOS tube to be turned on and the relay to be turned off when overcurrent or short circuit is confirmed, and control the first MOS tube and the second MOS tube to be turned off after a preset time.

10. A power converter, characterized in that: It comprises a power conversion circuit and a slow-start circuit as described in any one of claims 1 to 9; The slow-start circuit is connected to the input end of the power conversion circuit.

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