A driving circuit for a high-side switch

Abstract

The present invention discloses a driving circuit of a high-end switch, belonging to the technical field of switch driving circuits, comprising a first switch, a first capacitor, a first diode and a second diode, wherein the first end of the first switch is connected to a driving signal, the second end of the first switch is grounded, the third end of the first switch is connected to a first power supply, the third end of the first switch is connected to the first end of the first capacitor, the second end of the first capacitor is connected to the cathode of the first diode, the anode of the first diode is connected to the first end of the controlled switch, the second end of the first capacitor is connected to the anode of the second diode, and the cathode of the second diode is connected to the control end of the controlled switch. The driving circuit of a high-end switch of the present invention can simplify the transformer structure and does not require an optical coupler, thereby reducing costs, simplifying PCB layout, and having a wide range of applications.

Description

Technical Field

[0001] The present invention relates to the technical field of switch driving circuits, and in particular to a driving circuit for a high-end switch. Background Art

[0002] In lithium battery chargers, in order to ensure reliable charging and protect lithium batteries, two back-to-back connected N-type MOSFETs are usually added to the positive output end of the charger to provide reverse connection and backflow protection.

[0003] Since these two N-type MOSFETs are located at the high end of the transformer, it is difficult to drive and control their switching. A common method is to add an auxiliary winding on the secondary side of the transformer to power the MOSFET and use an optocoupler to control its on and off, such as Figure 1 As shown, the input terminals IN11 and IN12 of the front-stage conversion circuit 11 are connected to an AC voltage, the output terminal of the front-stage conversion circuit 11 is connected to both ends of a winding N11 of a transformer T11, both ends of a winding N12 of the transformer T11 are connected to the input terminal of a rear-stage conversion circuit 12, the output terminal of the rear-stage conversion circuit 12 is connected to a battery, and the output high end of the rear-stage conversion circuit 12 has two back-to-back connected N-type MOSFETs Q11 and MOSFET Q12, the source electrodes of the MOSFET Q11 and the MOSFET Q12 are connected together and then connected in series to the output high end of the rear-stage conversion circuit 12. One end of the auxiliary winding N13 is connected to the anode of the diode D11, the cathode of the diode D11 is connected to the positive output end of the optocoupler O11 through the resistor R11, the negative output end of the optocoupler Q11 is connected to the gates of the MOSFET Q11 and the MOSFET Q12, the second end of the auxiliary winding N13 is connected to the gates of the MOSFET Q11 and the MOSFET Q12 through the resistor R13, the capacitor C11 is connected in parallel between the second end of the auxiliary winding N13 and the cathode of the diode D11, the positive input end of the optocoupler O11 is connected to the I / O port IN13 of the MCU through the resistor R12, and the negative input end of the optocoupler O11 is grounded. The high and low levels are output through the I / O port IN13 of the MCU, so that the optocoupler O11 is turned on or off, thereby controlling the MOSFET Q11 and the MOSFET Q12 to be turned on or off.

[0004] However, this method has a complex transformer structure and uses an optocoupler, which occupies more PCB space and is more expensive. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a driving circuit for a high-side switch.

[0006] To achieve the above object, the technical solution of the present invention is:

[0007] A driving circuit for a high-end switch, the driving circuit for the high-end switch is used to drive a controlled switch connected in series to the high end of a transformer output, comprising a first switch, a first capacitor, a first diode and a second diode, wherein the first end of the first switch is connected to a driving signal, the second end of the first switch is grounded, the third end of the first switch is connected to a first power supply, the third end of the first switch is connected to the first end of the first capacitor, the second end of the first capacitor is connected to the cathode of the first diode, the anode of the first diode is connected to the first end of the controlled switch, the second end of the first capacitor is connected to the anode of the second diode, and the cathode of the second diode is connected to the control end of the controlled switch.

[0008] The above driving signal is a square wave.

[0009] In a specific embodiment, the square wave is generated by an MCU or a timer or an operational amplifier or a comparator.

[0010] In a specific embodiment, the first switch is a MOSFET.

[0011] In a specific embodiment, the first switch is a transistor.

[0012] The present invention further provides a DC / DC converter, comprising the driving circuit of the above-mentioned high-end switch, and also comprising a transformer and a first controlled switch, wherein the first controlled switch is connected in series to the output high end of the transformer.

[0013] In a specific embodiment, the DC / DC converter further includes a second controlled switch, and the first controlled switch and the second controlled switch are connected in reverse series to the output high end of the transformer.

[0014] The present invention also provides an AC / DC conversion device, comprising the above-mentioned DC / DC converter and a full-bridge converter, wherein the full-bridge converter is connected in parallel with the input end.

[0015] Beneficial effect: A driving circuit for a high-end switch of the present invention can simplify the transformer structure and does not require an optical coupler, thereby reducing costs, simplifying PCB layout, and having a wide range of applications.

[0016] In order to make the above features and advantages of the invention more obvious and easy to understand, embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of a MOSFET driving circuit in the prior art.

[0018] Figure 2The present invention is a circuit diagram of a driving circuit of a high-end switch.

[0019] Figure 3 The present invention is a circuit diagram of a specific embodiment of a high-side switch driving circuit of the present invention.

[0020] In the drawings, like reference numerals refer to the same drawing elements. DETAILED DESCRIPTION

[0021] In order to make the purpose and technical solution of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Figure 2 FIG. 1 is a circuit diagram of a driving circuit of a high-end switch of the present invention. Figure 1 As shown, the input terminals IN21 and IN22 of the front-stage conversion circuit 21 are connected to an AC voltage, the output terminal of the front-stage conversion circuit 21 is connected to both ends of a winding N21 of a transformer T21, both ends of a winding N22 of the transformer T21 are connected to the input terminal of a rear-stage conversion circuit 22, the output terminal of the rear-stage conversion circuit 22 is connected to a battery, and the output high end of the rear-stage conversion circuit 22 has two reversely connected N-type MOSFETs Q21 and N-type MOSFETs Q22, the source electrodes of the MOSFETs Q21 and Q22 are connected together and then connected in series to the output high end of the rear-stage conversion circuit 22.

[0023] The high-side switch driving circuit 23 includes a switch Q23, a capacitor C21, a diode D21 and a diode D22. The first end of the resistor R21 is connected to the PWM square wave, the second end of the resistor R21 is connected to the first end of the switch Q23, the second end of the switch Q23 is grounded GND2, the third end of the switch Q23 is connected to the first end of the resistor R23, the second end of the resistor R23 is connected to the power supply Vcc, the first end of the resistor R22 is connected to the first end of the switch Q23, and the second end of the resistor R22 is connected to the second end of the switch Q23; the third end of the switch Q23 is also connected to the first end of the capacitor C21, the second end of the capacitor C21 is connected to the cathode of the diode D21, the anode of the diode D21 is connected to the source of the MOSFET Q22, the second end of the capacitor C21 is connected to the anode of the diode D22, the cathode of the diode D22 is connected to the gates of the MOSFET Q21 and the MOSFET Q22, the first end of the capacitor C22 is connected to the source of the MOSFET Q22, the second end of the capacitor C22 is connected to the cathode of the diode D22, and the resistor R24 ​​is connected in parallel to the two ends of the capacitor C22.

[0024] The switch Q23 is a controllable switch. In a specific embodiment, the switch Q23 is a MOSFET. The first end of the switch Q23 is its gate, the second end of the switch Q23 is its source, and the third end of the switch Q23 is its drain.

[0025] In another specific embodiment, the switch Q23 is a triode, in which case the first end of the switch Q23 is its base, the second end of the switch Q23 is its emitter, and the third end of the switch Q23 is its collector.

[0026] In a specific embodiment, the PWM square wave can be generated from an MCU, a timer, an operational amplifier or a comparator.

[0027] Figure 3 FIG. 1 is a circuit diagram of a specific embodiment of a high-side switch driving circuit of the present invention. Figure 3As shown, the switch Q33 is a MOSFET. The input terminals IN31 and IN32 of the front-stage conversion circuit 31 are connected to the AC voltage, the output terminal of the front-stage conversion circuit 31 is connected to the two ends of the winding N31 of the transformer T31, the two ends of the winding N32 of the transformer T31 are connected to the input terminal of the rear-stage conversion circuit 32, the output terminal of the rear-stage conversion circuit 32 is connected to the battery, and the output high end of the rear-stage conversion circuit 32 has two reversely connected N-type MOSFETs Q31 and MOSFET Q32 in series, and the source electrodes of the MOSFET Q31 and the MOSFET Q32 are connected together and then connected in series to the output high end of the rear-stage conversion circuit 32.

[0028] The front-stage conversion circuit 31 includes a diode D33, a diode D34, a diode D35, a diode D36, a capacitor C33 and a switch tube Q34, wherein the anode of the diode D33 is connected to the cathode of the diode D34, the anode of the diode D35 is connected to the cathode of the diode D36, the cathode of the diode D33 is connected to the cathode of the diode D35, the anode of the diode D34 is connected to the anode of the diode D36, the anode of the diode D33 is connected to the input terminal IN31, the anode of the diode D35 is connected to the input terminal IN32, the first end of the capacitor C33 is connected to the cathode of the diode D35, the second end of the capacitor C33 is connected to the anode of the diode D36, the second end of the capacitor C33 is grounded GND1, the source of the switch tube Q34 is grounded GND1, the drain of the switch tube Q34 is connected to the second end of the winding N31 of the transformer T31, and the first end of the winding N31 is connected to the first end of the capacitor C33.

[0029] The post-stage conversion circuit 32 includes a diode D37, a capacitor C34 and a resistor R35, the anode of the diode D37 is connected to the first end of the winding N32, the cathode of the diode D37 is connected to the drain of the MOSFET Q31, the first end of the capacitor C34 is connected to the cathode of the diode D37, the second end of the capacitor C34 is grounded GND2, the first end of the resistor R35 is grounded GND2, and the second end of the resistor R35 is the output low end of the post-stage conversion circuit 32.

[0030] The high-side switch driving circuit 33 includes a switch Q33 , a capacitor C31 , a diode D31 , and a diode D32 . The first end of the resistor R31 is connected to the PWM square wave, the second end of the resistor R31 is connected to the gate of the switch Q33, the source of the switch Q33 is grounded GND2, the drain of the switch Q33 is connected to the first end of the resistor R33, the second end of the resistor R33 is connected to the voltage source Vcc, the first end of the resistor R32 is connected to the gate of the switch Q33, and the second end of the resistor R32 is connected to the source of the switch Q33; the drain of the switch Q33 is also connected to the first end of the capacitor C31, the second end of the capacitor C31 is connected to the cathode of the diode D31, the anode of the diode D31 is connected to the source of the MOSFET Q32, the second end of the capacitor C31 is connected to the anode of the diode D32, the cathode of the diode D32 is connected to the gates of the MOSFET Q31 and the MOSFET Q32, the first end of the capacitor C32 is connected to the source of the MOSFET Q32, the second end of the capacitor C32 is connected to the cathode of the diode D32, and the resistor R34 is connected in parallel to both ends of the capacitor C32.

[0031] Next, continue to combine Figure 3 The working principle of the present invention is introduced.

[0032] The PWM square wave is connected to the gate of the switch Q33 to control the on and off of the switch Q33, thereby generating a square wave with an opposite phase on the drain of the switch Q33. When the switch Q33 is turned on, the first end of the capacitor C31 is grounded, the diode D31 is turned on, and the MOSFET Q31 and the MOSFET Q32 are turned off. When the switch Q33 is turned off, the diode D31, the diode D32, and the capacitor C31 constitute a bootstrap module, and the power supply Vcc cyclically charges and discharges the capacitor C31 in the bootstrap module through the resistor R33, so that the voltage of the power supply Vcc is applied to the gates of the MOSFET Q31 and the MOSFET Q32, so that the gate-source voltage V gs Maintaining a voltage greater than the threshold voltage V gs-th , thereby turning on the MOSFET Q31 and the MOSFET Q32. When the duty cycle of the square wave is 0 or 100%, due to the capacitor blocking, the power supply Vcc cannot cyclically charge and discharge the capacitor C31, so it cannot raise the gate voltage of the MOSFET Q31 and the MOSFET Q32, and the MOSFET Q31 and the MOSFET Q32 are in the off state. The amplitude of the square wave is Vcc.

[0033] Although the present invention has been disclosed as above by way of embodiments, it is not intended to limit the present invention. Any person having ordinary knowledge in the technical field may make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the scope of the attached patent application.

Claims

1. A high-end switch driving circuit, the high-end switch driving circuit is used to drive a controlled switch connected in series to the high-end output of a transformer, characterized in that: The invention comprises a first switch, a first capacitor, a first diode and a second diode, wherein the first end of the first switch is connected to a driving signal, the second end of the first switch is grounded, the third end of the first switch is connected to a first power supply, the third end of the first switch is connected to the first end of the first capacitor, the second end of the first capacitor is connected to the cathode of the first diode, the anode of the first diode is connected to the first end of the controlled switch, the second end of the first capacitor is connected to the anode of the second diode, and the cathode of the second diode is connected to the control end of the controlled switch.

2. A high-side switch driving circuit as claimed in claim 1, characterized in that: The driving signal is a square wave.

3. A high-side switch driving circuit as claimed in claim 2, characterized in that: The square wave is generated by an MCU, a timer, an operational amplifier, or a comparator.

4. A high-side switch driving circuit as claimed in claim 1, characterized in that: The first switch is a MOSFET.

5. A high-side switch driving circuit as claimed in claim 1, characterized in that: The first switch is a transistor.

6. A DC / DC converter, characterized in that: A driving circuit for a high-end switch comprising a circuit as claimed in any one of claims 1 to 5, further comprising a transformer and a first controlled switch, wherein the first controlled switch is connected in series to the high-end output of the transformer.

7. A DC / DC converter as claimed in claim 6, characterized in that: The transformer further includes a second controlled switch, wherein the first controlled switch and the second controlled switch are connected in reverse series to the output high end of the transformer.

8. An AC / DC conversion device, characterized in that: It comprises a DC / DC converter as claimed in claim 6, and also comprises a full-bridge converter, wherein the full-bridge converter is connected in parallel with the input end.

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