Discrete, low-voltage n-type power mosfet driver

Abstract

FIELD: transistor driver circuits.SUBSTANCE: driver for a power MOSFET (Mosfet) of an N-type transistor on discrete components with a power supply from a reduced voltage is proposed, which includes an independent pumping circuit with multiplication of the bootstrap capacitor from an independent driver controlled by an external generator, which supplies a signal to the driver input in the form of a square wave of a given frequency and capable of charging the bootstrap capacitor above 10 V at a driver supply voltage of 6 V or more; a negative bias generating unit for reliable locking of the power transistor; a circuit for biasing the control signal level relative to the zero potential of the circuit to the level of the voltage applied to the power transistor and an amplifier of the control signal.EFFECT: ability to constantly keep the transistor in a fully open or closed state at any voltage applied to the power transistor, ensuring its reliable and complete unlocking or locking by a control signal relative to the zero potential of the circuit, and in ensuring small dimensions of the product.2 cl, 3 dwg

Description

[0001] The invention relates to transistor driver circuits and can be used in the design of control circuits for N-type transistor switches with a load in the drain or emitter circuit for connecting or disconnecting the load from the supply circuit, where it is necessary to keep the transistor in the open state for a long time.

[0002] To turn on an N-type transistor, the gate potential must be at least equal to the source potential, equal to the transistor's turn-on threshold voltage. As the voltage applied to the gate increases, the transistor's on-resistance decreases. It is believed that a voltage of approximately 10 V is required to reliably turn on an N-type power field-effect transistor. When turning on the transistor, the transistor's source potential is practically equal to the input voltage (the voltage applied to the drain). Therefore, powering the transistor driver requires a voltage 10...15 V higher than that switched by the power transistor. The two most common solutions to this problem are powering the driver from an additional isolated voltage source and generating additional power supply voltage for the driver using a step-up circuit (a bootstrap power supply circuit).

[0003] Driver-based solutions are widely used ("Components and Technologies" No. 3, 2003, "Characteristics and Application Features of MOSFET and IGBT Drivers" or "Power Electronics" No. 1, 2019, "Review of Modern Isolated MOSFET / IGBT Gate Drivers") using optocouplers or galvanically isolated drivers. Such drivers are powered from a separate, isolated power source and can generate positive voltage for gate-on and negative voltage for gate-off.

[0004] The disadvantage of such solutions is the need to use an additional isolated power source, which significantly increases the dimensions of the end node.

[0005] Various circuit solutions for controlling a power switch based on MOSFETs with a combined driver power supply from a control device signal through an isolating two-winding transformer are also known (Patent RU2825437C1, published 08 / 26 / 2024), where the alternating control signal is transmitted through a transformer, rectified by a rectifier and used to power the driver and control the power transistor.

[0006] The disadvantage of such solutions is the presence of a transformer, which significantly increases the dimensions of the unit, and it is also impossible to transmit a constant control signal through the transformer, i.e. it is impossible to keep the upper key open for a long time.

[0007] Upper transistor (switch) control drivers with a bootstrap power supply circuit are widely used ("Components and Technologies" No. 3, 2003, "Characteristics and Application Features of MOSFET and IGBT Drivers"). In such circuits, the upper switch driver is powered from a bootstrap capacitor, which is charged when the lower transistor or diode is periodically turned on. More advanced circuit designs also exist (Patent RU182848U1, published September 4, 2018), where the upper transistor driver is powered from a bootstrap capacitor C1, which is periodically recharged from source V2 through the charging circuit VD1-C1-VD3-VT2 when the lower transistor VT2 is turned on.

[0008] The disadvantage of such circuit solutions is the need to periodically lock the upper transistor and unlock the lower transistor or diode to recharge the bootstrap capacitor, i.e., the impossibility of keeping the upper switch in the open state for a long time, as well as the presence of a supply voltage higher than the threshold supply value of the driver circuit or the control threshold of the upper transistor.

[0009] The technical result consists in creating a driver for a power MOSFET (Mosfet) transistor of the N-type on discrete components with a power supply from a reduced voltage, capable of constantly holding the transistor in a fully open or closed state at any voltage applied to the power transistor, ensuring its reliable and complete unlocking or locking by a control signal relative to the zero potential of the circuit, while the driver is implemented on discrete, simple elements ensuring small dimensions of the product.

[0010] The technical result is achieved by the driver of the power MOSFET (MOSFET) transistor of the N-type on discrete components with power supply from a reduced voltage due to the use of an independent pumping circuit with multiplication by two, consisting of a resistor R1, one terminal connected to a capacitor C2, which is connected to the junction point of the capacitor C1 and the diode VD2, to the junction point of the capacitors C1 and C2 through the diodes VD1, VD3, VD4 are connected capacitors C3 and C4, which are connected to the bootstrap capacitor C5, the other terminal of the resistor R1 is connected to an independent driver D1, the bootstrap capacitor C5 through the zener diode VD5 is connected to the circuit for shifting the level of the control signal relative to the zero potential of the circuit to the level of the applied voltage to the power transistor, consisting of a resistor R2 connected to the transistor VT2 and resistors R5 and R6, and a diode VD6 connected to the resistor R3 and transistor VT1 and resistor R4,wherein the circuit for shifting the level of the control signal relative to the zero potential of the circuit to the level of the voltage applied to the power transistor through the control signal amplifier is connected to the gate of the power MOSFET (Mosfet) transistor VT5, the drain of which is connected to the negative bias generation unit for reliable locking of the power transistor, consisting of at least one diode VD7, shunted by the capacitor C6, wherein the independent driver D1, controlled by the external generator, is configured to supply a signal in the form of a square wave of a given frequency and capable of charging the bootstrap capacitor C5 above 10 V at a supply voltage of 6 V.

[0011] The essence of the proposed invention is explained by the drawings, where Fig. 1 shows a non-limiting example of a driver circuit for an N-type power MOSFET (MOS) transistor on discrete components with a power supply from a reduced voltage; Fig. 2 shows a non-limiting example of a driver circuit for an N-type power MOSFET (MOS) transistor on discrete components with a power supply from a reduced voltage with a control signal amplifier in the form of a driver in an integrated design; Fig. 3 shows a non-limiting example of a driver circuit for an N-type power MOSFET (MOS) transistor on discrete components with a power supply from a reduced voltage (two diodes connected in series - VD7, VD8).

[0012] The driver of the N-type power MOSFET (Mosfet) transistor on discrete components with power supply from reduced voltage is designed as follows.

[0013] The driver contains a bootstrap capacitor C5, which is charged by an independent pump circuit with a multiplication by two, implemented using components R1, C1-C4, VD1-VD4, from an independent driver D1. Driver D1 acts as an amplifier for the signal coming from an external generator, generating a square wave at the output with a level equal to the driver supply voltage. From the output of driver D1, the amplified generator signal is fed to the multiplication circuit through current-limiting resistor R1 and decoupling capacitor C2, which separates the driver operating voltage levels and the voltage applied to power transistor VT5. The signal is then fed to the multiplication circuit implemented using components C1, C3, C4, VD1-VD4, which doubles the voltage level at the driver output minus the voltage drop across diodes VD1-VD4 and resistor R1.

[0014] At low currents and when using low-dropout diodes, the voltage level at the multiplier output is almost twice the square wave voltage at the driver output. This voltage level is applied to capacitor C5, charging it.

[0015] Zener diode VD5 acts as a parametric stabilizer, limiting the voltage level to which bootstrap capacitor C5 charges. This voltage supplies the control signal amplifier implemented on VT3 and VT4.

[0016] Also, the control signal amplifier can be implemented as an integrated driver (Fig. 2, D2).

[0017] The control signal amplifier (VT3, VT4, or D2) applies a control signal to the gate of the power transistor via the current-limiting resistor R1, with a voltage level practically equal to the amplifier supply voltage. The negative bias generator, implemented on VD7 and C6, is designed to generate a negative bias for reliable turn-off of the power transistor VT5. Capacitor C6 charges to the forward bias level of diode VD7 when the bootstrap capacitance C5 is pumped or when the power transistor VT5 is turned on. When the turn-off (turn-off) signal for the power transistor VT5 appears, a low voltage level appears at the amplifier output. A positive voltage from capacitor C6 is applied to the drain of the power transistor relative to its gate, biasing the gate of the power transistor in the reverse direction. This ensures reliable turn-off of the power transistor VT5.

[0018] For correct operation of this circuit, diode VD7 is selected in such a way that its forward bias voltage is higher than the emitter-base voltage drop of the amplifier transistor VT4, or two diodes are used in series (Fig. 3, diodes VD7 and VD8). In order to improve reliability (circuit stability), it is permissible to increase the number of diodes in this section of the circuit, i.e., use two or more diodes. The circuit for shifting the level of the control signal R4, VT1, R3, VD6, R2, VT2, R5, R6 relative to the zero potential of the circuit to the level of the voltage applied to the power transistor VT5 shifts the control level. When a signal to enable (turn on) the power transistor VT5 is received from the external control circuit, transistor VT1 opens, and current begins to flow through the base of transistor VT2, enabling it. The signal goes to the amplifier input through the divider VT2, R5, R6.When a signal to turn off power transistor VT5 is received from the external control circuit, transistor VT1 closes, turning off transistor VT2. The resistance of transistor VT2 becomes significantly greater than resistor R6. The potential of the R5, R6 junction drops to the potential of the R6 junction, and the collector of VT4 generates a low voltage at the amplifier output, turning off the power transistor.

[0019] Thus, the driver of the power MOSFET (Mosfet) of the N-type transistor on discrete components with a power supply from a reduced voltage is capable of constantly keeping the transistor in a fully open or closed state at any voltage applied to the transistor, ensuring its reliable and complete unlocking or locking by a control signal, and the implementation of the driver on discrete (simple elements) ensures small dimensions of the product.

Claims

1. A driver for a discrete N-type power MOSFET transistor with low-voltage power supply, characterized in that it contains an independent pumping circuit with multiplication by two, consisting of a resistor R1, one terminal of which is connected to a capacitor C2, which is connected to the junction of capacitor C1 and diode VD2, capacitors C3 and C4 are connected to the junction of capacitors C1 and C2 through diodes VD1, VD3, VD4, which are connected to a bootstrap capacitor C5, the other terminal of resistor R1 is connected to an independent driver D1, bootstrap capacitor C5 is connected through zener diode VD5 to a circuit for shifting the level of the control signal relative to the zero potential of the circuit to the level of the voltage applied to the power transistor, consisting of a resistor R2 connected to transistor VT2 and resistors R5 and R6, and a diode VD6 connected to resistor R3 and transistor VT1 and resistor R4,wherein the circuit for shifting the level of the control signal relative to the zero potential of the circuit to the level of the voltage applied to the power transistor through the control signal amplifier is connected to the gate of the power MOSFET (Mosfet) transistor VT5, the drain of which is connected to the negative bias generation unit for reliable locking of the power transistor, consisting of at least one diode VD7, shunted by the capacitor C6, wherein the independent driver D1, controlled by the external generator, is configured to supply a signal in the form of a square wave of a given frequency and capable of charging the bootstrap capacitor C5 above 10 V at a supply voltage of 6 V.

2. A driver for a power MOSFET (Mosfet) transistor of the N-type on discrete components with power supply from a reduced voltage according to paragraph 1, characterized in that the control signal amplifier is made in the form of a driver in an integrated design.

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