Level adjusting circuit and gate driving device including the same

A level adjusting circuit includes a parallel resistor-capacitor (RC) sub-circuit, a first diode and an adjustable voltage supply. The RC sub-circuit includes an input capacitor and an input resistor, and includes an input node electrically connected to a driving signal source for receiving a driving signal therefrom, and an output node that outputs an adjusted driving signal. The first diode and the adjustable voltage supply are electrically connected, and are further electrically connected to the output node and a reference voltage node, respectively.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority of Taiwanese Patent Application No. 110101136, filed on Jan. 12, 2021.

FIELD

The disclosure relates to a level adjusting circuit and a driving device, and more particularly to a level adjusting circuit for adjusting a driving signal from a gate driver, and a gate driving device including the level adjusting circuit.

BACKGROUND

Wide-bandgap semiconductor (also known as the third generation semiconductor) materials include silicon carbide (SiC) and gallium nitride (GaN). The third generation semiconductor materials have favorable characteristics such as relatively high carrier mobility and a relatively large band-gap. For example, a semiconductor device manufactured using GaN material (also known as GaN devices) may have a figure of merit (FOM) that is 5 to 10 times higher than that of a semiconductor device manufactured using silicon material. As a result, the third generation semiconductor materials may be employed to manufacture devices for more advanced applications such as high-voltage power devices and high-frequency communication devices.

While GaN devices have passed the reliability standard issued by JEDEC Solid State Technology Association, since the performances of third generation semiconductor material devices under different conditions (such as a static condition, a dynamic condition, etc.) may vary, it is still desirable to establish an on-site testing mechanism for determining a number of qualities of GaN devices, such as robustness in applications and system-level reliability.

FIG.1is a circuit diagram illustrating a conventional gate driving device used for testing, for example, a power device. The gate driving device includes a commercially available gate driver11that receives an input signal (Vin) and outputs an output signal (Vout). The output signal (Vout) is provided to a gate of a to-be-tested device19(such as a field-effect transistor) for switching a mode of operation of the to-be-tested device19in order to test and determine the performance of the to-be-tested device19.

In this configuration, the range of voltage that can be outputted by the gate driving device is between a power supply voltage (Vcc) and a reference voltage (Vss, typically the voltage of ground).

SUMMARY

One object of the disclosure is to provide a level adjusting circuit that can adjust voltage of a driving signal outputted by a commercially available gate driver.

According to one embodiment of the disclosure, the level adjusting circuit includes:

a parallel resistor-capacitor (RC) sub-circuit that includes an input capacitor and an input resistor that are connected in parallel, the parallel RC sub-circuit including an input node electrically connected to a driving signal source for receiving a driving signal therefrom, and an output node that outputs an adjusted driving signal; and

a first diode and an adjustable voltage supply that are electrically connected, the first diode being further electrically connected to the output node, and the adjustable voltage supply being further electrically connected to a reference voltage node.

Another object of the disclosure is to provide a gate driving device that includes the above-mentioned level adjusting circuit.

According to one embodiment of the disclosure, the gate driving device includes:

a gate driver circuit that is configured to receive a supply voltage, and that is connected to a reference voltage node, the gate driver circuit including an input port that receives an input voltage signal and an output port that outputs a driving signal;

a parallel resistor-capacitor (RC) sub-circuit that includes an input capacitor and an input resistor (45) that are connected in parallel, the parallel resistor-capacitor sub-circuit including an input node electrically connected to the output port of the gate driver circuit for receiving the driving signal (Vout) therefrom, and an output node that outputs an adjusted driving signal to a to-be-supplied component;

a first diode and an adjustable voltage supply that are electrically connected, the first diode being further electrically connected to the output node, and said adjustable voltage supply being further electrically connected to the reference voltage node.

DETAILED DESCRIPTION

FIG.2is a circuit diagram illustrating a gate driving device200according to one embodiment of the disclosure.

In this embodiment, the gate driving device200includes a gate driver circuit3, a level adjusting circuit4, and a slew rate adjusting resistor6.

The gate driver circuit3may be embodied using a commercially available gate driver (which may be in the form of a discrete integrated circuit), is configured to receive a supply voltage (Vcc), and is connected to a reference voltage node41. The reference voltage node41has a reference voltage (Vss) which may be a ground voltage (Gnd).

The gate driver circuit3includes an input port22that receives an input voltage signal (Vin) and an output port that outputs a driving signal (Vout). In this embodiment, the input voltage signal (Vin) may be in the form of a rectangular pulse wave signal generated by, for example, a control circuit (not shown), and the driving signal (Vout) is an amplified version of the input voltage signal (Vin) with no phase difference with respect to the input voltage signal (Vin). That is, the driving signal (Vout) and the input voltage signal (Vin) are said to be in phase.

The level adjusting circuit4includes a parallel resistor-capacitor (RC) sub-circuit that includes an input capacitor44and an input resistor45that are connected in parallel, a first diode46, and an adjustable voltage supply47.

The parallel RC sub-circuit includes an input node43electrically connected to a driving signal source (i.e., the gate driver circuit3) for receiving the driving signal (Vout) therefrom, and an output node42that outputs an adjusted driving signal (Vgs). It is noted that the input capacitor44serves as a signal path for the driving signal (Vout) when the driving signal (Vout) is in a transient state, and the input resistor45serves as a signal path for the driving signal (Vout) when the driving signal (Vout) is in a steady state.

The first diode46and the adjustable voltage supply47are electrically connected, the first diode46is further electrically connected to the output node42, and the adjustable voltage supply47is further electrically connected to the reference voltage node41. In this embodiment, the first diode46is embodied using a Schottky diode that is known to have a low forward voltage drop and a high switching speed, and the adjustable voltage supply47may be embodied using a commercially available power supply that provides an adjustable voltage (Vset).

In this embodiment, the first diode46includes an anode that is electrically connected to the output node42, and a cathode. The adjustable voltage supply47includes a positive terminal that is electrically connected to the cathode of the first diode46, and a negative terminal that is electrically connected to the reference voltage node41.

The adjustable voltage supply47may be embodied using a four quadrant power supply that can provide positive or negative voltage, and that can source or sink electrical current.

In some embodiments, the level adjusting circuit4further includes a resistor51that is connected in parallel with the adjustable voltage supply47. The resistor51may act as a current path for an electrical current flowing through the first diode46—when the voltage supply47is not operating at the 4thquadrant mode (i.e., providing a positive voltage and sinking current). That is to say, the electrical current flowing through the first diode46may go into the resistor51path, under specified voltage and current settings from the adjustable voltage supply47.

In some embodiments, the level adjusting circuit4further includes a capacitor52that is connected in parallel with the adjustable voltage supply47. The capacitor52may act to reduce an adverse effect resulting from a sudden change of voltage across the adjustable voltage supply47.

The slew rate adjusting resistor6includes one end connected to the output node42and another end connected to a to-be-supplied component9. In this embodiment, the to-be-supplied component9is an N-channel field effect transistor, and may be other semiconductor devices, circuitry or system that are intended to be tested by applying a signal thereto. Said another end of the slew rate adjusting resistor6is connected to a gate of the to-be-supplied component9. It is noted that a resistance of the slew rate adjusting resistor6may be adjusted so that a slew rate associated with the to-be-supplied component9(and therefore, a switching speed) may also be adjusted to accommodate different conditions.

FIG.3is a signal diagram illustrating relationships among the input voltage signal (Vin), the driving signal (Vout) and the adjusted driving signal (Vgs) outputted by the level adjusting circuit4of the gate driving device200ofFIG.2. It is noted that the input voltage signal (Vin) and the driving signal (Vout) are rectangular pulse waves and are in phase, and the input voltage signal (Vin) varies between a low level and a high level.

In the case that the input voltage signal (Vin) is at the low level, the corresponding driving signal (Vout) is also at a low level that is close to the reference voltage (Vss), and therefore the first diode46experiences reverse bias. As such, the resulting voltage of the adjusted driving signal (Vgs) may be expressed as Vset+0.3−Vcc (volts), where 0.3 is a forward voltage drop of the first diode46.

On the other hand, in the case that the input voltage signal (Vin) is at the high level, the corresponding driving signal (Vout) is also at a high level that is close to the supply voltage (Vcc), and therefore the first diode46experiences a forward bias. As such, the resulting voltage of the adjusted driving signal (Vgs) may be expressed as Vset+0.3 (volts), where 0.3 is the forward voltage drop of the first diode46. In this case, an electrical current from the cathode of the first diode46and an electrical current from the positive terminal of the adjustable voltage supply47both flow to the reference voltage node41through the resistor51.

It is noted that the level adjusting circuit4of the gate driving device200ofFIG.2is capable of providing an adjusted driving signal (Vgs) with two different voltage levels that are different from the supply voltage (Vcc) and the reference voltage (Vss) and that can be adjusted by altering the adjustable voltage (Vset) supplied by the adjustable voltage supply47.

FIG.4is a circuit diagram illustrating a gate driving device400according to one embodiment of the disclosure.

In this embodiment, aside from the components of the gate driving device200ofFIG.2, the gate driving device400further includes a second diode53. The second diode53includes an anode that is electrically connected to the reference voltage node41, and a cathode that is electrically connected to the output node42. In this embodiment, the second diode53is embodied using a Schottky diode that is known to have a low forward voltage drop and a high switching speed.

FIG.5is a signal diagram illustrating relationships among the input voltage signal (Vin), the driving signal (Vout) and the adjusted driving signal (Vgs) outputted by the level adjusting circuit4of the gate driving device400ofFIG.4. It is noted that the input voltage signal (Vin) and the driving signal (Vout) are rectangular pulse waves and are in phase, and the input voltage signal (Vin) varies between a low level and a high level.

In the case that the input voltage signal (Vin) is at the low level, the corresponding driving signal (Vout) is also at a low level that is close to the reference voltage (Vss), and therefore the first diode46experiences reverse bias, and the second diode53experiences forward bias. Once the voltage across the input capacitor44drops to an extent that the second diode53is no longer forward-biased, the voltage of the adjusted driving signal (Vgs) is clamped by the second diode53. As such, the resulting voltage of the adjusted driving signal (Vgs) may be expressed as Vss−0.3 (volts), where 0.3 is a forward voltage drop of the second diode53.

On the other hand, in the case that the input voltage signal (Vin) is at the high level, the corresponding driving signal (Vout) is also at a high level that is close to the supply voltage (Vcc), and therefore the first diode46experiences forward bias, and the second diode53experiences reverse bias. As such, the resulting voltage of the adjusted driving signal (Vgs) may be expressed as Vset+0.3 (volts), where 0.3 is the forward voltage drop of the first diode46. In this case, an electrical current from the cathode of the first diode46and an electrical current from the positive terminal of the adjustable voltage supply47both flow to the reference voltage node41through the resistor51.

It is noted that the level adjusting circuit4of the gate driving device400ofFIG.4is capable of providing an adjusted driving signal (Vgs) with two different voltage levels that are different from the supply voltage (Vcc) and the reference voltage (Vss). One of the two different voltage levels can be adjusted by altering the adjustable voltage (Vset) supplied by the adjustable voltage supply47.

One effect of the embodiments of the disclosure is that, by configuring the level adjusting circuit of the gate driving device to output the adjusted driving signal (Vgs), where the voltage level(s) of the adjusted driving signal (Vgs) can be adjusted, the gate driving device may be used in a wide range of applications that require input signals of various voltage levels. For example, when a number of devices from different manufacturers are to be tested for comparing performance among the devices (an operation known as benchmarking), the operation may be done by using the same gate driving device and adjusting the voltage level (s) of the adjusted driving signal (Vgs) when necessary. In some cases where a driving level effect (e.g., a transient speed or on-state performances that depend on a driving level) for some devices, circuitry or systems may be optimized by adjusting the adjusted driving signal (Vgs) to specific voltage levels, the gate driving device described in the disclosure may be particularly useful.

According to one embodiment of the disclosure, there is provided a level adjusting circuit that is configured to be connected between a driving signal source (e.g., a gate driver circuit) and a to-be-supplied component.

The level adjusting circuit includes a parallel resistor-capacitor (RC) sub-circuit, a first diode and an adjustable voltage supply.

The RC sub-circuit includes an input capacitor and an input resistor that are connected in parallel. The parallel RC sub-circuit includes an input node electrically connected to the driving signal source for receiving a driving signal therefrom, and an output node that outputs an adjusted driving signal.

The first diode and the adjustable voltage supply are electrically connected, the first diode is further electrically connected to the output node, and the adjustable voltage supply is further electrically connected to a reference voltage node.