CN117318465A - High voltage electronic load with voltage buffer circuit - Google Patents

Abstract

The invention discloses a high-voltage electronic load with a voltage buffer circuit. The high-voltage electronic load with the voltage buffer circuit comprises a first power element and a second power element which is connected with the first power element in series to form a load loop. A voltage dividing circuit generates a divided voltage according to a voltage value to be measured. A current sensing circuit is connected in series with the load loop. A current control circuit connected to the current sensing circuit. A voltage buffer circuit is connected between a voltage divider circuit and the first power element. The voltage buffer circuit comprises a third power element, wherein the grid electrode of the third power element is connected with the voltage division connection point of the voltage division circuit, the drain electrode of the third power element is connected with the drain electrode of the first power element, the source electrode of the third power element is connected with the grid electrode of the first power element, and the source electrode of the third power element is also connected with the second connection line through a third resistor.

Description

High voltage electronic load with voltage snubber circuit

Technical field

The present invention relates to the circuit design of an electronic load, and in particular to a high-voltage electronic load with a voltage buffer circuit.

Background technique

At present, the development of electric vehicles and energy storage industry is moving towards high voltage and high power. In the field of electric vehicles and energy storage industry, it includes chargers or high-voltage batteries. A load is required when testing chargers or high voltage batteries. The load can be an actual load (such as a motor or specified electrical equipment) or an electronic load that can simulate the actual load.

Take the charger as an example. The input power of the charger is the mains power of the power grid, and the high-voltage direct current output by the charger can be used to charge the high-voltage battery on the vehicle. Therefore, the actual load at the output end of the charger is the battery. When the battery is charged, the power stored in the battery drives the motor and related electrical equipment through the inverter. So when the battery releases power, the battery becomes the power source to supply power, and the actual load of the battery is the inverter and the connected motor.

When you want to test the various electrical properties of the charger, if you use an actual battery to test, it will take a longer time to charge. The voltage of the battery corresponds to the battery power. Since the battery voltage cannot be controlled externally, electronic loads are used in the industry to simulate batteries.

The advantage of using electronic loads is that electronic loads have various load modes, including constant current, constant resistance, constant voltage, constant power and other load modes. By controlling the parameters of the load mode, you can easily and quickly test the charger's various features, functions, specifications and other data.

The battery charger includes a car charger or a fast charger at a charging station. Its function is to charge and store electric energy in the power battery of an electric vehicle. The charger's charging procedure for the battery is constant current and constant voltage charging. Generally, the battery is charged with constant current in the initial stage, and then switched to constant voltage charging when it is nearly fully charged. If the charger is tested using a battery, charging the battery will take tens of minutes to several hours, which obviously cannot meet the requirements for efficient testing. Therefore, an electronic load is used to test the charger. At this time, the electronic load simulates the terminal voltage of the battery. During the charging period, the battery is the load of the charger, and the constant voltage or constant resistance mode of the electronic load is used to simulate the terminal voltage of the battery or the charging load resistance.

On the other hand, when testing the battery, although the actual inverter and motor can be used as the load, if an inverter and a connected motor are used, the load current will change with the battery voltage and motor speed and torque. Since the control of inverters and motors is relatively complex, the constant current or constant power mode of electronic loads is mostly used as a load to provide electric energy output for battery discharge, which can easily control the current or electric power of battery discharge. Therefore, electronic loads are used in the industry to simulate various load modes, including constant current, constant resistance, constant voltage, constant power and other load modes. By controlling the parameters of the load mode, you can easily and quickly test various characteristics, functions and specifications of the battery. It is very convenient to test the discharge performance of the battery. .

As the industry continues to develop towards high power, it can achieve faster charging times and longer driving ranges when using electric vehicles. Therefore, the voltage continues to increase. It has currently exceeded 1000V and is increasing towards 1500V. In addition, the electric power is also Continuous improving.

Due to power semiconductor components, including bipolar transistors (bipolar), metal oxide field effect transistors (MOSFET), insulated gate bipolar transistors (IGBT), silicon carbide SIC, etc., the rated voltage of a single power component is limited and exceeds 1500V. The cost of power semiconductors is high, so two power transistors are generally connected in series to increase the rated voltage of the power component.

Contents of the invention

Although high-voltage electronic loads have high industrial utilization value, there are still some problems in the existing technology of high-voltage electronic loads. For example, the voltage divider circuit has load effect problems due to improper design of the subsequent circuit or the subsequent circuit is affected by the input current. In addition, when a high-voltage electronic load is instantaneously loaded with a high-voltage power supply to be tested, the voltages of the first power element and the second power element in the load circuit often cannot be effectively evenly distributed.

In the existing technology, some manufacturers use current-enhanced driving circuits to generate an enhanced rear-stage current by using the front-stage current taken from the voltage divider circuit in the form of current gain (for example, using a Darlington transistor), and then use Drive the power components in the load circuit. Such an approach will often cause the load effect of the voltage divider circuit or the subsequent circuit to be affected by the input current. Moreover, this prior art requires an additional voltage to be configured for the current-enhanced driving circuit. Furthermore, in applications where multiple groups of power transistors are connected in parallel to increase power, a current enhancement drive circuit must be configured in each load circuit, which increases the complexity of the circuit.

In view of the lack of existing technology, the object of the present invention is to provide a high-voltage electronic load with a voltage buffer circuit.

The technical means for solving the problem of the present invention is to include a first power element and a second power element connected in series with the first power element in a high-voltage electronic load to form a load loop. A voltage dividing circuit generates a divided voltage according to a voltage value to be measured. A current sensing circuit is connected in series to the load loop. A current control circuit is connected to the current sensing circuit. A voltage buffer circuit is connected between a voltage dividing circuit and the first power component. The voltage buffer circuit includes a third power element, the gate of which is connected to the voltage dividing connection point of the voltage dividing circuit, the drain is connected to the drain of the first power element, and the source is connected to the first power element. The gate electrode and the source electrode of the third power element are also connected to the second connection line through a third resistor.

In another embodiment of the present invention, a high-voltage electronic load includes a first power component and a second power component connected in series with the first power component to form a load loop. A voltage dividing circuit generates a divided voltage according to a voltage value to be measured. A current sensing circuit is connected in series to the load loop. A current control circuit is connected to the current sensing circuit. A voltage buffer circuit is connected between a voltage dividing circuit and the first power component. The voltage buffer circuit has a high input impedance relative to the second resistor of the voltage dividing circuit, and the voltage buffer circuit has a low output impedance relative to the first power component.

In yet another embodiment of the present invention, a high-voltage electronic load includes a plurality of load circuits, and each load circuit includes at least a first power component and a second power component connected in series with the first power component. A voltage dividing circuit generates a divided voltage according to a voltage value to be measured. A plurality of current sensing circuits are respectively connected in series to the load circuit. A plurality of current control circuits are respectively connected to the current sensing circuit. A voltage buffer circuit is connected between the voltage dividing circuit and the first power components in the plurality of load circuits.

In terms of efficacy, the voltage dividing circuit in the present invention uses two resistors with high resistance values, and the voltage buffer circuit has a high input impedance to avoid loading effects on the voltage dividing resistors of the voltage dividing circuit and will not be affected by the input current. Influence. In addition, the voltage buffer circuit has low output impedance and can effectively drive the first power component in the load loop. In practical applications, when the high-voltage electronic load of the present invention is instantaneously loaded with the power supply to be tested, the voltages of the first power element and the second power element in the load circuit can be effectively and evenly distributed.

In the present invention, since the drain of the power element in the voltage buffer circuit is connected to the drain of the first power element in the load circuit, there is no need for an additional applied voltage source in the prior art, and additional circuit design can be simplified.

The present invention is applied to embodiments in which multiple groups of power transistors are connected in parallel to increase power. Only one voltage buffer circuit is needed to drive each power element of multiple load circuits, without the need to set up multiple voltage dividing circuits and multiple voltage buffer circuits. Therefore, the complexity of the circuit can be effectively simplified.

The specific technology used in the present invention will be further explained through the following examples and drawings.

Description of drawings

Figure 1 is a system block diagram of the first embodiment of the present invention.

Figure 2 is a schematic circuit diagram of the first embodiment of the present invention.

Figure 3 is a system block diagram of the second embodiment of the present invention.

Reference number:

1. 1a: High voltage electronic load

2: Power supply to be tested

3: Voltage dividing circuit

4: Current control circuit

5: Voltage buffer circuit

AMP: amplifier

C1: Compensation capacitor

L, La, Lb: load circuit

L1: first connection line

L2: Second connection line

IL: load current

M1: the first power component

M2: Second power element

M3: The third power element

R1: first resistor

R2: second resistor

R3: The third resistor

Rs: sensing resistance

S1: Power component control signal

V1: voltage value to be measured

V2: sensing voltage

Vd: divided voltage

Vs: current control signal

Detailed ways

Referring to FIGS. 1 and 2 simultaneously, a high-voltage electronic load 1 according to a first embodiment of the present invention is connected to a power source 2 to be tested via a first connection line L1 and a second connection line L2. The high-voltage electronic load 1 includes a first power element M1, a second power element M2, a sensing resistor Rs, a voltage dividing circuit 3, a current control circuit 4, and a voltage buffer circuit 5.

The first power element M1, the second power element M2, and the sensing resistor Rs are connected in series to form a load loop L, and are connected to the power supply 2 under test via the first connection line L1 and the second connection line L2.

The drain of the first power element M1 is connected to the first connection line L1, and the source is connected to the drain of the second power element M2. The source of the second power element M2 is connected to the second connection line L2 after the sensing resistor Rs is connected in series. The sensing resistor Rs is used to sense the size of the load current IL passing through the load loop L.

The voltage dividing circuit 3 is connected in parallel between the first connection line L1 and the second connection line L2. The voltage dividing circuit 3 is composed of a first resistor R1 and a second resistor R2 connected in series.

The current control circuit 4 is connected to the gate of the second power element M2 and the sensing resistor Rs. The current control circuit 4 generates a power element control signal S1 to the gate of the second power element M2 based on the load current IL and the current control signal Vs. The current control signal Vs and the sensing resistor Rs determine the magnitude of the load current IL passing through the first power element M1, the second power element M2, and the sensing resistor Rs.

In the preferred embodiment, the current control circuit 4 includes a current control signal Vs and an amplifier AMP. One input terminal of the amplifier AMP is connected to the current control signal Vs, the other input terminal is connected between the sensing resistor Rs and the second power element M2, and its output terminal is connected to the gate of the second power element M2. The amplifier AMP generates the power element control signal S1 to the gate of the second power element M2 based on the sensing voltage V2 generated by the sensing resistor Rs and the current control signal Vs when the load current IL flows through the sensing resistor Rs.

In the aforementioned circuit structure, the first resistor R1 and the second resistor R2 are generally set to half of the voltage value V1 to be measured as the divided voltage Vd. Therefore, the first power element M1 and the second power element M2 each bear 1/2Vd. voltage.

The load current of the circuit composed of the second power element M2, the amplifier AMP and the sensing resistor Rs is equal to the load current IL flowing through the first power element M1. Therefore, if the load current IL is controlled by the current control signal Vs, the input voltage can reach twice the rated voltage of the first power element M1 or the second power element M2.

The present invention includes a voltage buffer circuit 5 (Voltagebuffer) between the voltage dividing circuit 3 and the first power element M1. The voltage buffer circuit 5 includes a third power component M3. The third power element M3 takes a MOSFET as an example. Its gate is connected to the voltage dividing connection point of the first resistor R1 and the second resistor R2, its drain is connected to the drain of the first power element M1, and its source is connected to the first power Gate of element M1.

The voltage dividing connection point of the first resistor R1 and the second resistor R2 of the voltage dividing circuit 3 generates a divided voltage Vd to the gate of the third power element M3 according to the magnitude of the voltage value V1 to be measured of the power supply 2 to be measured. The divided voltage Vd is approximately 1/2 of the voltage value to be measured V1. Since the voltage value V1 to be measured is high, in order to avoid the load effect of the high-voltage electronic load, the first resistor R1 and the second resistor R2 in the voltage dividing circuit 3 use resistive elements with high resistance values (for example, several MΩ or more).

The first power element M1 takes a MOSFET as an example, and its gate is connected to the source of the third power element M3 in the voltage buffer circuit 5 . The voltage buffer circuit 5 has a high input impedance relative to the second resistor R2 of the voltage dividing circuit 3, which can avoid causing a load effect on the first resistor R1 and the second resistor R2 of the voltage dividing circuit 3. For example, the input impedance of the third power element M3 is approximately 100 times or more than the second resistor R2, so that the divided voltage Vd of the first resistor R1 and the second resistor R2 of the voltage dividing circuit 3 is connected to the third power element M3. When the gate is connected, the voltage buffer circuit 5 will not cause a load effect on the voltage dividing circuit 3 .

The source of the third power element M3 is connected to a third resistor R3 to the negative electrode of the voltage value V1 to be measured to provide a DC operating voltage of the third power element M3. The source voltage of the third power element M3 is the gate voltage (Threshold voltage) minus the threshold voltage of the third power element M3. The third power element M3 works in the linear operating region. The source of the third power element M3 has a low output impedance relative to the first power element M1 and can drive the gate of the first power element M1.

The source voltage of the first power element M1 is the gate voltage minus the threshold voltage of the first power element M1, so the drain-to-source voltage of the first power element M1 is the divided voltage Vd minus the threshold voltage of the third power element M3 value voltage and the threshold voltage of the first power element M1. For the high voltage to be measured voltage value V1 of 2000V, the divided voltage Vd is about 1000V (volt), the threshold voltage of the third power element M3 and the threshold voltage of the first power element M1 are about 3V~4V, so the first The drain-to-source voltage of the power element M1 is approximately 1/2 of the voltage value V1 to be measured, and the drain-to-source voltage of the second power element M2 is also approximately 1/2 of the voltage value V1 to be measured.

The third power element M3 in the voltage buffer circuit 5 is between the resistor voltage dividing circuit 3 and the first power element M1. The source voltage of the third power element M3 changes with the gate voltage, and its source voltage is equal to its gate voltage minus the threshold voltage of the third power element M3.

The voltage buffer circuit 5 may also include a compensation capacitor C1, which is connected between the gate of the third power element M3 and the second connection line L2, and can be used to compensate for the interelectrode capacitance of the third power element M3 (i.e., if there is a power element The parasitic capacitance existing between any of the drain, gate, and source) can prevent a large surge current from being generated in the third power element M3 when the voltage value V1 to be measured is applied instantaneously.

In actual applications, the instantaneous voltage change rate (dv/dt) generated when the power supply under test is instantaneously applied to a high-voltage electronic load may cause the instantaneous voltage of the first power element and the second power element to be less than about 50% of the power supply under test. of partial pressure. The above circuit of the present invention can be combined with a buffer circuit at the input end of the electronic load to slow down the instantaneous voltage change rate between the power supply under test and the electronic load power element, so that the voltage on the electronic load presents a slowly rising voltage waveform, further ensuring the first The voltage distribution between the power element and the second element is approximately 50% each when connected instantaneously.

The voltage buffer circuit 5 has electrical characteristics of high input impedance and low output impedance. The high input impedance can avoid the load effect on the voltage dividing resistor of the voltage dividing circuit 3 and will not be affected by the input current. In addition, since the drain of the third power element M3 in the voltage buffer circuit 5 is connected to the drain of the first power element M1, no additional voltage is required. The low output impedance characteristic of the voltage buffer circuit 5 can effectively drive the gate of the first power element M1.

Therefore, the voltage buffer circuit 5 ensures that the first power element M1 and the second power element M2 can evenly distribute approximately 50% of each voltage value of the voltage value V1 to be measured, so that the first power element M1 and the second power element M2 can be connected in series. Increase the voltage rating to enable proper operation of the feature.

Figure 3 is a system block diagram of the second embodiment of the present invention. As shown in the figure, the high-voltage electronic load 1a of this embodiment is substantially the same as the circuit of the first embodiment, so the same components are marked with the same component numbers for correspondence. The difference between this embodiment and the aforementioned first embodiment is that the high-voltage electronic load 1a of this embodiment uses multiple groups of power transistors connected in parallel to increase power.

In the circuit diagram shown in Figure 2, two power components are connected in series to form a load loop L. Based on the circuit diagram of the embodiment shown in Figure 2, two or more power components can be connected in series to increase the rated voltage of a single power component by more than 2 times or more to control the current flowing through the power component. As the load of the power supply under test, it detects the voltage, current, electric power and other parameters of the power supply under test.

For high-power electronic loads, multiple load loops formed by connecting two power components in series are used to increase the power. For example, the load electric power of a load circuit can withstand 100W (Watt). If 10 load circuits are connected in parallel, the load current can be increased to 10 times, so the electric power of the electronic load can be increased to 1000W. If more load electric power is needed Just use more power components as needed.

As shown in FIG. 3 , two load loops La and Lb are included, and the gate of the first power element M1 in each load loop La and Lb is connected to the voltage buffer circuit 5 . Therefore, in the circuit of this embodiment, only one voltage buffer circuit 5 is needed to drive each power element of multiple load circuits, and there is no need to provide multiple voltage dividing circuits and multiple voltage buffer circuits.

The above embodiments are only illustrative of the structural design of the present invention and are not intended to limit the present invention. Those skilled in the art can modify and change the above embodiments within the structural design and spirit of the present invention, but these changes still fall within the spirit of the present invention and the patent scope defined below. Therefore, the scope of protection of the present invention should be as listed in the claims.

Claims (9)

1. A high-voltage electronic load with a voltage buffer circuit, connected to a power supply under test via a first connection line and a second connection line, including: a first power component; A second power component is connected in series with the first power component to form a load loop, and is connected to the power supply under test via the first connection line and the second connection line; A voltage dividing circuit is composed of a first resistor and a second resistor connected in series and connected between the first connection line and the second connection line. The first resistor is connected according to the voltage value to be measured of the power supply to be measured. A divided voltage connection point with the second resistor generates a divided voltage; a current sensing circuit, connected in series to the load circuit, for sensing the load current passing through the load circuit; a current control circuit connected to the current sensing circuit; Its characteristics are: A voltage buffer circuit is connected between the voltage dividing circuit and the first power element. The voltage buffer circuit includes a third power element. The gate of the third power element is connected to the voltage dividing connection point of the voltage dividing circuit. The drain is connected to the drain of the first power element, the source is connected to the gate of the first power element, and the source of the third power element is also connected to the second connection line through a third resistor. 2. The high-voltage electronic load with a voltage buffer circuit as claimed in claim 1, wherein the voltage buffer circuit further includes a compensation capacitor connected to the gate of the third power element and the second connection line. between. 3. A high-voltage electronic load with a voltage buffer circuit, connected to a power supply under test via a first connection line and a second connection line, including: a first power component; A second power component is connected in series with the first power component to form a load loop, and is connected to the power supply under test via the first connection line and the second connection line; A voltage dividing circuit is composed of a first resistor and a second resistor connected in series and connected between the first connection line and the second connection line. The first resistor is connected according to the voltage value to be measured of the power supply to be measured. A divided voltage connection point with the second resistor generates a divided voltage; a current sensing circuit, connected in series to the load circuit, for sensing the load current passing through the load circuit; a current control circuit connected to the current sensing circuit; Its characteristics are: The first resistor and the second resistor in the voltage dividing circuit each have a high resistance value; A voltage buffer circuit is connected between the voltage dividing circuit and the first power component. The voltage buffer circuit has a high input impedance relative to the second resistor of the voltage dividing circuit, and the voltage buffer circuit is connected relative to the first power component. Has low output impedance. 4. The high-voltage electronic load with a voltage buffer circuit as claimed in claim 3, wherein the voltage buffer circuit includes a third power element, and the gate of the third power element is connected to the divider of the voltage dividing circuit. The pressure connection point, the drain electrode is connected to the drain electrode of the first power element, the source electrode is connected to the gate electrode of the first power element, and the source electrode of the third power element is also connected to the second connection through a third resistor. Wire. 5. The high-voltage electronic load with a voltage buffer circuit as claimed in claim 4, wherein the input impedance of the third power element is 100 times or more than the resistance value of the second resistor. 6. The high-voltage electronic load with a voltage buffer circuit as claimed in claim 4, wherein the voltage buffer circuit further includes a compensation capacitor connected to the gate of the third power component and the second connection line. between. 7. A high-voltage electronic load with a voltage buffer circuit, connected to a power supply under test via a first connection line and a second connection line, including: A plurality of load loops are connected in parallel to the first connection line and the second connection line, and each load loop includes: at least one first power component; a second power component connected in series to the at least one first power component; A voltage dividing circuit is composed of a first resistor and a second resistor connected in series and connected between the first connection line and the second connection line. The first resistor is connected according to the voltage value to be measured of the power supply to be measured. A divided voltage connection point with the second resistor generates a divided voltage; A plurality of current sensing circuits are respectively connected in series to the plurality of load circuits for respectively sensing the load currents passing through the plurality of load circuits; A plurality of current control circuits respectively connected to the plurality of current sensing circuits; Its characteristics are: The first resistor and the second resistor in the voltage dividing circuit each have a high resistance value; A voltage buffer circuit is connected between the voltage dividing connection point of the voltage dividing circuit and the at least one first power element of the plurality of load circuits. 8. The high-voltage electronic load with a voltage buffer circuit as claimed in claim 7, wherein the voltage buffer circuit includes a third power element, and the gate of the third power element is connected to the divider of the voltage dividing circuit. The pressure connection point, the drain electrode is connected to the drain electrode of the at least one first power element of the plurality of load circuits, and the source electrode is connected to the gate electrode of the at least one first power element of the plurality of load circuits, and the third power The source of the component is also connected to the second connection line through a third resistor. 9. The high-voltage electronic load with a voltage buffer circuit as claimed in claim 8, wherein the voltage buffer circuit further includes a compensation capacitor connected to the gate of the third power component and the second connection line. between.