CN117318465A

CN117318465A - High voltage electronic load with voltage buffer circuit

Info

Publication number: CN117318465A
Application number: CN202210695716.2A
Authority: CN
Inventors: 刘英彰
Original assignee: Prodigit Electronics Co Ltd
Current assignee: Prodigit Electronics Co Ltd
Priority date: 2022-06-20
Filing date: 2022-06-20
Publication date: 2023-12-29

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 buffer circuit

Technical Field

The present invention relates to circuit designs of electronic loads, and more particularly to a high voltage electronic load with a voltage buffer circuit.

Background

At present, the development of electric vehicles and energy storage industry is towards high voltage and high power. In the electric vehicle and energy storage industry, chargers or high voltage batteries are included. A load is required when testing a charger or a high voltage battery. The load may take the form of an actual load (e.g., a motor or a designated electrical device) or an electronic load may be used that simulates an actual load.

Taking a charger as an example, the input electric energy of the charger is the commercial power of the power grid, and the high-voltage direct current output by the charger can be used for charging the high-voltage battery on the vehicle, so the actual load at the output end of the charger is the battery. When the battery is charged, the power stored by the battery drives the motor and related electrical devices via an Inverter (Inverter). 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 testing various electrical performances of the charger, if an actual battery is used for testing, a longer time is required for charging, and the voltage of the battery is a corresponding value along with the electric quantity of the battery. Since the battery cannot be controlled by an external voltage, an electronic load is used in industry to simulate the battery.

The electronic load has the advantages that the electronic load has various load modes including constant current, constant resistance, constant voltage, constant power and the like. The parameters of the load mode can be controlled to easily and quickly test the data of various characteristics, functions, specifications and the like of the charger.

The battery charger has a fast charging function, such as an on-board charger or a charging station, which is used for charging the power battery of the electric vehicle to store electric energy. The charging procedure of the charger to the battery is constant current and constant voltage charging. In general, the battery is charged with a constant current at an early stage, and is charged with a constant voltage when the battery is nearly fully charged. If the charger is tested by using a battery, the battery can take tens of minutes to hours to charge, and the test requirement of the efficiency cannot be satisfied obviously. Thus, the charger is tested with an electronic load, which is the terminal voltage of the analog battery. During charging, the battery is the load of the charger, and the terminal voltage or charging load resistance of the battery is simulated by using a constant voltage or a constant resistance mode of the electronic load.

On the other hand, in the battery test, although an actual inverter and motor may be used as the load, if the inverter and connected motor are used, the load current varies with the battery voltage, the motor rotation speed, the torque force, and the like. Because the control of the inverter and the motor is complex, the constant current or constant power mode of the electronic load is used as the load for discharging the battery to provide electric energy output, so that the current or electric power discharged by the battery can be easily controlled. Therefore, electronic loads are used in industry to simulate various load modes, including constant current, constant resistance, constant voltage, constant power, and other load modes. The parameters of the load mode can be controlled to easily and rapidly test various characteristics, functions, specifications and the like of the battery, and the discharge performance of the battery is very convenient to detect. .

Because the industry continues to develop to high power, a faster charging time during charging and a longer driving distance during using an electric vehicle can be obtained, and thus the voltage is continuously increased, currently more than 1000V, and in 1500V, and in addition, the electric power is continuously increased.

Because power semiconductor devices, including bipolar transistors (MOSFETs), metal oxide field effect transistors (MOSFETs), insulated Gate Bipolar Transistors (IGBTs), silicon carbide SIC, etc., have limited voltage ratings, and power semiconductors exceeding 1500V have high cost, 2 power transistors are typically connected in series to achieve voltage ratings of the power devices.

Disclosure of Invention

Although high voltage electronic loads have high industrial utility, there are still some problems in the prior art of high voltage electronic loads. For example, the voltage dividing circuit has a problem of a load effect due to an improper design of the subsequent circuit or the subsequent circuit is affected by an input current. In addition, when the high-voltage electronic load is instantaneously loaded on the high-voltage power supply to be tested, the voltages of the first power element and the second power element in the load loop cannot be effectively and evenly distributed.

In the prior art, current-enhanced driving circuits are used by the industry to generate an enhanced back-end current from the front-end current of the voltage divider circuit (e.g., using darlington transistors) in a current gain manner, and to drive the power devices in the load circuit accordingly. In this way, a problem of loading effect of the voltage divider circuit or influence of the input current on the subsequent circuit is often generated. And in this prior art, an extra voltage is required to be allocated to the current enhancement driving circuit. Furthermore, in the application of parallel boosting of power by multiple sets of power transistors, a current-enhanced driving circuit must be configured in each load loop, which increases the complexity of the circuit.

In view of the drawbacks of the prior art, an 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 invention is that the high-voltage electronic load 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.

In another embodiment of the present invention, a high voltage electronic load includes a first power device and a second power device connected in series with the first power device 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 has a high input impedance relative to the second resistor of the voltage divider circuit, and the voltage buffer circuit has a low output impedance relative to the first power element.

In yet another embodiment of the present invention, a plurality of load loops are included in a high voltage electronic load, each load loop including at least a first power element and a second power element connected in series with the first power element. 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. And the plurality of current control circuits are respectively connected with the current sensing circuits. A voltage buffer circuit is connected between the voltage dividing circuit and the first power element in the plurality of load loops.

In terms of efficacy, the voltage dividing circuit adopts 2 resistors with high resistance values, and the voltage buffer circuit has high input impedance, so that the load effect on the voltage dividing resistor of the voltage dividing circuit can be avoided, and the voltage dividing circuit is not influenced by input current. In addition, the voltage buffer circuit has low output impedance and can effectively drive the first power element in the load loop. In practical application, when the high-voltage electronic load is instantly loaded by a power supply to be tested, the voltages of the first power element and the second power element in the load loop can be effectively and evenly distributed.

In the invention, the drain electrode of the power element in the voltage buffer circuit is connected to the drain electrode of the first power element in the load loop, so that an additional applied voltage source in the prior art is not needed, and the additional circuit design can be simplified.

The invention is applied to the embodiment of parallel connection of multiple groups of power transistors to boost power, and can drive each power element of multiple load loops only by one voltage buffer circuit without arranging multiple voltage dividing circuits and multiple voltage buffer circuits, thereby effectively simplifying the complexity of the circuit.

The specific technology adopted by the invention will be further described through the following examples and the attached drawings.

Drawings

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

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

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

Reference numerals:

1. 1a: high voltage electronic load

2: power supply to be measured

3: voltage dividing circuit

4: current control circuit

5: voltage buffer circuit

AMP: amplifier

C1: compensation capacitor

L, la, lb: load circuit

L1: first connecting wire

L2: second connecting wire

IL: load current

M1: first power element

M2: second power element

M3: third power element

R1: first resistor

R2: second resistor

R3: third resistor

Rs: sensing resistor

S1: power element control signal

V1: voltage value to be measured

V2: sensing voltage

Vd: divided voltage

Vs: current control signal

Detailed Description

Referring to fig. 1 and fig. 2, 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 through a first connection line L1 and a second connection line L2. The high voltage electronic load 1 comprises 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 to be tested through the first connection line L1 and the second connection line L2.

The drain of the first power device M1 is connected to the first connection line L1, and the source is connected to the drain of the second power device M2. The source of the second power element M2 is connected to the second connection line L2 after the sense resistor Rs is connected in series. The sense resistor Rs is used for sensing the magnitude 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 configured by connecting a first resistor R1 and a second resistor R2 in series.

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

In the preferred embodiment, the current control circuit 4 includes a current control signal Vs and an amplifier AMP. The amplifier AMP has one input connected to the current control signal Vs, the other input connected between the sense resistor Rs and the second power element M2, and the output connected to the gate of the second power element M2. The amplifier AMP generates a power device control signal S1 to the gate of the second power device M2 according to the sense voltage V2 and the current control signal Vs generated by the sense resistor Rs when the load current IL flows through the sense resistor Rs.

In the circuit structure described above, 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, and thus the first power device M1 and the second power device M2 each receive a voltage of 1/2 Vd.

The load current of the circuit composed of the second power element M2, the amplifier AMP and the sense 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 be 2 times the rated voltage of the first power device M1 or the second power device M2.

The present invention includes a Voltage buffer circuit 5 (Voltage buffer) between the Voltage dividing circuit 3 and the first power element M1. The voltage buffer circuit 5 includes a third power device M3. The third power element M3 is exemplified as a MOSFET, and has a gate connected to the voltage dividing connection point of the first resistor R1 and the second resistor R2, a drain connected to the drain of the first power element M1, and a source connected to the gate of the first power element M1.

The voltage division connection point of the first resistor R1 and the second resistor R2 of the voltage division 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 about 1/2 of the voltage value V1 to be measured. Since the voltage of the voltage value V1 to be measured is high, the first resistor R1 and the second resistor R2 in the voltage dividing circuit 3 are resistive elements with high resistance values (for example, a number mΩ or more) in order to avoid a load effect of the high-voltage electronic load.

The first power element M1 is exemplified by a MOSFET, 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 divider circuit 3, so as to avoid loading effects on the first resistor R1 and the second resistor R2 of the voltage divider circuit 3. For example, the input impedance of the third power element M3 is about 100 times or more of the second resistor R2, so that the voltage buffer circuit 5 does not cause a load effect on the voltage dividing circuit 3 when the divided voltage Vd of the first resistor R1 and the second resistor R2 of the voltage dividing circuit 3 is connected to the gate of the third power element M3.

The source of the third power element M3 is connected to the negative electrode of the third resistor R3 to the voltage V1 to be measured, so as to provide the 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 operates in a linear operating region. The source of the third power element M3 has a low output impedance with respect 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 and the threshold voltage of the first power element M1. For the high voltage V1 of 2000V, the divided voltage Vd is about 1000V (volts), the threshold voltage of the third power device M3 and the threshold voltage of the first power device M1 are about 3V-4V, so that the drain-to-source voltage of the first power device M1 is about 1/2 of the voltage V1, and the drain-to-source voltage of the second power device M2 is about 1/2 of the voltage V1.

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

The voltage buffer circuit 5 may further include a compensation capacitor C1 connected between the gate of the third power device M3 and the second connection line L2, for compensating the inter-electrode capacitance of the third power device M3 (i.e. parasitic capacitance existing between any two of the drain, the gate and the source of the power device), so as to avoid generating a large surge current in the third power device M3 when the voltage value V1 to be measured is instantaneously applied.

In practical applications, the instantaneous voltage change rate (dv/dt) generated when the power to be tested is instantaneously applied to the high voltage electronic load may cause that the instantaneous voltages of the first power device and the second power device cannot be about 50% of the partial voltage of the power to be tested. The circuit of the invention can be matched with the buffer circuit at the input end of the electronic load to slow down the instant voltage change rate between the power supply to be tested and the power element of the electronic load, so that the voltage on the electronic load presents a slowly rising voltage waveform, and further ensures that the voltage distribution of the first power element and the second power element is about 50% respectively when in instant connection.

Since the voltage buffer circuit 5 has an electrical characteristic of high input impedance and low output impedance. The high input impedance can avoid the influence of the input current on the load effect caused by the voltage dividing resistance of the voltage dividing circuit 3. In addition, since the drain of the third power device M3 in the voltage buffer circuit 5 is connected to the drain of the first power device 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 be equally distributed to about 50% of the voltage value V1 to be measured, and the function of improving the voltage rating by connecting the first power element M1 and the second power element M2 in series can be normally operated is achieved.

Fig. 3 is a system block diagram of a second embodiment of the present invention. As shown in the figure, the high voltage electronic load 1a of the present embodiment is substantially the same as the circuit of the first embodiment, so the same elements are denoted by the same element numbers and correspond thereto. The difference between this embodiment and the foregoing first embodiment is that a plurality of sets of power transistors are employed in parallel in the high-voltage electronic load 1a of this embodiment to boost power.

In the circuit diagram shown in fig. 2, two power elements are connected in series to form a load loop L. Based on the circuit diagram of the embodiment shown in fig. 2, two or more power elements can be connected in series to boost the current flowing through the rated voltage control power element 2 times or more than that of a single power element, so that the current can be used as the load of the power supply to be tested, and the parameters such as the voltage, the current, the electric power and the like of the power supply to be tested can be detected.

For high-power electronic loads, a plurality of load loops with two power elements connected in series are used for boosting power. For example, the load power of one load loop can bear 100W (watts), if 10 load loops are used in parallel connection, the load current can be increased by 10 times, so the power of the electronic load can be increased to 1000W, and if more load power is needed, more power elements are adopted according to the requirement.

Fig. 3 shows two load loops La, lb, and the gate of the first power element M1 in each load loop La, lb is connected to the voltage buffer circuit 5. Therefore, in the circuit of the present embodiment, only one voltage buffer circuit 5 is needed to drive each power element of the plurality of load circuits, and a plurality of voltage dividing circuits and a plurality of voltage buffer circuits are not needed.

The above embodiments are merely illustrative of the structural design of the present invention and are not intended to limit the present invention. Modifications and variations of the above-described embodiments will occur to those skilled in the art, which will be within the spirit and scope of the invention as defined by the following claims. The scope of the invention is therefore intended to be indicated by the appended claims.

Claims

1. A high voltage electronic load having a voltage buffer circuit connected to a power source to be tested via a first connection line and a second connection line, comprising:

a first power element;

the second power element is connected with the first power element in series to form a load loop, and is connected with the power supply to be tested through the first connecting wire and the second connecting wire;

the voltage dividing circuit is connected between the first connecting wire and the second connecting wire after being connected in series by a first resistor and a second resistor, and generates a divided voltage at a divided connecting point of the first resistor and the second resistor according to the magnitude of the voltage value to be measured of the power supply to be measured;

a current sensing circuit connected in series with the load loop for sensing the magnitude of the load current passing through the load loop;

a current control circuit connected to the current sensing circuit;

the method is characterized in that:

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 connected with the second connection line through a third resistor.

2. The high voltage electronic load with voltage buffer circuit of claim 1 further comprising a compensation capacitor connected between the gate of the third power device and the second connection line.

3. A high voltage electronic load having a voltage buffer circuit connected to a power source to be tested via a first connection line and a second connection line, comprising:

a first power element;

a current control circuit connected to the current sensing circuit;

the method is characterized in that:

the first resistor and the second resistor in the voltage dividing circuit have high resistance values respectively;

a voltage buffer circuit is connected between the voltage dividing circuit and the first power element, the voltage buffer circuit has high input impedance relative to the second resistor of the voltage dividing circuit, and the voltage buffer circuit has low output impedance relative to the first power element.

4. The high voltage electronic load with voltage buffer circuit of claim 3 wherein said voltage buffer circuit comprises a third power element, the gate of said third power element being connected to said voltage dividing connection point of said voltage dividing circuit, the drain being connected to the drain of said first power element, the source being connected to the gate of said first power element, the source of said third power element being further connected to said second connection line through a third resistor.

5. The high voltage electronic load with voltage buffer circuit of claim 4 wherein the input impedance of the third power element is 100 times or more the resistance value of the second resistor.

6. The high voltage electronic load with voltage buffer circuit of claim 4 further comprising a compensation capacitor connected between the gate of the third power device and the second connection line.

7. A high voltage electronic load having a voltage buffer circuit connected to a power source to be tested via a first connection line and a second connection line, comprising:

a plurality of load circuits connected in parallel to the first connection line and the second connection line, each of the load circuits including:

at least one first power element;

a second power element connected in series with the at least one first power element;

the plurality of current sensing circuits are respectively connected in series with the plurality of load loops and are used for respectively sensing the magnitude of load current passing through the plurality of load loops;

a plurality of current control circuits respectively connected to the plurality of current sensing circuits;

the method is characterized in that:

the voltage buffer circuit is connected between the voltage division connection point of the voltage division circuit and the at least one first power element of the load loops.

8. The high voltage electronic load with voltage buffer circuit of claim 7, wherein the voltage buffer circuit comprises a third power element, the gate of the third power element is connected to the voltage division connection point of the voltage division circuit, the drain is connected to the drain of the at least one first power element of the plurality of load loops, the source is connected to the gate of the at least one first power element of the plurality of load loops, and the source of the third power element is further connected to the second connection line through a third resistor.

9. The high voltage electronic load with voltage buffer circuit of claim 8 further comprising a compensation capacitor connected between the gate of the third power device and the second connection line.