CN109062304B - Constant current load circuit, electronic load and related system - Google Patents
Constant current load circuit, electronic load and related system Download PDFInfo
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Abstract
The invention discloses a constant current load circuit, an electronic load and a related system. Wherein the constant current load circuit includes: a main operational amplifier, a gate driver, a MOS device and a current detection unit; the non-inverting input end of the main operational amplifier is grounded, the inverting input end of the main operational amplifier is connected to the first DA output end through an input resistor and connected to the current detection unit through a feedback resistor, and the output end of the main operational amplifier is connected with a grid electrode drive; the grid electrode of the MOS device is connected with the grid electrode drive, the drain electrode of the MOS device is connected with one electrode of the tested power supply, and the source electrode of the MOS device is connected with the current detection unit; one end of the current detection unit is grounded, and one end of the current detection unit is grounded and connected with the other electrode of the power supply to be detected. Constant current load can be realized, and the tested power supply is protected from being damaged; meanwhile, the method is safe and reliable, no bias current exists, and no load current and no external bias voltage exist when the tested power supply does not output.
Description
Technical Field
The invention relates to the field of electronic test instruments, in particular to a constant current load circuit, an electronic load and a related system.
Background
When testing parameters of the DC/DC power supply module, a specified load is required to be output to the tested power supply, and the load can be realized by using a resistor and a constant current source. The resistor is used as a load, so that the load is safe and reliable, but the output current can change along with the output voltage, and the adjustment is difficult, so that the automatic test requirement is not met; when the active constant current source is used as a load, the load current is constant and can be controlled in a programmable manner, but when the tested power supply is not output, the constant current source can generate voltage with the polarity opposite to that of the output of the tested power supply, and the tested power supply module is easy to damage.
Therefore, when the tested power supply is tested, whether the resistor is used as a load or the constant current source is used as a load, the defects exist, the requirement of the power supply safety test cannot be met, the programmable control of the load current cannot be realized, the load current cannot be ensured not to change along with the change of the output voltage of the tested power supply, and the constant current cannot be realized.
Disclosure of Invention
The present invention has been made in view of the above problems, and has as its object to provide a constant current load circuit and an electronic load and related systems which overcome or at least partially solve the above problems.
In a first aspect, an embodiment of the present invention provides a constant current load circuit, including: a main operational amplifier, a gate driver, a MOS device and a current detection unit;
the non-inverting input end of the main operational amplifier is grounded, the inverting input end of the main operational amplifier is connected to the first DA output end through an input resistor Rs and is connected to the current detection unit through a feedback resistor Rf, and the output end of the main operational amplifier is connected with the grid drive;
the grid electrode of the MOS device is connected with the grid electrode drive, the drain electrode of the MOS device is connected with one electrode of a tested power supply, and the source electrode of the MOS device is connected with the current detection unit;
one end of the current detection unit is grounded, and one grounded end is connected with the other electrode of the tested power supply.
In some alternative embodiments, the MOS device includes: an N channel MOS tube MOS1 and a P channel MOS tube MOS2, diodes D1 and D2 connected in series;
The grid electrodes of the MOS1 and the MOS2 are connected and are in driving connection with the grid electrodes;
The MOS1 is connected with the source electrode of the MOS2 and is connected with the current detection unit;
The negative electrode of D1 is connected with the drain electrode of the MOS1, the positive electrode of D2 is connected with the drain electrode of the MOS2, and the positive electrode of D1 is connected with the negative electrode of D2 and is connected with one electrode of a power supply to be tested.
In some alternative embodiments, the first DA output comprises: a first DAC conversion module;
one end of the first DAC conversion module is connected with the digital bus, and the other end of the first DAC conversion module is connected with the input resistor Rs.
In some alternative embodiments, the gate driving includes:
NPN triode, PNP triode, resistance R3 and resistance R4;
the collector of the NPN triode and the collector of the PNP triode are grounded;
One end of the resistor R3 is connected with the base electrode of the NPN triode and the base electrode of the PNP triode, and the other end of the resistor R is connected with the output end of the main operational amplifier;
one end of the resistor R4 is connected with the emitter of the NPN triode and the emitter of the PNP triode, and the other end of the resistor R is connected with the grid electrode of the MOS device.
In some optional embodiments, the constant current load circuit further includes a following operational amplifier unit, configured to boost and invert the voltage input by the current detection unit, and output the boosted voltage.
In some alternative embodiments, the following op-amp unit includes: an operational amplifier U, a feedback resistor R2 and an input resistor R1;
the inverting input end of the operational amplifier U is connected with the output end of the operational amplifier U through a feedback resistor R2, the non-inverting input end of the operational amplifier U is grounded, and the output end of the operational amplifier U is connected with a feedback resistor Rf;
One end of the input resistor R1 is connected with the current detection unit, and the other end of the input resistor R1 is connected with the inverting input end of the operational amplifier U.
In a second aspect, an embodiment of the present invention provides an electronic load, including:
in some alternative embodiments, the method comprises: the device comprises a main operational amplifier, a grid drive, a MOS device, a current detection unit, a gating switch and a switch control unit;
The non-inverting input end of the main operational amplifier is grounded, the inverting input end of the main operational amplifier is connected to the gating switch through the input resistor Rs and connected to the current detection unit through the feedback resistor Rf, and the output end of the main operational amplifier is connected with the grid drive;
the grid electrode of the MOS device is connected with the grid electrode drive, the drain electrode of the MOS device is connected with one electrode of a tested power supply, and the source electrode of the MOS device is connected with the current detection unit;
One end of the current detection unit is grounded, and one end of the current detection unit is grounded and connected with the other electrode of the tested power supply;
The input end of the switch control unit is connected with the tested power supply, the second DA output end and the third DA output end, and the output end controls the gating switch to be communicated with a feedback passage of the switch control unit or be communicated with the first DA output end according to an input signal of the input end.
In some alternative embodiments, the first DA output includes a first DAC conversion module, where one end of the first DAC conversion module is connected to a digital bus, and the other end of the first DAC conversion module is connected to or disconnected from the gate switch under the control of the switch control unit.
In some alternative embodiments, the switch control unit includes: a comparator and a multiplier;
the input end of the multiplier is respectively connected with the third DA output end and the tested power supply, and the output end of the multiplier is connected with the comparator;
The non-inverting input end of the comparator is connected with the second DA output end, the inverting input end of the comparator is connected with the multiplier, and the output end of the comparator is connected with the gating switch.
In some alternative embodiments, the second DA output includes a second DAC conversion module, where one end of the second DAC conversion module is connected to the digital bus, and the other end is connected to the non-inverting input of the comparator;
The third DA output end comprises a third DAC conversion module, one end of the third DAC conversion module is connected with the digital bus, and the other end of the third DAC conversion module is connected with the multiplier.
In some alternative embodiments, the MOS device includes: an N channel MOS tube MOS1 and a P channel MOS tube MOS2, diodes D1 and D2 connected in series;
The grid electrodes of the MOS1 and the MOS2 are connected and are in driving connection with the grid electrodes;
The MOS1 is connected with the source electrode of the MOS2 and is connected with the current detection unit;
The negative electrode of D1 is connected with the drain electrode of the MOS1, the positive electrode of D2 is connected with the drain electrode of the MOS2, and the positive electrode of D1 is connected with the negative electrode of D2 and is connected with one electrode of a power supply to be tested.
In some alternative embodiments, the gate driving includes:
NPN triode, PNP triode, resistance R3 and resistance R4;
the collector of the NPN triode and the collector of the PNP triode are grounded;
One end of the resistor R3 is connected with the base electrode of the NPN triode and the base electrode of the PNP triode, and the other end of the resistor R is connected with the output end of the main operational amplifier;
one end of the resistor R4 is connected with the emitter of the NPN triode and the emitter of the PNP triode, and the other end of the resistor R is connected with the grid electrode of the MOS device.
In some optional embodiments, the electronic load further includes a following operational amplifier unit, configured to boost and invert the voltage input by the current detection unit, and output the boosted voltage.
In some alternative embodiments, the following op-amp unit includes: an operational amplifier U, a feedback resistor R2 and an input resistor R1;
the inverting input end of the operational amplifier U is connected with the output end of the operational amplifier U through a feedback resistor R2, the non-inverting input end of the operational amplifier U is grounded, and the output end of the operational amplifier U is connected with a feedback resistor Rf;
One end of the input resistor R1 is connected with the current detection unit, and the other end of the input resistor R1 is connected with the inverting input end of the operational amplifier U.
In a third aspect, an embodiment of the present invention provides a power parameter testing system, including: a power supply to be tested and any one of the electronic loads described above.
In some optional embodiments, the switch control unit determines whether the output voltage of the tested power supply reaches the rated output voltage, and when the output voltage of the tested power supply does not reach the rated output voltage, the switch control unit controls the gating switch to be communicated with a feedback path of the switch control unit; and when the output voltage of the tested power supply reaches the rated output voltage, controlling the gating switch to be switched to be communicated with the first DA output end.
The technical scheme provided by the embodiment of the invention has the beneficial effects that at least:
1. according to the constant current load circuit and the electronic load provided by the embodiment of the invention, the grid voltage of the MOS device is controlled by utilizing the output of the main operational amplifier, and the drain current of the output end is controlled by the MOS device according to the grid voltage of the input end, so that the constant current load is realized. Meanwhile, the drain electrode of the MOS device is safe and reliable, no bias power supply is arranged on the drain electrode of the MOS device, the power supply is provided by the output of the tested power supply, and when the tested power supply does not have the output, no load current and no external bias voltage are generated, so that the tested power supply is protected from being damaged.
2. According to the constant current load circuit and the electronic load provided by the embodiment of the invention, the MOS device consists of the N-channel MOS tube, the P-channel MOS tube and the diodes D1 and D2 which are connected in series, so that the drain electrode of the MOS device can be connected with the positive electrode or the negative electrode of a tested power supply, and the constant current load circuit and the electronic load are convenient and safe to use.
3. The electronic load provided by the embodiment of the invention is a constant-resistance electronic load when the switch is connected with the switch control unit; when the switch is connected with the first DA output end, the drain electrode of the MOS device outputs a constant current load to the tested power supply, and the tested power supply is protected from being damaged.
Drawings
The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate the invention and together with the embodiments of the invention, serve to explain the invention. In the drawings:
FIG. 1 is a circuit diagram of a constant current load according to a first embodiment of the present invention;
FIG. 2 is a graph of V-I characteristics of a MOS transistor;
Fig. 3 is a circuit diagram of a specific implementation of the constant current load circuit according to the first embodiment of the present invention;
fig. 4 is a schematic structural diagram of an electronic load according to a second embodiment of the present invention;
Fig. 5 is a schematic diagram of a specific implementation structure of the electronic load according to the second embodiment of the present invention.
Detailed Description
Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
In order to solve the problems, the embodiment of the invention provides a constant current load circuit, an electronic load and a related system, which are used for realizing the constant current load and protecting a tested power supply from being damaged when a power supply device is tested; meanwhile, the method is safe and reliable, no bias current exists, and no load current and no external bias voltage exist when the tested power supply does not output.
Example 1
Referring to fig. 1, a constant current load circuit according to a first embodiment of the present invention includes: a main operational amplifier, a gate driver, a MOS device and a current detection unit; the non-inverting input end of the main operational amplifier is grounded, the inverting input end of the main operational amplifier is connected to the first DA output end through an input resistor Rs and connected to the current detection unit through a feedback resistor Rf, and the output end of the main operational amplifier is connected with a grid electrode drive; the grid electrode G of the MOS device is connected with a grid electrode drive, the drain electrode D is connected with one electrode of a tested power supply, and the source electrode S is connected with a current detection unit; one end of the current detection unit is grounded, and one end of the current detection unit is grounded and connected with the other electrode of the power supply to be detected.
The constant current load circuit controls the grid voltage of the MOS device by utilizing the output of the main operational amplifier, and the MOS device controls the drain current of the output end according to the grid voltage of the input end, so that the constant current load is realized. The drain electrode of the MOS device is free of a bias power supply, the power supply is provided by the output of a tested power supply, and the power supply of the tested power supply is provided by a power supply output end; when the power supply output end does not output, the tested power supply does not output, and the MOS device does not have load current and external bias voltage, so that the tested power supply is protected from being damaged.
Depending on the V-I characteristics of the MOS device under different gate voltage control, there will be a corresponding gate voltage VGS for a given drain voltage VD (approximately equal to the gate voltage VDs) and drain current ID. Referring to fig. 2, for example, let vd=5v, id=10a, and the corresponding gate voltage VGS is between 5.0V and 6V. Another characteristic of the MOS device IS that the drain current ID IS equal to the source current IS, with which the drain current ID can be detected at the source of the MOS device.
The current detection unit converts the current IS into a voltage, and the main operational amplifier calculates the voltage output by the current detection unit as a feedback amount and a set voltage (voltage Vda output by the first DA output terminal) due to the closed-loop control characteristic of the operational amplifier, and the output of the main operational amplifier controls the gate voltage variation of the MOS device, so that the drain current ID IS finally stabilized at the set value and becomes a constant current state.
The current in this constant current state satisfies the following formula:
ID＝Vda*(Rf/Rs)*B (1)
In the above formula (1), the parameter B is a voltage conversion coefficient of the current detection unit, and is a constant. The resistances Rf and Rs are also constant, so ID varies only with Vda. As long as Vda is set, a corresponding ID is obtained, thereby realizing ID programmable control.
For the problem of different polarities of the current ID required by different polarities of the power supply to be tested, only a MOS tube with opposite polarities is selected, and meanwhile, the polarity of Vda is reversed.
In one embodiment, referring to fig. 3, the MOS device may include: an N channel MOS tube MOS1 and a P channel MOS tube MOS2, diodes D1 and D2 connected in series; the grid electrodes G of the MOS1 and the MOS2 are connected and are connected with a grid electrode drive; the sources S of the MOS1 and the MOS2 are connected and connected with the current detection unit; the negative electrode of D1 is connected with the drain electrode D of MOS1, the positive electrode of D2 is connected with the drain electrode D of MOS2, and the positive electrode of D1 is connected with the negative electrode of D2 and is connected with one electrode of the power supply to be tested.
When the MOS device is connected with the positive electrode of the tested power supply, through the conduction of D1 and the gear separation of D2, current only flows in the MOS device, the MOS device 2 is disconnected in the circuit, the voltage Vda output by the first DA output end is positive, so that the drain electrode of the MOS device 1 outputs a negative constant current load to the tested power supply, at the moment, the load output end 1 is a low potential output end, and the load output end 2 is a high potential output end;
When the MOS device is connected with the negative electrode of the tested power supply, through the conduction of D2 and the blocking effect of D1, current only flows in the MOS2, the MOS1 is disconnected in the circuit, the voltage Vda output by the first DA output end is negative, so that the drain electrode of the MOS2 outputs a positive constant current load to the tested power supply, at the moment, the load output end 1 is a high-potential output end, and the load output end 2 is a low-potential output end.
The load output terminal 1 may be an output pin of the device under test, and the load output terminal 2 is a ground pin of the device under test.
The constant current load circuit provided by the embodiment is convenient to use, and the drain electrode of the MOS device is connected with the positive electrode or the negative electrode of the tested power supply; when the tested power supply reaches rated output, a constant current load is output to the tested power supply, so that the tested power supply is protected from being damaged.
In one embodiment, referring to fig. 3, the first DA output may include a first DAC conversion module; one end of the first DAC conversion module is connected with the digital bus, and the other end of the first DAC conversion module is connected with the input resistor Rs. The digital bus is used for sending digital signals to the first DAC conversion module, the first DAC conversion module converts control signals from the digital bus into an analog voltage Vda, the main operational amplifier performs operation according to the analog voltage Vda and the feedback voltage input by the first DAC conversion module, and the output of the main operational amplifier controls the change of the gate voltage of the MOS device through gate driving, so that the drain electrode of the MOS device is controlled to output a constant current load.
In one embodiment, as shown with reference to fig. 3, the gate driving includes: NPN triode, PNP triode, resistance R3 and resistance R4; the collector of the NPN triode and the collector of the PNP triode are grounded; one end of the resistor R3 is connected with the base electrode of the NPN triode and the base electrode of the PNP triode, and the other end of the resistor R is connected with the output end of the main operational amplifier; one end of the resistor R4 is connected with the emitter of the NPN triode and the emitter of the PNP triode, and the other end of the resistor R is connected with the grid electrode of the MOS device.
Since the current IS flowing through the current detecting unit IS smaller in normal cases, the conversion voltage VIsout of the current detecting unit IS smaller, and the calculation accuracy of the main operational amplifier IS affected; the switching voltage VIsout output by the current detecting unit is opposite to the analog voltage Vda output by the first DA output terminal. Therefore, in one embodiment, referring to fig. 3, the constant current load circuit may further include a following operational amplifier unit, configured to boost and invert the voltage VIsout input by the current detection unit, and output Vis. The following operational amplifier unit may include: an operational amplifier U, a feedback resistor R2 and an input resistor R1; the inverting input end of the operational amplifier U is connected with the output end of the operational amplifier U through a feedback resistor R2, the non-inverting input end of the operational amplifier U is grounded, and the output end of the operational amplifier U is connected with a feedback resistor Rf; one end of the input resistor R1 is connected with the current detection unit, and the other end of the input resistor R1 is connected with the inverting input end of the operational amplifier U.
The current flowing through the current detection unit conforms to the following formula:
in the above formula (2), b is the voltage conversion coefficient of the current detection unit, R1/R2 and Rf/Rs are the resistance ratios, and are constant. So I varies only with Vda. If Vda is set, the corresponding I is obtained.
When vda=0, the operational principle of the operational amplifier can be deduced: VIsout =vf= Vdas =0, where Vf and Vdas are voltages across the resistors Rf and Rs, respectively, of the converted output voltage of the VIsout current detecting unit. When vda=0, the voltages across Rs and Rf are also 0, i.e. vis=0, so VIsout is also 0, thus pushing out the current i=0.
For example, the current detecting means is 0 to 20A, and when i= +/-20A, VIsout = +/-4V (b=0.2), vda is output 0 to +/-10V, and the appropriate resistors R1, R2, rf, rs are selected so that i= -/+ Vda is 2. Then, by setting the output voltage Vda of the first DAC conversion module, a constant load current from-20A to +20a can be set, and the setting accuracy mainly depends on the resistance accuracy and the number of bits of the first DAC conversion module.
Example two
Referring to fig. 4, an electronic load according to a second embodiment of the present invention includes: the device comprises a main operational amplifier, a grid drive, a MOS device, a current detection unit, a gating switch and a switch control unit; the non-inverting input end of the main operational amplifier is grounded, the inverting input end is connected to the gating switch through an input resistor Rs and connected to the current detection unit through a feedback resistor Rf, and the output end is connected with the grid drive; the grid electrode G of the MOS device is connected with a grid electrode drive, the drain electrode D is connected with one electrode of a tested power supply, and the source electrode S is connected with a current detection unit; one end of the current detection unit is grounded, and one end of the current detection unit is grounded and connected with the other electrode of the power supply to be detected; the input end of the switch control unit is connected with the tested power supply, the second DA output end and the third DA output end, and the output end controls the gating switch to be communicated with a feedback passage of the switch control unit or be communicated with the first DA output end according to an input signal of the input end.
When the gating switch is connected with the switch control unit, the electronic load provided by the embodiment of the invention is a constant-resistance electronic load; when the on-off switch is connected to the first DA output terminal, the working principle is as described in the first embodiment, and the drain electrode of the MOS device outputs a constant current load to the power supply to be tested.
In one embodiment, the first DA output may include a first DAC conversion module, where one end of the first DAC conversion module is connected to the digital bus, and the other end of the first DAC conversion module is connected to or disconnected from the gate switch under the control of the switch control unit.
The electronic load provided by the embodiment is used for testing power supply devices, and can output a constant-resistance load before the output voltage of the tested power supply reaches the rated value and output a constant-current load after the output voltage of the tested power supply reaches the rated value, so that the electronic load is convenient to use and can protect the tested power supply from being damaged during testing.
The switch control unit may control the gating switch to selectively connect to the switch control unit or the first DA output by:
In one embodiment, referring to fig. 5, the switch control unit may include: a comparator and a multiplier; the input end of the multiplier is respectively connected with the third DA output end and the tested power supply, and the output end of the multiplier is connected with the comparator; the non-inverting input end of the comparator is connected with the second DA output end, the inverting input end of the comparator is connected with the multiplier, and the output end of the comparator is connected with the gating switch.
In one embodiment, the second DA output may include a second DAC conversion module, where one end of the second DAC conversion module is connected to the digital bus, and the other end is connected to the non-inverting input of the comparator; the third DA output end comprises a third DAC conversion module, one end of the third DAC conversion module is connected with the digital bus, and the other end of the third DAC conversion module is connected with the multiplier.
The multiplier is used for multiplying the analog voltage Vx input by the third DAC conversion module with the output voltage Vout of the tested power supply and outputting a result Vw; the comparator is used for comparing the analog voltage Vref input by the second DAC conversion module with the Vw input by the multiplier, and controlling the connection or disconnection of the gating switch and the first DAC conversion module through output. When the measured power supply output Vout is changed from 0 volts to a nominal value, the current flowing through the load circuit is as follows:
I=vwa= (vx×vout) ×rf/Rs) ×b equation (3)
In the above formula (3), a and Vx are constants, and when vout=0, the current i=0 increases with an increase in the output voltage of the power supply to be measured, and the output current of the load increases. The current variation amplitude can be changed by setting Vx.
The simplified formula (3) yields:
I a=vout formula (4)
The output voltage Vout of the current I and the current under test therefore complies with ohm's law:
R.i=v formula (5)
When Vw is smaller than Vref, the comparator controls the gating switch and the first DAC conversion module to be in a disconnected state through output, and the electronic load is equivalent to a resistor and is a constant-resistance load; when Vw is greater than or equal to Vref, the comparator outputs reverse phase, the gating switch and the first DAC conversion module are controlled to be in a connection state, and the electronic load is in a constant current state; the Vref is smaller than Vda.
In one embodiment, the electronic load may further include a following operational amplifier unit, configured to boost and invert the voltage input by the current detection unit and output the boosted voltage.
The specific implementation structures of the following operational amplifier unit, the MOS device and the gate driver are described in detail in the first embodiment, and will not be described herein.
Based on the same inventive concept, the embodiment of the invention further provides a power parameter testing system, which comprises: a power supply under test and any of the electronic loads described in example two.
In one embodiment, the switch control unit may determine whether the output voltage of the measured power supply reaches the rated output voltage, and when the output voltage of the measured power supply does not reach the rated output voltage, control the gating switch to communicate with a feedback path of the switch control unit, and the electronic load outputs a constant-resistance load to the measured power supply; when the output voltage of the tested power supply reaches the rated output voltage, the gating switch is controlled to be switched to be communicated with the first DA output end, and the electronic load outputs a constant current load to the tested power supply.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims (10)
1. A constant current load circuit, characterized by comprising: a main operational amplifier, a gate driver, a MOS device and a current detection unit;
the non-inverting input end of the main operational amplifier is grounded, the inverting input end of the main operational amplifier is connected to the first DA output end through an input resistor Rs and is connected to the current detection unit through a feedback resistor Rf, and the output end of the main operational amplifier is connected with the grid drive;
The grid electrode of the MOS device is connected with the grid electrode drive, the drain electrode of the MOS device is connected with one electrode of a tested power supply, and the source electrode of the MOS device is connected with the current detection unit;
one end of the current detection unit is grounded, and one grounded end is connected with the other electrode of the tested power supply.
2. The constant current load circuit of claim 1, wherein the MOS device comprises: an N channel MOS tube MOS1 and a P channel MOS tube MOS2, diodes D1 and D2 connected in series;
The grid electrodes of the MOS1 and the MOS2 are connected and are in driving connection with the grid electrodes;
The MOS1 is connected with the source electrode of the MOS2 and is connected with the current detection unit;
The negative electrode of D1 is connected with the drain electrode of the MOS1, the positive electrode of D2 is connected with the drain electrode of the MOS2, and the positive electrode of D1 is connected with the negative electrode of D2 and is connected with one electrode of a power supply to be tested.
3. The constant current load circuit according to claim 1, wherein the gate drive includes:
NPN triode, PNP triode, resistance R3 and resistance R4;
the collector of the NPN triode and the collector of the PNP triode are grounded;
One end of the resistor R3 is connected with the base electrode of the NPN triode and the base electrode of the PNP triode, and the other end of the resistor R is connected with the output end of the main operational amplifier;
one end of the resistor R4 is connected with the emitter of the NPN triode and the emitter of the PNP triode, and the other end of the resistor R is connected with the grid electrode of the MOS device.
4. A constant current load circuit according to any one of claims 1 to 3, further comprising a following operational amplifier unit for boosting and inverting the voltage input from the current detection unit and outputting the boosted voltage;
the following operational amplifier unit includes: an operational amplifier U, a feedback resistor R2 and an input resistor R1;
the inverting input end of the operational amplifier U is connected with the output end of the operational amplifier U through a feedback resistor R2, the non-inverting input end of the operational amplifier U is grounded, and the output end of the operational amplifier U is connected with a feedback resistor Rf;
One end of the input resistor R1 is connected with the current detection unit, and the other end of the input resistor R1 is connected with the inverting input end of the operational amplifier U.
5. An electronic load, comprising: the device comprises a main operational amplifier, a grid drive, a MOS device, a current detection unit, a gating switch and a switch control unit;
The non-inverting input end of the main operational amplifier is grounded, the inverting input end of the main operational amplifier is connected to the gating switch through the input resistor Rs and connected to the current detection unit through the feedback resistor Rf, and the output end of the main operational amplifier is connected with the grid drive;
the grid electrode of the MOS device is connected with the grid electrode drive, the drain electrode of the MOS device is connected with one electrode of a tested power supply, and the source electrode of the MOS device is connected with the current detection unit;
One end of the current detection unit is grounded, and one end of the current detection unit is grounded and connected with the other electrode of the tested power supply;
The input end of the switch control unit is connected with the tested power supply, the second DA output end and the third DA output end, and the output end controls the gating switch to be communicated with a feedback passage of the switch control unit or be communicated with the first DA output end according to an input signal of the input end.
6. The electronic load of claim 5, wherein the switch control unit comprises: a comparator and a multiplier;
the input end of the multiplier is respectively connected with the third DA output end and the tested power supply, and the output end of the multiplier is connected with the comparator;
The non-inverting input end of the comparator is connected with the second DA output end, the inverting input end of the comparator is connected with the multiplier, and the output end of the comparator is connected with the gating switch.
7. The electronic load of claim 6, wherein the first DA output comprises a first DAC conversion module, one end of the first DAC conversion module is connected to a digital bus, and the other end is connected to or disconnected from the gate switch under the control of the switch control unit;
Or alternatively, the first and second heat exchangers may be,
The second DA output end comprises a second DAC conversion module, one end of the second DAC conversion module is connected with the digital bus, and the other end of the second DAC conversion module is connected with the in-phase input end of the comparator;
Or alternatively, the first and second heat exchangers may be,
The third DA output end comprises a third DAC conversion module, one end of the third DAC conversion module is connected with the digital bus, and the other end of the third DAC conversion module is connected with the multiplier.
8. The electronic load of claim 5, wherein the MOS device comprises: an N channel MOS tube MOS1 and a P channel MOS tube MOS2, diodes D1 and D2 connected in series;
The grid electrodes of the MOS1 and the MOS2 are connected and are in driving connection with the grid electrodes;
The MOS1 is connected with the source electrode of the MOS2 and is connected with the current detection unit;
The negative electrode of D1 is connected with the drain electrode of the MOS1, the positive electrode of D2 is connected with the drain electrode of the MOS2, and the positive electrode of D1 is connected with the negative electrode of D2 and is connected with one electrode of a power supply to be tested.
9. The electronic load according to any one of claims 5 to 8, further comprising a following operational amplifier unit for boosting and inverting the voltage input by the current detection unit and outputting the boosted voltage;
the following operational amplifier unit includes: an operational amplifier U, a feedback resistor R2 and an input resistor R1;
the inverting input end of the operational amplifier U is connected with the output end of the operational amplifier U through a feedback resistor R2, the non-inverting input end of the operational amplifier U is grounded, and the output end of the operational amplifier U is connected with a feedback resistor Rf;
One end of the input resistor R1 is connected with the current detection unit, and the other end of the input resistor R1 is connected with the inverting input end of the operational amplifier U.
10. A power parameter testing system, comprising: a power supply under test and an electronic load as claimed in any one of claims 5 to 9;
The switch control unit judges whether the output voltage of the tested power supply reaches the rated output voltage, and when the output voltage of the tested power supply does not reach the rated output voltage, the switch control unit controls the gating switch to be communicated with a feedback channel of the switch control unit; and when the output voltage of the tested power supply reaches the rated output voltage, controlling the gating switch to be switched to be communicated with the first DA output end.
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| CN115185326B (en) * | 2021-04-07 | 2023-08-01 | 炬芯科技股份有限公司 | Active load circuit and active load module |
| CN113311218B (en) * | 2021-05-13 | 2022-08-30 | 苏州美恩斯电子科技有限公司 | Electronic load constant-resistance device and control method thereof |
| CN113472321B (en) * | 2021-06-07 | 2024-02-23 | 杭州领挚科技有限公司 | Constant current pulse source |
| CN114172365A (en) * | 2021-12-09 | 2022-03-11 | 厦门汉印电子技术有限公司 | Voltage drive circuit and printer |
| CN115776231B (en) * | 2022-12-26 | 2023-12-08 | 深圳市诚金晖精密机械有限公司 | High-precision power supply circuit for electronic equipment test |
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