A device and method for non-destructive measurement of bidirectional current in a DC-DC converter

Abstract

The present invention discloses a device for losslessly measuring bidirectional current in a DC-DC converter, wherein a low-pass filter is arranged in parallel at both ends of an inductor, the low-pass filter includes a capacitor and a resistor, a voltage-current conversion circuit is arranged in parallel at both ends of the capacitor, the output end of the voltage-current conversion circuit is connected to a dual-output mirror current source of PNP polarity, a bias current generating circuit is connected to a dual-output mirror current source of NPN polarity, two output circuits of the dual-output mirror current source of NPN polarity and two output circuits of the dual-output mirror current source of PNP polarity are respectively connected to form a No. 1 circuit and a No. 2 circuit, a No. 1 branch is arranged on the No. 1 circuit, a No. 2 branch is connected to the No. 2 circuit, and an output resistor is connected to the No. 2 branch. The present invention also provides a method for losslessly measuring bidirectional current in a DC-DC converter. No additional current sampling resistor is required in the present invention, which greatly reduces ohmic loss and improves overall efficiency.

Description

Technical Field

[0001] The invention relates to the field of high-current low-voltage DC-DC converters, and in particular to a device and method for losslessly measuring bidirectional current in a DC-DC converter. Background Art

[0002] In low-voltage and high-current DC-DC converters, due to the performance limitations of single semiconductor switching devices, it is generally necessary to connect multiple groups of DC-DC converters in parallel to provide sufficient current. When connecting multiple groups of DC converters in parallel, it is necessary to ensure the uniform distribution of load current, and it is necessary to collect the inductor current information of each converter to control the output current of a single converter. Traditional current sampling requires adding a sampling resistor to the current path, which will produce considerable losses under low-voltage and high-current working conditions, seriously affecting the overall efficiency of the converter. In addition, the commonly used differential amplifier circuit for amplifying the voltage signal across the sampling resistor also has problems such as strict requirements on component errors and limited bandwidth. The use of Hall current sensors can achieve bidirectional non-destructive detection of current, but Hall sensors are large in size, generally limited in bandwidth and relatively expensive, which will significantly increase the cost of the converter. Therefore, in bidirectional low-voltage and high-current converters, there is an urgent need for a method that can detect current at high speed and losslessly. Summary of the invention

[0003] The object of the present invention is to provide a device for losslessly measuring bidirectional current in a DC-DC converter.

[0004] The invention also provides a method for losslessly measuring bidirectional current in a DC-DC converter.

[0005] The innovation of the present invention is that no additional current sampling resistor is required, which greatly reduces ohmic loss and improves overall efficiency; and bidirectional current detection is achieved under the premise of low loss.

[0006] To achieve the above-mentioned invention object, the technical scheme of the present invention is: a device for lossless measurement of bidirectional current in a DC-DC converter, comprising a bidirectional DC-DC converter, a low-pass filter, a positive and negative voltage power supply circuit, a voltage-current conversion circuit, a bias current generating circuit, a dual-output mirror current source with NPN polarity, a dual-output mirror current source with PNP polarity, and an output resistor, an inductor is provided in the bidirectional DC-DC converter, a low-pass filter is arranged in parallel at both ends of the inductor, the low-pass filter includes a capacitor and a resistor, a voltage-current conversion circuit is arranged in parallel at both ends of the capacitor, and a positive and negative voltage The power supply circuit supplies power to the voltage-current conversion circuit, the output end of the voltage-current conversion circuit is connected to a dual-output mirror current source with a PNP polarity, the bias current generating circuit is connected to a dual-output mirror current source with an NPN polarity, the two output circuits of the dual-output mirror current source with an NPN polarity and the two output circuits of the dual-output mirror current source with a PNP polarity are respectively connected, and after the connection, a circuit No. 1 and a circuit No. 2 are formed, a branch No. 1 is provided on the circuit No. 1, and the branch No. 1 is connected to the voltage-current conversion circuit, a branch No. 2 is connected to the circuit No. 2, and an output resistor is connected to the branch No. 2.

[0007] Furthermore, the output tubes in the NPN polarity dual-output mirror current source and the PNP polarity dual-output mirror current source are twin transistor pairs. The use of twin transistor pairs can greatly reduce the mismatch between the feedback current and the output current, and improve the accuracy and linearity of the current detection circuit.

[0008] A method for losslessly measuring bidirectional current in a DC-DC converter comprises the following steps:

[0009] (1) The low-pass filter generates a pole, and the low-pass filter is adjusted so that the frequency of the pole coincides with the frequency of the inductor zero point;

[0010] (2) The voltage-to-current conversion circuit converts the voltage of the capacitor in the low-pass filter into a current signal in proportion;

[0011] (3) After the output end of the voltage-current conversion circuit is connected to a PNP polarity dual-output mirror current source, the PNP polarity dual-output mirror current source generates two currents of the same magnitude as the output current of the voltage-current conversion circuit;

[0012] (4) The bias current generating circuit inputs a dual-output mirror current source with NPN polarity to generate two bias currents of equal magnitude;

[0013] (5) After the two output circuits of the NPN polarity dual-output mirror current source and the two output circuits of the PNP polarity dual-output mirror current source are connected respectively, the NPN polarity dual-output mirror current source simultaneously subtracts the two bias currents from the two outputs of the PNP polarity dual-output mirror current source;

[0014] (6) After subtraction, the output current of circuit No. 2 generates a voltage drop on the output resistor, and the output current of circuit No. 1 is connected to the voltage-current conversion circuit to form a DC-coupled deep negative feedback closed loop;

[0015] (7) Measure the output voltage of the output resistor. The output voltage is proportional to the voltage flowing through the inductor.

[0016] The beneficial effects of the present invention are:

[0017] 1. The present invention does not require additional current sampling resistors, which greatly reduces ohmic losses and improves overall efficiency;

[0018] 2. The present invention realizes bidirectional current detection under the premise of low loss.

[0019] 3. The present invention achieves a relatively high bandwidth, and the instantaneous waveform of the inductor current is well preserved, while providing conditions for rapid current control.

[0020] 4. The present invention has a wide common mode voltage range, which can be very close to 0 V or lower than 0 V. The circuit can normally measure the inductor current waveform at a lower output voltage.

[0021] 5. The high loop gain in the present invention ensures a good linear relationship between the output voltage and the inductor current.

[0022] 6. In the present invention, since the output of the current measurement circuit has current source characteristics, the reference of the output voltage can be any external voltage specified by the designer, which is convenient for connection with the ADC of the subsequent analog circuit or digital circuit.

[0023] 7. The output tubes in the multi-output PNP and NPN current mirror sources of the present invention use twin transistor pairs, which can greatly reduce the mismatch between the feedback current and the output current and improve the accuracy and linearity of the current detection circuit.

[0024] 8. In the present invention, due to the existence of deep negative feedback, the error between the input tube and the output tube of the current mirror source basically does not affect the accuracy and linearity of the output. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of the present invention. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings.

[0027] Embodiment 1: A device for losslessly measuring bidirectional current in a DC-DC converter, comprising a bidirectional DC-DC converter 1, a low-pass filter 2, a positive and negative voltage power supply circuit 3, a voltage-current conversion circuit 4, a bias current generating circuit 5, a dual-output mirror current source of NPN polarity 6, a dual-output mirror current source of PNP polarity 7, and an output resistor 8. The bidirectional DC-DC converter 1 is provided with an inductor 1.1, the low-pass filter 2 is arranged in parallel at both ends of the inductor 1.1, the low-pass filter 2 includes a capacitor 2.1 and a resistor 2.2, the voltage-current conversion circuit 3 is arranged in parallel at both ends of the capacitor 2.1, and the positive and negative voltage power supply circuit 4 is provided. The voltage-current conversion circuit 3 is powered, the output end of the voltage-current conversion circuit 3 is connected to the dual-output mirror current source 7 of PNP polarity, the bias current generating circuit 5 is connected to the dual-output mirror current source 6 of NPN polarity, the two output circuits of the dual-output mirror current source 6 of NPN polarity and the two output circuits of the dual-output mirror current source 7 of PNP polarity are respectively connected, and after the connection, a circuit No. 1 9 and a circuit No. 2 10 are formed, and a branch No. 1 11 is provided on the circuit No. 1 9, and the branch No. 1 11 is connected to the voltage-current conversion circuit 4, and a branch No. 2 12 is connected to the circuit No. 2 10, and an output resistor 8 is connected to the branch No. 2 12. The output tubes in the dual-output mirror current source 6 of NPN polarity and the dual-output mirror current source 7 of PNP polarity are twin transistor pairs.

[0028] Embodiment 2: A method for losslessly measuring bidirectional current in a DC-DC converter, comprising the following steps: a low-pass filter 2 generates a pole, and the low-pass filter 2 is adjusted so that the frequency of the pole coincides with the frequency of the zero point of the inductor 1.1; a positive and negative voltage power supply circuit 3 supplies power to a voltage-current conversion circuit 4, and the voltage-current conversion circuit 4 converts the voltage of the capacitor 2.1 in the low-pass filter 2 into a current signal in proportion; after the output end of the voltage-current conversion circuit 4 is connected to a PNP polarity dual-output mirror current source 7, the PNP polarity dual-output mirror current source 7 generates two currents of the same magnitude as the output current of the voltage-current conversion circuit; a bias current generating circuit 5 inputs an NPN The dual-output mirror current source 6 of NPN polarity generates two bias currents of the same magnitude; after the two output circuits of the dual-output mirror current source 6 of NPN polarity and the two output circuits of the dual-output mirror current source 7 of PNP polarity are connected respectively, the dual-output mirror current source 6 of NPN polarity subtracts the two bias currents from the two outputs of the dual-output mirror current source 7 of PNP polarity at the same time; after the subtraction, the output current of the second circuit 10 generates a voltage drop on the output resistor 8, and the output current of the first circuit 9 is connected to the voltage-current conversion circuit 4, forming a DC-coupled deep negative feedback closed loop; the output voltage of the output resistor 8 is measured, and the output voltage 8 is proportional to the voltage flowing through the inductor 1.1. The output voltage of the output resistor 8 is equal to the current on the second circuit 10 minus the current on the NPN polarity dual output mirror current source 6 multiplied by the resistance of the output resistor 8. Since the output voltage of the output resistor 8, the resistance of the output resistor 8, and the NPN polarity dual output mirror current source 6 are known, the current on the second circuit 10 can be obtained. The current on the second circuit 10 is equal to the current on the first circuit 9. The voltage across the capacitor of the low-pass filter 2 can be deduced from the current on the first circuit 9. The voltage across the capacitor 2.1 of the low-pass filter 2 has a linear relationship with the current flowing through the inductor 1.1, so the current flowing through the inductor 1.1 can be calculated.

[0029] The described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. A device for lossless measurement of bidirectional current in a DC-DC converter, characterized in that: The invention comprises a bidirectional DC-DC converter, a low-pass filter, a positive and negative voltage power supply circuit, a voltage-current conversion circuit, a bias current generating circuit, a dual-output mirror current source of NPN polarity, a dual-output mirror current source of PNP polarity, and an output resistor. An inductor is arranged inside the bidirectional DC-DC converter. The low-pass filter is arranged in parallel at both ends of the inductor. The low-pass filter comprises a capacitor and a resistor. The voltage-current conversion circuit is arranged in parallel at both ends of the capacitor. The positive and negative voltage power supply circuit supplies power to the voltage-current conversion circuit. The output end of the voltage-current conversion circuit is connected to the dual-output mirror current source of PNP polarity. The bias current generating circuit is connected to the dual-output mirror current source of NPN polarity. The two output circuits of the dual-output mirror current source of NPN polarity and the two output circuits of the dual-output mirror current source of PNP polarity are respectively connected to form a No. 1 circuit and a No. 2 circuit after the connection. The No. 1 circuit is provided with a No. 1 branch, and the No. 1 branch is connected to the voltage-current conversion circuit. The No. 2 circuit is connected with a No. 2 branch, and the No. 2 branch is connected with an output resistor.

2. The device for lossless measurement of bidirectional current in a DC-DC converter according to claim 1, characterized in that: The output tubes in the dual-output mirror current source with NPN polarity and the dual-output mirror current source with PNP polarity are twin transistor pairs.

3. A method for lossless measurement of bidirectional current in a DC-DC converter, characterized in that: The following steps are involved: (1) The low-pass filter generates a pole, and the low-pass filter is adjusted so that the frequency of the pole coincides with the frequency of the zero point of the inductor in the bidirectional DC-DC converter; (2) The voltage-to-current conversion circuit converts the voltage of the capacitor in the low-pass filter into a current signal in proportion; (3) After the output end of the voltage-current conversion circuit is connected to a PNP polarity dual-output mirror current source, the PNP polarity dual-output mirror current source generates two currents of the same magnitude as the current signal output by the voltage-current conversion circuit; (4) The bias current generating circuit inputs a dual-output mirror current source with NPN polarity to generate two bias currents of equal magnitude; (5) The two output circuits of the dual-output mirror current source with NPN polarity and the two output circuits of the dual-output mirror current source with PNP polarity are connected to form circuit No. 1 and circuit No. 2 respectively, and the dual-output mirror current source with NPN polarity simultaneously subtracts the two bias currents from the two output currents of the dual-output mirror current source with PNP polarity; (6) After subtraction, the output current of circuit No. 2 generates a voltage drop on the output resistor, and the output current of circuit No. 1 is connected to the voltage-current conversion circuit to form a DC-coupled deep negative feedback closed loop; (7) Measure the output voltage of the output resistor. The output voltage is proportional to the voltage flowing through the inductor.

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