CN107453611A - Dc source noise modulate circuit based on constant-current source - Google Patents

Abstract

The invention discloses a kind of dc source modulate circuit based on constant-current source, including：Isolation boosting circuit module, constant-current source circuit module, feedback voltage stabilizing circuit module.Dc source noise modulate circuit of the present invention, dc source noise conditioning is carried out using constant-current source scheme, there is isolation and filter function.On the one hand it can effectively suppress the switching frequency noise of dc source noise, especially Switching Power Supply, ultra-low noise direct current supply is provided for load；On the other hand high resistant isolation can be carried out to caused high frequency spurs in loaded work piece, prevents clutter from polluting power bus.The modulate circuit meets the high stability requirement to power supply in high-precision Weak Signal Detection System, is a kind of Novel DC power supply modulate circuit.

Description

Noise Conditioning Circuit of DC Power Supply Based on Constant Current Source

technical field

The invention relates to a power supply noise conditioning circuit, in particular to a DC power supply noise conditioning circuit based on a constant current source.

Background technique

Out of the consideration of energy efficiency, switching power supply is widely used as the power supply scheme of the system in the current system. The output of the switching power supply is often accompanied by a lot of noise. The noise of the switching power supply has two forms: one is ripple noise, which is caused by the limitation of the filtering ability of the LC filter circuit of the switching power supply. Filter inductors and filter capacitors can reduce ripple noise; the other is spike noise. The switch tube in the switching power supply and the rectifier diode in the rectifier circuit will have a sudden change in current at the moment the transistor is cut off, resulting in the same frequency as the switching frequency. Spike noise, accompanied by radiation interference. Generally speaking, within the bandwidth of 200MHz, the peak-to-peak value of the peak glitch noise of the switching power supply can reach tens of mV or even hundreds of mV.

In specific applications, some systems have high requirements on the noise characteristics of the power supply, so they are called high power supply noise sensitivity systems. For example, the high-precision weak signal detection circuit puts forward extremely high requirements on its power supply noise. Generally speaking, the high-speed voltage detection system of uV level needs to achieve a peak-to-peak noise of less than 1mV within a 200M bandwidth. For a high-precision weak signal detection circuit, the spike noise of the power supply line can crosstalk into its sampling line, thereby causing spike interference in the sampling circuit, which will seriously affect the sampling results of the weak signal. Therefore, the high-precision weak signal The detection system is extremely sensitive to power supply noise, and an extremely low-noise power supply solution is required. Generally speaking, switching power supply solutions are difficult to apply to such systems with high power supply noise sensitivity due to their extremely high noise.

For system applications with low power consumption requirements, a switching power supply scheme must be used. When the load system has high power supply noise sensitivity, it is necessary to insert a first-level power supply noise conditioning circuit between the switching power supply and the load system to suppress the noise of the switching power supply. To meet the power supply noise requirements of high power supply noise sensitivity systems.

The constant current source circuit has a constant current output. Theoretically, the AC impedance of the constant current circuit approaches infinity. Therefore, the constant current source circuit is equivalent to an inductance with infinite inductance, which has a strong influence on the noise on the power transmission line. Inhibition can achieve high-impedance isolation of AC signals. Utilizing the high AC impedance characteristic of the constant current source circuit, a power conditioning circuit with a high noise rejection ratio can be realized to meet the power supply noise requirement of a system with high power supply noise sensitivity.

Contents of the invention

The purpose of the present invention is to address the deficiencies of the prior art, to provide a DC power supply conditioning circuit based on a constant current source, which can effectively filter power supply noise, and realize AC noise isolation between the load and the power supply, thereby meeting the requirements for power supply noise Ultra-low-noise power supply for extremely high-level systems, such as high-precision weak-signal detection systems.

The purpose of the present invention is achieved through the following technical solutions: a DC power conditioning circuit based on a constant current source, comprising:

The isolated boost circuit module is used to chop the DC signal of the power supply into an AC signal, and then output DC after isolation, boost, rectification and filtering;

The constant current source circuit module is used to perform V-I conversion on the DC output of the isolated boost circuit module to obtain a constant current output;

The feedback voltage stabilizing circuit module is used for feedback controlling the output voltage of the constant current source circuit module, so as to ensure the constant voltage output of the whole power supply noise conditioning circuit when the load changes.

Further, the isolated boost circuit module adopts an isolated DC-DC power topology circuit.

Further, the isolated step-up circuit module includes a switch circuit, an isolation transformer, and a rectifier filter circuit; the input end of the switch circuit is connected to the output end of the power supply, the output end of the switch circuit is connected to the input end of the isolation transformer, and the output end of the isolation transformer connected to the rectifier filter circuit.

Further, the constant current source circuit module includes a first voltage reference circuit and a V-I conversion circuit; the V-I conversion circuit has two input terminals and one output terminal, which are respectively a power supply input terminal, a reference input terminal and a constant current The output terminal; the power supply input terminal is connected to the output terminal of the isolated boost module, and the reference input terminal is connected to the output terminal of the first voltage reference circuit; the constant current output terminal is used as the output terminal of the constant current source circuit module to provide a DC constant current output.

Further, the feedback voltage stabilizing circuit module includes a second voltage reference circuit, a feedback control circuit and a switch tube circuit; the feedback control circuit has two input terminals and one output terminal, which are respectively a reference input terminal and a sampling input terminal , the control output terminal; the reference input terminal is connected to the output terminal of the second voltage reference circuit, the control output terminal is connected to the control input terminal of the switching tube circuit, and the sampling input terminal and the current input terminal of the switching tube circuit are connected to the constant current source circuit module The output terminal of the switch tube circuit is connected as the output of the whole power conditioning circuit.

The beneficial effects of the present invention are: utilizing the high AC impedance characteristics of the constant current source circuit to realize effective low-pass filtering of power supply noise, and at the same time realize physical isolation and high-impedance isolation between the load end and the power supply end, avoiding the influence of the power supply noise on the load circuit, and The clutter pollution of the load circuit to the power bus is avoided. It is a power conditioning scheme suitable for high-precision weak signal detection circuits with extremely high requirements on power supply noise.

The above-mentioned DC power supply conditioning circuit based on the constant current source can effectively suppress the high-frequency glitch noise generated by the DC-DC power supply, and is suitable for systems with high requirements on power supply noise performance, such as high-precision weak signal detection systems, which can effectively avoid power supply The impact of noise on the load system and improve the performance of the load system.

Description of drawings

Fig. 1 is a schematic diagram of the internal module design of the power conditioning circuit based on the constant current source of the present invention;

Fig. 2 is an internal circuit design diagram of the isolated boost circuit module of the present invention;

Fig. 3 is the internal circuit design diagram of the constant current source circuit module of the present invention;

Fig. 4 is the internal circuit design diagram of the feedback voltage stabilizing circuit module of the present invention;

Fig. 5 is a schematic diagram of a specific embodiment of the constant current source circuit module of the present invention;

Fig. 6 is a schematic diagram of a specific embodiment of the feedback regulator circuit module of the present invention;

FIG. 7 is a schematic diagram of an embodiment of a power conditioning circuit based on a constant current source in the present invention.

detailed description

The purpose and effects of the present invention will become more apparent as the present invention is described in detail below with reference to the accompanying drawings.

The present invention provides a DC power supply conditioning circuit based on a constant current source, which can effectively filter out power supply noise, and realize AC noise isolation between the load and the power supply, so as to provide a system with extremely high requirements on power supply noise (such as high-precision weak signal detection system) to provide ultra-low noise power supply.

As shown in FIG. 1 , a DC power conditioning circuit based on a constant current source includes an isolated boost circuit module, a constant current source circuit module and a feedback regulator circuit module connected in sequence. The input of the isolated boost circuit module is connected to the output of the external DC-DC power supply, the output of the isolated boost circuit module is connected to the input of the constant current source circuit module, the output of the constant current source circuit module is connected to the input of the feedback regulator circuit module connected, and the output of the feedback regulator circuit module is connected to the input of the external load.

As shown in FIG. 2 , the isolated boost circuit module adopts an isolated DC-DC power topology circuit, including a switch circuit, an isolation transformer, and a rectification and filtering circuit. This module has two functions, one is the boost function, which provides sufficient input and output pressure difference for the constant current source circuit module of the subsequent stage; the other is the isolation function, which realizes the physical isolation of the power supply terminal and the load terminal, to a certain extent Suppress the clutter pollution of the load to the power bus.

The internal structure of the isolated boost circuit module is as follows: the input end of the switch circuit is connected to the output end of the power supply, the output end of the switch circuit is connected to the input end of the isolation transformer, and the output end of the isolation transformer is connected to the rectification and filtering circuit.

The working principle of the isolated boost circuit module is as follows: the switch circuit receives the electric energy of the DC power supply, chops the DC signal of the power supply into an AC signal, realizes the isolated boost through the isolation transformer, and then realizes the boosted DC through the rectification filter circuit. output. The structure and working principle of the isolated boost circuit module are similar to the topology of a general isolated boost DC-DC circuit, and details will not be described here.

As shown in FIG. 3 , the constant current source circuit module includes a voltage reference circuit and a V-I conversion circuit. The module can provide a stable constant current output, utilize the high AC impedance performance of the constant current source circuit to suppress the noise of the power supply line, and realize high-impedance isolation of the AC signal at both ends of the power supply and the load.

The internal structure of the constant current circuit module is as follows: the V-I conversion circuit has two input terminals and an output terminal, which are respectively a power supply input terminal, a reference input terminal and a constant current output terminal; the power supply input terminal and the previous stage isolation booster module The output end of the reference circuit is connected; the reference input end is connected with the output end of the voltage reference circuit; the constant current output end is used as the output end of the constant current source circuit module to provide a DC constant current output.

The working principle of the constant current source circuit module is as follows: the V-I conversion circuit performs V-I conversion based on the voltage provided by the voltage reference circuit to realize constant current output; the input constant voltage power of the power supply terminal is converted into constant current power output, and the constant current The source has a high ability to suppress AC noise, which can suppress the high-frequency AC noise at the constant voltage power supply end, so it can obtain ultra-low noise constant current output, and the current setting value of the constant current output is equal to the maximum required by the load during operation current value.

As shown in FIG. 4 , the feedback regulator circuit module includes a voltage reference circuit, a feedback control circuit, and a switch tube circuit. The module can sample the voltage value of the constant current output terminal, and stabilize the voltage value of the constant current output terminal through feedback control, so that the output of the entire conditioning circuit maintains a constant voltage characteristic to meet the needs of constant voltage drive of the load.

The internal structure of the feedback voltage stabilizing circuit module is as follows: the feedback control circuit has two input terminals and one output terminal, which are respectively a reference input terminal, a sampling input terminal and a control output terminal; the reference input terminal is connected to the output terminal of the voltage reference circuit; The control output terminal is connected to the control input terminal of the switching tube circuit; the current input terminal of the switching tube circuit is connected to the output terminal of the constant current source circuit module; the current input terminal of the switching tube circuit is connected to the output terminal of the feedback regulator circuit module, as Output of the entire power conditioning circuit. The sampling input terminal is connected with the current input terminal of the switching tube circuit, that is, the output terminal of the feedback voltage stabilizing circuit module.

The working principle of the feedback voltage stabilizing circuit module is as follows: the voltage reference circuit provides a voltage reference, and the feedback control circuit samples the output voltage of the constant current source circuit module and compares it with the voltage reference. When the load resistance value increases, the constant current source The output voltage of the circuit module increases. At this time, the feedback control circuit controls to increase the shunt flow of the switch tube circuit, allowing more current to discharge through the switch tube, reducing the current received by the load end, so that the output voltage of the constant current source circuit decrease; when the resistance value of the load end decreases, the output voltage of the constant current source circuit module decreases, and at this time the feedback control circuit controls to reduce the shunt flow of the switch tube circuit and increase the current received by the load end, so that the constant current source circuit module The output voltage of the constant current source circuit module is increased to achieve a constant voltage value at the output terminal of the constant current source circuit module.

Utilize the high AC impedance characteristics of the constant current source circuit to achieve effective low-pass filtering of power supply noise, and at the same time realize physical isolation and high-impedance isolation between the load terminal and the power supply terminal, avoiding the impact of power supply noise on the load circuit and the impact of the load circuit on the power bus clutter pollution. It is a power conditioning scheme suitable for high-precision weak signal detection circuits with extremely high requirements on power supply noise. The above-mentioned DC power supply conditioning circuit based on the constant current source can effectively suppress the high-frequency glitch noise generated by the DC-DC power supply, and is suitable for systems that require high power supply noise performance (such as high-precision weak signal detection systems), and can effectively avoid power The impact of noise on the load system and improve the performance of the load system.

Example:

Several specific embodiments are given below for the specific sub-modules described in the present invention, and a specific embodiment of a complete technical solution is given at the end to illustrate the feasibility of the present invention in terms of implementation.

The isolated boost circuit module is similar to the commonly used isolated boost DC-DC circuit topology and has wide applicability, so no specific embodiments will be given here.

Fig. 5 shows a specific embodiment of the constant current source circuit module. In this embodiment, Vcc is the voltage output of the previous stage isolation boost circuit module, which is used as the voltage input of the constant current source circuit module; the voltage reference circuit adopts TI's low-noise reference chip REF5020, which provides a 2V reference voltage, and The input terminal and output terminal of the chip are respectively connected with 1uF and 22uF decoupling capacitors; the V-I conversion circuit converts the 2V voltage reference of the voltage reference circuit into a 1A constant current output, and the constant current output is sent to the next stage circuit.

Fig. 6 shows a specific embodiment of the feedback regulator circuit module. In this embodiment, Vcc isolates the voltage output of the boost circuit module, and I _IN is the constant current output of the previous stage constant current source circuit module, which is used as the current input of the feedback regulator circuit module. The voltage reference circuit adopts TI's low-noise reference chip REF5050, which provides a 5V reference voltage, and connects 1uF and 22uF decoupling capacitors at the input and output terminals of the chip respectively; the feedback control circuit controls the shunt flow I _d of the switching tube circuit to ensure stable I _out * R _L = 5V at the load end of the voltage circuit, so that the voltage at the load end is stabilized at 5V.

Figure 7 shows a specific embodiment of the entire conditioning circuit integrating all submodules, and the circuit is taken as an example below to illustrate the specific working process of the present invention:

In this embodiment, the high power supply sensitivity load requires a low-noise 5V power supply, but the 5V output DC-DC power supply used in the power supply system contains large switching frequency glitch noise, which will affect the performance of the load, so it is necessary to adopt the present invention The technical solution described in the design of the power supply noise conditioning circuit, in order to achieve the suppression of switching frequency glitch noise, to obtain a very low noise power supply output. The load in this embodiment requires 5V constant voltage power supply, and the load operating current varies between 200mA-350mA.

As shown in Figure 7, the power supply noise conditioning circuit based on the constant current source is connected between the 5V output of the system DC-DC power supply and the high power supply sensitivity load. The conditioning circuit is composed of an isolation boosting module, a constant current source circuit module, and a feedback voltage stabilizing circuit module. The isolated step-up module in this embodiment is implemented by a push-pull transformer driver, which realizes 7V output after rectification and voltage stabilization, and provides the required voltage difference for the current-voltage conversion circuit of the subsequent constant current source circuit module. The constant current source circuit module is realized by an instrument operational amplifier, a power operational amplifier, and a voltage reference. Its working principle is as follows: the gain of the instrument operational amplifier is set at G=10, Rset=0.5Ω, and the voltage Vset at both ends of Rset passes through The instrument operational amplifier is magnified by 10 times and transmitted to the non-inverting input terminal of the power operational amplifier. The inverting input terminal of the power operational amplifier is connected to the voltage reference. The reference voltage Vref1=2V, and the voltage relationship after the feedback control of the operational amplifier satisfies Vset*G=Vref1 , so there is Vset=Vref1/G=0.2V, the current output by the output terminal of the power operational amplifier is the output current of the constant current source circuit module, and the output current satisfies the relationship Iout1=Vset/Rset=400mA. The output current Iout1 of the constant current source circuit module flows into the load after being shunted by the feedback regulator circuit module. The feedback regulator circuit module is composed of a low-noise operational amplifier, a 5V voltage reference, and a high-power FET. The input current Iin=Iout1=400mA, wherein the input current Iin, the shunt flow Id of the high-power regulator tube, and the output current Iout2 of the feedback regulator circuit module satisfy the relationship: Iout2=Iin-Id, the non-inverting input terminal of the low-noise operational amplifier Connect the output of the feedback regulator circuit to sample the output voltage of the feedback regulator circuit in real time. The output of the 5V voltage reference Vref2=5V is connected to the inverting input terminal of the low-noise operational amplifier, and the output terminal of the low-noise operational amplifier is connected to the high-power field The G pole of the effect tube, the D pole of the high-power FET are connected to the output end of the feedback regulator circuit module, and the S pole of the high-power FET is connected to the output ground, thus realizing the feedback control of the output voltage of the feedback regulator circuit : The output voltage Vout of the feedback regulator circuit is controlled at Vout=Vref2=5V. When the operating current of the load decreases, that is, when the load equivalent resistance RL increases, because Vout=Iout2*RL, Vout rises, and the sampling feedback The control voltage output by the low-noise operational amplifier also rises thereupon, and the shunt flow Id of the control field effect transistor increases, so that the current output Iout2 of the feedback regulator circuit module decreases, so Vout also decreases until Vout=Vref2=5V; when the load When the working current of the current increases, that is, when the load equivalent resistance RL decreases, since Vout=Iout2*RL, Vout decreases, the control voltage of the low-noise operational amplifier output after sampling feedback also decreases, and the shunt flow Id of the control field effect tube decreases, so that the current output Iout2 of the feedback regulator circuit increases, so Vout also increases until Vout=Vref2=5V. It can be seen that the feedback regulator circuit module samples the output voltage and compares it with the internal reference of 5V, feedback controls the shunt flow of the high-power FET, increases the output voltage, increases the shunt flow, reduces the output current, and decreases the output voltage The flow is divided to increase the output current, so that the voltage at the output end of the feedback regulator circuit is constant and stable at 5V, which meets the demand of the load for 5V constant voltage output.

In this embodiment, on the one hand, the constant current source circuit module can effectively suppress the high-frequency glitch noise generated by the 5VDC-DC switching power supply to achieve an extremely low-noise power output; Impedance isolation avoids crosstalk between the power bus and the load; the feedback regulator module controls the output voltage at 5V to meet the load's 5V constant voltage power supply requirements; the first-level isolation boost module realizes physical isolation of the circuit At the same time, the boost is realized. On the one hand, the power operational amplifier of the constant current source circuit module provides the voltage difference required for current-voltage conversion. On the other hand, the physical isolation of the transformer is used to reduce the crosstalk between the power bus and the load.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the description of the present invention and the contents of the accompanying drawings, or directly or indirectly used in other related All technical fields are equally included in the scope of patent protection of the present invention.

Claims (5)

1. A DC power conditioning circuit based on a constant current source, characterized in that it comprises: The isolated step-up circuit module is used to chop the DC signal of the power supply into an AC signal, and then output the DC signal after being isolated and boosted, rectified and filtered. The constant current source circuit module is used to perform V-I conversion on the DC output of the isolated boost circuit module to obtain a constant current output. The feedback voltage stabilizing circuit module is used for feedback controlling the output voltage of the constant current source circuit module, so as to ensure the constant voltage output of the whole power supply noise conditioning circuit when the load changes. 2. A DC power conditioning circuit based on a constant current source according to claim 1, wherein the isolated boost circuit module adopts an isolated DC-DC power topology circuit. 3. A kind of DC power conditioning circuit based on constant current source according to claim 1 or 2, it is characterized in that, described isolation step-up circuit module comprises switch circuit, isolation transformer, rectification filter circuit; Described switch The input end of the circuit is connected with the output end of the power supply, the output end of the switch circuit is connected with the input end of the isolation transformer, and the output end of the isolation transformer is connected with the rectification filter circuit. 4. A kind of DC power conditioning circuit based on constant current source according to claim 1, it is characterized in that, described constant current source circuit module comprises the first voltage reference circuit and V-I conversion circuit; Described V-I conversion circuit There are two input terminals and one output terminal, which are power input terminal, reference input terminal and constant current output terminal; the power supply input terminal is connected to the output terminal of the isolated boost module, and the reference input terminal is connected to the output terminal of the first voltage reference circuit connected; the constant current output terminal is used as the output terminal of the constant current source circuit module to provide a DC constant current output. 5. A kind of DC power conditioning circuit based on constant current source according to claim 1, it is characterized in that, described feedback regulator circuit module comprises second voltage reference circuit, feedback control circuit and switch tube circuit; The feedback control circuit has two input terminals and one output terminal, which are respectively a reference input terminal, a sampling input terminal, and a control output terminal; the reference input terminal is connected to the output terminal of the second voltage reference circuit, and the control output terminal and the control of the switching tube circuit The input terminals are connected, and the sampling input terminal and the current input terminal of the switching tube circuit are connected with the output terminal of the constant current source circuit module; the current input terminal of the switching tube circuit is used as the output of the whole power conditioning circuit.