CN210536996U

CN210536996U - Current ripple control device of constant current source

Info

Publication number: CN210536996U
Application number: CN201920983516.0U
Authority: CN
Inventors: 邹勇; 吴殿升; 袁波; 史春杰; 贺星
Original assignee: Wuxi Grand Microelectronics Technology Co ltd
Current assignee: Wuxi Grand Microelectronics Technology Co ltd
Priority date: 2019-06-27
Filing date: 2019-06-27
Publication date: 2020-05-15
Anticipated expiration: 2029-06-27

Abstract

The utility model provides a current ripple controlling means and control method of constant current source mainly includes: an input electrolytic capacitor C1, a main control chip U1, control switches S1 and S2, power inductors L1 and L2, diodes D1 and D2, an output capacitor C2 and an LED load; the DRV1 of the control chip U1 is connected with R3 to control S1, and the DRV2 is connected with R5 to control S2; the control switch S1, the L1 and the D1 form a power loop 1; the control switch S2, the L2 and the D2 form a power loop 2; the two power loops are connected in parallel through power inductors L1 and L2 to provide conversion energy for the LED load. Form certain phase difference through the inductive current in control power return circuit 2 and the power return circuit 1, the utility model discloses can be using less output electric capacity C2, perhaps save output electric capacity C2 under the prerequisite with LED's ripple current control in certain extent, can not influence LED drive power supply's EMC, temperature rise and cost simultaneously.

Description

Current ripple control device of constant current source

Technical Field

The utility model relates to an electronic circuit technical field specifically is a current ripple controlling means and method of constant current source.

Background

At present, the demand for a non-isolated power supply in the LED lighting industry is more and more increased, and the demand far exceeds that of an isolated power supply; the advantages of non-isolated power supplies, including high conversion efficiency, simple periphery (operating in an inductor current critical continuous mode), and low cost, occupy a large portion of the market in applications of different lamps and power sections.

In the face of price competition, some manufacturers consider to omit output electrolysis on the framework of a non-isolated power supply, so that output ripple current is very large and almost equal to the ripple current; the lighting effect of the finished LED lamp is reduced, and the aging and the light decay of the LED lamp beads are aggravated; another part of manufacturers may reduce ripple current by using a non-isolated continuous mode (CCM) method after removing output electrolysis, but the problem of loss heating and EMI caused by reverse recovery time of the freewheeling diode in the CCM mode requires additional cost increase to ensure the reliability of the product. It can be seen that the above two methods have advantages and disadvantages.

The prior non-isolated power supply is limited to the application of outputting high voltage and low current and has the advantages over the isolation; if the power supply is used in different countries and regions, the application of full voltage input 100-.

Therefore, under the requirement of full voltage input 100-; however, this is not cost-effective: resulting in a preference for a relatively expensive isolated power supply under high output current applications.

Disclosure of Invention

The technical problem solved by the present invention is to provide a current ripple control device and method for a constant current source to solve the problems in the background art.

The utility model provides a technical problem adopt following technical scheme to realize: a current ripple control device of a constant current source mainly comprises: an input electrolytic capacitor C1, a main control chip U1, control switches S1 and S2, power inductors L1 and L2, diodes D1 and D2, an output capacitor C2 and an LED load; the DRV1 of the control chip U1 is connected with R3 to control S1, and the DRV2 is connected with R5 to control S2; the control switch S1, the L1 and the D1 form a power loop I; the control switch S2, the L2 and the D2 form a power loop II; the two paths are connected in parallel through power inductors L1 and L2 to provide conversion energy for an LED load, and meanwhile, the inductive currents in the power loop II and the power loop I are controlled to form a certain phase difference.

Furthermore, the capacity of the output electrolysis C2 connected with the power circuit I and the power circuit II after being connected in parallel is small or can be directly omitted.

Furthermore, the control strategy of the two ways of BUCKs adopts a master-slave control mode, and the control signals of the slave ways completely come from the master way.

Further, in the master-slave control mode, the master circuit and the slave circuit use the detected inductor current reaching a set value as their PWM off signals, the inductor current set value of the master circuit is IL1_ ref, and the inductor current set value of the slave circuit is IL2_ ref.

Furthermore, in a master-slave control mode, the natural zero crossing of the inductive current is used as a PWM (pulse-width modulation) opening signal of the master circuit; and the off signal of the main circuit is used as one of the PWM on signal references of the slave circuit.

Furthermore, in the master-slave control mode, the natural zero crossing of the inductance current of the slave circuit is used as the PWM opening signal of the slave circuit.

Furthermore, in the master-slave control mode, when the parameters of the two ways of BUCK are deviated, in order to prevent the slave from entering an inductive current discontinuous mode or an inductive current continuous mode to cause problems of efficiency, EMI and the like, the inductive current set value IL1_ ref of the master and the inductive current set value IL2_ ref of the slave are adjusted by judging the time difference △ Tson (△ Tson-tspf) between the inductive current zero-crossing time Tszcd of the slave and the PWM off time Tpoff of the master, so as to ensure that the inductive current of the slave is in a critical continuous mode.

Further, in the adjustment mode of the inductance current set values of the master circuit and the slave circuit, when the two △ tsons are greater than zero, the inductance current set value of the master circuit is adjusted to be IL1_ ref + △ IL, and the inductance current set value of the slave circuit is adjusted to be IL2_ ref- △ IL, wherein △ IL is a control quantity for the inductance current set values of the master circuit and the slave circuit.

Further, in the adjustment mode of the inductance current set values of the master circuit and the slave circuit, when the two △ tsons are less than zero, the inductance current set value of the master circuit is adjusted to be IL1_ ref- △ IL, and the inductance current set value of the slave circuit is adjusted to be IL2_ ref + △ IL, wherein △ IL is a control quantity for the inductance current set values of the master circuit and the slave circuit.

Further, the inductor current settings of the master and slave circuits are adjusted in such a way that the goal of the control is to △ Tson equal to zero, or close to zero (e.g., between negative 500ns and integer 500 ns).

Compared with the prior art, the beneficial effects of the utility model are that: the utility model can not only make the non-isolated power supply satisfy the application of 100-265V input of full voltage (application of large output current), but also save output electrolysis (reduce cost), and control the ripple within a certain range (can use smaller output capacitor or omit the capacitor, achieve the same effect); and the temperature rise and EMI of the driving power supply can not be influenced.

Drawings

Fig. 1 is a schematic structural diagram of the present invention.

Fig. 2 is a waveform diagram of the present invention.

Fig. 3 is a schematic circuit diagram of the present invention.

Detailed Description

In order to make the technical means, the creative features, the purpose and the efficacy of the present invention easily understood and appreciated, the present invention will be further explained with reference to the specific drawings, and in the description of the present invention, it should be noted that unless otherwise specified and limited, the terms "mounted", "connected" and "connected" should be understood broadly, for example, they may be fixed connection, detachable connection, or integrally connected, mechanically connected or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements.

As shown in fig. 3, a current ripple control device of a constant current source mainly includes: an input electrolytic capacitor C1, a main control chip U1, control switches S1 and S2, power inductors L1 and L2, diodes D1 and D2, an output capacitor C2 and an LED load; the DRV1 of the control chip U1 is connected with R3 to control S1, and the DRV2 is connected with R5 to control S2; the control switch S1, the L1 and the D1 form a power loop I; the control switch S2, the L2 and the D2 form a power loop II; the two power loops are connected in parallel through power inductors L1 and L2 to provide conversion energy for the LED load; actually, two BUCK topological structures work in parallel, and the two BUCKs are connected in parallel in a master-slave mode.

U1 is a control chip, mainly outputs two PWM signals (DRV1 and DRV2) to control S1 and S2, CS1 and CS2 are two ways of CS reference detection, L1 and L2 are power inductor output parallel connection, and C2 is output electrolysis; under an ideal working state, the phase difference of the PWM waveforms of the DRV1 and the DRV2 is about 90 degrees, and both BUCKs work in a BCM mode.

As shown in fig. 1 and fig. 2, the two parallel BUCK circuits are in a master-slave relationship (assuming that DRV1 is master and DRV2 is slave), and the slave PWM (DRV2) is turned on and the master PWM (DRV1) is turned off as a reference, so that the two inductive currents are staggered in phase, and thus the two inductive currents (IL1 and IL2) can be overlapped, and the total inductive current IL1+ IL2 forms a current waveform of CCM, so as to achieve a current effect of reducing ripple, and thus the output current (C2) can be reduced or omitted; still working in BCM mode from single BUCK point of view, so there is not the problem of loss heating and EMI that the backward recovery time caused in free wheeling diode.

Because the two ways of BUCKs have certain deviation in parameters and chip references, the main characteristic is that the inductance values of the two ways of inductors L1 and L2 have deviation, and the inductance values of the main circuit and the auxiliary circuit have 5-10% tolerance in practical application, which is a very normal phenomenon; the on-time of the slave circuit (namely the time when the inductance current of the slave circuit naturally crosses zero) and the off-time difference of the master circuit can be adopted for judgment, and the two-circuit BUCKs are ensured to always work in a BCM mode through the adjustment (reduction and rise) of two-circuit CS references.

When the inductance of the slave circuit is smaller than that of the master circuit, the on of the slave circuit to be followed is influenced by the off signal of the master circuit, and because the inductance of the slave circuit is smaller, the zero crossing is faster, the period is shorter, namely the master circuit is not turned off when the slave circuit crosses zero, the slave circuit has a certain time (entering a DCM mode) even longer when the inductance current of the slave circuit is zero, and the efficiency of the slave circuit is reduced due to the phenomenon; the time difference allowed in the control chip is 500ns, for example, once the slave circuit crosses zero too early, the time difference between the time and the turn-off time of the master circuit is greater than 500ns, the chip can increase the CS reference of the slave circuit (assuming that the CS references of the master circuit and the slave circuit are both 400mV under an ideal condition) by 410mV, and reduce the CS reference of the master circuit to 390mV at the same time, so that the regulated output current is unchanged, and the regulation can also make the zero-crossing time of the slave circuit close to the turn-off time of the master circuit, thereby ensuring the working efficiency of the slave circuit.

When the inductance of the slave circuit is larger than that of the master circuit, the switching period of the slave circuit is longer than that of the master circuit, and then when the master circuit is switched off, the inductive current of the slave circuit is switched off without zero crossing, so that the slave circuit enters a CCM mode (and the master circuit works in a BCM mode at the moment), the slave circuit has the problems of EMI (electro-magnetic interference) and switching loss caused by reverse recovery time, in the same control method, the CS reference of the slave circuit is reduced to 390mV so as to be detected by the CS reference earlier, the peak value of the inductive current is reduced, and meanwhile, the CS reference of the master circuit is increased to 410mV, so that the switching period of the slave circuit is increased and the switching period of the master circuit is reduced), and then the slave circuit can be switched to the BCM mode; the two paths of BUCKs always work in a BCM mode, and the time difference between the switching-on of the slave path and the switching-off of the master path can be effectively controlled and reduced.

The utility model discloses can solve and save the ripple problem after the output electrolysis, also can avoid the loss that similar CCM appears to generate heat and EMI's problem, can also let non-isolation power can realize high output voltage and high output current in limited scope and cost to satisfy full voltage's input 100 in the certain limit and give other words 265V's application.

The basic principles and the main features of the invention and the advantages of the invention have been shown and described above. It will be understood by those skilled in the art that the present invention is not limited to the above embodiments, and that the foregoing embodiments and descriptions are provided only to illustrate the principles of the present invention without departing from the spirit and scope of the present invention. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. A current ripple control device of a constant current source mainly comprises: an input electrolytic capacitor C1, a main control chip U1, control switches S1 and S2, power inductors L1 and L2, diodes D1 and D2, an output capacitor C2 and an LED load; the DRV1 of the control chip U1 is connected with R3 to control S1, and the DRV2 is connected with R5 to control S2; the control switch S1, the L1 and the D1 form a power loop I; the control switch S2, the L2 and the D2 form another power loop II; and the output end of the power loop I and the output end of the power loop II are connected in parallel and then provide conversion energy for the LED load.

2. The current ripple control device of a constant current source according to claim 1, wherein: the output electrolysis C2 connected with the power loop I and the power loop II after being connected in parallel has small capacity or can be directly omitted.

3. The current ripple control device of a constant current source according to claim 1, wherein: the control strategy of the two paths of BUCKs adopts a master-slave control mode, and control signals of the slave path completely come from the master path.

4. The current ripple control device of a constant current source according to claim 2, wherein: in the master-slave control mode, the master circuit and the slave circuit use the detected inductive current reaching a set value as the PWM off signal, the inductive current set value of the master circuit is IL1_ ref, and the inductive current set value of the slave circuit is IL2_ ref.

5. The current ripple control device of a constant current source according to claim 2, wherein: in the master-slave control mode, the natural zero crossing of the inductive current is used as a PWM (pulse width modulation) opening signal of the master circuit; and the off signal of the main circuit is used as one of the PWM on signal references of the slave circuit.

6. The current ripple control device of a constant current source according to claim 2, wherein: in the master-slave control mode, the natural zero crossing of the inductance current of the slave circuit is used as the PWM switching-on signal of the slave circuit.