CN202949598U - Integrated circuit (IC) power supply circuit applied to light-emitting diode (LED) string drive circuit - Google Patents

Abstract

The utility model relates to an integrated circuit (IC) power supply circuit applied to a light-emitting diode (LED) string drive circuit. The IC power supply circuit comprises a diode D1 and a resistor R1, wherein a positive pole of the diode D1 is connected to an LED string, a negative pole of the diode D1 is connected to the voltage to current converter (VCC) end of an IC chip through the resistor R1, the VCC end is grounded through a capacitor Cvcc and grounded through a current tapping loop L1, the positive pole of the diode D1 is connected to a node A on the LED string, and voltage Pn at the node A position is larger than VCC voltage of the VCC end of the IC chip. The IC power supply circuit applied to the LED string drive circuit occupies few printed circuit board (PCB) space and is low in power consumption.

Description

A kind of IC power supply circuits that are applied in LED string drive circuit

Technical field

The utility model relates to the IC power supply circuits in a kind of LED of being applied to string drive circuit, belongs to the LED technical field.

Background technology

In traditional LED string drive circuit, provide the peripheral power supply circuits of the energy generally to adopt two kinds of methods for driving control chip.

Shown the conventional charge pump configuration as Fig. 1, be mainly used in switching power circuit, by ancillary coil Lbias, resistance R 1, capacitor C 1, CVCC, Zener diode D1, diode D2 forms.Be coupled in energy storage inductor LP in Switching Power Supply by ancillary coil Lbias forward, the coupling part energy is used for chip power supply from energy storage inductor LP.Capacitor C 1 is used for storing the charge pump energy, and resistance R 1 is connected across between ancillary coil Lbias one end and capacitor C 1 positive plate, is used for Limited Current.Zener diode D1 oppositely is connected across between electric capacity negative plate and ground, is capacitor C 1 charging in its cathode potential when negative, is the size of current of timing restricted passage VCC in its cathode potential.Diode D2 forward is connected between Zener diode D1 and power supply VCC, is used for preventing the anti-charge pump that pours into of chip current.Capacitor C VCC is connected across between chip power VCC and ground, is used for storing charge pump current, makes chip power VCC stable.

When ancillary coil Lbias polarity inversion, in a switch periods, capacitor C 1 two ends change in pressure drop △ VC1 can be expressed as

Wherein VOUT is the output voltage of Switching Power Supply, and VCC is chip power voltage, and NP: Nbias is the turn ratio of energy storage coil and ancillary coil; Therefore, the electric current I AUX that can be chip power VCC charging can be expressed as

Wherein C1 is the capacitance of capacitor C 1, and fSW is switching frequency, and △ VC1 is capacitor C 1 two ends change in pressure drop amount.

Shown traditional buck configuration as Fig. 2, this structure can be applicable to comprise in all regulated power supply systems of Switching Power Supply, mainly by reduction voltage circuit, and Zener diode D1, capacitor C VCC forms; Reduction voltage circuit is a two terminal circuit network, be connected across between power-supply system input Vin or output end vo ut and chip power VCC, be used for extracting electric current from higher input voltage or input voltage, and provide the environment of a relatively low pressure for chip, reduction voltage circuit is usually by resitstance voltage divider, be operated in the high-voltage MOS pipe of saturation region, the compositions such as the BE knot of diode or triode.Zener diode D1 oppositely is connected across between chip power VCC and ground, is used for unnecessary current bypass is fallen, and capacitor C VCC is in parallel with Zener diode D1, is used for storing the energy from power-supply system input voltage or output voltage extraction, stablizes chip power voltage VCC.

The power consumption Pd that reduction voltage circuit self can produce is

Wherein Pd is the power consumption that produces in power circuit, and IIC drives the required electric current of control chip normal operation, and Vd is the higher pressure drop of voltage on reduction voltage circuit that input or output.

The major defect of method one is to have introduced a large amount of peripheral circuits that comprise resistance coil, makes the space increase of plate level, and manufacturing cost increases, and has increased design difficulty; Its current capacity also can be subject to the impact of switching frequency fSW, must consider when design.

The major defect of method two is that power consumption is larger, and the operating voltage that drives control chip is generally in 15V, and in the LED of high input voltage High voltage output string drive circuit, input, output voltage can reach several hectovolts, make pressure drop Vd very large, thereby causes Pd to increase.Power consumption Pd had not both increased the LED luminosity, did not enter to drive supporting chip work in control chip yet, but diffused in surrounding environment in the mode of heat energy.And, use the method power supply also can can't freely select to input or output voltage owing to driving the specific supply voltage value of control chip.

In sum, the charge pump that generally uses now and two kinds of methods of step-down have all been run counter to now power-supply system high efficiency, designer trends and principle cheaply to a certain extent.

Summary of the invention

The purpose of this utility model is to overcome above-mentioned deficiency, and a kind of less pcb board space and IC power supply circuits that are applied in LED string drive circuit low in energy consumption of taking are provided.

The purpose of this utility model is achieved in that the IC power supply circuits in a kind of LED of being applied to string drive circuit, described circuit includes diode D1 and resistance R 1, the positive pole of described diode D1 accesses in LED and goes here and there, the negative pole of described diode D1 accesses the VCC end of IC chip after resistance R 1, described VCC end is through a capacitor C vcc ground connection, and described VCC end is through a current drain loop L1 ground connection.

The utility model is a kind of is applied to IC power supply circuits in LED string drive circuit, the node A on the positive pole access LED string of diode D1, the voltage VCC that the voltage Pn at this node A place holds greater than IC chip VCC.

A kind of IC power supply circuits that are applied in LED string drive circuit of the utility model, above-mentioned LED is connected in series between Vout end and ground, and this LED string connected by m+n LED and consist of, and n LED wherein arranged between A point and ground, m diode arranged between A point and Vout, and m and n need to satisfy:

；

In above-mentioned formula: I1 is through the electric current on LED between A point and VCC end; I2 is through the electric current on LED between A point and ground; VT is thermal voltage, is 26mV under room temperature, and IS is the saturation current of diode.

The utility model is a kind of is applied to IC power supply circuits in LED string drive circuit, and described current drain loop is made of external zener diode or is made of the internal circuit of IC chip.

Compared with prior art, the beneficial effects of the utility model are:

(1) the utility model adopts less peripheral circuit to complete function, has saved plate level space and manufacturing cost, has reduced design complexities;

(2) in the utility model, system's output voltage V out is the pressure drop that produces on load LED string to the pressure drop of load LED string specific potential node A, and it is luminous that the power that consumes in this pressure drop is used for that LED goes here and there, and is not wasted; By about two inequality choice for uses of m, n and the less LED crosstalk position node A of IC chip power voltage VCC potential difference, can reduce the power loss of being brought to the pressure drop of chip power voltage VCC by this LED string node A;

(3) power supply capacity of the utility model after power-supply system starts and works is not subjected to the chip internal parameter, and be as the impact of switching frequency, duty ratio, relatively stable than the charge pump method under the corresponding different chip parameter environment of supply current.

Description of drawings

Fig. 1 is conventional circuit diagram.

Fig. 2 is conventional circuit diagram.

Fig. 3 is a kind of circuit diagram that is applied to the IC power supply circuits in LED string drive circuit of the utility model.

Fig. 4 is working timing figure of the present utility model.

Embodiment

Referring to Fig. 3, IC power supply circuits in a kind of LED of being applied to string drive circuit that the utility model relates to, described circuit includes diode D1 and resistance R 1, a node A on the positive pole access LED string of described diode D1, the negative pole of described diode D1 accesses the VCC end of IC chip after resistance R 1, the effect of diode D1 is to prevent that the electric current for the IC chip provides from pouring in down a chimney the string into LED, and resistance R 1 is current-limiting resistance, its role is to limit the size of current that is entered the VCC end by the LED crossfire; Described VCC end is through a capacitor C vcc ground connection, this capacitor C vcc is storage capacitor, described VCC end is through a current drain loop L1 ground connection, described current drain loop is the voltage stabilizing bleeder circuit, this current drain loop can have external zener diode to consist of, also can be completed by the internal circuit of IC chip, the effect of this current drain loop L1 is the unnecessary electric current of releasing, and stablizes the supply voltage of IC chip;

Below, analyze for the condition that node A need to satisfy:

Described LED is connected in series in that between Vout end and ground, (the Vout end provides drive current for the LED string, and the voltage of Vout end is Vout), and this LED string is made of m+n LED series connection, and n LED wherein arranged between A point and ground, and m diode arranged between A point and Vout;

Learnt by the diode electrically flow equation:

In this formula: VT is thermal voltage, is 26mV under room temperature; I2 is through the electric current on the LED between A point and ground; IS is the saturation current of diode; The supply power voltage of IC chip is VCC, and the power system design output voltage is Vout, and in like manner: I1 is through the electric current on the LED between A point and VCC end;

Voltage Vi on single light-emitting diode light between above-mentioned A point and ground is:

Therefore the voltage Pn at A point place is the series voltage after n Light-Emitting Diode connected:

Owing to only having the voltage Pn of ordering as A greater than the required VCC voltage of IC chip (VCC is the operating voltage of IC chip, and during design circuit, this is measured and is known quantity), the power supply circuits output VCC that could work uses to the IC chip, therefore , that is:

Changing this inequality can obtain:

When satisfying above-mentioned Pn〉during the condition of VCC, have one part of current I3 from flowing through higher than shunting the load LED electric current of Pn current potential out, inject storage capacitor Cvcc, for chip provides the energy, current-limiting resistance R1 is by the size of self pressure drop restriction I3; And general power management chip current sinking I3 is much smaller than the electric current that makes the LED normal operation, therefore the electric current I 2 that flows through in the load current I1 that flows through in the LED of current potential on Pn and the LED of current potential under Pn is without obviously difference, both brightness does not have significant change yet, therefore can not exert an influence to illuminating effect;

Simultaneously, according to Kirchhoff's law:

Wherein Vj represents the voltage on single light-emitting diode light between A point and level Vout end;

VD1 represents the voltage on diode D1, and VR1 represents the voltage on resistance R 1;

So according to the diode electrically flow equation:

Wherein, I1 is through the electric current on LED between A point and VCC end;

So:

Therefore

Changing this inequality can get:

By top can be calculated, need to satisfy with lower inequality for m, n, the utility model circuit just can work:

。

Referring to Fig. 4, the utility model work schedule requires as follows:

After system powers on, increase and arrival standard value along with input voltage, power supply control IC chip obtains supply voltage by input voltage and powers temporarily, after chip is started working, output voltage V out begins to preset value near also finally arriving design load, in this moment Fig. 3, A point current potential Pn has also arrived preset value higher than chip power supply voltage VCC, powered to the utility model IC power supply circuits by IC chip internal logic control self electrical source exchange, and system stable operation.

As seen the utility model is started working after power-supply system output enters the design load scope, utilize a part of pressure drop of load LED string to carry out the step-down processing to output voltage, make supply voltage be fit to the chip operation scope, utilize the fraction load current to carry out function to chip, do not affect the overall brightness of LED string.

The above; it is only preferred embodiment of the present utility model; be not that the utility model is imposed any restrictions; every according to the utility model technical spirit to any simple modification, change and equivalent structure transformation that above embodiment does, all still belong in the protection range of technical solutions of the utility model.

Claims (4)

1. IC power supply circuits that are applied in LED string drive circuit, it is characterized in that: described circuit includes diode D1 and resistance R 1, the positive pole of described diode D1 accesses in LED and goes here and there, the negative pole of described diode D1 accesses the VCC end of IC chip after resistance R 1, described VCC end is through a capacitor C vcc ground connection, and described VCC end is through a current drain loop L1 ground connection.

2. a kind of IC power supply circuits that are applied in LED string drive circuit as claimed in claim 1 is characterized in that: the node A on the positive pole access LED string of diode D1, the voltage VCC that the voltage Pn at this node A place holds greater than IC chip VCC.

3. a kind of IC power supply circuits that are applied in LED string drive circuit as claimed in claim 2, it is characterized in that: above-mentioned LED is connected in series between Vout end and ground, and this LED string is made of m+n LED series connection, n LED wherein arranged between A point and ground, m diode arranged between A point and Vout, and m and n need to satisfy:

；

In above-mentioned formula: I1 is through the electric current on LED between A point and VCC end; I2 is through the electric current on LED between A point and ground; VT is thermal voltage, is 26mV under room temperature, and IS is the saturation current of diode.

4. as a kind of IC power supply circuits that are applied in LED string drive circuit as described in claim 1,2 or 3, it is characterized in that: described current drain loop is made of external zener diode or is made of the internal circuit of IC chip.

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