CN102013669B - Adjustable overheat protection circuit in switching power supply - Google Patents

Abstract

The invention provides an adjustable overheat protection circuit in a switching power supply, aiming at solving the problems of high cost, large occupied space, difficulty in controlling protection temperature precision and inconvenience in regulating temperature range of the existing overheat protection circuit. The adjustable overheat protection circuit is used for detecting whether the temperature of a system is within the normal working range of a chip, outputting an overheat protection signal when the temperature exceeds the normal working temperature of the system, and outputting a normal temperature indicator signal when the temperature of the system returns to the normal working temperature again. The protection circuit can be integrated in a control chip, is of a reliable protection structure with a minimum circuit scale; and fine tuning can be carried out by means of variable resistance strings.

Description

Adjustable overheat protection circuit in a kind of Switching Power Supply

Technical field

The present invention relates to a kind of thermal-shutdown circuit, specifically a kind of adjustable thermal-shutdown circuit that is integrated in the Switching Power Supply control chip.

Background technology

Switching Power Supply is used widely in every field, for various kinds of equipment provides operating voltage.Existing switch power technology generally comprises control chip, drive circuit, switching circuit, transformer (what have does not have), rectification and filter circuit.As a rule, the control chip the inside comprises reference circuit, electric power management circuit, oscillating circuit and various protective circuits etc.Wherein protective circuit generally includes overvoltage protection, under-voltage protection, overcurrent protection and overheat protector etc.This patent relates generally to the overheat protector in the protective circuit, and a kind of circuit structure that can be integrated into practicality in the control chip is provided.Be illustrated in figure 1 as the application of thermal-shutdown circuit in Switching Power Supply.

Switching Power Supply is in when work, particularly in heavy duty condition lower time, and the rising that the temperature of power supply inside can be rapid.Modern Switching Power Supply is all at the future development towards high switching frequency and high power density, and the loss that the switching process of power transistor and magnetic device produce is the main thermal source in the Switching Power Supply, especially in the time of in they are encapsulated in a confined space simultaneously, it is more rapid that temperature rises.And the high-temperature condition meeting reduces the life-span of Switching Power Supply so that the hydraulic performance decline of whole Switching Power Supply, under the worst case even the destruction that also can cause complete machine, brings huge economic loss.Therefore; we can add thermal-shutdown circuit usually when relating to Switching Power Supply; when in case the temperature of Switching Power Supply inside surpasses the maximum temperature of its permission; to stop the power supply of internal circuit; the protection of self is provided for whole Switching Power Supply, and the circuitry of also having protected Switching Power Supply to power simultaneously exempts from destruction.And when the power supply internal temperature drops to the scope of permission work, can reactivate again Switching Power Supply and make it normal operation.

As a rule, multi-purpose adding, meeting are so that system is more complicated, no matter the increase of circuit on the increase of chip area or the plate all can cause the increase of area and the increase of cost.So as a requisite functional circuit, how to allow its miniaturization, simplification and don't lose the emphasis direction that accuracy will be research.

Summary of the invention

The object of the present invention is to provide a kind of adjustable thermal-shutdown circuit, be intended to solve that existing thermal-shutdown circuit cost is high, large, the bad control of precision of protection temperature and the problem that temperature range is not easy to regulate take up room.

According to technical scheme provided by the invention, adjustable overheat protection circuit in the described Switching Power Supply comprises: PNP pipe base stage links to each other with the base stage of the 2nd PNP pipe, and a PNP pipe collector, the 5th PNP pipe emitter, the 3rd PNP pipe base stage, the 4th PNP pipe base stage link to each other; The 2nd PNP pipe base stage links to each other with collector electrode, connects the emitter of the 6th PNP pipe again; The base stage of the 3rd PNP pipe collector, the 5th PNP pipe, a NPN pipe collector link to each other; The 5th PNP pipe collector is connected to the ground; The 6th PNP pipe base stage, the 4th PNP pipe collector, the 2nd NPN pipe collector link to each other; The 6th PNP pipe collector is by the second grounding through resistance; The one NPN pipe base stage links to each other with the 2nd NPN pipe base stage; The one NPN pipe emitter links to each other with collector electrode, the base stage of the 3rd NPN pipe; The 2nd NPN pipe emitter links to each other with collector electrode, the base stage of the 4th NPN pipe; The 3rd NPN pipe emitter connects the first resistance one end, and the first resistance other end connects respectively the 4th NPN pipe emitter and variable resistor string one end, variable resistor string other end ground connection; External power source is connected to the emitter terminal of PNP pipe, the 2nd PNP pipe, the 3rd PNP pipe, the 4th PNP pipe; Bias voltage is connected to the base terminal of NPN pipe, the 2nd NPN pipe; The variable resistor string is used for regulating the temperature of overturn point, and the variable resistor string has a plurality of overheat protector fine setting ends; Tie point between the 6th PNP pipe collector and the second resistance is output.

Described variable resistor string comprises 4 overheat protector fine setting ends, the 11 resistance one termination the first overheat protector fine setting end, another termination the second overheat protector fine setting end; The 21 resistance one termination the second overheat protector fine setting end, an end of another termination the 3rd overheat protector fine setting end, the 31 resistance and the 32 resistance; The 31 resistance and the 32 resistance other end link to each other and connect an end of the 4th overheat protector fine setting end and the 41 resistance, the 42 resistance, the 43 resistance, the 44 resistance, the 41 resistance, the 42 resistance, the 43 resistance, the 44 resistance other end ground connection.

Can change its resistance by multiple connection to the variable resistor string, one, the second overheat protector fine setting end, the 3rd overheat protector fine setting end, the 4th overheat protector fine setting end is shorted to ground together; Two, the 3rd overheat protector fine setting end, the 4th overheat protector fine setting end is shorted to ground together; Three, the 4th overheat protector fine setting end is shorted to ground.

Described PNP pipe base stage and the 2nd PNP pipe two pipes are symmetrical, the 3rd PNP pipe base stage and the 4th PNP pipe two pipes are symmetrical, the 3rd PNP pipe base stage and the 4th PNP manage the emitter area of two pipes greater than the emitter area of PNP pipe base stage and the 2nd PNP pipe, the 5th PNP pipe, the 6th PNP pipe emitter area is greater than PNP pipe base stage, the 2nd PNP pipe, the one NPN pipe is consistent with the emitter area that the 3rd NPN manages two pipes, the 2nd NPN pipe is consistent with the emitter area that the 4th NPN manages two pipes, NPN pipe, the 3rd NPN manages the emitter area of two pipes and manages greater than the 2nd NPN, the 4th NPN manages the emitter area of two pipes.

Described variable resistor string can adopt the resistance of the different resistances of series connection to realize, or adopts the resistance of series-parallel connection similar resistance to realize.

Advantage of the present invention is: the present invention is used for the temperature of detection system whether in the chip normal range of operation, when temperature surpasses system's normal operation, and overheat protector signal of this circuit output; When recovering normal working temperature again, system temperature is normal temperature indication signal of this circuit output.This protective circuit can be integrated in the control chip; can use simple circuit structure, provide accurate, adjustable, overheat protector solution cheaply, with the circuit scale of minimum; reliable protection structure is provided, and can finely tunes by the variable resistor string.

Description of drawings

Fig. 1 is the application drawing of thermal-shutdown circuit in Switching Power Supply;

Fig. 2 is the thermal-shutdown circuit structure chart;

Fig. 3 is the structure chart of RES variable resistor string;

Fig. 4 is the first embodiment;

Fig. 5 is the second embodiment;

Fig. 6 is the 3rd embodiment;

Fig. 7 is the 4th embodiment.

Embodiment

The invention will be further described below in conjunction with drawings and Examples.

As shown in Figure 2, thermal-shutdown circuit of the present invention comprises: the first branch road that is comprised of P3, N1, N3; The second branch road that is formed by P4, N2, N4; The reponse system that is formed by P1, P2, P5, P6; Current-limiting resistance R1 and R2; Variable resistor string RES as shown in Figure 3, is used for regulating the temperature of overturn point.VDD is the power supply that the outside provides, and is connected to the emitter terminal of P1, P2, P3, P4; V _RefBe the bias voltage that the outside provides, be connected to the base terminal of N1, N2; PAD1, PAD2, PAD3, PAD4 are overheat protector fine setting end, are connected between each resistance; V _OutBe output voltage, be connected between the collector electrode of R2 and P6.GND is the earth, links to each other with collector electrode, the R2 of RES, P5.

Be specially: PNP pipe P1 base stage links to each other with the base stage of the 2nd PNP pipe P2, and PNP pipe P1 collector electrode, the 5th PNP pipe P5 emitter, the 3rd PNP pipe P3 base stage, the 4th PNP pipe P4 base stage link to each other; The 2nd PNP pipe P2 base stage links to each other with collector electrode, connects the emitter of the 6th PNP pipe P6 again; The base stage of the 3rd PNP pipe P3 collector electrode, the 5th PNP pipe P5, NPN pipe N1 collector electrode link to each other; The 5th PNP pipe P5 collector electrode is connected to the ground; The 6th PNP pipe P6 base stage, the 4th PNP pipe P4 collector electrode, the 2nd NPN pipe N2 collector electrode link to each other; The 6th PNP pipe P6 collector electrode is by the second resistance R 2 ground connection; The one NPN pipe N1 base stage links to each other with the 2nd NPN pipe N2 base stage; The one NPN pipe N1 emitter links to each other with collector electrode, the base stage of the 3rd NPN pipe N3; The 2nd NPN pipe N2 emitter links to each other with collector electrode, the base stage of the 4th NPN pipe N4.

The 3rd NPN pipe N3 emitter connects the first resistance R 1 one ends, and the first resistance R 1 other end connects respectively the 4th NPN pipe N4 emitter and variable resistor string RES one end PAD1, variable resistor string RES other end ground connection; External power source VDD is connected to the emitter terminal of a PNP pipe P1, the 2nd PNP pipe P2, the 3rd PNP pipe P3, the 4th PNP pipe P4; Bias voltage V _RefBe connected to the base terminal of a NPN pipe N1, the 2nd NPN pipe N2.

The proportionate relationship of each bipolar transistor as shown in Figure 2.The target M of institute is the ratio of emitter area and master pattern on the figure, is specially: P1 M=0.4; P2 M=0.4; P3 M=5; P4 M=5; P5 M=0.8; P6 M=0.93; N1 M=2.4; N2 M=0.48; N3 M=2.4; N4 M=0.48.

Thermal-shutdown circuit provided by the present invention can be applied to Switching Power Supply etc. to be needed in the circuit and equipment of overheat protector, and details are as follows.

This module is used for the temperature of detection system whether in the chip normal range of operation, when temperature surpasses system's normal operation, and overheat protector signal of this module output.When system temperature recovers normal working temperature again, normal temperature indication signal of this module output.

Its basic principle is to utilize the size of current of the first branch road and the second branch road to concern variation with temperature, causes transistor P4 collector electrode V _AThe variation of node voltage, the turn-on and turn-off of control transistor P6 produce the high-low level signal.When temperature was low, the electric current that flows through on the resistance R 1 was less, and the upper pressure drop of R1 is less, and the b-e voltage difference of N1 and N3 and N2 and N4 is less, and the emitter area of N1 and N3 is much larger than the emitter area of N2 and N4.Current-voltage correlation formula I by bipolar transistor _c=I _sExp (V _Be/ V _T) as can be known, flow through the electric current of the first branch road greater than the electric current that flows through the second branch road this moment.Because emitter and the base voltage of P3 and P4 all equate, for the electric current that guarantees the first branch road greater than the electric current that flows through the second branch road, V _ANode voltage will be elevated, and transistor P6 turn-offs, V _OutBe low level.When temperature raise, the electric current that flows through on the resistance R 1 increased gradually, and the pressure drop on the R1 increases.Therefore, the b-e voltage difference of N1 and N3 and N2 and N4 increases.When temperature is elevated to a certain value, flow through the electric current of N1 and N3 less than the electric current that flows through N2 and N4.To V _ANode discharge makes V _ACurrent potential is very low, transistor P6 conducting, node V _OutBe high level, show the excess Temperature of system.

Under critical condition, the electric current that flows through N1 and N3 equals to flow through the electric current of N2 and N4, all is I if flow through the electric current of N1, N2, N3 and N4, can obtain:

Vref＝2V _{be_N3}+IR ₁+2I*RES (0-1)

Vref＝2V _{be_N4}+2I*RES (0-2)

V _{be_N3}＝V _Tln(I/I _{S_N3}) (0-3)

V _{be_N4}＝V _Tln(I/I _{S_N4}) (0-4)

Therefore,

$I=\frac{2}{R1}{V}_T\ln \left(\frac{I_{S\_N3}}{I_{S\_N4}}\right)=\frac{2\ln 5}{R1}{V}_T---(0-5)$

For example, if RES=R ₁, in formula (0-5) substitution (0-2), obtain:

$\mathrm{Vref}=2V_{\mathrm{be}\_N4}+4\mathrm{<figure-callout\; id="5"\; label="ln"\; filenames="HSA00000355998900012.png,HSA00000355998900041.png"\; state="\{\{state\}\}">ln</figure-callout>}5\frac{\mathrm{RES}}{R1}{V}_T=2V_{\mathrm{be}\_N4}+6.4V_T$

The first embodiment

As shown in Figure 7, variable resistor string RES comprises 4 overheat protector fine setting ends PAD1, PAD2, PAD3, PAD4, the 11 resistance R 11 1 terminations the first overheat protector fine setting end PAD1, another termination the second overheat protector fine setting end PAD2; The 21 resistance R 21 1 terminations the second overheat protector fine setting end PAD2, an end of another termination the 3rd overheat protector fine setting end PAD3, the 31 resistance R 31 and the 32 resistance R 32; The 31 resistance R 31 and the 32 resistance R 32 other ends link to each other and connect an end of the 4th overheat protector fine setting end PAD4 and the 41 resistance R 41, the 42 resistance R 42, the 43 resistance R 43, the 44 resistance R 44, the 41 resistance R 41, the 42 resistance R 42, the 43 resistance R 43, the 44 resistance R 44 other end ground connection.

In this execution mode, R1, R11, R21 series connection are connected with the parallel resistance that R31, R32 form simultaneously, and the parallel resistance that forms with R41, R42, R43, R44 again is connected in series to ground.

The second embodiment

As shown in Figure 4, variable resistor string RES is on the basis of the first embodiment, and PAD2, PAD3, PAD4 are shorted to ground together simultaneously, namely only have R1 and R11 to be connected in series to ground, and other resistance are bypassed.

The 3rd embodiment

As shown in Figure 5, variable resistor string RES is on the basis of the first embodiment, and PAD3, PAD4 are shorted to ground together simultaneously, and this moment, R1, R11 and R21 were connected in series to ground, and other resistance are bypassed.

The 4th embodiment

As shown in Figure 6, variable resistor string RES is on the basis of the first embodiment, and PAD4 is shorted to ground simultaneously, and R1, R11, R21 are connected in series to ground with the parallel resistance that R31 and R32 form at this moment, and other resistance are bypassed.

Above-mentioned each embodiment can be at same circuit by each input port realization of configuration, and circuit is simple, and is easy to use, accurately reliable.By configuring each port annexation, can provide the different guard signals that turn-off temperature.

Each transistor has certain relation in the circuit, and is as follows.

(1) P1 and P2 are all the PNP pipe, and emitter links to each other with VDD, should accomplish during its design that two pipes are symmetrical.

(2) P3 and P4 are all the PNP pipe, and emitter links to each other with VDD, should accomplish during its design that two pipes are symmetrical.

(3) emitter area of P3 and P4 two pipes should be greater than the emitter area of P1 and P2.

(4) P5 is the PNP pipe, and P6 is the PNP pipe, and its emitter area should be greater than P1, P2.

(5) N1 and N3 are all the NPN pipe, and the emitter area of two pipes should be consistent.

(6) N2 and N4 are all the NPN pipe, and the emitter area of two pipes should be consistent.

(7) emitter area of N1 and N3 two pipes should be greater than the emitter area of N2 and N4.

(8) RES is the variable resistor string, and an end links to each other with R1, and the other end is connected to the ground, and can adopt the resistance of the different resistances of series connection to realize in the design, also can adopt the resistance of series and parallel similar resistance to realize.

Claims (7)

1. the adjustable overheat protection circuit in the Switching Power Supply is characterized in that comprising:

The one PNP pipe (P1) base stage links to each other with the base stage that the 2nd PNP manages (P2), and PNP pipe (P1) collector electrode, the 5th PNP pipe (P5) emitter, the 3rd PNP pipe (P3) base stage, the 4th PNP pipe (P4) base stage link to each other;

The 2nd PNP pipe (P2) base stage links to each other with collector electrode, connects the emitter of the 6th PNP pipe (P6) again;

The base stage of the 3rd PNP pipe (P3) collector electrode, the 5th PNP pipe (P5), NPN pipe (N1) collector electrode link to each other;

The 5th PNP pipe (P5) collector electrode is connected to the ground;

The 6th PNP pipe (P6) base stage, the 4th PNP pipe (P4) collector electrode, the 2nd NPN pipe (N2) collector electrode link to each other; The 6th PNP pipe (P6) collector electrode is by the second resistance (R2) ground connection;

The one NPN pipe (N1) base stage is managed (N2) base stage with the 2nd NPN and is linked to each other; The one NPN pipe (N1) emitter links to each other with collector electrode, the base stage that the 3rd NPN manages (N3);

The 2nd NPN pipe (N2) emitter links to each other with collector electrode, the base stage that the 4th NPN manages (N4);

The 3rd NPN pipe (N3) emitter connects the first resistance (R1) end, the first resistance (R1) other end connects respectively the 4th NPN pipe (N4) emitter and variable resistor string (RES) end (PAD1), variable resistor string (RES) other end ground connection;

External power source (VDD) is connected to the emitter terminal of PNP pipe (P1), the 2nd PNP pipe (P2), the 3rd PNP pipe (P3), the 4th PNP pipe (P4); Bias voltage (V _Ref) be connected to the base terminal of NPN pipe (N1), the 2nd NPN pipe (N2);

The temperature that variable resistor string (RES) is used for regulating overturn point, variable resistor string (RES) have a plurality of overheat protector fine setting ends; Tie point between the 6th PNP pipe (P6) collector electrode and the second resistance (R2) is output (V _Out).

2. the adjustable overheat protection circuit in the Switching Power Supply as claimed in claim 1, it is characterized in that described variable resistor string (RES) comprises 4 overheat protector fine setting ends (PAD1, PAD2, PAD3, PAD4), the 11 resistance (R11) termination the first overheat protector fine setting end (PAD1), another termination the second overheat protector fine setting end (PAD2); The 21 resistance (R21) termination the second overheat protector fine setting end (PAD2), an end of another termination the 3rd overheat protector fine setting end (PAD3), the 31 resistance (R31) and the 32 resistance (R32); The 31 resistance (R31) links to each other with the 32 resistance (R32) other end and connects the end that (PAD4) and the 41 resistance (R41), the 42 resistance (R42), the 43 resistance (R43), the 44 resistance (R44) are held in the fine setting of the 4th overheat protector, the 41 resistance (R41), the 42 resistance (R42), the 43 resistance (R43), the 44 resistance (R44) other end ground connection.

3. the adjustable overheat protection circuit in the Switching Power Supply as claimed in claim 2 is characterized in that the second overheat protector fine setting end (PAD2), the 3rd overheat protector fine setting end (PAD3), and the 4th overheat protector fine setting end (PAD4) is shorted to ground together.

4. the adjustable overheat protection circuit in the Switching Power Supply as claimed in claim 2 is characterized in that the 3rd overheat protector fine setting end (PAD3), and the 4th overheat protector fine setting end (PAD4) is shorted to ground together.

5. the adjustable overheat protection circuit in the Switching Power Supply as claimed in claim 2 is characterized in that the 4th overheat protector fine setting end (PAD4) is shorted to ground.

6. the adjustable overheat protection circuit in the Switching Power Supply as claimed in claim 1; it is characterized in that described PNP pipe (P1) is symmetrical with the 2nd PNP pipe (P2) two pipes; the 3rd PNP pipe (P3) and the 4th PNP pipe (P4) two pipes are symmetrical; the emitter area of the 3rd PNP pipe (P3) and the 4th PNP pipe (P4) two pipes is managed the emitter area of (P1) and the 2nd PNP pipe (P2) greater than a PNP; the 5th PNP manages (P5); the 6th PNP pipe (P6) emitter area is managed (P1) greater than a PNP; the 2nd PNP manages (P2) emitter area; the one NPN pipe (N1) is consistent with the emitter area of the 3rd NPN pipe (N3) two pipes; the 2nd NPN pipe (N2) is consistent with the emitter area of the 4th NPN pipe (N4) two pipes, and a NPN manages (N1); the emitter area of the 3rd NPN pipe (N3) two pipes is managed (N2) greater than the 2nd NPN; the emitter area of the 4th NPN pipe (N4) two pipes.

7. the adjustable overheat protection circuit in the Switching Power Supply as claimed in claim 1 is characterized in that described variable resistor string (RES) adopts the resistance of the different resistances of series connection to realize, or adopts the resistance of series-parallel connection similar resistance to realize.

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