JPS59132721A - Thermal detecting circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a semiconductor integrated circuit (hereinafter abbreviated as IC), etc., in which the IC
IC't because the internal temperature of the chip rises and destroys it.
-Relating to heat detection circuits used in protection circuits, etc.

1V is an example of applying a conventional heat detector to the protection circuit of a power amplifier. In the figure, the transistor Q1os
, Qtos, Qtot, and QtosH constitute a single-ended push-pull output circuit, and are capacitors CA, DC blocking capacitors a, RL, and speakers. The input signal from the signal source S1 is sent to the transistor Q1.
070 pace, power amplified and speaker R1
, taken out from. Diode DIHI)1as1)
104 and D105 are transistors Qtos Q10
6 Q10?1 This is to give a shallow bias to Qsoi even when there is no signal.

Transistor Q102. Qlog, Q104 and Ql
og: When the temperature of the configured circuit drops below the temperature set by the thermal protection circuit, the output of the transistor Q1os draws the current of the constant current circuit I101 to prevent excessive current from flowing to the output transistors Q, os, and Qloa. Its operation will be explained below.

Transistors Q102 and Qtoa constitute a comparator. The constant voltage generated by the constant voltage diode Dial is taken out by the emitter follower circuit of the transistor Qlol,
Assuming that the voltage obtained by dividing the voltage by resistors R102 and R10B is 1, the comparator compares this voltage V1 with the transistor Q402. The sum of the voltages between the base and emitter of Q103 is compared with 8, and the comparison output is applied to the transistor Q+0.
It is generated from the output of 3. That is, at room temperature.

For example, if the voltage v2 is divided into O and SV,
Transistor QtozU is on because the base-emitter voltage is usually about H0.7V, but the base-emitter voltage t? 0. Since the voltage is as small as lV, the transistor Qtoslff is off.

Next, for example, the speaker RL is turned off, and an excessive current flows through the output stage transistor Qloa and QtoslC.

Assuming that the temperature of the KIC chip rises due to the heat generation,
Between the base and emitter of the transistor! pressure (hereinafter h VB
Since the custom temperature of the transistor QIOII (abbreviated as B) is normally -2 mV/C, it decreases as the VBB t'l temperature of the transistor QIOII increases. -10,000, Voltage VtH Zener diode DI
Although it is influenced by the temperature customization of OI and VBB of transistor Qlo1, the change is small and does not differ significantly from the value at room temperature. Therefore, the voltage applied to the VBE of the transistor Q1os increases as the temperature rises, and eventually a current flows through the transistor Qlos, and furthermore, the voltage applied to the VBE of the transistor Q10 increases.
4 and Qlos to draw the current from the constant current source 1101. When the current of the constant current source 11nl is drawn, the current of the output transistors Qrna and QloB decreases, and heat generation is suppressed.

The temperature of the IC chip does not rise above a certain set temperature, and destruction due to heat generation does not occur.

However, since this constant temperature is set higher than the maximum rating compensated for by ordinary ICs (for example, 170° C.), remaining in this state for a long time poses a problem in terms of the reliability of the IC. In addition, if the output transistor operates in a switching manner, if the current is limited by the output of the thermal protection circuit, the current of the output transistor will decrease, but the collector-emitter voltage will increase and the power consumption will decrease. This causes the inconvenience of an increase.

The present invention has been developed in view of the above points. The present invention aims to provide a comparator for realizing a protection circuit that instantly shuts off the output stage when the temperature exceeds the temperature of the IC chip, and resumes operation of the output stage after the temperature of the IC chip drops by a certain amount.

According to the present application, a first reference voltage whose input voltage changes depending on temperature is an input of 10,000, a second reference voltage having a custom temperature different from the first reference voltage is the other input, and This configuration has temperature hysteresis in the comparator that produces an output at a certain temperature.

The present invention will be explained in detail below with reference to the drawings.

FIG. 2 is an example of a concrete implementation of the present invention.

In the figure, the same reference numerals are given to those having the same function as in FIG. 1. RMh load resistance, transistor Q1
oo Quot! This is a drive circuit that supplies current to the load RL in response to a pulse signal from a signal source S2.As explained in FIG. 1, a resistor R is connected to the base of the transistor Qsot.
102 and R1, and when the load resistance KM becomes short-circuited or half-shorted, a large current flows through the transistor Q11o, and the IC chip temperature rises. When the temperature exceeds a certain temperature, the transistor Qxu conducts. However, in FIG. 2, transistor Q111 is connected as a load to transistor Qlos and its collector is connected to transistor Q1020 through resistor R111, so transistor Q102 is conductive and transistor Qsst is connected as a load. When conductive, the base potential of transistor Q102 increases. This feedback is positive feedback.

Transistors Q1oae Qllll, Q104 and Qloa are biased deeper and eventually reach the saturation region and all of the current in foot current 1101 flows through transistor Q
1os, thereby causing transistor Q
IIO is cut off. Further, since a current equal to the value of the resistor R41° is applied from the transistor Q11 to the base of the transistor Q102, the voltage at the bases of the transistors Q and 102 is increased by a constant voltage i. −10,000, output transistor Q
1t.

When Q is cut off, the temperature of the IC chip decreases and transistor Q
102. The voltage of VBil of Qtos increases. This increase in voltage of XBB and the above transistor Q102
When the temperature reaches a point where the increase in the base voltage of the transistor Q111 becomes equal, the collector current of the transistor Q111 decreases, and the decrease in the core current lowers the base potential of the transistor Qsoz.

6- Therefore, the pace potential of transistor Q1os falls.

A positive feedback operation occurs in which the current of transistor Qlll decreases, and transistors Ql11. Qlo4. Qlo5t
:II' is rapidly turned off and transistor QIIO becomes operational. When transistor Q1to becomes conductive, the temperature of the IC chip increases, and transistor Q, 1031 Q1
041 Q105 becomes conductive, transistors Q and go are turned off, and the temperature drops.

By repeating the above operations, the device is protected from destruction due to heat rise.

FIG. 3 shows another embodiment of the circuit according to the invention.

In Figure 3, +Dtt DzH diode for heat detection.

Q.1. Q1 is a PNP) transistor, Q3 to Q7 are NPN) transistors, R1 to Ret''j resistors, vs is a reference voltage, GND is a ground potential, and OUT is an output terminal.

A description will be given with this output terminal OUT connected to the input terminal IN of FIG. A drive signal is further supplied to the input terminal IN in FIG. 5, and this drive signal causes the transistor Qt
o, Qll is turned on and off to control the power supply to the load RL.

In Figure 3, R7-
If R5ff1 is selected, hQl will be on and Qll will be off.

Transistors QII to QtTrl are turned off and the power control circuit shown in FIG. 5 is not affected.

Now, if a large current flows through the power transistor Qs1 for some reason (for example, a load seat) and the chip temperature rises, the voltage drop at Dl, l') becomes LVt=Vg.
The following relationship holds here: vD; l),, 1) 2 forward direction 11L upward drop k; Dll Temperature coefficient T of forward voltage drop of Dl;
The ambient temperature at this time is, and as the temperature rises, Vl>V2, Qt is turned off + Qz is turned on, Qs to Q7 are turned on, and the fifth
Figure foot ML lead 1. (Qll), cuts off Qll, and suppresses the heat generation of the power transistor Qlt. Also, by turning on hQa, the potential of Vz is further lowered and Ql is completely turned on to vc. At this time, the potential of ■2 is.

becomes. After a while, when the temperature decreases and DVx = Vz, the following relationship holds.The temperature at this time becomes, and when the temperature decreases, V l(V z becomes hQl is on, Ql is off and bQs ~Q7 is off r
C, it returns to the power control circuit and starts operation. Further, it can be varied by adjusting the operating temperature T1μ and the resistors R7 to R9, and it can also be slightly varied by adjusting R6 to the return temperature T2. Figure 4 shows the relationship between the ambient temperature and the current flowing through the transistor Q7 in a circuit example using a non-exploding B13VC.
Since it has hysteresis, there are fewer malfunctions due to noise and oscillations due to thermal feedback, and it is possible to construct a protection circuit that does not increase power consumption even in a transient state when controlling the output stage current. Various circuits that provide temperature hysteresis can be considered, and are not limited to the specific circuit examples shown in the embodiments.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an example of a conventional heat retention system. FIG. 2-μ is a circuit diagram showing a simple embodiment of the present invention. In FIGS. 1 and 2, h Rto 1 to R1s o
Ttl resistor, Dlol ””D105 diode-
QIOI'QIIO is a transistor, 0 capacitors
, RL is the speaker, RM: load resistance & 1101 constant current source & 81.820 signal source m■s' bias power supply. FIG. 3 is a circuit diagram showing another embodiment of the invention. R1
R9: Resistor & D, Dl: Heat detection diode. Ql, Ql:PNP) transistor a Qs~Qf:
NPN) transistor h vs ' stabilized power supply, GND:
Reference potential. 10-OUT: Output terminal. FIG. 4 is a diagram showing a temperature customization of the circuit of FIG. 3, and FIG. 5 is a diagram showing an example of a power control circuit. Io bipedal current source,
Qlo: NPN) transistor, R16: resistance = Q
ll: NPN power transistor s RL: Load resistance h voo: Power supply terminal, GND reference potential, I
N Two-person terminal book 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] a first voltage generating circuit that includes a heat sensitive element and generates an output voltage depending on temperature; a second voltage generating circuit that has a custom temperature different from the output voltage of the first voltage generating circuit; a comparator inputting the output voltage of the voltage generating circuit No. 2;
and a positive feedback loop from the output of the comparator to one of the two inputs.