CROSS REFERENCE

The present invention claims priority to CN 201810884538.1, filed on Aug. 6, 2018.

BACKGROUND OF THE INVENTION

Field of Invention

The present invention relates to a heating apparatus. In particular, the present invention relates to such heating apparatus, which is capable of regulating powers of different heaters respectively by means of one single temperature sensor, so that there is a predetermined ratio between the average powers of the different heaters, whereby the heating apparatus can adjust the temperatures of the heaters each to a respective predetermined temperature level. In addition, the present invention relates to a temperature control circuit and a temperature control method of the above-mentioned heating apparatus.

Description of Related Art

Typically, a prior art heating apparatus includes plural (two or more) heaters. When these heaters are coupled in parallel or in series and the currents required by these heaters are supplied from one single common power supply, because each respective heater has its impedance (that is, different heaters may have different impedances from each other), the prior art heating apparatus cannot adjust the temperatures of different heaters to the same and uniform temperature. Consequently, different areas in a heating suit etc. will have different temperatures, which is a significant drawback of the prior art heating apparatus.

In another prior art heating apparatus, in order to ensure the temperatures of different heaters can be adjusted to one uniform temperature, plural temperature sensors corresponding to the number of heaters are installed. However, this arrangement increases the complexity of control and the manufacturing cost, which is disadvantageous.

For relevant details as to how the prior art heating apparatus operates, one can refer to U.S. Pat. No. 8,927,908.

In view of the above, to overcome the drawbacks in the prior art heating apparatuses, the present invention provides a heating apparatus and a temperature control circuit and a temperature control method thereof. The present invention is capable of regulating powers of different heaters respectively by means of one single temperature sensor, so that there is a predetermined ratio between the average powers of the different heaters, whereby the heating apparatus can adjust the temperatures of the heaters each to a respective predetermined temperature level.

SUMMARY OF THE INVENTION

From one perspective, the present invention provides a heating apparatus, comprising: a first heater and a second heater; a first switch coupled in series to the first heater, wherein the first switch and the first heater are coupled in series between a power supply and a ground voltage level, the first switch being configured to be operably turned ON or turned OFF according to a first switch signal, to control a first output current flowing through the first heater; a second switch coupled in series to the second heater, wherein the second switch and the second heater are coupled in series between the power supply and the ground voltage level, the second switch being configured to be operably turned ON or turned OFF according to a second switch signal, to control a second output current flowing through the second heater; a first ramp signal generation circuit, which is configured to operably generate a first ramp signal according to the first output current; a second ramp signal generation circuit, which is configured to operably generate a second ramp signal according to the second output current; a signal processor circuit, which is configured to operably sense a temperature to generate a temperature-related signal according to the temperature; a first comparison circuit, which is configured to operably compare the first ramp signal with the temperature-related signal, to generate a first pulse width modulation (PWM) signal; a second comparison circuit, which is configured to operably compare the second ramp signal with the temperature-related signal, to generate a second PWM signal; and a switch control circuit, which is coupled to the first comparison circuit and the second comparison circuit; wherein the switch control circuit is configured to operably generate the first switch signal according to the first PWM signal; wherein the switch control circuit is configured to operably generate the second switch signal according to the second PWM signal; whereby, there is a predetermined ratio between a first average power of the first heater and a second average power of the second heater.

From another perspective, the present invention provides a temperature control circuit of a heating apparatus, the heating apparatus including: a first heater and a second heater; the temperature control circuit of the heating apparatus comprising: a first switch coupled in series to the first heater, wherein the first switch and the first heater are coupled in series between a power supply and a ground voltage level, the first switch being configured to be operably turned ON or turned OFF according to a first switch signal, to control a first output current flowing through the first heater; a second switch coupled in series to the second heater, wherein the second switch and the second heater are coupled in series between the power supply and the ground voltage level, the second switch being configured to be operably turned ON or turned OFF according to a second switch signal, to control a second output current flowing through the second heater; a first ramp signal generation circuit, which is configured to operably generate a first ramp signal according to the first output current; a second ramp signal generation circuit, which is configured to operably generate a second ramp signal according to the second output current; a signal processor circuit, which is configured to operably sense a temperature to generate a temperature-related signal according to the temperature; a first comparison circuit, which is configured to operably compare the first ramp signal with the temperature-related signal, to generate a first pulse width modulation (PWM) signal; a second comparison circuit, which is configured to operably compare the second ramp signal with the temperature-related signal, to generate a second PWM signal; and a switch control circuit, which is coupled to the first comparison circuit and the second comparison circuit; wherein the switch control circuit is configured to operably generate the first switch signal according to the first PWM signal; wherein the switch control circuit is configured to operably generate the second switch signal according to the second PWM signal; whereby, there is a predetermined ratio between a first average power of the first heater and a second average power of the second heater.

In one embodiment, the first ramp signal has a first slope which is positively correlated with the first output current, such that an ON period of the first switch is negatively correlated with the first output current, and the second ramp signal has a second slope which is positively correlated with the second output current, such that an ON period of the second switch is negatively correlated with the second output current.

In one embodiment, the predetermined ratio of the first average power of the first heater to the second average power of the second heater is 1:1.

In one embodiment, the first switch and the second switch are turned-ON at the same timing.

In one embodiment, the first switch and the second switch are turned-ON at different timings, thereby lowering a peak value of a supply current provided by the power supply, wherein the supply current includes the first output current and the second output current.

In one embodiment, the ON period of the second switch is separated from ON period of the second switch.

In one embodiment, a turned-OFF timing of the first switch determines a turned-OFF timing of the second switch.

In one embodiment, a clock signal determines a turned-ON timing of the first switch and/or a turned-ON timing of the second switch.

In one embodiment, when the first ramp signal reaches the temperature-related signal, the first PWM signal turns OFF the first switch; and, when the second ramp signal reaches the temperature-related signal, the second PWM signal turns OFF the second switch.

In one embodiment, the signal processor circuit includes: a temperature sensing circuit, which is configured to operably sense the temperature to generate a temperature sensing signal; and an error amplifier circuit coupled to the temperature sensing circuit, the error amplifier circuit being configured to operably generate the temperature-related signal according to a difference between the temperature sensing signal and a reference voltage; whereby, the heating apparatus adjusts the temperature to a predetermined temperature level.

In one embodiment, the temperature sensing circuit includes: a current source, which is configured to operably supply an operation current to a temperature sensor, wherein the temperature sensor generate the temperature sensing signal according to the operation current and the temperature.

In one embodiment, the temperature sensor includes: a negative temperature coefficient thermistor.

In one embodiment, the first ramp signal generation circuit includes: a first current sensing circuit, which is configured to operably sense the first output current, wherein the first current sensing circuit is configured to operably generate a first sensing current according to the sensed first output current; and a first capacitor, which is configured to operably generate the first ramp signal according to the first sensing current flowing through the first capacitor.

In one embodiment, the second ramp signal generation circuit includes: a second current sensing circuit, which is configured to operably sense the second output current, wherein the second current sensing circuit is configured to operably generate a second sensing current according to the sensed second output current; and a second capacitor, which is configured to operably generate the second ramp signal according to the second sensing current flowing through the second capacitor.

From yet another perspective, the present invention provides a temperature control method of a heating apparatus, the heating apparatus including a first heater and a second heater; a first switch coupled in series to the first heater, wherein the first switch and the first heater are coupled in series between a power supply and a ground voltage level, the first switch being configured to control a first output current flowing through the first heater; and a second switch coupled in series to the second heater, wherein the second switch and the second heater are coupled in series between the power supply and the ground voltage level, the second switch being configured to control a second output current flowing through the second heater; the temperature control method comprising: generating a first ramp signal according to the first output current; generating a second ramp signal according to the second output current; generating a temperature-related signal according to a temperature; comparing the first ramp signal with the temperature-related signal, to generate a first PWM signal for controlling the first switch; and comparing the second ramp signal with the temperature-related signal, to generate a second PWM signal for controlling the second switch; whereby, there is a predetermined ratio between a first average power of the first heater and a second average power of the second heater.

In one embodiment, the step of generating a temperature-related signal includes the following steps: sensing the temperature to generate a temperature sensing signal; and generating the temperature-related signal according to a difference between the temperature sensing signal and a reference voltage, whereby, the heating apparatus adjusts the temperature to a predetermined temperature level.

The objectives, technical details, features, and effects of the present invention will be better understood with regard to the detailed description of the embodiments below.

