Temperature dependent current limit control for fast-charging and safe operating area (SOA) protection

Patent metadata

Field	Value
Publication number	US-10579082-B2
Application number	US-201816208159-A
Country	US
Kind code	B2
Filing date	Dec 3, 2018
Priority date	Jul 6, 2018
Publication date	Mar 3, 2020
Grant date	Mar 3, 2020

Abstract

An apparatus includes a power transistor to conduct a load current from a supply voltage node to an output node and a current sense circuit coupled to the power transistor. The current sense circuit generates a current sense current proportional to the load current. A temperature sense circuit is included to generate a temperature sense voltage proportional to the temperature of the power FET. A thermal limit circuit is coupled to the temperature sense circuit. A current limit circuit is coupled to the current sense circuit and to the thermal limit circuit. The current limit circuit generates a control signal on a current limit circuit output node. The control signal is responsive to the current sense current and to a first current from the thermal limit circuit. The current limit circuit output node is coupled to a control input of the power transistor.

First claim

What is claimed is:

1. An apparatus, comprising:
a power transistor to conduct a load current from a supply voltage node to an output node;
a current sense circuit coupled to the power transistor, the current sense circuit to generate a current sense current proportional to the load current;
a temperature sense circuit to generate a temperature sense voltage proportional to the temperature of the power FET, the temperature sense circuit having a proportional to absolute temperature (PTAT) element that senses an internal core temperature of the power transistor;
a thermal limit circuit coupled to the temperature sense circuit; and
a current limit circuit coupled to the current sense circuit and to the thermal limit circuit, the current limit circuit to generate a control signal on a current limit circuit output node, the control signal responsive to the current sense current and to a first current from the thermal limit circuit, the current limit circuit output node coupled to a control input of the power transistor.

2. The apparatus of claim 1 , wherein the thermal limit circuit comprises a transconductance amplifier to generate the first current and wherein the current limit circuit generates the control signal based on both the current sense current and the first current.

3. The apparatus of claim 1 , further comprising a limit resistor coupled between the current sense circuit and a ground node, the limit resistor to conduct both the current sense current and the first current.

4. The apparatus of claim 3 , wherein the thermal limit circuit includes a second resistor coupled to the limit resistor, and wherein the second resistor is to conduct the first current to the limit resistor.

5. The apparatus of claim 4 , wherein the current limit circuit includes an amplifier that amplifies a difference between a reference voltage and a voltage on a node of the second resistor opposite a node of the second resistor connected to the limit resistor.

6. The apparatus of claim 4 , wherein the thermal limit circuit includes a transconductance amplifier to generate the first current based on a difference between the temperature sense voltage and a reference voltage.

7. The apparatus of claim 1 , wherein the current sense circuit includes:
a sense transistor connected to the power transistor; and
an amplifier including a positive input and negative input, the negative input coupled to the output node and the positive input coupled to a current terminal of the sense transistor; and
a third transistor coupled in series between the sense transistor and a ground node, the third transistor having a control input that is coupled to an output of the amplifier.

8. An apparatus, comprising:
a power transistor including first and second current terminals and a first control input, the first current terminal connected to an input voltage node and the second current terminal connected to an output voltage node;
a second transistor including third and fourth current terminals, the third current terminal connected to the input voltage node;
a first resistor having first and second resistor terminals, the first resistor terminal connected to the fourth current terminal and the second resistor terminal connected to a ground node;
a second resistor having third and fourth resistor terminals, the fourth resistor terminal connected to the fourth current terminal and to the first resistor terminal;
a thermal limit circuit having a temperature sense circuit output node, the thermal limit circuit to generate an output signal on the thermal limit circuit output node that is based on a temperature of the power transistor;
a first amplifier including a first input and a second input and a first amplifier output, the first input connected to the thermal limit circuit output node and to the third resistor terminal, and the second input connected to a reference signal node; and
a third transistor including fifth and sixth current terminals and a control input, the control input of the third transistor connected to the first amplifier output, and the fifth current terminal coupled to the control input of the power transistor.

9. The apparatus of claim 8 , wherein the thermal limit circuit includes a transconductance amplifier to produce a current having a magnitude that is based on the temperature of the power transistor.

10. The apparatus of claim 8 , further including a charge pump circuit having an input and an output, the input of the charge pump circuit connected to the input voltage node and the output of the charge pump coupled to the control input of the power transistor.

11. The apparatus of claim 8 , further comprising a temperature sense circuit to generate a temperature sense voltage that is based on the temperature of the power transistor.

12. A system, comprising:
a load;
a capacitor connected to the load;
a power transistor connected to the load and to the capacitor, the power transistor to conduct load current from a supply voltage node to the load and to the capacitor, the current to the capacitor charges the capacitor;
a current sense circuit coupled to the power transistor, the current sense circuit to generate a current sense current proportional to the load current;
a temperature sense circuit to generate a temperature sense voltage proportional to the temperature of the power transistor, the temperature sense circuit having a proportional to absolute temperature (PTAT) element that senses an internal core temperature of the power transistor;
a thermal limit circuit coupled to the temperature sense circuit; and
a current limit circuit coupled to the current sense circuit and to the thermal limit circuit, the current limit circuit to generate a control signal on a current limit circuit output node, the control signal responsive to the current sense current and to a first current from the thermal limit circuit, the current limit circuit output node coupled to a control input of the power transistor.

13. The system of claim 12 , wherein the current limit circuit comprises an amplifier to generate the control signal as a current based on both the current sense current and the first current.

14. The system of claim 12 , further comprising a limit resistor coupled between the current sense circuit and a ground node, the limit resistor to conduct both the current sense current and the temperature sense current.

15. The system of claim 14 , wherein the thermal limit circuit includes a second resistor coupled to the limit resistor, and wherein the second resistor is to conduct the first current to the limit resistor.

16. The system of claim 15 , wherein the current limit circuit includes an amplifier that amplifies a difference between a reference voltage and a voltage on a node of the second resistor opposite a node of the second resistor connected to the limit resistor.

17. The system of claim 15 , wherein the thermal limit circuit includes a transconductance amplifier to generate the first current based on a difference the temperature sense voltage and a reference voltage.

18. The system of claim 12 , wherein the thermal limit circuit includes:
a transconductance amplifier to generate the first current a first resistor coupled to the limit resistor; and
a first resistor connected to an output of the transconductance amplifier.

19. The system of claim 18 , wherein the transconductance amplifier includes first, and second inputs, and the first input is coupled to the temperature sense circuit and the second input is coupled to a reference vol

Assignees

• Texas Instruments Inc

Inventors

• Saha Aalok Dyuti
• Ramachandran Bhaskar
• Baragur Suryanarayana Dattatreya

Classifications

• G01R31/3277

  of low voltage devices, e.g. domestic or industrial devices, such as motor protections, relays, rotation switches · CPC title

• G05F1/567 Primary

  for temperature compensation · CPC title

• H03F1/0233

  by using a signal derived from the output signal, e.g. bootstrapping the voltage supply · CPC title

• G05D23/2034

  the sensing element being a semiconductor · CPC title

• G01R19/16571

  comparing AC or DC current with one threshold, e.g. load current, over-current, surge current or fault current (G01R19/16514, G01R19/16519, G01R19/16528, G01R19/16533, G01R19/1659 take precedence; measuring currents by using elements sensitive to the magnetic field generated G01R15/14; measuring earth resistance G01R27/18; testing for leakage or short circuits in electrical apparatus G01R31/52) · CPC title