Methods and systems of detecting failure modes of DC to DC power converters

• US 10,236,771 B1
• Filed: 04/18/2018
• Issued: 03/19/2019
• Est. Priority Date: 12/20/2017
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Inventors: Plojhar, Jan, Horsky, Pavel
• Primary Examiner(s): Philogene, Haissa
• Application Number:
  US15/955,899
• Time in Patent Office: 335 Days
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 1/0025 Arrangements for modifying reference values, feedback values or error values in the control loop of a converter
• CPC Class Codes: H02M 1/08 Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
• CPC Class Codes: H02M 3/137 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H03M 1/1076 Detection or location of converter hardware failure, e.g. power supply failure, open or short circuit
• CPC Class Codes: H05B 45/325 Pulse-width modulation [PWM]
• CPC Class Codes: H05B 45/37 Converter circuits
• CPC Class Codes: H05B 45/50 responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits

Abstract

Detecting failure modes of DC to DC power converters. In a system comprising a lighting microcontroller communicatively coupled to a direct current (DC) to DC power converter coupled to light-emitting diodes (LEDs) by way of an inductor, an example method may include: commanding, by the lighting microcontroller, the power converter to control an average current provided to the LEDs; reading, by the lighting microcontroller, values from the power converter; and detecting, by the lighting controller, one or more failure modes of the power converter based on the values.

Claims

1. A method of operating a direct current (DC) to DC power converter, comprising:

commanding, by a lighting microcontroller, a power converter to control an average current provided to light-emitting diodes (LEDs) coupled to the power converter by way of an inductor;

reading, by the lighting microcontroller, values from the power converter; and

detecting, by the lighting microcontroller, one or more failure modes of the power converter based on the values.

2. The method of claim 1 wherein reading values from the power converter further comprises reading one or more registers implemented within the power converter, the reading across a communication bus coupled between the lighting microcontroller and the power converter.

3. The method of claim 2 further comprising reading the one or more registers across a serial peripheral interface (SPI) bus.

4. The method of claim 1:

wherein reading values further comprises;

reading a value indicative of on time of a power switch within the power converter;

reading a value indicative of input voltage to the power converter;

reading a value indicative of output voltage of the power converter;

wherein detecting one or more failure modes further comprises;

calculating, by the lighting microcontroller, an expected on time based on the value indicative of input voltage and the value indicative of output voltage;

sending, by the lighting microcontroller, an indication of a failure to an external device if the value indicative of on time differs from the expected on time by more than a predetermined amount.

5. The method of claim 1:

wherein reading values further comprises reading, by the lighting microcontroller, a value indicative of ripple current from the power converter;

wherein detecting the one or more failure modes further comprises;

calculating, by the lighting microcontroller, an expected ripple current based on inductance of the inductor; and

sending, by the lighting controller, an indication of a failure to an external device if the value indicative of ripple current differs from the expected ripple current by more than a predetermined threshold.

6. The method of claim 1 wherein reading values and detecting one or more failure modes further comprises:

reading, by the lighting microcontroller, a first value indicative of on time of a power switch within the power converter; and

then

commanding, by the lighting microcontroller, swapping of duties of two current sources within the power converter; and

then

reading, by the lighting microcontroller, a second value indicative of on time of the power switch; and

sending, by the lighting microcontroller, an indication of a failure to an external device if the first value indicative of on time differs from the second value indicative of on time by more than a predetermined threshold.

7. The method of claim 1:

wherein commanding further comprises writing a value indicative of average current to the power converter; and

wherein the power converter implements a control loop updating a controlled variable in the form of a value indicative of peak current.

8. The method of claim 1 wherein commanding further comprises:

writing a value indicative of average current to the power converter;

writing a value indicative of ripple current to the power converter; and

recursively reading a value indicative of on time from the power converter, and updating the value indicative of ripple current, to control to a balanced on time and off time.

9. A semiconductor device that implements a driver for a direct current (DC) to DC power converter for driving light-emitting diodes (LEDs), the semiconductor device comprising:

a power switch that has a gate input;

a current switch having a control input, a first switch lead, and a second switch lead, the first switch lead coupled to the power switch;

a regulating controller coupled to the gate input of the power switch and the control input of the current switch;

a first current source having a control input;

a second current source having a control input; and

a current swapping block coupled to the first current source and the second current source, the current swapping block defining a control input and a plurality of block leads for switching the first current source and the second current source between the second switch lead of the current switch and the power switch, the control input of the current swapping block controllable from a control device external to the semiconductor device;

wherein

the regulating controller is configured to receive from the control device an indication of off time, and the regulating controller is configured to generate a pulse signal on the gate input, with de-asserted time of the pulse signal based on the indication of off time, and with asserted time of the pulse signal based on a value indication of average current;

the semiconductor device configured such that a value indicative of ripple current provided to the control input of the first current source or the second current source is a control variable of a control loop for the DC to DC power converter; and

the current swapping block has a first configuration in which the first current source is coupled to the current switch and the second current source is coupled to the power switch, and the current swapping block has a second configuration in which the first current source is coupled to the power switch and the second current source is coupled to the current switch.

10. The semiconductor device of claim 9 further comprising:

a control swapping block coupled to the control input of the first current source and the control input of the second current source, the control swapping block defining a control input and a plurality of block leads for switching a value indicative of average current and a value indicative of ripple current between the control inputs of the first and second current swapping blocks, the control input of the control swapping block controllable from the control device external to the semiconductor device;

the control swapping block has a first configuration in which the value indicative of ripple current is coupled to the control input of the first current source and the value indicative of average current is coupled to the control input of the second current source, and a second configuration in which the value indicative of average current is coupled to the control input of the first current source and the value indicative of ripple current is coupled to the control input of the second current source.

11. The semiconductor device of claim 9 further comprising:

a bus controller that defines a bus interface over which the bus controller is configured to communicate with the control device;

an average current register accessible by the bus controller, the average current register configured to hold the value indicative of average current, and the average current register coupled to a first block connection of the control swapping block;

a ripple current register accessible by the bus controller and coupled to the regulating controller, the ripple current register configured to hold the value indicative of ripple current, and the ripple current register coupled to a second block connection of the control swapping block; and

a swap command register accessible by the bus controller, the swap command register coupled to the control input of the current swapping block, and the swap command register coupled to the control input of the control swapping block;

wherein the semiconductor device is configured to implement the first configuration of the current swapping block and the control swapping block based on a first value in the swap command register, and configured to implement the second configuration of the current swapping block and the control swapping block based on a second value in the swap command register.

12. The semiconductor device of claim 11 further comprising the regulating controller configured to implement a control loop that updates the value indicative of ripple current in the ripple current register to control average current produced to drive the LEDs.

13. The semiconductor device of claim 9 further comprising the regulating controller configured to implement a control loop that controls average current produced to drive the LEDs.

14. A system for operating a light-emitting diode (LED), comprising:

a lighting microcontroller;

a power converter communicatively coupled to the lighting microcontroller;

an LED coupled to the power converter by way of an inductor;

the power converter comprises;

a power switch that has a gate input, the power switch coupled to the LED by way of the inductor;

a current switch having a control input, a first switch lead, and a second switch lead, the first switch lead coupled to the power switch;

a regulating controller coupled to the gate input of the power switch and the control input of the current switch, the regulating controller configured to receive from the lighting microcontroller one or more commands to regulate an output current of the power converter;

wherein the regulating controller is configured to receive from the lighting microcontroller an indication of off time, and the regulating controller is configured to generate a pulse signal on the gate input, with de-asserted time of the pulse signal based on the indication of off time, and with asserted time of the pulse signal based on a value indicative of average current provided to the control input of the first current source;

the power converter configured such that a value indicative of ripple current provided to the control input of the second current source is a control variable of a control loop for the power converter;

wherein the lighting microcontroller is configured to read values from the power converter and detect one or more failure modes of the power converter based on the values from the power converter.

15. The system of claim 14:

wherein the power converter further comprises;

a bus controller that defines a bus interface coupled to the lighting microcontroller;

a plurality of registers accessible by the bus controller;

wherein reading values from the power converter by the lighting microcontroller further comprises reading one or more registers implemented within the power converter, the reading across the bus interface.

16. The system of claim 15 wherein the bus interface is a serial peripheral interface (SPI) bus.

17. The system of claim 15:

wherein the power converter further comprises;

a first analog-to-digital (A/D) converter having an analog input and a digital output, the analog input coupled to the inductor;

an output-voltage register coupled to the digital input and accessible by the bus controller, the output-voltage register configured to hold a value indicative of output voltage;

a second analog-to-digital (A/D) converter having an analog input and a digital output, the analog input of the second A/D converter coupled to a supply voltage;

an input-voltage register coupled to the digital input of the second A/D converter and accessible by the bus controller, the input-voltage register configured to hold a value indicative of input voltage;

an on-time register coupled to the regulating controller and accessible by the bus controller, the on-time register configured to hold a value indicative of on time of the pulse signal;

wherein when the lighting microcontroller reads values from the power converter, the lighting microcontroller is configured to read value indicative of output voltage, the value indicative of input voltage, and the value indicative of on time of the pulse signal;

wherein when the lighting microcontroller detects one or more failure modes the lighting microcontroller is configured to;

calculate an expected on time based on the value indicative of input voltage and the value indicative of output voltage; and

send an indication of a failure to an external device if the value indicative of on time differs from the expected on time by more than a predetermined amount.

18. The system of claim 15:

wherein the power converter further comprises a ripple current register accessible by the bus controller and coupled to the regulating controller, the ripple current register configured to hold the value indicative of ripple current;

wherein when the lighting microcontroller reads from the power converter, the lighting microcontroller is configured to read the value indicative of ripple current;

wherein when the lighting microcontroller detects one or more failure modes the lighting microcontroller is configured to;

calculate an expected ripple current based on inductance of the inductor; and

send an indication of a failure to an external device if the value indicative of ripple current differs from the expected ripple current by more than a predetermined threshold.

19. The system of claim 15:

wherein the power converter further comprises;

the power switch comprising a main transistor and a reference transistor, the main transistor coupled to the LED by way of the inductor;

a comparator that has a first comparator input, a second comparator input, and a comparator output, the first comparator input coupled to the main transistor and the second comparator input coupled to the reference transistor;

a first current source having a control input;

a second current source having a control input;

a current swapping block that defines a control input, a first block lead, a second block lead, a third block lead, and a fourth block lead, the first block lead coupled to the second switch lead of the current switch, and the second block lead connected to the second comparator input;

the first current source coupled to the third block lead;

the second current source coupled to the fourth block lead;

an on-time register coupled to the regulating controller and accessible by the bus controller, the on-time register configured to hold a value indicative of on time of the pulse signal;

a control register accessible by the bus controller and coupled to the control input of the current swapping block;

the current swapping block has a first configuration in which the first current source is coupled to the current switch and the second current source is coupled to the second comparator input, and the current swapping block has a second configuration in which the first current source is coupled to the second comparator input and the second current source is coupled to the current switch;

wherein when the lighting microcontroller reads values and detects one or more failure modes, the light microcontroller is further configured to;

read a first value indicative of on time of pulse signal; and

then

command swapping of duties of current sources by writing the control register; and

then

read a second value indicative of on time of the pulse signal; and

send an indication of a failure to an external device if the first value of indicative of on time differs from the second value indicative of on time by more than a predetermined threshold.

20. The system of claim 14 wherein the regulating controller further configured to implement a control loop that updates the value indicative of ripple current to control average current produced to drive the LEDs.