TOSHIBA RD206-SWGUIDE-01 Inverter Circuit for IH Cooker User Guide

Inverter Circuit for IH Cooker
SW Guide
RD206-SWGUIDE-01

TOSHIBA ELECTRONIC DEVICES & STORAGE CORPORATION

Introduction

This Guide describes the software (SW) of the IH Cooker (hereafter referred to as this reference design) using GT20N135SRA IGBT designed for Home Appliances. The block diagram and circuit of hardware (HW) controlled by the SW specified in this guide are shown below.

Fig. 1.1 Block Diagram of IH Cooker

Fig. 1.2 Circuit of Main Board

Software Files

The following table shows the files of Source code for this reference design.

Table 2.1 List of Source Code Files

Software Flowchart

The flowchart of the software is shown below.

Fig. 3.1 Software Flowchart

Data Acquisition from ADC

The following parameters are read using Analog to Digital Converter:

• IGBT temperature
• Pot bottom temperature
• Power supply voltage
• Electric current

Method of Reading Data:
10 samples are taken and an average of 8 samples are taken after ignoring the maximum and minimum values.

1. The sampling cycle starts every 20 ms in the “Process for every 20 ms” block.
2. For taking a sample, Analog to Digital conversion is performed at every 1 ms interrupt.
3. Systems take the average of samples for all four parameters.
4. The system waits for the next sampling cycle.

Meaning of ADC Output Values:

1. IGBT temperature
   For more description refer to MyType.h
   Table. 4.1 IGBT Temperature and ADC Value Relation** IGBT Temp.| A/D Value| Symbol**
   ---|---|---
   –| 253| c_NTC_OPENCIRCUIT
   50| 199| –
   52| 196| –
   63| 176| –
   65| 171| c_T_IGBT_RECOVER
   68| 166| –
   78| 145| –
   83| 135| c_T_IGBT_POWERDROP1
   85| 124| –
   85| 131| –
   88| 124| c_T_IGBT_POWERDROP
   100| 100| –
   105| 92| c_T_IGBT_OTEMP
   110| 84| –
   –| 3| c_NTC_SHORTCIRCUIT

Fig. 4.1 IGBT Temperature and ADC Value Relation Chart

2. Pot bottom temperature
   For more description refer to MyType.h
   Table 4.2 Pot Bottom Temperature and ADC Value Relation PAD Temperature| A/D Value| Symbol
   ---|---|---
   –| 3| c_NTC_SHORTCIRCUIT
   40| 17| –
   60| 22| c_T_PAD_RECOVER
   90| 35| –
   100| 45| –
   105| 82| –
   108| 88| –
   110| 92| –
   130| 101| –
   148| 108| –
   150| 116| –
   155| 119| –
   160| 149| –
   167| 181| –
   170| 184| –
   175| 188| c_T_PAD_OTEMP、c_T_PAD_OTEMP1
   235| 195| –
   240| 208| –
   260| 236| –
   280| 246| –
   –| 253| c_NTC_OPENCIRCUIT

Fig. 4.2 Pot Bottom Temperature and ADC Value Relation Chart

3. Power supply voltage
   For more description refer to MyType.h
   Table 4.3 Power Supply Voltage and ADC Value Relation** Power Supply Voltage| A/D Value| Power Supply Voltage| A/D Value**
   ---|---|---|---
   70| 45| 195| 126
   75| 48| 200| 129
   80| 52| 205| 132
   90| 58| 210| 135
   100| 65| 215| 139
   110| 71| 220| 142
   120| 77| 225| 145
   130| 84| 230| 148
   140| 87| 235| 152
   145| 94| 240| 155
   150| 97| 245| 158
   160| 103| 250| 161
   170| 110| 260| 168
   180| 116| 270| 174
   185| 119| 275| 177
   190| 123| 285| 184

Fig. 4.3 Power Supply Voltage and ADC Value Relation Chart

Error Processing

Power Supply Voltage Upper Limit Error

This error check is carried out using an ADC value upper/lower limit check.
If the value indicates 270 V or more, the count is incremented by 1. And when it is confirmed 10 times, it is judged to be an error.
And if the value indicates less than 270 V, the count is decremented by 1.
When it is judged to be an error, the IGBT is turned off, and the error status is recorded in the notification data sent to the DISPLAY_BOARD.
If the normal status is maintained for 3 seconds, the error status is cleared in the notification data sent to the DISPLAY_BOARD.

Power Supply Voltage Low Limit Error

This error check is carried out using an ADC value upper/lower limit check.
If the value indicates less than 150 V, the count is incremented by 1. And when it is confirmed 10 times, it is judged to be an error.
And if the value indicates 150 V or more, the count is decremented by 1.
When it is judged to be an error, IGBT is turned off, and the error status is recorded in the notification data sent to the DISPLAY_BOARD.
If the normal status is maintained for 3 seconds, the error status is cleared in the notification data sent to the DISPLAY_BOARD.

Overcurrent

This error check is carried out using an ADC value upper/lower limit check.
If the ADC value is 165 or more, the count is incremented by 1. And when it is confirmed 2 times, it is judged to be an error.
And if the value is below 165, the count is decremented by 1.
When it is judged to be an error, the error status is recorded in the notification data sent to the DISPLAY_BOARD.
If the normal status is maintained for 3 seconds, the error status is cleared in the notification data sent to the DISPLAY_BOARD.

IGBT Temp Sensor Open Circuit Error

This error check is carried out using ADC value upper/lower limit check in the “processing at every 1 s”.
If the ADC value is 253 or more, it is judged to be an error.
When it is judged to be an error, the error status is recorded in the notification data sent to the DISPLAY_BOARD.
It is restored after the restart.

IGBT Temperature Sensor Short Circuit Error

This error check is carried out using ADC value upper/lower limit check in the “processing at every 1 s”.
If the ADC value is 3 or less, it is judged to be an error.
When it is judged to be an error, the error status is recorded in the notification data sent to the DISPLAY_BOARD.
It is restored after the restart.

Pot Bottom Temperature Sensor Open Circuit Error

This error check is carried out using ADC value upper/lower limit check in the “processing at every 1 s”.
If the ADC value is 253 or more, it is judged to be an error.
When it is judged to be an error, the error status is recorded in the notification data sent to the DISPLAY_BOARD.
It is restored after the restart.

Pot Bottom Temperature Sensor Short Circuit Error

This error check is carried out using ADC value upper/lower limit check in the “processing at every 1 s”.
If the ADC value is 3 or less, it is judged to be an error.
When it is judged to be an error, the error status is recorded in the notification data sent to the DISPLAY_BOARD.
It is restored after the restart.

Pot Bottom High-Temperature Error

This error check is carried out using an ADC value upper/lower limit check.
If the pot bottom temperature is 175 degrees or more and the ADC value is below 253, the count is incremented by 1. And when it is confirmed 5 times, it is judged to be an error.
And if the above conditions are not met, the count is decremented by 1.
When it is judged to be an error, the IGBT is turned off, and the error status is recorded in the notification data sent to the DISPLAY_BOARD.
When the pot bottom temperature goes below 60 degrees, the error status is cleared in the notification data sent to the DISPLAY_BOARD.

IGBT High-Temperature Error

This error check is carried out using an ADC value upper/lower limit check.
If the IGBT temperature is 105 degrees or more and the ADC value is above 3, the count is incremented by 1.
And when it is confirmed 5 times, it is judged to be an error.
And if the above conditions are not met, the count is decremented by 1.
When it is judged to be an error, the IGBT is turned off, and the error status is recorded in the notification data sent to the DISPLAY_BOARD.
When the IGBT temperature goes below 65 degrees, the error status is cleared in the notification data sent to the DISPLAY_BOARD.

No Pot Error

This error check is carried out in the “processing at every 100 ms”.
Detection processing starts due to a decrease in the current flow value.
After one pulse is generated by the PPG, changes at both ends of the coil are counted by the comparator.
If the value is above the threshold value, it is assumed that no pot is set. If cooking is in progress, IGBT is
turned off, and the error status is recorded in the notification data sent to the DISPLAY_BOARD.
If the value is less than the threshold value, it is assumed that there is the pot, and if cooking is in progress, IGBT is turned on, and the error status is cleared in the notification data sent to the DISPLAY_BOARD.

IGBT High-Temperature Monitoring

This error check is carried out in the “processing at every 1 s”.
If the IGBT temperature is 88 degrees or more, the count is incremented by 1. And when it is confirmed 5 times, it is judged to be an error.
And if the above condition is not met, the count is decremented by 1.
After this error detection, if the IGBT temperature goes below 83 degrees, the heating is resumed.

Detection of Surge Current by Hardware

This flag is enabled by CMP2 interrupt, and it is checked in “processing at every 20 ms”.
IGBT is turned off when surge current is detected.
And if it does not recur for 3 s, normal operation is restored.

Detection of Overcurrent by Hardware

This flag is enabled by CMP3 interrupt, and it is checked in “processing at every 20 ms”.
IGBT is turned off when overcurrent is detected.
And if it does not recur within 1 s for the second time and within 3 seconds for other cases, normal operation is restored.

Detection of Overvoltage by Hardware

PPG is reset by OVP interrupt. At this time, the flag is enabled, checked by an interrupt of 10 ms, and the PPG is reset after 190 ms.

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