The Italian took over in the close season after a spectacular late run of form under Nigel Pearson helped the club narrowly avoid relegation from the Premier League last term.
"I want my players to come to the training ground laughing but when we start work to be very serious," Ranieri told a news conference ahead of Saturday's home game with Arsenal.
"I think when you go to your job and you're sad and not happy you don't work very well. I think now the players know me very well and they understand my philosophy.
"I want to joke a bit but when we are working I change face and I change my voice. They understand now the right moment to work."
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Former Chelsea manager Ranieri is popular among fans of other Premier League clubs but people should not underestimate his likeability.
Asked if he shouted at his players, he replied: "Yes... a lot.
"Sometimes I want to break the mind and change the chip," added Ranieri, gesturing in animated Latin-style by putting his hands to his head.
Leicester have three wins and three draws from their opening six league games of the season but the Italian knows things will get especially tough in November and December when they have to take on champions Chelsea, Manchester City and Manchester United.
Ranieri had his audience in fits of laughter when one reporter mentioned the fixtures that he had coming up.
"Stop, please," he giggled. "I know very well. Unbelievable. But it's okay because for now we are just thinking about Arsenal."
(Writing by Tony Jimenez,; Editing by Pritha Sarkar)
